Background of the Invention Technical Field The present invention relates generally to a system and method for controlling a cursor on a display screen, and more particularly to use of an acoustic based pointing device for controlling the cursor on the display screen.

Related Art A commercially available wireless pointing device exploits the gyroscopic effect. Consequently, such commercially available wireless pointing devices rely on the rotation of the pointing device which makes these pointing devices very unintuitive and inhibits the ability to track the positions of these pointing devices. Additionally, these pointing devices are fundamentally heavy since they need a large mass in order to exploit conservation of angular momentum.

Accordingly, there is a need for wireless pointing device that eliminate the aforementioned disadvantages of commercial wireless pointing devices that are currently available.

Summary of the Invention A first embodiment of the present invention provides a method for controlling a cursor on a display screen, comprising: detecting an acoustic signal at four microphones Ml, M2, M3, and M4, the four microphones being at fixed positions and the acoustic signal being propagated from a wireless pointing device having an acoustic source located at a position Po having an associated position vector Po, wherein Po is yet to be calculated; converting the acoustic signal detected at microphone Mi to a periodic electrical signal Si, for i=l, 2,3, and 4; calculating Po by solving triangulation equations that comprise a dependence on a phase-shift time delay between Si and Sj, for j=2, 3, and 4;

computing a position vector Pc for the cursor, wherein Pc depends on: Po, a scale vector A, and a shape function of the display screen; and positioning the cursor at a position Pc associated with the position vector Pc.

A second embodiment of the present invention provides a system for moving a cursor on a display screen, comprising: a display device having the display screen; four microphones Ml, M2, M3, and M4 at fixed positions; a wireless pointing device having an acoustic source, wherein the acoustic source is located at a position Po having an associated position vector Po, wherein the acoustic source is adapted to generate and propagate an acoustic signal, wherein the microphone Mi is adapted to detect the acoustic signal, and wherein the acoustic signal detected at the microphone Mi is adapted to be converted to a periodic electrical signal Si, for i=l, 2,3, and 4; a computing system to which the cursor, S1, S2, S3, and S4 are each electrically coupled, wherein the computing system is adapted to calculate Po by solving triangulation equations that comprise a dependence on a phase-shift time delay between Si and Sj, for j=2, 3, and 4, and wherein the computing system is adapted to compute a position vector Pc for the cursor such that Pc depends on: Po, a scale vector A, and a shape function of the display screen; and means for positioning the cursor at a position Pc associated with the position vector Pc- A third embodiment of the present invention provides a pointing device, said pointing device being wireless and comprising an acoustic source, wherein the acoustic source is adapted to generate and propagate an acoustic signal comprising a plurality of frequency components.

A fourth embodiment of the present invention provides a computing system, comprising: an output interface for controlling a display device having a display screen; an input interface for receiving a periodic electrical signal S ;, for i=l, 2,3, and 4 from four microphones Mi, M2, M3, and M4 located at fixed positions, each of the four microphones being able to detect an acoustic signal from a wireless pointing device having an acoustic source located at a position Po having an associated position vector Po ; and a control unit able to calculate Po by solving triangulation equations that comprise a dependence on a phase-shift time delay between Si and Sj, for j=2, 3, and 4, able

to compute a position vector Pc for the cursor such that Pc depends on: Po, a scale vector A, and a shape function of the display screen, and able to use the output interface to position the cursor at a position Pc associated with the position vector Pc.

The present invention provides a pointing device that eliminates the disadvantages associated with commercial wireless pointing devices that are currently available. For example, the acoustic based pointing device of the present invention is or may be: wireless, accurate, lightweight, hand held, and easily tracked with respect to its motions and spatial positions. Additionally, the user is able to use the pointing device of the present invention in a way that is analogous to use of a conventional computer mouse with the added advantage that the pointing device of the present invention is wireless.

Brief Description of the Drawings FIG. 1 depicts a three-dimensional view of a first embodiment of a system for controlling a cursor on a display screen of a display device, in accordance with embodiments of the present invention.

FIG. 2 depicts a three-dimensional view of a second embodiment of a system for controlling a cursor on a display screen of a display device, in accordance with embodiments of the present invention.

Detailed Description of the Invention FIG. 1 illustrates a three-dimensional view of a first embodiment of a system 10 for controlling a cursor 40 on a display screen 14 of a display device 12, in accordance with embodiments of the present invention. FIG. 1 shows a three-dimensional cartesian coordinate system having three mutually orthogonal axes identified as X, Y, and Z axes having a coordinate origin at the point 50. The Z axis is oriented in a"depth"direction into or out of the display screen 14 as perceived by a viewer who is viewing the display screen 14.

The X and Y axes define a plane, namely the X-Y plane, such that the Z axis is normal to the X-Y plane If the display screen 14 has a planar shape, then the display screen 14 is parallel to the X-Y plane. The present invention accounts for the shape of the display screen 14, regardless of whether the display screen 14 is planar or non-planar. Any vector shown in FIG. 1 is a three dimensional vector having components along the X, Y, and Z axes. The system 10 comprises the display device 12, a pointing device 20, four microphones denoted as Ml, M2, M3, and M4, and a computing system 30.

The display device 12 is capable of receiving an image in electronic form and displaying the image visually on the display screen 14. The display device 12 may comprise, inter alia, a television, a computer monitor, etc.

The pointing device 20 is capable of controlling motion of a cursor 40 on the display screen 14 of the display device 12. The pointing device 20 may comprise, inter alia, a mouse. The pointing device 20 includes an acoustic source 22 that is adapted to continuously <BR> <BR> generate and propagate an acoustic signal 28 (i. e. , longitudinal acoustic waves) through the ambient atmosphere. The acoustic source 22 has an associated wave front 26. The acoustic source 22 is at a position Po with an associated position vector Po. FIG. 1 also shows the acoustic source 22 at a reference position Po, REF with an associated position vector Po, REF.

Vectors Po and Po, REF each have a component along each of the X, Y, and Z axes.

The cursor 40 is at a position Pc having an associated position vector Pc, as measured from the coordinate origin 50. The position Pc may be on the display screen 14, or "behind"the display screen 14 to simulate an apparent depth of the cursor 40 relative to the display screen 14. For the case of no apparent depth, Pc and Pc trace a path on the surface of the display screen 14 as the cursor 40 moves. FIG. 1 also shows the cursor 40 at a position that has an associated reference position vector PC, REF-For simplicity, PC, REF may be chosen to be on the display screen 14. Vectors Pc and PC, REF each have a component along each of <BR> <BR> the X, Y, and Z axes. PC, REF corresponds to Po, REF (i. e. , the cursor 40 is at the reference screen position vector Pc, REF when the acoustic source 22 is at the reference position Po, REp).

The microphones Ml, M2, M3, and M4 are at positions Pi, P2, P3, and P4 with associated position vectors Pl, P2, P3, and P4, respectively. Pi, P2, P3, and P4 each have a component along each of the X, Y, and Z axes. While FIG. 1 shows the microphones Ml, M2, M3, and M4 to be positioned in a particular geometric arrangement on a surface of the display device 12, the microphones Ml, M2, M3, and M4 may be in any geometric arrangement relative to one another such that no three of Ml, M2, M3, and M4 are colinear. Each of the microphones Mi, M2, M3, and M4 may be independently located on, within, or outside of the display device 12.

The computing system 30 may comprise at least one semiconductor chip that has hardware-encoded algorithms. Alternatively, the computing system 30 may comprise a memory and processor (e. g. , a computer) for storing and executing software, respectively.

The computing system 30 is electrically coupled to the cursor 40 through an electrical path 32 (e. g. , electrical wiring), which enables the computing system 30 to control the motion and

position of the cursor 40. While FIG. 1 shows the computing system 30 to be located within the display device 12, the computing system 30 could be located on, within, or outside of the display device 12.

The acoustic source 22 continuously generates and propagates the acoustic signal 28. The microphones Ml, M2, M3, and M4 are each adapted to detect the acoustic signal 28. The acoustic signal 28 detected at the microphones Mi is adapted to be converted <BR> <BR> to a periodic electrical signal (e. g. , an alternating current sinusoidal signal) Si, for i=l, 2,3, and 4. Each electrical signal of the electrical signals Sl, S2, S3, and S4 is phase-shifted with respect to another signal of the electrical signals Sl, S2, S3, and S4, as a consequence of the difference in magnitude of the distance between the acoustic source 22 at the position Po and each of the positions Pi, P2, P3, and P4 of the microphones Ml, M2, M3, and M4, respectively.

The electrical signals Si, S2, S3, and S4 so generated are each electrically coupled to the computing system 30. If the pointing device 20 has been moved to the position Po corresponding to the associated position vector Po, then the cursor 44 must be moved to its position Pc corresponding to its associated position vector Pc. The computing system 30 is adapted to calculate the position vector Po of the acoustic source 22, by processing the electrical signals S1, S2, S3, and S4. For example, the computing system 30 may calculate Po by solving the triangulation equations jPi-Po)-tPj-Po)-CATij (1) for j=2, 3, and 4. ATij is defined as a phase-shift time delay between electrical signals S1 and Sj, for: i=l, 2,3, 4; j=l, 2,3, 4; and ixj. C is the speed of the acoustic signal 28 in the ambient atmosphere. Equations (1) comprise three equations corresponding to j = 2,3, and 4, which may be solved simultaneously for the three unknowns Pox, Poy, and Poz by any computational method known to a person of ordinary skill in the art of numerical analysis and computation. If the Equations (1) have two solutions for position Po, the sign of the phase-shift time delay may be used to determine the correct Po. Alternatively, if only one of the two solutions for position Po is in front of the display device 12, this one solution may be determined to be the correct Po. The unknowns Pox, Poy, and Poz are the components of the position vector Po along the X, Y, and Z axes, respectively. Note that the scope of the present invention includes any mathematically equivalent form of Equations (1), and includes any other applicable triangulation technique known to a person of ordinary skill in the art. If the computing system 30 comprises at least one semiconductor chip, then the solution to Equations (1) may be hardware-encoded within the at least one semiconductor chip. If the computing system 30 comprises a memory and processor (e. g. , a computer), then a solution

algorithm for Equations (1) may be stored as software (e. g. , as a computer program) in said memory and said software may be executed by said processor.

Following calculation of the position vector Po of the acoustic source 22, the vector position Pc of the cursor 44 is calculated via the equations Pcx = Pcx, REF + Ax (Pox-POX, REF) (2A) PcY= PCY, REF + Ay (Poy-POY, REF) (2B) Pcz= PCZ, REF + Az (Poz-POZ, REF) + (Zs (Pcx, PcY)-Pcz, REF) (2C) Pcx, Pcyp and Pcz are the components of Pc along the X, Y, and Z axes, respectively. PCX, REF and PcY, REF and Pcz, REF are the components of PC, REF along the X, Y, and Z axes, respectively. Pox, REF and POY, REF and Poz, REF are the components of PO, REF along the X, Y, and Z axes, respectively. Pcz, REF is assumed to describe a reference coordinate of the cursor 44 on the surface of the display screen 14. ZS (Pcx, Pcy) is the Z coordinate of the cursor 44 on the surface of the display screen 14 at Pcx and Pcy (i. e. , at the X and Y coordinates of the cursor 44). Generally, Zs (X, Y) is the Z coordinate of the surface of the display screen 14 as a function of X and Y. Thus, ZS (X, Y) is a"shape function"the display screen 14. If the display screen 14 is planar, then ZS (PCX, PCY) = PCZ, REF (i. e. , the shape function is"flat") and Equation (2C) for Pcz simplifies to Pcz= Pcz, REF + Az (Poz-POZ, REF), which is of the same form as Equations (2A) and (2B) for Pcx and Pcy, respectively.

However, the display screen 14 may be non-planar such that ZS (X, Y) is not constant and Zs (Pcx, Pcy) w PCZ, REF ((i. e. , the shape function is"not flat"). The scope of the present invention includes any mathematically equivalent form of Equations (2A), (2B), and (2C).

Following calculation of Pc, the cursor 44 is moved to the position Pc in response to movement of the pointing device 20 to the position Po. The physical motion of the cursor 44 to the position Pc is accomplished by using any electronics and hardware that is known to a person of ordinary skill in the art. The quantities Ax, Ay, and Az are components of a scale vector A and are scale factors in the X, Y, and Z directions, respectively; i. e. , the scale vector A governs the magnitude of the movement of the cursor 44 in response to the corresponding movement of the pointing device 20. In accordance with Equations (2A) and (2B), Ax and Ay govern motion of the cursor 44 in the X-Y plane. In accordance with Equation (2C), (ZS (Pcx PCY)-PCZ, REF) is the change in the Z coordinate of the cursor 44 from the reference cursor Z-coordinate Pcz, REF, due to the non-planarirty of the shape of the surface of the display screen 14. Also in accordance with Equation (2C), Az governs motion of the cursor 44 in an"apparent depth" (i. e. , along the Z axis). Since, the cursor 44 cannot physically move away from the display screen 14, the motion of the cursor 44 in the depth

direction is apparent, rather than real, in light of the ability of human vision to perceive depth in relation to a visual image that appears on the display screen 14. The scale factors Ax, Ay, and Az may be constants that have been determined prior to the calculation of Pc via Equation (2A), (2B), and (2C). Alternatively, Ax, Ay, and Az may be spatially dependent in order to simulate scaling that varies with spatial location of the cursor 44.

As a first example, a scale factor Ax of 0.5 cm/inch denotes that the cursor 44 moves 0.5 cm in the X direction per inch of movement of the acoustic source 22 (and thus also the pointing device 20) in the X direction. As a second example, a scale factor Ax of 0.1 inch/inch denotes that the cursor 44 moves 0.1 inches in the X direction per inch of movement of the acoustic source 22 (and thus also the pointing device 20) in the X direction.

As a third example, a scale factor Ax of 600 pixels/inch denotes that the cursor 44 moves 600 pixels in the X direction per inch of movement of the acoustic source 22 (and thus also the pointing device 20) in the X direction. The preceding examples also apply analogously for Ay and Az in relation to motion in the Y and Z directions, respectively, while recognizing that the depth motion of the cursor 44 in the Z direction is apparent motion rather than real motion.

The case of Az = 0 restricts all motion (i. e. , real and apparent motion) of the cursor 44 to the surface of the display screen 14, with no motion in the depth direction (i. e., behind the display screen 14). Thus if Az = 0, any motion of the acoustic source 22 (and thus also the pointing device 20) in the Z direction (or the-Z direction) will have no effect on the position of the cursor 44 on the display screen 14. In order for the cursor 44 to have apparent motion away or toward the display screen 14, the condition Az 0 0 must be satisfied.

The acoustic source 22 could generate the acoustic signal 28 at any acoustic frequencies. It is beneficial, however, for the acoustic source 22 to generate the acoustic signal 28 at frequencies above those frequencies that can be heard by a human being (i. e., above about 20kHz). Additionally, the phase-shift time delay period ATij (defined supra) should be less than the period T of the acoustic signal 28 so that ATij could be unambiguously calculated from comparison of the electrical signals S1 and Sj (for j = 2,3, and 4). It is noted that sound travels in air at room temperature at a speed (C) of about 1100 ft/sec, so that a value of 1 ft for (| Pl-Po l-| P2-Po |) has an associated phase-shift time delay period AT12 of less than 1 msec (see Equation (1) ). Since a frequency of 20kHz has a period of 50 microseconds, the acoustic signal 28 should include at least two discrete frequencies. For example, a composite signal of two frequencies, whose periods are 47 microseconds and 49 microseconds, would have a period of about 2.3 msec. As another example, a composite

signal of three frequencies, whose periods are 43 microseconds, 47 microseconds, and 49 microseconds, would have a period of about 99 msec. Thus, at frequencies of at least about 20 kHz, the acoustic signal 28 should have at least two frequency components. At frequencies of at least about 20 kHz with the acoustic signal 28 having at least three frequency components, the present invention would benefit from having the period T of the acoustic signal 28 substantially larger than the phase-shift time delay periods ATij (i=l, 2,3 and j=l, 2,3 and inj).

If the microphones Mi, M2, M3, and M4 are able to detect a range of acoustic frequencies, then the microphones MI, M2, M3, and M4 could potentially detect frequencies other than those frequencies present in the acoustic signal 28, which may cause erroneous calculations of the phase-shift time delay periods ATij (i=l, 2,3 and j=l, 2,3 and i#j).

Accordingly, filters Fl, F2, F3, and F4 (see FIG. 1) may be used to filter the electrical signals Sl, S2, S3, and S4, respectively, so as to remove from S1, S2, S3, and S4 all frequency components except those frequency components present in the acoustic signal 28.

FIG. 2 illustrates a three-dimensional view of a second embodiment of a system 10 for controlling a cursor 40 on a display screen 14 of a display device 12, in accordance with embodiments of the present invention. In this embodiment, the four microphones Ml, M2, M3, and M4 are at fixed positions such that no four of the positions of MI, M2, M3, and M4 are coplanar. This is illustrated by providing the microphone M3 on top of the system 10 instead of at the front-side of the system 10. Although in FIG. 2, the four microphones Ml, M2, M3, and M4 are also at fixed positions such that no three of the positions of MI, M2, M3, and M4 are colinear, this is not required if no four of the positions of MI, M2, M3, and M4 are coplanar.

Although the embodiments described herein disclose four microphones, namely Ml, M2, M3, and M4, the scope of the present invention includes N such microphones such that N>4. IfN>4 then the extra N-4 microphones could be used to, inter alia, infer more than one value of the position Po of the pointer device. Said multiple computed values of Po could be averaged to such that the resulting average value of Po has improved statistical accuracy as compared with Po that would be inferred from exactly four microphones.

While embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention. Computer program'is to be understood to mean any software product stored on a computer-readable medium, such as a floppy disk, downloadable via a network, such as the Internet, or marketable in any other manner.