JPH02157618A - High resolution encoder - Google Patents

Abstract

PURPOSE:To enable high-accuracy position detection by making the pitch of verneir slits slightly different from the pitches of main slits and index slits. CONSTITUTION:The pitch of the vernier slits on a fixed scale 4 is slightly different from the pitches of the index slits and the main slits on a moving scale 5 and light emitting elements 1 and 2 and photodetector 6 and 7 are provided opposite the vernier slits; and the elements 1 and 6 detect the interference between the slits 11 and 13 and the elements 2 and 7 detect the interference between the slits 12 and 13. The pitch of the slits 13 and 11 is denoted as d1, the pitch of the slits 12 is as d2, and the difference is as DELTA. When slits 11a and 13a, and 12a and 13a are put one over the other, the phase difference between 12n and 13n and nXDELTAn and a light emitting element 12b and succeeding elements are shielded from light. When the scale 5 is moved by DELTA, the slits 12b and 13b are put in phase with each other and a photodetector 7b receives light. Thus, the part between the scales 13a and 13b is divided equally into (n+1), etc., by the vernier slits 12 to obtain high resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high resolution encoder for highly accurate position or angle detection.

BACKGROUND OF THE INVENTION In recent years, as assembly precision has increased, there has been an increasing demand for high-resolution encoders that perform highly accurate position detection.

An example of the above-mentioned conventional high-resolution encoder will be described below with reference to the drawings. FIG. 8 is an overall diagram of a conventional encoder, FIG. 9 is a diagram showing the principle of position detection, and FIG. 10 is a diagram showing a method for making the encoder output high resolution.

In FIG. 8, 1 is a first light projecting element, 3 is a housing,
4 is a fixed scale, 6 is a moving scale, and 6 is a light receiving element. Further, in FIG. 9, 11 is an index slit provided on the fixed scale 4, and 13 is a main slit provided on the movable scale 6.

The operation of the encoder configured as described above will be explained below.

A fixed scale 4 and a movable scale 6 are provided between the first light projecting element 1 and the first light receiving element 6. Main slits having the same width as the index slits on the fixed scale 4 are provided on the moving scale 6 at equal intervals. When the slits of both scales completely overlap, light from the light emitting element is transmitted and enters the light receiving element. However, moving scale 6
As it moves relative to the fixed scale 4, the transmitted light gradually becomes weaker, and when the slit portion and the non-slit portion overlap, almost no light is transmitted.

The output of the light receiving element at this time becomes close to a sine wave as shown in FIG. The relative distance between both scales is determined based on this output signal, and high resolution has been achieved by electrically decomposing this output signal as shown in FIG.

Problems to be Solved by the Invention However, the above configuration has a problem in that the output signal from the light-receiving element is not a perfect sine wave and cannot be divided accurately.

Furthermore, if a laser or the like is used, a highly accurate encoder can be obtained, but there is a problem in that it is expensive.

In view of the above problems, the present invention provides an inexpensive and high-resolution encoder.

Means for Solving the Problems In order to solve the above problems, the high-resolution encoder of the present invention is an encoder consisting of a light emitting element, a light receiving element, a fixed scale, and a moving scale. Two rows of slits are provided, of which the pitch of the index slit is the same as the main slit provided on the moving scale, and the pitch of the other vernier slit is slightly different from that of the main slit provided on the moving scale. be.

For production The effect of this technical means is as follows.

An index slit provided on the fixed scale, a main slit provided on the movable scale, and a light emitting element.
First, the current position is detected by the light receiving element. This is the same as a conventional encoder.

Next, the main slit provided on the moving scale and the vernier slit provided on the fixed slit have different pitches, and the light emitting element and light receiving element provided opposite to the vernier slit are placed on the fixed slit. Detect which vernier slit overlaps with the main slit on the moving scale. This improves resolution and enables highly accurate position detection. This is possible because the vernier slit pitch on the fixed scale and the main slit pitch on the moving scale are different. In other words, if the vernier slit pitch on the fixed scale is d, the main slit pitch on the moving scale is dl, and the difference between them is Δd, then the phase difference between the vernier slit on the fixed scale and the main slit on the moving scale is 0. Δd, 2×Δd
, 3×Δd, 4XΔd..., nXΔd. Therefore, every time the movable scale moves by Δd, the vernier slit on the fixed school that overlaps with the main slit on the movable scale changes. Therefore, a light emitting element and a light receiving element are provided corresponding to the vernier slits on the fixed scale, and the interference between the slits provided on the moving scale and the fixed school is detected. -Find the near slit. The above enables high-resolution position detection.

Example Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 is an external view of a high-resolution encoder of the present invention, FIG. 2 is a side view, and FIG. 3 is a front view.

In FIG. 1, a fixed scale 4 is provided with an index slit 11 and a vernier slit 12. 6 is a moving scale, and a main slit 13 is provided therein. A first light emitting element 1 and a first light receiving element 6 are provided facing the index slit 11 on the fixed scale 4, and a second light emitting element 2 and a first light receiving element 6 are provided facing the vernier slit 12 on the fixed scale 4. Two light receiving elements 7 are provided. The first light emitting element 1, the second light emitting element 2, the fixed scale 4, the first light receiving element 6, and the second light receiving element 7 are as follows:
It is fixed to the housing 3. Further, as shown in FIG. 2, the movable body 8 performs a rectilinear movement by a rectilinear guide 9.

A moving scale 6 is attached to the moving body 8, and as the moving body 8 moves, the moving scale 6 also moves.

Regarding the high-resolution encoder configured as above,
The principle will be explained below using FIG. 4.

The first light emitting element 1 and the first light receiving element 6 have a fixed scale A/4.
Interference between the upper index slit 11 and the main slit 13 on the moving scale 6 is detected.

The second light projecting element 2 and the second light receiving element 7 detect interference between the vernier slit on the fixed scale 4 and the main slit 13 on the moving school 6. The pitch between the main slit 13 and the index slit 11 and the pitch of the vernier slit 12 is d2, and the difference therebetween is Δd. If the index slit 11a and the main slit 13
a, vernier slit 12a and main slit 1
3a are overlapped, the phase difference between the vernier slit 12b and the main slit 13b is Δd. Similarly, the phase difference between the vernier slit 12n and the main slit 13n is nXΔd.

In this way, when the index slit 11a1, the vernier slit 12a, and the main slit 13a are in the same phase, the other vernier slits 12b...t2
n has a different phase from the main slits 13b...13n, and blocks the light emitted from each of the light emitting elements 2b...2n, so the light receiving elements 7b...7n block the light. is not detected.

Considering the case where the moving scale 6 moves by Δd in the direction shown by the arrow 14 from this state, the main slide) 13a
. . . 13n moves to the left by Δd, so the index unit) 11a, the vernier slit 12a, and the main slit) 13a are no longer in the same phase. Instead, the vernier scale 12b and the main slit 13b are in the same phase, and the light projected from the light projecting element 2b is detected by the light receiving element 7b. Note that the output from the light receiving element at this time changes sinusoidally as shown in FIG. 6 as the moving scale 5 moves. Therefore, we decided on a certain threshold and
If the threshold value is exceeded, adjustments are made so that a signal is output. If the above operation is repeated, each time the moving scale 5 moves by Δd, the light receiving elements that detect the light from the light projecting element will move one by one as 7b, 70, . . . , 7n. If the movement scale of 6 moves by d, the index slit 11a and the vernier slit 12
a1 and the main slit 13b are in the same phase, and the above is repeated thereafter. In other words, main scale 1
3a and the main scale 13b due to the vernier slits 12a, 12b..., 12n, (n+1
) will be divided into equal parts, resulting in high resolution.

For example, d1=1 fl, d2=0.9511M
, n = 19, Δd = d1-d2 = 0.
05fl, and even though the main slits are only provided at 1H intervals, they are divided into 20 parts, and 0.0
An encoder with a resolution of 5jff is obtained.

In addition, in FIG. 4, the index slits are 11a,
Although there are three, 11b and 11C, this is to enhance the view of the light received by the light-receiving element, and there is no problem with just one.

FIG. 6 shows the above principle of operation.

Therefore, the circuit configuration, as shown in FIG. 7, consists of a circuit for detecting interference between the index slit and the main slit and a circuit for detecting interference between the vernier slit and the main slit.

Effects of the Invention As described above, the present invention adds vernier slits with slightly different pitches to the fixed scale in addition to the index slits on the fixed scale and the main slits on the movable scale, which conventionally had the same pitch. By providing a light emitting element and a light receiving element opposite to the vernier slit and detecting interference between the vernier slit and the main slit, a high-resolution encoder can be constructed at low cost.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a high-resolution encoder according to an embodiment of the present invention, FIG. 2 is a side view of the same, FIG. 3 is a front view of the same, and FIG.
The figure is an explanatory diagram showing the principle of Fig. 1, Fig. 5 is an output diagram showing the output of Fig. 1, Fig. 6 is a flowchart showing the operation of Fig. 1, and Fig. 7 is the diagram of Fig. 1. Fig. 8 is a perspective view of a conventional encoder, Fig. 9 is an explanatory diagram showing the principle of Fig. 8, and Fig. 10 is an output showing the output of a conventional high-resolution encoder. It is a diagram. 1... Light projecting element, 2... Light projecting element, 4
...Fixed scale, 6...Moving scale, e...Light receiving element, 7...Light receiving element, 11...Index slit, 12 ...
... Vernier slit, 13 ... Main slit 0 Agent's name Patent attorney Shigetaka Awano and 1 other person transferred 1
1vt Diagram Kutoshi X faction

Claims (1)

[Claims] An encoder consisting of a moving scale provided with a main slit and attached to a moving body, a fixed scale provided with an index slit and a vernier slit, and a light emitting element and a light receiving element provided opposite to each of the index slit and the vernier slit. A high-resolution encoder characterized in that the pitch of the vernier slit is slightly different from the pitch of the main slit and the index slit.