Lissajous Diffuser Actuator for Laser Projection Speckle Reduction
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Solution Overview
Problem
Coherent light sources in projection visual display systems produce visible speckle due to their narrowband and polarized nature, which affects image quality by creating a grainy pattern, and existing solutions fail to adequately address this issue.
Innovation Solution
A diffuser is placed in the optical path of the PVD system and actuated to move in a Lissajous curve transverse to the optical path using a single drive axis, coupled with a spring system, to reduce speckle by varying the polarization and phase of light diffused at different angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If coherent light sources such as lasers are used to increase brightness in PVD systems, then the brightness of the system is improved, but a grainy speckle pattern appears in the image
Solution Approach 1:
The patent applies the Dynamics principle by moving the diffuser at a controlled velocity through the optical path. This dynamic movement continuously changes the phase and polarization of the coherent light, causing the speckle pattern to fluctuate over time. When the diffuser moves at sufficient velocity, the temporal averaging of the fluctuating speckle patterns reduces the visibility of the grainy pattern while preserving the brightness enhancement provided by the coherent light source.
Solution Approach 2:
The patent employs the Parameter changes principle by modifying the velocity parameter of the diffuser movement. By controlling the diffuser to move at a minimum velocity greater than zero, the system changes the temporal characteristics of the light interaction with the diffuser. This velocity parameter control ensures that the speckle pattern fluctuates rapidly enough to be imperceptible to the human eye, thereby reducing the harmful speckle effect while maintaining the beneficial brightness.
2Object-generated harmful factors
If a diffuser is moved to reduce speckle, then the speckle visibility is reduced, but the device complexity increases due to the need for a diffuser actuator and control system
Solution Approach 1:
The patent applies the Mechanics substitution principle by replacing complex multi-axis mechanical diffuser actuators with a simpler single-axis linear actuator. Instead of requiring sophisticated mechanisms to move the diffuser in multiple dimensions, the invention achieves speckle reduction by moving the diffuser along a single linear path through the optical path. This substitution of a simple linear actuation mechanism for a complex multi-degree-of-freedom mechanical system significantly reduces device complexity while maintaining effective speckle suppression.
Solution Approach 2:
The patent employs the Taking out principle by extracting the essential function of speckle reduction from complex mechanical systems and isolating it to a single critical parameter: linear velocity along one axis. By removing unnecessary mechanical complexity and focusing only on the essential movement requirement (linear motion through the optical path at sufficient velocity), the invention simplifies the overall system architecture while preserving the core speckle-reduction functionality.
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 visible speckle by ensuring the diffuser always moves with a minimum velocity greater than zero, resulting in a significant reduction of subjective-speckle contrast to acceptable levels, enhancing image quality without increasing the size of the diffuser.
Implementation Method 1
Speckle scattering optical material is used in projection displays at the screen in order to expand the viewing angle. Within the illumination system scattering or diffusing material is needed to distribute the light over the area of the spatial light modulator.
Implementation Method 2
Speckle has been attributed to the fact that coherent light reflected by or through a diffuser produces a complex, random, but stationary diffraction pattern.
Implementation Method 3
This grainy pattern, also known as speckle or the scintillation effect, arises due to the highly narrowband and polarized nature of the coherent light incident on a diffuse surface.
Implementation Method 4
a diffuser actuator having a single drive axis configured to cause the diffuser to travel in a Lissajous curve at least partially transverse to the optical path
Data Source
AI summary
The disclosure provides an apparatus for reducing speckle in a projection visual display (PVD) system, a method of reducing visible speckle in a PVD system and a PVD system incorporating the method or apparatus. In one embodiment, the apparatus includes a diffuser interposable in an optical path of a PVD system and a diffuser actuator having a single drive axis configured to cause the diffuser to travel in a Lissajous curve at least partially transverse to the optical path.