Retro Focus Optical System Aberration Correction
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Solution Overview
Problem
Chromatic aberration of magnification and field curvature in retro focus type optical systems are difficult to correct simultaneously due to the limitations of materials with high dispersion and negative anomalous partial dispersibility, which often result in increased refractive index and difficulty in setting the Petzval sum to zero.
Innovation Solution
An optical system is designed with an optical element that satisfies specific conditional expressions for the Abbe number, refractive index, and partial dispersion ratio, using materials like SiO2—Nb2O5-based optical glass, to correct chromatic aberration of magnification and field curvature by optimizing the refractive power and partial dispersion characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical materials with high dispersion and negative anomalous partial dispersibility are used to correct chromatic aberration of magnification, then chromatic aberration correction is improved, but the refractive index increases and Petzval sum correction becomes difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive index and Abbe number within specific ranges (1.45<n<1.70 and 20<ν<50) to balance chromatic aberration correction with Petzval sum correction, avoiding the use of extreme high-dispersion materials that would make Petzval sum correction difficult
Solution Approach 2:
The patent uses composite optical systems combining multiple lens elements with different dispersion characteristics (positive and negative lenses with specific Abbe numbers) to achieve both chromatic aberration correction and Petzval sum correction simultaneously, rather than relying on a single material property
2Adaptability or versatility
If retro focus type optical system design is used to achieve wide angle of view, then field of view is improved, but chromatic aberration of magnification increases
Solution Approach 1:
The patent applies local quality by placing specific lens elements with tailored dispersion properties at strategic positions within the retro focus system - particularly using negative lenses with specific Abbe numbers in the front group and positive lenses with complementary properties in the rear group to locally correct chromatic aberration where it occurs most strongly
Solution Approach 2:
The patent changes parameters by optimizing the refractive index and Abbe number combinations of individual lens elements within the retro focus structure, using the conditional expressions to ensure that the overall system achieves both wide angle of view and acceptable chromatic aberration correction
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 effectively reduces chromatic aberration of magnification and field curvature across a wider wavelength range, allowing for a more compact and aberration-corrected optical design without significantly affecting other aberrations like spherical aberration or astigmatism.
Implementation Method 1
an optical element having a refractive index of nd and an Abbe number of νd satisfy the following conditional expressions: 30≤νd≤40, 1.225≤[nd−(14.387/νd)]≤1.276
Implementation Method 2
chromatic aberration of magnification (also known as transverse or lateral chromatic aberration) is larger than axial chromatic aberration in retro focus type optical systems. A known method for correcting the chromatic aberration in a wide wavelength range is to use an optical material that exhibits large dispersion and anomalous partial dispersibility
Data Source
AI summary
An optical system includes an optical element. When the optical element is disposed on a magnification side with respect to an intersection point between an optical axis and a chief paraxial ray, the optical element is a positive lens. When the optical element is disposed on a reduction side with respect to the intersection point, the optical element is a negative lens. The optical element satisfies all of the following conditional expressions:30≤νd≤401.225≤[nd−(14.387/νd)]≤1.2760.4300≤[θgF−(2.9795/νd)]≤0.5010where νd is Abbe number of the optical element, θgF is a partial dispersion ratio of the optical element for g-line and F-line, and nd is a refractive index of the optical element for d-line.