Folded Optical Path in Eyepiece Display Using Half-Mirror
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Solution Overview
Problem
The existing display devices face a limitation in reducing overall thickness without degrading the image quality due to the proximity of the eyepiece lens to the display module, which results in a non-display area being visible, especially when the distance between the two is less than a predetermined value.
Innovation Solution
Incorporating a half-mirror and a reflective polarizing plate with cholesteric liquid crystal between the eyepiece lens and the display module, along with a rear quarter-wave plate and a rear linear polarizing plate, to increase the light path and maintain image quality by adjusting the focal distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the eyepiece lens is located close to the display module to reduce overall thickness, then the device thickness is reduced, but the image quality is degraded due to visible non-display areas
Solution Approach 1:
A half-mirror is introduced as an intermediary component between the display module and the eyepiece lens. This half-mirror creates a folded optical path that allows the light to travel a longer distance between the display module and the eyepiece lens, thereby maintaining image quality while reducing the overall thickness of the device. The half-mirror reflects light from the display module to the eyepiece lens, enabling a compact design without compromising the required optical path length.
2Reliability
If the distance between the eyepiece lens and the display module is increased to improve image quality, then the image quality is improved, but the overall thickness of the device increases
Solution Approach 1:
The optical path is folded using the half-mirror, changing the spatial arrangement from a linear one-dimensional path to a two-dimensional folded path. This allows the light to travel a longer distance between the display module and the eyepiece lens while maintaining a compact overall device thickness. The half-mirror enables the optical path to bend at an angle, effectively utilizing vertical space to achieve the required optical path length without increasing the horizontal thickness of the device.
3Length of stationary object
If a half-mirror and reflective polarizing plate are added to increase the light path, then the overall thickness is reduced, but the device complexity increases
Solution Approach 1:
The reflective polarizing plate serves multiple functions: it reflects light to continue the optical path, it maintains polarization state of the light, and it contributes to the overall compact design. By combining these functions in a single component, the device achieves the required optical path length and thickness reduction without proportionally increasing complexity. The reflective polarizing plate is integrated into the existing optical system, sharing space and functionality with other components.
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 configuration allows for a reduction in the overall thickness of the display device while maintaining image quality by increasing the light path to the eyepiece lens, ensuring a normal-sized image is provided to the user without degrading the image quality.
Implementation Method 1
The reflective polarizing plate includes a cholesteric liquid crystal (CLC). A light circularly polarized in a first direction is reflected by the reflective polarizing plate, and a light circularly polarized in a second direction opposite to the first direction transmits through the reflective polarizing plate.
Implementation Method 2
The reflective polarizing plate includes a cholesteric liquid crystal (CLC).
Implementation Method 3
A half-mirror is disposed between the eyepiece lens and the display module.
Implementation Method 4
A rear quarter-wave plate may be disposed between the reflective polarizing plate and the eyepiece lens. A rear linear polarizing plate may be disposed between the rear quarter-wave plate and the eyepiece lens.
Data Source
AI summary
A display device including a display module and an eyepiece lens is provided. A user can view an image realized by the display module through the eyepiece lens. In the display play according to the present disclosure, a path of a light moving from the display module to the eyepiece lens may be increased by a half-mirror and a reflective polarizing plate which are located between the display module and the eyepiece lens. Thus, in the display device according to the present disclosure, the overall thickness may be decreased without degrading the quality of the image realized by the display module.