Retinal Projection Display Optics for Pupil-Tracking Alignment
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Solution Overview
Problem
Existing retinal projection HMDs face challenges in aligning light convergence with the pupil due to the narrow range of human pupil diameter and difficulty in making the ocular optical system smaller and lighter, which affects image stability and power consumption.
Innovation Solution
The image display apparatus employs an optical element that obliquely enters the pupil and is moved using a movement control apparatus to align with pupil position changes, incorporating a reflective hologram diffraction grating for light collection and a 4f optical system to reduce aberrations and maintain image stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a first reflecting surface is used to bend the pencil of light ninety degrees in the ocular optical system, then the light can reach the observer's eye, but the thickness of the ocular optical system increases making it difficult to make smaller
Solution Approach 1:
The patent changes the arrangement dimension by placing the image forming apparatus in the region behind the optical element rather than in front. This spatial reconfiguration allows the optical system to achieve the required light bending function while reducing the frontal thickness of the ocular optical system, directly addressing the contradiction between system size and light path alignment capability
2Reliability
If the first reflecting surface is made movable to follow eyeball movement, then the exit pupil can track the pupil position, but the first reflecting surface becomes difficult to make smaller and power consumption increases
Solution Approach 1:
The patent extracts the light bending function from the movable first reflecting surface and transfers it to the fixed optical element's fixed reflecting surface. This separation allows the optical element to remain stationary (reducing power consumption) while still achieving the necessary light path alignment through its fixed reflective geometry, resolving the contradiction between tracking reliability and energy consumption
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, lighter, and more stable image display apparatus that maintains image alignment with pupil movements, reducing power consumption and allowing see-through functionality.
Implementation Method 1
incorporating a reflective hologram diffraction grating for light collection
Implementation Method 2
reflected off the optical element to reach a pupil of the observer
Data Source
AI summary
There is provided an image display apparatus that includes an image forming apparatus, an optical element arranged in front of a face of an observer, and a movement control apparatus. When a region situated on the side of the ear of the observer, as viewed from the optical element, is referred to as a region situated behind the optical element, the image forming apparatus is in the region situated behind the optical element. An image exiting the image forming apparatus obliquely enters the optical element from the region situated behind the optical element, and is reflected off the optical element to reach the pupil of the observer. When there is a change in the position of the pupil of the observer, the optical element is moved using the movement control apparatus, and the position of the image exiting the image forming apparatus is controlled using the movement control apparatus.