JPH01143913A - Latitude meter - Google Patents

Abstract

PURPOSE:To easily measure latitude with simple constitution regardless of measurement conditions by measuring the latitude from a difference in sensitivity according to the revolution sensing ability of an optical gyro for the earth. CONSTITUTION:This instrument is set on a tripod stood on the equator 11 of the earth E so that the collimation axis of a telescope 4 is horizontal through a bubble tube 4a, and the meter is fixed through a leg 6 for fitting. Then an external frame 1 is rotated to find the position where a 1st gyro on a plane that the winding surface of the wound optical fiber of a 1st optical fiber gyro in the external frame 1 crosses at right angles in the revolving direction of the earth has zero sensitivity. Then an internal frame 3 is rotated along the inner periphery of the external frame 1 so that the ring center axes cross each other at right angles to find the position where a 2nd optical fiber gyro whose optical fiber winding surface is parallel to the revolving direction of the earth has the maximum sensitivity. Then similar operation is performed at latitude (h) and then the internal frame 3 rotates by variation in the perpendicular direction between the installation positions relatively to the external frame 1, so that the latitude is displayed on a scale 5 with an index 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a latitude meter for measuring latitude.

[Conventional technology]

Conventional latitude measurements include, for example, measuring the altitude of Polaris,
For example, they measured the altitude of the sun at its mid-south point and converted that altitude angle into latitude.

[Problem that the invention seeks to solve]

Such conventional latitude measurement has the disadvantage that measurement conditions are limited (the North Star must be visible at night, or the sun must be visible at mid-south time).

It is an object of the present invention to solve these drawbacks of the prior art and to provide a latitude meter that can easily measure latitude regardless of measurement conditions and with a simple configuration.

[Means for solving problems]

Therefore, the present invention includes a detection means for detecting north, an optical gyro supported by the detection means in a variable direction, and a display means for displaying latitude based on the maximum sensitivity position of the optical gyro with respect to the detection means. The above objective has been achieved by a latitude meter characterized by the following.

Note that the above-mentioned optical gyro is a general name for angular velocity detection means that uses the Saniac effect of light, and examples thereof include a ring laser gyro, a ring resonator gyro, and an optical fiber gyro.

[For production]

In the present invention, first, north is detected by the detection means, and the direction of the optical gyro is changed with respect to the detection means to find the position of the optical gyro with the highest sensitivity. Then, by reading the latitude displayed by the display means, the latitude of the measurement point can be determined. That is, the present invention is characterized by utilizing the fact that the optical gyro can sense the rotation of the earth, and measuring the latitude based on the difference in sensitivity.

〔Example〕

The present invention will be described below based on embodiments shown in the drawings.

FIG. 1 is a perspective view of an embodiment of the present invention, and FIG. 2 is a plan view of FIG. 1. The ring-shaped outer frame 1 houses a first optical fiber gyro having an optical fiber wound in a ring shape in a plane perpendicular to the ring center axis of the outer frame 1. A guide groove 2 is formed on the inner circumference of the outer frame 1 over the entire circumference.

A ring-shaped inner frame 3 having an outer diameter smaller than the inner diameter of the outer frame 1
has guide pins 3a and 3b that fit into the guide groove 2 and protrude outward from 180-degree opposing positions, and is rotatable with respect to the outer frame 1 about the guide pins 3a and 3b as rotation axes.
a, 3b are configured so that they can be rotated by being guided by the guide groove 2. Inner frame 3 inside inner frame 3
A second optical fiber gyro having an optical fiber wound in a ring shape in a plane perpendicular to the center axis of the ring is built-in. A reference telescope 4 is fixed to the upper part of the outer frame 1 so as to have its optical axis within a plane perpendicular to the ring center axis of the outer frame 1. This telescope 4 is provided with a bubble tube 4a for setting the horizontal direction.

Further, a latitude scale 5 is formed on the side surface of the outer frame 1, and legs 6 for attaching a tripod are provided on the bottom.

An indicator 7 for reading the latitude scale 5 of the outer frame 1 is formed on the side surface of the inner frame 3. May have a vernier.

Because of this structure, as shown in Figure 3 (a), the equator 2. A tripod is set up on top, and the latitude needle of the above embodiment is fixed to the tripod using tripod mounting legs 6. At this time, the reference axis (optical axis) of the telescope 4 is set to be horizontal using the bubble tube 4a.

Then, the outer frame 1 is rotated to find the zero sensitivity position of the first optical fiber gyro. Although it is not shown in the figure, when the plane (perpendicular to The above-mentioned operations are performed while looking at the display that displays the output signal of the fiber gyro.Of course, these operations may also be performed automatically by the rotation drive device of each frame and feedback control.

Next, while leaving the outer frame 1 in the same position, the inner frame 3 is expanded with respect to the outer frame 1 so that the center axes of both rings are perpendicular to each other.
The inner frame 3 is rotated along the inner circumference of the outer frame 1. And the second
Find the position where the sensitivity of the optical fiber gyro is maximum,
As a result, the optical fiber gyro has a winding surface of the wound optical fiber (a surface perpendicular to the ring center axis of the inner frame 3 mentioned above).
When is parallel to the direction of the earth's rotation, that is, Fig. 3 (a
) Sensitivity is maximum in the state shown. At this time, the latitude scale indicated by the index 7 is latitude zero corresponding to the equator.

Now, if you similarly set up a tripod at a latitude and search for the zero sensitivity position of the first optical fiber gyro, the winding surface of the optical fiber will be aligned in the direction of the earth's rotation, just as if it were placed on the equator. When it comes to the orthogonal plane (in the paper plane), that is, Fig. 3 (
b) Sensitivity becomes zero in the illustrated state. The inner frame 3 is rotated while leaving the outer frame 1 in the same position. Then, there are two cases: when the second fiber optic gyro is placed on the equator (Fig. 3 (a)) and when the second optical fiber gyro is placed at a latitude (Fig. 3 (b)). Since the direction of rotation of the earth does not change, the position of maximum sensitivity of the second fiber optic gyro is parallel to the position parallel to the equator.

Therefore, the inner frame 2 rotates with respect to the outer frame 1 by the amount of vertical change (angle θ in FIG. 3) between the positions where the latitude needle is set. As a result, Figure 3(a) and Figure 3(b)
In this case, the position of the scale 5 indicated by the index 6 is different. That is, the latitude can be read from the scale 5.

FIG. 4 shows the configuration of a phase modulation type optical fiber gyro. Among the above embodiments, both the first optical fiber gyro and the second optical fiber gyro are used as devices for efficiently detecting the rotation of the earth. An optical fiber gyro with this configuration can be used.

In FIG. 4, numeral 11 is a light source, which is a low coherence light source suitable for a phase modulation type optical fiber gyro, such as an LED.
(light emitting diode), etc.

21 and 22 are polarization adjusters that adjust the polarization efficiently (by twisting a small coil made of fiber so that it can be output).

3132 is a coupler (directional optical coupler) that splits incident light almost equally.

41 is a polarizer, for example, a polarization-maintaining fiber is wound so that the axes are aligned as much as possible. Fiber type polarizer is highly efficient.

51 is a fiber coil, which is made by winding fiber as many times as possible. The sensitivity of the signal output is proportional to the area A of the closed plane formed by this coil, and is also proportional to the number of turns N of the coil.

It is desirable that the coil 51 be wound in the same plane as much as possible. 61 is a phase modulator, for example, a piezoelectric element PZT61
This element converts a modulation signal from the oscillator 62 into a mechanical signal by winding a part of the coil 51 around it, and converts it into an optical modulation signal by expanding and contracting the optical fiber.

The Kabra 32 and the fiber coil 51
A loop is constructed that causes the gr+ac) effect.

A photodetector 71 detects optical output. Each element from the light source 11 to the photodetector 71 is connected with a single mode fiber such as a polarization maintaining fiber.

The coupling between these elements and the light guiding fibers, or between the fibers, is made as efficiently as possible.

72 is an amplifier for the photodetector 71.

81 is a lock-in amplifier, and the signal modulated by the phase modulator 61 and output from the photodetector 71 is transmitted to the oscillator 62.
Lock-in detection is performed using the reference signal from

A processing system 91 amplifies the lock-in detected angular velocity signal, removes noise, calculates, displays, and stores it.

If the entire phase modulation system is made of an absolutely polarized single-mode fiber, there will be no noise due to crosstalk or drift due to changes in temperature, and a highly accurate signal can be obtained.

Note that the amplifier 72, the oscillator 62, and the lock-in amplifier 81
, processing system 9.1, etc. may be incorporated into the tripod stand through the tripod mounting legs 6 of FIGS. 1 and 2.

In addition, the cables for transmitting power and signals are passed through the tripod mounting legs 6 for the first frame 1, and then passed through the tripod mounting legs 6 to the second frame (inner frame).
3, electric power and signals may be sent by sliding electrodes assembled on the guide pins 3a and 3b that fit into the guide groove 2.

Furthermore, not only the optical system of the fiber optic gyro but also the processing system and the battery as a power source can be simply incorporated into the frame.

〔Effect of the invention〕

As described above, according to the latitude meter of the present invention, it is possible to obtain a latitude meter that can perform simple latitude measurements with a simple configuration, regardless of measurement conditions. Further, according to the embodiment of the present invention, when not in use, the first frame and the second frame can be overlapped and can be made into a flat shape, making it easy to handle.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a plan view of FIG. 1, FIG. 3 is an explanatory diagram showing the state of use, and FIG. A block diagram of an embodiment,
It is. [Explanation of symbols of main parts] 1... Outer frame containing the first optical fiber gyro, 3
... Inner frame containing the second optical fiber gyro, 5.
...Latitude scale. Applicant Nippon Kogaku Kogyo Co., Ltd.

Claims (2)

[Claims] (1) It has a detection means for detecting north, an optical gyro supported by the detection means in a variable direction, and a display means for displaying latitude based on the maximum sensitivity position of the optical gyro with respect to the detection means. Characteristic latitude meter. (2) The latitude meter as set forth in claim (1), wherein the detection means comprises an optical gyro.