MEMS Mirror Image Projector with Beam Splitter for Speckle Reduction
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Solution Overview
Problem
Current projection systems for head-up displays face challenges in reducing both speckle and moire interference, with existing solutions either failing to address both issues effectively or being incompatible with polarized light, which affects image quality.
Innovation Solution
An image projector system utilizing a MEMS mirror and multiple-beam generators with a planar beam splitter and reflector, configured to create independent beams with an optical distance greater than half the coherent length, which are then focused onto a microlens array to average out speckle and moire patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a microlens array is used as the head-up-display to eliminate speckle, then speckle is reduced, but moire interference is created
Solution Approach 1:
The invention divides the single coherent light beam into multiple independent beams using a beam splitter and reflector arrangement. Each beam is then projected through the microlens array, creating multiple sets of speckle patterns that average out to reduce overall speckle. The optical path difference between beams (greater than coherence length) ensures statistical independence of the speckle patterns.
Solution Approach 2:
The invention changes the optical parameters by creating beams with different optical paths and angles. The beam splitter and reflector are positioned to create specific angular separations between beams, and the optical path difference is controlled to exceed the coherence length. This parameter modification allows the system to achieve both speckle reduction and moire elimination.
2Object-affected harmful factors
If conventional speckle reduction methods are used, then speckle is reduced, but they are not effective against moire interference
Solution Approach 1:
The invention adds a spatial dimension to the light beam by creating multiple beams at different angles and positions. Instead of treating the light as a single beam, the system projects multiple beams simultaneously, each creating its own interference pattern. This dimensional expansion allows the patterns to average out and reduces both speckle and moire effects.
3Object-generated harmful factors
If anti-moire filters are used to reduce moire, then moire is reduced, but speckle reduction capability is lost
Solution Approach 1:
The invention performs preliminary action by creating multiple independent beams before they reach the projection screen. The beam splitting and angular separation are established in advance, ensuring that the beams will create statistically independent speckle patterns. This preliminary structuring of the light paths enables simultaneous reduction of both speckle and moire without requiring post-processing filters.
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 and moire interference, improving the quality of the projected image by ensuring that the speckle and moire patterns from multiple independent beams overlap and average out, resulting in a clearer virtual image.
Implementation Method 1
a planar beam splitter which is arranged to receive the light beam reflected by the MEMS mirror, and a planar reflector which can receive the part of the light beam which is transmitted through the planar beam splitter
Implementation Method 2
the coherent light is projected onto the head-up-display so that a projected image appears on the head-up-display... the transparent screen will randomly diffuse the coherent light thereby creating random inference which causes speckle
Implementation Method 3
when the coherent light is projected onto the microlens array the microlens array will cause regular diffraction and regular interference known as moire
Implementation Method 4
a MEMS mirror which is arranged such that it can receive the light beam, and which can oscillate about at least one oscillation axis to scan said light beam
Implementation Method 5
a focusing lens which is arranged to receive multiple beams which are generated by the one or more multiple-beam-generators
Data Source
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AI summary
An image projector is disclosed that can include a light source and a MEMS mirror to receive a light beam emitted by the light source and oscillate to scan the light beam across multiple-beam-generators that each include a planar beam splitter arranged to receive the light beam and generate multiple beams to project an image.