JP2002116060A - Device and method for setting original signal on linear scale - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set the phase area of A-phase and B-phase signals and the output timing of an origin signal in a prescribed phase area. SOLUTION: The output timing of four detection signals comprising a sine wave A-phase signal indicating the relative movement amount of a linear scale, an inverted A-phase signal inverting the A-phase signal, a B-phase signal shifting 90 degrees for the A-phase signal, and an inverted B-phase signal inverting the B-phase signal and an origin signal indicating the origin passing position of the linear scale is detected, and the four detection signals are replaced by using chip jumper switches S1-S4 so as to make the phase area of the detected four detection signals the prescribed phase area to be output as the four output signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for setting an origin signal in a linear scale for measuring a relative movement amount between two objects.

[0002]

2. Description of the Related Art In a machine tool or the like, it is extremely important to accurately measure a relative movement amount of a tool with respect to a workpiece in performing precision machining, and various measuring devices have been commercialized. . As one of them, an optical scale using moire fringes obtained by superposing two optical gratings has been conventionally known. This optical scale is a transparent glass scale 100 as shown in FIG.
The main scale 101 is provided with a grid (marked line) so that the light-transmitting portion and the non-light-transmitting portion are arranged at a predetermined pitch on one surface, and the light-transmitting portion and the non-light-transmitting portion are provided on one surface of the transparent glass scale 102. And an index scale 103 provided with a grid (line) so that the index scale 103 is arranged at a pitch of .times .. As shown in FIG. As shown in FIG. 3B, the index scale 10 is tilted by a small angle with respect to the grid of the main scale 101.
3 grids are arranged. The main scale 101
The grid provided on the index scale 103 is formed of a grid having the same pitch formed by vacuum-depositing and etching chromium on the glass scales 100 and 102.

With this arrangement, moiré fringes shown in FIG. 4C occur. The interval between the moire fringes is W,
A dark portion or a bright portion occurs at every interval W. This dark or bright part is the main scale 10
In contrast to 1, the index scale 103 moves from top to bottom or from bottom to top depending on the direction in which the index scale 103 moves left and right relatively. In this case, if the pitch of the grids of the main scale 101 and the index scale 103 is P, and the mutual inclination angle is θ [rad], the interval W of the moire fringes is W
Is expressed as: W = P / θ, and the interval W between the moire fringes is an interval obtained by optically expanding the lattice interval P by 1 / θ. For this reason, when the grating moves by one pitch P, the moiré fringes are displaced by W, and by reading the change in the vertical direction of W, the amount of movement within the pitch P can be accurately measured. .

For example, as shown in FIG. 5, a photoelectric conversion element 110 for optically detecting a change in moire fringes is provided on an index scale, and a light source is provided on the opposite side of the main scale. The change in the current flowing through the photoelectric conversion element 110 is read while the scale 103 is relatively moved. That is, when the moire fringe pattern is in the state of A, the amount of light applied to the photoelectric conversion element 110 is the largest, and the current flowing through the photoelectric conversion element 110 is the maximum value I ₁ . Next, when the photoelectric conversion element 1 moves relatively to the state B, the photoelectric conversion element 1 is moved.
10 is slightly reduced, its current becomes I ₂ , and when it moves further to the state C, the photoelectric conversion element 1
10 is irradiated with the least amount of light, and its current is also the smallest I ₃ . Then, when further moved to the state D, the amount of light applied to the photoelectric conversion element 110 slightly increases,
Its current when moving to a state of I ₂ next, E, again becomes the most amount of high position, the current is a maximum value I _1. As described above, the current flowing through the photoelectric conversion element 110 changes sinusoidally, and the main scale 101 and the index scale 103 move relative to each other by the lattice interval P when one cycle of the change has elapsed.

In FIG. 5, only one photoelectric conversion element 110 is provided. However, as shown in FIG. 6, two photoelectric conversion elements 11 are shifted from one cycle (interval W) by 90 °.
1 and 112, the current flowing through the A-phase photoelectric conversion element 111 can be replaced by the B-phase photoelectric conversion element 112.
Is a current shifted by 90 ° as shown in FIG. That is, when the current flowing through the A-phase photoelectric conversion element 111 is a sine wave, the current flowing through the B-phase photoelectric conversion element 112 is a cosine wave. In this case, the phase of the current flowing in the B-phase photoelectric conversion element 112 with respect to the current flowing in the A-phase photoelectric conversion element 111 is 90 ° advanced or 90 ° depending on the relative movement direction of the main scale 101 and the index scale 103. If two photoelectric conversion elements are arranged shifted by 90 °, the relative movement direction can be detected by detecting the phase between the two. Actually, a photoelectric conversion element is additionally arranged at a predetermined position, and the A-phase signal and the B-phase signal are
° The inverted -A signal and the -B phase signal are configured to be output at the same time, and the inverted signal is used to remove the DC component included in the detection signal, and to improve the signal reliability and high-speed tracking performance. It is for securing.

FIG. 8 schematically shows a perspective view of an optical scale utilizing the principle described above. In this figure, a grid of the same pitch formed by evaporated chromium is engraved on one surface of an elongated main scale 101, and a U-shaped holder 10 holding the main scale 101 is provided.
The index scale 103 is fixed to one surface of the reference numeral 4. On the surface of the index scale 103 facing the main scale, a grid of the same pitch formed by chromium deposited in the same manner as the main scale 101 is engraved, and on the back side of the index scale 103, a photoelectric conversion element is provided. 113 are provided.

Further, as shown in FIG. 9, a light source 105 is disposed on a surface of the U-shaped holder 104 opposite to the main scale 101 to photoelectrically convert light transmitted through the main scale 101 and the index scale 103. Element 1
13 for detection. The main scale 101 and the index scale 103 are movable with respect to each other. Note that, as described above, the grid (index line) of the index scale 103 is opposed to the grid (index line) of the main scale 101 with a small interval, and is tilted by a small angle.

From the cross-sectional view 9 of the principle structure of the optical scale constructed as described above, the light emitted from the light source 105 passed through the glass main scale 101 and further passed through the glass index scale 103. Thereafter, the light is received as moire fringes by the photoelectric conversion element 113. From this photoelectric conversion element 113, 90
An A-phase signal and a B-phase signal having a phase difference of ゜ are output, and the moving direction and the moving distance can be measured from the two signals as described above. The photoelectric conversion element 11
3, three photoelectric conversion elements are provided, two of which output the A-phase signal and the B-phase signal, and the other outputs a reference level signal. Then, the light amount received by the photoelectric conversion element of this reference level is
By setting the average signal level (zero level) of the A phase or the B phase that changes in a sine wave shape, a detection signal with higher accuracy can be obtained.

FIG. 10A shows an apparatus for forming an A-phase signal and a B-phase signal, which is inverted from the A-phase signal obtained by providing four photoelectric conversion elements at predetermined positions on the index scale. The -A phase signal and the B phase signal and the inverted -B phase signal are shown. FIG. 10 (b)
Shows a circuit for forming a combined A-phase signal from the two A-phase signal waveforms. AP and -AP detect moiré fringes formed by light transmitted between the engraved lines of the scale. Photoelectric conversion element that converts the electric signal into an electric signal. One phase of the opposite sine wave current output from each photoelectric conversion element is inverted through an inverting amplifier A1, and is combined by an adder ADD using an operational amplifier OP.
A similar circuit is also used for synthesizing the B-phase signal. In this circuit configuration, the measurement signal from which the DC signal has been removed can be synthesized by one operational amplifier OP, so that the cost can be reduced. However, it is difficult to adjust the offset before the synthesis.
There is a problem that the balance between the A-phase (B-phase) signal and the -A-phase (-B-phase) signal is poor.

Therefore, as shown in FIG. 1C, the current-to-voltage converter A1 converts the signals output from the photoelectric conversion element AP and the signal output from the photoelectric conversion element -AP to a predetermined voltage level independently. , A2, and the two outputs are numerically added by a differential amplifier OP1 to obtain an A-phase signal. In this case, since the A-phase signal and the -A-phase signal are balanced, there is a feature that no distortion occurs in the signal waveform of the synthesized A-phase signal for measurement even when the scale moves at high speed.

FIG. 11 shows a main part of a signal generator for measuring a linear scale.
a ₁ , Pda ₂ , Pdb ₁ , A-phase signal as a detection signal output from Pdb ₂ , -A-phase signal, B-phase signal, and -B-phase signal are combined to measure A-phase signal and B-phase signal 1 shows a circuit configuration for forming a signal, and a circuit configuration for generating a later-described origin signal output from a photoelectric conversion element Pdz. In this figure, Ga1 is an amplifier for an A-phase signal as a detection signal, Ga2 is an amplifier for a -A signal as a detection signal, Gb1 is an amplifier for a B-phase signal as a detection signal, Gb
Reference numeral 2 denotes an amplifier for a −B phase signal as a detection signal, and Gz denotes an amplifier for an origin signal (hereinafter, referred to as a Z phase signal). These amplifiers are provided with a resistor R1 and a capacitor C1 as a feedback circuit, and as is well known, stabilize when configuring a high gain amplifier. In addition, for the amplifier of the -A phase signal as the detection signal and the -B phase signal as the detection signal output as the opposite phase signal, a part of the resistor R is a variable resistor ΔR, and the subsequent addition circuit Ga3 or Gb
3 is adjusted so that the amplitudes of the signals when they are combined are substantially the same.

The offset voltage is supplied from the positive-phase input terminal to each of the A-phase signal / B-phase signal amplifiers so that the DC components have the same level.
In this way, the negative-phase components of the amplifiers are supplied to the adders Ga3 and Gb3 via the resistor R2, and the sine wave-shaped measurement A-phase signal and the B-phase signal from which the DC component has been removed are formed at the output thereof. Is done. Each of the adders Ga3 and Gb3 is also provided with a feedback circuit having an impedance Z1 for stabilizing the phase state, so as to reduce unstable elements due to the phase rotation of the high frequency band.

The optical scale constructed as described above is mounted on an NC machine tool and measures the relative movement amount between the workpiece and the tool. In general, when performing numerical control, the optical scale from the origin is used. Since it is programmed as a movement amount, this relative movement amount needs to be measured as a movement amount from the origin. Therefore, an origin position is usually provided in advance on the main scale, and the origin is detected when the index scale passes through the origin position.
By resetting the NC device supplied to the C device, the origin position is set in the NC device.

Therefore, in the photoelectric linear scale as described above, as shown in FIGS. 11 and 12A, the origin Z serving as a reference point is set at a predetermined track position different from the engraved line position of the main scale 101. Marking line (grating) 10 shown
9 and a photoelectric conversion element Pdz that detects light passing through the grating 109 serving as the origin and the index scale 103 as moiré fringes is arranged, the main scale 101 and the index scale 103 have a specific positional relationship. Is detected as a signal of the origin (Z-phase signal).

That is, as shown in FIG. 12B, even at the position of the origin Z, a signal Sz that changes during one pitch P of the main scale 101 as in the case of FIG. 5 is detected as the origin position detection signal. Therefore, when the peak point of the waveform of the origin position detection signal Sz is clipped at a predetermined level TH, for example, as shown in FIG. The point can be set as the origin Z of the main scale, or the peak position of the origin pulse signal Pz can be detected and set as the origin Z of the main scale.

[0016]

The position detection signal Sz of the origin (hereinafter referred to as "Z-phase signal") is generally detected by the relative movement of the main scale 101 and the index scale 103. Since the Z-phase signal operates asynchronously with respect to the A-phase signal or the B-phase signal, as shown in FIG. Where the peak P of the Z-phase signal (hereinafter, also referred to as “Z-phase”) is detected in the four phase areas indicated by,..., Cannot be known until after outputting the Z-phase signal. Was. FIG.
In (c), the peak P of the Z-phase signal is detected in the phase area within one pitch.

The digital output type scale performs various adjustments at the time of assembly, but there is no need to adjust the timing for synchronizing the Z phase because the origin signal operates asynchronously. However, if this is to be used on an analog output type scale, a synchronized Z phase cannot be obtained, so that it cannot be used as it is. In the analog output scale, the peak position P of the Z-phase signal is
For the A-phase signal and the B-phase signal, they must be output in a certain fixed phase area shown in FIG.
That is, it is almost standardized that the signals are output in a phase area in which both the A-phase signal and the B-phase signal in FIG. 12C are positive (indicated by a hatched line in the figure). Which area of the phase area to which is output can be checked for the first time in the adjustment stage after assembly, and cannot be known in advance.

For this reason, a waveform shaping circuit HS as shown in FIG. 11 is provided to adjust the scale in order to obtain the timing (synchronization) of the phase area of the A-phase signal / B-phase signal and the output of the origin signal. Usually, the timing is adjusted by adjusting the detection timing of the Z-phase signal. Adjustment of the Z-phase detection timing is performed by changing the threshold value TH shown in FIG.
a method of shifting the detection timing to an area located in z,
There are a method of providing a delay circuit to delay the output timing, a method of providing a phase shift circuit to shift the phase, and the like. All of these methods work while the operator visually observes the oscilloscope. Tweaking was a rather difficult task.

[0019]

According to the present invention, the output timing of the Z-phase signal is determined by securing the output timing of the Z-phase signal and exchanging the A-phase signal / B-phase signal from the photocell. The origin signal is set so as to enter the phase area of the A-phase signal / B-phase signal.

According to the first aspect of the present invention, a linear scale provided with scales at regular intervals in the moving direction, a sine-wave A-phase signal representing the relative movement of the linear scale, and the A-phase signal inverted. Detecting as four sets of measurement signals including an A-phase signal, a B-phase signal shifted by 90 degrees from the A-phase signal, and an -B-phase signal obtained by inverting the B-phase signal;
Detecting means for detecting an origin signal indicating the origin passing position of the scale; signal synthesizing means for forming an A-phase measurement signal having a phase difference of 90 degrees from the four sets of measurement signals, and a B-phase measurement signal; Switching means for selectively supplying the four sets of measurement signals to the signal synthesizing means, and wherein the switching means selectively supplies the four sets of measurement signals to output the signal from the signal synthesizing means. An apparatus for setting an origin signal in a linear scale, wherein a predetermined phase region of an A-phase measurement signal or a B-phase measurement signal can be matched with the output timing of the origin signal.

According to a second aspect of the present invention, the relative movement amount of the linear scale is shifted by 90 degrees with respect to a sinusoidal A-phase signal, a -A-phase signal obtained by inverting the A-phase signal, and the A-phase signal. Detecting four sets of detection signals consisting of a B-phase signal and a −B-phase signal obtained by inverting the B-phase signal; detecting an origin signal indicating the origin passing position of the linear scale; Detecting the phase region of the detection signal and the output timing of the origin signal, and exchanging the four detection signals so that the four detection signal phase regions become a predetermined phase region. And forming an A-phase measurement signal and a B-phase measurement signal having a phase difference of 90 degrees from each other from the four sets of output signals. Swap four sets By outputting the signal as an output signal, a predetermined phase region of the A-phase measurement signal or the B-phase measurement signal output from the signal synthesizing unit can be matched with the output timing of the origin signal. This is how to set the origin signal in the linear scale.

[0022]

FIG. 1 is a block diagram of a measurement signal generation circuit according to the present invention. The same components as those in FIG. 11 are denoted by the same reference numerals, and detailed description thereof will be omitted. In addition,
Each phase signal output from the photoelectric conversion element is referred to as a detection signal, and is simply referred to as A, -A, B, or -B in the figure, and the signals output from the amplifiers Ga1, Ga2, Gb1, and Gb2 are output signals. In the figure, simply SA, -SA, SB,-
The signal synthesized by the amplifiers Ga3 and Gb3 is referred to as SB, and the signal synthesized by the amplifiers Ga3 and Gb3 is referred to as a measurement signal.

The measurement signal generation circuit includes an input section of the photoelectric conversion element, an output section of each phase signal as a detection signal, an output section of each phase signal as a detection signal after replacement, an output signal of each amplified phase, Each phase signal section as a synthesized measurement signal is configured, and between the output section of each phase signal as an output signal and the output section of each phase signal as a replacement detection signal, a detection signal as a detection signal is provided. Chip jumper switches S1 to S4 for replacing each phase signal are provided.

FIG. 2 is a waveform diagram showing the relationship between the output timing of the Z-phase signal (origin signal) and the area of each detected phase signal according to the embodiment of the present invention. In this figure,
A-phase signal, -A-phase signal, B-phase signal as each detection signal,
The -B phase signal waveform indicates a sinusoidal signal detected by the movement of the scale as described above, and 1P indicates a period passing between the engraved lines of the scale. A
Phase signal (hereinafter referred to as phase A), phase A signal inverted-
A-phase signal (hereinafter, referred to as -A phase), B-phase signal (hereinafter, referred to as -A phase)
It is called phase B. ), The -B phase signal obtained by inverting the B phase signal (hereinafter referred to as -B phase) is output as a signal of one pitch between times t0 and t1, and is one pitch (hereinafter, 1P).
That. A), -A phase, B phase, -B phase signal
Two phase areas (0 to 90 degrees, 90 to 180 degrees, 1
80 degrees to 270 degrees, 270 degrees to 360 degrees), a phase area of 0 degrees to 90 degrees, a phase area of 90 degrees to 180 degrees, and so on.

FIG. 3 shows that the B-phase signal is 90
When the signal of the A phase, -A phase, B phase, and -B phase is a positive signal in each phase area in 1P, it is 1 when the signal is a positive signal, and 0 when the signal is a negative signal in each phase area. Origin signal Z1
The case where Z4 is output is patterned by binary signals 1 and 0.

As described above, in the analog output type scale, it is almost standard that the A-phase and the B-phase both output in the positive phase area with respect to the A-phase and the B-phase as the measurement signals. Has been According to the present invention, when the scale is adjusted, the detected A (-A) phase and B (-B) phase signals are selected so as to match a predetermined phase area in accordance with the timing of the Z phase signal. This is for setting the origin signal. That is, in accordance with the timing of the output of the Z-phase signal (origin signal), the A-phase and -A detected from the photocell are detected.
By replacing the phase, B phase, and -B phase signals to obtain each phase signal as an output signal, the Z-phase origin signal is put into a predetermined phase region of the measurement A-phase signal and the B-phase signal. be able to. The phases (or polarities) of the A-phase, -A-phase, B-phase, and -B-phase signals can be displayed and confirmed using a display device such as an oscilloscope.

Origin signals Z1 to
Z4, the output generation timing of this signal and FIG.
The positive polarity phase signals of the phase signals shown in FIG. 3 are as follows. Generation timing Origin signal Positive polarity detection signal Phase area Z1 A phase, B phase Phase area Z2 A phase, -B phase area Z3 -A phase, -B phase Phase area Z4 -A phase, B phase

A phase for measurement at the timing of output of the Z phase,
To adjust so that both B phases are in the positive phase area,
The phase is changed by switching and supplying the signals of the A (-A) phase and the B (-B) phase. That is, as is clear from FIG. 3, the phase area becomes positive at the timing when the peak of the origin signal is output in the phase area,
A signal whose next phase area is also positive is defined as an A-phase signal for measurement, the A-phase signal is input as an SA signal to the differential amplifier Ga3 to form this signal, and the -SA signal is used as an -SA signal.
Select the A-phase signal. In this phase area, the B-phase signal is selected as the SB signal and the -B-phase signal is selected as the -SB signal for the differential amplifier Gb3 that forms the B-phase signal for measurement.

As described above, the generation timing of the origin signal Z1 is synchronized with the phase area. Since both the A phase and the B phase output in the phase area are positive, the signals of each phase are output as they are. Captured as signals SA and SB,
That is, the inverted signal may be taken in as -SA and -SB. The relationship between the detection signal and the output signal is as follows. A → SA −A → −SA, B → SB −B → −SB

When the generation timing of the origin signal Z2 is synchronized with the phase area, a positive signal is detected in both the phase area where the peak of the origin signal is output and the next phase area. Since the −B phase is obtained, the −B phase signal is taken in as the output signal SA phase signal, and the signal in which the phase area where the peak of the origin signal is output is positive and the next phase area is negative is the A phase signal. Therefore, it is sufficient to take in as the output signal SB. The relationship between the detection signal and the output signal is as follows. −B → SA B → −SA, A → SB −A → −SB

When the generation timing of the origin signal Z3 is synchronized with the phase area, a signal in each phase in which both the phase area where the peak of the origin signal is output and the next phase area are positive is: Since it is the detected -A phase, -A
The phase signal is captured as an output signal SA phase signal, and the signal in which the phase area where the peak of the origin signal is output is positive and the signal in the next phase area is negative is the -B phase signal.
What is necessary is to take in as B. The relationship between the detection signal and the output signal is as follows. −A → SA A → −SA, −B → SB B → −SB

When the generation timing of the origin signal Z4 is synchronized with the phase area, a signal in each phase in which both the phase area where the peak of the origin signal is output and the next phase area are positive is: Since it is a detected B-phase signal,
The B-phase signal is fetched as an output signal SA-phase signal, and the signal in which the phase area where the peak of the origin signal is output is positive and the next phase area is negative is the -A phase signal. What is necessary is just to take in as a phase signal. The relationship between the detection signal and the output signal is as follows. B → SA −B → −SA, −A → SB A → −SB

The chip jumper switches S1 to S4 shown in FIG. 1 replace the detection signals applied when the B-phase signal detected as described above is advanced in phase with respect to the A-phase signal. Switch. The operator installing the linear scale checks the phase area of the peak position of the origin signal using an oscilloscope. If the phase area is located in the area, the switches S1 to S4 are connected to the contact point P1.
And the connection state shown in FIG.

Similarly, when the peak position of the origin signal is located in the phase area, the operator switches each of the switches S1 to S1.
4 is connected to the contact point P4, and when the peak position of the origin signal is located in the phase area, the switches S1 to S4 are connected to the contact point P3. When the peak position of the origin signal is located in the phase area, each switch S1 is connected. To S4 are connected to the contact point P2 so that the Z-phase generation timing is always the A-phase signal, B-phase
The phase signal can be synchronized with a phase area of a positive phase. The switches S1 to S4 operate in conjunction with the contacts P
It is also possible to control to select 1 to P4.

[0035]

As described above, according to the present invention, since the generation timing of the origin signal and the phase regions of the A-phase signal and the B-phase signal can be selected at intervals of 90 degrees, a desired origin signal can be set. , The setting operation can be easily performed.

[Brief description of the drawings]

FIG. 1 shows a block diagram of a measurement signal generation circuit according to the present invention.

FIG. 2 is a waveform diagram showing one pitch of an A-phase signal and a B-phase signal according to the present invention in four regions (regions obtained by dividing one cycle by 90 degrees).

FIG. 3 shows the polarity of each phase signal for each phase area of one pitch,
It is a pattern diagram which shows the relationship of the timing which the generation timing of a Z phase is located as a polarity pattern.

FIG. 4 is a view showing the principle of an optical scale and showing moire fringes.

FIG. 5 is a diagram showing the movement of moiré fringes.

FIG. 6 is a diagram showing a position where a photoelectric conversion element is installed.

FIG. 7 is a waveform diagram of an A-phase signal and a B-phase signal.

FIG. 8 is a perspective view of an optical scale.

FIG. 9 is a sectional view of an optical scale.

FIG. 10 is a principle diagram of a measurement signal generation circuit.

FIG. 11 shows a block diagram of a measurement signal generation circuit.

FIG. 12 is an explanatory diagram showing a grid for detecting an origin position and a detected waveform.

[Explanation of symbols]

Pda1, Pda2, Pdb1, Pdb2 photoelectric conversion elements, Ga1, Ga2, Ga3, Gb1, Gb2, Gb3 amplifiers, S1 to S4 chip jumper switches,

Claims (2)

[Claims] A linear scale provided with scales at regular intervals in a moving direction; a sinusoidal A-phase signal representing a relative moving amount of the linear scale; a −A-phase signal obtained by inverting the A-phase signal; Detected as four sets of measurement signals consisting of a B-phase signal shifted by 90 degrees with respect to the A-phase signal and a −B-phase signal obtained by inverting the B-phase signal, and an origin indicating the origin passing position of the scale Detection means for detecting signals; signal synthesis means for forming an A-phase measurement signal and a B-phase measurement signal having a phase difference of 90 degrees from each other from the four sets of measurement signals; Switching means for selectively supplying a set of measurement signals, wherein the A-phase measurement signal or the B-phase measurement output from the signal synthesizing means by the selective supply of the four sets of measurement signals by the switching means. Faith Setting device the origin signal in the linear scale, characterized in that it is possible to match the output timing of a predetermined phase region and the origin signal. 2. A sinusoidal A-phase signal representing the relative movement of the linear scale, a -A-phase signal obtained by inverting the A-phase signal, and a B-phase signal shifted by 90 degrees with respect to the A-phase signal. Detecting the B-phase signal as an inverted set of -B-phase signals; detecting an origin signal indicating the origin passing position of the linear scale; and detecting the phase of the four sets of detected signals. Detecting the output timing of the area and the origin signal; and exchanging the four sets of detection signals so that the detected phase areas of the four sets of detection signals become a predetermined phase area, and outputting as four sets of output signals. And forming an A-phase measurement signal and a B-phase measurement signal having a phase difference of 90 degrees from each other from the four sets of output signals. The four sets of output signals are replaced by the four sets of detection signals. As a signal In the linear scale, a predetermined phase region of the A-phase measurement signal or the B-phase measurement signal output from the signal synthesizing unit can be matched with an output timing of the origin signal. How to set the origin signal.