Volume Reflection Hologram Recording with Single-Beam Substrate Guidance
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Solution Overview
Problem
The challenge in mass manufacturing volume reflection holograms with substrate-guided reconstruction beams and/or substrate-guided diffracted beams lies in the reliance on index matching mediums, which complicates process stability due to total internal reflection (TIR) and requires complex two-beam setups, especially when multiple holograms with different sensitivities need to be recorded.
Innovation Solution
A single-beam setup is employed using a laser beam source and a reflector arrangement to produce an interference pattern in a holographic recording medium, where the recording beam and reflected beam create a grating vector that allows for substrate-guided propagation without index matching mediums, enabling flexible manufacturing through adjustments like rotation and wavelength selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a two-beam setup with index matching medium is used to produce volume reflection holograms with substrate-guided beams, then the hologram quality and beam guidance are improved, but the device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The invention extracts and eliminates the index matching medium from the traditional two-beam setup. By using a single beam that reflects off a mirror positioned behind the holographic recording medium, the method removes the complex requirement for index matching between the medium and surrounding materials, thereby simplifying the device while maintaining hologram quality.
Solution Approach 2:
Instead of using two beams entering from opposite sides (traditional approach), the invention inverts the approach by using a single beam that enters from one side, reflects off a mirror behind the medium, and creates the interference pattern. This inversion simplifies the setup while achieving the same substrate-guided beam output.
2Productivity
If index matching mediums are used to achieve substrate-guided propagation, then the beam guidance efficiency is improved, but the process stability deteriorates due to total internal reflection constraints
Solution Approach 1:
The invention introduces a mirror as an intermediary element positioned behind the holographic recording medium. This mirror enables the single beam to create the necessary interference pattern without requiring index matching mediums, thereby maintaining beam guidance efficiency while eliminating the process instability caused by total internal reflection constraints.
3Adaptability or versatility
If multiple holograms with different sensitivities are recorded using traditional methods, then the versatility is improved, but the manufacturing time and complexity increase
Solution Approach 1:
The single-beam setup with mirror enables continuous recording of multiple holograms with different sensitivities without requiring reconfiguration of the optical setup. The mirror remains in place while the single beam can be used to record successive holograms, eliminating the time-consuming setup changes required by traditional two-beam methods and enabling efficient mass manufacturing.
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 method achieves cost-effective and stable production of volume reflection holograms with substrate-guided beams, allowing for mass manufacturing by eliminating the need for index matching mediums and enhancing process flexibility, particularly in near-eye display applications.
Implementation Method 1
the reflected beam produces an interference pattern with the recording beam in the holographic recording medium, the interference pattern having the form of a grating
Implementation Method 2
the recording beam passes through the holographic recording medium and the substrate, and is reflected by the reflector arrangement towards the holographic recording medium and the substrate as a reflected beam
Implementation Method 3
Substrate-guided reconstruction beams and/or substrate-guided diffracted beams propagate via total internal reflection (TIR) inside the medium because the reconstruction angle or the diffracted beam angle, respectively, is greater than the critical angle
Data Source
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AI summary
The invention relates to a method for producing volume reflection holograms with substrate- guided reconstruction beams and/or substrate-guided diffracted beams in a single-beam set- up, comprising the steps of (i) providing at least one laser beam source (100) producing a recording beam (101, 102) having a first wave vector (201, 302b, 307), (ii) providing a holographic recording medium (107, 200) on a transparent substrate (106), the substrate (106) having a first flat side facing the at least one laser beam source (100) and an second flat side facing away from the at least one laser beam source (100), wherein the holographic recording medium (107) is arranged on the first flat side or on the second flat side, (iii) providing a reflector arrangement (103, 103') arranged on the second flat side of the substrate (106), wherein the recording beam (101, 102) irradiates the holographic recording medium (107), wherein the recording beam (101, 102) passes through the holographic recording medium (107) and the substrate (106), and is reflected by the reflector arrangement (103, 103') towards the holographic recording medium (107) and the substrate (106) as a reflected beam (104) having a second wave vector (202, 303b, 306), wherein the reflected beam (104) produces an interference pattern with the recording beam in the holographic recording medium (107), the interference pattern having the form of a grating (110, 203) having a grating vector (305), the grating vector (305) being the difference vector of the wave vector (303b, 306) of the reflected beam (104) and the wave vector (302b, 307) of the recording beam (101, 102) and the grating vector (305) also being identical to the difference vector of the wave vector (303a) of a diffracted beam and the wave vector (302a) of a reconstruction beam, and wherein a first plane spanned by the recording beam and the reflected beam is different from a second plane spanned by the reconstruction beam and the diffracted beam and wherein the grating vector (305) of the grating (110, 203) is parallel to 30 the line of intersection of the first and the second plane. The invention further relates to an apparatus for producing volume reflection holograms with substrate-guided reconstruction beams and/or substrate-guided diffracted beams in a single-beam set-up..