Projection Zoom Lens Inversion for Compact Telecentric Design
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Solution Overview
Problem
Existing projection zoom lenses face challenges in miniaturization and cost reduction due to increased total length and lens diameters, which hinder their ability to maintain constant numerical aperture over the entire zoom range and satisfy demands for back focus and telecentricity.
Innovation Solution
A projection zoom lens configuration with a fixed positive refractive power first lens group, moving lens groups at the reduction side, and an aperture stop positioned between or within moving lens groups, ensuring constant numerical aperture and telecentricity, while reducing the total length and diameters of lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lens groups at the magnification side are fixed and aperture stop is fixed to maintain constant numerical aperture, then numerical aperture is maintained constant, but total length and lens diameters increase
Solution Approach 1:
The patent inverts the conventional configuration by fixing the aperture stop and magnification-side lens groups, while making the reduction-side lens groups movable. This inversion allows the numerical aperture to be maintained constant through the movable reduction-side groups, while avoiding the need for large diameters on the magnification side, thus reducing total length.
Solution Approach 2:
The patent introduces dynamic movement of the reduction-side lens groups (second through fifth lens groups) along the optical axis during zooming. This dynamic configuration allows the lens system to maintain constant numerical aperture while achieving high zoom ratios, without requiring increased total length or magnification-side lens diameters.
2Adaptability or versatility
If high zoom ratio is achieved with fixed aperture stop and magnification-side lens groups, then constant numerical aperture is maintained, but lens diameters and total length increase leading to higher costs
Solution Approach 1:
By inverting which side is fixed and which side moves, the patent achieves high zoom ratios with smaller, more cost-effective lens diameters on the magnification side, while the movable reduction-side groups handle the zooming function efficiently.
Solution Approach 2:
The patent changes the operational parameters by allowing the reduction-side lens groups to move dynamically during zooming, while keeping the magnification-side groups fixed. This parameter change enables high zoom ratios to be achieved with smaller lens diameters, reducing manufacturing costs.
3Reliability
If aperture stop and reduction-side lens groups are fixed to maintain constant numerical aperture, then numerical aperture is constant, but total length and lens diameters increase
Solution Approach 1:
The patent inverts the conventional approach by fixing the aperture stop and magnification-side groups while making reduction-side groups movable. This inversion maintains constant numerical aperture through the movable reduction-side groups, while keeping the stationary magnification-side lens diameters small, thus reducing total 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
This configuration allows for a compact and cost-effective projection zoom lens that maintains constant numerical aperture and telecentricity, enabling a high zoom ratio and reducing spherical and chromatic aberrations, while minimizing the size and weight of the lens system.
Implementation Method 1
a first lens group having a positive refractive power positioned at the most-magnification side and fixed while changing magnification
Implementation Method 2
at least two moving lens groups positioned at the reduction side of the first lens group, the moving lens groups moving while changing magnification
Implementation Method 3
an aperture stop positioned between adjacent moving lens groups or within one moving lens group
Data Source
AI summary
The projection zoom lens essentially consists of a positive first lens group fixed while changing magnification and the second lens group through the fourth lens group which move while changing magnification, and a fifth lens group fixed while changing magnification; and an aperture stop positioned between adjacent moving lens groups or within one moving lens group, whereinthe numerical number of the zoom lens is set to be constant over the entire zoom range,the reduction side is configured to be telecentric, andthe projection zoom lens satisfies conditional formulas (4) and (5):2.0<Bf/Imφ (4)L/Imφ<12 (5),where,Bf: the back focus (air converted length) at the reduction side of the entire system at the wide angle end,Imφ: the maximum effective image circle diameter, andL: the distance between the most-magnification-side lens surface and the most-reduction-side lens surface along the optical axis when the projection distance is infinite.