Contactless Hand Imaging via Dual-Wavelength Scheimpflug Optics
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Solution Overview
Problem
Existing devices for optical imaging of hand features, such as finger scanners, often require contact and are limited by the need for precise alignment and depth of field management, especially when using multiple wavelengths for enhanced imaging.
Innovation Solution
A contactless device employing a dual-wavelength illumination system and camera configuration with overlapping depth of field regions, utilizing a Scheimpflug layout to capture high-quality, three-dimensional images of hand features without the need for physical contact, allowing for improved image contrast and object definition across different wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If contactless optical imaging is used, then user experience and hygiene are improved, but alignment precision and depth of field management become more difficult
Solution Approach 1:
The patent introduces a Scheimpflug layout where the image plane is tilted relative to the object plane, creating a three-dimensional mapping relationship. This dimensional transformation allows the depth of field to be extended along the optical axis while maintaining focus across the tilted measurement plane, thereby achieving both contactless operation and precise alignment.
Solution Approach 2:
The patent employs multiple wavelengths of light (e.g., 532nm green and 635nm red) with different depth of field characteristics. By changing the wavelength parameter, the system can optimize the depth of field for different imaging requirements, allowing contactless imaging while maintaining measurement precision through wavelength-specific focus adjustment.
2Measurement precision
If multiple wavelengths are used for enhanced imaging, then image quality and contrast are improved, but device complexity and depth of field management worsen
Solution Approach 1:
The patent combines multiple wavelength sources (532nm and 635nm lasers) into a single illumination system that projects both wavelengths simultaneously onto the measurement plane. The camera sensor captures both wavelengths through a single optical path with a tilted image plane, merging the complexity of multi-wavelength management into a unified Scheimpflug imaging system that simplifies control while maintaining enhanced image quality.
3Length of stationary object
If a tilted image plane (Scheimpflug layout) is used, then depth of field is extended and contactless imaging is enabled, but optical system complexity increases
Solution Approach 1:
The Scheimpflug layout tilts the image plane relative to the object plane, creating a geometric relationship where the intersection line of these planes lies in the object plane. This dimensional reconfiguration extends the depth of field along the optical axis without requiring additional optical elements, achieving extended focus range while maintaining relatively simple optical system architecture.
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
Enables cost-effective, high-resolution, contactless optical imaging of hand features, specifically fingerprints, by ensuring that the depth of field for both wavelengths overlaps, enhancing image quality and eliminating the need for a contact window, thus improving the imaging process and user experience.
Implementation Method 1
an illumination arrangement for illuminating a measuring site with light of substantially a first wavelength and with light of at least substantially a second wavelength
Implementation Method 2
a camera comprising a detector and objective configured for imaging the measuring site on the detector
Implementation Method 3
Within the measuring site a region of depth of field of the objective with respect to the first wavelength overlaps with a region of depth of field of the objective with respect to the second wavelength
Data Source
AI summary
The present disclosure relates to a device for contactless optical imaging of features of a hand, wherein the device comprises an illumination arrangement for illuminating a measuring site with light of substantially a first wavelength and with light of at least substantially a second wavelength. The device further comprising a camera comprising a detector and objective configured for imaging the measuring site on the detector. Within the measuring site a region of depth of field of the objective with respect to the first wavelength overlaps with a region of depth of field of the objective with respect to the second wavelength.