Laser Projection Display Device Nonlinear Stability Control
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Solution Overview
Problem
Laser projection display devices using semiconductor lasers face instability in light emission due to nonlinear light-emitting characteristics, leading to unstable brightness modulation across a wide range, especially when operating near the threshold current.
Innovation Solution
A laser projection display device that employs a liquid crystal element to adjust transmittance and a control mechanism to shift the operation point of the semiconductor laser away from nonlinear areas, combining with a liquid crystal driver to manage transmittance and ensure stable light modulation across a wide brightness range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light modulation is performed in a wide range across the threshold current to adapt to different ambient brightness conditions, then adaptability is improved, but stability of light emission output deteriorates due to nonlinear characteristic
Solution Approach 1:
The light modulation range is segmented into two distinct regions: below-threshold current region and above-threshold current region. The image processing unit selectively operates in one region at a time, avoiding the nonlinear transition zone. This segmentation allows the system to maintain stability within each region while achieving wide overall adaptability through region switching.
Solution Approach 2:
The system dynamically switches between different operating regions (below-threshold and above-threshold) based on the required light modulation level. The image processing unit adjusts the driving current level dynamically, selecting the appropriate region to maintain stable operation while adapting to varying ambient brightness conditions.
2Illumination intensity
If the driving current is increased to operate above the threshold current for higher brightness output, then illumination intensity is improved, but light emission stability deteriorates due to nonlinear characteristic
Solution Approach 1:
The brightness output requirement is satisfied by selectively operating in the above-threshold current region only when high brightness is needed and stability can be maintained. The system segments the brightness range into low-brightness (below-threshold operation) and high-brightness (above-threshold operation) modes, choosing the appropriate mode based on display requirements.
Solution Approach 2:
The image processing unit changes the operating parameter (driving current level) to switch between below-threshold and above-threshold regions. By adjusting the current level parameter dynamically, the system can achieve different brightness outputs while maintaining stable operation in the selected region.
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
Enables stable light modulation over a broad brightness range by avoiding nonlinear operation areas of the semiconductor laser, ensuring consistent image brightness and preventing color balance issues.
Implementation Method 1
a liquid crystal element that transmits the laser light generated by the laser source at a predetermined transmittance, and a liquid crystal driver that changes the transmittance by applying a voltage to the liquid crystal element
Data Source
AI summary
A laser projection display device (1) includes a laser source (5), a laser driver (4) that drives the laser source, a scanning unit (7) that scans and projects laser light generated by the laser source, a liquid crystal element (14) that transmits the laser light at a predetermined transmittance, and a liquid crystal driver (17) that changes the transmittance by applying a voltage to the liquid crystal element. When a light quantity of the laser light generated by the laser source corresponds to a case in which the laser source operates in a nonlinear area, the laser driver shifts an operation point to an area other than the nonlinear area by increasing a driving level of the laser source by a predetermined amount G, and the liquid crystal driver decreases the transmittance of the liquid crystal element by a predetermined amount 1/G.