Image Sensor Transfer Circuit Parallel Signal Conversion
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Solution Overview
Problem
Prior art image sensors have a long pixel transfer time due to non-overlapped periods for receiving sample and hold signals, limiting the frame rate.
Innovation Solution
The image sensor employs a transfer circuit that converts sample signals to digital sensing signals and hold signals to digital reset signals at least partially within the same period, using a sensing ADC circuit and a reset ADC circuit, respectively, to generate pixel signals, thereby shortening the pixel transfer time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the transfer circuit receives sample signal and hold signal in non-overlapped different periods, then the signal conversion can be completed sequentially, but the pixel transfer time becomes long and frame rate is limited
Solution Approach 1:
The transfer circuit is divided into two independent conversion units: a first conversion unit for converting sample signals and a second conversion unit for converting hold signals. These units operate independently and simultaneously in overlapped periods, allowing parallel processing of different signal types without interfering with each other, thus reducing total conversion time while maintaining accuracy
Solution Approach 2:
The first and second conversion units operate in overlapped time periods, ensuring that signal conversion continues without idle waiting time. While the first conversion unit processes sample signals during its period, the second conversion unit simultaneously processes hold signals, maximizing the utilization of conversion resources and continuously producing digital output signals
2Reliability
If the transfer circuit processes one pixel circuit's sample and hold signals sequentially, then the conversion can be completed thoroughly, but the pixel transfer time is extended
Solution Approach 1:
The patent merges the processing of sample signals and hold signals into a unified parallel architecture where both conversion operations occur simultaneously in overlapped periods. This combining of parallel operations reduces the total pixel transfer time while ensuring both signal types are fully converted through dedicated conversion units
Solution Approach 2:
The first and second conversion units are designed to operate in overlapped periods that extend beyond the minimum necessary time, ensuring complete conversion of both sample and hold signals. This excessive action in time overlap guarantees thorough signal processing while still achieving net time reduction compared to sequential processing
Data Source
AI summary
An image sensor for capturing an image, includes: an array of pixel circuits, wherein each of the pixel circuits is for sensing a portion of the image, and generate a sample signal and a hold signal according to the portion of the image and a predetermined reset voltage respectively; and a transfer circuit, which is coupled to the array, and is for converting the sample signals and hold signals to corresponding digital sensing signals and corresponding digital reset signals respectively, to generate pixel signals respectively corresponding to the pixel circuits according to the digital sensing signals and the digital reset signals; wherein the transfer circuit converts the sample signal generated by one of the pixel circuits to the corresponding digital sensing signal and converts the hold signal generated by another one of the pixel circuits to the corresponding digital reset signal at least partially within a same period.