Passive detectors for imaging systems

Passive detector for imaging system

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority in the U.S. Provisional Patent No. 61/524,669 filed on August 17, 2011, the disclosure of which is incorporated herein by reference.

Technical field

[0003] The field generally relates to detector structures used in imaging systems, and in particular to passive front-end detector structures with direct-to-digital measurement data output for detecting various parts of the electromagnetic spectrum (for example, Incident photon radiation in heat (IR, near IR, UV and visible light).

Background technique

[0004] Infrared light detectors are usually constructed using MEMS technology. One such optical (IR photon) detector includes a MEMS structure with a capacitor and a cantilever. The capacitor has a fixed plate and a moving plate. The cantilever has a first end fixed to the base and a second end fixed to the moving capacitor plate. The cantilever also includes a bimorph portion that bends in response to being heated by absorbing infrared light. The bending of the bimorph part displaces the moving plate, so that the distance between the moving plate and the fixed plate of the absorber is changed. Therefore, the infrared light irradiates the MEMS structure to produce a measurable change in the electrical characteristics of the structure (that is, the capacitance of the capacitor). By measuring this change in capacitance, the photodetector can determine the intensity of the infrared light that illuminates each MEMS structure (that is, each pixel element of the detector).

[0005] Another common type of thermal radiation detector is an un-cooled microbolometer. Generally speaking, a microbolometer includes a thin film absorption detector and a thermal isolation structure. The incident radiation absorbed by the detector causes an increase in temperature, which further causes a change in the conductivity of the thin-film detector. This conductivity is used to determine the intensity of incident radiation.

[0006] The main limitation of detectors including cantilever and microbolometer-type structures is attributed to the electrical connections required to read temperature changes or electrical characteristics (eg, resistance, capacitance) changes caused by incident radiation. Moreover, the complexity of manufacturing pixel interconnects and readout circuits has made these detector structures too expensive to be used in many applications. In addition, these electrical interconnections impair the thermal isolation between the pixels and the readout system, and consequently limit the thermal sensitivity of the detector. Semiconductor and quantum electronic detection methods are easily affected by self-generated and external noise sources to reduce the sensitivity of the system, and complex and expensive methods are required to alleviate these problems.

Summary of the invention

[0007] The exemplary embodiment of the present invention includes a passive detector structure for imaging systems, and in particular includes an unpowered passive front-end detector structure with direct digital measurement data output for detecting in the electromagnetic spectrum Incident photon radiation in various parts (eg, heat (IR), near IR, UV, and visible light).

[0008] For example, in an exemplary embodiment of the present invention, the photon detector device includes: a substrate, a resonator member, a passive detector structure, and a digital circuit. The resonator member is arranged on the substrate, and outputs a signal having an oscillation frequency. The passive detector structure is configured on the substrate and mechanically coupled to the resonator member. The passive detector structure includes a detector member that is mechanically deformed in response to photon exposure to reduce the mechanical force

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Is applied to the resonator member and changes the oscillation frequency of the resonator member in response to the mechanical force. In some embodiments, the detector member is formed of one or more materials having a thermal expansion coefficient, so that the detector member is mechanically deformed by thermal expansion and contraction. The digital circuit is coupled to the resonator member. The digital circuit operation works, for example, by determining the oscillation frequency of the resonator member, and determining the amount of incident photon energy absorbed by the detector member based on the determined oscillation frequency of the resonator member, wherein The oscillation frequency of the resonator member changes due to the mechanical force applied to the resonator member by the passive detector structure.

[0009] In another exemplary embodiment, a method for detecting photon energy includes exposing a passive detector member to incident photon energy so that the detector member is mechanically deformed in response to photon exposure , Applying mechanical force to the resonator member in response to the mechanical deformation of the passive detector member, and determining the oscillation frequency of the resonator member (the oscillation frequency of the resonator member is due to the passive detector member being applied The mechanical force on the resonator member is changed), and the amount of incident photon energy absorbed by the detector member is determined based on the determined oscillation frequency of the resonator member. In other embodiments, the method further includes using the determined oscillation frequency to generate image data. The amount of incident photon energy absorbed by the detector member can be determined by the following steps: counting the number of digital pulses in the output signal of the resonator member in a given counting period to generate count data; and The count data determines the level of photon exposure of the detector member.

[0010] These and other exemplary embodiments of the present invention will become apparent through the following detailed description of the illustrative embodiments read in conjunction with the accompanying drawings.

Description of the drawings

[0011] FIG. 1 is a perspective view of a photon detector based on a coefficient of thermal expansion (CTE) frame according to an exemplary embodiment of the present invention.

[0012] FIG. 2 is a top view of a photon detector based on a CTE frame according to another exemplary embodiment of the present invention.

[0013] FIG. 3 is a top view of a photon detector based on a CTE frame according to another exemplary embodiment of the present invention. [0014] FIG. 4 is a top view of a photon detector based on a CTE frame according to another exemplary embodiment of the present invention. [0015] FIG. 5 is a perspective view of a photon detector based on a CTE frame according to another exemplary embodiment of the present invention.

[0016] FIGS. 6A and 6B show a photon detector based on a CTE frame according to another exemplary embodiment of the present invention, wherein FIG. 6A is a top perspective view of the photon detector, and FIG. 6B is along the line 6B in FIG. 6A -6B side view of the photon detector taken.

[0017] FIG. 7 is a perspective view of a visible light detector based on a photon-induced expansion coefficient (PICE) concept according to an exemplary embodiment of the present invention.

[0018] FIG. 8 is a perspective view of a detector based on a voltage-induced deformation (VID) frame according to another exemplary embodiment of the present invention.

[0019] FIG. 9 is a side view of a detector based on a VID frame according to another exemplary embodiment of the present invention.

[0020] FIG. 10 is a side view of a detector based on a VID frame according to another exemplary embodiment of the present invention.

[0021] FIG. 11 is a side view of a detector based on a VID frame according to another exemplary embodiment of the present invention.

[0022] FIG. 12 is a side view of a detector based on a VID frame according to another exemplary embodiment of the present invention.

[0023] FIG. 13 schematically shows a top view and a side view of a bellows-shaped detector member according to an exemplary embodiment of the present invention.

[0024] FIG. 14 schematically shows a top view and a side view of a bellows-shaped detector member alternately formed by different materials

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view.

15A and 15B show a photon detector based on a CTE frame according to another exemplary embodiment of the present invention, wherein FIG. 15A is a top view of the photon detector, and FIG. 15B is along the line 15B in FIG. 15A -15B is a cross-sectional view of the photon detector.

[0026] FIGS. 16A and 16B show a photon detector based on a CTE frame according to another exemplary embodiment of the present invention, wherein FIG. 16A is a cross-sectional view of the photon detector taken along the line 16A-16A in FIG. 16B , And Figure 16B is a top view of the photon detector.

[0027] FIGS. 17A and 17B show a photon detector based on a CTE frame according to another exemplary embodiment of the present invention, wherein FIG. 17A is a cross-sectional view of the photon detector taken along the line 17A-17A in FIG. 17B , And Fig. 17B is a top view of the photon detector taken along the line 17B-17B in Fig. 17A.

[0028] FIG. 18 illustrates the advantages of using a direct digital passive detector framework in accordance with an exemplary embodiment of the present invention over traditional analog signal detectors or quantum electronic designs.

[0029] FIG. 19 is a block diagram of an imaging system based on a passive detector according to an exemplary embodiment of the present invention.

[0030] FIG. 20 is a block diagram showing another exemplary embodiment of a pixel unit and a pixel circuit that can be implemented in the imaging system of FIG. 19.

Detailed ways

[0031] Exemplary embodiments of the present invention will now be described in further detail below, with regard to passive detector structures for imaging systems, and in particular, to passive front-end detectors without power with direct digital measurement data output The structure is used to detect incident photon radiation in various parts of the electromagnetic spectrum (for example, heat (IR), near IR, UV, and visible light). The exemplary passive detector framework described herein provides a new paradigm for detecting incident photon energy in the electromagnetic spectrum (e.g., infrared, visible, and ultraviolet) and electromagnetic radiation in the microwave, terahertz, and X-ray portions of the electromagnetic spectrum . The passive detector framework realizes direct digital measurement without analog front-end or quantum semiconductors, thereby providing a detector design with low noise, low power, low cost and easy manufacturing compared with traditional CMOS or CCD detector devices. The exemplary passive detector frame with direct digital measurement data output described herein does not use any quantum photon or electronic conversion technology, and does not have the above-mentioned technical, manufacturing problems or noise problems associated with traditional imaging technologies .

[0032] As discussed in further detail below, exemplary embodiments of the present invention are based on various passive detector methods to detect various wavelengths of UV, visible light, near infrared (IR) infrared and far infrared, and terahertz. radiation. The exemplary passive detector examples described herein include CTE (Coefficient of Thermal Expansion), PICE (Coefficient of Photon Induced Expansion), and VID (Voltage Induced Deformation) detector frames. Generally speaking, these detector frames implement a passive detector structure that includes mechanically deforming in response to photon or electromagnetic radiation exposure to apply mechanical force to the resonator member, and changing the resonance in response to the mechanical force. The oscillating frequency of the detector component is the detector component. The digital circuit is coupled to the resonator member and operates to determine the oscillation frequency of the resonator member (the oscillation frequency of the resonator member is changed due to the mechanical force exerted on the resonator member through the passive detector structure), and is based on the determined The oscillation frequency of the resonator member determines the amount of incident photon energy or the amount of electromagnetic radiation exposed to the detector member.

[0033] With a CTE frame, a passive detector member (for example, one or more strips, or one or more plates) is made of one or more materials having a coefficient of thermal expansion, wherein the detector member responds to The incident photons expand and contract with energy to apply mechanical force on the resonator member and change the oscillation frequency of the resonator member.

[0034] With the PICE frame, the passive detector component is made to change its shape and size when exposed to electromagnetic radiation of a specific wavelength.

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It is made of one or more materials of one inch. The detector member mechanically deforms (eg, expands and contracts) in response to exposure to incident electromagnetic radiation to apply mechanical force to the resonator member and change the frequency of oscillation of the resonator member.

[0035] With a VID frame, for wavelengths such as X-rays (1 nm) to near-infrared (3 Jie), the detector member may be formed of one or more materials that generate voltages in response to exposure of incident radiation. Applying the generated voltage to the resonator member (for example, a layer of piezoelectric material) mechanically deforms the resonator member and changes the oscillation frequency of the resonator member. For example, photon exposure to detector components formed from photovoltaic (PV) materials can generate voltages. In addition, for thermal IR wavelengths (3 to 14 J), the detector member may be formed of a pyroelectric material to generate a voltage, which may be applied to deform the piezoelectric resonator member and change the oscillation frequency of the resonator member.

[0036] FIGS. 1 to 6 are perspective views of various passive detector frames based on a CTE frame according to an exemplary embodiment of the present invention. For example, FIG. 1 is a perspective view of a photon detector according to an exemplary embodiment of the present invention. Generally speaking, the photon detector (100) includes a substrate (102), a digital logic circuit (104), a parabolic mirror (106) and a bridge structure formed on the substrate (102). The bridge structure includes a first support member (110) above a substrate (102), a second support member (120), and a detector member (130) suspended between the support members (110) and (120). The support member (120) is a resonator member working at a resonance frequency, and the second support member (110) is a fixed insulating support structure. The detector component (130) (or strip) includes a bimetal strip (132) with a coefficient of thermal expansion and a photon energy absorption layer (134). The bimetal strip (132) expands by absorbing incident infrared energy And contract to apply force on the resonator member (120). The isolation material layer (122) is disposed between the end of the strip (130) and the resonator member (120) to provide thermal isolation between the strip (130) and the resonator support structure (120). The digital logic circuit (104) is coupled to the resonator member (120) for Determine the change in the oscillation frequency of the resonator member (120) due to the force applied to the resonator member (120) by the thermal expansion and contraction of the band structure (130), where the frequency change is the same as that caused by the band structure (130). ) Is related to the amount of incident infrared energy absorbed.

[0037] More specifically, the ribbon (130) is made of a material sensitive to IR heat, and the ribbon (130) is expanded and contracted based on the absolute number of incident IR photons hitting the ribbon (130). The metal material forming the bimetallic strip layer (132) can be formed of any suitable material having a negative and/or positive thermal expansion coefficient. The photon energy absorption layer (134) may be formed of any suitable material (such as carbon, SiC, etc.) that has peak sensitivity to any desired IR wavelength in the IR spectrum of 1 micrometer to 30 micrometers. In other exemplary embodiments, a filter material may be deposited on top of the photon energy absorbing layer (134) to narrow the sensitivity. A narrower response can be obtained by doping the photon energy absorbing material layer (134) with spectral materials that do not need to reflect or eliminate the response of the IR spectrum.

[0038] As shown in FIG. 1, the strip (130) is suspended between the supports (110) and (120) like a bridge, so that the area under the strip (130) is open, unsupported, and connected to the pixel structure. Do not touch any part of the rest. Only the end of the strip (130) is attached to any part of the pixel structure (100). This design allows the ribbon (130) to have the smallest possible mass, so that the ribbon (130) with a small mass can absorb heat from the incident IR photons in the shortest time. This will make the sensor react as fast as possible. Fast reaction time will allow faster imaging. The parabolic reflector (106) can be placed on the substrate (102) below the strip (130) to increase the pixel fill factor that allows more IR photons to hit and affect the strip from the top and bottom. The fill factor is the total surface area of the pixel that can collect incoming incident photons. Pixels have limited size and limited area. The higher the percentage of the fill factor, the larger the area of the pixel used to collect photons. The higher the fill factor percentage, the better the pixel sensitivity and performance. The mirror 106 may be parabolic, flat, or V-shaped, or the mirror 106 may not be implemented at all.

[0039] FIG. 2 is a perspective view of a photon detector according to another exemplary embodiment of the present invention. Generally speaking, Figure 2 shows

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The photon detector (200) includes a substrate (102), a digital logic circuit (104), a parabolic mirror (106), and a bridge structure formed on the substrate (102). The bridge structure includes a first support member (210) above a base (102), a second support member (220), and two belt-shaped members (230) suspended between the support members (210) and (220) ) And (240). The first strip (230) includes a bimetal layer (232) and a photon energy absorption layer (234), and the second strip (240) includes a bimetal layer (242) and a photon energy absorption layer (244). The support (220) is a resonator member working at a resonance frequency, and the second support member (210) is a fixed isolation support structure. The isolation layer (222) is disposed between the strip structures (230) and (240) and the resonator support structure (220) to provide thermal isolation.

[0040] The thermal detector (200) is similar to the detector (100) of FIG. 1, except that it includes two strip-shaped members (230) and (240) that provide additional functions. In particular, in an exemplary embodiment, each of the strips (230) and (240) can be designed with different materials, so as to be able to affect two different parts of the IR spectrum (for example, 10 microns and 4 microns). Sensitivity to detect IR radiation, so that the detector (200) can provide greater sensitivity to more than one wavelength. In another exemplary embodiment, each strip (230) and (240) can be designed with similar materials to detect IR radiation with sensitivity to one part of the IR spectrum but with a wider bandwidth, enabling Control the linearity of the detector response, and tailor the linearity of the detector response in a given temperature range of pixel design specifications and parameters.

[0041] FIG. 3 is a perspective view of a photon detector according to another exemplary embodiment of the present invention. Generally speaking, FIG. 3 shows that the photon detector (300) includes a substrate (102), a digital logic circuit (104), a parabolic mirror (106) and a bridge structure formed on the substrate (102). The bridge structure includes a first support member (310), a second support member (320), and a plurality of band members (330), each band member (330) includes a bimetal layer (332) and a photon energy absorption layer (334). The support member (320) is a resonator member working at a resonance frequency, and the second support member (310) is a fixed isolation support structure. The isolation layer (322) is disposed between the strip structure (330) and the resonator support structure (320) to provide thermal isolation.

[0042] The thermal detector (300) is similar in operation to, for example, the detector (100) discussed above with reference to FIG. Outside the small ribbon structure (330). However, the use of multiple straps (330) allows each strap to have less mass than the single strap structure of FIG. 1. Each individual strip (330) has less mass, so that each strip (330) can react (expand and contract) faster to thermal energy, thereby reducing the response time of the pixel.

[0043] FIG. 4 is a perspective view of a photon detector according to another exemplary embodiment of the present invention. Generally speaking, FIG. 4 shows that the photon detector (400) includes a substrate (102), a digital logic circuit (104), a parabolic mirror (106), and a double bridge structure formed on the substrate (102). The double bridge structure includes a first support member (410), a first resonator support member (420), a second resonator support member (424), connected to the first support member (410) and the first resonator support member (420) between the first belt-shaped member (430), and the second belt-shaped member (440) connected between the first support member (410) and the second resonator support member (424). Each strip (430) and (440) includes a corresponding bimetal layer (432) and (442) and a corresponding photon energy absorption layer (434) and (444). The isolation layers (422) and (426) are arranged between the corresponding ends of the belt structures (430) and (440) and the corresponding resonator support members (420) and (424).

[0044] The thermal detector (400) is similar in operation and design, for example, to the above-mentioned detectors (100) and (200), except that the detector can work in two different frequency spectra that are independent of each other. This can be achieved by using separate ribbon structures (430) and (440) and independent resonator support members (420) and (424). In particular, each strip (430) and (440) can be designed with different materials to detect IR radiation with sensitivity to two different parts of the IR spectrum (for example, 10 microns and 4 microns), so that control The logic circuit (104) can work to detect the IR energy in one or two supported spectrums at a given time

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[0045] FIG. 5 is a perspective view of a photon detector according to another exemplary embodiment of the present invention. Generally speaking, Figure 5 shows that the photon detector (500) includes a substrate (102), a digital logic circuit (104), a first parabolic mirror (106) and a second parabolic mirror (108) and is formed on the substrate (102) Bridge structure. The bridge structure includes a first support member (510), a first resonator support member (420), a second resonator support member (424), connected to the first support member (510) and the first resonator support member ( The first belt-shaped member (530) between 520), and the second belt-shaped member (540) connected between the first support member (510) and the second resonator support member (424). Each strip (530) and (540) includes a corresponding bimetal layer (532) and (542) and a corresponding photon energy absorption layer (534) and (544). The isolation layers (522) and (526) are arranged between the corresponding ends of the belt structures (530) and (540) and the corresponding resonator support members (520) and (524).

[0046] The thermal detector (500) is similar in operation and design to the above-mentioned detector (100), except that each pixel in FIG. 1 includes a separate isolation support member. In the frame of FIG. 5, a pair of Adjacent pixels are designed to share a single isolation support member (510). The frame of Figure 5 provides a more compact design, and the detector frame shown in Figures 2 to 4 can also be implemented in this way.

[0047] FIGS. 6A and 6B illustrate a photon detector according to another exemplary embodiment of the present invention. In general, FIG. 6A is a schematic top perspective view of the photon detector (600), and FIG. 6B is a schematic side view of the photon detector (600) taken along the line 6B-6B in FIG. 6A. 6A and 6B, the photon detector (600) includes a substrate (102), a digital logic circuit (104), a parabolic mirror (106), and a bridge structure formed on the substrate (102). The bridge structure includes a first support member (610), a second support member (612), a third support member (614), a resonator member (620), an isolation layer (622), and a belt-shaped member (630). The resonator member (620) is connected between the second support member (612) and the third support member (614), wherein the resonator member (620) is suspended above the substrate (102) (in contrast to the previously discussed embodiment, Wherein the resonator member is used as a support member anchored to the substrate).

[0048] The belt structure (630) includes a bimetal layer (632) and a photon energy absorption layer (634) (for example, carbon, carbon nanotube, SiC, etc.). The belt structure (630) is connected between the first support member (610) and the resonator member (620). In particular, the belt-like structure (630) includes a plurality of fins (632A, 632B, 632C, and 632D), which are integrally formed as a part of the bimetal layer (632), wherein the belt-shaped member (630) passes through the fins (632A, 632B, 632C and 632D) are connected to the resonator member (620). The fins (632A, 632B, 632C, and 632D) and the isolation layer (622) are used to thermally isolate the resonator member (620) from the bimetal layer (632). In the exemplary embodiment shown in FIGS. 6A and 6B, the second support member (6 provides the power supply voltage V+ to the resonator member (620), and the third support member (614) provides the resonator member (620) Grounded.

[0049] For the PICE-based pixel frame, a material that deforms when exposed to a specific wavelength between X-ray (1 nm) and near IR (3 μ) is used. For example, the CdS structure changes shape when exposed to visible light. Fig. 7 is a perspective view of a visible light detector (700) frame based on the PICE concept according to an exemplary embodiment of the present invention. Generally speaking, the detector (700) includes a substrate (102), a digital logic circuit (104), and a bridge structure formed on the substrate (102). The bridge structure includes a first support member (710) above a base (102), a second support member (720), and a belt-shaped member (730) suspended between the support members (710) and (720) .

[0050] The support member (720) is a resonator member working at a resonance frequency, and the second support member (710) is a fixed isolation support structure. The ribbon structure (730) is made of a photosensitive material (such as CdS, ZnO) with a photon-induced expansion coefficient, and the photon exposure directly causes the mechanical deformation of the ribbon structure (730). The isolation material layer (722) is disposed between the end of the strip (730) and the resonator member (720) to provide thermal isolation and electrical isolation between the strip (730) and the resonator support structure (720). isolate.

[0051] The ribbon structure (730) includes a material that receives incident photons causing the ribbon (730) to be stressed and change length

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(For example, CdS) layer. This stress is transferred to the resonator (720), which causes the resonator (720) to change its resonant frequency in proportion to the amount of incident photon exposure. The digital logic circuit (104) is coupled to the resonator member (720) for determining the resonator member ( 720) The change of oscillation frequency, where the change of frequency is related to the amount of incident photon energy received by the band structure (730).

[0052] FIGS. 8 to 14 are perspective views of various detector frames based on the VID concept according to an exemplary embodiment of the present invention. These frames provide a passive detector configuration for wavelengths from X-rays (1nm) to near IR (3u), where the ribbon material generates a voltage through photon exposure, and where the voltage is applied to the piezoelectric material layer, which causes The material deforms and builds up stress to change the resonance frequency. In other embodiments, for thermal IR wavelengths, pyroelectric materials may be used to generate voltages that, when applied to the piezoelectric material layer, will cause the material to deform and build up stress to change the resonance frequency.

[0053] Specifically, FIG. 8 is a perspective view of a visible light/UV light detector (800) frame based on the VID concept according to an exemplary embodiment of the present invention. Generally speaking, the detector (800) includes a substrate and digital logic circuits (not specifically shown, but similar to all the embodiments discussed above) and a bridge structure formed on the substrate 102. The bridge structure includes a first support member (810) above a base, a second support member (820), and a belt structure (830) suspended between the support members (810) and (820).

[0054] The support member (820) is a resonator member working at a resonant frequency, and the support member (810) is a fixed isolation support structure. The ribbon structure (830) includes a photon sensitive layer (832), an isolation layer (834), a piezoelectric layer (836), and a connecting member (838) that provides electrical connection between the layers (832) and (836). The photon sensitive layer (832) is made of a light sensitive material that generates a voltage by being exposed to incident photons (visible light or UV radiation). The voltage generated by the layer (832) is transferred to the piezoelectric layer (836) via the connection (838), where the piezoelectric layer (836) responds to the voltage by establishing stress as it attempts to change its length. This stress is transferred to the resonator (820), which causes the resonator (820) to change its resonant frequency in proportion to the number of incident photons. The digital logic circuit coupled to the resonator member (820) determines the resonant frequency of the resonator member (820) that occurs due to the force applied to the resonator member (820) by the mechanical expansion and contraction of the piezoelectric layer (836) The change in frequency is related to the amount of incident photon energy received by the ribbon structure (830). This framework works with the photovoltaic effect.

[0055] FIG. 9 is a perspective view of a frame of a detector (900) based on the VID concept according to another exemplary embodiment of the present invention. Generally speaking, the detector (900) includes a substrate and a digital logic circuit (not specifically shown, but similar to all the embodiments discussed above) and a bridge structure formed on the substrate. The bridge structure includes a first support member (910), a second support member (920) on a base, and a belt structure (930) suspended between the support members (910) and (920).

[0056] The support member (920) is a resonator member working at a resonance frequency, and the support member (910) is a fixed isolation support structure. The ribbon structure (930) includes an IR sensitive layer (932), an isolation layer (934), a piezoelectric layer (936), and a connecting member (938) that provides electrical connection between the layers (932) and (936). IR The sensitive layer (932) is made of a pyroelectric material that generates a voltage by exposure to incident IR radiation. The voltage generated by the layer (932) is transferred to the piezoelectric layer (936) via the connection (938), where the piezoelectric layer (936) responds to the voltage by establishing stress as it attempts to change its length. This stress is transferred to the resonator (920), which causes the resonator (920) to change its resonant frequency in proportion to the amount of incident IR exposure. The digital logic circuit coupled to the resonator member (920) determines the oscillation frequency of the resonator member (920) that occurs due to the force applied to the resonator member (920) by the mechanical expansion and contraction of the piezoelectric layer (936) The change in frequency is related to the amount of incident photon energy received by the ribbon structure (930). This framework works with the photovoltaic effect to provide a detection structure for IR radiation.

[0057] FIG. 10 is a three-dimensional view of a detector (1000) frame based on the VID concept according to another exemplary embodiment of the present invention

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picture. Generally speaking, the detector (1000) includes a substrate and a digital logic circuit (not specifically shown, but similar to all the embodiments discussed above) and a bridge structure formed on the substrate. The bridge structure includes a first support member (1010), a second support member (1012) above the base, and a belt structure (1030) suspended between the support members (1010) and (1012). The support members (1010) and (1012) are both isolation members.

[0058] In the exemplary embodiment of FIG. 10, the ribbon structure (1030) includes an IR sensitive layer (1032) (thermoelectric layer), an isolation layer (1034), a piezoelectric layer (1036), an in-layer (1032), and (1036) The connecting member (1038), the second isolation layer (1037) and the resonator member (1039) providing electrical connection therebetween. The IR sensitive layer (1032) is made of a pyroelectric material that generates a voltage by exposure to incident IR radiation. The voltage generated by the layer (1032) is transferred to the piezoelectric layer (1036) via the connection (1038), where the piezoelectric layer (1036) responds to the voltage by establishing stress as it attempts to change its length. This stress is transferred to the resonator (1039) mechanically coupled to the piezoelectric layer (1036) via the second isolation layer (1037). The stress transferred from the piezoelectric layer (1036) to the resonator layer (1039) causes the resonator member (1039) to change its resonant frequency in proportion to the amount of incident IR exposure. The digital logic circuit coupled to the resonator member (1039) (via the support member (1010, 1012)) determines that it occurs due to the force applied to the resonator member (1039) ± by the mechanical expansion and contraction of the piezoelectric layer (1036) The change in the oscillation frequency of the resonator member (1039), where the change in frequency is related to the number of incident photon energy received by the ribbon structure (1030) Quantity related. This framework works with the photovoltaic effect to provide a detection structure for IR radiation.

[0059] FIG. 11 is a perspective view of a detector (1100) frame based on the VID concept according to another exemplary embodiment of the present invention. Generally speaking, the detector (1100) includes a substrate and a digital logic circuit (not specifically shown, but similar to all the embodiments discussed above) and a bridge structure formed on the substrate. The bridge structure includes a first support member (1110), a second support member (1120) above the base, and a belt structure (1130) suspended between the support members (1110) and (1120). The isolation layer (1122) is interposed between the belt structure (1130) and the support member (1120).

[0060] The support member (1120) is a resonator member working at a resonant frequency, and the support member (1110) is a fixed isolation support structure. The ribbon structure (1130) includes an IR sensitive layer (1132), an isolation layer (1134), a piezoelectric layer (1136), and a connecting member (1138) that provides electrical connection between the layers (1132) and (1136). The IR sensitive layer (1132) is made of a pyroelectric material that generates a voltage by exposure to incident IR radiation. The voltage generated by the layer (1132) is transferred to the piezoelectric layer (1136) via the connection (1138), where the piezoelectric layer (1136) responds to the voltage by establishing stress as it attempts to change its length. This stress is transferred to the resonator (1120), which causes the resonator (1120) to change its resonant frequency in proportion to the amount of incident IR exposure.

[0061] The frame and operation of the detector of FIG. 11 are similar to those of FIG. 9, but the belt-shaped structure (1130) of FIG. 11 is formed in a folded shape or a bellows shape. This shape increases the surface area exposed to incident photons. The increased area is used for more heating in the thermal IR mode and more voltage in the photovoltaic mode, enhancing the expansion characteristics.

[0062] FIG. 12 is a perspective view of a detector (1200) frame based on the VID concept according to another exemplary embodiment of the present invention. Generally speaking, the detector (1200) includes a substrate and a digital logic circuit (not specifically shown, but similar to all the embodiments discussed above) and a bridge structure formed on the substrate. The bridge structure includes a first support member (1210) above a base, a second support member (1212), and a belt structure (1230) suspended between the support members (1210) and (1212). The supporting members (1210) and (1212) are both insulating members.

[0063] In the exemplary embodiment of FIG. 12, similar to the exemplary embodiment of FIG. 10, the ribbon structure (1230) includes an IR sensitive layer (1232) (thermoelectric layer), an isolation layer (1234), and a piezoelectric layer (1236), a connecting member (1238) providing electrical connection between the layers (1232) and (1236), a second isolation layer (1237) and a resonator member (1239). The IR sensitive layer (1232) is made of a pyroelectric material that generates a voltage by being exposed to incident IR radiation. The voltage generated by the layer (1232) passes through the connector (1238)

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Is passed to the piezoelectric layer (1236), where the piezoelectric layer (1236) reacts to the voltage by establishing stress as it attempts to change its length. This stress is transferred to the resonator (1239) mechanically coupled to the piezoelectric layer (1236) via the second isolation layer (1237). The stress transferred from the piezoelectric layer (1236) to the resonator layer (1239) causes the resonator member (1239) to change its resonant frequency in proportion to the amount of incident IR exposure.

[0064] The frame and operation of the detector structure of FIG. 12 are similar to those of FIG. 10, but the belt-shaped structure (1230) of FIG. 12 is formed in a folded shape or a bellows shape. This shape increases the surface area exposed to incident photons. The increased area is used for more heating in the thermal IR mode and more voltage in the photovoltaic mode, enhancing the expansion characteristics.

[0065] FIG. 13 schematically shows a top view (10) and a side view (12) of a folded or bellows-shaped ribbon structure, in which the ribbon is made of a single material. Figure 14 schematically shows a top view (16) and a side view (14) of a folded or bellows-shaped belt-like structure, in which the belt-like pieces are made of alternating different materials A and B. The use of alternating materials on the photosensitive/1R sensitive band-shaped layer (for example, layers 1132, 1232) can make the sensitivity have better linearity or wider or different spectral wavelengths. Moreover, the use of alternating materials on the resonator or piezoelectric strip layer (for example, layers 1136, 1236, 1239) allows the materials to have different expansion coefficient characteristics to control the detector response, improve the linearity of the stress, and the linearity of the resonator. , Or allow customized response characteristics.

[0066] FIGS. 15A and 15B illustrate a CTE frame-based photon detector (1500) according to another exemplary embodiment of the present invention. FIG. 15A is a top view of the photon detector (1500), and FIG. 15B is a cross-sectional view of the photon detector (1500) taken along the line 15B-15B in FIG. 15A. Generally speaking, as shown in FIGS. 15A and 15B, the photon detector (1500) includes a base (1502), a first support member (1510), a second support member (1520), and a base (1502) fixedly connected to the base (1502). And a plate member (1530) arranged between the first support member (1510) and the second support member (1520). In the exemplary embodiment shown in FIG. 15, the first support member (1510) is a fixed isolation support structure, and the second support member (1520) is a fixed resonator member operating at a resonant frequency. The plate member (1530) is formed of one or more materials that are sensitive to IR energy and have the ability to cause the plate member (1530) to expand and contract by absorbing incident infrared energy to apply on the second support member (1520) The coefficient of thermal expansion of the force.

[0067] As further shown in FIGS. 15A and 15B, the first support member (1510) and the second support member (1520) include grooves that insertably receive opposite ends of the plate member (1530). The end of the plate member (1530) includes a supporting leg member (1532) for keeping the IR absorbing part of the plate member (1530) at a certain offset height from the surface of the substrate (1502). This allows the plate member (1530) to be substantially thermally isolated from the substrate (1502).

[0068] In one embodiment, the plate member (1530) is disposed between the first support member (1510) and the second support member (1520) in a "prestressed" state. In particular, in the "pre-stressed" state, when there is no IR exposure, the ends of the plate member (1530) in the grooves of the first support member (1510) and the second support member (1520) face the first The inner surfaces of the supporting member (1510) and the second supporting member (1520) exert a certain minimum force. In fact, there are many effects on the prestressing of the plate member (1530) between the first support member (1510) and the second support member (1520). For example, the prestress against the inner side of the groove and the top wall facing the plate member (1530) prevents the plate member (1530) from moving out of position due to vibration and movement of the camera. In addition, prestressing the plate member (1530) reduces or eliminates mechanical and vibration noise. In addition, prestressing the plate member (1530) against the resonator member (1520) eliminates the fluctuation of the data measurement caused by the non-uniform stress distribution. Prestressing the plate member (1530) makes it possible to directly read the Δ fo (oscillation frequency change) of the resonator member (1520) caused by the expansion of the plate member (1530) when the incident IR exposure on the plate member (1530) is increased .

[0069] In some embodiments, by sizing various supports and plate elements such that the ends of the plate member (1530) are firmly fitted (wedge) between the support member (1510) and the support member (1520) In the groove, the first support can be realized

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The plate member (1530) between the member (1510) and the second support member (1520) is arranged in a "prestressed" state. In other embodiments, fillers can be used to fill any small gaps or gaps between the end of the plate member (1530) and the inner side and the top wall of the groove of the first support member (1510) and the second support member (1520). space. The filler may be such that it does not cause the plate member (1530) to adhere to the substrate (1502) or the first support member (1510) and the second support member (1520), and is not caused by heat during repeated and operational use of the detector (1500). Any suitable material that deteriorates due to mechanical conditions. For example, Teflon is a suitable material that can be used for this purpose.

[0070] As in other embodiments, a digital logic circuit (not specifically shown) is coupled to the resonator member (1520) for determining that due to the thermal expansion and contraction of the plate member (1530) applied to the resonator member (1520) The change in the oscillation frequency of the resonator member (1520) occurs due to the force on the ), where the change in frequency is related to the amount of incident infrared energy absorbed by the plate member (1530).

[0071] It should be understood that the specifications and materials used to construct detectors (pixels) such as those shown in FIGS. 15A/15B may vary according to different applications. For example, the substrate (1502) may be made of materials such as silicon, glass, ceramics, and the like. The size of each detector (pixel) can be about 40wn×45wn, with a pixel pitch of about 50wn. The plate member (1530) can be provided with sufficient thermal expansion and thermal expansion such as Zn, Au, SiC (silicon carbide), ZnS (zinc selenide), BN (boron nitride), ZnO (zinc oxide) or Si3N4 (silicon nitride), etc. Made of thermally conductive materials or layers of different materials. The thermally conductive plate material can be manufactured to promote a greater direction of heat conduction in a direction that is beneficial to design, where the greater direction of conduction is parallel to the direction of the crystal grains produced by the manufacturing. In other words, in the exemplary embodiment of FIGS. 15A and 15B, the stress direction of the plate member (1530) may be along the first support member (1510) determined by the grain structure direction of the plate member (1530) produced by manufacturing. And the direction of the substrate between the second support member (1520)

[0072] In other embodiments, the plate member (1530) may be coated with any suitable material such as DLC, SiC, CaF2, etc., to improve the thermal IR absorption of, for example, 4 «n and 10 wn spectrum. These coating materials should have sufficient expansion and adhesion properties to prevent delamination over time. The resonator member (1520) can be made of, for example, lead zirconate titanate (PZT), lead pincers, total titanate, sodium pin titanate (BNT), and titanate (MHz range). The thermal and stress response time constant of the plate member (1530) should be fast enough for standard or faster video frame rates. For example, a cycle time of rise and fall of <2ms is sufficient for a frame rate of 30 frames per second.

[0073] FIGS. 16A and 16B illustrate a CTE frame-based photon detector according to another exemplary embodiment of the present invention. Fig. 16A is a cross-sectional view of the photon detector (1600) taken along the line 16A-16A in Fig. 16B, and Fig. 16B is a top view of the photon detector. Generally speaking, as shown in Figures 16A and 16B, the photon detector (1600) includes a substrate (1602), a first support member (1610), a second support member (1620), a plate member (1630), and a resonator Component (1640). The first support member (1610) and the second support member (1620) are fixed isolation support structures. The resonator member (1640) X operates at the resonant frequency. The plate member (1530) is formed of one or more materials sensitive to IR energy, the material having a coefficient of thermal expansion that causes the plate member (1630) to expand and contract by absorbing incident infrared energy to apply force to the resonator member (1640) ).

[0074] As further shown in FIGS. 16A and 16B, the first support member (1610) includes a slot (1612) formed on its side wall. The second support member (1620) is formed by two separate support elements including a first lower support element (1622) and a second upper support element (1624), which are fixedly arranged to the side wall of the resonator member (1640) Proximity and contact. The lower support element (1622) and the upper support element (1624) are spaced apart to form a slot area (1626) therebetween. The plate member (1630) has one end inserted into the slot (1612) of the first support member (1610) and the other end inserted into the slot (1626) formed by the lower support element (1622) and the upper support element (1624). The first support member (1610) and the second support member (1620) keep the plate member (1630) at a certain offset height from the surface of the base (1602), so that the plate member (1530) and the base (1602)

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Completely thermally isolated.

[0075] As in other embodiments discussed herein, a digital logic circuit (not specifically shown) is coupled to the resonator member (1640) for determining that due to the thermal expansion and contraction of the plate member (1630) applied to the resonator The force on the member (1620) changes the oscillation frequency of the resonator member (1620), wherein the frequency change is related to the amount of incident infrared energy absorbed by the plate member (1630).

[0076] In addition, it should be understood that the specifications and materials used to construct a detector (pixel) such as those shown in FIGS. 16A/16B may be the same as discussed above with reference to FIGS. 15A/15B. Moreover, in some embodiments, the plate member (1630) may be configured in a "pre-stressed" state between the first support member (1610) and the resonator member (1640) due to the reasons discussed above. Various structures can be sized such that the ends of the plate member (1630) are firmly fitted (wedged) in the slots (1612) and (1626). In other embodiments, fillers may be used to fill any small gaps or spaces between the end of the plate member (1630) and the inner surfaces of the slots (1612) and (1626) and the side walls of the resonator member (1640) .

[0077] FIGS. 17A and 17B illustrate a CTE frame-based photon detector (1700) according to another exemplary embodiment of the present invention. Fig. 17A is a cross-sectional view of the photon detector taken along the line 17A-17A in Fig. 17B, and Fig. 17B is a top view of the photon detector taken along the line 17B-17B in Fig. 17A. Generally speaking, as shown in FIGS. 17A and 17B, the photon detector (1700) includes a substrate (1702), a first support member (1710), a second support member (1720) and a plate disposed on the substrate (1702). Components (1730). In this exemplary embodiment, the second support member (1720) is a rectangular resonator member having a cavity region (1722) forming one of its surfaces. An optional thin thermal isolation layer (not shown) may be configured on Between the bottom surface of the resonator member (1720) and the surface of the substrate (1702).

[0078] The plate member (1730) is arranged in the cavity region (1722) of the resonator member (1720). The plate member (1730) is fastened in place in the cavity area (1722) by the first support member (1710). The first support member (1710) may be a continuous rectangular frame structure fixedly fastened to the top surface of the resonator member (1720), wherein a part of the first support member (1710) overlaps the inner side of the cavity region (1722) The wall provides a lip covering the upper peripheral surface edge of the plate member (1730), while leaving a large surface area for the plate member (1730) to absorb incident IR energy. In other embodiments, the first support member (1710) may include a specific area disposed around the periphery of the cavity area (1722) (for example, at each sidewall corner or at the midpoint along the sidewall, etc.) sufficient to A plurality of individual elements in the cavity area (1722) held by the plate member (1730).

[0079] In some embodiments, due to the reasons discussed above, the plate member (1730) may be configured in a "pre-stressed" state within the region (1722) of the resonator member (1720). The resonator structure (1720) operates at a resonant frequency. The plate member (1730) is formed of one or more materials that are sensitive to IR energy, the material having a coefficient of thermal expansion that causes the plate member (1730) to expand and contract by absorbing incident infrared energy to apply force to the resonator member (1720) ). In the exemplary embodiment of FIG. 17A/FIG. 17B, since the plate member (1730) expands in response to heating caused by absorption of incident infrared energy, the plate member (1730) applies force in three dimensions to the resonator member ( 1720) on. As particularly shown in FIG. 17B, the plate member (1730) applies a first horizontal force (Fx) in the x direction to the first pair of opposed inner side walls of the cavity region (1720) of the resonator member (1720), and A second horizontal force (Fy) is applied to the second pair of opposite inner sidewalls of the cavity region (1722) of the resonator member (1720) in the y direction.

[0080] In addition, as shown in FIG. 17A, as the plate member (1730) expands in the z direction between the overlapping lip of the first support member (1710) and the bottom surface of the cavity region (1722), the plate member ( 1730) applies a vertical force (Fz) with respect to the cavity area (1722) of the resonator member (1720). Moreover, the vertical force (Fz) applied with respect to the bottom surface of the first support member element (1710) will be converted along the sidewall (that defines the cavity area (1722)) to the top surface of the resonator member (1720). Vertical force.

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[0081] As in other embodiments discussed herein, a digital logic circuit (not specifically shown) is coupled to the resonator member (1720) for determining that due to the thermal expansion and contraction of the plate member (1720) applied to the resonance The change in the oscillation frequency of the resonator member (1720) occurs due to the force on the resonator member (1720), where the change in frequency is related to the amount of incident infrared energy absorbed by the plate member (1630). With the exemplary embodiment of FIG. 17A/FIG. 17B, the sensitivity of the detector varies with the resonant frequency of the resonator member (1720) due to the stress applied to the resonator member (1720) in three dimensions (xyz). Frequency changes and increases.

[0082] In all the exemplary embodiments discussed above, the detector frame is passive, that is, the detector element (eg, CTE strip, CTE board) is not part of the active electronic circuit. When the device uses an active power circuit, it is easily affected by electrical noise. This concept will be illustrated with reference to FIG. 18. FIG. 18 is a schematic diagram (20) of a graph showing the advantages of using a direct digital passive detector framework compared to a traditional analog signal detector or quantum electronic design according to an exemplary embodiment of the present invention. Figure 18 shows electrical noise (26), which can mask or interfere with the analog signal (22) containing the required sensor data, which will be lost in the noise (24). In order to detect signal data, the signal data must be greater than the noise level (or "noise floor") (26). Any part of the analog signal (24) below the "noise floor" (26) is lost information. Noise limits the sensor system to the level of the noise floor. Some systems spare no effort to reduce the noise level to obtain better sensitivity. An example is cryogenic cooling. Although good sensitivity is achieved, it is complicated, expensive, bulky and dangerous.

[0083] One advantage of digital electronic equipment is that it can transmit data with the greatest possible noise immunity. Because small changes in signal data can be smaller in amplitude than the system noise level or noise floor, and the noise floor masks part of the analog signal (and thus loses part of the analog signal), the analog signal (22) shown in Figure 18 is susceptible to noise interference. This is the main limiting factor for the overall sensitivity and performance of any system. In Figure 18, the analog signal (22) can be converted into a series of binary numbers (logic 1 and logic 0). These binary numbers are represented by a square wave (23) modulated between the low and high points of the system voltage. In order to detect it, the square wave only needs to switch between higher or lower than the system conversion level (21) to be valid data. The digital design makes it possible to obtain valid data through the leading or falling edge of the square wave signal. This trigger point is obvious even in a high-noise environment. Therefore, it is an obvious advantage to make the system data digital as early as possible in the data creation scheme, because it is more resistant to noise than active circuits.

[0084] FIG. 19 is a block diagram of an imaging system implementing a passive detector according to an exemplary embodiment of the present invention. Generally speaking, FIG. 19 shows a pixel structure (50), a pixel circuit (60), a readout integrated circuit (70) ("ROIC"), a controller (80), and an image rendering system (90). Imaging circuit. The pixel (50) includes a passive detector front-end structure (52) and a resonator structure (54). The pixel circuit (60) includes a digital counter (62) and a tri-state register (64). The controller (80) includes a counter enable/hold control block (81), a register reset block (82), a ROIC control block (83), a data input control block (84), and a video output control block (85).

[0085] In the pixel structure (50) of FIG. 19, the passive detector front-end structure (52) generally represents any one of the passive pixel detector structures discussed herein, including a support structure and a detection element (such as a CTE strip , Plate structure, etc.), the detection element is designed, for example, to mechanically deform in response to photon exposure and apply mechanical stress (force) to the resonator structure (54). The detector front end structure (54) is electrically passive and noise-free generating electronics.

[0086] The resonator structure (54) oscillates at the resonance frequency F0 and outputs a square wave signal. The resonator structure (54) is designed to have a reference (or reference) resonance in a state where no additional stress due to photon exposure is applied to the resonator member (54) except for the amount of prestress by the detector front end (52) Frequency (no photon exposure). As the mechanical stress due to photon exposure is applied from the detector front end (52) to the resonator member (54), the oscillation frequency of the resonator member (54) increases from its reference (reference) resonance frequency. In an exemplary embodiment, the digital circuits (60), (70) and (80) work together to

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Determine the resonator member (54) due to the force applied to the resonator member (54) by the expansion and contraction of the passive detector element (e.g., ribbon, plate) of the detector front end structure (52) The output frequency F0 is based on the determined resonant frequency F0 of the resonator member (54) at a given time to determine the amount of incident photon energy absorbed by the passive detector element, and at a given time based on the determined incidence The amount of photon energy is used to generate image data, which is then presented by the imaging system (90).

[0087] In particular, the output signal generated by the resonator component (54) is a digital square wave signal having a frequency F0, which depends on the value applied to the resonator component (54) by the passive detector front-end structure (52) Stress changes. The output signal generated by the resonator member (54) is input to the clock input port of the digital counter (62). For each read cycle (or frame) of the imager, the digital counter (62) counts the pulses of the output signal from the resonator member (54) during a given "count period" (or reference period) of the read cycle. The counting operation of the digital counter (62) is controlled by the CLK enable signal generated by the counter control block (81) of the controller (80). For each read cycle, the count information generated by the counter (62) is output to the tri-state register (64) as an n-bit count value.

[0088] For each read cycle, the ROIC 70 reads out the count value (pixel data) from the pixel circuit (60) of a given pixel (50). It should be understood that, for ease of description, FIG. 19 shows a pixel unit (50) and a corresponding pixel circuit (60), but the imager may have a plurality of pixel units forming a linear pixel array or a 2D focus plane pixel array, for example. (50) and the corresponding pixel circuit (60). In this case, the ROIC (70) connects each pixel circuit (60) through a shared n-bit data bus (66) for controllably transferring individual pixel data from each pixel counting circuit (60) (preferably The ground is formed in the surface of the active silicon substrate under each corresponding pixel structure (50)) and is transmitted to the controller (80).

[0089] In particular, in response to the control signal received from the ROIC control block (83) of the controller (80), the ROIC (70) will output a tri-state control signal to the pixel circuit (60) of a given pixel (50) to The count data stored in the shift register (64) is read out to the shared data bus (66) ±ο The shift register (64) of each pixel circuit (60) is individually controlled by the ROIC (70) to be in the data bus (66) ) The count data was obtained for each pixel last time. The count data is transmitted from the ROIC (70) to the controller (80) through a dedicated data bus (72) connected to the n-bit input data control block (84) of the controller (80). After each readout cycle, the tri-state register (64) of each pixel is reset via the control signal output from the register reset control block (82) of the controller (80).

[0090] The controller (80) processes the count data (or video frame) obtained from each pixel in each readout period to determine the incident photon exposure of each pixel, and uses the determined exposure data To create a video image. The video data is output to the image rendering system (90) via the video output block (85) to display the image. In some embodiments of the present invention, by directly counting the output frequency generated by the resonator member (54), the counter (62) obtains the count data of the given pixel (50) for the given pixel (50), and the controller (80) The count data will be used to determine the gray level of the pixel, which corresponds to the number of incident photon exposures of the pixel. For example, in some embodiments, the gray level can be determined using a gray level algorithm or a look-up table. In the look-up table, different gray values (from black to white) are related to a range of count values. In conjunction, these count values have a priori determined increment of the change in the oscillation frequency of the resonator component from the reference reference frequency to the maximum oscillation frequency. The maximum oscillation frequency is the highest frequency that can be output from the resonator member in response to the maximum amount of stress that can be established by a given passive detector front-end structure.

[0091] In other embodiments of the present invention, the pixel structure and pixel circuit of FIG. 19 may be modified so that the counter compares the reference resonance frequency of the resonator member (54) with the reference resonance frequency of the resonator member (54) at a given time. The signal frequency count of the difference between the actual output frequencies generated in response to the stress applied by the passive detector front end (52). For example, FIG. 20 illustrates another exemplary embodiment of a pixel unit and a pixel circuit that can be implemented in the imaging system of FIG. 19. In Figure 20,

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The pixel (50) (of FIG. 19) is modified to include a reference oscillator (56) that outputs a reference resonance frequency Fref. The pixel circuit (60) (of FIG. 19) is modified to include an exclusive OR gate ( 66). The exclusive OR gate (66) operates to remove the reference frequency component of the signal F0 output from the resonator member (54) based on the reference frequency of the reference oscillator (56), and output a frequency change equal to the resonator member (54) A square wave signal with the frequency of F0. The frequency signal of the resonator member (54), which is much lower than the oscillation frequency F0 of the resonator member (54), requires a counter (62) with a lower number of bits to count the signal ΔF0, making it easier to implement. As the embodiment of FIG. 19, the signal AF0 is counted over a reference period of time and the count value is used to determine the incident photon exposure of the pixel as described above.

[0092] Although exemplary embodiments have been described with reference to the accompanying drawings for the purpose of illustration, it should be understood that the present invention is not limited to those specific embodiments, and those skilled in the art can perform various operations herein without departing from the scope of the present invention. Other changes and modifications.

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