Endoscope Light Source Color Balance Control
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Solution Overview
Problem
Endoscope apparatuses face challenges in maintaining color balance during light adjustment, as variations in driving time of the light source lead to imbalances in the relative ratio of light emission intensity between fluorescence and excitation light, resulting in undesirable color illumination.
Innovation Solution
The endoscope apparatus employs a light source with a white LED that includes a blue LED and a yellow fluorescent substance, using PWM signal control to adjust the pulse width and maintain color balance by deriving correction parameters based on the pulse width to perform color correction processing on the video signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM control is used to adjust light emission intensity by varying pulse width, then light intensity can be controlled, but color balance is lost due to differential changes in fluorescence and excitation light intensity ratios
Solution Approach 1:
The patent changes the control parameter from pulse width (time-based) to current value (amplitude-based). By adjusting the current supplied to the light emitting source while maintaining a constant pulse width, the system achieves light intensity control without altering the temporal characteristics that cause differential intensity changes between fluorescence and excitation light. This parameter substitution resolves the contradiction by decoupling intensity control from color balance disruption.
Solution Approach 2:
The patent implements feedback control by detecting the actual light emission intensity and using this information to adjust the current value supplied to the light emitting source. The control section continuously monitors the illumination output and modifies the current to maintain the desired light intensity while preserving the correct intensity ratio between fluorescence and excitation light components, thereby maintaining color balance during dynamic adjustment.
2Stability of the object's composition
If variable current control is used to adjust light intensity, then color balance can be maintained, but energy consumption increases due to higher current values
Solution Approach 1:
The patent applies partial action by using pulse width modulation to control the average power delivery to the light emitting source. Instead of continuously supplying high current, the system uses intermittent pulses with optimized width and amplitude, delivering only the necessary energy to achieve the desired light intensity while maintaining color balance. This reduces overall energy consumption compared to continuous variable current control.
3Stability of the object's composition
If electronic shutter is added to perform light adjustment in the image pickup device, then color balance can be maintained, but device complexity and circuit scale increase
Solution Approach 1:
The patent extracts the light adjustment function from the image pickup device and relocates it to the light source control section. By performing intensity control at the illumination stage rather than at the detection stage, the system eliminates the need for electronic shutter circuits in the image pickup device. This functional relocation reduces device complexity and circuit scale while maintaining color balance through the current-based control method.
Solution Approach 2:
The patent introduces a control section as an intermediary between the light source and the image pickup device. This intermediary performs the light intensity adjustment and color balance maintenance functions, eliminating the need for complex electronic shutter mechanisms in the image pickup device. The control section acts as a mediator that simplifies the overall system architecture by centralizing the adjustment functionality.
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 solution ensures that the endoscope apparatus maintains appropriate color balance even when light adjustments are made, preventing loss of color balance due to changes in driving time, thereby ensuring consistent illumination.
Implementation Method 1
a blue LED that emits blue light
Implementation Method 2
a yellow fluorescent substance that absorbs a part of energy of the blue light and emits green-yellow fluorescent light
Implementation Method 3
a yellow fluorescent substance that absorbs a part of energy of the blue light and emits green-yellow fluorescent light by being exited by the blue light
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An endoscope apparatus 1 includes a white LED 17 that includes a light emitting section, a CCD 9 that picks up an image of an observation part illuminated by light from the white LED 17, a light adjusting circuit 14 that is capable of adjusting driving time of the light emitting section in each image pickup period of the CCD 9, a monitor 4 that displays an image of the observation part picked up by the CCD 9, and a video signal processing section 23 that converts an image pickup signal transmitted from the CCD 9 to an image signal to be displayed by the monitor 4. The video signal processing section 23 includes a color correction parameter deriving section 31 that derives a color correction parameter corresponding to the driving time of the light emitting section, and a color tone varying section 32 that performs color correction of the image signal with the color correction parameter derived by the color correction parameter deriving section 31.