Endoscopic Light Source Control via Segmented Pulse Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Endoscopic apparatuses using semiconductor light sources face challenges in achieving a wide dynamic range and high light quantity resolution, with limited accuracy in controlling light quantity due to temperature dependency and high costs of advanced control devices.
Innovation Solution
An endoscopic apparatus with a semiconductor light source, an imaging unit, and a light source control unit that performs first, second, and third pulse modulation controls to adjust the number, density, and width of driving pulses, allowing for precise control of light quantity, combining PNM, PDM, and PWM controls with current value control to achieve a wide dynamic range and high resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a semiconductor light source is used to control light quantity by increasing/decreasing driving current or modulating pulse width, then the device can be simplified and cost reduced, but the dynamic range and light quantity resolution are limited
Solution Approach 1:
The patent segments the pulse control into three distinct regions (first, second, and third pulse modulation regions) with different control strategies. In the first region, the number of pulses is reduced to shorten lighting time. In the second region, pulses are thinned at predetermined intervals to reduce pulse density. In the third region, pulse width is reduced. This segmentation allows achieving a wide dynamic range (up to 2400:1) and high light quantity resolution without requiring complex high-resolution PWM controllers, thus resolving the contradiction between device simplicity and measurement precision.
2Measurement precision
If a narrow pulse generator or high-resolution PWM controller is used to control light quantity with high accuracy, then light quantity control accuracy is improved, but the device becomes too expensive for practical use in endoscopic apparatus
Solution Approach 1:
The patent dynamically adapts the pulse control strategy based on the target light quantity. By defining three modulation regions with different control approaches (pulse number reduction, pulse density reduction, and pulse width reduction), the system can achieve high accuracy light quantity control across a wide dynamic range without requiring a single expensive high-resolution PWM controller. The control method adjusts its behavior dynamically according to the required light level, making high precision achievable at lower cost.
3Ease of operation
If the light quantity of a semiconductor light source is controlled by simple current or pulse width modulation, then the control method is simple, but the light quantity fluctuates due to temperature dependency
Solution Approach 1:
The patent implements a feedback mechanism where the light quantity control is based on detected light levels and target light quantity comparisons. The control unit adjusts the driving pulses according to the difference between actual and target light quantities, compensating for temperature dependency and other fluctuations. This feedback approach maintains reliable light quantity control while keeping the overall method simple, as the feedback loop automatically adapts to temperature changes and other environmental factors.
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 secures a wide dynamic range and high light quantity resolution, enabling accurate control of illumination light intensity for both normal and special light observations, comparable to xenon lamp systems, while reducing costs and maintaining high precision.
Implementation Method 1
a semiconductor light source, an imaging unit and a light source control unit. The semiconductor light source generates the illumination light
Implementation Method 2
The imaging unit adjusts an exposure time by using an electronic shutter
Implementation Method 3
The light source control unit performs first pulse modulation control, second pulse modulation control and third pulse modulation control in descending order of the target light quantity. In the first pulse modulation control, the number of the driving pulses is reduced to shorten a lighting time
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An endoscopic apparatus includes a semiconductor light source for generating illumination light and a light source control unit for generating driving pulses to drive and light the semiconductor light source. The light source control unit performs first, second and third pulse modulation controls in descending order of a target light quantity. In the first pulse modulation control, the number of the driving pulses is reduced so that a lighting time of the semiconductor light source is shortened to a predetermined lighting time for an exposure time of an electronic shutter within one frame. In the second pulse modulation control, the driving pulses are thinned at predetermined intervals so that pulse density is reduced in the lighting time. In the third pulse modulation control, pulse width of each of the driving pulses whose number is minimized in a region where the second pulse modulation control is performed is reduced.