Iris recognizing preprocessing method based on grey level information

A technology of iris recognition and grayscale information, which is applied in the field of image processing and can solve problems such as low stability, interference from eyelash occlusion, and poor versatility of iris image quality evaluation methods.

Inactive Publication Date: 2008-06-18
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AI-Extracted Technical Summary

Problems solved by technology

[0010] The above-mentioned iris image preprocessing algorithms all have problems to a certain extent. The positioning algorithm takes a lot of ti...
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The invention provides a pretreatment method of iris images based on gray information. A rough circle center (xo, yo) of a pupil is located through binary, mathematical morphology, gray projection and other operations, the point, which has a gray value larger than T and the shortest distance to the (xo, yo), is searched at a plurality of lines close to the (xo, yo) from the center to the two sides as a pupil boundary point; the accurate circle center and the radius of the pupil can be located through curve fitting; the gray level first difference of the lines where the searched pixel points lie is calculated and the point with the largest value of the sum of the level first difference is searched in the range of places where iris external boundary point possibly appears and taken as the iris external boundary point; the accurate circle center and radius of the iris external boundary is obtained after curve fitting. The quality of iris image is judged through calculating point sharpness and number of effective pixel points according to the normalized image. The pretreatment method of iris images of the invention not only can decrease the time needed by repeated iteration during location, but also can judge the quality of iris image accurately and quickly according to the extracted iris image.

Application Domain

Character and pattern recognition

Technology Topic

Computer visionGray level +8


  • Iris recognizing preprocessing method based on grey level information
  • Iris recognizing preprocessing method based on grey level information
  • Iris recognizing preprocessing method based on grey level information


  • Experimental program(1)

Example Embodiment

[0067] Using the method of the present invention, firstly use C language and assembly language to write the iris preprocessing program; then use CMOS or CCD camera to automatically capture the original image of the iris; then input the captured original image of the iris as source data to the DSP embedded system Processed in the iris preprocessing program; after iris positioning and image quality evaluation, the qualified iris image is positioned and then outputs a normalized iris image containing rich texture information. Using 2400 captured gray-scale iris images with different lighting conditions and different shooting postures as source data, the positioning accuracy rate is 97.5%, and it only takes 100ms to locate an image.
[0068] In summary, the method of the present invention makes full use of the gray information of the iris image, combined with the circle fitting method, so as to quickly and accurately locate the iris area from the provided iris original image and make an accurate quality assessment.


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