A method and device for determining the number of partial palm prints to be acquired in order to reconstruct an entire palm print, and a corresponding acquisition method and system.

Abstract

The present invention provides a method and device for determining the number of partial palm prints to be acquired in order to reconstruct an entire palm print, as well as a corresponding acquisition method and system. [Solution] The present invention relates to a method for determining the number of palm print partial images acquired using a nipple print acquisition device, wherein the nipple print acquisition device comprises an acquisition area smaller in size than the area of ​​the palm representing a group of individuals.

Description

[Technical Field]

[0001] This invention relates to the field of biometric imaging, and more particularly to palm print imaging. [Background technology]

[0002] It is common practice to obtain fingerprints, which are more commonly known by the general term "papillary prints," encompassing both "fingerprints" and "palm prints." Fingerprints are patterns formed by the dermal ridges of the fingers, and palm prints are patterns formed by the dermal ridges of the palms. Dermal ridges are superficial grooves formed by skin ridges on the palms, soles of the feet, and fingertips, arranged in lines or spirals. They are unique to each individual. The patterns they form constitute a biometric "identification card," thereby allowing for the identification of an individual. Taking fingerprints is common practice in various administrative procedures carried out by state agencies, and in work carried out by law enforcement agencies in connection with suspects or defendants in the context of violations, crimes, offenses, or criminal investigations.

[0003] It is known that complete palm prints can be acquired using devices with an acquisition area that allows for the acquisition of an individual's entire palm in a single acquisition, regardless of palm size. However, such devices are bulky and not very portable. In practice, smaller mobile devices are preferred, especially in the context of field activities, because they are more ergonomic. An example of a common mobile device is one with an acquisition area whose dimensions conform to the "FAP60" standard (76mm x 81mm).

[0004] However, the average palm width for men is 89 mm. Therefore, such a device cannot capture the palm print of the entire palm of the vast majority of individuals in a single acquisition.

[0005] One solution is to obtain a partial palm print and then use image processing to reconstruct the entire palm.

[0006] (Patent Document 1) describes a method for reconstructing a palm from images such as images of partial palm prints that have overlapping regions.

[0007] Nevertheless, the completeness and accuracy of such reconstructions depend primarily on the extent of the palm that the partial print images tend to allow during their assembly. However, it is common for the number of partial fingerprint images to be insufficient, and / or for these images not to cover all relevant areas of the palm. Faced with this problem, human operators using small acquisition devices to acquire partial palm prints of an individual with the aim of reconstructing the entire palm print often tend to unnecessarily increase the number of acquisitions, even if this does not guarantee that the entire palm is actually covered. As a result, time is wasted and operational efficiency decreases. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] European Patent Application Publication No. 4273815 [Non-patent literature]

[0009] [Non-Patent Document 1] NASA MAN-SYSTEMS STANDARDS-3 ANTHROPOMETRY AND BIOMECHANICS,Revision B,July 1995,Volume 1,Section 3 [Non-Patent Document 2] Sharma et al.(2022).Is fingerprint ridge density influenced by hand dimensions?Acta Biomed [Overview of the project]

[0010] The present invention makes it possible to improve the reconstruction of the entire palm print from partial palm prints by determining the number of partial palm prints to be acquired in order to cover the entire palm. In certain embodiments, the present invention also makes it possible to reduce the risk of operator error by using a partial print acquisition sequence in which each acquisition corresponds to one specific position on the individual's palm relative to the acquisition area of ​​the acquisition device.

[0011] According to a first aspect of the present invention, a method is provided for determining the number of palm print partial images to be acquired using a nipple print acquisition device, wherein the nipple print acquisition device has an acquisition area smaller in size than the palm area representing a group of individuals, and the method is implemented by a computer, and consists of the following steps: a) The step of acquiring an image of an individual's nipple print using the acquisition device, b) Using a nipple print image, the step of measuring at least one geometric dimension of the nipple print, c) For example, the step of estimating at least one geometric dimension of an individual's palm from at least one geometric dimension of a nipple print, preferably using one or more interpolation functions calculated based on statistics of various measurements of multiple individuals, d) From at least one estimated geometric dimension of the individual's palm, an image of the individual's palm I1, ..., I required to cover the entire area of ​​the palm. N A step to determine the number of acquisitions N, where each acquisition is one position P1, ..., P on the acquisition area of ​​the acquisition device of the individual's palm. N The corresponding steps and Includes.

[0012] The present invention is advantageously complemented by the following features, which can be implemented individually or in any technically possible combination thereof.

[0013] - In step a), the papillary纹 image includes at least one fingerprint of an individual. In step c), the first geometric dimension of the individual's palm is the width of the palm, and the said width of the palm is estimated using a first interpolation function based on the measured geometric dimensions of the papillary纹. The second geometric dimension of the individual's palm is the length of the palm, and the said length of the palm is estimated using a second interpolation function based on the measured geometric dimensions of the papillary纹.

[0014] - The first interpolation function is a function for interpolating the widths of the palms of a plurality of individuals based on at least one geometric dimension of their fingerprints. The second interpolation function is a function for interpolating the lengths of the palms of a plurality of individuals based on one length of their palms.

[0015] - In step b), at least one measured geometric dimension of the fingerprint is selected from the width, length, or area of the fingerprint, or a combination thereof.

[0016] - In step a), the papillary纹 image includes the interdigital part of the individual's palm. In step b), the width of the interdigital part is measured. In step c), the width and length of the palm are estimated using a first interpolation function for interpolating the width of the palm and a second interpolation function for interpolating the length of the palm, respectively, based on the measured width of the interdigital part.

[0017] In step b), at least one distance between two papillary ridges is measured in the papillary纹 image captured in step a). In step c), the width and length of the palm are estimated using a first function for interpolating the width of the palm and a second function for interpolating the length of the palm, respectively, according to the distance measured between two papillary ridges.

[0018] Step d) includes the following sub-steps: - A sub-step of comparing the estimated geometric dimensions of the palm with the geometric dimensions of the acquisition area of the acquisition device, and - From the result of the comparison, images I1, ···, I of the individual's palm on the acquisition area of the acquisition device NUpon each acquisition, positions P1, ···, P N A sub-step of determining and are included.

[0019] - If the estimated width and the estimated length are smaller than the geometric dimensions of the acquisition area of the acquisition device, the number N of image acquisitions is a single image I1 associated with a position P1 centered on the acquisition area of the acquisition device.

[0020] - If either the estimated length or the estimated width of the palm is greater than the geometric dimensions of the acquisition area of the acquisition device, then a) For the length, the number N of image acquisitions is at least two images I1, I2 respectively associated with a first position P1 corresponding to the upper part of the palm, preferably at least the upper half of the palm, and a second position P2 corresponding to the lower part of the palm, preferably at least the lower half of the palm, or b) For the width, the number N of image acquisitions is at least two images I1, I2 respectively associated with a first position P1 corresponding to the right half of the palm and a second position P2 corresponding to the left half of the palm.

[0021] - If the estimated width and the estimated length are greater than the geometric dimensions of the acquisition area of the acquisition device, the number N of image acquisitions is at least four images I1, I2, I3, I4 respectively associated with a first position P1 corresponding to the upper half of the palm, a second position P2 corresponding to the lower half of the palm, a third position P3 corresponding to the right half of the palm, and a fourth position P4 corresponding to the left half of the palm.

[0022] According to a second aspect, the present invention is a method for acquiring an image of a pattern, comprising the following steps: e) Using a papillary pattern acquisition device having an acquisition area smaller than the palm area representing a group of individuals, obtaining the number N of acquisitions of the individual palm images I1, ···, I N required to cover the entire palm area, each acquisition being at one position P1, ···, P of the individual's palm on the acquisition area of the acquisition device NCorresponding to the above number, the number is obtained by the method according to the first aspect of the present invention, step and f) A step to verify that the acquired image covers the entire palm of the individual, g) If the acquired image does not cover the entire palm, the step is to acquire at least one corrected image at a given position, h) Reconstructing the entire palm from the images obtained in step e) and possibly step g) This provides a method that includes [something].

[0023] The present invention in a second aspect is advantageously supplemented by the following features, which can be implemented individually or in any technically possible combination.

[0024] -Verification includes the following steps: reconstructing the palm from the acquired images; calculating the width and / or length of the reconstructed palm; and comparing the calculated width and / or length with a reference value.

[0025] - In step e), the acquired image includes at least one palm edge, and the verification includes the following steps: detecting palm edges in the acquired image, and verifying the presence of all palm edges, and if any palm edges are missing, at least one corrected image is acquired.

[0026] -The method according to the second embodiment further includes the steps of: calculating a width and / or length from the edge of the palm; comparing the calculated width and / or length with a reference value; and at least one corrected image is obtained as a result of the comparison.

[0027] According to a third aspect, the present invention provides a nipple print acquisition device comprising a sensor, wherein the sensor has an acquisition area smaller than the entire palm area of ​​a group of individuals, and the device comprises a computer configured to implement the method according to a second aspect of the present invention. [Brief explanation of the drawing]

[0028] [Figure 1] This is a schematic diagram of an example of a mobile pattern acquisition device. [Figure 2] The markings are shown, classified into 11 classes C1 to C11 using known methods. [Figure 3] The steps of a method for determining a palm print image according to one embodiment of the present invention are shown. [Figure 4] The following describes a step in a method for determining the number of images to be acquired according to one embodiment of the present invention. [Figure 5] This shows the hand position for obtaining the pattern in the first embodiment of the present invention. [Figure 6] This shows the hand position for obtaining the pattern in the second embodiment of the present invention. [Figure 7] This shows the hand position for obtaining the pattern in the first embodiment of the present invention. [Figure 8] This shows the correlation between the width (in pixels) of the finger patterns on an individual's hand and the width (in pixels) of their palm. [Figure 9] This shows various hand positions for obtaining different images of the palm. [Figure 10] This shows various hand positions for obtaining different images of the palm. [Figure 11] This shows various hand positions for obtaining different images of the palm. [Figure 12] This shows various hand positions for obtaining different images of the palm. [Modes for carrying out the invention]

[0029] In all figures, similar elements are indicated by the same reference numeral.

[0030] Figure 1 shows a contact-type mobile device 1 for acquiring nipple prints, comprising a sensor 2, a computer 3 configured to implement the steps described below, and a memory 4 for storing pattern images and code instructions for implementing various steps (see below). The computer 3 and memory 4 are integrated, for example, into a PC, tablet or smartphone, or another type of system with a user interface. The computer 3 may be independent of the sensor 2 or may be directly integrated into the sensor 2.

[0031] Sensor 2 is small, ensuring the mobility of the device. It conforms to the FAP60 standard and has an acquisition area 21 with dimensions of 3 × 3.2 inches, or 76 × 81 mm.

[0032] The sensor's acquisition area 21 is approximately rectangular. The operator prompts the individual to place their hand M in a determined position. Depending on the type of fingerprint or palm print to be acquired, one or more fingers, hands, or parts of hands may be offered.

[0033] Fingerprints and palm prints can be classified into several membership classes, each corresponding to a specific anatomical region of the palmar surface of the hand. The “palmar surface” of the hand is understood to mean the surface of the hand including the palm, as opposed to the back. The palmar surface includes the palm and all the fingers, in other words, the thumb, index finger, middle finger, ring finger, auricle, thenar eminence, palmar cavity, and hypothenar eminence. The palm is the portion of the palmar surface between the wrist and the base of the fingers. These definitions correspond to those generally accepted in anatomy.

[0034] In practice, referring to Figure 2, it is possible to distinguish among various types of fingerprint diagrams 11 membership classes C1 to C11 that correspond to different anatomical regions of the palmar surface of the hand and are adapted to a very large number of requirements and use cases, namely, the complete right hand (C1), the complete left hand (C2), the palm of the right hand (C3), the palm of the left hand (C4), the interdigital region of the right hand (C5), the interdigital region of the left hand (C6), the palm of a right-handed writer (C7), the palm of a left-handed writer (C8), at least two, preferably three, preferably four fingers of the right hand (C9), at least two, preferably three, preferably four fingers of the left hand (C10), and the thumbs of the right and left hands (C11).

[0035] Sensor 2 has an acquisition area with dimensions conforming to the FAP60 standard (76mm x 81mm), and for most individuals, it is not possible to obtain a complete palm print in a single acquisition. The average palm width for male individuals is 89mm. In particular, the fingerprints of classes C3 and C4 shown in Figure 2 cannot be obtained in a single acquisition for most individuals.

[0036] As shown in Figure 3, using the acquisition device, multiple partial palm print images are determined to be acquired to enable a complete acquisition of the individual's palm (step DET), with each image corresponding to one position on the individual's palm on the sensor's acquisition area 21.

[0037] Complementarily, the acquisition step for each image (step ACQ) is implemented.

[0038] Complementarily, a verification step (step VER) is implemented to ensure that one or more acquired images actually cover the entire palm. If the verification is not definitive, a corrective acquisition may be required and performed (step DETS), or a warning may be generated to invalidate the acquisition (step GEN).

[0039] Figure 4 shows all the substeps of the step of determining the number N acquisitions of an individual's palm required to cover the entire palm area (see step DET described in Figure 3), where each acquisition corresponds to one position P1, ..., PN on the individual's palm on the acquisition area 21 of device 1 for acquiring nipple prints.

[0040] Complementarily, it is also a matter of obtaining one or more instructions on where the individual's hand should be positioned on the acquisition area 21, and these instructions may be visual or auditory, as described above.

[0041] Therefore, the step (step DET) of determining the number of images N of an individual's palm required to cover the entire surface of the palm includes a preliminary step (step E0) of acquiring initial images of the individual's nipple prints (see images Ia, Ib, and Ic in Figures 5, 6, and 7, respectively). For this purpose, the individual is prompted by an operator to position their hand M on the acquisition area 21 of sensor 2. These initial images (Ia, Ib, Ic) are received by a computer for processing (step E1). When referring to a given acquisition of an image, it means that each image is associated with one specific position of the individual's hand on the acquisition area 21 of sensor 2.

[0042] Using the initial images Ia, Ib, and Ic, the geometric dimensions of the individual's nipple prints are measured (Step E2).

[0043] Next, based on the measured geometric dimensions, at least one geometric dimension of the individual's palm is estimated using one or more interpolation functions (Step E3). The geometric dimension of the individual's palm may be selected from length, width, and / or area. For simplicity, we assume that the palm is generally rectangular in shape.

[0044] Based on the geometric dimensions of the individual's palm thus estimated, the number of acquisitions N that allow the entire palm of the individual to be covered, and the hand positions corresponding to these N acquisitions are determined (step E4).

[0045] Each position is stored in the memory 4 of the data processing device in the form of visual and / or audible indication for the purpose of subsequent acquisition (step ACQ) of each image.

[0046] First Embodiment In the first embodiment, referring to Figure 5, the initial image Ia includes at least one fingerprint of an individual, for example, the fingerprints of four fingers of the left or right hand. In the example shown in Figure 5, the individual positions their fingers on the acquisition area 21 of sensor 2 such that the tips of the four fingers (shown in black) are positioned on the sensor, and then the initial image is acquired (step E0a).

[0047] In this initial image, at least one geometric dimension of one or more fingerprints is measured (step E2). Such measurements are made in pixels or dimensions, and these two quantities are generally proportional. One geometric dimension of a fingerprint is the width, length, or area of ​​the fingerprint.

[0048] Next, the palm width is estimated based on the geometric dimensions of the pattern that were measured previously (step E3).

[0049] Such width estimation is performed, for example, based on reference measurements that give the geometric dimensions of the fingerprint relative to the width of the reference individual's palm, and these reference measurements are stored in memory 4.

[0050] Therefore, the problem is to determine the closest geometric reference pattern dimension to the measured geometric pattern dimension and then estimate the individual's palm width from there.

[0051] To do this, a first interpolation function f1 is obtained from a set of palm width measurements of multiple individuals as a function of at least one geometric dimension of their fingerprints.

[0052] The first interpolation function f1 is obtained, for example, from an analysis of the correlation between the geometric dimensions of a fingerprint and the palm width of a statistical population of reference individuals. The geometric dimensions of a fingerprint may be the dimensions of a single finger in particular, or the dimensions of all or some combinations of fingers, with or without averaging and weighting.

[0053] Preferably, the palm width is determined using a first interpolation function f1 that interpolates the palm width A from the width of the finger fingerprints. Thus, an estimate of the palm width is obtained based on the measurement of the width of an individual's finger fingerprints (step E3).

[0054] Figure 8 shows an example of the correlation between the width of various finger fingerprints and the width of the palm. In this figure, dimensions are represented in pixels. For each hand of multiple individuals, the x-axis represents the width of the middle finger, and the y-axis represents the width of the palm. The center line represents the linear relationship (constant finger / palm ratio) between the width of the palm and the width of the finger fingerprints. The upper and lower lines represent the upper and lower limits of the 95% confidence interval centered on the center line. Almost all measurement points lie between the upper and lower lines.

[0055] Complementarily, any geometric parameter obtained using the first interpolation function f1 is accompanied by a confidence interval.

[0056] Based on the palm width A, the palm length L is determined using the second interpolation function f2 (step E3).

[0057] The second interpolation function f2 is, for example, the result of an anthropometric study showing the 5th and 95th percentiles of palm width and length measurements. An example of such a study is described in (Non-Patent Literature 1).

[0058] In this example, the second interpolation function f2 allows for the establishment of a correspondence between an individual's palm width and length, for example, through a linear relationship between palm width and length based on the 5th and 95th percentiles of these lengths and widths.

[0059] Second Embodiment In the second embodiment, referring to Figure 6, the initial image Ib of the nipple print includes the interdigital portion of the individual's palm. This image can be acquired by positioning the interdigital portion of the individual's hand M along the diagonal of the acquisition area 21 of the sensor 2, as shown in Figure 6 (step E0b). The interdigital portion corresponds to the upper part of the palm at the base of the fingers.

[0060] For example, using sensor 2 with a diagonal of 111 mm, it is possible to obtain the palm width (measured between the fingers) of almost any individual.

[0061] Specifically, according to certain anthropometric studies, particularly the one mentioned above, 95% of male individuals have a palm width of less than 96 mm, and 50% of male individuals have a palm width of less than 89 mm (a difference of 7 mm). A diagonal of 111 mm (and therefore 15 mm larger than 96 mm) is sufficient for the vast majority of individuals.

[0062] Using the initial image Ib, the interdigital width is measured (step E2), and the distance between the edges of the palm is measured, for example, using image processing. The interdigital width approximately corresponds to the width of the palm.

[0063] Similar to the first embodiment, the length L of an individual's palm is estimated using a function f3 that interpolates the length of the palm according to the width of the interfacial space.

[0064] Third Embodiment In the third embodiment, the initial nipple print image includes nipple ridges. The initial image may be an image of a portion of the palm and / or a portion of the fingers, as shown in the example in Figure 7. In this example, the initial image may be acquired with the individual's hand positioned so that the central part of the palm is in good contact with the acquisition area 21 of the sensor 2 (step E0). As an example, Figure 7 shows the position where the individual's hand must acquire (in grayscale) an initial image Ic characterizing the central part of the palm (step E0).

[0065] Based on the initial image Ic, at least one distance between two papillary ridges is measured. Alternatively, the average width between the papillary ridges can be used to achieve a better representation of the statistics.

[0066] Next, based on the measured distance between the two papillary ridges, it is possible to estimate the length and width of an individual's palm using a function that interpolates the length and width of the palm as a function of the measured distance between the two papillary ridges. An example of such a function is described in the paper (Non-Patent Document 2). This function can advantageously be refined using a measurement campaign for a representative group of individuals.

[0067] Determination of the number N of acquisitions (step E4) When the length and width of the palm are obtained, the number N of acquisitions required to cover the entire area is determined, and optionally, instructions for guiding the operator and the individual from whom the fingerprint is acquired are generated (step E4). Different cases can be distinguished.

[0068] Case 1) - When the estimated length L and width A of the palm are smaller than the geometric dimensions of the acquisition area 21 of sensor 2 (the length L of the acquisition area sensor and the width l of the acquisition area sensor ), for example, length 8.1 cm and width 7.6 cm, the number N of acquisitions is a single image I1 associated with the position P1 of the hand at the center of the acquisition area (see Fig. 9).

[0069] Case 2) - When the estimated length L of the palm is greater than the length L of the acquisition area 21 of sensor 2 sensor and the estimated width A of the palm is smaller than the width l of the sensor sensor ), the number N of image acquisitions is two images I1 and I2 respectively associated with a first position P1 corresponding to the upper part of the palm, preferably at least the upper half of the palm, and a second position P2 corresponding to the lower part of the palm, preferably at least the lower half of the palm (see Fig. ⑩).

[0070] [[ID=二十九]] Case 3) - When the estimated length L is the length L of the acquisition area 21 of sensor 2 sensorIt is less than the estimated width A of the palm and the width l of the acquired area 21. sensor If the value is greater than this, the number of acquisitions N is two images I1 and I2 (see Figure 11) associated with a first position P1 corresponding to the left half of the palm and a second position P2 corresponding to the right half of the palm, respectively.

[0071] Case 4) - The estimated palm length L is equal to the length L of the acquisition area 21 of sensor 2. sensor Larger than the estimated palm width A is greater than the sensor width l sensor If the number of acquisitions is greater than , the number of image acquisitions N is four images I1, I2, I3, I4, associated with a first position P1 corresponding to the upper half of the palm, a second position P2 corresponding to the lower half of the palm, a third position P3 corresponding to the right half of the palm, and a fourth position P4 corresponding to the left half of the palm, respectively. Thus, a total of N=4 acquisitions I1, I2, I3, I4 are required, one for each of the following palm sectors (see Figure 12), namely, the upper left, upper right, lower left, and lower right. While various orders of acquisition are possible, it should be noted that in practice, it is preferable not to start with two sectors located diagonally opposite each other, because in this case there is less image overlap (specifically, overlap allows the palm to be reconstructed from various acquisitions).

[0072] In cases 1, 2, and 4, partial images at various locations are required based on estimated geometric dimensions of the palm. In some cases, only a small number of images are needed compared to processes that require a much larger number to ensure the entire palm is covered.

[0073] Acquisition of pattern images After determining the number of acquisitions needed to completely cover an individual's palm, each image I1, ..., I N The acquisition (step ACQ) of sensor 2 on the acquisition area 21 is performed at the associated positions P1, ..., P N It is executed in [location].

[0074] In certain embodiments, the method further includes verifying (VER) that the acquired image covers the entire palm, and if the acquired image does not cover the entire palm, acquiring (ACQS) at a given location. Finally, a reconstruction of the entire palm is performed from the acquired image, optionally supplemented by at least one corrective image (step REC).

[0075] The verification step can be implemented in several ways.

[0076] In the first method, the palm is first reconstructed from the acquired image (step E51), and then the width and / or length of the reconstructed palm are calculated (step E52). Next, the calculated width and / or length are compared with one or more reference values ​​(step E53). Then, depending on the result of the comparison, at least one corrected image is acquired at a given location (step ACQS).

[0077] The entire palm can be reconstructed from acquired images using various methods, particularly the method described in (Patent Document 1). Such reconstruction (step E51) includes the steps of aligning and fusing various images (if at least two images at two different locations are required).

[0078] If the reconstructed palm width and / or length are below a threshold (or interval of values), the acquired image quality is likely to be poor, particularly because the hand may not be properly positioned to cover the entire area of ​​the palm (the same reasoning can be applied to the length of the hand). Several corrective acquisitions (step ACQS) are then taken to acquire one or two additional acquisitions to cover the entire width and / or one or two additional acquisitions to fully cover the entire length of the palm. The acquisition device may be configured to alert the operator using an audible or visual signal.

[0079] In the second method, if the acquired image contains at least one palm edge, the palm edge is detected in the acquired image (step E61) in order to detect all boundaries of the palm (step E62). If the palm edge is missing, at least one corrected image is acquired (step ACQS).

[0080] If these boundaries are detected, and the detected width and length (and therefore area) are greater than the baseline, and the detected shape matches the shape of the palm, it can be inferred that the entire palm was actually detected. In contrast, if one or more boundaries are missing, and / or the detected length or width is below the lower limit of the confidence interval, at least one corrected image is taken for the purpose of detecting the corresponding boundaries.

[0081] In particular, the corrective acquisition involves positioning the portion of the palm corresponding to the missing edge toward the center of the acquisition area 21. For example, if the left edge of the palm is missing, it means that the left portion of the palm is shifted to the left of the left portion of the sensor, and therefore the individual is prompted to position the left portion of the palm toward the center of the sensor 2, or advantageously between the center and the left of the sensor, so that the left edge is within the acquisition area 21. If the left edge and upper edge are missing, the individual is prompted to position the upper left portion of the palm toward the center, or at least (and advantageously) between the center and the upper left quadrant.

[0082] In a third method that complements the second method, the width and / or length are calculated from the edge of the palm (step E63), and the calculated width and / or length are compared to reference values ​​(step E64). Such reference values ​​are, for example, the lower and upper limits of the confidence interval associated with the interpolation function (see above).

[0083] If the calculated width or length is greater than the reference value, the hand may be positioned at an incorrect angle on the sensor ("distorted"), and the diagonal measurement may have been incorrectly considered as the palm width or length measurement. To limit the risk of errors during complete palm print reconstruction, it is advisable to generate a warning message for the operator (Step GEN) and instruct the operator to check the hand position and resume acquisition. [Explanation of symbols]

[0084] 1. Contactless mobile devices 2 sensors 3 Computers 4 memory 21 Acquisition area

Claims

1. A method for determining (DET) the number of palm print partial images to be acquired using a nipple print acquisition device (1), wherein the nipple print acquisition device comprises an acquisition area (21) smaller than the area of ​​the palm representing a group of individuals, and the method is implemented by a computer (3), comprising the following steps: a) Step (E1) to acquire an image of an individual's nipple print obtained using the acquisition device (1), b) A step (E2) of measuring at least one geometric dimension of the nipple print using the nipple print image, c) A step (E3) of estimating at least one geometric dimension of the individual's palm based on at least one geometric dimension of the nipple print, d) From the at least one estimated geometric dimension of the palm of the individual, an image I of the individual's palm is required to cover the entire area of ​​the palm. １ , , , I Ｎ Step (E4) of determining the number of acquisitions N, wherein each acquisition is one position P of the individual's palm on the acquisition area (21) of the acquisition device (2). １ , ..., P Ｎ The corresponding step (E4) and Methods that include...

2. The method according to claim 1, wherein the nipple print image includes at least one fingerprint of the individual, and in step c), a first geometric dimension of the individual's palm is the width of the palm, the width of the palm is estimated using a first interpolation function (f1) based on the measured geometric dimension of the nipple print, and a second geometric dimension of the individual's palm is the length of the palm, the length of the palm is estimated using a second interpolation function (f2) based on the measured geometric dimension of the nipple print.

3. The method according to claim 2, wherein the first interpolation function is a function (f1) for interpolating the width of the palms of a plurality of individuals based on at least one geometric dimension of their fingerprints, and the second interpolation function (f2) is a function (f2) for interpolating the length of the palms of a plurality of individuals based on one length of their palms.

4. The method according to claim 2, wherein the at least one geometric dimension of the fingerprint is selected from the width (A), length (L), or area (S) of the fingerprint, or a combination thereof.

5. The method according to claim 1, wherein the nipple print image includes the interdigital portion of the palm of the individual, and in step b), the width of the interdigital portion is measured, and in step c), the width and length of the palm are estimated using a first interpolation function for interpolating the width of the palm and a second interpolation function for interpolating the length of the palm, respectively, based on the measured width of the interdigital portion.

6. The method according to claim 1, wherein in step b), at least one distance between two nipple ridges is measured in the nipple print image taken in step a), and in step c), the width and length of the palm are estimated, respectively, using a first function (f3) for interpolating the width of the palm and a second function (f4) for interpolating the length of the palm, depending on the distance measured between the two nipple ridges.

7. Step d) is the following substep: - A substep of comparing the at least one estimated geometric dimension of the palm with the geometric dimension of the acquisition area of ​​the acquisition device, - From the results of the above comparison, the image I of the individual's palm on the acquisition area of ​​the acquisition device １ , , , I Ｎ Each time a location P is acquired, １ , ..., P Ｎ Substeps to determine The method according to claim 1, including the method described in claim 1.

8. The method according to claim 7, wherein if the estimated width and the estimated length are smaller than the geometric dimensions of the acquisition region (21) of the acquisition device (2), the number of image acquisitions N is a single image I1 associated with a position P1 centered on the acquisition region of the acquisition device.

9. If either the estimated length or estimated width of the palm is greater than the geometric dimensions of the acquisition area (21) of the acquisition device (2), - Regarding the length, the number N of image acquisitions is at least two images I1, I2 associated with a first position P1 corresponding to the upper part of the palm, preferably at least the upper half of the palm, and a second position P2 corresponding to the lower part of the palm, preferably at least the lower half of the palm, or - Regarding the width, the number N of image acquisitions is at least two images I1 and I2 associated with a first position P1 corresponding to the right half of the palm and a second position P2 corresponding to the left half of the palm, respectively. The method according to claim 7.

10. The method according to claim 7, wherein if the estimated width and estimated length are greater than the geometric dimensions of the acquisition area (21) of the acquisition device, the number N of image acquisitions is at least four images I1, I2, I3, I4 associated with a first position P1 corresponding to the upper half of the palm, a second position P2 corresponding to the lower half of the palm, a third position P3 corresponding to the right half of the palm, and a fourth position P4 corresponding to the left half of the palm, respectively.

11. A method for obtaining an image of the nipple prints across the entire palm, following these steps: e) Using a papillary pattern acquisition device (1) having an acquisition area (21) smaller than the area of the palm representing a group of individuals, the image I of the palm of said individual necessary to cover the entire area of said palm １ ,..., I Ｎ obtaining the number N of acquisitions of, each acquisition corresponding to one position P of the palm of said individual on said acquisition area (21) of said acquisition device (2) １ ,..., P Ｎ and the number being obtained by the method according to claim 1, the step and f) A step (VER) to verify that the acquired image covers the entire palm of the individual, g) If the acquired image does not cover the entire palm, the step of acquiring at least one corrected image (ACQS) at a given position, h) A step (REC) of reconstructing the entire palm from the images obtained in step e) and optionally step g) Methods that include...

12. The verification (VER) described above involves the following steps: - The step of reconstructing the palm from the acquired image (E51), - A step (E52) of calculating the width and / or length of the reconstructed palm, - A step (E53) of comparing the calculated width and / or the calculated length with a reference value. The method according to claim 11, including the method described in claim 11.

13. In step e), the acquired image includes at least one palm edge, and the verification (VER) is performed in the following steps: - The step of detecting the edge of the palm in the acquired image (E61), - Step (E62) to verify the presence of all the edges of the palm If the edges of the palm are missing, at least one corrected image is obtained. The method according to claim 11.

14. The following steps: - A step (E63) of calculating the width and / or length from the edge of the palm, - A step (E64) of comparing the calculated width and / or the calculated length with at least one reference value. The method according to claim 13, further comprising, wherein at least one corrected image is obtained in accordance with the result of the comparison.

15. A nipple print acquisition device (1) comprising a sensor (2), wherein the sensor (2) comprises an acquisition area (21) smaller than the entire area of ​​the palm of the entire group of individuals, and the device (1) comprises a computer (3) configured to implement the method according to any one of claims 1 to 14.

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