JPS6086411A - Optical fiber type gyroscope - 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 Application of the Invention] The present invention relates to a gyroscope for measuring the angular velocity and direction of motion of a moving object, and particularly to a gyroscope that utilizes the Sagnac effect of light.

[Background of the invention]

In general, a fiber optic laser gyroscope that utilizes the Sagnac effect of light is configured as shown in FIG. 1, for example. That is, the beam splitter 2 is installed in the direction in which the laser beam of the laser generator l that generates the beam light travels, and the condenser lenses 3a and 3b are installed in the direction in which the split light beams travel, and, Each condenser lens 3a, 3b
The ends of the fiber loop 40 formed by winding the optical fiber multiple times are positioned at the focal point of the fiber loop 40, and the laser generator l is positioned in the direction in which the light passing through the fiber loop 4 is transmitted through the beam splitter 2 or reflected. An optical device is provided with an optical sensor 5 installed at a different position.

The laser light emitted from the laser generator 1 is split by the beam splitter 2, and the split beam travels simultaneously from both ends of the fiber loop 140 in opposite directions. The light emitted from the fiber loop 4 is combined and incident on the surface of the optical sensor 5. Here, if the fiber loop 4 is stationary, there is no phase difference in the combined light, and the incident light is stationary. Here, when the fiber loop is rotated, an optical path difference is created between the lights traveling in opposite directions inside the fiber loop 4, and as a result, a phase difference is created between the combined lights that reach the surface of the optical sensor 5, and the light Since there is an interference state of

According to the literature, the phase difference θ between the two lights induced by the Sagnac effect is: where, L; length of the optical fiber a: radius of the optical fiber loop C: speed of light λ: wavelength of the laser beam Ω: inertia of the fiber loop Rotational angular velocity relative to space.

In the optical device shown in FIG. 1, the output of the optical sensor 5 is proportional to l+θ. However, this makes it difficult to use it as a gyroscope.

In other words, when a gyroscope measures the entire angular velocity of a moving object, especially the rotational angular velocity, the range is, for example, 0 per second.
．． Generally, rotations ranging from minute rotations of less than 0.01 degrees per second to rotations exceeding 100 degrees per second are required. The output of CIJSθ cannot provide sensitivity to minute rotations. In order to solve this drawback, an optical device shown in FIG. 2 is known. Beam splitter 7a.

7b and 7c are provided, and a phase shifter 8 is installed between the beam splitters 7b and 70. Now, the beam light emitted from the laser generator R1 is divided into two by the beam splitter 2, into a transmitted beam and a reflected beam.

The transmitted light is divided into transmitted light and reflected light by the beam splitter 7CV. The reflected light exits the optical device and serves no function.

It is usually treated by absorbing it with black cloth or anti-reflection material.

The beam light transmitted through the beam splitter 7Ct is passed through the condenser lens 3a.
'& street, light enters fiber loop 4.

The light beam that has rotated counterclockwise and passed through the inside of the fiber loop 4 is reflected by the condenser lens 3b, beam splitters 7a and 7b, and is incident on the optical sensor 6. On the other hand, the light reflected by the beam splitter 2 is transmitted to the beam splitter 7.
AI transmission, through condensing lens 3BL, fiber loop 4
sunlight enters.

The light beam that rotates clockwise inside the fiber loop 4 passes through the condensing lens 3a, and then passes through the beam splitter 7C.
and enters the phase shifter 8.

When the light propagating in the left and right directions inside the fiber loop 4 is incident on the surface of the optical sensor 6, the phase shifter 8 applies a phase difference bias of π/2 between the left and right lights. The beam light that has passed through the phase shifter 8 is passed through the beam splitter 7b'Th.
The light passes through and enters the optical sensor 6 by 1'. Since there is a phase difference between the left and right sides of the incident light, interference occurs,
The output of the optical sensor 6 is proportional to sin θ (θ is the phase difference due to the Sagnac effect), and the sensitivity during minute rotations can be optimized and the drawbacks of the optical device shown in FIG. 1 can be improved. However, even with the optical device shown in Figure 2 that applies this phase difference bias, the sensitivity decreases as the rotational angular velocity to be detected increases and the phase difference θ due to the Sagnac effect approaches 90 degrees per second. There are problems such as the inability to determine whether or not the rotation has occurred, and there are drawbacks such as the range of rotational angular velocity to be detected is limited.

To overcome this drawback, the optical device shown in FIG. 3 is known.

In addition to the optical sensor 6, another optical sensor 9 is provided to obtain optical signal outputs based on sin θ and sin θ, respectively. Then, as shown in Fig. 4, the outputs of the sin θ and the output of the tuft θ are used by switching between the extraction θ and the output θ, depending on the range of the phase difference θ proportional to the rotational angular velocity (the graph in Fig. 4 (range indicated by thick line). In this way, sin θ
, the detection sensitivity is improved by changing CO3θ, but in order to avoid any deviation in the detection time, it is necessary to change θ from sinθ.
There are many disadvantages in that calculations for subtracting θ from θ must be performed at the same time, requiring the use of multiple sets of calculators, and discontinuities occur in detected values at switching points.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber type gyroscope that is capable of detecting minute rotations and expanding the range of detected rotational angular velocities.

[Embodiments of the invention]

An embodiment of the invention is shown in FIGS. 5 and 6. In FIG. 5, lQa and lOb are amplifiers that amplify the outputs of sin θ and cgs θ from the optical sensors 6 and 9. Then, this amplified light is subjected to A/D conversion by converters 11a and llb, and calculations are performed by computer 12.

The calculation method is as shown in FIG. That is, (1) Multiply the output of sinθ by the constant Affi to obtain As1n
Let it be θ.

(2) Multiply the output of coSθ by a constant Bk to obtain BcO8θ.

(3) When the output of sinθ is negative, set it to -Bcosθ (switch the sign to negative) (4) When the output of sinθ is positive, set it as A31nθ+B
- Perform all calculations of B cos θ.

(5) When the output of sinθ is negative, As1nθ−B
10B (company) θ is calculated.

With this configuration, the following calculations are performed inside the computer 12.

When the output of sinθ is positive, As1nθ+B-BIXISθ = B +, 'λ1+B' sin (θ-φ) where, φ: tan -' - Also, when the output of sinθ is negative, As1nθ-B
+BOQSθ 1 − B 0 m σ Shimoichi F 8 City (θ 0 φ) From each equation, the phase difference θ can be calculated, and therefore,
The rotational angular velocity of the gyroscope is measured.

The effects obtained by this are as follows.

(1) Output (direction) is larger than when using by switching the value of sin θ or hoe θ, and therefore sensitivity is improved, so rotational angular velocity detection performance as a gyroscope is improved.
In other words, resolution is improved.

(There is one set of two output values, and only one set of calculation function is required to calculate the phase difference θ from sin θ.

(3) Constants A and B? By selecting the phase difference θ
The entire detection range can be set optimally.

That is, B ten, '7 door seal] positive sin (θ-φ) - B ten"te)
The following ranges can be found from the calculation formulas for B'' sin (θ + φ).

The constants A and Bk may be selected depending on the range of the phase difference θ.

Further, as an application of the present invention, a constant C may be used in addition to the constants A and B, for example, As1nθ−Bcosθ+C As1nθ+BCIJ2θ−C, but in this case, when the phase difference θ=0, Discontinuities will occur in the output values.

[Brief explanation of the drawing]

1 and 2 are structural diagrams showing a conventional optical device, FIG. 3 is a structural diagram of an optical device according to an embodiment of the present invention, FIG. 4 is an explanatory diagram of a conventional output calculation method, and FIG. 5 is a block diagram of the output processing device of the present invention, and FIG. 6 is an explanatory diagram of the output calculation of the present invention. l... Laser generator, 2... Beam splitter, 4...
...Fiber Roug, 5... Optical sensor, 6... Optical sensor, 7... Beam splitter, 8... Phase shifter, 9...
・Koshana/S. 7th day 4th mouth CO8θ th, 5th figure

Claims (1)

[Claims] 1. Light is simultaneously introduced into the same closed optical path from opposite directions, and two outputs are simultaneously taken out from the light led out from the optical path, and furthermore, there is a gap between the outputs of the two lights. In an optical device configured such that the phase difference is π/2, (a) the two output values are each multiplied by a certain constant, and then addition and subtraction are performed to obtain one output value. (b) An optical fiber type gyroscope, characterized in that it is provided with a means for performing the calculation of inverting the sign of the other output, that is, the cosine function output when the sine function output tube has a negative sign.