Three-Lens Zoom Optical System with Telephoto First Unit
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Solution Overview
Problem
Existing optical systems for telescopes with variable focal length suffer from issues such as large overall length, fluctuating image plane, significant spherical aberration, and chromatic errors, particularly at high magnification, which result in color fringes and undesirable length changes during zooming.
Innovation Solution
An optical system comprising three lens units, where the first lens unit is fixed with a telephoto effect, and the second and third lens units are movable for zooming, with specific lens group configurations and materials selected to minimize spherical aberration and secondary spectrum, maintaining a constant field of vision across magnification ranges and reducing overall length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a four-number zoom objective system with main objective and afocal adapter is used, then variable magnification is achieved, but the overall objective length becomes excessively large compared to the maximum focal length
Solution Approach 1:
The objective is divided into three lens units with specific functions: the first lens unit (with positive and negative lens groups) provides the main refractive power and telephoto effect, the second lens unit controls zooming by changing focal length, and the third lens unit fine-tunes the optical path. This segmentation allows compact design while maintaining variable magnification capability.
Solution Approach 2:
The patent employs a nested structure where the second and third lens units are positioned within the optical path defined by the first lens unit. The movable lens groups are arranged concentrically along the optical axis, allowing the zoom mechanism to be compactly integrated without increasing overall length disproportionately.
2Adaptability or versatility
If optical compensation principle is used with movable lens units, then variable focal length is achieved, but the image plane location fluctuates over the magnification range
Solution Approach 1:
The patent implements an optical compensation mechanism where the third lens unit moves in coordination with the second lens unit to counteract image plane fluctuations. The movement distances and positions are precisely designed to maintain the image plane at a constant location throughout the zoom range, effectively compensating for focal length changes.
3Ease of operation
If the entire first lens unit is displaced to set finite object distances, then focusing is achieved, but the overall length of the objective changes
Solution Approach 1:
The patent extracts the focusing function from the entire first lens unit and assigns it specifically to the negative lens group within the first lens unit. This allows focusing to be achieved by moving only the negative lens group, maintaining a constant overall objective length while still enabling finite object distance setting.
4Length of moving object
If only a single lens is displaced for internal focusing, then overall length is maintained, but spherical aberration and chromatic errors change very strongly
Solution Approach 1:
The patent combines multiple lens groups (positive and negative lens groups in the first lens unit, and additional lens groups in the second and third lens units) to share the focusing and aberration correction functions. This distributed approach allows maintaining constant overall length while distributing the correction of spherical aberration and chromatic errors across multiple elements working together.
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 corrects spherical aberration and Gaussian errors, maintains a constant field of vision, and reduces the secondary spectrum, achieving a more compact design with improved optical performance across the magnification range, including at high focal lengths.
Implementation Method 1
The first lens unit has a telephoto effect
Implementation Method 2
an optical system (200) for imaging an object on an image acquisition unit
Implementation Method 3
corrects spherical aberration and the Gaussian error
Data Source
AI summary
An optical system for imaging an object on an image acquisition unit has a variable focal length for zooming. The optical system has precisely three lens units from the object in the direction of an image acquisition unit, namely a first lens unit, a second lens unit, and a third lens unit. The second lens unit and the third lens unit are movably situated along an optical axis of the optical system for a change of the focal length. The first lens unit includes a first lens group and a second lens group. The first lens group of the first lens unit is fixedly situated on the optical axis of the optical system. The second lens group of the first lens unit is movably situated along the optical axis of the optical system for focusing. The second lens group includes at least two lenses.