WO2008048036A1

WO2008048036A1 - Method and apparatus for tracking 3-dimensional position of the object

Info

Publication number: WO2008048036A1
Application number: PCT/KR2007/005063
Authority: WO
Inventors: Do Young Ko; Jae Jun Lee
Original assignee: PNF Co Ltd
Current assignee: PNF Co Ltd
Priority date: 2006-10-17
Filing date: 2007-10-16
Publication date: 2008-04-24
Anticipated expiration: 2009-04-17
Also published as: KR100813998B1

Abstract

Provided is a 3D position tracking method and apparatus. The 3D position tracking method and apparatus measures a 3D position of a signal generator by using distances between a signal generator and ultrasonic signal receivers calculated by using differences between a time at which an ultrasonic signal is generated by the signal generator and times at which the ultrasonic signal is received to the ultrasonic signal receivers that are disposed at predetermined intervals to receive the ultrasonic signal, and distances between the ultrasonic signal receivers. Accordingly, a 3D position of a moving object in a 3D space can be accurately measured without excessive costs, and a 3D position tracking method and apparatus according to the present invention can be applied to a 3D mouse, a 3D pointer, a 3D video game input device, and the like.

Description

METHOD AND APPARATUS FOR TRACKING 3-DIMENSIONAL POSITION OF THE OBJECT

Technical Field

[1] The present invention relates to a position tracking method and apparatus, and more particularly, to a method and apparatus for tracking a 3D position of an object moving in a 3D space by using ultrasonic waves. Background Art

[2] Conventionally, methods of tracking a 3D position of an object and apparatuses applying the methods are disclosed. As examples of disclosed 3D position measuring apparatuses, apparatuses for measuring a 3D position by providing a gyro sensor to an inside of an object, measuring gyro sensor values according to movements of the object in a 3D space, and calculating 3D coordinates of the object by using the gyro sensor values are disclosed.

[3] However, in the apparatus using the gyro sensor, accuracy of the 3D position measurements of the object depends on precision of the gyro sensor. Therefore, for the accurate measurements, a high-cost gyro sensor with high precision has to be used. Accordingly, there is a problem in that the apparatus using the high-cost gyro sensor cannot be applied to apparatuses used by general users such as mice operating in the 3D space and input devices of 3D video games.

[4] In addition, as an example of measuring a 3D position of an object, a method of measuring a position of an object by providing a plurality of markers which are distinguished from each other to a moving object, shooting the moving object, and measuring positions of the markers in the shot image is disclosed. However, in this method, shooting the object in real-time and processing the image that needs heavy data processing have to be performed, and this causes a slow response speed. Therefore, there is a problem in that measuring the 3D position of the object in realtime is difficult.

Disclosure of Invention

Technical Problem

[5] The present invention provides a 3D position tracking method and apparatus capable of measuring a 3D position of a moving object in a 3D space in real-time without excessive costs.

Technical Solution [6] According to an aspect of the present invention, there is provided a 3D position measuring apparatus including: a signal generator generating an ultrasonic signal; a signal receiver comprising three or more ultrasonic signal receivers receiving the ultrasonic signal; and a position measuring unit measuring a position of the signal generator in a 3D space by using a difference between a time at which the ultrasonic signal is generated and a time at which the ultrasonic signal is received to the signal receiver.

[7] In the above aspect of the present invention, the signal generator may simultaneously generate a reference signal and the ultrasonic signal, and the position measuring unit may set a time at which the reference signal is received to the signal receiver as the time at which the ultrasonic signal is generated to measure the position of the signal generator in the 3D space.

[8] In addition, the signal generator may include a plurality of ultrasonic signal generators, each of the ultrasonic signal generators may generate an ultrasonic signal at a reference time corresponding to a time slot allocated to each of the ultrasonic signal generators, and the position measuring unit may measure a position of the ultrasonic signal generator to which a time slot is allocated by using a difference between the reference time of each time slot and the time at which the ultrasonic signal generated at each time slot is received, in order to measure the position of the signal generator in the 3D space.

[9] In addition, the signal generator may simultaneously generate a reference signal and the ultrasonic signal, and the position measuring unit may set a time at which the reference signal is received to the signal receiver as a reference time of a first time slot of a plurality of the time slots to set a reference time of each time slot.

[10] In addition, the signal generator may generate the ultrasonic signal when receives a control signal for instructing the signal generator to generate the ultrasonic signal from the position measuring unit, and the position measuring unit may output the control signal to the signal generator and measure a position of the signal generator in the 3D space by using a difference between a time at which the control signal is output and a time at which the ultrasonic signal is received.

[11] According to another aspect of the present invention, there is provided a 3D position measuring method including: (a) a predetermined signal generator generating an ultrasonic signal; (b) a signal receiver comprising three or more ultrasonic signal receivers disposed at predetermined intervals and receiving the ultrasonic signal; and (c) a position measuring unit measuring a position of the signal generator in a 3D space by using a difference between a time at which the ultrasonic signal is generated and a time at which the ultrasonic signal is received to the signal receiver.

[12] In the above aspect of the present invention, in (a), the signal generator may simultaneously generate a reference signal and the ultrasonic signal, and in (c), the position measuring unit may set a time at which the reference signal is received to the signal receiver as a time at which the ultrasonic signal is generated to measure the position of the signal generator in the 3D space.

[13] In the above aspect of the present invention, in (a), each of the ultrasonic signal generators provided to the signal generator may generate the ultrasonic signal at a reference time corresponding to a time slot allocated to each of the ultrasonic signal generators, and in (c), the position measuring unit may measure a position of the ultrasonic signal generator to which each time slot is allocated by using a difference between the reference time of each time slot and a time at which the ultrasonic signal generated at each time slot is received to measure the space of the signal generator in the 3D space.

[14] In addition, the 3D position measuring method may further include, before (a), outputting a control signal for instructing the signal generator to generate the ultrasonic signal to the signal generator by the position measuring unit. In addition, in (a), the signal generator may receive the control signal and generate the ultrasonic signal, and in (c), the position measuring unit may measure a position of the signal generator in the 3D space by using a time at which the control signal is output and a time at which the ultrasonic signal is received.

Advantageous Effects

[15] A 3D position of a signal generator is measured by using distances between a signal generator and ultrasonic signal receivers calculated by using differences between a time at which an ultrasonic signal is generated by the signal generator and times at which the ultrasonic signal is received to the ultrasonic signal receivers that are disposed at predetermined intervals to receive the ultrasonic signal, and distances between the ultrasonic signal receivers. Accordingly, a 3D position of a moving object in a 3D space can be accurately measured without excessive costs, and a 3D position tracking method and apparatus according to the present invention can be applied to a 3D mouse, a 3D pointer, a 3D video game input device, and the like. Brief Description of the Drawings

[16] FIG. 1 is a view for explaining a construction of a 3D position tracking apparatus according to a first embodiment of the present invention.

[17] FIG. 2 is a block diagram illustrating details of a signal generator of FIG. 1.

[18] FIGS. 3 to 6 are views for explaining a method of calculating coordinate values of the signal generator performed by a position measuring unit of FIG. 1.

[19] FIG. 7 is a view illustrating a construction of a signal generator implemented in a stick shape according to a second embodiment of the present invention.

[20] FIG. 8 is a timing diagram illustrating time relationships between a reference signal and first and second ultrasonic signals generated according to the second embodiment of the present invention.

[21] FIG. 9 is a view illustrating an example of applying a 3D position tracking method and apparatus to a 3D simulation game according to the second embodiment of the present invention.

[22] FIG. 10 is a view illustrating an example of a construction of a 3D position tracking apparatus including four ultrasonic signal receivers.

[23] FIG. 11 is a view for explaining a 3D position tracking method and apparatus according to a third embodiment of the present invention. Best Mode for Carrying Out the Invention

[24] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings.

[25] FIG. 1 is a view for explaining a construction of a 3D position tracking apparatus according to a first embodiment of the present invention. Referring to FIG. 1, the 3D position tracking apparatus according to the first embodiment of the present invention includes a signal generator 20 for generating an ultrasonic signal and a reference signal by predetermined time periods, a signal receiver 10 for receiving the reference signal and the ultrasonic signal generated by the signal generator 20, and a position measuring unit 30 for measuring a position of the signal generator 20 in a 3D space by using a difference between a time at which the reference signal is received by the signal receiver 10 and a time at which the ultrasonic signal is received by the signal receiver 10.

[26] First, details of the signal generator 20 are described with reference to a block diagram of FIG. 2. As illustrated in FIG. 2, the signal generator 20 includes a reference signal generator 22, an ultrasonic signal generator 24, a controller 28, and a power supply 26. An outer appearance of the signal generator 20 may have a shape of a pen or the like.

[27] The controller 28 simultaneously generates and outputs control signals for instructing the reference signal generator 22 and the ultrasonic signal generator 24 to generate the reference signal and the ultrasonic by predetermined time periods (for example, l/50sec) to the reference signal generator 22 and the ultrasonic signal generator 24, respectively.

[28] The reference signal generator 22 generates the reference signal that is implemented as an infrared signal or a radio frequency (RF) signal according to the control signal input from the controller 28, and simultaneously, the ultrasonic signal generator 24 generates the ultrasonic signal according to the control signal input from the controller 28.

[29] The power supply 26 supplies predetermined power to the reference signal generator 22, the ultrasonic signal generator 24, and the controller 28. The power supply 26 may be implemented as a predetermined battery.

[30] The signal receiver 10 includes a reference signal receiver 10-1 and three or more ultrasonic signal receivers 10-2. First, the reference signal receiver 10-1 receives the infrared signal or the RF signal generated by the signal generator 10 to output the received signal to the position measuring unit 30 or notify the position measuring unit 30 of reception of the reference signal. The reference signal receiver 10-1 may be disposed at an arbitrary position.

[31] Each of the three or more ultrasonic signal receivers 10-2 receives the ultrasonic signal generated by the signal generator 20 to output the received ultrasonic signal to the position measuring unit 30 or notify the position measuring unit 30 of reception of the ultra sonic signal. The ultrasonic signal receivers 10-2 are disposed at predetermined intervals to measure the position of the signal generator 20 by using distances between the ultrasonic signal receivers 10-2 as described later.

[32] In FIG. 1, the three ultrasonic signal receivers 10-2 are disposed at edge portions of a computer monitor. However, if predetermined distances between the ultrasonic signal receivers 10-2 are provided, the ultrasonic signal receivers 10-2 may be disposed at other positions unlike in FIG. 1. In addition, if the distances between the ultrasonic signal receivers 10-2 are accurately measured and input to the position measuring unit 30, the distances between the ultrasonic signal receivers 10-2 do not need to be the predetermined distances.

[33] When the position measuring unit 30 receives the reference signal and the ultrasonic signal from the reference signal receiver 10-1 and each of the ultrasonic signal receivers 10-2 or a fact that the signals are received, the position measuring unit 30 uses a time at which the reference signal is received as a time at which the ultrasonic signal is generated by the signal generator 20 and calculates a distance between the signal generator 20 and each of the ultrasonic signal generators 10-2 by using the differences between the reference time and the times at which the ultrasonic signals are received.

[34] In addition, by using a distance between the signal generator 20 and each of the ultrasonic signal receivers 10-2 and distances between the ultrasonic signal receivers 10-2 that are stored in advance or externally input, coordinate values of the signal generator 20 in the 3D space are generated according to Math Figure 1 described later to measure the position of the signal generator 20 in 3D space. FIGS. 3 to 6 are views for explaining a method of calculating the coordinate values of the signal generator 20 performed by the position measuring unit 20.

[35] An example of the method of calculating the coordinate values of the signal generator 20 is described with reference to FIGS. 3 to 6. First, referring to FIG. 3, it is assumed that three sensors for implementing the ultrasonic signal receivers 10-2 are called sensors Sl, S2, and S3, the sensors are disposed to have a right angle in the same plane, coordinates of the sensors Sl, S2, and S3 are set to (0,0,0), (Lx,0,0), and (Lx,Ly,0) for the convenience, and coordinates of a position P of the signal generator 20 in the 3D space is set to (x,y,z).

[36] Here, the distance Lx between the sensors Sl and S2 and the distance Ly between the sensors S2 and S3 are known in advance. In addition, a distance Ll between the signal generator 20 and the sensor Sl, a distance S2 between the signal generator 20 and the sensor S2, and a distance L3 between the signal generator 20 and the sensor S3 can be obtained by using the differences between the reference time and the times at which the ultrasonic signals are received as described above.

[37] Here, in order to obtain an x-coordinate of the signal generator 20, as illustrated in

FIG. 4, a triangle having side lengths Ll, L2, and Lx is set, and Math Figure 1 is obtained. When Math Figure 1 is solved for the length x, the x-coordinate value can be obtained as shown in Math Figure 2.

[38] MathFigure 1

2 2 2

L γ = X +L ₄

[39]

2 2 2

L ₂= (L_x-x) +L ₄

[40] MathFigure 2

2 2 2

_ L ,+L ₁-L ₂ x

2L_x

[41] Here, in order to obtain a y-coordinate of the signal generator 20, as illustrated in

FIG. 5, a triangle having side lengths L2, L3, and Ly is set, and the y-coordinate value can be obtained as shown in Math Figure 3 by using Math Figure 1.

[42] MathFigure 3

[43] In addition, seen in a direction A as illustrated in FIG. 3, as illustrated in FIG. 6, a triangle having side lengths L4, y, and z is set, and by using the lengths, a value of the length z can be obtained as shown in Math Figure 4.

[44] MathFigure 4 z —-\j / L T ² _λ- x ² -y ²

[45] As described above, by using Math Figures 1 to 4, the coordinate values of the signal generator 20 in the 3D space can be obtained. In addition, besides the method described in association with Math Figures 1 to 4, various methods can be used to measure the position coordinates of the signal generator 20.

[46] The position measuring unit 30 may be implemented as software in electronic devices such as a desktop computer, a notebook computer, a personal digital assistant (PDA), a mobile terminal, and the like. In addition, the 3D coordinate values of the signal generator 20 measured by performing the aforementioned operations can be provided as input values of various programs such as video games executed by the electronic devices. For example, the signal generator 20 may be applied to a mouse or a 3D pointer operating in the 3D space or used as an input unit such as a mouse or a joystick for the video games.

[47] The first embodiment of the present invention is described above. According to first embodiment described above, the signal generator 20 is implemented to have a single ultrasonic signal generator 24. However, according to a second embodiment of the present invention, the signal generator 20 has two or more ultrasonic signal generators. The second embodiment and differences between the first and the second embodiments are described.

[48] FIG. 7 is a view illustrating a construction of a signal generator implemented in a stick shape according to the second embodiment of the present invention. Referring to FIG. 7, the signal generator 20 according to the second embodiment includes first and second ultrasonic signal generators 24- 1 and 24-2. In addition, similar to the first embodiment, the signal generator 20 includes the reference signal generator 22, the controller 28, and the power supply 26.

[49] The power supply 26 supplies power to the first and second ultrasonic signal generators 24-1 and 24-2, the reference signal generator 22, and the controller 28. The reference signal generator 22 generates an infrared signal or an RF signal as a reference signal according to control signals input from the controller 28.

[50] The controller 28 generates and outputs the control signals for instructing the reference signal generator 22 to generate the reference signal by a predetermined time period (for example, l/50sec) to the reference signal generator 22.

[51] In addition, the controller 28 divides the time period for generating the reference signal by the number of ultrasonic signal generators provided to the signal generator 20, allocates a time slot to each ultrasonic signal generator, and outputs a control signal for instructing the ultrasonic signal generator to which the time slot is allocated to generate the ultrasonic signal at a time corresponding to the time slot to the corresponding ultrasonic signal generator.

[52] In the example illustrated in FIG. 7, the two ultrasonic signal generators 24-1 and

24-2 are provided to the signal generator 20. Therefore, the controller 28 divides the time period by 2 to allocate time slots to the fist and the second ultrasonic signal generators 24-1 and 24-2, respectively, and outputs a control signal for instructing the first ultrasonic signal generator 24- 1 to generate an ultrasonic signal at the same time when the reference signal is generated to the first ultrasonic signal generator 24-1, and after half a period after the reference signal is generated, outputs a control signal for instructing the second ultrasonic signal generator 24-2 to generate an ultrasonic signal to the second ultrasonic signal generator 24-2.

[53] The first and second ultrasonic signal generators 24-1 and 24-2 generate the ultrasonic signals according to the control signals input from the controller 28.

[54] FIG. 8 is a timing diagram illustrating time relationships between the reference signal and the first and second ultrasonic signals generated according to the second embodiment. As illustrated in FIG. 8, the time period is divided into the two time slots. At the first time slot, the reference signal is generated, and at the same time, the first ultrasonic signal is generated. After half the period, that is, at the second time slot, the second ultrasonic signal is generated. Here, the time period has to be determined to generate the reference signal so that the ultrasonic signal generated at each time slot is received to the corresponding ultrasonic signal receiver within the same time slot.

[55] The reference signal and the first and second ultrasonic signals generated by the signal generator 20 are received by the reference signal receiver 10-1 and the ultrasonic signal receivers 10-2, respectively, and output to the position measuring unit 30.

[56] Since the position measuring unit 30 is provided with information on the number of the ultrasonic signal generators in advance, the position measuring unit 30 sets the reference time of each slot from the time at which the reference signal is received and measures a position of the ultrasonic signal generator to which a corresponding time slot is allocated by using a difference between the reference time of each time slot and the time at which the ultrasonic signal is received.

[57] In the example illustrated in FIG. 8, during the time period, the two time slots are allocated, and by using the difference between the time at which the reference signal is received (hereinafter, called a first reference time) and the time at which the first ultrasonic signal is received within half the period after the first reference time (hereinafter, called a second reference time), a position of the first ultrasonic signal generator 24-1 is measured according to the aforementioned Math Figure 1.

[58] In addition, the position measuring unit 30 measures a position of the second ultrasonic signal generator 24-2 according to the aforementioned Math Figure 1 by using a difference between times at which the second reference time and the second ultrasonic signal are received.

[59] If a distance between the first and second ultrasonic signal generators 24-1 and 24-2 is set in advance, the position measuring unit 30 can represent a spatial movement of the signal generator 20 by using coordinates of the positions of the first and second ultrasonic signal generators 24- 1 and 24-2.

[60] FIG. 9 is a view illustrating an example of applying a 3D position tracking method and apparatus to a 3D simulation game according to the second embodiment of the present invention. Referring to FIG. 9, the 3D position tracking apparatus according to the present invention is used as an input unit of the game, and the signal generator 20 moved by the user corresponds to a knife 60 hold by a game character.

[61] When the user spatially holds and moves an end portion of the signal generator 20 implemented in the stick shape, the position of the first ultrasonic signal generator 24- 1 measured by the position measuring unit 30 is input as an upper position 60- 1 of the knife in the game, and the position of the second ultrasonic signal generator 24-2 measured by the second ultrasonic signal generator 24-2 is input as a lower position 60-2 in the game. Therefore, the user can move the knife to desired positions and directions in the game by moving the signal generator 20.

[62] Although the signal receiver 10 is described to include the three ultrasonic signal receivers 10-2 in FIG. 2 referred to explain the first and second embodiments according to the present invention, the signal receiver 10 may include more than three ultrasonic signal receivers. In addition, as the number of the ultrasonic signal receivers increases, accurate measurements can be performed.

[63] For example, as illustrated in FIG. 1, when the three ultrasonic signal receivers 10-2 are provided and a barrier is disposed between one of the three ultrasonic signal receivers 10-2 and the signal generator 20, there is a problem in that accurate position measurement is difficult. However, as illustrated in FIG. 10, when four ultrasonic signal receivers 10-2 are provided at arbitrary positions or at edge portions of a monitor to have predetermined distances from each other, although a barrier is disposed between one of the four ultrasonic signal receivers 10-2 and the signal generator 20, accurate position measurement performed by the signal generator 20 using the remaining three ultrasonic signal receivers 10-2 is possible.

[64] FIG. 11 is a view for explaining a 3D position tracking method and apparatus according to a third embodiment of the present invention. The third embodiment illustrated in FIG. 11 is different from the aforementioned first and second embodiments in that the signal generator 20 and the position measuring unit 30 according to the third embodiment is connected in wired, control signals for generating ultrasonic signals and power to be supplied are provided from the position measuring unit 30 to the signal generator 20, and the position measuring unit 30 can know a time at which the ultrasonic signal is generated, so that an additional reference signal needs not to be generated.

[65] The third embodiment according to the present invention is described with reference to FIG. 11. The 3D position tracking apparatus according to the third embodiment includes a signal generator 20-3, signal receivers 10-3, and a position measuring unit 30-3.

[66] First, the signal generator 20-3 is connected to the position measuring unit 30-3 in wired to receive power needed to generate the ultrasonic signal and the control signal for instructing the signal generator 20-3 to generate the ultrasonic signal from the position measuring unit 30-3 to generate the ultrasonic signal. The signal generator 20-3 may include a signal ultrasonic signal generator as in the first embodiment or a plurality of the ultrasonic signal generators as in the second embodiment.

[67] The signal receiver 10-3 includes three or more ultrasonic signal receivers. Each ultrasonic signal receiver receives an ultrasonic signal and outputs the received ul trasonic signal to the position measuring unit 30-3 or a fact that the ultrasonic signal is received to the position measuring unit 30-3. In this case, unlike the first and second embodiments, the signal receivers 10-3 according to the third embodiment may not include a reference signal receiver.

[68] The position measuring unit 30-3 generates and outputs a control signal for instructing the signal generator 20-3 to generate the ultrasonic signal by a predetermined time period to the signal generator 20-3 and measures a position of the signal generator 20-3 by using a difference between the reference time for outputting the control signal and the time at which the ultrasonic signal is received to the signal receiver 10-3.

[69] In addition, similar to the aforementioned second embodiment, when a plurality of the ultrasonic signal generators are provided to the signal generator 20-3, the position measuring unit 30-3 divides the time period for generating the ultrasonic signal to allocates a time slot to each ultrasonic signal generator provided to the signal generator 20-3 and measures a position of the ultrasonic signal generator 20-3 to which a corresponding time slot is allocated according to the aforementioned Math Figure 1 by using the difference between the reference time corresponding to each time slot and the time at which the ultrasonic signal is received.

[70] The method of the present invention can also be embodied as computer readable codes on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable recording medium include readonly memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. [71] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.

Claims

[1] A 3D position measuring apparatus comprising: a signal generator generating an ultrasonic signal; a signal receiver comprising three or more ultrasonic signal receivers receiving the ultrasonic signal; and a position measuring unit measuring a position of the signal generator in a 3D space by using a difference between a time at which the ultrasonic signal is generated and a time at which the ultrasonic signal is received to the signal receiver.

[2] The apparatus of claim 1, wherein the signal generator simultaneously generates a reference signal and the ultrasonic signal, and wherein the position measuring unit sets a time at which the reference signal is received to the signal receiver as the time at which the ultrasonic signal is generated to measure the position of the signal generator in the 3D space.

[3] The apparatus of claim 1, wherein the signal generator comprises a plurality of ultrasonic signal generators, wherein each of the ultrasonic signal generators generates an ultrasonic signal at a reference time corresponding to a time slot allocated to each of the ultrasonic signal generators, and wherein the position measuring unit measures a position of the ultrasonic signal generator to which a time slot is allocated by using a difference between the reference time of each time slot and the time at which the ultrasonic signal generated at each time slot is received, in order to measure the position of the signal generator in the 3D space.

[4] The apparatus of claim 3, wherein the signal generator simultaneously generates a reference signal and the ultrasonic signal, and wherein the position measuring unit sets a time at which the reference signal is received to the signal receiver as a reference time of a first time slot of a plurality of the time slots to set a reference time of each time slot.

[5] The apparatus of claim 1 or 3, wherein the signal generator generates the ultrasonic signal when receives a control signal for instructing the signal generator to generate the ultrasonic signal from the position measuring unit, and wherein the position measuring unit outputs the control signal to the signal generator and measures a position of the signal generator in the 3D space by using a difference between a time at which the control signal is output and a time at which the ultrasonic signal is received.

[6] A 3D position measuring method comprising:

(a) a predetermined signal generator generating an ultrasonic signal;

(b) a signal receiver comprising three or more ultrasonic signal receivers disposed at predetermined intervals receiving the ultrasonic signal; and

(c) a position measuring unit measuring a position of the signal generator in a 3D space by using a difference between a time at which the ultrasonic signal is generated and a time at which the ultrasonic signal is received to the signal receiver.

[7] The method of claim 6, wherein in (a), the signal generator simultaneously generates a reference signal and the ultrasonic signal, and wherein in (c), the position measuring unit sets a time at which the reference signal is received to the signal receiver as a time at which the ultrasonic signal is generated to measure the position of the signal generator in the 3D space.

[8] The method of claim 6, wherein in (a), each of the ultrasonic signal generators provided to the signal generator generates the ultrasonic signal at a reference time corresponding to a time slot allocated to each of the ultrasonic signal generators, and wherein in (c), the position measuring unit measures a position of the ultrasonic signal generator to which each time slot is allocated by using a difference between the reference time of each time slot and a time at which the ultrasonic signal generated at each time slot is received to measure the space of the signal generator in the 3D space.

[9] The method of claim 6 or 8, further comprising, before (a), outputting a control signal for instructing the signal generator to generate the ultrasonic signal to the signal generator by the position measuring unit, wherein in (a), the signal generator receives the control signal and generates the ultrasonic signal, and wherein in (c), the position measuring unit measures a position of the signal generator in the 3D space by using a time at which the control signal is output and a time at which the ultrasonic signal is received.