METHODS OF CALIBRATING KNEE-POINT AND LOGARITHMIC SLOPE IN LINEAR-LOGARITHMIC IMAGE SENSORS

摘要

Methods of performing two point calibration of a linear-logarithmic image sensor pixel include measuring voltages of a floating diffusion region of the pixel after establishing a plurality of unequal sub-threshold currents through a transfer transistor of the pixel. These sub-threshold currents operate to sequentially increase a voltage of the floating diffusion region to respective voltage levels that enable knee-point (KNPT) voltage and logarithmic sensitivity (LOGS) determination. The methods also include depleting a photodiode within the pixel by driving a cathode of the photodiode with a pull-up current in advance of establishing the sub-threshold currents. The method is photocurrent-independent.

主权项

1. A method of calibrating a linear-logarithmic image sensor pixel, comprising:
at least partially depleting a photodiode within the pixel; supplying a floating diffusion region within the pixel with a first subthreshold current by passing charge carriers from the at least partially depleted photodiode to the floating diffusion region; then reading a first voltage of the floating diffusion region; and determining a knee-point voltage associated with a transition from a linear to logarithmic response of the pixel from the first voltage.