WO2002023130A1

WO2002023130A1 - Optical encoder

Info

Publication number: WO2002023130A1
Application number: PCT/JP2000/006276
Authority: WO
Inventors: Toshikazu Satone
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2000-09-13
Filing date: 2000-09-13
Publication date: 2002-03-21
Also published as: JPWO2002023130A1

Abstract

An optical encoder comprises a scale plate (101) disposed in the optical path to light receiving elements (5a, 5b) receiving light emitted from a light emitting element (3) and coupled fixedly to a movable shaft (2), first patterns (4, 14) provided on the front of the scale plate (101) and including first reflecting parts (4b, 14b) reflecting light emitted from the light emitting element (3) and a large number of first slitlike light passing parts (4a, 14a) arranged at a specified intervakl, and second patterns (104, 114) provided on the back of the scale plate (101) oppositely to the first patterns (4, 14) and including second reflecting parts (104b, 114b) reflecting light emitted from the light emitting element (3) and second light transmitting parts (104a, 114a) transmitting light passed through the first light transmitting parts (4, 14a).

Description

Description Optical encoder Technical field

The present invention relates to an improvement in an optical encoder used for a position detector such as a servo system.

Background art

A conventional optical encoder will be described with reference to FIG. FIG. 8 is a side view of a conventional optical encoder. In FIG. 8, the optical encoder is fixed to the shaft 2 of the module to be detected, and is provided opposite to the scale disk 1 formed of glass or the like and the scale disk 1. The light-emitting diode 3 includes a light-emitting diode 3 and a photodiode 5 that receives light emitted from the light-emitting diode 3 via the scale disk 1 at the light-receiving units 5a and 5b.

The scale disk 1 includes a ring-shaped outer pattern 4 and an inner pattern 14, and the outer pattern 4 includes a reflective portion 4b for reflecting light and a slit portion 4a for transmitting light. Similarly, in the inner pattern 14, a reflection portion 14b and a slit portion 14a are formed periodically and repeatedly.

Next, the operation of the optical encoder configured as described above will be described with reference to FIG. When the shaft 2 rotates, the scale disk 1 rotates, and the light emitted from the light emitting diode 3 passes through the slit 4a (14a) of the pattern 4 (14) to the photodiode 5 Light is received by the light receiving section 5a (5b). The signal output from the light receiving section 5a (5b) has a rectangular waveform in proportion to the slit section 4a (14a) of the pattern 4 (14). The signal output from the light receiving unit 5b is generated by shifting the phase of the signal output from the light receiving unit 5a by 7Γ / 2 because the pattern 4 and the pattern 14 are out of phase by 7ΓΖ2. .

However, as shown in FIGS. 8 and 9, the light emitted from the light emitting diode 3 is not only parallel light Ps generated in parallel from the central axis of the light emitting diode 3, but also several degrees with respect to the central axis. Includes shifted oblique lights PL1 to PL4. In particular, light at the end of the light emitting diode 3 is more likely to generate oblique lights PL1 to PL4. The oblique lights PL1 to PL4 distorted the output signal of the photodiode 5 as shown below.

The distortion of the output signal, as shown in FIG.

As shown in Fig. 9, the adjacent slits 4a (4) of the same pattern 4 (14) as shown in Fig. 9 are caused by the oblique light PL1 and PL2 that pass through the slits 4a and 14a. 14 a) There are two types of light, oblique light from PL 3 and PL 4.

The former is due to mutual interference between the slits 4a and 14a. That is, the parallel light Ps emitted from the light emitting diode 3 passes through the scale disk 1 from the slit portion 4a (14a) of the scale disk 1 and is received by the light receiving portion 5a (5b), and the oblique light PL 2 (PL 1) passes through the adjacent disk portion 14 a (4 a) through the scale disk 1 and is received by the light receiving portion 5 a (5 b).

Therefore, the output signal from the photodiode 5 is not a signal completely proportional to the slit 4a of the pattern 4 and the slit 14a of the pattern 14, but is oblique from the slit 14a (4a) adjacent to each other. Under the influence of light PL 2 (PL 1), it becomes a distorted rectangular wave.

The latter is due to the interference of the adjacent slit portions 4a of the same pattern 4, as shown in FIG. That is, next to the same pattern 4 Assuming that the phase difference between the slit portions 4a is 2 TV and the center line of the light receiving portion 5a is the phase difference X with respect to the pattern 4, the phase difference of the parallel light P s emitted from the light emitting diode 3 is given. Is X, and the light passes through the scale disk 1 from the slit portion 4a and is received by the light receiving portion 5a.

The phase difference of the oblique light PL 3 (PL 4) is y, which is transmitted through the scale disk 1 from the slit portion 4 a and received by the light receiving portion 5 a.

Therefore, since the light receiving section 5a receives both the light having the phase difference X and the light having the phase difference y, the light is a distorted signal including the output signal of the photodiode 5 (or the signal 'component of the phase difference y).

Therefore, in order to make the optical encoder less susceptible to the effects of the oblique lights PL1 to PL4, the interval between pattern 4 and pattern 14 and the interval between the repetition periods of the slit portions 4a and 14a are made wider. Therefore, there is a problem that it is impossible to manufacture a device having a small size and high resolution performance.

Disclosure of the invention

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical encoder that is hardly affected by oblique light generated from a light emitting element even when a pattern or the like is narrowed.

An optical encoder according to the present invention includes: a light emitting element that emits light; a light receiving element that receives light emitted from the light emitting element at a predetermined distance and outputs a signal based on the light amount; At least one plate-shaped scale member provided in a light path to a light-receiving element for receiving light emitted from the light source, and connected and fixed to a movable movable portion, wherein the scale member includes: A first reflecting portion for reflecting the light emitted from the light emitting element, and a plurality of slit-shaped first transmitting portions for transmitting the light at predetermined intervals in the first reflecting portion; A first pattern layer provided on the front side and a back side opposed to the first pattern layer; A second reflecting portion that reflects light emitted from the light emitting element; a second transmitting portion that transmits light that has passed through the first transmitting portion in the second reflecting portion; And a second pattern layer provided on the substrate.

The first pattern layer in the optical encoder according to the next invention is provided on the front surface, has an inner pattern and an outer pattern arranged side by side, and the second pattern layer is provided on the back surface. The second transmission section has the same shape as the first transmission section, and is provided to face the first transmission section.

The scale member in the optical encoder according to the next invention comprises at least a first and a second scale plate, wherein the first scale plate is provided with a first pattern layer, The second scale layer is provided on the second scale plate, and the first scale plate and the second scale plate are arranged in parallel.

An optical encoder according to the next invention is characterized in that the first scale plate and the second scale plate are joined via an adhesive. In the optical encoder according to the next invention, the second transmission section is provided continuously in a track shape, and has a plurality of the first pattern layers.

The optical encoder according to the next invention is characterized in that a light absorbing portion for absorbing the light emitted from the light emitting element is provided instead of the second reflecting portion for reflecting the light emitted from the light emitting element. Is what you do.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a partial front sectional view of an optical encoder according to an embodiment of the present invention.

Fig. 2 shows the front surface (a) and back surface (b) of the scale disk in Fig. 1. FIG.

FIG. 3 is a process diagram showing a manufacturing process of the scale disk shown in FIG. FIG. 4 is a front sectional view showing that there is no influence of oblique light between slits in the same pattern in the optical encoder shown in FIG.

FIG. 5 is a front cross-sectional view (a) in which two scale disks according to another embodiment of the present invention are stuck together so that the reflecting portion is on the surface, and a front cross-sectional view in which the two scale discs are stuck together ( b).

FIG. 6 is a front sectional view of an optical encoder according to another embodiment of the present invention.

FIG. 7 is a plan view of a scale disk according to another embodiment of the present invention. FIG. 8 is a partial front sectional view of a conventional optical encoder. .

FIG. 9 is a partial front sectional view showing the effect of oblique light between slits in the same pattern in a conventional optical encoder. BEST MODE FOR CARRYING OUT THE INVENTION

Example 1

One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a side view of an optical encoder according to an embodiment of the present invention, and FIG. 2 is a plan view showing a front surface (a) and a back surface (b) of the scale disk in FIG. The same reference numerals as those in the related art indicate the same or corresponding parts.

In FIG. 1, an optical encoder is fixed to a shaft (movable part) 2 of a motor to be detected, and a scale disk 101 as a plate-like scale member formed of glass or the like; A light emitting diode 3 provided as a light emitting element provided opposite to the disk 101 and light emitted from the light emitting diode 3 is used as a light emitting diode 4, 1 4, 104 on the scale disk 101. , 1 14 through which the photodiodes as light receiving elements are received by the light receiving sections 5a and 5b. And five.

In FIG. 2, the scale disk 101 has exactly the same pattern formed on the front and rear surfaces, and the surface of the scale disk 101 has the same ring-shaped first pattern as the conventional one. The outer surface pattern 4 has an outer surface pattern 4 and an inner surface layer 14 as an evening layer, and the outer surface pattern 4 has a reflective portion 4b (a hatched portion) on which chrome is deposited (hatched portion) for reflecting light. 1), and a slit portion 4a (first transmitting portion) that transmits light is formed periodically in the reflecting portion 4b. Similarly, a reflection portion 14b (first reflection portion) is formed, and a slit portion 14a (first transmission portion) is periodically formed in the reflection portion 14b. It is formed repeatedly.

On the back surface of the scale disk 101, there is a second pattern layer formed opposite to the outer front pattern 4 and the inner front pattern 14 and the outer back pattern 104 and the inner back pattern 1 1 The outer back pattern 104 includes a chrome-deposited (hatched portion) reflecting portion 104 b (second reflecting portion) and a reflecting portion 104 for reflecting light. In b, a slit portion 104 a as a second transmitting portion for transmitting light is formed periodically and repeatedly, and the inner back pattern 114 also has a reflecting portion 114 b similarly. (Second reflection part) is formed, and a slit-shaped transmission part 114a (second transmission part) is formed periodically and repeatedly in the reflection part 114b.

Here, since the patterns formed on the front surface and the back surface of the scale disk 101 are completely the same, the slit portion 4a and the slit portion 104a have the same surface area and are located at positions facing each other. The slits 14a and the slits 114a have the same relationship.

In the optical encoder configured as above, the scale disk The method of depositing chromium or the like on both sides will be described with reference to FIG. FIG. 3 is a process diagram showing a manufacturing process of the scale disk shown in FIG.

First, an outer surface pattern 4 having a slit portion 4a and a reflecting portion 4b on which chromium is deposited, and an inner surface pattern 1 having a slit portion 14a and a reflecting portion 14b by a conventional manufacturing method. Then, a scale disk 1 having 4 is obtained (FIG. 3 (a)).

Next, only the exposed portions of the back surface of the scale disk 1 are coated with the remaining liquid resist 150 thicker than the thicknesses of the reflection portions 4b and 14b (third layer). Figure (b)).

After irradiating a beam from a laser light generator (not shown) facing the surface of the scale disk 1, the resist 150 is immersed in the imaging solution to face the reflecting portions 4b and 14b. to resist 1 5 0 parts only are removed allowed formed a concave portion 1 5 0 a, the resist 1 5 0 is cured (FIG. 3 (c)) to the back surface of the _c scale disc 1 resist 1 5 0 Chromium 160 thinner than the thickness is deposited (Fig. 3 (d)). The resist 150 is removed using a solvent such as thinner to form slits 104a and 114a, and the reflecting portions 104b and 114b with chromium deposited on both surfaces. A scale disk 101 having the inner back pattern 114 and the outer back pattern 104 is formed (FIG. 3 (e)).

Next, the operation of the optical encoder configured as described above will be described with reference to FIG. 1 and FIG. Figure 4 is the same in an optical Enko one da shown in FIG. _1: is a view to a front cross-sectional view that there is no influence of the oblique light between the slits in the first pattern.

As shown in FIG. 1, the parallel light Ps of the light emitted from the light emitting diode 3 is divided into the slit portions 4 a, 1 in the outer surface pattern 4 and the inner surface pattern 14 of the scale disk 101. 4 Inside the scale disk 1 0 1 when incident on a Then, the light is emitted from the slit portions 104a and 114a of the outer back pattern 104 and the inner back pattern 114, and is received by the light receiving portions 5a and 5b of the photodiode 5.

On the other hand, the oblique light PL 1 (PL 2) emitted from the light-emitting diode 3 enters the slit portion 4 a (14 a), passes through the inside of the scale disk 101, and reflects at the central reflecting portion 104 b , 114b, and further reflected by the central reflectors 4b, 14b and incident on the slit 114a (104a), but is incident on the light-receiving section 5a (5b) of the photodiode 5. No light is received.

Similarly, as shown in FIG. 4, the parallel light Ps of the light emitted from the light emitting diode 3 enters the slit portion 4a of the scale disk 101 and transmits through the inside of the scale disk 101. Then, the light is emitted from the slit portion 104a and received by the light receiving portion 5a of the photodiode 5.

On the other hand, the oblique light PL.3, PL4 emitted from the light emitting diode 3 enters the slit portion 4a, passes through the inside of the scale disk 101, is reflected by the reflecting portion 104b, and The light is reflected by the reflecting portion 4b and is incident on the slit portion 104a, but is not received by the light receiving portion 5a of the photodiode 5 ₍ as described above, the output signal of the photodiode 5a is ~ Output a square wave signal without distortion proportional to the slits 4a, 14a, 104a, 114a of pattern 4, 14, 104, 114 without being affected by PL4 Can be.

In the above embodiment, the reflecting portions 104b and 114b were provided on the back surface of the scale disk 101, but instead of the reflecting portions 104b and 114b, a chromium oxide film and a chromium film were used. And a light absorbing portion for absorbing the emitted light formed by the step (b).

According to the scale disk provided with such a light absorbing portion, in FIG. The oblique light PL 1 (PL 2) emitted from the light emitting diode 3 enters the slit portion 4 a (14 a), passes through the inside of the scale disk 101, and receives the light absorption portion 104 b at the center. , 114b and is not received by the light receiving section 5a (5b) of the photodiode 5.

Further, in addition to the light absorbing portion, a front side light absorbing portion may be provided instead of the reflecting portions 4b and 14b of the scale disk 101. ―

Example 2.

Another embodiment of the present invention will be described with reference to FIG. Fig. 5 is a front cross-sectional view (a) in which two scale disks are stuck together so that the reflection part is on the surface, and a front cross-sectional view (b) in which two scale disks are stuck together.

In the first embodiment, the patterns 4, 14, 104, 114 are formed on both sides of one scale disk 101, but in this embodiment, two scale disks 201, 203 are used. By forming one scale member 200 (250), the step of forming a pattern on the back surface becomes unnecessary.

In FIG. 5 (a), the scale member 200 has the patterns 204, 2

The scale disk shown in Example 1 is obtained by joining flat surfaces of a scale disk 201 having 14 and scale disks 203 having patterns 206 and 216 via an adhesive 210. This realizes a plate 101 equivalent.

In FIG. 5 (b), the scale member 250 connects the plane of the scale disk 201 with the reflecting portions 206b, 216b of the scale disk 203 via an adhesive 210. By joining, the scale disk 101 shown in Example 1 is realized.

According to the scale members 200 and 250 obtained in this manner, the steps shown in FIGS. 3 (b) to (e) for forming the patterns 104 and 114 on the back surface as in the first embodiment become unnecessary. . Example 3.

Another embodiment of the present invention will be described with reference to FIG. FIG. 6 is a front sectional view of the optical encoder.

In FIG. 6, the scale member 40.0 has a scale disk 201, 203 having reflecting portions 204b, 206b on one side, and a motor shaft 2 so that the reflecting portions 204b, 206b are on the outside. This is to obtain encoders 300 which are arranged side by side with a slight gap formed in the direction.

According to the scale member 400 obtained in this manner, the steps shown in FIGS. 3 (b) to (e) for forming the patterns 104 and 114 on the back surface as in Example 1 become unnecessary, and It is unnecessary to bond the scale disks 201, 203 as in Example 2.

The scale disk 201 may be fixed to the motor shaft 2 so that the reflecting portions 204b and 206b are on the upper side as shown by the dashed line in FIG. Example 4.

Another embodiment of the present invention will be described with reference to FIG. FIG. 7 is a plan view of a scale disk.

In the first to third embodiments, the same pattern 4, 14, 104, 114, etc. was formed on both sides of the scale disk 101 or the scale members 200, 250, 400. The scale disk 500 having e is provided with a pattern (not shown) similar to that of the first to third embodiments on the front surface, and a track 500 a, 500 formed of a ring-shaped recess as shown in FIG. b and reflecting portions 5110 and 520.

According to the scale disk 500 obtained in this manner, the formation of the tracks 500a and 500b on the back surface and the reflection portions 510 and 520 correspond to the patterns 104 and 114 of Examples 1 to 3. It is simpler than that.

Furthermore, the back side of the scale disk 500 is flat like the scale disk 201. In this case, the pattern may not be formed, and the surface may be composed of tracks 500a and 500b and reflecting portions 5100 and 520 as shown in FIG.

Such a scale disk 500 and the scale disk 210 shown in Example 2 or 3 are joined by an adhesive, or the scale disk 201 and the scale disk 500 are juxtaposed. The scale member may be formed by joining to the shaft 2 of the motor or the like.

According to the scale member obtained in this manner, the time required to match the pattern 204 of the scale disk 201 and the pattern of the scale disk 214 with the pattern of the scale disk 500 is the same as that of the absence of the slit portion. Only easier.

According to the scale disk 500 or the scale member of the fourth embodiment, as in the first to third embodiments, the oblique light transmitted through the adjacent slit portions 4a and 14a is blocked by the reflection portion. I can't.

The patterns 4, 14, etc. of the above-described Examples 1 to 4 are provided on the front and back surfaces of the scale disk 101, etc., but may be provided inside the scale disk 101, etc.

The present invention is configured as described above, and has the following effects.

According to the present invention, the second transmitting portion may have, for example, a slit shape or a continuous track shape. If the second transmitting portion has the slit shape, it is difficult for the light receiving element to receive oblique light from the first transmitting portion. On the other hand, in the case of a track shape, if there are a plurality of first pattern layers, it is difficult for the light receiving element to receive oblique light from the first transmitting portion in different patterns. Therefore, since the light receiving element receives only the parallel light emitted from the light emitting element, the output signal of the light receiving element is less likely to be distorted, the distance between the slits in the same pattern can be reduced, and the encoder can be reduced in size. There is. According to the next invention, oblique light emitted from the first transmitting portion of the inner pattern and the outer pattern in the adjacent first pattern is shielded by the second reflecting portion of the second pattern. As a result, the distance between the inner pattern and the outer pattern can be shortened, which has the effect of reducing the size of the encoder.

According to the following invention, since the first pattern layer is provided on the first scale plate and the second pattern layer is provided on the second scale plate, the scale having the first and second pattern layers is provided. There is no need to provide a member, which has the effect of facilitating the manufacture of the scale member.

According to the next invention, there is an effect that the distance from the light emitting element to the light receiving element is shortened, and the encoder is downsized.

According to the following invention, there is an effect that the second pattern layer of the scale member can be easily formed.

Moreover, when the scale member is composed of the first and second scale plates, the first pattern layer provided on the first scale plate and the second pattern layer provided on the second scale plate are provided. When matching layers, there is an effect that matching can be easily performed.

According to the next invention, oblique light emitted from the first transmitting portion between the inner pattern and the outer pattern in the adjacent first pattern is absorbed by the light absorbing portion of the second pattern. This has the effect of reducing the distance between the pattern and the outer pattern, and consequently the encoder becomes smaller. Industrial applicability

As described above, the optical encoder according to the present invention is suitable for use in detecting the position of a movable part.

Claims

The scope of the claims

1. a light emitting element for emitting light,

A light receiving element that receives light emitted from the light emitting element at a predetermined distance and outputs a signal based on the light amount;

At least one plate-shaped scale member provided in a light path to a light-receiving element that receives light emitted from the light-emitting element and connected and fixed to a movable movable portion;

The scale member has a first reflecting portion for reflecting light emitted from the light emitting element, and a plurality of slit-shaped first transmitting portions for transmitting the light in the first reflecting portion. A first pattern layer having at a predetermined interval and provided on the front side,

A second reflection portion provided on the back side to face the first pattern layer and configured to reflect light emitted from the light emitting element, wherein the first transmission portion is provided in the second reflection portion; A second pattern layer provided on the back side, having a second transmission portion for transmitting light passing through the portion;

An optical encoder comprising:

2. The first pattern layer has an inner pattern and an outer pattern which are provided on the surface and are juxtaposed with each other.

The second pattern layer is provided on the back surface,

The second transmission section has the same shape as the first transmission section, and is provided to face the first transmission section.

2. The optical encoder according to claim 1, wherein:

3. The scale member includes at least first and second scale plates,

The first scale plate is provided with the first pattern layer, The second scale plate is provided with the second pattern layer, and the first scale plate and the second scale plate are arranged in parallel with each other, wherein the first scale plate and the second scale plate are arranged in parallel. The optical encoder according to 1.

4. The first scale plate and the second scale plate are joined via an adhesive,

4. The optical encoder according to claim 3, wherein:

5. The second transmission portion is provided continuously in a track shape, and has a plurality of the first pattern layers.

The optical encoder according to claim 1 or 4, wherein:

6. A light absorbing portion that absorbs light emitted from the light emitting element, instead of at least the second reflecting portion, of the first and second reflecting portions that reflect light emitted from the light emitting element. ,

3. The optical encoder according to claim 1, wherein: