Contactless Biometric Optics Layout for Distortion-Free Finger Imaging
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Solution Overview
Problem
Existing contactless biometric data acquisition devices face challenges in achieving high-quality fingerprint acquisition while maintaining a compact structure, often resulting in image distortion due to the overlap of camera and projector depth of fields.
Innovation Solution
The device employs an offset arrangement of sensor and emitter optics relative to their respective optical sensors and light emitters, allowing for a significant overlap of focal planes without distortion, using reflective optics to fold the beam paths and maintain a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the camera and projector are positioned close to each other to make the device compact, then the device size is reduced, but image distortion occurs due to overlap of depth of field
Solution Approach 1:
The patent introduces a third dimension by offsetting the sensor optics arrangement laterally from the optical sensor along the optical main plane. This lateral displacement allows the focal plane section of the image acquisition unit to overlap with the focal plane section of the illumination unit without causing image distortion, thereby resolving the contradiction between compact device size and image quality
Solution Approach 2:
The patent employs asymmetric arrangement where the sensor optics arrangement is offset relative to the optical sensor, creating an asymmetric optical path. This asymmetric configuration enables the focal planes to align properly while maintaining compact dimensions, avoiding the symmetric Scheimpflug arrangement that causes distortion
2Device complexity
If a Scheimpflug arrangement is used to resolve depth of field overlap, then the device can be compact, but image distortion occurs
Solution Approach 1:
Instead of tilting the optics arrangements as in the conventional Scheimpflug arrangement, the patent inverts the approach by laterally offsetting the sensor optics arrangement from the optical sensor along the optical main plane. This inverted configuration achieves focal plane alignment without the distortion-causing tilt, maintaining structural compactness while preserving 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
This configuration enhances the quality and quantity of acquired biometric data, enabling efficient 3D data generation with reduced device size and improved user comfort, while avoiding geometric distortions and shadowing effects.
Implementation Method 1
at least one image acquisition unit, which comprises an optical sensor and is configured for contactless acquisition of image data from illuminated skin areas
Implementation Method 2
at least one illumination unit, which comprises a light emitter and is configured to illuminate the skin areas to be acquired
Implementation Method 3
the sensor optics arrangement is arranged offset relative to the optical sensor along the optical main planes of the sensor optics arrangement or the emitter optics arrangement is arranged offset relative to the light emitter along the optical main planes of the emitter optics arrangement, so that the focal plane section of the image acquisition unit and the focal plane section of the illumination unit have the greatest possible overlap with one another
Data Source
AI summary
The present disclosure relates to a device 1000 for contactless acquisition of biometric data from skin areas. For example, a sensor optics arrangement 120 of the image acquisition unit 100 or an emitter optics arrangement 220 of the illumination unit 200 is offset such that the focal planes 135, 235 of the image acquisition unit 100 and the illumination unit 200 essentially completely overlap. As a result, for example, the area of the optical sensor 115 of the image acquisition unit 100 or the area of the light emitter 215 of the illumination unit 200 can be used to the maximum, thereby resulting in a significantly improved quality of the acquisition of the biometric features of a hand, in particular the fingers. In addition, the compactness of the device 1000 can be further increased, for example by beam folding using reflective optical elements 700.