Gapless Prism Color Synthesis for HMD Miniaturization
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Solution Overview
Problem
Existing image display devices face challenges in miniaturization due to the visual recognition of a center line issue caused by the configuration of color synthesis prisms, particularly the cross dichroic prism, which results in a larger device size when using Philips or gapless prisms to avoid this issue.
Innovation Solution
An image light generation device incorporating a color synthesis element with a gapless prism configuration, where three prisms are joined without air layers, and specific dichroic films are used to reflect and transmit light beams at optimized angles, allowing for miniaturization while avoiding the center line visibility problem.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a cross dichroic prism is used to minimize optical path length and device size, then the device size is reduced, but a center line becomes visually recognized in the image due to the joining portion of four triangular columnar prisms
Solution Approach 1:
The invention extracts and eliminates the harmful air layer and adhesive layer from the joining portion of the prisms. By removing these intermediate layers that cause the center line to form, the patent resolves the contradiction between miniaturization and image quality, allowing the use of compact cross dichroic prism configuration without the visual defect.
Solution Approach 2:
The invention introduces a refractive index matching liquid as an intermediary substance between the prisms. This mediator has a refractive index that matches the prism material, eliminating the optical discontinuity that causes the center line. This allows the prisms to be joined without air gaps or adhesive layers, resolving the technical contradiction.
2Object-affected harmful factors
If Philips prism or gapless prism is used to avoid center line visibility, then center line is not visually recognized, but the optical path length and device size become larger
Solution Approach 1:
The invention changes the refractive index parameter of the joining medium to match the prism material. By adjusting this physical parameter, the optical properties at the joining interface are optimized to eliminate the center line effect, allowing the use of compact prism configurations without the visual defect that would otherwise require larger alternative prism designs.
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 enables a smaller size for the image light generation device without compromising image visibility, as the gapless prism configuration and optimized dichroic film angles reduce the optical path length and prevent center line visibility, achieving a compact design for applications like head-mounted displays.
Implementation Method 1
a first dichroic film configured to reflect the first color light and transmit the second color light and the third color light
Implementation Method 2
a first dichroic film configured to reflect the first color light
Implementation Method 3
a second dichroic film configured to reflect the second color light and transmit the third color light
Implementation Method 4
a second dichroic film configured to reflect the second color light
Implementation Method 5
a first prism including a first incident surface on which the first color light is incident and an emission surface from which the synthetic light is emitted
Data Source
AI summary
An image light generation device of the present disclosure includes first to third display elements configured to emit first to third color light, respectively, and a color synthesis element configured to synthesize the first to third color light. The color synthesis element includes first to third prisms, a first dichroic film configured to reflect the first color light and transmit the second and third color light, and a second dichroic film configured to reflect the second color light and transmit the third color light. The first and second prisms are joined together through a first dichroic film with no air layer therebetween, the second and third prisms are joined together through a second dichroic film with no air layer therebetween, and the main light beam incidence angle of the third color light to the second dichroic film is 40 degrees or greater.