Compact Zoom Lens Unit with Dynamic Aperture Stop
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Solution Overview
Problem
Current zoom lens units fail to achieve a half-field angle of 38 degrees or more with a high magnification ratio of 6.5 times or more while maintaining compactness and resolution corresponding to 10 to 15 million pixel imaging elements, using fewer than 10 lenses.
Innovation Solution
A zoom lens unit configuration with four lens groups, including a first lens group with positive refracting power, a second lens group with negative refracting power, a third lens group with positive refracting power, and a fourth lens group, where the third lens group is made of optical glass material satisfying specific refractive index, Abbe number, and partial dispersion ratio criteria, and an aperture stop is disposed between the second and third lens groups, allowing for movement that adjusts the lens groups' positions to optimize magnification and aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a zoom lens unit uses a conventional four-lens-group configuration (positive-negative-positive-positive) to achieve high magnification ratio, then the magnification ratio increases, but the first lens group size increases and the total length increases
Solution Approach 1:
The patent employs dynamic movement of lens groups during zooming, where the first lens group moves forward (toward the object) as magnification increases, rather than remaining fixed or moving backward. This dynamic positioning allows the aperture stop to remain closer to the first lens group throughout the zoom range, preventing the first lens group from needing to be oversized, thus controlling the total length while achieving high magnification ratio
Solution Approach 2:
The patent optimizes specific parameters including setting the half-field angle at wide-angle end to 38 degrees or more, controlling the focal length ratio between telephoto and wide-angle ends to achieve 6.5x magnification or higher, and positioning the aperture stop between the second and third lens groups. These parameter optimizations enable high magnification while maintaining compact dimensions
2Length of moving object
If the first lens group is moved forward at telephoto end to reduce its size, then the total length is reduced, but the aperture stop moves away from the first lens group at wide-angle end
Solution Approach 1:
The aperture stop is designed to move dynamically with the lens groups during zooming. By positioning it between the second and third lens groups, it naturally maintains appropriate proximity to the first lens group across the zoom range, simplifying the overall system design while achieving the desired compact form factor
3Adaptability or versatility
If lens groups are moved to achieve wide angle and high magnification, then the field angle increases, but chromatic aberration increases
Solution Approach 1:
The patent carefully selects and optimizes optical parameters including the refractive indices and Abbe numbers of the lens materials in each group. By controlling these material parameters and the spacing between lens groups during zooming, the system achieves wide field angle (38 degrees or more at wide-angle end) while correcting chromatic aberration across the entire zoom range
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 zoom lens unit with a half-field angle of 38 degrees or more and a magnification ratio of 6.5 times or more, achieving sufficient resolution for 10 to 15 million pixel imaging elements with fewer lenses, while effectively correcting chromatic and monochromatic aberrations.
Implementation Method 1
the third lens group has a positive lens made of an optical glass material which satisfies the following formulae: 1.52<nd<2.10... Pg,F−(−0.001802×νd+0.6483)=0.020 to 0.025
Data Source
AI summary
A zoom lens unit, including in order from an object side to an image side: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; and a fourth lens group having a positive refracting power, an aperture stop being disposed between the second and the third lens groups, and the third lens group having a positive lens made of an optical glass material which satisfies the following formulae: (1) 1.52<nd<1.62; (2) 65.0<νd<75.0; (3) 0.015<Pg,F−(−0.001802×νd+0.6483)<0.050, where, nd represents a refractive index, νd represents an Abbe number, and Pg,F represents a partial dispersion ratio being defined as follows: Pg,F=(ng−nF)/(nF−nC), where, ng, nF and nC represent refractive indexes for g line, F line and C line, respectively.