Optical System Aberration Correction via Cemented Lens Parameter Control
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Solution Overview
Problem
Optical systems for cameras face challenges in correcting chromatic aberration, maintaining the Petzval sum, and curvature of field while managing the back focal length and total length to ensure high-quality image signals and appropriate filter placement.
Innovation Solution
The optical system comprises a first lens group, an aperture stop, and a rear group with a first cemented lens consisting of a positive and negative lens, satisfying specific conditional expressions to optimize the back focal length, total length, refractive indices, and central thickness ratios, which corrects aberrations and maintains the Petzval sum effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the back focal length is increased to allow filter placement, then the total length of the optical system increases, making the system less compact
Solution Approach 1:
The patent applies parameter changes by precisely controlling the back focal length within the range 0.25y ≤ Bf < 0.40y and the total length within 1.70y ≤ TL < 2.10y. By optimizing these dimensional parameters and the refractive indices of lens materials, the system achieves appropriate filter placement space while maintaining compact overall dimensions.
2Reliability
If chromatic aberration is corrected by adjusting refractive indices, then the design complexity increases due to multiple conditional expressions
Solution Approach 1:
The patent resolves design complexity by establishing specific parameter ranges for refractive indices (NP1 > NN1 and NP2 > NN2) and their differences (0.10 < NP1 - NN1 < 0.40 and 0.10 < NP2 - NN2 < 0.40). These quantified parameters provide clear design guidelines that simplify the correction of chromatic aberration while maintaining systematic control.
3Reliability
If the Petzval sum is maintained for flat field correction, then the curvature of field correction becomes more difficult
Solution Approach 1:
The patent resolves the conflict between maintaining Petzval sum and correcting curvature of field by introducing specific parameter ranges for the second cemented lens. By controlling the refractive indices (NP2 > NN2) and their difference (0.10 < NP2 - NN2 < 0.40), the system achieves both flat field correction and curvature of field control through coordinated parameter optimization.
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 ensures a compact optical system with improved aberration correction, appropriate back focal length, and reduced shading, enabling high-quality image signals and effective filter placement.
Implementation Method 1
the rear group includes a first cemented lens comprising a positive lens and a negative lens... Np1: the refractive index of the positive lens constituting the first cemented lens... Nn1: the refractive index of the negative lens constituting the first cemented lens
Data Source
AI summary
An optical system comprising, in order from an object side, a first lens group, an aperture stop, and a rear group that includes a first cemented lens comprising a positive lens and a negative lens is configured so as to satisfy the following conditional expressions:0.350<Bf/y<0.7001.350<TL/y<2.0000.050<Np1−Nn1<0.400where Bf is a back focal length in air; y is maximum image height; TL is the distance from a lens surface closest to the object side to an image plane; and Np1 and Nn1 are the refractive indices of the positive and negative lenses constituting the first cemented lens, respectively.