Transparent Screen Speckle Reduction via Wavefront Modulation
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Solution Overview
Problem
Conventional projection display units face the challenge of reducing speckle noise while maintaining image brightness, as the diverging angle required to spread image light leads to dimming due to energy conservation laws.
Innovation Solution
Incorporating a wavefront-dividing phase-modulating component before the optical diffusing component to divide and modulate the wavefront of image light emitted from the Fresnel optical component, reducing speckle noise without compromising brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the diverging angle is increased to spread image light and reduce speckle noise, then speckle noise is reduced, but image brightness decreases due to energy conservation
Solution Approach 1:
The invention segments the wavefront of image light into multiple sub-wavefronts using a wavefront-dividing phase-modulating component. This segmentation allows the light to be divided into multiple paths that can be independently modulated, reducing speckle noise through wavefront diversity while maintaining the total energy and brightness of the image light.
Solution Approach 2:
The invention changes the phase parameter of the image light wavefront using a phase-modulating component. By modulating the phase rather than increasing the diverging angle, the system reduces speckle noise through phase diversity while conserving energy and maintaining image brightness.
2Object-affected harmful factors
If a speckle reduction micro-lenticular lens is disposed on the light source side of the Fresnel lens screen, then speckle noise is reduced, but the device complexity increases
Solution Approach 1:
The invention merges the wavefront-dividing phase-modulating component with the existing optical path between the Fresnel lens screen and the optical diffusing component. This integration allows speckle reduction functionality to be added without requiring separate lens assemblies or complex additional optical paths, thereby reducing device complexity compared to conventional approaches.
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 configuration effectively reduces speckle noise while maintaining the brightness of the image light by providing the image light with various inclinations and phase differences, thereby minimizing the need for increased diverging angles.
Implementation Method 1
a wavefront-dividing phase-modulating component for dividing the wavefront of the image light emitted from a Fresnel optical component and for modulating the phase of the wavefront
Implementation Method 2
a Fresnel lens screen 7 which is a Fresnel optical component for bending the image light radiated from the projector 1 toward the observer side
Implementation Method 3
an optical diffusing component 10 for providing a diverging angle to the image light to spread it
Data Source
AI summary
A transparent screen and a projection display unit capable of reducing the speckle with maintaining the brightness of the image light. A wavefront-dividing phase-modulating component 21, which divides the wavefront of the image light emitted from a Fresnel lens screen 7 and modulates the phases of the wavefronts divided, is disposed before an optical diffusing component 10. Alternatively, a spatial frequency modulating component 22, which modulates the spatial frequency of the image light diffused by the optical diffusing component 10, is disposed on the light-output side (observer side) of the optical diffusing component 10.