JPH011906A - Hikari fiber gyro - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical fiber gyro that detects angular velocity by interference of light propagating within an optical fiber loop, and is particularly applicable to navigation of moving objects such as automobiles. The present invention relates to an optical fiber gyro suitable for position detection in a system.

[Conventional technology]

Regarding optical fiber gyros, there has been a
This optical fiber gyro is known from Japanese Patent Publication No. 116614 and Japanese Patent Application Laid-open No. 117410/1983, but in this optical fiber gyro, if the intensity of light from the light source changes, it affects the detection accuracy of angular velocity.

Therefore, in the conventional technology described above, the intensity of light from the light source is monitored, and the amount of light emitted from the light source is controlled according to the monitoring results, thereby compensating for changes in the light intensity due to environmental changes and maintaining the light intensity at a constant level. It was designed so that the intensity of light could be obtained.

[Problem that the invention seeks to solve]

Here, the operating principle of the optical fiber gyro will be explained as follows. That is, if a rotational angular velocity Ω is given to the optical fiber gyro, 3 agnac
As a result, a phase difference Δθ is generated between the light propagating clockwise in the optical fiber loop and the light propagating counterclockwise in the optical fiber loop as expressed by the following equation.

2πLD Δθ−□・Ω ・・・・・・・・・(1) Co
λ.

Here, L: optical fiber loop length D=optical fiber loop diameter C0: speed of light λ. : Wavelength of light When the phase difference Δθ appears in this way, it is observed as a light intensity at the signal receiving end due to light interference, and therefore the rotational angular velocity Ω can be detected by the light receiving element.

By the way, in the above-mentioned conventional technology, in order to keep the intensity of light constant excluding the influence of environmental changes, etc., the light emission output of the light emitting element is feedback-controlled.

On the other hand, in such an optical fiber gyro, a light emitting element represented by a semiconductor laser is mainly used as the light emitting element, but when the light emitting element such as a semiconductor laser is changed in light emitting output, As a result, the oscillation wavelength shifts.

However, when the oscillation wavelength shifts in this way, the above (
1) Wavelength λ in the formula. has changed, and the phase difference Δθ changes for a constant rotational angular velocity Ω. Therefore,
The above conventional technology has a problem with output stability.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above, and to provide an optical fiber gyro that has excellent output stability and sufficient environmental resistance.

[Means for solving problems]

The above object is achieved by driving the light emitting element with a constant current and responding to changes in the light emission output intensity due to environmental changes by controlling the gain of the light reception signal.

[Effect]

Since the light-emitting element is driven with a constant current, the shift in the oscillation wavelength is suppressed, apart from the light-emission output intensity, so there is no decrease in output stability in this respect. can be eliminated by controlling the gain of the light-receiving signal, and deterioration in environmental resistance can also be effectively suppressed.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the optical fiber gyro according to the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, and the optical fiber gyro according to this embodiment includes a light emitting element 1 made of a semiconductor laser, a polarization preserving type optical directional coupler 2.3, a polarization filter 4, and a polarization preserving type optical fiber gyro. It has an optical system connecting an optical fiber loop 5 made of a single mode fiber wound into a coil, an optical modulator 6, and a light receiving element 7.8, and further includes an amplifier circuit 9.10, a gain adjustment circuit 11, and a synchronous detection circuit 12. , multiplexer 13,
sample hold circuit 14, A/D converter 15,
It has an electronic circuit consisting of a microcomputer 16, a signal input/output circuit 17, and an oscillator 18, and performs signal processing on the light receiving element 8 to obtain a rotational angular velocity signal.

On the other hand, 19 is a constant current drive circuit that supplies a constant current TD to the light emitting element 1 and drives it with a constant current.

Next, the operation of this embodiment will be explained.

The detection operation of the rotational angular velocity Ω as an optical fiber gyro is the same as in the conventional example.The light reception signal from the light receiving element 7 is input to the synchronous detection circuit 12, and only the components common to the phase modulation signal from the optical modulation period 6 are detected. The data is input to the microcomputer 16 via the multiplexer 13, sample hold circuit 14, and A/D converter 15, and the phase difference Δθ is detected.
The rotational angular velocity Ω is calculated using equation 1) and then output from the signal output circuit 17.

At this time, the light emitting element 1 is driven by the constant current drive circuit 19 with a constant current of 2, so its oscillation wavelength is λ. This wavelength λ is kept constant. No drift occurs due to fluctuations in , and detection accuracy does not deteriorate due to this.

However, at this time, if there is an environmental change such as a change in ambient temperature, the light emission output intensity P of the light emitting element 1 made of a semiconductor radar changes, causing a drift.

FIG. 2 shows an example of the characteristics of a semiconductor laser used as the light emitting element 1. As is clear from FIG. The light output intensity P is determined by the temperature θ℃, 25℃, 50℃
℃, it changes to Pa −* P b −4P c.

Therefore, if left as is, the peak output value of the oscillation wavelength of the light-emitting element 1 will change depending on the environment, the level of the light-receiving output voltage (■) detected by the light-receiving element 8 will drift, and the detection accuracy of the rotational angular velocity Ω will increase. (It will decrease.

Therefore, in the embodiment shown in FIG. 1, a light-receiving element 8 and an amplifier circuit 10 are provided so that the light output from the light-emitting element 1 can be monitored, and a gain adjustment circuit 11 is provided to control the gain of the amplifier circuit 9. Microcontroller 1
6 performs gain feedback control based on the above-mentioned optical output monitoring result, so that the output of the amplifier circuit 9 does not include drift due to changes in the optical output intensity of the light emitting element 1.

That is, in this embodiment, by driving the light emitting element 1 with a constant current iD, first, the oscillation wavelength λ of this light emitting element 1 is
. On the other hand, gain control in the detection signal system is applied to the drift that appears in the light emission output intensity, thereby canceling out the drift given to the detection of the rotational angular velocity. As a result, detection without any drift can be obtained.

Next, the gain control operation according to this embodiment will be explained.

First, in this embodiment, as shown in FIG. 3, a temperature range TL, 'I', is set for the operation of the light emitting element l, and the monitor voltage V, obtained by the amplifier circuit 10 at that time, is set as follows. Multiplexer 13, sample bold circuit 14, A
/D converter 15 and input into the microcomputer 16 as VL and vN, respectively, and when this monitor voltage V is VL < V, < VH, the light emitting element l is in the safe operating area. shall be.

After that, the gain adjustment circuit 11 is adjusted according to the increase or decrease of the monitor voltage.
outputs control data G to adjust the gain of the amplifier circuit 9,
Feedback control is performed so that the level of the detection signal converges to a desired value. When the monitor voltage V is outside the set range, the light emitting element 1 is determined to have exceeded the rated operating range, and immediately stops operating and enters a standby state, thereby minimizing the deterioration of the life of the light emitting element. I have to.

Next, the control of the gain adjustment by the microcomputer 16 described above will be explained in more detail with reference to the flowchart shown in FIG.

First, as initial values, the upper limit value vH1 of the monitor voltage, the lower limit value V, and the received power P0, which is the desired received power, and the initial gain G0 are set (Sl).

Next, the A/D converter continues to monitor the voltage (
S2), store this value in memory as V (S3)
. Then, in order to confirm whether the light emitting element 1 is in the safe operation area, V is compared with ■Y+VL (S4). If the set condition value is false, the standby state is entered (S5), and if true, the received power P, is read from the A/D converter 15 (S(i).

P, is stored in the memory (S7), then P0 and P,
Find the difference ΔP (S8), and set G so that ΔP becomes zero.

39.310) to obtain the desired received power.

Here, monitor voltage ■1 is continued (Bll) in the same manner as above, and V! (S12)
, VL, and V (S13) to check the operating state of the light emitting element.

Here, if the set condition value is false, it will be in a standby state (S14), but if it is true, it will be in a running state,
A routine is entered to detect temperature fluctuations in optical output and control the gain of the amplifier circuit.

That is, when there is a temperature change, the light output changes and v2 increases or decreases. Therefore, in order to obtain the amount of change from the initial state, the difference ΔV between ■1 and ■8 is calculated (S15), and this ΔV is calculated (S15).
Calculate the gain variable amount ΔG of the amplifier circuit 9 from V.S16
), are integrated into the initial gain G0 (S17).

Therefore, according to this embodiment, saturation or insufficient amplification of the amplifier circuit 9 of the light receiving element 7 due to fluctuations in the optical output of the light emitting element 1 can be prevented.

By the way, when manufacturing such an optical fiber gyro, the light receiving level of the light receiving element 7 varies due to individual differences in each optical element or variations during manufacturing, which occur in the completed optical system. Difficult to maintain constant performance. However, according to this embodiment, all such variations can be canceled by the gain control of the amplifier circuit 9, and therefore products can be easily made uniform.
An optical fiber gyro suitable for mass production can be obtained.

〔Effect of the invention〕

According to the present invention, it is possible to keep the oscillation peak wavelength of the light emitting element constant, and to prevent excess or deficiency of received power due to fluctuations in optical power caused by temperature changes, or deterioration of the service life due to limitations on the optical power of the light emitting element. Since fluctuations in received power due to manufacturing variations can be easily compensated for, output stability, reliability, and productivity are effectively improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the optical fiber gyro according to the present invention, FIG. 2 is a characteristic diagram of a light emitting element, and FIG.
The figure is an explanatory diagram showing the operating area of the light emitting element, and FIG. 4 is a flowchart showing the operation of an embodiment of the present invention. 1...... Light emitting element, 2, 3......
...Optical directional coupler, 4...Polarizing filter, 5...Optical fiber loop, 6...
...... Optical modulator, 7.8 ...... Light receiving element, 9.10 ...... Amplification circuit, 11...
......Gain adjustment circuit, 12...
Synchronous detection circuit, 13...Multiplexer, 14...Sample and hold circuit, 15
・・・・・・・・・A/D converter, 16・・・・・・
...Microcomputer, 17...
......Signal input/output circuit, 18...
- Oscillator, 19... Constant current drive circuit. Figure 2 Figure 3 Temperature Figure 4

Claims (1)

[Claims] 1. An optical fiber gyro that includes a light emitting element that emits monochromatic light and detects an angular velocity given to the optical fiber loop by interference of light propagating through the optical fiber loop, drive power supply means for driving the element at a constant current; light intensity detection means for detecting the intensity of light incident on the optical fiber loop from the light emitting element; and a detection level for controlling the level of light output for detecting the angular velocity. 1. An optical fiber gyro, comprising: a control means, and is configured to control the detection level control means based on the detection result of the light intensity detection means. 2. The optical fiber gyro according to claim 1, wherein the light emitting element is a semiconductor laser element. 3. In claim 2, a predetermined intensity range is set for the detection results by the light intensity detection means, and for detection results exceeding the upper and lower limits of this predetermined intensity range,
An optical fiber gyro, characterized in that the optical fiber gyro is configured to stop the operation of the semiconductor laser element by the drive power supply means. 4. The optical fiber gyro according to claim 1, wherein the detection level control means is constituted by a variable gain amplifier using a negative feedback amount control method, which inputs a photoelectric conversion signal for detecting angular velocity. .