RU2507482C2 - Laser gyroscope - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: gyroscope comprises a triangular optical monoblock with formed optical channels, mirrors of total reflection, a semitransparent mirror, a prism and a source of optical radiation on the basis of a semiconductor laser. To ensure a single-mode radiation regime, a semiconducting laser is equipped with an additional external optical resonator in the form of a truncated prism, which is coated with a light-reflecting coating. On side faces of the truncated prism, which form an angle 40÷60 degrees in respect to its base, in parallel to the base and symmetrically there are two optically transparent holes at the level that matches with the level of optical channels of the monoblock, to create in the resonator a longitudinal optical channel by geometry and position of the monoblock that matches with the main optical channel.

EFFECT: improved reliability of a system.

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Description

The invention relates to the field of laser technology and can be used to create navigation systems of various types, in particular in non-inertial navigation systems.

The main elements of the navigation system is the angular velocity sensor (TLS) of the object, which allows you to measure the angular velocity of the object in inertial space. DLS, as a rule, are built according to the gyroscopic scheme.

The well-known mechanical systems of TLS are currently being actively replaced by laser systems as having greater functionality and higher parameters. Such systems are called "laser gyroscopes" [Bayborodin Yu.V. The basics of laser technology. - 2nd ed., Revised. and add. - Kiev: High school. Head Publishing House, 1988 .-- 383 p. - S.281]. In a laser gyroscope, the carrier of information about the angular velocity relative to the inertial space is electromagnetic radiation, the parameters of which vary depending on the angular velocity vector of rotation. In fact, this is a quantum device with an active ring resonator, in which the radiation propagates towards each other and is output to an interference optical mixer, at the output of which a difference frequency signal of interfering counterpropagating waves is generated. This phenomenon received a specific name by the name of its discoverer - the effect of M. Sanyak.

A ring resonator is an optical system consisting of three or more reflectors, in which the trajectory of the laser beam is closed and the laser beam, passing through all the optical elements, is closed to itself in the plane of the resonator.

In recent years, the efforts of the developers have been aimed at creating a rigid, small-sized and monolithic design of the ring resonator of a laser gyro. In modern designs of laser gyroscopes, as a rule, triangular, quadrangular and fiber-optic ring resonators are used.

Various fiber-optic designs of a laser gyroscope are known [Ivanov VV, Novikov MA, Gelikonov VM Observation of the Sagnac effect in a ring resonator interferometer with a low coherent light source. / Quantum Electronics, 30, No. 2 (2000) - S.119-124; Butusov M.M. Fiber optics in instrument making. - M. Mechanical Engineering, 1985. - S.143-159].

A typical design of a fiber-optic laser gyro is described in [Bayborodin Yu.V. The basics of laser technology. - 2nd ed., Revised. and add. - K .: Higher school. Head Publishing House, 1988. - S.299-302]. The essence of the design solution of the analogue discloses the drawing in figure 1.

Structurally, the system contains: 1 - a laser diode; 2 - radiation input-output device; 3 - coil with fiber optic; 4 - lens; 5 - photodiode; 6 - translucent mirror.

The constructive basis of the device is the coil frame itself, on which a long fiber (500-1000 m) is wound around the coil to increase the sensitivity of the gyroscope. To ensure the condition of monochrome optical fiber is used single-mode. All other elements are mounted on the frame. Lens 4 in conjunction with a translucent mirror 6 form a fiber coupler / splitter of the optical gyro beam, realizing the oncoming movement of radiant energy along the ring resonator and its partial removal in the form of an interference pattern on photodiode 5. Due to this, the Sagnac effect in the passive circuit is realized.

The advantages of this design should be considered:

1. The reliability of the system, which is determined by a semiconductor radiation source, low-voltage power supply.

2. Constructive simplicity of the device with the maximum number of standardized parts.

3. Economic feasibility, which is determined by the maximum level of standardized parts.

The disadvantages of this design include:

1. Non-linearity of the output signal at low angular velocity due to the low sensitivity of the system, even with fiber lengths of 1000 m

2. Lack of structural rigidity, which determines the drift of the output signal due to the displacement of the turns of the coil during strong vibrations of the object on which the gyroscope is mounted.

3. The change in the length of the optical path under the influence of thermal expansion, pressure and mechanical deformation.

Closest to the claimed device is a monoblock design of a laser gyro developed by the American company "Honeywell" [Gorenstein I.A., Shulman I.A. Inertial navigation systems. / Ed. Cand. tech. Sciences I.A. Gorenstein - Moscow: Engineering, 1970 .-- 230 p. - S.161-164]. The essence of the design solution of the prototype discloses the drawing in figure 2.

Structurally, the system contains: 1 - housing; 2 - anodes; 3.6 - mirrors with high reflectivity; 4 - cylindrical channels; 5 - cathode; 7 - aperture; 8 - translucent mirror; 9 - prism.

The housing 1 of the device is a monolithic block of fused quartz, in which cylindrical channels are drilled 4. The axes of these channels lie in the same plane and form an equilateral triangle, at the tops of which there are mirrors 3, 6 and 8. Mirrors 3 and 6 have a reflective surface with a very high reflectivity in the range of operating frequencies of radiation, which is achieved, for example, by the use of a multilayer dielectric coating. The mirror 8 is translucent, due to which the output of radiant energy from the circuit is carried out to pick up the output signal. The surface of the reflecting mirror 3 is made in the form of a section of a sphere of large radius, which can significantly simplify the alignment of the optical circuit.

To ensure sufficient rigidity, the mirrors are connected to the quartz block 1 by molecular adhesion, for which the contacting surfaces of the quartz block and mirrors are made extremely flat and carefully polished. The internal cavities of the block are filled with a mixture of helium and neon under a pressure of about 5 mm Hg. Art. and form together with the mirrors a cavity resonator. In the quartz block are also the electrodes of the self-excitation system of an optical quantum generator (OCG) - two anodes 2 and a cathode 5. A translucent mirror 8 is in contact with a prism 9, which supplies radiant energy to the photoelectric reader. In one of the resonator channels there is a diaphragm 7, the adjustment of which provides a single-mode laser operation mode.

The advantages of this design should be considered:

1. High rigidity of the structure, which is determined by the monoblock of the ring resonator and the integration of the optical quantum generator.

2. Sufficiently high electrical characteristics of the gyroscopic system.

The disadvantages of this design include:

1. The lack of reliability of the system, which is determined by the gas radiation source, structurally performed inside the optical channels of the monoblock; high voltage power.

2. Non-linearity of the output signal at low angular velocity due to the presence of the effect of synchronism in the active gas medium of the laser.

3. The drift of the output signal due to gas flows in a ring laser.

4. Change in the optical path length under the influence of thermal expansion, pressure, and mechanical deformations.

5. High economic costs and the complexity of the assembly technology of the monoblock and the mirror system of the device.

A common feature of known laser gyroscopes are: a laser emitter, a ring resonator with a system of mirrors to create a closed motion of the optical beam, a system for acquiring information in the form of radiant energy of the interference pattern.

The technical result of the invention is to create a laser gyro with the advantages of a gas and fiber-optic gyroscopes, the parameters of which remain acceptable for navigation tasks with increased overall system reliability.

The inventive device comprises a triangular optical monoblock with formed optical channels, mirrors of full reflection of radiant energy, a translucent mirror and a prism for acquiring information in the form of radiant energy of the interference pattern, and a semiconductor laser is included in the device as an optical radiation source, to ensure the single-mode radiation of which equipped with an additional external optical resonator in the form of a truncated prism, the angles at the base of which are 40-60 degrees ow, the thickness is equal to the thickness of the optical monoblock, and the surface is covered with a reflective coating, and parallel to its base, symmetrically, two optically transparent holes are formed on the side faces at a level that coincides with the level of the optical channels of the monoblock and implements a longitudinal optical channel in the resonator cavity, in geometry and the position coincides with the main channel of the monoblock, and for pairing the radiation source in the optical monoblock, a seat is formed, the geometry of which coincides with the geometer the optical resonator of the emitter so that the formed optical channel is a continuation of the optical channel of the monoblock, closing the ring optical circuit of the monoblock.

Common to the claimed device and prototype are the following features:

- triangular optical monoblock,

- optical channels formed in a triangular optical monoblock,

- mirrors of the full reflection of radiant energy,

- translucent mirror;

- a prism for acquiring information in the form of radiant energy of the interference pattern.

Distinctive from the prototype are the following features:

- a semiconductor laser as a source of optical radiation,

- an additional external optical resonator in the form of a truncated prism, the angles at the base of which are 40-60 degrees, and the thickness is equal to the thickness of the optical monoblock,

- the external optical resonator is coated with a reflective coating, and parallel to its base, symmetrically, two optically transparent holes are formed on the side faces at a level that coincides with the level of the optical channels of the monoblock and implements a longitudinal optical channel in the emitter cavity, coinciding in geometry and position with the main cylindrical channel monoblock

- to couple the radiation source in the optical monoblock, a seat is formed, the geometry of which coincides with the geometry of the optical resonator of the emitter so that the formed optical channel is a continuation of the optical channel of the monoblock, closing the ring optical circuit of the monoblock.

The essence of the constructive solution of the claimed device discloses the drawing in Fig.3. The inventive design of the device contains: 1 - triangular optical candy bar; 2 - cylindrical channels; 3, 4 - mirrors with high reflectivity; 5 - translucent mirror; 6 - prism; 7 - additional optical resonator; 8 - semiconductor laser.

The triangular optical monoblock 1 is made of optically transparent material, for example, fused silica or organic glass, in which cylindrical channels 2 are drilled. The axes of these channels lie in the same plane and form an equilateral triangle, at the tops of which there are mirrors 3, 4 and 5. Mirrors 3 and 4 have a reflective surface with a very high reflectivity in the range of operating frequencies of the radiation, which is achieved, for example, by using a multilayer dielectric coating. The mirror is translucent, due to which the output of radiant energy from the circuit is carried out to pick up the output signal. The surface of the reflecting mirror 3 is made in the form of a section of a sphere of large radius, which can significantly simplify the alignment of the optical circuit of monoblock 1.

The internal cavities of the block are polished and connected to the surrounding space. In fact, the monoblock 1 forms, together with the mirrors, a passive ring resonator. Since the internal cavities are not hermetic (they are not filled with active gas, as is the case in a gas laser), this condition reduces the technological requirements for hermetically fixing the mirrors relative to the monoblock 1. The translucent mirror 5 is in contact with the prism 6, which provides the supply of radiant energy to the photoelectric readout device.

A semiconductor laser 8 is included in the device as a source of optical radiation. To ensure a single-mode radiation mode, the latter is equipped with an additional external optical resonator in the form of a truncated prism 7 with a base L, height H, and thickness equal to the thickness of a monoblock. The lateral faces of the truncated prism 7 are formed with an angle β equal to 40 ÷ 60 degrees. A seat is formed in the optical cavity under the semiconductor laser diode with a diameter of C. This optical cavity is designed to further correct the wavefront of the radiation of the semiconductor laser, since the semiconductor laser itself is a multimode structure. The essence of the constructive solution of the additional optical resonator is revealed by the drawing in Fig. 4. The truncated prism of the resonator 7 is made of the same material as the monoblock 1. The surface of the resonator 7 is coated with a reflective coating, for example, a thin film coating of copper (Cu), silver (Ag) or aluminum (Al). In parallel to the base of the resonator 7, two optically transparent holes are formed on the lateral faces at a level H, which coincides with the level of the optical cylindrical channels 2 of monoblock 1. This allows you to create a longitudinal optical channel with a diameter B in the resonator cavity 7, coinciding in geometry and position with the main cylindrical channel 2 of the monoblock one.

As a result, the radiation from the semiconductor laser 8 is formed in the form of a parallel beam along the created channel, i.e. an almost flat wavefront takes place, and the radiation is narrowly directed and two-sided.

To pair the optical radiation source 8 in the optical monoblock 1, a seat is formed, the geometry of which coincides with the geometry of the optical resonator 7 of the emitter so that the formed optical channel is a continuation of the optical channel 2 of the monoblock 1, which allows you to close the ring optical circuit of the monoblock 1.

The device of the laser gyro operates as follows. When applying low-voltage power to the laser diode 8, the latter generates multimode radiation. For the normal functioning of the inventive device, it is advisable that the radiation is as close as possible to a single-mode. The additional optical resonator 7 is actually a passive Fabry-Perot resonator. Its design allows the formation of narrowly and bi-directional radiation from the laser diode 8 in a horizontal optical channel. This radiation is mirrored by a system of mirrors 3, 4, 5 so that the light beam moves unhindered along a closed loop formed by three cylindrical channels 2. As a result, the electromagnetic fields of the radiation of the laser diode 8 circulate in opposite directions and in the absence of a changing absolute angular velocity a system of standing waves is established. The average angular position of the nodes and antinodes of this coordinate system does not change when the contour (monoblock 1) rotates around its axis perpendicular to its plane, which is explained by the corresponding radiation of the frequencies of the radiation propagating in different directions.

To pick up the output signal of the laser angular velocity sensor (laser gyroscope), the translucent mirror 5 and the prism 6 of the oncoming rays are output from the contour at a small angle to each other. The interference pattern formed in this case, which is interference fringes following each other with a certain frequency difference, is fixed by a photodetector included in the processing system of the information signal from the laser gyroscope. An electrical signal of alternating current is obtained at its output. The frequency of this current is proportional to the measured absolute angular velocity of rotation of the monoblock 1 around its axis. The phase component of the frequency of the output signal indicates the direction of the angular velocity of rotation.

Using the inventive device allows you to create a laser monoblock gyroscopes with semiconductor radiation sources for navigation systems of objects that, in the process of performing their functions, are subjected to significant mechanical stresses, wide-range temperature effects and other destabilizing factors, while having high reliability and acceptable technical parameters as angular velocity sensors.

Claims (1)

A laser gyroscope containing a triangular optical monoblock with formed optical channels, mirrors of full reflection of radiant energy, a translucent mirror and a prism, characterized in that a semiconductor laser is included in the design as a source of optical radiation, to ensure the single-mode radiation mode of which the latter is equipped with an additional external optical resonator in the form of a truncated prism, the angles at the base of which are 40 ÷ 60 °, the thickness is equal to the thickness of the optical monoblock, and the surface The component is coated with a reflective coating, and parallel to its base, symmetrically, two optically transparent holes are formed on the side faces at a level that coincides with the level of the optical channels of the monoblock and implements a longitudinal optical channel in the emitter cavity that coincides in geometry and position with the main cylindrical channel of the monoblock, and to couple the radiation source in the optical monoblock, a seat is formed, the geometry of which coincides with the geometry of the optical resonator of the emitter so, then the formed optical channel was a continuation of the optical channel of the monoblock, closing the ring optical circuit of the monoblock.

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