Single-Layer Diffractive Combiner for Vehicle HUD
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Solution Overview
Problem
Current head-up display technologies for motor vehicles are costly and difficult to mass-produce due to complex manufacturing processes and instability of optical characteristics, particularly in diffractive combiners, which are sensitive to UV radiation and require multiple layers, limiting their reliability and scalability.
Innovation Solution
A method using nano-lithography by laser interference to produce a single-layer diffractive combiner on a transparent plastic material, allowing for mass production with a simple surface process, enabling stable optical characteristics and durability, and eliminating the need for a lens function by creating a variable-pitch diffractive grating with curved fringe lines for consistent magnification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gelatin-based photosensitive layers are used for holographic combiners, then optical processing for multiple wavelengths is achieved, but manufacturing cost increases and mass production becomes difficult
Solution Approach 1:
The patent uses a master holographic plate to create multiple copies of the diffractive combiner structure through injection molding. The master plate is fabricated using conventional holographic techniques with gelatin photosensitive material, but then used to produce numerous identical plastic combiners, enabling mass production while maintaining optical performance for multiple wavelengths
Solution Approach 2:
The patent transitions from gelatin-based holographic material to plastic material with embedded diffractive structures. By changing the material parameter from gelatin to plastic and the fabrication method from direct holographic recording to injection molding with master plate, the system achieves both multi-wavelength optical processing and mass production capability
2Adaptability or versatility
If multiple holographic layers are used in the combiner, then multicolour display is enabled, but manufacturing complexity and instability of optical characteristics increase
Solution Approach 1:
The patent combines multiple wavelength-specific diffractive structures into a single integrated plastic combiner layer. Instead of stacking multiple separate holographic layers, the injection molding process creates one combiner containing diffractive structures optimized for multiple wavelengths simultaneously, reducing complexity while maintaining multicolour display capability
Solution Approach 2:
The single plastic combiner structure is designed to perform multiple optical functions for different wavelengths within one component. The diffractive structures are engineered to handle red, green, and blue wavelengths simultaneously, making the combiner universal for multicolour display without requiring separate layers for each color
3Reliability
If conventional holographic methods are used, then optical characteristics can be achieved, but stability and durability against UV radiation deteriorate
Solution Approach 1:
The patent replaces sensitive gelatin holographic material with durable plastic material that is resistant to UV degradation. While the master plate requires careful fabrication, the resulting plastic combiners are robust, stable, and resistant to environmental factors including UV radiation, eliminating the need for protective layers
Solution Approach 2:
The patent uses plastic material with embedded diffractive structures created through injection molding. This composite approach combines the optical precision of holographically-patterned surfaces with the durability and UV resistance of plastic, achieving both stability and protection without additional layers
4Manufacturing precision
If computer calculation-based multilevel diffractive structures are used, then optical function approximation is achieved, but manufacturing precision and scalability are limited
Solution Approach 1:
The patent creates a master holographic plate with precise diffractive structures using conventional holographic techniques, then uses this master to produce numerous identical plastic combiners through injection molding. This copying approach maintains manufacturing precision while enabling mass production, overcoming the scalability limits of computer-calculated multilevel structures
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 approach enables cost-effective mass production of stable, durable diffractive combiners that can produce virtual images in single or multiple colors, with controlled magnification and improved diffraction efficiency, suitable for head-up displays in vehicles, reducing manufacturing complexity and increasing transparency and reliability.
Implementation Method 1
the two light beams coming from the same source are sent onto the flat surface of the photosensitive layer, causing interference fringes over the entire surface to be exposed
Implementation Method 2
The existence of these interferences leads to a variable insolation of the surface of the photosensitive layer, which is then subjected to a chemical substance having the property of dissolving the material according to its degree of insolation
Implementation Method 3
A diffractive component generating a figure of backlighting... a diffractive element which diffracts light in several orders
Data Source
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Figure 5~6
AI summary
The invention relates to a method for producing a single-layer diffractive combiner used in a head-up display device for motor vehicles, comprising a projection unit provided with a display element which is backlit by n=1 light sources of ?i wavelength(s), where i=1 to n, lighting at least one area of said display element, and sending a light beam towards the combiner at an angle ?p. Said method comprises the following steps: a) deposition of a photosensitive layer of a uniform thickness on a plane surface of a solid substrate; b) insulation of the interference fringes on the photosensitive layer due to the interference of two light beams R1 and R2 from a laser source; c) transformation of the insulated areas corresponding to the interference fringes into relief variations in the photosensitive layer and production of a mould reproducing said variations; and d) use of said mould for transferring the diffractive structure protruding from the substrate onto an element consisting of a homogeneous transparent plastic material forming the diffractive combiner. Step b) is carried out n times, from two light beams R1 and R2 from the same laser source of wavelength ?e, at an angle ?i, where i=1 to n between the beam R1 and the beam R2 equal to ?i=arcsin ( ?e/?i·sin(?p)), one of said interfering beams being divergent and having a spherical wave front and the other being a plane wave, the interference of the beams generating a diffractive network with an adjustable pitch and curved contour fringe lines.