Image Combiner PBS Angle Optimization for Thin Substrates
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Solution Overview
Problem
Conventional see-through head-mounted image display devices face challenges in achieving a wide field of view while minimizing substrate thickness and light intensity loss, primarily due to the large area required by the polarization beam splitter (PBS) for a wide field of view, which increases substrate thickness.
Innovation Solution
The solution involves optimizing the angle between the PBS and the substrate to be between 30° and 42°, and inclining the user's line of sight to reduce the substrate thickness and minimize light intensity loss by enhancing the reflectance of the s-polarized component and reducing the extinction ratio, using a polarization beam splitter with reflection wavelength selectivity and a concave mirror or reflective-type holographic optical element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the PBS is inclined at 45° to the substrate surface to reduce light intensity loss, then the reflectance for s-polarized component is enhanced, but the substrate thickness increases when a wide field of view is required
Solution Approach 1:
The patent changes the inclination angle parameter of the PBS from the conventional 45° to a range of 25°-35°, and adjusts the exit angle parameter to 2°-7°. This parameter optimization allows the system to achieve wide field of view while reducing substrate thickness to below 5.0mm and minimizing light intensity loss through the optimized angle configuration.
2Area of stationary object
If the PBS area is increased to achieve a wide field of view, then the field of view expands, but the substrate thickness increases
Solution Approach 1:
By optimizing the PBS inclination angle to 25°-35° and the exit angle to 2°-7°, the patent achieves a wide field of view (15.6° diagonal) without requiring excessive PBS area, thereby keeping substrate thickness below 5.0mm. The parameter optimization allows efficient use of PBS area while controlling substrate thickness.
3Length of stationary object
If the PBS inclination angle is reduced to decrease substrate thickness, then the substrate becomes thinner, but light intensity loss increases due to deviation from Brewster angle
Solution Approach 1:
The patent optimizes the PBS inclination angle to a specific range of 25°-35° (rather than reducing it too much) and coordinates it with an exit angle of 2°-7°. This balanced parameter configuration maintains sufficient reflectance for s-polarized light while achieving substrate thickness below 5.0mm, preventing excessive light intensity loss.
4Area of stationary object
If the exit angle is increased to widen the field of view, then the field of view expands, but the PBS inclination angle must be adjusted which may increase substrate thickness
Solution Approach 1:
The patent achieves a wide field of view (15.6° diagonal) by optimizing the exit angle to 2°-7° and coordinating it with a PBS inclination angle of 25°-35°. This parameter combination allows the system to expand the field of view while maintaining substrate thickness below 5.0mm through efficient optical path design.
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 wider field of view with reduced substrate thickness and minimized light intensity loss, enabling users to switch between outside and display surface views without significant eye fatigue.
Implementation Method 1
a polarization beam splitter installed in the substrate, to reflect a light flux emitted from image forming means and passing through the substrate
Implementation Method 2
since the reflectance for the p-polarized component is zero when an incident angle of the light matches with a Brewster angle, the optical thin film should be designed so as to enhance reflectance for the s-polarized component at this time
Implementation Method 3
The reflection member may be designed to allow the angle θ0 and the angle θ2 to satisfy the respective conditions
Data Source
AI summary
The present invention aims to provide an image combiner and an image display device which can easily have a wide field of view and reduce a thickness of a substrate while reducing loss of light intensity by means of a PBS. An image combiner includes a substrate transparent to visible light; and a polarization beam splitter installed in the substrate to reflect a light flux introduced into the substrate from an image-display element and to make the light flux incident on an exit pupil outside the substrate. An exit angle θ0 at which a principal ray of the light flux emitted from a center of a display surface of the image-display element is emitted from a surface of the substrate toward a center of the exit pupil satisfies a condition of 3°≦θ0.