DE8106441U1 - RINGLASER GYROSCOPE - Google Patents

Description

description

The invention relates to a ring laser gyroscope and, more particularly, to an improved ring laser gyroscope in which the Frequency trapping of oppositely directed light waves prevented by an oscillating flow of the laser medium will.

It is well known that with a sufficiently large Rotational speed of the frequency difference between Äwei light waves rotating in the opposite direction in a ring laser are directly proportional to the speed with which the laser rotates. The frequency difference or the beat tone can thus be used To measure rotation, from which the term ring laser gyroscope is derived. However, backscattering of the radiation couples the two oppositely directed light bundles and causes at low rotational speeds that the rays a frequency inclusion sets. This means that the Beat tone becomes zero although the rotational speed of the gyroscope is different from zero. The beat tone 0 * is a function of the floating contribution and is mathematically described by:

0 ' ■ a + b sin (0 - 0 _Q ) ,

where a is essentially the speed of rotation and b is the backscatter coefficient. As long as a essential is greater than b in the previous equation, no frequency lock-in occurs. However, if a ^ b, trapping occurs, causing JP * to disappear,

One way to include this mode problem

fix is to frequency modulate the gyroscope using an 'optical, non-reciprocal technique,

; for example by the fact that the entire system is mechanical

is subjected to a trembling motion. Such a system

for mechanical dither motion is disclosed in U.S. Patent 4,115,004.

Another way of overcoming the problem of mode locking is to use a device which operates on the principle of optical tremble. This means that the oppositely directed light bundles are generated by exciting the laser medium * If the laser is pumped with additional energy beyond that which is required to generate the first mode pair of light bundles, the laser generates a \ additional mode pair, which corresponds to the next longitudinal mode. This so-called four-mode laser is described in an article entitled "Novel Multioscillator Approach to the Problem of Locking In Two-Mode Ring Laser Gyros," by Marian O. Scully, Virgil E. Sanders, and Murray Sargent III , Optics Letters, Vol. 5, page 43, August 1978.

Although the mechanical induction of a tremor movement and to a lesser extent optical tremor of a laser body have been used in practical implementations, simpler and more practical devices are of great interest. the The simpler device proposed according to the invention is a ring laser gyroscope with acoustically induced Trembling motion in which the dielectric medium which forms the laser medium is caused to oscillate or flows swinging. When the two are opposite to each other

directed light bundle through the oscillating, dielectric Passing medium, "the medium causes a frequency shift of each of the bundles of rays, as predicted by the Fresnel-Fizeau effect. Through modulation the size and direction of the flow of the dielectric Medium, the effects of either mechanical or optical tremors can be mimicked.

In 1018 Fresnel derived from the ether theory that the velocity V of light in a dielectric medium moving in the direction of propagation should: to:

^v ■ S V- E ² >

where η is the refractive index of the medium and V _{m is} the speed of the medium. The existence of the Fresnel-Fizeau effect or the Fresnel drag effect has been confirmed by various experimenters, including Fizeau, who did this for the first time in 1851. As an example of a more recent publication, see "The Ring Laser" by Warren M. Macel and Earl JM Cartney published in Sperry Rand Engineering Review, Vol. 8, Spring 1966. This publication deals with the use of a ring laser to achieve the effect by itself to investigate dielectrics moving the laser path. A second paper examining Fresnel drag is entitled "A Precision Measurement of Fresnel Drag In A Ring Laser," by Walter K. Stokwell, Oklahoma State University, Ph.D., 1974, Engineering, electrical, published by Xerox University Microfilms, Ann Arbor, Michigai No. 75-8899 · In this publication a circular disk made of quartz glass is used to show and measure the Fresnel drag effect.

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While Hinglaser have been used to create the Fresnel dragging effect to measure, "a ring laser was not yet known, namely the Fresnel drag effect as a device for frequency modulation is used to prevent mode locking and thus a To create a single laser gyroscope.

Other methods of solving the problem of mode trapping to remedy are known from the prior art, such as from US Pat. No. 3,533,014, in which a method for Oscillation of the mirrors within a ring laser gyroscope is described from US Pat. No. 3,612,690 in which a method is described in which a random electrical tremor is generated, from US Pat. No. 3,721,497, in which a Technique for electrically modulating the laser beam is described and from US Pat. No. 3,743,969, in which still another type of electrically induced tremor is indicated.

The invention provides a ring laser gyroscope in which a tremble is caused acoustically, as a result of which a frequency inclusion at low speed of movement due to radiation backscatter is prevented, and in which the need for the known mechanical or optical tremors does not arise. A ring laser gyroscope is formed within a body having through-channels in the form of a closed web, which are filled with a laser medium such as a mixture of gaseous helium and neon. The laser medium is a dielectric and the Fresnel-Fizeau effect occurs on it when it is subjected to movement.

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The movement of the medium "causes the acceleration or Deceleration of a passing light beam, which depends on whether the medium is in the direction of the light or moved in the opposite direction. The acceleration or deceleration of the light beam causes it to change Fundamental frequency so that the focusing of the beam on one surface in combination with a second beam a change in the interference fringes due to the cancellation and / or amplifying the electromagnetic energy within the beams. The changing Interference fringes are then detected using an overlay detection device to indicate the rotation speed of the ring laser gyroscope.

The dielectric medium within the laser passageways is created through the use of an acoustic dither mechanism, such as a membrane exposed to movement. The membrane can be in a separate from the passage channel and next to it arranged cavity and to vibrate either by the use of an electromagnetic coil or excited by forming the diaphragm from a piece of piezoelectric material. Another The arrangement to induce a flow of the laser medium consists in placing a toroidal membrane directly inside the Arrange laser passage channel and this also by either an electromagnetic coil or a piezoelectric Operate converter. With this arrangement it is possible to eliminate the need for a mechanical dither system or to cancel an optical system, in the third and fourth modes are generated.

It is an object of the invention to provide an improved single laser gyroscope that incorporates an acoustic dither mechanism is provided, which prevents the inclusion of oppositely directed light rays.

Another object of the invention is that Need for a mechanically or optically induced Exclude trembling motion in a single-laser gyroscope.

Another object of the invention is to provide the To use the Fresnel-Fizeau effect to create an improved laser gyroscope which is an acoustic Trembling used.

The invention is illustrated below with the aid of exemplary embodiments explained in more detail with reference to the drawings. Show it:

Fig. 1 is a top plan view, partly in section, showing a typical single laser gyroscope used at the invention can be used,

Fig. 2 is a partial sectional view taken along line 2-2

in Fig. 1, showing an acoustic dither mechanism according to the invention,

Fig. 3 is a partial sectional view taken along line 3-3 in Fig. Λ showing another acoustic tremor mechanism;

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Fig. 4 is a partial sectional view taken along line 4-4 of Fig. 3, and

Figure 5 is a view similar to Pig. 3 making an amendment shows the acoustic tremor mechanism according to the invention.

Figure 1 shows a typical ring laser gyroscope 10, which is formed in a body 12, for example in one Quartz or an extremely low expansion material such as titanium silicate. The laser body 12 is four Through channels 14 are formed which are arranged so that they form a closed, rectangular path therein. The passage channels 14 are sealed so that they retain a gas mixture consisting of approximately 90% helium and 10% neon in a vacuum of approximately 3 torr, where the atmospheric pressure is assumed to be about 760 torr.

In accordance with known laser technology, the body 12 is provided with two cathodes 16 and 18 and two anodes 20 and 22 which are attached to the body in a manner known in the art. the Gas is supplied between the cathode 16 and the anode 20 in the passage 14 and between the cathode 18 and the anode 22. A gate 24 is provided to absorb impurities contained in the gas in the passage 14 available. At the four corners of the optical path that is inside the passage channel 14 of the ring laser gyroscope 10, mirrors 28, 30, 32 and 34 are arranged, two of the mirrors 28 and 34 on photo-detection devices 36 and 38 are attached. The photo verification facilities

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measure the beat frequency of the opposite to each other Directed light beams to the rotation of the ring laser gyroscope 10 by an overlay detection indicate as it is known «

Attached to the outer surface of the laser body 12 is a pair of acoustic tremor mechanisms 40, one of which is best seen in Figure 2, in which the passageway 14 has been rotated 90 degrees for clarity. The acoustic tremor mechanism 40 is within one Cylindrical housing 42 is formed, which consists of a non-magnetic material and has a threaded end which engages in a threaded bore 44 within the laser body 12. The threaded bore 44 has a smaller diameter at its inner end to form a shoulder 46 and a chamber 47. In the most inner surface of the chamber 47, a through-hole is provided which runs at an angle in order to form a second through-channel 48 to the through-channel 14. An O-ring 50 is provided between the shoulder 46 and the innermost end of the housing 42 to seal the housing when it is screwed into the laser body 12. The angular arrangement of the second passage 48 ensures that the vibrational displacement of the laser medium within the passage 14 is a laminar flow without introducing cavitation or other anomalies which could impair the Fresnel-Fizeau effect. The pair of acoustic trembling mechanisms 40 are arranged to generate a push-pull flow of the medium and thus a vibration displacement between the zv. ^r ei arranged at angles

Passage channels 48, creating the Fresnel-Fizeau effect occurs only on the relatively short distance in between, as shown by Heil 49.

The acoustic dither mechanism 40 comprises a coil 52, which is inserted into the housing 42 and which with transformer wire 54 is wound, which is connected to terminals 56. A longitudinal bore 58 within the Spool 52 receives a rod 60 made of a corrosion-resistant magnetic steel * The lower end of the rod 60 is connected to an anchor membrane 62, which slidably fits into the chamber 47. A spring 64 presses armature 62 downward or in an inward direction. As is known, an alternating current causes the Connections 46 that the spring-loaded armature 62 against the compressive force of the spring 64 in an upward direction Eichtung is drawn into the coil 42 due to the electromagnetic field generated by the transformer wire 54 is created. When the field collapses due to the alternating current, the armature is lifted by the force of the spring 64 printed down. This causes the laser medium to vibrate within the passage channel 14 the pumping action flows softly through the anchor membrane 62 of each mechanism 40 is caused as it moves the medium in and out of the medium in a push-pull combination second passage 48 moves or forces.

An arrangement which differs from the acoustic trembling mechanism 40 according to FIG. 1 is the second, acoustic one Trembling mechanism 70. As best shown in Figures 3 and 4 can be seen, the second, acoustic tremor

Mechonismus 70 fixed within a bore 72, which is arranged in the side wall of the laser body 12 Cer. the Through hole 72 goes through the passage 14 and is threaded at its outer end The acoustic dither mechanism 70 is shown in FIG a non-magnetic housing 76 is formed, which is cylindrical in order to be used as a plug in the opening 72 fit. A pierced chamber 78 passes through the housing 76 at a right angle to the main axis of the housing through * This hole 78 is arranged so that it can be used for Passage channel 14 is concentric. In. the hole 78 is a tubular sleeve 80 made of non-magnetic material fitted and with a recessed cylindrical surface 81 configured to receive and hold transformer wire 82. The bore 78 within the cylindrical * Housing 76 significantly reduces the lateral working Cj area within which the acoustic tremor mechanism formed in the sleeve 80 can be attached, such as

- it can best be seen in FIG. The sleeve 80 takes in the bore 78 the housing 76 not with any positive retention means other than an adhesive held>; ground, since the inner surface of the opening 72 the

Lateral movement of the housing 76 is prevented.

The non-magnetic sleeve 80 has a longitudinal bore which is enlarged at one end by a main shoulder 86 to form. Within the bore 84- a tubular anchor 88 is slidably attached, v / elcher consists of a magnetic material and at one end of which a disk-shaped membrane 90 is attached,

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-loMitte has an opening 92 which allows the passage of the mutually oppositely directed light beams within the passage 14. The armature 88 is retained in the bore 84 by a C-shaped pinch clip 94 located in a groove in the inner surface of the bore 84. A spring 96 presses the armature and the membrane 90 against the terminal 9 ^. ^The application of an alternating current to the connections 98, which are connected to the transformer wire 82, generates an electromagnetic force ₁ which pulls the magnetic armature 88 into the coil formed by the transformer wire 82 against the force of the spring 96. Removal of the current causes armature 88 and diaphragm 90 to move in the opposite direction. In this way, the armature and the membrane cause the laminar flow of the laser medium at a frequency caused by the signal applied to the terminals 98.

The top or extreme end of the housing 76 is provided with a Groove 100 is formed, in which an O-ring 102 is arranged. When the housing 76 is inserted into the drilled opening 72 has been, the O-ring 102 seals the passage 14. The housing 76 is in the opening 72 by a cap 104 held, which is screwed into a threaded section 74 and carries the terminals 98, thereby completing the acoustic dither mechanism 70 au.

The electromagnetic coil arrangement according to Figures 3 and 4 can be replaced by a piezoelectric crystal, as described below. While only single the mechanism 70 was shown, it goes without saying that a pair of these mechanisms are in a push-pull combination

can be used as previously described. However, the design of the mechanism 70 leads itself to a single unit application.

Another embodiment of the acoustic dither mechanism is shown in FIG. In this arrangement there is a acoustic tremor mechanism 110 formed in a cavity 112 in the form of a blind hole made in a side wall of the laser body 12 is arranged. The blind hole is connected to the through-channel 14 via a second through-channel 114 in "Connection. This passage channel extends at an angle to the passage channel 14 to to support a laminar flow of the displaced laser medium, as described with reference to FIG became. The upper portion of the cavity 112 in the form of a blind hole is expanded around a shoulder 116 form. A membrane 118, which is made from a disk of a piezoelectric material, rests against the shoulder 116 is formed. The outer circumference of the cavity 112 in the form of a blind hole is designed with a thread, to receive a cap 120 that carries the terminals 122. An O-input 124 rests on the top outer surface of the piezoelectric Diaphragm 118 on and cap 120 presses against the O-ring to seal cavity 112. At the connections 122 spring contacts 126 are attached which contact opposite ends of the piezoelectric diaphragm 118. When a voltage is applied to the terminals 122, the piezoelectric membrane is displaced as a voltage occurs at her in order to increase or decrease the volume of the cavity 112 and thus a vibrational © Causing flow of the laser medium within the passage channels 114 and 14.

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As can best be seen in Figure 5, it is desirable to use two acoustic trembling mechanisms 110, the second passage channels 114 of which converging below Angles are arranged to the passage channel 14, so that the first, acoustic trembling mechanism 110 the flow of the laser medium in one direction and the second, acoustic tremor mechanism 110 causes flow in the second direction. In this way are the two trembling mechanisms 110 arranged in a push-pull configuration to enhance the oscillatory flow of the laser medium, as shown by arrow 49.

The various acoustic dither mechanisms described above, including mechanisms 40, 70 and 110 can be modified within the illustrated configurations or other configurations are for the average specialist possible. Whether an electromagnetic coil or a piezoelectric transducer can be used to produce an oscillatory Stx'Ömungsbewegung on the laser medium, is a matter of preferred construction. The essential feature of the invention is that thereby, that the laser medium is exposed to a flow condition, the ring laser gyroscope 10 is acoustically subjected to a trembling motion can be. This acoustic tremor removes the need for either mechanical or optical tremors as is known in the art. As described above, does this cause flowing ?, medium a change in the speed of the oppositely directed light rays when the electromagnetic Energy passes through the flowing medium due to the refractive index according to the Fresnel-Fizeau effect.

While "ring lasers have been used to date Fresnel-Fizeau effect or the Fresnel-pounding effect to investigate, it was not known from the prior art to use this effect to produce a single-laser gyroscope subject to a tremor and thereby prevent mode lock-in caused by the Inclination of the mutually oppositely directed light rays is caused to "lock themselves in at similar frequencies, when the moving speed of the gyroscope is small.

The acoustic tremor mechanism created on the basis of the invention is connected with the mechanical citing in it. Equivalent to the fact that both the amplitude and the frequency can be changed and controlled. It turned out that the optical tremor in which a third and fourth mode are optically generated, not in that can be controlled to the same extent, since the amplitude and the frequency are determined by the parameters of the system are. Thus, from the preceding explanation there is an arrangement in which the advantages that are achieved with a mechanical System exist, "are retained, while the numerous, expensive and complicated elements of a mechanical dither system through the use of the extremely simple acoustic mechanism were excluded.

summary

Ring laser gyroscope, in which light beams in opposite directions in the same closed Circulate passage channel. The passage channel is filled with a dielectric laser medium - through a acoustic tremor mechanism is attached to the dielectric Medium caused a flow within the passage channel in opposite directions, so that at the Light passing through the flowing medium emits a change in speed and thus a change in frequency in accordance with the Fresnel-Fizeau effect is caused to avoid frequency trapping.

Claims (10)

LITiPON SYSTEMS, INC. 360 North Crescent Drive, Beverly Hills, California 90210 USA P 16 003-46 / L Single laser gyro scope - ¥ sr n si) rü ch e .1. Single laser gyroscope consisting of a laser body, in which a passage channel is formed which is filled with a laser medium, and a device to two modes of laser oscillation within the laser medium to generate, these modes propagating in mutually opposite directions, characterized in that a device (40; 70; 110) is provided through which an oscillating flow of the laser medium can be generated within the passage channel (14), creating a frequency difference between the two laser modes Telephone (οββ) auaeeä · · '< icle »be-aaaeo! TsLsanAMMB μοναρλτ can be caused due to the oscillating flowing medium in order to prevent a frequency inclusion of these modes. 2. Single-laser gyroscope according to claim 1, characterized in that the device (40; 70; 110) for generating an oscillating flow of the laser medium comprises a membrane device (62; 90; 118). 3- single-laser gyroscope according to claim 2, characterized in that the membrane device (90) is toroidal is formed around the passage channel (14). 4. Single-lens gyroscope according to claim 2, characterized in that the membrane device (40; 110) in a chamber (47; 112) is formed, which next to the Passage channel (14) lies and is connected to this by a second passage channel (48; 114). 5- single-laser gyroscope according to claim 2, characterized in that the membrane device (40; 70) by an electromagnetic coil (54; 82) is operable. 6. Bing laser gyroscope according to claim 3, characterized in that the membrane device (110) can be operated with a piezoelectric transducer (118). 7-Bing laser gyroscope according to Claim 2, characterized in that the Merobran device (40; 110) is a A pair of diaphragms (62; 118) arranged in a push-pull sequence operate. I III · I I ι ι ·· ■ · 4 · 4 * 11 8. Ring laser gyroscope consisting of a laser body in which a passage channel is formed which is filled with a laser medium, and a device for Exciting the laser medium in order to generate light waves that run in opposite directions in the passage channel of the Hinglasers, characterized in that a device (40; 70; 110) is provided, to cause a flow of the lasing medium in a first and then in another direction, whereby through the Fresnel-Fizeau effect on the opposite to each other directed light waves in the flowing laser medium produce a frequency difference in the oppositely directed Light waves can be generated by including the frequency of the oppositely directed Waves can be prevented. 9 «ring laser gyroscope according to claim 8, characterized in that the device (40; 70; 110) for causing a flow of the laser medium has an oscillating membrane device (62; 90 »118). 10. Ring laser gyroscope according to claim 9, characterized shows that the vibrating diaphragm means comprises a pair of acoustic dither mechanisms (40; 110), which are arranged in next to the through-channel (14) and with the through-channel (14) through the second Passage channels (48; 114) are connected, which at a converging angle to the first-mentioned passage channel (14) are arranged.