JPH05296797A - Zero position detector of encoder - Google Patents

Abstract

PURPOSE:To provide a zero position detector of an encoder that makes hysteresis better as well as to improve the extent of S/N. CONSTITUTION:Each of equipitched grating graduations are carved in a main scale 3 and an index scale 4 and opposedly set up at minute intervals. In addition, a random number pattern 8b and a constant pitch pattern 7 are installed in the main scale 3, and likewise a random number pattern 8a corresponding to the main scale 3 and a window 6 are installed in the index scale 4 too. When the main scale 3 is shifted toward an arrow, an illuminating light out of a light source is passed through or interruped by a relative positional relationship with the index scale 4. In succession, on the basis of information on a difference in respective output signals subjected to photoelectric transfer after passing through the random number patterns 8a, 8b, the constant pitch pattern 7 and the window 6 and receiving light, a zero position is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder for detecting the amount of displacement or speed of linear movement or rotation of a machine or the like, and more particularly to an origin detection device for an encoder for detecting the origin position in the above operation.

[0002]

2. Description of the Related Art Conventionally, an optical encoder has been used as a position detector for detecting a displacement amount or speed of a straight movement or a rotation of a mechanical device in the form of an electric signal. This optical encoder is a kind of analog / digital (A / D) converter, is configured by using an optical scale, a light source, a detector, and the like, and is also called a photoelectric encoder because it is read photoelectrically.

In these encoders, the origin, which is the initial position of the movable body, is detected. For example, Japanese Patent Publication No. 1-45849 discloses a technique relating to a photoelectric incremental positioning device. ..

[0004]

However, in the above-described conventional encoder origin detecting device, the signal-to-noise ratio (S / N) is low, and the origin position cannot always be detected accurately.

The present invention has been made in view of the above problems, and an object thereof is to improve hysteresis.
An object is to provide an origin detection device for an encoder with improved S / N.

[0006]

In order to achieve the above object, an encoder origin detecting device according to a first aspect of the present invention is an origin which is an initial position of an encoder which outputs an electric signal according to a displacement of a movable body. In an origin detection device for an encoder that detects light, a light source that irradiates light, an optical system that collimates the light emitted from the light source, and a first random pattern that blocks a part of the light beam from the optical system. Main scale means having a portion and a constant pitch pattern portion or window,
A second device which is arranged at a position facing the main scale device and blocks a part of the light passing through the main scale device.
Index scale means having a random pattern portion and a window, light that has passed through the window and the constant pitch pattern portion, and light that has passed through the first and second random pattern portions, respectively, and at least first photoelectric conversion is performed. And a second photoelectric conversion means, and a detection means for detecting the origin position based on the difference between the output signals photoelectrically converted by the first and second photoelectric conversion means.

An encoder origin detecting device according to a second aspect of the present invention is an encoder origin detecting device for detecting an origin which is an initial position of an encoder for outputting an electric signal according to a displacement of a movable body. A light source to illuminate,
An optical system for converting light emitted from the light source into a parallel light flux, a main scale means having first and second random pattern portions having different phases for blocking a part of the light flux from the optical system, and the main scale. Index scale means arranged at a position facing the means and having third and fourth random pattern portions for blocking a part of the light passing through the main scale means, and the first and third random pattern portions. By the at least first and second photoelectric conversion means for receiving and photoelectrically converting the light that has passed through and the light that has passed through the second and fourth random pattern portions, respectively, by the first and second photoelectric conversion means. And a detection means for detecting the origin position based on the difference between the photoelectrically converted output signals.

[0008]

That is, in the encoder origin detecting device according to the first aspect of the present invention, when light is emitted from the light source, the emitted light is made into a parallel light flux by the optical system. Then, a part of the light flux from the optical system is blocked by the first random pattern portion and the constant pitch pattern portion or window of the mains scale means. A part of the light passing through the main scale means is blocked by the second random pattern portion and the window of the index scale arranged at a position facing the main scale means. Then, the light passing through the window and the constant pitch pattern portion and the light passing through the first and second random pattern portions are received and photoelectrically converted by the first and second photoelectric conversion means, respectively. Then, the origin position is detected based on the difference between the output signals photoelectrically converted by the first and second photoelectric conversion means by the detection means.

In the encoder origin detecting device according to the second aspect, when light is emitted from the light source, the emitted light is collimated by the optical system. Then, a part of the light flux from the optical system is blocked by the first and second random pattern portions having different phases of the main scale means. Part of the light that has passed through the main scale means is blocked by the third and fourth random pattern portions of the index scale means arranged at a position facing the movable index scale means. And the first
And the light passing through the third random pattern portion and the light passing through the second and fourth random pattern portions are the first
And the second photoelectric conversion means respectively receives and photoelectrically converts the light. Then, the origin position is detected by the detection means based on the difference between the output signals photoelectrically converted by the first and second photoelectric conversion means.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining an origin detection device for an encoder according to a first embodiment of the present invention.

As shown in FIG. 1A, the light from the light source 1 is collimated by the collimator lens 2 and radiated onto the main scale 3. Then, the light passing through the grid scale of the main scale 3 is irradiated onto the index scale 4, and the light passing through the grid scale of the index scale 4 is received by the detector 5.

FIG. 1B is a diagram showing a detailed structure of the main scale 3 and the index scale 4. The main scale 3 and the movable index scale 4 are engraved with a grid scale having an equal pitch and have a minute interval. It is arranged to face each other.

Further, the main scale 3 is provided with a random number pattern 8b and a constant pitch pattern 7, and the index scale 4 is also provided with a random number pattern 8a and a window 6 so as to correspond to the main scale 3. ..

In such a structure, when the main scale 3 is moved in the direction of the arrow, the light emitted from the light source 1 may pass or be blocked depending on the relative positional relationship with the index scale 4. And
When this transmitted light is detected by the detector 5 provided on the rear surface of the index scale 4, an output signal as shown in FIG. 2 is obtained.

That is, FIG. 2A shows the random number patterns 8a and 8a.
2 shows the output signal when the light passed or blocked by b is received by the detector 5 and photoelectrically converted.
(B) shows an output signal when the light passed or blocked by the window 6 and the constant pitch pattern 7 is received by the detector 5 and photoelectrically converted.

2C shows an output signal when the difference between the output signal shown in FIG. 2A and the output signal shown in FIG. 2B is calculated. The S / N of this output signal is twice that of the conventional output signal, and the hysteresis is 1/2.

FIG. 3 is a diagram showing the configuration of the origin detection circuit 30 for calculating the difference between the output signals, and FIG. 2 (a).
When the output signal shown in FIG. 2 and the output signal shown in FIG. 2B are input, the difference is calculated by the differential amplifier 301, and the difference is compared with the reference voltage in the comparator 302, so that the origin signal is output. To be done.

FIG. 4 is a diagram showing a configuration of a circuit example to which the present embodiment is applied. The origin signal from the origin detecting circuit 30 is inputted to one terminal of the NAND gate 41,
A signal from the CPU 45 is input to the other terminal of the NAND gate 41. The output signal from the NAND gate 41 is input to the counter 43.

The UP and DOWN signals from the interpolation circuit 42 are input to the counter 43, and the output signal from the counter 43 is input to the latch 44. And latch 4
The output signal from the CPU 4 is input to the CPU 45,
45 sends a signal to the display circuit 46, and the latch 4
A latch signal is also output to 4. The origin detecting device for the encoder according to the first embodiment of the present invention has been described above, and the second embodiment of the present invention will be described next. Figure 5
FIG. 6 is a diagram for explaining an origin detection device for an encoder according to a second embodiment of the present invention.

First, as shown in FIG. 5A, the light from the light source 1 is collimated by the collimator lens 2 and irradiated onto the main scale 3. Then, the light passing through the grid scale of the main scale 3 is irradiated onto the index scale 4, and the light passing through the grid scale of the index scale 4 is received by the detector 5.

FIG. 5 (b) is a diagram showing a detailed structure of the main scale 3 and the index scale 4. The main scale 3 and the index scale 4 are engraved with grid marks of equal pitch, and at a minute interval. It is arranged opposite.

Further, the main scale 3 is provided with two random number patterns 8b and 8d whose phases are shifted, and the index scale 4 is provided with two random number patterns 8a and 8c having the same phase.

In such a structure, when the main scale 3 is moved in the direction of the arrow, a phenomenon occurs in which the irradiation light from the light source 1 passes or is blocked depending on the relative positional relationship with the index scale 4.

When the transmitted light is detected by the detector 5 provided behind the index scale 4, an output signal as shown in FIG. 6 is obtained. That is, FIG. 6A shows an output signal when the light passed or blocked by the random number patterns 8a and 8b is received by the detector 5 and photoelectrically converted, and FIG. 6B shows the phase-shifted random number pattern 8
The output signal is shown when the light passed or blocked by c and 8d is received by the detector 5 and photoelectrically converted. Here, the output signals shown in FIGS. 6A and 6B have a phase difference. The output signal when the difference between the output signal shown in FIG. 6 (a) and the output signal shown in FIG. 6 (b) is calculated is as shown in FIG. 6 (c). The S / N of this output signal is double that of the conventional output signal, and the hysteresis is "0".

FIG. 7 is a diagram showing the configuration of the origin detection circuit 70 for calculating the difference between the output signals. FIG.
When the output signals shown in (a) and (b) are input, the difference is calculated by the differential amplifier.

FIG. 8 is a diagram showing a configuration of a circuit example to which the present embodiment is applied. The difference signal calculated by the origin detecting circuit 70 is output to the comparators 81, 82 and 8.
Input to 3. Then, the comparator 81 makes a comparison with the reference voltage V1, and the comparator 82 makes a comparison with the reference voltage V2.

The output signal from the comparator 81 is N
The output signal from the comparator 82, which is input to one terminal of the OR gate 85, is NO through the inverter 84.
It is input to the other terminal of the R gate 85.

The output signal of the NOR gate 85 is input to the JK flip-flop 86, and the output signal of the JK flip-flop 86 is input to one terminal of the NAND gate 88. Further, the output signal of the comparator 83 is input to the edge detection circuit 87, and the signal detected by the edge detection circuit 87 is input to the other terminal of the NAND gate 88. Thus, the above NAN
An edge signal is output from the D gate 88.

Here, the output signals from the respective parts of the above circuit are shown in the time chart of FIG. That is, the U signal which is the output signal from the comparator 81 becomes high level when the difference signal is equal to or higher than the reference voltage V1. Then, the D signal which is the output signal from the inverter 84 becomes high level when the difference signal is equal to or lower than the reference voltage V2. The GATE signal, which is the output signal from the JK flip-flop 86, is at a high level from the rise of the U signal to the rise of the D signal.

Then, the A signal which is the output signal from the comparator 83 becomes high level in synchronization with the difference signal zero-crossing during the period when the GATE signal is high level.

Further, the B signal which is the output signal from the edge detection circuit 87 rises in synchronization with the rise of the A signal. The edge signal becomes low level only when the GATE signal is high level and the B signal is high level.

As described above in detail, in the encoder origin detecting device of the present invention, a random number pattern is provided on the movable index scale and the main scale, and when the random number patterns match, the position can be detected as the origin position. .. Although the linear encoder has been described as an example in the description of the embodiment, a similar result can be obtained even if a rotary encoder is adopted.

[0033]

According to the present invention, it is possible to provide an origin detection device for an encoder with improved hysteresis and improved S / N.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an encoder origin detection device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a state of an output waveform according to the present embodiment.

FIG. 3 is a diagram showing a configuration of an origin detection circuit adopted in this embodiment.

FIG. 4 is a diagram showing a configuration of a circuit example to which the first embodiment is applied.

FIG. 5 is a diagram showing a configuration of an encoder origin detection device according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a state of an output waveform according to the present embodiment.

FIG. 7 is a diagram showing a configuration of an origin detection circuit adopted in this embodiment.

FIG. 8 is a diagram showing a configuration of a circuit example to which the second embodiment is applied.

9 is a diagram showing an output signal in each part of the circuit shown in FIG. 7. FIG.

[Explanation of symbols]

1 ... Light source, 2 ... Collimator lens, 3 ... Main scale, 4 ... Index scale, 5 ... Detector, 6 ...
Window, 7 ... Constant pitch pattern, 8 ... Random number pattern.

Claims (2)

[Claims] 1. An origin detection device for an encoder that detects an origin, which is an initial position of an encoder that outputs an electric signal according to a displacement of a movable body, wherein a light source that emits light and a light that is emitted from the light source are parallel to each other. An optical system for converting a light beam, a main scale means having a first random pattern part and a constant pitch pattern part or a window for blocking a part of the light beam from the optical system, and a main scale means arranged at a position facing the main smear means. The index scale means is provided and has a second random pattern portion and a window for blocking a part of the light passing through the main scale means, the constant pitch pattern portion and the light passing through the window, and the first and the first At least first and second photoelectric conversion means for receiving and photoelectrically converting light that has passed through the two random pattern portions, and the first and second photoelectric conversions An origin detection device for an encoder, comprising: a detection means for detecting the origin position based on a difference between output signals photoelectrically converted by the means. 2. An origin detection device for an encoder that detects an origin, which is an initial position of an encoder that outputs an electric signal according to a displacement of a movable body, wherein a light source that emits light and a light that is emitted from the light source are parallel to each other. An optical system for converting a light beam, a main scale means having first and second random pattern portions for blocking a part of the light beam from the optical system, and a main scale means arranged to face the main scale means. Index scale means having third and fourth random pattern portions having different phases for blocking a part of the light having passed through the scale means; light having passed through the first and third random pattern portions; And at least first and second photoelectric conversion means for receiving and photoelectrically converting light that has passed through the fourth random pattern portion, respectively, and the first and second photoelectric conversion means. An origin detection device for an encoder, comprising: a detection unit that detects the origin position based on a difference between output signals photoelectrically converted by the conversion unit.