Projection Optical System with Folded Mirrors for Compact Design
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Solution Overview
Problem
Existing projection devices with reflection surfaces suffer from increased size due to the distance between reflection surfaces, leading to enlarged devices and reduced image quality due to chromatic aberration and distortion.
Innovation Solution
A compact projection optical system is designed using a combination of transmission and reflection optical systems, including a stop and multiple lenses, with specific mirror configurations and conditional expressions to optimize focal lengths and distances, reducing image distortion and device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the distance between the first reflection surface and the second reflection surface is lengthened to reduce chromatic aberration and distortion, then the image quality is improved, but the device size is enlarged
Solution Approach 1:
The patent employs a folded optical path configuration where the light flux is reflected multiple times between mirrors arranged in a nested manner. The first mirror reflects light from the transmission optical system, and the second mirror reflects it toward the projection surface, creating a compact folded path that reduces the overall device length while maintaining the necessary optical path length for aberration correction
Solution Approach 2:
The patent transitions from a linear optical path to a three-dimensional folded optical path by introducing multiple reflection surfaces at different spatial positions and angles. This dimensional reconfiguration allows the optical system to achieve the required path length for aberration correction without increasing the device's external dimensions
2Manufacturing precision
If a reflection optical system is used to correct image distortion, then the image quality is improved, but the device complexity increases
Solution Approach 1:
The patent combines the transmission optical system with the reflection optical system into a unified integrated design. The transmission optical system forms an intermediate image, and the reflection optical system (first and second mirrors) projects this intermediate image onto the projection surface, creating a merged system that achieves distortion correction without requiring separate independent subsystems
Solution Approach 2:
The mirrors in the reflection optical system serve multiple functions: they redirect the light flux path, correct image distortion, and contribute to the overall focal length control. This multi-functionality reduces the need for additional dedicated components, thereby managing system complexity while achieving correction goals
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 achieves a compact image projection device with reduced image distortion while downsizing the optical system, maintaining good optical performance and correcting field curvature and coma aberrations.
Implementation Method 1
The first mirror reflects light output from the transmission optical system
Implementation Method 2
The second mirror reflects reflected light of the first mirror toward the projection surface
Data Source
AI summary
A projection optical system is an optical system for projecting an image light flux formed in an image display element onto a projection surface, and includes a transmission optical system and a reflection optical system. The transmission optical system is located on an emission surface side of the image display element and includes a stop and a plurality of lenses. The reflection optical system includes a positive-power first mirror and a second mirror. Conditional Expression (1) is satisfied0<TL/ft<10 (1)whereft is a focal length of the transmission optical system, andTL is a distance parallel to an optical axis of the transmission optical system from a position where the first mirror reflects a principal ray of the image light flux, to the image display element.