Image signal processing apparatus, image signal processing method and camera using the image signal processing apparatus
First Claim
1. An image signal processing apparatus for applying processing to image signals from a solid state image sensor having a plurality of effective pixels and a plurality of light shielded pixels configured to output an optical black outputs, comprising:
- an optical black level determining portion configured to compare the optical black outputs from the light shielded pixels with a predetermined clamp level and outputting as difference outputs a difference between the optical black outputs and the predetermined clamp level;
a holding portion configured to hold the difference outputs;
an adding and subtracting circuit configured to clamp the image signals in accordance with the difference outputs;
a control unit configured to selectively transmit the difference outputs to the holding portion, wherein the control unit includes a comparator configured to compare the difference outputs of the light shielded pixels with a predetermined comparison level, and a counter portion configured to count the number of times that the difference outputs are larger than the predetermined comparison level,wherein when the number of times that the difference outputs are larger than the predetermined comparison level exceeds a predetermined number of comparison times, the control unit blocks further transmission of a difference output to the holding portion, andwherein an already-held difference output is output from the holding portion to the adding and subtracting circuit.
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Abstract
When clamping a signal from a solid state image sensor, float of an optical black pixel output due to incoming of infrared light avoids a malfunction of a clamp from occurring. When clamping a signal from the solid state image sensor, the difference between the optical black pixel output and a clamp target level is output as a difference output, the difference output is compared with a comparison level to integrate the number of times larger than the comparison level every horizontal line. When the number of times is equal to or more than a certain rate (⅔) from the number of optical black pixels on the horizontal line, an optical black float state is determined and clamping operation is performed in accordance with a held value immediately before.
26 Citations
11 Claims
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1. An image signal processing apparatus for applying processing to image signals from a solid state image sensor having a plurality of effective pixels and a plurality of light shielded pixels configured to output an optical black outputs, comprising:
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an optical black level determining portion configured to compare the optical black outputs from the light shielded pixels with a predetermined clamp level and outputting as difference outputs a difference between the optical black outputs and the predetermined clamp level; a holding portion configured to hold the difference outputs; an adding and subtracting circuit configured to clamp the image signals in accordance with the difference outputs; a control unit configured to selectively transmit the difference outputs to the holding portion, wherein the control unit includes a comparator configured to compare the difference outputs of the light shielded pixels with a predetermined comparison level, and a counter portion configured to count the number of times that the difference outputs are larger than the predetermined comparison level, wherein when the number of times that the difference outputs are larger than the predetermined comparison level exceeds a predetermined number of comparison times, the control unit blocks further transmission of a difference output to the holding portion, and wherein an already-held difference output is output from the holding portion to the adding and subtracting circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An image signal processing method for applying processing to image signals from a solid state image sensor having a plurality of effective pixels and a plurality of light shielded pixels, comprising:
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a step of comparing optical black outputs from the light shielded pixels with a set clamp level, and counting the number of times that difference outputs, comprising the difference between the optical black outputs and the set clamp level, are larger than a set comparison level; a step of outputting the difference outputs; a step of setting the clamp level clamping the image signals in accordance with the difference outputs; a step of holding the difference outputs; a step of comparing the difference outputs of the light shielded pixels with the set comparison level for every horizontal line of the light shielded pixels; and a step of blocking the holding of the difference outputs, and clamping the image signals by the already-held difference outputs on the horizontal lines, based on the result of the counting, when the number of times that the difference outputs are larger than the set comparison level exceeds a predetermined number of comparison times. - View Dependent Claims (10)
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11. An image signal processing method for applying processing to image signals from a solid state image sensor having a plurality of effective pixels and a plurality of light shielded pixels, comprising:
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a step of correcting the image signals based on optical black outputs from the light shielded pixels; a step of comparing the optical black outputs with a predetermined level; a step of counting a number of times at which the optical black outputs are greater than the predetermined level; and a step of blocking the usage of the optical black outputs when the number of times exceeds a predetermined threshold.
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Specification