Four-Group Optical System Aberration Control During Focusing
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Solution Overview
Problem
Conventional optical systems that focus by moving lens groups on the optical axis face challenges in suppressing aberration fluctuation during focusing.
Innovation Solution
An optical system comprising a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with negative refractive power, where the second and third lens groups move on the optical axis, and specific conditional expressions are satisfied to control the distances between lens groups and their refractive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical systems move lens groups on the optical axis for focusing, then focusing function is achieved, but aberration fluctuation increases
Solution Approach 1:
The patent applies the Dynamics principle by making the lens groups movable along the optical axis during focusing operations. Specifically, the second and third lens groups are configured to move on the optical axis, allowing the system to dynamically adjust focal length while maintaining aberration control through carefully designed movement ranges and conditional expressions for inter-group distances
Solution Approach 2:
The patent employs Parameter changes by establishing specific conditional expressions that constrain the relationships between lens group distances and focal lengths during focusing. The conditional expressions (0.20 ≤ DG4/TL ≤ 0.40, 3.00 ≤ (LnR2+LnR1)/(LnR2−LnR1) ≤ 5.00, 0.75 ≤ f1/(−f2) ≤ 1.30) dynamically adjust optical parameters to suppress aberration fluctuation while maintaining focusing capability
2Adaptability or versatility
If lens groups are moved to achieve focusing, then focusing range is extended, but distances between lens groups become difficult to control
Solution Approach 1:
The patent usesParameter changes to establish conditional expressions that define precise relationships between lens group distances and focal lengths. These expressions (0.20 ≤ DG4/TL ≤ 0.40, 3.00 ≤ (LnR2+LnR1)/(LnR2−LnR1) ≤ 5.00, 0.75 ≤ f1/(−f2) ≤ 1.30) ensure that as lens groups move to achieve different focusing ranges, the inter-group distances remain within controlled parameters, thereby maintaining manufacturing precision across the entire focusing range
3Reliability
If multiple lens groups are made movable for focusing, then focusing performance is improved, but device complexity increases
Solution Approach 1:
The patent appliesSegmentation by dividing the optical system into four distinct lens groups with alternating positive and negative refractive powers. This segmentation allows independent control of each group's movement and optical properties, improving focusing performance while managing complexity through modular design where each group has a specific function
Solution Approach 2:
The patent implementsDynamics by configuring the second and third lens groups to move on the optical axis during focusing, while the first and fourth lens groups remain fixed. This selective dynamic configuration optimizes focusing performance without making the entire system complex, as only specific groups require actuation mechanisms
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 optical system achieves small aberration fluctuation during focusing, effectively correcting curvature of field, coma aberration, spherical aberration, and chromatic aberration across various magnification ranges.
Implementation Method 1
an optical system OL comprises, in order from an object on an optical axis, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a negative refractive power
Data Source
AI summary
An optical system (OL) comprising, sequentially along an optical axis from the objective side, a first lens group (G1) having a positive refractive power, a second lens group (G2) having a negative refractive power, a third lens group (G3) having a positive refractive power, and a fourth lens group (G4) having a negative refractive power, wherein, when focusing the optical system, the following conditional expression is satisfied as a result of moving the second lens group (G2) and the third lens group (G3) along the optical axis and changing the interval between adjacent lens groups. 0.20<DG4/TL<0.40 wherein DG4 represents the length of the fourth lens group (G4) on the optical axis, and TL represents the full length of the optical system (OL) when the optical system (OL) comes into focus at an infinite distance.