JPS59173713A - Method for measuring optical reflection type displacement - Google Patents

Abstract

PURPOSE:To obtain a titled device which is not influenced by an electric noise by providing a projecting fiber for leading a light from a light source to an object to be measured, and a photodetecting fiber for photodetecting a reflected light from a reflecting body and leading it to a photoelectric converting means. CONSTITUTION:An optical reflection type pickup 8 is constituted by providing in parallel and coupling the tip part of a projecting fiber bundle 10 and the base end part of a photodetecting fiber bundle 11, and attaching a hemispherical lens to these end faces. In this state, a continuous optical signal from the projecting fiber 10 is sent to the photodetecting fiber bundle 11 as an optical blinking signal in accordance with a rotation of a rotary slit plate 7. Also, this optical blinking signal passes through each photodetecting fiber bundle 11 from each reflection type pickup 8, is sent to a photodetector 13, converted to an electrical signal and amplified. In this way, the measurement can be executed exactly without being influenced by an electric noise.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light reflection type displacement measuring device using an optical fiber, and in particular, the present invention relates to a light reflection type displacement measuring device using an optical fiber, and in particular, it has a configuration in which no electrical components are installed near the object to be measured due to optical signal transmission using an optical fiber. It can be used even at high and low temperatures without being affected by noise. In addition, we have adopted a method that reflects light for displacement detection.
The present invention relates to a light reflection type displacement measuring device that can be made smaller and easier to assemble by integrating the light emitting and receiving parts of an optical fiber.

Encoders are used in the detection parts of measuring instruments that measure the position, speed, etc. of equipment, but conventional optical encoders have the following problems.

a) Since electrical components such as light emitting elements and light receiving elements (light emitting diodes, photodiodes, etc.) for emitting and receiving light are built-in, they are easily affected by external electrical noise, especially welding machines, electrical discharge machines, etc. It cannot be applied to the environment, and it is difficult to use it at high or low temperatures.

b) Even if electrical components are installed externally, the same problem as a) still remains because in the conventional encoder, it is necessary to provide at least an optical semiconductor inside the encoder body. Furthermore, as the length of the cable connecting the encoder body and the circuit that processes the electrical signals sent from it increases, stray capacitance and resistance increase, making the electrical signals sent through the cable susceptible to external influences. This can lead to malfunction.

C> Conventional optical encoders use a transmitted-light displacement detection section, so the accuracy of mounting the light-emitting and light-receiving elements has a large impact on performance, and the structure is complex, impeding miniaturization. I'm reading.

The present invention was devised in view of the above-mentioned conventional problems and to effectively solve these problems, and an object of the present invention is to provide a system that can be used even under high and low temperatures without being affected by external electrical noise. Another object of the present invention is to provide a light reflection type displacement measuring device that can be miniaturized and easily assembled.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes an object to be measured whose angle (rotational displacement) is measured or a rotating body attached to the measured object. is rotatably supported. This device for measuring the rotational displacement of the rotating body 1 includes a displacement detecting section 4 that detects the displacement of the rotating body 1, and a displacement detecting section 4 that generates light for displacement detection and converts the optical signal reflected from the displacement detecting section 4 into an electrical signal. It mainly consists of an electric circuit section 5 that converts and processes the displacement detection section 4 and the electric circuit section 5, and an optical transmission section 6 that optically connects the displacement detection section 4 and the electric circuit section 5 and transmits light.

The displacement detection unit 4 includes a rotating slit plate 7 attached to the tip of the rotating body 1, and a sensor located in front of the rotating slit plate 7 (facing the rotating slit plate 7).
It consists of a light reflection type pickup 8 which is installed on the right side in Fig. 1 and emits and receives light, and a fixed reflection slit plate 9 which is attached to the end of the casing 3 in close proximity to the rotating slit plate 7. . Further, the light transmission section 6 includes a light emitting element 12
a light-emitting fiber bundle 10 that transmits the light emitted from the displacement detector 4 to the displacement detector 4; and a light-receiving fiber bundle 11 that transmits the optical signal (blinking light signal) obtained from the displacement detector 4 to the light-receiving element 13.
Consisting of The electric circuit unit 5 includes a light emitting element 12 that is provided facing the base end of the light emitting fiber bundle 10 and generates light, and a light emitting element 12 that is provided facing the base end of each of the light receiving fiber bundles 11 and a displacement detector 4 that is provided facing the tip end of each light receiving fiber bundle 11. A light receiving element 13 that converts an optical signal into an electrical signal, an amplifier circuit 14 that amplifies the electrical signal from each light receiving element 13, and a plurality of electrical signals corresponding to each light receiving element 13 from the amplifier circuit 14 are combined as appropriate. A comparator 15.1'6.1 that compares the electrical signals and outputs a rectangular wave signal.
7 and N.

As shown in FIG. 2, the periphery of the rotating slit plate 7 has
Transmitting portions 18 that transmit light alternately with a width of P/2 along the circumferential direction (=rotation direction) of the rotating slit plate 7 all around the circumference.
(voids) and a light shielding part 19 that absorbs and blocks light, and a grid-like continuous slit (pitch P) is formed at the peripheral edge of the rotating slit plate 7. Further, the fixed reflective slit plate 9 is provided to face the light reflective pickup 8 with the rotating slit plate 7 in between. A fixed reflective slit plate 9 located behind the slit of the rotating slit plate 7
As shown in FIG. 3, a rectangular reflecting portion 20 having a width of P/2 is formed concentrically with the slit of the rotary slit plate 7 and at the same pitch P. As shown in FIG. Fixed reflective slit plate 9
, such reflecting portions 20 are provided on three tracks α, β, and γ divided in the radial direction of the rotating slit plate 7, and slits of reflective surfaces are formed in each track α, β, and γ. ing. Reflection part 20 of outer track α...
A reflective section 20 consisting of a reflective slit and a central track β.
As shown in the figure, the reflective slit consisting of <P/
The reflective slits of the track γ are arranged at a position shifted by 4te from that of the track β by P/4. What is track β?
/2 position shifted. Each track α, β,
Between the reflective parts 20 of γ is a non-reflective part 21 that absorbs light but does not reflect it.
It becomes. In addition, there is one rectangular reflecting surface 22 (in the illustrated example, P
/2 width> is formed.

The light reflection type pickup 8 is provided in close proximity to the displacement indexing section consisting of the rotating slit plate 7 and the fixed reflecting slit plate 9, and tracks α, β, and γ of the fixed reflecting slit plate 9 and the rotating slit plate 7. Four slits are arranged in parallel in the radial direction of the rotating slit plate 7, each facing the reflecting surface 22.

As shown in FIG. 4 or FIG. 5, each light reflection type pickup 8 has a distal end 10a of a light emitting fiber bundle 10 and a base end 11a of a light receiving fiber bundle 11 connected in parallel. A hemispherical condensing lens 23 is attached to these end faces. The condensing lens 23 focuses the light emitted from the tip 10a of the light projection fiber bundle 10 onto the displacement indexing part and projects the light, and the condensed light is reflected by the reflection part 20 of the fixed reflection slit plate 9. It is provided in order to collect the reflected light that has been reflected back to the base end of the light receiving fiber 11 and to effectively utilize the optical signal. The light reflection type pickup 8 is fixedly attached to a cover 3a that covers the tip of the casing 3.

The comparator 15 also receives an optical signal from the track α of the fixed reflective slit plate 9, which is converted into an electrical signal by the light receiving element 13, and is further amplified by the amplifier circuit 14, and an optical signal from the track β. An electric signal B corresponding to the signal is input, and a rectangular wave signal X is output from the comparator 15.

Further, the comparator 16 receives the electric signal B and the electric signal corresponding to the optical signal from the track γ, and outputs the signal Y. An electrical signal corresponding to the optical signal from the reflective surface 22 and a preset low voltage signal are input, and a signal Z is output.

Next, the operation of this embodiment will be described.

The light emitted from the light emitting element 12 is transmitted to the light emitting fiber bundle 1.
0, the light is emitted from the tip 10a, focused by the condenser lens 23, and emitted toward the fixed reflective slit plate 9. However, there is a rotating body 1 in front of the fixed reflective slit plate 9.
Since there is a rotating slit plate 7 which is attached to the rotating body 1 and rotates together with the rotating body 1, the transmission state of the light focused by the condensing lens 23 to the fixed reflecting slit plate 9 changes with this rotation.

That is, when the rotating slit plate 7 rotates and the light shielding part 19 of the rotating slit plate 7 and the reflecting part 20 of the fixed reflective slit plate 9 overlap as shown in FIG.
The light from 3 is absorbed by the light shielding part 19 of the rotating slit plate 7, or the light transmitted through the transmitting part 18 and reaching the fixed reflective slit plate 9 is also absorbed by the non-reflecting part 21 behind the transmitting part 18. Absorbed. Therefore, in this case, the light emitting fiber bundle 1
The light projected from 0 is not reflected by the reflection section 20, and the light is not sent to the light-receiving fiber bundle 11.

On the other hand, as shown in FIG. The light is absorbed by the light shielding part 1 of the slit plate 7, but the light transmitted through the remaining transmitting part 18 is absorbed by the reflection part 2 of the fixed reflection slit plate 9.
It is reflected at 0.

Then, the reflected light passes through the transmitting section 18 again and returns to the base end 11a side of the light-receiving fiber bundle 11, is further focused by the condenser lens 23, and is received by the light-receiving fiber bundle 11. In this way, the continuous optical signal from the light emitting fiber bundle 10 is transmitted as a light brightness reduction signal containing rotational displacement information of the rotating body 1 according to the rotation of the rotating slit plate 7, that is, the rotation of the rotating body 1. It is sent to fiber bundle 11.

This light dimming signal is sent from each light reflection type pickup 8 through each light receiving fiber bundle 11 to a light receiving element 13 provided at the tip of each light receiving fiber bundle 11, respectively.

Then, the light receiving element 13 converts it into an electric signal, and this electric signal is further amplified by the amplifier circuit 14. By the way, since the reflection slits constituted by the reflection sections 20 of each track α, β, and γ of the fixed reflection slit plate 9 are shifted by P/4 as described above, the distance from the amplifier circuit 14 is Each track α obtained.

As shown in FIG. 6, the electrical signals A, B, and r corresponding to β and γ are 1/4 wavelength (
It becomes a three-phase signal with a phase difference of /4λ). When the rotation of the rotating body 1 is constant, the reflection cross section of the reflection section 20 changes linearly, resulting in a triangular wave electric signal as shown in FIG.

These electrical signals A, B, and r are combined into A, B, and B, respectively, and input to comparators 15 and 16. Comparator 1
5.16, the output is switched at the intersection of the differential signals each consisting of two signals, and the logic 1 state and logic 0 state are switched.
A voltage signal train of the state is output as shown in FIG. The electrical signal X output from the comparator 15 and the electrical signal Y output from the comparator 16 are two-phase rectangular wave signals with a phase difference of 1/4 wavelength. If electric signals X and Y are used, then X.

Which Y goes first from 1lO1l/J1. It is possible to determine whether the rotating body 1 rotates in the forward or reverse direction by electrically detecting whether the rotation speed changes to /l. In addition, without changing the pitch P of the reflection slits in each track α, β, and γ of the reflection unit 20, these are shifted to obtain three-phase signals, and from these differential signals, a 1/4 wavelength phase difference is obtained. Since a two-phase rectangular wave signal of X and Y with Obtainable.

Note that the reflective surface 22 of the rotating slit plate 7 faces the optical reflective pickup 8 once for each rotation of the rotating slit plate 71, and at this time, the reflected light from the reflective surface 22 is converted into an electrical signal in the same manner as described above. The electric signal Δ is converted and amplified into an electric signal Δ from the amplifier circuit 14. The signal Δ is compared with a constant voltage signal by a comparator 17, and a signal 2 that generates one pulse per rotation of the rotating body 1 is output. If this electric signal Z is detected, it can be conveniently used to find the origin of the machine.

As described above, in the present invention, since the light emitting fiber bundle 10 and the light receiving fiber bundle 11 are used, the emitting element 12,
All electric components such as the light receiving element 13 and the amplifier circuit 14 can be installed as a single module outside the encoder as the electric circuit section 5, and the encoder main body and the electric circuit section can be connected using light having a non-inductive characteristic. Therefore, the encoder body consisting of the rotary slit plate 7, etc. can be applied to measuring objects with large electrical noise such as welding machines, and accurate measurement can be performed without being affected by induced noise even during optical transmission. , it can be used even at low temperatures. In addition, the present invention employs a light reflection type pickup 8 which is a light reflection type and integrates the light emitting and receiving parts of the light emitting fiber bundle 10 and the light receiving fiber bundle 11, so it is more effective than the conventional transmitted light type. It is easier to assemble and install, the structure is simple, and the encoder can be made smaller. Furthermore, since there are no electrical parts in the encoder section and no electricity is required, it has a completely explosion-proof structure.

In addition, conventionally, the detected electrical signal and a preset fixed comparison voltage are compared using a comparator to shape the waveform. However, in this example, a circuit processing method is used that uses differential signals to cancel common mode components that degrade accuracy, so high-speed response and high accuracy can be ensured, and the output There is little variation in accuracy. Furthermore, conventionally, the arrangement of optical detection sections for generating differential signals consists of four detection sections in the circumferential direction, and the slit width differences of the rotating slit plate cause variations in the phase difference, reducing accuracy. However, in this embodiment, the reflecting portions 20 of the plate 9 are arranged in one row in the radial direction, and the configuration includes three detecting portions, so that the phase difference can be minimized. Relative phase relationships can be maintained.

In the above embodiments, the angle (rotational displacement) of the object to be measured is detected, but the present invention can also be applied to linear displacement detection. Further, the fixed reflective slit plate 9 is attached to the rotating body 1 to form a rotating slit plate, and the rotating slit plate 7 is fixedly installed between the rotating slit plate and the light reflective pickup 8. Also, the same displacement measurement as in the above embodiment can be performed. Furthermore, if the light beam from the light projecting fiber bundle 10 is narrowed down through a lens, and a rotating slit plate having a slit-shaped reflective surface in the rotating direction of the rotating body 1 is provided, the fixed slit plate can be omitted.

In summary, according to the present invention, the following excellent effects can be achieved.

(1) Since the optical fiber is used and a light reflection method is adopted, all electrical parts of the device can be installed in a place where they will not be affected by the electrical noise of the object to be measured. Can also be used for targets. Also, since it is an optical transmission method,
Accurate measurements can be made without being affected by induced noise. Furthermore,
Since there are no electrical parts near the measured object, it can be applied to high or low temperature objects.

(2) In the conventional transmitted light method, if the light emitting element and the light receiving element for displacement detection are not placed facing each other with high accuracy, the amount of smallpox will be greatly reduced and it will take up space. Since the light emitting and receiving parts of the optical fiber and the light receiving fiber are integrated, assembly is easy, the device can be made smaller, and accuracy can be maintained.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is an overall configuration diagram of the device according to the invention, Fig. 2 is a partially enlarged front view of the rotating slit plate, and Fig. 3 is a fixed reflection slit. Figures 4 and 5 are enlarged front views of the plate, Figures 4 and 5 are enlarged front views of the displacement detection section, Figure 6 is a waveform diagram showing the output waveform of the electrical signal obtained from the amplifier circuit, and Figure 7 is the waveform diagram from the comparator. FIG. 3 is a waveform diagram showing an output electrical signal. In the figure, 1 is a rotating body (object to be measured), 4 is a displacement detection section, 5 is an electric circuit section, 6 is an optical transmission section, 7 is a rotating slit plate, 8 is a light reflective pickup, and 9 is a fixed reflective slit. board, 1
0 is a fiber bundle for light emission, 11 is a fiber bundle for light reception, 12
13 is a light-emitting element (light source), 13 is a light-receiving element (photoelectric conversion means)
, 15, 16, and 17 are comparators, 18 is a transmission part, 19 is a light shielding part, 20 is a reflection part (reflector), 21 is a non-reflection part, 23
is a condensing lens.

Claims (1)

[Claims] (For use with displacement measuring devices for measuring the displacement of objects to be measured)
A light projection fiber for guiding light from a light source to the object to be measured, and a reflector provided on the side of the object to be measured to reflect the light emitted from the tip of the light projection fiber. and a light-receiving fiber for receiving reflected light from the light source and guiding it to the photoelectric conversion means, and the distal end of the light-emitting fiber and the light-receiving base end of the light-receiving fiber are coupled in parallel. A light reflection type displacement measuring device characterized by: