Rolling Shutter Brightness Uniformity via Line Gain Control
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Solution Overview
Problem
Imaging devices with CMOS image sensors using the rolling shutter method face issues with brightness and darkness differences between horizontal lines due to varying exposure start times, leading to screen flickering, blackout, and reduced image quality, especially when tracking moving objects.
Innovation Solution
An imaging device with a gain setting unit that adjusts the gain for each line based on diaphragm drive information, allowing for correction of light amount differences between lines without changing the exposure period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the exposure period is corrected to suppress brightness differences between lines, then image quality improves, but the shutter speed becomes restricted and the solution is insufficient
Solution Approach 1:
The patent applies different gain values to different horizontal lines based on their specific exposure characteristics. Each line's signal is amplified by a locally optimized gain factor calculated from the diaphragm drive locus, allowing precise compensation for brightness differences without uniformly restricting shutter speed across all lines.
Solution Approach 2:
The patent changes the gain parameter for each horizontal line based on the diaphragm drive locus information. By calculating and applying line-specific gain values, the system compensates for brightness differences caused by varying exposure start times while maintaining the original exposure period and shutter speed settings.
2Manufacturing precision
If the exposure period is changed to suppress brightness differences, then image quality improves, but the device complexity increases
Solution Approach 1:
The patent replaces mechanical/exposure-based solutions with an electronic signal processing approach. Instead of physically adjusting exposure timing or diaphragm positions, the system uses electronic gain amplification applied to each line's signal, simplifying the control mechanism while achieving brightness uniformity.
Solution Approach 2:
The patent introduces gain amplification as an intermediary processing step between signal acquisition and image output. The gain setting unit acts as a mediator that compensates for brightness differences without requiring changes to the exposure mechanism itself, reducing overall system complexity.
3Illumination intensity
If the diaphragm value changes during exposure, then light amounts differ between lines, but maintaining diaphragm drive for other functions reduces correction effectiveness
Solution Approach 1:
The patent performs preliminary calculation of the diaphragm drive locus and determines appropriate gain values for each horizontal line before the actual exposure and signal processing. This advance preparation allows the diaphragm to perform its normal drive functions during exposure while the pre-calculated gain values ensure proper brightness compensation is applied afterward.
Data Source
AI summary
To suppress a difference in brightness and darkness in a captured image caused by a difference in an exposure start time by a rolling shutter even if the exposure period is not changed. Provided is an imaging device including a gain setting unit configured to set a gain for each line in which a plurality of pixels is arrayed, the plurality of pixels being two-dimensionally arranged in a matrix in an image sensor, on the basis of diaphragm drive information regarding a diaphragm drive locus representing a time-series change in a diaphragm value. Thereby, the difference in brightness and darkness in a captured image caused by the difference in an exposure start time by a rolling shutter can be suppressed even if the exposure period is not changed.