Projection Optical System with Aspherical Mirror and Resin Lens
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Solution Overview
Problem
Existing projection optical systems for projectors face challenges in achieving a wide range of magnification change while maintaining high resolution and brightness, particularly in ultra-wide angle applications, where the system tends to be bulky, and brightness is compromised due to the need for numerous lenses and mirrors, leading to portability and contrast issues.
Innovation Solution
A projection optical system comprising a first optical group with positive power lenses and a second optical group featuring a concave aspherical mirror, where the 1-2nd lens group includes a fixed lens group and a moving lens group to adjust for magnification changes, using a combination of glass and resin lenses to manage aberrations and maintain performance across varying magnifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a refraction optical system uses only lenses to achieve a wide angle of view, then the angle of view is increased, but the lens size and the number of lenses needed increase enormously
Solution Approach 1:
The optical system is divided into two functional groups: a refraction optical system for image formation and a reflection optical system for light redirection. This segmentation allows each group to specialize in specific functions, reducing the overall complexity while achieving the desired wide angle of view
Solution Approach 2:
A reflective mirror is introduced as an intermediary element between the refraction optical system and the image display element. This mediator redirects light paths, enabling a wide angle of view without requiring an excessive number of lenses
2Area of moving object
If a refraction/reflection complex optical system uses a concave mirror to achieve a significantly wide angle of view, then the angle of view is increased, but the mirror size and entire length increase enormously
Solution Approach 1:
The reflective mirror is designed with a specific curvature radius that is 0.05 times or more the focal length of the refraction optical system. This localized optimization of the mirror's geometric properties enables it to achieve the desired wide angle of view while maintaining a compact overall length
3Illumination intensity
If the F-number is reduced to about 1.7 for brightness, then brightness is improved, but the range of magnification change is narrowed to about 1.2 times
Solution Approach 1:
The optical system incorporates a zoom mechanism that dynamically adjusts the focal lengths of the refraction and reflection optical systems. This allows the system to maintain an F-number of about 1.7 for brightness while achieving a magnification change range of about 2 times through coordinated movement of optical elements
4Volume of stationary object
If two mirrors with aspherical surfaces are used to decrease mirror size, then the device size is reduced, but the difficulty of achieving accuracy and assembly increases
Solution Approach 1:
The system uses only one aspherical reflective mirror instead of two mirrors with aspherical surfaces. By extracting the unnecessary mirror and its associated aspherical surface requirements, the system achieves compact size while significantly reducing manufacturing and assembly complexity
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 allows for a wide range of magnification change while maintaining high resolution and brightness, reducing the size and complexity of the optical system, and enhancing portability and contrast, even in bright environments.
Implementation Method 1
a second optical group which has one reflective surface having a concave aspherical shape
Implementation Method 2
the 1-2nd lens group includes an enlargement-side fixed lens group which is disposed on the outermost enlargement side, is fixed when focusing is performed
Data Source
AI summary
In a 1-2nd lens group, an aspherical resin lens is disposed on the outermost enlargement side, an enlargement-side fixed lens group (second fixed lens group) as a fixed group is disposed, a moving lens group, which move when focusing is performed in response to the magnification change, is disposed further on the reduction side from the second fixed lens group. Even in a case where the second optical group is configured of one mirror, it is possible for a primary image to have appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.