Projection Lens Aspheric Design for Compact Rear Display
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Solution Overview
Problem
Existing wide-angle projection lenses for rear projection displays face challenges in miniaturization due to the need for a large back focal distance and increased manufacturing costs, often requiring a large number of lenses and being prone to deformation from temperature changes.
Innovation Solution
A projection lens configuration with a first lens group having a negative refractive power, a second lens group with positive refractive power, and a third lens group including cemented and positive lenses, optimized to allow for a compact design with an optical path deflecting unit, while reducing the number of lenses and maintaining high projection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reflecting mirror is inserted into the projection lens to achieve wide-angle and long back focal distance, then the projection performance is improved, but the number of lenses increases and manufacturing cost increases
Solution Approach 1:
The patent employs aspheric surfaces on specific lens elements to correct optical aberrations and achieve the desired wide-angle performance and back focal distance without adding a reflecting mirror. The aspheric surfaces enable compact design while maintaining projection quality.
2Device complexity
If the power of an aspheric lens is made high to reduce the number of lenses, then the manufacturing cost is reduced, but the lens shape deforms excessively due to temperature change
Solution Approach 1:
The patent optimizes the refractive power distribution across multiple lens elements, avoiding excessive power concentration in a single aspheric lens. This parameter optimization maintains thermal stability while achieving compact design and reduced lens count.
3Ease of manufacture
If the number of lenses is reduced to improve manufacturing cost, then the manufacturing cost is reduced, but the ability to correct aberrations and maintain image plane balance deteriorates
Solution Approach 1:
The patent uses a composite lens structure combining cemented lens portions and positive lens portions with aspheric surfaces. This composite design corrects various aberrations and maintains image plane balance while using a reduced number of lens elements for cost-effective manufacturing.
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 enables a compact, high-performance wide-angle projection lens that reduces manufacturing costs and corrects various aberrations, allowing for a low-profile, high-resolution large-screen display with improved thermal stability.
Implementation Method 1
a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power
Data Source
AI summary
A projection lens is provided and includes: in order from the object, a first lens group having a negative refractive power and including an aspheric lens and a double-concave lens in this order from the magnification side; a second lens group having a positive refractive power and including one positive lens or one positive lens and one negative lens; and a third lens group having a positive refractive power, including three to five lenses including a cemented lens portion and a positive lens portion in this order from the magnification side, and including a surface closest to the magnification side as an aspheric surface. The projection lens has a substantially telecentricity on the reduction side, the third lens group has a magnification-side focal position located between the third and second lens groups, the projection lens has the longest air space between the first and second lens groups, and the projection lens satisfies specific conditions.