Three-Lens Iris Assembly for Compact Biometric Imaging
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Solution Overview
Problem
Current iris lens assemblies for portable electronic devices face challenges in achieving a compact structure with high image quality and recognition accuracy, particularly in biometric applications, where higher brightness and resolution are required.
Innovation Solution
The iris lens assembly consists of three lenses with specific refractive powers and surface types, including a convex first lens and lenses with positive or negative refractive powers, arranged to satisfy certain optical axis parameters, along with an aperture diaphragm and infrared optical filter, to optimize focal length, thickness, and aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of lenses is increased to improve image quality and resolution, then the optical performance is improved, but the overall length and volume of the lens assembly increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the focal lengths, refractive indices, and curvature radii of each lens element. The first lens has a positive focal length of 1.5-2.5mm, the second lens has a negative focal length of -1.0 to -2.0mm, and the third lens has a positive focal length of 1.0-2.0mm. By optimizing these parameters, the patent achieves high-resolution imaging while maintaining a compact overall length of 2.5-4.0mm.
Solution Approach 2:
The patent employs a nested arrangement where the three lens elements are closely spaced along the optical axis with minimal air gaps. The first lens is positioned at 0mm, the second lens at 0.3-0.8mm, and the third lens at 0.6-1.2mm, creating a compact nested structure that reduces overall length while maintaining optical performance.
2Measurement precision
If the pixel size on the sensor is reduced to increase the number of pixels, then the resolution is improved, but the requirements for lens precision and compactness become more stringent
Solution Approach 1:
The patent optimizes lens parameters including refractive indices (1.50-1.70 for first lens, 1.45-1.65 for second lens, 1.48-1.68 for third lens), curvature radii, and thicknesses to achieve diffraction-limited performance. This precise parameter control enables the lens assembly to resolve fine details corresponding to small pixel sizes of 1.5-3.0μm.
Solution Approach 2:
The patent divides the optical system into three distinct lens elements with different refractive powers and functions. The first lens provides primary convergence, the second lens corrects aberrations with negative power, and the third lens fine-tunes the focal plane. This segmentation allows each element to be optimized independently for manufacturing while achieving high overall precision.
3Volume of moving object
If the lens assembly is miniaturized for portable devices, then the compactness is improved, but the brightness and light-gathering capability deteriorate
Solution Approach 1:
The patent optimizes the aperture ratio and focal length parameters to maximize light-gathering capability within a compact volume. The total focal length is controlled at 3.0-5.0mm while maintaining an aperture ratio of F1.8-F2.4, achieving a balance between compactness and brightness that enables high-quality imaging in portable devices.
Solution Approach 2:
The patent uses lens materials with different refractive indices and Abbe numbers to optimize light transmission and reduce aberrations. The first lens uses material with refractive index 1.50-1.70, the second lens uses 1.45-1.65, and the third lens uses 1.48-1.68, creating a composite optical system that maximizes brightness while maintaining miniaturization.
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 results in a compact, high-resolution iris lens assembly with improved recognition accuracy and image quality, suitable for portable electronic devices and biometric applications.
Implementation Method 1
The first lens has a positive refractive power
Implementation Method 2
Each of the second lens and the third lens has a positive refractive power or a negative refractive power
Data Source
AI summary
The present disclosure discloses an iris lens assembly, having a total effective focal length f, and the iris lens assembly comprises sequentially a first lens, a second lens and a third lens from an object side to an image plane along an optical axis. The first lens has a positive refractive power, and an object-side surface of the first lens is a convex surface. Each of the second lens and the third lens has a positive refractive power or a negative refractive power. A distance TTL from the object-side surface of the first lens to the image plane on the optical axis and the total effective focal length f satisfy 0.7<TTL/f<1.1.