JPS6336498A - Optical fiber signal transmitter for incremental encoder - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal transmission device in an incremental encoder used for position detection and speed control of general machines such as machine tools and measuring instruments.

[Prior art]

Conventionally, this type of incremental encoder (hereinafter simply referred to as an encoder) has a basic operation as shown in FIG.
The three light-receiving elements 3 (Light-emitting element for A phase 3
It is generally known that the light passing through the slit plate 1 is received by the light emitting element 3b for the B phase and the light emitting element 3c for the Z phase, and after photoelectric conversion is transmitted as an electrical signal via the cable 4. [Problems to be solved by this invention] However, in this conventional encoder, the transmission path is an electric cable 4, so transmission errors often occur when long-distance transmission is performed in an environment with a lot of electromagnetic noise, such as in a factory. .

This invention was devised in view of the above-mentioned circumstances, and its purpose is to eliminate the influence of external electromagnetic noise during signal transmission, reduce the transmission error rate, and provide a highly reliable encoder, as well as having a simple structure and low cost. The goal is to provide an encoder that is easy to use.

[Failure to solve the problem]

According to the signal transmission device in the encoder of this invention,
A main scale that has a light emitting element that emits multiple lights of different wavelengths, a slit for modulating the light into a pulse wave that waits for each wavelength emitted from the light emitting element, and each light that is modulated into a pulse wave by the main scale. a multiplexer that converges the light into a beam and sends it to an optical fiber, and a wavelength selection demultiplexer that splits the convergent light sent from the optical fiber into each of the above-mentioned lights and sends them to each light receiving element. shall be taken as a thing.

Then, without changing the light passing through the slit into an electrical signal, it is possible to converge and send multiple lights of different wavelengths as they are to the optical fiber, reducing the number of electro-optical converters, optical fiber photoelectric converters, etc. That's how it is.

〔Example〕

The present invention will be explained below with reference to an illustrated embodiment.

The encoder 5 includes a light emitting element 6 that emits a plurality of lights of different wavelengths for position detection or speed control, and a main scale 7 that has a slit for modulating the light into a pulse wave that waits for each wavelength emitted from the light emitting element. , this main scale 7
a multiplexer 9 that converges each light modulated into a pulse wave into a beam shape and sends it to an optical fiber 8; and a multiplexer 9 that demultiplexes the converged light sent from the optical fiber 8 into each of the above-mentioned lights and receives each light. It is equipped with a wavelength selective demultiplexer 11 that sends signals to the element 10. (See FIG. 1) The light emitting element 6 includes three laser diodes 5a.

6b, 6c, and each laser diode 5a.

It consists of a laser diode drive circuit 6d that causes lights 6b and 6c to emit light. and each laser diode 5a
, 5b, 5c are each slit A phase of the main scale 7,
They are arranged corresponding to the B phase and Z phase, and each laser emission wavelength is different from λA, λB, and λZ.

Note that the A phase and B phase of the main scale 7 are for position detection, and the Z phase is for zero point detection.

The multiplexer 9 consists of two reflecting mirrors 9a, 9b and two half mirrors 9d and 9c, and combines three light beams into one.
Converge and combine into the book's light beam.

The demultiplexer 1 consists of two first and second dichroic mirrors 11a and llb, and converts the convergent light sent from the optical fiber 8 into λA.

The wavelengths λB and λZ are separated.

The light receiving element 10 includes three photodiodes 10a and 3
It consists of two amplifiers 10b.

The function of the encoder 1 having such a configuration is to cause the three laser diodes 6a, 6b, and 6c to emit light by the if laser diode drive circuit 6d. The three lights of different wavelengths λA, λB, and λZ that have passed through the main scale 7 are sent to the reflectors 9a and gb of the multiplexer 9 and the half mirror 9d.

By interaction with 9C, the light beams are converged and combined into one light beam, and the light beams are input to the optical fiber 8 via the lens 12.

Next, the output light from the optical fiber 8 is separated into three light beams by a wavelength selective demultiplexer 9.

That is, the first clockwise mirror 118 has an angle of λA.

Since λB is transmitted and λZ is reflected, only λZ can be separated, and the second dichroic mirror 1.1b transmits λA and reflects λB, so λA and λB can be separated, so that λA, λB, and λZ can be separated. It is separated into light beams of each wavelength. Note that FIGS. 2 and 3 show the first and second mechanical mirrors 11a.

11b.

And each separated light beam is 1, photodiode 1
After photoelectric conversion at 0a, the signal is amplified by amplifier 10b and output.

〔Effect of the invention〕

■ The error rate due to electromagnetic noise can be reduced by transmitting the light that passes through the slit in the encoder as it is through the optical fiber without converting it into an electrical signal.

■ By using light-emitting elements that can emit light of multiple different wavelengths, multiple signals can be transmitted through optical fibers.

Therefore, it is possible to reduce the number of electro-optical converters, photoelectric converters, etc. that accompany the encoder, and it is possible to reduce the cost of the encoder.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an encoder of the present invention, FIGS. 2 and 3 are graphs showing characteristics of first and second dichroic mirrors, and FIG. 4 is a circuit diagram showing a conventional encoder. 1... Slit plate, 2... Light emitting element 3... Light receiving element, 4... Electric cable 5... Encoder, 6... Light emitting element 5a, 5b, 5c... Laser diode 6d... Laser diode drive circuit 7.・Main scale, 8...
Optical fiber 9...multiplexer, 9a, 9b...reflector
Ward 9ci, 9c...Half Mirror-110.
・Light receiving element 10a...Photodiode, 10b
・・Amplifier Castle 11・・Wavelength selective demultiplexer, lla・
・First dichroic mirror, 11b...Second dichroic mirror, 12.13...Lens, 樗尰朶

Claims (1)

[Claims] A light emitting element that emits a plurality of lights of different wavelengths for position detection or speed control, a main scale that has a slit for modulating the light into a pulse wave that waits for each of the wavelengths emitted from the light emitting element, and this main scale. a multiplexer that converges each of the lights modulated into a pulse wave into a beam and sends it to an optical fiber; and a light-receiving element that splits the convergent light sent from the optical fiber into each of the lights. An optical fiber signal transmission device for an incremental encoder, which is equipped with a wavelength-selective demultiplexer.