Aspherical Lens Unit for Iris Authentication Aberration Correction
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Solution Overview
Problem
Existing imaging optical systems for iris authentication suffer from insufficient aberration correction and are not suitable for high-performance imaging due to large negative power of the second lens and narrow interval between lenses, leading to unsatisfactory spherical aberration and field curvature correction.
Innovation Solution
A lens unit with a telephoto configuration, including a positive first lens, an aspherical second lens, and a negative third lens with an aspherical surface having an inflection point other than the optical axis, satisfying specific conditional expressions to achieve reduced aberration and a compact size suitable for mobile devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional imaging optical system with spherical lenses is used, then the structure is simple, but aberration correction is insufficient
Solution Approach 1:
The patent applies aspherical surfaces to the second and third lenses to correct aberrations. The aspherical shape allows for better control of light rays across the entire lens aperture, improving spherical aberration and field curvature correction compared to conventional spherical lenses, while maintaining a compact three-lens configuration.
2Length of moving object
If the interval between the first lens and the second lens is narrowed to reduce size, then the device becomes more compact, but aberration correction becomes insufficient
Solution Approach 1:
The aspherical surfaces on the second and third lenses enable effective aberration correction even with a compact lens spacing. The aspherical geometry compensates for the reduced distance by providing enhanced control over ray paths, allowing the system to maintain short length while achieving satisfactory aberration correction.
3Length of moving object
If the negative power of the second lens is increased to achieve telephoto configuration, then the system length is reduced, but aberration correction becomes insufficient
Solution Approach 1:
The patent uses aspherical surfaces on both the second and third lenses to correct the aberrations introduced by the high negative power of the second lens. This combination of strong negative power for telephoto effect and aspherical correction surfaces achieves both compact size and satisfactory aberration correction.
Solution Approach 2:
The aspherical surfaces provide localized correction zones that address specific aberration problems created by the strong negative power lens. The varying curvature across the aspherical surface allows different regions to correct different types of aberrations, enabling the system to tolerate higher negative power while maintaining 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 solution enables highly accurate small-angle imaging with improved aberration correction, allowing for enhanced security and reliability in iris authentication while being compact enough for integration into mobile devices.
Implementation Method 1
the imaging optical system includes, in order from an object side, a first lens L1 having positive refractive power, a second lens L2 including at least one surface having an aspherical shape, and a third lens L3 having negative refractive power, the third lens including at least one surface having an aspherical shape
Data Source
AI summary
A lens unit includes: an imaging optical system; and a lens barrel holding the imaging optical system. The imaging optical system includes, in order from an object side: a first lens having a positive refractive power; a second lens including at least one surface having an aspherical shape; and a third lens having a negative refractive power, at least one surface having an aspherical shape, and an inflection point other than an intersection with an optical axis.