JPS6089759A - Optical rotation sensor - Google Patents

Abstract

PURPOSE:To making the sectional shape of luminous flux passed through a slit elliptic and to equalize the slit width to its short diameter by beveling an end surface of an optical fiber for projection and also setting the tilt angle of the optical fiber properly, and allowing refracted light to pass through the slit. CONSTITUTION:The optical fiber 4 for projection and an optical fiber 5 for photodetection are installed at both sides of a rotary code disk 3 provided with numbers of slits 2, and end surfaces of both optical fibers 4 and 5 face each other at both sides of slits 2. The fiber axis of the optical fiber 4 for projection is slanted at a specific tilt angle alpha to the rotary code disk 3, and its end surface is beveled at a constant tilt angle beta to the fiber axis; and the tilt angles alpha and beta are so set that projection light is refracted by the slanting surface and passed through a slit to enter a photodetecting element. Light parallel to the axis of the projection fiber 4 is sectionally elliptic having a long diameter d1 and d2 after being refracted. Consequently, slits 2 are formed so that their width is equalized to the short diameter d2.

Description

[Detailed Description of the Invention] (a) Field of Industrial Application This invention relates to an optical rotation sensor consisting of a combination of a rotating +1 plate and an optical fiber, and is used to detect rotational speed, rotational speed, etc. by being attached to a rotating body. It is used.

(b) Prior art As shown in FIG.
An optical rotation sensor consisting of a light-emitting optical fiber 4 and a light-receiving optical fiber 5 facing each other is conventionally known.

(c) Intermittent problem to be solved by the invention When a conventional optical rotation sensor as mentioned above requires a large number of pulses per rotation.

If there is a limit to the size of the rotary plate 1, the width of the slit 2 must be reduced.

In this case, the amount of light that can pass through the slit 2 is reduced, so the absolute amount of light that enters the light-receiving optical fiber 5 is reduced, and the margin for reception sensitivity is reduced.

In addition, the output angle of the light projected from the optical fiber 4 for projection is larger than the slit width as shown in FIG.
The amount of leakage increases, and this also becomes a cause of not being able to obtain a sufficient absolute amount of light.

Furthermore, as the width of the slits 2 becomes smaller, the distance between the shielding parts 6 between the slits 2 also becomes smaller, so that f as shown in FIG.
When the slit 2 is cut off, the leaked light may enter the slit 2 adjacent to the slit 2, and there may be cases where the S/N ratio cannot be kept large.

Conventionally, an optical system such as a converging lens was required to eliminate such an optical system, but this invention solves the above-mentioned optical rotation without using such an optical system. The purpose is to provide sensors.

(c) Means for resolving inter-junction points In order to solve the above problems, this invention.

The fiber axis of the light emitting optical fiber is installed at a constant angle a with respect to the rotary code plate, and the end face of the optical fiber is formed into an inclined plane with a constant angle of inclination β relative to the fiber axis 1. The above-mentioned arrangement α is formed so that the projected light is refracted at the inclined surface, passes through the slit, and enters the light receiving member.
The configuration is such that the same β is set.

(B) Embodiment In the embodiment shown in FIGS. 4 to 6, a light-emitting optical fiber 4 and a light-receiving optical fiber 5 are installed on both sides of a rotary code plate 3 provided with a large number of slits 2. The end surfaces of both optical fibers 4 and 5 are made to face each other on both sides of the slit 2, and one basic feature is the same as the conventional one.

The difference from the conventional structure is that the fiber axis of each optical fiber 4.5 has an angle α of M with respect to the rotary code plate 3, as shown in FIG. The point is that the end faces 4a and 5b of the fiber ring are formed as inclined surfaces having an angle β with respect to the fiber ring. .

When the above angles a and β are appropriately set, the light emitted from the light emitting optical fiber 4 is refracted at its end face 4a, passes through the slit 2, and enters the end face I of the light receiving optical fiber 5. The light is refracted and enters the optical fiber 5.

Now, the diameter of the light emitting optical fiber 4 is dl, and the refractive index is nl.
, the angle of incidence is θ1, and the diameter of the refracted and broken beam is d.
2. If the external refractive index is n2 and the exit angle is θ2, it follows from Snell's law 1 and is also geometrical.

Since n+>n2, there is a relationship of d+>d2.

Since light refraction occurs only in one fixed direction, Figures 5 and 90
It does not refract in a different direction (see Figure 6).

Therefore, when light parallel to the axis of the light emitting fiber is taken out, the cross section of the refracted light beam becomes an ellipse with major axis d and minor axis d2.

As a result, the width of the slit 2 can be formed to match the short axis dz.

Note that although the luminous flux after being refracted by one angle becomes narrower as described above, the amount of light does not change.

In the above embodiment, the light receiving optical fiber 5 is provided on the light receiving side,
The end face 5a is formed into an inclined surface similar to the end face 4a of the light emitting optical fiber 4, but this end face 5a is formed at right angles to the fiber axis 1 of the optical fiber 5, and the rotation code plate It may also be installed so that it is parallel to one surface of 3. Further, instead of the light-receiving optical fiber 5, a light-receiving element such as a photoelectric conversion element may be directly installed.

(Feather effect) As described above, this invention forms the end face of the light emitting optical fiber into an inclined surface, and sets the inclination angle of the optical fiber appropriately so that only the refracted light passes through the slit. Since the cross-sectional shape of the light beam passing through the slit is elliptical, the width of the slit is made equal to the short axis of the slit, making it possible to form a narrower slit than in the conventional case. Moreover, it has the effect of ensuring the same amount of light as in the conventional case.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the conventional example, FIGS. 2 and 3 are sectional views of the conventional example, FIG. 4 is a partially omitted perspective view of the embodiment, FIG. 5 is a cross-sectional plan view of the embodiment, and FIG. The figure is a longitudinal sectional front view of the embodiment. DESCRIPTION OF SYMBOLS 1... Rotating plate, 2... Slit, 3... Rotating code plate, 4... Optical fiber for light emission, 5... Optical fiber for light reception, 4a, 5a... End face patent Applicant Sumitomo Electric Industries Co., Ltd. Agent Kama 1) Bun 2

Claims (1)

[Claims] In an optical rotation sensor, a light-emitting optical fiber is provided on one side of a rotary code plate provided with a large number of slits, and a light-receiving element such as a light-receiving optical fiber is provided facing the optical fiber through the slit. The fiber axis of the fiber is installed with a constant angle ff4q with respect to the rotary code plate, and the end face of the optical fiber is formed with an M slope f having a constant angle β with respect to the fiber axis, and the projected light is An optical rotation sensor characterized in that the angle α and β are set to be the same as the angle α described in -h so that the light is refracted at the slope of the surface, passes through the slit, and enters the light receiving element.