Leaf Spring Diffuser Assembly for Speckle Reduction
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Solution Overview
Problem
Existing diffuser assemblies in holographic projectors, particularly in head-up displays, face challenges in maintaining image quality due to laser speckle and require complex control methods to synchronize motor vibrations, which can introduce noise and limit the use of different diffusion angles.
Innovation Solution
A diffuser assembly utilizing a leaf spring structure with high out-of-plane stiffness and low in-plane stiffness, allowing for circular movement without rotation, which is supported by a frame and actuated by motors with eccentric loads to synchronize vibrations constructively and mitigate speckle while preserving image focus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a moving diffuser is used to mitigate laser speckle, then image quality is improved, but complex control methods are required to synchronize motor vibrations which introduces noise
Solution Approach 1:
The patent employs controlled mechanical vibration of the diffuser through an actuator to mitigate laser speckle. The diffuser is vibrated at specific frequencies and amplitudes to randomize the interference pattern of coherent light, thereby reducing speckle noise in the projected image while maintaining system quietness through optimized vibration characteristics.
Solution Approach 2:
The patent utilizes variable stiffness characteristics of the leaf spring assembly to control the diffuser's motion parameters. By adjusting the stiffness parameters of the leaf springs, the system can optimize the vibration amplitude and frequency response of the diffuser, achieving effective speckle reduction while maintaining controlled and quiet operation.
2Object-affected harmful factors
If a moving diffuser is used to improve image quality, then speckle is reduced, but complex control methods are required to synchronize motor vibrations
Solution Approach 1:
The patent employs a single actuator that self-generates the vibrational motion of the diffuser without requiring complex multi-motor synchronization control. The actuator is directly coupled to the diffuser through the leaf spring assembly, creating a self-contained vibration mechanism that eliminates the need for complex control algorithms to coordinate multiple motors.
Solution Approach 2:
The patent extracts the vibration generation function from complex motor synchronization systems and consolidates it into a single dedicated actuator. This simplification removes the need for complex control methods to synchronize multiple motors, while still achieving the desired diffuser vibration for speckle reduction.
3Measurement precision
If high out-of-plane stiffness is provided to maintain focus, then image quality is improved, but in-plane movement is restricted
Solution Approach 1:
The patent applies different stiffness characteristics to different directions of the leaf spring assembly. The leaf springs are designed with high stiffness in the out-of-plane direction (perpendicular to the diffuser surface) to maintain focus, while maintaining lower stiffness in the in-plane directions to allow the necessary movement range for speckle mitigation. This directional differentiation of mechanical properties resolves the contradiction between focus maintenance and movement freedom.
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 provides improved image quality by reducing laser speckle, maintaining focus during movement, and allowing for different diffusion angles without increasing package size or introducing significant noise, enhancing the performance of holographic projectors in head-up displays.
Implementation Method 1
The leaf spring is elastic - that is, the assembly causes the diffuser to return to a mean state, or rest position, when all forces - such as those provided by the at least one actuator - are removed. The out-of-plane stiffness is relatively high to provide relatively high resistance to movement in this direction because in-plane movement is preferred
Implementation Method 2
A moving diffuser may be used to improve image quality in devices, such as picture generating units for HUD, which use coherent light, such as holographic projectors, to form images. The at least one actuator arranged to provide in-plane translation of the diffuser
Data Source
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AI summary
There is described herein a diffuser assembly comprising a leaf spring, diffuser and at least one actuator. The leaf spring is arranged as a rectangular frame having a width, x, and height, y. The diffuser is suspended by the frame such as within the frame. The at least one actuator arranged to move, such as translate, the diffuser. The assembly is arranged such that the leaf spring provides in-plane (x-y plane) stiffness, kx and ky, less than the out-of-plane (z-direction) stiffness, kz.