JPH10104017A - Detecting apparatus for origin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detecting apparatus by which a constant position on a scale blank can be detected always as an absolute origin before and after the interruption of its detection by measuring the distance between a position on a scale in which a fixed-point signal generation means generates a fixed-point signal and a position on a scale in which a λ-signal generation means generates a λ-signal. SOLUTION: When the detection of the first displacement amount of a magnetic digital scale is started, a CPU 11 gives a control signal '1' to a selector 10. In this state, when a Z-signal is output from a fixed-point-signal detection circuit, the Z-signal is supplied to an interrupt terminal IRQ via the selector 10. In this manner, when an interrupt is performed, the CPU 11 changes over a control signal, to be given to the selector 10, to '0', and it starts the counting operation of the number of output pulses of an UP/DOWN signal which is supplied from an interpolation circuit. The displacement amount is detected, its detection is interrupted, and the detection is then resumed. Then, the CPU 11 measures the distance between a position on a scale in which the Z-signal is obtained and a position on the scale in which a λ-signal is obtained when an origin is detected after the interruption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an origin detecting device suitable for application to a scale device for detecting a relative displacement between two members which are relatively displaced in, for example, a machine tool or a precision measuring device.

[0002]

2. Description of the Related Art An incremental signal (hereinafter, referred to as a scale signal) representing a relative displacement amount is used on a digital scale used for detecting a displacement amount between two members relatively displaced in a metal working machine, a precision measuring device, or the like. In addition to the output function, a function of outputting a signal indicating the absolute origin (hereinafter referred to as an origin signal) has been conventionally provided in order to realize highly accurate and reliable measurement.

[0003] Among such digital scales, in a magnetic digital scale (for example, Magnescale (registered trademark of the present applicant)), the scale material generally has a coaxial shape and a relatively small diameter (for example, 2.
0 mm), it is technically difficult to record the magnetic scale for the origin signal on the same scale material as the magnetic scale for the scale signal. Therefore, in the magnetic digital scale, the scale for the fixed-point signal is recorded separately from the scale material, and the fixed-point signal itself obtained therefrom is used as the origin signal, or the fixed-point signal is used as a gate for the scale material. Is selected, and the scale signal is used as the origin signal.

FIG. 10 is a block diagram schematically showing the overall configuration of a well-known phase detection type displacement amount detecting device in a magnetic digital scale. The scale section 1 has a wavelength λ for a scale signal along the longitudinal direction of the coaxial scale material.
A scale 1a on which a magnetic scale of 200 μm (for example) is recorded, and two magnetic heads (for example, magnetic flux responsive magnetic heads) 1b separated from each other by (n ± 1/4) λ (n is an arbitrary natural number) , 1c. Each of the magnetic heads 1b and 1c has a structure in which an excitation winding and an output winding are wound around a saturable core. When a magnetic digital scale is used for a machine tool, a precision measuring device, or the like, the scale 1a is attached to one of a movable portion and a fixed portion, and the magnetic head 1b,
1c is attached to the other one.

[0005] scaling signal detection circuit 2, in particular an oscillator for generating a current signal (not shown) the frequency f _c (angular frequency _{ω c = 2π · f c)} , the frequency f _c by decreasing the signal from the oscillator / 2 and a phase shifter for shifting the phase of the signal from the frequency down converter by .pi. / 4. The signals from the frequency down converter are used as magnetic heads 1b and 1c. Is supplied to one of the excitation windings as an excitation signal, and the signal from the phase shifter is supplied to the other excitation winding as an excitation signal. Thus, balanced modulation signals corresponding to the relative displacement x between the scale 1a and the magnetic heads 1b, 1c are obtained in the output windings of the magnetic heads 1b, 1c, respectively.

[0006] These balanced modulation signals are sent to the scale signal detection circuit 2. The scale signal detection circuit 2 also includes a mixer that mixes these balanced modulation signals, and a band-pass filter that passes only the second harmonic of the signal from the mixer. A phase modulation signal e _PM having a phase amount corresponding to the displacement amount x and having an angular frequency ω _c twice as large as that of the excitation signal as shown in the following equation (1) is obtained. e _PM = E _PM sin (ω _c · t + 2πx / λ) (1) where E _PM is a constant and t is time.

[0007] scaling signal detecting circuit 2, a rectangular wave signal of the phase modulation signal e _PM also includes a pulsing circuit for waveform-shaping (e.g. Schmitt trigger circuit), and the frequency f _c obtained by the pulse forming circuit (Hereinafter referred to as S signal)
Is sent from the scale signal detection circuit 2 to the interpolation circuit 3.

[0008] interpolator 3, using the interpolating clock pulse of frequency Nf _c of N times the S signal (200 times for example) (hereinafter referred to as CKI signal), scale 1a and the magnetic head 1b, and 1c Resolution λ / N according to relative movement direction
(Hereinafter referred to as UP / DOWN signal). Accordingly, the number of output pulses of the UP / DOWN signal is proportional to the amount of displacement on the scale 1a. For example, when the amount of displacement is λ, the number of output pulses is 200.
Becomes

Next, the origin detection circuit will be described. The fixed point signal generating section 4 includes a magnetic body 4a on which a magnetic scale for a fixed point signal is recorded and a magnetic head 4b. When a magnetic digital scale is used for a machine tool, a precision measuring instrument, or the like, the magnetic body is set in a state where the positional relationship with the scale 1a is set so that a fixed point signal is obtained at a specific position in the longitudinal direction of the scale 1a. 4a is attached to one of the movable part and the fixed part, and the magnetic head 4
b is attached to the other one.

The signal from the magnetic head 4b is sent to a fixed point signal detection circuit 5. The fixed point signal detection circuit 5 shapes this signal into a rectangular wave signal and outputs a rectangular wave signal (hereinafter referred to as an RG signal) as shown in FIG. 11A (for example, a Schmitt trigger circuit). And a differentiating circuit for detecting a rising edge of the signal and outputting a signal as shown in FIG. 11B (hereinafter referred to as a Z signal). This Z
The signal is sent from the fixed point signal detection circuit 5 to the control circuit 6 as a fixed point signal corresponding to a specific position of the scale 1a.

Meanwhile, the scale signal detection circuit 2, in addition to the S signal, the phase-modulated signal e _PM Like the angular frequency omega _c of equation (2) pulsing circuit the phase comparison reference signal eREF like (e.g. rectangular wave signal of a frequency f _c which is waveform-shaped by Schmitt trigger circuit) (hereinafter referred to as REF signal)
The REF signal is sent from the scale signal detection circuit 2 to the λ signal generation circuit 7 together with the S signal. eREF = EREFsin (ω _c · t) (2) where EREF is a constant.

Further, the CKI signal is sent from the interpolation circuit 3 to the λ signal generation circuit 7. The λ signal generation circuit 7
A circuit that digitally compares the phase of the signal and the REF signal to output one pulse in the CKI signal while discriminating the moving direction for each displacement λ of the recording wavelength of the magnetic scale of the scale 1a (hereinafter, referred to as a circuit). , Λ signal generation circuit 7 is referred to as a λ signal, an example of which is shown in FIG. 11C). This λ signal is sent from the λ signal generation circuit 7 to the control circuit 6.

The control circuit 6 uses the Z signal from the fixed point signal detection circuit 5 as a gate, for example, as shown in FIG.
This is a circuit that outputs a pulse P of the λ signal output first after the output of the Z signal as an origin signal.

[0014]

By the way, in order to detect a displacement amount with high accuracy and stably using a digital scale, a fixed position on the scale material is always set to the absolute origin over the entire period of detection. Must be detected as

However, in the case where the detection is interrupted halfway and the power of the digital scale is turned off for the reason that the detection is performed for a long period of time or the like, the scale material is not used like a magnetic digital scale. In a digital scale with a magnetic scale for a fixed point signal recorded on a separate magnet, the position on the scale material where the fixed point signal is obtained when the origin is detected before the interruption and when the detection is resumed after the interruption is resumed. It is somewhat unavoidable that the amount slightly fluctuates (usually within the range of half the recording wavelength λ of the magnetic scale for the scale signal).

That is, for example, after detecting the absolute origin before interruption,
The position of the magnetizing body with respect to the scale material may slightly move due to vibration during work in a metal processing machine or precision measuring equipment, etc., which may cause a difference between the origin detection before interruption and the origin detection after interruption. The position on the scale material from which the fixed point signal is obtained fluctuates. Also, for example, at the absolute home position after the interruption, the magnetic body may expand or contract slightly more than at the absolute home position before the interruption due to a temperature change. The position on the scale material at which the fixed point signal is obtained fluctuates between when the origin is detected after the interruption.

Therefore, in a conventional digital scale in which a magnetic scale for a fixed point signal is recorded separately from the scale material, it is difficult to detect a fixed position on the scale material as an absolute origin before and after the detection is interrupted. there were.

The present invention has been made in view of the above points, and always keeps a fixed position on the scale material before and after the interruption of the detection, despite the fluctuation of the position on the scale material from which the fixed point signal is obtained. It is an object of the present invention to provide an origin detecting device capable of detecting an origin.

[0019]

SUMMARY OF THE INVENTION An origin detecting apparatus according to the present invention provides a signal (λ) corresponding to a recording wavelength of a scale on a scale.
Signal generating means for generating a signal, a displacement signal generating means for generating an output signal corresponding to the displacement on the scale, and a signal (fixed point signal) at a specific position on the scale. An origin detecting device for a digital scale having fixed point signal generating means, wherein a distance between a position on the scale at which the fixed point signal generating means generates the fixed point signal and a position on the scale at which the λ signal generating means generates the λ signal is calculated. Measuring means for measuring using a signal generated by the displacement amount signal generating means between the positions of: a storage means for storing a distance measured by the measuring means; and a distance measured by the measuring means, Comparing means for comparing the distance measured with the distance stored in the storage means, and the origin position on the scale detected based on the fixed point signal generated by the fixed point signal generating means. Is characterized in that a correcting means for correcting in accordance with the comparison result of the compare means.

When the origin is detected before the interruption, the distance between the position on the scale where the fixed point signal generating means has generated the fixed point signal and the position on the scale where the λ signal generating means has generated the λ signal is determined by the displacement amount signal generating means. It is measured by the measuring means using the generated signal and stored in the storage means.

Thereafter, when the detection is interrupted, and the detection is resumed after the interruption, when the origin is detected, the position on the scale where the fixed point signal generating means generates the fixed point signal and the position on the scale where the λ signal generating means generates the λ signal are determined. Is measured again by the measuring means, and this distance is compared by the comparing means with the distance already measured by the measuring means before the interruption and stored in the storage means. Here, if there is a change in the position on the scale material where the fixed point signal is generated before and after the interruption of the detection, a comparison result that the two distances are different is obtained. Then, based on the comparison result, the origin position on the scale detected based on the fixed point signal generated by the fixed point signal generation means after the interruption is corrected by the correction means.

As described above, if there is a change in the position on the scale material where the fixed point signal is generated before and after the interruption of the detection, the origin position after the interruption is corrected based on the change. Thus, a fixed position on the scale material is always detected as the absolute origin before and after the interruption of the detection, despite the change in the position on the scale material at which the fixed point signal is generated.

[0023]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a magnetic digital scale having the displacement amount detecting device shown in FIG. 10. Parts and signals corresponding to those in FIG. Description is omitted. In this displacement amount detection device, the UP / DOWN signal output from the interpolation circuit 3, the Z signal output from the fixed point signal detection circuit 5, and the λ signal output from the λ signal generation circuit 7 are used to detect the origin. It is sent to the circuit 8.

The origin detecting circuit 8 includes a selector 10, a CPU 11, and a memory 12, as shown in FIG.
The UP / DOWN signal from the interpolation circuit 3 is supplied to two Counter terminals of the CPU 11, respectively. The Z signal from the fixed point signal detection circuit 5 is supplied to one selection input terminal S1 of the selector 10, and the Z signal from the λ signal generation circuit 7
The signal is supplied to the other selection input terminal S2 of the selector 10.

The control input terminal C of the selector 10
A control signal (for example, a binary signal of “1” or “0”) output from the Port terminal of U11 is supplied. For example, when the value of the control signal is “1”, the selector 10 selects the input signal to the selection input terminal S1, and the value is “0”.
At this time, the input signal to the selection input terminal S2 is selected. The selection output signal of the selector 10 is supplied to an interrupt terminal IRQ of the CPU 11.

Data is written to and read from the memory 12 under the control of the CPU 11. As the memory 12, for example, a non-volatile RAM (NV-RAM) or an EEPROM (electrically erasable programmable ROM) is used so that the stored contents are not lost even when the power of the magnetic digital scale is turned off. ing.

Next, the operation of the origin detecting device will be described. When the detection of the amount of displacement is first started in a magnetic digital scale attached to a metal working machine or a precision measuring device, the CPU 11 supplies a control signal “1” to the selector 10. In this state, the fixed point signal detection circuit 5
When the Z signal is output as shown in FIG.
A signal is supplied to the interrupt terminal IRQ via the selector 10.

When an interrupt is applied, the CPU 11
Switches the control signal to be supplied to the selector 10 to “0”, and the UP / DO supplied from the interpolation circuit 3.
The counting of the number of output pulses of the WN signal is started.

After the interruption, when the first pulse P1 of the λ signal is output from the λ signal generation circuit 7 as shown in FIG. 3B, the pulse is supplied to the interrupt terminal IRQ via the selector 10.

When the interrupt is again applied, the CPU
11 finishes counting the UP / DOWN signal and writes the count value _C0 into the memory 12. Then, the pulse P1 of the λ signal is output as the origin signal, and the origin detection processing at the time of the first origin detection ends.

Since the number of output pulses of the UP / DOWN signal is proportional to the amount of displacement on the scale 1a, the position on the scale 1a at which the Z signal was obtained at the time of the first detection of the origin and λ The distance L ₀ (see FIG. 3) from the position on the scale 1a where the signal was obtained was measured in the form of a count value of the UP / DOWN signal.

After the displacement is detected and displayed on the magnetic digital scale, the detection is interrupted and the power of the magnetic digital scale is turned off. After the interruption, the power of the magnetic digital scale is turned on again. When the detection of the displacement is restarted, the CPU 11 first counts the UP / DOWN signal in the same manner as in the above-described processing, so that the Z signal is obtained at the time of detecting the origin after the interruption. distance L _n (n in this case the position on the scale 1a position and the λ signal is obtained on the scale 1a is an integer of 2 or more, that the distance measured by the time of the second and subsequent origin detection Measurement).
Then, when the first pulse of the λ signal is supplied to the interrupt terminal IRQ and an interrupt occurs, the count value C ₀ of the UP / DOWN signal written in the memory 12 before the interruption is read out from the memory 12 and shown in FIG. The following processing is performed.

First, an absolute value | C _n -C ₀ | of a value obtained by subtracting the count value C ₀ before the interruption (ie, the first count value C ₀ ) from the count value C _n after the interruption is given by UP / DOWN
100, which is one half of the number of output pulses of the signal (here, the number of output pulses is 200 as in the above-described example)
It is determined whether or not it is below (step S1).

Here, the deviation of the position on the scale 1a from which the Z signal was obtained when the origin was detected after the interruption to the position on the scale 1a from which the Z signal was obtained at the time of the initial origin detection is ±.
Assuming that the deviation is within the range of λ / 2 or less (as described above, this deviation due to vibration or temperature change at the time of work in a metal working machine or a precision measuring instrument equipped with a magnetic digital scale). Is usually within the range of ± λ / 2 or less), and when the absolute value | C _n -C ₀ | is 100 or less, the position on the scale 1a where the Z signal was obtained at the time of the first detection of the origin and the interruption The position on the scale 1a where the Z signal was obtained at the time of detection of the origin later is located before the position where the same pulse of the λ signal was obtained.

That is, as shown in FIG. 5, when the first count value C ₀ is in the range of 101 to 200, the absolute value |
C _n -C ₀ | is 100 or less when the position where the Z signal after interruption is obtained is within the range of the hatched portion in the figure.
First count value C ₀ as shown in the other 6 1-10
0, the absolute value | C _n -C ₀ |
The value of 0 or less is obtained when the position where the Z signal after the interruption is obtained is within the hatched area in the figure. As described above, when the absolute value | C _n -C ₀ | is equal to or less than 100, the first count value C ₀ is any value of 1 to 200, and the first count value C ₀ is the value at the time of the first detection of the origin and after the interruption. The position on the scale 1a where the Z signal was obtained at the time of origin detection is the same as the pulse P of the λ signal.
1 will be present before the position where it was obtained.

If the result of the determination in step S1 is YES, the pulse of the λ signal first supplied to the interrupt terminal IRQ after the Z signal is supplied to the interrupt terminal IRQ is output to the output terminal (not shown). Is output as it is as an origin signal (step S2). Then, the process returns, and the origin detection processing ends. Thus, as is clear from FIGS. 5 and 6, the same position as the position on the scale 1a at which the λ signal was output as the origin signal at the time of the first origin detection becomes the origin.

[0038] By contrast, the judgment result at Step S1 is when it becomes a no, also determines whether smaller towards the count value C _n after interruption from the first count value C ₀ (Step S3) .

Here, the reason that the absolute value | C _n -C ₀ | exceeds 100 and the count value C _n after the interruption becomes smaller is that the first count value C ₀ is 101 as shown in FIG.
7 and the position where the Z signal after the interruption is obtained is within the range of the oblique line in FIG. Therefore, in this case, the position on the scale 1a where the Z signal was obtained at the time of the first detection of the origin exists before the position of the pulse P1 of the λ signal, whereas the Z signal is obtained at the time of the detection of the origin after the interruption. The position on the scale 1a exists before the pulse P0 which is one before the pulse P1.

If the result of the determination in step S3 is YES, the position on the scale 1a when the pulse of the λ signal is supplied to the interrupt terminal IRQ after the Z signal is supplied to the interrupt terminal IRQ. The position corresponds to a position behind by a distance λ (step S4). Then, the process returns, and the origin detection processing ends. As a result, as is clear from FIG. 7, the same position as the position on the scale 1a at which the λ signal was output as the origin signal at the time of the first origin detection becomes the origin.

On the other hand, the reason why the absolute value | C _n -C ₀ | exceeds 100 and the count value C _n after the interruption becomes larger is that the first count value C ₀ is 0 to ₁ as shown in FIG.
This is a case where the position of the Z signal after the interruption is within the range of 00 and within the range of the oblique line in FIG. Therefore, in this case, the position on the scale 1a where the Z signal was obtained at the time of the first detection of the origin exists before the position of the pulse P1 of the λ signal, whereas the Z signal is obtained at the time of the detection of the origin after the interruption. The position on the scale 1a is located before the pulse P2 which is one position behind the pulse P1.

If the result of the determination in step S3 is negative, the position on the scale 1a when the pulse of the λ signal is supplied to the interrupt terminal IRQ after the Z signal is supplied to the interrupt terminal IRQ. It is equivalent to a position ahead by a distance λ (step S5). Then, the process returns, and the origin detection processing ends. As a result, as is clear from FIG. 8, the origin is the same as the position on the scale 1a where the λ signal was output as the origin signal at the time of the first origin detection.

As long as the range of the position change on the scale 1a from which the Z signal is obtained is within ± λ / 2 with respect to the recording wavelength λ of the magnetic scale of the scale 1a by the above-mentioned origin detection processing, Nevertheless, the position on the scale 1a where the pulse of the λ signal is supplied to the interrupt terminal IRQ of the CPU 11 at the time of the first detection of the origin (the position where the pulse P1 is obtained in the examples of FIGS. 5 to 8) is the origin detection after the interruption. Sometimes it is always detected as the origin.

The above-mentioned flowchart of FIG. 4 shows the processing when the λ signal is used as the origin signal. In the origin detection processing, the Z signal itself is used as the origin signal instead of the λ signal. Of course it is good. When the Z signal itself is used as the origin signal, the CPU 11 replaces the interrupt processing of FIG.
It is assumed that the interrupt processing shown in FIG.

First step S11 of this interrupt processing
Is the same as step S1 in FIG.
Is the λ signal after the Z signal is supplied to the interrupt terminal IRQ.
When the pulse is supplied to the interrupt terminal IRQ
Distance L from the position on the rule 1a ₀Only corresponds to the forward position
(Step S12). And return. to this
As can be seen from FIGS. 5 and 6,
Scale 1a that outputs Z signal as origin signal during detection
The same position as the upper position is the origin.

If the answer is no in step S11,
In step S13, the same determination as in step S4 of FIG. 4 is performed. In the case of Yes, after the Z signal is supplied to the interrupt terminal IRQ, the distance λ−L is larger than the position on the scale 1a when the pulse of the λ signal is supplied to the interrupt terminal IRQ.
_This corresponds to a position behind by ₀ (step S14). And return. Thus, as is clear from FIG. 7, the position on the scale 1a where the Z signal was output as the origin signal at the time of the first origin detection becomes the origin.

On the other hand, if the result of step S13 is NO, the signal λ is supplied after the Z signal is supplied to the interrupt terminal IRQ.
This corresponds to a position that is a distance λ + L ₀ ahead of the position on the scale 1a when the signal pulse is supplied to the interrupt terminal IRQ (step S15). And return. Thus, as is clear from FIG. 8, the scale 1 which outputs the Z signal as the origin signal at the time of the first origin detection.
The same position as the position on a is set as the origin.

As described above, when the first origin is detected, the CP
The position on the scale 1a where the Z signal is supplied to the interrupt terminal IRQ of U11 is always detected as the origin even when the origin is detected after the interruption.

In the interrupt processing of FIGS. 4 and 9, if the CPU 11 is also made to determine the moving direction and the polarity, only one of the positive and negative moving directions (only the UP signal is output). Direction, or only the direction in which only the DOWN signal is output), the same position on the scale 1a is not limited to the case where the moving direction changes between the positive direction and the negative direction. Needless to say, it can always be detected as the origin.

In the above embodiment, the selector 10 is provided to select which of the Z signal and the λ signal is to be supplied to the interrupt terminal IRQ of the CPU 11, but a CPU provided with two or more interrupt terminals IRQ is provided. Is used, the Z signal and the λ signal may be directly supplied to separate interrupt terminals IRQ without providing a selector. Also in this case, the number of output pulses of the UP / DOWN signal is counted from the time when the Z signal is supplied to the interrupt terminal IRQ to the time when the first pulse of the λ signal is supplied to another interrupt terminal IRQ. Scale 1a obtained
Of course, the distance between the upper position and the position on the scale 1a from which the λ signal was obtained can be measured.

In the above embodiment, UP / DOWN
Although the CPU 11 executes the signal counting and the comparison of the count value, it goes without saying that a dedicated hardware circuit for performing such counting and comparison may be provided.

Further, in the above embodiment, the position on the scale 1a where the Z signal was obtained at the time of the first detection of the origin and λ
The distance from the position on the scale 1a where the signal was obtained is indicated by UP
Although the measurement is performed by counting the / DOWN signal, the present invention is not limited to this, and an appropriate signal that generates an output corresponding to the amount of displacement on the scale 1a (for example, A that generates a phase change corresponding to the amount of displacement on the scale 1a). / B-phase signal).

In the above embodiment, the present invention is applied to a magnetic digital scale. However, the present invention may be applied to an optical digital scale.

In this embodiment, the present invention is applied to a digital scale in which a magnetic scale for a fixed point signal is recorded on a magnet other than the scale material. However, even with a digital scale in which the magnetic scale for the fixed-point signal is recorded on the same scale material as the magnetic scale for the scale signal, expansion due to temperature change may occur depending on the positional relationship of the magnetic scales on the scale material. It cannot be said that there is no fluctuation at the position on the scale where the fixed point signal is obtained due to the contraction or shrinkage. Therefore, the present invention may be applied to such a digital scale.

The present invention is not limited to the above embodiment,
It goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0056]

As described above, according to the origin detection apparatus of the present invention, the position on the scale material at which the fixed point signal is obtained fluctuates before and after the interruption of the origin detection due to vibration, temperature change, and the like. Even in this case, a fixed position on the scale material can always be detected as the absolute origin before and after the interruption.

Therefore, there is an advantage that highly accurate and highly reliable measurement can be performed with a digital scale based on the origin.

Further, a circuit for generating a λ signal and an UP /
In a digital scale having a circuit for generating an output signal corresponding to the amount of displacement on the scale such as a DOWN signal and a circuit for generating a fixed point signal, such a highly accurate and reliable circuit is constructed by a relatively simple circuit configuration and processing. There is an advantage that highly accurate measurement can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a configuration of a displacement amount detection device employing the present invention.

FIG. 2 is a block diagram showing an example of a configuration of an origin detecting device of FIG.

FIG. 3 is a diagram illustrating an example of a signal supplied to a CPU in FIG. 2;

FIG. 4 is a flowchart illustrating an example of a process executed by a CPU in FIG. 2;

FIG. 5 is a diagram illustrating an example of a signal supplied to a CPU in FIG. 2;

FIG. 6 is a diagram illustrating an example of a signal supplied to the CPU of FIG. 2;

FIG. 7 is a diagram illustrating an example of a signal supplied to the CPU of FIG. 2;

FIG. 8 is a diagram illustrating an example of a signal supplied to the CPU in FIG. 2;

FIG. 9 is a flowchart illustrating another example of the processing executed by the CPU of FIG. 2;

FIG. 10 is a block diagram illustrating an example of a configuration of a conventional displacement amount detection device.

11 is a diagram illustrating an example of input / output signals of the control circuit of FIG.

[Explanation of symbols]

1 scale part, 1a scale, 1b, 1c, 4b
Magnetic head, 2 scale signal detection circuit, 3 interpolation circuit, 4 fixed-point signal generator, 4a magnetizing body, 5
Fixed point signal detection circuit, 7λ signal generation circuit, 10 selector, 11 CPU, 12 memory

Claims (1)

[Claims] 1. A λ signal generating means for generating a signal (λ signal) corresponding to a recording wavelength of a scale on a scale, and a displacement signal generating means for generating an output signal corresponding to a displacement on the scale And a signal (fixed-point signal) at a specific position on the scale
And a fixed-point signal generating means for generating the origin, wherein the fixed-point signal generating means generates a fixed-point signal on the scale and the λ signal generating means generates a λ signal on the scale. Measurement means for measuring the distance between the positions using the signal generated by the displacement signal generation means, storage means for storing the distance measured by the measurement means, and measurement by the measurement means Comparing means for comparing the distance with the distance already measured by the measuring means and stored in the storage means; and an origin position on a scale detected by the fixed point signal generating means based on the fixed point signal at which the fixed point signal is generated. And a correction means for correcting the difference according to the comparison result of the comparison means.