System and method for auto focusing an optical code reader

Description of equivalent WO 2004059566 A1

SYSTEM AND METHOD FOR AUTO FOCUSING AN OPTICAL CODE READER

1. Field of the Invention

This invention relates to imaging in optical code reading engines. Aspects of the

invention are particularly useful in solid state, area image sensing based, handheld code readers

which are positioned at variable orientations and distances with respect to a target code.

BACKGROUND OF THE INVENTION

2. Description of the Related Art

Optical codes are patterns made up of image areas having different light reflective or light emissive properties, which are typically assembled in accordance with a priori rules. The term "barcode" is sometimes used to describe certain kinds of optical codes. The optical properties

and patterns of optical codes are selected to distinguish them in appearance from the background environments in which they are used. Devices for identifying or extracting data from optical codes are sometimes referred to as "optical code readers" of which barcode scanners are one type. Optical code readers are used in both fixed or portable installations in many diverse environments such as in stores for check-out services, in manufacturing locations for work flow and inventory control and in transport vehicles for tracking package handling. The optical code

can be used as a rapid, generalized means of data entry, for example, by reading a target barcode

from a printed listing of many barcodes. In some uses, the optical code reader is connected to a

portable data processing device or a data collection and transmission device. Frequently, the

optical code reader includes a handheld sensor which is manually directed at a target code.

Most conventional optical scanning systems are designed to read one-dimensional

barcode symbols. The barcode is a pattern of variable-width rectangular bars separated by fixed or variable width spaces. The bars and spaces have different light reflecting characteristics. One

example of a one dimensional barcode is the UPC/EAN code used to identify, for example,

product inventory. An example of a two-dimensional or stacked barcode is the PDF417 barcode.

A description of PDF417 barcode and techniques for decoding it are disclosed in U.S. Pat. No.

5,635,697 to Shellhammer et al., and assigned to Symbol Technologies, Inc., which is

incorporated herein by reference in its entirety. Another conventional optical code is known as

"MaxiCode". It consists of a central finder pattern or bull's eye center and a grid of hexagons

surrounding the central finder. It should be noted that the aspects of the inventions disclosed in this patent application are applicable to optical code readers, in general, without regard to the particular type of optical codes which they are adapted to read. The invention described may also

be applicable to some associated image recognition or analysis.

Most conventional scanning systems generate one or more beams of laser light which reflects off a barcode symbol and back to the scanning system. The system obtains a continuous analog waveform corresponding to the light reflected by the code along one or more scan lines of the system. The system then decodes the waveform to extract information from the barcode. A system of this general type is disclosed, for example, in U.S. Pat. No. 4,251,798, assigned to

Symbol Technologies, Inc. A beam scanning system for detecting and decoding one and two

dimensional barcodes is disclosed in U.S. Pat. No. 5,561,283, also assigned to Symbol Technologies, Inc.

Some such scanning systems are deployed in handheld units which may be manually

pointed at the target. Often an individual scanner is a component of a much larger system

including other scanners, computers, cabling, data terminals, etc. Such systems are frequently

designed and constructed on the basis of mechanical and optical specifications for the scanning engine, sometimes called "form factors". One such form factor is the SE1200 form factor

designed by Symbol Technologies, Inc.

Optical codes can also be read by employing optical code readers having an imaging

engine. An imaging engine includes an image sensor having a two-dimensional array of cells or

photo sensors, such as an area charge coupled device (CCD), which correspond to image

elements or pixels in a field of view of the engine. The imaging engine further includes a lens

assembly for focusing light incident on the image sensor and associated circuitry coupled to the image sensor outputting electronic signals corresponding to a two-dimensional array of pixel

information for the field of view. The electrical signals are processed by a processor for extracting information indicative of the focus quality of an image corresponding to the field of

view.

An optical code reader having selectable fields of view and working depths of view is disclosed in U.S. Patent No. 6,340,114 BI, assigned to Symbol Technologies, Inc., the contents of which are incorporated by reference in their entirety. An imaging optical code reader adapted

for use in producing video displays, such as for use in motion detection surveillance is disclosed in U.S. Patent No. 6,336,587, assigned to Symbol Technologies, Inc, the contents of which are incorporated by reference in their entirety. However, the above assemblies do not analyze an

image to determine the quality of focusing for adjusting the lens assembly in order to improve

focusing of the light incident on the image sensor.

Accordingly, it is an object of the present invention to provide an optical code reader

having an imaging engine with an image sensor and an adjustable lens assembly, and a

computing device for processing information provided by electrical signals generated by the

image sensor for determining focus quality, and generating lens adjustment control signals for adjusting the position of a lens assembly to adjust the focus quality of an image produced by an

image sensor.

It is a further object of the present invention to reduce processing time for processing the

electrical signals generated by the imaging sensor in order to provide rapid focusing and rapid

scanning.

It is an additional object of the present invention to provide an imaging engine which can

be substituted for a predetermined form factor scanning engine, such as the SE900 and SE1200 form factor scanning engines which are utilized in currently deployed optical code readers to increase the reliability, versatility and focusing ability of such readers

SUMMARY OF THE INVENTION

An optical code reader is provided including an imaging engine having an adjustable lens assembly and an image sensor with an array of photo sensors generating electrical signals indicative of sensed light incident on the photo sensors. The reader further includes a sensor select module and a computing device for generating sensor select signals for controlling selection of sensors of the array of photo sensors, processing information provided by electrical

signals produced by the image sensor to determine focus quality, and generating lens adjustment control signals in accordance with the processed information until a predetermined degree of

focus quality is achieved. The sensor select module is responsive to the sensor activation signals,

and the adjustable lens assembly is responsive to the lens adjustment control signals.

The present invention may be provided as a single optical code reading engine or optical

code reader system having the same. With the addition of appropriate control circuitry and data

processing software, an imaging system may be constructed serving the object of producing a

compact, inexpensively fabricated imaging engine which may be substituted for existing line scan engines. The imaging engine may be adapted for use in many different environments, with

various optical fields and focal distances, for reading various codes of different size. The system

may also be used for image recognition or analysis, including acquisition of data concerning the

target and its environment.

In accordance with a preferred embodiment of the present invention an optical code

reader is provided which includes imaging circuitry having an array of photo sensing devices

capable of sensing light incident on the array and outputting a plurality of pixel signals

corresponding to the sensed light; and control and logic circuitry for receiving a subset of the plurality of pixel signals, processing the received subset of the plurality of pixel signals for

determining if the received pixel signals meet at least one predetermined condition, and outputting a selection control signal in accordance with the processing results. The reader further includes a focus analysis software module executable by the control and logic circuitry for determining focus quality of the received pixel signals; a selector control software module executable by the control and logic circuitry for generating a selection control signal in accordance with the determined focus quality of the received pixel signals; and selector circuitry

for selectively enabling the imaging circuitry to output selected pixel signals of the plurality of pixel signals in accordance with the selection control signal.

In the preferred embodiment, the optical code reader further includes a lens assembly for

focusing incident light on the array of sensing devices. The lens assembly includes at least one

lens; a lens guidance assembly; and a lens adjustment mechanism for moving the at least one lens

along the lens guidance assembly. A lens adjustment software module is provided which is

executable by the control and logic circuitry for generating a lens adjustment control signal in

accordance with the determined focus quality of the received pixel signals for controlling the lens adjustment mechanism to move the at least one lens along the lens guidance assembly.

Preferably, the optical code reader is configured for imaging optical codes, and further includes a

software decoder module for decoding the received pixel signals for decoding at least one imaged

optical code.

Furthermore, a method is provided in accordance with the present invention for analyzing

and image. The method includes the steps of: imaging an object by sensing incident light and

generating a plurality of pixel signals corresponding to the sensed light; selecting a subset of

pixel signals from the plurality of pixel signals in accordance with the selection control signal; and outputting the selected pixel signals. The method further includes the steps of determining the focus quality of the selected subset of pixel signals; generating a lens adjustment signal in

accordance with the determined focus quality; adjusting the position of at least one lens of a lens assembly in accordance with the lens adjustment signal; and determining if the determined focus quality is within a predetermined threshold range. If the determined focus quality has a value outside the predetermined threshold range the object is re-imaged. If the determined focus quality has a value within the predetermined threshold range, all the pixel signals are selected.

The method further includes the step of decoding the selected pixel signals.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will be described herein below with reference to

the figures wherein:

FIG. 1 is a pictorial view of a handheld optical code reader and host terminal in

accordance with the present invention;

FIG. 2 is a sectional view of a preferred embodiment of the optical code reader of FIG. 1 ; FIG. 3 is a block diagram of an imaging engine of an imaging optical code reader in

accordance with the present invention;

FIG. 4 is a block diagram of a circuit board used in an imaging optical code reader in

accordance with the present invention;

FIG. 5 is a simplified functional block diagram of a control and logic circuit board and an

imaging engine of an imaging optical code reader in accordance with a preferred embodiment of

the present invention;

FIG. 6 is a block diagram of the control and logic circuit board of FIG. 5; and

FIGS. 7A-C illustrate a flowchart showing operation of the control and logic circuit board

and imaging engine of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an imaging optical code reader having an image sensor including an array of sensors generating respective pixel data indicative of incident light on the image sensor, and a processing system which determines the focus quality of the pixel data obtained during imaging of an object within a field of view of the optical code reader. The

processing system analyzes selected pixel data. The selected pixel data are obtained by using circuitry and/or software to control the image sensor to image the object by generating only a pre¬

selected set of pixel data for analysis. After analyzing the pixel data, if the focus quality or other

parameter is outside a predetermined threshold focus range, a lens assembly focusing light on the

image sensor is moved by an amount determined by the processing system by controllably

actuating the lens assembly. The pixel analysis method is repeated until the focus quality is

acceptable by the processing system, e.g., the focus quality is within the predetermined threshold

focus range, at which time the object is imaged using all the pixels, or, in the case where the object is constantly imaged using all of the pixels, the last captured image is provided for image

processing.

By analyzing only selected pixel data to determine the focus quality, the focus quality

determination method of the present invention is significantly faster than methods performed by

image processing systems which analyze all of the pixel data to determine the focus quality.

Further, the focus quality determination method assists in automatically focusing the object to be

imaged by fine tuning the position of the lens assembly.

System Overview

FIG. 1 is a pictorial view of a handheld optical code reader 12 and a schematic view of a host terminal 26 which may be used for various imaging functions of the present invention. The

handheld code reader 12 includes a housing 14 having a generally elongated handle or hand grip 16 and an upper portion 18 for housing an imaging engine 10. The front face 15 of the imaging engine 10 appears at the forward end of the upper portion 18 of the handheld optical code reader 12. The cross-sectional dimensions and overall size of the handle portion 16 are such that the optical code reader 12 can conveniently be held in the user's hand.

The optical code reader 12 senses incident light reflected off of an object (the object may

be a plurality of objects) within a field of view of the optical code reader 12 for obtaining image data. The object may be a code, such as a bar code, or a non-code object. An imaging actuation

means, such as a manual trigger 20 is mounted in moving relationship on the handle portion 16 in a forward facing region of the optical code reader 12. The user's forefinger is normally used to

actuate the optical code reader 12 by depressing the trigger 20 for actuating sensing and imaging of the object. A flexible electrical cable 22 is provided to connect the optical code reader 12 to the host

terminal 26. In alternative embodiments the cable 22 may also provide electrical power to the

imaging engine 10. In a further alternative embodiment, the cable 22 may be partially or fully

replaced by wireless communication means such as radio frequency, optical or cellular

communication means. In preferred embodiments the optical code reader 12 includes a means

for processing the pixel signals, and the processed information may be transmitted via cable 22

from the optical code reader 12 to the host terminal 26. A decode module may be provided in the

optical code reader 12 and/or in the host terminal 26 for decoding image data corresponding to an optical code. An image data compression module may be provided for compressing the image data.

The host terminal 26 includes at least one data processor, where the at least one data

processor may be connected to one or more peripherals or computing devices, such as a video monitor, and/or a network. Compressed image data may be transmitted to the host terminal 26 over electrical cable 22. The transmission of video data may be triggered by pressing the trigger 20 or by actuating another switch on the optical code reader 12. The image data may then be applied to the host terminal 26. The compressed image data may be applied to a serial communication port of the host terminal 26 such as the serial communication port of a personal

computer when such a device is used as the host terminal 26. The image data may be processed

by a data processor (not shown) within the personal computer and selectively displayed on

monitor (not shown). A color video image may be obtained.

FIG. 2 is a sectional view of a preferred embodiment of the optical code reader 12 in

accordance with preferred embodiments of the present invention showing internal components of

the optical code reader 12, including the imaging engine 10, a trigger board 34, a control and a logic circuit (CLC) board 40. The trigger circuit board 34 located in the handle portion 16 of the

handheld optical code reader 12 is electrically connected to switch means associated with the

trigger 20 of the optical code reader 12 and processes signals indicative of the operator's

depressing of the trigger 20 in order to initiate, or continue reading of optical codes. It is

contemplated that actuation means that are known in the art, such as a pedal actuator or an

automatic actuator responsive to a sensed or processed signal may be included in addition to or

instead of trigger 20 and/or trigger board 34. The CLC board 40, or portions thereof, may

alternatively be provided externally from the optical code reader 12, such as in the host terminal

26. In circumstances where the optical code reader 12 of FIG. 2 is to be retrofitted from a laser line scan engine to an optical imaging engine 10, the imaging engine 10 and CLC board 40 may be inserted in place of the line scan engine and circuit board in the optical code reader 12. In this

way previously designed toolings, housings and host devices may be employed and provide continuity in upgrading the code reading system.

In alternate embodiments described in US Patent No. 6,336,587 described above, the optical code reader 12 includes a radio frequency board and an antenna which provide a mobile radio link to one or more data terminals, such as host terminal 26. Electrical power for the optical code reader 12 may be provided by battery. An infrared data interface (IRDA) or multi-

contact shoe may also be provided to communicate data between the optical code reader 12 and

an external receiver or docking device, respectively. Compressed image data may be transmitted

to the host terminal 26 via a radio frequency link, IR communication link, or direct contact with

the docking device.

It will be understood that aspects of the present invention are also applicable to imaging

engines which are not located in conventional handheld scanners or guns. For example, the imaging engine 10 may be incorporated into a computer terminal in a fixed location or in a

rotating turret. Such arrangements are particularly well adapted for using the imaging engine 10

as part of a video phone system which also uses the display, processing and I/O capabilities of

the computer.

The optical code reader 12 of the present invention may further include frame grabbing

circuitry for providing video signals for displaying images produced by the apparatus on a

terminal monitor. In this case hardware modification of existing terminals may be avoided.

Alternatively, the imaging engine 10 may be attached to a portable computer device such

as a PDA, or attached to portable scanning systems or terminals such as those available from assignee, Symbol Technologies, Inc. Such systems may be incorporated as part of a local area, cellular or wide area network to coordinate scanning and other image processing functions described below.

In portable applications where electrical power is supplied by batteries, it is particularly important to conserve energy. Power management techniques for such portable images may include the provision to switch the images to lower resolution or frame rates to conserve power.

Alternatively, the imaging engine 10 or CLC board, or portions thereof, may be periodically shut down or enter a sleep mode, or shut down when the system senses that the battery charge level

has dropped below a pre-selected level.

Imaging Engine

With reference to FIG. 3, the imaging engine 10 includes a lens assembly 102 having a

least one lens for focusing light incident on a photo sensor, where the lens assembly 102 is

mounted on a lens guidance assembly 103, and having a lens adjustment mechanism 104 for

moving at least one lens of the lens assembly 102 along the lens guidance assembly 103 for changing the focal length of the lens assembly 102. Lens adjustment mechanism 104 is

operatively connected to the lens assembly 102 and/or the lens guidance assembly 103 for

moving the one or more optical lenses of the lens assembly 102 along the lens guidance assembly

103. The lens adjustment mechanism 104 may be located within the imaging engine 10 or

external to the imaging engine 10.

The imaging engine 10 further includes circuitry for capturing an image 106, including circuitry for photo sensing, analog-to-digital conversion, timing generation, automatic gain

control (AGC) and peripheral circuits to control the above components. The circuitry for

capturing an image 106 preferably includes an area based image sensor, preferably a charge coupled-device (CCD). In other embodiments the image sensor may be a CMOS device, a CMD (charge modulated device) or a CID (charge injection device) sensor. In other embodiments, the imaging engine 10 further includes an illumination system and an aiming system (not shown) as known in the art.

With reference to FIG. 4, a CCD circuit board 200 included in a preferred embodiment of the circuitry for capturing an image 106 is shown. The CCD circuit board 200 includes a CCD

detector 202 having an array of photo sensors (not shown) and a sensor selector 204. Each photo sensor of the array of photo sensors senses light incident on the photo sensor during an imaging

session and outputs an electrical signal, also referred to herein as a pixel signal indicative of at

least one parameter of the light sensed. The CCD detector 202 outputs a pixel signal associated

with each photo sensor of the array of photo sensor which is propagated along path 206, where

path 206 includes a plurality of signal paths, each signal path corresponding to a respective pixel

signal. A sensor selector 204 is provided along path 206 which includes means for selectively

opening signal paths of path 206 of a selected subset of signal paths for disconnecting the opened

signal paths of path 206. Accordingly, sensor selector 204 selectively allows all of the pixel

signals, or a selected subset of the pixel signals to propagate through signal conditioning blocks

210, 212, 214 and 216 to produce digital pixel 216, also referred to as image data, which is

output by the CCD circuit board, such as for being applied to the CLC board 40. The sensor

selector 204 preferably includes switching means, such as a transistor electrically connected to

each signal path of path 206 for selectively opening the respective signal path. As described below, sensor selector 204 receives a control signal for controlling its operation for selectively

disabling signal paths of path 206.

Accordingly, selected pixel data elements, i.e., a reduced number of pixel data elements, are propagated to the CLC board 40 for processing therein. Propagation of the pixel data from the photo sensor array is a major factor in determining the speed of acquiring and processing the pixel data. Thus, a significant increase in speed in acquiring and processing the pixel data are achieved by reducing the amount of pixel data propagated from the photo sensor array at times when full resolution, i.e., pixel data associated with all of the photo sensors, is not needed.

The CCD detector 202 is further provided with clock driver signals by the clock driver

circuit 218. Various sync pulses and control signals 222 are applied to a clock generator 220 from the CLC unit 40, as described further below.

It is contemplated that one or more of components 204, 210, 212, 214, 216, 218, 220 may

be located external from the CCD circuit board 200. It is further contemplated that the sensor

selector 204 may be positioned at another position along path 206 of the pixel signals or other

propagation paths of the pixel data. In preferred embodiments, the imaging engine is less than two cubic inches in volume

and is dimensioned to replace a moving laser beam scanning engine in a handheld barcode

scanner, such as SE900 and SE1200 form factor scanning engines. Such an imaging engine may

be designed to read a variety of types of optical codes including high and low density barcodes at

a working range of between IV2 and 18 inches, or more.

Data Processing Units

With reference to FIG. 5, CLC board 40 is shown in communication with the imaging

engine 10. The CLC board 40 receives the pixel data from the CCD circuit board 200 via data path 502, processes the pixel data, generates control signals including at least one lens adjustment control signal 504 and at least one sensor selector control signal 506 in accordance

with the processed pixel data and outputs the control signals to the imaging engine 10, where the sensor selector control signal 506 is provided to the sensor selector 204 of the CCD circuit board 200, and the lens adjustment control signal 504 is provided to the lens adjustment mechanism 104.

With reference to FIG. 6, a preferred embodiment of the CLC board 40 is shown. The CLC board 40 includes data processing components, including a microprocessor 602 and a field

programmable gate array (FPGA) 604; software modules executable on the microprocessor 602 including a focus analyzer module 606, a lens adjustment control module 607, a sensor selector

control module 608, and a decoder module 610; storage components, including a flash memory

device 612 and a DRAM memory device 614; a voltage generation circuit 616 and a data bus

driver 618. It is contemplated that one or more functions performed by the microprocessor 602

may be performed by the FPGA 604, and vice versa, in accordance with need and design choice. The FPGA 604 provides an interface and a buffer between the imaging engine 10 and the

microprocessor 602. Digital pixel data from the CCD circuit board 200 is supplied to the

microprocessor 602 via the FPGA 604. Control signals generated by the microprocessor 602 are

provided via the FPGA 604 to the imaging engine 10 and a power supply board (not shown).

The microprocessor 602 may include more than one processor. In preferred embodiments the

microprocessor is a 32 bit RISC embedded controller which provides high performance and

functional integration with low power consumption.

The microprocessor 602 may communicate with an external device such as the host terminal 26 via the bus driver 618. Preferably, the bus driver 618 is an RS232 driver. It is

envisioned that alternate bus drivers may be used as well as alternate communication means, such as wireless communication means, as described above. The flash memory device 612 and DRAM device 614 provide storage for programmable code executable by the microprocessor 602 and/or FPGA 604 as well as permanent and temporary storage of data. Alternate storage may be

provided instead of or in addition to flash memory device 612 and DRAM device 614.

The voltage generation circuit 616 receives power from a power source (i.e., via cable 22

shown in FIG. 1 or a battery (not shown),) and modulates the voltage for providing the necessary voltage to the microprocessor 602 and the power supply board. In a preferred embodiment, the

voltage generation circuit 616 generates a 3.3 volt signal. In alternate embodiments, one or more

functions or components of the CLC board 40, such as the microprocessor 602 or portions thereof, may be included in the host terminal 26.

Conventional video data compression software may be stored in the DRAM 614 and be executed by the microprocessor 602. Compressed video images may be transmitted to the

external world, such as to a serial port of the host terminal 26 to permit display or recording of

the image incident on the CCD detector 202.

The control signals generated by the microprocessor 602 include the lens adjustment

control signal 504 which is generated by the lens adjustment control module 607 and provided to

the lens adjustment mechanism 104; and the sensor select control signal 506 which is generated

by the sensor select control module 608 and provided to the sensor selector 204. Additional

control signals may be provided to the image engine 10, such as to a power circuit board, to an illumination system, to an aiming system, and sync pulses and control signals 222 to the CCD circuit board 200, as described in above-mentioned U.S. Patent No. 6,340,114.

Focus Analysis

Focus analysis is performed by the focus analysis module 606 by determining the focus quality of current pixel data and determining if the focus quality is within a focus quality threshold range. The focus analysis module 606 generates an output indicative of the determination results, such as by setting a focus quality range flag to indicate when the focus quality of the current pixel data are outside of the focus quality threshold range and/or providing

a quantitative output, such as a relative focus quality signal indicative of the degree and polarity (+/-) of the focus quality of the current pixel data. Focus analysis algorithms for determining

focus quality are known in the art, and may employ a frequency analysis algorithm.

Further still, the focus analysis module 606 may be used to auto-discriminate between

barcodes and other objects by analyzing the pixel data. Hence, a signal indicating the type of

object and other information describing the object can be provided to an image processing system

before a full set of pixel data associated with the object has been generated. Additionally, by knowing the type of object, the threshold focus quality range or image

resolution can be adjusted "on-the-fly" or in real-time. For example, if the object being imaged

is determined to be a bar code, the threshold focus quality can be adjusted to be within a range

indicative of low to medium image resolution. If the object being imaged is determined to be a

fine-printed number, the threshold focus quality can be adjusted to be within a range indicative of

medium to high image resolution. It is contemplated that a scale, such as a numbering system,

can also be used to quantify the focus quality. For example, the range of one to ten can be used,

where the number one is equivalent to extremely poor focus quality or image resolution and the number ten is equivalent to extremely high focus quality or image resolution.

Lens Adjustment

The lens adjustment module 607 accesses the output of the focus analysis module 606,

such as by checking the status of the focus quality range flag and/or accessing the relative focus quality signal. When the focus quality range flag is set, the lens adjustment module 607 generates a lens adjustment control signal 504 for controlling the lens adjustment mechanism 104 to move at least one lens of the lens assembly 106 in a directed and quantitative amount, such as by a multiple of incremental amounts. The lens adjustment control signal 504 provides either a relative (i.e., relative to the current (last stored) position), an absolute target position for the lens

assembly 106, or a time interval for operating the lens adjustment mechanism 104 to move the

specified lens(es) for the duration of the time interval in the specified direction. The lens

adjustment control signal 504 actuates the lens adjustment mechanism 104 for moving one or

more lenses of the lens assembly 106 to the target position. The lens adjustment mechanism 104

includes means such as a servo control unit (not shown) for translating the lens adjustment

control signal 504 into mechanical action. Upon adjustment of the lens assembly 106, the target position may be stored as the current position of the lens assembly 106 by the lens adjustment

module 607.

Sensor Selection

Sensor selection of the pixel signals and/or pixel data to be generated, propagated and/or

processed is determined by the sensor selector control module 608. Preferably, upon

initialization for performing a scan, i.e., actuation of trigger 20, the sensor selector control

module 608 is initialized to generate a sensor selector control signal 506 for controlling the sensor selector 204 to select a predetermined subset of pixel signals. The selected set of pixel

signals are processed and analyzed. Upon determination that focus quality of the selected pixel signals is within the predetermined focus quality range, the sensor selector control module 608 selects all of the pixel signals.

The predetermined subset of pixel signals is determined at the design stage in accordance with the application, such as the configuration of the optical code reader 12 and the type of optical code being read. For example, in an optical code reader configured to read one- dimensional codes, the predetermined subset of pixel signals may be associated with sensors located at the center of the of the sensor array, and in an optical code reader configured to read

two-dimensional codes, the predetermined subset of pixel signals may be associated with sensors located along a selected horizontal line of the sensor array. Furthermore, the predetermined

subset of pixel signals may be empirically determined.

In another embodiment, in an optical code reader 12 capable of operating in more than

one configuration, the sensor selector control module 608 may be controlled (automatically or by

user input via a user interface on the optical code reader 12 or associated with the host terminal

26) to operate in more than one mode. For example, in a first mode the sensor selector control module 608 will select a first predetermined set of pixel signals, and in a second mode the sensor

selector module 608 will select a second predetermined set of pixel signals, etc. The sensor

selector control module 608 may include software executable by the microprocessor 602 or

circuitiy, such as one or more logic circuits, or a combination thereof.

i In the preferred embodiment, as described above with reference to FIG. 4, the sensor

selector 204 is circuitry integrated into the CCD circuit board 200 capable of disabling selected

signal paths traveled by the pixel signals. In an alternative embodiment, the sensor selector 204

is circuitry integrated into the CCD circuit board 200 capable of selectively disabling sensors of the CCD detector 202. In another embodiment, the sensor selector 204 is circuitry coupled to the

I CCD circuit board 200 capable of disabling selected outputs of the CCD circuit board 200. In another embodiment still, the sensor selector 204 is a software module executable by the

microprocessor 602. The sensor selector 204 may be included in the sensor selector control module 608 or controlled by the sensor selector control module 608 for disabling processing of selected pixel data elements by other software modules executed on the microprocessor 602.

Decoding

The decoder module 610 decodes the pixel data after the focus quality of the image data

has been determined to be within the predetermined focus quality range and all the pixel signals have been enabled. The decoder module 610 may be executable on the host terminal 26 instead

of the microprocessor 602. In an alternative embodiment, the optical code reader 12 may be

capable of imaging non-code objects in addition to optical codes, wherein the decoder module

610 may not be executed for decoding the non-code object. Alternatively, the optical code reader

12 may be used for imaging only non-code objects, and the decoder module 610 may be omitted.

Applications The optical code reader 12 or alternative imager may use a different focus quality

threshold range for different respective applications of the optical code reader 12. The focus

quality threshold range may be set by default, automatically in response to a sensed or processed

condition, or by user entry via a switch or other user interface.

A variety of parameters sensed by the optical code reader 12 during an imaging session

may be used to select the focus quality threshold and/or the predetermined subset of pixel signals.

For example, in alternate embodiments, the optical code reader 12 may be capable of imaging non-code objects. The optical code reader 12 may include a software module executable on the

microprocessor 602 that is capable of determining if the object being imaged is a code or a non- code object. The focus analysis module 606 may select a stricter focus quality threshold for the non-code object, and the sensor select control module 608 may select a different predetermined subset of pixel signals than is currently selected (such as by default) for the non-code object.

The optical code reader 12 may include, in addition to; or instead of the focus analysis

module 606, a module for analyzing one or more parameters of the pixel data other than focus quality, such as color, intensity, contrast, and pixel locations for non-background pixels, and for determining if the one or more parameters are within a predetermined threshold range. The sensor selector control module 608 selects a subset of pixels and generates a sensor select control

signal 506 in accordance with results of the analysis. Furthermore, an adjustment control

module, in addition to, or instead of the lens adjustment control module 607, generates an

adjustment control signal to an adjustable component of the imaging engine 10 in response to the

analysis results. Upon the analysis results falling within the predetermined threshold range, a

different set of pixel data, such as a full set of pixel data, are selected for processing thereof, such as for decoding. Operation

Operation of the preferred embodiment of the optical code reader 12 is described with

reference to the flowchart shown in FIGS. 7A-C. With reference to FIG. 7 A, at step 704, at

initialization of an imaging session, sense select control signals are generated for selecting a

subset of pixel signal lines from a plurality of pixel signal lines. At step 708, the array of sensors

sense incident light. At step 712, the sensors generate a plurality of pixel signals corresponding

to the sensed light, where each pixel signal corresponds to an associated sensor. At step 716, a

subset of pixel signals of the plurality of pixel signals are propagated along respective signal

lines of the selected subset of pixel signal lines.

At step 720, the propagated pixel signals are processed and pixel data are generated, including a pixel data element corresponding to each of the propagated pixel signals. At step 724, the focus quality control module 606 determines the focus quality of the pixel data. At step

728, the focus quality control module 606 determines if the determined focus quality is within a predetermined threshold range. If not, control is transferred to step 732 of FIG. 7B, in which the

lens adjustment control module 607 generates a lens adjustment control signal 504 in accordance with the determined focus quality. At step 736 control is transferred to step 708 of FIG. 7A.

If yes, control is transferred to step 740 of FIG. 7C, in which the sensor select control module 608 generates a sensor select control signal 506 for selecting all pixel signal lines of the

plurality of pixel signal lines. At step 742 the sensor array senses incident light and at step 746,

the sensor array generates a plurality of pixel signals corresponding to the sensed light. At step

750, all of the pixel signals of the plurality of pixel signals are propagated along respective signal

lines of the selected pixel signal lines (i.e., all of the selected pixel signal lines). At step 754, the

propagated pixel signals are processed and pixel data are generated including a pixel data element corresponding to each of the propagated pixel signals. At step 758, the pixel data are

decoded, and at step 762, the decoded data are transmitted to the host terminal 26.

An imaging system is disclosed having an imaging apparatus including an array of photo

sensors for obtaining pixel data, a data processor for processing selected pixel data, a sensor

selector controlled by the data processor for selecting pixel data. The data processor controls the

sensor selector to selectively disable a subset of photo sensors or disable an output data path

exiting from the photo sensor, so that pixel data are provided to the data processor or other component of the imaging system from only the enabled photo sensors or photo sensors having

an enabled output data path. The pixel data are analyzed by the data processor or another data processor and an adjustment is made to the imaging apparatus in accordance with the analysis results. Upon the analysis results meeting a predetermined condition, a different subset or none of the photo sensors or photo sensor output data paths are selected for disabling.

The described embodiments of the present invention are intended to be illustrative rather

than restrictive, and are not intended to represent every embodiment of the present invention. Various modifications and variations can be made without departing from the spirit or scope of the invention as set forth in the following claims both literally and in equivalents recognized in law.