Wide-Angle Plastic Lens Optical System for Thermal Stability
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Solution Overview
Problem
Optical systems for in-vehicle and surveillance cameras face challenges in maintaining a wide field of view and high resolution in dark environments, particularly due to the use of plastic lenses which exhibit significant focal length fluctuations with temperature changes and are prone to various aberrations.
Innovation Solution
An optical system design comprising a first negative lens with an aspherical object-side surface, a second negative lens, a first positive lens adjacent to an aperture stop, and a third negative lens, with specific focal length relationships and aspherical surface inflection points, is employed to stabilize focal length and correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plastic lenses are used to form aspherical surfaces, then manufacturing ease and cost-effectiveness are improved, but focal length stability deteriorates due to significant fluctuations with temperature changes
Solution Approach 1:
The optical system divides the correction of temperature-induced focal length changes across multiple plastic lenses (first negative lens, second negative lens, first positive lens, and third negative lens) arranged in a specific configuration. Each lens contributes to the overall temperature compensation effect, allowing the system to maintain focal length stability while using easily manufacturable plastic materials with aspherical surfaces.
Solution Approach 2:
The patent employs specific focal length relationships between the lenses (expressed as inequalities involving fp1, fp2, fp3, and f) to optimize temperature compensation. By carefully selecting and adjusting the focal lengths of individual plastic lenses, the system achieves focal length stability despite temperature variations, while maintaining the manufacturing advantages of plastic materials.
2Ease of manufacture
If plastic lenses are used to reduce cost, then manufacturing cost is improved, but optical quality deteriorates due to aberrations
Solution Approach 1:
The optical system segments the aberration correction function across multiple plastic lenses, with each lens (first negative lens, second negative lens, first positive lens, third negative lens) designed to correct specific types of aberrations. This distributed approach allows cost-effective plastic materials to achieve high optical quality that would be difficult to obtain with a single lens element.
Solution Approach 2:
The patent utilizes aspherical surfaces on the plastic lenses to correct optical aberrations more effectively than spherical surfaces alone. The aspherical shapes allow the plastic lenses to achieve higher optical precision while maintaining cost-effectiveness, as aspherical plastic lenses can be manufactured more easily than traditional glass lenses with complex surface profiles.
3Area of stationary object
If a wide field of view is achieved, then coverage area is improved, but resolution in the screen center region deteriorates
Solution Approach 1:
The optical system applies local quality optimization by using aspherical surfaces on specific lenses (particularly the first negative lens and third negative lens) to correct aberrations in different regions of the field. The aspherical profiles are designed to maintain high resolution in the screen center region while preserving the wide field of view, creating different optical qualities in different parts of the system to address the specific contradiction.
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 achieves a wide field angle and high resolution in the screen center region while effectively compensating for temperature-induced focal length changes and correcting various aberrations, using plastic lenses that are cost-effective and suitable for mass production.
Implementation Method 1
a first negative lens (Li1) with an aspherical object-side surface; the aspherical surface has an inflection point in a cross section including an optical axis
Implementation Method 2
an optical system including, in order from an object side to an image side
Data Source
AI summary
An optical system includes, in order from an object side to an image side, a first negative lens having an aspherical object-side surface, a second negative lens, a first positive lens, and a third negative lens. The first negative lens is disposed closest to an object, the aspherical surface has an inflection point in a cross section including an optical axis, the first positive lens is disposed adjacent to an aperture stop, and individual parameters are appropriately set.