Near-Infrared Fingerprint Imaging for Ridge-Valley Contrast
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Solution Overview
Problem
Fingerprint images captured by existing devices often have low quality due to variations in capturing conditions, leading to insufficient contrast between ridge and valley line parts, uneven brightness, or partial deletion of fingerprints due to misalignment with the image sensor.
Innovation Solution
A fingerprint capture system using a near-infrared light source and a CMOS image sensor to capture fingerprints, where near-infrared light is emitted onto the finger, scattered, and received by the sensor to differentiate ridge and valley line parts based on intensity, resulting in a clear contrast in the captured image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a transmission type fingerprint input device is used to capture fingerprints, then the fingerprint image can be obtained through light scattering in the finger, but the quality of the captured fingerprint image may vary due to capturing conditions, resulting in insufficient contrast between ridge and valley line parts
Solution Approach 1:
The patent changes the wavelength parameter of light from visible light to near-infrared light (700nm to 2500nm). This parameter change allows light to penetrate deeper into the finger and scatter differently, providing better contrast between ridge and valley line parts while maintaining reliable fingerprint image quality under various capturing conditions
Solution Approach 2:
The patent introduces a display unit that displays captured fingerprint images in real-time, allowing the capturing conditions to be dynamically adjusted based on the displayed image quality. This dynamic feedback mechanism ensures optimal contrast and image quality by enabling operators to re-capture images when conditions are not ideal
2Device complexity
If the fingerprint capturing region is fixed on the image sensor, then the device structure is simplified, but misalignment of the finger with the capturing region may cause partial deletion of the fingerprint
Solution Approach 1:
The patent adds a display dimension by showing the captured fingerprint image on a display unit. This allows operators to verify complete fingerprint capture in real-time and re-position the finger if partial deletion occurs, maintaining complete fingerprint acquisition without complicating the sensor structure
Solution Approach 2:
The patent implements a feedback mechanism where the captured fingerprint image is displayed back to the operator, who can then determine whether the fingerprint is completely captured. If partial deletion is detected, the operator can re-capture the image by re-positioning the finger, ensuring complete fingerprint data acquisition
3Measurement precision
If multiple fingerprint images are captured to ensure quality, then the identification accuracy is improved, but the time required for fingerprint acquisition increases
Solution Approach 1:
The patent performs preliminary display of captured fingerprint images before final identification processing. This allows operators to quickly verify image quality and determine whether re-capture is needed, reducing unnecessary repeated captures and minimizing acquisition time while maintaining identification accuracy
Solution Approach 2:
The system enables operators to self-evaluate fingerprint image quality through the display unit and make real-time decisions about whether additional captures are needed. This self-service approach reduces reliance on automated multiple captures, speeding up the acquisition process while ensuring sufficient identification accuracy
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 system achieves high-quality fingerprint images by effectively distinguishing ridge and valley line parts, enhancing identification accuracy.
Implementation Method 1
a near-infrared light source (700 nm to 2500 nm) that emits near-infrared light
Implementation Method 2
a light from a light source is caused to enter a finger and is scattered therein
Data Source
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AI summary
A fingerprint capture system, a fingerprint capture device, an image processing apparatus, a fingerprint capture method, and a storage medium that can acquire a high quality fingerprint image are provided. A disclosed example includes: a capture unit that captures a fingerprint; an image processing unit that processes a transferred fingerprint image captured by the capture unit; a display unit on which the fingerprint image transferred to the image processing unit is displayed; a recording unit where the fingerprint image transferred to the image processing unit is recorded by the image processing unit; and an instruction unit that inputs, in the image processing unit, a record instruction that instructs the image processing unit to record the fingerprint image in the recording unit. The image processing unit records, in the recording unit, the fingerprint image displayed on the display unit at the time the record instruction is input by the instruction unit.