Polarization Converting Element Using Quartz Crystal Phase Compensation
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Solution Overview
Problem
The existing polarization converting elements in liquid crystal projectors face challenges with polarization conversion efficiency due to deviations in the cutting angle of quartz crystal ½-wavelength plates, leading to defective products and reduced efficiency, especially at shorter wavelengths.
Innovation Solution
A polarization converting element with a translucent substrate made of an inorganic crystal material, where the plate thickness and cutting angle are adjusted to satisfy specific conditions, ensuring high polarization conversion efficiency across a predetermined wavelength region, and using a dielectric multi-layer film for the polarization separating portion, allowing for a compact structure without a glass intermediary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a quartz crystal ½-wavelength plate is used to increase heat resistance, then thermal stability is improved, but polarization conversion efficiency deteriorates when cutting angle deviates from design value
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between plate thickness, cutting angle, and design wavelength to compensate for cutting angle deviations. The formulas provided allow adjustment of plate thickness based on actual cutting angle measurements to maintain the required phase difference of 180 degrees, thereby preserving polarization conversion efficiency while using heat-resistant quartz crystal material.
2Ease of manufacture
If organic material ½-wavelength plate is used, then ease of manufacture is improved, but heat resistance deteriorates
Solution Approach 1:
The patent transitions from organic materials to inorganic quartz crystal materials, representing a composite material substitution. This change provides superior heat resistance and durability while the provided formulas enable precise control of optical properties, maintaining polarization conversion efficiency despite the more rigorous manufacturing requirements of quartz crystal.
3Reliability
If cutting angle is adjusted to compensate for deviation, then polarization conversion efficiency is maintained, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements a feedback mechanism where the actual cutting angle is measured, and based on this measurement, the plate thickness is adjusted according to the provided formulas. This closed-loop approach compensates for cutting angle deviations and maintains the required phase difference, ensuring polarization conversion efficiency while providing a systematic method to handle manufacturing variations.
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 achieves reliable polarization conversion efficiency of 0.8 or higher across 400 nm to 700 nm wavelengths, with improved heat dissipation and longer service life, while maintaining the polarization state, thus enhancing the performance and reliability of projection-type imaging devices.
Implementation Method 1
a translucent substrate made of an inorganic crystal material having birefringent properties and optically rotatory power
Implementation Method 2
a translucent substrate made of an inorganic crystal material having birefringent properties and optically rotatory power
Data Source
AI summary
A polarization separating element is configured to include a translucent substrate formed of a crystal material having birefringent properties and optically rotatory power and a polarization separating portion formed on the incidence-side surface of the translucent substrate so as to transmit a P-polarized light beam and reflect an S-polarized light beam. A reflecting element that reflects the S-polarized light beam reflected by the polarization separating portion is disposed so as to be separated approximately in parallel to the translucent substrate. A predetermined function is set such that the P-polarized light beam having passed through the polarization separating portion and been incident to the translucent substrate is converted so as to be parallel to the polarization plane of the S-polarized light beam so that the P-polarized light beam is output as the S-polarized light beam.