US 4,506,354 AGranted

Ultrasonic position detecting system

AssigneePosition Orientation Systems, Ltd.

InventorPer K. Hansen

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Abstract

A system measures the (x, y) coordinates of a target, for example, a pointed finger on a flat surface such as a rectangular plate. A pair of ultrasonic transducers are placed on the plate so that one transducer is located at each of the two left corners of the plate or at each of the two top corners of the plate. The transducers transmit short ultrasonic pulses which are reflected as echos off the target and then received by the transducers. The time elapsed between the transmitting of each pulse and receiving its echo is converted into distances between the transducers and the target, which distances are then converted into the target's (x, y) coordinates. The system is designed to clamp onto a number of flat surfaces, thereby allowing the system to be used with printed representations of keyboards, graphs, CRT monitors and standard television screens. The system is interfaced with any of a variety of computers and provides a signal representative of the location of the target to the computer. The system is also designed so that it can be placed inside any new or existing frame around the flat surface.

An apparatus for determining the position of any of a variety of objects in a preferred region of a plane comprised of:

(a) first and second means, each said means transmitting and receiving ultrasonic pulses;
(b) an ultrasonic driving means providing driving power to said first and second means in a series of pulses, the driving means driving said first and second means at a plurality of different frequencies and each pulse being a monofrequency output;
(c) a receiving means to receive an echo of a sound pulse from said first and/or second means;
(d) a discriminator means to elect preferred echos in accordance with a time delay and magnitude of signals representing the echos received from said first and/or second means, the election criteria including
(i) the elected echos must be received after a first time period in which said means has transmitted an ultrasonic pulse and blanking of said means during a blanking period has occurred, said first and second means being separated by more than twice a distance determined by multiplying half of said first time period with the speed of sound;
(ii) when the apparatus is operated whereby one of said means transmits and the other of said means receives, the elected echos must be received within a second time period determined by the greatest distance from one of said means to the furthest part of said preferred region of said plane and back to the other of said means as divided by the speed of sound;
(iii) when the apparatus is operated whereby one of said means both transmits and receives said pulses, the elected echos must be received within a third time period determined by twice the shortest distance from said one of said means to the preferred region of said plane divided by the speed of sound;
(e) a time-measuring means to measure the time delay between each transmitted pulse and each elected echo;
(f) a means to determine a location of the source of the elected echos by deriving information from the measured time delays;
(g) a computing module means including a microprocessor to (i) generate signals controlling said first and second means and (ii) calculate said positon;
and
(h) a computer interface means to provide a signal representative of the location of the source of the echos to a computer.

9 more elements

Facts

Application

06/429,856Filed 30 Sep 1982

Granted

19 Mar 1985

Term ends

Not estimatedThe source records don’t support an estimate.

Classification7 codes

G06F 3/0436
Using propagating acoustic waves: in which generating transducers and detecting transducers are attached to a single acoustic waves transmission…
G01S 5/28
Using ultrasonic, sonic or infrasonic waves: by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
G01S 15/874
Combinations of sonar systems: combination of several spaced transponders or reflectors of known location for determining the position of a receiver
Y10S 367/907
Communications, electrical: acoustic wave systems and devices: coordinate determination

Abstract

Claims26