CA1252551A - Laser angular rate sensor with dithered mirrors - Google Patents
Laser angular rate sensor with dithered mirrorsInfo
- Publication number
- CA1252551A CA1252551A CA000464060A CA464060A CA1252551A CA 1252551 A CA1252551 A CA 1252551A CA 000464060 A CA000464060 A CA 000464060A CA 464060 A CA464060 A CA 464060A CA 1252551 A CA1252551 A CA 1252551A
- Authority
- CA
- Canada
- Prior art keywords
- mirrors
- laser
- vibrating
- mirror
- angular rate
- 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
Classifications
-
- 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
- G01C19/68—Lock-in prevention
- G01C19/70—Lock-in prevention by mechanical means
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Optics & Photonics (AREA)
- Electromagnetism (AREA)
- Power Engineering (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Gyroscopes (AREA)
- Lasers (AREA)
Abstract
ABSTRACT
LASER ANGULAR RATE SENSOR
WITH DITHERED MIRRORS
by Graham Martin A laser angular rate sensor has four mirrors appropriately arranged at the corners of a square to reflect two oppositely directed layer beams around a closed path. Vibrators are interconnected with two adjacent mirrors for effecting oscillation perpendicular to the mirror major surface and at 180 degree phasing. The vibrator drive circuit is controlled by actual mirror displacement to tune and maintain dither amplitude at a predetermined value which preferably is 0.271 of the laser radiation wavelength corresponding to the modulation index of a zero of the zeroth order Bessel function, Jo. The vibrator drive circuit incorporates the capability for dithering when the angular rate of input to the gyro is close to zero, but switches off for other values.
LASER ANGULAR RATE SENSOR
WITH DITHERED MIRRORS
by Graham Martin A laser angular rate sensor has four mirrors appropriately arranged at the corners of a square to reflect two oppositely directed layer beams around a closed path. Vibrators are interconnected with two adjacent mirrors for effecting oscillation perpendicular to the mirror major surface and at 180 degree phasing. The vibrator drive circuit is controlled by actual mirror displacement to tune and maintain dither amplitude at a predetermined value which preferably is 0.271 of the laser radiation wavelength corresponding to the modulation index of a zero of the zeroth order Bessel function, Jo. The vibrator drive circuit incorporates the capability for dithering when the angular rate of input to the gyro is close to zero, but switches off for other values.
Description
~$~
The present invention relates generally to a laser angular rate ~ensor, and, more p~rticularly, to an improved mirror mechanical o~c~llation tec~nlque in ~uch an angular rate ~en~or for overcoming lock-in errors that occur during low angular rate sensing.
BACKGROUND
A la~er angular rate ~en~or, or rinB laser gyro, has two counterrotating monoobromatic la3er b~ams moving around a clo~ed path by ~ucces~ive reflections from three or four mirrors. On rotation of the ~ensor about it~ sensing axi~, the effective path length for the two beams is changed resulting in a fr~quency differential bet~een the beams which is proportional to the angular rotation rate. At low rotation rate~ where the frequency differential between the ~wo 12~er beams would be expected to be small, it i~ found that the beam~ tend to "lock-in" or oscillate at the same frequency so that a frequency dlfferential ie not detected.
One general approach $n the prior art for eliminatlng lock-in has been to mechanically vibrate (dither) the la~er angular sensor ln order to rai~e low ~ensor rotation rate3 out of the lock~in range.
Although useful in reduclng lock-ln, thi~ so-called body dither does not completely remove lock in and it is generally undesirable to sub~ect the entire ~ensor to sustained vibrations.
s An alternative dither ~cheme described ln United States 3,533,014 consists in each mirror of a three-mirror being sinusoidally vibrated in a direction parallel to the reflective surface. This l~ difficult to achieYe in practice since relatively large ~hearing forces are needed to move the mirrors in such a manner.
.
A still further approach set forth in United State~ Patent 4,281,933 involveq vibrating all three lS mirrors of a laser gyro orthogonally to the reflective surface. Although vibrating the mirrors ln this manner i~ relatively easy to achieve, unless a correct pha e relation~hip is precisely maintained the cavity length for the beam~ will change ~uring the dither cycle which 20 is undesirable.
SUMMARY OF T~E DISCLOSURE
A la~er angular rate ~ensor has four ~nirror~
appropriately arranged at the corners of a 3quare to reflect two oppo~itely directed laser beams around a closed path which lies along the optical axis of the cavity. Dithering means are interconnected with two adjacent mirrors for effecting longitudirlal o~cillatlon of these mirrors (i.e., perpendicular to the mirror major surface), the relative phaae for the two mirrors being maintained at 180 de8ree~ so that the cavity length will be unchanged~ The dithering means drive circuit is controlled by monitori~g actual mirror 5~~
displacement in order to tune and maintaln the dither amplitude at a predetermined value which preferably i5 0.271 of the laser radiation wavelength corre~pon~ing to the modulation index of the zeroth order Bessel function, JO.
The dlthering means drive circult incorporate the capability for dithering when the angular rata of input to the gyro is close to zero (i.e., in the lock-in band~, but switches off for values outside the dither band.
The present invention relates generally to a laser angular rate ~ensor, and, more p~rticularly, to an improved mirror mechanical o~c~llation tec~nlque in ~uch an angular rate ~en~or for overcoming lock-in errors that occur during low angular rate sensing.
BACKGROUND
A la~er angular rate ~en~or, or rinB laser gyro, has two counterrotating monoobromatic la3er b~ams moving around a clo~ed path by ~ucces~ive reflections from three or four mirrors. On rotation of the ~ensor about it~ sensing axi~, the effective path length for the two beams is changed resulting in a fr~quency differential bet~een the beams which is proportional to the angular rotation rate. At low rotation rate~ where the frequency differential between the ~wo 12~er beams would be expected to be small, it i~ found that the beam~ tend to "lock-in" or oscillate at the same frequency so that a frequency dlfferential ie not detected.
One general approach $n the prior art for eliminatlng lock-in has been to mechanically vibrate (dither) the la~er angular sensor ln order to rai~e low ~ensor rotation rate3 out of the lock~in range.
Although useful in reduclng lock-ln, thi~ so-called body dither does not completely remove lock in and it is generally undesirable to sub~ect the entire ~ensor to sustained vibrations.
s An alternative dither ~cheme described ln United States 3,533,014 consists in each mirror of a three-mirror being sinusoidally vibrated in a direction parallel to the reflective surface. This l~ difficult to achieYe in practice since relatively large ~hearing forces are needed to move the mirrors in such a manner.
.
A still further approach set forth in United State~ Patent 4,281,933 involveq vibrating all three lS mirrors of a laser gyro orthogonally to the reflective surface. Although vibrating the mirrors ln this manner i~ relatively easy to achieve, unless a correct pha e relation~hip is precisely maintained the cavity length for the beam~ will change ~uring the dither cycle which 20 is undesirable.
SUMMARY OF T~E DISCLOSURE
A la~er angular rate ~ensor has four ~nirror~
appropriately arranged at the corners of a 3quare to reflect two oppo~itely directed laser beams around a closed path which lies along the optical axis of the cavity. Dithering means are interconnected with two adjacent mirrors for effecting longitudirlal o~cillatlon of these mirrors (i.e., perpendicular to the mirror major surface), the relative phaae for the two mirrors being maintained at 180 de8ree~ so that the cavity length will be unchanged~ The dithering means drive circuit is controlled by monitori~g actual mirror 5~~
displacement in order to tune and maintaln the dither amplitude at a predetermined value which preferably i5 0.271 of the laser radiation wavelength corre~pon~ing to the modulation index of the zeroth order Bessel function, JO.
The dlthering means drive circult incorporate the capability for dithering when the angular rata of input to the gyro is close to zero (i.e., in the lock-in band~, but switches off for values outside the dither band.
2~ DESCRIPTION OF THE DRAWING
Figure 1 is a qchematic repreaentation of a la~er angular rate sensor in accordance with the present invention.
~5 Figure 2 is a sectional, elevational view of a mirror and mirror dithering ~eans.
Figure 3 is a function block circuit diagram for dither drive and control.
Figure 4 is an alternate circuit for dither drive and control.
DESCRIPTION OF PREFERRED EM~ODIMENTS
Turning now to the drawing and particularly Flgure 1, a laser angular rate sensor 10 is seen to include a one-piece instrument block 11 with a cavity 12 extending along a square path. Typically, a mixture of neon and helium are contained in the cavity at very low pre~sure (e.g., 3 torr). On e~tablishing an elevated potential difference between cathode 13 and anode 14 as well as ~etween cathode 15 and anode 16, two monochromatic laser beams are generated whlch pa~s in opposlte direction~ along the cavity axis indicated generally by the line 17.
Mirrors 18-21 are loc~ted at each corner of the square cavity and serve first of all to direct the two laser beams along the cavity path indicated generally as at 17. The two ad~acent mirrors 18 an~ 19 include piezoelectric mechanlcal osoillators 22 and 23, respectively, which when energlze~ vibrate or d~ther the mirrors in a direction perpendicular to the flat rerlecting surface of the mirror. When the mirror~
-5~
have a curved reflecting 3uface, ~hen mlrror dither la along the optical axi~.
Turning now to Figure 2I piezoelectric vlbrator~
or oscillator~ 22, 23 3ati~faotory for present purpo~e~
include a material that expand~ and contract~ a~ an eleotr~c potential differential 1~ applled to and removed from opposite face~ Accordlngly, application of a cyclically changing voltage potential to the piezoelectric materlal cau~e~ an alternatin~
lengthening and ~hortening of the mat~rial which, in turn, acts through the vibrator housing 25 to dither ~he mirror. An excellent mean3 for producing thia dither is the plezoelectric ceramlo operaking a~ a bimorph described in United State~ patent No.
4,383,763, CONTROLLA~LE MIRRORS by T. J. Hutchings, et al.
For the ensuing de~crlptlon of a fir~t form of 2~ mirrQr control and drive circuît reference is now made ~,~ to Fisure 3. Typically, in a la~er gyro a mirror t20) iq partially transmis~ive to the laser beams which allow~ them to $mpinge upon conventional optics and photo detector meanq 26 to produce signals re~pon~ive to the laser beat frequeney wave repre~entativ~ o~ the input rate to th~ gyro. Signal3 ~rom 26 are fed lnto conventional count proce~ing circultry for producing output information on both the magnitude and th~ siBn of the input rota~ion. The input rate i~ormati~n is also fed into a microprocessor 28, the ~urpose of which is to decide if the gyro is well outside the lock band.
A sine wave generator 29 provides an A.C. signal to a variable gain ampllfier 30 which, in turn, is lnterconnected with a driver 31 for the plezoelectric vibrator 22 of mirror 18. Slmilarly, the 3ine wave signal from generator 29 ia applied to a second amplifier 32 the output of which i~ fed to a phase shifter 33 where the phase i5 changed by 180 degrees before application to driver 34 for mirror 19 piezoelectric vlbrator 23. As to operatlon of the dither drive cicuit described to this point, the two mirror vibrator 22 and 23 are cyclically driven at the same frequency and amplitude, but 180 de8rees out of phase. This phase difference insureY that the cavity length for the two laser beam~ is maintained constant which is desirable~
The absolute value of the count from the optic~
2~ and photo deteckor 26 for an lntegral number of ~irror oscillation~ is accumulated in a counter 35 A
~ynchronizing pulse is sent from the ~ine wave generator to the counter in order to accompli~h thi~.
The pul~e count of 35 i~ converted to an analog equivalent in digital-to-analog ¢onvertor 36 which iq applied to both gain controls of amplifiers 30 and 32 to effect a corresponding change in the output magnitude of drivers 31, 34.
~ ~r ~æ~
The microprocessor 28 provides an enabllng ~lgnal to the sine wave generator 29 on line 37 aq long as the BYro input i~ within the predetermined lock-in range.
When the gyro input is well in exce3g of the undithered lock-in limit, but before first-order lock band created by the dither at the first harmonic of the dither frequency is reached, the sine wave generator is disabled so that mirror dither iq completely terminated at that time.
Figure 4 depicts a further version of dither drlve and control circuit. As in the first described embodiment, a ~ine wave Benerator 38 i~ interconnected through an amplifier 39 and driver 4G to cyclically dither mirror 18. A1YO~ a~ before, the sine wave generator applies an A.C. voltage through the a~nplifier 41, pha3e shifter 42 and driver 43 to dither mirror 19 at the ~ame frequency and amplitude a~ mirror 18, but 180 degrees ouk of p'nase.
Partially transparent mirror 21 passes a single la~er beam to photodiode 44 which form~ a qignal corresponding to the single beam lnten~ityL This signal will contain an A.C. component as the normal ~5 gyro heterodyne output 9 becau~e of back~catter within the cavity primarily from the mirror~. Output o~ the photodiode 44 i~ formed in peak-to~peak detector 45 and an error signal created in 46. This ~ignal i3 used to control the gain of amplifie~a 39 and 41 such tha~ khe mirrors are servoed to be driven at an amplitude that minimizes the A.C. component (at the gyro output beat frequency) on the ~ignal from photodiode 44O
In the practice of the described invention two immediately adjacent (i.e., con~ecutive) mirror~ in a laser gyro are dithered at the aame freq~ency and amplitude, but 180 degree phase relationsh~p, alang a path perpendicular to the mirror plane. Both veraion~
automatically di~continue mlrror ditherin~ when the 8Yro input rate exceed~ the lock-ln range.
.
Figure 1 is a qchematic repreaentation of a la~er angular rate sensor in accordance with the present invention.
~5 Figure 2 is a sectional, elevational view of a mirror and mirror dithering ~eans.
Figure 3 is a function block circuit diagram for dither drive and control.
Figure 4 is an alternate circuit for dither drive and control.
DESCRIPTION OF PREFERRED EM~ODIMENTS
Turning now to the drawing and particularly Flgure 1, a laser angular rate sensor 10 is seen to include a one-piece instrument block 11 with a cavity 12 extending along a square path. Typically, a mixture of neon and helium are contained in the cavity at very low pre~sure (e.g., 3 torr). On e~tablishing an elevated potential difference between cathode 13 and anode 14 as well as ~etween cathode 15 and anode 16, two monochromatic laser beams are generated whlch pa~s in opposlte direction~ along the cavity axis indicated generally by the line 17.
Mirrors 18-21 are loc~ted at each corner of the square cavity and serve first of all to direct the two laser beams along the cavity path indicated generally as at 17. The two ad~acent mirrors 18 an~ 19 include piezoelectric mechanlcal osoillators 22 and 23, respectively, which when energlze~ vibrate or d~ther the mirrors in a direction perpendicular to the flat rerlecting surface of the mirror. When the mirror~
-5~
have a curved reflecting 3uface, ~hen mlrror dither la along the optical axi~.
Turning now to Figure 2I piezoelectric vlbrator~
or oscillator~ 22, 23 3ati~faotory for present purpo~e~
include a material that expand~ and contract~ a~ an eleotr~c potential differential 1~ applled to and removed from opposite face~ Accordlngly, application of a cyclically changing voltage potential to the piezoelectric materlal cau~e~ an alternatin~
lengthening and ~hortening of the mat~rial which, in turn, acts through the vibrator housing 25 to dither ~he mirror. An excellent mean3 for producing thia dither is the plezoelectric ceramlo operaking a~ a bimorph described in United State~ patent No.
4,383,763, CONTROLLA~LE MIRRORS by T. J. Hutchings, et al.
For the ensuing de~crlptlon of a fir~t form of 2~ mirrQr control and drive circuît reference is now made ~,~ to Fisure 3. Typically, in a la~er gyro a mirror t20) iq partially transmis~ive to the laser beams which allow~ them to $mpinge upon conventional optics and photo detector meanq 26 to produce signals re~pon~ive to the laser beat frequeney wave repre~entativ~ o~ the input rate to th~ gyro. Signal3 ~rom 26 are fed lnto conventional count proce~ing circultry for producing output information on both the magnitude and th~ siBn of the input rota~ion. The input rate i~ormati~n is also fed into a microprocessor 28, the ~urpose of which is to decide if the gyro is well outside the lock band.
A sine wave generator 29 provides an A.C. signal to a variable gain ampllfier 30 which, in turn, is lnterconnected with a driver 31 for the plezoelectric vibrator 22 of mirror 18. Slmilarly, the 3ine wave signal from generator 29 ia applied to a second amplifier 32 the output of which i~ fed to a phase shifter 33 where the phase i5 changed by 180 degrees before application to driver 34 for mirror 19 piezoelectric vlbrator 23. As to operatlon of the dither drive cicuit described to this point, the two mirror vibrator 22 and 23 are cyclically driven at the same frequency and amplitude, but 180 de8rees out of phase. This phase difference insureY that the cavity length for the two laser beam~ is maintained constant which is desirable~
The absolute value of the count from the optic~
2~ and photo deteckor 26 for an lntegral number of ~irror oscillation~ is accumulated in a counter 35 A
~ynchronizing pulse is sent from the ~ine wave generator to the counter in order to accompli~h thi~.
The pul~e count of 35 i~ converted to an analog equivalent in digital-to-analog ¢onvertor 36 which iq applied to both gain controls of amplifiers 30 and 32 to effect a corresponding change in the output magnitude of drivers 31, 34.
~ ~r ~æ~
The microprocessor 28 provides an enabllng ~lgnal to the sine wave generator 29 on line 37 aq long as the BYro input i~ within the predetermined lock-in range.
When the gyro input is well in exce3g of the undithered lock-in limit, but before first-order lock band created by the dither at the first harmonic of the dither frequency is reached, the sine wave generator is disabled so that mirror dither iq completely terminated at that time.
Figure 4 depicts a further version of dither drlve and control circuit. As in the first described embodiment, a ~ine wave Benerator 38 i~ interconnected through an amplifier 39 and driver 4G to cyclically dither mirror 18. A1YO~ a~ before, the sine wave generator applies an A.C. voltage through the a~nplifier 41, pha3e shifter 42 and driver 43 to dither mirror 19 at the ~ame frequency and amplitude a~ mirror 18, but 180 degrees ouk of p'nase.
Partially transparent mirror 21 passes a single la~er beam to photodiode 44 which form~ a qignal corresponding to the single beam lnten~ityL This signal will contain an A.C. component as the normal ~5 gyro heterodyne output 9 becau~e of back~catter within the cavity primarily from the mirror~. Output o~ the photodiode 44 i~ formed in peak-to~peak detector 45 and an error signal created in 46. This ~ignal i3 used to control the gain of amplifie~a 39 and 41 such tha~ khe mirrors are servoed to be driven at an amplitude that minimizes the A.C. component (at the gyro output beat frequency) on the ~ignal from photodiode 44O
In the practice of the described invention two immediately adjacent (i.e., con~ecutive) mirror~ in a laser gyro are dithered at the aame freq~ency and amplitude, but 180 degree phase relationsh~p, alang a path perpendicular to the mirror plane. Both veraion~
automatically di~continue mlrror ditherin~ when the 8Yro input rate exceed~ the lock-ln range.
.
Claims (5)
1. In a laser angular rate sensor where first and second oppositely directed laser beams are reflected from four mirrors so as to traverse a closed path about an input rate sensing axis, the improvement comprising:
first vibrating means for moving a first one of said mirrors perpendicularly to the reflective surface of said first mirror;
second vibrating means for moving a second mirror immediately adjacent said first mirror perpendicularly to the reflective surface of said second mirror; and drive circuit means for energizing said first and second vibrating means in a 180 degree phase relationship and to the same predetermined amplitude.
first vibrating means for moving a first one of said mirrors perpendicularly to the reflective surface of said first mirror;
second vibrating means for moving a second mirror immediately adjacent said first mirror perpendicularly to the reflective surface of said second mirror; and drive circuit means for energizing said first and second vibrating means in a 180 degree phase relationship and to the same predetermined amplitude.
2. A laser angular rate sensor as in claim 1, in which said drive circuit means includes means for interrupting energizing of said first and second vibrating means when the sensor is receiving an angular input rate in excess of a predetermined lock-in rate.
3. A laser angular rate sensor as in claim 1, in which said first and second vibrating means are energized to provide a vibration amplitude equal to 0.271 of the laser beam wavelength.
4. A ring laser gyro, comprising:
a ring laser gyro having two counterrotating laser beams and including four mirrors;
means for translating an adjacent pair of said mirrors in an oscillating mode at the same frequency substantially only vertically to the reflective surfaces of said mirrors; and means for phasing the movements at said vibrating mirrors to maintain constant primary laser beam path length as said vibrating mirrors are displaced.
a ring laser gyro having two counterrotating laser beams and including four mirrors;
means for translating an adjacent pair of said mirrors in an oscillating mode at the same frequency substantially only vertically to the reflective surfaces of said mirrors; and means for phasing the movements at said vibrating mirrors to maintain constant primary laser beam path length as said vibrating mirrors are displaced.
5. A ring laser gyro comprising:
means forming a closed loop optical cavity containing an active lasing medium for generating counterrotating laser beams therein, the frequency difference between the light beams being a measure of the rate of rotation experienced by the ring laser gyro, said cavity forming means including for mirrors for reflecting said light beams; and means for vibrating an adjacent pair of said mirrors in translation at the same frequency in a direction only perpendicular to the surfaces of the mirrors with said vibrating mirrors having nonzero amplitudes of vibration and phases of vibration to cause the total distance around said closed loop to remain substantially constant.
means forming a closed loop optical cavity containing an active lasing medium for generating counterrotating laser beams therein, the frequency difference between the light beams being a measure of the rate of rotation experienced by the ring laser gyro, said cavity forming means including for mirrors for reflecting said light beams; and means for vibrating an adjacent pair of said mirrors in translation at the same frequency in a direction only perpendicular to the surfaces of the mirrors with said vibrating mirrors having nonzero amplitudes of vibration and phases of vibration to cause the total distance around said closed loop to remain substantially constant.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US56907984A | 1984-01-09 | 1984-01-09 | |
| US569,079 | 1984-01-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1252551A true CA1252551A (en) | 1989-04-11 |
Family
ID=24274019
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000464060A Expired CA1252551A (en) | 1984-01-09 | 1984-09-26 | Laser angular rate sensor with dithered mirrors |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS60160677A (en) |
| CA (1) | CA1252551A (en) |
| DE (1) | DE3500044A1 (en) |
| FR (1) | FR2557970B1 (en) |
| GB (2) | GB2152739B (en) |
| IL (1) | IL73151A (en) |
| IT (1) | IT1181841B (en) |
| NO (1) | NO844141L (en) |
| SE (1) | SE458722B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9115538D0 (en) * | 1991-07-18 | 1991-09-04 | Secr Defence | Dither generation for ring laser gyroscopes |
| US5359413A (en) * | 1992-01-13 | 1994-10-25 | Kearfott Guidance And Navigation Corporation | System for substantially eleminating lock-in in a ring laser gyroscope |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4152071A (en) * | 1976-08-02 | 1979-05-01 | Honeywell Inc. | Control apparatus |
| US4281930A (en) * | 1978-12-18 | 1981-08-04 | Litton Systems, Inc. | Laser gyro with phased dithered mirrors |
| JPS5628036A (en) * | 1979-08-14 | 1981-03-19 | Toyota Motor Corp | Tandem brake oil-hydraulic controller having bypass means |
| US4410276A (en) * | 1981-06-15 | 1983-10-18 | The Singer Company | Ring laser gyroscope with doppler mirrors |
| US4653919A (en) * | 1982-02-08 | 1987-03-31 | Sundstrand Optical Technologies, Inc. | Laser gyro with dithered mirrors and current dither |
| US4551021A (en) * | 1982-03-01 | 1985-11-05 | Honeywell Inc. | Discriminant apparatus for laser gyros |
| US4824252A (en) * | 1982-06-25 | 1989-04-25 | Honeywell Inc. | Laser gyro system |
| ZA844479B (en) * | 1983-06-20 | 1985-04-24 | Sunstrand Optical Technologies | Downhole ring laser gyro |
-
1984
- 1984-09-26 CA CA000464060A patent/CA1252551A/en not_active Expired
- 1984-10-03 IL IL73151A patent/IL73151A/en not_active IP Right Cessation
- 1984-10-17 NO NO844141A patent/NO844141L/en unknown
- 1984-12-03 GB GB08430489A patent/GB2152739B/en not_active Expired
- 1984-12-25 JP JP59272146A patent/JPS60160677A/en active Pending
-
1985
- 1985-01-03 DE DE19853500044 patent/DE3500044A1/en not_active Ceased
- 1985-01-07 IT IT47526/85A patent/IT1181841B/en active
- 1985-01-07 SE SE8500057A patent/SE458722B/en not_active IP Right Cessation
- 1985-01-08 FR FR8500176A patent/FR2557970B1/en not_active Expired
-
1986
- 1986-12-30 GB GB08630989A patent/GB2185147B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| IT8547526A1 (en) | 1986-07-07 |
| GB2152739B (en) | 1987-11-25 |
| FR2557970B1 (en) | 1988-11-25 |
| IT8547526A0 (en) | 1985-01-07 |
| SE8500057D0 (en) | 1985-01-07 |
| IT1181841B (en) | 1987-09-30 |
| SE458722B (en) | 1989-04-24 |
| DE3500044A1 (en) | 1985-07-18 |
| GB8630989D0 (en) | 1987-02-04 |
| JPS60160677A (en) | 1985-08-22 |
| NO844141L (en) | 1985-07-10 |
| GB2152739A (en) | 1985-08-07 |
| SE8500057L (en) | 1985-07-10 |
| GB8430489D0 (en) | 1985-01-09 |
| GB2185147A (en) | 1987-07-08 |
| FR2557970A1 (en) | 1985-07-12 |
| GB2185147B (en) | 1987-11-25 |
| IL73151A (en) | 1989-02-28 |
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