Triaxial laser rate gyro symmetrized with respect to its axis of

Details Triaxial laser rate gyro symmetrized with respect to its axis of Triaxial laser rate gyro symmetrized with respect to its axis of

1998-10-05

2000-05-30

Turner, Samuel A.

Optics: measuring and testing

By dispersed light spectroscopy

Utilizing a spectrometer

372 94, G01C 1966

Patent

active

060696990

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The subject of the present invention is a triaxial laser rate gyro symmetrized with respect to its cathode axis and to its activation axis.
It relates more particularly to a laser rate gyro with monoblock optics comprising an optical block, made for example of quartz or Zerodur, comprising three intercommunicating resonant optical cavities (one per detection axis), for example of the type which is described in patent FR No. 80 06298, filed on Mar. 21, 1980 in the name of Societe Francaise d'Equipments pour la Navigation Aerienne (S.F.E.N.A.), and transferred to Sextant Avionique. In this example, these three cavities together 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 devised in such a way that each of the corners of a cavity coincides and communicates with the corner of another cavity. A mirror associated with each pair of coincident corners is oriented in such a way as to be used by the two cavities forming the said pair. In each cavity one of these mirrors, termed the reading mirror, is associated with a mixing prism which makes it possible to create an interference phenomenon for detecting the motions of the rate gyro and hence of the vehicle which supports it. Another mirror, termed the control mirror, is mounted on a transducer support in such a way as to be able to control the length of the cavity with a view to obtaining maximum output power. Each of the cavities which enclose a gas under low pressure is fitted with at least one cathode and with two suitably placed anodes, so as to cause excitation of the electrons of the atoms of the gas and to produce two counter-propagating beams of laser radiation inside the cavity which propagate in opposite directions along the optical path. To compensate for the frequency offset between the two counter-propagating waves, two symmetric discharges are created in the cavity by virtue of a cathode, the housing of the cathode being in communication, by virtue of two capillaries, with the two opposite regions of the cavity in which it is desired to obtain the two discharges.
In fact, in a three-axis rate gyro of the aforesaid type, a single cathode is used which links the three cavities by way of three cathode capillaries.
Consequently, this cathode constitutes a concentrated source of heat on one side of the optical block and therefore creates, in this bloc, a thermal gradient which disturbs the flows of the gas streams. Compounded with this problem is the one 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.
To solve these problems it has already been proposed, especially by patent application ER No. 95 01645, filed on Feb. 10, 1995 in the name of Sextant Avionique, to compensate for the asymmetry created in the optical block by the cathode chamber by virtue of an equilibration chamber communicating with the cavity of the rate gyro and made in the optical block on the opposite side from the cathode chamber. This equilibration chamber is advantageously arranged symmetrically in relation to the cathode chamber with respect to a plane, an axis or a centre of symmetry of the block.


SUMMARY OF THE INVENTION

The purpose of the invention is more particularly to improve the performance of this type of rate gyro.
It proposes, on the one hand, to distribute the various categories of elements: control mirrors, reading mirrors, active capillaries, passive capillaries, anodes, of a triaxial laser rate gyro constructed from an optical block provided with a cathode chamber and with an equilibration chamber, which are coaxial, in and around the optical block in such a way as to comply with, in respect of each category of elements, a symmetry of revolution of order 3 about the axis .DELTA. which is common to the cathode chamber and to the equilibration chamber and

REFERENCES:
patent: 4837774 (1989-06-01), Jabr et al.
patent: 4839903 (1989-06-01), Simms et al.
patent: 5940179 (1999-08-01), Jaulain et al.

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