Compact Collimating Optical Device for Wide FOV HMDs
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Solution Overview
Problem
Conventional compact optical devices for head-mounted displays (HMDs) and head-up displays (HUDs) face challenges with increasing field-of-view (FOV) requirements, leading to bulkier and heavier designs, and suffer from limitations in manufacturability and eye-motion-box constraints, which restrict pupil motion and image quality.
Innovation Solution
A compact collimating optical system using a light-guide with a light-waves transmitting substrate, polarizing beamsplitters, retardation plates, and a prism, where input light-waves intersect the substrate at an oblique angle greater than the critical angle for total internal reflection, allowing for a compact and high-quality image with wide FOV and large eye-motion-box.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional free-space optical modules are used to increase field-of-view, then the field-of-view increases, but the device becomes larger, heavier, and bulkier
Solution Approach 1:
The patent combines multiple optical functions (collimation, reflection, beam steering) into a single integrated light-guide module. The light guide integrates a collimating lens, reflecting surfaces, and beam steering mechanisms within one compact substrate, eliminating the need for separate conventional optical modules and achieving both wide FOV and compact form factor
Solution Approach 2:
The patent uses a planar light-guide substrate that directs light in multiple dimensions through integrated reflecting surfaces and beam steering elements. By transitioning from conventional three-dimensional optical module stacking to a two-dimensional planar integration approach, the system achieves wide field-of-view without increasing device bulk
2Volume of moving object
If compact optical solutions are implemented, then device size decreases, but manufacturability suffers and eye-motion-box becomes very small
Solution Approach 1:
The light guide serves multiple functions simultaneously: it acts as a collimating element, a beam steering device, a reflecting surface, and an optical waveguide. This multi-functionality reduces the number of separate components needed, simplifying the overall manufacturing process while maintaining compact dimensions and adequate eye-motion-box
Solution Approach 2:
The patent employs specific refractive index matching between the light guide substrate and surrounding media, along with precisely controlled angles of incidence for light coupling, to optimize total internal reflection efficiency. These parameter optimizations enable compact design without compromising manufacturability or eye-motion performance
3Volume of moving object
If compact optical solutions are implemented, then device size decreases, but eye-motion-box becomes very small restricting pupil motion
Solution Approach 1:
The patent implements dynamic beam steering capabilities within the compact light guide using movable or adjustable reflecting surfaces. This allows the optical system to dynamically track and follow pupil movements, maintaining a functional eye-motion-box within a compact form factor by actively adapting the light path to user eye position
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 compact, high-quality optical system with a wide field-of-view and large eye-motion-box, suitable for HMDs and HUDs, allowing for comfortable viewing and improved image quality across various applications, including mobile devices.
Implementation Method 1
input light-waves coupled in the light-waves transmitting substrate intersect an input aperture of the light-waves transmitting substrate at an oblique angle, wherein the oblique angle is larger than the critical angle for total internal reflection inside the light-waves transmitting substrate
Implementation Method 2
at least one light-waves polarizing beamsplitter disposed at an angle to at least one of said light-waves entrance or exit surfaces
Implementation Method 3
two or more retardation plates carried by the light-guide on at least a portion of said external surfaces
Data Source
Figure 1~2
Figure 3
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AI summary
There is provided a light-guide, compact collimating optical device, including a light-guide having a light-waves entrance surface, a light-waves exit surface and a plurality of external surfaces, a light-waves reflecting surface carried by the light- guide at one of the external surfaces, two retardation plates carried by light-guides on a portion of the external surfaces, a light- waves polarizing beamsplitter disposed at an angle to one of the light-waves entrance or exit surfaces, and a light-waves collimating component covering a portion of one of the retardation plates. A system including the optical device and a substrate, is also provided.