JPS63117214A - Displacement measuring device - Google Patents

Abstract

PURPOSE:To calculate the displacement of a body to be measured with high accuracy and high resolving power, by simultaneously reading an incremental signal and an absolute signal from a chart panel to use both of the signals. CONSTITUTION:A regularly arranged lattice part 1A for generating an incremental signal, a code lattice part 1C for generating an absolute signal and a reference position lattice part 1B for obtaining a reference position signal if necessary are provided on the chart panel 1 allowed to communicate with a body to be measured. Then, luminous flux L is incident to the lattice part 1A and reflected as shown by a numeral 3 so that diffracted light is incident to the original position. Further, the directly reflected light and directly transmitted light of the luminous flux incident to the lattice parts 1A, 1B, 1C inclusive of a separate light source or reflected or transmitted diffracted light are detected by reading devices 2A, 2B, 2C to obtain respective predetermined signals. By this method, the displacement of the body to be measured is calculated using the incremental signal and the absolute signal. Furthermore, the lattice part 1B is provided so as to correspond to the lattice part 1C to measure displacement with higher accuracy.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a displacement measuring device for measuring the displacement of an object to be measured in its rotational state, moving state, etc. Circumference 1t) A beam of light is incident on a grating section with a single or predetermined pattern, and reflected light or transmitted light from the grating section is detected, or diffracted lights generated from the grating section are made to interfere with each other to form interference fringes. The present invention relates to a displacement measuring device that detects the interference fringes to determine the displacement of an object to be measured.

(Prior art) Conventionally, it has been used as a displacement 411 fixing device for detecting the amount of movement of a moving object in an industrial machine tool, detecting two rotational positions of a robot arm, and detecting the amount of rotation and one rotational speed of a rotating mechanism. Photoelectric encoders have been widely used.

Among these, a rotary encoder for photoelectrically determining the rotation amount and rotation speed of the object to be measured has a configuration shown in FIG. 8 (8), for example. The rotary encoder shown in the figure has a so-called main scale 81 in which light-transmitting parts and light-shielding parts are provided at equal intervals around a disk 85 connected to a rotary fi 80, and a corresponding light-transmitting part at equal intervals to the main scale. A so-called fixed index scale 82 having a light-shielding portion and a light-shielding portion are arranged in a so-called index scale type configuration in which both scales are placed facing each other with the light projecting means 83 and the light receiving means 84 sandwiching the scales. In this method, as the main scale rotates, a signal is obtained that is synchronized with the interval between the light-transmitting part and the light-blocking part of both scales, and this signal is frequency-analyzed to detect fluctuations in the rotational speed of the rotating shaft. . Therefore, the finer the scale interval between the light-transmitting part and the light-blocking part of both scales, the higher the detection accuracy can be.

This type of rotary encoder is called an incremental encoder, and generates a signal with a period of -.times. for each unit angle, and calculates the amount of rotation by counting the frequency at this time. An arbitrary position is then determined by constantly counting the amount of relative deviation from a certain rotational position. However, with this incremental encoder, if the device is turned off or rotates in a state where it cannot count, even if the power is turned on afterwards, it will not return to its current state even if it is equipped with a mechanism to remember the previous state. It has the disadvantage that it is not possible to determine the position of

On the other hand, there is a rotary encoder called an absolute encoder that determines absolute displacement in a rotating state. This rotary encoder is shown in Figure 8 (B).
When transparent parts and light shielding parts are regularly arranged on the circumference of a disk 85 connected to a rotating shaft 80 with different radii as shown in FIG. 8
6 is configured to differ for each unit angle. A light-transmitting means 83 consisting of a plurality of light sources and a light-receiving means 84 consisting of a plurality of light-receiving elements are arranged facing each other on different radial circumferences to read the codes 86, respectively. The specific angle of the disk 85 is determined by reading the code at this time.

When this rotary encoder reads the code provided on the disc 85, it is possible to know the absolute position at that time. Therefore, reading cannot be performed while the device is not powered on, but if the power is turned on after 9 rotations, the correct absolute position after rotation can be read. For this reason, in industrial robots, machine tools, etc., absolute encoders are often used because the information of the rotary encoder, which is the displacement measuring means, will not be incorrect even if an unexpected event such as a sudden power-off occurs. However, with absolute encoders, code elements (
As a result, the amount of information provided on circumferences (tracks) with different radii increases, the radial direction becomes longer, and the disk becomes larger.

(Problems to be Solved by the Invention) The present invention detects displacement such as rotation or movement of an object with high precision and high resolution by combining an incremental encoder and an absolute encoder in a fixed relationship. The purpose is to provide a displacement measuring device that can

(Means for solving the problem) A regularly arranged grid section for generating an incremental No. 13 signal and a code section for generating an absolute signal are provided on a chart board connected to the object to be measured.
irt, the incremental signal and solution signal were simultaneously detected by each reading means, and the two signals were used to determine the displacement of the object to be measured.

Further, by providing a reference position grid section for obtaining a reference position signal on the chart board in correspondence with each element of the code grid section, displacement measurement can be performed with higher precision.

(Embodiment) FIG. 1 is a schematic diagram of an optical system of an embodiment when the present invention is applied to a rotary encoder. In the figure, reference numeral 1 denotes a rotating chart plate connected to an object to be measured (not shown). IA is a grid section for generating incremental signals, and is regularly arranged radially around the rotation axis 10 on the outer periphery of the chart board 1. 2A is a reading device which outputs an incremental signal 1:# via the grid section IA.

Reference numeral 1B denotes a reference position grid section for obtaining a reference position signal, which is provided as needed, and is provided adjacent to the inside of the grid section IA. 2B is a reading device which obtains a reference position signal via the reference position grid section IB. The IC is a code section for obtaining an absolute signal, and is composed of a binary code formed by a transmitting section and a light shielding section, and is provided adjacent to the inside of the reference position grid section IB. 2C is a reading device, which obtains an absolute signal via the code section IC. 1 is a light beam, and 3A is a reflecting means, which reflects the diffracted light that has entered the grating portion IA on the chart board 1 and been refracted nine times so as to be incident on the original position.

Although not shown in the figure, there are two reading devices 2B and 2.
Light sources are provided for C with the chart board 1 in between.

In this embodiment, each predetermined signal is obtained by detecting the directly reflected light, the directly transmitted light, or the reflected or transmitted diffracted light of the light beam incident on each grating portion on the chart board 1 using each reading device. ing.

For example, a light beam from a light source is made incident on the grating part IA on the chart board 1, a transmitted light beam from the grating part IA is detected, and the number of periods at this time is counted, or two diffracted lights generated from the grating part IA are detected. They interfere with each other to form interference fringes, and the rotational state of the object to be measured is determined by counting the brightness and darkness of the interference fringes.

? /S2 Figure is each reading device 2A, 2B of Figure 1.

FIG. 2 is an explanatory diagram of a signal obtained from 2C. In the same figure, a
is an incremental signal obtained from the reading device 2A, b is a reference position signal obtained from the reading device 2B, C
1, C2, C3, ---1 are absolute signals obtained from the reading device 2C, respectively.

In this embodiment, each element is set so that the accuracy of the reference position signal is equal to or higher than the accuracy of the incremental signal. In this way, by using the reference position signal and reading the absolute position at the moment the reference position signal is generated, it is possible to prevent a decrease in detection accuracy when there is ambiguity in output No. 13 when the absolute signal is replaced. ing.

In this way, in this embodiment, the absolute signal and the incremental signal are detected simultaneously, the absolute signal is used to detect a highly accurate absolute position with coarse resolution, and the incremental signal is used to interpolate between each code. A high-resolution encoder has been achieved.

If the reference position grid section IB is not provided and the reference position signal is not detected, the incremental signal may be read at the time when the absolute signal is replaced, although the accuracy will be somewhat degraded.

FIGS. 3(A), 3(B), and 3(C) are explanatory diagrams of optical systems for detecting a reference position signal when the displacement measuring device according to the present invention is applied to a linear encoder. In this embodiment, the patterns of each lattice portion on the chart board 1 are arranged in a one-dimensional direction for use in a linear encoder.

The reference position grid section 34 for obtaining the reference position signal is shown in the same figure (^
) shows thin rectangles arranged periodically.

In the same figure (B), two rectangles with discrepancies are arranged periodically, and in the same figure (C), the pattern in the same figure (B) is developed and the two rows of rectangular patterns are alternated periodically. Arranged.

In each embodiment, 31 is a light beam from a light source (not shown), which is reflected by a half mirror 32 and then incident on the grating section 34 via a cylindrical lens 33. Then, the reflected light beam from the grating section 34 is transferred to a cylindrical lens 33.
．． The light is guided to a reading device 35 via a half mirror 34. The reading device 35 includes, for example, two light receiving elements 'f
35 A.

35B, and the reflected light flux is read in time series as the chart plate l moves.

fRl 36 is a grid section for obtaining an incremental signal, and 37 is a code section for obtaining an absolute signal.

In FIG. 3A, a light beam focused to approximately twice the width of a rectangular line is incident on the grating portion 34, and a light beam reflected from the grating portion 34 is received by a reading device 35. The signal obtained by the reading device 35 changes as shown in FIG. 4(A) as the chart board 1 moves. In this actual Mi example, there are two light receiving elements 3.
A difference signal as shown in FIG. 4(B) is created from the output signals from the light receiving elements 7-5A and 35B, and this difference signal is differentiated. At the moment when the output levels of the two light-receiving elements 7-35A and 35B match, the fourth light-receiving element 7-35A and 35B are A pulse signal as shown in Figure (C) is generated. As a result, a reference position signal as shown in FIG. 2 is obtained.

In this embodiment, the chart board 1 is constituted by a rotating disk, and a grating section made of a rectangular reflector with a line width of 5 μm is provided at a position with a radius of 7 mm, so that a light beam with a line width of about 10 μm is incident on the grating portion. A rotary encoder with a reproducible accuracy of 8 degrees/sec has been achieved.

The signals shown in FIGS. 4(D) and 4(F) are obtained from the reading device in the embodiment shown in FIGS. 3(B) and 3(C), respectively. Similarly to the above description, we create the difference signals shown in Figure 4 (ε) and (G) from these two signals, differentiate this difference signal, and generate a pulse signal at the moment the two output levels match. In this way, a reference position signal as shown in FIG. 4(C) is obtained.

FIGS. 5(A) and 5(B) show the chart board 1 according to the present invention.
FIG. 6 is an explanatory diagram of another embodiment of the code grid section for obtaining the above absolute signal. In FIGS. 5(A) and 5(B), 51 is a code grid section for obtaining an absolute signal;
Transmitted light V or reflected light is 1 per rotation of chart board 1
A member 2 whose period changes continuously includes, for example, an ND filter whose density changes continuously. The fifth of these
Figure (8) shows a member in which the code grid portion 51 is one piece, and Figure 5 (II
) consists of two parts.

Figure 6 (8) and (B) are respectively Figure 5 (8) and (
FIG. 3 is an explanatory diagram of output signals obtained from each reading device when using the chart board 1 shown in FIG. The output signal C in FIG. 6(A) is a signal obtained via the code grid section 51 in FIG. 5(A), and the output signals CI and C2 in FIG. This is a signal obtained through the code grid section 51 of B). In FIG. 6(B), the absolute position can be determined with higher precision by combining the two output signals CI and C2.

In each of the embodiments shown in FIGS. 5(A) and 5(R), the interval between the reference position grid portions a is determined by the analog absolute signal C.
Alternatively, the signal levels of CI and C2 can be freely set in a range where they can be sufficiently separated. At this time, as long as the recording accuracy of the reference position grid section is maintained, it is possible to ensure accuracy with reproducibility equivalent to that of an incremental signal.

Note that the case r provided on the chart board IL in each of the above embodiments
The order of arrangement of the part, the code part, and the reference position grid part may be arbitrary. Further, the light flux from each grating portion may be a reflected light flux or a transmitted light flux. Further, this embodiment is not limited to a rotary encoder, but can be applied to a linear encoder as well.

The base level green signal obtained in each of the above embodiments can be treated as an absolute signal as follows.

For example, in a first method, as shown in FIG. 7(A), an absolute signal is read every time a reference position signal is generated and held until the next reference position signal is input. Further, the numerical value of the incremental signal counter 72 is returned to zero each time the reference position signal is generated. Then, when detecting the general A1 device using the absolute No. 1 and counting the time using the incremental signal, there will be no imbalance between the accuracy of the switching timing of the absolute signal and the accuracy of the incremental signal. By combining numerical values from direct and absolute signals, it becomes a high-precision, high-resolution absolute (No. 2).

The reference position No. 15 is generated by the reading device 2B at every rotation angle. Absolute signal is read by reading device 2
C, the signals are always outputted and stored in the memory group 73 at the timing of generation of the reference position signal. Then, it is immediately read out and manually applied to the 1st finger of the decoder section 71. The incremental signal is generated by the reading device 2A, its cycle is counted by a counter 72, and the sign of the value is output and inputted to the lower finger section of the decoder section 71. This counter 72 is reset when the reference position signal is input manually.

In addition, a second method is to read the absolute signal when the first reference position signal is generated, store the initial value, and then reset the incremental signal counter 72, as shown in FIG. 7(B). . Thereafter, the data in the decoder section 71 is changed only by the updated output code of the counter 72 without rereading the absolute signal or resetting the incremental signal counter.

According to such a method, the absolute position value is detected from the reference position signal that is first generated during driving, and the value is subtracted or added using an incremental signal to obtain a highly accurate and high resolution absolute signal.

The reference position signal is generated by the reading device 2B at each rotation angle. The circuit 74 is configured such that only the first reference position signal is taken out and subsequent reference position signals are not output. The absolute signal is always outputted by the reading device 2C and passed through the gate 75 at the timing of the reference position signal outputted from the right circuit 74 to the decoder section 7.
It is manually applied to the upper finger section of 1. In this way, initial values are set. The incremental signal is read by the reader 2.
The period is counted by the counter 72, and a signal corresponding to the value is outputted and inputted to the lower finger section of the decoder section 71. This counter 72 is reset when the reference position signal obtained by the circuit 74 is input manually.

The reference position signal in each of the embodiments 1- below has a 4R effect for realizing a high-granularity, high-resolution encoder by combining a high-grained incremental encoder and a low-granularity absolute encoder, but Simply adding it to an absolute encoder has the effect of improving grain size.

In particular, if the reference position grid section is provided with high accuracy, more accurate detection is possible than detection based on replacement of absolute signals.

(Effects of the Invention) As described above, according to the present invention, the displacement of the object to be measured can be determined with high accuracy and high resolution by simultaneously reading the incremental signal and the absolute signal from the chart board and using these signals. A displacement measuring device can be achieved.

That is, by detecting the absolute position with coarse resolution and high precision using an absolute signal and interpolating between each coat using an incremental signal, a displacement measuring device with high precision and high resolution can be achieved.

Furthermore, if a means for detecting a reference position signal is provided at the same time and used in combination with the above two signals, a displacement measuring device with even higher precision and resolution can be achieved.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a schematic diagram of an optical system of an embodiment when the present invention is applied to a rotary encoder, Fig. 2 is an explanatory diagram of a signal obtained from the embodiment of Fig. 1, Figure 3 (8), (
B) and (C) are explanatory diagrams of other embodiments in which a reference position grid portion is obtained in the present invention, respectively, and FIGS. 4(^) to (
G) is an explanatory diagram of signals obtained from the embodiments shown in FIGS. 3(8), (11), and (C), and FIG. 5(8),
(B) is an explanatory diagram of another embodiment when obtaining an absolute signal in the present invention, and FIG. 6(A) and (+3
) are explanatory diagrams of signals obtained from the embodiments shown in FIGS. 5 (8) and (B), respectively, and FIG. Figure 8 (8). (B) is a schematic diagram of the optical system of 42 conventional incremental type rotary encoders and absolute type rotary encoder. In the figure, 1 is a chart board, 1^,
36 is a lattice portion; 18. :+4 is the reference position grid part, I
G, 37 are code grid sections, 2A, 2B, 2G, :15 are reading devices, and 10 is a rotating shaft. Patent applicant Akira Canon Co., Ltd.] Akira Ha 2 Figure C6 Hiroshi 3 Figure (△) 夷 3 times (B) 3rd time (C) 3,5 兇 4 times (C) 1 ↑ Engraving of drawings (changes in content) None) Figure 5 (A) Figure 5 (B) Month 6 (A) Figure 6 (B) Figure 7 (A) Full 7 Hard (B) 7 Kamoichi Procedure Ne 111 Regular Book (Method) % Formula % 2. Name of the invention Displacement measuring device 3. Person making the correction/relationship with the seven cases Patent applicant address 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (+00
) Canon Co., Ltd. Representative Kaku 0″iL
3 Part 4. Agent residence: 301 Helheim Jiyugaoka, 2-17-3 Okusawa, IW Taya-ku, Tokyo 158 (Telephone: 718-5614) Name: (8681) Patent attorney Yukio Takanashi Z-, 15, Date of amendment order: -,
-J January 27, 1986 (Delivery date) 6. Subject of amendment (1) Drawing 7 attached to the application, contents of amendment

Claims (2)

[Claims] (1) A regularly arranged grid section for generating incremental signals and a code section for generating an absolute signal are provided on a chart board connected to the object to be measured,
A displacement measuring device characterized in that the incremental signal and the absolute signal are simultaneously detected by respective reading means, and the displacement of the object to be measured is determined using the two signals. (2) A reference position grid section for generating a reference position signal for each element of the code section is provided on the chart board, and the reference position signal is obtained together with the incremental signal and the absolute signal. A displacement measuring device according to claim 1.