JPH03137513A - Device for controlling frequency of light beam in ring resonance gyroscope - Google Patents

Abstract

PURPOSE: To obtain an improved frequency control device by receiving the part of beams that advances in the opposite direction to the advancing direction of electronic clock hands with a detector device and controlling amplitude so that amplification difference between both channels can be set to 0. CONSTITUTION: A ring resonance gyroscope 10 is operated by introducing laser beams into a resonator so that the beams in the electronic clock hand direction of a clock and those in the electronic clock hand direction of a counter clock can be formed. The gyroscope 10 includes a fiber resonator 12 that is formed by binding the certain length of an optical fiber 14 in a coupler 16 with a high binding ratio onto itself. A laser 18 can be inserted into both directions in the resonator 12 and generates laser beams with a narrow line width being split by a beam splitter 20 for achieving separate monitoring of light in each direction. Acoustic-ray deflectors 22 and 24 are arranged in each path so that the relative frequency of beams in counterclockwise and clockwise directions can be adjusted. Beams in clockwise direction are deflected in the direction of the deflector 24 and objective lenses 26 and 28 focus laser beams on both ends of the fiber 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a ring resonant gyroscope KrA.

A conventionally known ring resonant gyroscope is shown in the attached drawing.
, will be explained below with reference to FIGS. 1 to 4.

FIG. 1 is a schematic explanatory diagram of a ring resonant gyroscope, and FIG. 2 shows the components of the frequency and wavelength control device used in the ring resonant gyroscope shown in FIG. The figure shows the resonance characteristics of a ring resonant gyroscope, and FIG. 4 shows the light intensity at two frequencies Wc and 2Wc as a function of detuning from the centerline.

Referring to FIG.
It works by inserting a laser beam into a resonator to form a counterclockwise (CCW) beam. A ring resonant gyroscope includes a fiber resonator 12 formed by coupling a length of optical fiber 14 back onto itself into a coupler 16 with a high coupling ratio.

The laser 18 is split by a narrow beam splitter 20 to allow light to be inserted into the fiber resonator 12 in both directions, and also to allow separate monitoring of the light in each direction. Generates a line-width laser beam.

Acoustic-beam deflectors 22 and 24 are positioned in each path so that the relative frequencies of the beams in the CCW and CW directions, respectively, can be adjusted. The CW beam is deflected by a reflecting mirror 25 toward the deflector 24 .

Microscope objectives 26 and 27 focus the laser beam onto the ends of fiber 140.

A portion of the CW beam and CCW beam exit fiber resonator 12 via coupler 16 .

Beam splitters 28 and 29 reflect the outgoing CW and CCW beams into photodetectors 30 and 32, respectively.

The intensity of the output is obtained by the additive addition of all the combined delayed waves varying in amplitude and phase, and it depends on the coupling ratio of the coupler 16, the wavelength from the laser source, and the fiber resonance. It depends on the slow g time of the device 12.

FIG. 3 shows the resonance characteristics of the fiber resonator. Changing the phase path of a fiber resonator by changing the length of the fiber resonator, or the wavelength of the source, changes the resonant properties due to the inevitable change in the relative phase of the combined wavelengths. will change. When the phase path is a certain integer wavelength, the resonance characteristic exhibits zero. The strength inside the loop has a function that is inversely proportional to the strength of the output. At resonance with zero output strength, the wave continuously recirculates within the loop and is lost by scattering K from the loop.

The resonance peak occurs in the fiber resonator at frequencies separated by the free vector range J (FSR) °C,
where: F S R = c / n L where C is the speed of light n is the refractive index of the fiber L#i the length of the fiber cavity.

The characteristics of the cavity are the initial FSRO with respect to the resonance linewidth (Δf).
is limited by the finesse J (F), which is the ratio: F-F8R/Δf.

If a typical fiber resonator is considered to have a loop length of 10 m, the spacing between modes is about 20 MHz, and if the resonator precision is 100 m
, the half-width of resonance is 200 KHz.

In FIG. 1, the light impinging on the C1 photodetector 30 is used to control the path length of the single fiber resonator 12 to maintain resonance. This requires a cylindrical piezoelectric transducer (PZT) 3 around which a fiber 14 is wrapped and which can be actuated to stretch the fiber 14.
This is accomplished by sending an electrical control signal to 4.

Referring to FIG. 2, the frequency and path length control system is indicated generally by the numeral 40 and consists of two low noise amplifiers 42 and 44 to which photodetectors 30 and 32 are connected, respectively. A differential amplifier 46 receives the outputs of the first amplifiers 42 and 44, and two blocking amplifiers 50 and 52 whose inputs are connected to the outputs of the low noise amplifier 42 and the differential amplifier 46, respectively. an oscillator 48 operating at a frequency Wc; integrators 54 and 56 having inputs connected to blocking amplifiers 50 and 52, respectively; and inputs connected to oscillator 48 and integrator 54 and PZ
an at voltage amplifier 58 having an output connected to T34 and an input connected to an integrator 56 and an acoustic-to-beam deflector 2;
a voltage-to-frequency converter 60 having an output connected to 2;
It is becoming more and more.

In FIG. 2, the difference in the intensities of the CW and Ccw beams sensed by the photodetectors 3o and 32 at the frequency WC is an error signal for manipulating the frequency of the acoustic-light beam deflector 24 to the minimum value of the CW common loss. used as.

The length of the path is determined by the frequency Wc (
is varied by applying sinusoidal modulation to the PCZ34 at a typical KFilOkHz). If the path length is not held accurately, there will be a signal at the photodetector 30 at frequency Wc, and that signal determines which side of the resonance is the length of the fiber. Figure 4 shows the change in luminous intensity at frequencies Wc and 2Wc from #I from the center line.
It is shown as a function of key. Since the former (in the case of Wc) passes through zero at the center line, it can be used as a rounding error signal for manipulating the length of the course toward the center line. The arrangement shown in FIG.
This is accomplished by a coherent detection design that uses a reference signal at c. If there is a trade-off in the path length during automatic path length control (so the automatic control # is not an exact minimum of the CW resonance), then this means that the path length is the same in both directions. Because it affects, CCW
It also appears in the beam, so that the signals operating the frequency automatic control (ie operating the acoustic-optical director 24) are only responsive to non-alternating signals.

The music beam deflector 22 is held at a constant frequency for the CCW beam. The CW beam of light travels through the acoustic-to-optic deflector 24, which provides variable frequency cancellation by the voltage-to-frequency converter 60 tok output.

The disadvantage of the arrangement shown in Figure wc2 is that it provides only a small amount of shared sound rejection due to the mutual amplification of the two low noise amplifiers 42 and 44. In addition, two photodetectors 30 and 3
Although there may be slight differences in the intensity of the light falling on the two, this will further reduce the noise of this device as it attempts to reduce the error in the shared sound signal.

It is an object of this invention to provide an improved frequency control arrangement for a ring resonant gyroscope.

According to the invention in question, we use two beams of light in a resonant gyroscope, where two beams are used, one clockwise traveling beam and another counterclockwise traveling beam, including: To control the frequency, a system tζ is provided.

a first channel comprising a first detector medium that receives a portion of the clockwise beam and a first amplifier medium that amplifies the signal from the first detector medium to form a clockwise signal; a counterclockwise beam; a second detector medium that receives a portion of the second detector medium and a second amplifier medium that amplifies the signal from the second detector medium to form a counterclockwise signal; and the first channel and the second channel. Media containing clockwise and counterclockwise signals, characterized by an amplification control media to zero the amplification difference between the channels.

The system according to the subject invention suffers significantly from shared sound rejection with offset wire lengths due to errors in the servomechanism of the wire range, thus improving the performance of resonant gyroscopes.

In the embodiment to be described, the amplification control medium is operable to control the amplification of one of the first amplifier medium and the second amplifier medium.

The system can adjust the wiring length of the resonant gyroscope at frequency W c kC, compare the mutual strength of signals at frequency 2 WcK in clockwise and counterclockwise beams, and adjust the amplification control signal. It may include mediation such as using intensity differences to cause

Both the clockwise and counterclockwise signals have a strong second harmonic signal relative to the harmonic unaffected first order near the centerline. Indeed, it is less sensitive to wire length positions closer to the centerline than the first overtone signal as seen in FIG. The mutual strength of the second overtone signal is
A control signal is therefore provided to eliminate the increase=i between the first channel and the second channel.

The amplification control medium may include two channel filters for each of the first channel and the second channel. Here, each channel filter is 11C2W c on one channel used during amplification control.
It has been implemented to select a signal at a frequency of 2 Wc or to suppress a signal at a frequency of 2 Wc on another channel that provides the signal used during wire length control.

In the embodiment to be described, the amplification control medium is connected to the output of said one channel of the two channel filter, which is a resistant medium that controls the amplification of one of the first channel and the second channel. Connect, 2
It includes a differential amplifier that compares whether it is connected to a bidirectional fixed amplifier with respect to Wc.

The implementation of the system according to the invention in question will now be described by way of example with reference to the accompanying drawing, FIG. 5, which shows the components in the system for controlling the frequency of the light beam and the resonant wire length in a resonant gyroscope.

In FIG. 5, components of the system, designated generally by 100, which are common with previously described known systems, are given the same reference numerals as used in FIGS. 1 and 2.

System 100 includes a first channel 102 and a second channel 104 that separately detect clockwise and counterclockwise beams and generate clockwise and counterclockwise signals, and an amplification control medium 106. .

The first channel 102 includes a photodetector 30, a low-noise amplifier 108, and a two-channel switch and capacitor filter ttol.

an amplification control medium 106Fi, a differential amplifier 116 connected to the second channel 104 and connected to the filter 110 and the output of the filter 114, a fixed amplifier ttS referred to as 20 KHz, an integrator 119 and an automatic n1 width control medium 120; and a multiplier for controlling the ramp-up of the first channel 102.

As with the 20KHz reference, the 1OKHz reference originates from the same source and therefore occurs at the same time.

Instrumentation amplifier 122 receives the rAJ channel output from filter 110 and filter 114 and provides a discrimination signal to bidirectional fixed amplifier 52.

During operation, light from the right-handed beam and the left-handed beam are detected by photodetectors 30 and 32, and the resulting signals are amplified separately in amplifier 108 and amplifier 112. The counterclockwise signal is automatically amplified through a control medium 1 that ensures that the amplitudes of the clockwise and counterclockwise signals are equalized.
20 depending on the various amplification adjustments. In this example, a carrier frequency of 10 KHz is used to allow the 20 KHz signal to come out of the clock rather than allowing it to come out as well.

Filter 110 and filter 114, respectively, generate a large number of 20KHz signals on these two channels compared to a small 10KHz signal with small offset from centerline.
In order to suppress the Hz signal, pco2 on channel rAJ is
It has a notch of 0KHz.

Notching a 20KHz signal can be done without the risk of amplifying the small 1KHz signal that is present.
It will be further amplified later. On channel rBJ,
There are 20KHz frequency band pass filters that allow 20KHz signals to pass. Logically, it never stops near the Chuo Line. The two 20 KHz signals are compared by differential amplifier 116 and the difference is used as an error signal for fixed amplifier 118. The output from the integrator 119 is
The second channel 104 is fed to an automatic amplification control medium 120 that includes a multiplier circuit that controls the amplification.

The signals of the two channels "A" are connected to the instrumentation amplifier 122.
differentiated within. The discrimination signal is then used to control the frequency of the sidetone polarizer 24, as well as to vary the discrimination frequency between the right-handed and counter-clockwise beams.

Therefore, the system described above consists of a clockwise beam and a counterclockwise beam providing control signals to zero the amplification difference between the photodetector and the preamplifier in the first and second channels. utilizes the mutual strength of the second overtone signals present in the beam.

This technique suffers from greater distortion of wire lengths and shared sound rejection due to errors in the servo mechanism of the wire range than in known systems. A typical figure might be that the line length is kept to 10-4 of the resonant linewidth. and then there is a 10(1)42 factor denying the shared sound the use of amplification commensurate with the technology of the invention in question.
The frequency servomechanism should be accurate to 10 degrees of linewidth.

The ongoing refinement thus feeds directly into the harmonic deformation of the gyroscope bias error.

In contrast, the scheme used earlier shows that once the aging and temperature stability of the two photodiode amplifier assemblies is taken into account,
One might expect it to provide only one factor in the rejection of the shared tone of 0. Therefore, by making the invention in question effective, an improvement by a factor of 1 in 10 can be achieved in the performance of the gyroscope bias.

[Brief explanation of the drawing]

BRIEF DESCRIPTION OF THE DRAWINGS A conventional ring resonant gyroscope will be described below with reference to FIGS. 1-4 of the accompanying drawings. Fig. 1 is a schematic explanatory diagram of a ring resonant gyroscope, showing the components in the frequency and wavelength control device used in the ring resonant gyroscope shown in Fig. 2 #ii1, and Fig. 3 FIG. 4 shows the resonance characteristics of a ring resonant gyroscope, and also shows the intensity of light at the two-column frequency Wc and 2WcK as a function of detuning from the center line. FIG. 5 is a diagram illustrating an embodiment of the present invention. In the figure, 42.44.108.112 is a low noise amplifier,
48 indicates an oscillator, and 54.56.119 indicates an integrator. Procedural amendment (directive) February 5, 1990

Claims (1)

[Claims] 1. In a device for controlling the frequency of a light beam in a ring resonant gyroscope in which two beams are used, one of which travels in a clockwise direction and the other travels in a counterclockwise direction. , a first detector device for receiving a portion of the beam traveling in a clockwise direction, and a first amplifier for amplifying a signal from the first detector device forming a signal of the beam traveling in a counterclockwise direction. a first channel comprising a device, a second detector device receiving a portion of the beam traveling in a counterclockwise direction; and a second detector device forming a signal of the beam traveling in a counterclockwise direction; a clockwise channel characterized by a second channel including a second amplifier device for amplifying the signal; and an amplification control medium for zeroing the amplification difference between the first channel and the second channel. Intermediate containing traffic lights and counterclockwise signals. 2. The system according to claim 1, wherein the amplification control medium allows controlling the amplification of one of the first amplifier medium and the second amplifier medium. 3. A medium for adjusting the wiring length of the resonant gyroscope at the frequency Wc, a medium for comparing the mutual strength of the signals at the frequency 2Wc in the clockwise beam and the counterclockwise beam, and amplification control. 3. A system according to claim 1 or claim 2, comprising a medium for using intensity differences to generate a signal. 4. Channel filters each select a signal at a frequency of 2 Wc on one channel to be used during amplification control, and a signal at a frequency of 2 Wc on another channel to provide the signal used during wire length control. Claim 3 comprising a two channel filter in each of the first channel and the second channel making it possible to suppress.
System according to. 5. Bidirectional with respect to 2Wc, where the amplification control medium connects the output of said one channel of the two channel filter and which one connects to a multiplier circuit that controls the amplification of one of the first channel and the second channel. 5. A system according to claim 4, including a differential amplifier for comparing whether connected to a fixed amplifier. 6. A system according to claim 4 or claim 5, in which the two channel filters include switched capacitor filters. 7. A system according to any preceding claim, wherein the first channel includes a wire length control medium, the second channel includes a frequency control medium, and the amplification control medium is connected to the second channel.