Vibrating Diffusing Screen for Laser Speckle Reduction
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Solution Overview
Problem
Conventional laser projectors suffer from unwanted speckle patterns due to the coherent nature of laser light interacting with non-specular surfaces, which can distort the projected image and cause sparkle-like effects.
Innovation Solution
Incorporating a diffusing screen, either transmissive or reflective, phase-modulates the laser light to create multiple virtual sources, reducing speckle interference by vibrating the screen in-plane at a speed faster than the human eye's response time, thereby minimizing perceived speckle patterns without affecting the projected image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser light is used as the light source, then brightness and lifespan are improved, but speckle patterns are generated
Solution Approach 1:
The patent applies mechanical vibration by vibrating the diffusing screen in-plane at a frequency faster than the human eye's response time. This vibration causes the screen to dynamically change its diffusing characteristics, preventing the formation of stable speckle patterns while maintaining the projected image quality. The vibration frequency is specifically chosen to exceed the persistence of vision threshold, effectively averaging out the speckle interference over time.
Solution Approach 2:
The patent introduces a diffusing screen as an intermediary component between the laser light source and the projection display. This screen acts as a mediator that phase-modulates the coherent laser light, converting it into a state that reduces speckle interference. The diffusing screen creates multiple virtual sources that disrupt the coherent interference patterns, thereby reducing harmful speckles while preserving the overall image quality.
2Object-generated harmful factors
If a diffusing screen is introduced to reduce speckle, then speckle patterns are reduced, but device complexity increases
Solution Approach 1:
The diffusing screen serves multiple functions simultaneously: it phase-modulates the laser light to create multiple virtual sources, diffuses the coherent light to reduce speckle interference, and when vibrated, dynamically adjusts its diffusing characteristics to prevent stable speckle formation. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving effective speckle reduction.
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 or eliminates speckle patterns in projected images, maintaining image quality while utilizing the advantages of laser light sources such as high brightness, long lifespan, and compact size, suitable for pico projectors.
Implementation Method 1
a diffusing screen, either transmissive or reflective, phase-modulates the laser light to create multiple virtual sources
Implementation Method 2
A coherent laser beam incident on a non-specular reflecting surface such as a display screen or a wall, may be scattered with random phase by the surface
Implementation Method 3
reducing speckle interference by vibrating the screen in-plane at a speed faster than the human eye's response time
Implementation Method 4
The coherent nature of laser light can cause undesired laser speckles. A coherent laser beam incident on a non-specular reflecting surface... the scattered light with random phase will interfere to form a speckle pattern in the retina of the observer
Data Source
AI summary
An image projector includes a light source for displaying light and a diffusing screen coupled to an in-plane vibrator. The diffusing screen is positioned to receive the display light from the light source and generate phase-modulated display light. The image projector also includes a collimating element positioned to receive the phase-modulated display light. The image projector further includes a display panel positioned to receive the phase-modulated display light after being collimated by the collimating element. The display panel is configured to generate a projectable image using the phase-modulated display light.