Multiple wavelength sensor emitters

BACKGROUND OF THE INVENTION

0001Spectroscopy is a common technique for measuring the concentration of organic and some inorganic constituents of a solution. The theoretical basis of this technique is the Beer-Lambert law, which states that the concentration <i>c_i</i> of an absorbent in solution can be determined by the intensity of light transmitted through the solution, knowing the pathlength <i>d_λ</i>, the intensity of the incident light <i>I_0,λ</i>, and the extinction coefficient <i>ε</i>_{<i>i</i>,<i>λ</i>} at a particular wavelength λ. In generalized form, the Beer-Lambert law is expressed as: <maths id="math0001" num="(1)"><math display="block"><msub><mi>I</mi><mi>λ</mi></msub><mo>=</mo><msub><mi>I</mi><mrow><mn>0</mn><mo>,</mo><mi>λ</mi></mrow></msub><msup><mi>e</mi><mrow><mo>−</mo><msub><mi>d</mi><mi>λ</mi></msub><mo>⋅</mo><msub><mi>μ</mi><mrow><mi>a</mi><mo>,</mo><mi>λ</mi></mrow></msub></mrow></msup></math><img file="EP3662817B1_D0001.tif" /></maths><maths id="math0002" num="(2)"><math display="block"><msub><mi>μ</mi><mrow><mi>a</mi><mo>,</mo><mi>λ</mi></mrow></msub><mo>=</mo><mstyle displaystyle="true"><munderover><mo>∑</mo><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mi>n</mi></munderover><mrow><msub><mi>ε</mi><mrow><mi>i</mi><mo>,</mo><mi>λ</mi></mrow></msub><mo>⋅</mo><msub><mi>c</mi><mi>i</mi></msub></mrow></mstyle></math><img file="EP3662817B1_D0002.tif" /></maths> where <i>µ</i>_{<i>a</i>,<i>λ</i>} is the bulk absorption coefficient and represents the probability of absorption per unit length. The minimum number of discrete wavelengths that are required to solve EQS. <b>1-2</b> are the number of significant absorbers that are present in the solution.

0002A practical application of this technique is pulse oximetry, which utilizes a noninvasive sensor to measure oxygen saturation (SpO₂) and pulse rate. In general, the sensor has light emitting diodes (LEDs) that transmit optical radiation of red and infrared wavelengths into a tissue site and a detector that responds to the intensity of the optical radiation after absorption (e.g., by transmission or transreflectance) by pulsatile arterial blood flowing within the tissue site. Based on this response, a processor determines measurements for SpO₂, pulse rate, and can output representative plethysmographic waveforms. Thus, "pulse oximetry" as used herein encompasses its broad ordinary meaning known to one of skill in the art, which includes at least those noninvasive procedures for measuring parameters of circulating blood through spectroscopy. Moreover, "plethysmograph" as used herein (commonly referred to as "photoplethysmograph"), encompasses its broad ordinary meaning known to one of skill in the art, which includes at least data representative of a change in the absorption of particular wavelengths of light as a function of the changes in body tissue resulting from pulsing blood. Pulse oximeters capable of reading through motion induced noise are available from Masimo Corporation ("Masimo") of Irvine, California. Moreover, portable and other oximeters capable of reading through motion induced noise are disclosed in at least <patcit id="pcit0001" dnum="US6770028B"><text>U.S. Pat. Nos. 6,770,028</text></patcit>, <patcit id="pcit0002" dnum="US6658276B"><text>6,658,276</text></patcit>, <patcit id="pcit0003" dnum="US6157850A"><text>6,157,850</text></patcit>, <patcit id="pcit0004" dnum="US6002952A"><text>6,002,952</text></patcit><patcit id="pcit0005" dnum="US5769785A"><text>5,769,785</text></patcit>, and <patcit id="pcit0006" dnum="US5758644A"><text>5,758,644</text></patcit>. Such reading through motion oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all types of monitoring scenarios.

0003<patcit id="pcit0007" dnum="US6697656B1"><text>US 6,697,656 B1</text></patcit> relates to an oximeter sensor which can be used with multiple oximeter systems. The oximeter sensor includes a first light-emitting diode, a second light-emitting diode and a photodetector. Electrical connections to the anode and the cathode of each light-emitting diode and electrical connections to the terminals of the photodetector are provided on a connector. An interconnector is interposed between the connector of the oximeter sensor and a connector in communication with an oximeter system. The interconnector has interconnection wiring selected to electrically connect the sensor connector and the system connector in a manner to configure the light-emitting diodes in a configuration compatible with the oximeter system.

0004<patcit id="pcit0008" dnum="US6356774B1"><text>US 6,356,774 B1</text></patcit> discloses a method for operating an oximeter sensor and a corresponding apparatus which includes an encoded temperature characteristic of a light emitter in the sensor. The encoded temperature characteristic is read and is used to modify a drive of the light emitter in the sensor. This enables a light emitter to be operated at its maximum allowable intensity to maximize a signal to noise ratio, without burning a patient, in accordance with the particular characteristics of that light emitter.

SUMMARY OF THE INVENTION

0005The present invention is defined by the features of the independent claims. Further preferred embodiments of the present invention are defined in the dependent claims.

0006According to a first aspect of the present invention there is provided a physiological sensor comprising: a first light emitting source comprising an anode and a cathode, the cathode of the first light emitting source connected to a first contact, the first contact in communications with a first row conductor and a first column conductor of an electrical grid, the anode of the first light emitting source connected to a second contact, the second contact in communications with a second row conductor and a second column conductor of the electrical grid, the first light emitting source configured to activate by addressing the first row conductor and the second column conductor of the electrical grid; and a second light emitting source comprising an anode and a cathode, the cathode of the second light emitting source connected to the second contact, the anode of the second light emitting source connected to the first contact, the second light emitting source configured to activate by addressing the second row conductor and the first column conductor of the electrical grid.

0007According to a further aspect of the present invention there is provided a physiological sensor method, particularly to be used for a physiological sensor according to the first aspect, the method comprising: sequentially addressing a first light emitting source and a second light emitting source using a first row conductor, a second row conductor, a first column conductor, and a second column conductor of an electrical grid so as to emit light having a plurality of wavelengths that when attenuated by body tissue is indicative of at least one physiological characteristic, wherein the first light emitting source is configured to activate by addressing the first row conductor and the second column conductor of the electrical grid, wherein the second light emitting source configured to activate by addressing the second row conductor and the first column conductor of the electrical grid; and detecting the emitted light after attenuation by body tissue.

0008In particular, there is a need to noninvasively measure multiple physiological parameters, other than, or in addition to, oxygen saturation and pulse rate. For example, hemoglobin species that are also significant under certain circumstances are carboxyhemoglobin and methemoglobin. Other blood parameters that may be measured to provide important clinical information are fractional oxygen saturation, total hemaglobin (Hbt), bilirubin and blood glucose, to name a few.

0009Disclosed is a physiological sensor having optical intensity compensation introduced along an optical path from emission to detection so as to compensate for unequal tissue attenuation as a function of wavelength is emitters configured to transmit optical radiation having multiple wavelengths into a tissue site. At least one detector is capable of receiving the optical radiation after tissue attenuation. An equalization is capable of compensating optical radiation intensity so as to account for differences in tissue attenuation across at least a portion of the multiple wavelengths.

0010In another example of a physiological sensor, emitters emit optical radiation having multiple wavelengths. The optical radiation is detected after tissue attenuation and is transmitted through a medium. At least one of emission, detection and transmission is adapted to at least partially reduce wavelength dependence of the tissue attenuation.

0011A further example of a physiological sensor is an emitter means for emitting optical radiation having multiple wavelengths into a tissue site. The sensor includes a detector means for detecting the optical radiation after tissue attenuation and an equalization means for compensating the optical radiation intensity so as to account for differences in tissue attenuation of the optical radiation across at least a portion of the multiple wavelengths.

BRIEF DESCRIPTION OF THE DRAWINGS

0012<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. <b>1</b></figref> is a perspective view of a physiological measurement system utilizing a multiple wavelength sensor;</li><li><figref idref="f0002 f0003">FIGS. 2A-C</figref> are perspective views of multiple wavelength sensor embodiments;</li><li><figref idref="f0004">FIG. <b>3</b></figref> is a general block diagram of a multiple wavelength sensor and sensor controller;</li><li><figref idref="f0005">FIG. <b>4</b></figref> is an exploded perspective view of a multiple wavelength sensor embodiment;</li><li><figref idref="f0006">FIG. <b>5</b></figref> is a general block diagram of an emitter assembly;</li><li><figref idref="f0007">FIG. <b>6</b></figref> is a perspective view of an emitter assembly embodiment;</li><li><figref idref="f0008">FIG. <b>7</b></figref> is a general block diagram of an emitter array;</li><li><figref idref="f0009">FIG. <b>8</b></figref> is a schematic diagram of an emitter array embodiment not falling withing the claimed subject-matter;</li><li><figref idref="f0010">FIG. <b>9</b></figref> is a general block diagram of equalization;</li><li><figref idref="f0011">FIGS. 10A-D</figref> are block diagrams of various equalization embodiments;</li><li><figref idref="f0012">FIGS. 11A-C</figref> are perspective views of an emitter assembly incorporating various equalization embodiments;</li><li><figref idref="f0013">FIG. <b>12</b></figref> is a general block diagram of an emitter substrate;</li><li><figref idref="f0014">FIGS. <b>13-14</b></figref> are top and detailed side views of an emitter substrate embodiment;</li><li><figref idref="f0015">FIG. <b>15-16</b></figref> are top and bottom component layout views of an emitter substrate embodiment;</li><li><figref idref="f0016">FIG. <b>17</b></figref> is a schematic diagram of an emitter substrate embodiment not falling withing the claimed subject-matter;</li><li><figref idref="f0017">FIG. <b>18</b></figref> is a plan view of an inner layer of an emitter substrate embodiment;</li><li><figref idref="f0018">FIG. <b>19</b></figref> is a general block diagram of an interconnect assembly in relationship to other sensor assemblies;</li><li><figref idref="f0019">FIG. <b>20</b></figref> is a block diagram of an interconnect assembly embodiment;</li><li><figref idref="f0020">FIG. <b>21</b></figref> is a partially-exploded perspective view of a flex circuit assembly embodiment of an interconnect assembly;</li><li><figref idref="f0021">FIG. <b>22</b></figref> is a top plan view of a flex circuit;</li><li><figref idref="f0022">FIG. <b>23</b></figref> is an exploded perspective view of an emitter portion of a flex circuit assembly;</li><li><figref idref="f0023">FIG. <b>24</b></figref> is an exploded perspective view of a detector assembly embodiment;</li><li><figref idref="f0024">FIGS. <b>25-26</b></figref> are block diagrams of adjacent detector and stacked detector embodiments;</li><li><figref idref="f0025">FIG. <b>27</b></figref> is a block diagram of a finger clip embodiment of an attachment assembly;</li><li><figref idref="f0026">FIG. <b>28</b></figref> is a general block diagram of a detector pad;</li><li><figref idref="f0027">FIGS. 29A-B</figref> are perspective views of detector pad embodiments;</li><li><figref idref="f0028 f0029">FIGS. 30A-H</figref> are perspective bottom, perspective top, bottom, back, top, side cross sectional, side, and front cross sectional views of an emitter pad embodiment;</li><li><figref idref="f0030 f0031">FIGS. 31A-H</figref> are perspective bottom, perspective top, top, back, bottom, side cross sectional, side, and front cross sectional views of a detector pad embodiment;</li><li><figref idref="f0032 f0033">FIGS. 32A-H</figref> are perspective bottom, perspective top, top, back, bottom, side cross sectional, side, and front cross sectional views of a shoe box;</li><li><figref idref="f0034 f0035">FIGS. 33A-H</figref> are perspective bottom, perspective top, top, back, bottom, side cross sectional, side, and front cross sectional views of a slim-finger emitter pad embodiment;</li><li><figref idref="f0036 f0037">FIGS. 34A-H</figref> are perspective bottom, perspective top, top, back, bottom, side cross sectional, side, and front cross sectional views of a slim-finger detector pad embodiment;</li><li><figref idref="f0038">FIGS. 35A-B </figref>are plan and cross sectional views, respectively, of a spring assembly embodiment;</li><li><figref idref="f0039">FIGS. 36A-C</figref> are top, perspective and side views of a finger clip spring;</li><li><figref idref="f0040">FIGS. 37A-D</figref> are top, back, bottom, and side views of a spring plate;</li><li><figref idref="f0041">FIGS. 38A-D</figref> are front cross sectional, bottom, front and side cross sectional views of an emitter-pad shell;</li><li><figref idref="f0042">FIGS. 39A-D</figref> are back, top, front and side cross sectional views of a detector-pad shell;</li><li><figref idref="f0043">FIG. <b>40</b></figref> is a general block diagram of a monitor and a sensor;</li><li><figref idref="f0044">FIGS. <b>41A</b></figref> is a schematic diagram of a grid drive embodiment for a sensor of the present invention having back-to-back diodes and an information element, and <figref idref="f0044">FIGS. 41B-C</figref> are schematic diagrams of grid drive alternative examples for a sensor having back-to-back diodes and an information element not falling withing the claimed subject-matter;</li><li><figref idref="f0045">FIGS. <b>42</b></figref> is a schematic diagrams of a grid drive embodiment for an information element;</li><li><figref idref="f0045">FIGS. 43A-C</figref> are schematic diagrams for grid drive readable information elements;</li><li><figref idref="f0046">FIGS. 44A-B</figref> are cross sectional and side cut away views of a sensor cable;</li><li><figref idref="f0047">FIG. <b>45</b></figref> is a block diagram of a sensor controller embodiment; and</li><li><figref idref="f0048">FIG. <b>46</b></figref> is a detailed exploded perspective view of a multiple wavelength sensor embodiment.</li></ul>

0013The present invention is based on <figref idref="f0044">figure 41A</figref>. All other figures and corresponding passages of the description relate to relevant background art and are not part of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Overview

0014In this application, reference is made to many blood parameters. Some references that have common shorthand designations are referenced through such shorthand designations. For example, as used herein, HbCO designates carboxyhemoglobin, HbMet designates methemoglobin, and Hbt designates total hemoglobin. Other shorthand designations such as COHb, MetHb, and tHb are also common in the art for these same constituents. These constituents are generally reported in terms of a percentage, often referred to as saturation, relative concentration or fractional saturation. Total hemoglobin is generally reported as a concentration in g/dL. The use of the particular shorthand designators presented in this application does not restrict the term to any particular manner in which the designated constituent is reported.

0015<figref idref="f0001">FIG. <b>1</b></figref> illustrates a physiological measurement system <b>10</b> having a monitor <b>100</b> and a multiple wavelength sensor assembly <b>200</b> with enhanced measurement capabilities as compared with conventional pulse oximetry. The physiological measurement system <b>10</b> allows the monitoring of a person, including a patient. In particular, the multiple wavelength sensor assembly <b>200</b> allows the measurement of blood constituent and related parameters in addition to oxygen saturation and pulse rate. Alternatively, the multiple wavelength sensor assembly <b>200</b> allows the measurement of oxygen saturation and pulse rate with increased accuracy or robustness as compared with conventional pulse oximetry.

0016In one embodiment, the sensor assembly <b>200</b> is configured to plug into a monitor sensor port <b>110.</b> Monitor keys <b>160</b> provide control over operating modes and alarms, to name a few. A display <b>170</b> provides readouts of measured parameters, such as oxygen saturation, pulse rate, HbCO and HbMet to name a few.

0017<figref idref="f0002">FIGS. <b>2A</b></figref> illustrates a multiple wavelength sensor assembly <b>200</b> having a sensor <b>400</b> adapted to attach to a tissue site, a sensor cable <b>4400</b> and a monitor connector <b>210.</b> In one embodiment, the sensor <b>400</b> is incorporated into a reusable finger clip adapted to removably attach to, and transmit light through, a fingertip. The sensor cable <b>4400</b> and monitor connector <b>210</b> are integral to the sensor <b>400,</b> as shown. In alternative embodiments, the sensor <b>400</b> may be configured separately from the cable <b>4400</b> and connector <b>210.</b>

0018<figref idref="f0003">FIGS. 2B-C</figref> illustrate alternative sensor embodiments, including a sensor <b>401</b> (<figref idref="f0003">FIG. <b>2B</b></figref>) partially disposable and partially reusable (resposable) and utilizing an adhesive attachment mechanism. Also shown is a sensor <b>402</b> (<figref idref="f0003">FIG. <b>2C</b></figref><b>)</b> being disposable and utilizing an adhesive attachment mechanism. In other embodiments, a sensor may be configured to attach to various tissue sites other than a finger, such as a foot or an ear. Also a sensor may be configured as a reflectance or transflectance device that attaches to a forehead or other tissue surface.

0019<figref idref="f0004">FIG. <b>3</b></figref> illustrates a sensor assembly <b>400</b> having an emitter assembly <b>500,</b> a detector assembly <b>2400,</b> an interconnect assembly <b>1900</b> and an attachment assembly <b>2700.</b> The emitter assembly <b>500</b> responds to drive signals received from a sensor controller <b>4500</b> in the monitor <b>100</b> via the cable <b>4400</b> so as to transmit optical radiation having a plurality of wavelengths into a tissue site. The detector assembly <b>2400</b> provides a sensor signal to the monitor <b>100</b> via the cable <b>4400</b> in response to optical radiation received after attenuation by the tissue site. The interconnect assembly <b>1900</b> provides electrical communication between the cable <b>4400</b> and both the emitter assembly <b>500</b> and the detector assembly <b>2400.</b> The attachment assembly <b>2700</b> attaches the emitter assembly <b>500</b> and detector assembly <b>2400</b> to a tissue site, as described above. The emitter assembly <b>500</b> is described in further detail with respect to <figref idref="f0006">FIG. <b>5</b></figref><b>,</b> below. The interconnect assembly <b>1900</b> is described in further detail with respect to <figref idref="f0018">FIG. <b>19</b></figref><b>,</b> below. The detector assembly <b>2400</b> is described in further detail with respect to <figref idref="f0023">FIG. <b>24</b></figref><b>,</b> below. The attachment assembly <b>2700</b> is described in further detail with respect to <figref idref="f0025">FIG. <b>27</b></figref><b>,</b> below.

0020<figref idref="f0005">FIG. <b>4</b></figref> illustrates a sensor <b>400</b> embodiment that removably attaches to a fingertip. The sensor <b>400</b> houses a multiple wavelength emitter assembly <b>500</b> and corresponding detector assembly <b>2400.</b> A flex circuit assembly <b>1900</b> mounts the emitter and detector assemblies <b>500, 2400</b> and interconnects them to a multiwire sensor cable <b>4400.</b> Advantageously, the sensor <b>400</b> is configured in several respects for both wearer comfort and parameter measurement performance. The flex circuit assembly <b>1900</b> is configured to mechanically decouple the cable <b>4400</b> wires from the emitter and detector assemblies <b>500, 2400</b> to reduce pad stiffness and wearer discomfort. The pads <b>3000, 3100</b> are mechanically decoupled from shells <b>3800, 3900</b> to increase flexibility and wearer comfort. A spring <b>3600</b> is configured in hinged shells <b>3800, 3900</b> so that the pivot point of the finger clip is well behind the fingertip, improving finger attachment and more evenly distributing the clip pressure along the finger.

0021As shown in <figref idref="f0005">FIG. <b>4</b></figref><b>,</b> the detector pad <b>3100</b> is structured to properly position a fingertip in relationship to the detector assembly <b>2400.</b> The pads have flaps that block ambient light. The detector assembly <b>2400</b> is housed in an enclosure so as to reduce light piping from the emitter assembly to the detector assembly without passing through fingertip tissue. These and other features are described in detail below. Specifically, emitter assembly embodiments are described with respect to <figref idref="f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017">FIGS. <b>5-18</b></figref><b>.</b> Interconnect assembly embodiments, including the flexible circuit assembly <b>1900,</b> are described with respect to <figref idref="f0018 f0019 f0020 f0021 f0022">FIGS. <b>19-23</b></figref><b>.</b> Detector assembly embodiments are described with respect to <figref idref="f0023">FIGS. <b>24-</b></figref><b>26.</b> Attachment assembly embodiments are described with respect to <figref idref="f0025">FIGS. <b>27-</b></figref><b>39.</b>

Emitter Assembly

0022<figref idref="f0006">FIG. <b>5</b></figref> illustrates an emitter assembly <b>500</b> having an emitter array <b>700,</b> a substrate <b>1200</b> and equalization <b>900.</b> The emitter array <b>700</b> has multiple light emitting sources, each activated by addressing at least one row and at least one column of an electrical grid. The light emitting sources are capable of transmitting optical radiation having multiple wavelengths. The equalization <b>900</b> accounts for differences in tissue attenuation of the optical radiation across the multiple wavelengths so as to at least reduce wavelength-dependent variations in detected intensity. The substrate <b>1200</b> provides a physical mount for the emitter array and emitter-related equalization and a connection between the emitter array and the interconnection assembly. Advantageously, the substrate <b>1200</b> also provides a bulk temperature measurement so as to calculate the operating wavelengths for the light emitting sources. The emitter array <b>700</b> is described in further detail with respect to <figref idref="f0008">FIG. <b>7</b></figref><b>,</b> below. Equalization is described in further detail with respect to <figref idref="f0010">FIG. <b>9</b></figref><b>,</b> below. The substrate <b>1200</b> is described in further detail with respect to <figref idref="f0013">FIG. <b>12</b></figref><b>,</b> below.

0023<figref idref="f0007">FIG. <b>6</b></figref> illustrates an emitter assembly <b>500</b> embodiment having an emitter array <b>700,</b> an encapsulant <b>600,</b> an optical filter <b>1100</b> and a substrate <b>1200.</b> Various aspects of the emitter assembly <b>500</b> are described with respect to <figref idref="f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017">FIGS. <b>7-18</b></figref><b>,</b> below. The emitter array <b>700</b> emits optical radiation having multiple wavelengths of predetermined nominal values, advantageously allowing multiple parameter measurements. In particular, the emitter array <b>700</b> has multiple light emitting diodes (LEDs) <b>710</b> that are physically arranged and electrically connected in an electrical grid to facilitate drive control, equalization, and minimization of optical pathlength differences at particular wavelengths. The optical filter <b>1100</b> is advantageously configured to provide intensity equalization across a specific LED subset. The substrate <b>1200</b> is configured to provide a bulk temperature of the emitter array <b>700</b> so as to better determine LED operating wavelengths.

Emitter Array

0024<figref idref="f0008">FIG. <b>7</b></figref> illustrates an emitter array <b>700</b> having multiple light emitters (LE) <b>710</b> capable of emitting light <b>702</b> having multiple wavelengths into a tissue site <b>1.</b> Row drivers <b>4530</b> and column drivers <b>4560</b> are electrically connected to the light emitters <b>710</b> and activate one or more light emitters <b>710</b> by addressing at least one row <b>720</b> and at least one column <b>740</b> of an electrical grid. In one embodiment, the light emitters <b>710</b> each include a first contact <b>712</b> and a second contact <b>714.</b> The first contact <b>712</b> of a first subset <b>730</b> of light emitters is in communication with a first conductor <b>720</b> of the electrical grid. The second contact <b>714</b> of a second subset <b>750</b> of light emitters is in communication with a second conductor <b>740.</b> Each subset comprises at least two light emitters, and at least one of the light emitters of the first and second subsets <b>730, 750</b> are not in common. A detector <b>2400</b> is capable of detecting the emitted light <b>702</b> and outputting a sensor signal <b>2500</b> responsive to the emitted light <b>702</b> after attenuation by the tissue site <b>1.</b> As such, the sensor signal <b>2500</b> is indicative of at least one physiological parameter corresponding to the tissue site <b>1,</b> as described above.

0025<figref idref="f0009">FIG. <b>8</b></figref> illustrates an emitter array <b>700</b> not falling withing the claimed subject-matter having LEDs <b>801</b> connected within an electrical grid of n rows and m columns totaling n + m drive lines <b>4501, 4502,</b> where n and m integers greater than one. The electrical grid advantageously minimizes the number of drive lines required to activate the LEDs <b>801</b> while preserving flexibility to selectively activate individual LEDs <b>801</b> in any sequence and multiple LEDs <b>801</b> simultaneously. The electrical grid also facilitates setting LED currents so as to control intensity at each wavelength, determining operating wavelengths and monitoring total grid current so as to limit power dissipation. The emitter array <b>700</b> is also physically configured in rows <b>810.</b> This physical organization facilitates clustering LEDs <b>801</b> according to wavelength so as to minimize pathlength variations and facilitates equalization of LED intensities.

0026As shown in <figref idref="f0009">FIG. <b>8</b></figref><b>,</b> one embodiment of an emitter array <b>700</b> comprises up to sixteen LEDs <b>801</b> configured in an electrical grid of four rows <b>810</b> and four columns <b>820.</b> Each of the four row drive lines <b>4501</b> provide a common anode connection to four LEDs <b>801,</b> and each of the four column drive lines <b>4502</b> provide a common cathode connection to four LEDs <b>801.</b> Thus, the sixteen LEDs <b>801</b> are advantageously driven with only eight wires, including four anode drive lines <b>812</b> and four cathode drive lines <b>822.</b> This compares favorably to conventional common anode or cathode LED configurations, which require more drive lines. In a particular embodiment, the emitter array <b>700</b> is partially populated with eight LEDs having nominal wavelengths as shown in TABLE <b>1.</b> Further, LEDs having wavelengths in the range of 610-630 nm are grouped together in the same row. The emitter array <b>700</b> is adapted to a physiological measurement system <b>10</b> (<figref idref="f0001">FIG. <b>1</b></figref>) for measuring H_bCO and/or METHb in addition to S_pO₂ and pulse rate. <tables id="tabl0001" num="0001"><table frame="all"><title>TABLE <b>1:</b> Nominal LED Wavelengths</title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="14mm" /><colspec colnum="2" colname="col2" colwidth="14mm" align="center" /><colspec colnum="3" colname="col3" colwidth="15mm" align="center" /><colspec colnum="4" colname="col4" colwidth="14mm" align="center" /><thead valign="middle"><row><entry align="center"><b>LED</b></entry><entry><b>λ</b></entry><entry><b>Row</b></entry><entry><b>Col</b></entry></row></thead><tbody valign="middle"><row><entry>D1</entry><entry>630</entry><entry>1</entry><entry>1</entry></row><row><entry>D2</entry><entry>620</entry><entry>1</entry><entry>2</entry></row><row><entry>D3</entry><entry>610</entry><entry>1</entry><entry>3</entry></row><row><entry>D4</entry><entry /><entry>1</entry><entry>4</entry></row><row><entry>D5</entry><entry>700</entry><entry>2</entry><entry>1</entry></row><row><entry>D6</entry><entry>730</entry><entry>2</entry><entry>2</entry></row><row><entry>D7</entry><entry>660</entry><entry>2</entry><entry>3</entry></row><row><entry>D8</entry><entry>805</entry><entry>2</entry><entry>4</entry></row><row><entry>D9</entry><entry /><entry>3</entry><entry>1</entry></row><row><entry>D10</entry><entry /><entry>3</entry><entry>2</entry></row><row><entry>D11</entry><entry /><entry>3</entry><entry>3</entry></row><row><entry>D12</entry><entry>905</entry><entry>3</entry><entry>4</entry></row><row><entry>D13</entry><entry /><entry>4</entry><entry>1</entry></row><row><entry>D14</entry><entry /><entry>4</entry><entry>2</entry></row><row><entry>D15</entry><entry /><entry>4</entry><entry>3</entry></row><row><entry>D16</entry><entry /><entry>4</entry><entry>4</entry></row></tbody></tgroup></table></tables>

0027Also shown in <figref idref="f0009">FIG. <b>8</b></figref><b>,</b> row drivers <b>4530</b> and column drivers <b>4560</b> located in the monitor <b>100</b> selectively activate the LEDs <b>801.</b> In particular, row and column drivers <b>4530, 4560</b> function together as switches to Vcc and current sinks, respectively, to activate LEDs and as switches to ground and Vcc, respectively, to deactivate LEDs. This push-pull drive configuration advantageously prevents parasitic current flow in deactivated LEDs. In a particular embodiment, only one row drive line <b>4501</b> is switched to Vcc at a time. One to four column drive lines <b>4502,</b> however, can be simultaneously switched to a current sink so as to simultaneously activate multiple LEDs within a particular row. Activation of two or more LEDs of the same wavelength facilitates intensity equalization, as described with respect to <figref idref="f0010 f0011 f0012">FIGS. <b>9-11</b></figref><b>,</b> below. LED drivers are described in further detail with respect to <figref idref="f0047">FIG. <b>45</b></figref><b>,</b> below.

0028Although an emitter assembly is described above with respect to an array of light emitters each configured to transmit optical radiation centered around a nominal wavelength, in another embodiment, an emitter assembly advantageously utilizes one or more tunable broadband light sources, including the use of filters to select the wavelength, so as to minimize wavelength-dependent pathlength differences from emitter to detector. In yet another emitter assembly embodiment, optical radiation from multiple emitters each configured to transmit optical radiation centered around a nominal wavelength is funneled to a tissue site point so as to minimize wavelength-dependent pathlength differences. This funneling may be accomplish with fiberoptics or mirrors, for example. In further embodiments, the LEDs <b>801</b> can be configured with alternative orientations with correspondingly different drivers among various other configurations of LEDs, drivers and interconnecting conductors.

Equalization

0029<figref idref="f0010">FIG. <b>9</b></figref> illustrate a physiological parameter measurement system <b>10</b> having a controller <b>4500,</b> an emitter assembly <b>500,</b> a detector assembly <b>2400</b> and a front-end <b>4030.</b> The emitter assembly <b>500</b> is configured to transmit optical radiation having multiple wavelengths into the tissue site <b>1.</b> The detector assembly <b>2400</b> is configured to generate a sensor signal <b>2500</b> responsive to the optical radiation after tissue attenuation. The front-end <b>4030</b> conditions the sensor signal <b>2500</b> prior to analog-to-digital conversion (ADC).

0030<figref idref="f0010">FIG. <b>9</b></figref> also generally illustrates equalization <b>900</b> in a physiological measurement system <b>10</b> operating on a tissue site <b>1.</b> Equalization encompasses features incorporated into the system <b>10</b> in order to provide a sensor signal <b>2500</b> that falls well within the dynamic range of the ADC across the entire spectrum of emitter wavelengths. In particular, equalization compensates for the imbalance in tissue light absorption due to Hb and HbO₂<b>910</b>. Specifically, these blood constituents attenuate red wavelengths greater than IR wavelengths. Ideally, equalization <b>900</b> balances this unequal attenuation. Equalization <b>900</b> can be introduced anywhere in the system <b>10</b> from the controller <b>4500</b> to front-end <b>4000</b> and can include compensatory attenuation versus wavelength, as shown, or compensatory amplification versus or both.

0031Equalization can be achieved to a limited extent by adjusting drive currents from the controller <b>4500</b> and front-end <b>4030</b> amplification accordingly to wavelength so as to compensate for tissue absorption characteristics. Signal demodulation constraints, however, limit the magnitude of these adjustments. Advantageously, equalization <b>900</b> is also provided along the optical path from emitters <b>500</b> to detector <b>2400.</b> Equalization embodiments are described in further detail with respect to <figref idref="f0011 f0012">FIGS. <b>10-11</b></figref><b>,</b> below.

0032<figref idref="f0011">FIGS. 10A-D</figref> illustrate various equalization embodiments having an emitter array <b>700</b> adapted to transmit optical radiation into a tissue site <b>1</b> and a detector assembly <b>2400</b> adapted to generate a sensor signal <b>2500</b> responsive to the optical radiation after tissue attenuation. <figref idref="f0011">FIG. <b>10A</b></figref> illustrates an optical filter <b>1100</b> that attenuates at least a portion of the optical radiation before it is transmitted into a tissue site 1. In particular, the optical filter <b>1100</b> attenuates at least a portion of the IR wavelength spectrum of the optical radiation so as to approximate an equalization curve <b>900</b> (<figref idref="f0010">FIG. 9</figref>). <figref idref="f0011">FIG. <b>10B</b></figref> illustrates an optical filter <b>1100</b> that attenuates at least a portion of the optical radiation after it is attenuated by a tissue site <b>1,</b> where the optical filter <b>1100</b> approximates an equalization curve <b>900</b> (<figref idref="f0010">FIG. <b>9</b></figref>).

0033<figref idref="f0011">FIG. <b>10C</b></figref> illustrates an emitter array <b>700</b> where at least a portion of the emitter array generates one or more wavelengths from multiple light emitters <b>710</b> of the same wavelength. In particular, the same-wavelength light emitters <b>710</b> boost at least a portion of the red wavelength spectrum so as to approximately equalize the attenuation curves <b>910</b> (<figref idref="f0010">FIG. <b>9</b></figref>). <figref idref="f0011">FIG. <b>10D</b></figref> illustrates a detector assembly <b>2400</b> having multiple detectors <b>2610, 2620</b> selected so as to equalize the attenuation curves <b>910</b> (<figref idref="f0010">FIG. <b>9</b></figref>)<b>.</b> To a limited extent, optical equalization can also be achieved by selection of particular emitter array <b>700</b> and detector <b>2400</b> components, e.g. LEDs having higher output intensities or detectors having higher sensitivities at red wavelengths. Although equalization embodiments are described above with respect to red and IR wavelengths, these equalization embodiments can be applied to equalize tissue characteristics across any portion of the optical spectrum.

0034<figref idref="f0012">FIGS. 11A-C</figref> illustrates an optical filter <b>1100</b> for an emitter assembly <b>500</b> that advantageously provides optical equalization, as described above. LEDs within the emitter array <b>700</b> may be grouped according to output intensity or wavelength or both. Such a grouping facilitates equalization of LED intensity across the array. In particular, relatively low tissue absorption and/or relatively high output intensity LEDs can be grouped together under a relatively high attenuation optical filter. Likewise, relatively low tissue absorption and/or relatively low output intensity LEDs can be grouped together without an optical filter or under a relatively low or negligible attenuation optical filter. Further, high tissue absorption and/or low intensity LEDs can be grouped within the same row with one or more LEDs of the same wavelength being simultaneously activated, as described with respect to <figref idref="f0011">FIG. <b>10C</b></figref><b>,</b> above. In general, there can be any number of LED groups and any number of LEDs within a group. There can also be any number of optical filters corresponding to the groups having a range of attenuation, including no optical filter and/or a "clear" filter having negligible attenuation.

0035As shown in <figref idref="f0012">FIGS. 11A-C</figref>, a filtering media may be advantageously added to an encapsulant that functions both as a cover to protect LEDs and bonding wires and as an optical filter <b>1100.</b> In one embodiment, a filtering media <b>1100</b> encapsulates a select group of LEDs and a clear media <b>600</b> (<figref idref="f0007">FIG. <b>6</b></figref>) encapsulates the entire array <b>700</b> and the filtering media <b>1000</b> (<figref idref="f0007">FIG. <b>6</b></figref>)<b>.</b> In a particular embodiment, corresponding to TABLE <b>1,</b> above, five LEDs nominally emitting at 660-905 nm are encapsulated with both a filtering media <b>1100</b> and an overlying clear media <b>600</b> (<figref idref="f0007">FIG. <b>6</b></figref>), i.e. attenuated. In a particular embodiment, the filtering media 1100 is a 40:1 mixture of a clear encapsulant (EPO-TEK OG147-7) and an opaque encapsulate (EPO-TEK OG147) both available from Epoxy Technology, Inc., Billerica, MA. Three LEDs nominally emitting at 610-630 nm are only encapsulated with the clear media <b>600</b> (<figref idref="f0007">FIG. <b>6</b></figref>), i.e. unattenuated. In alternative embodiments, individual LEDs may be singly or multiply encapsulated according to tissue absorption and/or output intensity. In other alternative embodiments, filtering media may be separately attachable optical filters or a combination of encapsulants and separately attachable optical filters. In a particular embodiment, the emitter assembly <b>500</b> has one or more notches along each side proximate the component end <b>1305</b> (<figref idref="f0014">FIG. <b>13</b></figref>) for retaining one or more clip-on optical filters.

Substrate

0036<figref idref="f0013">FIG. <b>12</b></figref> illustrates light emitters <b>710</b> configured to transmit optical radiation <b>1201</b> having multiple wavelengths in response to corresponding drive currents <b>1210.</b> A thermal mass <b>1220</b> is disposed proximate the emitters <b>710</b> so as to stabilize a bulk temperature <b>1202</b> for the emitters. A temperature sensor <b>1230</b> is thermally coupled to the thermal mass <b>1220,</b> wherein the temperature sensor <b>1230</b> provides a temperature sensor output <b>1232</b> responsive to the bulk temperature <b>1202</b> so that the wavelengths are determinable as a function of the drive currents <b>1210</b> and the bulk temperature <b>1202.</b>

0037In one embodiment, an operating wavelength λ_a of each light emitter <b>710</b> is determined according to EQ. <b>3</b><maths id="math0003" num="(3)"><math display="block"><msub><mi>λ</mi><mi>a</mi></msub><mo>=</mo><mi>ƒ</mi><mfenced><msub><mi>T</mi><mi>b</mi></msub><msub><mi>I</mi><mi mathvariant="italic">drive</mi></msub><mstyle displaystyle="true"><mo>∑</mo><msub><mi>I</mi><mi mathvariant="italic">drive</mi></msub></mstyle></mfenced></math><img file="EP3662817B1_D0003.tif" /></maths> where T_b is the bulk temperature, I_drive is the drive current for a particular light emitter, as determined by the sensor controller <b>4500</b> (<figref idref="f0047">FIG. <b>45</b></figref><b>),</b> described below, and ΣI_drive is the total drive current for all light emitters. In another embodiment, temperature sensors are configured to measure the temperature of each light emitter <b>710</b> and an operating wavelength λ_a of each light emitter <b>710</b> is determined according to EQ. <b>4</b><maths id="math0004" num="(4)"><math display="block"><msub><mi>λ</mi><mi>a</mi></msub><mo>=</mo><mi>ƒ</mi><mfenced><msub><mi>T</mi><mi>a</mi></msub><msub><mi>I</mi><mi mathvariant="italic">drive</mi></msub><mstyle displaystyle="true"><mo>∑</mo><msub><mi>I</mi><mi mathvariant="italic">drive</mi></msub></mstyle></mfenced></math><img file="EP3662817B1_D0004.tif" /></maths> where T_a is the temperature of a particular light emitter, I_drive is the drive current for that light emitter and ΣI_drive is the total drive current for all light emitters.

0038In yet another embodiment, an operating wavelength for each light emitter is determined by measuring the junction voltage for each light emitter <b>710.</b> In a further embodiment, the temperature of each light emitter <b>710</b> is controlled, such as by one or more Peltier cells coupled to each light emitter <b>710,</b> and an operating wavelength for each light emitter <b>710</b> is determined as a function of the resulting controlled temperature or temperatures. In other embodiments, the operating wavelength for each light emitter <b>710</b> is determined directly, for example by attaching a charge coupled device (CCD) to each light emitter or by attaching a fiberoptic to each light emitter and coupling the fiberoptics to a wavelength measuring device, to name a few.

0039<figref idref="f0014 f0015 f0016 f0017">FIGS. <b>13-18</b></figref> illustrate one embodiment of a substrate <b>1200</b> configured to provide thermal conductivity between an emitter array <b>700</b> (<figref idref="f0009">FIG. <b>8</b></figref>) and a thermistor <b>1540</b> (<figref idref="f0015">FIG. <b>16</b></figref>)<b>.</b> In this manner, the resistance of the thermistor <b>1540</b> (<figref idref="f0015">FIG. <b>16</b></figref>) can be measured in order to determine the bulk temperature of LEDs <b>801</b> (<figref idref="f0009">FIG. <b>8</b></figref>) mounted on the substrate <b>1200.</b> The substrate <b>1200</b> is also configured with a relatively significant thermal mass, which stabilizes and normalizes the bulk temperature so that the thermistor measurement of bulk temperature is meaningful.

0040<figref idref="f0014">FIGS. <b>13-14</b></figref> illustrate a substrate <b>1200</b> having a component side <b>1301,</b> a solder side <b>1302,</b> a component end <b>1305</b> and a connector end <b>1306.</b> Alignment notches <b>1310</b> are disposed between the ends <b>1305, 1306.</b> The substrate <b>1200</b> further has a component layer <b>1401,</b> inner layers <b>1402-1405</b> and a solder layer <b>1406.</b> The inner layers <b>1402-1405,</b> e.g. inner layer <b>1402</b> (<figref idref="f0017">FIG. <b>18</b></figref><b>),</b> have substantial metallized areas <b>1411</b> that provide a thermal mass <b>1220</b> (<figref idref="f0013">FIG. <b>12</b></figref><b>)</b> to stabilize a bulk temperature for the emitter array <b>700</b> (<figref idref="f0013">FIG. <b>12</b></figref>). The metallized areas <b>1411</b> also function to interconnect component pads <b>1510</b> and wire bond pads <b>1520</b> (<figref idref="f0015">FIG. <b>15</b></figref>) to the connector <b>1530.</b>

0041<figref idref="f0015">FIGS. <b>15-16</b></figref> illustrate a substrate <b>1200</b> having component pads <b>1510</b> and wire bond pads <b>1520</b> at a component end <b>1305.</b> The component pads <b>1510</b> mount and electrically connect a first side (anode or cathode) of the LEDs <b>801</b> (<figref idref="f0009">FIG. <b>8</b></figref>) to the substrate <b>1200.</b> Wire bond pads <b>1520</b> electrically connect a second side (cathode or anode) of the LEDs <b>801</b> (<figref idref="f0009">FIG. <b>8</b></figref>) to the substrate <b>1200.</b> The connector end <b>1306</b> has a connector <b>1530</b> with connector pads <b>1532, 1534</b> that mount and electrically connect the emitter assembly <b>500</b> (<figref idref="f0022">FIG. <b>23</b></figref>)<b>,</b> including the substrate <b>1200,</b> to the flex circuit <b>2200</b> (<figref idref="f0021">FIG. <b>22</b></figref>). Substrate layers <b>1401-1406</b> (<figref idref="f0014">FIG. <b>14</b></figref>) have traces that electrically connect the component pads <b>1510</b> and wire bond pads <b>1520</b> to the connector <b>1532-1534.</b> A thermistor <b>1540</b> is mounted to thermistor pads <b>1550</b> at the component end <b>1305,</b> which are also electrically connected with traces to the connector <b>1530.</b> Plated thru holes electrically connect the connector pads <b>1532, 1534</b> on the component and solder sides <b>1301, 1302,</b> respectively.

0042<figref idref="f0016">FIG. <b>17</b></figref> illustrates the electrical layout of a substrate <b>1200.</b> A portion of the LEDs <b>801,</b> including D1-D4 and D13-D16 have cathodes physically and electrically connected to component pads <b>1510</b> (<figref idref="f0015">FIG. <b>15</b></figref>) and corresponding anodes wire bonded to wire bond pads <b>1520.</b> Another portion of the LEDs <b>801,</b> including D5-D8 and D9-D12, have anodes physically and electrically connected to component pads <b>1510</b> (<figref idref="f0015">FIG. <b>15</b></figref>) and corresponding cathodes wire bonded to wire bond pads <b>1520.</b> The connector <b>1530</b> has row pinouts J21-J24, column pinouts J31-J34 and thermistor pinouts J40-J41 for the LEDs <b>801</b> and thermistor <b>1540.</b>

Interconnect Assembly

0043<figref idref="f0018">FIG. <b>19</b></figref> illustrates an interconnect assembly <b>1900</b> that mounts the emitter assembly <b>500</b> and detector assembly <b>2400,</b> connects to the sensor cable <b>4400</b> and provides electrical communications between the cable and each of the emitter assembly <b>500</b> and detector assembly <b>2400.</b> In one embodiment, the interconnect assembly <b>1900</b> is incorporated with the attachment assembly <b>2700,</b> which holds the emitter and detector assemblies to a tissue site. An interconnect assembly embodiment utilizing a flexible (flex) circuit is described with respect to <figref idref="f0019 f0020 f0021 f0022 f0023">FIGS. <b>20-24</b></figref><b>,</b> below.

0044<figref idref="f0019">FIG. <b>20</b></figref> illustrates an interconnect assembly <b>1900</b> embodiment having a circuit substrate <b>2200,</b> an emitter mount <b>2210,</b> a detector mount <b>2220</b> and a cable connector <b>2230.</b> The emitter mount <b>2210,</b> detector mount <b>2220</b> and cable connector <b>2230</b> are disposed on the circuit substrate <b>2200.</b> The emitter mount <b>2210</b> is adapted to mount an emitter assembly <b>500</b> having multiple emitters. The detector mount <b>2220</b> is adapted to mount a detector assembly <b>2400</b> having a detector. The cable connector <b>2230</b> is adapted to attach a sensor cable <b>4400.</b> A first plurality of conductors <b>2040</b> disposed on the circuit substrate <b>2200</b> electrically interconnects the emitter mount <b>2210</b> and the cable connector <b>2230.</b> A second plurality of conductors <b>2050</b> disposed on the circuit substrate <b>2200</b> electrically interconnects the detector mount <b>2220</b> and the cable connector <b>2230.</b> A decoupling <b>2060</b> disposed proximate the cable connector <b>2230</b> substantially mechanically isolates the cable connector <b>2230</b> from both the emitter mount <b>2210</b> and the detector mount <b>2220</b> so that sensor cable stiffness is not translated to the emitter assembly <b>500</b> or the detector assembly <b>2400.</b> A shield <b>2070</b> is adapted to fold over and shield one or more wires or pairs of wires of the sensor cable <b>4400.</b>

0045<figref idref="f0020">FIG. <b>21</b></figref> illustrates a flex circuit assembly <b>1900</b> having a flex circuit <b>2200,</b> an emitter assembly <b>500</b> and a detector assembly <b>2400,</b> which is configured to terminate the sensor end of a sensor cable <b>4400.</b> The flex circuit assembly <b>1900</b> advantageously provides a structure that electrically connects yet mechanically isolates the sensor cable <b>4400,</b> the emitter assembly <b>500</b> and the detector assembly <b>2400.</b> As a result, the mechanical stiffness of the sensor cable <b>4400</b> is not translated to the sensor pads <b>3000, 3100</b> (<figref idref="f0029 f0030 f0031">FIGS. <b>30-31</b></figref>), allowing a comfortable finger attachment for the sensor <b>200</b> (<figref idref="f0001">FIG. <b>1</b></figref>). In particular, the emitter assembly <b>500</b> and detector assembly <b>2400</b> are mounted to opposite ends <b>2201, 2202</b> (<figref idref="f0021">FIG. <b>22</b></figref>) of an elongated flex circuit <b>2200.</b> The sensor cable <b>4400</b> is mounted to a cable connector <b>2230</b> extending from a middle portion of the flex circuit <b>2200.</b> Detector wires <b>4470</b> are shielded at the flex circuit junction by a fold-over conductive ink flap <b>2240,</b> which is connected to a cable inner shield <b>4450.</b> The flex circuit <b>2200</b> is described in further detail with respect to <figref idref="f0021">FIG. <b>22</b></figref><b>.</b> The emitter portion of the flex circuit assembly <b>1900</b> is described in further detail with respect to <figref idref="f0022">FIG. <b>23</b></figref><b>.</b> The detector assembly <b>2400</b> is described with respect to <figref idref="f0023">FIG. <b>24</b></figref><b>.</b> The sensor cable <b>4400</b> is described with respect to <figref idref="f0046">FIGS. 44A-B</figref>, below.

0046<figref idref="f0021">FIG. <b>22</b></figref> illustrates a sensor flex circuit <b>2200</b> having an emitter end <b>2201,</b> a detector end <b>2202,</b> an elongated interconnect <b>2204, 2206</b> between the ends <b>2201, 2202</b> and a cable connector <b>2230</b> extending from the interconnect <b>2204, 2206.</b> The emitter end <b>2201</b> forms a "head" having emitter solder pads <b>2210</b> for attaching the emitter assembly <b>500</b> (<figref idref="f0007">FIG. <b>6</b></figref>) and mounting ears <b>2214</b> for attaching to the emitter pad <b>3000</b> (<figref idref="f0028">FIG. <b>30B</b></figref>), as described below. The detector end <b>2202</b> has detector solder pads for attaching the detector <b>2410</b> (<figref idref="f0023">FIG. <b>24</b></figref>). The interconnect <b>2204</b> between the emitter end <b>2201</b> and the cable connector <b>2230</b> forms a "neck," and the interconnect <b>2206</b> between the detector end <b>2202</b> and the cable connector <b>2230</b> forms a "tail." The cable connector <b>2230</b> forms "wings" that extend from the interconnect <b>2204, 2206</b> between the neck <b>2204</b> and tail <b>2206.</b> A conductive ink flap <b>2240</b> connects to the cable inner shield <b>4450</b> (<figref idref="f0046">FIGS. 44A-B</figref>) and folds over to shield the detector wires <b>4470</b> (<figref idref="f0046">FIGS. 44A-B</figref>) soldered to the detector wire pads <b>2236.</b> The outer wire pads <b>2238</b> connect to the remaining cable wires <b>4430</b> (<figref idref="f0046">FIGS. 44A-B</figref>). The flex circuit <b>2200</b> has top coverlay, top ink, inner coverlay, trace, trace base, bottom ink and bottom coverlay layers.

0047The flex circuit <b>2200</b> advantageously provides a connection between a multiple wire sensor cable <b>4400</b> (<figref idref="f0046">FIGS. 44A-B</figref>), a multiple wavelength emitter assembly <b>500</b> (<figref idref="f0007">FIG. <b>6</b></figref>) and a detector assembly <b>2400</b> (<figref idref="f0023">FIG. <b>24</b></figref>) without rendering the emitter and detector assemblies unwieldy and stiff. In particular, the wings <b>2230</b> provide a relatively large solder pad area <b>2232</b> that is narrowed at the neck <b>2204</b> and tail <b>2206</b> to mechanically isolate the cable <b>4400</b> (<figref idref="f0046">FIGS. 44A-B</figref>) from the remainder of the flex circuit <b>2200.</b> Further, the neck <b>2206</b> is folded (see <figref idref="f0005">FIG. <b>4</b></figref>) for installation in the emitter pad <b>3000</b> (<figref idref="f0028 f0029">FIGS. 30A-H</figref>) and acts as a flexible spring to further mechanically isolate the cable <b>4400</b> (<figref idref="f0046">FIGS. 44A-B</figref>) from the emitter assembly <b>500</b> (<figref idref="f0005">FIG. <b>4</b></figref>). The tail <b>2206</b> provides an integrated connectivity path between the detector assembly <b>2400</b> (<figref idref="f0023">FIG. <b>24</b></figref>) mounted in the detector pad <b>3100</b> (<figref idref="f0030 f0031">FIGS. 31A-H</figref>) and the cable connector <b>2230</b> mounted in the opposite emitter pad <b>3000</b> (<figref idref="f0028 f0029">FIGS. 30A-H</figref>).

0048<figref idref="f0022">FIG. <b>23</b></figref> illustrates the emitter portion of the flex circuit assembly <b>1900</b> (<figref idref="f0020">FIG. <b>21</b></figref>) having the emitter assembly <b>500.</b> The emitter assembly connector <b>1530</b> is attached to the emitter end <b>2210</b> of the flex circuit <b>2200</b> (<figref idref="f0021">FIG. <b>22</b></figref>). In particular, reflow solder <b>2330</b> connects thru hole pads <b>1532, 1534</b> of the emitter assembly <b>500</b> to corresponding emitter pads <b>2310</b> of the flex circuit <b>2200</b> (<figref idref="f0021">FIG. <b>22</b></figref>).

0049<figref idref="f0023">FIG. <b>24</b></figref> illustrates a detector assembly <b>2400</b> including a detector <b>2410,</b> solder pads <b>2420,</b> copper mesh tape <b>2430,</b> an EMI shield <b>2440</b> and foil <b>2450.</b> The detector <b>2410</b> is soldered <b>2460</b> chip side down to detector solder pads <b>2420</b> of the flex circuit <b>2200.</b> The detector solder joint and detector ground pads <b>2420</b> are wrapped with the Kapton tape <b>2470.</b> EMI shield tabs <b>2442</b> are folded onto the detector pads <b>2420</b> and soldered. The EMI shield walls are folded around the detector <b>2410</b> and the remaining tabs <b>2442</b> are soldered to the back of the EMI shield <b>2440.</b> The copper mesh tape <b>2430</b> is cut to size and the shielded detector and flex circuit solder joint are wrapped with the copper mesh tape <b>2430.</b> The foil <b>2450</b> is cut to size with a predetermined aperture <b>2452.</b> The foil <b>2450</b> is wrapped around shielded detector with the foil side in and the aperture <b>2452</b> is aligned with the EMI shield grid <b>2444.</b>

Detector Assembly

0050<figref idref="f0024">FIG. <b>25</b></figref> illustrates an alternative detector assembly <b>2400</b> embodiment having adjacent detectors. Optical radiation having multiple wavelengths generated by emitters <b>700</b> is transmitted into a tissue site <b>1.</b> Optical radiation at a first set of wavelengths is detected by a first detector <b>2510,</b> such as, for example, a Si detector. Optical radiation at a second set of wavelengths is detected by a second detector <b>2520,</b> such as, for example, a GaAs detector.

0051<figref idref="f0024">FIG. <b>26</b></figref> illustrates another alternative detector assembly <b>2400</b> embodiment having stacked detectors coaxial along a light path. Optical radiation having multiple wavelengths generated by emitters <b>700</b> is transmitted into a tissue site <b>1.</b> Optical radiation at a first set of wavelengths is detected by a first detector <b>2610.</b> Optical radiation at a second set of wavelengths passes through the first detector <b>2610</b> and is detected by a second detector <b>2620.</b> In a particular embodiment, a silicon (Si) detector and a gallium arsenide (GaAs) detector are used. The Si detector is placed on top of the GaAs detector so that light must pass through the Si detector before reaching the GaAs detector. The Si detector can be placed directly on top of the GaAs detector or the Si and GaAs detector can be separated by some other medium, such as a transparent medium or air. In another particular embodiment, a germanium detector is used instead of the GaAs detector. Advantageously, the stacked detector arrangement minimizes error caused by pathlength differences as compared with the adjacent detector embodiment.

Finger Clip

0052<figref idref="f0025">FIG. <b>27</b></figref> illustrates a finger clip embodiment <b>2700</b> of a physiological sensor attachment assembly. The finger clip <b>2700</b> is configured to removably attach an emitter assembly <b>500</b> (<figref idref="f0007">FIG. <b>6</b></figref><b>)</b> and detector assembly <b>2400</b> (<figref idref="f0023">FIG. <b>24</b></figref><b>),</b> interconnected by a flex circuit assembly <b>1900,</b> to a fingertip. The finger clip <b>2700</b> has an emitter shell <b>3800,</b> an emitter pad <b>3000,</b> a detector pad <b>2800</b> and a detector shell <b>3900.</b> The emitter shell <b>3800</b> and the detector shell <b>3900</b> are rotatably connected and urged together by the spring assembly <b>3500.</b> The emitter pad <b>3000</b> is fixedly retained by the emitter shell. The emitter assembly <b>500</b> (<figref idref="f0007">FIG. <b>6</b></figref>) is mounted proximate the emitter pad <b>3000</b> and adapted to transmit optical radiation having a plurality of wavelengths into fingertip tissue. The detector pad <b>2800</b> is fixedly retained by the detector shell <b>3900.</b> The detector assembly <b>3500</b> is mounted proximate the detector pad <b>2800</b> and adapted to receive the optical radiation after attenuation by fingertip tissue.

0053<figref idref="f0026">FIG. <b>28</b></figref> illustrates a detector pad <b>2800</b> advantageously configured to position and comfortably maintain a fingertip relative to a detector assembly for accurate sensor measurements. In particular, the detector pad has fingertip positioning features including a guide <b>2810,</b> a contour <b>2820</b> and a stop <b>2830.</b> The guide <b>2810</b> is raised from the pad surface <b>2803</b> and narrows as the guide <b>2810</b> extends from a first end <b>2801</b> to a second end <b>2802</b> so as to increasingly conform to a fingertip as a fingertip is inserted along the pad surface <b>2803</b> from the first end <b>2801.</b> The contour <b>2820</b> has an indentation defined along the pad surface <b>2803</b> generally shaped to conform to a fingertip positioned over a detector aperture <b>2840</b> located within the contour <b>2820</b>. The stop <b>2830</b> is raised from the pad surface <b>2803</b> so as to block the end of a finger from inserting beyond the second end <b>2802</b>. <figref idref="f0027">FIGS. 29A-B</figref> illustrate detector pad embodiments <b>3100</b>, <b>3400</b> each having a guide <b>2810</b>, a contour <b>2820</b> and a stop <b>2830</b>, described in further detail with respect to <figref idref="f0030 f0031">FIGS. <b>31</b></figref> and <figref idref="f0036 f0037"><b>34</b></figref><b>,</b> respectively.

0054<figref idref="f0028 f0029">FIGS. 30A-H</figref> illustrate an emitter pad <b>3000</b> having emitter pad flaps <b>3010,</b> an emitter window <b>3020,</b> mounting pins <b>3030,</b> an emitter assembly cavity <b>3040,</b> isolation notches <b>3050,</b> a flex circuit notch <b>3070</b> and a cable notch <b>3080.</b> The emitter pad flaps <b>3010</b> overlap with detector pad flaps <b>3110</b> (<figref idref="f0030 f0031">FIGS. 31A-H</figref>) to block ambient light. The emitter window <b>3020</b> provides an optical path from the emitter array <b>700</b> (<figref idref="f0009">FIG. <b>8</b></figref>) to a tissue site. The mounting pins <b>3030</b> accommodate apertures in the flex circuit mounting ears <b>2214</b> (<figref idref="f0021">FIG. <b>22</b></figref>), and the cavity <b>3040</b> accommodates the emitter assembly <b>500</b> (<figref idref="f0020">FIG. <b>21</b></figref>). Isolation notches <b>3050</b> mechanically decouple the shell attachment 3060 from the remainder of the emitter pad <b>3000.</b> The flex circuit notch <b>3070</b> accommodates the flex circuit tail <b>2206</b> (<figref idref="f0021">FIG. <b>22</b></figref>) routed to the detector pad <b>3100</b> (<figref idref="f0030 f0031">FIGS. 31A-H</figref>). The cable notch <b>3080</b> accommodates the sensor cable <b>4400</b> (<figref idref="f0046">FIGS. 44A-B</figref>). <figref idref="f0034 f0035">FIGS. 33A-H</figref> illustrate an alternative slim finger emitter pad <b>3300</b> embodiment.

0055<figref idref="f0030 f0031">FIGS. 31A-H</figref> illustrate a detector pad <b>3100</b> having detector pad flaps <b>3110,</b> a shoe box cavity <b>3120</b> and isolation notches <b>3150.</b> The detector pad flaps <b>3110</b> overlap with emitter pad flaps <b>3010</b> (<figref idref="f0028 f0029">FIGS. 30A-H</figref>), interleaving to block ambient light. The shoe box cavity <b>3120</b> accommodates a shoe box <b>3200</b> (<figref idref="f0032 f0033">FIG. 32A-H</figref>) described below. Isolation notches <b>3150</b> mechanically decouple the attachment points <b>3160</b> from the remainder of the detector pad 3100. <figref idref="f0036 f0037">FIGS. 34A-H</figref> illustrate an alternative slim finger detector pad <b>3400</b> embodiment.

0056<figref idref="f0032 f0033">FIGS. 32A-H</figref> illustrate a shoe box <b>3200</b> that accommodates the detector assembly <b>2400</b> (<figref idref="f0023">FIG. <b>24</b></figref>). A detector window <b>3210</b> provides an optical path from a tissue site to the detector <b>2410</b> (<figref idref="f0023">FIG. <b>24</b></figref>). A flex circuit notch <b>3220</b> accommodates the flex circuit tail <b>2206</b> (<figref idref="f0021">FIG. <b>22</b></figref>) routed from the emitter pad <b>3000</b> (<figref idref="f0028 f0029">FIGS. 30A-H</figref>). In one embodiment, the shoe box <b>3200</b> is colored black or other substantially light absorbing color and the emitter pad <b>3000</b> and detector pad <b>3100</b> are each colored white or other substantially light reflecting color.

0057<figref idref="f0038 f0039 f0040">FIGS. <b>35-37</b></figref> illustrate a spring assembly <b>3500</b> having a spring <b>3600</b> configured to urge together an emitter shell <b>3800</b> (<figref idref="f0048">FIG. <b>46</b></figref>) and a detector shell <b>3900.</b> The detector shell is rotatably connected to the emitter shell. The spring is disposed between the shells <b>3800, 3900</b> and adapted to create a pivot point along a finger gripped between the shells that is substantially behind the fingertip. This advantageously allows the shell hinge <b>3810, 3910</b> (<figref idref="f0041 f0042">FIGS. <b>38-39</b></figref>) to expand so as to distribute finger clip force along the inserted finger, comfortably keeping the fingertip in position over the detector without excessive force.

0058As shown in <figref idref="f0039">FIGS 36A-C</figref>, the spring <b>3600</b> has coils <b>3610,</b> an emitter shell leg <b>3620</b> and a detector shell leg <b>3630.</b> The emitter shell leg <b>3620</b> presses against the emitter shell <b>3800</b> (<figref idref="f0041">FIGS. 38A-D</figref>) proximate a grip <b>3820</b> (<figref idref="f0041">FIGS. <b>38A-</b></figref><b>D</b>). The detector shell legs <b>3630</b> extend along the detector shell <b>3900</b> (<figref idref="f0042">FIGS.39A-D</figref>) to a spring plate <b>3700</b> (<figref idref="f0040">FIGS. 37A-D</figref>) attachment point. The coil <b>3610</b> is secured by hinge pins <b>410</b> (<figref idref="f0048">FIG. <b>46</b></figref>) and is configured to wind as the finger clip is opened, reducing its diameter and stress accordingly.

0059As shown in <figref idref="f0040">FIGS. 37A-D</figref> the spring plate <b>3700</b> has attachment apertures <b>3710,</b> spring leg slots <b>3720,</b> and a shelf <b>3730.</b> The attachment apertures <b>3710</b> accept corresponding shell posts <b>3930</b> (<figref idref="f0042">FIGS. 39A-D</figref>) so as to secure the spring plate <b>3700</b> to the detector shell <b>3900</b> (<figref idref="f0042">FIG. 39A-D</figref>). Spring legs <b>3630</b> (<figref idref="f0039">FIG. 36A-C</figref>) are slidably anchored to the detector shell <b>3900</b> (<figref idref="f0042">FIG. 39A-D</figref>) by the shelf <b>3730,</b> advantageously allowing the combination of spring <b>3600,</b> shells <b>3800, 3900</b> and hinges <b>3810, 3910</b> to adjust to various finger sizes and shapes.

0060<figref idref="f0041 f0042">FIGS. <b>38-39</b></figref> illustrate the emitter and detector shells <b>3800, 3900,</b> respectively, having hinges <b>3810, 3910</b> and grips <b>3820, 3920.</b> Hinge apertures <b>3812, 3912</b> accept hinge pins <b>410</b> (<figref idref="f0048">FIG. <b>46</b></figref>) so as to create a finger clip. The detector shell hinge aperture <b>3912</b> is elongated, allowing the hinge to expand to accommodate a finger.

Monitor And Sensor

0061<figref idref="f0043">FIG. <b>40</b></figref> illustrates a monitor <b>100</b> and a corresponding sensor assembly <b>200,</b> as described generally with respect to <figref idref="f0001 f0002 f0003 f0004">FIGS. <b>1-3</b></figref><b>,</b> above. The sensor assembly <b>200</b> has a sensor <b>400</b> and a sensor cable <b>4400.</b> The sensor <b>400</b> houses an emitter assembly <b>500</b> having emitters responsive to drivers within a sensor controller <b>4500</b> so as to transmit optical radiation into a tissue site. The sensor <b>400</b> also houses a detector assembly <b>2400</b> that provides a sensor signal <b>2500</b> responsive to the optical radiation after tissue attenuation. The sensor signal <b>2500</b> is filtered, amplified, sampled and digitized by the front-end <b>4030</b> and input to a DSP (digital signal processor) <b>4040,</b> which also commands the sensor controller <b>4500.</b> The sensor cable <b>4400</b> electrically communicates drive signals from the sensor controller <b>4500</b> to the emitter assembly <b>500</b> and a sensor signal <b>2500</b> from the detector assembly <b>2400</b> to the front-end <b>4030.</b> The sensor cable <b>4400</b> has a monitor connector <b>210</b> that plugs into a monitor sensor port <b>110.</b>

0062In one embodiment, the monitor <b>100</b> also has a reader <b>4020</b> capable of obtaining information from an information element (IE) in the sensor assembly <b>200</b> and transferring that information to the DSP <b>4040,</b> to another processor or component within the monitor <b>100,</b> or to an external component or device that is at least temporarily in communication with the monitor <b>100.</b> In an alternative embodiment, the reader function is incorporated within the DSP <b>4040</b>, utilizing one or more of DSP I/O, ADC, DAC features and corresponding processing routines, as examples.

0063In one embodiment, the monitor connector <b>210</b> houses the information element <b>4000,</b> which may be a memory device or other active or passive electrical component. In a particular embodiment, the information element <b>4000</b> is an EPROM, or other programmable memory, or an EEPROM, or other reprogrammable memory, or both. In an alternative embodiment, the information element <b>4000</b> is housed within the sensor <b>400,</b> or an information element <b>4000</b> is housed within both the monitor connector <b>4000</b> and the sensor <b>400.</b> In yet another embodiment, the emitter assembly <b>500</b> has an information element <b>4000,</b> which is read in response to one or more drive signals from the sensor controller <b>4500,</b> as described with respect to <figref idref="f0044 f0045">FIGS. <b>41-43</b></figref><b>,</b> below. In a further embodiment, a memory information element is incorporated into the emitter array <b>700</b> (<figref idref="f0009">FIG. <b>8</b></figref>) and has characterization information relating to the LEDs <b>801</b> (<figref idref="f0009">FIG. <b>8</b></figref>). In one advantageous embodiment, trend data relating to slowly varying parameters, such as perfusion index, HbCO or METHb, to name a few, are stored in an IE memory device, such as EEPROM.

Back-to-Back LEDs

0064<figref idref="f0044 f0045">FIGS. <b>41-43</b></figref> illustrate alternative sensor embodiments, wherein <figref idref="f0044">Fig. 41A</figref> illustrates the embodiment of the present invention and the other embodiments do not fall under the claimed subject-matter. A sensor controller <b>4500</b> configured to activate an emitter array <b>700</b> (<figref idref="f0008">FIG. <b>7</b></figref>) arranged in an electrical grid, is described with respect to <figref idref="f0008">FIG. <b>7</b></figref><b>,</b> above. Advantageously, a sensor controller <b>4500</b> so configured is also capable of driving a conventional two-wavelength (red and IR) sensor <b>4100</b> having back-to-back LEDs <b>4110, 4120</b> or an information element <b>4300</b> or both.

0065<figref idref="f0044">FIG. <b>41A</b></figref> illustrates a sensor <b>4100</b> according to the present invention having an electrical grid <b>4130</b> configured to activate light emitting sources by addressing at least one row conductor and at least one column conductor. A first LED <b>4110</b> and a second LED <b>4120</b> are configured in a back-to-back arrangement so that a first contact <b>4152</b> is connected to a first LED <b>4110</b> cathode and a second LED <b>4120</b> anode and a second contact <b>4154</b> is connected to a first LED <b>4110</b> anode and a second LED <b>4120</b> cathode. The first contact <b>4152</b> is in communications with a first row conductor <b>4132</b> and a first column conductor <b>4134.</b> The second contact is in communications with a second row conductor <b>4136</b> and a second column conductor <b>4138.</b> The first LED <b>4110</b> is activated by addressing the first row conductor <b>4132</b> and the second column conductor <b>4138.</b> The second LED <b>4120</b> is activated by addressing the second row conductor <b>4136</b> and the first column conductor <b>4134.</b>

0066<figref idref="f0044">FIG. <b>41B</b></figref> illustrates an alternative sensor cable <b>4400</b> embodiment not falling under the claimed subject-matter capable of communicating signals between a monitor <b>100</b> and a sensor <b>4100.</b> The cable <b>4400</b> has a first row input <b>4132,</b> a first column input <b>4134,</b> a second row input <b>4136</b> and a second column input <b>4138.</b> A first output <b>4152</b> combines the first row input <b>4132</b> and the first column input <b>4134.</b> A second output <b>4154</b> combines a second row input <b>4136</b> and second column input <b>4138.</b>

0067<figref idref="f0044">FIG. <b>41C</b></figref> illustrates a monitor <b>100</b> capable of communicating drive signals to a sensor <b>4100</b> not falling under the claimed subject-matter. The monitor <b>4400</b> has a first row signal <b>4132,</b> a first column signal <b>4134,</b> a second row signal <b>4136</b> and a second column signal <b>4138.</b> A first output signal <b>4152</b> combines the first row signal <b>4132</b> and the first column signal <b>4134.</b> A second output signal <b>4154</b> combines a second row signal <b>4136</b> and second column signal <b>4138.</b>

information Elements

0068<figref idref="f0045">FIGS. <b>42-43</b></figref> illustrate information element <b>4200-4300</b> embodiments in communications with emitter array drivers configured to activate light emitters connected in an electrical grid. The information elements are configured to provide information as DC values, AC values or a combination of DC and AC values in response corresponding DC, AC or combination DC and AC electrical grid drive signals. <figref idref="f0045">FIG. <b>42</b></figref> illustrates information element embodiment <b>4200</b> advantageously driven directly by an electrical grid having rows <b>710</b> and columns <b>720.</b> In particular, the information element <b>4200</b> has a series connected resistor R₂<b>4210</b> and diode <b>4220</b> connected between a row line <b>710</b> and a column line <b>720</b> of an electrical grid. In this manner, the resistor R₂ value can be read in a similar manner that LEDs <b>810</b> (<figref idref="f0009">FIG. <b>8</b></figref>) are activated. The diode <b>4220</b> is oriented, e.g. anode to row and cathode to column as the LEDs so as to prevent parasitic currents from unwanted activation of LEDs <b>810</b> (<figref idref="f0009">FIG. <b>8</b></figref>).

0069<figref idref="f0045">FIGS. 43A-C</figref> illustrate other embodiments where the value of R₁ is read with a DC grid drive current and a corresponding grid output voltage level. In other particular embodiments, the combined values of R₁, R₂ and Cor, alternatively, R₁, R₂ and L are read with a varying (AC) grid drive currents and a corresponding grid output voltage waveform. As one example, a step in grid drive current is used to determine component values from the time constant of a corresponding rise in grid voltage. As another example, a sinusoidal grid drive current is used to determine component values from the magnitude or phase or both of a corresponding sinusoidal grid voltage. The component values determined by DC or AC electrical grid drive currents can represent sensor types, authorized suppliers or manufacturers, emitter wavelengths among others. Further, a diode D (<figref idref="f0045">FIG. <b>43C</b></figref>) can be used to provide one information element reading R₁ at one drive level or polarity and another information element reading, combining R₁ and R₂, at a second drive level or polarity, i.e. when the diode is forward biased.

0070Passive information element <b>4300</b> embodiments may include any of various combinations of resistors, capacitors or inductors connected in series and parallel, for example. Other information element <b>4300</b> embodiments connected to an electrical grid and read utilizing emitter array drivers incorporate other passive components, active components or memory components, alone or in combination, including transistor networks, PROMs, ROMs, EPROMs, EEPROMs, gate arrays and PLAs to name a few.

Sensor Cable

0071<figref idref="f0046">FIGS. 44A-B</figref> illustrate a sensor cable <b>4400</b> having an outer jacket <b>4410,</b> an outer shield <b>4420,</b> multiple outer wires <b>4430,</b> an inner jacket <b>4440,</b> an inner shield <b>4450,</b> a conductive polymer <b>4460</b> and an inner twisted wire pair <b>4470.</b> The outer wires <b>4430</b> are advantageously configured to compactly carry multiple drive signals to the emitter array <b>700</b> (<figref idref="f0008">FIG. <b>7</b></figref>). In one embodiment, there are twelve outer wires <b>4430</b> corresponding to four anode drive signals <b>4501</b> (<figref idref="f0047">FIG. <b>45</b></figref>), four cathode drive signals <b>4502</b> (<figref idref="f0047">FIG. <b>45</b></figref>), two thermistor pinouts <b>1450</b> (<figref idref="f0015">FIG. <b>15</b></figref>) and two spares. The inner twisted wire pair <b>4470</b> corresponds to the sensor signal <b>2500</b> (<figref idref="f0024">FIG. <b>25</b></figref>) and is extruded within the conductive polymer <b>4460</b> so as to reduce triboelectric noise. The shields <b>4420, 4450</b> and the twisted pair <b>4470</b> boost EMI and crosstalk immunity for the sensor signal <b>2500</b> (<figref idref="f0024">FIG. <b>25</b></figref>).

Controller

0072<figref idref="f0047">FIG. <b>45</b></figref> illustrates a sensor controller <b>4500</b> located in the monitor <b>100</b> (<figref idref="f0001">FIG. <b>1</b></figref>) and configured to provide anode drive signals <b>4501</b> and cathode drive signals <b>4502</b> to the emitter array <b>700</b> (<figref idref="f0008">FIG. <b>7</b></figref>). The DSP (digital signal processor) <b>4040,</b> which performs signal processing functions for the monitor, also provides commands <b>4042</b> to the sensor controller <b>4500.</b> These commands determine drive signal <b>4501, 4502</b> levels and timing. The sensor controller <b>4500</b> has a command register <b>4510,</b> an anode selector <b>4520,</b> anode drivers <b>4530,</b> current DACs (digital-to-analog converters) <b>4540,</b> a current multiplexer <b>4550,</b> cathode drivers <b>4560,</b> a current meter <b>4570</b> and a current limiter <b>4580.</b> The command register <b>4510</b> provides control signals responsive to the DSP commands <b>4042.</b> In one embodiment, the command register <b>4510</b> is a shift register that loads serial command data <b>4042</b> from the DSP <b>4040</b> and synchronously sets output bits that select or enable various functions within the sensor controller <b>4500,</b> as described below.

0073As shown in <figref idref="f0047">FIG. <b>45</b></figref><b>,</b> the anode selector <b>4520</b> is responsive to anode select <b>4516</b> inputs from the command register <b>4510</b> that determine which emitter array row <b>810</b> (<figref idref="f0009">FIG. <b>8</b></figref>) is active. Accordingly, the anode selector <b>4520</b> sets one of the anode on <b>4522</b> outputs to the anode drivers <b>4530,</b> which pulls up to Vcc one of the anode outputs <b>4501</b> to the emitter array <b>700</b> (<figref idref="f0009">FIG. <b>8</b></figref>).

0074Also shown in <figref idref="f0047">FIG. <b>45</b></figref><b>,</b> the current DACs <b>4540</b> are responsive to command register data <b>4519</b> that determines the currents through each emitter array column <b>820</b> (<figref idref="f0009">FIG. <b>8</b></figref>). In one embodiment, there are four, 12-bit DACs associated with each emitter array column <b>820</b> (<figref idref="f0009">FIG. <b>8</b></figref>), sixteen DACs in total. That is, there are four DAC outputs <b>4542</b> associated with each emitter array column <b>820</b> (<figref idref="f0009">FIG. <b>8</b></figref>) corresponding to the currents associated with each row <b>810</b> (<figref idref="f0009">FIG. <b>8</b></figref>) along that column <b>820</b> (<figref idref="f0009">FIG. <b>8</b></figref>). In a particular embodiment, all sixteen DACs <b>4540</b> are organized as a single shift register, and the command register <b>4510</b> serially clocks DAC data <b>4519</b> into the DACs <b>4540.</b> A current multiplexer <b>4550</b> is responsive to cathode on <b>4518</b> inputs from the command register <b>4510</b> and anode on <b>4522</b> inputs from the anode selector <b>4520</b> so as to convert the appropriate DAC outputs <b>4542</b> to current set <b>4552</b> inputs to the cathode drivers <b>4560.</b> The cathode drivers <b>4560</b> are responsive to the current set <b>4552</b> inputs to pull down to ground one to four of the cathode outputs <b>4502</b> to the emitter array <b>700</b> (<figref idref="f0009">FIG. <b>8</b></figref>).

0075The current meter <b>4570</b> outputs a current measure <b>4572</b> that indicates the total LED current driving the emitter array <b>700</b> (<figref idref="f0009">FIG. <b>8</b></figref>). The current limiter <b>4580</b> is responsive to the current measure <b>4572</b> and limits specified by the command register <b>4510</b> so as to prevent excessive power dissipation by the emitter array <b>700</b> (<figref idref="f0009">FIG. <b>8</b></figref>). The current limiter <b>4580</b> provides an enable <b>4582</b> output to the anode selector <b>4520</b>. A Hi Limit <b>4512</b> input specifies the higher of two preset current limits. The current limiter <b>4580</b> latches the enable <b>4582</b> output in an off condition when the current limit is exceeded, disabling the anode selector <b>4520.</b> A trip reset <b>4514</b> input resets the enable <b>4582</b> output to re-enable the anode selector <b>4520.</b>

Sensor Assembly

0076As shown in <figref idref="f0048">FIG. <b>46</b></figref><b>,</b> the sensor <b>400</b> has an emitter shell <b>3800,</b> an emitter pad <b>3000,</b> a flex circuit assembly <b>2200,</b> a detector pad <b>3100</b> and a detector shell <b>3900.</b> A sensor cable <b>4400</b> attaches to the flex circuit assembly <b>2200,</b> which includes a flex circuit <b>2100,</b> an emitter assembly <b>500</b> and a detector assembly <b>2400.</b> The portion of the flex circuit assembly <b>2200</b> having the sensor cable <b>4400</b> attachment and emitter assembly <b>500</b> is housed by the emitter shell <b>3800</b> and emitter pad <b>3000.</b> The portion of the flex circuit assembly <b>2200</b> having the detector assembly <b>2400</b> is housed by the detector shell <b>3900</b> and detector pad <b>3100.</b> In particular, the detector assembly <b>2400</b> inserts into a shoe <b>3200,</b> and the shoe <b>3200</b> inserts into the detector pad <b>3100.</b> The emitter shell <b>3800</b> and detector shell <b>3900</b> are fastened by and rotate about hinge pins <b>410,</b> which insert through coils of a spring <b>3600.</b> The spring <b>3600</b> is held to the detector shell <b>3900</b> with a spring plate <b>3700</b>. A finger stop <b>450</b> attaches to the detector shell. In one embodiment, a silicon adhesive <b>420</b> is used to attach the pads <b>3000</b>, <b>3100</b> to the shells <b>3800</b>, <b>3900</b>, a silicon potting compound <b>430</b> is used to secure the emitter and detector assemblies <b>500</b>, <b>2400</b> within the pads <b>3000</b>, <b>3100</b>, and a cyanoacrylic adhesive <b>440</b> secures the sensor cable <b>4400</b> to the emitter shell <b>3800</b>.

0077A multiple wavelength sensor has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in art will appreciate many variations and modifications.