SE448576B - PROCEDURE AND DEVICE FOR REDUCING BACKGROUND SPREADS IN VIBRATING CIRCUITS - Google Patents

Description

10 15 20 25 30 35 448 576 2 A major cause of entrapment is the mutual energy the leakage from each beam in the direction of the other beam.

This mutual leakage or backward radiation is explained in 148 - 153. In short, the frequency the difference between two opposite waves in a ring laser detail by Aronowitz on p. largely according to the equation: @ = the instantaneous phase difference between the two opposite a + b. sin W where w is the waves, a is proportional to the angular velocity of the ring laser and proportional to the size of the backward rotation b is the energy.

When a is less than b, the oscillation frequency becomes equal to zero and the ring laser is locked. To get an output signal that constitutes a measurement greater than b.

An arrangement to reduce the effects of on the rotational speed of the ring laser body must be a locking is to mechanically oscillate the ring laser body at an angle against its delicate shoulder. By oscillating or vibrating the laser device, a rotational speed is superimposed on the gyroscope. pet so that a is mostly greater than b, whereby the effects of b is kept to a minimum or eliminated. vibration is discussed in U.S. Patent H 115 OBH.

U.S. Patent H 152,071 discloses that technique A gyro with mechanical which comes closest to the present invention. In this patent writing indicates a device with a ring laser that has three mirrors and a path length guide arranged on one of the mirrors while a locking control device is arranged on another mirror for controlling the mirror position. The path length control is one fast servo while the locking control is a less fast The third mirror conveys part of the laser beam The signal from the light sensor servo. light to a light sensor. machined by the two servos and the device according to the control controls the locking mirror to reduce the amplitude the variation to a minimum of only one beam signal at the vibration speed. c- 10 15 20 25 30 35 ~ nxw 448 576 Disclosure of the invention When the frequencies of the roads facing each other frequency modulated by mechanical vibration of the ring laser at an angle to its sensing axis, the sum signal for The modulation curves, also called the boundary curves, to the two opposite waves become equal to zero.

When backscattering appears on the surface of the mirrors increases or decreases the amplitude of the low-frequency alternating current the components of the AM signal curves in step with the interference of the backward wave and the main wave. A purpose with invent-f is therefore to regulate the AC amplitudes for the the low frequency AC components of the AM signal curves in the opposite waves by moving the mirrors inwards and outwards until the sum of the AC amplitudes for the low frequency AC components of the AM signal curves in the waves is as close to the minimum as possible.

A mechanism for regulating the amplitude of the low the frequent AC components of the AM signals for the both opposing waves are to power the mirrors according to a signal which is a measure of the AC amplitude the difference between two successively measured sums of the the low frequency AC components in the AM signal curves for facing waves. After the signal, which centers the sum of the low-frequency AC components in the AM signal curves for the opposite waves, has reduced to a minimum in a mirror the regulation scratched at the other mirrors. Alternatively, can simultaneously three mirrors are regulated simultaneously. If they are regulated at the same time is it is desirable to make the actuation times for the different servos different, so the servos do not get the mirrors in oscillation.

After the mirrors have been adjusted for reduction of the low frequency AC components in the AM signal curve the sum of the opposite waves to a minimum mum, they can optionally be adjusted to keep the difference between such AC components for the opposite road at a minimum. The regulation is then repeated for bringing the sum of such AC components for those directed the waves to a minimum. 10 15 20 25 30 35 448 576 4 The inventive idea is not limited to a triangular shape ring laser with three mirrors but can be used for example a ring laser with four, six or eight mirrors, but is not completely is limited to this number of mirrors.

When one or more mirrors are servo controlled according to it In the present invention, it is advantageous to have a mirror controlled by a fast servo for regulating the total length, to keep the working point of the gyro essentially on the peak value of the gain curve.

Advantageous embodiments In one embodiment of the invention, for example two out of three mirrors in the ring laser with slow servos while the third mirror is quickly controlled according to the better known function for tuning the laser and keeping the the point of the gyro mainly at the peak value of the gain curve.

It is also conceivable to be entirely inconsistent with the invention frame to distribute the steering mirrors so that, for example, mirror number 1 was used to control the total length of the laser path while the mirrors numbers 2 and 8 are controlled according to the present invention.

After a while, mirror number 2 can be used to control the total length of the laser path while the number 1 and 3 mirrors controlled according to the invention. The mirrors number 1 and 8 can then are used to control the total length of the laser path while they the remaining mirrors are power-operated according to the present invention. the finding.

In a preferred embodiment of the invention feel the AC amplitudes of the signal curves for those the opposite waves and the sum of the amplitudes race in a logic circuit, which may form part of a microcomputer.

The AC amplitudes of the signal curves for each other the opposite waves are sensed again and added. The new sum subtracted from the stored sum signal. Depending on it sensed difference value, a voltage is emitted to the piezo electric crystals that regulate the mirror position of step of this mirror stepwise inwards or outwards. Thereafter, the signals are recognized again and added and compared. Regular the ring continues until a minimum difference is reached between two 10 15 20 25 30 448 576 5 successive sum signals received. This minimum is proven by changing the character for the difference value.

The measurements can be repeated again, but now one is regulated andnusegulläge in response to the difference between the channels generated by the AC amplitudes of the signal the curves of the two opposing waves. The measurements can be repeated over and over again for adjusting different mirrors with regard to the minimum difference between successive measured sums of the AC amplitudes of the signal curves for the two opposite waves.

I After the sums of the AC amplitudes has been reduced to a minimum, it is within the scope of the invention framework to also reduce the differences to a minimum. In a typical embodiment of the invention is subtracted for it due to the AC amplitudes and stored. The location for one mirror is then moved after which the AC amplitudes again subtracted. The differences are compared and the mirror is moved again in a direction to reduce the difference to one minimum. Since the mirror positions have first been set for bringing the sum to a minimum value, it is not appropriate to completely reduce the difference signal to the minimum value because this would have a detrimental effect on the sum signals. Follow-up only a predetermined number, for example five, difference signals to be calculated before the device is reset to the work team where the sum signals are kept to a minimum.

An object of the present invention is therefore to keep the optical scattering in a ring laser to a minimum.

Another purpose is to reduce the spread to a minimum in such a ring laser which is vibrated about its sensing axis.

Furthermore, it is an object of the invention to power steering at least one corner mirror in a ring laser to such a position that the sum of the low-frequency AC amplitudes of the signal curves for the opposite waves become minimal. Another purpose is to control at least one corner mirror in the ring laser to such a position that the difference between the voltage amplitudes of the signal curves of the directed waves become minimal. The purpose is also to be able to 10 15 20 25 30 35 448 576 6 consecutive power steering mirrors located one after the other specified way. Furthermore, it is a purpose to be able to achieve the above stated purposes through the use of a digital computer.

Other purposes and purposes will be apparent from it the following detailed description of the invention, which description is given with reference to the accompanying drawings, where Fig. 1 shows a section through a normal ring laser there the position of its corner mirrors are arranged to be servo-controlled, Fig. 2 shows a flow chart of a computer with sum routine for power steering of a corner mirror system according to the invention and Fig. 3 shows an optional flow chart for a difference determination routine according to a possible further development of the invention. 1 encloses a ring laser, intended to used as a gyro, in a substantially rigid block 10.

A polygonal channel 12 for a laser path (indicated by arrows 14) is formed in block 10 and encloses a laser gas, e.g. According to FIG. a mixture of helium e, neon 20 and neon 22. Laser the path is rendered triangular but may have other polygons shapes and does not need to be flat either. Normally, the track is tri- At the tips of the polygon 163, 16C to reflect angular or rectangular. the path there are corner mirrors 16A, the laser light in the annular path, the laser light being emitted spreads both clockwise and counterclockwise along the laser path. Lasers stimulated in amplifier sections 18 where electrons and ions passes the laser gas between the cathodes 24 and the anodes 26. channels 28 connect the anodes 26 and the cathodes 24 to amplifiers. sections 18.

The length of the laser path is regulated by displacing one 160 inwards and outwards so that the length of the track This shift of mirrors 16A, 18B, becomes a multiple of the wavelength of the laser light. controlled by circuit 32. The purpose of the present invention is to The solution is to correct all 16A, 1GB, 16C mirrors with with respect to backscatter. When a certain mirror is switched on backscatter correction, it is not regulated by the path length control circuit 32. A logic circuit 3% consequently affects the circuit 10 15 20 30 35 448 576 7 then 32 to transmit control signals to alternative mirrors 16A, 16B, 16C during periods when this particular mirror is not subject to correction according to the invention. IN Each mirror has a piezoelectric transducer 36A, 36B, 360, which may, for example, be of the type described in U.S. patent (application 7N 619/1979). The length control for the cavity may, for example, be designed as described in U.S. Patent R 152,072.

At small angular velocities, they show each other directed the waves at almost the same frequency as the waves to lock at the same frequency. The phenomenon is called fixed locking. Locking is caused by backscattering of the light from one direction of propagation to the opposite direction of propagation and synchronization between the primary beam and the reverse beam scattered light.

A way to reduce the effect of backscattering The minimum is to ensure that the angle of the ring laser gyro speed is within the angular velocity locking range area only for a very small part of the total the time. By mechanically vibrating the ring laser by means of a - vibrating device # 2 around the sensing shaft 40 is possible ensure that the angular velocity is low below only one short period of time. The vibration can be cyclic, sinusoidal or random. The vibration produces a frequency modulation of the opposite ring laser waves. By regulating the frequency or velocity as well as the amplitude of the vibration you can ensure that the angular speed of the ring laser is. within the locking range during a very small prooentual part of the time.

The effective path length for each other counteracting the waves can likewise be kept separate by vibration, at the Faraday effect in U.S. Patent 3,373,659.

To further reduce the risk of locking is it is desirable to adjust the mirrors 16A, 163, 160 so that the the spread is reduced to a minimum. It has been found that the rearward scattering of the mirrors is minimal when the sum of them the alternating voltage amplitudes of the frequency modulated curves are minimal. IN (__- 10 15 20 30 35 448 576 8 The process of the present invention is discontinued therefore from the problem of reducing the sum of the frequency modul ~ the alternating voltage amplitudes of the curves to a minimum first first mirror and then at the next and next and so on until the sum is minimal for all mirrors. by a further After the sum of the frequency modulated cur- their alternating voltage amplitudes have become minimal too all mirrors, the technology according to the present 'invention is refined by moving the mirrors one by one to reduce the difference between the frequency modulated ones the AC amplitudes of the curves to a minimum. In order to avoid setting the minimum value of the sum done, however, the difference values will rather only reduced but not necessarily reduced to a minimum. Eczema pelvis, the size of the mirror movement can be limited to one predetermined low value during the process of making a difference minimal signals.

At least two of the mirrors 16A, 168, 160 are advantageous partially permeable, so that a pair of photosensitive organs such as photodiodes 44, # 6 can be used to monitor both the individual laser beams. Two other detectors at another permeable mirror, which is combined with a combination means, as disclosed in U.S. Patent 3,373,650, are utilized normally to measure the heterodyne difference of the gyro- the frequency signal. The output signals from such photosensitive organs 44, # 6 is supplied to the channel length control circuit, as indicated with included arrows, to be used in conjunction with the steering of the total length of the laser cavity. The photosensitive organs signals are also fed to the logic circuit 3% according to the included ones the arrows to be used to bring the mirrors backwards. spread to a minimum according to the present invention.

The connection 50 between the logic circuit 34 and the control the channel length circuit 32 indicates that the logic circuit affects this control circuit to switch from one sail to another different as different mirrors are corrected according to the invention ningen. Normally the detectors HN, H6 are used for a mirror while another mirror was used to control the channel length _. _ a .. m .... », ............... <..... 10 15 20 25 30 35 448 576 9 and a third mirror is corrected for backscatter. ningen. The mirrors are then switched sequentially as shown below. written way.

SSB, 36C is indicated by Normally, vibrating The control of the transducers 36A, input arrows on these converters. with a frequency of up to 500 Hz, the oscillation the amplitude is such that the frequency of the directional waves are frequency modulated over a range of magnitudes the game scheme 1,250 kHz. The vibration will thus be cyclic at frequencies not normally exceeding 500 Hz and If the vibration is random, they should be highest against each other it is sinusoidal. the frequency components of the frequency modulated, directed waves be of the order of 1,250 kHz.

The cannula length control circuit 32 includes a servo that is fast compared to the speed for the 3% influence of the logic circuit, so that the channel length continuously tuned by moving a mirror for adaptation to the movements of the other mirrors, which moved to reduce the backward spread to a minimum.

In Fig. 2, "L" refers to the inward / outward the position of the mirrors 16A, 168, 16C and the piezoelectric ones 3GB, 360. The suffix "i" refers to In 36C referred to. The number of converters converters 36A, which converter 36A, 36B, and mirrors need not be limited to three.

Nevertheless, the suffixes correspond to "1", "2", "3" when assigned "L" the three positions "A", "B", "C" for the three displayed the mirrors.

The designation "AM1", "AM2" refers to the AC voltage amplifier the tude of the signal curves of the frequency modulated signals, detected by the detectors MN, M6.

The designations "A1", "A2" refer to the signals stored and represents the signals detected by the two optical sensors, for example in the form of the detectors 44, 46. The terms "A3", "Au" refer to the signals which were stored immediately before the sensing of the signals A1, A2.

The signal "A" refers to the equation A = (A1 + A2) - (A3 + An) when the device is operating in the position where the sum of the such as C-'I 10 15 20 25 30 35 448 576 10 the signal amplitudes of the curve for the two opposite to each other the waves of alternating voltage signals shall be reduced to a minimum, as shown in Fig. 2.

It should be noted that the procedure according to the invention can be performed without a computer. For example, two voltage meters are connected to the sensors, such as to the torene 4%, queue. Their sum values can be entered in a table.

After a number of seconds, the modes of the converters 36B, 360 can moved in one direction or another a predetermined small stretch. If the sum of the voltage meter values increases, the the direction is reversed. The converter can be moved further until the sum of the meter readings becomes minimal.

Similarly, an analog servo may be used. turn. The signals detected by the detectors H4, # 6 can filtered with a low-pass filter to be fed to a top voltmeter and then to a buzzer circuit, the output of which can be used for power steering of a converter 36A or ' 36B until the sum is minimal.

The manual and analog embodiments described above has not been shown in the figures.

In the preferred embodiment of Fig. 2, the signals A1, A2 are detected and stored and further fed to signals A3, Au. The converter 36B is actuated with a bestänw minus value and new signals A1, A2 are stored. Real sig- feed from one memory element to another is necessary may not be as durable as the time during which the computer keeps open for the position of each data part. Sum A1 + A2 subtra- + An. If the sign of the difference Å is negative, indicating that the effects of the inverter 36B was in the right direction, a new influence occurs through the control signal L2 on the converter 36B with a value OFF with the same sign as earlier. The process is repeated until A becomes positive.

When A becomes positive, L2 acts with a value ~ OFF.

The difference signal A thus fluctuates slightly around the minimum value.

After AV has changed characters a predetermined number times "n" the control is switched from L2 to L3, which controls the converter 360. The whole process is repeated again, now for heras from the sum A3 10 15 20 25 30 35 44sis7e P llyi converter 36C until the minimum value of difference A is reached again.

The process is then repeated to control the transducer 36A.

I If during the minimization process the sum of the the voltage amplitudes of the signal curves of the acting waves occur that the controlled converter reaches end of its area, this is sensed and a value V1 of the control signal with the opposite sign is input to the converter p to cause the steered mirror to jump away from its area- end position so that the total perimeter shifts substantially one wavelength for used laser light. Alternatively, the mode for two mirrors are increased to make the perimeter length shift one or multiple wavelengths for used laser light. At a preferred shape, all mirrors shift equally to increase peri- meter length one or more wavelengths for used laser light.

By bringing all the mirrors to the same shift remains the spread of the mirrors unchanged. _ After the AC amplitudes of the signal the curves of the opposite waves have been reduced at a minimum, it is desirable, ¿but not necessary, that reduce the difference between the AC amplitudes of the signal curves of the opposing waves. For this purpose, according to Fig. 3, the differences between the signals A1 and A2 to be stored and the position of the controlled converter moved with a predetermined value OFF. The signals are read again and the new difference amplitude is subtracted from the old one the difference amplitude for determining whether the converter is movable in the right direction. If this is the case, the process is repeated.

If not, the sign changes to OFF. The comparison takes place only a predetermined number of times "m" due to the fact that the merger of the difference can f..da1fidigare calibration, which was achieved by minimum formation with respect to the sum, -i illegal.

Reducing the difference m times (eg five times) will consequently in fact_trim the converters and the positions of the mirrors away from the value where the sum is minimal.

The weighting factor n / m is chosen as it best suits each individual gyro. _ After the difference has been reduced m times for one mirror switches the process to the next mirror and thereafter (e.g. 10 15 448 576 n 9.12 to the third mirror. After you1 that the difference has been reduced for all mirrors, the same gear ratio is again minimized. voltage signals for all mirrors. The process continues.

While a mirror is positioned according to the present According to the invention, another mirror is regulated by means of the quick gyro for the channel length control 32, so that it is relative slow motion reflected according to the present the finding does not disturb the tuning of the laser. 1 Thus, an ongoing regulation of the situation for laser mirrors to reduce backscatter to a minimum and thus of the locking. Although the invention has been described in detail above is not the intention that it should be considered limited to this description, but the scope of protection is determined solely by the following claims. .¶

Claims (12)

10 15 20 25 30 (a) (Il 448 576 13 PATENTKRAV A method for reducing backscatter in vibrating ring lasers with adjustable corner mirrors and transducers for regulating the position of the mirrors, the means generating electrical signals which are measures of low-frequency alternating current components in a boundary curve of the mutually opposite laser waves, which are frequency modulated, characterized in that the amplitudes of said electrical signals are measured and combined by addition, and in that position control is effected by at least one of the transducers and mirrors to reduce the amplitude of the sum signal of the combined amplitudes to a minimum. Method according to Claim 1, characterized in that the amplitudes of the electrical signals are combined by subtraction and the position of at least one of the transducers and / or the mirrors is regulated, so that the absolute value of the difference value obtained by the subtraction is reduced. n e t e c k- 3. A method according to claim 1 or 2, characterized in that the mirrors are regulated in sequence with a predetermined limited range of motion for limiting the absolute value or the amplitude of the difference value obtained by subtraction. H. method according to claim 1, characterized in that the mirrors are regulated in sequence to reduce the amplitude of the sum signal for the combined signal to a minimum value. Device for reducing backscatter in vibrated ring lasers, wherein a ring laser has a plurality of corner mirrors (IBA - C) defining a ring laser path (14) and transducers (BSA - C) for inward and outward control of the position of the mirrors, wherein a detector device (44, 46) is arranged to sense alternating voltage amplitudes in a boundary curve of two opposite frequency modulated laser waves in the ring laser path and a vibration device (42) is arranged to vibrate the laser path (14) of the ring laser with different values while the servo means are arranged to control the position of at least one of the converters Ln 10 15 20 25 30 35 zmnnauuwz-aaiu-uz-nn-ms - p 1.- n ...- l. . 448 576 14 and the mirrors for regulating and tuning the length of the laser path, characterized by a device connected to the detector device (H4, 46) for generating two signals, which are measured at said AC voltage amplitudes, and are input to a summing means for to form a sum signal, which is a measure of the sum of said two signals, wherein the position control of the servo means of at least one of the transducers and the mirrors is arranged to take place by means of means for making the sum signal minimal. Device according to claim 5, characterized in that a device for subtracting the two signals, which constitute measures of the alternating voltage amplitudes, from each other to form a difference signal, which is a measure of the absolute value of the difference amplitude, wherein switching means comprise means for to sense when the sum signal is minimal and are arranged to switch the control signal of the servo means for the position control of the transducers and mirrors from being the sum signal to being the difference signal and by means for limiting the positional movements of the transducers and mirrors when controlled by the difference signal. 7. Device according to claim 6, characterized in that the switching means comprise means for sensing the movement of the controlled mirrors (16A - C) which depends on said difference signals, so that switching from the difference signal to the sum signal takes place depending on it. Device according to one of Claims 5 to 7, characterized by switching means intended for switching the control signal of the servo member from one to the other mirror (16A - C). Device according to one of Claims 5 to 7, characterized by additional detector devices for detecting the end positions of the transducers (36A - C) and means for adjusting the positions of the transducers and the mirrors so that relevant perimeters are shifted by substantially an integer number of laser light wavelengths. Device according to one of Claims 5 to 7, characterized in that the servo member is of the digital type. \\ 448- 576 15 11. Device according to claims 8 and 10, characterized in that the switching means comprise a digital computer. 12. AHnrqH, ng according to pqLenLkravct 11, k J nnutec kn that the digital computer is arranged to disconnect the control of the length of the laser path from the converter (SGA - C), which is controlled with respect to the correction of the backscatter. , to one of the other converters. ff! '~ _un ~ u- | qwmu -.-- .. ~.-... ». fl _..... ~ ..» <- ~> - - ~ »-