Four-Lens Imaging System for Compact Wide-Angle Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wide-angle lenses for digital input devices, such as surveillance and vehicle-mounting cameras, face challenges in achieving a balance between a wide viewing angle, small size, and minimal image distortion, often resulting in large lens size and significant distortion due to their fisheye-like configuration.
Innovation Solution
A four-lens system comprising a negative meniscus first lens, a negative second lens, a positive third lens with a convex surface, and a biconvex fourth lens, where specific conditional expressions for focal lengths and curvature radii are satisfied to optimize lens configuration, allowing for a compact design with reduced back focus and improved aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a conventional eight-lens-group wide-angle lens is used, then the viewing angle is wide, but the lens size becomes large
Solution Approach 1:
The lens system is divided into only four lens groups instead of eight, with each lens having a specific function (first lens for divergence, second lens for additional divergence, third lens for convergence, fourth lens for final focusing). This segmentation achieves wide-angle capability with minimal lens elements, reducing overall lens size while maintaining viewing angle
Solution Approach 2:
The patent applies specific conditional expressions for focal lengths and curvature radii (e.g., -0.5 < f1/fa < -0.2, -2.0 < (r3+r4)/(r3-r4) < -0.5) to optimize the optical parameters of each lens. These parameter constraints enable the system to achieve wide viewing angle with compact dimensions by precisely controlling the optical power distribution across the four lens groups
2Area of stationary object
If the lens size is reduced, then the back focus becomes short, but a long back focus is required for digital input devices
Solution Approach 1:
Instead of placing the aperture stop at the traditional position, the patent positions it between the third and fourth lens groups. This inverted positioning, combined with the specific arrangement of positive and negative lens groups, creates a telecentric optical system that achieves long back focus while maintaining compact lens size
Solution Approach 2:
The conditional expression -0.5 < f1/fa < -0.2 for the first lens focal length and the curvature radius relationship -2.0 < (r3+r4)/(r3-r4) < -0.5 are optimized to control the optical path length and back focus distance, enabling long back focus in a compact configuration
3Area of moving object
If a fisheye-type lens configuration is used to achieve wide angle, then the viewing angle is wide, but image distortion becomes large
Solution Approach 1:
Each lens group has a specific local function: the first two negative lens groups handle light divergence for wide angle, the third positive lens group begins convergence, and the fourth biconvex lens group completes focusing. This localized functional distribution corrects distortion while maintaining wide viewing angle, unlike uniform fisheye configurations
Solution Approach 2:
The patent applies conditional expressions controlling the focal length ratios and curvature radius relationships to optimize the optical parameters, achieving distortion correction with wide viewing angle by precisely tuning the optical power distribution across the four lens groups
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
This configuration enables a wide-angle lens system with high optical performance, achieving a wide viewing angle, small size, and minimal image distortion while effectively correcting aberrations and maintaining a long back focus, thereby enhancing image resolution and reducing distortion across the entire image formation range.
Implementation Method 1
The first lens is a negative lens having a meniscus shape with a convex surface directed to the object side
Implementation Method 2
The second lens is a negative lens
Implementation Method 3
The third lens is a positive lens having a convex surface directed to the object side
Implementation Method 4
The fourth lens is a biconvex lens
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An imaging lens includes, in order from an object side, a first lens G1, a second lens G2, a third lens G3, an aperture stop St and a fourth lens G4. The first lens is a negative lens having a meniscus shape with a convex surface directed to the object side. The second lens is a negative lens. The third lens is a positive lens having a convex surface directed to the object side. The fourth lens is a biconvex lens. The following conditional expression is satisfied: 1.5<f4/fa<2.7 where fa denotes a focal length of the whole lens system, and f4 denotes a focal length of the fourth lens.