Display Optical System Adhesive Control for Wide-Angle HMDs
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Solution Overview
Problem
Existing display optical systems for head-mounted displays (HMDs) face challenges in maintaining high image contrast and reducing thickness and focal length while achieving a wide angle of view, due to unevenness in adhesive layers causing local optical power and focus shifts.
Innovation Solution
The display optical system incorporates a configuration with a half-transmissive reflective surface, polarization separation surfaces, and polarization elements, where adhesive layers between these components are maintained within specific thickness and variation ranges to minimize unevenness, ensuring adhesion without generating local optical power, thereby enhancing image contrast and reducing system thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive layers are used to attach film elements to polarization elements or lenses, then the components can be assembled together, but unevenness in the adhesive layers causes local optical power and focus shifts, degrading image contrast
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the adhesive layer (first adhesive layer) to satisfy a specific inequality relationship. By optimizing this dimensional parameter, the adhesive layer provides sufficient bonding strength while minimizing thickness variations that would cause local optical power and focus shifts, thus resolving the contradiction between ease of assembly and surface uniformity.
2Adaptability or versatility
If the display optical system includes multiple polarization elements and film elements, then the angle of view can be widened, but the system thickness increases
Solution Approach 1:
The patent merges multiple optical components (polarization elements, film elements, and lenses) into a compact integrated structure. The film element is adhered directly to the polarization element or lens via the adhesive layer, eliminating the need for separate mounting structures and reducing overall system thickness while maintaining the widened angle of view functionality.
Solution Approach 2:
The patent employs a nested configuration where the film element is positioned between the polarization element and the lens, with the adhesive layer bonding them together. This nesting arrangement allows multiple functional elements to occupy overlapping or adjacent spatial zones, reducing the total thickness of the optical system while preserving all necessary optical functions for wide angle of view.
3Reliability
If the adhesive layer thickness is increased to improve bonding strength, then the attachment reliability improves, but the unevenness and local optical power increase, degrading image quality
Solution Approach 1:
The patent resolves this contradiction by changing the thickness parameter of the adhesive layer to an optimized value that satisfies a specific mathematical inequality. This parameter optimization ensures the adhesive layer is thick enough to provide reliable bonding between components while thin enough to minimize thickness variations that would cause local optical power and focus shifts, thereby maintaining image quality.
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 improved image contrast by minimizing local contrast decreases and reduces the thickness and focal length of the display optical system, enabling a wider angle of view and lighter, more comfortable HMDs.
Implementation Method 1
an optical system that folds an optical path by utilizing polarization and includes a polarization selective element (polarization separation element) and a half-mirror
Implementation Method 2
The film element is adhered to one of the plurality of polarization elements or a lens via a first adhesive layer on a reflection side of the film element
Implementation Method 3
At least one of surfaces having refractive power in the display optical system is aspheric
Data Source
AI summary
A display optical system is configured to guide light from a display element to an observation side. The display optical system includes a half-transmissive reflective surface, a polarization separation surface, and a plurality of polarization elements. At least one of surfaces having refractive power in the display optical system is aspheric. At least one of the half-transmissive reflective surface or the polarization separation surface includes a film element. The film element is adhered to one of the plurality of polarization elements or a lens via a first adhesive layer on a reflection side of the film element. A predetermined inequality is satisfied.