Patterned Optical Retarder Surface Roughness Compensation
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Solution Overview
Problem
Optical systems, such as those used in head-mounted displays, face issues with reduced brightness and contrast due to manufacturing variances and misalignments, which affect the uniformity of optical retardance across different regions of the optical surface, leading to undesirable changes in light polarization and optical performance.
Innovation Solution
A patterned optical retarder with non-overlapping regions of varying RMS surface roughness is created, allowing for different retardances in each region to compensate for alignment errors and surface curvatures, achieved through etching techniques like reactive ion etching to adjust the optical thickness and retardance of polymeric retarder layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform polymeric optical retarder layer is used, then the manufacturing process is simple, but the optical performance is reduced due to manufacturing variances and misalignments causing non-uniform retardance
Solution Approach 1:
The patent divides the optical retarder into multiple regions with different surface roughness characteristics. Specifically, a first region has a first surface roughness while a second region has a second surface roughness different from the first. This local differentiation allows each region to be optimized for specific optical functions, compensating for manufacturing variances and misalignments in different areas of the optical system.
Solution Approach 2:
The optical retarder is segmented into distinct regions (first region and second region) with different optical properties. Each region can have different retardance values and surface roughness characteristics, allowing the system to address local optical imperfections rather than requiring perfect uniformity across the entire retarder.
2Reliability
If the optical retarder has different retardances in different regions, then alignment errors and surface curvatures are compensated, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes surface roughness as a controllable parameter to achieve different optical retardances in different regions. By varying the RMS surface roughness between regions (first region has first surface roughness, second region has second surface roughness), the optical path difference is modified to compensate for alignment errors and surface curvatures. This approach transforms the manufacturing challenge into controlling surface texture rather than requiring extremely precise thickness control.
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
The solution enhances optical performance by improving contrast and compensating for optical defects, particularly in compact folded systems, by ensuring uniform retardance across the optical surface, thereby maintaining optimal light transmission and polarization.
Implementation Method 1
reactive ion etching the surface of the polymeric optical retarder layer such that a second region thereof uncovered by the mask has an optical thickness different from the optical thickness of the first region
Data Source
AI summary
A patterned optical retarder including non-overlapping first (21) and second (27) regions with respective first and second major surfaces having different RMS surface roughnesses. For substantially normally incident light over a wavelength range from about 400 nm to about 1000 nm, the optical retarder has different retardances in the respective first and second regions.