JPH08178676A - Optical rotation detecting device - Google Patents

Abstract

PURPOSE: To provide stable zero point characteristic and scale factor characteristic by providing a mechanism for regulating the emission of a light source or a mechanism for controlling it. CONSTITUTION: A regulating mechanism 105 is provided in a position different from a regulating mechanism 104 within the light source driving part 102 of a signal processing circuit 20 to set the light quantity in two stages. The mechanism 105 regulates the light source light quantity on the basis of the electric signal 33 outputted from a light receiving means 13 and amplified by a preamplifier 201. Concretely, this device is constituted so that the voltage signal inputted to a driving circuit 103 can be regulated by the respective variable resistances included in the mechanisms 104 and 105. According to such a constitution, the initial regulation is roughly set by the variable resistance of the mechanism 105, and the fine regulation is set by the variable resistance of the mechanism 106. The converse can be also performed. Thus, the electric load added to a specified circuit element is reduced, the temperature drift or linearity fluctuation of the circuit is reduced, and the zero-point drift and scale factor fluctuation as optical rotation detecting device is consequently reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical rotation detecting device used for a moving body or the like, and more particularly to an optical fiber gyro.

[0002]

2. Description of the Related Art Among devices used as an optical rotation detecting device is a gyroscope.

This gyroscope can obtain not only angular velocity but also azimuth data by time-integrating it.

Among these gyroscopes is an optical fiber gyro using an optical fiber as a sensing coil.

This optical fiber gyro has no moving parts and can be miniaturized, and further, in terms of minimum detectable angular velocity (sensitivity), zero point drift, measurable range (dynamic range), and stability of scale factor. ,
It is superior to the conventional mechanical gyroscope, and has been attracting attention in recent years and has been actively researched and developed.

A phase modulation method, a frequency modulation method, an optical heterodyne method, etc. have been proposed as a signal processing method for the output light of the optical fiber gyro, but here, a conventional optical fiber adopting the phase modulation method is proposed. A gyro will be described as an example with reference to FIG.

In FIG. 9, 11 is a light source and optical means for propagating light from the light source, for example, a light source module having a lens, 12 and 15 are optical fiber couplers for branching and recombining light, 13 is a light receiving means, and 14 is a light receiving means. A polarizer, 16 is an optical fiber coil, 17 is a phase modulator, 18 is a sensing loop unit including the optical fiber coil 16 and the phase modulator 17, etc., and 21 to 29 are optical paths.

The operation of the optical fiber gyro configured as above will be described. First, the light source module 1
The light excited and oscillated by the first light source enters the optical path 21 via the lens in the light source module 11.

Next, the light incident on the optical path 21 is branched into two by the optical fiber coupler 12, and one of the two branched light is incident on the polarizer 14 via the optical path 23. At this time, the other light is emitted to the outside from the end face of the optical path 24 which is the open end.

The light emitted from the polarizer 14 is
It is incident on the optical fiber coupler 15 through the optical path 25, and
Branched.

At this time, one of the two branched light beams has an optical path 2
It is incident on the optical fiber coil 16 which is a sensing coil via 7. The other light enters the phase modulator 17 via the optical path 28, and then enters the optical fiber coil 16 via the optical path 29.

The phase modulator 17 has a structure in which an optical fiber is wound around a cylindrical piezoelectric vibrator or the like, and a piezoelectric modulator is applied by applying a predetermined modulation signal, for example, a sine wave signal. Is expanded and contracted, and the length, propagation constant, etc. of the optical fiber generated in accordance with the expansion and contraction are changed to cause phase modulation when light propagates in the wound optical fiber.

As described above, the lights that are incident on the sensing loop portion 18 and propagate in the counterclockwise and counterclockwise opposite directions are recombined by the optical fiber coupler 15, and one of the combined lights is passed through the optical path 25. It is incident on the polarizer 14 via. The other of the combined lights is emitted from the end face which is the open end to the outside through the optical path 26.

The light emitted from the polarizer 14 is
It is incident on the optical fiber coupler 12 through the optical path 23, and is branched into two by the optical fiber coupler 12.

One of the two light beams thus branched enters the light receiving means 13 such as a photoelectric detector through the optical path 22.

The light received by the light receiving means 13 is
It is converted into an electric signal and then processed by a signal processing system (not shown).

The optical fiber gyro which operates as described above is provided with the optical fiber coil 16 of the sensing loop section 18.
However, when it is moved due to rotation, etc., Sagnac (Sagna)
Due to the effect c), a phase difference occurs in the lights propagating in opposite directions.

The light having the phase difference is coupled by the optical fiber coupler 15 to cause interference, the interference light is received and detected by the light receiving means 13, and then signal processing is performed to obtain the angular velocity of movement or the like.

In the optical fiber gyro, the zero point drift characteristic and the scale factor stability are typical performance indicators. The zero-point drift indicates the rotation output even in the stationary state (the rotation angular velocity is zero), and the scale factor is the ratio between the input angular velocity and the output value when the rotation is received.

In the case of an optical fiber gyro, if a single mode optical fiber is used for the sensing coil, the plane of polarization changes due to disturbance such as temperature change, and a large zero point drift occurs. In order to reduce such zero-point drift, a polarization preserving optical fiber may be used for the sensing coil, or depolarization means may be inserted in the sensing loop unit 18 to cancel the fluctuation of the polarization plane.

The scale factor stability is easily affected by the characteristics of the light source. For example, when the temperature changes, the peak wavelength of light emitted from the light source changes, and the scale factor changes. However, the change of the peak wavelength with respect to the temperature change has an approximately constant proportional relation, and normally, the calculation process is performed from this relation to correct it, or a correspondence table is prepared in advance to correct the change. The method is adopted.

Further, in the optical fiber gyro, since the amplitude (light receiving power) of the interference light received by the light receiving means 13 is detected and the amplitude value of the photoelectrically converted output signal is converted into an angular velocity, the light receiving power fluctuates. Then, the amplitude value of the output signal fluctuates. That is, the scale factor fluctuates even when receiving a constant rotational angular velocity. A factor of such a fluctuation of the received light power is a fluctuation of the light emission amount of the light source. Normally, the light emission amount is detected by a photodiode (PD) built in the light source module 11, and A
By applying PC (Automatic Power Control), the drive current of the light source is controlled so that the light emission amount becomes constant.

[0023]

However, in the above-mentioned conventional optical rotation detecting device, the fluctuation of the received light power is caused not only by the fluctuation of the light emission amount of the light source but also by the fluctuation of the coupling efficiency between the light source and the end face of the optical path 21. There is a problem. That is, with the built-in PD of the light source module 11, the APC
Even if it is controlled, if the coupling efficiency changes, the optical path 21
Since the amount of light incident on the light fluctuates, as a result, the light receiving means 1
The light receiving power received by 3 also fluctuates, and the scale factor becomes unstable.

Further, when the circuit is designed so that the light emission amount of the light source can be adjusted in a wide range as much as possible, a particular circuit element in the signal processing circuit is likely to be overloaded, and for example, an offset voltage or temperature drift occurs in an operational amplifier or the like. However, the zero point drift increases.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a high-performance optical rotation detection device having stable zero point characteristics and scale factor characteristics.

[0026]

In order to achieve this object, an optical rotation detecting device of the present invention has a light source including a light emitting element and a light receiving means for monitoring a light emission output, and a light emitted from the light source. A first optical fiber coupler that splits into two
A polarizer into which one of the light beams branched by the first optical fiber coupler is incident, a second optical fiber coupler into which the light emitted from the polarizer is incident and is branched into two, and an optical fiber which produces a Sagnac effect A sensing loop unit having a coil and a phase modulation unit and coupled to the second optical fiber coupler, and a first optical fiber coupler that is emitted from the sensing loop unit and passes through the second optical fiber coupler and the polarizer.
An interference light receiving means for receiving the light emitted from the optical fiber which is split into two by the optical fiber coupler, and a signal processing circuit for calculating the rotational angular velocity using the interference light output signal output from the interference light receiving means. And the interference light output signal is output from the interference light receiving means, a monitor output signal is output from the light emission output monitoring light receiving means, and the signal processing circuit uses at least one output signal. It has an adjusting mechanism for adjusting the light emission amount of the light source or a control mechanism for controlling the light emission amount of the light source.

Further, in the optical rotation detection device of the present invention, the signal processing circuit selects a larger one of the interference light output signal and the monitor output signal and outputs a proper signal. And a control mechanism for controlling the light emission amount of the light source using the output signal of the comparator.

Further, in the optical rotation detecting device of the present invention, the signal processing circuit has a control mechanism for controlling the light emission amount of the light source by using one of the interference light output signal and the monitor output signal. In addition, a determination mechanism that determines whether one of the output signals is within or outside a predetermined range, and a signal used by the control mechanism when the output signal is out of the range is used as the other output signal. It also has a switching mechanism for switching to.

Further, in the optical rotation detection device of the present invention, the signal processing circuit has an adjusting mechanism for adjusting the light emission amount of the light source by using the monitor output signal, and further, the light source by using the interference light output signal. It also has a control mechanism for controlling the amount of light emission.

[0030]

With this configuration, in the optical rotation detecting device of the present invention, the fluctuation of the light emission amount of the light source is reduced and the fluctuation of the light amount incident on the optical path from the light source is also reduced. As a result, the fluctuation of the light receiving power of the light receiving means is changed. Is reduced, a stable scale factor characteristic can be obtained.

Further, in the signal processing circuit, the load on a specific circuit element is reduced, and as a result, the offset and drift on the circuit are reduced, so that the zero point drift can be reduced and the stability is further improved. The scale factor characteristic can be obtained.

[0032]

First Embodiment A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical rotation detecting device according to the first embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a light source module using a super luminescent diode as a light emitting element, inside of which a lens into which light emitted from the light emitting element is incident, an optical fiber as an optical path, and a light emitting state are monitored. And a light receiving means for monitoring the light emission output.

Next, 12 is an optical fiber coupler for splitting the light from the light source module 11 into two, 13 is a light receiving means for receiving the light propagating in the optical fiber and converting it into an electric signal, and 14 is Of the light split into two by the optical fiber coupler 12, a polarizer for defining the polarization direction of one of the lights and making it linearly polarized (for example, a laminated type or a fiber type polarizer can be used), Reference numeral 15 is an optical fiber coupler for splitting the light linearly polarized by the polarizer 14 into two.

Here, the optical fiber couplers 12 and 15 are
An optical fiber type coupler using a single mode optical fiber which is inexpensive and highly reliable and whose branching ratio is adjusted to about 1: 1 was used.

Next, 16 is an optical fiber coil constructed by winding a single mode optical fiber around a bobbin, and is for obtaining a phase difference between the counterclockwise light and the clockwise light by the Sagnac effect. Reference numeral 17 denotes a phase modulator formed by winding a single mode optical fiber around a cylindrical piezoelectric vibrator, and between the counterclockwise light and the clockwise light passing through this portion,
It provides a predetermined amount of phase difference at a predetermined timing.

Next, 19 is a depolarizing means, which is adjacent to the optical fiber coil 16 for the purpose of forcibly depolarizing the propagating light and removing unnecessary interference noise components due to fluctuations in the polarization state. Has been inserted.

However, the position where the depolarizing means 19 is inserted is not limited to the position shown in FIG.
And the phase modulator 17 or the optical fiber coupler 1
5 and the optical fiber coil 16 are possible, and they may be inserted at a plurality of positions among these positions.

Further, although the depolarizing means is arranged in the sensing loop portion 18 in this embodiment, the depolarizing means may not be provided.

As the depolarizing means, LY in which the principal axis angle of the polarization-maintaining optical fiber is inclined by about 45 degrees and fused is used.
A fiber type depolarizer of OT type is suitable.

The depolarizing means may be a bulk type depolarizer in which crystal plates having optical anisotropy are combined so that their principal axes are displaced by about 45 degrees.

In this embodiment, 21 to 30 are optical paths, and the optical paths 21 to 30 and the optical path of the optical fiber coil 16 and the optical path of the phase modulator 17 are all single mode optical fibers. It is composed of.

A structure in which some or all of these optical fibers are replaced by polarization-maintaining optical fibers may be used.

In this embodiment, 31 to 34 are electric signals. FIG. 2 is a diagram showing the concept of the signal processing circuit in the first embodiment of the present invention.

In FIG. 2, the light source module 11, the light receiving means 13, the signal processing circuit 20 and the electric signals 31, 32, 3 are shown.
3 corresponds to FIG. Reference numeral 101 is a calculation unit that mainly calculates the rotational angular velocity, 102 is a light source drive unit, and 201 is an electrical signal 33 that is output from the light receiving means and input to the signal processing circuit.
Is a preamplifier for amplifying the
2 is a drive circuit for sending a drive current to the light source, 104 is an adjusting mechanism for adjusting the light emission amount of the light source based on the electric signal 32 output from the light emitting output monitor light receiving means in the light source module 11, and 105 is the light receiving means. It is an adjusting mechanism that adjusts the light emission amount of the light source based on the electric signal 33 output from 13.

Next, the operation of the present optical rotation detector will be described in detail with reference to FIGS. 1 and 2. The light output from the light source module 11 passes through the optical path 21 and passes through the optical fiber coupler 12
Is input to

The light bifurcated by the optical fiber coupler 12 sequentially passes through the optical path 23, the polarizer 14 which defines the polarization state in only one direction, and the optical path 25, and then enters the optical fiber coupler 15.

The light input to the optical fiber coupler 15 is
The optical paths 27 and 28 are bifurcated substantially evenly.

The input light to the optical path 27 travels clockwise in the optical fiber coil 16, then passes through the optical path 30, is depolarized by the depolarizing means 19, and passes through the optical path 29 to have a preset optical phase. After passing through the optical path 28 via the phase modulator 17 to be added, the light is input to the optical fiber coupler 15 in the opposite direction.

Here, the phase modulator 17 adds a preset optical phase in order to enhance the detection sensitivity of the Sagnac phase difference generated in the optical fiber coil 16.

On the other hand, the light split into two in the optical fiber coupler 15 and input to the optical path 28 travels in the direction completely opposite to the above-described light wave.

That is, the light that has passed through the optical path 28, the phase modulator 17, the optical path 29, the depolarizing means 19, and the optical path 30 in this order propagates counterclockwise in the optical fiber coil 16 and then passes through the optical path 27. It is input to the fiber coupler 15.

Then, in this way, the optical fiber coupler 15
The light beams that have been bifurcated in the opposite directions are propagated through the sensing loop unit 18 and are then coupled again by the optical fiber coupler 15.

After the combined light passes through the optical path 25, it propagates in the reverse direction through the polarizer 14, the optical path 23 and the optical fiber coupler 12, and is input to the light receiving means 13 by the optical path 22 and converted into an electric signal.

Conventionally, in order to adjust the light emission amount of the light source of such an optical rotation detecting device, a control loop is constructed which detects the light emission amount by the built-in PD of the light source module 11 and uses the electric signal to perform the APC operation. In the circuit, an adjusting mechanism 104 such as a variable resistor is used to adjust to an appropriate drive current.

However, if only the control by the APC operation is performed,
There is a possibility that the light-receiving power may fluctuate significantly due to fluctuations in the coupling efficiency between the light source and the end face of the optical path 21. In consideration of such a variation, a circuit design for adjusting the light emission amount of the light source by only the adjusting mechanism 104 is performed so that the light amount setting range can be adjusted to cover a wide range. In this case, problems such as offset voltage and temperature drift occur, and the linearity and zero point stability of the circuit become very poor.

Further, since the linearity / zero point stability of the circuit fluctuates, the scale factor of the optical rotation detecting device also fluctuates, and the zero point drift also increases.

For this reason, in order to cover a wide light amount setting range and avoid the deterioration of the performance of the optical rotation detecting device, the electrical mechanism applied to a specific circuit element, which is caused by the single adjusting mechanism, is generated. We must avoid increasing the burden.

In this embodiment, the adjusting mechanism 105 is provided at a position different from the adjusting mechanism 104 in the light source driving section 102 of the signal processing circuit 20, and a circuit capable of setting the light amount in two steps is manufactured.

The adjusting mechanism 105 adjusts the light emission amount of the light source based on the electric signal 33 output from the light receiving means 13. In FIG.
The signal amplified by is used.

Specifically, an electric signal input to the drive circuit 103 by a variable resistor included in the adjusting mechanism 104,
Here, the voltage signal is adjustable, and similarly, the drive circuit 103 is controlled by the variable resistor included in the adjusting mechanism 105.
The voltage signal input to is adjustable.

With such a configuration, for example, initial adjustment can be roughly set by the variable resistance included in the adjusting mechanism 104, and subsequent fine adjustment can be set by the variable resistance included in the adjusting mechanism 105. Or vice versa.

When the adjusting mechanism 105 as described above is provided in the light source driving section 102 in the signal processing circuit 20, the electrical load on a specific circuit element is reduced and the temperature drift and linearity fluctuation in the circuit are reduced. As a result, the zero point drift and scale factor fluctuations of the optical rotation detector were reduced.

The electric signal input to the light source driving section 102, and in the present embodiment, the adjusting mechanism 105, is the electric signal 33 output from the light receiving means 13 as the preamplifier 201.
In addition to directly inputting the amplified and output electric signal to the adjusting mechanism 105 as shown in FIG.
As shown in FIG. 3, the signal is converted into a digital signal through the arithmetic unit 101, for example, the lock-in amplifier 202 and the A / D converter 203, and is converted into an appropriate light amount adjustment signal by the CPU 204, and then the light source driving unit 102, here. Then, it may be input to the adjustment mechanism 105 and used for adjustment.

Further, as shown in FIG. 8, in order to correct the influence of the temperature on the electric signal 33 output from the light receiving means 13, a temperature detecting means 113 is provided, and the temperature is corrected by the correcting means in the arithmetic unit 101. The electric signal obtained by performing the above may be used as the light amount adjustment signal.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical rotation detector according to the second embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a light source module using a super luminescent diode as a light emitting element, inside of which a lens into which light emitted from the light emitting element is incident, an optical fiber as an optical path, and a light emitting state are monitored. And a light receiving means for monitoring the light emission output.

Next, 12 is an optical fiber coupler for splitting the light from the light source module 11 into two, 13 is a light receiving means for receiving the light propagating in the optical fiber and converting it into an electric signal, and 14 is Of the light split into two by the optical fiber coupler 12, a polarizer for defining the polarization direction of one of the lights and making it linearly polarized (for example, a laminated type or a fiber type polarizer can be used), Reference numeral 15 is an optical fiber coupler for splitting the light linearly polarized by the polarizer 14 into two.

Here, the optical fiber couplers 12 and 15 are
An optical fiber type coupler using a single mode optical fiber which is inexpensive and highly reliable and whose branching ratio is adjusted to about 1: 1 was used.

Next, 16 is an optical fiber coil constructed by winding a single mode optical fiber around a bobbin, and is for obtaining a phase difference between the counterclockwise light and the clockwise light by the Sagnac effect. Reference numeral 17 denotes a phase modulator formed by winding a single mode optical fiber around a cylindrical piezoelectric vibrator, and between the counterclockwise light and the clockwise light passing through this portion,
It provides a predetermined amount of phase difference at a predetermined timing.

Next, 19 is a depolarizer, which is adjacent to the optical fiber coil 16 for the purpose of forcibly depolarizing the propagating light and removing unnecessary interference noise components due to changes in the polarization state. Has been inserted.

However, the position where the depolarizing means 19 is inserted is not limited to the position shown in FIG.
And the phase modulator 17 or the optical fiber coupler 1
5 and the optical fiber coil 16 are possible, and they may be inserted at a plurality of positions among these positions.

Further, in the present embodiment, the depolarizing means is arranged in the sensing loop portion 18, but the depolarizing means may not be provided.

As the depolarizing means, LY in which the principal axis angle of the polarization-maintaining optical fiber is inclined by about 45 degrees and fused is used.
A fiber type depolarizer of OT type is suitable.

The depolarizing means may be a bulk depolarizer in which crystal plates having optical anisotropy are combined so that their principal axes are displaced by about 45 degrees.

In the present embodiment, 21 to 30 are optical paths, and these optical paths 21 to 30, the optical path of the optical fiber coil 16 and the optical path of the phase modulator 17 are all single mode optical fibers. It is composed of.

A structure in which some or all of these optical fibers are replaced by polarization-maintaining optical fibers may be used.

In this embodiment, 31 to 34 are electric signals. FIG. 4 is a drawing showing the concept of the signal processing circuit in the second embodiment of the present invention.

In FIG. 4, the light source module 11, the light receiving means 13, the signal processing circuit 20 and the electric signals 31, 32, 3 are shown.
3 corresponds to FIG. Reference numeral 101 is a calculation unit that mainly calculates the rotational angular velocity, 102 is a light source drive unit, and 201 is an electrical signal 33 that is output from the light receiving means and input to the signal processing circuit.
Is a preamplifier for amplifying the
2 is a drive circuit for sending a drive current to the light source, 106 is a control mechanism for controlling the light emission amount of the light source based on the electric signal 32 output from the light emitting output monitor light receiving means in the light source module 11, and 107 is the light receiving means. It is a control mechanism that controls the light emission amount of the light source based on the electric signal 33 output from 13.

Next, the operation of the present optical rotation detecting device will be described in detail with reference to FIGS. The light output from the light source module 11 passes through the optical path 21 and passes through the optical fiber coupler 12
Is input to

The light bifurcated by the optical fiber coupler 12 sequentially passes through the optical path 23, the polarizer 14 which defines the polarization state in only one direction, and the optical path 25, and then enters the optical fiber coupler 15.

The light input to the optical fiber coupler 15 is
The optical paths 27 and 28 are bifurcated substantially evenly.

The input light to the optical path 27 travels clockwise in the optical fiber coil 16, then passes through the optical path 30, is depolarized by the depolarizer 19, and passes through the optical path 29 to have a preset optical phase. After passing through the optical path 28 via the phase modulator 17 to be added, the light is input to the optical fiber coupler 15 in the opposite direction.

Here, the phase modulator 17 adds a preset optical phase in order to enhance the detection sensitivity of the Sagnac phase difference generated in the optical fiber coil 16.

On the other hand, the light split into two in the optical fiber coupler 15 and input to the optical path 28 travels in the direction completely opposite to the above-described light wave.

That is, the light that has passed through the optical path 28, the phase modulator 17, the optical path 29, the depolarizing means 19, and the optical path 30 in this order propagates counterclockwise in the optical fiber coil 16 and then passes through the optical path 27. It is input to the fiber coupler 15.

Then, in this way, the optical fiber coupler 15
The light beams that have been bifurcated in the opposite directions are propagated through the sensing loop unit 18 and are then coupled again by the optical fiber coupler 15.

After the combined light passes through the optical path 25, it propagates in the reverse direction through the polarizer 14, the optical path 23 and the optical fiber coupler 12, and is input to the light receiving means 13 by the optical path 22 and converted into an electric signal.

Conventionally, the control of the light emission amount of the light source of such an optical rotation detecting device is performed by the control mechanism 106 for detecting the light emission amount by the built-in PD of the light source module 11 and performing the APC operation using the electric signal. The drive current is controlled so that the light emission amount of the light source is constant.

However, if only the control by the APC operation is performed,
There is a possibility that the light-receiving power may fluctuate significantly due to fluctuations in the coupling efficiency between the light source and the end face of the optical path 21. In consideration of such a variation, a circuit design that controls the light emission amount of the light source only by the control mechanism 106 is performed so that control can be performed so that the light amount control range covers a wide range to some extent. In this case, problems such as offset voltage and temperature drift occur, and the linearity and zero point stability of the circuit become very poor.

Further, since the linearity / zero point stability of the circuit fluctuates, the scale factor of the optical rotation detecting device also fluctuates, and the zero point drift also increases.

For this reason, in order to cover a wide light amount control range and avoid the deterioration of the performance of the optical rotation detection device, the electrical mechanism for a specific circuit element, which is caused by the single control mechanism, is generated. We must avoid increasing the burden.

In this embodiment, the control mechanism 107 is provided in the light source driving section 102 of the signal processing circuit 20 at a position different from the control mechanism 106, and a circuit in which the light amount can be set in two steps is manufactured.

The control mechanism 107 controls the light emission amount of the light source based on the electric signal 33 output from the light receiving means 13. In FIG. 4, the electric signal 33 is supplied to the preamplifier 201.
The signal amplified by is used.

Specifically, an operational amplifier included in the control mechanism 106 can control an electric signal, here a voltage signal, input to the drive circuit 103, and similarly,
The voltage signal input to the drive circuit 103 can be controlled by the operational amplifier included in the control mechanism 107.

With such a configuration, the control mechanism 10 is controlled so that the light emission amount of the light source is initially adjusted, for example.
Control is performed by the operational amplifier included in 6 such that the voltage is balanced, and thereafter, the voltage is controlled by the operational amplifier included in the control mechanism 107 so that the necessary light source emission amount can be controlled based on the electric signal 33 by the optical interference output. Can be controlled.

When the control mechanism 107 as described above is provided in the light source driving section 102 in the signal processing circuit 20, the electrical load on a specific circuit element is reduced and the temperature drift and linearity fluctuation in the circuit are reduced. As a result, the zero point drift and scale factor fluctuations of the optical rotation detector were reduced.

The electric signal input to the light source driving section 102, and in the present embodiment, the control mechanism 107, is the electric signal 33 output from the light receiving means 13 as the preamplifier 201.
In addition to inputting, amplifying, and outputting the electric signal directly into the control mechanism 107 as shown in FIG.
As shown in FIG. 3, the signal is converted into a digital signal via the calculation unit 101, for example, the lock-in amplifier 202 and the A / D converter 203, and is converted into an appropriate light amount control signal by the CPU 204, and then the light source driving unit 102, Then, it may be input to the control mechanism 107 and used for control.

Further, as shown in FIG. 8, in order to correct the influence of the temperature on the electric signal 33 output from the light receiving means 13, the temperature detecting means 113 is provided, and the temperature is corrected by using the correcting means in the arithmetic unit 101. The electric signal obtained by performing the above may be used as the light amount control signal.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an optical rotation detecting device in a third embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a light source module using a super luminescent diode as a light emitting element, inside of which a lens into which light emitted from the light emitting element is incident, an optical fiber as an optical path, and a light emitting state are monitored. And a light receiving means for monitoring the light emission output.

Next, 12 is an optical fiber coupler for splitting the light from the light source module 11 into two, 13 is a light receiving means for receiving the light propagating in the optical fiber and converting it into an electric signal, and 14 is Of the light split into two by the optical fiber coupler 12, a polarizer for defining the polarization direction of one of the lights and making it linearly polarized (for example, a laminated type or a fiber type polarizer can be used), Reference numeral 15 is an optical fiber coupler for splitting the light linearly polarized by the polarizer 14 into two.

Here, the optical fiber couplers 12 and 15 are
An optical fiber type coupler using a single mode optical fiber which is inexpensive and highly reliable and whose branching ratio is adjusted to about 1: 1 was used.

Next, 16 is an optical fiber coil constructed by winding a single mode optical fiber around a bobbin, and is for obtaining the phase difference between the counterclockwise light and the clockwise light by the Sagnac effect. Reference numeral 17 denotes a phase modulator formed by winding a single mode optical fiber around a cylindrical piezoelectric vibrator, and between the counterclockwise light and the clockwise light passing through this portion,
It provides a predetermined amount of phase difference at a predetermined timing.

Next, 19 is a depolarizing means, which is adjacent to the optical fiber coil 16 for the purpose of forcibly depolarizing the propagating light and removing unnecessary interference noise components due to changes in the polarization state. Has been inserted.

However, the position where the depolarizing means 19 is inserted is not limited to the position shown in FIG.
And the phase modulator 17 or the optical fiber coupler 1
5 and the optical fiber coil 16 are possible, and they may be inserted at a plurality of positions among these positions.

Further, in the present embodiment, the depolarizing means is arranged in the sensing loop portion 18, but the depolarizing means may not be provided.

As the depolarizing means, LY in which the principal axis angle of the polarization-maintaining optical fiber is inclined by about 45 degrees and fused is used.
A fiber type depolarizer of OT type is suitable.

Further, as the depolarizing means, a bulk type depolarizer in which crystal plates having optical anisotropy are combined so that their principal axes are displaced by about 45 degrees may be used.

In the present embodiment, 21 to 30 are optical paths, and these optical paths 21 to 30, the optical path of the optical fiber coil 16 and the optical path of the phase modulator 17 are all single mode optical fibers. It is composed of.

A structure in which some or all of these optical fibers are replaced by polarization maintaining optical fibers may be used.

In the present embodiment, 31 to 34 are electric signals. FIG. 5 is a drawing showing the concept of the signal processing circuit in the third embodiment of the present invention.

In FIG. 5, the light source module 11, the light receiving means 13, the signal processing circuit 20 and the electric signals 31, 32, 3 are shown.
3 corresponds to FIG. Reference numeral 101 is a calculation unit that mainly calculates the rotational angular velocity, 102 is a light source drive unit, and 201 is an electrical signal 33 that is output from the light receiving means and input to the signal processing circuit.
Is a preamplifier for amplifying the
2, a drive circuit for sending a drive current to the light source, 108 receives the electric signal 32 output from the light emitting output monitor light receiving means in the light source module 11 and the electric signal 33 output from the light receiving means 13. A comparator that selects and outputs the one with the higher signal intensity, and 109 is a control mechanism that controls the light emission amount of the light source based on the output of the comparator.

Next, the operation of the present optical rotation detector will be described in detail with reference to FIGS. 1 and 5. The light output from the light source module 11 passes through the optical path 21 and passes through the optical fiber coupler 12
Is input to

The light bifurcated by the optical fiber coupler 12 sequentially passes through the optical path 23, the polarizer 14 which defines the polarization state in only one direction, and the optical path 25, and then enters the optical fiber coupler 15.

The light input to the optical fiber coupler 15 is
The optical paths 27 and 28 are bifurcated substantially evenly.

The input light to the optical path 27 travels clockwise through the optical fiber coil 16, then passes through the optical path 30, is depolarized by the depolarizing means 19, and passes through the optical path 29 to have a preset optical phase. After passing through the optical path 28 via the phase modulator 17 to be added, the light is input to the optical fiber coupler 15 in the opposite direction.

Here, the phase modulator 17 adds a preset optical phase in order to enhance the detection sensitivity of the Sagnac phase difference generated in the optical fiber coil 16.

On the other hand, the light split into two in the optical fiber coupler 15 and input to the optical path 28 travels in the direction completely opposite to the above-described light wave.

That is, the light that has passed through the optical path 28, the phase modulator 17, the optical path 29, the depolarizer 19 and the optical path 30 in this order propagates counterclockwise in the optical fiber coil 16 and then passes through the optical path 27 to produce the light. It is input to the fiber coupler 15. Then, the lights thus branched into two opposite directions by the optical fiber coupler 15 propagate through the sensing loop portion 18 and are then coupled again by the optical fiber coupler 15.

After the combined light passes through the optical path 25, it propagates in the reverse direction through the polarizer 14, the optical path 23 and the optical fiber coupler 12, and is input to the light receiving means 13 by the optical path 22 and converted into an electric signal.

Conventionally, for controlling the light emission amount of the light source of such an optical rotation detecting device, a control loop for detecting the light emission amount by the built-in PD of the light source module 11 and using the electric signal to perform the APC operation is constructed. In the circuit, the drive current was controlled so that the light emission amount of the light source was constant.

However, if only the control by the APC operation is performed,
There is a possibility that the light-receiving power may fluctuate significantly due to fluctuations in the coupling efficiency between the light source and the end face of the optical path 21. In consideration of such a variation, a circuit design for controlling the light emission amount of the light source with only one control mechanism using the electric signal 32 as it is so that the control so that the light source control range covers a wide range to some extent can be performed. If this is done, problems such as offset voltage and temperature drift will occur in circuit elements such as operational amplifiers, and the linearity and zero-point stability of the circuit will become extremely poor.

Further, since the linearity / zero point stability of the circuit fluctuates, the scale factor of the optical rotation detecting device also fluctuates, and the zero point drift also increases.

For this reason, in order to cover a wide light amount control range and avoid the deterioration of the performance of the optical rotation detection device, the number of signals used for control is not one, but a plurality of signals are used for control. By doing so, it is necessary to avoid an increase in electrical load on a specific circuit element, which is caused by a single control mechanism.

In the present embodiment, the comparator 108 is provided in the light source driving section 102 of the signal processing circuit 20 so that the range of the signal to the control mechanism 109 is not too wide, that is, the specific circuit element is excessively large. We created a circuit that does not burden the user.

The comparator 108 includes the light source module 11
Electric signal 32 output from the built-in PD of the
3, the electric signal 33 output from FIG. 3, but in FIG. 5, a signal obtained by amplifying the electric signal 33 to an appropriate size by the preamplifier 201 is input, these input signals are compared, and the one having the larger intensity is selected. An appropriate control signal is output to the control mechanism 109 based on the signal.

Specifically, the comparator 108 includes a subtractor and a changeover switch, and the two input signals are each divided into two, one of which is a subtractor and the other of which is a changeover switch. Enter on the switch. The subtractor takes the difference between the two input divided signals and outputs it to the changeover switch. When the sign of the output of the subtractor is inverted, the changeover switch changes over one of the two input divided signals, which was being output to the control mechanism 109, to the other signal. The signal output from the changeover switch was set so that the signal having the higher intensity was selected from the two signals input to the comparator 108.

With such a configuration, even when the light emission amount of the light source fluctuates greatly and the light emission amount fluctuates over a wide range of the light amount control range, a certain level is maintained for a specific circuit element in the control mechanism 109. It is possible to perform control so that an electric signal in the above and an appropriate range is input.

Such a comparator 108 is used as the signal processing circuit 2
When the light source driving unit 102 in 0 is provided, an electric signal of a certain level or more and an appropriate value is input, so that an excessive load is not applied to a specific circuit element in the control mechanism 109, and the temperature in the circuit is reduced. Drift and linearity fluctuations were reduced, and as a result, zero-point drift and scale factor fluctuations as an optical rotation detector were reduced.

Of the electric signals input to the light source driving section 102, in this embodiment, the comparator 108, the electric signal based on the output of the light receiving means 13 is amplified by the electric signal 33 being input to the preamplifier 201. , The output electric signal is directly input to the comparator 108 as shown in FIG. 5 and used for control. In addition to the lock-in amplifier 202 and the A / D converter as shown in FIG. 203
Alternatively, the signal may be converted into a digital signal via, and converted into an appropriate light amount control signal by the CPU 204, and then input to the light source driving unit 102, here the comparator 108, and used for control.

Further, as shown in FIG. 8, in order to correct the influence of the temperature on the electric signal 33 output from the light receiving means 13, a temperature detecting means 113 is provided and the temperature is corrected by using the correcting means in the arithmetic unit 101. The electric signal obtained by performing the above may be used as the light amount control signal.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical rotation detecting device according to the fourth embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a light source module using a super luminescent diode as a light emitting element, inside of which a lens into which light emitted from the light emitting element is incident, an optical fiber as an optical path, and a light emitting state are monitored. And a light receiving means for monitoring the light emission output.

Next, 12 is an optical fiber coupler for splitting the light from the light source module 11 into two, 13 is a light receiving means for receiving the light propagating in the optical fiber and converting it into an electric signal, and 14 is Of the light split into two by the optical fiber coupler 12, a polarizer for defining the polarization direction of one of the lights and making it linearly polarized (for example, a laminated type or a fiber type polarizer can be used), Reference numeral 15 is an optical fiber coupler for splitting the light linearly polarized by the polarizer 14 into two.

Here, the optical fiber couplers 12 and 15 are
An optical fiber type coupler using a single mode optical fiber which is inexpensive and highly reliable and whose branching ratio is adjusted to about 1: 1 was used.

Next, 16 is an optical fiber coil constructed by winding a single mode optical fiber around a bobbin, and is for obtaining the phase difference between the counterclockwise light and the clockwise light by the Sagnac effect. Reference numeral 17 denotes a phase modulator formed by winding a single mode optical fiber around a cylindrical piezoelectric vibrator, and between the counterclockwise light and the clockwise light passing through this portion,
It provides a predetermined amount of phase difference at a predetermined timing.

Next, reference numeral 19 denotes a depolarizer, which is adjacent to the optical fiber coil 16 for the purpose of forcibly depolarizing the propagating light and removing unnecessary interference noise components due to changes in the polarization state. Has been inserted.

However, in addition to the position shown in FIG. 1, the depolarizer 19 is inserted in the optical fiber coupler 15 as well.
And the phase modulator 17 or the optical fiber coupler 1
5 and the optical fiber coil 16 are possible, and they may be inserted at a plurality of positions among these positions.

Further, in the present embodiment, the depolarizing means is arranged in the sensing loop portion 18, but the depolarizing means may not be provided.

As the depolarizing means, LY is prepared by fusing the polarization-maintaining optical fiber with the principal axis angle inclined by about 45 degrees.
A fiber type depolarizer of OT type is suitable.

Further, as the depolarizing means, a bulk type depolarizer in which crystal plates having optical anisotropy are combined so that their principal axes are displaced by about 45 degrees may be used.

In the present embodiment, 21 to 30 are optical paths, and these optical paths 21 to 30, the optical path of the optical fiber coil 16 and the optical path of the phase modulator 17 are all single mode optical fibers. It is composed of.

A structure in which some or all of these optical fibers are replaced by polarization-maintaining optical fibers may be used.

In this embodiment, 31 to 34 are electric signals. FIG. 6 is a diagram showing the concept of a signal processing circuit according to the fourth embodiment of the present invention.

In FIG. 6, the light source module 11, the light receiving means 13, the signal processing circuit 20, and the electric signals 31, 32, 3 are shown.
3 corresponds to FIG. Reference numeral 101 is a calculation unit that mainly calculates the rotational angular velocity, 102 is a light source drive unit, and 201 is an electrical signal 33 that is output from the light receiving means and input to the signal processing circuit.
Is a preamplifier for amplifying the
2, a drive circuit for sending a drive current to the light source, 110 indicates whether the electric signal 32 output from the light emitting output monitor light receiving means in the light source module 11 is within or outside a predetermined range. A determination mechanism that determines and outputs a determination signal, 111 a determination mechanism that determines whether the electric signal 33 output from the light receiving unit 13 is within or outside a predetermined range, and outputs a determination signal, 11
Reference numeral 2 is a switch for inputting the determination signal from the determination mechanism 110 and the determination signal from the determination mechanism 111 and outputting either of them, and switching the output to the other determination signal when the determination signal is out of the range. A mechanism 109 is a control mechanism that controls the light emission amount of the light source based on the determination signal output from the switching mechanism 112.

Next, the operation of the present optical rotation detection device will be described in detail with reference to FIGS. 1 and 6. The light output from the light source module 11 passes through the optical path 21 and passes through the optical fiber coupler 12
Is input to

The light split into two by the optical fiber coupler 12 sequentially passes through the optical path 23, the polarizer 14 which defines the polarization state in only one direction, and the optical path 25, and then enters the optical fiber coupler 15.

The light input to the optical fiber coupler 15 is
The optical paths 27 and 28 are bifurcated substantially evenly.

The input light to the optical path 27 travels clockwise through the optical fiber coil 16, then passes through the optical path 30, is depolarized by the depolarizing means 19, and passes through the optical path 29 to have a preset optical phase. After passing through the optical path 28 via the phase modulator 17 to be added, the light is input to the optical fiber coupler 15 in the opposite direction.

Here, the phase modulator 17 adds a preset optical phase in order to enhance the detection sensitivity of the Sagnac phase difference generated in the optical fiber coil 16.

On the other hand, the light split into two in the optical fiber coupler 15 and input to the optical path 28 travels in the direction completely opposite to the above-described light wave.

That is, the light that has passed through the optical path 28, the phase modulator 17, the optical path 29, the depolarizer 19 and the optical path 30 in this order propagates counterclockwise in the optical fiber coil 16 and then passes through the optical path 27 to produce the light. It is input to the fiber coupler 15.

Then, in this way, the optical fiber coupler 15
The light beams that have been bifurcated in the opposite directions are propagated through the sensing loop unit 18 and are then coupled again by the optical fiber coupler 15.

After the combined light passes through the optical path 25, it propagates in the reverse direction through the polarizer 14, the optical path 23 and the optical fiber coupler 12, and is input into the light receiving means 13 by the optical path 22 and converted into an electric signal.

Conventionally, in controlling the light emission amount of the light source of such an optical rotation detecting device, a control loop for detecting the light emission amount by the built-in PD of the light source module 11 and using the electric signal to perform the APC operation is constructed. In the circuit, the drive current was controlled so that the light emission amount of the light source was constant.

However, if only the control by the APC operation is performed,
There is a possibility that the light-receiving power may fluctuate significantly due to fluctuations in the coupling efficiency between the light source and the end face of the optical path 21. In consideration of such a variation, a circuit design for controlling the light emission amount of the light source with only one control mechanism using the electric signal 32 as it is so that the control so that the light source control range covers a wide range to some extent can be performed. If this is done, problems such as offset voltage and temperature drift will occur in circuit elements such as operational amplifiers, and the linearity and zero-point stability of the circuit will become extremely poor.

Further, since the linearity / zero point stability of the circuit fluctuates, the scale factor of the optical rotation detecting device also fluctuates, and the zero point drift also increases.

For this reason, in order to cover a wide light amount control range and avoid the deterioration of the performance of the optical rotation detecting device, the number of signals used for control is not one, but a plurality of signals are used for control. By doing so, it is necessary to avoid an increase in electrical load on a specific circuit element, which is caused by a single control mechanism.

In the present embodiment, in the light source driving section 102 of the signal processing circuit 20, a judgment mechanism 110 for judging a signal based on the electric signal 32 and a judgment mechanism 111 for judging a signal based on the electric signal 33 are provided. A switching mechanism 112 to which a signal from the determination mechanism is input is provided, and a circuit is manufactured so that the range of the signal to the control mechanism 109 does not become too wide, that is, a particular circuit element is not overloaded.

The judgment mechanism 110 receives the electric signal 32 output from the built-in PD of the light source module 11, judges whether this input signal is within or outside the predetermined range, and judges the judgment signal. Is input to the switching mechanism 112. The determination mechanism 111 inputs the electric signal 33 output from the light receiving means 13, but in FIG. 6, a signal obtained by amplifying the electric signal 33 to an appropriate magnitude by the preamplifier 201 is input, and this input signal is within a predetermined range. It judges whether it is within the range or out of the range, and inputs the judgment signal to the switching mechanism 112.

The switching mechanism 112 outputs the control signal to the control mechanism 109 by using one of the two input determination signals which is predetermined at the time of activation, and outputs the control signal to the control mechanism 109. When a signal that the signal is out of range is output to the switching mechanism 112, the used determination signal is switched to the other determination signal, and a control signal based on that is input to the control mechanism 109.

Specifically, the determination mechanisms 110 and 111 are
Each includes a subtractor, and the input signal is input to the subtractor in the form of voltage. Both subtracters take the difference between a predetermined constant voltage and the input signal, and if the difference is positive, judge that it is within the range and use it as the judgment signal, and if it is less than zero, judge that it is outside the range. And outputs the determination signal zero to the switching mechanism 112. The switching mechanism 112 converts one of the two input determination signals, which has been determined at the time of activation, into a control signal having a proper size and outputs the control signal to the control mechanism 109. Whenever it is zero, i.e. out of range,
The signal to be used is switched to the other input determination signal, and the control signal is converted into a control signal of an appropriate size to control the control mechanism 109.
Output to.

With such a structure, even when the light emission amount of the light source fluctuates greatly and the light emission amount fluctuates over a wide range of the light amount control range, it is suitable for a specific circuit element in the control mechanism 109. It is possible to perform control such that the electric signal of the range is input.

When the determination mechanisms 110 and 111 as described above are provided in the light source drive section 102 in the signal processing circuit 20, an electric signal in an appropriate range is input to the control mechanism 109, so that an excessive amount is applied to a specific circuit element. The load is eliminated, temperature drift and linearity fluctuations in the circuit are reduced, and as a result, zero-point drift and scale factor fluctuations as an optical rotation detection device are reduced.

Of the electric signals input to the light source drive unit 102, and in this embodiment, the determination mechanism 111, the electric signal based on the output of the light receiving means 13 is amplified by the electric signal 33 being input to the preamplifier 201. In addition to directly inputting the output electric signal to the determination mechanism 111 as shown in FIG. 6 and using it for control, as shown in FIG.
For example, the lock-in amplifier 202 and the A / D converter 20
3 is converted into a digital signal and converted into an appropriate light amount control signal by the CPU 204, and then the light source drive unit 102,
Here, it may be input to the determination mechanism 111 and used for control.

Further, as shown in FIG. 8, in order to correct the influence of the temperature on the electric signal 33 output from the light receiving means 13, the temperature detecting means 113 is provided, and the temperature is corrected by the correcting means in the arithmetic unit 101. The electric signal obtained by performing the above may be used as the light amount adjustment signal.

(Embodiment 5) A fifth embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical rotation detecting device according to the fifth embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a light source module using a super luminescent diode as a light emitting element, inside of which a lens into which light emitted from the light emitting element is incident, an optical fiber as an optical path, and a light emitting state are monitored. And a light receiving means for monitoring the light emission output.

Next, 12 is an optical fiber coupler for splitting the light from the light source module 11 into two, 13 is a light receiving means for receiving the light propagating in the optical fiber and converting it into an electric signal, and 14 is Of the light split into two by the optical fiber coupler 12, a polarizer for defining the polarization direction of one of the lights and making it linearly polarized (for example, a laminated type or a fiber type polarizer can be used), Reference numeral 15 is an optical fiber coupler for splitting the light linearly polarized by the polarizer 14 into two.

Here, the optical fiber couplers 12 and 15 are
An optical fiber type coupler using a single mode optical fiber which is inexpensive and highly reliable and whose branching ratio is adjusted to about 1: 1 was used.

Next, 16 is an optical fiber coil constructed by winding a single mode optical fiber around a bobbin, and is for obtaining the phase difference between the counterclockwise light and the clockwise light by the Sagnac effect. Reference numeral 17 denotes a phase modulator formed by winding a single mode optical fiber around a cylindrical piezoelectric vibrator, and between the counterclockwise light and the clockwise light passing through this portion,
It provides a predetermined amount of phase difference at a predetermined timing.

Next, 19 is a depolarizing means, which is adjacent to the optical fiber coil 16 for the purpose of forcibly depolarizing the propagating light and removing unnecessary interference noise components due to changes in the polarization state. Has been inserted.

However, the position for inserting the depolarizer 19 is not limited to the position shown in FIG.
And the phase modulator 17 or the optical fiber coupler 1
5 and the optical fiber coil 16 are possible, and they may be inserted at a plurality of positions among these positions.

Further, in the present embodiment, the depolarizing means is arranged in the sensing loop portion 18, but the depolarizing means may not be provided.

As the depolarizing means, the LY fused by inclining the principal axis angle of the polarization-maintaining optical fiber by about 45 degrees.
A fiber type depolarizer of OT type is suitable.

The depolarizing means may be a bulk type depolarizer in which crystal plates having optical anisotropy are combined so that their principal axes are displaced by about 45 degrees.

In the present embodiment, 21 to 30 are optical paths, and these optical paths 21 to 30 and the optical path of the optical fiber coil 16 and the optical path of the phase modulator 17 are all single mode optical fibers. It is composed of.

A structure in which some or all of these optical fibers are replaced by polarization-maintaining optical fibers may be used.

In this embodiment, 31 to 34 are electric signals. FIG. 7 is a drawing showing the concept of the signal processing circuit in the fifth embodiment of the present invention.

In FIG. 7, the light source module 11, the light receiving means 13, the signal processing circuit 20 and the electric signals 31, 32, 3 are shown.
3 corresponds to FIG. Reference numeral 101 is a calculation unit that mainly calculates the rotational angular velocity, 102 is a light source drive unit, and 201 is an electrical signal 33 that is output from the light receiving means and input to the signal processing circuit.
Is a preamplifier for amplifying the
2 is a drive circuit for sending a drive current to the light source, 104 is an adjusting mechanism for adjusting the light emission amount of the light source based on the electric signal 32 output from the light emitting output monitor light receiving means in the light source module 11, and 105 is the light receiving means. It is a control mechanism that controls the light emission amount of the light source based on the electric signal 33 output from 13.

Next, the operation of the present optical rotation detection device will be described in detail with reference to FIGS. 1 and 7. The light output from the light source module 11 passes through the optical path 21 and passes through the optical fiber coupler 12
Is input to

The light bifurcated by the optical fiber coupler 12 sequentially passes through the optical path 23, the polarizer 14 which defines the polarization state in only one direction, and the optical path 25, and then enters the optical fiber coupler 15.

The light input to the optical fiber coupler 15 is
The optical paths 27 and 28 are bifurcated substantially evenly.

The input light to the optical path 27 travels clockwise in the optical fiber coil 16, then passes through the optical path 30, is depolarized by the depolarizing means 19, and passes through the optical path 29 to have a preset optical phase. After passing through the optical path 28 via the phase modulator 17 to be added, the light is input to the optical fiber coupler 15 in the opposite direction.

Here, the phase modulator 17 adds a preset optical phase in order to enhance the detection sensitivity of the Sagnac phase difference generated in the optical fiber coil 16.

On the other hand, the light split into two in the optical fiber coupler 15 and input to the optical path 28 travels in the direction completely opposite to the above-described light wave.

That is, the light that has passed through the optical path 28, the phase modulator 17, the optical path 29, the depolarizing means 19, and the optical path 30 in this order propagates counterclockwise in the optical fiber coil 16 and then passes through the optical path 27. It is input to the fiber coupler 15.

Then, in this way, the optical fiber coupler 15
The light beams that have been bifurcated in the opposite directions are propagated through the sensing loop unit 18 and are then coupled again by the optical fiber coupler 15.

After the combined light passes through the optical path 25, it propagates in the reverse direction through the polarizer 14, the optical path 23 and the optical fiber coupler 12, and is input to the light receiving means 13 by the optical path 22 and converted into an electric signal.

Conventionally, for the control of the light emission amount of the light source of such an optical rotation detecting device, a control loop for detecting the light emission amount by the built-in PD of the light source module 11 and using the electric signal to perform the APC operation is constructed. In the circuit, the drive current was controlled so that the light emission amount of the light source was constant.

However, if only the control by the APC operation is performed,
There is a possibility that the light-receiving power may fluctuate significantly due to fluctuations in the coupling efficiency between the light source and the end face of the optical path 21. In consideration of such a variation, a circuit design for controlling the light emission amount of the light source with only one control mechanism using only the electric signal 32 as it is so that the control so that the light amount control range covers a certain wide range can be performed. If this is done, problems such as offset voltage and temperature drift will occur in circuit elements such as operational amplifiers, and the linearity and zero-point stability of the circuit will become extremely poor.

Further, since the linearity / zero point stability of the circuit fluctuates, the scale factor of the optical rotation detecting device also fluctuates, and the zero point drift also increases.

For this reason, in order to cover a wide light amount control range and avoid the deterioration of the performance of the optical rotation detection device, the number of signals used for control is not one, but a plurality of signals are used for control. By doing so, it is necessary to avoid an increase in electrical load on a specific circuit element, which is caused by a single control mechanism.

In this embodiment, an adjusting mechanism 104 and a control mechanism 107 are provided in the light source driving section 102 of the signal processing circuit 20, the adjusting mechanism 104 adjusts the light source emission amount to an appropriate value, and the control mechanism 107 controls the subsequent light amount fluctuation. We created a circuit that can deal with the amount of light emitted from the light source in two steps.

The adjusting mechanism 104 receives the electric signal 32 output by detecting the light emission amount with the built-in PD of the light source module 11, and adjusts the light emission amount of the light source based on the electric signal 32. The control mechanism 107 controls the light emission amount of the light source based on the electric signal 33 output from the light receiving means 13. In FIG. 7, a signal obtained by amplifying the electric signal 33 by the preamplifier 201 is used.

Specifically, an electric signal input to the drive circuit 103 by a variable resistor included in the adjusting mechanism 104,
Here, the control mechanism 10 has a structure in which the voltage signal can be adjusted.
An electric signal, here a voltage signal, input to the drive circuit 103 is controllable by an operational amplifier included in 7.

With such a configuration, for example, the initial adjustment of the light emission amount of the light source is set by the variable resistor included in the adjusting mechanism 104, and the voltage change is performed by the operational amplifier included in the control mechanism 107 with respect to the light amount variation that occurs thereafter. Can be controlled so that they are balanced.

The adjusting mechanism 104 and the control mechanism 10 as described above
7 is provided in the light source driving unit 102 in the signal processing circuit 20, the adjustment work and the control operation are performed at different positions on the circuit, so that the electrical load on a specific circuit element is reduced and the circuit is reduced. The temperature drift and the linearity fluctuation were reduced, and as a result, the zero point drift and scale factor fluctuation as the optical rotation detector were reduced.

The electric signal input to the light source drive unit 102, and in the present embodiment, the control mechanism 107, is the electric signal 33 output from the light receiving means 13 as the preamplifier 201.
In addition to directly inputting the amplified and output electric signal to the control mechanism 107 as shown in FIG.
As shown in FIG. 3, the signal is converted into a digital signal via the calculation unit 101, for example, the lock-in amplifier 202 and the A / D converter 203, and is converted into an appropriate light amount control signal by the CPU 204, and then the light source driving unit 102, Then, it may be input to the control mechanism 107 and used for control.

Further, as shown in FIG. 8, in order to correct the influence of the temperature on the electric signal 33 output from the light receiving means 13, the temperature detecting means 113 is provided, and the temperature correcting means is used in the calculating section 101 by using the correcting means. The electric signal obtained by performing the above may be used as the light amount adjustment signal.

[0202]

As described above, according to the first aspect of the present invention, the signal processing circuit adjusts the light emission amount of the light source using the interference light output signal and the monitor output signal output from the light emission output monitor light receiving means. Since the light source emission amount can be adjusted in two stages by the structure that has the mechanism, it is possible to perform more precise light amount adjustment, reduce the electrical load on specific circuit elements, and reduce the drift and linearity fluctuation in the circuit. However, it is possible to reduce zero-point drift and scale factor fluctuations in the entire optical rotation detection device.

Secondly, the signal processing circuit has a control mechanism for controlling the light emission amount of the light source by using the interference light output signal and the monitor output signal outputted from the light emission output monitor light receiving means. Since the light emission amount of the light source can be controlled, more precise light amount control can be performed, and
It is possible to reduce the electrical load on a specific circuit element, reduce the drift and linearity variation in the circuit, and reduce the zero point drift and scale factor variation in the entire optical rotation detection device.

Thirdly, the signal processing circuit selects a larger one of the interference light output signal and the monitor output signal output from the light emitting output monitor light receiving means and outputs a proper signal. In addition to the above, the control mechanism that controls the light emission amount of the light source by using the output signal of the comparator allows the electric signal of a certain level or more and in an appropriate range to be input to the control mechanism. It is possible to reduce the electrical load on the circuit element, to reduce the drift and linearity fluctuation in the circuit, and to reduce the zero point drift and the scale factor fluctuation in the entire optical rotation detection device.

Fourthly, the signal processing circuit has a control mechanism for controlling the light emission amount of the light source by using either one of the interference light output signal and the monitor output signal output from the light emission output monitor light receiving means. At the same time, a determination mechanism that determines whether one of the output signals is within or outside a predetermined range and a signal used by the control mechanism when the output signal is out of the range is switched to the other output signal. With the configuration having a switching mechanism, an electric signal in an appropriate range is input to the control mechanism, so that the electrical load on a specific circuit element in the control mechanism is reduced, drift in the circuit and linearity variation are reduced, and It is possible to reduce zero-point drift and scale factor fluctuations in the rotation detection device as a whole.

Fifth, the signal processing circuit adjusts the light emission amount of the light source by using the monitor output signal outputted from the light receiving means for light emission output monitor, and controls the light emission amount of the light source by using the interference light output signal. With the configuration that has a control mechanism that enables the adjustment work and the control operation to be performed at different places on the circuit, the electrical load on a specific circuit element is reduced, the temperature drift and linearity variation in the circuit are reduced, and It is possible to reduce zero-point drift and scale factor fluctuations in the rotation detection device as a whole.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical rotation detection device according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of a signal processing circuit of the optical rotation detection device according to the first embodiment of the present invention.

FIG. 3 is a conceptual diagram of a signal processing circuit of the optical rotation detection device according to the first embodiment of the present invention.

FIG. 4 is a conceptual diagram of a signal processing circuit of an optical rotation detection device according to a second embodiment of the present invention.

FIG. 5 is a conceptual diagram of a signal processing circuit of an optical rotation detection device according to a third embodiment of the present invention.

FIG. 6 is a conceptual diagram of a signal processing circuit of an optical rotation detection device according to a fourth embodiment of the present invention.

FIG. 7 is a conceptual diagram of a signal processing circuit of an optical rotation detection device according to a fifth embodiment of the present invention.

FIG. 8 is a conceptual diagram of a signal processing circuit of the optical rotation detection device according to the first embodiment of the present invention.

FIG. 9 is a configuration diagram of an optical rotation detection device in a conventional example.

[Explanation of symbols]

 11 Light source module 12 Optical fiber coupler 13 Light receiving means 14 Polarizer 15 Optical fiber coupler 16 Optical fiber coil 17 Phase modulator 18 Sensing loop section 19 Depolarization means 20 Signal processing circuit 21 Optical path 22 Optical path 23 Optical path 24 Optical path 25 Optical path 26 Optical path 27 Optical path 28 Optical path 29 Optical path 30 Optical path 31 Electric signal 32 Electric signal 33 Electric signal 34 Electric signal 101 Arithmetic unit 102 Light source driving unit 103 Driving circuit 104 Adjustment mechanism 105 Adjustment mechanism 106 Control mechanism 107 Control mechanism 108 Comparator 109 Control mechanism 110 Judgment mechanism 111 determination mechanism 112 switching mechanism 113 temperature detection means 201 preamplifier 202 lock-in amplifier 203 A / D converter 204 CPU

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidehiko Negishi 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd.

Claims (8)

[Claims] 1. A light source including a light emitting element and a light emitting output monitoring light receiving means for monitoring a light emitting output of the light emitting element, and a first optical fiber coupler for branching the light emitted from the light source into two beams. A polarizer into which one of the light beams branched by the first optical fiber coupler is incident and which transmits only light in a predetermined polarization direction; and a light beam emitted from the polarizer, which is incident and bifurcated into two. Fiber optic coupler,
A sensing loop unit that has an optical fiber coil that produces a Sagnac effect and a phase modulation unit that modulates the phase of light and that is coupled to the second optical fiber coupler; Interference light receiving means for receiving the light emitted from the optical fiber which is split into two by the first optical fiber coupler via the optical fiber coupler and the polarizer, and the interference light output signal output from the interference light receiving means. And a signal processing circuit for calculating a rotation angular velocity using the signal processing circuit, wherein the signal processing circuit outputs at least one of the interference light output signal and the monitor output signal output from the light emission output monitor light receiving means. An optical rotation detection device having an adjusting mechanism for adjusting the amount of light emitted from a light source. 2. A light source including a light emitting element and a light emitting output monitoring light receiving means for monitoring a light emitting output of the light emitting element, and a first optical fiber coupler for branching the light emitted from the light source into two beams. A polarizer into which one of the light beams branched by the first optical fiber coupler is incident and which transmits only light in a predetermined polarization direction; and a light beam emitted from the polarizer, which is incident and bifurcated into two. Fiber optic coupler,
A sensing loop unit that has an optical fiber coil that produces a Sagnac effect and a phase modulation unit that modulates the phase of light and that is coupled to the second optical fiber coupler; Interference light receiving means for receiving the light emitted from the optical fiber which is split into two by the first optical fiber coupler via the optical fiber coupler and the polarizer, and the interference light output signal output from the interference light receiving means. And a signal processing circuit for calculating a rotation angular velocity using the signal processing circuit, wherein the signal processing circuit outputs at least one of the interference light output signal and the monitor output signal output from the light emission output monitor light receiving means. An optical rotation detection device having a control mechanism for controlling a light emission amount of a light source using the light rotation detection device. 3. A light source including a light emitting element and a light emitting output monitoring light receiving means for monitoring the light emission output of the light emitting element, and a first optical fiber coupler for branching the light emitted from the light source into two beams. A polarizer into which one of the light beams branched by the first optical fiber coupler is incident and which transmits only light in a predetermined polarization direction; and a light beam emitted from the polarizer, which is incident and bifurcated into two. Fiber optic coupler,
A sensing loop unit that has an optical fiber coil that produces a Sagnac effect and a phase modulation unit that modulates the phase of light and that is coupled to the second optical fiber coupler; Interference light receiving means for receiving the light emitted from the optical fiber which is split into two by the first optical fiber coupler via the optical fiber coupler and the polarizer, and the interference light output signal output from the interference light receiving means. And a signal processing circuit for calculating the rotational angular velocity using the signal processing circuit, wherein the signal processing circuit selects one of the interference light output signal and the monitor output signal output from the light-emission output monitor light-receiving means that has a larger signal intensity. An optical rotation detection device comprising: a comparator which selectively outputs the light source; and a control mechanism which controls a light emission amount of a light source by using an output signal of the comparator. 4. A light source including a light emitting element and a light emitting output monitoring light receiving means for monitoring a light emitting output of the light emitting element, and a first optical fiber coupler for branching the light emitted from the light source into two beams. A polarizer into which one of the light beams branched by the first optical fiber coupler is incident and which transmits only light in a predetermined polarization direction; and a light beam emitted from the polarizer, which is incident and bifurcated into two. Fiber optic coupler,
A sensing loop unit that has an optical fiber coil that produces a Sagnac effect and a phase modulation unit that modulates the phase of light and that is coupled to the second optical fiber coupler; Interference light receiving means for receiving the light emitted from the optical fiber which is split into two by the first optical fiber coupler via the optical fiber coupler and the polarizer, and the interference light output signal output from the interference light receiving means. And a signal processing circuit for calculating a rotation angular velocity using the signal processing circuit, wherein the signal processing circuit uses an output signal of any one of the interference light output signal and the monitor output signal output from the light emission output monitor light receiving unit. A control mechanism for controlling the light emission amount of the light source, and a determination mechanism for determining whether the one output signal is within or outside a predetermined range. Optical rotation detecting apparatus characterized by having a switching mechanism for switching the signal used in the control mechanism when the outside to the other output signal. 5. A light source including a light emitting element and a light emitting output monitoring light receiving means for monitoring a light emitting output of the light emitting element, and a first optical fiber coupler for branching the light emitted from the light source into two beams. A polarizer into which one of the light beams branched by the first optical fiber coupler is incident and which transmits only light in a predetermined polarization direction; and a light beam emitted from the polarizer, which is incident and bifurcated into two. Fiber optic coupler,
A sensing loop unit that has an optical fiber coil that produces a Sagnac effect and a phase modulation unit that modulates the phase of light and that is coupled to the second optical fiber coupler; Interference light receiving means for receiving the light emitted from the optical fiber which is split into two by the first optical fiber coupler via the optical fiber coupler and the polarizer, and the interference light output signal output from the interference light receiving means. And a signal processing circuit for calculating a rotation angular velocity using the signal processing circuit, wherein the signal processing circuit adjusts the light emission amount of the light source using the monitor output signal output from the light emitting output monitor light receiving means, and the interference. An optical rotation detection device having a control mechanism for controlling the light emission amount of the light source using an optical output signal. 6. The optical rotation detection device according to claim 1, wherein the interference light output signal is a DC component. 7. The optical rotation detecting device according to claim 1, wherein the interference light output signal is the second harmonic component of the modulation frequency of the phase modulating means. 8. The temperature detection means for detecting the temperature is provided, and the signal processing circuit calculates the rotational angular velocity by using a signal output from the temperature detection means.
The optical rotation detection device according to claim 7.