JPH01113616A - Position detector - Google Patents

Abstract

PURPOSE:To detect the position of a code plate based on the change in the read-out phase of a detector and the phase of an operated output, by providing a light source, one slit plate, detector which are arranged at a specified pitch, a detected signal dividing switch, a sampling circuit, a filter and an operating circuit. CONSTITUTION:Laser light from a laser 21 is made parallel through a lens 22 and projected on a slit plate 23. The transmitted light is detected with detectors 24. A binary coded pattern 26 is detected, the codes are converted and a coarse absolute position is measured. A pitch dp=(k/m)ds of the detectors 24, which are arranged in the moving direction of the slit plates, are selected with respect to a pitch ds of the slits [(m) is a number of the phase signals of 2 or more, 1<k<=1.25 or 0.75<=k<1]. With respect to (n) satisfying the expression [(n) is an integer], mXn pieces are arranged. The outputs of (m) number are sequentially divided and made to pass through a sampling circuit, a filter and an operating circuit. The precise position is detected based on the output phases of the operating circuit with respect to the sequentially read-out phases of the detectors 24. In this constitution, the various causes of the errors in detected positions can be removed. Thus, the detection of the minute position can be performed highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a position detection device in a positioning device or a measuring instrument.

Conventional technology In recent years, optical scale type position detection devices have adopted a method of increasing resolution by arranging multiple detectors by dividing the intensity signal of light transmitted through a conventional periodic slit etc. in the amplitude direction. By scanning this to obtain a phase signal and detecting the phase, high resolution is being achieved. Furthermore, in recent years, with the digitalization and multiplication of control, the need for absolute encoders as position detection devices has increased.

An example of the above-mentioned conventional position detection device will be described below with reference to the drawings.

FIG. 7 shows the configuration of a conventional position detection device.

In FIG. 7, 1 is a code plate, 2 is a mask, 3 is a light source, 4 is a light receiver, 6 is an amplifier, 6 is a bandpass filter,
7 is a slit, 8,9゜10.11 is a photodetecting element, 12
is lens, swl.

SW2. SW3. SW4 is a switch that sequentially outputs several signals from photodetecting elements 8, 9, and 10°11 at a fixed timing. The slit pitch d on the mask 2 is arranged to be s, /4ds with respect to the pitch dIi of the slits 7 on the code plate 1.

The operation of the position detector configured as above will be explained below.

The light emitted from the light source 3 is collimated by the lens 12, passes through the slit 7 and the mask 2, and then passes through the photodetector element 8.
, 9, 10.11, and the switches sw1. s
w2. sw3. The signal is switched and extracted at a constant timing via SW4, the signal is amplified, the fundamental wave component of the output signal is extracted by bandpass filter 6, and the phase of the obtained sine wave signal is the phase of the above switching. The position is detected by comparison.

Problems to be Solved by the Invention However, with the above configuration, problems occur due to changes in the light output of the light source, uneven distribution of light intensity of the light source, drift of the photodetector, and fluctuations in the position between the slit and the photodetector. Changes in the transmitted light amount distribution and disturbance light cause fluctuations in the DC level, low frequency noise, and waveform distortion in the detection signal of the photodetector, which inevitably causes distortion in the phase detection signal. This has the problem of causing non-linear positional errors.

The present invention overcomes the above-mentioned problems and provides a small and simple position detection device with small non-linear errors and high position detection resolution. It is something.

Means for Solving the Problems In order to solve the above problems, the position detection device of the first aspect of the present invention includes a light source, one slit plate having periodic slits, and a position detecting device according to the movement of the slit plate. a plurality of photodetectors arranged periodically in substantially the moving direction of the slit plate for detecting changes in light amount; The number of phase signals obtained, k, is 1≦1
．． 25.

Or it is a constant that satisfies 0.76≦1. ), and if n is an integer that satisfies and satisfies the relationship, the photodetector is m x
n or more switches are provided, further reading out the photodetector sequentially and sequentially distributing it to m outputs, m sample holds for holding output data of the switches, and outputs from the sample holds. m filters for filtering, an arithmetic circuit for calculating and outputting the outputs of the m filters, and a phase change between the phase of the output signal from the arithmetic circuit and the phase for sequentially reading out the photodetector. and a phase detector for detecting the position of the code plate.

Further, the position detection device according to the second aspect of the present invention further includes a reader for simultaneously reading a rough position detection pattern on the slit plate by the photodetector and detecting the rough position on the slit plate. It is prepared.

Operation Since the present invention has the above configuration, the light from the light source is irradiated onto the slit plate, and the change in the amount of light due to the slit plate is detected by a plurality of photodetectors installed under the above conditions dp=,ds. By switching this photodetector at the same time as detection, a plurality of phase signals with different phases are obtained by the photodetector, and these phase signals are subjected to calculations by a calculation unit, and an output signal from this calculation unit is obtained. and the switching phase of the photodetector, and detect changes in the light output of the light source, non-uniformity of the light intensity distribution of the light source, and drift of the photodetector depending on the phase detection and position detection configurations. , changes in the amount of transmitted light distribution due to changes in the position between the slit photodetectors, changes in the DC level of the detection signal of the photodetector caused by the drift of ambient light, and irregularities in the detection position due to low frequency noise and waveform distortion. The causes of linear errors can be eliminated, and highly accurate minute position detection can be performed.

Moreover, by simultaneously forming a pattern for coarse position detection on the slit plate and reading this at the same time as fine position detection, an absolute encoder with high resolution can be realized.

Embodiment Hereinafter, a position detection device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the overall configuration of a position detection device in a first embodiment of the present invention.

In FIG. 1, 21 is a semiconductor laser, 22 is a lens that converts the light from the semiconductor laser into a parallel beam, 23 is a slit plate, and 24 is a plurality of periodically arranged photodetectors that detect horizontal pinch points. 25 is a periodic slit for detecting minute positions with a slit pitch of d3, and 26 is a binary code pattern for detecting coarse absolute positions.

Regarding the position detector configured as above, the first
The operation will be explained using FIG. 2, the second tooth, FIG. 3, FIG.

First, FIG. 1 shows the overall configuration, in which the light emitted by the semiconductor laser 21 is collimated by the lens 22, and the light that is irradiated onto the slit plate 23 and transmitted is transmitted to the photodetector 2.
Detected by 4. Here, the binary code pattern 26 for coarse position detection can also be read out by the photodetector 24.

The light is irradiated onto the binary code pattern, and depending on the presence or absence of the pattern, light is transmitted or blocked, the resulting pattern is detected by a photodetector, and the rough absolute position is measured by performing code conversion.

Still, FIG. 2a is an explanatory diagram of the slit plate 26, and the slit pitch ds is 20 μm. The same figure is an explanatory diagram of the photodetector 24, and the pitch dp is 12.5 μm. dse is an explanatory diagram of the detection signal, and C is an example of the intensity distribution of the optical signal transmitted through the slit 26.

Here, the amount of light detected by photodetector fish 1 is part (a), the amount of light detected by photodetector 3 is part (c), etc., and these signals are sampled one by one. Samples and holds are sequentially carried out by a hold, and the output of the sample and hold is filtered by a filter, and the resulting signal is used as a physiognomy signal d. Also, the amount of light detected by photodetector 2 is (b)
The detected light amount of the part and the part of &4 is this part...
. . . Similarly, these signals are sequentially sampled and held by a sample hold, skipping one signal at a time, and the output of the sample hold is filtered by a filter, and the resulting signal is used as the B-phase signal e. Actual signals have variations in light intensity, and in FIG. 5, the A phase is sla and the B phase is 31b. The phase signal is obtained by reading out four output signals of the photodetector, one at a time, and AI, 3, 5.
．． Phase signal 31 obtained by the photodetector of 7...
a and the phase signal 31b obtained from the photodetectors of Fx 2, 4, 6, 8... are different in phase by 18oO, and these signals are subtracted using an arithmetic unit. In each case, a phase signal 32a shown in FIG. 6 can be obtained. Then, minute position detection is performed by comparing this phase signal with the switching phase of the photodetector.

Here, m is the phase number and is an integer of 2 or more.

When the number of divisions of one period of the phase signal is 4 or more, k must be a constant that satisfies 1≦1.26 or 0.76≦k (1, and there is a relationship of dp=-ds.k is for each phase. There is the following relationship with the number n of photodetectors for detecting for one period or more, and in the case of k)1, n-1<()≦n.

k (If 1, n-1 is an integer satisfying (-)≦n and is at 1-. dp = 12.5 μm, ds = 20 μm
In the case of m=2, k=1.25, n=4
, the minimum number of photodetectors required to detect each phase for one period or more is mXn = 8.

As described above, according to this embodiment, a binary code for coarse position detection, a slit pitch for fine positioning,
Slit plate with ds=20 μm and pitch dp=12.5
By providing a μm photodetector and a calculation unit, the slit shape can be easily
It is possible to obtain two signals with different phases, input phase and B phase signals, and by performing calculations with the arithmetic unit (subtractor) and detecting the output by phase detection, non-linear errors can be eliminated. It is possible to construct a small and simple phase detector with high position detection resolution.

FIG. 3 is an explanatory diagram of the configuration of a slit plate and a photodetector according to a second embodiment of the present invention. In the explanatory diagram of the detector 24, the pitch ds is 12.5 μm, dte+' + q is an explanatory diagram of the detection signal, and C is an example of the intensity distribution of the optical signal transmitted through the slit 25. Here, the amount of light at photodetector AI is the part (a) of transmitted signal C,
The amount of light at A5 is shown in part (E), and these signals are sequentially sampled and held by a sample hold, skipping three signals, and the output of the sample hold is filtered by a filter Ki, and the signal is In the same way, the signals of 711L2, 6, 10.14 are taken as phase B, the signals of bad 3, 7, 11.15 are taken as phase C, and so on. 4,8
The signal at ゜12.16 is assumed to be the C phase. These physiognomy, B phase,
The phases of the C-phase and C-phase signals differ by 900 in this order, and by performing calculations including subtraction between at least two of these signals, a phase signal is obtained and compared with the switching phase of the photodetector. By doing this, minute positioning is performed.

Here, m is the phase number and is an integer of 2 or more.

When the number of divisions of one period of the phase signal is 4 or more, k is 1≦1.25 or 0.75≦k (must be a constant that satisfies 1, and there is a relationship dp==ds.k is for each phase The number of photodetectors for detecting one period or more is n.dp=1
2.5μm, d5=40μm, m=4゜k=1
．． 25, n=4, and the minimum number of photodetectors required to detect each phase for one period or more is mxn=16.

As described above, according to this embodiment, the binary code for coarse position detection and the slit pitch d for fine positioning are used.
Slit plate with s=4oμm and pitch dp=12.5
By providing a μm photodetector and a calculation unit, the slit shape can be easily
Four signals with different phases by o, A phase, B phase, C phase, C
The number of phases can be increased compared to the first embodiment, and the number of phases can be increased compared to the first embodiment.
By performing an arithmetic operation (including multiple subtracters) and detecting the output by phase detection, a small and simple position detector with small non-linear errors and high position detection resolution can be constructed. Can be done.

Further, FIG. 4 is an explanatory diagram of the configuration of a slit plate and a photodetector according to a third embodiment of the present invention. In the explanatory diagram of the detector 24, the pitch dp is 46 μm, the same dse is an explanatory diagram of the detection signal, and the same C is an example of the intensity distribution of the optical signal transmitted through the slit 26. Here, the light intensity at photodetector point 1 is the part (a) of the transmitted signal C, the light intensity at photodetector point A3 is the part (e), etc., and these signals are sampled and held one by one. The output of the sample and hold is filtered by a filter, and the resulting signal is taken as the A-phase signal d. Similarly, &2, 4, 6, 8, and so on. ...18,2
Let the signal of 0 be the B-phase signal e. The signals obtained for the human phase and B phase differ in phase by 1800 degrees, and by subtracting these signals using a calculator, a phase signal is obtained.
Fine positioning is performed by comparing the switching phase of the photodetector.

Here, m is the phase number and is an integer of 2 or more.

When the number of divisions of one period of the phase signal is 4 or more, k must be a constant that satisfies 1≦1.25 or 0.75≦1, and has the relationship dp=-ds. k is the number n of photodetectors for detecting each phase for one period or more. d
When p=45μm, d8=100t1m, m=2゜k=0.9, n=10, the minimum number of photodetectors required to detect each phase for more than one period is m x n = 2
It becomes 0.

As described above, according to this embodiment, a binary code for coarse position detection, a slit pitch for fine positioning,
Slit plate with ds=100μm and pitch dp=45μ
By providing a photodetector of 180 m and a computing unit for calculation, 180
Two signals with different 0 phases, input phase and B phase, can be obtained, and this is compared to the first embodiment, and the number of photodetectors corresponding to the 1st position can be increased. By performing an arithmetic operation using a subtracter and detecting the output by phase detection, a small and simple position detector with small non-linear errors and high position detection resolution can be constructed.

Further, in the above embodiment, the photodetector 24 is used alone, but a mask having regular slits may be added to the front surface of the photodetector.

In addition, in the embodiment, the pitch dp of the photodetector 24 is specially manufactured so that the pitch dp satisfies the above formula.

It may be arranged parallel to the moving direction of the scale plate.

Furthermore, the present invention is not limited to the linear encoder as in the above embodiment, but is equally applicable to a rotary encoder in which the code plate is a rotating disk.

Effects of the Invention As described above, according to the first aspect of the present invention, there is provided a light source, a slit plate having periodic slits, and a substantial movement of the slit plate for detecting a change in the amount of light due to the movement of the slit plate. dp = (k/m) dB (ds = slit pitch, dp = photodetector arrangement pitch, 1(k(1,2s) or 0.75(k(1.

(m is an integer of 2 or more), a switch that sequentially reads out the photodetector and sequentially distributes it to m outputs, and m that holds the output data of the switch and the other. m sample holds, m filters for filtering the outputs from the sample holds, an arithmetic circuit for calculating and outputting the outputs of the m filters, and an arithmetic circuit for sequentially reading out the photodetector. and a phase detector that detects the position of the code plate based on the phase change with respect to the phase of the output signal of the output signal. The phase signal is calculated by a calculator (subtracter), and the output signal from the calculator and the phase for switching the photodetector are used to detect multiple positions by phase detection. DC level of the detection signal of the photodetector caused by changes in output, non-uniform distribution of light intensity of the light source, drift of the photodetector, changes in the amount of transmitted light distribution due to variations in the position between the slit photodetectors, and disturbance light. It is possible to eliminate the causes of non-linear errors in the detected position due to fluctuations in the waveform, low frequency noise, and distortion of the waveform, making it possible to perform highly accurate minute position detection.

Further, according to the second aspect of the present invention, there is provided a reader that also reads a rough position detection pattern on the slit plate by the photodetector to detect the rough position on the slit plate. Therefore, it is possible to realize an absolute encoder with high resolution. ′

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a position detector according to an embodiment of the present invention, and FIG. 2 is a diagram of the slit plate 25, photodetector 24, and light transmitted through the slit shown in FIG. 1 in the first embodiment of the present invention. FIG. 3 is an explanatory diagram of the intensity distribution and detection signal, and FIG. 4 is an explanatory diagram of the intensity distribution and detection signal of the optical signal transmitted through the slit plate 25, the photodetector 24, and the slit in the second embodiment of the present invention. 6 is an explanatory diagram of the slit plate 26, the photodetector 24, the intensity distribution of the optical signal transmitted through the slit, and the detection signal in the third embodiment of the present invention, and FIG. 6 shows the m factor. 21... Semiconductor v-4, 22 Old... Lens,
23...Slit plate, 24...Photodetector, 26...Slit, 26...Binary code, 31a...Phase signal A, 31b...
... Phase signal B, 32a ... Phase signal (A-
B), 32b... phase signal (B-A). Name of agent: Patent attorney Toshio Nakao and 1 other person3
-Eleven Slit Gosarashina-Maruya and Volume 2, 3, and 4! ! Law school 0

Claims (2)

[Claims] (1) A light source, a slit plate having periodic slits, and a plurality of photodetectors periodically arranged approximately in the direction of movement of the slit plate for detecting changes in light intensity as the slit plate moves. and d_p is the pitch d_s of the slit and the arrangement pitch of the photodetector in the moving direction of the slit, d_p=(k/m)d_s (where m
is the number of phase signals obtained as an integer greater than or equal to 2, and k is 1<
It is a constant that satisfies k≦1.25 or 0.76≦k<1. ), and when k>1, n-1<(1/k-1)≦n, and when k<1, n-1<(1/1-k)≦n, let n be an integer. In this case, m×n or more of the photodetectors are provided, and the photodetectors are sequentially read out and m
a switch for sequentially distributing the data to the outputs; and m sample holds for holding the output data from the switches;
m filters that filter outputs from the sample and hold; an arithmetic circuit that calculates and outputs the outputs of the m filters; and a phase of an output signal from the arithmetic circuit with respect to a phase that sequentially reads out the photodetector. a phase detector that detects the position of the code plate based on a phase change of the code plate. (2) a light source, a slit plate having periodic slits, and a plurality of photodetectors periodically arranged approximately in the direction of movement of the slit plate for detecting changes in light amount as the slit plate moves; and d_p is the pitch d_s of the slit and the arrangement pitch of the photodetector in the moving direction of the slit, d_p=(k/m)d_s (where m
is the number of phase signals obtained as an integer greater than or equal to 2, and k is 1<
It is a constant that satisfies k≦1.25 or 0.75≦k<1. ), and when k>1, n-1<(1/k-1)≦n, and when k<1, n-1<(1/1-k)≦n, let n be an integer. In this case, m×n or more of the photodetectors are provided, and the photodetectors are sequentially read out and m
a switch for sequentially distributing the data to the outputs; and m sample holds for holding the output data from the switches;
m filters that filter outputs from the sample and hold; an arithmetic circuit that calculates and outputs the outputs of the m filters; and a phase of an output signal from the arithmetic circuit with respect to a phase that sequentially reads out the photodetector. a phase detector that detects the position of the code plate based on a phase change of the code plate; and a reader that simultaneously reads a rough position detection pattern on the slit plate using the photodetector to detect the rough position on the slit plate. A position detection device equipped with.