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
  • G01C19/668—Assemblies for measuring along different axes, e.g. triads

Definitions

• the subject of the present invention is a triaxial laser gyrometer symmetrized with respect to its cathode axis and to its activation axis.
• a laser gyrometer with a monobloc optic comprising an optical block, for example made of quartz or Zerodur, comprising three resonant optical cavities (one per detection axis) intercommunicating, for example of the type described in the patent FR No 80 06298, filed on March 21, 1980 on behalf of the French Society of Equipment for Air Navigation (SFENA), sold to Sextant Avionique.
• SFENA French Society of Equipment for Air Navigation
• all of these three cavities form a regular octahedron having eight triangular faces: the cavities each have a square shape and extend in three orthogonal planes (respectively perpendicular to the three sensitive axes). These cavities are arranged so that each of the angles of one cavity coincides and communicates with the angle of another cavity.
• a mirror associated with each pair of coincident angles is oriented so as to be used by the two cavities forming said pair.
• one of these mirrors called a reading mirror
• a mixing prism which makes it possible to generate an interference phenomenon making it possible to detect the movements of the gyrometer and therefore of the vehicle which supports it.
• Another mirror called servo mirror, is mounted on a transducer support so as to be able to slave the length of the cavity in order to obtain maximum output power.
• Each of the cavities which contain a gas under low pressure is provided with at least one cathode and two anodes suitably placed, so as to cause an excitation of the electrons of the atoms of the gas and to produce inside the cavity, two beams of counterpropagative laser radiation which propagate in opposite directions along the optical path.
• two symmetrical discharges are generated in the cavity thanks to a cathode whose cathodic housing is in commumcation, thanks to two capillaries, with the two opposite regions of the cavity where wishes to obtain the two discharges.
• a single cathode is used which connects the three cavities by means of three cathode capillaries.
• this cathode constitutes a concentrated heat source on the same side of the optical unit and therefore generates, in this unit, a thermal gradient disturbing the flows of the gas flows.
• this problem is added that due to the fact that there is a pressure difference between the two ends of the discharge and, in particular, between the anode and the gas reserve constituted by the cathode.
• the invention more particularly aims to improve the performance of this type of gyrometer.
• FIG. 1 is a diagrammatic representation, in perspective, of the cavities of a three-piece mono-block laser gyrometer with six mirrors according to the invention
• FIG. 2 shows a cavity of the gyrometer shown in FIG. 1 with its connections to the cathode and to the compensation chamber as well as its two anodes;
• Figure 3 shows, in perspective, the optical unit of a gyrometer with the IFe »m m proceedingsfc.annniiscmmpe r dT'anrcttiiv / a ⁇ irtiinonn n quuii l luuii p es ⁇ tt aç ⁇ snorcviitig
• the gyrometer comprises an optical block 1 of octahedral shape with chamfered edges (FIG. 3) inside which are produced, in three orthogonal planes, three cavities B, C, D comprising the capillary segments Bj to B 4 - C. to C 4 - D. to D 4 and each delimiting an optical path of square shape.
• cavities B, C, D are arranged so that each of the angles of one cavity coincides and communicates with the angle of another cavity. They therefore define, in the interior space of the block, a regular octahedron having eight triangular faces parallel to those of the block and six vertices at the level of which are placed six respective mirrors M., M 2 , M 3 , M, M 5 , M 6 which extend respectively in the planes of the faces of a cube in which the octahedron is located.
• the mirrors Mi, M 2 , M 3 are reading mirrors
• the mirrors M 4 , M 5 , M 6 are servo mirrors associated with piezoelectric transducers making it possible to adjust the lengths cavities.
• the gyrometer To generate the pairs of counterpropagative beams inside the three cavities B, C, D, the gyrometer includes a cathode K and six anodes A.
• the cathode K equips a cathode chamber CK whose axis ⁇ is perpendicular to the cathode face F. of the octahedron delimited by the capillary segments B 3 , C 3 , D 3 and passes through the center of this face F ..
• This chamber CK which is external to the octahedral volume defined by the cavities B, C, D, communicates with these at the level of the three servo mirrors M 4 , M 5 , M 6 which define the face F., via three respective capillaries CK 1; CK 2 , CK 3 .
• These three cathodic capillaries are arranged symmetrically according to a symmetry of revolution of order 3 around the axis ⁇ (that is to say are deduced from each other by a rotation of 120 ° around the axis ⁇ ), which is , as can be seen a trisector of the cube enveloping the optical unit 1 of octahedral shape and having the mirrors at the centers of its faces.
• capillaries CK., CK 2 , CK 3 (or cathode outlets) allow the ionization of the active capillaries between cathode K and anode A.
• the six anodes A are arranged so as to obtain in each cavity a pair of discharge zones "active zones" symmetrical with respect to an axis of symmetry distinct from the axis of symmetry ⁇ .
• Each pair of anodes A extends in the plane of the corresponding cavity B, C, D.
• Thermal and thermodynamic balancing is obtained here by means of a balancing chamber CE of cylindrical shape, substantially identical to that of the cathode chamber CK and arranged coaxially, relatively to the latter, outside the octahedral volume opposite of the face F 2 opposite the face F. (these two faces being perpendicular to the axis ⁇ ).
• This face F 2 is delimited by three capillary segments B., C h D. which each have in their central region a diaphragm DC.
• These three DC diaphragms are arranged symmetrically, according to a symmetry of revolution of order 3 by relative to the axis ⁇ and are deduced from each other by a rotation of 120 ° around this axis of revolution ⁇ ..
• the balancing chamber CE communicates with the three cavities B, C, D at the level of the three reading mirrors M 1 ⁇ M 2 , M 3 which define the face F 2 , by means of three balancing capillaries CE., CE 2 , CE 3 arranged symmetrically, according to a symmetry of revolution of order 3 with respect to the axis ⁇ and are deduced from each other by a rotation of 120 ° around this axis of revolution ⁇ .
• the three capillaries CE., CE 2 , CE 3 can be arranged in the same plane perpendicular to the axis ⁇ . The same is true for the three capillaries CK., CK 2 , CK 3 .
• the balancing chamber CE achieves a pressure balance, on the anode side A of each of the six active zones.
• the assembly comprising the cathode chamber CK and the three capillaries CK., CK 2 , CK 3 which are associated with it ensures, meanwhile, the pressure equalization of the six active zones, cathode side K.
• the six active zones are subjected to the same pressure difference and give rise to the same flows, even in the case where these flows are disturbed by thermal gradients, which are inimited for the reasons described above.
• the balancing chamber may include means making it possible to obtain a Getter effect, or even to exercise a thermal compensation heating of the block.
• the optical unit of the gyroscope is mounted on an activation mechanism in such a way that the axis of symmetry of revolution ⁇ is coincident with the axis of activation of the gyrometer.
• the activation mechanism firstly comprises an activation wheel R. comprising two coaxial rings CA., CA 2 connected to each other by a plurality of radial fins L. These fins L comprise a piezoelectric motor and detection element connected to an amplifier so as to cause an alternating rotational movement of one of the rings CA 2 relative to the other CA ..
• the optical unit 1 is fixed to the central crown CA 2 (activation crown) of the activation mechanism is carried out by means of a fixing crown CF l5 substantially of the same diameter as the activation crown CA 2 on which it can be assembled coaxially by screwing.
• This CF fixing crown which is intended to be arranged coaxially with the cathode K, comprises three pairs of bevelled wedges (not visible) located at 120 ° from one another, and intended to come respectively to stick on the central regions of the chamfered edges surrounding the face F. of the block.
• the activation mechanism also comprises a balancing wheel R 2 comprising two coaxial rings CA '., CA' 2 connected to each other by a plurality of flexible radial fins L '.
• the crown CA ' 2 is fixed to the optical unit 1 (opposite its equatorial plane relative to the activation wheel R.) is carried out by means of a crown CF 2 fastener of substantially the same diameter as the CF crown. and identical to the crown CA ' 2 on which it can be assembled coaxially using screws.
• This CF 2 fixing ring which is intended to be arranged coaxially with the balancing chamber CE comprises three pairs of beveled shims CB, CB ′ located at 120 ° from one another and intended to be bonded respectively to the central regions of the chamfered edges surrounding the face F 2 .
• This method of attachment has the advantage of considerably reducing the tearing stresses between the shims CB and CB 'and the optical unit during the latter's rotational drive.
• the CA crowns. and that'. of the two wheels R l5 R 2 may be secured to one another. Thanks to these arrangements, an excellent balancing of the optical unit 1 is obtained and a corresponding reduction of the conical movement (this is already considerably reduced thanks to the fact that the center of gravity and the center of inertia are on the axis d 'activation).
• the axis ⁇ of the optical unit will be vertical. Indeed, in this case, the gas flows as well as the thermal gradients remain perfectly symmetrical and therefore the effects induced on the false zero are zero.

Landscapes

• 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)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9503329

Family Applications (1)

Country Status (5)

Families Citing this family (9)

Family Cites Families (6)

• 1997
  • 1997-02-05 FR FR9701267A patent/FR2759160B1/fr not_active Expired - Lifetime
• 1998
  • 1998-02-03 EP EP98905482A patent/EP0898695A1/de not_active Withdrawn
  • 1998-02-03 WO PCT/FR1998/000192 patent/WO1998035207A1/fr not_active Application Discontinuation
  • 1998-02-03 RU RU98119963/28A patent/RU2210737C2/ru not_active IP Right Cessation
  • 1998-02-03 US US09/147,103 patent/US6069699A/en not_active Expired - Lifetime

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events