CMOS Image Sensor Down-Sampling High Dynamic Range
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Solution Overview
Problem
CMOS image sensors face challenges in achieving high dynamic range without increasing chip area or complexity, as existing techniques either fail to enhance dynamic range effectively or incur significant costs.
Innovation Solution
The implementation of a CMOS image sensor with a line-by-line read out architecture and alternating row exposure times in a down-sampling mode, where the vertical pixel resolution is reduced by combining data from sets of rows with different exposure times, allowing for a high dynamic range while maintaining cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional approaches are used to achieve high dynamic range, then dynamic range is improved, but chip area and device complexity increase significantly
Solution Approach 1:
The pixel array is divided into multiple rows that are read out in a line-by-line sequence, allowing different exposure times to be applied to different rows. This segmentation enables high dynamic range functionality without requiring additional hardware components, thereby avoiding increases in chip area while achieving improved measurement precision through varied exposure times across row sets.
2Adaptability or versatility
If exposure time is adjusted over a sequence of frames, then response to varying light conditions is improved, but actual dynamic range for a particular frame does not increase
Solution Approach 1:
Different exposure times are pre-assigned to different rows before the actual imaging process. This preliminary assignment of varied exposure times to different row sets allows the sensor to capture both bright and dark regions simultaneously within a single frame, achieving actual dynamic range improvement rather than just post-processing adjustment.
Solution Approach 2:
Different rows are assigned different exposure times based on their local requirements - rows capturing brighter regions use shorter exposure times while rows capturing darker regions use longer exposure times. This local quality approach ensures that each row is optimized for its specific lighting conditions, achieving high dynamic range within a single frame.
3Productivity
If down-sampling is performed with uniform exposure times, then vertical resolution is reduced, but dynamic range is not improved
Solution Approach 1:
The exposure time parameter is made dynamic and variable across different rows rather than uniform. In down-sampling mode, alternating rows are assigned different exposure times, allowing the system to maintain high dynamic range while performing down-sampling. This dynamic approach to exposure time assignment enables both productivity through down-sampling and improved measurement precision through varied exposure times.
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 achieves a high dynamic range in a cost-effective manner by varying exposure times in a down-sampling mode, reducing vertical resolution and enhancing image sensor performance without significant increases in chip area or complexity.
Implementation Method 1
Each pixel includes a photodetector that transforms incident light photons into current signals
Data Source
AI summary
An image sensor has an array of photo-sensitive pixels and supports a line-by-line read out of rows. In a normal resolution each row has the same nominal gain and exposure time. In a down-sampling mode the exposure times of the rows are varied according to an alternating sequence having at least two different exposure times. During down-sampling, raw pixel data from rows with different exposure times is combined to simultaneously achieve down-sampling and a high dynamic range.