Asymmetric Light Pipe Illumination for Virtual Image Displays
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Solution Overview
Problem
Existing virtual image displays face challenges in achieving efficient illumination with asymmetric light distribution, leading to reduced illumination efficiency and peripheral brightness, particularly due to the strong asymmetric properties of illumination light between the X-direction and Y-direction within the light guide plate.
Innovation Solution
An illumination optical device featuring a light pipe with an emitting surface that is wider in the horizontal direction than the illuminated object and narrower in the vertical direction, combined with a diffuser, to produce anisotropic illumination light, ensuring uniform angular distribution in the horizontal direction and angled distribution in the vertical direction, thereby enhancing illumination efficiency without compromising peripheral brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional light pipe with symmetric emitting surface is used, then the illumination light has uniform distribution, but the illumination efficiency is reduced due to the need for wide angle illumination in Y-direction
Solution Approach 1:
The light pipe emitting surface is designed with asymmetric dimensions where the width in X-direction (d1) is greater than the width in Y-direction (d2). This asymmetric geometry creates anisotropic light distribution that provides wide angle illumination in the X-direction while maintaining adequate illumination in the Y-direction, thereby improving illumination efficiency without sacrificing peripheral brightness.
Solution Approach 2:
The illumination optical system uses a reflective spatial light modulator that selectively reflects S-polarized components while transmitting P-polarized components. This local optical property variation allows the system to control light distribution directionally, enhancing illumination efficiency by directing light where needed while maintaining peripheral brightness through polarizing beam splitter configuration.
2Ease of operation
If the light pipe emitting surface width in Y-direction is increased to improve peripheral brightness, then the angular distribution becomes less controlled, but the illumination efficiency decreases due to reduced numerical aperture
Solution Approach 1:
The light pipe emitting surface dimensions are set such that d1 (X-direction width) > d2 (Y-direction width). This asymmetric configuration allows the system to achieve wide angular distribution in X-direction for peripheral brightness while maintaining controlled numerical aperture in Y-direction for illumination efficiency, resolving the contradiction between these two parameters.
3Use of energy by moving object
If the numerical aperture is increased to improve illumination efficiency, then the angular distribution becomes too concentrated, but the peripheral brightness is reduced
Solution Approach 1:
The asymmetric light pipe geometry with d1 > d2 creates anisotropic light distribution that concentrates light within an optimized numerical aperture for efficiency while the larger X-direction width provides sufficient angular spread for peripheral brightness, simultaneously satisfying both requirements.
Solution Approach 2:
The polarizing beam splitter and reflective spatial light modulator create local optical property variations that control light distribution, allowing concentrated illumination for efficiency while directing light to peripheral areas through polarized component separation, thereby maintaining both illumination efficiency and peripheral brightness.
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 solution effectively produces asymmetric illumination light, improving illumination efficiency and maintaining peripheral brightness by optimizing the light pipe's dimensions and diffuser placement, resulting in a more efficient virtual image display system.
Implementation Method 1
illumination light from the light source 104 is repeatedly undergone total reflection within the light pipe 105
Implementation Method 2
a diffuser 107, and a polarizing beam splitter 108... The diffuser 107 delivers higher diffusibility to light in the directions in which optical power is higher
Implementation Method 3
The polarizing beam splitter 108 having received the illumination light reflects only an S-polarized component
Implementation Method 4
The reflective spatial light modulator 102 modulates the S-polarized component light into image light according to an image. Then the image light is reflected off
Implementation Method 5
The image light is converted by the collimating optical system 110 into groups of parallel rays, which are in turn incident in the light guide plate 112 through one end of the optical surface 115, are diffracted and reflected by the first reflective volume holographic grating 113 and travel toward the other end while repeatedly undergoing total internal reflection within the light guide plate 112
Implementation Method 6
The first reflective volume holographic grating 113 is placed on one end of an optical surface (back face) 116 of the light guide plate 112... The image light is converted by the collimating optical system 110 into groups of parallel rays, which are in turn incident in the light guide plate 112 through one end of the optical surface 115, are diffracted and reflected by the first reflective volume holographic grating 113
Data Source
AI summary
An illumination optical device includes a light source, a light pipe guiding illumination light from the light source, a diffuser arranged on an emitting surface side of the light pipe. A width of the emitting surface of the light pipe in the horizontal direction is set greater than a width of an illuminated object, and a width of the emitting surface of the light pipe in the vertical direction is set smaller than a width of the illuminated object.