Projection Lens Design with Aspherical Groups
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Solution Overview
Problem
Existing projection devices face challenges in achieving high-quality image projection with a reduced number of lens groups and lenses, leading to increased complexity and potential aberrations due to longer lens lengths and back focal lengths.
Innovation Solution
A projection lens comprising two lens groups with a first lens group having negative refracting power and an aspherical lens surface, and a second lens group with positive refracting power, where the focal lengths satisfy specific conditions to minimize overall length and reduce aberrations, while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of lens groups and lenses is reduced to achieve lightweight and compact design, then device complexity and size are reduced, but image quality deteriorates due to increased aberrations and longer back focal length
Solution Approach 1:
The patent applies parameter changes by optimizing the focal length ratio between the first and second lens groups (0.5 < |f1/f2| < 2.0) and using aspherical lens surfaces to correct aberrations. This allows achieving high image quality with only two lens groups by precisely controlling optical parameters rather than simply adding more lenses.
Solution Approach 2:
The patent employs aspherical lens surfaces in both the first and second lens groups to correct spherical aberration and other optical imperfections. The aspherical surfaces enable compact lens design while maintaining high image quality without requiring additional lens elements.
2Manufacturing precision
If more lens groups are used to improve image quality, then manufacturing precision and image quality are improved, but device complexity and assembly errors increase
Solution Approach 1:
The patent achieves high image quality with minimal lens groups by optimizing key parameters: the focal length ratio (0.5 < |f1/f2| < 2.0) and using aspherical surfaces. This parameter optimization allows two lens groups to perform the optical correction function that would traditionally require more complex multi-group designs.
Solution Approach 2:
The patent extracts and concentrates the essential optical correction functions into two specialized lens groups with aspherical surfaces, removing the need for additional lens groups. This extraction of core functions into simplified structures reduces assembly complexity while maintaining image quality.
3Manufacturing precision
If the back focal length is increased to accommodate more lens groups, then image quality is improved, but device complexity and length are increased
Solution Approach 1:
The patent optimizes the back focal length to a specific range (0.05 < back focal length/EFL < 0.5) that enables effective aberration correction with only two lens groups. By controlling this parameter, the design achieves compact length while maintaining high image quality without requiring extended back focal length.
Solution Approach 2:
The aspherical lens surfaces enable effective aberration correction within a compact back focal length. The curved aspherical surfaces focus and correct light paths more efficiently than spherical surfaces, allowing high image quality in a shorter optical path length.
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 simplified projection lens design that reduces the number of lenses, decreases assembly errors, and improves image quality by minimizing back focal length and aberrations, resulting in a compact and efficient projection device.
Implementation Method 1
The first lens group has a negative refracting power, and the first lens group includes an aspherical lens surface. The second lens group has a positive refracting power.
Data Source
AI summary
A projection lens and a projection device using the same are provided. The projection device includes a projection lens and an optical element. The projection lens includes a first lens group and a second lens group from an image side sequentially. The first lens group has a negative refracting power, and the first lens group includes an aspherical lens surface. The second lens group has a positive refracting power. The first lens group has a first focal length f1, and the second lens group has a second focal length f2. The first focal length f1 and the second focal length f2 satisfy the following two conditions: 0.5<|f1/f2|<1.5, and −35 mm<f1<−15 mm.