CMOS Image Sensor Shading Pixel Readout Region Control
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Solution Overview
Problem
CMOS image sensors generate vertical streaks due to variations in electrical characteristics of column amplifiers, leading to degradation in image quality when the readout region is changed, as precise correction data is not generated quickly enough.
Innovation Solution
An image capturing apparatus with a setting unit to variably set the effective and shading pixel signal readout regions, a readout unit to read these signals, and a correction unit to generate and apply correction data for each column or row, ensuring the shading pixel signal readout region is wider than the effective pixel signal readout region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the readout region is changed for electronic antivibration, then vibration compensation is improved, but vertical streak correction precision deteriorates
Solution Approach 1:
The patent performs preliminary action by generating correction data in advance using shading pixel signals read from a fixed reference region. This correction data is stored and then applied to effective pixel signals even when the readout region changes for antivibration, allowing the system to maintain correction precision without requiring the readout region to remain fixed.
Solution Approach 2:
The patent introduces an intermediary mechanism by using shading pixel signals as a mediator to generate correction data. These shading pixel signals serve as a reference that remains stable even when the effective pixel readout region changes, enabling the system to decouple the correction data generation from the variable readout region and maintain consistent correction precision.
2Measurement precision
If correction data is generated by averaging VOB signals, then random noise is reduced, but processing time increases
Solution Approach 1:
The patent applies partial action by using only the necessary number of shading pixel signals (about 10 lines) for correction data generation, rather than requiring the full 256 signals that would be needed for complete convergence. This partial sampling approach generates sufficient correction data quickly without requiring the full averaging process, thus reducing processing time while maintaining acceptable accuracy.
3Measurement precision
If the shading pixel signal readout region is made wider than the effective pixel signal readout region, then correction data accuracy is improved, but signal transfer load increases
Solution Approach 1:
The patent applies local quality by creating a spatial distinction between the shading pixel signal readout region and the effective pixel signal readout region. The shading region is made wider to ensure sufficient correction data accuracy, while the effective pixel region can be optimized for signal transfer efficiency. This local differentiation allows each region to serve its specific function optimally without compromising the other.
Data Source
AI summary
An image capturing apparatus comprises an image sensing element including an effective pixel portion, and a shading pixel portion; a setting unit which variably sets, in at least one of row and column directions, an effective pixel signal readout region and shading pixel signal readout region; a readout unit which reads out the effective pixel signals and reads out the shading pixel signals; a correction data generation unit which generates correction data for each column or each row; a correction unit which corrects luminance levels of the effective pixel signals, for each column or each row; and a control unit which controls the setting unit so that the shading pixel signal readout region becomes wider than the effective pixel signal readout region.