Adjustable Virtual Image Distance in See-Through Head-Mounted Display
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Solution Overview
Problem
Conventional see-through head-mounted displays require frequent adjustments to the crystalline lens to view both real and virtual images due to a fixed virtual image distance, leading to user discomfort and reliability issues with exposed mechanical components.
Innovation Solution
The design incorporates a driving motor to adjust the distance between the concave mirror and the quarter wave plate within the inner optical mechanism, allowing for variable virtual image distance to match the real image distance, while maintaining the optical components within a nontransparent housing for improved reliability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the virtual image distance is fixed according to the optical mechanism, then the optical structure is simple, but the user's eye has to continuously adjust the focal lengths to see both virtual and real images, causing eye fatigue
Solution Approach 1:
The patent applies the Dynamics principle by making the virtual image distance adjustable rather than fixed. A driving mechanism moves the mirror along the optical path, changing the distance between the mirror and the quarter wave plate. This dynamic adjustment allows the virtual image distance to be varied, enabling the user to view both virtual and real images at different distances without continuous focal adjustment, thereby resolving the contradiction between optical structure simplicity and viewing comfort.
2Adaptability or versatility
If the mirror and driving mechanism are exposed outside, then the virtual image distance can be adjusted, but the reliability, stability, and durability (water-proof or dust-proof) are substantially reduced
Solution Approach 1:
The patent applies the Nested doll principle by placing the mirror and driving mechanism inside the nontransparent housing of the inner optical mechanism. The housing encloses these components, providing protection against water and dust while maintaining the adjustment functionality. The driving mechanism operates within the sealed housing, allowing virtual image distance adjustment without compromising the reliability and durability of the overall device.
3Stability of the object's composition
If the virtual image distance is fixed at about 3m, then the optical mechanism is stable, but it is inconvenient for users to view objects at different distances such as when driving or reading
Solution Approach 1:
The patent resolves this contradiction by introducing dynamic adjustability to the virtual image distance while maintaining optical mechanism stability. The driving mechanism enables controlled movement of the mirror along the optical path, allowing the system to adapt to different viewing distances (e.g., 3m for driving, 30cm for reading) without compromising the overall stability of the optical mechanism. The stable housing provides a fixed reference frame while the movable mirror component enables distance adaptation.
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 solution enables seamless viewing of both real and virtual images without frequent lens adjustments, enhancing user comfort and addressing reliability and durability concerns by encapsulating the optical components.
Implementation Method 1
The polarizer 102 passes the light of a specific polarization (S-polarized beam shown in FIG. 2 is an example) and blocks the light of other polarizations
Implementation Method 2
The collimating lens 103 converts the light that travels through the polarizer 102 into parallel light
Implementation Method 3
The polarizing beam splitter 104 is a P-type polarizing beam splitter which transmits the P-polarized beam and reflects the S-polarized beam
Implementation Method 4
The LCOS panel 105 has a liquid-crystal layer which can rotate the polarization of the incident light and a reflecting layer which reflects the incident light back to the incident direction
Implementation Method 5
The LCOS panel 105 is driven by voltage to control the polarization of light of each pixel
Implementation Method 6
The quarter wave plate 107 converts the P-polarized beam into a circularly polarized beam
Implementation Method 7
The circularly polarized beam is reflected by the concave mirror 108
Data Source
AI summary
The invention provides a see-through head-mounted display, including: an inner optical mechanism covered by a nontransparent housing having an opening and providing an image beam from the opening; and an outer optical mechanism including an outer polarizing beam splitter guiding the image beam from the opening and an environment beam to the same direction. The inner optical mechanism includes at least a mirror and a driving motor. The mirror reflects the image beam to make the image beam incident to the outer optical mechanism. The driving motor moves the mirror to vary the image distance from the mirror.