JP6276074B2 - Position detection device - Google Patents

Description

  The present invention relates to a position detection device that detects a relative position between a scale such as a magnetic scale and an optical scale and a head.

  Conventionally, a position detection device including a scale and a detection head is known as a position detection device that detects a precise displacement position such as a linear displacement or a rotational displacement. This position detection device is widely used in, for example, an electronic component mounting device that requires highly accurate positioning control of a conveyed product, a detection (measurement) device that detects (measures) the dimensions of the component, and the like. The detection method of such a position detection device is roughly divided into a magnetic type and an optical type.

FIG. 9 is a diagram showing a principle configuration of a conventional magnetic position detection device. The position detection device of FIG. 9 detects a linear displacement and includes a magnetic scale 1 made of a magnetic medium. In the magnetic scale 1, the magnetization directions of the S pole and the N pole are reversed every certain distance. One unit in which the S pole and the N pole are repeated is one wavelength of the recording signal of the magnetic scale 1.
In the position detection apparatus of FIG. 9, a magnetic head 2 that moves along the longitudinal direction (the x direction in the figure) in which the magnetization direction of the magnetic scale 1 is reversed is prepared, and the magnetic head 2 includes two magnetic sensors. 2a and 2b are arranged. Each of the magnetic sensors 2a and 2b is a sensor for detecting the magnetization direction recorded on the adjacent magnetic scale 1, and the arrangement position is shifted by a distance corresponding to a quarter period of one wavelength of the recording signal. Therefore, one magnetic sensor 2a detects the recording signal of the magnetic scale 1 as a sine waveform signal (SIN signal), and the other magnetic sensor 2b detects the recording signal of the magnetic scale 1 as a cosine waveform signal (COS signal). ) To detect.

Here, the relative position between the magnetic scale 1 and the magnetic head 2 is x, and sin (x) is obtained from the SIN signal sin (x) output from the magnetic sensor 2a and the COS signal cos (x) output from the magnetic sensor 2b. Tan (x) is obtained by calculating / cos (x), and the relative position x is calculated from the value of tan (x). When the relative position x between the magnetic scale 1 and the magnetic head 2 is obtained, an interpolation process is performed to calculate the position x with an accuracy finer than the length of one wavelength.
The calculated position information is transmitted to a position information display device or control device.
Patent Document 1 describes an example of such a magnetic position detection device.

JP 2009-36637 A

  By the way, the signal representing the position coordinates of the scale is as fine as possible in order to improve the measurement accuracy. For example, in order to obtain an accuracy of 0.2 μm, a signal having a wavelength of 80 μm is recorded on a scale. On the other hand, the distance between the scale and the head (clearance) has a relationship that the amplitude of the read signal decreases if the clearance is large, so it is necessary to make the clearance sufficiently shorter than the wavelength in order to obtain a signal amplitude that maintains accuracy. is there. For example, when a signal having a wavelength of 80 μm is recorded on a scale, conventionally, a clearance of 20 μm has been required.

Here, in order to keep the clearance between the scale and the head small, a highly accurate mechanism for that purpose is required. Therefore, in order to simplify the configuration of the position detection device, it is desirable to increase the clearance. This is contrary to reducing the clearance in order to obtain the measurement accuracy described above. In order to increase the clearance, it is necessary to enable highly accurate detection even when the amplitude of the read signal is small, and it is necessary to remove noise components included in the signal read by the head.
In addition, when the clearance between the scale and the head is increased, the attenuation amount of the signal recorded on the scale is larger than the attenuation amount of the noise component that appears in a cycle longer than the wavelength of the signal recorded on the scale. . For this reason, when the clearance is large, the ratio of the noise component is remarkably increased, leading to deterioration in position detection accuracy.

  An object of the present invention is to provide a position detection device capable of ensuring position detection accuracy while allowing a clearance between a scale and a head for reading signals to be wider than before.

The position detection device of the present invention extends along the moving direction of an object to be position-detected, and has a scale on which position detection signals are repeatedly recorded at a fixed period, and a position detection that can move with the object and is recorded on the scale. And a position acquisition unit that acquires the position of the object based on the output signal of the sensor.
The sensor includes a main sensor and a sub sensor.
The main sensor is movable together with the object, is disposed opposite to the scale, and detects a position detection signal recorded on the scale.
The secondary sensor is located adjacent to the main sensor in a direction perpendicular to the moving direction of the object, and detects an averaged signal for position detection within a fixed period or an integral multiple of the fixed period recorded on the scale. To do.
The position acquisition unit acquires the position of the object based on the output signal of the main sensor and the output signal of the sub sensor.

According to the present invention, the sub-sensor can obtain a signal obtained by averaging the signal for position detection recorded in the scale at a constant period or an integer multiple thereof. For this reason, in the secondary sensor, only the long wavelength component of the signal recorded on the scale is detected, the scale recording signal has no detection sensitivity, and the signal detected by this secondary sensor is used. It is possible to remove a long wavelength noise component from the signal detected by the main sensor.
By removing the long-wavelength noise component in this way, position detection that is not affected by noise can be performed. For example, even if the clearance between the scale and the sensor is increased, the position detection accuracy can be improved or maintained. Become. In addition, since the clearance between the scale and the sensor can be increased, a complicated configuration for maintaining the clearance between the scale and the sensor with high accuracy is not necessary, and the position detection device can be simplified and reduced in cost and high in cost. Reliability can be improved.

It is a perspective view which shows the example of arrangement | positioning with the magnetic scale and head by one embodiment of this invention. It is a top view which shows the example of arrangement | positioning with the magnetic scale and head by one embodiment of this invention. It is a block diagram which shows the example of a process of the output signal of each sensor by one embodiment of this invention. It is a wave form diagram which shows the example of an output signal by one embodiment of this invention. It is a top view which shows the head structural example (example provided with the harmonic removal sensor) by other embodiment of this invention. It is a top view which shows the head structural example (example provided with several sub sensor) by other embodiment of this invention. FIG. 7 is a block diagram illustrating a processing example of an output signal of each sensor in the example of FIG. 6. It is a principle figure which shows the structural example (example of an optical scale) by other embodiment of this invention. It is a perspective view which shows the example of arrangement | positioning of the conventional magnetic scale and a head.

  Hereinafter, an example of an embodiment of the present invention (hereinafter referred to as “this example”) will be described with reference to FIGS. This example is an example applied to a magnetic scale type position detecting device using a magnetic scale.

[1. Configuration of magnetic scale and head]
FIG. 1 and FIG. 2 are diagrams showing examples of the arrangement state of the magnetic scale and the magnetic head of the position detection device of this example. FIG. 1 is a perspective view, and FIG. 2 is a plan view in which a magnetic scale and a magnetic head are overlapped.
As shown in FIG. 1, the magnetic scale 10 has a configuration in which a magnetic medium in which a signal is recorded by alternately magnetizing a north pole and a south pole every predetermined distance is attached to the surface of a metal plate. . The magnetic scale 10 is formed to have a length equal to or longer than the maximum distance for detecting movement by the position detection device. One period in which the N pole and the S pole change is one wavelength. The length of one wavelength is, for example, 400 μm.

  The magnetic head 20 is attached to an object (not shown) that moves in the longitudinal direction (x direction) of the magnetic scale 10 and moves with a certain distance (clearance) from the surface of the magnetic scale 10. When one wavelength of the signal recorded on the magnetic scale 10 is 400 μm, the clearance between the magnetic scale 10 and the magnetic head 20 is selected within a range of about 150 μm to 350 μm, for example. As an example, the clearance is set to 250 μm.

  The magnetic head 20 includes a plurality of magnetic sensors 21, 22, 23, and 24 that detect recording signals of the magnetic scale 10. For each of the magnetic sensors 21 to 24, for example, an AMR (Anisotropic Magneto Resistive) element or a TMR (Tunnel Magneto Resistance) element is used. In a magnetic sensor formed by these elements, the resistance value changes corresponding to the change in the magnetization direction of the recording signal. The above-described values of one wavelength and clearance are values applied when a TMR element is used as a magnetic sensor.

  Of the four magnetic sensors 21, 22, 23, and 24 provided in the magnetic head 20, the magnetic sensor 21 is a sensor that detects a recording signal as a sine waveform signal (SIN signal). The magnetic sensor 23 is a sensor that is disposed at a position shifted in the longitudinal direction of the magnetic scale 10 by a distance of ¼ wavelength with respect to the magnetic sensor 21 and detects a recording signal as a cosine waveform signal (COS signal). is there. These magnetic sensors 21 and 23 function as a main sensor that detects a SIN signal or a COS signal. The magnetic sensor 21 for detecting the SIN signal and the magnetic sensor 23 for detecting the COS signal are sensors for detecting the magnetization direction of the recording signal, and the length in the x direction is sufficiently smaller than the length of one wavelength.

A magnetic sensor 22 is arranged next to the magnetic sensor 21 that detects the SIN signal. Similarly, a magnetic sensor 24 is disposed next to the magnetic sensor 23 that detects the COS signal.
These magnetic sensors 22 and 24 are arranged at positions adjacent to the adjacent magnetic sensor 21 or 23 in the direction orthogonal to the x direction.
As shown in FIG. 2, in the magnetic sensors 22 and 24, the lengths L1 and L2 in the x direction are set to be equal to the length of one wavelength of the recording signal of the magnetic scale 10. For example, when one wavelength of the signal recorded on the magnetic scale 10 is 400 μm, the lengths L1 and L2 in the x direction of the magnetic sensors 22 and 24 are set to 400 μm.

  In the example of FIGS. 1 and 2, the magnetic sensor 21 is disposed adjacent to the center position in the x direction of the magnetic sensor 22 having a length of one wavelength. Similarly, the magnetic sensor 22 is disposed adjacent to the center position in the x direction of the magnetic sensor 24 having a length of one wavelength. Therefore, the magnetic sensor 22 detects a signal at the same position as the magnetic sensor 21, and the magnetic sensor 24 detects a signal at the same position as the magnetic sensor 23. It is to be noted that the magnetic sensors 21 and 23 are arranged at the center positions of the magnetic sensors 22 and 24 as described above, which is an example. If the recording signal can be detected, the magnetic sensors 21 and 23 may be arranged at positions slightly deviated from the center positions of the magnetic sensors 22 and 24.

  From these magnetic sensors 22 and 24, signals obtained by averaging the signals of the magnetic field in the range of one wavelength of the recording signal of the magnetic scale 10 are detected. That is, since the component (DC component) independent of the wavelength of the signal recorded on the magnetic scale 10 is detected from the magnetic sensors 22 and 24, the magnetic sensors 22 and 24 themselves have the signals recorded on the magnetic scale 10. Sensitivity to wavelength is zero. The component that does not depend on the wavelength is an unnecessary component for position detection, and corresponds to noise that is unrelated to the position detection signal recorded on the magnetic scale 10. In the following description, the detection signal of the magnetic sensor 22 disposed adjacent to the magnetic sensor 21 that detects the SIN signal is referred to as a SIN-DC signal, and the magnetic sensor disposed adjacent to the magnetic sensor 21 that detects the COS signal. A detection signal of the sensor 22 is referred to as a COS-DC signal.

[2. Example of output signal processing of each sensor]
FIG. 3 shows a circuit configuration for processing the output signals of the four magnetic sensors 21, 22, 23, 24 arranged in the magnetic head 20.
The SIN signal detected by the magnetic sensor 21 and the SIN-DC signal detected by the magnetic sensor 22 are supplied to the subtractor 31. The subtractor 31 detects a difference between the SIN signal output from the magnetic sensor 21 and the SIN-DC signal output from the magnetic sensor 22. The difference signal obtained by the subtracter 31 is supplied to the position acquisition unit 33 as a detection signal SIN (x) having a sine waveform.

  The COS signal detected by the magnetic sensor 23 and the COS-DC signal detected by the magnetic sensor 24 are supplied to the subtractor 32. The subtracter 32 detects a difference between the COS signal output from the magnetic sensor 23 and the COS-DC signal output from the magnetic sensor 24. The difference signal obtained by the subtracter 32 is supplied to the position acquisition unit 33 as a cosine waveform detection signal COS (x).

  The position acquisition unit 33 calculates the relative position x between the magnetic head 20 and the magnetic scale 10 by an arithmetic process using the two detection signals SIN (x) and COS (x) supplied. That is, from the calculation of [detection signal SIN (x) / detection signal COS (x)], the tangent waveform signal TAN (x) is obtained, and the value x of the signal TAN (x) is obtained to obtain the relative position x. Is done.

FIG. 4 shows a waveform example of each detection signal.
FIG. 4A shows a detection signal SIN (x) having a sine waveform output from the subtractor 31. The SIN signal detected by the magnetic sensor 21 includes a SIN-DC signal that is a noise component having a period longer than one wavelength. The signal SIN (x) from which the noise component has been removed by the subtractor 31 is included. can get.
FIG. 4B shows a cosine waveform detection signal COS (x) output from the subtractor 32. The COS signal detected by the magnetic sensor 23 includes a COS-DC signal that is a noise component having a period longer than one wavelength. A signal COS (x) from which the noise component has been removed by the subtractor 32 is obtained. can get.

  As shown in FIG. 4C, the position calculator 33 calculates TAN (x) = [detection signal SIN (x) / detection signal COS (x)] to detect the signal TAN (x). From this signal TAN (x), position information x is calculated as shown in FIG. 4D.

  Information on the relative position between the magnetic head 20 and the magnetic scale 10 calculated in this way is highly accurate position information based on a detection signal with little noise. That is, in the position detection device of this example, noise having a period longer than one wavelength period or noise having no periodicity is detected by the magnetic sensors 22 and 24, and the noise detected by the respective magnetic sensors 22 and 24 is detected. In use, a process of removing noise included in the magnetic sensors 21 and 23 is performed. Therefore, the sinusoidal detection signal SIN (x) and the cosine waveform detection signal COS (x) supplied to the position calculation unit 33 are not distorted by noise of a long wavelength component, and the position detection accuracy is improved. .

  The effect of removing this noise is particularly remarkable when the clearance between each magnetic sensor 21, 22, 23, 24 and the magnetic scale 10 is large. That is, when the clearance is large, the attenuation amount of the signal waveform recorded on the magnetic scale 10 is larger than the attenuation amount of the noise component that appears in a cycle longer than the wavelength of the signal recorded on the magnetic scale 10. End up. Here, by removing noise with the configuration of this example, even if the clearance between each magnetic sensor 21, 22, 23, 24 and the magnetic scale 10 is large, the detection accuracy can be improved.

[3. Other Embodiments (Examples with Harmonic Elimination Sensors)]
Next, another embodiment of the present invention will be described.
Each of the magnetic sensor 21 for detecting the SIN signal and the magnetic sensor 23 for detecting the COS signal included in the magnetic head 20 shown in FIGS. 1 and 2 is composed of one sensor. On the other hand, the magnetic sensors 21 and 23 for detecting the respective signals are constituted by a plurality of sensors, and the harmonic components of the sine waveform and the cosine waveform are removed by the calculation processing of the signals of the plurality of sensors. May be.

In FIG. 5, eight magnetic sensors 21a to 21h are arranged to remove harmonics of the SIN signal, and eight magnetic sensors 23 to 23h are arranged to remove harmonics of the COS signal. An example is shown.
For example, the eight magnetic sensors 21a to 21h that detect SIN signals are divided into a first group of magnetic sensors 21a to 21d and a second group of magnetic sensors 21e to 21h, and the four magnetic sensors of each group. The sensor is bridged to cancel even-order distortion. In addition, the two groups of magnetic sensors are arranged at intervals such that the resistance increases and decreases in the two groups are in opposite phases. Then, signals obtained by two groups of bridge connections are added by a differential amplifier to cancel odd-order (such as third-order) harmonic distortion.

  The eight magnetic sensors 23a to 23h that detect the COS signal are also divided into a first group of magnetic sensors 23a to 23d and a second group of magnetic sensors 23e to 23h. Bridge connection is performed, and signals obtained by the bridge connection of the two groups are added by a differential amplifier. In this way, the COS signal is also a signal in which even-order distortion and odd-order distortion are canceled.

  A magnetic sensor 22 having a length of one wavelength is disposed adjacent to the eight magnetic sensors 21a to 21h that detect the SIN signal, and the SIN-DC signal is detected by the magnetic sensor 22. Further, a magnetic sensor 24 having a length of one wavelength is disposed adjacent to the eight magnetic sensors 23a to 23h that detect the COS signal, and the COS-DC signal is detected by the magnetic sensor 24.

  The SIN signal obtained from the eight magnetic sensors 21a to 21h and the SIN-DC signal obtained from the magnetic sensor 22 are subtracted by the subtractor 31 shown in FIG. x) is obtained. Similarly, the COS signal obtained from the eight magnetic sensors 23a to 23h and the COS-DC signal obtained from the magnetic sensor 24 are subtracted by the subtractor 32 shown in FIG. (X) is obtained. The subsequent processing is the same as the processing described in FIG.

  As shown in FIG. 5, the sensor array for removing the harmonic distortion eliminates the harmonic distortion in the signal for position detection, and noise having a period longer than one wavelength period or noise having no periodicity. Together with the point to be removed, the detection accuracy is further improved. Note that the number and arrangement of a plurality of sensors for removing harmonic distortion shown in FIG. 5 are examples, and other numbers and arrangements of sensors may be applied.

[4. Other embodiment examples (examples having a plurality of sub-sensors)]
In the magnetic head described so far, an example in which one magnetic sensor 22 and 24 for noise component detection is arranged adjacent to one or one set of magnetic sensors is shown. On the other hand, a total of two sensors for detecting noise components may be arranged, one on each side of one or one set of magnetic sensors.
That is, for example, as shown in FIG. 6, a magnetic sensor 21 that detects a SIN signal and a magnetic sensor 23 that detects a COS signal are arranged on the magnetic head 20. A magnetic sensor 22a having a length L1 of one wavelength of the recording signal is arranged next to one of the magnetic sensors 21 for detecting the SIN signal, and the length of one wavelength of the recording signal is adjacent to the other of the magnetic sensors 21. An L2 magnetic sensor 22b is arranged.

  Further, a magnetic sensor 24a having a length L2 of one wavelength of the recording signal is arranged next to one of the magnetic sensors 23 for detecting the COS signal, and the length of one wavelength of the recording signal is arranged next to the other of the magnetic sensors 23. An L2 magnetic sensor 24b is arranged.

FIG. 7 is a diagram showing a circuit configuration for processing a detection signal of the magnetic head 20 in the example of FIG.
The adder 34 adds the detection signals of the two magnetic sensors 22a and 22b having one wavelength length. The signal added by the adder 34 becomes a SIN-DC signal. The subtractor 31 obtains the difference between the SIN-DC signal, which is a noise component obtained by the adder 34, and the SIN signal obtained by the magnetic sensor 21, thereby obtaining a sinusoidal signal SIN (x). .
Similarly, the adder 35 adds the detection signals of the two magnetic sensors 24a and 24b having a length of one wavelength. The signal added by the adder 35 becomes a COS-DC signal. The subtractor 32 obtains the difference between the COS-DC signal, which is a noise component obtained by the adder 35, and the COS signal obtained by the magnetic sensor 23, thereby obtaining a signal COS (x) having a cosine waveform. It is done.

Thus, by arranging the magnetic sensor for detecting the noise component on both sides in the direction orthogonal to the longitudinal direction of the magnetic scale 10, the removal of the noise component can be performed more effectively.
6 and 7 show an example in which one magnetic sensor 21 that detects a SIN signal and one magnetic sensor 23 that detects a COS signal are arranged. On the other hand, as shown in FIG. 5, in the case of a sensor configured to remove harmonic distortion, similarly, a magnetic sensor for detecting a noise component is arranged on both sides of each group of magnetic sensors. You may make it do.

[5. Other embodiments (example of optical scale)]
FIG. 8 is a diagram showing an example in which the present invention is applied to an optical scale.
The optical scale shown in FIG. 8 is prepared with a main scale 101 and a subscale 102 each having a lattice having a constant pitch, and the scales 101 and 102 are stacked with a certain angle. Then, light from the light source 110 is transmitted through the main scale 101 and the subscale 102, and the transmitted light is received by the optical head 120. Here, since the optical head 120 moves in the direction in which the grating of the main scale 101 is arranged, the waveform corresponding to the arrangement state of the grating is detected from the change in the light receiving state of the optical head 120, and the optical head 120 A moving position is detected.

Here, the optical head 120 includes a main sensor having a relatively narrow light receiving range and a sub sensor having a wide light receiving range. The sub-sensor is a sensor having a wide light receiving range that receives a signal having a width of one pitch (or an integer multiple of one pitch) of the grating disposed on the main scale 101. Therefore, the signal received and output by the main sensor is a signal whose level varies depending on the position of the lattice pattern. On the other hand, the signal received and output by the sub sensor is a signal that is not affected by the position of the lattice pattern.
Then, the output of the main sensor and the output of the sub sensor in the optical head 120 are supplied to the subtractor 121, and the subtracter 121 acquires the difference between both sensors. The output of the subtracter 121 becomes a detection signal for position detection.
With this configuration, it is possible to remove a noise component included in a signal received by the optical head 120, and it is possible to perform good position detection.

[6. Other variations]
The values such as 400 μm shown as the value of one wavelength and 250 μm shown as the numerical value of the clearance described in the above-described embodiment examples show a preferable example. It is not limited to. In addition, although the position detection device of this example has been described as one of the effects that the clearance can be expanded as compared with the conventional case, the present invention may be applied to a position detection device in which the clearance between the scale and the head is narrow. Of course. When the clearance is narrow, the amplitude of the detection signal of the sensor can be ensured accordingly, and the detection accuracy can be improved accordingly.

  In the above-described embodiment, the magnetic sensors 22 and 24 that are sub-sensors for detecting a noise component have a length of one wavelength of the signal recorded on the magnetic scale 10. On the other hand, the magnetic sensors 22 and 24 may have a length that is an integral multiple of one wavelength of the signal recorded on the magnetic scale 10. Even when the sensor has a length that is an integral multiple of the length of one wavelength, the sensitivity to the wavelength of the signal recorded on the magnetic scale 10 can be made zero, and the magnetic sensors 22 and 24 having a length of one wavelength can be set. The same effect as when used is obtained.

  In the example shown in FIGS. 1 to 3, a configuration is shown in which position detection is performed using a sinusoidal SIN signal and a cosine waveform COS signal. On the other hand, a magnetic sensor that obtains a -SIN signal or a -COS signal that has a phase opposite to that of each signal may be arranged to use the -SIN signal or the -COS signal when performing position detection. . Also in this case, a magnetic sensor having a length of one wavelength (or an integral multiple thereof) is arranged adjacent to the magnetic sensor that obtains the -SIN signal or -COS signal, and noise is removed from each signal. What should I do?

Further, the detection signal processing configuration of each sensor shown in FIGS. 3 and 7 is also a preferable example, and is not limited to the configuration described in FIGS. 3 and 7. For example, in the example shown in FIG. 3, the output signals of the magnetic sensors 21 and 23 that are the main sensors and the output signals of the magnetic sensors 22 and 24 that are the sub sensors are supplied to the subtracters 31 and 32. , 32 to take the difference. On the other hand, a position where two detection signals of the output signal of the main sensor and the output signal of the sub sensor are obtained, and other arithmetic processing using the two detection signals is performed to eliminate the influence of the noise component. Detection processing may be performed.
Further, in the configurations shown in FIGS. 3 and 7, only the configuration in which the calculation is performed by the subtractor or the adder is shown, but before performing the calculation such as the subtraction or addition, the detection signal of each sensor is displayed. On the other hand, after adjusting the amplitude (gain), subtraction or addition may be performed.

  In the above-described embodiment, the example in which the scale is applied to a linear position detection device has been described. On the other hand, the present invention may be applied to a position detection device that detects a relative rotation angle between a scale and a head by arranging a magnetic scale or an optical scale in a circular shape.

  DESCRIPTION OF SYMBOLS 1 ... Magnetic scale, 2 ... Magnetic head, 2a, 2b ... Magnetic sensor, 10 ... Magnetic scale, 20 ... Magnetic head, 21, 21a-21h, 22, 22a, 22b, 23, 23a-23h, 24, 24a, 24b DESCRIPTION OF SYMBOLS ... Magnetic sensor 31, 32 ... Subtractor, 33 ... Position calculating part, 34, 35 ... Adder, 101 ... Main scale, 102 ... Sub scale, 110 ... Light source, 120 ... Optical head, 121 ... Subtractor

Claims (7)

A scale that extends along the moving direction of the object to be position-detected, and repeatedly records signals for position detection at a fixed period;
A main sensor that is movable with the object, is disposed opposite to the scale, and detects a signal for position detection recorded on the scale;
A signal obtained by averaging signals for position detection within a range of the fixed period or an integral multiple of the fixed period, which is arranged at a position adjacent to the main sensor in a direction perpendicular to the moving direction of the object, is recorded on the scale. A secondary sensor to
A position detection device comprising: a position acquisition unit configured to acquire a position of the object based on an output signal of the main sensor and an output signal of the sub sensor. The position detection device according to claim 1, wherein the position acquisition unit acquires the position of the object based on a signal obtained by subtracting the output signal of the sub sensor from the output signal of the main sensor. The scale includes a magnetic medium, and the position detection signal is a signal in which a change in the magnetization direction of the magnetic medium is repeated at the predetermined period,
The said main sensor and the said subsensor consist of magnetic sensors, and the said subsensor is a magnetic sensor which has a detection sensitivity with respect to the signal of the range of the said fixed period, or its integral multiple signal. Position detection device. The main sensor includes a first phase main sensor and a second phase main sensor shifted by a predetermined phase with respect to the fixed period,
The position detection device according to claim 1, wherein the sub sensor is provided at a position adjacent to each of the first phase main sensor and the second phase main sensor. The position detection according to any one of claims 1 to 4, wherein the main sensor includes a plurality of sensors for detecting and canceling a harmonic component having a period of 1 / integer of the constant period. apparatus. The sub sensor includes a first sub sensor disposed at a position adjacent to one of the main sensors, and a second sub sensor disposed at a position adjacent to the other of the main sensors,
The position detection device according to any one of claims 1 to 5, wherein a signal obtained by averaging signals for position detection within a fixed period is detected from output signals of the first sub sensor and the second sub sensor. . In the scale, a signal for position detection is recorded by repeating a change in light transmission characteristics or reflection characteristics at the predetermined period,
The main sensor and the sub sensor are optical sensors that detect light transmission characteristics or reflection characteristics of the scale, and the sub sensor has a detection sensitivity with respect to a change in transmission characteristics or reflection characteristics within the fixed period. The position detection device according to claim 1 or 2.

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