Semiconductor Laser Speckle Noise Reduction via Current Intensity Switching
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Solution Overview
Problem
Display apparatus using semiconductor lasers suffer from speckle noise due to the coherence properties of the lasers, leading to deterioration in image quality, as existing techniques for reducing speckle noise, such as high-speed voltage switching, are not effective with conventional laser diode drivers.
Innovation Solution
A laser light source device and display apparatus that generate and switch multiple sets of current intensity data to drive semiconductor lasers, increasing the width of the light emission wavelength, thereby reducing speckle noise by averaging gray scale gaps between lines and frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor laser is used as a light source, then color reproducibility and operating life are improved, but speckle noise increases due to coherence properties
Solution Approach 1:
The patent applies dynamics by switching the driving current intensity dynamically between multiple predetermined intensity levels during laser light emission. This temporal variation in current intensity causes corresponding variations in emission wavelength, transforming a static monochromatic source into a dynamic multi-wavelength source that reduces speckle noise while maintaining the reliability advantages of semiconductor lasers.
Solution Approach 2:
The patent changes the physical parameter of emission wavelength by varying the driving current intensity. By switching between multiple current intensity levels, the laser emits light at multiple slightly different wavelengths, which broadens the effective wavelength spectrum and reduces the coherence-induced speckle noise while preserving color reproducibility.
2Object-generated harmful factors
If high-speed voltage switching is used to reduce speckle noise, then speckle noise is reduced, but conventional laser diode drivers are not effective
Solution Approach 1:
The patent implements periodic action by switching the driving current intensity between multiple predetermined levels in a systematic manner during the emission period. This periodic modulation of current intensity creates corresponding periodic variations in emission wavelength, which effectively reduces speckle noise through temporal averaging while being compatible with conventional laser diode driver capabilities.
3Illumination intensity
If multiple sets of current intensity data are switched, then light emission wavelength width increases, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing multiple sets of current intensity data corresponding to different emission wavelengths before operation. These predetermined current intensity levels are stored and systematically switched during emission, allowing the system to achieve broad wavelength coverage without requiring complex real-time control algorithms or additional hardware components.
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 reduces speckle noise and improves image quality by increasing the light emission wavelength width and averaging gray scale gaps, enhancing the performance of semiconductor laser-based display systems.
Implementation Method 1
a semiconductor laser for emitting laser light
Implementation Method 2
Since the semiconductor laser slightly changes its light emission wavelength depending on the switching of the driving current, a width of a light emission wavelength of synthesized laser light is able to increase
Data Source
AI summary
A laser light source device includes a semiconductor laser, a current supplying unit to supply a driving current to the semiconductor laser, and a signal generator to generate current intensity data for setting an intensity of the driving current. The signal generator generates, for an input signal corresponding to continuous pixels for a same color, a plurality of sets of the current intensity data indicating current intensities different from each other, and transmits the plurality of sets of the current intensity data to the current supplying unit while sequentially switching the plurality of sets of the current intensity data. The current supplying unit drives the semiconductor laser based on the plurality of different sets of the current intensity data.