Automatic electronic camera for label image capture

• US 5,818,528 A
• Filed: 05/30/1996
• Issued: 10/06/1998
• Est. Priority Date: 10/25/1994
• Status: Expired due to Term

• Current Assignee: United Parcel Service of America (United Parcel Service Incorporated)
• Original Assignee: United Parcel Service of America (United Parcel Service Incorporated)
• Inventors: Roth, Stephen Anthony, Garland, Lance Gordon, Kruse, Ross Napoleon, Sussmeier, John William
• Primary Examiner(s): Faile, Andrew I.
• Assistant Examiner(s): Vu, Ngoc-Yen, VU, NGOC YEN T
• Application Number:
  US08/657,625
• Time in Patent Office: 859 Days
• Field of Search: 348/207, 348/221, 348/222, 348/229, 348/230, 348/362, 348/363, 348/364, 348/365, 250/214 AG, 235/455, 396/213
• US Class Current: 348/364
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10742 including a diffuser for diffusing the light from the light source to create substantially uniform illumination of the target record carrier
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/1092 sensing by means of TV-scanning
• CPC Class Codes: G06K 7/1417 2D bar codes
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/72 Combination of two or more compensation controls

Abstract

A hand held label reader is capable of illuminating a label, capturing a digital image of two-dimensional information indicia on the label, and decoding the digital image to provide decoded output data to a terminal. The target label is illuminated by a low variation illuminator that includes a circular LED array mounted behind a plano-concave dispersing lens. The automatic electronic camera, which includes a CCD camera and control circuitry, uses three images to adjust the intensity of the digital image and store a properly exposed image of the label in video RAM. The intensity of the digital image is adjusted by controlling the video system gain via adjusting the CCD array'"'"'s integration time, the gain of a video amplifier, and the gain provided by an analog-to-digital converter. The gain provided by the analog-digital-converter is adjusted to compensate for the attenuation of light through the camera'"'"'s lens assembly. For the first image, the digital image is obtained using a default setting for the gain. The image intensity is analyzed using a histogram process and new gain setting are determined. The second image is obtained using the gain settings derived from the first image. The second image intensity is analyzed and the gain settings are adjusted. These settings are used for the third video image. The digital image from the third image is stored in video RAM, where it is available to be decoded by a microprocessor.

Claims

1. In an electronic camera system for producing an image including a plurality of pixels, a method for evaluating the intensity of an image, comprising the steps of:

providing a first memory including a plurality of bits, each bit corresponding to one of the pixels, the plurality of bits identifying a preselected subset of the pixels to be sampled to determine the intensity of the image;

providing a second memory including a plurality of bins, each bin corresponding to one of a plurality of possible intensity levels associated with the preselected subset of the plurality of pixels; and

computing an output indicative of the brightness of the image by

for each pixel of the preselected subset, determining the intensity of the pixel and incrementing a bin value of a particular one of the bins in the second memory corresponding to the intensity of the pixel;

beginning with the one of the bins corresponding to the lowest of the possible intensity levels, sequentially summing the bin values in increasing intensity level order to compute a bin-value sum;

determining a last bin when the bin-value sum exceeds a predetermined portion of the sampled subset of the pixels; and

assigning to the output a value corresponding to the intensity level associated with the last bin.

2. A method for evaluating the intensity of an image as recited in claim 1, wherein said preselected subset of pixels defines a pixel pattern within said image.

3. A method for evaluating the intensity of an image as recited in claim 2, wherein said pixel pattern is weighted toward the center of said image.

4. A method for evaluating the intensity of an image as recited in claim 2, wherein said pixel pattern is approximately a shotgun pattern centered at the approximate center of said image.

5. An electronic camera for producing a digital image over a range of light intensities;

comprising;

an image sensor assembly including an adjustable shutter speed control and means for generating an analog image signal, said image signal including a plurality of pixels;

a video gain circuit configured to receive said analog image signal and to output an amplified analog image signal;

an analog-to-digital converter including an A/D gain controller responsive to an A/D reference input and configured to convert said amplified analog image signal to a digital image signal; and

an intensity evaluator circuit configured to receive said digital image signal and to output a correction signal varying with the intensity of at least a portion of said digital image signal;

said shutter speed control, said video gain circuit, and said A/D reference input being responsive to said correction signal,

said intensity evaluator circuit including

a first memory including a plurality of bits, each of said plurality of bits corresponding to one of said plurality of pixels, said plurality of bits including a predetermined number of hit bits, said hit bits identifying a preselected subset of said plurality of pixels to be sampled to determine the intensity of said image;

a second memory including a plurality of bins, each of said bins corresponding to one of a plurality of possible intensity levels associated with said preselected subset of said plurality of pixels,

said correction signal being determined by

determining, for each of said preselected subset of said plurality of pixels, the intensity of said pixel and incrementing the bin in said second memory corresponding to the intensity of said pixel;

sequentially summing the values in said bins;

determining when said sum exceeds a predetermined number; and

defining a last bin value responsive to said sum exceeding said predetermined number.

6. An electronic camera as recited in claim 5, wherein said intensity evaluator circuit generates a shutter trigger pulse derived from said correction signal, and wherein said shutter speed control is response to said trigger pulse.

7. An electronic camera as recited in claim 5, wherein said intensity evaluator circuit generates a digital value derived from said correction signal, and wherein said video gain circuit is responsive to said digital value.

8. An electronic camera as recited in claim 5, wherein said intensity evaluator circuit generates an analog voltage level derived from said correction signal, and wherein said A/D gain controller is responsive to said analog voltage level.

9. An electronic camera system for producing an image including a plurality of pixels and evaluating the intensity of an image, comprising:

a first memory including a plurality of bits, each bit corresponding to one of the pixels, the plurality of bits identifying a preselected subset of the pixels to be sampled to determine the intensity of the image;

a second memory including a plurality of bins, each bin corresponding to one of a plurality of possible intensity levels associated with the preselected subset of the plurality of pixels; and

means for computing an output indicative of the brightness of the image by

for each pixel of the preselected subset, determining the intensity of the pixel and incrementing a bin value of a particular one of the bins in the second memory corresponding to the intensity of the pixel;

beginning with the one of the bins corresponding to the lowest of the possible intensity levels, sequentially summing the bin values in increasing intensity level order to compute a bin-value sum;

determining a last bin when the bin-value sum exceeds a predetermined portion of the sampled subset of the pixels; and

assigning to the output a value corresponding to the intensity level associated with the last bin.