Semiconductor Laser Drive Current Correction Pattern
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Solution Overview
Problem
Existing methods for driving semiconductor lasers, such as ACC and APC drive methods, face challenges in maintaining stable high output due to self-heating effects, leading to increased takt time and reduced laser life, especially in high-output GaN type lasers, and require additional feedback loops that reduce usable light and increase costs.
Innovation Solution
A method that detects the output of semiconductor lasers using photodetectors, compares it to a set value, and adjusts the drive current based on a correction pattern defined by the time since initiation to achieve uniform light output, allowing for stable high-output laser beams without long startup times and reducing costs by utilizing internal photodetectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ACC drive method is used to maintain constant drive current, then device complexity is reduced, but light output stability deteriorates due to self-heating effects
Solution Approach 1:
The patent pre-calculates and stores correction values in a lookup table that compensates for self-heating effects before they occur. During operation, the system simply retrieves the appropriate correction value based on operating conditions rather than performing real-time complex calculations, thus maintaining light output stability without requiring complex real-time control mechanisms.
Solution Approach 2:
The patent introduces an intermediate correction value that mediates between the simple ACC drive current and the desired stable light output. This correction value, stored in advance, acts as a bridge that compensates for self-heating effects without requiring complex real-time feedback control mechanisms.
2Stability of the object's composition
If APC drive method is used to stabilize light output, then light output stability is improved, but device complexity increases due to additional feedback loop
Solution Approach 1:
The patent extracts only the essential correction functionality from a full APC system by using pre-calculated correction values stored in a lookup table. This eliminates the need for complex real-time feedback control hardware while retaining the light output stabilization benefit, thus reducing device complexity.
Solution Approach 2:
The correction values are calculated and stored in advance during system setup or calibration, rather than being computed in real-time during operation. This preliminary action allows the system to achieve APC-like stabilization with much simpler real-time control logic.
3Stability of the object's composition
If APC drive method is used with monitoring photodetectors, then light output stability is improved, but loss of useful light increases due to light diverted to monitoring
Solution Approach 1:
The patent uses the semiconductor laser's own characteristics (such as voltage-current relationships or known self-heating patterns) to generate correction values without requiring external monitoring photodetectors. The laser essentially monitors and corrects its own output based on pre-stored correction data, eliminating the need to divert light to separate monitoring devices.
4Productivity
If startup time is reduced by immediate high-output driving, then productivity is improved, but light output stability deteriorates due to self-heating effects
Solution Approach 1:
The patent pre-calculates correction values for various operating conditions including the transient startup phase. During startup, the system immediately applies the appropriate correction value from the lookup table based on the current operating point, enabling high output from the start while maintaining stability through the pre-computed compensation for self-heating effects.
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 enables stable high-output laser beams with reduced startup times and lower production costs, stabilizing light output and extending laser life by using a correction pattern to adjust drive current over time, effectively addressing the limitations of existing drive methods.
Implementation Method 1
detecting the output of the semiconductor laser with a photodetector
Data Source
AI summary
Semiconductor lasers are driven such that high output laser beams are stably obtained without a long start up time. The light outputs of a plurality of semiconductor lasers are detected by photodetectors. The semiconductor lasers are driven by automatic power control based on comparison results between the output of the photodetectors and a set value corresponding to a target light output for the semiconductor lasers. A correction pattern that corrects the set value and/or the output of the photodetectors such that the actual light output becomes uniform is generated in advance. The set value and/or the output are varied according to the correction pattern for a predetermined period of time from initiation of drive. A single correction pattern is employed in common with respect to the plurality of semiconductor lasers.