JPS5832116A - Encoder - Google Patents

Abstract

PURPOSE:To obtain a less-distortion sine wave even if the light and dark part ratio of a stripe pattern on a scale is not 1:1, by providing a means of regulating the gap between the scale and a photodetecting means having a mask plate. CONSTITUTION:Light from an infrared light emitting diode 2 is reflected by a scale 1 having a light and dark stripe pattern with pitch L and detected by a phototransistor 3. Said diode 2 and phototransistor 3 are constituted by using a united photoreflector, and a mask plate 4 having a slit of L/2 is provided on the photodetection surface. The gap between the mask plate 4 and scale 1 is adjusted by turning an adjusting screw 11 provided to an encoder moving means 10 to control the level of light incidents to the phototransistor, thus obtaining a less-distortion sine wave.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a scale in which a fundamental sine wave-like signal, which is a fundamental signal for interpolation operation to improve positional resolution in an optical scale device, etc., is given a light and dark striped pattern at a constant pitch. Regarding the encoder that can be easily read directly from It is an object of the present invention to provide an optical sine wave encoder that can easily output a sine wave-like signal with little waveform distortion by adjusting the gap with the light receiving means.

Conventionally, rotary encoders and linear encoders are well-known devices for extracting signals from scales with bright and dark striped patterns, but most of these encoders are designed for the sole purpose of obtaining pulse-like signals. However, compared to the above-mentioned school, there are few simple encoders that aim to directly output an optical sine wave-like signal.

The present invention provides a mask plate provided with a slit window having a width half the pitch (L) of the striped pattern on the scale.
The center of the slit window is positioned at the maximum sensitivity point of the light receiving means, and means for adjusting the gap between the school and the light receiving element is provided to adjust the ratio between the bright and dark parts of the school. Even if they are not necessarily one-to-one, if they are the same everywhere, it is possible to easily output a sine wave-like signal with less waveform distortion. Let's explain based on an example.

FIGS. 1(a) and 1(b) are main part configuration diagrams of a first embodiment of the present invention, where (a) is a side view thereof, and 1(b) is a top view thereof. However, in Figures (a) and (b), the details of the mechanism for moving the entire encoder including the light emitting means and the light receiving means relative to the school in parallel,
Also, lead wires for the light emitting means and light receiving means are omitted.

In the same figures (a) and (b), 1 is a constant pitch L
A striped pattern of light and dark is applied, and the ratio of bright and dark parts within the striped pattern is the same everywhere.
A phototransistor 2 receives the reflected light from the scale 1 of the school 1 diode 2. In the same figures (al and (bl), the infrared light-emitting diode 2 and phototransistor 3 are constructed using an integrated photoreflector. 4 is attached in contact with the light-receiving surface of the photoreflector. It is a mask plate, and 6 is a slit window provided in the mask plate 4 and having a slit width of L72.

Reference numeral 6 denotes a sensor housing for positioning the center of the slit window 6 at the position of the maximum sensitivity point of the phototransistor 3. The sensor housing 6 has three bottles 7.
8.9 is erected perpendicularly to the sensor housing surface.

1o is an encoder moving means for moving the entire encoder relative to the scale 1 in parallel, and the sensor housing 6 is connected to the bins 7, . 8.9 and a gap adjustment screw 11. Said bin 7.8.9
is a guide hole 7 made in the encoder moving means 10.
′, 8・, α can be moved up and down smoothly. A spring 12 is inserted into the gap adjustment screw 11 and serves to prevent the gap adjustment screw 11 from loosening.

By rotating the gap adjustment screw 11 left and right, the phototransistor 3 and the school 1 can be adjusted while maintaining parallelism between the mask plate 4 and the scale 1.
The gap between the two can be adjusted. In addition, Figure 1 (C1
FIG. 1(2L) shows the directional sensitivity characteristic in the longitudinal direction of the school 1 through the mask plate 4 of the phototransistor 3 in bl [X direction shown in FIG. 1(3) and (b)].

Next, a description will be given of how a sine wave-like signal can be extracted using the encoder of the present invention. Second
The solid line in Figure (a) indicates the width in the relative motion direction at the position of the maximum sensitivity point of the light receiving means on a scale where the width of the dark part of the striped pattern is W and the pitch of the striped pattern is L. It is assumed that an encoder having a mask plate provided with a slit window, which is a WM, has parallel directivity sensitivity characteristics as shown in FIG. 2(C). In the figure (a), lB is the width of the output waveform when the light receiving means scans the bright part of the striped pattern, and h is the width of the output waveform when the light receiving means scans the dark part of the striped pattern. Not wide enough. Furthermore, a schematic diagram of the scale and slit window is shown in FIG. 2(b).

To obtain a sine wave with less waveform distortion, 11m = 1D
This condition is necessary. Furthermore, the directional sensitivity characteristic of the light receiving means through the mask plate is actually shown in Fig. 2 (
As shown in Fig. 2(a), the actual output waveform is attenuated slowly from the center position of the light receiving means.
), the shape is close to a sine wave, as shown by the dotted line. Here 1. The condition B=lo will be considered in various cases of the magnitude relationship of the pitch L of the striped pattern, the width W of the dark part of the striped pattern, and the slit window width WM. Here, the directional sensitivity characteristics of the front 14 light receiving means through the mask plate are shown in FIG.
).

(1) When WIJL/2 (i) If WM 4 W, 1B=L -W-w.

From lD=w −wM −′−AB=llD, w = L/2, WM,,
4. L/2(++)W≦WM≦t, if -W then pm =
From L −W −Wiiln, =WM W ・°・Ih=lIll, WM=L/2. W≦L/2(
nil If L-w≦wM<L, then lJB=WM, L
From +W10=wM-w-', 1B=AD, W = L/2, L/24W
If 1 < L(2), L/2 riW (i)W, 4L-W then 1. = L, −W −W.

From In=W-WM, °, la = AIn, W=L/2. W hat≦L/
2(ll l L -W 4 WM 4 W (If L then Ilth = WML + W1o = oath - WM , ', llm = 1o, WM = L/2, L/2
IW<L(iii) If WOWM<L then l a =
From WM +W LIn=Wm'W -', Ilv, = lo, W = L/2,
L/2≦wM<L or more, combining (i) to (iii) of [1] and (1) to QiD of [2], 1h=l
The condition D is satisfied in two cases: ■WM = L/2 and W (L).In the case of ■, the slit width WM is a value within one pitch of the striped pattern (less than or equal to L). However, the width of the dark part of the striped pattern must be equal to the pitch (L/2), and the ratio of the bright part to the dark part of the striped pattern must be 1:1. This method cannot be applied in cases where the ratio of bright and dark parts of the striped pattern cannot be made 1:1.

On the other hand, in the case of (2), the ratio of the bright part to the dark part of the striped pattern is not specified, and the width of the slit window provided at the maximum sensitivity point of the light receiving means in the mask plate is L/2. It is very useful because all you need to do is to put it on. The present invention relates to the case (2), in which the width of the slit window is V2 (that is, L/2) with a uniform pitch of stripes on the school, and the striped pattern is bright. Even in a school where the ratio of the area to the dark area cannot be 1:1, the condition for outputting a sine wave-like signal is satisfied. Furthermore, since the directional sensitivity characteristic of the light receiving means through the mask plate actually attenuates gradually from the center position of the light receiving means as shown in FIG. 2(d), as described above, The actual output waveform of the light receiving means is sinusoidal. However, when the gap between the light receiving means and the school is fixed, the level of light entering the light receiving means differs depending on the ratio of the bright and dark parts of the striped pattern.

As shown by the dotted line in FIG. 2 (+5), there are cases where the signal becomes a sine wave-like signal with large waveform distortion. In such a case, adjust the gap between the light receiving means and the scale,
by controlling the level of light entering the light receiving means;
It is possible to obtain a sine wave with little waveform distortion as shown by the dotted line in Figure 2 (0).In the first embodiment of the present invention, by rotating the gap adjustment screw shown at 11 in Figure 1 left and right So you can do this.

FIG. 3 is a block diagram of a main part of a second embodiment of the present invention, and is an example in which the stator of a linear stepping motor is used as both the stator and the scale. Such an arrangement is used to obtain a position signal of the motor. In this case, the ratio of convex portions to concave portions of the tooth profile of the stator is usually not 1:1. As mentioned above, the encoder of the present invention is very useful in such cases because it can easily output a sine wave-like signal with little waveform distortion. The second embodiment of the present invention shown in FIG.
This embodiment differs from the first embodiment of the present invention shown in FIG. 1 only in scale, and everything else is the same.
The explanation of the operation here will be omitted.

As is clear from the above explanation, the encoder of the present invention has a mask plate provided with a slit window having a width half the pitch of the striped pattern formed on the school. The scale is characterized by having means for positioning the scale to be at the position of the sensitivity point and for adjusting the gap between the school and the light receiving means, and for adjusting the distance between the bright and dark parts of the striped pattern on the scale. Even if the ratio is not necessarily 1:1, it can easily output a sine wave-like signal, and it is a very useful encoder that can be applied to a wide range of applications.

[Brief explanation of the drawing]

FIG. 1 (a), (bl, and (c)) are the first
(11, (e), (f)
) is a diagram for explaining the output waveform side of the encoder of the present invention, FIG. Fig. 2 (C) is a directional sensitivity characteristic diagram of the light receiving means assumed in the theoretical analysis through the mask plate, Fig. 2 (d) is an actual directional sensitivity characteristic diagram of the light receiving means through the mask plate, and Fig. 3 Figures (2L), (b), and (C) are a side view of the main part and a top view of the main part of the second embodiment of the present invention, and a directional sensitivity characteristic diagram in the longitudinal direction of the school through the mask plate of the phototransistor. It is. 1...Scale, 2...Infrared light emitting diode, 3...Stomach; "odotransistor, 4...
...Mask plate, 6...Slit window, 6
...Sensor housing, 7, 8.9...
・Pin, 7', 8', 9'... mark ・Guide hole, 10...
... Encoder moving means, 11 ... Gap adjustment screw, 12 ... Spring. Name of agent: Patent attorney Toshio Nakao and one other name
11Q Figure 2 (C) (d)

Claims (1)

[Claims] A school configured to have a bright and dark striped pattern at a constant pitch (L) and have the same ratio of bright and dark parts within the striped pattern, and a school that is parallel to the scale. An encoder comprising a light-emitting means and a light-receiving means that perform a relative movement to take out a sine wave-like signal, the mask plate being attached to a light-receiving surface of the light-receiving means in parallel with the school. An IA hitter is provided on the mask plate to output a sine wave-like signal, and has a striped width in the relative movement direction.
L/2) slit window, a senna housing incorporating a light receiving means such that the center of the slit window matches the position of the maximum sensitivity point of the light receiving means, and having the mask plate attached thereto, the mask grate, and the school. 1. An encoder comprising a gap adjusting means capable of adjusting a gap between the light receiving means and the school while maintaining parallelism between the light receiving means and the school.