RU2488773C2 - Laser gyroscope - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: laser gyroscope includes a triangular optic monoblock with shaped optic channels, mirrors of full reflection of radiant energy, a semi-transparent mirror, a prism and an optic emission source based on a semiconductor laser. In order to provide a single-mode radiation condition of the semiconductor laser, the latter is equipped with an additional external optic resonator in the form of a semi-sphere that is truncated symmetrically relative to central symmetry axis on both sides to thickness of the optic monoblock and covered with a reflective coating. Along its longitudinal symmetry axis there formed are two optically transparent holes at the level coinciding with the level of optic channels of the monoblock, which implement in the resonator of the emitter a longitudinal optic channel that is a continued part of the optic channel of the monoblock, thus closing an annular optic scheme of the monoblock.

EFFECT: higher reliability of the design and its manufacturability.

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Description

The invention relates to the field of measuring technology, namely, devices for measuring angular velocity, made on ring lasers, in orientation systems and navigation of moving objects.

The main element of the navigation system is the angular velocity sensor (DLS) 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 M. Sagnac effect.

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. 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 increase the reliability of the design, its manufacturability and, in general, the creation of a laser gyro with the advantages of gas and fiber-optic gyroscopes, the parameters of which remain acceptable for navigation tasks with increased overall reliability of the system.

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 hemisphere, which is truncated symmetrically relatively centrally the axis of symmetry on both sides to the thickness of the optical monoblock and is covered with a reflective coating, and along its longitudinal axis of symmetry two optically transparent holes are formed at a level that coincides with the level of the optical channels of the monoblock, realizing in the resonator cavity a longitudinal optical channel in geometry and position coinciding with the main channel monoblock, and for pairing the source of optical radiation in the optical monoblock, a seat is formed with a radius matching the radius of the hemisphere of the optical the 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 hemisphere, which is truncated symmetrically relative to the Central axis of symmetry on both sides to the thickness of the optical monoblock,

- the external optical resonator is coated with a reflective coating, and two optically transparent holes are formed along its longitudinal axis of symmetry at a level that coincides with the level of the optical channels of the monoblock, realizing a longitudinal optical channel in the resonator cavity, coinciding in geometry and position with the main channel of the monoblock,

- for pairing the optical radiation source and the monoblock in the latter, a seat is formed with a radius that coincides with the radius of the hemisphere 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 5 is translucent, due to which the output of radiant energy from the circuit is carried out for the removal of 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 hemisphere 7 of diameter D. A seat for a semiconductor laser diode of diameter C is formed in the optical cavity. This optical resonator is intended to be further adjusted wavefront of radiation of a semiconductor laser, since the semiconductor laser itself is multimode th structure. The essence of the constructive solution of the additional optical resonator is revealed by the drawing in Fig. 4. The hemisphere of the resonator 7 is made of the same material as the monoblock 1. Structurally, the hemisphere of the resonator is truncated symmetrically relative to the central axis of symmetry on both sides to the thickness of the optical monoblock L and is coated with a reflective coating, for example, a thin film coating of gold (Au), silver (Ag) or aluminum (Al). Along the longitudinal axis of symmetry of the optical resonator, two optically transparent holes are formed at level H, which coincides with the level of the optical channels of the monoblock, due to which a longitudinal optical channel with a diameter of B is realized in the emitter cavity, coinciding in geometry and position with the main cylindrical channel 2 of monoblock 1. 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 couple the optical radiation source 8 in the optical monoblock 1, a seat is formed with a radius coinciding with the radius of the hemisphere of the optical resonator 7 of the emitter so that the formed optical channel is a continuation of the cylindrical optical channel 2 of the monoblock 1, closing the optical circuit of the ring resonator.

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, which 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 total 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 provide a single-mode radiation mode the latter is equipped with an additional external optical resonator in the form of a hemisphere, which is truncated symmetrically relative to the central axis of symmetry on both sides to the thickness of the optical monoblock and is covered with a reflective coating, and along its longitudinal axis of symmetry two optically transparent holes are formed at a level that coincides with the level of the optical channels of the monoblock, realizing a longitudinal optical channel in the emitter cavity, coinciding in geometry and position with the main channel of the monoblock, and for interfacing the optical source radiation in the optical monoblock, a seat is formed with a radius coinciding with the radius of the hemisphere of the optical resonator of the emitter so that the formed ptichesky passage is continuation of the optical channel monobloc closing the annular monoblock optical circuit.

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