Compact Wide-Angle Lens Using Free-Form Prism
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Solution Overview
Problem
Conventional wide-angle imaging lens systems face challenges in achieving compact size, low cost, and high image quality due to difficulties in correcting aberrations and machinability, particularly with spherical glass lenses and complex free-form surface prisms.
Innovation Solution
A compact wide-angle imaging lens system incorporating a free-form surface prism with aspheric surfaces, a biconcave lens, and a cemented doublet lens, made from plastics and glass, which reduces the total length and volume by folding the optical path and simplifies machining, while maintaining high image resolution and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional spherical ground glass lenses are used, then material availability and color aberration correction are improved, but spherical aberration and astigmatic aberration correction becomes difficult with small F-number and wide angle of field
Solution Approach 1:
The patent employs aspheric lens elements with asymmetric surfaces that deviate from spherical geometry. This asymmetry enables effective correction of spherical aberration and astigmatic aberration in wide-angle, small F-number configurations, directly resolving the aberration correction difficulty while maintaining manufacturability through injection molding of aspheric plastic lenses.
Solution Approach 2:
The patent changes the surface curvature parameters of lens elements by introducing aspheric surfaces with varying curvature radii across the aperture. This parameter change allows simultaneous correction of multiple aberration types (spherical, astigmatic, coma) that cannot be corrected by conventional spherical surfaces, particularly effective in wide-angle designs with small F-numbers.
2Manufacturing precision
If aspheric glass lens elements are used to correct aberrations, then image quality and barrel distortion reduction are improved, but machining difficulty increases and system cost increases
Solution Approach 1:
The patent substitutes expensive, difficult-to-machine aspheric glass lens elements with cheaper, easily manufactured aspheric plastic lens elements. The plastic lenses are produced via injection molding, which is a cost-effective, high-volume manufacturing process that eliminates the complex and expensive machining required for aspheric glass surfaces, thereby reducing both cost and machining difficulty while maintaining aberration correction performance.
Solution Approach 2:
The patent changes the material parameter from glass to plastic, which fundamentally alters the manufacturing method from precision machining to injection molding. This material substitution maintains the aspheric surface geometry needed for aberration correction while dramatically improving ease of manufacture and reducing cost.
3Manufacturing precision
If conventional glass lens systems are used to correct off-axis aberrations and color aberrations, then aberration correction is improved, but system length and volume increase
Solution Approach 1:
The patent merges multiple aberration correction functions into fewer lens elements by using aspheric surfaces. A single aspheric lens element can simultaneously correct spherical aberration, coma, and astigmatism, whereas conventional spherical glass lens systems require multiple separate elements for each correction, thereby reducing the total number of elements and system length.
Solution Approach 2:
The aspheric lens elements in the patent serve multiple functions simultaneously: they provide the primary optical power for the lens system, correct spherical aberration, correct coma aberration, and reduce barrel distortion. This multi-functionality reduces the number of required lens elements compared to conventional systems where each element has a specialized single function.
4Length of stationary object
If free-form surface prisms are used to reduce system length, then total length reduction is achieved, but construction complexity increases making design and fixing difficult
Solution Approach 1:
The patent uses a right-angled prism with asymmetric orientation (45-degree angle to the optical axis) to fold the optical path by 90 degrees. This asymmetric configuration achieves compactness by reducing system length while the standard right-angled prism geometry maintains manufacturing simplicity and ease of assembly, avoiding the complexity of free-form surface prisms.
Solution Approach 2:
The patent introduces a spatial dimension change by using a prism to fold the optical path at a 90-degree angle. This dimensional reconfiguration allows the optical system to achieve a compact form factor by directing light perpendicular to the original optical axis, effectively reducing the system's length in the original direction while maintaining all necessary optical functions.
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 system achieves a wide angle of view, small size, and light weight with improved machinability and reduced production costs, while effectively correcting aberrations and maintaining high image quality, making it suitable for portable devices.
Implementation Method 1
The above-mentioned prism type design folds the optical path by 90 degrees by means of a 45° reflecting minor that has no aberration correction function
Implementation Method 2
Both the incidence surface and the exit surface of the prism are convex surfaces, and the reflection surface of the prism is a planar surface
Data Source
AI summary
A compact wide-angle imaging lens system includes, in order from the object side to the image side, a first lens (1) of negative refractive power, a free-form surface prism (2) of positive refractive power, a second lens (3) of positive refractive power and a third lens (7) of negative refractive power. The free-form surface prism has an incidence surface (S3), a reflection surface (S4) and an exit surface (S5). The first lens and the free-form surface prism are arranged in a juxtaposed manner, and the second and third lenses are disposed below the free-form surface prism and adjacent to the image side. The free-form surface prism functions equivalent to a right-angle prism with aspheric surfaces.