Aspheric Lens Optical System for Compact Wide-Angle Imaging
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Solution Overview
Problem
Existing optical systems for imaging apparatuses, such as on-vehicle cameras, face challenges in reducing the diameter of the first lens and the second lens while maintaining a wide angle of view and minimizing the overall system length.
Innovation Solution
The optical system comprises a front group with positive refractive power, an aperture diaphragm, and a rear group with positive refractive power, where the front group includes a first lens with negative refractive power, a second lens with negative refractive power, a third lens, and a fourth lens with positive refractive power. The second lens has an aspheric surface with an inflection point, and specific conditional expressions are satisfied to optimize the focal distances and distances between lenses, achieving a wide angle of view with reduced system size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional optical systems with seven lenses are used to achieve wide angle of view, then the angle of view is wide, but the diameter of the first lens and second lens cannot be reduced and the system length cannot be minimized
Solution Approach 1:
The patent applies aspheric surfaces to the second lens (L2) with specific inflection point conditions, and the third lens (L3) with positive or negative power. These curved surfaces enable more efficient light control and aberration correction compared to conventional spherical lenses, allowing reduction of lens diameters while maintaining wide angle of view and correcting image plane curvature and chromatic aberration of magnification.
Solution Approach 2:
The patent employs specific conditional expressions for focal distances and spacing parameters (f1/d12, f23/fa1, fG1/fG2) to optimize the optical system. By carefully controlling these parameters, the system achieves compact size with reduced first and second lens diameters while maintaining wide angle of view and proper aberration correction through precise parameter optimization.
2Volume of moving object
If the diameter of the first lens and second lens is reduced, then the system size is reduced, but the ability to correct image plane curvature and chromatic aberration of magnification deteriorates
Solution Approach 1:
The aspheric surface on the second lens with inflection point conditions enables the lens to maintain reduced diameter while effectively correcting image plane curvature. The curved surface profile allows light rays from different field positions to converge properly on the image plane, compensating for the reduced lens size and maintaining aberration correction reliability.
Solution Approach 2:
The patent assigns specific optical properties to different lenses: the second lens has aspheric surface with inflection points for correcting image plane curvature, while the third lens has positive or negative power for correcting chromatic aberration of magnification. This localized optimization of each lens's properties enables compact size while maintaining overall system correction performance.
3Length of moving object
If the length of the entire system is minimized, then the system becomes compact, but the optical performance and aberration correction become difficult to maintain
Solution Approach 1:
The aspheric surfaces on the second and third lenses enable more compact lens spacing while maintaining optical performance. The curved surface profiles allow for shorter focal lengths and reduced back focal length, achieving compact system length without sacrificing the ability to correct aberrations through optimized surface geometry.
Solution Approach 2:
The patent uses specific conditional expressions for focal distances and spacing (f1/d12, f23/fa1, fG1/fG2) to optimize the compact configuration. These parameter constraints ensure that even in a minimized system length, the optical performance and aberration correction are maintained through precise control of focal ratios and lens spacing.
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
This configuration enables the achievement of a small-sized optical system with a wide angle of view, while effectively correcting image plane curvature and chromatic aberration of magnification, thus improving the imaging performance and reducing manufacturing complexities.
Implementation Method 1
an object side surface of the second lens is an aspheric surface having an inflection point in a cross-section including an optical axis
Implementation Method 2
a chart representing a curvature of the aspheric surface with respect to radial positions in the cross-section including the optical axis includes a first extremal value and a second extremal value
Data Source
AI summary
An optical system includes a front group having positive refractive power, an aperture diaphragm, and a rear group having positive refractive power, which are disposed from an object side to an image side in this order, wherein the front group includes a first lens having negative refractive power, a second lens having negative refractive power, a third lens, and a fourth lens having positive refractive power, which are disposed from the object side to the image side in this order, wherein the rear group includes a cemented lens and a positive lens disposed closest to the image side, wherein an object side surface of the second lens is an aspheric surface, and wherein a predetermined conditional expression is satisfied.