Systems and methods for mitigating image sensor pixel value clipping
View Patent ↗An imaging system may include image sensor pixels, converter circuitry, denoising circuitry, dark current subtraction circuitry, and storage and processing circuitry. The image sensor pixels may generate analog image signals and the converter circuitry may convert the analog image signals into digital pixel values. The denoising circuitry may generate denoised pixel values based on the digital pixel values. The dark current subtraction circuitry may subtract a dark current value from the denoised pixel values. The image sensor pixels and converter circuitry may generate pixel values in multiple color channels. The image sensor pixels may include clear color filter elements for generating clear pixel values. The storage and processing circuitry may determine different black pedestal values for each color channel and may add the black pedestal values to the pixel values from the corresponding color channel to mitigate pixel value clipping in a final image generated by the imaging system.
1. A method for operating an imaging system comprising processing circuitry and an image sensor having an array of image pixels, the method comprising:
capturing, by the image sensor, first pixel values of a first color in response to image light;
capturing, by the image sensor, second pixel values of a second color that is different from the first color in response to the image light;
with the processing circuitry, determining a first black pedestal value based on the first pixel values;
with the processing circuitry, determining a second black pedestal value based on the second pixel values, wherein the second black pedestal value is different from the first black pedestal value;
with the processing circuitry, adding the first black pedestal value to the first pixel values to generate first corrected pixel values;
with the processing circuitry, adding the second black pedestal value to the second pixel values to generate second corrected pixel values, wherein the first and second corrected pixel values are substantially free from clipping; and
generating, by the processing circuitry, an output image based on the generated first and second corrected pixel values.
2. The method defined in claim 1 , wherein the first pixel values comprise clear pixel values and wherein determining the first black pedestal value comprises:
determining the first black pedestal value based on the clear pixel values.
3. The method defined in claim 2 further comprising:
capturing, by the image sensor, blue pixel values in response to the image light; and
with the processing circuitry, determining a third black pedestal value based on the blue pixel values, wherein the third black pedestal value is different from the first and second black pedestal values.
4. The method defined in claim 3 , further comprising:
with the processing circuitry, adding the third black pedestal value to the blue pixel values to generate third corrected pixel values; and
generating, by the processing circuitry, the output image based on the generated first, second, and third corrected pixel values.
5. The method defined in claim 2 , wherein adding the first black pedestal value to the first pixel values comprises:
adding the first black pedestal value to the clear pixel values.
6. The method defined in claim 5 , wherein determining the first black pedestal value based on the clear pixel values comprises:
generating a set of pixel value statistics based on the clear pixel values; and
determining the first black pedestal value based on the set of pixel value statistics.
7. The method defined in claim 6 , wherein generating the set of pixel value statistics comprises:
generating a clear pixel value histogram based on the clear pixel values; and
generating the set of pixel value statistics based on the clear pixel value histogram.
8. The method defined in claim 6 , wherein determining the second black pedestal value based on the second pixel values comprises:
generating an additional set of pixel value statistics based on the second pixel values; and
determining the second black pedestal value based on the additional set of pixel value statistics.
9. The method defined in claim 5 , wherein determining the first black pedestal value comprises:
identifying a light level associated with the clear pixel values; and
determining the first black pedestal value based on the identified light level.
10. The method defined in claim 5 , wherein determining the first black pedestal value comprises:
identifying a signal to noise ratio value associated with the clear pixel values; and
determining the first black pedestal value based on the signal to noise ratio value.
11. The method defined in claim 1 further comprising:
capturing, by the image sensor, third pixel values of a third color in response to the image light, wherein the third color is different from the first and second colors;
with the processing circuitry, determining a third black pedestal value based on the third pixel values, wherein the third black pedestal value is different from the first and second black pedestal values; and
with the processing circuitry, adding the third black pedestal value to the third pixel values to generate third corrected pixel values.
12. The method defined in claim 1 , wherein the first pixel values comprise red pixel values.
13. The method defined in claim 12 , wherein the second pixel values comprise blue pixel values.
14. The method defined in claim 12 , wherein the second pixel values comprise clear pixel values.
15. The method defined in claim 1 , wherein determining the first black pedestal value comprises:
identifying a signal to noise ratio value associated with the first pixel values; and
determining the first black pedestal value based on the signal to noise ratio value.
16. The method defined in claim 15 , wherein the first pixel values comprise yellow pixel values and wherein determining the first black pedestal value comprises:
identifying a signal to noise ratio value associated with the yellow pixel values; and
determining the first black pedestal value based on the signal to noise ratio value associated with the yellow pixel values.
17. The method defined in claim 1 , wherein determining the first black pedestal value comprises:
identifying a mean value associated with the first pixel values; and
determining the first black pedestal value based on the mean value.
18. The method defined in claim 11 , further comprising:
generating, by the processing circuitry, the output image based on the generated first, second, and third corrected pixel values.
19. The method defined in claim 18 , wherein the third pixel values comprise yellow pixels captured in response to yellow light.
20. The method defined in claim 19 , wherein the first pixel values comprise blue pixel values generated in response to blue light and the second pixel values comprise red pixel values generated in response to red light.