Four-Lens Smartphone Camera with Aspherical Elements
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Solution Overview
Problem
The challenge is to develop a small lens system for smartphones that balances high performance, sensitivity, and miniaturization while minimizing distortion and tolerance sensitivity, given the constraints of reduced total track length and size requirements.
Innovation Solution
A four-lens system with specific refractive powers and shapes, including a first lens with negative refractive power and concave surfaces, second and third lenses with positive refractive power and convex surfaces, and a fourth lens with negative refractive power and concave surfaces, all with aspherical surfaces, is designed to achieve improved performance and reduced tolerance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the total track length (TTL) is reduced to miniaturize the lens system, then the size and weight of the lens system are improved, but the tolerance sensitivity increases and design errors become more likely
Solution Approach 1:
The patent applies parameter changes by carefully controlling the refractive powers, focal lengths, and curvature ratios of each lens element. Specifically, it sets the refractive powers P1, P2, P3, P4 to satisfy −1 < P1 + P2 − (P3 + P4) < 1, and controls the ratio (R1+R2)/(R1-R2) within −2 to 2, where R1 and R2 are object-side and image-side curvatures of the first lens. These parameter optimizations reduce tolerance sensitivity while maintaining miniaturization.
Solution Approach 2:
The patent uses composite optical design by combining four lens elements with different refractive powers and aspherical surfaces. Each lens element contributes differently to the overall optical performance, with the first lens having negative refractive power and concave-convex surfaces, the second and third lenses having positive refractive power with convex surfaces, and the fourth lens having negative refractive power with concave surfaces. This composite structure achieves both miniaturization and reduced tolerance sensitivity.
2Reliability
If the number of lenses is increased to improve optical performance, then the performance and sensitivity are improved, but the total track length and device complexity increase
Solution Approach 1:
The patent optimizes the focal lengths f1, f2, f3, f4 of the four lenses to satisfy F/f1 + F/f2 + F/f3 + F/f4 = 1, where F is the effective focal length of the entire system. It also controls the ratio f1/f2 and f1/f4 within specific ranges, and sets the center thickness ratio (L1_CT + L3_CT + L4_CT)/L2_CT between 1.3 and 3.0. These parameter optimizations enable high optical performance with a compact total track length.
Solution Approach 2:
The patent employs aspherical surfaces on all lens elements to improve optical performance while maintaining compact dimensions. The aspherical surfaces are defined by specific curvature relationships, such as controlling (R1+R2)/(R1-R2) within −2 to 2 for the first lens and (R3+R4)/(R3-R4) within −2 to 2 for the second lens, where R represents object-side and image-side curvatures. This curvature optimization reduces the number of lenses needed while achieving high performance.
3Volume of moving object
If the effective diameter of the first lens is reduced to miniaturize the camera, then the size is improved, but the light gathering ability and image quality deteriorate
Solution Approach 1:
The patent optimizes the refractive power P1 of the first lens and its curvature ratio (R1+R2)/(R1-R2) within −2 to 2 to maximize light gathering ability within a small effective diameter. The controlled parameter relationships enable the first lens to maintain adequate aperture while keeping the overall camera size miniaturized.
Solution Approach 2:
The patent uses a composite four-lens system where each element compensates for the limitations of small aperture. The combination of negative and positive refractive power lenses, all with aspherical surfaces, enables effective light gathering and aberration correction despite the reduced effective diameter of the first lens, thereby maintaining image quality in a miniaturized camera.
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 superior performance and productivity by correcting color aberration, minimizing distortion, and reducing tolerance sensitivity, while maintaining a small size and weight, suitable for high-definition and wide-angle applications in smartphone cameras.
Implementation Method 1
The first lens may have a negative refractive power and includes a surface concave surface on an object side and a convex surface on an image side. The second lens may have a positive refractive power and includes convex surfaces on both sides.
Implementation Method 2
All surfaces of the first to fourth lenses may be aspherical
Data Source
AI summary
Proposed is a small lens system including a first lens, a second lens, a third lens, and a fourth lens arranged along an optical axis from an object. The iris diaphragm is located between the first lens and the second lens. The first lens has a negative refractive power and includes a surface concave surface on an object side and a convex surface on an image side. The second lens has a positive refractive power and includes convex surfaces on both sides. The third lens has a positive refractive power and includes convex surfaces on both sides. The fourth lens has a negative refractive power and includes concave surfaces on both sides. All surfaces of the first to fourth lenses are aspherical.