Projection Lens with Concave Reflective Surface for Short Throw
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Solution Overview
Problem
In projection systems with a concave reflective surface on the magnifying side, shortening the projection distance leads to an increase in the size of the reflective surface, causing field curvature and necessitating a longer optical system.
Innovation Solution
A projection system with a second optical system comprising a lens having a first transmissive surface, a reflective surface, and a second transmissive surface, where the reflective surface is concave and the second transmissive surface is convex, allowing the intermediate image to be formed between the first and reflective surfaces, reducing trapezoidal distortion and suppressing the increase in reflective surface size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the projection distance is shortened in a projection system with a concave reflective surface, then the projection system becomes more compact, but the size of the reflective surface increases
Solution Approach 1:
The projection system is divided into two separate optical systems: a first optical system (refractive) and a second optical system (reflective). This segmentation allows each system to handle specific portions of the light path, enabling the reflective surface to maintain a smaller size while achieving short projection distance through the combined effect of both systems.
Solution Approach 2:
The patent combines a refractive optical system and a reflective optical system into a unified projection system. The first optical system forms an intermediate image, and the second optical system projects this intermediate image to the screen. This merging of different optical principles allows the system to achieve short projection distance without increasing the reflective surface area.
2Length of moving object
If the projection distance is shortened, then the overall system becomes more compact, but field curvature increases
Solution Approach 1:
The first optical system is designed with specific local optical properties (refractive elements with particular focal lengths and arrangements) that correct field curvature in the intermediate image formation stage. This localized correction ensures that when the second optical system projects the intermediate image, the final image on the screen maintains proper focus across the entire field, even at short projection distances.
3Length of moving object
If the reflective surface size is increased to maintain short projection distance, then the projection distance can be shortened, but the optical system length increases
Solution Approach 1:
The patent employs dynamic optical design where the first optical system creates a virtual intermediate image that can be positioned at different locations. By dynamically adjusting the optical path through the refractive system, the intermediate image is formed at a position that allows the second optical system to achieve short projection distance without requiring a long overall optical system length or large reflective surface.
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 effectively maintains the size of the reflective surface even at short projection distances, reducing field curvature and allowing for a shorter overall optical system length while minimizing trapezoidal distortion.
Implementation Method 1
The lens has a first transmissive surface, a reflective surface, and a second transmissive surface sequentially arranged from the demagnifying side toward the magnifying side
Implementation Method 2
The reflective surface has a concave shape
Data Source
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AI summary
A projection system is formed of a first optical system and a second optical system sequentially arranged from the demagnifying side and forms an intermediate image in a position between a demagnifying-side image formation plane and a magnifying-side image formation plane of the projection system. The second optical system is a lens. The lens has a first transmissive surface, a reflective surface, and a second transmissive surface sequentially arranged from the demagnifying side toward the magnifying side. The reflective surface has a concave shape, and the second transmissive surface has a convex shape protruding toward the magnifying side. An imaginary line specified in the lens inclines with respect to an imaginary vertical line perpendicular to the imaginary axis in a plane YZ, and the intermediate image is located in the lens between the first transmissive surface and the reflective surface.