Single-exposure high dynamic range CMOS image sensor pixel with internal charge amplifier

摘要

A single-exposure high dynamic range (HDR) image sensor utilizes a charge amplifier having two different charge-to-voltage conversion capacitors that read a single photodiode charge during a two-phase readout operation. The first capacitor has a lower capacitance and therefore higher conversion gain (sensitivity), and the second capacitor has a higher capacitance and therefore lower conversion gain (sensitivity). The two-phase readout operation samples the photodiode charge twice, once using the high sensitivity capacitor and once using the low sensitivity capacitor. The high sensitivity readout phase provides detailed low light condition data but is saturated under brighter light conditions, and the low sensitivity readout phase provides weak data under low light conditions but provides high quality image data under brighter light conditions. The final HDR image is created by combining both high and low sensitivity images into a single image while giving each of them the correct weighted value.

主权项

1. A CMOS image sensor comprising:
at least one current source for generating a predetermined signal current on a signal line; and a first pixel including: a photodiode connected between a first voltage source and a first node; and a select transistor connected between the signal line and a second node; a charge amplifier coupled between the first node and the second node, the charge amplifier including:
a first capacitor coupled between the first and second nodes;a second capacitor having a first terminal connected to the second node; anda mode control transistor connected between the first node and the second capacitor; and means for controlling the mode control transistor such that:
during a first readout phase, the second capacitor is de-coupled from the first node and a photodiode charge generated by the photodiode during an integration period preceding the first readout phase is stored on the first capacitor, andduring a second readout phase, the second capacitor is coupled to the first node such that at least a portion of the photodiode charge is stored on the second capacitor.