Embodiments of the present invention relate to a touch position determining device and method, and to an electronic touch-sensitive device. In the ensuing treatment, particular reference will be made, without this implying any loss of generality, to the field of touch-sensitive display devices (touch displays), i.e., devices where functions are activated by mere physical contact.
As is known, the use of electronic devices provided with touch displays, which enable a user to activate given functions via a physical contact (touch) on pre-set points of a corresponding display screen, is increasing. The contact can be originated directly by the touch of a user's finger, or else can occur via a purposely provided input device, such as for example a stylus. Touch displays are provided with touch position determining devices, configured to determine the position of contact in terms of coordinates in the plane in which the display screen lies, and to transmit the position to the corresponding electronic device, in such a manner that it will issue a command for activation of corresponding functions.
A wide range of touch position determining devices are currently known, which are based principally on three technologies: capacitive technology, resistive technology, and ultrasound technology. In any case, the production of the determining devices involves complex additional processing steps in the manufacturing process of the display devices, with considerable repercussions on the manufacturing costs.
In detail, in the case of capacitive technology, an array of electrostatic capacitances is formed together with a pixel array of the display device. The array of electrostatic capacitances is constituted by electrodes made of transparent metallic material (for example, ITO—Indium Tin Oxide) so as not to be evident to the user. The physical contact on the screen causes a local variation of the capacitance value in the area in which the contact has occurred. An electronic circuit detects the capacitance variation and determines the position of contact. This solution is expensive, and is not in any case altogether invisible to the user, who perceives, in fact, a certain degradation in the quality of the images displayed. Consequently, this solution can be implemented only in applications in which image resolution and quality are not constraining design characteristics.
Resistive technology envisages formation of an array of transparent metallic wires (made, for example, of ITO), whose resistance value is altered by a touch on the display screen. The determining devices employing this technology are widely used, for example, in the aeronautic sector, but the array of metallic wires is visible to the naked eye, and consequently also in this case a non-negligible degradation in the quality of the displayed images occurs.
Ultrasound technology envisages generation of surface acoustic waves with a frequency equal to some tens of megahertz, which distribute with a given pattern over the surface of the display screen. The physical contact determines a local variation of this pattern, from which it is possible, by means of appropriate algorithms, to trace the position at which the contact has occurred. The acoustic waves are generated by a first set of piezoelectric transducers, whilst a second set of piezoelectric transducers, located in appropriate positions of the display screen, detects the pattern of acoustic waves and its alterations. This solution, unlike the ones previously described, is of an active type; i.e., it requires continuous generation of a pattern of acoustic waves on the surface of the display screen, with a consequent considerable expenditure in terms of energy.
An aim of embodiments of the present invention is consequently to provide a touch position determining device and method which is free from the drawbacks outlined above and, in particular, which is simple to produce at contained costs and, at the same time, has a high degree of precision in determining the position of contact.
For a better understanding of the present invention, embodiments thereof are now described purely by way of non-limiting example, with reference to the attached drawings, wherein:
The following discussion is presented to enable a person skilled in the art to make and use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
The touch panel 1 is made of a rigid material, for example, glass, wood or plastic, and has an outer contact surface 1a, on which contacts are generated, and an inner surface 1b. The outer contact surface 1a lies in a plane xy, and the points belonging to the outer contact surface 1a are univocally defined in a two-dimensional coordinate system (x, y). In particular, the mechanical characteristics of the touch panel 1 are such as to enable propagation of mechanical vibrations, advantageously in an isotropic manner (i.e., irrespective of the direction of propagation).
The touch position determining device 2 comprises a plurality of vibration sensors 4, in particular accelerometer sensors, fixedly coupled to the touch panel 1, and a processing circuit 6, of an electronic type, connected to the vibration sensors 4. Conveniently, the vibration sensors 4 are fixed (for example, bonded) to the inner surface 1b of the touch panel 1 so as to not be accessible to the user and so as to prevent any risks of manipulation and failure. In particular, for reasons that will be clarified hereinafter, the number of vibration sensors 4 is not less than three.
The processing circuit 6 comprises an interface stage 7, configured to acquire vibration signals generated by the vibration sensors 4, and a processing stage 8, connected to the interface stage 7 and configured to carry out, as will be described in detail hereinafter, appropriate processing operations from the vibration signals, in order to determine the position of the contact on the outer contact surface 1a.
General operation of the touch position determining device 2 is described in what follows (reference is made also to
A touch in a point of contact P1(x, y) of the outer contact surface 1a generates a pattern of mechanical vibrations, designated as a whole by 9 in
The vibration sensors 4 detect (block 10) the mechanical vibrations 9 generated by the touch. In particular, detection of the mechanical vibrations 9 by the various vibration sensors 4 occurs at detection times that differ according to the position of the vibration sensors 4 and to their distance from the point of contact P1(x, y) (in particular, the term “detection time” is used to indicate the instant at which a vibration sensor 4 detects the mechanical vibrations 9).
The processing stage 8 receives the vibration signals generated by the vibration sensors 4, processes them (blocks 11-13) using an appropriate algorithm based on the time of flight, i.e., on the difference between the detection times of the various vibration sensors 4 (or, in a similar manner, between the times of arrival of the mechanical vibrations 9 in positions corresponding to the vibration sensors 4), and determines the position of the contact (block 14), in terms of coordinates (x, y) within the outer contact surface 1a.
In detail, at least three vibration sensors 4 are used to univocally obtain the position of the contact by means of an algorithm based on the time of flight.
Let P1(x, y) (see, in particular,
Given that the propagation of the mechanical vibrations 9 through the touch panel 1 occurs isotropically, the following relation applies: t3>t2>t1. Then, the processing stage 8 calculates (block 11) the temporal differences (in absolute value, i.e., without the information of sign) t2−t1, t3−t1 and t3−t2 between the detection times of all the possible pairs formed by the vibration sensors 4. From these temporal differences, given that the speed of propagation of the mechanical vibrations 9 is known, the processing stage 8 calculates the corresponding distance differences d2−d1, d3−d1 and d3−d2 between the distances of the point of contact P1(x, y) from the vibration sensors 4 belonging to each pair. Then, the processing stage 8 associates to each of the distance differences (block 12) a locus of points in the plane xy that are equivalent as regards the time of flight (i.e., they give rise to the same temporal difference between the times of detection of the mechanical vibrations 9 by the vibration sensors 4 of the pair). In particular, the locus of points is a hyperbola having as focuses the positions of the two respective vibration sensors 4′, 4″, 4′″ of the pair. The hyperbola is in fact by definition the locus of the points whereby the difference of the distances from two fixed points referred to as focuses is constant. Accordingly, the processing stage 8 identifies: a first hyperbola I1 having as focuses the first vibration sensor 4′ and the second vibration sensor 4″, a second hyperbola I2 having as focuses the first vibration sensor 4′ and the third vibration sensor 4′″, and a third hyperbola I3 having as focuses the second vibration sensor 4″ and the third vibration sensor 4′″. As illustrated in
In particular, just two vibration sensors 4′, 4″ are not sufficient to univocally determine the point of contact P1(x, y): in fact, the algorithm described, on the basis of the only difference t2−t1 between the detection times of the two vibration sensors, would lead in this case to determination of a locus of points (i.e., the hyperbola having as focuses the positions of the two vibration sensors 4′, 4″) that are absolutely equivalent, and hence are indistinguishable as regards the time of flight.
Furthermore, the effective position of the vibration sensors 4 with respect to the touch panel 1 is not a determining factor for the purposes of the algorithm described, and consequently the vibration sensors 4 can be arranged at arbitrary positions (provided that they are arranged, however, in the proximity of the periphery of the touch panel 1), according, for example, to specific production requirements.
Advantageously, the number of vibration sensors 4 used for determining the point of contact P1(x, y) can be greater than three. In particular, if at least four vibration sensors 4 are used, the intersection of the hyperbolas identified as previously described is just one (in a position corresponding to the point of contact P1(x, y)). In this case, consequently, it is not necessary to arrange the vibration sensors 4 in the proximity of the edges of the touch panel 1 (thus, the vibration sensors 4 can be arranged in an altogether arbitrary manner with respect to the touch panel 1), and the processing stage 8 does not carry out any further processing operations beyond determination of the intersection, in order to identify the point of contact P1(x, y).
Texts, icons, or other graphic signs are displayed on the display screen 17, and to each of them is associated a given function of the electronic device 15 or a given visualization on the display screen 17. A touch on the outer contact surface 1a generates mechanical vibrations which propagate towards, and are detected by, the vibration sensors 4. The processing circuit 6 (
Various embodiments of the touch position determining device have the following advantages, with all such advantages not necessarily being present in all embodiments and not limiting the scope of the appended claims.
In the first place, embodiments of the present invention do not entail any complex and costly additional manufacturing steps, in so far as the vibration sensors 4 can be applied in a simple manner at the end of the manufacturing process of any display device or of a generic electronic device. Furthermore, the presence and provision of electrodes and/or wires that would be visible to the naked eye, thus jeopardizing the quality of display of the images, is not necessary.
The spatial resolution with which the position of contact is determined is high. In fact, considering a typical speed of propagation of mechanical vibrations of 3.5 km/s, to have a spatial resolution Δx of 1 mm, it is necessary for the electronic circuit 6 to appreciate a temporal difference Δt between the detection times of the various vibration sensors 4 of:
It is consequently necessary to discriminate the time of flight with a precision in the region of a microsecond, a temporal difference that is altogether compatible with the electronics available on the market.
The power consumption is reduced, in so far as the determining device is of a passive type and does not envisage continuous generation of a pattern of acoustic waves. The determining device is sturdy and not easily subject to damage.
In addition, use of a number of vibration sensors 4 greater than three (for example, four vibration sensors) is advantageous in so far as the point of intersection between the various hyperbolas is unique.
Finally, it is clear that modifications and variations may be made to what is described and illustrated herein without thereby departing from the scope of the present invention, as defined in the annexed claims.
In particular, if a number of vibration sensors 4 equal to three is used, the problem of the non-uniqueness of the intersection between the various hyperbolas I1-I3 can be solved in an alternative way, without arranging the vibration sensors 4 in the proximity of the edges of the control panel 1. In detail, the processing stage 8 (
The vibration sensors 4 may be microphones or piezoelectric sensors, instead of accelerometer sensors, or in any case sensors of movement capable of detecting the presence of the vibrations generated by the touch on the contact surface.
The described device can advantageously be applied in numerous other applications, for example, in the field of toys, for making a light-up board that changes color or lights up where a contact has occurred (the coordinates of contact being determined as previously described). In this case, the touch panel 1 is constituted by the same light-up board, or by an outer casing thereof.
The touch position determining device can advantageously be used not only in display devices of an LCD type, but also to make touch sensitive display devices of any other type (for example, Cathode Ray Tube (CRT), Organic Light Emitting Diode (OLED), etc.).
The arrangement of the vibration sensors 4 can be different; for example, they can be fixed to the outer contact surface 1a, instead of to the inner surface 1b. The vibration sensors 4 can also be directly fixed to the screen 17 of the display device 16, without any need for providing any additional touch panel.
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention.
Number | Date | Country | Kind |
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TO2005A000569 | Aug 2005 | IT | national |
The present application is a national phase application filed pursuant to 35 USC § 371 of International Patent Application Serial No. PCT/EP2006/065163, published in English, filed Aug. 8, 2006; which application claims the benefit of Italian Patent Application Serial No. TO2005A000569, filed Aug. 9, 2005; all of the foregoing applications are incorporated herein by reference in their entireties.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/065163 | 8/8/2006 | WO | 00 | 6/5/2009 |