FIELD OF THE INVENTION

The invention relates to image data collection in general and particularly to an image data collector with coordinated illumination and global shutter control.

BACKGROUND OF THE INVENTION

Many traditional imager readers, such as hand held and fixed mounted bar code and machine code readers, employ charge-coupled device (CCDs) based image sensors. A CCD based image sensor contains an array of electrically coupled light sensitive photodiodes that convert incident light energy into packets of electric charge. In operation, the charge packets are shifted out of the CCD imager sensor for subsequent processing.

Some image readers employ CMOS based image sensors as an alternative imaging technology. As with CCDs, CMOS based image sensors contain arrays of light sensitive photodiodes that convert incident light energy into electric charge. Unlike CCDs, however, CMOS based image sensors allow each pixel in a two-dimensional array to be directly addressed. One advantage of this is that sub-regions of a full frame of image data can be independently accessed. Another advantage of CMOS based image sensors is that in general they have lower costs per pixel. This is primarily due to the fact that CMOS image sensors are made with standard CMOS processes in high volume wafer fabrication facilities that produce common integrated circuits such as microprocessors and the like. In addition to lower cost, the common fabrication process means that a CMOS pixel array can be integrated on a single circuit with other standard electronic devices such as clock drivers, digital logic, analog/digital converters and the like. This in turn has the further advantage of reducing space requirements and lowering power usage.

CMOS based image readers have traditionally employed rolling shutters to expose pixels in the sensor array. In a rolling shutter architecture, rows of pixels are activated and read out in sequence. The exposure or integration time for a pixel is the time between a pixel being reset and its value being read out. This concept is presented inFIG. 2A. InFIG. 2A, the exposure for each of the rows “a” though “n” is diagrammatically represented by the bars4a. . .4n(generally4). The horizontal extent8of each bar is intended to correspond to the exposure period for a particular row. The horizontal displacement of each bar4is suggestive of the shifting time period during which each row of pixels is exposed. As can be seen inFIG. 2A, the exposure period for sequential rows overlap. This is shown in more detail with respect to the timing diagrams for a rolling shutter architecture shown inFIG. 2B. The second 12 and third 16 lines of the timing diagram represent the reset timing signal and the read out timing signal, respectively, for row “a.” The fourth 20 and fifth 24 lines represent the reset and the read out timing signals, respectively for row “b.” As shown in bothFIGS. 2A and 2B, the exposure for row “b” is initiated before the values for row “a” are read out. The exposure periods for adjacent rows of pixels typically overlap substantially as several hundred rows of pixels must be exposed and read during the capture of a frame of data. As shown by the illumination timing signal on the first line28, the rolling shutter architecture with its overlapping exposure periods requires that the illumination source remain on during substantially all of the time required to capture a frame of data so that illumination is provided for all of the rows.

In operation, the rolling shutter architecture suffers from at least two disadvantages: image distortion and image blur. Image distortion is an artifact of the different times at which each row of pixels is exposed. The effect of image distortion is most pronounced when fast moving objects are visually recorded. The effect is demonstrated in the image shown inFIG. 3that shows a representation of an image taken with a rolling shutter of a bus image pixels50passing through the field of view from right to left. As the top row of bus image pixels54of the bus was taken earlier than the bottom row of pixels58, and as the bus was traveling to the left, the bottom row of bus image pixels58is displaced to the left relative to the top row of bus image pixels54.

Image blur is an artifact of the long exposure periods typically required in a rolling shutter architecture in an image reader. As indicated above, in a rolling shutter architecture the illumination source must remain on during substantially all of the time required to capture a frame of data. Due to battery and/or illumination source limitations, the light provided during the capture of an entire frame of data is usually not adequate for short exposure times. Without a short exposure time, blur inducing effects become pronounced. Common examples of blur inducing effects include the displacement of an image sensor due to, for example, hand shake with a hand held image reader.

What is needed is an image reader that overcomes the drawbacks of current CMOS image readers including image distortion and image blur.

SUMMARY OF THE INVENTION

In one aspect, the invention features a complementary metal oxide semiconductor (CMOS) based image reader for collecting image data from a target. The CMOS based imager reader comprises a CMOS based image sensor array; a timing module in electrical communication with the CMOS based image sensor array. The timing module is capable of simultaneously exposing an entire frame of pixels of the CMOS based image sensor array during an exposure period. The CMOS based image reader also comprises an illumination module capable of illuminating the target during an illumination period. The illumination module is in electrical communication with the timing module. The CMOS based image reader further comprises a control module in electrical communication with the timing module and the illumination module. The control module is capable of causing at least a portion of the exposure period to occur during the illumination period. In one embodiment of the CMOS based image reader, illuminating the target comprises overdriving light sources in the illumination module. In another embodiment of the CMOS based image reader, the light sources comprise light emitting diodes. In a further embodiment of the CMOS based image reader, the exposure period starts after the start of the illumination period and the exposure period ends before the end of the illumination period. In yet another embodiment of the CMOS based image reader, the illumination period starts after the start of the exposure period and the illumination period ends before the end of the exposure period. In yet an additional embodiment of the CMOS based image reader, the illumination period starts before the start of the exposure period and the illumination period ends before the end of the exposure period. In yet a further embodiment of the CMOS based image reader, the exposure period has a duration of less than 3.7 milliseconds. In various embodiments of the CMOS based image reader, the target includes a symbology such as a one-dimensional bar code such as a Code 39 or a UPC code or a two-dimensional bar code such as a PDF417 bar code, an Aztec symbol or Datamatrix symbol.

In another aspect the invention features a complementary metal oxide semiconductor (CMOS) based image reader for collecting image data from a target. The CMOS based imager reader comprises an integrated circuit including at least a CMOS based image sensor array and global electronic shutter control circuitry. The global electronic shutter control circuitry is capable of generating an exposure control timing pulse that is capable of causing the simultaneous exposure of substantially all of an entire frame of pixels of the CMOS based image sensor array. The CMOS based image reader also comprises light sources in electrical communication with the integrated circuit. The light sources are capable of illuminating the target including the symbology in response to an illumination control timing pulse. At least a portion of the illumination control timing pulse occurs during the exposure control timing pulse. In one embodiment of the CMOS based image reader, illuminating the target comprises overdriving light sources. In another embodiment of the CMOS based image reader, the light sources comprise light emitting diodes. In a further embodiment of the CMOS based image reader, the exposure period starts after the start of the illumination period and the exposure period ends before the end of the illumination period. In yet another embodiment of the CMOS based image reader, the illumination period starts after the start of the exposure period and the illumination period ends before the end of the exposure period. In yet an additional embodiment of the CMOS based image reader, the illumination period starts before the start of the exposure period and the illumination period ends before the end of the exposure period. In yet a further embodiment of the CMOS based image reader, the exposure period has a duration of less than 3.7 milliseconds. In various embodiments of the CMOS based image reader, the target includes a symbology such as a one-dimensional bar code such as a Code 39 or a UPC code or a two-dimensional bar code such as a PDF417 bar code, an Aztec symbol or Datamatrix symbol.

In a further aspect, the invention features an image reader for collecting image data from a target. The imager reader comprises an integrated circuit including at least an image sensor array and exposure timing control circuitry. The exposure timing control circuitry is capable of generating an exposure control timing pulse that is capable of simultaneously exposing substantially all of the pixels in the image sensor array. The image reader also comprises an illumination module in electrical communication with the integrated circuit. The illumination module comprises light sources that are capable of illuminating the target in response to an illumination control timing pulse. At least a portion of the illumination control timing pulse occurs during the exposure control timing pulse. In one embodiment of the image reader, the illumination control timing pulse is generated by an illumination module. In another embodiment of the image reader, the overlap between the illumination control timing pulse and the exposure control timing pulse is coordinated by a control module that is in electrical communication with the integrated circuit and the illumination module. In a further embodiment of the image reader, the control module comprises a microprocessor. In one embodiment of the image reader, illuminating the target comprises overdriving light sources. In another embodiment of the image reader, the light sources comprise light emitting diodes. In a further embodiment of the image reader, the exposure period starts after the start of the illumination period and the exposure period ends before the end of the illumination period. In yet another embodiment of the image reader, the illumination period starts after the start of the exposure period and the illumination period ends before the end of the exposure period. In yet an additional embodiment of the image reader, the illumination period starts before the start of the exposure period and the illumination period ends before the end of the exposure period. In yet a further embodiment of the image reader, the exposure period has a duration of less than 3.7 milliseconds. In various embodiments of the CMOS based image reader, the target includes a symbology such as a one-dimensional bar code such as a Code 39 or a UPC code or a two-dimensional bar code such as a PDF417 bar code, an Aztec symbol or Datamatrix symbol.

In another aspect, the invention features a method for collecting image data from a target. The method comprises activating light sources to illuminate the target in response to an illumination control timing pulse. The activation of the light sources occurs for the duration of the illumination control timing pulse. The method also comprises simultaneously activating a plurality of pixels to photoconvert incident radiation. The activation of the plurality of pixels occurs in response to an exposure control timing pulse. The method additionally comprises storing image data collected by each of the plurality of pixels in a shielded portion of each of the plurality of pixels. The storing of the image data occurs in response to the exposure control timing pulse. The method further comprises reading out image data from the plurality of pixels wherein at least a portion of the exposure control timing pulse occurs during the illumination control timing pulse. In one embodiment, the method further comprises coordinating the overlap between the illumination control timing pulse and the exposure control timing pulse. The coordination is directed by a control module. In one such embodiment of the method, the control module comprises a microprocessor. In another embodiment of the method, illuminating the target comprises overdriving light sources in an illumination module. In an additional embodiment of the method, the light sources comprise light emitting diodes. In a further embodiment of the method, the storing of image data occurs in response to a stop portion of the exposure control timing pulse. In an additional embodiment of the method, the exposure period starts after the start of the illumination period and the exposure period ends before the end of the illumination period. In yet another embodiment of the method, the illumination period starts after the start of the exposure period and the illumination period ends before the end of the exposure period. In yet an additional embodiment of the method, the illumination period starts before the start of the exposure period and the illumination period ends before the end of the exposure period. In yet a further embodiment of the method, the exposure period has a duration of less than 3.7 milliseconds. In various embodiments of the CMOS based image reader, the target includes a symbology such as a one-dimensional bar code such as a Code 39 or a UPC code or a two-dimensional bar code such as a PDF417 bar code, an Aztec symbol or Datamatrix symbol.

In another aspect, the invention features a bar code image reader for collecting and processing bar code data from a bar code symbol. The image reader comprises a two-dimensional array of pixels for receiving light radiation reflected from the bar code symbol, the two-dimensional array of pixels comprising a first plurality of pixels and a second plurality of pixels, the two-dimensional array capable of reading out the first plurality of pixels independently of reading out the second plurality, each of the pixels comprising a photosensitive region and an opaque shielded data storage region. The image reader also comprising an optics assembly for directing light radiation reflected from the bar code symbol onto the two-dimensional array of pixels. The image reader further comprising a global electronic shutter associated with the two-dimensional array of pixels, the global electronic shutter capable of simultaneously exposing substantially all of the pixels in the two-dimensional array. The image reader additionally comprising a processor module, the processor module in electronic communication with the two-dimensional array of pixels, the processor module capable of processing image data from the two-dimensional array of pixels to generate decoded bar code data. In one embodiment of the bar code image reader, the two-dimensional image sensor array is a complementary metal oxide (CMOS) image sensor. In another embodiment of the bar code image reader, processing the image data to generate output data comprises automatically discriminating between a plurality of bar code types.

In another aspect, the invention features a complementary metal oxide semiconductor (CMOS) based image reader for collecting image data from a target. The CMOS based imager reader comprises a CMOS based image sensor array, the CMOS based image sensor array comprising a first plurality of pixels and a second plurality of pixels, the CMOS based image sensor array capable of reading out the first plurality of pixels independently of reading out the second plurality, each of the pixels of the CMOS based image sensor array comprising a photosensitive region and an opaque shielded data storage region. The CMOS based image reader also comprising a timing module in electrical communication with the CMOS based image sensor array, the timing module configured to simultaneously expose an entire frame of pixels of the CMOS based image sensor array during an exposure period. The CMOS based image sensor array further comprising an illumination module configured to illuminate the target during an illumination period, the illumination module in electrical communication with the timing module. The CMOS based image sensor array additionally comprising a control module in electrical communication with the timing module and the illumination module, the control module configured to cause at least a portion of the exposure period to occur during the illumination period.

In a further aspect, the invention features a complementary metal oxide semiconductor (CMOS) based image reader for collecting image data from a target. The CMOS based imager reader comprising an integrated circuit including at least a CMOS based image sensor array, the CMOS based image sensor array comprising a first plurality of pixels and a second plurality of pixels, the CMOS based image sensor array capable of reading out the first plurality of pixels independently of reading out the second plurality, each of the pixels of the CMOS based image sensor array comprising a photosensitive region and an opaque shielded data storage region. The CMOS based image sensor array also comprising a global electronic shutter control circuitry, the global electronic shutter control circuitry configured to generate an exposure control timing pulse that is capable of causing the simultaneous exposure of substantially all of an entire frame of pixels of the CMOS based image sensor array. The CMOS based image sensor array further comprising light sources configured to illuminate the target in response to an illumination control timing pulse, the light sources in electrical communication with the integrated circuit. In operation of the CMOS based image reader at least a portion of the illumination control timing pulse overlaps with at least a portion of the exposure control timing pulse. In one embodiment of the CMOS based image reader, illuminating the target comprises overdriving light sources in the illumination module. In another embodiment of the CMOS based reader the light sources comprise light emitting diodes. In a further embodiment of the CMOS based image reader, the exposure control timing pulse has a shorter duration than the illumination control timing pulse. In an additional embodiment of the CMOS based image reader, the illumination control timing pulse has a shorter duration than the exposure control timing pulse. In still another embodiment of the CMOS based imager reader, the illumination control timing pulse starts before the start of the exposure control timing pulse and the illumination control timing pulse ends before the end of the exposure control timing pulse. In still a further embodiment of the CMOS based imager reader, the exposure control timing pulse has a duration of less than 3.7 milliseconds. In still an additional embodiment of the CMOS based imager reader, the target includes a symbology. In one such embodiment, the symbology is a one-dimensional bar code. In another such embodiment, the symbology is a two-dimensional bar code. In one such embodiment, the two-dimensional bar code is a PDF417 bar code.

In a further aspect, the invention features a bar code image reader for collecting image data from a bar code. The imager reader comprises an integrated circuit including at least a two-dimensional image sensor array, the two-dimensional image sensor array including a plurality of active pixels, each active pixel including at least a shielded data storage area, the two-dimensional image sensor array capable of employing a transfer function to convert an incident light intensity into an output voltage, the transfer function having a first region with a first slope and a second region with a second slope, the two-dimensional image sensor array capable of employing the second region of the transfer function when the incident light intensity is above a specified level and the two-dimensional image sensor array capable of employing the first region of the transfer function when the incident intensity is below a specified level. The bar code image reader also comprises an exposure timing control circuitry, the exposure timing control circuitry configured to generate an exposure control timing pulse that is capable of simultaneously exposing all or substantially all of the pixels in the image sensor array to photoconvert incident radiation. In one embodiment, the exposure control timing pulse has a duration of less than 3.7 milliseconds. In another embodiment, a dynamic range of the two-dimensional image array sensor is greater than 65 decibels.

In yet another aspect, the invention features a method for automatically focusing an image reader. The method comprises directing with an optical system light energy reflected from a target onto an image sensor. The method also comprises exposing sequentially a plurality of rows of pixels in the image sensor during a frame exposure period, the frame exposure period being defined as a time duration extending from the beginning of the exposure of the first of the plurality of rows to the end of the exposure of the last of the plurality of rows. The method further comprising varying in incremental steps an optical system from a first setting where a distinct image of objects located at a first distance from the image reader is formed on the image sensor to a second setting where a distinct image of objects located at a second distance from the image reader is formed on the image sensor. The method additionally comprising reading out a plurality of rows of image data from the plurality of rows of pixels in the image sensor, wherein the varying in incremental steps the optical system occurs during at least a portion of the frame exposure period. In one embodiment, the method further comprises analyzing the plurality of rows of image data to determine a proper setting for the optical system corresponding to a distinct image of the target being formed on the image sensor. In an additional embodiment, the method also comprises simultaneously exposing the plurality of rows in the image sensor to generate an image of the target. In one embodiment of the method, the exposure period for adjacent lines of pixels in image reader overlap. In another embodiment of the method, the target includes a symbology. In one such embodiment, the symbology is a one-dimensional bar code. In another such embodiment, the symbology is a two-dimensional bar code.

In another aspect, the invention features an image reader with an automatic focusing capability. The imager reader comprising an integrated circuit including at least an image sensor array. The image reader also comprising an optical system capable of directing light reflected from a target onto the image sensor array, the optical system having a plurality of focus settings, a first focus setting corresponding to distinct images of objects located at a first distance from the image reader being formed on the image sensor array and a second focus setting corresponding to distinct images of objects located at a second distance from the image reader being formed on the image sensor array. The image reader further comprising a rolling shutter control module configured to sequentially expose a plurality of rows of pixels in the image sensor array to collect focusing image data. The imager reader additionally comprising an automatic focusing module configured to analyze the focusing image data to determine a focus setting for the target corresponding to a distinct image of the target being formed on the image sensor, wherein the optical system is capable of being varied in incremental steps from the first focus setting to the second focus setting during at least a portion of a time period during which the rolling shutter control module is sequentially exposing the plurality of rows of pixels. In one embodiment, the imager reader further comprises a global electronic shutter control module configured to simultaneously expose the plurality of lines of pixels in the image sensor array to collect a frame of image data once the focus setting for the target has been determined. In another embodiment of the image reader, the rolling shutter control module and the global electronic shutter control module are integrated on the same integrated circuit containing the image sensor array. In a further embodiment of the image reader, the rolling shutter control module and the global electronic shutter control module are combined in a single image array control module. In an additional embodiment of the image reader, the rolling shutter control module is capable of causing exposure periods for adjacent rows of pixels to overlap.

In another aspect, the invention features an image reader for minimizing ambient light image degradation. The image reader comprises an integrated circuit including at least an image sensor array, the image sensor array providing a signal suitable for light intensity determination. The image reader also comprises a rolling shutter control module configured to sequentially expose a plurality line of pixels in the image sensor array. The image reader further comprises a global electronic shutter control module configured to simultaneously expose the plurality of lines of pixels in the image sensor array, wherein one of the rolling shutter control module and the global electronic shutter control module is capable of being selected to control the image sensor array in response to the signal suitable for light intensity determination. In one embodiment of the image reader, the signal suitable for light intensity determination includes information related to an intensity of a light source of the image reader. In another embodiment of the image reader, the signal suitable for light intensity determination is useful for determining whether a minimum integration time is satisfied. In a further embodiment of the image reader, the signal suitable for light intensity determination is useful for determining whether the exposure time (also known as the integration time) for the current environmental condition is less than a calculated minimum integration time. In yet another embodiment of the image reader, the rolling shutter control module and the global electronic shutter control module are integrated on the same integrated circuit containing the image sensor array.

In still another aspect, the invention features a method for minimizing image data degradation collected by an image reader. The method comprises determining at least one parameter related to an ambient light intensity and analyzing the at least one parameter. The method also comprises switching control of an image sensor array in the image reader from a global electronic shutter control module to a rolling shutter control module in response to the analysis of the at least one parameter. In one embodiment of the method, the at least one parameter includes an exposure time for current environmental conditions. In another embodiment of the method, the analyzing the at least one parameter includes calculating a ratio of the exposure time for current environmental conditions to a predetermined exposure time. In one such embodiment, the predetermined exposure time is based on illumination supplied by light sources of the image reader. In another embodiment of the method, analyzing the at least one parameter includes determining whether a ratio of the ambient light intensity to an intensity of a light source of the image reader exceeds a specified threshold.

The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.

