Apparatus and method for eliminating artifacts in active pixel sensor (APS) imagers
First Claim
Patent Images
1. An imaging device comprising:
- a pixel comprising a photo detector; and
a readout circuit coupled to said pixel, said readout circuit providing a first pixel signal representing a reset voltage of said pixel and a second pixel signal representing light incident voltage produced from said photo detector;
a circuit for producing a pixel output voltage from said first and second pixel voltage signals;
a detecting circuit for determining when said pixel is in at least a near saturated condition; and
a circuit responsive to said detecting circuit for substituting a different pixel output voltage for a produced pixel output voltage when said at least near saturated condition is detected.
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Abstract
An active pixel sensor (APS) that includes circuitry to eliminate artifacts in digital images. The APS includes a comparator for comparing a signal level from a pixel to an adjusted saturation voltage to determine if the pixel is saturated. If the pixel is saturated, the signal output from the pixel is replaced with an analog voltage having a maximum value corresponding to a brightest pixel in the image.
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Citations
54 Claims
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1. An imaging device comprising:
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a pixel comprising a photo detector; and a readout circuit coupled to said pixel, said readout circuit providing a first pixel signal representing a reset voltage of said pixel and a second pixel signal representing light incident voltage produced from said photo detector; a circuit for producing a pixel output voltage from said first and second pixel voltage signals; a detecting circuit for determining when said pixel is in at least a near saturated condition; and a circuit responsive to said detecting circuit for substituting a different pixel output voltage for a produced pixel output voltage when said at least near saturated condition is detected. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An imaging device comprising:
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a pixel comprising a photo detector; and a readout circuit coupled to said photo detector, said readout circuit providing a first pixel signal representing a reset voltage of said pixel and a second pixel signal representing light incident voltage produced from said photo detector; a circuit for producing a pixel output signal voltage from said first and second pixel voltage signals; a circuit responsive to a signal produced by said pixel for detecting at least a near saturated pixel condition; and a circuit responsive to said detecting circuit for changing said pixel output voltage when said at least near saturated condition is detected.
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8. An active pixel sensor comprising:
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a pixel comprising a photo detector and readout circuit for providing respective output signals representing a pixel voltage reset and a pixel detected light voltage; a circuit for producing a pixel output voltage based on said reset voltage and detected light voltage; a detecting circuit for determining when said pixel is in an at least near saturated condition; and a circuit for substituting a predetermined output signal voltage for said pixel output signal voltage when said at least near saturated condition is detected.
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9. An active pixel sensor, comprising:
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a pixel comprising a photodiode to receive light, the pixel to provide a pixel value; a first circuit to compare the pixel value to a reference signal to determine if the photodiode of the pixel is at least nearly saturated by the light; and a second circuit to provide a first signal, associated with the pixel, if the first circuit indicates that the pixel value is above the reference signal, and to provide a second signal, associated with a constant value which is independent of saturation of the photodiode by the light, if the first circuit indicates that the pixel value is below the reference signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An active pixel sensor comprising:
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a pixel for providing a pixel voltage on a column output line; a first circuit coupled to the column output line for comparing the pixel voltage on the column output line to a reference voltage to determine if the pixel is at least near a saturated condition; an output circuit coupled to the column output line for providing an output signal representing the amount of light detected by the pixel when the pixel is not at least near a saturated condition; and a circuit coupled to the first circuit for substituting a constant voltage for the output signal when the pixel is at least near a saturated condition.
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20. An active pixel sensor, comprising:
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a pixel comprising a photodiode to receive light, the pixel to provide a pixel value; a comparator to compare the pixel value to a reference signal to determine if the photodiode of the pixel is at least nearly saturated by the light; a multiplexer to provide a first signal associated with the pixel, if the comparator indicates that the pixel value is above the reference signal, and to provide a second signal, corresponding to a predetermined value which is independent of photodiode received light, if the first circuit indicates that the pixel value is below the reference signal. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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29. A method comprising:
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receiving light at a photodiode of a pixel in an active pixel sensor; providing a pixel voltage value to a column output line from the pixel; and replacing a first signal, corresponding to a pixel value, with a predetermined signal that is substantially independent of a measurement of received light if the photodiode is at least nearly saturated by light to generate a pixel voltage value corresponding to a predetermined brightness state. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36)
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37. A method comprising:
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generating a pixel value from an imaging pixel; comparing the pixel value to a reference signal to determine if said pixel is in at least a nearly saturated state; providing a first pixel output signal if the pixel value is above the reference signal and providing a second pixel output signal corresponding to a constant value which is independent of pixel received light if the pixel value is below the reference signal. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44, 45, 46)
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47. A method comprising:
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providing a pixel voltage on a column line; comparing the pixel voltage provided on the column line to a reference voltage to determine if the pixel is near or at a saturated condition; providing an output signal representing the amount of light detected by the pixel when said pixel is not at least near saturation; providing a predetermined constant value pixel output signal when the pixel is at least near saturation.
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48. A method comprising:
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generating a pixel value from an imaging pixel; comparing the pixel value to a reference signal to determine if a photodiode of the pixel is at least nearly saturated by light; providing a first signal associated with the pixel if the pixel value is above the reference signal; providing a second signal corresponding to a predetermined value which is independent of photodiode received light, if the pixel value is below the reference signal. - View Dependent Claims (49, 50, 51, 52, 53, 54)
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Specification