HMD Lens Transmittance Balancing for Uniform Image Brightness
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Solution Overview
Problem
Conventional head-mounted display apparatuses suffer from poor image quality due to improper lens arrangement, leading to discomfort and reduced recognition comfort for the user's eyes.
Innovation Solution
The lens is designed with a specific transmittance ratio between its parts, using a free-form prism, beam splitter, and compensating prism, along with a transmittance-reductive film or color masterbatch, to ensure uniform brightness and reduce ambient light differences, enhancing user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the lens uses a conventional structure for transmitting display light and ambient light, then the device complexity is reduced, but the image quality and brightness uniformity deteriorate
Solution Approach 1:
The lens is divided into multiple parts: a first part including a free-form prism, beam splitter, and compensating prism for transmitting display light and ambient light; and a second part including an optical lens with a transmittance-reductive film for reducing ambient light transmittance. This segmentation allows each part to be optimized independently for its specific function while maintaining overall system performance.
Solution Approach 2:
Different regions of the lens are assigned different optical properties. The first part maintains high transmittance for display light and ambient light, while the second part has reduced ambient light transmittance. The transmittance ratio between the two parts is controlled within 0.5-1.5 to achieve local optimization of brightness uniformity without compromising overall image quality.
2Ease of manufacture
If the transmittance of different parts of the lens is not balanced, then the manufacturing process is simplified, but the brightness uniformity and user comfort deteriorate
Solution Approach 1:
The transmittance of the second part is adjusted by introducing a transmittance-reductive film or color masterbatch, changing the optical parameter to achieve a transmittance ratio between 0.5-1.5 relative to the first part. This parameter optimization ensures uniform brightness across different lens regions while maintaining ease of manufacturing through standard optical film technologies.
3Device complexity
If the lens structure does not properly separate display light and ambient light paths, then the device complexity is reduced, but the image quality and virtual reality display effect deteriorate
Solution Approach 1:
The optical system is segmented into distinct functional zones: the free-form prism receives display light from the display module and directs it to the user's eyes, while simultaneously allowing ambient light to pass through. The beam splitter separates the optical paths for display and ambient light, and the compensating prism corrects optical aberrations. This segmentation enables proper light path separation without excessive complexity.
Solution Approach 2:
The first part of the lens serves multiple functions simultaneously: it transmits display light from the display module to the user's eyes, transmits ambient light from the real world, and integrates the beam splitter and compensating prism to manage both light paths. This multi-functionality reduces the need for separate components while maintaining image quality.
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 design provides improved image quality and comfort by maintaining consistent brightness across different regions of the lens, reducing user discomfort when shifting gaze between parts, and simplifying assembly and reducing costs.
Implementation Method 1
the beam splitter is configured to reflect, to the first exit plane, the display light received by the second incident plane
Implementation Method 2
the transmittance-reductive film is configured to reduce a permeability of the ambient light, so as to reduce the transmittance of the second part
Implementation Method 3
The ambient light sequentially passes through the first incidence plane and transmittance-reductive film, and then exits from the second exit plane
Data Source
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AI summary
A head-mounted display apparatus (100) includes a lens frame (10), a lens (30), and a display module (20). Both the lens (30) and the display module (20) are disposed on the lens frame (10). The lens (30) includes a first part (31) and a second part (32). The first part (31) is adjacent to the second part (32). The first part (31) is configured to transmit ambient light. The second part (32) is configured to transmit the ambient light. The first part (31) is further configured to transmit display light emitted by the display module (20). A ratio of a transmittance of the second part (32) to a transmittance of the first part (31) is within a threshold range. The threshold range is 0.5 to 1.5. Quality of an image displayed by the head-mounted display apparatus (100) is relatively good.