Projector Optics With Concave Reflection Surface And Negative-Power Lens
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Solution Overview
Problem
Existing projection systems with short focal lengths produce significant aberrations and increase in size due to the need for larger enlargement-side lenses, leading to difficulties in reducing the projector's diameter and maintaining resolution.
Innovation Solution
A projection system with a first optical system and a second optical system, including a diaphragm, a concave reflection surface, and a first lens with negative power, forming an intermediate image and satisfying specific conditional expressions to control lens protrusion and aberrations, allowing for a smaller projector size while maintaining resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the focal length is shortened to reduce projection distance and throw ratio, then the projection system can achieve shorter projection distance and smaller throw ratio, but the amount of aberrations increases and the diameter of the projection system increases
Solution Approach 1:
The projection system is divided into multiple optical systems: a first optical system including a diaphragm, and a second optical system including a concave reflection surface and a first lens with negative power. This segmentation allows each subsystem to be optimized independently, with the first optical system controlling aberrations and the second optical system enabling short focal length projection, thereby resolving the contradiction between short projection distance and aberration control.
Solution Approach 2:
The patent introduces an intermediate image conjugate plane between the reduction-side and enlargement-side conjugate planes, adding a dimensional intermediate stage to the optical path. This intermediate image formation allows the system to manage aberrations at one stage while achieving short throw ratio at another stage, effectively decoupling the two conflicting requirements.
2Object-affected harmful factors
If the effective radius of the enlargement-side lens is increased to correct aberrations, then the aberration correction capability is improved, but the amount of protrusion increases and the diameter of the projection system increases
Solution Approach 1:
Instead of using a large positive power lens at the enlargement side for aberration correction, the patent employs a first lens with negative power in the second optical system. This inversion of the conventional approach allows aberration correction to be achieved through the negative power lens combined with the concave reflection surface, avoiding the need for a large effective radius and thus preventing increase in system diameter.
Solution Approach 2:
The concave reflection surface acts as an intermediary element between the first optical system and the first lens with negative power. This intermediary component helps to control the beam paths and reduce the required effective radius of the first lens while maintaining aberration correction capability, thereby preventing increase in the overall diameter of the projection system.
3Manufacturing precision
If the size of the enlargement-side lens is increased to provide sufficient effective radius, then the aberration correction is improved, but the protrusion from the optical axis increases resulting in larger projector diameter
Solution Approach 1:
The patent changes the power parameter of the first lens to negative power, which fundamentally alters the aberration correction mechanism. This parameter change allows the lens to correct aberrations with a smaller effective radius, thereby maintaining manufacturing precision while reducing the projector diameter.
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 system effectively suppresses lens protrusion, reduces the projector's diameter, and maintains optical performance by correcting aberrations, achieving stable and compact projection with improved manufacturing precision and optical accuracy.
Implementation Method 1
an optical element having a concave reflection surface
Implementation Method 2
a first lens having negative power
Data Source
AI summary
A projection system includes a first and second optical system arranged from a reduction side toward an enlargement side. The second optical system includes an optical element having a concave reflection surface and a first lens having negative power, the optical element and first lens arranged from reduction side toward enlargement side. The projection system satisfies the following expressions:TR≤0.3 (1)35≤(OAL/imy)×(LL/imy)×TR×(1/NA)≤60 (2)OAL represents an axial inter-surface spacing from an image formation device to the reflection surface, imy represents a first distance from an optical axis to the largest image height at the image formation device, LL represents the largest radius of the first lens, TR represents a throw ratio, and NA represents the numerical aperture of the image formation device.