System and method for canceling dark photocurrent in a color sensor circuit

Abstract

A system and method for canceling dark photocurrent in a color sensor circuit is disclosed. A color sensor is described including a color sensor circuit, a dark color sensor circuit, and a differential amplifier circuit. The color sensor circuit receives photocurrent from a color component of a light input. The color sensor circuit outputs a first voltage indicating intensity of the color component. The dark color sensor circuit receives dark photocurrent and outputs a second voltage indicating an offset voltage. The differential amplifier circuit is coupled to the color sensor circuit and tothe dark color sensor circuit. The differential amplifier circuit receives the first and second voltages and outputs a final output that cancels contributions of the offset voltage in the first voltage due to the dark photo current.

Description

technical field [0001] The present invention relates to the field of color sensors, and more particularly, the present invention relates to systems and methods for canceling dark current shifts and temperature variations in color sensors. Background technique [0002] At the heart of a color sensor is a photodetector. The purpose of a photodetector is to capture electromagnetic radiation and convert it into an electrical signal. Typically, the electrical signal generated is proportional to the intensity of the incident light. Traditional color sensor circuits use p-i-n or pn junction photodiodes as photodetectors. Generally, photodiodes capture and absorb light energy. The generated carriers sweep across the p-i-n or pn junction of the photodiode and generate a small photocurrent that can be detected. Typically, photodiodes exhibit a linear response over a large operating range. [0003] In color sensors, a transimpedance amplifier is used to convert the photocurrent in...

AI Technical Summary

Problems solved by technology

Thus, the color sensor is temperature sensitive since the voltage reading from the color sensor does not provide a constant linear response over a range of temperatures, which can adversely affect the response of the transimpedance amplifier in the color sensor

[0007] As a result, a disadvantage of conventional color sensors is the degraded DC response (zero offset) of the color sensor because conventional color sensor amplifiers exhibit a dark current zero offset in their voltage output

In addition, another disadvantage is that temperature changes in the voltage response of the color sensor's transimpedance amplifiers cause changes in the slope of the linear response, which can adversely lead to variations in the color sensor's voltage response over a range of temperatures

[0008] Therefore, prior art systems and methods provide color sensors that suffer from dark current voltage offsets and lower temperature robustness

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