Abstract: An image sensor may have an array of pixels and readout circuitry. The array may include image pixels that generate signals in response to image light and reference pixels that generate signals in response to electrical noise. The readout circuitry may obtain first pixel values from the image pixels and may obtain second pixel values from the reference pixels. The readout circuitry may generate an extended precision pixel value based on the second pixel values that have an extended bit width relative to the each of the second pixel values. The readout circuitry may generate multiple dithered correction values by adding randomized sequences of least significant bits to the extended precision pixel value. The readout circuitry may mitigate visible quantization error and noise such as row-correlated and column-correlated noise in the final image by subtracting the dithered correction values from corresponding first pixel values.

Abstract: A method for removing background signal values from readout signal values generated by image pixels in a pixel array may include generating background signal values using optically black pixels formed around a border of the pixel array. The background signal values may be separated into blocks. Block average values may be calculated based on the background signal values included in each of the blocks. Corner regions of the pixel array may be free of image pixels and optically black pixels. Corner background signal values may be extrapolated based on the block average values. Image pixel background signal values may be interpolated based on the block average values and the corner background signal values. The image pixel background signal values may be subtracted from the readout values.

Abstract: A method for removing background signal values from readout signal values generated by image pixels in a pixel array may include generating background signal values using optically black pixels formed around a border of the pixel array. The background signal values may be separated into blocks. Block average values may be calculated based on the background signal values included in each of the blocks. Corner regions of the pixel array may be free of image pixels and optically black pixels. Corner background signal values may be extrapolated based on the block average values. Image pixel background signal values may be interpolated based on the block average values and the corner background signal values. The image pixel background signal values may be subtracted from the readout values.

Abstract: An image sensor may have an array of pixels and readout circuitry. The array may include image pixels that generate signals in response to image light and reference pixels that generate signals in response to electrical noise. The readout circuitry may obtain first pixel values from the image pixels and may obtain second pixel values from the reference pixels. The readout circuitry may generate an extended precision pixel value based on the second pixel values that have an extended bit width relative to the each of the second pixel values. The readout circuitry may generate multiple dithered correction values by adding randomized sequences of least significant bits to the extended precision pixel value. The readout circuitry may mitigate visible quantization error and noise such as row-correlated and column-correlated noise in the final image by subtracting the dithered correction values from corresponding first pixel values.