Imaging structure including a pixel with multiple signal readout circuits and methods of operation for imaging structure
First Claim
1. A pixel circuit comprising:
- a photosensor for generating and accumulating charge during an integration period in response to incident light;
a first readout circuit operative at the end of said integration period for receiving charges accumulated by said photosensor during said integration period and for producing an output signal based on said accumulated charge; and
a second readout circuit operative at a time during said integration period to produce a readout signal representing charge accumulated by said photosensor up to said time.
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Accused Products
Abstract
A pixel cell allows both correlated double sampling (CDS) and automatic light control (ALC) operations through a non-destructive, parallel readout. An image sensor may include an array of pixel cells, some or all of which include a photosensor with two readout circuits attached; peripheral circuitry can sample charges generated from the photosensor through one readout circuit, then perform array readout through the other. One readout circuit connected to the photosensor provides a non-destructive readout of the generated charge. The other readout circuit can, for example, be a multiple-transistor circuit that transfers charge from the photosensor to a floating diffusion node for readout. The image sensor'"'"'s readout circuitry may thus monitor the light reaching the photosensor of the cell to determine when to read out signals from the entire array.
19 Citations
63 Claims
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1. A pixel circuit comprising:
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a photosensor for generating and accumulating charge during an integration period in response to incident light; a first readout circuit operative at the end of said integration period for receiving charges accumulated by said photosensor during said integration period and for producing an output signal based on said accumulated charge; and a second readout circuit operative at a time during said integration period to produce a readout signal representing charge accumulated by said photosensor up to said time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 51)
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12. A pixel cell comprising:
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a photo-conversion device for generating charge; a first readout circuit connected to said photo-conversion device for providing first readout signals indicating charge generated by said photo-conversion device; and a second readout circuit connected to said photo-conversion device for providing second readout signals indicating charge generated by said photoconversion device, wherein the charges indicated by said first and second readout signals are generated in response to substantially the same spectral wavelengths of light received by said photo-conversion device. - View Dependent Claims (52, 57)
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13. A pixel circuit comprising:
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a first readout circuit connected to a photosensor that provides readout signals representing charge at a storage node, said charge being generated by said photosensor, wherein said first readout circuit comprises; a reset transistor for resetting the charge at said storage node to a predetermined level; a source follower transistor having a gate connected to the storage node for producing a signal based on said charge at said storage node; and a row select transistor having a gate for selectively outputting said signal produced by the source follower transistor; and a second readout circuit connected to said photosensor for providing a light control signal. - View Dependent Claims (14, 23, 53)
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15. A pixel circuit comprising:
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a photosensor for generating charge during an integration period; a storage region for storing said generated charge; a first readout circuit connected to said photosensor for providing readout signals indicating charge generated by said photosensor and stored in said storage region, wherein said first readout circuit comprises; a reset transistor for resetting the charge at said storage region to a predetermined level; a transfer transistor for transferring said generated charge from said photosensor to said storage region; a source follower transistor having a gate connected to said storage region for producing a signal representing said charge stored at said storage region; and a row select transistor for selectively gating said signal produced by said source follower transistor; and a second readout circuit connected to said photosensor that provides second readout signals indicating charge generated by said photosensor, wherein the charges indicated by said first and second readout signals are generated in response to substantially the same spectral wavelengths of light received by said photosensor. - View Dependent Claims (16, 58)
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17. An array of pixel cells, comprising:
a plurality of pixel cells, wherein at least one pixel cell comprises; a photosensor for generating and accumulating charge during an integration period in response to incident light; a first readout circuit operative at the end of said integration period for receiving accumulated charges by said photosensor during said integration period and for producing an output signal based on said accumulated charge; and a second readout circuit operative at a time during said integration period to readout charge generated by said photosensor up to said time. - View Dependent Claims (54)
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18. An image sensor, comprising:
an array of pixel cells, wherein at least one pixel cell of said array comprises; a photosensor for generating and accumulating charge during an integration period in response to incident light; a first readout circuit operative at the end of said integration period for receiving accumulated charges by said photosensor during said integration period and for producing an output signal based on said accumulated charge; and a second readout circuit operative at a time during said integration period to readout charge generated by said photosensor up to said time. - View Dependent Claims (19, 55)
- 20. The image sensor of 18, wherein said first readout circuit comprises at least a source follower transistor for receiving accumulated charges at a gate thereof and for producing said output signal.
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24. An integrated circuit, comprising:
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an array of pixel cells on a substrate, wherein at least one pixel cell comprises; a photo-conversion device for generating and accumulating charge; a first readout circuit connected to said photo-conversion device for providing first readout signals representing charge generated by said photo-conversion device; and a second readout circuit connected to said photo-conversion device that provides second readout signals indicating instantaneous charge generated by said photo-conversion device; and signal processing circuitry formed on said substrate and electrically connected to the array for receiving and processing signals representing an image output by the array and for providing output data representing said image, wherein the charges indicated by said first and second readout signals are generated in response to substantially the same spectral wavelengths of light received by said photo-conversion device. - View Dependent Claims (25, 26, 27, 28, 56, 59)
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29. A processing system comprising:
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a processor; and an imaging device coupled to said processor, said imaging device having at least one pixel sensor cell comprising; a photo-conversion device for generating and accumulating charge; a first readout circuit, connected to said photo-conversion device, said first readout circuit for providing first readout signals representing charge generated by said photo-conversion device; and a second readout circuit connected to said photo-conversion device, for providing second readout signals representing charge generated by said photo-conversion device wherein the charges represented by said first and second readout signals are generated in response to substantially the same spectral wavelengths of light received by said photo-conversion device. - View Dependent Claims (30, 31, 60)
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32. An integrated circuit comprising:
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a substrate; an array of pixel cells formed on said substrate, wherein at least one of the pixel cells comprises;
a photo-conversion device for generating charge;
a storage area for receiving said charge generated by said photo-conversion device;
a first readout circuit that provides first readout signals representing said charge in said storage area; and
a second readout circuit that provides second readout signals representing charge generated by said photo-conversion device; andsignal processing circuitry formed in said substrate and electrically connected to the array for receiving and processing signals representing an image output by the array and for providing output data representing said images, wherein the charges represented by said first and second readout signals are generated in response to substantially the same spectral wavelengths of light received by said photo-conversion device. - View Dependent Claims (33, 34, 35, 61)
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36. A method for forming a pixel cell, the method comprising:
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forming a photosensor on a substrate, said photosensor capable of generating charge in response to light; forming a storage region near said photosensor for receiving said generated charge; forming a first readout circuit that provides first readout signals representing the generated charge stored in said storage region; and forming a second readout circuit that provides second readout signals representing the charge generated by the photosensor, wherein the charges represented by said first and second readout signals are generated in response to substantially the same spectral wavelengths of light received by said photosensor. - View Dependent Claims (37, 38, 39, 40, 41, 62)
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42. A method of operating a pixel cell, said pixel cell comprising a photosensor, a storage node, and first and second readout circuits, said method comprising:
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applying light to said photosensor; generating charge by said photosensor during an integration period in response to said applied light; receiving and outputting a signal representing said charge generated by said photo sensor up to the time of readout by said second readout circuit during said integration period; storing said generated charge at said storage node; and receiving and outputting a signal representing said stored charge through said first readout circuit at a time representing the end of said integration period. - View Dependent Claims (43, 44, 45)
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46. A method of operating an image sensor, the method comprising:
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applying an image to an array of pixel cells of said image sensor, each pixel cell of said array having a photosensor and a storage node; obtaining a first readout signal for each of a subset of the pixel cells in the array, the first readout signal indicating charge generated by said photosensor; comparing said first readout signal to a predetermined criterion; transferring charge from the photosensor to the storage node; and obtaining a second readout signal indicating the charge received by said storage node from the photosensor, wherein the charges indicated by said first and second readout signals are generated in response to substantially the same spectral wavelengths of light received by said photosensor. - View Dependent Claims (47, 48, 49, 50, 63)
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Specification