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CMOS image sensor, pixel unit and control method thereof

An image sensor and pixel unit technology, applied in the field of image sensors, can solve the problem that the global exposure structure does not have high dynamic range, etc., and achieve the effect of high dynamic range and extended dynamic range.

Active Publication Date: 2021-08-17
BRIGATES MICROELECTRONICS KUNSHAN
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0010] However, the global exposure structure including two-stage source follower does not have high dynamic range

Method used

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  • CMOS image sensor, pixel unit and control method thereof
  • CMOS image sensor, pixel unit and control method thereof

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Embodiment Construction

[0054] Existing global exposure structures including two-stage source followers (such as 8T type global exposure structure and 9T type global exposure structure) do not have a high dynamic range, and their dynamic range can only reach about 50 dB.

[0055] The technical solution of the present invention takes into account two characteristics of the storage node FD (for example, the capacitance C of the storage node FD FD The smaller the signal-to-noise ratio, the better, but the corresponding Q pd The smaller it is, the lower the dynamic range), and then provide two types of storage nodes, wherein the storage node with a smaller capacitance (Small FD, referred to as "SFD"; as known in the art, it belongs to parasitic capacitance, See Figure 1-3 The capacitance shown by the dotted line in the middle) is coupled to the first-stage source follower, and the storage node with a larger capacitance (Large FD, referred to as "LFD") is arranged in the overflow structure (the overflow...

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Abstract

A CMOS image sensor, a pixel unit and a control method thereof, the pixel unit includes a global exposure structure, an overflow structure and a frame processing module, the overflow structure includes a second transfer transistor, a second storage node and an overflow control transistor, the second transfer transistor The first terminal is coupled to the cathode terminal of the photoelectric conversion element, the second terminal is coupled to the first terminal of the second storage node, the second terminal of the second storage node is coupled to the first power line, and the first terminal of the overflow control transistor is coupled to Connected to the second end of the second transfer transistor, the second end is coupled to the gate of the second stage source follower, the frame processing module quantizes the first frame analog signal and obtains the first frame based on the quantized first frame analog signal Quantize the data, quantize the second frame analog signal and obtain the second frame quantized data based on the quantized first frame analog signal, and add the first frame quantized data and the second frame quantized data to obtain the final quantized data. The technical solution of the invention expands the dynamic range of the pixel unit.

Description

technical field [0001] The invention relates to the technical field of image sensors, in particular to a CMOS image sensor, a pixel unit and a control method thereof. Background technique [0002] The image quality produced by the CMOS image sensor depends on the signal-to-noise ratio of the image signal, in which the signal intensity depends on the light intensity, exposure time, photoelectric conversion efficiency, etc. The noise mainly includes solid noise and random noise, and random noise includes shot noise and reset noise etc. [0003] The dynamic range of a CMOS image sensor is the ratio of the brightest signal to noise that the sensor can quantify. The lower limit of the dynamic range is determined by the noise. ), bitline (Bitline) swing, storage node (also known as floating diffusion area, Floating Diffusion, referred to as "FD") size and other factors, among which the Bitline swing is about 1V-1.5V, which is limited by the later terminal analog circuit design. ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04N5/374H04N5/355H04N5/357H04N5/363
CPCH04N25/57H04N25/616H04N25/65H04N25/76
Inventor 张琦
Owner BRIGATES MICROELECTRONICS KUNSHAN