Rolling Shutter CMOS Sensor Illumination Synchronization
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Solution Overview
Problem
Rolling shutter type CMOS image sensors used in frame sequential imaging methods face challenges with exposure timing discrepancies across horizontal pixel lines, leading to unnatural images and reduced video responsiveness when switching between multiple illumination light beams, resulting in color shifts during fast-moving subject imaging.
Innovation Solution
An imaging device configuration that includes a light source capable of emitting various illumination light beams, a rolling shutter type imaging unit, a light source control unit for precise illumination switching, and an imaging signal generation unit that adjusts exposure frames to synchronize illumination periods, allowing for improved color reproducibility and video responsiveness by generating imaging signals from pixels exposed to the same illumination light across multiple frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a rolling shutter type CMOS image sensor is used for frame sequential imaging with multiple illumination light beams, then power consumption is reduced and reading speed is improved, but exposure timing discrepancies occur across horizontal pixel lines leading to unnatural images and color shifts
Solution Approach 1:
The patent applies preliminary action by controlling the light source to emit illumination light beams in synchronization with the exposure timing of each horizontal pixel line before the rolling shutter scan begins. This ensures that each line is exposed to the correct illumination light (first, second, or third light beam) according to its specific exposure period, eliminating exposure timing discrepancies and color shifts while maintaining the power consumption benefits of the rolling shutter type sensor.
2Manufacturing precision
If illumination light switching is performed in units of imaging frame using rolling shutter method, then color shifts are reduced, but the number of imaging frames required for composite image generation increases reducing video responsiveness
Solution Approach 1:
The patent applies dynamics by making the illumination light switching flexible and adaptive to the rolling shutter scan progress. Instead of fixed frame-based switching, the light source control unit dynamically switches between the first, second, and third illumination light beams according to the actual exposure timing of each horizontal pixel line. This dynamic synchronization reduces the number of frames needed for composite image generation while maintaining color reproducibility, thereby improving video responsiveness.
3Adaptability or versatility
If frame sequential imaging is performed by switching multiple illumination light beams, then spectral information is captured, but exposure period mismatches occur causing unnatural captured images
Solution Approach 1:
The patent applies local quality by assigning different illumination light beams (first, second, and third light beams with different spectra) to different horizontal pixel lines based on their specific exposure timing. Each line group is exposed to the appropriate illumination light corresponding to its position in the rolling shutter scan, ensuring that spectral information is captured correctly for each region without exposure period mismatches, thus maintaining both spectral imaging capability and image quality.
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 configuration enhances video responsiveness and color reproducibility by reducing the number of frames required for composite image generation, minimizing color shifts, and achieving performance comparable to global shutter methods.
Implementation Method 1
an imaging element in which a plurality of pixels are arrayed in a horizontal direction and a vertical direction and which includes a plurality of horizontal pixel lines formed by pixels arrayed in the horizontal direction
Data Source
AI summary
An imaging device includes a light source capable of emitting multi-types of illumination light beams, an imaging unit including an imaging element driven by a rolling shutter method, a light source control unit, a frame image control unit, and an image generation unit. The frame image control unit controls the light source control unit and the imaging unit so as to obtain an output having a frame group, in which second exposure frames Exp2 and Exp4 are respectively disposed before and after a first exposure frame Exp3, as one period. The imaging signal generation unit generates an imaging signal according to illumination light using a ratio of a period from the exposure start timing of each horizontal pixel line to the switching timing of the illumination light and a period from the switching timing of the illumination light to the exposure end timing in the first and second exposure frames.