CMOS active pixel sensor with a sample and hold circuit having multiple injection capacitors and a fully differential charge mode linear synthesizer with skew control
First Claim
1. A method for processing a pixel in a CMOS active pixel sensor, comprising:
- reading an analog pixel signal from the pixel;
reading a digital correction value associated with said pixel;
producing an analog correction signal based upon said digital correction value;
summing said analog pixel signal and said analog correction signal to produce a corrected analog signal; and
converting said corrected analog signal into a digital signal.
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Accused Products
Abstract
An CMOS active pixel sensor (APS) imaging system include circuitry to compensate for different analog offset levels from the CMOS pixel array. More specifically, the compensation is performed in the analog (charge) domain. A digital correction value, which may be measured as part of the operation or testing of the CMOS APS system, is provided to a offset correction block circuit, to generate an analog electrical signal. The analog electrical signal is supplied to a sample-and-hold circuit including a charge amplifier. The signal read from the pixel array, after conditioning through an analog signal chain, is also supplied to the charge amplifier, which has a linear transfer function and outputs the compensated signal.
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Citations
41 Claims
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1. A method for processing a pixel in a CMOS active pixel sensor, comprising:
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reading an analog pixel signal from the pixel;
reading a digital correction value associated with said pixel;
producing an analog correction signal based upon said digital correction value;
summing said analog pixel signal and said analog correction signal to produce a corrected analog signal; and
converting said corrected analog signal into a digital signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for compensating for an unwanted offset voltage from a pixel in an CMOS active pixel sensor array, comprising:
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reading a pixel signal from the pixel;
conditioning the pixel signal into a conditioned pixel signal;
charging a first capacitor coupled to a first input of a charge amplifier with said conditioned pixel signal to produce a first charge;
reading a correction value for the pixel;
generating an analog correction signal based on the correction value;
charging a second capacitor coupled to a second input of the charge amplifier with said analog correction signal to produce a second charge;
amplifying said first and second charge to produce an output signal;
wherein said output signal is a function of said first charge and said second charge. - View Dependent Claims (9, 10, 11, 12, 13)
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14. An apparatus for processing a pixel in a CMOS active pixel sensor, comprising:
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a first circuit for producing an analog correction signal;
a summing circuit, coupled to said first circuit, for receiving and summing an analog pixel signal with the analog correction signal to produce a corrected analog signal; and
a digital to analog converter for converting said corrected analog signal into a digital word. - View Dependent Claims (15, 16, 17)
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18. An apparatus for correcting for an unwanted offset voltage from a pixel in an CMOS active pixel sensor array, comprising:
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an offset correction block for receiving a digital correctional value and outputting an analog correction signal; and
a sample-and-hold circuit, said sample-and-hold circuit further comprising a charge amplifier having a first input coupled to a first set of capacitors charged by an electrical signal produced by said pixel and a second input coupled to a second set of capacitors charged by the analog correction signal, and outputting a compensated signal as a linear function of the charge on said first and second sets of capacitors. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. An imaging system for processing a pixel in a CMOS active pixel sensor, comprising:
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a lens, for focusing at least a portion of an image upon said CMOS active pixel sensor;
a controller, for supplying a digital correction value;
a first circuit for producing an analog correction signal proportional said digital correction value;
an amplifier, coupled to said first circuit, for receiving and summing an analog pixel signal with the analog correction signal to produce a corrected analog signal;
a digital to analog converter for converting said corrected analog signal into a digital signal; and
a memory, coupled to said digital to analog converter, for storing said digital signal. - View Dependent Claims (30, 31)
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32. An imaging system, comprising:
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a lens;
a CMOS pixel array, said CMOS pixel array further comprising a plurality of pixels;
a controller, for supplying digital correction value corresponding to each of said plurality of pixels;
a digital-to-analog converter, for converting an electrical signal output by one of said plurality of pixels into a digital signal;
a storage device for storing said digital signal; and
a circuit for correcting for an unwanted offset voltage in said pixel, said circuit for correcting further comprising, an offset correction circuit, coupled to said controller and receiving said digital correctional value and outputting an analog correction signal; and
a sample-and-hold circuit, said sample-and-hold circuit further comprising a charge amplifier having a first input coupled to a first set of capacitors charged by an electrical signal produced by said pixel and a second input coupled to a second set of capacitors charged by the analog correction signal, and outputting a compensated signal as a linear function of the charge on said first and second sets of capacitors. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41)
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Specification