Laser Diode Bias Current Control for Endoscope Reliability
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Solution Overview
Problem
Existing light source devices for endoscopes, such as those using laser diodes, face challenges in maintaining reliability and efficiency due to rapid state changes and heat generation, leading to potential deterioration and power consumption issues.
Innovation Solution
A light source device configuration that includes a laser diode, a determination unit, and a driver, which applies a bias current based on determined operation modes to manage power consumption and reduce heat generation, thereby maintaining reliability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If discrete drive current is applied to the laser diode in a fixed period to adjust brightness, then the illumination brightness can be controlled, but the laser diode undergoes rapid state changes between LED emission mode, laser oscillation mode, and zero-current state, causing deterioration and reliability issues
Solution Approach 1:
The patent applies a bias current to the laser diode before the main drive current is applied. This preliminary action prepares the laser diode by maintaining it in a stable laser oscillation state, preventing the harmful rapid transitions between different emission modes that occur when drive current is suddenly applied from zero. The bias current is applied continuously or periodically in advance to ensure the laser diode is ready for high-output operation without undergoing detrimental state changes.
Solution Approach 2:
The patent employs periodic application of bias current to the laser diode, synchronizing it with the periodic drive current cycles. During each drive period, the bias current maintains the laser diode in a stable state, and during the off-period, the bias current prevents the laser diode from transitioning to harmful intermediate states. This periodic action pattern resolves the contradiction by making the current application rhythmical and controlled rather than abrupt and random.
2Reliability
If bias current is continuously applied to the laser diode to prevent deterioration, then reliability is improved, but power consumption increases
Solution Approach 1:
The patent dynamically adjusts the bias current application based on the operational requirements. Instead of continuously applying bias current at maximum level, the system applies bias current only when and where needed - specifically during periods when the main drive current is not applied or when transitioning between operational states. The bias current magnitude and duration are dynamically controlled to provide just enough protection against deterioration while minimizing unnecessary power consumption.
Solution Approach 2:
The patent changes the parameters of bias current application (magnitude, duration, timing) based on operational conditions. The bias current is applied at lower magnitudes during idle periods and only at higher magnitudes when high-output laser operation is required. This parameter adjustment allows the system to maintain reliability through bias current application while significantly reducing overall power consumption compared to continuous full-level bias current application.
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
The solution effectively suppresses laser diode deterioration when external power is available and achieves power saving when power is limited, ensuring high reliability and efficient operation.
Implementation Method 1
a laser diode that emits a laser light used as an illumination light
Implementation Method 2
the laser diode changes in a very short time from a state in which no drive current is applied at all to a high-output laser mode, after going through an LED emission mode and a laser oscillation mode
Data Source
AI summary
A light source device includes a laser diode configured to emit a laser light used as an illumination light, a determination unit configured to determine one of a plurality of modes as an operation mode of the laser diode based on usage state of the light source device; and a driver configured to drive the laser diode in a condition that a bias current to the laser diode is applied depending on the operation mode determined by the determination unit.