Asynchronous CMOS pixel circuit with light adaptive threshold voltage adjustment mechanism

Abstract

The invention relates to a digital-analog hybrid integrated circuit design field and provides an asynchronous CMOS pixel circuit with a light adaptive threshold voltage adjustment mechanism. The objectives of the invention are to maintain the advantages of high dynamic range and low fixed-model noise of a circuit, and compress time for measuring light intensity in a relatively small range, and improve the response speed of the circuit. In order to achieve the above objectives, the following technical schemes are adopted: the asynchronous CMOS pixel circuit with the light adaptive threshold voltage adjustment mechanism is composed of a light intensity change detection unit (CD), an exposure measurement unit (EM) using a PWM mode and a VrefL reference voltage switching unit; and output signals Rst of the output end R of the change detection unit are connected with the input end Reset of the exposure measurement unit and the input end T1 of the VrefL reference voltage switching unit and are respectively used for controlling signals of measurement initiating of the exposure measurement unit and controlling the evaluation of light intensity. The asynchronous CMOS pixel circuit with the light adaptive threshold voltage adjustment mechanism of the invention is mainly applied to the digital-analog hybrid integrated circuit design.

Description

technical field [0001] The invention relates to the field of digital-analog hybrid integrated circuit design, in particular to an asynchronous CMOS pixel circuit with a light-adaptive threshold voltage adjustment mechanism. technical background [0002] The asynchronous CMOS image sensor is a brand-new image sensor, which abandons the frame-based concept in traditional image sensors, and replaces it with the AER (Address Event Representation) communication method to realize that events are generated when there are changes, and events are used to represent Optical information, so as to realize asynchronous autonomous pixels, which can overcome many shortcomings and deficiencies in frame mode. [0003] Most of the asynchronous CMOS image sensors adopt a method of expressing light intensity based on voltage, which is different from traditional image sensors, but a method of expressing light intensity based on time, that is, starting from pixel reset, rather than fixing its disc...

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Problems solved by technology

[0004] However, another problem with applying this method to asynchronous CMOS pixels is that for the fixed reference voltages of the two comparators, the time required for measurement will vary greatly under different light intensity conditions.

Since the asynchronous pixel uses the change as a sign to start measurement, if the difference between the two reference voltages is large, then, under weak light conditions, the measurement time will be longer than the change time, and it will not be possible to measure This time the light intensity information; if the difference between the two reference voltages is small, then under the condition of strong light, the measurement time will be very short, which will affect the accuracy of the digitally quantized light intensity information

One way to solve this problem is to set a larger reference voltage difference, and for weak light conditions, only take the time to reach the first threshold to represent the light intensity, the cost of this is to introduce a larger fixed pattern noise

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