ITRM20130579A1 - METHOD FOR THE ACQUISITION OF THE NATURAL SIGNATURE BY MEANS OF A DIGITIZING TABLET OF THE ¿TOUCH SCREEN¿ TYPE. - Google Patents

Description

"METHOD FOR THE ACQUISITION OF THE NATURAL SIGNATURE FOR MEZ-ZO OF A" TOUCH SCREEN "TYPE DIGITIZING TABLET"

DESCRIPTION

Technical sector

The present invention generally refers to a data authentication system, more particularly it refers to the use of the digitized signature for the immediate and accurate identification of a person in relation to commercial banking transactions.

State of the art

In the field of computer hardware, digitizing tablets have existed for many years to collect the handwritten signature.

These tablets are formed by a digitizing surface on which you sign using a special pen. The most advanced models differ significantly from the normal digitizing tablets used for drawing, because they collect in real time not only the graphic form of the signature, but also various graphometric data such as the instantaneous speed, the instantaneous pressure exerted by the pen and the time duration of the stretches and breaks. These models are normally called "Biometric signature tablets" or better "Graphometric signature tablets".

The signature collected with one of these tablets, in the form of a set of digital data, has the fundamental characteristic of being able to be used, in case of need, for the expertise carried out by an expert graphologist. In fact, the graphological characteristics that uniquely distinguish a person's signature are recorded in it, as and better than on paper. The graphometric signature allows a better estimate than the one on paper, because the best tablets also collect timing data (duration of each phase of the signature and of the pauses) that cannot be obtained in any way by examining a signature affixed to paper.

The use of the graphometric signature therefore has great economic advantages (elimination of paper and its management) and security (better reliability of the graphological report).

All the tablets made before the present invention have some characteristics in common.

The signature surface is in glossy plastic material (eg polyester), in glossy glass or in glass with anti-reflective treatment.

The pen has a slightly rounded tip in plastic material (eg methacrylate or polycarbonate).

The tablet has a certain height with respect to the table top and in many cases has a curved or rounded upper surface. In pre-existing products - such as the device shown in Fig. 1 - the signature surface is embedded in a frame with a height difference of a few mm with respect to the upper surface of the device. The difference in height, which in some products reaches 8-10 mm, is in any case such as to force you to hold the pen higher than normal.

After all, even if all the existing tablets effectively digitize the signature, they all have the same drawback: the signature affixed does not have the same appearance and does not have the same graphometric data as the equivalent signature on paper, for a variety of reasons. , the main ones of which are set out below.

The surface of the digitizing area is too smooth and the pen runs through it much easier than on paper. The consequence is that the shape, the instantaneous speed and the instant pressure are distorted compared to those of an equivalent signature on paper. The hand must "hold" the pen in the most straight lines, distorting the speed profile, and at the same time "press less" in some points, distorting the pressure profile.

The shape and inclination of the signature surface are such as to force the signatory to an unnatural hand position. This happens because:

- the tablet is too high in relation to the table top and you are forced to sign with your hand suspended,

- the digitizing area is recessed, lower than the body of the tablet: this forces you to grip the pen farther from the tip,

- the surface is rounded, while the signature on paper would be affixed flat, - the signature surface and the tip of the pen are hard and do not yield to pressure, while the paper has a certain yield (in fact the line on paper is more or less recessed), this also makes the signature feel more unnatural.

The consequences of these problems are considerable.

The graphic form of the digitized signature is different from that of the paper signature; this raises doubts about the authenticity of a signature, even just by observing its graphic form.

The graphologist expert is not able to effectively compare a digitized graphometric signature with a pre-existing signature on paper: he must limit himself to comparing signatures of the same nature with each other. This problem is strongly felt, for example, in banking applications: in fact, banks always have paper signature "specimens" of customers, but they must again collect digital specimens when they adopt the digital signature.

Even by carrying out the appraisal only between digitized signatures, the graphologist (although in reality he has more data such as timings) cannot use the evaluation criteria he has been accustomed to from a long tradition: certain rules are no longer respected. For example, in the signature on paper an increase in pressure invariably leads to a decrease in speed due to the effort, but this is no longer true for a smooth surface with which the effort is much less.

The lack of naturalness of the signature makes people who use it feel uncomfortable, and this limits the adoption of digital technology by preventing them from taking advantage of the advantages it provides.

Concluding in the recognition technologies suitable for the creation of "Touch Screens" or "Screens operated by touch" (of a finger or a stylus), the environmental variations on two dimensions in the trace performed by the stylus tip, which constitute a manual signature, they are already different in themselves every time the same person goes to affix his signature. This randomness clearly poses recognition problems for the device and makes it difficult to use a computer device that analyzes these authentication techniques. Other variables are available - such as the speed or acceleration of the stylus - with respect to the spatial variations of the stylus path on the touch screen, for signature authentication. These variables can be derived from stylus tip dynamics with reference to changes in stylus positioning over time. However, they should refer to the pressure (force per unit area) exerted by the tip of the stylus on the signature surface and on the type of contact that is established between the stylus and the tablet. It is therefore an object of the present invention to provide a signature acquisition technique in which the hand and wrist rest comfortably, making the signature shape more consistent with that on paper and making signature tracking a reliable and suitable process for processing. to the computer for authentication purposes.

On the other hand, we want to provide a method for acquiring signatures from "Touch Screen" that is based on widespread components - of the general purpose type -, and on the related techniques of use known for the realization of the detection functions. It is therefore planned to use standard mechanical and electronic components, in the sector of acquisition and processing of the signals detected on the touch screen, in order to make the new acquisition devices low in costs, highly reliable and immediately usable.

These purposes are achieved by an apparatus for the acquisition of the natural signature by means of a digitizing tablet of the "Touch Screen" type, which is characterized in accordance with claim 1 that follows. The subordinate claims will allow to outline a series of optional configurations of the inventive principle.

Brief description of the drawings

The invention will now be described in greater detail with reference to an example of practical implementation, given only as an indication and not a limitation, illustrated in the attached drawings in which:

Figure 1 is an axonometric representation of a graphic tablet according to the known art;

Figure 2 is a schematic representation of the tip of the pen according to the present invention;

Figures 3a and 3b are three-dimensional views of the pen, as it appears respectively on the outside and inside;

Figure 4 is a three-dimensional representation of a support cabinet according to the present invention;

figure 5 is a three-dimensional representation in a rear view of a support cabinet according to the present invention;

figure 6 is a schematic representation of the collection volume obtained for positioning in the cabinet;

Figure 7 is a plan representation of the cutout used for the insertion of the cabinet with its signature surface;

Figures 8a and 8b are representations of different embodiments of the pen according to the present invention;

Figure 9 is a representation of a different configuration of the signature surface support.

Description of the invention

The apparatus and the technique according to the invention are based on the derivation of a series of data from the sliding of a stylus (1) on a graphic tablet (9) of the touch screen type, and in the processing of said data so as to provide the direction of a vector in a system of Cartesian axes, in real time. The purpose is a comparison with a predetermined reference or with the characteristics of an already stored signature, in order to establish a match which is followed by the acquisition of the natural signature by means of a digitizing tablet of the "Touch Screen" type.

The tip 5 of the pen 1 has the optimal shape which can be deduced from Figure 2, in section, and from the three-dimensional view of Fig. 3a and 3b. The tip is a 3.7 mm high cone, 3 mm base diameter, terminated by a 0.2 mm radius hemisphere. The material is methacrylate (Plexiglas). The 200 micron radius of the tip is much larger than the average size (1.6 micron) of the signature surface roughness. This allows a smooth sliding even with a certain resistance; a thinner tip would have produced a “grounding” effect and an irregular sliding, while a thicker tip would have excessively reduced the resistance, returning to the problem of excessive smoothness which instead is to be eliminated.

The characteristic of the upper surface of the signature device, unique of its kind, is that it is perfectly flat, as can be seen in the three-dimensional views of figs 4 and 5 which show 3D images of the container. The signature surface 9 is flush with the upper surface 6 of the cabinet 8 and there are no continuity solutions between the signature area 9, under which the display with touch panel sensor is arranged, and the rest 6 of the upper surface of the device. In pre-existing products (see for example Fig. 1) the signature surface 9 is embedded in a frame 25 with a difference in level of a few mm with respect to the surface of the device. The difference in height, which in some products reaches 8-10 mm, is in any case such as to force the pen 1 to be held higher than normal.

As for the plastic support used for the signature surface, the reference material is 3M 7962 which is a double protection adhesive transfer tape. More specifically, the component used is Scotchmark ™ 7952 MP - 7955 MP as an adhesive that fixes the flexible polyester front to the device cabinet. The 200 MP high temperature acrylic adhesive film - which each face is equipped with - is protected by a protective polyethylene kraft paper. The thickness is available in different sizes ranging from 0.05 to 0.200 mm, with three basic components:

<a-> The protective layer printed with kraft polyethylene coating with weight: 94.4 g / m <2>, or kraft polyethylene coating with weight: 140 g / m <2>

b- The 200 MP type "high performance" acrylic adhesive component c- The Protective in polyethylene kraft coating with a weight of 94.4 g / m <2>. Determining a total thickness ranging from 0.250 mm to 0.400 mm.

The characteristics of the 200 MP type adhesive gives an assembly resistant to environmental attacks, that is, an excellent behavior of the transfer tapes in the face of high temperatures, humidity and chemicals. In addition, the high cohesion of the adhesive provides good resistance to repeated pressing of the keyboard keys.

Another feature of the tablet is that the signature surface is replaceable in case of wear; even, the entire front of the device is self-adhesive and can be replaced by tearing it off and attaching a new one. This performance is interesting because the front, outside the signature surface which represents only a part of it, can be printed with the logo of the organization using the tablet. This possibility is interesting for its advertising and image effect. Printing is done on the back by screen printing, even in multiple colors. The adhesive is chosen for the right compromise between the adhesiveness necessary to avoid accidental detachment especially in the corners and the need to allow removal.

Mac Dermid Autotex F200 material is used for the front. It is polyester with a thickness of 200 microns (0.2 mm). The upper surface is finely embossed: size of the irregularities statistically equal to 1.6 microns. The lower surface is treated with a special UV-cured primer to allow the adhesion of the screen printing ink and the underlying self-adhesive layer.

The measure of opacity is 55%, while that of reflection is 7%.

The Autotype Autoflex EB G180 material is instead an example of an equivalent material, with a thickness of 180 microns and a glossy upper surface, which was used previously and which presented the problem of excessive smoothness, similar to what is found for all signature devices on the market.

The tablet object of this patent allows two modes of use: resting on the work surface or embedded in the work surface.

In the case of the support on the top, the fact that the signature surface A 9 is located asymmetrically and close to the rear side of the cabinet means that, towards the front side of the cabinet, there remains a large surface B on which to rest the hand during the signature. Since there is no step between the front edge and the table top, if the support of the hand on the tablet is not sufficient, this can continue without discomfort even on the table top in front of the tablet. The inclination angle of the tablet top with respect to the table top is designed to make this support comfortable, even if it is divided between two surfaces angled to each other.

In the case of recessed into the top, there is no longer any solution of continuity between the signature surface 9, the upper surface of the tablet 6 and the surface of the table; this arrangement makes the signature with a tablet identical to the one you would have with a sheet of paper placed on the table. It should be noted that the possibility of recessing is given by the rectangular shape of the tablet 8, which allows it to be recessed by making a simple rectangular hole 11 in the top, and by the presence, all around the upper edge 8 of the tablet, of a protruding edge 12 suitable to cover the gap that remains between the table top and the tablet 8 along the perimeter of the cut area.

From the 3D drawings of the tablet 8, 9 and from the representation of the drilling of the lower side of the top of Fig. 6 and of the hole at two levels, it is possible to note the details relating to the drilling that must be made in the support surface of the table to allow the recessed. It should be noted that, in the back 10 of the tablet, there is the output 13 of the two cables 14a and 14b (respectively, the USB one for connecting to the computer and the one for connecting the pen). The two cables, 14a and 14b, come out at the bottom and, between their exit and the upper surface of the tablet, there is a distance of about 20 mm. So, if the table top has a thickness of less than or equal to 20 mm, the cables come out below the table and just drill a rectangular hole, 157 x 142 mm, with a 2 mm radius fillet in the corners. This hole can also be drilled with a normal jigsaw, taking care to first drill four holes with the drill at the corners.

If the thickness of the top is greater than 20 mm, the cables 14 would interfere with the table top in the area where they come out of the tablet cabinet. In this case, as can be seen in the drawing in Fig. 7 which shows the drilling from below, it is advisable to drill the hole by means of a cutter and make a recess, from the lower side of the top, with dimensions of about 40 x 40 mm and of such depth as to leave 20 mm of material between the bottom of the cutout and the upper surface of the top. In case of built-in, the cable 14b that connects the pen to the tablet, and which comes out under the top, is passed through the table top by means of a hole protected by a normal rubber grommet.

As for the spring 2 present inside the pen, from the representation of Fig. 3, it can be seen that it works by compression. Its modulus of elasticity is 3.52 N / mm; its maximum stroke, limited by a special stop ring obtained in the plastic casting that makes up the body of the pen, is 0.7 mm. The maximum force at which the elasticity of the spring ceases is therefore approximately 2.5 N; above this force the pen behaves like a rigid body.

The constructive characteristics of the spring are:

• External diameter 4.8 mm

• 0.8 mm wire diameter

• Free length 28 mm

• Material: harmonic steel for springs.

The importance given to these functional numerical parameters of the spring is significant for what has already been pointed out previously. The spatial variations of the trace of the stylus 1 on the screen 9 can be derived from the dynamics of the stylus tip with reference to the changes in the positioning of the stylus itself over time. However, they refer to the pressure (force per unit area) exerted by the tip of the stylus on the screen and to the types of contact that is established between stylus 1 and graphics tablet 9.

From this point of view, the solution devised provides that the tablet 8, 9 with the pen 1, made according to the present invention, have the following characteristics.

• The signature surface 9 is made of finely embossed plastic material, with an opaque surface similar to that of a sheet of paper. This feature makes the surface less smooth, the signature is more natural and the graphometric characteristics are very similar to those of the signature on paper.

• The upper surface 6 of the tablet is completely flat and the digitizing surface 9 is at the same level as this surface, without any recess.

• The upper surface 6 of the tablet has, with respect to the table top, an inclination designed to make the position of the hand natural during the signature; in particular, it allows to rest the wrist partly on the tablet and partly on the table top, according to the size of the hand.

• The tip 5 of the pen is not rigid, but is suspended by a spring 2, inside the body of the pen, with a constant of force and a maximum stroke designed to simulate the softness of the paper: therefore, even if the digitizing surface is not very yielding, the slight sagging of the tip 5 of pen 1 makes the signature experience more natural.

• The tablet can be easily recessed into the table top by first making a simple rectangular hole. In this way the signature surface reaches the maximum naturalness, because it is exactly flat with respect to the table, as happens by placing a sheet of paper on it.

• The compliance of the pen is similar to that of paper.

In a preferred embodiment of the present invention - relating to the representation of Figure 8 - this principle of the slight yielding of the tip of the pen is optimized. The compliance can take on significant importance if a disturbance or distortion condition in the detection is also considered. The extent of the support force of the pen 1 must therefore be considered on the basis of the stress to which the spring 2 is subjected. There is no one who does not see that the support of a pen on a sheet, in general, is different from a person per person, the positioning being able to be among the most varied. If we refer to the axis of the pen positioned approximately perpendicular to the plane, it is evident that the stress on plane 9, of the signature surface of the digitizing tablet, can change from person to person and the same person may find himself in an unusual position - compared to the execution of a signature on paper - by having a digital medium that is being used for the first time.

It is clear that if a person has the pen 1 perpendicular to the plane of the tablet 9, the force is maximum. As the axis of the stylus lowers / bends, the force that intervenes on the tablet surface becomes less relevant while allowing to obtain a less reliable path. In summary, the operating conditions can be extremely random, disturbances and any distortions are factors that constitute a continuous pitfall in detecting a sufficiently faithful signal. For these reasons, operating conditions in which the spring 2 is not properly calibrated should be avoided. Hence a series of tools illustrated below with the aid of Figs. 8a and 8b, which allow the pen 1 to be periodically subjected to a recalibration activity by means of a special microsensor 15, with micrometric adjustment through a dedicated display.

In the present invention, a fairly common force detector is used, that is to say a micro force sensor of the optical reflection type (detects the displacement of the tip according to the shortening of the spring), as well as other types of detectors such as piezoelectric sensors. Surprisingly, it was found that the fundamental parameter on which to establish a correlation, in fact linear, with the force exerted for the translation of the pen, was the force exerted on the basis of the elasticity of the spring with reference to its maximum stroke. This feature also constituted a reason for choosing the force detector of the optical reflection type which detects the displacement of the tip precisely on the basis of the shortening of the spring.

In practice, a millimetric graduated washer 18 has been provided in the body of the pen 1 in correspondence with the sensor 15, in series with the termination of the spring 2.

The insertion of the washer 18 on a cylindrical thread 26 causes the spring 2 to be compressed to a more or less significant extent, in relation to an optimal reference value estimated at around 10 millinewton.

It is important to note how functionally according to the present invention there are two specific operating sections which work together to achieve the stated purposes:

a- a first section of the electronic / digital type designed to perform the optimal calibration of the detected force loaded on the spring 2;

b- a second electrical-mechanical section responsible for detecting the signature according to the layout affixed to the digital tablet 9.

Moreover, the dimensions of this microsensor 15 are of the order of a millimeter, that is to say the order of magnitude of a pencil tip, this characteristic means that it can be inserted in very small spaces and makes it ideal for application in spaces left free inside the pen.

This construction allows the calibration of the detection device in an accurate and reproducible way. For the translation of the detected signal into an electrical signal, a Wheastone resistance bridge is usually used, which outputs a sensitive and linearly proportional signal to the force itself. The implantation and preset techniques of the force sensor of the optical reflection type 15 can be the most varied. They are detectable directly from the data sheets of the manufacturer, for this reason they are not the subject of further study here.

In this different embodiment configuration the pen 1 is equipped with a series of components dedicated to the calibration operations. In particular, there will be a hold button 17, a display 16, a force sensor 15 of the optical reflection type, a micrometric washer 18, and a sliding cap 19 to have access to the micrometric washer itself.

The internal conformation of the pen 1 in this preferred embodiment which provides for calibration in real time, therefore comprises the manual ring regulator 18 with internal thread which advances or is withdrawn on the nut screw 26 due to the rotation as a micro-washer accessible inside the pen, to the user, once the sliding sleeve cap 19 has been lifted. The advancement or withdrawal of the micrometric washer 18 with respect to the spring 2 allows the force sensor 15 of the optical reflection type to be loaded, directly providing the measurement of the compression force exerted on the tip 5 subject to adjustment.

A zeroing procedure is foreseen for calibration. Over time, the value of '0' shown on display 16 may deviate by a few digits. This is caused by deformations of the spring 2 or the tip 5 of the pen, as well as variations in temperature, battery voltage and other aging factors. Usually this small variation is not significant for typical handwritten signature detections, it is however useful to optimize the procedure by minimizing the effect of spurious signals. To remove the error, the calibration step involves discovering the access to the micrometric screw 18 by lifting the cap 19 and always maintaining contact with the plane of the digitizing surface 9, producing a test signal which must be adjusted through the micrometric washer 18, at the same time producing a slide of the stylus 1 on the tablet 9.

At the same time as this transport operation of the stylus 1 on the tablet 9, the instrument is reset by rotating the micrometric washer 18 forward or backward until the display shows '0'. Access to the micrometric washer 18 is protected from inadvertent access by means of the cap 19 which is removed at the time of calibration and then returns to its position to protect the operation of the stylus. Moreover, the rotation of the micrometric washer 18 requires the application of a significant force that would not allow accidental rotation due to a banal rubbing on the washer itself.

In a further preferred embodiment of the present invention a tilting or tilting tablet is provided which allows simultaneous 360 ° indexing. This tilting tablet is provided with a hemispherical support element 30 capable of providing a calibrated oscillation referred to the axis perpendicular to the digitizing surface 9. A very precise positioning of the signature surface 9 is associated with this tablet thanks to a measurement taken direct, by means of an accelerometric sensor 22. The advantage of this configuration is that a high precision is obtained even for people who arrange the pen in an unusual way.

On the other hand, this leads to the advantage of a shorter learning time in calibration, a shorter preparation time and greater operational flexibility. This vectorial management, sui generis, makes it possible to detect and therefore control the angle of support of the pen 1 on the digitizing signature surface 9. The angle with which the surface itself must incline with respect to the point of contact is defined from the relative positions. on surface 9 by pen 1.

The integrated design of the self-pivoting tablet allows you to define an operational zero once and for all. The geometric compensation obtained eliminates the need to calibrate the force exerted by the spring 2 from time to time, if the diameter of the tip 5 of the pen 1 is changed due to wear or replacement of the same. The operator determines the working point on which to set the pen to obtain a specific surface inclination and thus extend the duration of the calibration. From here it is also advantageously obtained the function of compensating the wear of the tip 5 without the need to make replacements. This vector management, as specified below, also allows automatic control of the support angle with which the user must tilt the pen with respect to the contact point on the surface.

For this purpose, the central tilting constraint, without translation, of the tablet is configured, by means of a support hemisphere 30 - terminating at the top with the rectangular signature surface 9 - and of the embossed contours 31 ', 31 "of the surface signature 9 - figure 9 - with respect to the parallelepiped containment space obtained in the cabinet 8.

The purpose of this configuration is to optimize the arrangement of the signature surface 9 of the tablet with respect to the inclination of the pen 1 imposed by the person who is signing. In order to obtain a certain degree of freedom in the displacement (in any case constrained) of the digitizing surface 9 with respect to the external support 8, at the contour, a coupling with slight play between the two sections is provided, imperceptible to the user who in any case detects that the presence of a adaptation to the differently applied force based on varying boundary conditions. For this purpose, it is sufficient to allow a minimum possibility of translation - downwards or upwards - keeping the reference axis fixed between the support structure 8 and the signature surface 9. This slight play is however able to provide a angular displacement of 1 ° / 2 ° sufficient to provide an ideal incidence condition, perpendicular, between pen and surface.

To obtain this tilting - however constrained and of limited amplitude -, starting from the slight play of the centered position, it is sufficient to apply a significant pressure on any point of the digitizing surface 9 until reaching an interference condition on the terminal edges 31 ', 31 "of the translating section, which blocks the tilting effect.

In a different configuration in which the adjustment of the loading on the tip 5 is of the automatic type, with feedback, the signal detected 22 due to the tilting effect when the pen is placed on the tablet is transmitted to a data processor 21 comprising the firmware dedicated to processing and to output a signal which in turn can be re-entered into the closed-chain control to perform - in relation to the requirements of optimal signature detection - an interactive adjustment of the force exerted by the tip 5, on the digitizing tablet. This adjustment is based on the tilting movement of the signature surface 9, as a reference, in order to then be able to vary the force of the spring 2 on the tip 5 by commanding the advancement or withdrawal of the spring 2, still automatically.

In this way, one operates on a parameter indicative of the operating conditions of the spring 2 so as to regulate its load and, ultimately, the resistance of the pen opposed to the roughness of the tablet surface.

In order to be able to adjust the feedback / feedback level between the tilting function and the function of adjusting the load on the tip through the spring 2, an accelerometric microsensor 22 is used, designed to provide a measurement that is both precise and extremely sensitive in in relation to the extent of the initial support made by the user on the detection surface 9. This sensor makes it possible to detect variations in the inclination ranging from one degree up to one hundredth of a degree. At the same time it is extremely precise and fast in producing a signal that allows to work with the measurements relating to the detection of the forces that are involved in the tracing of the signature on the surface 9.

Prior to the signature tracking activity, it is useful to monitor the applied force so that the detection can be carried out with the highest possible precision.

The internal configuration of the pen 1 also in this embodiment is predisposed for real-time calibration. It comprises a manual ring regulator 18 which advances or is withdrawn on threaded screw 26, due to the rotation of the washer accessible externally to the pen 1 by the user.

The advancement or retraction of the ring of the micrometric washer 18 with respect to the spring 2 allows the force sensor 15 of the optical reflection type to be loaded, directly providing the measurement of the compression force exerted on the tip 5. Through a Wheastone bridge the measurement is converted into an electrical signal and digitized for the display.

The adjustment device 15 can be set (settable) by the operator based on the type of digitizing tablet, as well as based on the position of the pen 1 for each particular case. The acceptable force values can be derived from a table, stored and dynamically managed by means of an algorithm associated with the force sensor 15. The latter interfaces with a program for automatic control - resident in the processor unit 21 - which is able, by means of the dedicated transducer 15, to provide the corrections to be implemented in the detection of the signature by means of a variation of the force exerted by the spring 2. In fact, the tilting sensor unit 22 provides in real time a signal indicative of the effective load force exerted from the tip 5, on the signature surface 9, in the process of acquiring the natural signature by means of a digitizing tablet. The firmware residing in the memory unit - processor 21 on the one hand acquires information from the sensor 22 on the extent of tilting and at the same time intervenes on the calibration process, interactively providing a variation over time of the force to be applied on the spring 2 that presses the tip 5.

The functionalities of the force sensor 15 of the optical reflection type, according to the present invention, can be activated to provide signals indicative of one or more parameters associated with the state of pressure exerted by the spring 2.

In a particular embodiment, several signals are acquired simultaneously, both by the tilting sensor 22 and on the basis of the force exerted by the spring 2 on the tip 5, and they are interrelated and processed. These directly detectable signals are reported to a processor 21 which on the basis of a table system and a dedicated algorithm is able to interactively monitor the progress or better, ultimately, the lesser or greater grounding resulting from the tilting and therefore the amount of force to be exerted on the tip 5 by means of the spring 2.

In this embodiment, for calibration, the user is first asked to draw a (calibration) sign on the tablet, on the basis of which the reference force is obtained with which to obtain:

- the orientation of the tilting surface 9, e

- the indication of '0' on a display 16 with which to establish the baseline reference.

Advantages and industriality of the invention

By examining the characteristics of the natural signature tablet, also better clarified by the tables, it can be seen that all the problems listed are effectively solved. With a surface similar to that of paper, there is no need to exercise special precautions to control the movement of the hand. Shape, instantaneous speed and instantaneous pressure are very similar to those of an equivalent signature on paper and the graphologist can continue to use the evaluation criteria he knows well, in addition to the additional ones provided by the timing data of the graphometric signature.

The hand and wrist rest comfortably, making the shape of the signature more consistent with that on paper and making the signature experience more relaxing. Since the digitizing area is not recessed, you can hold the pen at the height you are used to. It is signed on a plane, as in the case of a sheet of paper placed on a plane. The graphic form of the digitized signature is very similar to that of the signature on paper, allowing a good first evaluation even to the general observation of an operator without graphological knowledge. Moreover, the graphological expert can also compare, with a certain reliability, a digitized graphometric signature with a pre-existing signature on paper.

Claims (12)

CLAIMS 1. Touch Screen digitizing tablet for natural signature acquisition consisting of a tracing section consisting of a pen (1) and a fixed section consisting of a containment body (8) of a signature surface (9), under the which is arranged the display with touch panel sensor, characterized by the fact that the upper surface (6) of the cabinet (8) is completely coplanar with the digitizing surface (9), flush with the upper section of the cabinet (8) without any continuity solutions between the signature area (9), and the rest of the upper surface of the containment body (8), e from the fact that the tip (5) of the pen (1) is elastically suspended from a spring (2), inside the body of the pen (1), with a constant of force and a maximum stroke that simulate the softness of the paper, called pen (1) providing a replaceable tip (5), with more or less rounded conformations to respectively allow greater or lesser smoothness, the user adopting the tip (5) that he deems most comfortable, based on how the tablet is used such as placement, on a table, and the type of people who will have to sign, said digitizing tablet presenting two different structures and types of positioning in which: a- the cabinet (8) with the signature surface (9) is embedded in the table top, inside a parallelepiped perforation prepared with the signature surface (9) exactly level with the table, or, b- the upper surface (6) of the tablet is raised with respect to the table top, and has an inclination that makes the position of the hand natural during the signature, allowing to rest the wrist partly on the tablet and partly on the table top, according to the size of the hand , the storage cabinet (8) being configured as a semi-parallelepiped body obtained by bisection of a rectangular paralleliped, with a diagonal symmetry plane that gives the structure an inclined conformation with a rear area (10) in relief and a front area in relief null, level with the support table. 2. Digitizing tablet of the Touch Screen type for acquisition of the natural signature according to claim 1 characterized in that the signature surface (9, A) is configured asymmetrically, at the top on the plane of the containment body (8) and close to the rear side (10) of the body itself making sure that, towards the front side of the cabinet, there is a large surface (B) on which to place the hand during the signature. 3. Digitizing tablet of the Touch Screen type for acquiring the natural signature according to each of the preceding claims characterized by the fact that the signature surface (9) is made of finely embossed plastic material, thereby making the surface less smooth, the signature resulting more natural and the graphometric characteristics resulting very similar to those of the signature on paper. 4. Touch Screen digitizing tablet for acquiring the natural signature according to each of the preceding claims characterized by the fact that the entire front of the device is self-adhesive, to be replaced by tearing it off and attaching a new one. 5. Digitizing tablet of the Touch Screen type for acquiring the natural signature according to each of the preceding claims characterized in that the tip (5) of the pen (1) assumes the shape of a cone preferably, 3.7 mm high, and diameter of base 3 mm, terminated by a hemisphere with a radius of 0.2 mm, this radius of the tip being much greater than the average size - 1.6 microns - of the roughness of the signature surface (9). 6. Digitizing tablet of the Touch Screen type for acquiring the natural signature according to each of the preceding claims, characterized by the fact that the cabinet requires the provision of a recess in the table corresponding to the parallelepiped shape of the cabinet itself (8), allowing its subsequent insertion the execution of a simple rectangular hole (11), with the presence, all around the upper edge (8) of the tablet, of a protruding edge (12) designed to cover the gap that remains between the table top and the cabinet ( 8) along the perimeter of the cut area. 7. Digitizing tablet of the Touch Screen type for acquisition of the natural signature according to each of the preceding claims, characterized in that for the cabinet of type a) the output of two cables (14a and 14b) respectively is configured in the rear part 10 of the tablet for the USB connection with the computer and for the connection of the pen (1), said two cables (14a and 14b) being directed downwards providing between their output and the upper surface of the tablet, a distance of the order of 20 mm . 8. Digitizing tablet of the Touch Screen type for acquisition of the natural signature according to the preceding claim 7 characterized in that if the table top has a thickness of less than or equal to about 20 mm, the cables come out under the table by means of a rectangular hole, of suitable size. 9. Digitizing tablet of the Touch Screen type for acquisition of the natural signature according to claim 7 characterized by the fact that in the case in which the thickness of the top is greater than 20 mm, the cables (14a and 14b) the tablet finds its own positioning by means of of an adequate hole of such depth as to leave 20 mm of material between the bottom of the hole and the top surface of the top, the cable (14b) that connects the pen to the tablet, and which comes out under the top, being passed through the top of the table by means of a hole protected by a normal rubber grommet. 10. Digitizing tablet of the Touch Screen type for acquisition of the natural signature according to each of the preceding claims characterized by the fact of comprising a tilting and tilting signature plane (9), which allows simultaneous 360 ° indexing, having a shape (30) hemispherical at the bottom able to provide an oscillation referable to the axis perpendicular to the digitizing surface (9), the tilting without translation of the signature plane (9), being delimited by the contours in relief (31 ', 31 ") with respect to the edges of the containing parallelepiped obtained in the cabinet (8), in order to obtain a certain degree of freedom in the displacement of the digitizing surface (9) with respect to the external support 8, on the edge, a coupling with slight play being provided between the two sections (8, 9) constitutive, which ends in the interference of said contours in relief with the upper edges of the containing parallelepiped obtained in the mo bed (8). 11. Digitizing tablet of the Touch Screen type for acquisition of the natural signature according to each of the preceding claims characterized in that the tracing pen (1) comprises a hold button (17), a display (16), a force sensor of the type optical reflection (15), a micrometric washer (18), and a cap (19) to have access to the micrometric washer itself, the shape of the pen (1) providing for the calibration in real time, the manual washer regulator being included ( 18) which advances or is withdrawn on a threaded shaft (26) accessible once the cap (19) has been lifted, the advancement and withdrawal of the micrometric washer (18) with respect to the spring (2) allows to load a force sensor of optical reflection type (15) providing directly the measurement of the compression force exerted on the tip (5). 12. Digitizing tablet of the Touch Screen type for acquisition of the natural signature according to each of the preceding claims characterized by the fact of comprising a microprocessor for the automatic adjustment, with feedback, of the signal detected due to the tilting effect when the pen is placed on the tablet, to perform an optimal detection of the signature through an interactive adjustment of the force exerted on the digitizing tablet according to the tilting movement, to vary the force exerted by the spring (2) on the tip (5).