CMOS Rolling Shutter Illumination Timing Control
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Solution Overview
Problem
Conventional CMOS image sensors with rolling shutters face challenges in reducing luminance unevenness when capturing images with pulsed illumination, especially in endoscopes with high pixel counts, where simultaneous exposure periods for all horizontal lines are not feasible, leading to difficulties in achieving uniform brightness.
Innovation Solution
An imaging system comprising a CMOS image pickup device, a light source device generating pulsed illumination, and a control unit that adjusts the irradiation timing of the light source between successive picture periods, allowing for differential exposure control and image correction to achieve uniform brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rolling shutter method is applied in a CMOS image sensor to enable high-speed readout, then productivity is improved, but luminance unevenness occurs across different horizontal lines due to temporal displacement between illumination pulse and readout timing
Solution Approach 1:
The patent applies dynamics by making the illumination timing variable across different picture periods. The control unit adjusts the irradiation timing of the illumination light in successive picture periods to account for the temporal displacement caused by rolling shutter readout, thereby dynamically compensating for luminance unevenness while maintaining high readout speed
Solution Approach 2:
The patent changes the timing parameter of illumination light irradiation across different picture periods. By varying the irradiation timing in successive picture periods according to the readout timing of each horizontal line, the system compensates for the temporal displacement without sacrificing readout speed, thus resolving the luminance uniformity issue
2Manufacturing precision
If the illumination pulse duration is extended to cover all horizontal lines, then luminance uniformity is improved, but heat generation increases and simultaneous exposure becomes infeasible in high pixel count endoscopes
Solution Approach 1:
The patent uses periodic action by illuminating different horizontal lines at different picture periods rather than illuminating all lines simultaneously. The control unit irradiates illumination light to different horizontal lines in different picture periods, achieving uniform luminance while avoiding the heat generation associated with extended simultaneous illumination
Solution Approach 2:
The patent segments the illumination process into multiple picture periods, where each horizontal line or group of horizontal lines is illuminated in separate periods. This segmentation allows the system to achieve luminance uniformity without requiring all pixels to be exposed simultaneously, thereby reducing heat generation in high pixel count endoscopes
3Manufacturing precision
If different exposure timings are applied to different horizontal lines, then luminance uniformity can be achieved, but device complexity increases due to the need for precise timing control between illumination and readout
Solution Approach 1:
The control unit performs multiple functions: it controls both the illumination timing and the readout timing coordination. By making the control unit multi-functional, the system achieves luminance uniformity without adding separate dedicated control mechanisms, thus managing device complexity while maintaining precise timing control
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
The system effectively reduces luminance unevenness by controlling illumination timing and correcting images between frames, ensuring appropriate brightness even without simultaneous exposure for all horizontal lines, thereby improving image quality in endoscopic imaging.
Implementation Method 1
a plurality of pixels are arranged in two dimensions to generate an imaging signal by performing photoelectric conversion on an optical image of a subject
Data Source
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AI summary
A control apparatus includes a control unit configured to control an irradiation timing at which pulsed illumination light is radiated in a first picture period in which an image pickup device performs reading so as to differ from an irradiation timing at which the illumination light is irradiated in a second picture period succeeding the first picture period and having the same cycle as the first picture period. In the image pickup device, a plurality of pixels are arranged in two dimensions to generate an imaging signal by performing photoelectric conversion on an optical image of a subject. The image pickup device is configured to read out the imaging signal generated by the plurality of pixels for each horizontal line.