JPH04130218A - Position detecting apparatus - Google Patents

Abstract

PURPOSE:To make the positions of the original points of a plurality of graduations formed on a scale in parallel agree substantially in a broad range by shifting the phases so that the difference between the amounts of the phases become the zero value when the positions of the original points of the first and second graduations are detected. CONSTITUTION:When an original-point positions S2 of a second graduation 3 is made to agree with an original-point position S1 of a first graduation 2, the original-point position S2 of the graduation 2 is detected with a phase detecting circuit 5 based on a phase amount theta1, and the original-point position S2 of the graduation 3 is detected with a phase detecting circuit 7 based on the phase amount theta2. For example, the phase amount theta2 detected with the phase detecting circuit 7 is shifted with a phase shifting circuit 11 so that the difference theta2 - theta1 between the phase amounts becomes the zero value. Thus, the original-point position S2 of the graduation 3 can be made to agree substantially with the original-point position S1 of the graduation 2. When the original-point position S1 of the graduation 2 is made to agree with the original- point position of the graduation 3, the phase shifting circuit 11 is inserted between the phase detecting circuit 5 and an absolute-position detecting circuit 8. Thus, the agreement can be obtained by the same way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a position detection device suitable for application to, for example, machine tools and precision length and angle measurement devices.

[Summary of the Invention] The present invention provides a position detection device suitable for application to, for example, machine tools and precision length and angle measuring devices, which includes at least first and second scales having different wavelengths and formed in parallel. and the first and second scale in this scale.
first and second phase detection circuits that detect the phase amount of the scale; and an absolute position detection circuit that calculates the absolute position on the scale based on the phase amount detected by the first and second phase detection circuits. A position detection device comprising: a phase shift circuit connected to the first or second phase detection circuit; the phase shift circuit detects the phase detected by the first or second phase detection circuit; By shifting the phase of the amount, the origins of the first scale and the second scale formed on the scale are made to substantially coincide.

In addition, the present invention provides a scale in which a periodic scale and a non-periodic scale arranged in parallel with the periodic scale and encoded with an absolute position are formed in such a position detection device, and a scale in which an absolute position is coded. a phase detection circuit that detects the phase amount of the periodic scale; a code detection circuit that detects a code from the aperiodic scale on the scale; and a phase detection circuit that detects the phase amount detected by the phase detection circuit and the code detection circuit. A position detection device includes an absolute position detection circuit that calculates the absolute position of the scale from the detected code, and a phase shift circuit connected to the phase detection circuit, and the phase shift circuit detects the phase. By shifting the phase amount detected by the circuit, the origins of the periodic scale and the aperiodic scale formed on the scale are made to substantially coincide.

[Prior Art] Various absolute position detection devices have been proposed in the past that detect the amount of relative displacement between two relatively displaced members as an absolute position from an origin on a scale.

For example, the patent application filed by the present applicant in Japanese Patent Publication No. 50-2361
A magnetic absolute type position detection device disclosed in Publication No. 8 can be cited (see FIG. 5). In FIG. 5, (1) is a scale, which is made of magnetic material. On this scale (1), a first magnetic scale (2) with a wavelength λ1 and a second magnetic scale (3) with a wavelength λ2 (λ2 x λ1) are formed in parallel. In addition,
For example, in optical scales, the term grating pitch is used instead of the term wavelength, but in order to avoid complexity, the term wavelength will be used in the following explanation.

A pair of magnetic flux-responsive magnetic heads (4A) (4B) for reading the first magnetic scale (2) are arranged at intervals (integer ±17
4) This magnetic head (4A) (4B
) is a phase detection circuit (
5). Also, a pair of magnetic flux responsive magnetic heads (6A) for reading the second magnetic scale (3).
(6B) are provided at intervals (integer ±174) λ2, and this magnetic head (6A) (6B) is used to detect the phase amount θ2 (absolute position within one wavelength λ2) within one wavelength λ2 (2π radians). is connected to the phase detection circuit (7).

The phase amount θ1, which is the output signal of the phase detection circuit (5), is supplied to one input terminal of the absolute position detection circuit (8). The phase amount θ2, which is the output signal of the phase detection circuit (7), is supplied to the other input terminal of the absolute position calculation and detection circuit (8).

In the absolute position detection circuit (8), the phase difference Δθ (θ2-01)
is calculated, and based on this phase difference Δθ, the origin position on the scale (1), for example, the first and second
The displacement amount from the left end of the magnetic scales (2) and (3) is calculated, and the calculated displacement amount is displayed on the display (10).

Next, the operation of the above conventional example will be explained in more detail.

First, from the phase detection circuit (5) to the magnetic head (4A) (
4B), excitation signals IA and IB shown in equations (1) and (2) are supplied.

I A = A coslcf t = (1)
IB=A cos (πft+π/4)・・・・・・(
2) However, A is a constant and f/2 is the excitation frequency. In this case, the phase detection signal KA expressed by the following equations (3) and (4) from the magnetic heads (4A) (4B)
and KB are supplied to the phase detection circuit (5).

KA=A1sin (2z x /λ1) cos 2
x f t = (3) KB-Alcos (2z x
/λ1) sin 2g f t ... (4) However, A1 is a constant, and X is the left end of the magnetic opening @ (2) < 3)
This is the amount of displacement when = 0 (origin position).

Then, in the phase detection circuit (5), the phase detection signal K
A and KB are added to form a displacement signal d (Equation (5)), and from this displacement signal d, a phase amount θ1 (Equation (6)) is obtained.
form).

d=KA+KB=A1ain (2z f t +2$ x /λ1)
-Alsin (2K f t+01) -(
5) θ1-2πX/λ1...(
6) The relationship between the phase amount θ1 and the displacement amount X is as shown in FIG. 6A, for example, when the phase amount θ1 is π, the displacement amount X is xo+xL x2. Although it is not possible to determine which of
Therefore, the amount of displacement X can be detected as an absolute position.

Similarly, the phase detection circuit (7) measures the phase amount θ2 which takes a value of 0 to 2π at the wavelength λ2 with respect to the displacement amount X. Therefore, the phase amount θ2 is θ2=2πX/λ2 (7
) (see Figure 6B).

The above-mentioned phase amount θ1 and phase amount θ2 are supplied to the absolute position detection circuit (8), and the phase difference Δθ (Δθ=02-61) is first calculated in the absolute position detection circuit (8). This phase difference Δθ is expressed as follows from equations (6) and (7).

Δθ = 02-01 = 2gx (1/λ2-1/λ1) = 2πX (λ1-λ2)/(λ1λ2)...(8) Solving this equation for the displacement amount X yields equation (9). .

! == (Δθ/2π)λ1λ2/(λ1−λ2)
(9) Next, the absolute position detection circuit (8) calculates the displacement amount X based on this equation (9) and supplies it to the display (9).

The display (9) visually displays the amount of displacement X. In this case, if the phase difference Δθ is within the range shown by equation (10), the displacement X can be uniquely determined, so the maximum measurement length at which the displacement X can be accurately measured as an absolute position is 11) It is expressed by the formula.

O, ≦ Δθ ku2π ... (10)
L-(λ1λ2)/(λ1-λ2) ...(1
1) Therefore, the relationship between the displacement amount X and the phase difference Δθ is the sixth
As shown in FIG. C, by measuring the phase amount θ1 and the phase amount θ2, the displacement amount X can be accurately measured using an absolute method.

Further, as another conventional absolute type position detection device, there is also a device using a gray code as shown in FIG. In this Fig. 7, (17) is the base of the scale, and this base (17) is attached to one of the two relatively displaceable members, and a magnetic material is attached to the negative side of this base (17). A first scale (18) on which a magnetic graduation (2o) with a wavelength λ is formed is attached, and a non-magnetic material (for example, a non-magnetic stainless steel sheet) is attached so as to cover the first scale (18). The second scale (19) is formed of a gray code (21) of bits with a resolution r
Attach.

For example, the second gray code (21) may include depositing an anti-reflection film on the outer surface of the second reflective scale (19) except for the portion corresponding to the high level "1", or The surface of the non-reflective second scale (19) is roughened by etching except for the part corresponding to the high level "1", or a reflective metal film (chrome It can be formed by a method such as vapor deposition (film, etc.).

A detection head (22) facing the gray code (21) is attached to the other of the two relatively displaceable members and is movable in the direction of arrow X.
) are placed. This detection head (22) is connected to a signal processing device by a signal cable (22a).

Figure 8 shows the internal structure and signal processing device of the detection head (22), including a first detector (23A) for reading the magnetic scale (20) and a second detector for reading the Gray code (21). The first detector (23A) includes a pair of flux-responsive magnetic heads (24A) spaced apart by (integer ±174)λ.
(24B). This magnetic head (24
A) A phase detection circuit (25) is connected to (24B), and this phase detection circuit (25) is connected to the position detector (24B) of the example in FIG.
5) Similar to (7), magnetic head (24A) (24B)
In addition to supplying excitation signals to the magnetic heads (2
4^) The phase detection signal output from (24B) is processed to detect the displacement amount X of the detection head (22) as the phase amount θ. Similarly to equation (6), the phase amount θ is θ=
Since it is expressed as 2πX/λ (6A), the relationship between the phase amount θ and the displacement amount X is as shown in FIG. 9B.

The second detector (23B) includes a light emitting element (26), a collimator lens (27), and a second scale (19) that measures parallel light beams.
), a cylindrical lens (29) that converges the parallel rays reflected from the second scale (19), and a reference window corresponding to the gray code (21). Index plate (30)
and a photodetector array (31) consisting of photodetectors.
The absolute position code detection circuit (32
), and this absolute position code detection circuit (32) decodes the bit output signal thereto to obtain absolute position data N.
get. The phase amount θ obtained by the phase detection circuit (25) and the absolute position data N obtained by the absolute position code detection circuit (32) are respectively supplied to the absolute position detection circuit (33). 33) supplies the displacement amount (ie, absolute position X) determined according to the procedure described later to the display (34). A display (34) displays the absolute position X.

In explaining the operation of the absolute position detection circuit (33),
In this example, the magnetic scale (20) and the gray code (
21), but for convenience of explanation, both are
As shown in Figure A, the magnetic scale (
It is assumed that the first detector (23A) and the second detector (23B) corresponding to the gray code (20) and the gray code (21), respectively, are located at a position P in the X direction (FIG. 9B). In this case, if the absolute position within one wavelength λ of the magnetic scale (20) including the position P is ΔX, one wavelength of the magnetic scale (20) including the position P is from the origin x=0 to the nth (n=1
．． 2. ...), the amount of displacement X at that position P is x=(n-1)λ+Δx = (12)
It is expressed as In this case, since the phase amount θ is known,
Since ΔX is expressed by equation (6A) as ΔX=λθ/2π (13), the displacement amount X can be calculated by finding the integer n.

In this example, in order to facilitate the calculation of the integer n, the resolution rm of the Gray code (21) is calculated using an integer m of 2 or more with respect to the wavelength λ of the magnetic scale (20). =λ/m (14) Assume that the relationship holds. The state shown in FIG. 9 corresponds to the case where rm=λ/2, that is, m=2. In this case, by generalizing the state in FIG. 9, the Gray code at position P (
There is a difference between the absolute position data N obtained by decoding FIG. 9C) and the integer n-1 indicating the period of the magnetic scale (20).
n −1= I NT (N7m) ”(15
) is clearly related. Note that in equation (15), INT(N7m) represents the integer part of N/m. In the example in Figure 9, the value of N at position P is 2 (
n-1), INT (N7m) is n-1.

As is clear from the above explanation, the absolute position detection circuit (33
), first, the absolute position ΔX within one wavelength λ of the magnetic scale (20) is calculated according to equation (13) using the phase amount θ supplied from the phase detection circuit (25),
Also, according to Equation 15, one wavelength λ of the magnetic scale (20)
An integer n-1 indicating the position of the unit is calculated. Then, the calculated absolute position ΔX and integer n-1 are set to the (12th
), the displacement amount X, which is the absolute position as a whole, is calculated.

In this way, an absolute type position detection device can also be realized in the example shown in FIG.

[Problems to be Solved by the Invention] By the way, in the conventional position detecting device shown in the examples of FIGS. , a second magnetic scale (3) with a wavelength λ2 (λ2≠λ1, similarly, one wavelength corresponds to 2π radians), and in this case, the first magnetic scale (2) and the second magnetic scale (3) are formed in parallel. It is necessary that the origin positions in the length direction (for example, the respective left end positions) of the magnetic scales (3) of No. 2 and No. 2 coincide with each other. When measuring the displacement amount X in the length direction, the first phase amount θ detected from the first magnetic scale (2)
1 and the second phase amount θ2 detected from the second magnetic scale (3), the displacement amount This is because if the origin position deviates, a so-called offset error will occur.

However, when manufacturing the position detection device shown in the examples in FIGS. 5 and 6, it is difficult to manufacture the position detection device due to limitations such as the accuracy of the manufacturing equipment and the restriction that the magnetic scale cannot be seen with the naked eye. 1 magnetic scale (2) and the second magnetic scale (
There was a problem in that it was difficult to accurately match the origin position with 3).

Further, when one of the scales is a printed scale, there is a further problem in that it is difficult to accurately align the origin positions.

Furthermore, in the conventional position detection devices shown in the examples of FIGS. 7 to 9, it is difficult to always accurately form the resolution rm of the Gray code (21) to 1/m of the wavelength λ of the magnetic scale (20). , and the integer n− calculated according to equation (15)
1 may include an error of ±1. To explain in detail, when the origin of the magnetic scale (20) and the origin of the Gray code (21) match, including the detector, and rs+=λ/m holds, as shown in FIG. 10A, The point at which the phase amount θ of the magnetic scale (20) returns to zero value (hereinafter referred to as the change point of the magnetic scale (20) as necessary) coincides with the code change point of the Gray code (21), so there is no difference. There is no inconvenience. However, in reality, it is difficult to match both origins, and manufacturing variations occur in the resolution r- of the Gray code (21). Between the change point of 20) is the magnetic scale (20)
For example, as shown in FIG. 10B, the Gray code (
If the code change point in 21) is deviated by 61 in the child direction, the value of TNT (N/m) will be smaller than the original value within the range where the detector position P is in the region of deviation δ1. is also reduced by 1, causing the disadvantage that the displacement amount X calculated from equation (12) becomes a value smaller than the true value by λ.

Therefore, in order to eliminate these drawbacks of the conventional position detecting devices shown in the examples of FIGS. 7 to 10, the present applicant has proposed a technique disclosed in Japanese Patent Application No. 1-189166. This technique, for example, as shown in FIG.
The scale (3
5), a first detector (39) that reads the first scale (36) and generates a position detection signal, and a Gray code (37).
) to generate an absolute position signal by reading the second detector (
40) and a detection head (38) arranged to be movable relative to the scale (35), and a phase detection head (38) for detecting the absolute position within one wavelength of the first scale (36) from the phase detection signal. a detection circuit (41); an absolute position code detection circuit (42) for detecting the absolute position of the first scale (36) with a resolution λ/l from the absolute position signal; A correction value calculation circuit (43) that determines a correction value so that it matches the absolute position with a resolution of λ/2.
and an absolute position detection circuit (44), and the absolute position detection circuit (44) detects the absolute position with the resolution λ/l,
This technique is capable of detecting the amount of displacement between the scale (35) and the detection head (38) as an absolute position using the absolute position within one wavelength λ and the correction value.

Further, the technique shown in the example of FIG. 11 will be explained in detail. As the periodic eye 1 (36), a magnetic scale, an optical grating, an electromagnetic induction conductive pattern, etc. can be used, and as the Gray code (37), for example, the Gray code (
21).

In this example, the resolution λj of the Gray code (37) is λl=λ/l (16
). However, in this example, the resolution λl of the Gray code (37) does not need to satisfy Equation (15) over the entire measurement range, and is allowed to have some error. If the deviation of the code change point of the Gray code (37) with respect to the position where the phase amount θ of the scale (36) is 0 is δ, then in this example, δ1<λ/3 ... (17
) is allowed within the range in which the deviation δ is allowed. Therefore, errors in the resolution λ of the Gray code (37) and deviations in the origin between the Gray code (37) and the scale (36) are allowed as long as Equation (17) is satisfied.

Also, in actual manufacturing, the deviation δ is 100% of the pitch λ.
Since it falls within about 1/10 to 1/10, equation (17) can be easily satisfied.

The detection head (38) is arranged so as to be relatively displaceable in the X direction with respect to the scale (35).
8) includes a first detector (39) that reads the eye a (36) and generates a phase detection signal, and a second detector that reads the Gray code (37) and generates an absolute position signal. (40) is attached. Note that the phase detection signal is not only a phase modulation signal as shown in the example in FIG.
Naturally, signals represented by s θ and the like are also included. The phase detection signal and absolute position signal are respectively output by the phase detection circuit (
41) and the absolute position code detection circuit (42), and the phase detection circuit (41) detects the scale (
36) Detect the phase amount θ corresponding to the above-mentioned (13)
The absolute position ΔX within one wavelength λ of the scale (36) is calculated from the formula, and this absolute position ΔX is supplied to the correction value calculation circuit (43) and the absolute position calculation circuit (44), and the absolute position code detection circuit ( 42) detects the absolute position data N corresponding to the gray code (37) from the absolute position signal and sends it to the correction value calculation circuit (43) and the absolute position detection circuit (42).
4).

The correction value calculation circuit (43) calculates −1°0,
A correction value ΔF that takes one of +1 is calculated and supplied to the absolute position calculation circuit (44).
4) corresponds to equations (12) and (15) in the example in FIG. 7, and calculates the relative displacement amount (i.e., , absolute position) X is calculated.

x = (I N T (N / i) + ΔF) λ+
Δx...= (18) This calculated absolute position X is supplied to the display (45).

The difference between this example and the example in Fig. 7 is that a correction value F is added in equation (18).
A method of calculating the correction value ΔF will be explained with reference to FIGS. 2 and 13.

In this case, as shown in FIG. 12A, the detection head (38)
Assuming that is at position P with respect to scale (35),
The correction value calculation circuit (43) calculates the scale (3) at the position P.
6) absolute position ΔX within one wavelength λ and Gray code (3
7) (step (101) in Fig. 13). In this example, since ff1=2, the value of the absolute position data N is equal to the scale (with no error).
2n in the first half (0≦θ<π) within 1 pitch λ of 36)
(n=0.1, 2...), the second half (π≦θ〈2π
) is expressed as 2n+1. However, as shown in FIGS. 12C and 12D, due to the accumulation of various errors, the position where the value of the absolute position data N changes from 2n-1 to 2n is deviated by 6 times in the child direction. Based on the condition of equation (17), these deviations δ7. δ2 is a value smaller than λ/3.

Next, in the correction value calculation circuit (43), the scale (36
) in the following three sections XI r XZ +
Divide it equally into X (.

X, :Q≦Δx×λ/3 X2:λ/3≦Δx<2λ/3 ) formula, the absolute position data N is a correct value, so the value of the correction value ΔF is set to 0 (step (102)
), (103), (104)).

On the other hand, if the current absolute position ΔX is in the section X or X3, the value of the variable f corresponding to the section to which the ΔX belongs is determined (step (105)). If f=2, then f=o or f= depending on whether the interval is X+ or X3, respectively.
After setting it to 1, the absolute position data N! Calculate MOD (N/f), which is the remainder after dividing by (step (1)
06)). In this example, as shown in FIG. 12B and D,
Since the variable f and MOD (N/f) have different values in the region of 0≦Δx δ1 or λ-δ2 ≦Δx (37) can be identified as being deviated. In the case of 0≦ΔX<δ1, from Fig. 12 E, I
NT (N# value (=n-1) is smaller than the original value (=n) by 1, so +1 is assigned to the correction value ΔF, and if λ-δ2≦Δx×λ, then Since the value of INT(N#) is larger than the original value by l, -1 is assigned to the correction value ΔF. However, in reality, the correction value calculation circuit (43) uses the table shown in Table 1. is stored in a ROM, and the correction value ΔF is mechanically read out from the ROM table (step (107)).

Next, the process moves to operation step (10B) of this example, and in this step (10B), the absolute position calculation circuit (44) Table 1 Correction value table (for l=2) calculates the absolute position ΔX within 1 pitch λ, the absolute The position data N and the correction value ΔF are taken in, and then, in step (109), the final absolute position X is calculated according to equation (18).

next,! An example of a method for calculating the correction value ΔF in the case of =3 will be explained with reference to FIG.
6) Divide the section of one wavelength λ into three equal parts to obtain the section X I-X s
(Fig. 14A), these sections X, ,X,,X
, respectively, are assigned 0 and 1.2 as the values of the variable f (FIG. 14B), and the original value of the absolute position data N is in the interval X, , X,.

Since they are expressed as 3n and 3n+1.3n±2 corresponding to
By comparing the value of MOD (N/l) (FIG. 14D), which is the remainder after dividing by =3), with the value of the variable f, the correction value ΔF can be determined according to Table 2.

From Table 2, for example, in section XI, MOD (N/11
) is 1 and the variable f is 00, the value of the correction value ΔF Table 2 is set to 0. This is because, as is clear from FIG. 14, when MOD (N/f) is 1 and f is O, the value of INT (N/f) is the original n and there is no need to perform correction.

Another example of the method of calculating the correction value ΔF in the case of 1=3 will be explained with reference to FIG. 15. In this case, the scale (
The section of 1 wavelength λ of 36) is divided into two parts, XI and X2 (FIG. 15A).

X, :O≦Δx×λ/2 Xz:λ/2≦Δx×λ Set the value of variable f to 0 or 1 corresponding to the two sections XI or Data N
is 3n at one wavelength λ of the scale (36), as in the example in Fig. 14,
3n+l, 3n+2 (Figure 15C)
), in this case, as is clear from FIG.
MOD (When the value of N# is 2, the correction value Δ
The value of F may be set to +1. This relationship is summarized in Table 3.

As mentioned above, according to this example, the maximum measurement length can be set within a practical range, similar to the example in Fig. 7, and the resolution can be adjusted using the incremental method. The displacement detection device has been significantly improved, and the scale (3
6) There is an advantage that the occurrence of an error in the measurement value for one wavelength λ can be reliably prevented. In addition, when manufacturing the scale (35) of this example, the resolution λ1 of the Gray code (37) with respect to the scale (36) of the wavelength λ varies within a range where the cumulative error does not exceed λ/3, but the measurement accuracy is maintained. Since no deterioration occurs, the scale (35) can be manufactured easily.

In the above example, a Gray code is used as the non-periodic scale, but a binary code or the like may also be used. Moreover, it can be applied not only to linear encoders but also to rotary encoders.

As described above, according to the example in FIG. 11, it is possible to accurately read the absolute position even if the scale (36) and the gray code (37) are deviated by about λ/3.

However, even in the technique disclosed in Japanese Patent Application No. 1-189166, if the origin position is shifted, that is, if the left end of the scale (36) and the left end of the gray code (37) are shifted, There is a problem in that an offset error occurs in the absolute position.

The present invention has been made in view of the above, and an object of the present invention is to provide a position detection device that can substantially accurately match the origin positions of a plurality of scales formed in parallel on a scale over a wide range. shall be.

[Means for Solving the Problem] For example, as shown in FIG. 1, the position detection device according to the invention has at least first and second scales (two ) (3), and first and second phase detection circuits (5) ( 7) and the phase amount θ1. detected by these first and second phase detection circuits (5) (7). In a position detection device comprising an absolute position detection circuit (8) that calculates an absolute position on the scale (1) based on θ2, the first or second phase detection circuit (
5) A phase shift circuit (11) connected to (7) is provided, and this phase shift circuit (11) shifts the phase amount detected by the first or second phase detection circuit (5) (7). They are designed to match each other.

As shown in FIG. 4, the position detecting device according to the invention includes, for example, a periodic scale (36) and an aperiodic scale (36) disposed in parallel with the periodic scale (36) on which the absolute position is coded. 3
7), a phase detection circuit (41) for detecting the phase amount of the periodic graduation (36) on this scale (35), and a scale (35) formed with the scale (35).
), a code detection circuit (42) detects a code from the aperiodic scale (37) in
In a position detection device comprising an absolute position detection circuit (44) that calculates the absolute position of the scale (35) from the code detected in step 2), a phase shift circuit (44) connected to the phase detection circuit (41) is provided. 52) is provided, and the phase amount detected by the phase detection circuit (41) is shifted by this phase shift circuit (52).

[Operation] According to the invention position detection device according to claim 1, the first eye 1
The origin position S of the second scale (3) is set to the origin position S1 of (2).
2, the first phase detection circuit (5
), the origin position S1 of the first scale (2) is detected by the phase amount θ1, and the second phase detection circuit (7) detects the origin position S1 of the first scale (3).
) is detected by the phase amount θ2, the phase amount θ detected by the second phase detection circuit (7) is set so that the difference θ2−θ1 between these phase amounts becomes zero value.
2 by the phase shift circuit (11).
The origin position S2 of the second scale (3) can be made to substantially match the origin position S1 of the scale (2). When aligning the origin position S1 of the first scale (2) with the origin position S2 of the second scale (3), the phase shift circuit (11) is connected to the phase detection circuit (5) and the absolute position detection circuit (8). By inserting it in between, matching can be achieved in the same way.

According to the position detection device according to the invention, when trying to match the origin position of the periodic scale (36) with the origin position of the aperiodic scale (37), the phase detection circuit (41)
The origin position of the periodic scale (36) is detected by the phase amount, and the code detection circuit (42) detects the origin position of the periodic scale (37).
When a code corresponding to the origin position is detected, a phase shift circuit changes the phase amount detected by the phase detection circuit (41) so that the absolute position calculated by the absolute position detection circuit (44) corresponds to the origin position. By shifting the phase at (52), the periodic scale (36) returns to the origin position of the aperiodic scale (37).
The origin positions of the two can be made to substantially match.

[Example] Hereinafter, an example of the position detection device of the present invention will be described with reference to FIGS. 1 to 4. In FIGS. 1 to 4, parts corresponding to those shown in FIGS. 5 to 15 described above are given the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, a phase shift circuit (11) with a phase shift amount Δφ is inserted between the input terminals of the phase detection circuit (7) and the absolute position detection circuit (8).

In this case, the phase amount θ output from the phase detection circuit (7)
2 is made into a phase amount θ3 (see equation (21)) and is supplied to the absolute position detection circuit (8).

θ3-θ2-Δφ...(21) Also, in this FIG. 1, it is easy to form the first magnetic scale (2) and the second magnetic scale (3) to have the same length. However, if each origin position S1 and origin position S2 are aligned at the origin position in the length direction, for example, at the left end (
It is not easy in manufacturing to match the left end of one scale to the left end of the other scale, and in this embodiment as well, as shown in the figure, the origin position S2 of the second magnetic scale (3) corresponds to the displacement position ΔX. It is assumed that the first magnetic scale (2) is deviated from the origin position S1 by an amount corresponding to that amount in the negative direction.

In the absolute position detection circuit (8), the phase difference Δθ (θ3-01)
is calculated, and the displacement amount X from the origin position 5l (x=0) on the scale (1) is calculated based on this phase difference Δθ, and the calculated displacement amount X is displayed on the display (9). Ru.

Therefore, the operation for electrically and substantially aligning the origin position S2 of the second magnetic scale (3) with the origin position fs1 of the first magnetic scale (2) will be described.

First, the phase amount θ1 is expressed by the same formula as shown in (6) No. 2 above.

θ1; 2πX/λ1 (22) On the other hand,
In the phase detection circuit (7), the amount of displacement X is 0 at wavelength λ2.
A phase amount θ2 that takes a value of ~2π is measured, but the origin position S2 of the magnetic scale (3) is the origin position S1 of the magnetic scale (2).
Since it is shifted to the negative side by the displacement amount ΔX compared to , the phase amount θ2 at the origin position Sl is 02M=2π(X+ΔX)/
λ2...(23)=2πX/λ2+2πΔ
X/λ2 ・-(24)=2πX/λ2+Δψ
...(25).

That is, the first magnetic scale (2) of the second magnetic scale (3)
), in other words, at the point where the displacement amount x=0, the value of the phase amount θ2 is θ2=Δψ(x
= 0) = 2zΔX/λ2 - (26), Figure 2B
As shown by the two-dot chain line, a so-called offset error of the phase amount Δψ occurs.

Therefore, the phase shift amount Δφ shifted by the phase shift circuit (11)
By setting the value equal to the value of the phase amount Δψ (Δφ=Δφ), the value of the phase amount θ3 output from the phase shift circuit (11) becomes 2π as shown in equation (27).
X/λ2 (see Figure 2B).

θ3=θ2−Δφ=2πX/λ2+Δψ−Δφ=2πX/λ2 (27) The above-mentioned phase amount θ1 and phase amount θ3 are determined by the absolute position detection circuit (
8), and in this absolute position detection circuit (8), the phase difference Δθ (Δθ=θ3
-θ1) is calculated in the same way as the above equation (12), and the displacement amount X is calculated in the same way as the above equation (13) ((1
2) and equation (13) are reproduced).

Δθ = 2πX(λ1-λ2)/(λ1λ2)...(
12) x=(Δθ/2π)λ1λ2/(λ1−λ2)
...(13) Therefore, the absolute position detection circuit (8) calculates the displacement amount X based on this equation (13) and displays it on the display (9).
supply to The display (9) visually displays the amount of displacement X.

In this case, if the phase difference Δθ is within the range shown by equation (14) above, the amount of displacement X can be uniquely determined.
The maximum measurement length at which the displacement amount X can be accurately measured as an absolute position is expressed by the above equation (15) (Equations (14) and (15) are listed again).

0 ≦ Δθ < 2 x ... (1
4) L=(λ1λ2)/(λ1−λ2) ...(
15) Therefore, the relationship between the displacement amount X and the phase difference Δθ becomes as shown in FIG. 2C, and no error occurs at the origin position 5L (x=0).

In this way, according to the example in FIG. 1, even if the origin positions of the first magnetic scale (2) and the second magnetic scale (3) formed in parallel on the scale (1) are shifted, the phase shift circuit (1
1), the first and second magnetic scales (2) (3)
) can substantially accurately match the origin positions. Note that this phase shift circuit (11
) is inserted after the phase detection circuit (7), so
Magnetic head (4A), (4B) and magnetic head (
6A) and (6B) in which the scale (1) is attached in the longitudinal direction at the absolute position has the advantage that even if there is an error, it can be corrected at the same time.

Note that the phase shift circuit receives the phase detection signal KA shown in FIG.
, the line for detecting KB, in other words, the magnetic head (6
A) A similar effect can be obtained by inserting it between (6B) and the phase detection circuit (7) to shift the phases of the phase detection signals KA and KB.

FIG. 3 shows the configuration of another embodiment of the present invention. The position detection device shown in FIG. 3 has a phase detection circuit (25) and an absolute position detection circuit (33) of the position detection device shown in FIG. A phase shift circuit (51) with a phase shift amount Δφ is inserted in between, and the detection head (22) is moved relative to the origin position in the X direction (see Figure 7) from the negative side to the positive side. The phase shift amount is set so that the phase amount θ obtained by the phase detection circuit (25) at the same time when the absolute position data N output from the absolute position code detection circuit (32) changes from zero value when What is necessary is to set Δφ. Even in this case, the phase shift circuit (51) may be changed to an analog signal processing phase shift circuit and inserted into the output side line (magnetic head (24A) side line) of the first detector (23A). A similar effect can be obtained.

FIG. 4 shows the configuration of still another embodiment of the present invention.
The position detection device shown in the figure has an aperiodic scale (
A phase shift circuit (37) with a phase shift amount Δφ is provided between the phase detection circuit (41) and the detector (39) of the position detection device having a phase shift amount Δφ.
52) was inserted. Even in this case, when the detection head (38) is moved relatively from the negative side to the positive side of the origin position in the X direction, the absolute position code detection circuit (
The phase shift amount Δφ may be set so that the phase amount θ obtained by the phase detection circuit (41) becomes zero at the same time when the absolute position data N output from the phase detection circuit (42) changes from zero value.

In this way, according to the above-mentioned examples in Fig. 1, Fig. 3, and Fig. 4, by inserting a phase shift circuit, the origin position of each magnetic scale formed on the scale can be electrically adjusted. Since they can be substantially matched, for example, the yield during scale production can be improved.

Note that the present invention is not limited to the above-described embodiments, and it goes without saying that various configurations may be adopted without departing from the gist of the present invention.

[Effects of the Invention] According to the inventive position detection device according to claim 1, when trying to match the origin of the first scale with the origin of the second scale,
When the first phase detection circuit detects the origin position of the first scale using the phase amount, and the second phase detection circuit detects the origin position of the second scale using the phase amount, the difference between these phase amounts is By shifting the phase amount detected by the second phase detection circuit with a phase shift circuit so that the value becomes zero, the origin position of the second scale is made to substantially match the origin position of the first scale. You can get the effect that you can.

The same holds true when aligning the origin position of the first scale with the origin position of the second scale. Further, since the origin position can be matched, there is also an advantage that the yield during manufacturing of the scale is improved.

According to the position detection device according to the second aspect of the invention, when trying to match the origin of the periodic scale with the origin of the aperiodic scale, the phase detection circuit detects the origin position of the periodic scale by the phase amount. When the code detection circuit detects a code corresponding to the origin position of the aperiodic scale, the phase detection circuit detects the absolute position calculated by the absolute position detection circuit so that it corresponds to the origin position. By shifting the phase amount using the phase shift circuit, it is possible to obtain the effect that the origin of the periodic scale can substantially match the origin of the non-periodic scale. Further, since the origin position can be matched, there is also an advantage that the yield during manufacturing of the scale is improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the position detection device according to the present invention, FIG. 2 is a diagram illustrating the operation of the example shown in FIG. 1, and FIG. FIG. 4 is a diagram showing the configuration of a further embodiment of the position detection device according to the present invention, FIG. 5 is a diagram showing the configuration of a conventional position detection device, and FIG. 6 is a diagram for explaining the operation of the example in FIG. 5, FIG. 7 is a diagram showing the configuration of another conventional position detection device, and FIG. 8 is a diagram showing the detailed configuration of the detection head, etc. in the example in FIG. 7. Figure 9 is a diagram for explaining the operation of the example in Figure 7, Figure 10 is a diagram showing the problem in the example in Figure 7, and Figure 11 is a diagram to solve the problem in the example in Figure 7. 12 is a diagram showing the configuration of the position detection device in the example shown in FIG. 11, FIG. 13 is a flow chart explaining the operation in the example shown in FIG. 11, and FIG. 14 is a diagram showing the example shown in FIG. FIG. 15 is a diagram used to explain the operation of the example shown in FIG. 11. (1) is the scale, (2) (3) is the first and second scale, (5) (7) is the first and second phase detection circuit, (8) is the absolute position detection circuit, (11) is a phase shift circuit, θ1. θ2 is the phase amount, (35) is the scale, (36
) is a periodic scale, (37) is an aperiodic scale, (41
) is a phase detection circuit, (42) is a code detection circuit, (44
) is an absolute position detection circuit→←, and (52) is a phase shift circuit. Agent Hidemori Matsukuma A (Department B Month's Eve [1 [Sake 4 Toyu 11 Kuhi 1]) Figure 4: Conventional technique - Nail sand 7 Figure 5: j 85 - Line of action - Figure 6: 17 [a example - movement (m-2) Figure 8: Figure 7: Example n: Conspiracy Figure 10: F舖゛正qΔF +1 Figure 11 v′j of !=2 Situation 1PJ11 country example l=3 food 8(1)

Claims (1)

[Claims] 1. A scale having at least first and second scales having different wavelengths and formed in parallel, and a first scale for detecting the phase amount of the first and second scales on this scale.
and a second phase detection circuit, and an absolute position detection circuit that calculates an absolute position on the scale based on the phase amounts detected by the first and second phase detection circuits, A phase shift circuit connected to the first or second phase detection circuit is provided, and the phase amount detected by the first or second phase detection circuit is shifted by the phase shift circuit. position detection device. 2. A scale with periodic graduations and non-periodic graduations arranged in parallel to the periodic graduations on which absolute positions are coded, and a phase for detecting the phase amount of the periodic graduations on this scale. a detection circuit; a code detection circuit that detects a code from the non-periodic graduations on the scale; and a code detection circuit that detects the absolute position of the scale from the phase amount detected by the phase detection circuit and the code detected by the code detection circuit. In a position detection device comprising an absolute position detection circuit that calculates a position, a phase shift circuit connected to the phase detection circuit is provided,
A position detection device characterized in that the phase shift circuit shifts the phase amount detected by the phase detection circuit.