Semiconductor Laser Speckle Noise Reduction via Dynamic Current Modulation
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Solution Overview
Problem
Semiconductor laser-based display devices face degradation in display quality due to speckle noise, which is not effectively addressed by existing technologies.
Innovation Solution
A semiconductor laser with a drive current composed of a direct current and a superposed alternating current, where the alternating current has a non-square waveform and a frequency between 50 Hz to 500 kHz, is used to reduce speckle noise by expanding the emission wavelength range and reducing coherence length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor laser is used as a light source in display devices, then high coherence and laser performance are achieved, but speckle noise is generated that degrades display quality
Solution Approach 1:
The patent applies dynamics by modulating the drive current with a non-square wave alternating current component superposed on the direct current. This dynamic current modulation causes the emission wavelength to vary over time, which in turn varies the coherence length dynamically. This temporal variation in coherence length effectively reduces speckle noise while maintaining laser performance.
Solution Approach 2:
The patent changes the electrical parameter (drive current waveform) by introducing a non-square wave alternating current component with specific frequency (50 Hz to 500 kHz). This parameter change causes corresponding changes in the optical parameters (emission wavelength and coherence length), thereby reducing speckle noise without sacrificing laser performance.
2Object-affected harmful factors
If a non-square wave alternating current is superposed on the direct current to reduce speckle noise, then display quality is improved, but the drive current complexity increases
Solution Approach 1:
The patent employs periodic action by using an alternating current component with a specific frequency range (50 Hz to 500 kHz) superposed on the direct current. This periodic modulation of the drive current creates time-varying emission wavelength and coherence length, which reduces speckle noise. The periodic nature provides a systematic and controllable approach to managing the current waveform complexity.
3Object-affected harmful factors
If the emission wavelength range is expanded to reduce coherence length, then speckle noise is reduced, but the precision of wavelength control may be affected
Solution Approach 1:
The patent applies partial action by introducing an alternating current component that modulates the emission wavelength within a controlled range. The modulation amplitude and frequency are optimized to achieve sufficient wavelength variation for speckle noise reduction (excessive action in terms of variation) while maintaining adequate wavelength control precision (avoiding complete loss of control). This balanced approach allows both goals to be achieved.
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 to an unnoticeable level, improving display quality by expanding the emission wavelength range and enhancing responsiveness of the semiconductor laser's emission wavelength and output changes.
Implementation Method 1
a semiconductor laser element LD that emits light having an emission main wavelength λ within a visible light wavelength range in response to a drive current C
Data Source
AI summary
According to one embodiment, a semiconductor laser includes a semiconductor laser element. A drive current which is composed of a direct current and an alternating current superposed thereon is applied to the semiconductor laser element. A waveform of the alternating current is a non-square wave. A frequency of the alternating current is from 50 Hz to 500 kHz.