CMOS image sensor with noise cancellation
First Claim
1. An image sensor, comprising:
- a photodetector;
an output transistor having a gate coupled to receive a signal from said photodetector;
a reset transistor having a drain terminal coupled to reset said photodetector;
a sample circuit coupled to receive an output signal from said output transistor; and
a control circuit having a configuration to switch said reset transistor to a triode region such that said output transistor provides a sampled first reference output signal and to subsequently switch said reset transistor to an OFF state such that said output transistor provides a sampled reset output signal that has a voltage different from a voltage of said sampled first reference output signal and a configuration to switch said sample circuit to sample and store said sampled first reference output signal when said reset transistor is in said triode region and to sample and store said sampled reset output signal when said reset transistor is in said OFF state.
1 Assignment
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Accused Products
Abstract
An image sensor that has one or more pixels within a pixel array. The pixel array may be coupled to a control circuit and one or more subtraction circuits. The control circuit may cause each pixel to provide a first reference output signal and a reset output signal. The control circuit may then cause each pixel to provide a light response output signal and a second reference output signal. The light response output signal corresponds to the image that is to be captured by the sensor. The subtraction circuit may provide a difference between the reset output signal and the first reference output signal to create a noise signal that is stored in memory. The subtraction circuit may also provide a difference between the second reference output signal and the light response output signal to create a normalized light response output signal. The noise signal may then be subtracted from the normalized light response output signal to generate the output data of the sensor. The second reference output signal is the same as the first reference output signal so that the process in essence subtracts the reset noise from the light response signal.
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Citations
29 Claims
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1. An image sensor, comprising:
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a photodetector; an output transistor having a gate coupled to receive a signal from said photodetector; a reset transistor having a drain terminal coupled to reset said photodetector; a sample circuit coupled to receive an output signal from said output transistor; and a control circuit having a configuration to switch said reset transistor to a triode region such that said output transistor provides a sampled first reference output signal and to subsequently switch said reset transistor to an OFF state such that said output transistor provides a sampled reset output signal that has a voltage different from a voltage of said sampled first reference output signal and a configuration to switch said sample circuit to sample and store said sampled first reference output signal when said reset transistor is in said triode region and to sample and store said sampled reset output signal when said reset transistor is in said OFF state. - View Dependent Claims (2, 3, 4, 5)
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6. An image sensor, comprising:
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a photodetector; a reset transistor having a drain terminal coupled to reset said photodetector; an output transistor having a gate coupled to receive a signal from said photodetector; a sample circuit coupled to receive an output signal from said output transistor; and control means for switching said reset transistor into triode region so that said output transistor provides a sampled first reference output signal, for switching said reset transistor into an OFF state so that said output transistor provides a sampled reset output signal that has a voltage different from a voltage of said sampled first reference output signal and for directing said sample circuit to sample and store said sampled first reference output signal when said reset transistor is in said triode region and to sample and store said sampled reset output signal when said reset transistor is in said OFF state. - View Dependent Claims (7, 8, 9, 10)
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11. A method for generating signals from a pixel of an image sensor, the pixel having a reset transistor and an output transistor having a gate coupled to receive a signal from a photodetector, the reset transistor having a source terminal connected to receive a signal from an IN line and a drain terminal coupled to reset the photodetector, the output transistor being coupled to provide a signal to an OUT line, comprising:
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switching the reset transistor into a triode region, providing a reference signal on the IN line so that an output reference signal is provided on the OUT line; sampling said output reference signal while the reset transistor is in the triode region; switching the reset transistor to an OFF state; sampling a reset output signal provided on the OUT line while the reset transistor is in the OFF state, the reset output signal having a voltage different from a voltage of the output reference signal. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. An image sensor, comprising:
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a photodetector; a reset transistor having a drain terminal coupled to reset said photodetector; an output transistor having a gate coupled to receive a signal from said drain terminal of said reset transistor, said output transistor configured to output a sampled first reference output signal when said reset transistor is in a triode region and a sampled reset output signal when said reset transistor is in an OFF state; and a sample circuit configured to sample and store said sampled first reference output signal when said reset transistor is in said triode region and to sample and store said sampled reset output signal when said reset transistor is in said OFF state. - View Dependent Claims (19, 20, 21, 22, 23)
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24. An image sensor, comprising:
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a photodetector; a reset transistor having a drain terminal coupled to reset said photodetector; an output transistor having a gate coupled to receive a signal from said drain terminal of said reset transistor, said output transistor outputting a sampled first reference output signal when said reset transistor is in a triode region and a sampled reset output signal when said reset transistor is in an OFF state; and a sample circuit that samples and stores said sampled first reference output signal when said reset transistor is in said triode region and that samples and stores said sampled reset output signal when said reset transistor is in said OFF state. - View Dependent Claims (25, 26, 27, 28, 29)
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Specification