Zoom Lens Material Layout for Axial Chromatic Aberration Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing zoom lenses for monitoring cameras struggle to correct axial chromatic aberration effectively in the visible to near-infrared wavelength range, particularly at the wide-angle end, which affects image quality and focusing accuracy.
Innovation Solution
A zoom lens configuration with specific power arrangements and optical material characteristics, including inequalities for focal length ratios, refractive indices, and partial dispersion ratios, to correct axial chromatic aberration across a wide wavelength range, ensuring high zoom ratios and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a high zoom ratio is implemented in a monitoring zoom lens, then the ability to perform remote monitoring and image pickup in various conditions is improved, but axial chromatic aberration correction becomes insufficient, particularly at the wide angle end
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the refractive index (Ndn) and partial dispersion ratio (θsn) of the optical materials used in the negative lenses of the rear lens unit. By setting specific ranges for these parameters (1.55≤Ndn≤1.75 and 2.10≤θsn≤2.60), the invention achieves effective axial chromatic aberration correction across the visible to near-infrared wavelength range while maintaining the high zoom ratio capability. This parameter optimization allows the lens to correct chromatic aberration in the SWIR region (0.9-1.71μm) without compromising the zoom performance.
2Adaptability or versatility
If the zoom lens is designed to cover a wide wavelength range from visible to near-infrared, then the ability to capture images in nighttime or dense fog conditions is improved, but the complexity of correcting chromatic aberration across all wavelengths increases
Solution Approach 1:
The patent applies local quality by focusing the chromatic aberration correction effort specifically on the rear lens unit, which contains multiple negative lenses with optimized material properties. Rather than attempting to correct aberrations uniformly across the entire lens system, the invention concentrates the correction function in the rear lens unit by selecting materials with specific refractive indices (1.55≤Ndn≤1.75) and partial dispersion ratios (2.10≤θsn≤2.60). This localized approach effectively manages the complexity while achieving wide wavelength range coverage from visible to near-infrared (0.3-1.71μm).
Solution Approach 2:
The patent employs composite materials strategy by using multiple different optical materials in the rear lens unit, each with specifically selected refractive index and partial dispersion ratio characteristics. The combination of negative lenses made from materials satisfying 1.55≤Ndn≤1.75 and 2.10≤θsn≤2.60 creates a composite optical system that can correct chromatic aberration across the extended wavelength range. This use of composite materials with tailored properties enables the lens to handle nighttime and dense fog conditions while managing the inherent complexity of multi-wavelength 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 proposed zoom lens design satisfactorily corrects axial chromatic aberration from visible to near-infrared wavelengths, improving image quality and focusing accuracy while maintaining a compact size and weight, suitable for monitoring applications.
Implementation Method 1
a first lens unit having a positive refractive power which does not move for zooming, a plurality of movable lens units including at least one lens unit having a negative refractive power, and a rear lens unit having a positive refractive power
Implementation Method 2
the rear lens unit includes a plurality of negative lenses formed of a material that satisfies the following inequalities, 1.55≤Ndn≤1.75, 2.10≤θsn≤2.60, where Ndn represents a refractive index with respect to the d-line and θsn represents a first partial dispersion ratio
Data Source
AI summary
A zoom lens including in order from object side to image side: a first lens unit having a positive refractive power that does not move for zooming; movable lens units including a lens unit having a negative refractive power; and a rear lens unit having a positive refractive power that does not move for zooming, in which an interval between lens units adjacent to each other changes for zooming, in which focal lengths of the zoom lens when focused on an infinity object at the wide angle end and at the telephoto end, a focal length of the first lens unit, and an F-number at maximum aperture of the zoom lens at the wide angle end are appropriately set, in which the rear lens unit includes a plurality of negative lenses formed of a material whose refractive index with respect to d-line and first partial dispersion ratio are appropriately set.