Off-Axis Virtual Image Display Prism with Intermediate Pupil
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Solution Overview
Problem
Existing virtual image display apparatuses face challenges in size reduction while maintaining optical performance and resolution, particularly in head-mounted displays, due to the need for a long optical path and limited aberration correction, which results in an awkward appearance and reduced usability.
Innovation Solution
A virtual image display apparatus featuring a projection lens, a prism with internal reflecting surfaces, and a see-through mirror arranged in an off-axis system, where an intermediate pupil is positioned between the projection lens and the prism's internal reflecting surface, forming an intermediate image between the prism and the see-through mirror, allowing for aberration correction and size reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long optical path is used to achieve aberration correction, then optical performance is improved, but device size increases
Solution Approach 1:
The patent places the intermediate image formation within the prism structure itself, nesting multiple optical functions (refraction, reflection, and image formation) into a single compact component. This allows the optical path to be folded back on itself, achieving effective aberration correction without extending the overall device length.
Solution Approach 2:
The patent transitions from a linear optical path to a three-dimensional folded path by utilizing the prism's internal reflecting surfaces. The light path enters the prism, reflects off internal surfaces, forms an intermediate image, and exits through different faces, effectively using spatial dimensions to compact the optical system while maintaining the required optical path length for aberration correction.
2Measurement precision
If optical components are increased in size to improve optical performance, then resolution is improved, but device thickness and peripheral expansion increase
Solution Approach 1:
The projection lens, prism, and see-through mirror are arranged in a nested configuration where the intermediate image is formed within the prism structure. This nesting allows high-resolution imaging without requiring large separation distances between components, thereby reducing device thickness while maintaining optical performance.
Solution Approach 2:
The patent uses a folded optical path that moves from a single-dimensional linear arrangement to a three-dimensional configuration. By folding the light path through the prism's internal surfaces, the system achieves high resolution with compact component spacing, reducing the device's thickness and peripheral expansion.
3Volume of moving object
If a compact optical system is designed to reduce device size, then portability is improved, but aberration correction capability is reduced
Solution Approach 1:
The patent designs the prism to perform multiple functions simultaneously: it refracts light entering and exiting the prism, reflects light off its internal surfaces to fold the optical path, and serves as the location for intermediate image formation. This multi-functionality allows effective aberration correction in a compact volume by eliminating the need for separate dedicated components for each function.
Solution Approach 2:
The folded optical path within the prism uses three-dimensional spatial arrangement to achieve sufficient optical path length for aberration correction while maintaining a compact external device size. The light traverses multiple faces of the prism in a folded configuration, effectively using spatial dimensions to decouple optical path length from device volume.
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 compact and efficient optical system that reduces aberration and enhances resolution, allowing for a smaller and more user-friendly head-mounted display design while maintaining a clear see-through view.
Implementation Method 1
a projection lens configured to converge image light emitted from the display element
Implementation Method 2
a prism configured to cause the image light emitted from the projection lens to enter an incident surface thereof while refracting the image light and totally reflect the image light by an internal reflecting surface thereof
Implementation Method 3
totally reflect the image light by an internal reflecting surface thereof
Implementation Method 4
a see-through mirror configured to reflect the image light emitted from the prism toward a pupil position
Data Source
AI summary
A virtual image display apparatus includes a display element, a projection lens configured to converge image light emitted from the display element, a prism configured to cause the image light by an internal reflecting surface thereof and moreover emit the image light from an emission surface thereof while refracting the image light, and a see-through mirror configured to reflect the image light emitted from the prism toward a pupil position. The projection lens, the prism, and the see-through mirror are arranged to form an off-axis system. AT an off-axis surface of the off-axis system, an intermediate pupil is arranged between the projection lens and the internal reflecting surface, with the intermediate pupil being arranged to be farther to the incident surface side of the prism than to the projection lens and the internal reflecting surface, and an intermediate image is formed between the prism and the see-through mirror.