Method and apparatus for optimizing exposure time in image acquisitions
First Claim
1. A method for optimizing an exposure time of an image sensor during an exposure of a target, the method comprising:
- a) obtaining a number of digital image signals from a corresponding number of pixels from said image sensor;
b) performing statistical analysis on luminance values derived from said number of digital image signals;
c) deriving one or more control parameters from the statistical analysis; and
d) using said one or more control parameters to alter the exposure time for said pixels in said image sensor during said exposure of a target;
wherein said exposure time comprises a number of preset time intervals and wherein said obtaining of a number of digital signals is accomplished by repeatedly sampling said number of digital signals at an end of one of said preset time intervals; and
wherein said using said control parameter to alter the exposure time comprises causing a last one of said preset time intervals to be reduced to avoid some of said digital signals reaching saturation.
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Abstract
A method of optimizing the exposure times of regions of pixels of an image sensor array during exposure is accomplished by utilizing time interval sampling of an image sensor array comprising of pixels configured to generate digital image signals. Luminance values are extracted from each digital image signal and analyzed to determine if a pixel has reached the optimal exposure. If a pixel has reached the optimal exposure, subsequent digital image signals from this pixel will not be recorded. This preserves the recording of the optimal digital image signal generated by the pixel at the time when the pixel reached its optimal exposure. This process of selectively terminating the recording of digital image signals based on optimal exposures of the pixels can be performed on individual pixels or can be performed on a region of pixels.
115 Citations
20 Claims
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1. A method for optimizing an exposure time of an image sensor during an exposure of a target, the method comprising:
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a) obtaining a number of digital image signals from a corresponding number of pixels from said image sensor;
b) performing statistical analysis on luminance values derived from said number of digital image signals;
c) deriving one or more control parameters from the statistical analysis; and
d) using said one or more control parameters to alter the exposure time for said pixels in said image sensor during said exposure of a target;
wherein said exposure time comprises a number of preset time intervals and wherein said obtaining of a number of digital signals is accomplished by repeatedly sampling said number of digital signals at an end of one of said preset time intervals; and
wherein said using said control parameter to alter the exposure time comprises causing a last one of said preset time intervals to be reduced to avoid some of said digital signals reaching saturation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An image sensor system with an optimized exposure time having an image sensor comprising:
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an array of pixel elements, each of said pixel elements having a saturation ceiling, said pixel elements producing digital signals when being exposed to a target;
a monitoring unit for sampling the digital signals at each of preset time intervals, wherein an exposure time includes a number of said preset time intervals; and
a control circuit in communication with said monitoring unit for terminating a recording of said digital signals from said pixel elements during an exposure in response to one or more control parameters derived by a statistical analysis from the sampled digital signals from said pixel elements, wherein each of said pixel elements includes a photodetector and an analog-to-digital circuit, said photodetector generating an analog signal when being exposed to a target, said analog-to-digital circuit converting said analog signal to said digital signal;
wherein said control circuit causes a last one of said preset time intervals to be reduced to avoid some of said photodetectors from being saturated based on said one or more control parameters. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification