Image Sensor Multi-Sampling Circuit for Faster Low-Noise Readout
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Solution Overview
Problem
Current image sensors face inefficiencies in reducing noise and sampling time when capturing pixel signals, particularly in the readout process, which affects the quality and speed of image acquisition.
Innovation Solution
The implementation of an image sensor system that utilizes an analog comparator, counter, and digital comparing circuit to compare pixel signals with ramp signals and reference codes, allowing for efficient sampling and noise reduction by generating digital signals based on counting data and binary comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixel signal is sampled multiple times during readout time to reduce noise, then noise reduction is improved, but sampling time increases
Solution Approach 1:
The patent implements dynamic sampling where the number of sampling times is adjusted based on illumination levels. During bright periods, fewer samples are taken while during dark periods, more samples are taken to maintain signal quality. This dynamic adaptation resolves the contradiction by making sampling time variable rather than fixed, optimizing both noise reduction and readout speed根据不同光照条件
Solution Approach 2:
The system changes the sampling parameter (number of samples) based on illumination conditions. By monitoring ambient light levels, the system adjusts the sampling count to achieve optimal noise reduction only when necessary, thereby reducing overall sampling time while maintaining reliability when it matters most
2Measurement precision
If pixel signal is sampled multiple times during readout time, then image quality is improved, but readout speed decreases
Solution Approach 1:
The patent employs dynamic sampling strategies where the sampling rate and number of samples are adjusted in real-time based on scene illumination and motion characteristics. This allows the system to maintain high image quality when conditions warrant it while speeding up readout when full sampling is unnecessary, thus resolving the speed-quality tradeoff
Solution Approach 2:
By changing sampling parameters adaptively based on illumination levels and scene conditions, the system optimizes the balance between image quality and readout speed. When lighting is good or motion is minimal, fewer samples are taken to increase speed; when lighting is poor or motion is detected, sampling increases to maintain quality
3Reliability
If complex comparison operations are performed on pixel signals, then noise reduction is improved, but device complexity increases
Solution Approach 1:
The patent divides the comparison operation into segmented stages: first comparing pixel signals against reference levels to generate preliminary comparison results, then using these results to guide subsequent sampling and comparison operations. This segmentation allows complex noise reduction to be achieved through multiple simple comparison stages rather than one complex operation, managing device complexity while maintaining effectiveness
Data Source
AI summary
An image sensor for sampling a pixel signal a plurality of times during a readout time includes an analog comparator configured to compare a signal level of the pixel signal with a signal level of a target ramp signal that is any one of a plurality of ramp signals, a counter configured to output counting data based on a comparison result of the analog comparator, and a digital comparing circuit configured to compare a binary value of a target reference code corresponding to the target ramp signal with a binary value of the counting data and determine whether to output a digital signal corresponding to the counting data to a data output circuit based on a result of the comparison between the binary value of the counting data and the binary value of the target reference code.