JPH0510784A - Optical fiber encoder - Google Patents

Abstract

PURPOSE:To provide a small optical fiber encoder of high resolving power by constructing a rotary code from plural layers each made of a material whose reflectance differs in each wavelength. CONSTITUTION:An optical fiber encoder applies pulse light lambda1, lambda2, via optical fibers 24,25 to a rotary code 29a provided on a rotary code panel 29 and detects the reflected pulse light lambda1a, lambda2b via optical fiber 30, thereby detecting rotation of the rotary code panel 29. The pulse light lambda1, lambda2 consists of plural pulses of different wavelengths and the rotary code 29a is comprised of plural layers each made of a material whose reflectance varies in each wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber encoder, and more particularly to a novel improvement for forming a rotary code with a plurality of layers made of a material having different reflectance depending on wavelength to obtain a small size and high resolution.

[0002]

2. Description of the Related Art There are various optical fiber encoders of this type that have been conventionally used. Among them, a typical configuration will be described below. As shown in FIG. it can.

That is, a reference numeral 1 in the drawing is a rotary shaft rotatably provided in a casing 2 through a bearing 3, and an upper portion of the rotary shaft 1 has a predetermined pattern shape. First pattern 4 and second pattern 8
And the rotary plate 29 having the third pattern 6 on its surface 7a.
Are integrally attached. In the casing 2,
An optical connector 8 is provided, and an optical distributor 10 is connected to the optical connector 8 via a first optical fiber 9, and the optical distributor 10 has first and second optical fibers 10 each having a significantly different length. Two optical fibers 11, a third optical fiber 12 and a fourth optical fiber 13 are provided. The second optical fiber 1
The first detection light outlet 11a of 1 corresponds to the first pattern 4 and the second detection light outlet 12a of the third optical fiber 12 corresponds to the second pattern 5. Furthermore, the third detection light outlet 13a of the fourth optical fiber 13 is positioned corresponding to the third pattern 6.

The above-mentioned optical fibers 11, 12 and 1
The length of 3 from the optical distributor 10 is 1 when indicated by a symbol.
The relationship is 1 <12 <13. An optical coupler 15 is coupled to the optical connector 8 via a fifth optical fiber 14 which is a single-core optical fiber.
5, an input optical fiber 16 is provided so as to face the light emitter 17. A light receiver 19 is provided at the output light outlet 18a of the output optical fiber 18 provided in the optical coupler 15.
Are arranged to face each other. The conventional optical fiber absolute encoder is configured as described above,
The operation will be described below. First, the luminous body 17
The light from the input optical fiber 16, the optical coupler 15, the fifth optical fiber 14, the optical connector 8, the first optical fiber 9,
Each optical fiber 11, 12 and 1 via the optical distributor 10.
The light exits 11a, 12a and 13a for detection of 3 reach the respective patterns 4, 5 and 6. Since the lengths of the respective optical fibers 11, 12 and 13 are different from each other and are set in the above-described relationship, the light from the second optical fiber 11 reaches the first pattern 4 earliest and the first pattern 4 is read, and the read optical signal is received by the light receiving body 19 from the output optical outlet 18a of the output optical fiber 18 via the above-described path in reverse. Further, the optical signals obtained by reading the second pattern 5 and the third pattern 6 through the other third optical fiber 12 and the fourth optical fiber 13 are serial signals with a time difference delayed from the first optical signal. The light is received by the light receiver 19.

Therefore, the serial signals obtained by reading the patterns 4, 5 and 6 are read from the photodetector 19 with a time lag from each other, and the number of revolutions of the rotary shaft 1 and Absolute rotation information such as the rotation angle can be obtained.

[0006]

Since the conventional optical fiber absolute encoder is configured as described above, it has the following problems. That is, since the absolute rotation information after reading each pattern of the rotating plate is a serial signal, it is necessary to change the length of each optical fiber from the light distributor to each detection light outlet,
For example, it is necessary to make a difference of 10 m for each 1-bit signal, and the length of the optical fiber becomes abnormally long, which is the greatest obstacle to miniaturization. In addition, since all the patterns formed on the rotary plate were made of the same material, in the case of an absolute pattern, all the patterns had to be arranged in the radial direction, which resulted in the diameter of the rotary plate. Could not be miniaturized.

The present invention has been made in order to solve the above problems, and in particular, a small-sized and high-resolution optical fiber in which a rotary code is constituted by a plurality of layers made of materials having different reflectances depending on wavelengths. The purpose is to provide an encoder.

[0008]

An optical fiber encoder according to the present invention irradiates a rotary code provided on a rotary code plate through an optical fiber, and detects reflected pulsed light reflected through the optical fiber. In the optical fiber encoder configured to detect the rotation of the rotation code plate, the pulsed light includes a plurality of pulsed lights having different wavelengths, and the rotation code has a plurality of layers made of a material having different reflectances depending on the wavelengths. It is composed of.

Further in detail, the pulsed light is obtained from a plurality of laser diodes.

[0010]

In the optical fiber encoder according to the present invention, the pulsed lights of different wavelengths emitted from the respective laser diodes at the same time are incident on the optical fiber. However, since one optical fiber has a delay device inserted, The optical pulse passing through this delay device is delayed by a certain time from the other optical pulses passing through the other optical fiber, and thereafter, they are multiplexed and propagate in one optical fiber to reach the multiplexer / demultiplexer.

Here, these optical pulses are evenly branched, and further passed through a delay device provided for each branched channel. Each delay device is adjusted so that a certain time difference occurs between the respective pulsed lights. The pulsed light from each diode is reflected by the rotation code and returns again following the same optical path. As shown in Figs. 2 and 3, the pattern of the rotation code is double drawn by the material having the reflectance different depending on the wavelength, and the reflection at which the reflectance has a peak is one of the wavelengths of the above two optical pulses. It matches
As a result, the double rotation code is read for each wavelength. The reflected pulsed light that has been reflected is again delayed and combined, propagates back through one fiber, returns, is extracted by the multiplexer / demultiplexer, and is converted into an electrical signal by the photodiode. The signal received by the photodiode at this time is shown in FIG. Therefore, by using one optical fiber and a plurality of layers of rotation codes, optical pulses can be transmitted by time division and frequency multiplexing, and a compact and multifunctional optical fiber encoder can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an optical fiber encoder according to the present invention will be described in detail below with reference to the drawings. It should be noted that the same or equivalent parts as those of the conventional example will be described by attaching the same reference numerals. 1 to 7 show an optical fiber encoder according to the present invention. FIG. 1 is a block diagram, FIG. 2 is a plan view showing an upper layer rotation code of a rotary code plate, and FIG. 3 is a lower layer rotation of a rotary code plate. 4 is a cross-sectional view of the rotary code plate, FIGS. 5 and 6 are characteristic diagrams showing reflected pulsed light, and FIG. 7 is a characteristic diagram showing pulsed light and reflected pulsed light.

A reference numeral 20 in FIG. 1 is a pulse driving circuit, and the pulse driving circuit 20 includes a first laser diode 17 and a second laser diode 17.
a is connected. Each of the laser diodes 17, 1
7a emits first pulsed light λ _{1 of} different wavelengths
And second pulse light lambda _2, as well as through the optical fiber 24, 25 is input to the multiplexer 23, the second pulse light lambda ₂ is transmitted through the first delay unit 26.

Each pulsed light λ ₁ , λ ₂ that has passed through the multiplexer 23
Is sent from the multiplexer / demultiplexer 27A to the second delay device 28 via the demultiplexer 27, and this second delay device 28 causes a certain time difference between the pulse lights λ ₁ and λ _2. Has been adjusted.

Each pulsed light λ emitted from the delay device 28
₁ , ₁ and λ ₂ are reflected by the rotation code 29a of the rotation code plate 29, pass through the demultiplexer 27A through the demultiplexer 27, and further pass through the optical fiber 30 through the photodiode 31 and the amplifier 32 and the serial / parallel converter 33. To the binary parallel output 34.

The rotation code 29a has a pattern as shown in FIGS. That is, the upper layer rotation code 29aA and the lower layer rotation code 2 having different reflectances from each other.
9aB and each of these rotation codes 29aA,
29aB has a plurality of layers as shown in FIG.

Next, in the configuration described above, the pulsed light lambda ₁ separate wavelength launched simultaneously from the laser diodes 17, 17a, of lambda _2, one pulse light lambda ₁ enters directly multiplexer 23 At the same time, the other pulsed light λ ₂ passes through the first delay device 26 and is delayed and input to the multiplexer 23.

The respective pulsed lights λ ₁ and λ ₂ are branched for each channel via the demultiplexer 27 and the multiplexer / demultiplexer 27A and input to the second delay device 28. In the second delay device 28, , The respective pulsed lights λ ₁ and λ ₂ are adjusted so that a constant time difference is generated, and the respective pulsed lights λ ₁ and λ ₂ emitted from the second delay device 28 are It is reflected at each rotation code 29a.

In the above case, each rotation code 29a has an upper layer rotation code 29aA and a lower layer rotation code 2 which have different reflectances.
9aB, the reflected pulsed light λ
_1a and λ _2a are generated in different wavelength ranges as shown in FIGS.

Therefore, the rotation code 29 drawn in double is shown.
a is read for each wavelength and each reflected pulse λ _1a ,
λ _2a is converted into an electric signal by a photodiode 31 via one optical fiber 30, amplified by an amplifier 32, and output as a binary parallel output 34 by a serial / parallel converter 33.

Therefore, each of the above-mentioned laser diodes 17,
The respective pulsed lights λ ₁ and λ ₂ sent from 17a are sent to the delay device 28 in a time-divided state as shown in FIG.
Each reflected pulsed light λ _1a input to the photodiode 31,
λ _2a is a combination of time division multiplexing and frequency multiplexing.
It is possible to obtain an absolute signal composed of the synchronization signal of 1010111.

[0022]

The optical fiber encoder according to the present invention,
Since it is configured as described above, the following effects can be obtained. That is, the rotation code of the rotation code plate is
Since it is composed of multiple layers of materials with different reflectance depending on the wavelength, the radius of the rotary code plate can be significantly reduced compared to the conventional configuration with a pattern of the same reflectance. It is possible to obtain a compact and high resolution optical fiber encoder.

[Brief description of drawings]

FIG. 1 is a block diagram showing an optical fiber encoder according to the present invention.

FIG. 2 is a plan view showing an upper layer rotation code of the rotation code plate of FIG.

3 is a plan view showing a lower layer rotation code of the rotation code plate of FIG. 1. FIG.

4 is a sectional view of the rotary code plate of FIG. 1. FIG.

FIG. 5 is a reflection characteristic diagram of an upper layer rotation code.

FIG. 6 is a reflection characteristic diagram of a lower layer rotation code.

FIG. 7 is a waveform diagram of pulsed light and reflected pulsed light.

FIG. 8 is a configuration diagram showing a conventional optical fiber encoder.

[Explanation of symbols]

17 First Laser Diode 19 Second Laser Diode λ ₁ Pulsed Light λ ₂ Pulsed Light λ _1a Reflected Pulsed Light λ _2a Reflected Pulsed Light 24 Optical Fiber 25 Optical Fiber 30 Optical Fiber 29 Rotation Code Board 29a Rotation Code

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Seiji Shiozawa             1879 Okyu, Iida City, Nagano Prefecture Tamagawa Seiki Co., Ltd.             Ceremony company Iida factory

Claims (2)

[Claims] 1. A rotation code (2) provided on a rotation code plate (29).
9a) is irradiated with pulsed light (λ ₁ , λ ₂ ) through the optical fiber (24, 25), and reflected reflected pulsed light (λ _1a , λ _2a ) is detected through the optical fiber (30). The rotation code plate (2
In the optical fiber encoder configured to perform the rotation detection of 9), the pulsed light (λ ₁ , λ ₂ ) is composed of a plurality of pulsed lights having different wavelengths, and the rotation code (29a) has different reflectance depending on the wavelength. An optical fiber encoder comprising a plurality of layers made of a material having: 2. The optical fiber encoder according to claim ₁ , wherein the pulsed lights (λ ₁ , λ ₂ ) are obtained from a plurality of laser diodes (17, 19).