Anamorphic Optical System for Thinner Virtual-Image Displays
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Solution Overview
Problem
Existing virtual image display devices face challenges in reducing the thickness of the lens due to the configuration of collimated light proceeding through a light guide, which makes it difficult to minimize the overall device size.
Innovation Solution
An optical system with a first optical portion having an anamorphic surface forming an intermediate image in a light guide, where the first optical portion has different magnifications in two directions, allowing for a thinner light guide by forming the intermediate image closer to the second optical portion, and using partial reflectors to split and direct image light to the eyes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If collimated light is caused to proceed through the lens serving as a light guide component, then the virtual image can be displayed to the observer, but the thickness of the lens cannot be reduced
Solution Approach 1:
The optical system is divided into three distinct portions: a first optical portion that forms an intermediate image, a light guide that transports the light, and a second optical portion that forms the final virtual image. This segmentation allows the light guide thickness to be reduced while maintaining the overall optical function through coordinated design of the separate optical portions.
Solution Approach 2:
The patent introduces anamorphic surfaces with different curvatures in the meridional and sagittal directions, transforming the optical design from a single-dimensional approach to a two-dimensional curvature approach. This allows independent optimization of light convergence in different planes, enabling thinner light guide design while maintaining image quality.
2Length of stationary object
If the thickness of the light guide is reduced, then the device becomes more compact, but the angle of view and aberration correction become more difficult to maintain
Solution Approach 1:
The first optical portion employs anamorphic surfaces with asymmetric curvatures where the meridional curvature differs from the sagittal curvature. This asymmetric design enables different magnifications in the vertical and horizontal directions, allowing the system to maintain a wide angle of view and correct aberrations even with a reduced light guide thickness.
Solution Approach 2:
The patent utilizes variable magnification parameters through the anamorphic surfaces, where the magnification in the vertical direction differs from the magnification in the horizontal direction. By adjusting these parameter ratios, the system can optimize both the angle of view and aberration correction performance while using a thinner light guide.
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 enables a reduction in the thickness of the light guide while maintaining a wide angle of view and correcting various aberrations, resulting in a more compact and lightweight virtual image display device.
Implementation Method 1
The first optical portion has an anamorphic surface having: a first shape in a first direction; and a second shape in a second direction different from the first direction, the first shape being different from the second shape. The first optical portion forms an intermediate image of the image light.
Implementation Method 2
a light guide configured to guide the image light incident from the first optical portion
Implementation Method 3
a second optical portion configured to direct the image light guided in the light guide to an object
Data Source
AI summary
An optical system includes: a first optical portion, on which image light from an image display element is incident; a light guide configured to guide the image light incident from the first optical portion; and a second optical portion configured to direct the image light guided in the light guide to an object. The first optical portion has an anamorphic surface having: a first shape in a first direction; and a second shape in a second direction different from the first direction, the first shape being different from the second shape. The first optical portion forms an intermediate image of the image light.