HUD Image Generator Microstructure Matrix Speckle Reduction
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Solution Overview
Problem
Head-up display systems in vehicles suffer from speckle and moiré effects due to coherent laser sources interacting with diffusing screens, causing discomfort for drivers as these random spots change intensity and visibility with driver position.
Innovation Solution
Incorporating diffraction means with a matrix of microstructures arranged in distinct patterns in the intermediate image plane to control interference, breaking local periodicity and reducing or eliminating speckles and moiré effects, while using a diffracting optical element with varying thickness levels to manage light diffraction and scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a coherent laser source is projected onto a diffusing screen, then the driver can see information in his field of vision, but random spots (speckles) appear on the image causing discomfort
Solution Approach 1:
The patent divides the single diffusing screen into multiple sub-screens or diffusing elements arranged in a matrix. Each sub-screen receives a portion of the laser beam and diffuses it independently. This segmentation breaks the coherent interference pattern that causes speckles, as the speckle patterns from each sub-screen are spatially separated and do not constructively interfere with each other in the same way.
Solution Approach 2:
The patent applies different optical properties to different regions of the display system. Specifically, different zones or sub-screens may have different diffusion characteristics, orientations, or optical densities. This local variation in optical quality ensures that coherent light is scattered differently across various regions, preventing the formation of uniform speckle patterns while maintaining overall image brightness and information visibility.
2Ease of operation
If a diffusing screen with a rough face is used to diffuse the collimated beam, then the light is dispersed, but structured interferences (moiré effects) appear due to pattern repetitiveness
Solution Approach 1:
The patent introduces asymmetry in the arrangement and optical properties of the diffusing elements. Instead of using identical repeating patterns throughout the display, the matrix of sub-screens or diffusing elements varies in orientation, size, or diffusion characteristics. This asymmetric distribution disrupts the periodicity required for moiré effect formation, eliminating the structured interference patterns while preserving the light diffusion function.
Solution Approach 2:
The patent transitions from a two-dimensional repeating pattern to a three-dimensional or multi-layered structure. By arranging diffusing elements in depth or using multiple layers with different orientations, the system breaks the planar periodicity that causes moiré effects. This dimensional change allows light to be diffused effectively while preventing the formation of repetitive interference patterns that would otherwise appear on the display surface.
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 minimizes speckle and moiré effects, enhancing image quality and driver comfort by controlling interference patterns and maintaining high contrast for virtual images displayed in the vehicle's field of view.
Implementation Method 1
diffraction means placed in an intermediate image plane, provided with a plurality of microstructures arranged according to a matrix to form a matrix of microstructures
Implementation Method 2
control the interference occurring within the light beam. These interferences, which are the cause of speckles and/or moiré effects
Implementation Method 3
This screen makes it possible to diffuse the collimated beam. Such a diffuser generally comprises a rough face, causing the dispersion of the light beam
Data Source
AI summary
The invention relates to an image generator (100), particularly for a head-up display device, comprising at least one laser source (101) producing a light beam (10), and means (102) for forming an image in an intermediate image plane (111), the image generator being characterised in that it also comprises diffraction means (140) located in the intermediate image plane (111) and provided with a plurality of microstructures (711-714, 7201-7225) arranged in a matrix (700) in order to form a matrix of microstructures, each microstructure being defined by a pattern, the matrix of microstructures comprising at least two different patterns.