Folded Optical Path for Compact Head Mount Display
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing head mount displays have a long optical system due to the requirement of a long light path for image enlargement, making them large and inconvenient to wear.
Innovation Solution
An optical module with a glued lens system, including a first and second lens, a beam-splitting element, a quarter-wave plate, and a polarization-reflecting film, which reduces the total optical length by refracting and reflecting light in a limited space, and a head mount display with an overall optical length of less than 25 mm, enhancing imaging quality and clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a long light path is used for image enlargement, then the imaging quality is improved, but the total optical length increases making the head mount display large and inconvenient to wear
Solution Approach 1:
The patent implements a folded optical path where light reflects multiple times between mirrors and passes through the same lens system repeatedly. This nesting of optical paths allows the light to traverse an extended effective optical distance (through the lens multiple times) while maintaining a compact physical footprint, thereby achieving high imaging quality without increasing the overall device length
Solution Approach 2:
The patent transitions from a linear optical path to a multi-dimensional folded path using mirrors at various angles. The light path is bent and redirected through space, creating a three-dimensional optical configuration that achieves long effective optical length through spatial folding rather than linear extension, thus improving imaging quality without increasing the device's linear dimensions
2Ease of operation
If the optical system is shortened to reduce device size, then the wearability is improved, but the imaging quality may deteriorate
Solution Approach 1:
The folded optical design nests multiple light passes through the same compact lens assembly, effectively multiplying the optical interaction length without increasing physical size. This allows the system to maintain high imaging quality while keeping the device compact and wearable
Solution Approach 2:
The patent optimizes specific parameters including the focal length of the lens (f=15mm), the angles of mirror reflections (45 degrees), and the spacing between optical elements to achieve the desired balance between compact size and imaging quality. By carefully controlling these parameters, the system achieves high-quality imaging in a shortened optical path
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 optical module effectively reduces the size of the head mount display while maintaining high imaging quality by ensuring the beam diameter is less than twice the pixel size at the full field of view, allowing for clearer and more compact virtual reality and augmented reality experiences.
Implementation Method 1
The light transmitted through the beam-splitting element continues to transmit to the first quarter-wave plate, the polarization state of the circularly polarized light being changed from the circularly polarized light to the linearly polarized light
Implementation Method 2
When the linearly polarized light is emitted to the polarization-reflecting film, the vibration direction of the linearly polarized light is different from the transmission direction of the polarization-reflecting film, and the light is reflected
Implementation Method 3
the light is refracted and reflected as it passes by the glued lens, and in the process, the light is continuously enlarged and transmitted
Implementation Method 4
the light is refracted and reflected as it passes by the glued lens, and in the process, the light is continuously enlarged and transmitted
Implementation Method 5
the fourth surface of the second lens is convex in a direction facing away from the display, therefore it is possible to converge the light and thereby reduce the total optical length
Data Source
AI summary
Disclosed are an optical module and a head mount display. The optical module comprises: a display configured for emitting a light for imaging display; a glued lens provided in a light-emergent direction of the display and comprising a first lens and a second lens sequentially provided along a propagation direction of an optical path; a beam-splitting element provided on a side of the first lens facing the display; a first quarter-wave plate provided between the first lens and the second lens; and a polarization-reflecting film provided between the quarter-wave plate and the second lens.