Micro Lens Aspherical Fourth Element Aberration Control
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Solution Overview
Problem
Conventional portable camera lenses are bulky, heavy, and costly due to the need for multiple spherical lenses to compensate for spherical image aberration, which increases the weight and cost while compromising image quality.
Innovation Solution
A micro lens design comprising a stop, a biconvex first lens, a biconcave second lens, a positive third lens with an aspherical surface, and a negative fourth lens with decreasing refractive power from center to periphery, all made of plastic with refractive indexes less than 1.6, optimized to satisfy focal length ratios and reduce total length, tolerance sensitivity, and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple spherical lenses are used to compensate for spherical image aberration, then image quality is improved, but total length, weight, and cost increase
Solution Approach 1:
The patent employs aspherical surfaces on the third and fourth lenses to correct spherical image aberration. The aspherical surfaces have curvature that varies from the optical axis to the periphery, allowing a single lens element to compensate for aberrations that traditionally required multiple spherical lenses. This reduces the total number of lens elements and overall system length while maintaining high image quality.
2Manufacturing precision
If glass lenses are used, then light-transmission coefficient and image quality improve, but weight and cost increase
Solution Approach 1:
The patent specifies that all four lenses are made of plastic material with refractive indexes less than 1.6 at d-lines. This parameter change from glass to plastic materials significantly reduces the weight of the lens assembly while maintaining adequate optical performance through careful design of the aspherical surfaces and lens configurations.
3Length of stationary object
If a single aspherical lens is used to compensate for spherical image aberration, then size and weight are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent divides the optical system into four distinct lens elements with specific functions: the first two lenses provide basic focusing power, while the third and fourth lenses with aspherical surfaces specifically address aberration correction. This segmentation allows the complex aspherical manufacturing requirements to be concentrated on only two lenses rather than all four, simplifying the overall manufacturing process compared to making all lenses aspherical.
4Ease of manufacture
If the fourth lens has uniform refractive power, then manufacturing is simpler, but resolution of imaged surfaces decreases
Solution Approach 1:
The fourth lens is designed with non-uniform refractive power distribution, where the negative refractive power gradually decreases from the center to the periphery. This local variation in optical properties allows the lens to compensate for field curvature and improve the resolution of imaged surfaces across the entire field of view, not just at the center. The periphery of the fourth lens has positive refractive power to specifically address off-axis image quality.
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 micro lens achieves a compact, low-cost, high-resolution design with reduced weight and sensitivity, providing a large viewing angle and numerical aperture while maintaining high image quality.
Implementation Method 1
a first lens having a positive refractive power
Implementation Method 2
a second lens having a negative refractive power
Implementation Method 3
a third lens having a positive refractive power, and the third and fourth lenses respectively comprise at least one aspherical surface
Implementation Method 4
a fourth lens having a negative refractive power, and the negative refractive power gradually decreases from the center to the periphery of the fourth lens
Data Source
AI summary
A micro lens, from an object side to an image side, sequentially includes a stop, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a fourth lens having a negative refractive power. The third and fourth lenses respectively comprise at least one aspherical surface. The negative refractive power gradually decreases from the center to the periphery of the fourth lens, and the refractive power of the periphery of the fourth lens is turned to positive. The relationship of the first lens and the focal length of the micro lens of the micro lens and the relationship of the third lens and the first lens satisfy the desired requirements, thus, to reduce the total length of the micro lens, tolerance sensitivity and cost.