Laser Illumination Device Speckle Reduction Mechanism
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Solution Overview
Problem
Laser-based projectors suffer from speckle patterns due to coherent light interference, leading to degraded image quality, and existing solutions either increase apparatus size or reduce light efficiency.
Innovation Solution
An illumination device with a laser light source, an optical device, and a driving section that displaces the relative position between the optical device and the optical member to vary the incidence position and angle of the laser light, reducing speckle pattern generation while minimizing light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a laser light source is used in a projector, then color reproduction range and power consumption are improved, but speckle pattern generation occurs which degrades image quality
Solution Approach 1:
The patent applies the dynamics principle by mechanically oscillating the diffusion surface (screen or diffusion plate) at a frequency that prevents the human eye from detecting speckle patterns. The diffusion surface is mounted on a vibration mechanism that moves it dynamically, causing the speckle pattern to shift and average out over time, thereby reducing visible speckle noise while maintaining the benefits of laser light sources.
2Object-affected harmful factors
If the diffusion surface is mechanically oscillated to reduce speckle pattern, then speckle noise is reduced, but the apparatus size increases
Solution Approach 1:
The patent applies segmentation by dividing the diffusion function into multiple components: a primary diffusion plate and a secondary diffusion surface (screen). The vibration mechanism is applied only to the smaller diffusion plate rather than the entire screen assembly, reducing the mass and size requirements while still achieving effective speckle reduction through the segmented diffusion structure.
3Object-affected harmful factors
If a diffusion device is mechanically rotated to displace speckle pattern, then speckle noise is reduced, but light use efficiency decreases
Solution Approach 1:
The patent applies periodic action by oscillating the diffusion surface at a specific frequency range (20-50 Hz) that corresponds to the temporal resolution limits of the human eye. This periodic motion causes the speckle pattern to dynamically shift and average out, reducing visible speckle noise without requiring continuous high-speed rotation that would waste light. The oscillation frequency is carefully selected to balance speckle reduction with light efficiency.
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 effectively reduces speckle noise, improves image quality, and achieves downsizing and enhanced light use efficiency in laser-based projectors.
Implementation Method 1
The speckle pattern is generated due to mutual interference of light beams scattered at respective point on the diffusion surface in a random phase relationship corresponding to a microscopic irregularity on the surface.
Data Source
AI summary
Provided are an illumination device and a display apparatus capable of reducing generation of an interference pattern, while achieving downsizing and enhancing light use efficiency. An illumination device includes: a light source section that includes a laser light source; an optical device disposed on a light path through which laser light from the laser light source travels; an optical member that outputs illumination light; and a driving section that displaces a relative position between the optical device and the optical member to vary at least one of an incidence position and an incidence angle, in an incidence surface of the optical member, of the laser light.