Optical Fingerprint Acquisition with Distortion Correction Lenses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical fingerprint acquisition processes using light refractors like prisms often result in rectangular and trapezoidal distortions of fingerprint images, which affect the accuracy and reliability of fingerprint authentication.
Innovation Solution
An optical fingerprint acquisition apparatus is designed with a combination of plano-cylindrical lenses and an aperture stop to correct distortions, where the first lens provides positive magnification and the second lens provides demagnification, ensuring that the emission angles from both the Y-section and X-section optical systems are nearly equal, and the image sensor is tilted to align with the optical axis of the light emitted from the second lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a light refractor (prism) is used to acquire fingerprint images, then the acquisition process is simple and widely applicable, but rectangular and trapezoidal distortions occur in the fingerprint images
Solution Approach 1:
A distortion correction lens is introduced as an intermediary component between the light refractor and image sensor. This lens specifically counteracts the rectangular and trapezoidal distortions caused by the prism, allowing the system to maintain both simplicity and image accuracy simultaneously
2Productivity
If multiple fingerprints are acquired simultaneously by increasing prism size, then productivity increases, but image distortion becomes more severe
Solution Approach 1:
The distortion correction lens serves as a mediator that enables multiple fingerprints to be captured simultaneously without proportionally increasing distortion. The lens compensates for the increased optical path variations that occur with larger prism dimensions, maintaining image quality across multiple fingerprint acquisition zones
3Device complexity
If the optical system is simplified using a single prism, then device complexity is reduced, but measurement precision of fingerprint details deteriorates due to distortion
Solution Approach 1:
The distortion correction lens is positioned within the optical system to act as a precision-correcting intermediary. It specifically addresses geometric distortions while preserving the simplicity of the single-prism design, enabling accurate measurement of fingerprint minutiae without requiring complex multi-element optical systems
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 effectively corrects distortions, ensuring that the acquired fingerprint images are undistorted and accurately represent the original shape, improving the reliability of fingerprint authentication, especially when acquiring multiple fingerprints simultaneously.
Implementation Method 1
an optical fingerprint acquisition apparatus capable of acquiring a fingerprint image without distortion by correcting rectangular deformation and trapezoidal distortion that may occur in an optical fingerprint acquisition process using a light refractor such as a prism
Implementation Method 2
light emitted from the light source 11 is incident on the fingerprint contact surface 10a through the prism 10. The light reflected, scattered or refracted according to the shape of a fingerprint in contact with the fingerprint contact surface 10a is emitted to the lens 15 to create an image
Implementation Method 3
an aperture stop provided between the first lens and the second lens or behind the second lens
Data Source
AI summary
Provided is an optical fingerprint acquisition apparatus. The fingerprint acquisition apparatus has an improved optical lens unit and can correct distortion of an image caused by a light refractor. The optical lens unit includes two cylindrical lenses disposed so that an optical axis of incident light does not coincide with a central axis of the lenses. The optical lens unit corrects an image that is distorted into a rectangle by a light refractor, thereby restoring a square shape. In particular, the fingerprint acquisition apparatus is useful in the simultaneous acquisition of multiple fingerprints as well as the acquisition of a single fingerprint.