Optical System With Multi-Reflection Path for Wide-View HMDs
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Solution Overview
Problem
Existing optical systems for head-mounted displays struggle to achieve both a reduced focal length and a widened angle of view without interfering with the display element, as they require a short distance that does not allow sufficient space for components.
Innovation Solution
An optical system comprising a first optical element with a transmission surface, reflection-transmission surface, and reflection surface, and a negative lens with a concave surface on the exit pupil side, where the reflection-transmission surface and negative lens are adjacent, and a second optical element such as a prism is inserted to shift the image side principal plane closer to the display element, ensuring sufficient space and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the optical system is made to have a short focal length to widen the angle of view, then the angle of view is widened, but the distance from the principal plane to the display element becomes so short that space cannot be ensured for disposing parts and the optical system parts interfere with the display element
Solution Approach 1:
The patent introduces a second decentered optical element between the observer and the first decentered optical element, adding a dimensional layer to the optical system. This allows the light beam to be reflected multiple times through a more complex spatial arrangement, achieving a widened angle of view while maintaining sufficient distance between the principal plane and the display element.
Solution Approach 2:
The patent employs a nested structure where the second decentered optical element is positioned within the optical path created by the first decentered optical element. The light beam passes through multiple reflection surfaces in a nested sequence, allowing compact arrangement while maintaining the required optical path length and angle of view.
2Length of moving object
If the distance from the principal plane to the display element is reduced to shorten the focal length, then the focal length is reduced, but the space for disposing necessary parts cannot be ensured
Solution Approach 1:
By introducing the second decentered optical element and creating multiple reflection surfaces, the patent extends the optical path in a dimensional sense. This allows the focal length to be reduced while the physical space between the principal plane and display element is maintained through the complex light path arrangement.
Solution Approach 2:
The optical system is segmented into multiple decentered optical elements, each contributing to the overall optical function. This segmentation allows the light beam to undergo multiple reflections, effectively reducing the focal length while distributing the optical function across multiple components that occupy different spatial positions.
3Area of stationary object
If multiple decentered optical elements are used to widen the angle of view, then the angle of view is widened, but the device complexity increases
Solution Approach 1:
The patent combines multiple decentered optical elements into a single integrated optical system. The second decentered optical element is positioned and configured to work in conjunction with the first, creating a unified system that achieves a widened angle of view while managing complexity through coordinated design of the reflection surfaces and optical paths.
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 system achieves a wide angle of view of up to 45° while maintaining a compact size, preventing physical interference with the display element and allowing for a sufficient eye relief.
Implementation Method 1
a first optical element (102) including a transmission surface (102C), a reflection-transmission surface (102A), and a reflection surface (102B)... The light beam from the display element heads toward the exit pupil via the transmission surface, the reflection-transmission surface, the reflection surface
Implementation Method 2
a first optical element (102) including a transmission surface (102C)... The light beam from the display element heads toward the exit pupil via the transmission surface
Implementation Method 3
a negative lens (104) having a concave surface on an exit pupil side... The light beam from the display element heads toward the exit pupil via the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, and the negative lens
Data Source
AI summary
The present disclosure relates to optical system and display apparatus. An optical system guides a light beam from a display element to an exit pupil. The optical system includes a first optical element including a transmission surface, a reflection-transmission surface, and a reflection surface, and a negative lens including a concave surface on an exit pupil side. The light beam from the display element heads toward the exit pupil via the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, and the negative lens in this order. A predetermined condition is satisfied.