JPS61241621A - Optical fiber rotary encoder - 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] This invention relates to an optical fiber rotary encoder that detects the rotation angle and rotation direction of a rotating body.

"Conventional technology" Figure 3 shows a conventional optical fiber rotary encoder.

FIG.

One end surface of the case 11 is an open surface 11a, and an end plate 12 is attached to the open surface 11a.

A rotary shaft 13 is rotatably held by a bearing 14 by inserting the end plate 12 from the outside, and a disc-shaped movable slit plate 15 is attached to the tip of the rotary shaft 13 within the case 11 so that it can rotate freely. be done.

A fixed slit plate 16 is disposed parallel to the surface of the movable slit plate 15, which is rotatable in this manner, in close proximity to and opposite to the peripheral edge portion of the movable slit plate 15. On both sides of the movable slit plate 15 and the fixed slit plate 16, there are two slit plates 1
The light emitting optical fiber 17 that irradiates light onto the slit plate 15.16 and the light receiving optical fiber that receives the irradiated light that has passed through the two slit plates 15.16 are connected to the holding block 21. and are provided facing each other, and in this example, the first
, and a second light-receiving optical fiber 18 and 19 are provided.

Further, in this example, a reflecting prism 22 is provided at the light output end of the light emitting optical fiber 17, and a light receiving lens 22 is provided at the light receiving end of the first and second light receiving optical fibers 18 and 19, respectively.
An example in which 3.24 is provided is shown below. In this example, the light emitting optical fiber 17 is arranged on the fixed slit plate 16 side.

The reflective prism 22 is an isosceles triangular right-angled prism,
One short side 22a is closely opposed to the fixed slit plate 16, and the light emitting optical fiber 17 is connected to the short side 22b of the pond perpendicularly to that surface. The light projecting optical fiber 17 is directly extended from the connection surface with the light projecting prism 22, and one curved end of the light projecting optical fiber 17 is guided out of the case 11.

The first and second light-receiving lenses 23 and 24 have a cylindrical shape, and one cylindrical end surface 23a, 24a of each of them faces the movable slit plate 15 in parallel and close proximity to the light-receiving surface 23a'.
+248, and its curved end surface 23b.

First and second light-receiving optical fibers 18 and 19 are connected to 24b, respectively. These first and second light-receiving optical fibers 18.19 are smoothly bent from the connecting surfaces 23b and 24b to the first and second light-receiving lenses 23.24 until they are at right angles, and then the light-emitting optical fibers are 17 and are each led out to the outside of the case 11 in the same direction.

FIG. 4 is a diagram showing the movable slit plate 15.

In the movable slit plate 15, rectangular movable slits 25 are arranged in a ring along the peripheral edge 15a so as to go around the disk surface. The long sides of these movable slits 25 coincide with a part of the straight line Li passing through the rotation center 15b of the movable slit plate 15, and the short sides have different radii R1, centering on the rotation center 15b, respectively. They are each made to coincide with a part of the circumference of a circle having R2. These movable slits 25 have a circumference 915a of the surface of the movable slit plate 15.
The light projected from the reflecting prisms 22 passes through these movable slits 25 and reaches the receiving optical fibers on the opposite side of the movable slit plate 15. It allows light to pass in both directions.

On the other hand, the fixed slit plate 16 is provided with two rows of fixed slits 26, which are called first and second slit rows 27 and 28, respectively. FIG. 5 is a diagram showing an example of this fixed slit plate 16.

Each of the short sides of these fixed slits 26 is made approximately equal to the short side of the movable slit 25, and they are arranged at a pitch angle that is approximately the same as that of the movable slit, but each of the long sides is equal to 1 of the length of the long side of the movable slit 25. /2 or less, and these fixed slits 2
6 is located at a portion facing the arrangement of the movable slits 25 on the surface of the movable slit plate 15. That is, at the fixed position of the fixed slit plate 16, the first and second slit rows 27
28 are arranged in a fan shape, and the center of the fan shape is the same as the rotation center 15b of the movable slit plate 15, and is arranged opposite to the area where the movable slits 25 are arranged.

Also, the first and second slit rows arranged in two rows 27°28
are arranged so that the pitch of the arrangement is shifted from each other. The case in FIG. 5 is a case where the pitch is shifted by 1/4 pitch. First and second slits 27.2 whose arrangement pitch is shifted from each other
8 are a slit for angle detection and a slit for rotational direction detection, respectively, and the light passing through these slits 27 and 28 and passing through the movable slit 25 is used as a signal light for angle detection and a signal light for rotational direction detection, respectively. . In addition, the incident surfaces 23a124a of the first and second light receiving lenses 23.24 face the first and second slits 27.28, respectively, and the angle detection signal light and the rotational direction detection signal light are transmitted to the first and second light receiving lenses 23.24. , the light is vertically incident on the light receiving surface 23a'+248 of the second light receiving lens 23.24.

That is, the light emitting fiber '1 led out to the outside of the case 11
The projection light sent into the optical fiber from one end of the optical fiber 17 is guided into the case 11 through the optical fiber 17, and is emitted from one end surface of the pond into the reflecting prism 22.The emitted light is One side 22C constituting the reflective right angle prism 22
It is reflected from H and travels in a curved direction of ＂；9090 degrees, exits from the reflection prism 22 from one side 22a of the pond, and is projected at a right angle to the fixed slit plate 16 and the movable slit plate 15. be done. The projected light passes through the first or second slits 27 and 28 of the fixed slit plate 16 and is projected onto the movable slit plate 15.

The light projected onto the movable slit plate 15
Due to the rotation of 5, the movable slit 25 converts the light into interrupted signal light, which is incident on the first and second light-receiving lenses 23 and 24.

FIG. 6 is a diagram showing how each of the signal lights mentioned above enters the light receiving lens.

The first and second light-receiving lenses 23 and 24 are cylindrical lenses, and are made to have a refractive index distribution symmetrical about the cylindrical axis. That is, the closer the lens is to the cylindrical axis, the higher the refractive index is, and as shown in FIG. 6A, the light receiving surface 2 of the light receiving lens is
3a+24'', the signal light incident so perpendicularly is refracted toward the cylindrical axis due to the refractive index distribution, and is converged at the center of the connection surfaces 23b and 24b with the light-receiving optical fiber. Ru.

Each of the converged signal lights is guided through the first and second light-receiving optical fibers 18 and 19, and is led out of the case 11.

"Problem to be Solved by the Invention" An optical fiber cable consisting of a light emitting optical fiber and a light receiving optical fiber is connected to the rotary encoder body, and these light emitting optical fibers and light receiving optical fibers are connected to movable and fixed slits. Since it is necessary to guide the light to the reflecting prism and the light receiving lens which are arranged opposite to each other via the plate, it is necessary to connect the light emitting optical fiber and the light receiving optical fiber in a curved manner.

The light-receiving lens must be placed perpendicular to the slit plate in order to obtain good signal light, but since the light-emitting optical fiber and the light-receiving optical fiber are placed facing each other through each slit plate, The light receiving optical fiber must be bent to lead the signal light to the outside. In other words, in order to pull out the light emitting optical fiber and the light receiving optical fiber in the same direction, it is not possible to bend the optical fibers to an extreme degree, and there is a natural limit to the curvature that can be bent. It was not possible to make it compact.

"Means for solving the problem" A light emitting optical fiber is provided on one side of the movable and fixed slit plates, that is, on the side where the light receiving optical fiber is provided,
The output light emitted from the light-emitting optical fiber is reflected using a light reflector and guided to the side of each slit plate facing the light-receiving optical fiber, so that the light is reflected and projected toward the light-receiving optical fiber. Configure.

That is, a movable slit plate having movable slits formed at equal intervals on a disc that is attached to a rotating shaft and is rotatable around the rotating shaft, and a movable slit plate that is arranged so as to face the movable slit portion at equal intervals. and a fixed slit plate in which the first and second slit rows are formed so that the pitches of the arranged slits are shifted from each other, the movable slits are arranged close to the outer peripheral surface of the movable slit plate. A light emitting optical fiber is provided almost perpendicularly to the plate surface of the plate, and after receiving the light emitted from the light emitting optical fiber and reflecting it toward the rotating shaft side, the light is transmitted through the first and second slits of the movable slit plate. The plate surface of the movable slit plate is configured such that the light from the reflector that has passed through the first and second slits of the fixed slit plate and the movable slit is received. ＼゛Arrange the first and second light-receiving optical fibers vertically. That is, the first and second light-receiving optical fibers are provided in parallel with the light-emitting optical fiber, and these optical fibers can be led out of the case without being bent.

Embodiment FIG. 1 is a diagram showing an embodiment of the present invention. Parts that are the same as those previously described will be described with the same numbers.

A rotary shaft 13 is rotatably held in the case 11 by a bearing 14 through which an end plate 12 is inserted from the outside and transmits the rotation of the object to be measured, and a disc-shaped movable slit plate 15 is provided at the tip of the rotary shaft 13. is installed. Movable slit plate 15
has a disk shape, and movable slits 25 are provided in a ring shape in a row along the outer peripheral edge 1.58 of the disk.

This is a case where the fixed slit plate 16 is provided close to and facing the portion of the movable slit plate 15 where the movable slits 25 are provided. The example shown in FIG. 1 is a case where a fixed slit plate 16 is provided on the side of the rotary shaft 13 of the movable slit plate 15. The fixed slit plate 16 is provided with first and second slit rows 27° and 28 as in the conventional case. The long sides of these slit rows 27 and 28 are approximately half the length of the movable slit 25, and each slit row 27
, 28 are arranged in a fan shape at the same pitch as the row of movable slits 25.

A light projecting optical fiber 17 is provided in the slit plate 15.16 in a direction perpendicular to the outer peripheral surfaces of these two slit plates 15.16. In this example, the light emitting optical fiber 1
A case is shown in which a cylindrical light projection lens 31 is attached to the tip of 7, and projection light is projected from the cylindrical end face in the direction of the rotation axis of the movable slit plate 15.

Further, here, an example is shown in which a right-angle prism 22 is used as a reflector that reflects light projected from a projection lens. Of the three sides of the isosceles rectangular prism 22 for reflection, the long side 22a is connected to the fixed slit plate 16 and the projection lens 3.
The light projected from the projection lens 31 enters the prism 22 almost perpendicularly, is reflected by the first reflecting surface 22b, changes its traveling direction, and goes around the back side of the fixed slit plate 16. The light is then reflected by the second reflecting surface 22C of the prism 22, and changes its traveling direction again, that is, it heads in the opposite direction to the direction in which it was emitted.
The light is projected vertically toward the fixed slit plate 16.

The first. Second light-receiving optical fibers 18 and 19 are provided, and the signal light that has passed through the fixed slit 16 and the movable slit 15 is received by the first and second light-receiving optical fibers 18 and 19. In other words, the first and second light receiving optical fibers 18.19 are arranged parallel to the light emitting optical fiber, and these optical fibers 17, 18, 19 are connected to the case 11.
It is led out to the outside of the case through an opening 29 provided in the closed surface 11b of.

In this example, light receiving lenses 23 and 24 are attached to the tip of the light receiving optical fiber 17 facing the movable slit plate 15 in order to improve light receiving efficiency. These light receiving lenses 23 and 24 are connected to the rotation center 15 of the movable slit plate 15.
The first and second slit rows 27 and 28 of the fixed slit plate 16 and the movable slit plate 15 are provided so as to face each other on a straight line passing through b.

The light that has passed through the first or second slit of the fixed slit plate is projected perpendicularly onto the movable slit plate, and as the movable slit plate rotates, the light is transmitted or blocked as a blinking signal light, and the light is transmitted through the light receiving lens. is incident on the

The light-receiving lens receives signal light incident on its entrance end face, converges the incident light, and sends it from the curved end face to the light-receiving optical fiber.

In the case of a multi-channel optical fiber rotary encoder, a plurality of light receiving sections that receive signal light are provided. Therefore, it is necessary to project the light emitted from the light projecting optical fiber 17 onto the plurality of light receiving sections as uniformly as possible. For this purpose, in the example shown in FIG. 1, a projection lens 31 is attached to the tip of the projection optical fiber 17, so that the projected light is projected with a divergence angle with respect to the optical axis.

In this case, since a plurality of light receiving sections are provided facing the movable slit 15, it is not possible to arrange each light receiving section on the central optical axis of the projected light.

That is, as shown in FIG. 6B, the light receiving lens 23°24
is arranged at a position away from the central optical axis of the projected light, so the incident light is transmitted to the light receiving surface 23ae24a of the light receiving lens 23.24.
Therefore, the signal light converged by the light-receiving lenses 23 and 24 deviates from the center of the end faces on the connection end faces 23b and 24b with the light-receiving optical fibers 18 and 19. As a result, the signal light is not transmitted correctly to the light receiving fibers 18 and 19.

FIGS. 2A and 2B are diagrams showing essential parts of an embodiment in which the present invention is applied to a multi-channel optical fiber rotary encoder.

That is, as shown in FIG. 2A, the light receiving lens 23°24
connection surface 23b with the light receiving optical fiber 18.19, 2
The light-receiving end surface 23a of the light-receiving lens 23, 24 so that the signal light is converged at the center of the lens 4b.

24. Finish a so that it is oblique to the central axis of the lens. FIG. 6C is a diagram showing how the incident light at that time is converged at the center of the connection surface with the optical fiber. That is, the incident surfaces 23a, 24a of the light receiving lenses 23, 24 are tilted obliquely with respect to the central axis of the lens, so that the signal light is refracted by the lens light receiving surfaces 23a, 24a. That is, the lens entrance surface 23a.

By selecting the above-mentioned inclination angle of 24a, the lens light-receiving surface 2
It is possible to match the traveling direction of the signal light refracted by the light receiving lens 23.24 with the central axis direction of the light receiving lens 23.24, and the incident signal light is connected to the light receiving optical fiber 1'8.19 at the connection surface 23b, 24b.

Figure 2 B +-! , /112 is an example. In this example, the light receiving optical fibers 18 and 19 are arranged so as to match the spread angle of the diffused projected light. Therefore, the signal light is perpendicularly incident on the light receiving surfaces 23a and 24a of the light receiving lenses 23 and 24, and the signal light is connected to the connecting end surface 23b and the optical fiber 18, 19.
24b.

At this time, the light-receiving optical fibers 18 and 19 are not parallel to each other, but the degree of this is much smaller than that in the conventional example shown in Fig. 3, where they are arranged at right angles. Yes, there is no practical problem.

In the multi-channel optical fiber rotary encoder, in order to project the light projected from the optical fiber with a divergence angle with respect to the projection center optical axis, the first. Second reflective surface 22a.

Light is no longer incident at right angles to 22b. Therefore, the angle of incidence of light that enters the reflective surface of the right-angle reflective prism 22 may be lower than the critical angle of reflection of the optical glass, which is the material of the right-angle reflective prism 22, from the surrounding atmosphere, and as a result, the amount of light reflected may decrease. . As a countermeasure for such a reduction in the amount of light, if the first and second reflective surfaces 22b and 22C of the reflecting right-angle prism 22, which serves as a reflector for the projected light, are metallized by vapor deposition, etc., the resulting reduction in the amount of light can be avoided. No problems arise.

The movable slit plate and the fixed slit plate shown in the above embodiments can also be made by metal vapor deposition.

That is, the metal-deposited portion can be used as a light-blocking portion, and the metal-undeposited portion can be used as a light-transmitting portion, such as the movable slit 25 and the first and second slits 27 and 28 of the fixed slit.

In this example, the first and second slits 27 and 28 of the fixed slit plate 16 are arranged in two rows with different diameters from the rotation center of the movable slit plate 15.
The slits 27, 28 may be arranged with the same diameter, but may be arranged so as to be offset from each other by a quarter pitch angle.

In addition, this is an example where the slit width, that is, the pitch, is very small compared to the lens diameter of the light receiving lens, and this is a case where a fixed slit is provided. If the size corresponds to the diameter, the fixed slit plate may be omitted.

In this case, if the first and second light-receiving lenses 23 and 24 are provided shifted by 1/4 pitch angle, the signal light incident on each light-receiving lens will have a phase difference of 174, and each will be used for angle detection. It is used as a signal light and a signal light for detecting rotational direction. This is the same even when a fixed slit plate is provided, and the first and second slits of the fixed slit plate)27.28
Alternatively, the first and second light-receiving lenses 23 and 24 may be arranged in a staggered manner so that each incident light has a phase difference of 174.

"Effects of the Invention" As described above, the light-receiving optical fiber is provided on the side opposite to the rotation axis of the movable slit plate, and the light-emitting optical fiber is provided in parallel on the same side as the light-receiving optical fiber, and the light-emitting The light projected from the optical fiber is reflected using a reflector, and
The structure is configured so that the light is guided through two slit plates to the side facing the receiving optical fiber, and the light is projected onto the slit plate.
It is not necessary to curve the optical fiber and guide it to a portion facing the light projecting optical fiber as in the conventional case, and the optical fiber rotary encoder can be configured in a small size.

In addition, in the case of a multi-channel optical fiber rotary encoder, if the light receiving surface of the light receiving lens is tilted with respect to the lens center axis according to the spread angle of the projected light, the incident signal light can be connected to the connection surface with the optical fiber. It becomes possible to correctly converge the image to the center of the area.

Alternatively, by arranging a plurality of receiving optical fibers in accordance with the spread angle of the projected light, it is possible to similarly converge the signal light to the center of the receiving lens, thereby ensuring correct transmission to the optical fiber. It becomes possible.

Furthermore, if the reflective surface of the right-angle reflective prism used as a reflector is coated with metal evaporation to increase the reflectance, it is possible to prevent the reduction in reflected light due to the spread angle of the projected light falling below the critical angle of reflection. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the invention, and FIG. 2A is a diagram showing an embodiment of the present invention. B is a diagram showing the main parts of an embodiment of a multi-channel type optical fiber rotary encoder, FIG. 3 is a diagram showing the configuration of a conventional optical fiber rotary encoder, and FIG. 4 is a movable Figure 5 shows a slit plate, Figure 5 shows an example of a fixed slit plate, and Figures 6A and B show how the projected light enters the light receiving lens. Fig. 6C shows the lens proposed in this application, and shows the situation when the incident end surface is oblique to the lens axis. . 11: Case, 12: End plate, 13: Rotating shaft, 14: Bearing, 15: Movable slit plate, 16: Fixed slit plate, 17: Light emitting optical fiber, 18: First light receiving optical fiber, 19: First 2 optical fiber for light reception, 21: holding block, 22: reflection prism, 23: 11th light reception lens,
24: Second light receiving lens, 25: Movable slit, 26:
Fixed slit, 27: first slit, 28: second slit, 29: opening, 31: light projection lens. 7172 Figure A O 2 Figure B +173 Figure 1 + Optical paper fiber: XL

Claims (1)

[Claims] (1) A movable slit plate that is attached to a rotating shaft and has movable slits formed at equal intervals on a disc centered on the rotating shaft, and a movable slit plate that is provided close to the outer peripheral surface of the movable slit plate. A light emitting optical fiber arranged substantially perpendicular to the plate surface, and after receiving the light from the light emitting optical fiber and reflecting it toward the rotating shaft side, the first and second slits of the movable slit plate a reflector that re-reflects the light from the movable slit, and first and second light-receiving optical fibers that respectively receive light from the reflector that has passed through the movable slit and are arranged substantially perpendicular to the plate surface of the movable slit plate. An optical fiber rotary encoder comprising: