Precise mos imager transfer function control for expanded dynamic range imaging

Abstract

There is provided an imaging system including a MOS pixel array having a number, r, of rows of pixels. Each pixel of the array includes a light detecting element, a reset node connected to the light detecting element for controlling dissipation of photogenerated charge produced by the light detecting element, and a sense node connected to the light detecting element for measuring photogenerated charge produced by the light detecting element. A charge control voltage generation circuit is provided, having a topology for producing a plurality of charge control voltages selected to control dissipation of photogenerated charge produced by the light detecting element, in accordance with a corresponding pixel transfer function. A switch circuit is connected to the voltage generation circuit and to the pixel array to apply voltages produced by the charge control voltage generation circuit to reset nodes of pixels. The application by the switch circuit of each of the charge control voltages to a row of pixel reset nodes is characterized by a voltage application settling time, t , that is less than about 1/Nrf, where N is an integer and f is imager frame rate. This provides the ability to implement a desired transfer function, to expand imager dynamic range, in a manner that is immune to capacitances of the imager, by causing the voltage spikes, or glitches, associated with imager row capacitance, to decay substantially completely during the time over which an imager pixel row is accessed to apply a control voltage.