Circuitry and methods for mitigating gradient effects in image sensors

Imaging circuitry comprising:

• a pixel array;
• and
• delay calibration circuitry including
• a row of dummy pixels,
• a calibration row driver configured to output a row control signal to the row of dummy pixels via a row line, and
• at least one sampling circuit coupled one or more dummy pixels in the row of dummy pixels and that is used to measure a propagation delay of the row control signal along the row line.

A method of operating an image sensor, comprising:

• generating a calibration row control signal;
• propagating the calibration row control signal down a row of dummy pixels;
• with one or more sampling circuits coupled to one or more tap points in the row of dummy pixels, monitoring when the calibration row control signal arrives at the one or more tap points as the calibration row control signal propagates down the row of dummy pixels;
• outputting signals from a pixel array separate from the row of dummy pixels;
• and
• controlling column readout circuitry that receives the signals from the pixel array using sampling signals that are progressively delayed based on count values output from the one or more sampling circuits.