Camera system and associated method for removing reset noise and fixed offset noise from the output of an active pixel array
First Claim
1. A low noise operation method for a camera system having an image sensing active pixel array, the method comprising the steps of:
- (a) providing an optical shutter in front of an image sensing pixel array of a camera system, said image sensing pixel array having an image sensing face defined by a series of active pixels arranged in rows and columns;
(b) while said shutter is closed, resetting each said pixel and then reading a first output from each such pixel;
(c) opening said optical shutter for a predetermined exposure period so as to allow light to be incident upon said image sensing face of said pixel array;
(d) closing said optical shutter and then reading a second output from each said pixel, without resetting said pixels; and
(e) for each said pixel, subtracting one of said first and second outputs thereof from the other of said first and second outputs thereof, so as to obtain a first difference signal for each said pixel, which first difference signal is substantially free of reset and fixed offset noise components.
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Abstract
A low noise operation method for a camera system having an image sensing active pixel array, the method comprising the steps of: (a) providing an optical shutter in front of an image sensing pixel array of a camera system, said image sensing pixel array having an image sensing face defined by a series of active pixels arranged in rows and columns; (b) while said shutter is closed, resetting each said pixel and then reading a first output from each said pixel; (c) opening said optical shutter for a predetermined exposure period so as to allow light to be incident upon said image sensing face of said pixel array; (d) closing said optical shutter and then reading a second output from each said pixel, without resetting said pixels; and (e) subtracting one of said first and second outputs from the other of said first and second outputs for each said pixel, so as to obtain a first difference signal for each said pixel, which first difference signal is substantially free of reset and fixed offset noise components. The first and second pixel outputs are preferably subtracted on-the-fly. The method may also include additional steps for estimating dark current fixed pattern noise and producing a modified pixel output signal which is substantially free of reset noise, fixed offset noise and dark current fixed pattern noise.
130 Citations
20 Claims
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1. A low noise operation method for a camera system having an image sensing active pixel array, the method comprising the steps of:
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(a) providing an optical shutter in front of an image sensing pixel array of a camera system, said image sensing pixel array having an image sensing face defined by a series of active pixels arranged in rows and columns; (b) while said shutter is closed, resetting each said pixel and then reading a first output from each such pixel; (c) opening said optical shutter for a predetermined exposure period so as to allow light to be incident upon said image sensing face of said pixel array; (d) closing said optical shutter and then reading a second output from each said pixel, without resetting said pixels; and (e) for each said pixel, subtracting one of said first and second outputs thereof from the other of said first and second outputs thereof, so as to obtain a first difference signal for each said pixel, which first difference signal is substantially free of reset and fixed offset noise components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A camera system having:
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an image sensing active pixel array having an image sensing face defined by a series of active pixels arranged in rows and columns, pixel read and reset means in electronic communication with each said pixel, for reading and for resetting said pixels, and a signal output at which signals read from said pixels are output; an optical shutter positioned in front of said image sensing pixel array so as to control the amount of light incident on said image sensing face; system control means formed and arranged for controlling opening and closing of said optical shutter and for controlling reading and resetting of said pixels, so as to obtain first and second outputs from each said pixel, said second output representing an image signal including reset and fixed offset noise components and said first output representing the sum of said reset and fixed offset noise components; an image frame store in electronic communication with said signal output of said image sensing pixel array and having memory means for storing, at least temporarily, said first outputs from said pixels; and arithmetic circuit means electronically connected between said image frame store and said signal output of said image sensing pixel array, for subtracting, for each said pixel, one of said first and second outputs thereof from the other of said first and second outputs thereof, so as to obtain a modified image signal for each said pixel, which modified image signal is substantially free of reset and fixed offset noise components. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification