Front Light Unit Holographic Optical Element for Compact Displays
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Solution Overview
Problem
Conventional image display devices are limited in size reduction due to the space occupied by expensive polarization beam splitters, which also affect light efficiency.
Innovation Solution
A front light unit incorporating a holographic optical element unit replaces the polarization beam splitter, guiding light to a display unit, and an image display device with a pentaprism and virtual image optical unit provides a magnified virtual image, enhancing light efficiency and reducing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polarization beam splitter is used to transfer light from the light source to the display unit, then the light transfer function is achieved, but the device size is increased and cost is increased
Solution Approach 1:
The patent extracts and removes the polarization beam splitter from the optical system, replacing it with a reflection-type liquid crystal display that directly reflects light from the light source. This eliminates the need for the bulky polarization beam splitter while maintaining the essential light transfer function, thereby reducing device size without compromising reliability
Solution Approach 2:
The reflection-type liquid crystal display serves multiple functions: it acts as both the display element and the light redirecting component that previously required separate polarization beam splitter optics. By integrating these functions into a single component, the patent reduces the overall device volume while maintaining effective light transfer to the user's eye
2Reliability
If a polarization beam splitter is used to transfer light from the light source to the display unit, then the light transfer function is achieved, but the cost is increased
Solution Approach 1:
The patent removes the expensive polarization beam splitter from the system and replaces it with a reflection-type liquid crystal display that performs the same light redirecting function. This substitution significantly reduces manufacturing cost while maintaining the essential light transfer capability, as the reflection-type display is a more cost-effective component
Solution Approach 2:
The patent substitutes an expensive, complex optical component (polarization beam splitter) with a more affordable, simpler component (reflection-type liquid crystal display). This replacement reduces the overall system cost while maintaining functional equivalence, making the device more economically viable for mass production
3Reliability
If a polarization beam splitter is used in the image display device, then light can be divided into P-wave and S-wave components, but light efficiency is reduced
Solution Approach 1:
The patent removes the polarization beam splitter that causes light loss through polarization filtering. Instead, it uses a reflection-type liquid crystal display that redirects light without the need for polarization-based separation, thereby eliminating the inherent light efficiency losses associated with polarization beam splitting while maintaining sufficient light control for display functionality
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 minimizes light loss, improves light efficiency, and significantly reduces the size of the light unit and display device, enabling efficient image guidance to the user while providing a magnified virtual image.
Implementation Method 1
The holographic optical element unit may have a larger refractive index than the light guide unit. The hologram patterns may collimate light emitted from the light guide unit.
Implementation Method 2
a light guide unit for guiding light incident thereon from the light source unit so that the light is transferred to a display unit
Implementation Method 3
a pentaprism disposed in front of the display unit in order to change a path of light emitted from the display unit and to transmit the light
Implementation Method 4
a virtual image optical unit for changing a path of light emitted from the pentaprism in order to provide a magnified virtual image corresponding to an image displayed on the display unit for an observer
Data Source
AI summary
A front light unit of an embodiment comprises: a light source unit for an image display device; a light guide unit for guiding light incident from the light source unit and outputting the guided light to a display unit; and a holographic optical element unit being opposite to the display unit and disposed on the light guide unit. Therefore, the present invention can adjust the direction of light output from the light source unit and increase the quantity of light transferred to the display unit, using a pattern formed in the holographical optical element unit, thereby improving the efficiency of light supplied from the light source unit and reducing the sizes of the light unit and the display device including the same.