US 8,896,733 B2 · Imaging system with automatic conversion gain selection

Abstract

An image sensor may include an image pixel array. The image sensor may be provided with automatic conversion gain selection on a pixel-by-pixel basis to produce a high-dynamic-range image. Each image pixel may include a capacitor and a conversion gain transistor coupled in series between a power supply line and a floating diffusion node. The conversion gain transistor may be coupled to a control line through a gating transistor. The gating transistor may have a gate connected to a row select line. The image pixel may have an output line that is coupled to a column amplifier and a comparator. The column amplifier may generate a difference voltage based on reset and image signals. The comparator may compare the difference voltage with a predetermined threshold to determine whether to place the selected pixel in a high or low conversion gain mode.

Claims10

Dependent claims

An image sensor comprising:

a power supply line;
a first image pixel having a first floating diffusion node and a first conversion gain circuit, wherein the first conversion gain circuit is coupled between the power supply line and the first floating diffusion node and wherein the first conversion gain circuit is configured to provide a first conversion gain for the first image pixel;
a second image pixel having a second floating diffusion node and a second conversion gain circuit, wherein the second conversion gain circuit is coupled between the power supply line and the second floating diffusion node, wherein the second conversion gain circuit is configured to provide a second conversion gain for the second image pixel, and wherein the second conversion gain is different than the first conversion gain;
a conversion gain control line;
a first switch coupled between the first conversion gain circuit and the conversion gain control line;
and
a second switch coupled between the second conversion gain circuit and the conversion gain control line, wherein the first and second switches are controlled by different signals.

4 more elements

A method of generating a high-dynamic-range image using a plurality of image pixels in an electronic device each of which is operable in a high conversion gain mode and a low conversion gain mode, the method comprising:

configuring a first portion of the plurality of image pixels in the high conversion gain mode by deasserting a control signal on a column control line to configure the first portion of the plurality of image pixels in the high conversion gain mode;
configuring a second portion of the plurality of image pixels in the low conversion gain mode by asserting the control signal on the column control line to the configure the second portion of the plurality of image pixels in the low conversion gain mode;
with an amplifier having first and second inputs, receiving the first signal at its first input from a selected one of the image pixels, receiving a second signal at its second input from the selected image pixel, and generating a corresponding difference voltage that is proportional to the difference between the first and second signals;
and
with a comparator having first and second inputs, receiving the difference voltage at its first input and a predetermined threshold voltage at its second input.

2 more elements

Dependencies are inferred from the claim text.

Imaging system with automatic conversion gain selection

Life of this patent

Imaging system with automatic conversion gain selection

Life of this patent

Abstract

Claims10