Optical Element Production via High-Intensity Holographic Exposure
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Solution Overview
Problem
Existing methods for producing optical elements through multiple recording exposure suffer from significant holographic scattering, which reduces diffraction efficiency and introduces noise into AR images.
Innovation Solution
The method involves performing multiple recording exposure on a hologram recording medium with a recording layer containing a polymerizable compound and a photopolymerization initiator, ensuring an average exposure intensity of 6 mW/cm2 or more, and maintaining a refractive index difference (Δn) of 0.02 or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple recording exposure is performed with conventional parameters, then the optical element can be produced, but significant holographic scattering occurs which reduces diffraction efficiency and introduces noise
Solution Approach 1:
The patent applies parameter changes by optimizing the exposure intensity to maintain it above a specific threshold during multiple recording exposure. This parameter control prevents the polymerizable compound from excessive diffusion while still allowing sufficient polymerization to occur, thereby reducing holographic scattering and improving diffraction efficiency without sacrificing the ability to produce the optical element
2Quantity of substance
If multiple recording exposure is performed to create volume type hologram, then space is saved and high diffraction efficiency is achieved, but holographic scattering increases
Solution Approach 1:
The patent resolves this contradiction by changing the exposure intensity parameter during multiple recording exposure. By maintaining exposure intensity above a specific threshold, the method enables volume type hologram recording that efficiently uses space while suppressing holographic scattering through controlled polymerization that prevents excessive concentration distribution of the polymerizable compound
3Manufacturing precision
If photopolymerization initiator causes chemical reaction in high light intensity area, then interference patterns are recorded as refractive index difference, but concentration distribution of polymerizable compound occurs causing holographic scattering
Solution Approach 1:
The patent applies parameter changes by controlling the exposure intensity to remain above a specific threshold during multiple recording exposure. This controlled parameter approach allows the photopolymerization initiator to create the necessary refractive index differences for recording interference patterns, while simultaneously preventing excessive concentration distribution of the polymerizable compound that would cause holographic scattering
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 effectively minimizes holographic scattering, thereby enhancing the diffraction efficiency and improving the quality of AR images by reducing noise.
Implementation Method 1
a photopolymerization initiator causes a chemical reaction and becomes an active substance in the area of high light intensity among the interference patterns. This then acts on the polymerizable compound, causing it to polymerize.
Implementation Method 2
A hologram is a recording method in which an interference pattern created by interference fringes of two lights (referred to as recording lights) called a reference light and an object light (also referred to as information light or signal light) is three-dimensionally recorded inside a recording medium.
Implementation Method 3
a holographic recording medium, which has been attracting attention in recent years, is a recording medium that utilizes light interference and diffraction phenomena
Data Source
AI summary
A method for producing an optical element, wherein a hologram recording medium having a recording layer containing a polymerizable compound and a photopolymerization initiator is subjected to multiple recording exposure of a hologram under conditions where average exposure intensity based on the following formula (1) is 6 mW/cm2 or more.Average exposure intensity=∑ i=1m(ETi×EPWi)∑ i=1m(ETi+EITi-1)(1)(In the formula (1), ETi is a single exposure time, which indicates exposure time (seconds) per multiple recording exposure. EPWi is exposure light intensity, which indicates total light intensity (mW/cm2) of reference light and object light. EITi-1 is exposure interval time, which indicates time (seconds) between one recording exposure and another recording exposure in the multiple recording exposure. m is a natural number indicating a total number of multiplexes. With the proviso that when i=1, EITi-1 is treated as zero.)