Compact Image Pickup Lens with Negative Fourth Element
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Solution Overview
Problem
Existing image pickup lenses for mobile terminals face challenges in achieving a wide field angle, correcting various aberrations, and accommodating image pickup elements with a large number of pixels, particularly due to limitations in downsizing and aberration correction.
Innovation Solution
An image pickup lens configuration comprising an aperture stop, a first positive refractive lens, a second negative refractive lens with a concave surface, a third positive refractive lens, and a fourth negative refractive lens with a concave surface, where specific curvature radius and focal length relationships are maintained to ensure proper aberration correction and telecentricity, along with aspherical surfaces to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inverted Ernostar type image pickup lens with a positive fourth lens is used, then the principal point position is closer to the image side and the back focus is longer, but the total length of the lens cannot be shortened for downsizing
Solution Approach 1:
The patent changes the refractive power parameter of the fourth lens from positive (inverted Ernostar type) to negative (telephoto type), which fundamentally alters the optical path and allows the principal point to move closer to the object side, thereby shortening the total lens length while maintaining adequate back focus
Solution Approach 2:
The patent inverts the conventional inverted Ernostar configuration by making the fourth lens negative instead of positive, effectively reversing the traditional approach to achieve both wide angle and compact size
2Device complexity
If only one lens with negative refractive power is used among four lenses, then the structure is simpler, but it becomes difficult to correct Petzval sum and secure excellent performance on the periphery portion of the image area
Solution Approach 1:
The patent changes the refractive power parameter of the fourth lens from positive to negative, increasing the number of negative lenses from one to two. This parameter change enables better correction of Petzval sum and peripheral aberrations while maintaining a relatively simple four-lens structure
Solution Approach 2:
The patent creates a composite optical system with two positive lenses and two negative lenses, where the combination of different refractive power lenses works synergistically to correct various aberrations including Petzval sum and peripheral distortion
3Length of moving object
If the total length of the image pickup lens is further shortened, then downsizing is achieved, but it becomes difficult to be used with an image pickup element with a large number of pixels due to deterioration of performance
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: the curvature radii of the second and fourth lenses are specifically designed to satisfy certain relationships, the refractive powers are balanced between positive and negative lenses, and the spacing between lenses is optimized to maintain image quality while achieving compact size
Solution Approach 2:
The patent employs aspherical surfaces on the second and fourth lenses, which allows for better control of light rays across the entire field of view. The aspherical shapes enable more precise aberration correction in a compact configuration, maintaining high image quality for multi-pixel sensors
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 a compact image pickup lens that secures excellent aberration correction and a wide field angle, suitable for image pickup elements with a large number of pixels, while maintaining a short total length and reducing weight, thus enhancing the performance and size efficiency of mobile terminals.
Implementation Method 1
an image pickup lens for forming a light flux from a subject into an image on an image pickup element
Data Source
AI summary
The present invention provides an image pickup lens for forming a light flux from a subject into an image on an image pickup element, and the image pickup lens includes, in order from an object side thereof: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power and comprising a concave surface facing an image side of the image pickup lens; a third lens having a positive refractive power; and a fourth lens having a negative refractive power and comprising a concave surface facing the image side. The image pickup lens satisfies the predetermined condition according to a curvature radius of the surface facing the image side on the second lens, and a focal length of the image pickup lens.