CA1210842A - Piezoelectric transducer with integral driver and sensor - Google Patents
Piezoelectric transducer with integral driver and sensorInfo
- Publication number
- CA1210842A CA1210842A CA000407970A CA407970A CA1210842A CA 1210842 A CA1210842 A CA 1210842A CA 000407970 A CA000407970 A CA 000407970A CA 407970 A CA407970 A CA 407970A CA 1210842 A CA1210842 A CA 1210842A
- Authority
- CA
- Canada
- Prior art keywords
- crystal
- piezoelectric
- electrode
- membrane
- coating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000013078 crystal Substances 0.000 claims abstract description 68
- 239000012528 membrane Substances 0.000 claims abstract description 25
- 239000011248 coating agent Substances 0.000 claims abstract description 19
- 238000000576 coating method Methods 0.000 claims abstract description 19
- 239000007769 metal material Substances 0.000 claims abstract 6
- 238000006073 displacement reaction Methods 0.000 claims 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 239000007789 gas Substances 0.000 description 3
- 238000006873 Coates reaction Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 101100096502 Danio rerio spring gene Proteins 0.000 description 1
- 241000282326 Felis catus Species 0.000 description 1
- 101100400378 Mus musculus Marveld2 gene Proteins 0.000 description 1
- 101100096504 Mus musculus Spring1 gene Proteins 0.000 description 1
- 101100426090 Rattus norvegicus Trim9 gene Proteins 0.000 description 1
- 101100096505 Xenopus laevis spring1 gene Proteins 0.000 description 1
- GNKTZDSRQHMHLZ-UHFFFAOYSA-N [Si].[Si].[Si].[Ti].[Ti].[Ti].[Ti].[Ti] Chemical compound [Si].[Si].[Si].[Ti].[Ti].[Ti].[Ti].[Ti] GNKTZDSRQHMHLZ-UHFFFAOYSA-N 0.000 description 1
- 230000035559 beat frequency Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 239000003351 stiffener Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/086—One or more reflectors having variable properties or positions for initial adjustment of the resonator
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/58—Turn-sensitive devices without moving masses
- G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
- G01C19/66—Ring laser gyrometers
- G01C19/661—Ring laser gyrometers details
- G01C19/665—Ring laser gyrometers details control of the cavity
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R17/00—Piezoelectric transducers; Electrostrictive transducers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
Abstract
PIEZOELECTRIC TRANSDUCER WITH INTEGRAL DRIVER AND SENSOR
ABSTRACT
A transducer is shown wherein a piezoelectric crystal is mounted within a housing upon a thin, flexible membrane. The crystal is coated with a metallic material which permits a potential to be placed across the crystals for displacing the membrane to produce useful motion. The metalic coating is interrupted to form a first and second electrode. The crystal thus is driven by a drive circuit connected to the first electrode while a sensor circuit connected to the second electrode generates a sensor signal useful to determine the position of the crystal.
ABSTRACT
A transducer is shown wherein a piezoelectric crystal is mounted within a housing upon a thin, flexible membrane. The crystal is coated with a metallic material which permits a potential to be placed across the crystals for displacing the membrane to produce useful motion. The metalic coating is interrupted to form a first and second electrode. The crystal thus is driven by a drive circuit connected to the first electrode while a sensor circuit connected to the second electrode generates a sensor signal useful to determine the position of the crystal.
Description
--ZOEI.ECT C T~DI)CEP~ WITH INTEGR R~ R A~ID ~N5 The present invention relat:es to a piezoelectri~
transau~er an~, more particularly, to a transducer which achieves better thermal compensation through the utilization of a common piezoelectric crystal for both driving the transducer and sensing t:he posltion thereof~
BACRG~OUND OF T~E INVENTIO.~
~ he piezoelectric transducer with integral driver and sensor has particular applicat;on within a ring laser gyro for a~justing the cavity length of the gyro~
The essence of a ring laser gyro i^~ that two light lS waves, circulating in opposite directions aroun;~ the same path, undergo fre~uency shifts when the path i~ rotated.
~ The ~r~quency shifts are in opposite directions to pro~uce optical ~requen~y differences between the two waves, The two fre~uencies heterodyne at a common photo-detector giving rise to a beat frequency directly proportional to the angular rotational rate.
The laser cavity is often create~ w.ithin a guartz body having a number of apertures cut into it. The apertures form the inner passages which make up the cavity of the ring laser. Each corner of ~he cavity, forme~ by the intersection of the passages, is provi~e~ with a reflective mirror which reflects the twn counter~
propagating light waves from one passageway to the next.
For proper functioning of the ring laser, it is 30 importa~t that the amplitu~e of the two oppositely cîrculatirJg light waves which make up the gyro ~e substantially equal. Ihe character~stic intermo~ulation of the ~cwo light waves is the classical form of amplitu~le modulation with maxima occur ing when the sum of the 3~ ~nstantaneous ~omponents ~re in phase, al~a the minima occurin~ when these components are 1~0 out of phase. If ` `~f~`
~ G~D ~0 ~ n one of the twn light wave signals is significantly greater than the other, the beat signal dloes no ~rop to zero.
Proper ring laser gyro action may be achieve~ by detecting the minimum point of the k,eat signal an~3 then dete~minin~ whether these points are actually zero. If the miniml3m points are not zero, ~che length of the laser cavity is adjusted to drive the minimum p~in~s towar~ zero. To adjust the length of ~he laser cavi~y a piezoelectric tran~ducer is attached ~o one o~ the laser mirrors. A
cavity control circuit ~rives the piezoelectric trans~ucer and, in the prior art, receive~ its input signal from the 1~ ou~pu~ signal of the laser. See U;S~ Letters Patent NoO
4,123,16~ issue~ October 31, 1978 by V.E. Sanders entltled MULTIOSCTLLATOR RING LASER GYRO OUTP~T INFORMATION
PROCES5ING SY~TE~ assigned to the same assignee as the present inventionO
SUMMARY OP THE INVENTI ON - -It i5 therefore an object of the present invention to track the location o~ the ring laser corner mirrors~
Another object o~ the present invention is to cause a piezoelectric transducer to generate its own feedback ~ignal for indicating the position of that trans~ucer.
Still a fur~her object of the present invention is to produce both driver an~ sensor signals from a piezoelectric transducer symmetrical assembly. Symmetry reduces error ~5 cause~ by thermal distortion which is inherent in separately attached sensors such as a piezoelec~ric chip, strain gauge, electromagnetic device or capacitanc2 pi~koff.
~ piezoelectric trans~ucer is formed from a thin metal membrane having a piezoelec~ric ~isk mounlted upon one surface or sandwiched between wo piezoelec~ric disks. The disks ~re coate~ with a metalli~ coatin~. The first pie~oelectric disk, if used, supports the metal membrane.
The metal coating upon the f~rst disks ~rms a ~irst ~ ~ ~ GCD 80 20 electrode while the metal coating upon the secon~
pie20electric disk is divide~ symme~rically to form secon~
an~ thir~ electro~es. The piezoelectric ~isks will hereinafter be called crystals. Tbe secon~ crystal, covered by two separate areas of conductive material, becomes two crystals in one structure. The portion of the crystal structure un~er the second electrode may be use~
either as a driver or sensor crystal, and the portion of the crystal s~ructure under the thirg electrode may also be be used either as a sensor or ~river. The actual portion of the crystal that is use~ to ~rive or sense depends upon the internal structure of the crystal. The area of maximum strain and usually maximum ~tress of the crystal structure is the preferre~ portion for the sensor.
The design of the transducer should be s~mmetrical ~ since symmetry tends to eliminate thermal distortion lS inherent in a separately attache~ sensor. Further, by using the same crystal structure for the ~rlver an~ the sensor, direct monitoring of the driver by the sen~or without interme~iate attachments, such as mechanical or a~hesive layers, eliminates many components which might cause error through manufacturing tolerance, assembly errors, mismatches in alignment, or thermal distortion.
BRIEF DESCRIPTION OF T~E DRAWINGS
Other objects and further a~vantages of the present invention will become apparent to those skilled in the art after a careful consi~eration of the following specification and accompanying arawings wherein:
F;go 1 is a top plan view, partially in section, showin~ a typical ring laser gyro in which the trans~ucer of the present invention may be u~ilized;
Fig. 2 is a cross section taken alon~ lines 2 - 2 of Fig. 1 showing the piezoelectric tran~ucer of the present invention;
Fig. 3 is a plan view of a piezoelectric trans~ucer .
~ 2 ~ GCD 80-20 utilized within ~he present invention;
Fig. 4 is a si~e view of the transducer sf Fig. 3;
Fig. 5 is a plan view Gf an alternative piezoelectric transducer which may be u~ilized;
Fig. 6 is a side view of the ~rans~ucer of Fig. 5;
Fig. 7 i a plan view o anot~er alternative piezoelectric transducer which may be utilize~
incorporatin~ the present invention;
Fig. 8 is a side view oE Fig. 7; ~nd Fig. 9 illustrates the electrical connection o~ the trans~ucer ~hown in Figs. 1-4.
DETAILED DESCRIPTION OF THE PREFERRED EMBOD~MENTS
Referring now to the drawings, Fig. 1 illustrates a typical ring laser gyro 10 which is formed in a bo~y 1~, e.g., ~uartz or an ul~ra-low expansion material, such as lS titanium silicate. The laser body 12 is Gonstructe~ with four passages 14 therein which are arranged ~o form a close~ rectangular path. Alternative configurations such as a triangle or other polygon are knc~wn. Further the laser need not be planar. The passages 14 are sealed to retain a gas mixture consisting, typically, of approximately 90% helium and 10% neon in a vacuum of approximately 3 torr. It is understood that atmospheric pressure i~ approximately 760 torrs.
The body 12 is typically provi~ed with two cathodes 16 and 18 an~ two ano~es 20 and 22 which may be secure~ to the body in a manner that i5 known in he art. Other energiziny means are known, for example, it is common to use a single cat~de~ Gas ~ischarges are establishe~ in passage 14 between catho~e 16 and ano~e ~0 and between ca~hode 18 and anode 22. A getter 24 may be provi~ed to absorb impurities foun~ within the gas in the passageway 14. Mirrors 28, 30 t 32 an~ 34 ~re locate~ at the four corners of the laser optical path for~e~ withln the passageway 14 of the rin~ laser gyro 10. Mirror 2~ i~
12~42 ? GCD R0-20 mounte~ upon a photo-detection ~evice 36. The photo~detection device 36 pro:3uces the bea~ frequency signal generated by the coun~:er-propagating laser beams as a measure of the angular rate of the r ing laser gyro 10 about it~ sensing axis.
Mirror 3~ is mounted upon a piezoelectric transf~ucer 38 which controls the cavi~y 14 position of mirror 34 to control the length of the laser o:E the ring laser gyro.
The piezoelectric trans~ucer 38 is shown in ~3reater ~etail in Fig. 2~ Typically the transducer 3~ has a housing 40 formed by a thin cup-shapea metallic member whose bottom 10 surface forms a flexible ~iaphram 42 which is mounted against the ~uartz body 12 and is sealed thereto by suitable bonding. The surface of the diaphram 42 which mounts against the inner passages of the ~uartz body 12 supports the mirror 34. A post 44, used to Arive th~
diaphram 42, extends from the center of the diaphraym 42.
The cup shaped housing 40 is closed by a trans~ucer housing 48 whose toroidally-shape~ outer rim 49 inclu~e~, for exa~ple, eight spring loaded finyers 50, only five of which are ~hown in Fig. 2, that extend over the outer surface of cup 40. The spring ~ingers are provi~ed with an arcuate surface 51 whioh is urge~ snugly against the outer surface of cup 40 and ~ecured thereto, as by bonding. ~he outer toroidal rim 49 of the housing 48 is connected to a eenter hub 52 by a thin, flexible membrane 54. ~ounted on the inner and outer surfaces of the membrane 54 are disk-shape~
pie~oelecSric crystals 56 and 58, respec~ively.
In the preferred embodiment, it is not necessary to use the inner piezoelectric disk 56. Alternatively, this disk may be used solely as a stiffener~ A~ best seen in Figs. 3 and 4, a pieæoelectric disk structure 5B is coated with a me~al coating 59 to form ~wo concentric electro~es on the surface of the disk. The coating 59 is interrupte~
by a toroidally-shaped cut 60 which forms the concentric inner and outer electrodes 62 and fi4. Interruption o~ the _.
GCD ~0-2 0 metal coa~ing ~9 may be accompl ished by several metho~s including masking the areas o~ the metal coating 5g which are desired and abrading the unmaske~ areas, ~oroidal ring 60, that one wishes to remove.
A stud 65 is ~hreadably mounte~ in the center of hub 5~ for contacting the pos~ 44 of diaphragm cup 40. I~he threaded stu~ 56 is adjus~e~ until it firmly engages the inner surface of post 44. When an electrical poten~ial is placed across the pie~oelectric crystal 58, the crystal will go convexe~, when viewed frorn the left-han~ side of Fig. 2, fs>r removing a pre-set ~isplacement of d:iaphra~n 42 caused by the s~ud 66. This permits mirror 3~ to more, thus adjusting the len~th of laser cavity passage 14.
As seen in Fig. 9, the crystal 58 may be connected to an electrical potential by connecting the membrane 54 to a common po~ential, such as system groun~, and connecting the outer electrode 64 between the common potential and a source of adjustable potential 68. The inner electrode 62 is then connected from the common potential at membrane ~4 to a voltage ~etector 70.
Should two cryst~ls be use~ as shown in Fig. 2, tbe common potential may be connected to a metallic coating over the full surface of the first crystal 56. In this configuration, the crystal 56 is driven to a concave position while ~he crystal ~8 is ~riven to a convex position when viewed from the left-hand side of Fig. 2.
As seen in Figs. 3, 4 an~ 9 the sensor represente~ by voltage ~etector 70 is preferably connecte~ t~ the inner ~lec~rode 52 which is arrange~ over the portion D~ the crystal 58 that experiences maximum strain. It has been found axperimentally tha~ ~n annular piezoelec~ric crys~al having a ~mall ~nternal diameter undergoes maximum stress and strain at or near its in~ernal diameter.
~owever, as the internal ~iameter of an annular piezoele~tric crystal ~ncrease in size, there are some situations in which the ~ensor undergoes maximum stress an~
10~ 2 ! G~D 8 û - 2 0 s~rain near its ~uter ~iameter. ~he outer electrode 64 would then be used as a sensor. As shown in FigsO 5 and 6, a membrane 7~ may be provi~ed with an aperture 74 havins a large internal diame~er and at least one surface upon which is mounte~ a piezoe~ ectric crystal 75~ The crystal is covered with a metallic coating 78 which is interrupte~ by a toroidal cut 80 for forming an inner electrode ~2 and an outer electrode 84. The inner electrode 82 may then be connecte~ to a source of a~ justable voltage potential, such as the adju~table DC source 68, to ~rive the crystal 76.
The outer electrode 84 then produces a voltage which may be measured by voltage detector 70 to produce a useful feedb~c k s ignal .
In ~ome uses of the invention not involving control of cavity le~g~h, it is desired to measure the flexure of a bar. For example, a thin elongated metallic bar is used ln a spring system which mechanically dithers a ring laser gyro about its input axis. hs shown in Figs. 7 an~ R, such a drive system may incorporate a bar-shape~ flexure spring 86 against which is mounte~ a qua~rilaterally-profiled piezoelectric crystal ~ whicht in the embodiment shown, has a rectangular profile. The surface of crystal ~8 is coate~ with a metallic coating 90 which is interrupted by a cut 92, generally perpen~icular to the longitudinal axis of crystal 88, to form a ma jor electrode 94 and a minor electrode 96. The minor elec~rode ~5 i8 preferably located at one en~ o~ crystal 88 which is positioned a~jacent a position of maximum strain of the spring 86. Electrode 46 acts as a sensor electro~e to generate a sensor signal to be applie~ to a voltage detector 70. The major electro~e 94 may then be connecte~ to a source of variable potential 3g 68 for contracting or expan~ing crystal 88 and driving spr ing 8 6 .
Although Fig. 9 shows a separate co~trol voltage source 68 and sensor voltage measuring device 70, it is slear that a typical servo ampliEier (not shown) coul~ ~e _.
~2~4~
used to dri-re the source 68, and ~he voltage measured at 70 could be the feedback voltage which is deliver~d lto the servo ampl if ier .
While ~he plezoelectric ~ransducer of the pre5ent invention has been described for use wi.~hin a ring laser gyro t i~ will be Imderstood that similar trarlsducers may be used in any number o~ devices. Further, the configuration shown as the preferred embodiment within the presen$
invention may be modified to include many variations including a variation with a larger internal diameter, a qua~3r ilateral prof ile or rectangular prof ile . Accor~ ingly, the present invention shoul~ be 1 imited only by the appended claims.
transau~er an~, more particularly, to a transducer which achieves better thermal compensation through the utilization of a common piezoelectric crystal for both driving the transducer and sensing t:he posltion thereof~
BACRG~OUND OF T~E INVENTIO.~
~ he piezoelectric transducer with integral driver and sensor has particular applicat;on within a ring laser gyro for a~justing the cavity length of the gyro~
The essence of a ring laser gyro i^~ that two light lS waves, circulating in opposite directions aroun;~ the same path, undergo fre~uency shifts when the path i~ rotated.
~ The ~r~quency shifts are in opposite directions to pro~uce optical ~requen~y differences between the two waves, The two fre~uencies heterodyne at a common photo-detector giving rise to a beat frequency directly proportional to the angular rotational rate.
The laser cavity is often create~ w.ithin a guartz body having a number of apertures cut into it. The apertures form the inner passages which make up the cavity of the ring laser. Each corner of ~he cavity, forme~ by the intersection of the passages, is provi~e~ with a reflective mirror which reflects the twn counter~
propagating light waves from one passageway to the next.
For proper functioning of the ring laser, it is 30 importa~t that the amplitu~e of the two oppositely cîrculatirJg light waves which make up the gyro ~e substantially equal. Ihe character~stic intermo~ulation of the ~cwo light waves is the classical form of amplitu~le modulation with maxima occur ing when the sum of the 3~ ~nstantaneous ~omponents ~re in phase, al~a the minima occurin~ when these components are 1~0 out of phase. If ` `~f~`
~ G~D ~0 ~ n one of the twn light wave signals is significantly greater than the other, the beat signal dloes no ~rop to zero.
Proper ring laser gyro action may be achieve~ by detecting the minimum point of the k,eat signal an~3 then dete~minin~ whether these points are actually zero. If the miniml3m points are not zero, ~che length of the laser cavity is adjusted to drive the minimum p~in~s towar~ zero. To adjust the length of ~he laser cavi~y a piezoelectric tran~ducer is attached ~o one o~ the laser mirrors. A
cavity control circuit ~rives the piezoelectric trans~ucer and, in the prior art, receive~ its input signal from the 1~ ou~pu~ signal of the laser. See U;S~ Letters Patent NoO
4,123,16~ issue~ October 31, 1978 by V.E. Sanders entltled MULTIOSCTLLATOR RING LASER GYRO OUTP~T INFORMATION
PROCES5ING SY~TE~ assigned to the same assignee as the present inventionO
SUMMARY OP THE INVENTI ON - -It i5 therefore an object of the present invention to track the location o~ the ring laser corner mirrors~
Another object o~ the present invention is to cause a piezoelectric transducer to generate its own feedback ~ignal for indicating the position of that trans~ucer.
Still a fur~her object of the present invention is to produce both driver an~ sensor signals from a piezoelectric transducer symmetrical assembly. Symmetry reduces error ~5 cause~ by thermal distortion which is inherent in separately attached sensors such as a piezoelec~ric chip, strain gauge, electromagnetic device or capacitanc2 pi~koff.
~ piezoelectric trans~ucer is formed from a thin metal membrane having a piezoelec~ric ~isk mounlted upon one surface or sandwiched between wo piezoelec~ric disks. The disks ~re coate~ with a metalli~ coatin~. The first pie~oelectric disk, if used, supports the metal membrane.
The metal coating upon the f~rst disks ~rms a ~irst ~ ~ ~ GCD 80 20 electrode while the metal coating upon the secon~
pie20electric disk is divide~ symme~rically to form secon~
an~ thir~ electro~es. The piezoelectric ~isks will hereinafter be called crystals. Tbe secon~ crystal, covered by two separate areas of conductive material, becomes two crystals in one structure. The portion of the crystal structure un~er the second electrode may be use~
either as a driver or sensor crystal, and the portion of the crystal s~ructure under the thirg electrode may also be be used either as a sensor or ~river. The actual portion of the crystal that is use~ to ~rive or sense depends upon the internal structure of the crystal. The area of maximum strain and usually maximum ~tress of the crystal structure is the preferre~ portion for the sensor.
The design of the transducer should be s~mmetrical ~ since symmetry tends to eliminate thermal distortion lS inherent in a separately attache~ sensor. Further, by using the same crystal structure for the ~rlver an~ the sensor, direct monitoring of the driver by the sen~or without interme~iate attachments, such as mechanical or a~hesive layers, eliminates many components which might cause error through manufacturing tolerance, assembly errors, mismatches in alignment, or thermal distortion.
BRIEF DESCRIPTION OF T~E DRAWINGS
Other objects and further a~vantages of the present invention will become apparent to those skilled in the art after a careful consi~eration of the following specification and accompanying arawings wherein:
F;go 1 is a top plan view, partially in section, showin~ a typical ring laser gyro in which the trans~ucer of the present invention may be u~ilized;
Fig. 2 is a cross section taken alon~ lines 2 - 2 of Fig. 1 showing the piezoelectric tran~ucer of the present invention;
Fig. 3 is a plan view of a piezoelectric trans~ucer .
~ 2 ~ GCD 80-20 utilized within ~he present invention;
Fig. 4 is a si~e view of the transducer sf Fig. 3;
Fig. 5 is a plan view Gf an alternative piezoelectric transducer which may be u~ilized;
Fig. 6 is a side view of the ~rans~ucer of Fig. 5;
Fig. 7 i a plan view o anot~er alternative piezoelectric transducer which may be utilize~
incorporatin~ the present invention;
Fig. 8 is a side view oE Fig. 7; ~nd Fig. 9 illustrates the electrical connection o~ the trans~ucer ~hown in Figs. 1-4.
DETAILED DESCRIPTION OF THE PREFERRED EMBOD~MENTS
Referring now to the drawings, Fig. 1 illustrates a typical ring laser gyro 10 which is formed in a bo~y 1~, e.g., ~uartz or an ul~ra-low expansion material, such as lS titanium silicate. The laser body 12 is Gonstructe~ with four passages 14 therein which are arranged ~o form a close~ rectangular path. Alternative configurations such as a triangle or other polygon are knc~wn. Further the laser need not be planar. The passages 14 are sealed to retain a gas mixture consisting, typically, of approximately 90% helium and 10% neon in a vacuum of approximately 3 torr. It is understood that atmospheric pressure i~ approximately 760 torrs.
The body 12 is typically provi~ed with two cathodes 16 and 18 an~ two ano~es 20 and 22 which may be secure~ to the body in a manner that i5 known in he art. Other energiziny means are known, for example, it is common to use a single cat~de~ Gas ~ischarges are establishe~ in passage 14 between catho~e 16 and ano~e ~0 and between ca~hode 18 and anode 22. A getter 24 may be provi~ed to absorb impurities foun~ within the gas in the passageway 14. Mirrors 28, 30 t 32 an~ 34 ~re locate~ at the four corners of the laser optical path for~e~ withln the passageway 14 of the rin~ laser gyro 10. Mirror 2~ i~
12~42 ? GCD R0-20 mounte~ upon a photo-detection ~evice 36. The photo~detection device 36 pro:3uces the bea~ frequency signal generated by the coun~:er-propagating laser beams as a measure of the angular rate of the r ing laser gyro 10 about it~ sensing axis.
Mirror 3~ is mounted upon a piezoelectric transf~ucer 38 which controls the cavi~y 14 position of mirror 34 to control the length of the laser o:E the ring laser gyro.
The piezoelectric trans~ucer 38 is shown in ~3reater ~etail in Fig. 2~ Typically the transducer 3~ has a housing 40 formed by a thin cup-shapea metallic member whose bottom 10 surface forms a flexible ~iaphram 42 which is mounted against the ~uartz body 12 and is sealed thereto by suitable bonding. The surface of the diaphram 42 which mounts against the inner passages of the ~uartz body 12 supports the mirror 34. A post 44, used to Arive th~
diaphram 42, extends from the center of the diaphraym 42.
The cup shaped housing 40 is closed by a trans~ucer housing 48 whose toroidally-shape~ outer rim 49 inclu~e~, for exa~ple, eight spring loaded finyers 50, only five of which are ~hown in Fig. 2, that extend over the outer surface of cup 40. The spring ~ingers are provi~ed with an arcuate surface 51 whioh is urge~ snugly against the outer surface of cup 40 and ~ecured thereto, as by bonding. ~he outer toroidal rim 49 of the housing 48 is connected to a eenter hub 52 by a thin, flexible membrane 54. ~ounted on the inner and outer surfaces of the membrane 54 are disk-shape~
pie~oelecSric crystals 56 and 58, respec~ively.
In the preferred embodiment, it is not necessary to use the inner piezoelectric disk 56. Alternatively, this disk may be used solely as a stiffener~ A~ best seen in Figs. 3 and 4, a pieæoelectric disk structure 5B is coated with a me~al coating 59 to form ~wo concentric electro~es on the surface of the disk. The coating 59 is interrupte~
by a toroidally-shaped cut 60 which forms the concentric inner and outer electrodes 62 and fi4. Interruption o~ the _.
GCD ~0-2 0 metal coa~ing ~9 may be accompl ished by several metho~s including masking the areas o~ the metal coating 5g which are desired and abrading the unmaske~ areas, ~oroidal ring 60, that one wishes to remove.
A stud 65 is ~hreadably mounte~ in the center of hub 5~ for contacting the pos~ 44 of diaphragm cup 40. I~he threaded stu~ 56 is adjus~e~ until it firmly engages the inner surface of post 44. When an electrical poten~ial is placed across the pie~oelectric crystal 58, the crystal will go convexe~, when viewed frorn the left-han~ side of Fig. 2, fs>r removing a pre-set ~isplacement of d:iaphra~n 42 caused by the s~ud 66. This permits mirror 3~ to more, thus adjusting the len~th of laser cavity passage 14.
As seen in Fig. 9, the crystal 58 may be connected to an electrical potential by connecting the membrane 54 to a common po~ential, such as system groun~, and connecting the outer electrode 64 between the common potential and a source of adjustable potential 68. The inner electrode 62 is then connected from the common potential at membrane ~4 to a voltage ~etector 70.
Should two cryst~ls be use~ as shown in Fig. 2, tbe common potential may be connected to a metallic coating over the full surface of the first crystal 56. In this configuration, the crystal 56 is driven to a concave position while ~he crystal ~8 is ~riven to a convex position when viewed from the left-hand side of Fig. 2.
As seen in Figs. 3, 4 an~ 9 the sensor represente~ by voltage ~etector 70 is preferably connecte~ t~ the inner ~lec~rode 52 which is arrange~ over the portion D~ the crystal 58 that experiences maximum strain. It has been found axperimentally tha~ ~n annular piezoelec~ric crys~al having a ~mall ~nternal diameter undergoes maximum stress and strain at or near its in~ernal diameter.
~owever, as the internal ~iameter of an annular piezoele~tric crystal ~ncrease in size, there are some situations in which the ~ensor undergoes maximum stress an~
10~ 2 ! G~D 8 û - 2 0 s~rain near its ~uter ~iameter. ~he outer electrode 64 would then be used as a sensor. As shown in FigsO 5 and 6, a membrane 7~ may be provi~ed with an aperture 74 havins a large internal diame~er and at least one surface upon which is mounte~ a piezoe~ ectric crystal 75~ The crystal is covered with a metallic coating 78 which is interrupte~ by a toroidal cut 80 for forming an inner electrode ~2 and an outer electrode 84. The inner electrode 82 may then be connecte~ to a source of a~ justable voltage potential, such as the adju~table DC source 68, to ~rive the crystal 76.
The outer electrode 84 then produces a voltage which may be measured by voltage detector 70 to produce a useful feedb~c k s ignal .
In ~ome uses of the invention not involving control of cavity le~g~h, it is desired to measure the flexure of a bar. For example, a thin elongated metallic bar is used ln a spring system which mechanically dithers a ring laser gyro about its input axis. hs shown in Figs. 7 an~ R, such a drive system may incorporate a bar-shape~ flexure spring 86 against which is mounte~ a qua~rilaterally-profiled piezoelectric crystal ~ whicht in the embodiment shown, has a rectangular profile. The surface of crystal ~8 is coate~ with a metallic coating 90 which is interrupted by a cut 92, generally perpen~icular to the longitudinal axis of crystal 88, to form a ma jor electrode 94 and a minor electrode 96. The minor elec~rode ~5 i8 preferably located at one en~ o~ crystal 88 which is positioned a~jacent a position of maximum strain of the spring 86. Electrode 46 acts as a sensor electro~e to generate a sensor signal to be applie~ to a voltage detector 70. The major electro~e 94 may then be connecte~ to a source of variable potential 3g 68 for contracting or expan~ing crystal 88 and driving spr ing 8 6 .
Although Fig. 9 shows a separate co~trol voltage source 68 and sensor voltage measuring device 70, it is slear that a typical servo ampliEier (not shown) coul~ ~e _.
~2~4~
used to dri-re the source 68, and ~he voltage measured at 70 could be the feedback voltage which is deliver~d lto the servo ampl if ier .
While ~he plezoelectric ~ransducer of the pre5ent invention has been described for use wi.~hin a ring laser gyro t i~ will be Imderstood that similar trarlsducers may be used in any number o~ devices. Further, the configuration shown as the preferred embodiment within the presen$
invention may be modified to include many variations including a variation with a larger internal diameter, a qua~3r ilateral prof ile or rectangular prof ile . Accor~ ingly, the present invention shoul~ be 1 imited only by the appended claims.
Claims (13)
1. A piezoelectric transducer comprising:
a flexible member;
a piezoelectric crystal mounted upon one surface of said flexible member;
first and second metallic electrodes positioned in contact with a first surface of said piezoelectric crystal;
a third metallic electrode contacting the second surface of said piezoelectric crystal;
driver voltage means connected between said first and third electrodes; and sensor means connected between said second and third electrodes, wherein said piezoelectric crystal produced both driving displacement force to said flexible member and sensing signals for sensing displacement of said flexible member.
a flexible member;
a piezoelectric crystal mounted upon one surface of said flexible member;
first and second metallic electrodes positioned in contact with a first surface of said piezoelectric crystal;
a third metallic electrode contacting the second surface of said piezoelectric crystal;
driver voltage means connected between said first and third electrodes; and sensor means connected between said second and third electrodes, wherein said piezoelectric crystal produced both driving displacement force to said flexible member and sensing signals for sensing displacement of said flexible member.
2. A piezoelectric transducer free of thermal distortion for displacing a membrane, comprising:
housing means for mounting said membrane;
a piezoelectric crystal mounted upon one surface of said membrane;
a coating of metallic material over said piezoelectric crystal to form an electrode upon said crystal;
said coating of metallic material upon said piezoelectric crystal interrupted to form first and second electrodes upon said crystal;
means electrically connecting said membrane to a common potential;
driver means connected to said first electrode on said crystal and then to said common potential; and sensor means connected to said second electrode on said crystal and then to said common potential, wherein said piezoelectric crystal produces both driving displacement and sensing signals with reduced thermal distortion between said signals due to a common use of said crystal.
housing means for mounting said membrane;
a piezoelectric crystal mounted upon one surface of said membrane;
a coating of metallic material over said piezoelectric crystal to form an electrode upon said crystal;
said coating of metallic material upon said piezoelectric crystal interrupted to form first and second electrodes upon said crystal;
means electrically connecting said membrane to a common potential;
driver means connected to said first electrode on said crystal and then to said common potential; and sensor means connected to said second electrode on said crystal and then to said common potential, wherein said piezoelectric crystal produces both driving displacement and sensing signals with reduced thermal distortion between said signals due to a common use of said crystal.
3. A piezoelectric transducer, as claimed in claim 2, wherein said crystal has a quadrilateral profile and said first and second electrodes are formed by a straight line interrupting said metallic coating upon said quadrilateral profile of said crystal.
4. A piezoelectric transducer, as claimed in claim 2, wherein said crystal has a circular profile and said first and second electrodes are formed by an inner diameter interrupting said metallic coating upon said circular profile.
5. A piezoelectric transducer, as claimed in claim 4, wherein the surface area inside said inner diameter interruption of said circular profile forms said second electrode to which is connected said sensor means.
6. A piezoelectric transducer; as claimed in claim 4, wherein the surface area outside said inner diameter interruption of said circular profile forms said second electrode to which is connected said sensor means.
7. A piezoelectric transducer, as claimed in claim 4, wherein said profile of said first and second electrodes is symmetrical to avoid assymetric displacement of said transducer.
8. A piezoelectric transducer as claimed in claims 4, 5 or 6 wherein said sensor means is connected to the electrode on the surface of said piezoelectric crystal that undergoes the maximum amount of strain.
9. A piezoelectric transducer, as claimed in claim 2, wherein said membrane is attached to a mirror driven by said driver means, connected across said membrane and said first electrode, whose driven displacement is sensed by said sensor means, connected across said membrane and second electrode.
10. A piezoelectric transducer, as claimed in claim 2, additionally comprising:
a second piezoelectric crystal connected to the opposite surface of said membrane from said first mentioned piezoelectric crystal;
a coating of metallic material over said second piezoelectric crystal to form a third electrode; and said second crystal coating connected to said common potential in place of said membrane.
a second piezoelectric crystal connected to the opposite surface of said membrane from said first mentioned piezoelectric crystal;
a coating of metallic material over said second piezoelectric crystal to form a third electrode; and said second crystal coating connected to said common potential in place of said membrane.
11. A piezoelectric transducer for driving a mirror in a direction normal to its plane with reduced thermal distortion, comprising:
a housing for mounting the mirror;
a membrane mounted within said housing having its plane parallel to the plane of said mirror;
a disk-shaped piezoelectric crystal mounted upon one surface of said membrane;
a coating of metallic material over said piezoelectric crystals to form an electrode upon said crystals;
said coating of metallic material upon said piezoelectric crystal interrupted to form a first, outer diameter electrode and a second, inner diameter electrode on said crystal;
means electrically connecting said membrane to a common potential;
driver means connected to said first electrode on said crystal and then to said common potential at said membrane;
sensor means connected to said second electrode on said crystal and then to said common potential at said membrane; wherein said piezoelectric crystal produces both driving displacement and sensing signals with reduced thermal distortion therebetween due to a common use of said crystal.
a housing for mounting the mirror;
a membrane mounted within said housing having its plane parallel to the plane of said mirror;
a disk-shaped piezoelectric crystal mounted upon one surface of said membrane;
a coating of metallic material over said piezoelectric crystals to form an electrode upon said crystals;
said coating of metallic material upon said piezoelectric crystal interrupted to form a first, outer diameter electrode and a second, inner diameter electrode on said crystal;
means electrically connecting said membrane to a common potential;
driver means connected to said first electrode on said crystal and then to said common potential at said membrane;
sensor means connected to said second electrode on said crystal and then to said common potential at said membrane; wherein said piezoelectric crystal produces both driving displacement and sensing signals with reduced thermal distortion therebetween due to a common use of said crystal.
12. A piezoelectric transducer, as claimed in claim 11, additionally comprising:
a second piezoelectric crystal connected to the opposite surface of said membrane from said first mentioned crystal;
a metallic coating upon said second crystal to form a third electrode; and said second crystal coating connected to said common potential in place of said membrane.
a second piezoelectric crystal connected to the opposite surface of said membrane from said first mentioned crystal;
a metallic coating upon said second crystal to form a third electrode; and said second crystal coating connected to said common potential in place of said membrane.
13. A piezoelectric transducer as claimed in claim 3 wherein said sensor means is connected to the electrode on the surface of said piezoelectric crystal that undergoes the maximum amount of strain.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US28641481A | 1981-07-24 | 1981-07-24 | |
| US286,414 | 1981-07-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1210842A true CA1210842A (en) | 1986-09-02 |
Family
ID=23098501
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000407970A Expired CA1210842A (en) | 1981-07-24 | 1982-07-23 | Piezoelectric transducer with integral driver and sensor |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5827387A (en) |
| CA (1) | CA1210842A (en) |
| DE (1) | DE3227451A1 (en) |
| FR (1) | FR2510336B1 (en) |
| GB (2) | GB2104283B (en) |
| IL (1) | IL66379A (en) |
| IT (1) | IT1148381B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3218528C2 (en) * | 1982-05-17 | 1984-11-08 | Honeywell Gmbh, 6050 Offenbach | Parallel displacement device |
| WO1986001887A1 (en) * | 1984-09-14 | 1986-03-27 | Honeywell Inc. | Stable path length control elements |
| JPS61292078A (en) * | 1985-05-31 | 1986-12-22 | Tech Res & Dev Inst Of Japan Def Agency | Structure of searching radar and tracking device |
| US4969726A (en) * | 1985-06-03 | 1990-11-13 | Northrop Corporation | Ring laser gyro path-length-control mechanism |
| FR2628201B1 (en) * | 1988-03-04 | 1990-07-13 | Sfena | PIEZOELECTRIC MIRROR FOR LASER GYROMETER |
| FR2630551B1 (en) * | 1988-04-21 | 1993-06-04 | Salaberry Bernard De | COMPENSATED PIEZOELECTRIC MIRROR FOR LASER GYROMETER |
| DE3934968A1 (en) * | 1988-12-23 | 1990-07-05 | Teldix Gmbh | Piezo-drive for axial movement or for mirrors in laser gyroscope - has layers of piezoelectric material or of metal which are glued together at constant distance |
| DE3935891A1 (en) * | 1988-12-23 | 1990-07-19 | Teldix Gmbh | Laser gyro mirror positioner with two piezoelectrical devices - ensures purely axial movement under pressure from leaf spring with decoupling from radial tilt-provoking efforts |
| JP2669916B2 (en) * | 1990-02-02 | 1997-10-29 | キヤノン株式会社 | Vibration wave motor |
| JP6155460B2 (en) | 2013-06-06 | 2017-07-05 | 新シコー科技株式会社 | Drive member, linear drive device, camera device, and electronic device |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1105114A (en) * | 1964-04-13 | 1968-03-06 | Kokusai Electric Co Ltd | Electromechanical resonators and electric circuit devices utilizing the same |
| US4106065A (en) * | 1976-03-19 | 1978-08-08 | Ampex Corporation | Drive circuitry for controlling movable video head |
| US4193010A (en) * | 1976-12-09 | 1980-03-11 | Essex Transducers Corporation | Sensor device using piezoelectric coating subjected to bending |
-
1982
- 1982-07-16 GB GB08220717A patent/GB2104283B/en not_active Expired
- 1982-07-22 IT IT48865/82A patent/IT1148381B/en active
- 1982-07-22 JP JP57126830A patent/JPS5827387A/en active Pending
- 1982-07-22 DE DE19823227451 patent/DE3227451A1/en not_active Withdrawn
- 1982-07-23 FR FR8212928A patent/FR2510336B1/en not_active Expired
- 1982-07-23 IL IL66379A patent/IL66379A/en unknown
- 1982-07-23 CA CA000407970A patent/CA1210842A/en not_active Expired
-
1984
- 1984-12-11 GB GB08431194A patent/GB2149570A/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB2104283B (en) | 1986-02-05 |
| DE3227451A1 (en) | 1983-02-24 |
| FR2510336B1 (en) | 1986-10-24 |
| IT8248865A0 (en) | 1982-07-22 |
| GB8431194D0 (en) | 1985-01-23 |
| JPS5827387A (en) | 1983-02-18 |
| IL66379A0 (en) | 1982-11-30 |
| FR2510336A1 (en) | 1983-01-28 |
| GB2149570A (en) | 1985-06-12 |
| GB2104283A (en) | 1983-03-02 |
| IT1148381B (en) | 1986-12-03 |
| IL66379A (en) | 1987-10-30 |
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