Optical System Angle of View Stability via Rear Group Focusing
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Solution Overview
Problem
Conventional optical systems for cameras experience significant fluctuations in angle of view during focusing, which are difficult to suppress effectively.
Innovation Solution
The optical system consists of a front group, an aperture stop, and a rear group with a focusing lens group that has negative refractive power, where the focusing lens group moves on the optical axis, and the distances between lens groups change, satisfying specific conditional expressions to minimize angle of view fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional optical system is used for focusing, then the focusing function is achieved, but the angle of view fluctuates significantly
Solution Approach 1:
The patent applies parameter changes by carefully controlling the conditional expression 0.50 < ST/TL < 0.95, where ST is the distance from the aperture stop to the image surface and TL is the entire length of the optical system. By optimizing this parameter range, the system achieves both stable angle of view during focusing and good focusing performance
Solution Approach 2:
The patent employs a focusing lens group with negative refractive power that moves on the optical axis during focusing. This dynamic configuration allows the distances between lens groups to change, enabling the system to maintain angle of view stability while achieving effective focusing across different object distances
2Ease of operation
If the focusing lens group moves on the optical axis to change distances between lens groups, then focusing is achieved, but the angle of view fluctuation increases
Solution Approach 1:
The patent resolves this contradiction by constraining the movement of the focusing lens group within specific parameter boundaries defined by the conditional expression 0.50 < ST/TL < 0.95. This ensures that while the lens group moves for focusing, the angle of view remains stable
Solution Approach 2:
The patent assigns a specific negative refractive power to the focusing lens group, which is positioned closest to the object in the rear group. This localized optical property enables the lens group to perform focusing while minimizing angle of view fluctuation
3Stability of the object's composition
If the distance ST from aperture stop to image surface is increased, then the angle of view stability improves, but the entire length TL of the optical system increases
Solution Approach 1:
The patent optimizes the ratio ST/TL within the range 0.50 < ST/TL < 0.95, allowing the system to achieve angle of view stability without excessive increase in overall length. This ratio-based parameter control enables compact design while maintaining stability
Solution Approach 2:
By using a movable focusing lens group with negative refractive power, the patent dynamically adjusts the optical path to achieve stable angle of view without requiring a fixed increase in system length. The moving lens group compensates for changes in ST while maintaining compact TL
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 reduces angle of view fluctuations and maintains favorable optical performance across various focusing distances, correcting aberrations such as curvature of field, spherical aberration, and coma aberration.
Implementation Method 1
a focusing lens group which is disposed closest to the object in the rear group and has a negative refractive power
Data Source
AI summary
This optical system (OL) comprises a front group (GA), an aperture stop (S), and a rear group (GB) that are arranged in order from the object side along an optical axis. The rear group (GB) has a focusing lens group (GF1) disposed closest to the object side in the rear group (GB) and having negative refractive power, during focusing, the focusing lens group moves along the optical axis, and the spacing between adjacent lens groups changes, and the following conditional expression is satisfied. 0.50<ST/TL<0.95, where ST is the distance on the optical axis from the aperture stop (S) to an image surface (I), and TL is the total length of the optical system (OL).