US3090030A

US3090030A - Variable focus transducer

Info

Publication number: US3090030A
Application number: US682791A
Authority: US
Inventors: Schuck Oscar Hugo
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1957-09-09
Filing date: 1957-09-09
Publication date: 1963-05-14
Anticipated expiration: 1980-05-14

Description

May 14, 1963 o. H. SCHUCK VARIABLE 1=*ocus TRANSDUCER 2 Sheets-Sheec 1 Filed Sept. 9. 1957 GENERATOR TRANSMITTER 78 May 14, 1963 o. H. SCHUCK VARIABLE FOCUS TRANSDUCER 2 Sheets-Sheet 2 Filed Sept. 9. 1957 A TTORNE Y United States Patent O 3,090030 VARIABLE FOCUS TRANSDUCER Oscar Hugo Schuck, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Mirm., a corporation 01 Delaware Fileti Sept. 9, 1957, Ser. N0. 682,791 3 Claims. (Cl. 340-16) This invention relates to transducers and is more partieularly related to the variable focusing of a bilateral transducer to be used for transmitting and receiving in a propagative Wave system.

It has been known for sorne time in the prior art that a bilateral transducer of this general type was capable of producing an output pattern which could be caused to focus at a particular given distance from the surface of the transducer. T'nis has been accomplished by roviding the transducer itself with a spherical or curved surface having a radius of curvature equal to the dis-tance at Which the focal point was desired. This scheme produced a satisfactory transducer which had the shortcoming of having only one center of -focus and also was difiicult to produce for short foeal lengths.

It is an object of: this invention -to provide a variable focus transducer which may be controlled according to a tirne va.ried function so as to provide a sweeping eflect between varying distarxces from the transducer.

Other objects and advantages of rny invention will become apparent to those skilled in the art, from a reading of the appended speeification, claims and drawing in which:

FIGURE 1 is an illustration, largely schematic, of a variable focus transducer embodied as a receiver for observing the presence and location of a source of oscillatory energy;

FIGURE 2 is a front view of the variable focus transducer shown in FIGURE 1;

FIGURE 3 is a sehernatic diagram of another embodiment in which a variable focus transducer is utilized in conjunetion with a -transmitter to propagate oscillatory energy into a mediurn; and

FIGURE 4 is a d-iagram illustrating some of the mathematical principles to aid in explaining the operation.

FIGURE 5 is a block diagram of an echo-ranging systern of rny invention including a variable focus transducer.

FIGURE 1 shows a variable focus piezoelectric transducer =10, a sonrce of sound energy 30, to be observed by transducer 10, and indicating means 40, shown as a cathode ray tube indicator, to provide an indication of the output of variable focus transducer '10.

Variable focus transducer cornprises a body of piezoelectric material 1 1, a first electrode 12, covering the entire face of piezoelectric body 1-1, and second and third electrodes =13 and 14 (shown as concentrie annular electrodes) applied to the opposite face of piezoelectric material 1:1. Electrode 14 is an annular concentric ring isolated from circular electrode 13 which comprises the central Portion o-f the face of piezoelectric material 11. The well known properties exhibited by piezoelectric material are such that a voltage is produced across the electrodes when the material is mechanically excited. lt is also well known that transducers 01 this general type exhib-it a bilateral characteristic in that they may also produce a mechanical output When electrically excited. It should be obvious to those skilled in the art that other types of transducers may be used, in practicing my invention, Where -suita=ble sirnilar outputs are obtainable. It is to be noted that the annular shape of the electrodes is used here for purposes of illustration only. The physical configuration 01 the electrodes is immaterial as long as a signal may be obtained fromportions of the transducer that are equi- Palzented May 14, 1963 distant from an axis through the center of the transducer and normal to its plane. As an exarnple, one could have a composite transducer made up of a nurnber of individual transducers and by choosing -groups of transducers positioned at equal distances from the center of the composite transducer, the focal point of the composite transducer may also be controlled by su-itably connecting these groups as described above.

The source of sound, 3, may be a reflector for reflecting energy from another source of oscillatory energy or may be a self-contained source of oscillatory energy.

Cathode ray -tube indicator 40 is connected to a transformer 41 having a primary winding 42 and a secondary Winding 43. The right band end of prirnary winding 42 is connected to first electrode 12 through conductor 44. The left hand end of transforrner prirnary winding 42 is connected to third elec-trode 14 through conductor 45. Second electrode 13, is connected to the left band end of transformer primary Winding 42 through conductor 46, phase delay network 20 and conductor 15. It should be obvious to those skilled in the art that cathode ray tube 40 may be replaced by any suitable signal utilization device or apparatus.

Phase delay network 20 is comprised of an inductor 21, connected at its right band end to conductor 15, a capacitor 22, connected between the right band end of inductor 21 and concluctor 46, a capacitor 23, connected between the left band end of inductor 21 and conductor 46, and a variable resistance 25, shown as a triode, connected through a bat-tery 24 frorn the left band end of inductor 21 to conductor 46. Triode 25 includes the usual plate, grid and cathode electrodes indicated respectively by

reference characters

27, 28 and 29. A function generator 26 is utilized to control the conductivity, and therefore resistance, of triode 25 to control the phase delay provided by the phase delay network 20. Function generator 26 is shown connected between grid electrode 28 and cathode ele-otrode 29 so as to control the conductivity of triode 25 in accordance With a voltage generated by function generator 26. One example of a device that might be used as function generator 26 is shown and described at page 189, aragraph 47c(1) of Radar Electronic Fundamentals Navships 900,016, published by the Bureau of Ships, Navy Department, Inne 1944. The device referred to is a thyratron saw tooth generator having a saw tooth sweep output and would be used to supply a sweeping effect on the focal point of transducer 10. More simply, function generator 26 might be a calibrated potentiorneter energized from a suitable source of potential. lt should be apparen-t to those skilled in the art that phase delay network 20 is an example of only one of many types of hase or tirne delay networks.

FIGURE 2 is a front view of transducer 10 in FIG- URE 1. In FIGURE 2 second electrode 13 has a m0- ment arm radius a and third electrode 14 has a moment arm a. For purposes of illustration, the sizes of electrodes 16 and 14, relative to each other, are shown with electrode 13 larger than would normally be used.

FIGU=RE 4 is a diagram showing the conditions required for proper focusing of the variable focus transducer. In FIGURE 4 the first electrode 12, the surface norrnally in contact with the medium, and piezoelectric body 11 have been rernoved to show only the second central electrode 13 and the third annular electrode 14. In receiving energy -from a point '50, since the sound arrives at the central second electrode 13 before arriving at the third annular electrode 14, a phase or time delay is necessary to provide a focusing effect. This may be a.rrived by the approximation;

sin cz tan a whcre a-tan d ;b=necessary phase delay in radians, =wave length in medium, a =rnoment arm of electrode 14, and d=distance to signal source. It has been observed that optimum focusing may be obtained when a phase or tirne delay, substantially equal to this value, is inserted in the electrical path frorn the second central electrode 13 to the cathode ray tube indicator 40.

OPERATION OF FIGURE 1 Assuming for the moment that the function generator 26 is a simple calibrated otentiometer for varying the conductivity and thereby resistance of triode 25 by varying the potential applied across grid and

cathode electrodes

28 and 29, it may be seen that the sound ernanating frorn source of sound energy 30, at any given distance frorn variable focus transducer 10, Will intersect the transducer at its center portion at sorne earlier tirne than at its outer portions. In order to obtain maximum energy from the source of sound energy 30 it is necessary that all of the signal, emanating frorn the source of sound 30 reach the cathode ray tube indicator 40 at the sarne time. lt is to be understood that time, in the sense used here, may also be expressed as a phased relationsh-ip between two or more oscillatory signals. This is done by delaying the signal impingin'g on the central portion of transducer 10, that is central electrode 13, -by an amount of time such that it will be applied to oathode ray tube indicator 40, at the sarne time the signal received from source of sound 30 is applied to cathode ray tube indicator 40 from the third annular electrode 14 on trans ducer 10. The time delay is accornplished by the variable phase delay or time delay network 20, which is in turn controlled by the resistance of triode 25. If a otentiometer is used as function generator 26 to control the resistance of triode 2.5, and is calibrated in distance, the sigmal, comprising the

signals frorn electrodes

13 and 14, 1eoeived by cathode ray tube indicator 40 may be adjusted for maxirnurn value by varying the voltage applied to the control grid of triode 25 by the potentiometer rneans and then' reading directly on a scale the distance of the source of sound 30 from variable focus transducer 10.

An example of a transducer used in one embodiment of my invention follows;

Material quartz.

Diameter .25 ineh.

Thickness .001 inch.

Eleotrode material silver.

Number of annuli 4.

Frequency rnegaeycles per second.

Amount of phase delay at outer annulus a distance of 1" 4 =.0174 microsecond.

The above described transducer was utilized in the field cf medical research for accurately detecting and locating the presence of non-hornogeneous areas such as may occur in human flesh as a result of oancerous growth of the body cells.

lt should be apparent to those skilled in the art that the function generator 26 may be of the type that varies from a maxirnum to a minimum or vice versa and that the cathode ray tube indicator 40 may also, in con'junction with the function generator variation, provide a sweep so that the variable focus transducer will scan an area frorn a minimurn to a maxirnum distance and provide an indication on the face of the indicator 40 of the distance of a source of sound or energy frorn the variable focus transducer 10. It should likewise be apparent t0 those skilled in the art that the number of annular electrodes, such as shown on the left band face of variable focus transducer 10, is not limited to the number shown on FIGURE 1 and that the resolution which may be obtained from a variable focus transducer of this nature is increased with an increase in the number of annular electrodes. lt should be understood that suitable tirne or phase delay networks are inserted between each of said annular electrodes and the signal utilization means such as cathode ray tube indicator 40.

Referring now to FIGURE 3; a variable focus transducer 60 is shown adapted to transmit energy from a transmitter 70 so that it may be focused on objects or 91 which are situated =at particular distances from transducer 60.

Transducer 60 includes a piezoelectric body 66, an electrode 67, positioned on the right hand face of piezoelectric body 66, a central electrode 64 positioned in the center of the left band face cf piezoelectric body 66, and con'centric annular electrodes 63 and 62 positioned also on the left band face of piezoelectric body 66.

Eleetrode 67 is connected to ground through conductor 65. Central electrode 64 is connected to transrnitter 70 through a phase delay network 73 and conductor 71; electrode 63 is connected to transmitter 70 through a phase delay network 74 and conductor 71; and electrode 62 is connected to transmitter 70 through a phase delay network 75 and a conductor 71. Transmitter 70 provides an output for the energization of transducer 60 through a conductor 71 and to ground through a conductor 72.

The phase or time delays alfected by the phase delay networks 73, 74 and 75 are controlled by the voltage appearing across potentiometer 85. Phase delay networks 73, 74 and 75 may be similar 10 the type described above in connection With FIGURE 1, i.e. the amount of phase delay may be controlled by the application of a suitable potential to a control device incorporated in the phase delay network. Funther, since the amount of delay needed between successive electrodes is not a linear function, phase delay networks 73, 74 and 75 may also incorporate a means responsive to the potential supplied from otentiometer winding for modifying the amount of phase delay as the focal point is moved away from the right side of transducer 60. Adjustable taps 86, 87 and 88 are provided on otentiometer 85 for adjusting the potential applied to the phase delay networks. Wiper 86 is connected to phase delay network 73 through conductor 76; wiper 87 is connected 10 phase delay network 74 through conductor 77; and wiper 88 is connected to phase delay network 75 through a conductor 78. A triode 83 is utilized to energize -the winding of potentiometer 85 through a circuit including the plate electrode 95 of triode 83, battery 84, otentiometer winding 85, and conductor 92 connected to ground at 93 and also to the cathode 97 of triode 83. Triode 83 includes the usual plate, grid, and cathode electrodes indicated respect1vely by reference characters 95, 96 and 97. The conduotion 0f triode 83 is controlled by a function generator shown connected across the grid and cathode electrodes 96 and 97 of triode 83 so as to control the conductivity of triode 83 in accordance with the output of function generator 90.

OPERATION OF FIGURE 3 The operation of FIGURE 3 is very similar to that of FJGURE 1 in that the signal, in this case a transmitted signal, is caused to be propagated from the various annular sections of transducer 60 so that it arrives in phase or at the same tirne at a given point in space from the face of transducer 60. It is the purpose of the phase delay networks 73, 74 and 75 to provide the proper delays in the application of the signal to transducer 60 so that this phenomenum occurs.

From a consideration of the two embodiments shown and described above, it should be apparent that the transmitting and receiv=ing characteristics may be combined in one device.

Referring now to FIGURE 5 in which a variable focus transducer 100, is connected to be utilized in conjunction with an echoranging System of a type generally wellknown in the art; the echo-ranging system includes a transmitter 130, a keyer 140, a receiver 150, a sweep generator 146, a relay 110, an indicator 160, and a transducer 100.

Keyer 140 includes a common terminal 143 connected to ground, an output terminal 141 for providing a signal for activating transmitter 130, an output terminal 144 for energizing the winding of transrnitting-receiving relay 110, and an output terminal 145 for supplying a signal to initiate the action of sweep generator 146. Transmitter 130 includes a pair of terminals 131 and 132 for connection to a source of alternating current to supply operating voltage thereto, a common =terrninal 134 comnected to ground, an input terminal 133, and an output terminal 135. Sweep generator 146 includes a cornrnon terminal 149 connected to ground, an input terminal 147, and an output terminal 148. Receiver 150 includes a pair of terminals 151 and 152 for connection to a source of alternating current to supply operatin g voltage thereto, a common terminal 154 connected to ground, an input te1rninal 153, and an output terminal 155. Indicator 160, which may be of a type comrnonly known in the art as a cathode ray tube indicator, includes a comrnon terminal 165 connected to ground, an input signal terminal 162, and a further swep Signal input terminal 164. The winding of transmitting-receiving relay 110 iS connected gronnd and is adapted to actuate normally open rnovable relay contacts 111 and 112 and normally closed

movable relay contacts

113 and 114. Stationary relay contacts 115 and 116 are associated with movable relay contacts 111 and 112 respectively.

Stationary relay contacts

117 and 118 are associated with

movable relay contacts

113 and 114 respectively. Phase delay network 126 includes a comxnon terminal 159 connected to ground, control signal input terminal 161, Signal input terminal 157, and signal output terminal 158. Transducer 100 includes a first electrode 101 connected to ground at terminal 102, a first annnlar electrode 104, and a second annular electrode 103. An illustration of the characteristic radia-tion pattern of the transducer When used for transmitting is indicated by dotted line 107.

Output terminal 141 on keyer 140 is connected to input terminal 133 on transmitter 130 through conductor 142. Output terminal 144 on keyer 140 is connected 10 the winding of relay 110 throngh conductor 123. Output terminal 145 on keyer 140 is connected to input termnal 147 on sweep generator 146 through conductor 127. Output terminal 135 on transmitter 130 is comnected to rnovable relay contacts 111 and 112 through conductor 156. Output terminal 148 on sweep generator 146 is connected 10 control signal input terminal 161 on phase delay network 126 through

conductors

127 and 128. Outpnt terminal 148 on sweep generator 146 is connected to control Signal input terminal 164 on indicator 160 through conductor 127. Input terminal 153 on receiver 150 ds connected to movable relay contact 114 through conductor 124 and output terminal 155 on receiver 150 is connected to signal input terminal 162 on indicator 160. Input terminal 157 on phase delay network 126 is connected to movable relay oontact 113 1hrough conductor 122. Output terminal 158 on phase delay netzwork 126 is connected to input terminal 153 on receiver 150 through conductor 125 and conductor 124. Second annular electrode 103 on transdueer 100 is connected 10

stationary relay contacts

115 and 118 through conductors .120 and 121. First annular electrode 104 on transducer 100 is connected to stationary relay contacts 116 and 117.

OPERATION OF FIGURE 5 The apparatus shown in FIGURE 5 is a standard type of echo-ranging System that is well-known in the art with exceptions as Will be noted below. Basically, the operation consists 0f periodically illuminating the field of observation, here the field indicated by the dotted line 107, and then scanning the field at progressively increasing distances with variable focus transducer to determine the presence and distance of objects existing within the field cf observation. In operation, the keyer 140 provides a Signal to activate transmitter 130, to energize the winding of relay so as to connect transrnitter to transducer 100, and to initiate the operation of sweep generator 146. After a Short interval of time, the Signal from the keyer stops and the Winding of relay 110 is deenergized to connect receiver to transducer 100 so that any signals received may be applied to indicator 160, and transrnitter 130 is inoperative.

It may be Seen that the operation of FIGURE 5 may oe divided into two parts, that is a first transmitting interval in which annular electrodes 103 and 104 connect to transmitter 130 through the normally open relay comtacts 111 and 112; and a second position in which the receiver is connected to the transducer annular electrodes 103 and 104 through the normally closed

movable comtacts

113 and 114. lt is during this second operation of the echo-ranging system that rny invention is utflized to improve angnlar resolution in longitudinally scanning the area in front of the transducer by changing the eflective focal point of the transducer so that it moves an ever increasing distance frorn the face of the transducer, in FIGURE 5 from left to right. The focusing efiect is provided as explained in the operation of FIGURE 1 in that a phase delay networl; 126 is used to operate on the signal appearing on second annular electrode 104 so that Signals reflected from an object, such as object 106, and received by annular electrodes 103 and 104 Will arrive at the input terminal 153 of receiver 150 in the same hase relationship.

It should be apparent to those skilled in the art that the hase delay network 126 may include a further function generator aS shown in FIGURES 1 and 3 to provide the desired relationship between the phase delay applied to the Signal from annular electrode 104 and the sweep Signal supplied to indicator from sweep generator 146. It should further be apparent to one skilled in the art that the dimensions of the transducer used in any particular application are commensurate With the desired operating characteristics according to the principles of my invention as explained above in conjunction with FIGURES 1 and 4.

As another example, one might utilize the focusing properties obtainable through the use of my invention for both transrnitting and receiving energy to a field of observation to obtain even greater angular resolution, particularly at relatively short distances.

It should be apparent to those skilled in the art that a hase delay is desirable where a continuous wave or modulated pulse System is used and that a time delay is desirable where a pulse system is used for transmission. It has been observed that if the proper relationship between the phase or tirne delay fo1' each annular elec- (rode is maintained, the focal point of the propagative Signal may be varied at will in accordance With the generated signal of the function generator. Various means for providing a suitable relationship between signals on each annnlar electrode to provide the desired focusing effect will be apparent to those skilled in the art.

lt should now be apparent to those skilled in the art that transducers 10, 60, and 100 may be of the bilateral type, i.e. transducers that may be used as transmitters 01' receivers of oscillatory energy and that an adjustable focus action may be obtained either in transm-itting or receiving.

1't has been observecl that the accuracy of focusing and azimuthal resolution will be increased With an increase in the total nurnber of electrodes used.

These und otner embodiments and modifications will be apparent to those skilled in tne art and it is therefore my Wish to be limited only by the scope of the appended clairns.

I claim:

1. Control apparatus for a wave transducer to produce a sweep focus thereof as a function of time, cornprising;

bilateral voltage transducer rneans having first and second concentric electrodes formed in a given plane ancl defining an axis normal to said plane,

voltage responsive means,

circuit means connecting one of said electrodes to said voltage responsive rneans,

variable phase control means,

circuit means, including said phase control means,

connecting tne other of said electrodes to said voltage responsive rneans,

and sweep control means connected in contrlling relation to said phase control rneans to continuously vary, as a function of tirne, the relative phase between the voltages received by said voltage responsive means from said first and second concentric electrodes t0 provide a continuously variable focus of said transducer means along said axis.

2. In combination, transducer means having a disc formed of a material having piezoelectric properties, a first planar electrode formed on one surface of said disc, 811d a plurality of concentric planar electrodes formed on a surface of said disc spaced from said one surface of said disc, said transducer means having an axis generally normal to the planes 0f said first electrode and said plurality of electrodes,

signal responsive rneans,

circuit means connecting one of said electrodes to said signal responsive means,

variable signal delay rneans,

circuit means, including said variable signal delay means, connecting the other of said concentric electrodes to said signal responsive means,

sweep generator means,

and circuit means connecting said sweep generator means in controlling relation to said signal delay means to vary the degreeof Signal delay as a function of time 10 provide variable focusing of said transducer means alo'ng said axis, as csntrolled by said sweep generatorrneans.

3. Energy translating apparatus including bilateral energy transducer means having first and second concentrie electrodes positioned in a given plane on one surfaee of said energy transducer means, and having a further electrode positioned in a second plane on a sunface of said energy transducer means which is spaced from said one surface,

voltage responsive rneans,

means connecting one cf said electrodes to said voltage responsive means,

voltage controlling means for controlling the relative time relationship between a voltage applied at the input thereof and a resulting voltage appearing at the output thereof,

means including said voltage controlling means comnecting the other of said electrodes to said voltage responsive means, the input 0f said voltage controlling means being connected to said other electrode and the output of said voltage controlling means being connected to said voltage responsive means, and further rneans connected in controlling relation to said voltage controlling means to control said voltage controlling means as a function of time so tl1at the relative tirne relationship between the Voltages received by said voltage responsive means from said first and second concentric electrodes is caused to vary as a function cf tirne to provicle variable focusing cf said transducer means along said axis.

Referenees Cited in the file of this patent UNITED STATES PATENTS

Claims

1. CONTROL APPARATUS FOR A WAVE TRANSDUCER TO PRODUCE A SWEEP FOCUS THEREOF AS A FUNCTION OF TIME, COMPRISING; BILATERAL VOLTAGE TRANSDUCER MEANS HAVING FIRST AND SECOND CONCENTRIC ELECTRODES FORMED IN A GIVEN PLANE AND DEFINING AN AXIS NORMAL TO SAID PLANE, VOLTAGE RESPONSIVE MEANS, CIRCUIT MEANS CONNECTING ONE OF SAID ELECTRODES TO SAID VOLTAGE RESPONSIVE MEANS, VARIABLE PHASE CONTROL MEANS, CIRCUIT MEANS, INCLUDING SAID PHASE CONTROL MEANS, CONNECTING THE OTHER OF SAID ELECTRODES TO SAID VOLTAGE RESPONSIVE MEANS, AND SWEEP CONTROL MEANS CONNECTED IN CONTROLLING RELATION TO SAID PHASE CONTROL MEANS TO CONTINUOUSLY VARY, AS A FUNCTION OF TIME, THE RELATIVE PHASE BE-