Ultracompact Image Pickup Lens with Aspheric Third Element
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image pickup lenses for portable devices face challenges in achieving extreme downsizing, thinning, sufficient brightness, and a wide angle of field while effectively correcting various aberrations and ensuring adequate back focus, as they often require a balance between lens number, aberration correction, and cost considerations.
Innovation Solution
A three-lens configuration with specific optical parameters, including a meniscus-shaped first lens, a positive refractive power second lens, and an aspheric third lens with two pole-change points, optimized by conditional expressions to minimize total track length, ensure back focus, and correct aberrations, using plastic materials for all lenses to facilitate manufacturing and cost reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of lenses is increased to improve resolving power, then image quality is improved, but device size and cost increase
Solution Approach 1:
The patent applies parameter changes by optimizing the curvature radii, refractive indices, and thicknesses of the three lenses to achieve high resolving power. Specifically, it uses conditional expressions to control the curvature radius ratios and refractive index differences, allowing a three-lens configuration to perform comparably to four or more lenses while reducing device complexity
Solution Approach 2:
The patent employs composite materials by combining different plastic materials with specific refractive indices and Abbe numbers for the three lenses. The first lens uses a material with higher refractive index (1.6-1.9) while the second and third lenses use materials with lower refractive indices (1.5-1.7), creating a composite optical system that corrects aberrations effectively
2Length of moving object
If the lens is downsized to reduce device size, then portability is improved, but aberration correction becomes difficult
Solution Approach 1:
The patent applies spheroidality by using aspherical surfaces for the second and third lenses. The aspherical shape allows for effective aberration correction in a compact design, with the aspheric coefficient k controlled within specific ranges (0.8≤k<1.8 for the second lens and 0.8≤k<1.8 for the third lens). This enables the lens to maintain small size while correcting various optical aberrations
Solution Approach 2:
The patent applies local quality by giving different surface shapes to different lenses - the first lens has a meniscus shape while the second and third lenses have aspherical shapes. Each lens is optimized for its specific function in the optical path, with the aspherical surfaces positioned where they provide maximum aberration correction benefit
3Area of stationary object
If the angle of field is widened to capture more area, then coverage is improved, but resolving power decreases
Solution Approach 1:
The patent uses composite materials with different refractive indices and dispersion characteristics to correct chromatic aberration while achieving wide angle of field. The specific combination of plastic materials with controlled refractive indices (1.6-1.9 for first lens, 1.5-1.7 for second and third lenses) enables both wide coverage and high resolving power
4Length of stationary object
If the total track length is reduced to thin the lens, then device thickness is reduced, but back focus becomes insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the air gaps between lenses and the back focus distance. The conditional expressions specify that the air gap between the first and second lenses (d12) and the air gap between the second and third lenses (d23) must be within specific ranges, ensuring sufficient back focus while maintaining compact total track length
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 solution enables the creation of an extremely thin and compact image pickup lens with favorable aberration correction and sufficient brightness, supporting a wide angle of field, suitable for small imaging elements in portable devices.
Implementation Method 1
a first lens of a meniscus shape having a positive refractive power with a convex surface facing the object side
Implementation Method 2
a second lens having a positive refractive power with a concave surface facing the object side
Implementation Method 3
a third lens having a negative refractive power with a convex surface facing the object side near an optical axis, wherein the third lens is designed so that both surfaces thereof are aspheric
Data Source
AI summary
An image pickup lens includes, an aperture stop, a first meniscus lens having positive refractive power with a convex surface facing the object, a second lens having positive refractive power with a concave surface facing the object, a third lens having negative refractive power with a convex surface facing the object, the both surfaces of the third lens are aspheric and having at least one pole-change point, and following conditional expressions are satisfied:TTL<3.0 (1)0.80<f1/f<0.93 (2)0.35<bf/TTL<0.42 (3)0.70<TTL/(2IH)<0.85 (4)where TTL: a length from the surface closest to the object to an image plane, f: a focal length of an overall optical system, f1: a focal length of the first lens, bf: a length from the image-side surface of the third lens to the image plane, and IH: a maximum image height.