Image Sensor Column Readout Noise Reduction via Temporal Segmentation
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Solution Overview
Problem
Conventional CMOS image sensors face challenges in reducing sampling system noise and row-correlated visual artifacts due to overlapping sampling and readout operations, which increase susceptibility to noise during concurrent processing.
Innovation Solution
Implementing an image sensor with a two-dimensional array of pixels and output circuits that allow concurrent sample and read operations, where the AFE clock and column address sequences are suspended during sampling to minimize noise interference, enabling uninterrupted data flow and reduced noise capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If concurrent sampling and readout operations are implemented to reduce readout time, then productivity is improved, but susceptibility to system noise increases causing row-correlated visual artifacts
Solution Approach 1:
The patent segments the concurrent sampling and readout operation into distinct time phases by suspending the column address sequence during sampling periods. This temporal segmentation allows sampling to occur without simultaneous readout activity, eliminating the noise correlation problem while preserving the overall concurrent operation architecture.
Solution Approach 2:
The patent implements periodic suspension of the column address sequence at specific intervals during the sampling operation. This periodic control mechanism temporarily halts readout addressing during critical sampling windows, reducing noise susceptibility while maintaining high overall productivity through rapid resumption of readout operations.
2Measurement precision
If clock signals are turned off during sampling to reduce system noise, then measurement precision is improved, but readout operation cannot proceed concurrently
Solution Approach 1:
The patent segments the clock signal control into row-specific intervals, suspending the column address sequence only during sampling periods for individual rows while maintaining continuous operation for other rows. This selective temporal segmentation reduces noise during sampling without halting the entire readout operation, preserving productivity.
Solution Approach 2:
The patent dynamically adjusts the column address sequence timing based on the sampling phase. The suspension and resumption of addressing signals is controlled adaptively during the sampling window, allowing the system to optimize noise reduction for each row while maintaining continuous throughput across the entire array.
Data Source
AI summary
An image sensor includes a two-dimensional array of pixels having multiple column outputs and an output circuit connected to each column output. Each output circuit is configured to operate concurrent sample and read operations. An analog front end (AFE) circuit processes pixel data output from the output circuits and an AFE clock controller transmits an AFE clocking signal to the AFE circuit to effect processing of the pixel data. A timing generator outputs a column address sequence that is received by a column decoder. During one or more sample operations the AFE clock controller suspends the output of the AFE clocking signal and the timing generator suspends the output of the column address sequence during the sample operation. The output of the AFE clocking signal and the column address sequence resume at the end of the sample operation.