DC restoration of sampled imagery signals
First Claim
1. For use with a signal processing apparatus in which successive samples of an input are processed by a signal processing circuit, the operation of which is established in accordance with a reference signal level representative of the contents of selected ones of said successive samples, a method of preventing said reference signal level from being influenced by switching transitions occurring in the course of obtaining successive samples of said input signal, comprising the steps of:
- a) enabling said signal processing circuit to process said successive samples at times exclusive of said switching transitions; and
b) generating said reference signal level in accordance with the contents of said selected ones of said successive samples, which contents are exclusive of said switching transitions.
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Accused Products
Abstract
The problem of error-introducing artifacts associated with the sampling of the pixels of a solid state imager is obviated by controllably clocking the A-D converter to which the sampled pixel signals are applied, such that the A-D converter digitizes successive pixel samples only during those times that are exclusive of those times when switching transitions occur during the sampling of the imager pixels. The D.C. restoration level is established in accordance with the contents of `dark ` pixel samples, which are exclusive of the switching transitions. In one embodiment, the selective D.C. restoration process is accomplished by coupling the output of the A-D converter to a digital-to-analog (D-A) converter. The D-A converter is clocked during the times that the A-D converter digitizes dark samples, so that it generates successive dark sample-representative voltages. Difference between these analog voltage values and a prescribed level are integrated and fed back to the input to the (A-D) converter as a D.C. restoration offset. In a second embodiment of the invention, the difference between the output of the analog-to-digital converter and a prescribed digital code is used to control the operation of a digital counter. The D.C. reference level is established in accordance with the contents of the digital counter.
62 Citations
30 Claims
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1. For use with a signal processing apparatus in which successive samples of an input are processed by a signal processing circuit, the operation of which is established in accordance with a reference signal level representative of the contents of selected ones of said successive samples, a method of preventing said reference signal level from being influenced by switching transitions occurring in the course of obtaining successive samples of said input signal, comprising the steps of:
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a) enabling said signal processing circuit to process said successive samples at times exclusive of said switching transitions; and b) generating said reference signal level in accordance with the contents of said selected ones of said successive samples, which contents are exclusive of said switching transitions. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. For use with an imagery signal processor in which the responses of respective ones of a plurality of image receiving locations of an image receiving device, upon which light from an image source is incident, are sampled and coupled to an analog-to-digital converter for conversion into digital format, the value of a sampled signal input to said analog-to-digital converter being defined relative to a reference signal level, said reference signal level being associated with the response of one or more locations of said image receiving device which are effectively shielded from light from said image source, a method of controlling said reference signal level comprising the steps of:
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(a) causing the times at which said analog-to-digital converter digitizes the sampled signal input for conversion into digital format to occur between times at which transitions in the sampling of the responses of said respective ones of a plurality of image receiving locations of said image receiving device occur; (b) for times at which said analog-to-digital converter digitizes the response of said one or more locations of said image receiving device which are effectively shielded from light from said image source, generating an output signal representative of the difference between the value of the output of said analog-to-digital converter and a prescribed level; and (c) establishing said reference level in accordance with the difference representative output signal generated in step (b). - View Dependent Claims (9, 10, 11, 12, 13)
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14. For use with an imagery signal processor in which electrical signal responses of respective ones of a plurality of image receiving regions of an image detector, upon which light from an image source is incident, are sampled and coupled to an analog-to-digital converter for conversion into digital format, the digitized value of a sampled signal input to said analog-to-digital converter being defined relative to a reference dark level, said reference dark level being associated with the averaged response of a plurality of regions of said image detector which are effectively shielded from light, a method of controlling said reference dark level comprising the steps of:
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(a) causing the times at which said analog-to-digital converter digitizes the sampled signal input for conversion into digital format to occur between times at which transitions in the sampling of the responses of said respective ones of a plurality of image receiving regions of said image detector occur; (b) for times at which said analog-to-digital converter digitizes the response of said one or more regions of said image detector which are effectively shielded from light, generating an output signal representative of the difference between the value of the output of said analog-to-digital converter and a prescribed dark level; and (c) establishing said reference dark level in accordance with the difference representative output signal generated in step (b). - View Dependent Claims (15, 16, 17, 18, 19)
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20. For use with a signal processing apparatus in which successive samples of an input are processed by a signal processing circuit, the operation of which is established in accordance with a reference signal level representative of the contents of selected ones of said successive samples, an apparatus for preventing said reference signal level from being influenced by switching transitions occurring in the course of obtaining successive samples of said input signal, comprising in combination:
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first means for enabling said signal processing circuit to process said successive samples at times exclusive of said switching transitions; and second means, coupled to said first means, for generating said reference signal level in accordance with the contents of said selected ones of said successive samples, which contents are exclusive of said switching transitions. - View Dependent Claims (21, 22, 23, 24, 25)
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26. For use with an imagery signal processor in which the responses of respective ones of a plurality of image receiving locations of an image receiving device, upon which light from an image source is incident, are sampled and coupled to an analog-to-digital converter for conversion into digital format, the value of a sampled signal input to said analog-to-digital converter being defined relative to a reference signal level, said reference signal level being associated with the response of one or more locations of said image receiving device which are effectively shielded from light from said image source, an apparatus for controlling said reference signal level comprising, in combination:
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first means for causing the times at which said analog-to-digital converter digitizes the sampled signal input for conversion into digital format to occur between times at which transitions in the sampling of the responses of said respective ones of a plurality of image receiving locations of said image receiving device occur; second means, coupled to said first means, for generating, at times at which said analog-to-digital converter digitizes the response of said one or more locations of said image receiving device which are effectively shielded from light from said image source, an output signal representative of the difference between the value of the output of said analog-to-digital converter and a prescribed level; and third means, coupled to said second means, for establishing said reference level in accordance with the difference representative output signal generated by said second means. - View Dependent Claims (27, 28, 29, 30)
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Specification