Optically pumped gyroscope vapor cell

Abstract

TITLE: Vapor Cell for Optically Pumped Gyroscope Vapor cell (10) for an optically pumped gyroscope, having a rectangular or n-sided cylindrical shape. Figure 1

Description

Title of the invention: Optically pumped gyroscope vapor cell FIELD OF THE INVENTION

[0001] The present invention relates to an optically pumped gyroscope vapor cell. STATE OF THE ART

[0002] Optically pumped gyroscopes are known in principle. However, they have a high drift stability and are also sensitive to the electric field gradient if the reactive gas used in the vapor cell has a quadrupole moment. The interaction with the electric field intensity splits the energy levels. To minimize this effect, the gyroscopes known according to the state of the art are limited to a cubic or spherical geometry, which does not allow efficient mass production. For the rest, complicated correction mechanisms are required to compensate for the interactions.

[0003] PURPOSE OF THE INVENTION

[0004] The present invention aims to develop an optical gyroscope vapor cell by improving it so as not to require correction based on the quadrupole moment and to allow more economical and thus more efficient manufacturing.

[0005] DISCLOSURE AND ADVANTAGES OF THE INVENTION

[0006] To this end, the invention relates to a vapor cell for an optically pumped gyroscope, characterized in that it has a rectangular or n-sided cylindrical shape.

[0007] A vapor cell is in particular a cell provided with a cavity filled with a reactive gas. Vapor cells serve as an optical resonator. In particular, the vapor cell is hermetically sealed. The reactive gas trapped in the vapor cell comprises in particular an isotope of Xenon, preferably two isotopes of Xenon and particularly preferably the isotopes XE-129 and XE-131. The isotope XE-131 has a quadrupole moment and thus it is sensitive to the gradient of the electric field causing a splitting of the quadrupole.

[0008] Quadrupole splitting is produced by the electric field developed in optically pumped systems by the reaction mechanism at the cell surface. The intensity of the interaction effect thus depends on the materials used. In addition, the electric field deforms when departing from a cubic or spherical geometry. It is known that a cubic or spherical geometry has no negative influence on the quadrupole splitting on the gyroscope measurement signal.

[0009] In particular, the steam cell is made of two different materials, these materials are preferably glass, in particular borosilicate glass or quartz glass and silicon.

[0010] In particular, at least one side of the vapor cell is made of glass. This side delimits the cavity. In addition, at least two sides of the vapor cell may be made of glass. These include two opposite sides delimiting the cavity. In general, the two glass sides are necessary to allow a laser beam to pass through and thus excite the reactive gas. The glass sides are, for example, the bottom cover of the vapor cell. In principle, two different types of glass can be used.

[0011] At least one other side of the glass cell delimiting the cavity is made of silicon. Preferably, all other sides delimiting the cavity and which are not made of glass are made of silicon.

[0012] Preferably, all sides of the vapor cell are made of glass and preferably at least two different types of glass are used. Preferably, however, two sides are made of glass and four sides are made of silicon. It is also advantageous if four sides are made of glass and two sides are made of another material, preferably silicon.

[0013] At least one side of the vapor cell can be coated. This is, for example, a glass side, preferably all glass sides are provided with an anti-reaction coating. In addition, one side, preferably all sides, can also be made of silicon, i.e. provided with such a coating so that fewer atoms relax on the corresponding surface and thus reduce the properties of the quadrupole.

[0014] The shape of the vapor cell and the choice of material are preferably such that the quadrupole splitting of the reactive gas has no effect on the measuring signal of the gyroscope. Thus, the correction of the quadrupole splitting is already provided during the manufacture of the vapor cell and thus it is no longer necessary to make a complicated correction afterwards. This results from the fact that the effects through the different surfaces are compensated by the corresponding effects thanks to the chosen geometry. This also allows freedom of choice of the shape of the vapor cell, which allows efficient series production in particular by a MEMS process.

[0015] The optically pumped gyroscope is in particular a rotational speed sensor. In particular, the gyroscope is used for the navigation of vehicles traveling at least partly autonomously, in particular vehicles transporting people. The very high precision of the gyroscope, in the event of failure of other measuring systems of the vehicle, guarantees the safety of stopping. The present invention improves in In addition, it significantly improves drift stability and significantly reduces noise. This improves the safety and comfort of vehicles traveling in autonomous mode. Overall, this allows purely inertial navigation and thus longer journeys even in cases where there is a poor connection to GPS, radar or other systems, for example, in tunnels or between rows of buildings. Brief description of the drawings

[0016] A steam cell according to the invention will be described below in more detail with the aid of the attached drawings in which:

[0017] [Fig.l] perspective view of a steam cell according to the invention, and

[0018] [Fig.2] Perspective view of another steam cell according to the invention.

[0019] DESCRIPTION OF AN EMBODIMENT

[0020] [Fig.l] is a perspective view of a vapor cell 10 according to the invention comprising a cavity 11 filled with a reactive gas. At least a portion of the reactive gas has a quadrupole moment. The cavity 11a has a cylindrical shape. The vapor cell 10 has a rectangular shape. The vapor cell 10 has a first side 12 made of glass 18. The opposite side of the vapor cell 10 is a second side 13 also made of glass 18. Since the first side 12 is made of glass 18, it is possible, in the example of [Fig.l], to see through the second side 13.

[0021] The first side 12 and the second side 13 respectively constitute the cover and the bottom of the vapor cell 10. In the direction perpendicular to the first direction 20, the cavity 11 is delimited by a third side 14 made of silicon 19. The geometry of the vapor cell 10 and the materials are chosen to compensate for the effect of the splitting of the quadrupole of the reactive gas on the measurement signal.

[0022] The vapor cell 10 can also be made as shown in the perspective view of [Fig. 2]. In this case, the first side 12 and the second side 13 are made of glass while the cavity 11 is rectangular in shape. There are thus several sides delimiting the cavity in the direction perpendicular to the first direction 20. [Fig. 2] thus shows a third side 14 and a fourth side 15 which are made of silicon 19. The fifth side and the sixth side are also made of silicon 19.

[0023] NOMENCLATURE OF MAIN ELEMENTS

[0024] 10 Steam cell

[0025] 11 Cavity

[0026] 12 First side of the cavity

[0027] 13 Second side of the cavity

[0028] 14 Third side

[0029] 15 Fourth side

[0030] 18 Glass

[0031] 19 Silicon

[0032] 20 First direction

Claims

Claims

1. Vapor cell (10) for an optically pumped gyroscope, comprising a cavity (11) filled with a reactive gas of cylindrical or rectangular shape and not of cubic shape, made of two different materials, cell characterized in that - two opposite sides of the vapor cell (10) delimiting the cavity (1), a first side (12) and a second side (13) respectively constituting the cover and the bottom of the vapor cell 10, and crossed by the laser beam are made of glass all the sides of the vapor cell (10) delimiting the cavity (11) and which are not made of glass are made of silicon, - the shape of the vapor cell and the materials are chosen so that the division of the quadrupole has no influence on the measurement signal of the gyroscope.

2. Steam cell (10) according to claim 1, characterized in that at least one side delimiting the cavity (11) of the steam cell (10) is provided with a coating.

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