Electronic Endoscope Flash Timing for Rolling Shutter Imaging
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Solution Overview
Problem
In electronic endoscope systems using a rolling shutter method, the flash exposure period needs to be shorter than the read time of the CMOS image sensor, necessitating high light intensity from the light source, which leads to heat dissipation issues and decreased S/N ratio when gain is increased.
Innovation Solution
An imaging system with a light source unit that emits flashes with a longer period between emissions, allowing for flexible flash exposure times, and an image processing unit that generates display images by combining frames based on flash emission timing, applying gain and spatial filters, and performing interpolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the flash exposure period is set to be shorter than the read time of one line of the CMOS image sensor, then strobe imaging can be performed with the rolling shutter method, but the light intensity of the light source must be increased, causing heat dissipation issues and reduced light source durability
Solution Approach 1:
The patent applies dynamics by making the flash exposure period variable and adaptable to the rolling shutter read time. The system dynamically adjusts the flash timing and duration to match the specific readout characteristics of the CMOS sensor, allowing the flash to occur during the exposure period of each line without being constrained by fixed timing. This dynamic synchronization enables adequate exposure time without requiring excessive light intensity, thereby reducing heat generation and improving light source durability.
2Speed
If the flash exposure period is set to be shorter than the read time of one line of the CMOS image sensor, then strobe imaging can be performed, but the gain of the CMOS image sensor must be increased, causing a decrease in the S/N ratio
Solution Approach 1:
The system dynamically synchronizes the flash timing with the rolling shutter readout process, allowing the flash to occur at the appropriate moment during the exposure period of each line. This dynamic timing adjustment ensures that the flash exposure period is optimized for each line's readout time, providing sufficient light exposure without requiring excessive sensor gain amplification, thereby maintaining a high signal-to-noise ratio.
Solution Approach 2:
The patent changes the timing parameters of the flash relative to the rolling shutter readout. Instead of using a fixed flash duration that is shorter than the minimum line read time, the system adjusts the flash timing to occur during the exposure period of each line as it is being read. This parameter adjustment allows the flash exposure period to be effectively extended across multiple lines without requiring increased light intensity or sensor gain, thus preserving the S/N ratio.
3Productivity
If the flash is emitted in synchronization with the rolling shutter readout, then an image for one frame can be obtained without providing a period for strobe exposure, but the flash exposure period must be less than the read time of one line
Solution Approach 1:
The patent implements continuity of useful action by integrating the flash emission continuously with the rolling shutter readout process. Instead of providing separate strobe exposure periods, the flash is emitted in synchronization with each line's exposure and readout, ensuring that every line captured during the flash period contributes to the final stroboscopic image. This continuous synchronization eliminates dead time and allows the flash exposure period to span multiple lines without reducing frame acquisition efficiency.
Data Source
AI summary
According to an aspect of the present invention, provided is an electronic endoscope system including a CMOS image sensor that images an object using a rolling shutter method and a light source device that emits a flash to perform strobe imaging of the object. In the system, the light source device emits a flash such that a period from a flash end time of a certain flash to a flash start time of a next flash is longer than a flash prohibition period during which the emission of the flash is prohibited for at least one frame period. The electronic endoscope system processes a captured image for each frame obtained by the CMOS image sensor on the basis of the emission timing of the flash from the light source device to generate a display image.