Variable Magnification Optical System Using Reflective Mirrors
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Solution Overview
Problem
Existing variable magnification optical systems for surveillance cameras, such as those used in harbors and airports, face challenges with high costs, weight imbalance, and limited optical performance due to large aperture aspheric elements and numerous lenses, which hinder achieving a high variable magnification ratio while reducing load on the object side.
Innovation Solution
A variable magnification optical system comprising two stationary reflecting mirrors and moving lens groups, with a field lens group and correction lens group, where the first optical system includes two reflecting mirrors and the second optical system consists of lens groups that move during magnification, optimizing the optical path and reducing the number of optical elements to minimize weight and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large aperture aspheric optical elements are used to achieve high variable magnification ratio, then optical performance is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive aspheric optical elements with spherical lenses that can be manufactured more cheaply. While spherical lenses may have slightly different optical characteristics, the overall system design with multiple movable lens groups achieves the required optical performance through geometric arrangement rather than relying on expensive aspheric surfaces.
Solution Approach 2:
The patent divides the optical system into multiple lens groups (first through fourth lens groups) with different functions. By segmenting the system, each lens group can be optimized for specific tasks (focusing, magnification, aberration correction), allowing the use of simpler spherical lenses instead of requiring a single complex aspheric element to handle all optical functions.
2Manufacturing precision
If numerous lenses with large diameters are used on the object side to achieve high variable magnification ratio, then optical performance is improved, but weight balance deteriorates and load on object side increases
Solution Approach 1:
The patent implements a dynamic optical system where lens groups move along the optical axis during magnification changes. The first lens group moves toward the object side when changing from wide-angle to telephoto, while other groups move in coordinated fashion. This dynamic arrangement allows the system to achieve high variable magnification ratio without requiring all lenses to be large and heavy, as the optical path is reconfigured during operation.
Solution Approach 2:
The patent extends the optical system in the longitudinal dimension by introducing multiple lens groups at different positions along the optical axis. Instead of increasing lens diameter in the transverse dimension, the system uses extended longitudinal arrangement with movable groups, achieving high magnification ratio through increased optical path length rather than larger aperture.
3Manufacturing precision
If heavy objects are positioned at the tip portion on the object side to achieve high variable magnification ratio, then optical performance is improved, but weight balance and ease of operation worsen
Solution Approach 1:
The patent uses a dynamic lens group configuration where the first lens group moves toward the object side during magnification changes, rather than positioning heavy fixed objects at the tip. This dynamic approach allows the system to achieve high variable magnification ratio while maintaining better weight balance, as the mass is distributed and moved rather than concentrated and fixed at the tip portion.
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 achieves a high variable magnification ratio with reduced load on the object side, lower costs, and improved optical performance by shortening the optical path, minimizing weight, and effectively correcting aberrations, while maintaining image quality across a wide range of magnifications.
Implementation Method 1
a first reflecting mirror that is an optical element having a power at a position closest to the object side on an optical path, has a reflective surface concave toward the object side, and reflects light, which is originated from the object, toward the object side
Implementation Method 2
a second reflecting mirror that has a reflective surface convex toward an image side and reflects the reflected light, which is reflected from the first reflecting mirror, toward the image side
Implementation Method 3
a second optical system that includes a plurality of lens groups moving during changing magnification
Data Source
AI summary
A variable magnification optical system consists of, in order from an object side, a first optical system remaining stationary during changing magnification and a second optical system including a plurality of lens groups moving during changing magnification. The first optical system includes a first mirror and a second mirror having reflective surfaces arranged to face each other. The first mirror is an optical element having a power at a position closest to the object side on an optical path and has a reflective surface concave toward the object side. The second mirror has a reflective surface convex toward the image side. An intermediate image is formed between the second mirror and the second optical system.