Liquid Crystal Optical Diffraction Element for Compact Optical Pickups
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Solution Overview
Problem
Conventional optical diffraction elements used in optical pickups, such as those for CDs, DVDs, and Blu-rays, require additional components like polarization filters and half-wave plates to manage light polarization, leading to increased size and complexity due to the need for thicker substrates and light prevention mechanisms.
Innovation Solution
An optical diffraction element comprising a substrate with an orientation layer of anisotropic polymers and a liquid crystal layer, where the liquid crystal molecules are oriented perpendicular or inclined relative to the substrate, allowing for controlled diffraction efficiency based on polarization direction without the need for additional filters or plates, achieved through specific manufacturing processes involving linearly polarized light and polymeric liquid crystal solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional optical diffraction element uses a substrate with recessed portions formed by etching, then the diffraction function is achieved, but the substrate thickness must be increased to maintain structural strength
Solution Approach 1:
The patent combines the diffraction function and polarization control function into a single integrated optical element. The liquid crystal layer with specific orientation patterns is formed on the substrate surface, merging the diffraction grating function with the polarization-selective light control function, thereby eliminating the need for separate polarization filters and half-wave plates that would increase overall thickness
Solution Approach 2:
The patent changes the optical parameters of the substrate surface by forming a liquid crystal layer with controlled orientation patterns. By adjusting the liquid crystal molecule orientation (parallel or perpendicular to the substrate surface) and the refractive index distribution, the diffraction efficiency and polarization control are achieved without increasing substrate thickness
2Reliability
If polarization filters and half-wave plates are affixed to the optical diffraction element, then light polarization control is improved, but the overall apparatus size increases
Solution Approach 1:
The patent integrates the polarization control function directly into the optical diffraction element by forming a liquid crystal layer with specific orientation patterns on the substrate. This merging of functions eliminates the need for separate polarization filters and half-wave plates, thereby reducing the overall apparatus volume while maintaining reliable polarization control
Solution Approach 2:
The optical element achieves multi-functionality by simultaneously providing diffraction and polarization control through the liquid crystal layer. The same liquid crystal layer that provides diffraction also controls light polarization through its molecular orientation, making the element universal in handling both functions without requiring additional components
3Reliability
If the optical diffraction element uses additional components for polarization management, then light polarization control is improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple optical functions (diffraction and polarization control) into a single integrated element with a liquid crystal layer. This reduces device complexity by eliminating the need for multiple separate components while maintaining reliable polarization management through the oriented liquid crystal molecules
Solution Approach 2:
The liquid crystal layer inherently provides both diffraction and polarization control functions through its molecular orientation and optical properties. The oriented liquid crystal molecules automatically manage light polarization without requiring external control mechanisms, making the device simpler while maintaining reliable polarization management
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 configuration enables a compact optical diffraction element with differential diffraction efficiencies for different polarization directions, preventing light from returning to the laser and stabilizing the output, thus reducing the overall apparatus size while maintaining effective light management.
Implementation Method 1
a liquid crystal layer formed on the orientation layer. The liquid crystal layer includes a plurality of orientation patterns that are formed periodically and include liquid crystal molecules having different orientation directions, and the orientation direction for at least some of the orientation patterns is perpendicular to or inclined relative to the surface of the substrate, as a result of aligning with the orientation of the orientation layer
Implementation Method 2
An optical diffraction element comprising a substrate; an orientation layer that is formed on one surface of the substrate and includes anisotropic polymers that are oriented perpendicular to or inclined relative to a surface of the substrate
Implementation Method 3
irradiating a partial region of the optical orientation layer with first linearly polarized light from a direction normal to the surface of the substrate, such that the polymers are oriented in a polarization direction of the linearly polarized light parallel to the substrate
Implementation Method 4
applying on the optical orientation layer a polymeric liquid crystal solution that includes polymeric liquid crystal molecules; and hardening the polymeric liquid crystal molecules through polymerization
Data Source
AI summary
Provided is an optical diffraction element that restricts overall thickness of the element while maintaining strength. The optical diffraction element comprises a substrate; an orientation layer that is formed on one surface of the substrate and includes anisotropic polymers that are oriented perpendicular to or inclined relative to a surface of the substrate in at least a partial region of the orientation layer; and a liquid crystal layer formed on the orientation layer. The liquid crystal layer includes a plurality of orientation patterns that are formed periodically and include liquid crystal molecules having different orientation directions, and the orientation direction for at least some of the orientation patterns is perpendicular to or inclined relative to the surface of the substrate, as a result of aligning with the orientation of the orientation layer formed on a bottom surface of the orientation patterns.