CMOS Endoscope Illumination Timing for Rolling Shutter Imaging
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Solution Overview
Problem
In electronic endoscope systems using CMOS image sensors, the lighting start time of the light emitting device can be delayed from the light emission start time, leading to deterioration of still images when the distance from the endoscope's distal end to the object is short, particularly during weak pulse light emission.
Innovation Solution
The system includes a control unit that stabilizes the lighting start time by controlling the current setting signal to rise before the light emission start time, with a preliminary light emission period and additional light emission periods to ensure consistent LED lighting, and a calibration process to adjust light amounts among multiple LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the current setting signal is synchronized with the light emission start time, then the control timing is simplified, but the lighting start time is delayed and image quality deteriorates
Solution Approach 1:
The current setting signal is advanced to rise before the light emission start time, allowing the light emitting device to reach its operating current level in advance. This preliminary action ensures that the lighting start time is synchronized with the image sensor's exposure timing, preventing image quality deterioration while maintaining controlled timing complexity.
2Use of energy by moving object
If weak pulse light emission is used, then the energy consumption is reduced, but the lighting start time delay becomes more significant and image quality deteriorates
Solution Approach 1:
For weak pulse light emission, the current setting signal is advanced even more significantly before the light emission start time. This allows the light emitting device sufficient time to reach its operating current level despite the low pulse width, ensuring synchronized lighting start time with the image sensor while maintaining low energy consumption through the brief pulse duration.
3Area of stationary object
If multiple light emitting devices are used, then the illumination coverage is improved, but the consistency of light amounts among devices becomes difficult to maintain
Solution Approach 1:
The system performs individual calibration for each light emitting device, adjusting the current setting signal parameters (rise time, amplitude, timing) specific to each device's characteristics. This local quality adjustment ensures that each device contributes consistent light amount to the overall illumination, maintaining uniformity across the entire illumination coverage area.
Solution Approach 2:
The system includes a calibration process that measures the actual light output of each light emitting device and adjusts the current setting signal accordingly. This feedback mechanism compensates for variations in device characteristics, ensuring consistent light amounts among multiple devices while maintaining broad illumination coverage.
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 approach stabilizes the lighting start time, preventing image quality deterioration and ensuring consistent illumination across the endoscope's field of view.
Implementation Method 1
a semiconductor light source including a light emitting device such as a light emitting diode (LED) that emits light having a specific wavelength band
Data Source
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AI summary
One aspect of the present invention is an electronic endoscope system including an electronic scope including a CMOS image sensor configured to image a biological tissue in a rolling shutter method, a light source device including a light emitting device for generating illumination light for the biological tissue, and a driver signal processing unit. The driver signal processing unit allows the light emitting device to perform a light emission operation on the basis of a signal of a level corresponding to an amplitude of a current allowed to flow through each of the light emitting devices, a current setting signal for setting the current allowed to flow through the light emitting device, and controls the current setting signal in such a manner that a level of the current setting signal rises from zero before a light emission start time of a frame when the CMOS image sensor images.