JPH04232814A - High-resolution absolute value encoder - Google Patents

Abstract

PURPOSE:To detect a high-resolution absolute value with a few number of tracks by arranging a pattern with the transmission light quantity monotonously increased in conjunction with the shift quantity and a striped pattern dividing the arrangement range at a uniform interval on a moving slit plate. CONSTITUTION:A signal with the transmission light quantity monotonously increased in conjunction with the shift quantity of a moving slit plate 10 is obtained from a photo-sensor corresponding to the first pattern 11, and two pairs of pseudo sine-wave signals out of phase by 90 deg. with a cycle of bright/dark patterns are obtained from photo-sensors corresponding to the second and third patterns 12, 13. Three pairs of signals are processed by an interpolation processing section at the same timing to obtain three absolute value data of the coarse position, intermediate position and precise position, and the three position data are combined to obtain the continuous absolute value data. The number of tracks of the code pattern can be decreased, a device can be miniaturized, and the high-resolution absolute value position can be detected at optional resolution.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder used for detecting position, length, etc., and particularly to a high-resolution linear encoder equipped with an absolute value position detection function.

0002

2. Description of the Related Art FIG. 6 is a schematic diagram showing an example of a conventional absolute value type linear encoder. In the figure, 61 is a slit plate on the movable side, and a plurality of tracks 62 are provided in parallel on the movable slit plate 61. Each track 62 is provided with an absolute value pattern, for example, a gray code pattern consisting of a plurality of slits 63 consisting of areas through which light passes and areas through which light does not pass. 65 is a fixed slit plate. Reference numeral 66 denotes a slit array for position detection, which is provided on the fixed slit plate 65 and has a plurality of openings for selectively passing the light beam from the slit pattern of each track 62. 68 is a light emitting unit having a plurality of light emitting elements; 69
is a light receiving section having a plurality of light receiving elements.

In the configuration shown in the figure, the light flux emitted from each light emitting element of the light emitting section 68 passes through the slit 63 and the position detection slit array 66 and enters each light receiving element of the light receiving section 69 . Each light receiving element generates an output signal corresponding to the amount of incident light, and the absolute position of the movable slit plate 61 is determined from a combination of the output signals.

0004

However, if a high-resolution absolute value encoder is constructed using only binary codes such as Gray codes, all code patterns corresponding to the resolution must be created. For example,
To realize an encoder with a length of 100 mm and a minimum resolution of 0.1 μm, the number of divisions is 1,000,000, so 220 = 1,048,576, so 20 tracks are required for the pattern, and pattern creation is required. Not only is it extremely difficult, but there are also two
This requires 0 sets of light emitting elements, light receiving elements, and their processing circuits, making them expensive.

[0005] Furthermore, the slit width of the position detection slit array 66 needs to be less than or equal to the minimum resolution, and in this case, it is at most 0.1 μm. However, as a practical matter, there is a limit to the slit width that can be realized due to the phenomenon of light diffraction, and the minimum slit width determines the minimum resolution of the encoder. Furthermore, if the slit width is narrowed in this manner, the amount of light obtained by the light receiving element becomes weak, which necessitates increasing the amplification factor of the processing circuit section, which also has the disadvantage of making it more susceptible to noise. The metric system is the international standard for measuring length, but the inch system remains deeply rooted in the United States. For inch measurements,
There was no choice but to measure on a metric scale and convert the value to an inch scale, or use a scale calibrated in inches, and there was no scale that could measure in either way.

The purpose of the present invention is to solve these problems, and to provide an absolute value linear encoder with high resolution and arbitrary resolution without increasing the size of the entire device. .

[0007]

[Means for Solving the Problems] Therefore, the high-resolution absolute value encoder of the present invention has a first pattern on a moving slit plate consisting of a sign in which the amount of transmitted light monotonically increases with the amount of movement; A second pattern consisting of striped codes that divide the range where the patterns are arranged at equal intervals is arranged. From the first pattern, a signal that monotonically increases with the amount of movement within the measurement range is detected, and by electrically interpolating it, absolute value data of the rough position is obtained. From the second pattern, two pseudo sine waves with a phase shift of 90 degrees are detected at a predetermined period, and these are electrically interpolated to obtain absolute value data for medium and fine positions, and absolute value data for coarse position is obtained. Combine the data to obtain continuous absolute value data. Any resolution can be achieved by appropriately selecting the period of the second pattern and the interpolation magnification. By the above method, the number of tracks of the code pattern can be reduced, miniaturization is possible, and a high-resolution absolute value encoder having arbitrary resolution can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An absolute value encoder having a measurement range of 100 mm and a minimum resolution of 0.1 μm will be described below as an embodiment of the present invention with reference to the drawings. FIG. 1 is a diagram showing a part of the pattern of the movable slit plate of the encoder, FIG. 2 is a diagram showing the pattern of the fixed slit of the encoder, and FIG. 3 is a signal processing system of the absolute value encoder to which the present invention is applied. 4 is a diagram showing the relationship between coarse position data, medium position data, and fine position data, and FIG. 5 is a flowchart showing a processing method for combining coarse position data, medium position data, and fine position data. be.

<Basic concept> Three types of patterns are recorded on the moving slit plate 10, and from the first pattern, a signal that increases monotonically as the amount of movement increases within the measurement range is detected, and this signal is internally detected. By dividing it into 100 parts by inserting it, 1 mm can be detected per division. From the second pattern as the subsequent stage of the first pattern, the number of divisions of the first pattern is 2.
By multiplying the signal by 2 mm (100 mm/100) x 2 = 2 mm, one cycle of the signal is detected and divided into 200 by interpolation, thereby detecting 0.01 mm per division. Furthermore, from the third pattern as a subsequent stage of the second pattern, the number of divisions is twice as large as that of the second pattern, that is,
(2mm/200)×2=0.02mm=1 at 20μm
By detecting a periodic signal and dividing it into 200 parts by interpolation, a resolution of 0.1 μm per division can be obtained. Through the above processing, a resolution of 0.1 μm can be obtained per 100 mm, and the number of divisions is 1,000,000.

<Position Detection> On the moving slit plate 10,
As shown in FIG. 1, a pattern 11 in which the opening length monotonically increases with the amount of movement is formed as the first pattern.
As the second pattern, 1/50 (
100mm/50=2mm) is formed as one period, and a pattern 12 is formed in which light passing areas and non-light passing areas are repeated every 1mm.The third pattern is 1/100 of the second pattern, (2mm/100 = 20 μm) as one period, and a pattern 13 is formed in which a light passing region and a light non-passing region are repeated every 10 μm.

As shown in FIG. 2, the fixed slit plate 20 has a width narrower than the interpolation resolution of 1 mm, for example 0.0 mm, corresponding to the first pattern 11 on the movable slit plate 10.
A light passing portion 21 with a width of 5 mm is formed. Moving slit plate 1
Slit groups 22a, which have the same width and pitch as the respective patterns, correspond to the second and third patterns 12 and 13 on 0.
22b, 23a, 23b are formed. The slit groups 22b and 23b are the slit groups 22a and 23a.
They are formed at positions shifted by 1/4 period from each other. Five slit groups 21, 22a, 22b, 2
A total of five photosensors 31, 32a, 32b, 33a, and 33b are arranged, one for each photo sensor 3a and 23b.

A current signal proportional to the amount of light received is obtained from the photosensor groups 31, 32a to 33b, and is converted into a voltage by a current/voltage conversion circuit 34 as shown in FIG. A signal 41 that monotonically increases with the amount of movement of the movable slit plate 10 is obtained from the photosensor 31 corresponding to the first pattern 11, and photosensors 32a, 32b, corresponding to the second and third patterns 12, 13, From 33a and 33b, pseudo sine wave signals 42a and 42b, 43a and 43 whose phases are shifted by 90 degrees, each having a light and dark pattern as one cycle, are generated.
b is obtained.

<Data combination> These three sets of signals 41,
Interpolation processing for 42a, 42b, 43a, and 43b is started at the same timing in the interpolation processing unit 35, and as a result, three absolute value data of coarse position, medium position, and fine position are obtained, and these are data combined. The three position data are input to the unit 36 and combined to form continuous absolute value data. Figure 5 is a flowchart showing the contents of the data combination process.
Explain using. In Figure 5, fin is the fine position data, mid is the medium position data, crs is the coarse position data, Fmgf is the interpolation magnification of the fine position data, Mmgf is the interpolation magnification of the medium position data, and Cmgf is the interpolation of the coarse position data. The magnification, MID, represents the medium position data after correction, and CRS represents the coarse position data after correction.

From FIG. 4, the middle position data mid is 10μ
It can be seen that the precise position data fin changes every 20 μm. Therefore, when the absolute value data fin of the fine position increases monotonically, at the point where it changes from the maximum value to 0, the absolute value data mi of the middle position
d is always either an odd number or an even number. This is determined by design. Incidentally, when the absolute value data fin of the precise position monotonically decreases, the same thing can be said in that it changes from 0 to the maximum value. Also, the change point is 2
It is possible to shift by adjusting the phase of 2a, 22b, 23a, 23b (FIG. 2).

Here, for example, if the middle position data mid is an odd number at the point where the fine position data fin changes from the maximum value to 0 as shown in FIG.
If m is an even number, the corrected middle position data MID
m/2, ■ If m is an odd number and the fine position data fin is more than half of the interpolation magnification Fmgf of the fine position data, the corrected intermediate position data MID is (m-1)/2, ■ m is If it is an odd number and the fine position data fin is less than half the interpolation magnification Fmgf of the fine position data, the corrected medium position data MID is (m+1)/2, but this MID is more than half the interpolation magnification Mmgf. When this happens, it is set to 0.

On the other hand, although not shown in the flowchart of FIG. 5, if the intermediate position data mid is an even number at the point where the fine position data fin changes from the maximum value to 0, the value of the intermediate position data mid is Then, if ■'m is an odd number, then the corrected medium position data MID is m/2, and if ■'m is an even number and the fine position data fin is more than half of the interpolation magnification Fmgf of the fine position data, then , the corrected middle position data MID is (m-1)/2, however, when the middle position data m is 0, the interpolation magnification value Mm of the middle position data is
Calculate as gf, ■´m is an even number and precise position data f
If in is less than half of the interpolation magnification Fmgf of the fine position data, the corrected medium position data MID is (m+1)/
2. After performing any operation of ■´■´■´, take the quotient.

By the above calculation, the solution MID becomes a value in which one period of 20 μm of the precise position data fin is taken as one unit. In this way, by setting one period of the fine position data fin to be twice the minimum resolution of the medium position data mid, at the point where the fine position data fin changes from the maximum value to 0, the corresponding medium position Even if a deviation occurs within a range where the data mid does not change, the error can be absorbed.

Further, the rough position data crs changes every 1 mm, and the intermediate position data mid changes every 2 mm. These relationships are exactly the same as the relationship between the medium position data mid and fine position data fin mentioned earlier, except for the dividing length and interpolation magnification, and the solution CRS can be calculated using the same calculation process as the medium position data mid and fine position data fin. One period of 2mm
The value is taken as one unit. Continuous absolute value data can be obtained by using the solution obtained through the above two calculation processes as the minimum unit of precise position. Specifically, it is based on the following formula. Absolute value data = precise position data
+ Medium position data after correction × Interpolation magnification of fine position data
+ Rough position data after correction ×
Interpolation magnification for middle position data
× Interpolation magnification of precise position data ÷
2 = fin + MI
D ×Fmgf+CRS ×Mmgf×Fmgf÷2Although the obtained position data can be directly output in parallel, as shown in FIG.
By performing P/S conversion processing and transmitting it as serial data, the number of signal lines can be reduced.

Above, we have explained how to realize an encoder with a measurement range of 100 mm and a minimum resolution of 0.1 μm, that is, the number of divisions is 1,000,000.
It is determined by the first interpolation magnification/2) × (second interpolation magnification/2) × third interpolation magnification, and any number of divisions can be obtained by appropriately combining the interpolation magnifications at each stage. It will be done. For example, if the measurement range is 127mm, the second pattern is 5.0mm.
The third pattern was formed so that 8mm was formed as one period, the third pattern was formed as 25.4μm as one period, and the first
By setting the interpolation magnification to 100, the second interpolation magnification to 200, and the third interpolation magnification to 100, measurement can be performed in units of 0.254 μm, that is, in units of 1/100,000 inch. Also,
Using the same slit plate, only the third interpolation magnification is 254
By changing to , it becomes possible to measure in units of 0.1 μm. By using an interpolation circuit to change the interpolation magnification using a switch, a scale that can measure in metric and inch systems can be created using the same slit plate.

Furthermore, if a larger number of divisions is required, the number of interpolation stages can be increased; conversely, if a large number of decompositions is not required, two stages of interpolation can be used.
With a simpler configuration, about 20,000 divisions (for example, a measurement range of 100 mm and a minimum resolution of 5 μm) are possible using a similar method. Furthermore, the number of divisions can be increased by increasing the interpolation magnification.

[0021]

[Effects of the Invention] As detailed above, according to the high-resolution absolute value encoder that adopts the detection method of the present invention, high-resolution detection is possible with a small number of tracks, so the overall size of the device does not need to be increased. Absolute value detection becomes possible. Also,
Using the same slit plate, a scale capable of measuring in metric and inch systems can be constructed. Furthermore, since the slit width of the fixed mask can be set sufficiently wide, the amplification factor of the current/voltage conversion circuit can be kept low, making it less susceptible to noise.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a pattern of a moving slit plate in an embodiment of a high-resolution absolute value encoder according to the present invention.

FIG. 2 is a diagram showing a pattern of fixed slits in an example.

FIG. 3 is a block diagram showing an embodiment of a signal processing system of a high-resolution absolute value encoder to which the present invention is applied.

FIG. 4 is a diagram showing the relationship between coarse position data, medium position data, and fine position data.

FIG. 5 is a flowchart illustrating a processing method for combining coarse position data, intermediate position data, and fine position data.

FIG. 6 is a perspective view of a conventional absolute value detection type linear encoder.

[Explanation of symbols]

10　Moving slit plate 11 First pattern 12 Second pattern 13 Third pattern 20 Fixed slit plate 34 Current/voltage converter 35 Interpolation processing section 36 Data connection section 61　Moving slit plate 65 Fixed slit plate

Claims (3)

[Claims] 1. A movable slit plate on which first and second patterns are arranged, a first detection means for detecting a waveform signal that monotonically increases with the amount of movement from the first pattern, and a second a second detection means for detecting two waveform signals having a phase shift of 90 degrees from the pattern; a first interpolation processing means for interpolating the waveform signal detected by the first detection means; a second interpolation processing means for interpolating the two waveform signals detected by the second detection means; and a data combination means for combining the interpolation data obtained by the first and second interpolation processing means. , the first pattern consists of a code in which the amount of transmitted light monotonically increases with the amount of movement, and the second pattern divides the range in which the first pattern is arranged at equal intervals. A high-resolution absolute value encoder comprising a striped code. 2. The second pattern is composed of a plurality of tracks in which the intervals between the striped codes are successively finer according to a predetermined integer ratio, and the second interpolation processing means is configured to perform a plurality of interpolation processing means corresponding to each of the tracks. 2. A high-resolution absolute value encoder according to claim 1, further comprising: a high-resolution absolute value encoder. 3. Among the adjacent patterns, the latter pattern has a period of 90 times the resolution of the interpolation data obtained by the interpolation processing means that interpolates the signal obtained from the previous pattern. 3. The high-resolution absolute value encoder according to claim 1, wherein the high-resolution absolute value encoder is configured to obtain two pseudo-sinusoidal output signals whose phases are shifted by a degree.