Free-form Compensating Lens for Vehicle Windshield Astigmatism Correction
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Solution Overview
Problem
The use of prisms to improve the resolution of front-view cameras in vehicles is expensive, bulky, and limited to single lens assemblies, and cannot correct the irregular astigmatism caused by windshield curvature.
Innovation Solution
An optical system with a lens group and a compensating lens featuring a free-form surface, disposed on the inner side of the windshield, to form a corrected optical system with improved Modulation Transfer Function (MTF) values, specifically designed to address astigmatism and field curvature issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a prism is added to the windshield to improve resolution, then the resolution of the front-view camera is improved, but the device becomes more expensive, bulky, and aesthetically compromised
Solution Approach 1:
The patent extracts the astigmatism correction function from a separate prism component and integrates it directly into the windshield structure. The free-form surface is molded into the windshield itself, eliminating the need for an additional prism while maintaining correction effectiveness. This reduces device complexity and cost while preserving the resolution improvement benefit.
Solution Approach 2:
The patent merges the astigmatism correction function with the windshield structure by incorporating a free-form surface directly into the windshield. This combines two previously separate elements (windshield and correction prism) into a single integrated component, reducing overall device complexity and aesthetic impact while maintaining optical correction performance.
2Measurement precision
If a prism is used to improve resolution, then the resolution is improved for a single lens assembly, but the solution cannot be applied to combinations of multiple lens assemblies
Solution Approach 1:
The free-form surface design provides universal astigmatism correction that works across multiple lens assemblies. By correcting the astigmatism at the windshield level rather than at individual lens level, the solution becomes applicable to any lens assembly or combination of lens assemblies, enhancing adaptability while maintaining resolution improvement.
3Measurement precision
If a prism is used to correct astigmatism, then some resolution improvement is achieved, but the irregular astigmatism caused by windshield curvature cannot be completely corrected
Solution Approach 1:
The patent applies local quality by using a free-form surface with specifically tailored curvature variations at different locations on the windshield. This allows the correction to be optimized for the specific irregular astigmatism patterns caused by windshield curvature, achieving complete correction across different field of view regions rather than uniform correction that leaves residual errors.
Solution Approach 2:
The patent changes the surface curvature parameters of the windshield by incorporating a free-form surface design. This modifies the optical path in a way that specifically addresses irregular astigmatism, transforming the windshield from a source of optical distortion to an active correction element, thereby achieving complete astigmatism correction and improved reliability.
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 achieves enhanced imaging quality with improved MTF values, particularly in the field-of-view below the optical axis, by correcting irregular astigmatism and field curvature, while maintaining a small volume and aesthetic appeal.
Implementation Method 1
an MTF value of the corrected optical system for optical path at at least one field-of-view in a portion below the optical axis is greater than or equal to 40% @60 lp/mm
Data Source
AI summary
An optical system, a vehicle-mounted camera, and a vehicle are provided. The optical system is applied to a vehicle, including: a lens group, including a plurality of lenses disposed sequentially along an optical axis from an object side to an image side; and a compensating lens, at least one of an object-side surface or an image-side surface of the compensating lens being a free-form surface; where, the free-form surface of the compensating lens is adapted to be disposed on an inner side of a windshield of the vehicle, such that the optical system and the windshield form a corrected optical system, and an MTF value of the corrected optical system is within a preset range.