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US 8,013,911 B2Granted
Method for mixing high-gain and low-gain signal for wide dynamic range image sensor
AssigneeTexas Instruments Incorporated
InventorsEmi Arai, Yuji Itoh
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Abstract
A wide dynamic range image sensor method combines the response of high-gain sensing cells and low-gain sensing cells with better linearity than the prior art. A search is made in successive central regions within the response curve of the high-gain and low-gain cells to find a highest slope linear fit. This highest slope and the corresponding offset are used in mixing the high-gain and low-gain responses to achieve a wide dynamic range.
Claims13
A method of mixing high-gain and low-gain signals for a wide dynamic range image sensor comprising the steps of:
- sensing a scene with a combined array of concurrent high-gain sensing cells and low-gain sensing cells;
- plotting a response curve of high-gain sensing cells against the response of low-gain sensing cells for each light level;
- for a plurality of subsets of the plot
- calculating a slope of the response curve and an offset between the high-gain response and the low-gain response,
- comparing the current calculated slope with a maximum previously observed calculated slope,
- if the current calculated slope is greater than the previously observed calculated slope, saving the current calculate slope as the maximum previously calculated slope and a corresponding calculated offset, and
- repeating for all of the plurality of subsets;
- and
- mixing the high-gain response and the low-gain response according to the saved maximum previously calculated slope and the corresponding calculated offset.
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