Zoom Lens Aberration Correction Using Aspheric and High-Abbe Lenses
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Solution Overview
Problem
Conventional zoom lenses for surveillance cameras face challenges in maintaining high optical performance while achieving a higher focal ratio and smaller size, which makes it difficult to correct various types of aberration across the visible and near-infrared light spectrum, especially when increasing pixel density.
Innovation Solution
A zoom lens design featuring a first lens group with negative refractive power and a second lens group with positive refractive power, where the second lens group includes at least one aspheric surface, and specific Abbe number conditions are met to correct chromatic aberration, allowing for a higher focal ratio and smaller size while maintaining high optical performance across the zoom range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a higher focal ratio and smaller size are achieved, then the compactness and light-gathering capability are improved, but the correction of various types of aberration across the visible to near-infrared spectrum becomes difficult
Solution Approach 1:
The patent applies parameter changes by specifying precise Abbe number ranges for the lenses (υd21>63 and υd22>70) to control chromatic aberration across the visible to near-infrared spectrum. The aspheric surface parameters are also optimized to correct spherical aberration while maintaining a compact form factor with higher focal ratio
Solution Approach 2:
The patent uses composite optical materials with different dispersion properties (lenses with different Abbe numbers) to correct chromatic aberration. The combination of a positive lens with υd21>63 and a negative lens with υd22>70 creates a cemented lens group that simultaneously corrects chromatic aberration across multiple wavelengths while maintaining compact size
2Measurement precision
If the pixel density is increased to megapixel order, then the image detail capability is improved, but the requirement for aberration correction across the entire zoom range becomes more stringent
Solution Approach 1:
The patent employs an aspheric surface on the positive lens in the second lens group to correct spherical aberration. The aspheric coefficient is optimized to ensure that high-resolution megapixel images are captured without spherical distortion across the entire zoom range from wide angle to telephoto
Solution Approach 2:
The patent specifies precise parameter ranges including the aspheric coefficient and Abbe numbers to ensure that chromatic and spherical aberrations are corrected simultaneously. These parameter optimizations enable megapixel-level image quality while maintaining performance across the full zoom range
3Volume of moving object
If a compact design with higher focal ratio is implemented, then the portability and low-light performance are improved, but the correction of chromatic aberration in the near-infrared range becomes difficult
Solution Approach 1:
The patent addresses near-infrared chromatic aberration by specifying extended Abbe number ranges that account for both visible and near-infrared wavelengths. The condition υd21>63 and υd22>70 ensures that the cemented lens group effectively corrects chromatic aberration across the 400-1000nm spectrum while maintaining a compact design
Solution Approach 2:
The patent uses a composite lens design with a positive lens (υd21>63) and a negative lens (υd22>70) cemented together. This composite structure creates opposite chromatic aberration effects that cancel each other out, enabling correction across the visible to near-infrared range in a compact form factor
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 design effectively corrects various types of aberration over the entire zoom range, enabling sharp images in both visible and near-infrared light ranges, suitable for megapixel surveillance cameras with improved optical performance.
Implementation Method 1
a positive first lens having at least on aspheric surface
Implementation Method 2
a first condition υd21>63 and a second condition υd22>70 are satisfied, υd21 being the Abbe number for a d-line in the first lens of the second lens group and υd22 being the Abbe number for a d-line in the second lens of the second lens group
Data Source
AI summary
A zoom lens includes sequentially from an object side a first lens group having a negative refractive power; a diaphragm; and a second lens group having a positive refractive power. Zoom from a wide angle edge to a telephoto edge is performed by displacement of the second lens group along an optical axis, toward the object side. Correction of imaging plane variation accompanying the zoom, is performed by displacement of the first lens group along the optical axis. The second lens group includes sequentially from the object side, a positive first lens having at least on aspheric surface and a positive second lens. Furthermore, a first condition υd21>63 and a second condition υd22>70 are satisfied, υd21 being the Abbe number for a d-line in the first lens of the second lens group and υd22 being the Abbe number for a d-line in the second lens of the second lens group.