Variable Capacitor Trimming for Image Sensor Non-Uniformity
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Solution Overview
Problem
Conventional image sensors suffer from pixel image non-uniformity due to variations in the optical and illumination systems, leading to brightness degradation and noise, which affects the performance of devices like optical mice and digital cameras.
Innovation Solution
A method and image sensor design that utilize pixels with variable capacitors, where the capacitance of each pixel is trimmed based on brightness information to compensate for non-uniformity, with a digital signal controlling the conduction of compensation capacitors to adjust the capacitance accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional image sensors are used, then the device structure is simple, but pixel image non-uniformity occurs leading to brightness degradation and noise
Solution Approach 1:
The patent applies local quality by providing different capacitance values to different pixels based on their specific brightness characteristics. Each pixel is equipped with a variable capacitor that can be individually trimmed to compensate for local non-uniformity, rather than applying a uniform solution across all pixels. This is achieved through the capacitor trimming module that adjusts capacitance values according to brightness information of each pixel.
Solution Approach 2:
The patent implements dynamics by using variable capacitors with switchable configurations instead of fixed capacitors. The capacitance value of each pixel's capacitor can be dynamically adjusted through the trimming process, where switches connect different capacitor configurations (e.g., single capacitor, series connection, parallel connection) based on the pixel's brightness characteristics. This dynamic adjustment enables compensation for pixel non-uniformity.
2Manufacturing precision
If capacitance trimming is implemented to compensate non-uniformity, then image quality improves, but device complexity increases due to additional components and control circuits
Solution Approach 1:
The patent applies universality by designing a multi-functional pixel structure where the variable capacitor serves multiple purposes: it acts as a storage capacitor for the photodetector signal and simultaneously functions as a trimming element for non-uniformity compensation. The same capacitor structure is used across all pixels, with universal trimming circuits that can adjust each pixel's capacitance. This reduces the need for additional dedicated compensation components in each pixel.
Solution Approach 2:
The patent implements parameter changes by adjusting the capacitance value parameter of the variable capacitors to compensate for pixel non-uniformity. The trimming process modifies the electrical parameter (capacitance) of existing components rather than adding new components or changing structural parameters. This is achieved through switchable capacitor configurations that change the effective capacitance value based on brightness information.
3Object-affected harmful factors
If variable capacitors are added to each pixel for compensation, then non-uniformity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by performing capacitance trimming during the manufacturing or initialization process before the image sensor is deployed for actual imaging. The trimming module calculates the required capacitance adjustment based on measured brightness information and configures the appropriate switch states for each pixel's variable capacitor in advance. This preliminary configuration eliminates the need for real-time adjustment during operation and reduces the precision requirements for ongoing manufacturing variations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively compensates for pixel non-uniformity by adjusting capacitance, improving image quality and reducing noise, thereby enhancing the performance of image sensors and related devices.
Implementation Method 1
a variable capacitor unit coupled to the optical signal receiver unit for storing second charges, wherein the amount of second charges stored in the variable capacitor unit is related to the amount of first charges generated in response to the received light
Data Source
AI summary
The present invention discloses a method for pixel image non-uniformity compensation. The method including the steps of: first, receiving an input image by an image sensor having a plurality of pixels, wherein each pixel includes a variable capacitor; next, calculating brightness information of at least a portion of the pixels; and further, trimming the capacitances of the variable capacitors in the portion of pixels respectively according to the brightness information.