Dual conversion gain image sensor

Abstract

The invention provides a dual conversion gain image sensor comprising: a pixel circuit through which noise of a pixel power supply voltage is transmitted to a bit line; a power supply noise elimination circuit, wherein the voltage of the input end of the power supply noise elimination circuit is pixel power supply voltage, the power supply noise elimination circuit simulates and generates a first transfer function through a low conversion gain path, and the power supply noise elimination circuit simulates and generates a second transfer function through a high conversion gain path; and a comparator. Through two independent power supply noise elimination paths, namely a low conversion gain (lcg) path and a high conversion gain (hcg) path, the pixel power supply voltage change can be tracked by different transfer functions in an lcg mode and an hcg mode, and the power supply noise influence of the low conversion gain mode and the high conversion gain mode is weakened respectively; and noise elimination of the lcg mode and the hcg mode does not interfere with each other, so that the influence of power supply noise is reduced, and the image quality is improved.

Description

technical field [0001] The invention belongs to the technical field of image sensors, and in particular relates to a double conversion gain image sensor. Background technique [0002] Image sensors are widely used in digital still cameras, cellular phones, security cameras, and also in medical, automotive, and other applications. [0003] The DCG (Dual Conversion Gain, dual conversion gain) image sensor adopts the DCG mode to obtain high dynamic range images. A high dynamic range image can be obtained by reading from a pixel at lcg (low conversion gain), then at hcg (high conversion gain), and then combining the two readouts to render a high dynamic range image . The lcg output value of the pixel can be used in bright light conditions, and the hcg output value of the pixel can be used in low light conditions, thus obtaining high dynamic range. [0004] The DCG image sensor has the problem of affecting the image quality due to the noise interference of the pixel power supp...

AI Technical Summary

Problems solved by technology

On the one hand, the pixel power supply is not clean and has noise ripples in a certain frequency range

On the other hand, the pixel layout creates parasitic capacitance; through the parasitic path, the pixel power supply noise appears on the bit line; the pixel power supply noise is quantized after the comparator and degrades the image quality

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