Four-Element Image Pickup Lens Design for Mobile Terminals
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Solution Overview
Problem
Conventional image pickup lenses with four elements face challenges in downsizing while maintaining optical performance, particularly in correcting aberrations and accommodating higher-pixel image pickup elements, due to issues with refractive power distribution and focal length.
Innovation Solution
An image pickup lens design comprising an aperture stop, a positive first lens, a negative second lens, a positive meniscus third lens, and a negative meniscus fourth lens, with specific optical parameters such as composite focal lengths, air space lengths, and curvature radii to correct various aberrations and reduce the total lens length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the image pickup lens uses an inverted Ernostar type design with a positive fourth lens, then the back focal length is longer, but the total lens length becomes excessive and downsizing is difficult
Solution Approach 1:
The patent changes the refractive power distribution and curvature radii parameters of the lens elements. Specifically, it uses a negative fourth lens instead of a positive one, and optimizes the curvature radius of the second lens surface to achieve both adequate back focal length and reduced total lens length.
2Device complexity
If the image pickup lens uses an inverted Ernostar type with one negative lens, then the structure is simplified, but Petzval's sum correction becomes difficult and peripheral image performance deteriorates
Solution Approach 1:
The patent applies different refractive powers and curvature radii to different lens elements to address local optical quality requirements. The second lens has a specifically optimized negative curvature radius on its image-side surface, while the fourth lens has a positive curvature radius, creating local variations in optical properties that correct Petzval's sum and improve peripheral image quality.
3Length of moving object
If the image pickup lens is designed for shorter total length, then downsizing is achieved, but the angle of view becomes narrow and aberration correction becomes insufficient
Solution Approach 1:
The patent performs preliminary optimization of the curvature radius of the second lens surface and the refractive power distribution before final lens assembly. By pre-calculating and setting the negative curvature radius of the second lens image-side surface within a specific range, the design achieves adequate aberration correction and angle of view even with reduced total lens length.
4Ease of manufacture
If the image pickup lens uses conventional four-element design, then the basic optical function is achieved, but it cannot properly correct various aberrations for high-pixel image pickup elements
Solution Approach 1:
The patent optimizes specific parameters including the negative curvature radius of the second lens image-side surface and the positive curvature radius of the fourth lens object-side surface. These parameter changes enable the conventional four-element structure to achieve superior aberration correction suitable for high-pixel solid-state image pickup elements.
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 design achieves proper aberration correction and downsizing, enabling high-performance image pickup with improved telecentricity and reduced length, suitable for mobile terminals with solid-state image sensors.
Implementation Method 1
a first lens having a positive power and comprising a convex surface facing the object side
Implementation Method 2
a second lens having a negative power and comprising a concave surface facing an image side of the image pickup lens
Implementation Method 3
a third lens in a meniscus shape having a positive power and comprising a convex surface facing the image side
Implementation Method 4
a fourth lens in a meniscus shape having a negative power and comprising a convex surface facing the object side
Data Source
AI summary
An image pickup lens includes: an aperture stop; a first lens having a positive power and including a convex surface facing an object side; a second lens having a negative power and including a concave surface facing an image side; a third lens in a meniscus shape having a positive power and including a convex surface facing the image side; and a fourth lens in a meniscus shape having a negative power and including a convex surface facing the object side. The image pickup lens satisfies predetermined conditions relating to a composite focal length of the first through third lenses, a length of an air space between the third lens and the fourth lens along the optical axis, and a curvature radius of a surface of the second lens facing the image side.