Overview of Fingerprint Identification Technology in Fingerprint Scanners

The texture direction calculation method globally estimates the direction of each part of the fingerprint image based on the direction field model. The proposed method generates the direction field of the fingerprint image according to the position of the midpoint and triangle point of the fingerprint image, but the core point and triangle point Two fingerprint images with the same relative position of points may have different fingerprint orientation fields, but the gbdtok method cannot distinguish such changes.

An effective use of the direction field model is to generate fingerprint images, such as the texture direction of the fingerprint image based on the direction field model proposed by CapPen2t1", especially when the image does not contain core points and triangle points or cannot detect their positions correctly, In this regard, ht" and 9mN combined with the gradient method to establish a direction field model, which is used to globally calculate and correct the direction of the texture. Wildy's Fingerprint Scanner also uses this principle.
The correct calculation of the texture orientation of low-quality fingerprint images is still a challenge. Algorithms for estimating texture orientations as accurately as possible and effective post-processing algorithms need to be proposed and improved. The calculation of texture frequency refers to the calculation of texture spacing. Many algorithms, such as segmentation algorithms , enhancement algorithm, texture extraction algorithm, etc., often use frequency features, a method to calculate the texture frequency is Fourier analysis method, the original image area (a) through.
The spectrum image (b) is obtained after Fourier transform, and there are two peaks in the spectrum image. The direction of connecting the peaks is the vertical direction of the lines, and the length of the lines is related to the average spacing of the lines in the image area (a). The length can calculate the texture rate, but the low-quality image area will not have obvious peaks after the Qiao Liye transformation. Another method to calculate the frequency is the projection method 'aM'J, first place the image area on the texture. Project in the vertical direction, and then calculate the frequency of the projected signal.