Real-time exposure control for automatic light control
First Claim
Patent Images
1. A method of automatic exposure control for an imager comprising an array of pixels, the method comprising the acts of:
- setting a reference pixel signal level;
starting an exposure period;
obtaining pixel signals from a subset of pixels in the array;
comparing a value of each pixel signal to the reference pixel signal level;
determining if a predetermined number of pixels have a pixel signal value greater than the reference pixel signal level;
comparing a current exposure time to a maximum exposure time; and
based on the exposure time comparison and a result of the determining, adjusting at least one exposure control parameter of the imager,wherein the reference pixel signal level is initially set to be equal to a value of a full scale signal divided by a maximum gain value.
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Abstract
An imager and a method for real-time, non-destructive monitoring of light incident on imager pixels during their exposure to light. Real-time or present pixel signals, which are indicative of present illumination on the pixels, are compared to a reference signal during the exposure. Adjustments, if necessary, are made to programmable parameters such as gain and/or exposure time to automatically control the imager'"'"'s exposure to the light. In a preferred exemplary embodiment, only a selected number of pixels are monitored for exposure control as opposed to monitoring the entire pixel array.
148 Citations
15 Claims
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1. A method of automatic exposure control for an imager comprising an array of pixels, the method comprising the acts of:
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setting a reference pixel signal level; starting an exposure period; obtaining pixel signals from a subset of pixels in the array; comparing a value of each pixel signal to the reference pixel signal level; determining if a predetermined number of pixels have a pixel signal value greater than the reference pixel signal level; comparing a current exposure time to a maximum exposure time; and based on the exposure time comparison and a result of the determining, adjusting at least one exposure control parameter of the imager, wherein the reference pixel signal level is initially set to be equal to a value of a full scale signal divided by a maximum gain value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of automatic exposure control for an imager comprising an array of pixels, the method comprising the acts of:
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setting a reference pixel signal level; starting an exposure period; obtaining pixel signals from a subset of pixels in the array; comparing a value of each pixel signal to the reference pixel signal level, determining if a predetermined number of pixels have a pixel signal value greater than the reference pixel signal level; comparing a current exposure time to a maximum exposure time; and based on the exposure time comparison and a result of the determining, adjusting at least one exposure control parameter of the imager, wherein, if it is determined that the predetermined number of pixels have a pixel signal value greater than the reference signal value level and the current exposure time is less than the maximum exposure time, the adjusting act comprises setting a readout gain of the imager to a minimum gain value and setting the reference pixel signal value to a value of a full scale signal.
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14. A method of automatic exposure control for an imager comprising an array of pixels, the method comprising the acts of:
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setting a reference pixel signal level; starting an exposure period; obtaining pixel signals from a subset of pixels in the array; comparing a value of each pixel signal to the reference pixel signal level; determining if a predetermined number of pixels have a pixel signal value greater than the reference pixel signal level; comparing a current exposure time to a maximum exposure time; and based on the exposure time comparison and a result of the determining, adjusting at least one exposure control parameter of the imager, wherein, if it is determined that a predetermined number of pixels have a pixel signal value greater than the reference pixel signal level and the current exposure time is within a predetermined time interval, the adjusting act comprises setting a readout gain to a gain value between a maximum gain value and a minimum gain value and setting the reference pixel signal level to a value of a full scale signal divided by the readout gain value set to be between the maximum gain and the minimum gain value. - View Dependent Claims (15)
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Specification