Portable data collection device including color imaging dataform reader assembly

• US 6,062,475 A
• Filed: 06/25/1997
• Issued: 05/16/2000
• Est. Priority Date: 06/25/1997
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Metanetics Corporation
• Inventors: Feng, Chen
• Primary Examiner(s): Le, Thien M.
• Assistant Examiner(s): Sherr, Daniel H.
• Application Number:
  US08/882,025
• Time in Patent Office: 1,056 Days
• Field of Search: 235/462.06, 235/469, 235/462.04, 348/272, 348/273, 348/274, 348/275, 348/276, 348/277, 348/278, 348/279, 348/280, 348/281, 348/282, 382/167, 382/163, 382/162, 382/274, 382/275
• US Class Current: 235/462.06
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: H04N 23/00 Cameras or camera modules comprising electronic image sensors; Control thereof
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof
• CPC Class Codes: H04N 23/84 for processing colour signals
• CPC Class Codes: H04N 25/136 using complementary colours

Abstract

A portable data collection device providing for dataform decoding and color imaging. An imaging assembly is provided that includes a board camera having black and white circuitry and generates a composite video signal representing an image of a target area of the imaging assembly when actuated. The imaging assembly includes a two dimensional photosensor array overlaid by a color filter having a repeating pattern of four color filter elements. The imaging assembly is selectively actuatable with a first trigger for reading a target dataform in the imaging assembly'"'"'s target area and actuatable with a second trigger for capturing a image of the target object in the target area. When the device is operated in the dataform reading mode, compensation circuitry is actuated to operate on digital gray scale values extracted from the composite video signal to adjust gray scale value magnitudes to compensate for the transmittivity differences of the color filter elements to improve decodability of the imaged dataform. When the device is operated in the imaging mode, conversion circuitry is actuated to convert the gray scale values to either Y-C or RGB digital data and a D/A converter further processes the Y-C or RGB digital data to provide an analog Y-C or RGB output signal.

Claims

1. A portable data collection device comprising:

a) a black and white modular camera assembly including a photosensor array having a two dimensional array of photosensors overlaid by a color filter, the color filter including a plurality of color filter elements each overlying at least one photosensor, the plurality of color filter elements including a first set of filter elements having a first color and a second set of filter elements having a second color, a transmittivity of filter elements in the first set of filter elements being different than a transmittivity of the filter elements in photosensors being read out after an exposure period to generate an analog video signal representative of an image of a target area, the target area including a target dataform, the analog video signal including image signal portions wherein a magnitude of the signal represents respective charges accumulated on individual photo sensors of the array of photosensors during the exposure period;

b) a modular camera assembly housing for supporting components of the modular camera assembly;

c) an optic assembly including lens assembly supported within a shroud assembly and positioned to focus illumination reflected from the target area onto the array of photosensors, the optic assembly having a best focus position at a predetermined distance from an outwardly facing optic surface of an outermost lens which results in a clearest image of the target area being focused onto the array of photosensors;

d) an illumination assembly supported within the housing and directing illumination towards the target area and including a lens array having a plurality of optic surfaces for directing illumination generated by illumination sources toward an illumination area substantially congruent with the target area;

e) analog to digital conversion circuitry for converting the image signal portions of the analog video signal into a set of gray scale values, a magnitude of a given gray scale value proportional to an intensity of illumination incident on a given photosensor of the array of photosensors during the exposure period, the intensity of illumination incident on the given photosensor dependent upon a transmittivity of the color filter element overlying the given photosensor;

f) compensation circuitry for generating a set of adjusted gray scale value magnitudes by adjusting magnitudes of selected gray scale values of the set of gray scale values, the magnitudes of the selected gray scale values being adjusted to compensate for differences in intensity of illumination incident on a subset of photosensors of the photosensor array corresponding to the selected gray scale values during the exposure period, the differences in intensity of illumination being due to differences in transmittivity of different colored color filter elements overlying different photosensors of the subset of photosensors; and

g) image processing and decoding circuitry receiving as input the set of adjusted gray scale value magnitudes and decoding a portion of the imaged target area representing the target dataform.

2. The portable data collection device of claim 1 wherein the selected gray scale values correspond to a portions of the image of the target area representing the target dataform.

3. The portable data collection device of claim 1 wherein the device further includes conversion circuitry for converting the set of gray scale values into an analog color signal.

4. The portable data collection device of claim 3 wherein the analog signal is a Y-C color signal.

5. The portable data collection device of claim 3 wherein the analog signal is a RGB color signal.

6. The portable data collection device of claim 3 wherein the conversion circuitry converts the set of gray scale values to a selected one of an analog Y-C color signal and an analog RGB color signal.

7. The portable data collection device of claim 6 further including an operator accessible switch electrically coupled to the conversion circuitry to permit the operator to switch the conversion circuitry between converting the set of gray scale values to the Y-C signal and the RGB signal.

8. The portable data collection device of claim 1 wherein the color filter includes magenta colored color filter elements, green colored color filter elements, yellow colored color filter elements and cyan colored color filter elements.

9. The portable data collection device of claim 1 wherein the compensation circuitry includes circuitry that determines a color of color filter element associated with each selected gray scale value, calculates an average magnitude of the selected gray scale values for each color of color filter elements, and calculates an overall average magnitude for all selected gray scale values and then adjusts a magnitude of each of the selected gray scale values by multiplying the magnitude by a ratio of the overall average magnitude to the average magnitude of the color of color filter associated with the selected gray scale value.

10. The portable data collection device of claim 1 wherein the compensation circuitry includes circuitry that determines a set of average gray scale value magnitudes wherein each average gray scale value magnitude is corresponds to an average magnitude of a group of four gray scale values of the selected gray scale values, the group of four gray scale values corresponding to a contiguous two by two matrix of photosensors of the array of photosensors and then uses the selected gray scale values for each color of color filter elements, and calculates an overall average magnitude for all selected gray scale values and further adjusts a magnitude of each of the selected gray scale values by multiplying the magnitude by a ratio of the overall average magnitude to the average magnitude of the color of color filter associated with the selected gray scale value.

11. A portable data collection device comprising:

a) a black and white modular camera assembly including a photosensor array having a two dimensional array of photosensors overlaid by a color filter, the color filter including a plurality of color filter elements each overlying at least one photosensor, the plurality of color filter elements including a first set of filter elements having a first color and a second set of filter elements having a second color, a transmittivity of filter elements in the first set of filter elements being different than a transmittivity of the filter elements in the second set of filter elements, the photosensors of the array of photosensors being read out after an exposure period to generate an analog video signal representative of an image of a target area, the target area including a target dataform;

b) a modular camera assembly housing for supporting components of the modular camera assembly;

c) an optic assembly including lens assembly supported within a shroud assembly and positioned to focus illumination reflected from the target area onto the array of photosensors, the optic assembly having a best focus position at a predetermined distance from an outwardly facing optic surface of an outermost lens which results in a clearest image of the target area being focused onto the array of photosensors;

d) an illumination assembly supported within the housing and directing illumination towards the target area and including a lens array having a plurality of optic surfaces for directing illumination generated by illumination sources toward an illumination area substantially congruent with the target area;

e) analog to digital conversion circuitry for converting the analog video signal into a set of gray scale values, a magnitude of a given gray scale value proportional to an intensity of illumination incident on a given photosensor of the array of photosensors during the exposure period, the intensity of illumination incident on the given photosensor dependent upon a transmittivity of the color filter element overlying the given photosensor;

f) compensation circuitry for generating a set of adjusted gray scale value magnitudes by adjusting magnitudes of selected gray scale values of the set of gray scale values, the magnitudes of the selected gray scale values being adjusted to compensate for differences in intensity of illumination incident on a subset of photosensors of the photosensor array corresponding to the selected gray scale values during the exposure period, the differences in intensity of illumination being due to differences in transmittivity of different colored color filter elements overlying different photosensors of the subset of photosensors;

g) image processing and decoding circuitry receiving as input the set of adjusted gray scale value magnitudes and decoding a portion of the imaged target area representing the target dataform; and

h) wherein the color filter includes magenta colored color filter elements, green colored color filter elements, yellow colored color filter elements and cyan colored color filter elements.

12. The portable data collection device of claim 11 wherein the magenta colored color filter elements, green colored color filter elements, yellow colored color filter elements and cyan colored color filter elements of the color filter have found in a repeating pattern such that any two by two matrix of photosensors of the photosensor array includes a first photosensor overlaid by a magenta colored color filter element, a second photosensor overlaid by a green colored color filter element, a third photosensor overlaid by a yellow colored color filter element, and a fourth photosensor overlaid by a cyan colored color filter element.

13. The portable data collection device of claim 11 wherein the magenta colored color filter elements, green colored color filter elements, yellow colored color filter elements and cyan colored color filter elements of the color filter have found in a repeating pattern such that any two by two matrix of photosensors of the photosensor array includes a first photosensor overlaid by a magenta colored color filter element, a second photosensor overlaid by a green colored color filter element, a third photosensor overlaid by a yellow colored color filter element, and a fourth photosensor overlaid by a cyan colored color filter element.

14. A portable data collection device comprising:

a) a black and white modular camera assembly including a photosensor array having a two dimensional array of photosensors overlaid by a color filter, the color filter including a plurality of color filter elements each overlying at least one photosensor, the plurality of color filter elements including a first set of filter elements having a first color and a second set of filter elements having a second color, a transmittivity of filter elements in the first set of filter elements being different than a transmittivity of the filter elements in the second set of filter elements, the photosensors of the array of photosensors being read out after an exposure period to generate an analog video signal representative of an image of a target area, the target area including a target dataform;

b) a modular camera assembly housing for supporting components of the modular camera assembly;

c) an optic assembly including lens assembly supported within a shroud assembly and positioned to focus illumination reflected from the target area onto the array of photosensors, the optic assembly having a best focus position at a predetermined distance from an outwardly facing optic surface of an outermost lens which results in a clearest image of the target area being focused onto the array of photosensors;

d) an illumination assembly supported within the housing and directing illumination towards the target area and including a lens array having a plurality of optic surfaces for directing illumination generated by illumination sources toward an illumination area substantially congruent with the target area;

e) analog to digital conversion circuitry for converting the analog video signal into a set of gray scale values, a magnitude of a given gray scale value proportional to an intensity of illumination incident on a given photosensor of the array of photosensors during the exposure period, the intensity of illumination incident on the given photosensor dependent upon a transmittivity of the color filter element overlying the given photosensor;

f) compensation circuitry for generating a set of adjusted gray scale value magnitudes by adjusting magnitudes of selected gray scale values of the set of gray scale values, the magnitudes of the selected gray scale values being adjusted to compensate for differences in intensity of illumination incident on a subset of photosensors of the photosensor array corresponding to the selected gray scale values during the exposure period, the differences in intensity of illumination being due to differences in transmittivity of different colored color filter elements overlying different photosensors of the subset of photosensors;

g) image processing and decoding circuitry receiving as input the set of adjusted gray scale value magnitudes and decoding a portion of the imaged target area representing the target dataform; and

h) wherein the compensation circuitry includes circuitry that determines a color of color filter element associated with each selected gray scale value, calculates an average magnitude of the selected gray scale values for each color of color filter elements, and calculates an overall average magnitude for all selected gray scale values and then adjusts a magnitude of each of the selected gray scale values by multiplying the magnitude by a ratio of the overall average magnitude to the average magnitude of the color of color filter associated with the selected gray scale value.

15. A portable data collection device comprising:

a) a black and white modular camera assembly including a photosensor array having a two dimensional array of photosensors overlaid by a color filter, the color filter including a plurality of color filter elements each overlying at least one photosensor, the plurality of color filter elements including a first set of filter elements having a first color and a second set of filter elements having a second color, a transmittivity of filter elements in the first set of filter elements being different than a transmittivity of the filter elements in the second set of filter elements, the photosensors of the array of photosensors being read out after an exposure period to generate an analog video signal representative of an image of a target area, the target area including a target dataform;

b) a modular camera assembly housing for supporting components of the modular camera assembly;

c) an optic assembly including lens assembly supported within a shroud assembly and positioned to focus illumination reflected from the target area onto the array of photosensors, the optic assembly having a best focus position at a predetermined distance from an outwardly facing optic surface of an outermost lens which results in a clearest image of the target area being focused onto the array of photosensors;

d) an illumination assembly supported within the housing and directing illumination towards the target area and including a lens array having a plurality of optic surfaces for directing illumination generated by illumination sources toward an illumination area substantially congruent with the target area;

e) analog to digital conversion circuitry for converting the analog video signal into a set of gray scale values, a magnitude of a given gray scale value proportional to an intensity of illumination incident on a given photosensor of the array of photosensors during the exposure period, the intensity of illumination incident on the given photosensor dependent upon a transmittivity of the color filter element overlying the given photosensor;

f) compensation circuitry for generating a set of adjusted gray scale value magnitudes by adjusting magnitudes of selected gray scale values of the set of gray scale values, the magnitudes of the selected gray scale values being adjusted to compensate for differences in intensity of illumination incident on a subset of photosensors of the photosensor array corresponding to the selected gray scale values during the exposure period, the differences in intensity of illumination being due to differences in transmittivity of different colored color filter elements overlying different photosensors of the subset of photosensors;

g) image processing and decoding circuitry receiving as input the set of adjusted gray scale value magnitudes and decoding a portion of the imaged target area representing the target dataform; and

h) wherein the compensation circuitry includes circuitry that determines a set of average gray scale value magnitudes wherein each average gray scale value magnitude is corresponds to an average magnitude of a group of four gray scale values of the selected gray scale values, the group of four gray scale values corresponding to a contiguous two by two matrix of photosensors of the array of photosensors and then uses the selected gray scale values for each color of color filter elements, and calculates an overall average magnitude for all selected gray scale values and further adjusts a magnitude of each of the selected gray scale values by multiplying the magnitude by a ratio of the overall average magnitude to the average magnitude of the color of color filter associated with the selected gray scale value.

16. A portable data collection device comprising:

a) a black and white camera assembly including a photosensor array having a two dimensional array of photosensors overlaid by a color filter, the color filter including a plurality of color filter elements each overlying at least one photosensor, the plurality of color filter elements including a first set of filter elements having a first color and a second set of filter elements having a second color, a transmittivity of filter elements in the first set of filter elements being different than a transmittivity of the filter elements in the second set of filter elements, the photosensors of the array of photosensors being read out after an exposure period to generate an analog video signal representative of an image of a target area, the target area including a target dataform, the analog video signal including image signal portions wherein a magnitude of the signal represents respective charges accumulated on individual photosensors of the array of photosensors during the exposure period;

b) an optic assembly positioned to focus illumination reflected from the target area onto the array of photosensors

c) analog to digital conversion circuitry for converting the analog video signal into a set of gray scale values, a magnitude of a given gray scale value proportional to an intensity of illumination incident on a given photosensor of the array of photosensors during the exposure period, the intensity of illumination incident on the given photosensor dependent upon a transmittivity of the color filter element overlying the given photosensor;

d) compensation circuitry for generating a set of adjusted gray scale value magnitudes by adjusting magnitudes of selected gray scale values of the set of gray scale values, the magnitudes of the selected gray scale values being adjusted to compensate for differences in intensity of illumination incident on a subset of photosensors of the photosensor array corresponding to the selected gray scale values during the exposure period, the differences in intensity of illumination being due to differences in transmittivity of different colored color filter elements overlying different photosensors of the subset of photosensors; and

e) image processing and decoding circuitry receiving as input the set of adjusted gray scale value magnitudes and decoding a portion of the imaged target area representing the target dataform.

17. The portable data collection device of claim 16 wherein the selected gray scale values correspond to a portions of the image of the target area representing the target dataform.

18. The portable data collection device of claim 16 wherein the color filter includes magenta colored color filter elements, green colored color filter elements, yellow colored color filter elements and cyan colored color filter elements.

19. The portable data collection device of claim 18 wherein the magenta colored color filter elements, green colored color filter elements, yellow colored color filter elements and cyan colored color filter elements of the color filter have found in a repeating pattern such that any two by two matrix of photosensors of the photosensor array includes a first photosensor overlaid by a magenta colored color filter element, a second photosensor overlaid by a green colored color filter element, a third photosensor overlaid by a yellow colored color filter element, and a fourth photosensor overlaid by a cyan colored color filter element.

20. The portable data collection device of claim 16 wherein the compensation circuitry includes circuitry that determines a color of color filter element associated with each selected gray scale value, calculates an average magnitude of the selected gray scale values for each color of color filter elements, and calculates an overall average magnitude for all selected gray scale values and then adjusts a magnitude of each of the selected gray scale values by multiplying the magnitude by a ratio of the overall average magnitude to the average magnitude of the color of color filter associated with the selected gray scale value.

21. The portable data collection device of claim 16 wherein the compensation circuitry includes circuitry that determines a set of average gray scale value magnitudes wherein each average gray scale value magnitude is corresponds to an average magnitude of a group of four gray scale values of the selected gray scale values, the group of four gray scale values corresponding to a contiguous two by two matrix of photosensors of the array of photosensors and then uses the selected gray scale values for each color of color filter elements, and calculates an overall average magnitude for all selected gray scale values and further adjusts a magnitude of each of the selected gray scale values by multiplying the magnitude by a ratio of the overall average magnitude to the average magnitude of the color of color filter associated with the selected gray scale value.