Method for segmenting fingers

1. A method for segmenting fingers, said segmentation method being implemented by a segmentation device comprising a processing unit, an acquisition device intended to capture an image of said fingers when they pass in front of said acquisition device in a direction of advancement and a projection device intended to project a sight having an isointensity axis on said fingers, said segmentation method comprising:

a capture step during which the acquisition device captures an image of the fingers and of the sight,

a computing step during which the processing unit computes the unrolled phase image from the image of the sight thus captured,

a derivation step during which, for each pixel of the phase image thus computed, the processing unit computes the derivative of the phase along the isointensity axis of the sight, and

a regionalisation step during which the processing unit associates each pixel where the derivative of the phase has been computed with a region grouping all the adjoining pixels step by step where the derivative of the phase has the same polarity, and

a recognition step during which the location of each finger is recognised from the analysis of the regions thus determined.

2. The segmentation method according to claim 1 , wherein the regionalisation step consists of:

an initialisation step during which a first pixel where the derivative of the phase has been computed is chosen,

a creation step during which a region having the polarity of the derivative of said first pixel is created,

for each pixel related to said first pixel,

a step of comparing the polarity of the derivative of the phase of said related pixel with respect to the polarity of the derivative of the phase of said first pixel,

a positive-grouping step during which said related pixel is grouped in the region including said first pixel when the result of the comparison step is positive,

when each pixel related to said first pixel has thus been processed,

a designation step during which one of said related pixels is designated as the first pixel,

a first looping step during which the process is looped onto the comparison step so as thus step by step to progress and cover the whole of the image, and

when all the pixels adjacent step by step and having a derivative of the phase with the same polarity as the derivative of the phase of said first pixels have been processed,

a choosing step during which a pixel not yet processed is chosen as the first pixel, and

a second looping step during which the process loops onto the creation step.

3. A device for segmenting fingers, comprising:

a projection device intended to project a sight having an isointensity axis on said fingers,

an acquisition device intended to capture an image of said fingers and of the sight thus projected when the fingers pass in front of said acquisition device in an advancement direction, and

a processing unit comprising:

computing means intended to compute the unrolled phase image from the image of the sight captured,

derivation means intended to compute, for each pixel of the phase image, the derivative of the phase along the isointensity axis,

regionalisation means intended to associate each pixel with a region grouping together all the adjacent pixels step by step where the derivative of the phase has the same polarity, and

recognition means intended to locate each finger by analysing the regions.