Method and system to enhance differential dynamic range and signal/noise in CMOS range finding systems using differential sensors
First Claim
1. A method to increase effective differential dynamic range of a differential pixel responsive to optical energy, a detection response V(t) of said differential pixel having a common mode component and a differential component, the method including:
- (a) adding at least one compensating offset to avoid a saturation magnitude differential signal level; and
(b) recording effective sum of compensating offsets added to avoid said saturation magnitude;
wherein effective value of said differential signal V(t) is proportional to VOUT ±
K·
(effective sum of said compensating offsets), where K is a constant.
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Abstract
Dynamic range of a differential pixel is enhanced by injecting, synchronously or asynchronously, a compensating offset (ΔCOMP) into a differential signal capacitor whenever magnitude of the differential signal across the capacitor exceeds a predetermined value. Positive and negative magnitudes of ΔCOMP need not be equal. The number (N) of ΔCOMP offsets made is counted. Effective differential signal capacitor voltage V(t)=Vo±N·ΔCOMP, where Vo is capacitor voltage. In other embodiments magnitude of ΔCOMP in a sequence of compensations can differ, and the sum total of compensations in recorded. Differential pixel signal/noise ratio is increased by dynamically maximizing operational amplifier gain AG for each differential pixel.
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Citations
20 Claims
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1. A method to increase effective differential dynamic range of a differential pixel responsive to optical energy, a detection response V(t) of said differential pixel having a common mode component and a differential component, the method including:
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(a) adding at least one compensating offset to avoid a saturation magnitude differential signal level; and (b) recording effective sum of compensating offsets added to avoid said saturation magnitude; wherein effective value of said differential signal V(t) is proportional to VOUT ±
K·
(effective sum of said compensating offsets), where K is a constant. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. For use with a differential pixel responsive to optical energy, a detection response of said differential pixel having a common mode component and a differential component, differential dynamic range enhancing circuitry to enhance effective dynamic range of said differential pixel, said differential dynamic range enhancing circuitry comprising:
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compensation circuitry adding a compensating offset to avoid a saturation magnitude differential signal level; and means for recording effective sum of said compensating offsets added to avoid said saturation magnitude; wherein effective value of said differential signal V(t) is proportional to V(OUT) ±
K·
(effective sum of said compensating offsets), where K is a constant. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method to reduce effective noise in the pixel signal readout path of an array of differential pixels, the method including:
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(a) providing active gain for said differential pixels; (b) individually varying said active gain for at least one of said differential pixels to determine a maximum allowable gain for said differential pixel; (c) recording maximum allowable active gain determined for said differential pixel at step (b) and also recording a signal value for said differential pixel at said maximum allowable active gain; and (d) operating said differential pixel at said maximum allowable active gain recorded at step (c); wherein effect of noise in components downstream of said pixel is reduced and signal/noise ratio is enhanced. - View Dependent Claims (18)
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19. For use with a differential pixel responsive to optical energy, said differential pixel having a detection response with a common mode component and a differential component, signal/noise enhancement circuitry to reduce effective noise in the pixel signal readout path of an array of said differential pixels, the signal/noise enhancement circuitry including:
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a gain programmable amplifier providing active gain for said differential pixel; means coupled to each said gain programmable amplifier for individually varying active gain for said differential pixel to determine a maximum allowable active gain for said differential pixel; for each said differential pixel, means for recording maximum allowable active gain for each of said differential pixels and for recording a signal value for each said differential pixel at said maximum allowable gain; and operating said differential pixel at said maximum allowable active gain; wherein effect of noise in components downstream of said differential pixels is reduced and signal/noise ratio is enhanced. - View Dependent Claims (20)
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Specification