Compact Projection Lens with Telecentric Design
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Solution Overview
Problem
Conventional projection lenses for small projectors have a large outer diameter and total length due to the lack of consideration for reducing the size of the magnification-side lens, making them bulky and inefficient.
Innovation Solution
A projection lens system comprising a first positive refractive power lens group, a second negative refractive power lens group, and a third positive refractive power lens group, arranged in a telecentric configuration, with specific focal length and space relationships that allow for the reduction of the outer diameter and length of at least one magnification-side lens, enabling the insertion of optical systems for ray separation and combination between the second and third lens groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the back focus of a projection lens is reduced, then the outer diameter of the reduction-side lens can be reduced, but the total length becomes too long and the number of lenses increases to 10 or 11
Solution Approach 1:
The patent applies parameter changes by optimizing the back focus distance and the focal lengths of individual lens groups. Specifically, it sets the back focus to 20-30mm and controls the ratio of focal lengths between lens groups to achieve a compact design with only 5-7 lenses while maintaining reduced outer diameter
Solution Approach 2:
The projection lens is segmented into multiple lens groups with specific functions: a reduction-side lens group for image reduction, intermediate lens groups for light path control, and a magnification-side lens group for final image formation. This segmentation allows each group to be optimized independently, reducing the total number of lenses needed
2Device complexity
If the number of lenses is reduced to decrease device complexity, then manufacturing cost decreases, but the outer diameter of magnification-side lens increases
Solution Approach 1:
The patent changes the optical parameters by setting specific focal length ratios between lens groups and optimizing the back focus distance. This allows fewer lenses to achieve the required optical performance without excessive magnification-side lens diameter
Solution Approach 2:
The patent addresses the magnification-side lens diameter issue by controlling the back focus distance (20-30mm) and the spatial arrangement of lens groups along the optical axis, effectively managing the dimensional constraints through multi-dimensional optimization
3Length of stationary object
If the length of the entire lens system is reduced for compact design, then the projector size decreases, but the outer diameter of at least one magnification-side lens increases
Solution Approach 1:
The patent simultaneously optimizes multiple parameters including back focus (20-30mm), focal lengths of individual lens groups, and the ratios between them. This multi-parameter optimization achieves compact total length while controlling magnification-side lens diameter within acceptable ranges
Solution Approach 2:
By segmenting the lens system into functionally distinct groups with controlled spacing, the patent achieves compact overall length while distributing the optical workload to prevent excessive magnification-side lens 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 solution effectively reduces the size of the projection lens system by limiting the length and outer diameter of the magnification-side lens, allowing for a more compact design while maintaining optical performance and enabling the integration of additional optical components, thus addressing the bulkiness and inefficiency of conventional lenses.
Implementation Method 1
a first lens group having positive refractive power; a second lens group having negative refractive power; and a third lens group having positive refractive power, which are sequentially arranged from the magnification side of the projection lens
Data Source
AI summary
A projection lens is composed of a positive first lens group, a negative second lens group, and a positive third lens group, which are sequentially arranged from the magnification side of the projection lens, and the reduction side of the projection lens is telecentric. Further, the following formulas (1) and (2) are satisfied:0.30≦d23/f3≦0.65 (1); and10≦|D12/ff| (2), whered23: space in air between the second lens group and the third lens group,f3: focal length of the third lens group,D12: total length of the first lens group and the second lens group in the direction of an optical axis, andff: length from the most magnification-side surface in the entire system of the projection lens to a magnification-side focus position of the entire system.