Anisotropic Diffuser Plate for Laser Projection Speckle Reduction
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Solution Overview
Problem
Projection display apparatuses face challenges in suppressing speckle noise due to the high coherence of laser light sources, which affects image quality and uniformity.
Innovation Solution
Incorporating a solid-state light source array, a first diffuser plate with anisotropic diffusion characteristics, and a light uniformizing element to modulate and diffuse light, ensuring an aspect ratio of 1 in the angle distribution of light incident on the rod integrator, thereby reducing speckle noise and enhancing light uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a laser light source is used to provide high brightness and coherence, then illumination intensity is improved, but speckle noise increases due to high coherence
Solution Approach 1:
The light source is divided into multiple laser elements (first, second, third laser light sources) with different wavelengths. By segmenting the single coherent source into multiple incoherent sources, the patent reduces speckle noise while maintaining high brightness through combined output.
Solution Approach 2:
The patent changes the wavelength parameter by using laser sources with different wavelengths (e.g., blue, green, red). This parameter diversity reduces coherence between light sources, thereby suppressing speckle noise while preserving illumination intensity.
2Object-generated harmful factors
If a diffuser plate is used to reduce speckle noise, then speckle noise is suppressed, but light loss increases
Solution Approach 1:
The patent uses a composite optical system combining multiple laser sources with different wavelengths and a diffuser plate. This composite approach allows the diffuser to reduce speckle from each wavelength while the combined multi-wavelength output maintains overall light efficiency and reduces total light loss.
3Object-generated harmful factors
If multiple laser sources with different wavelengths are used to reduce speckle noise, then speckle noise is suppressed, but device complexity increases
Solution Approach 1:
The patent merges multiple laser sources with different wavelengths into a single integrated light source device. This combining approach achieves speckle reduction through wavelength diversity while consolidating the system into one device unit, thereby managing complexity rather than increasing it significantly.
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 light loss, improving image quality and uniformity by expanding the light intensity distribution within the exit pupil of the projection unit, while preventing damage to optical components.
Implementation Method 1
a first diffuser plate that diffuses light emitted from the solid-state light source array
Implementation Method 2
a light uniformizing element that uniformizes the light diffused by the first diffuser plate
Implementation Method 3
a light modulation element that modulates the light uniformized by the light uniformizing element with an image signal to generate image light
Data Source
AI summary
A projection display apparatus of the present disclosure includes a solid-state light source array that includes a plurality of solid-state light sources, a first diffuser plate that diffuses light emitted from the solid-state light source array, a light uniformizing element that uniformizes the light diffused by the first diffuser plate, a light modulation element that modulates the light uniformized by the light uniformizing element with an image signal to generate image light, and a projection unit that projects the image light generated by the light modulation element. The first diffuser plate has different diffusion characteristics in a first direction and a second direction perpendicular to the first direction, and allows the light emitted from the solid-state light source array to be transmitted through the first diffuser plate to diffuse the light emitted to have an aspect ratio of an angle distribution that is approximately 1.