JP4917185B1 - Absolute encoder - Google Patents

Abstract

【Task】
Provided is an encoder capable of accurately performing address determination and having high accuracy and low cost. Furthermore, the vicinity of the address switching position can be easily identified.
[Solution]
The absolute encoder of the present invention is configured such that a first graduation having equal intervals is formed at a first wavelength (λ), and a first address section is defined by nλ (where n is an expansion number and λ is a first wavelength). The second graduations are formed at equal intervals so that the main track is adjacent to the main track and the same address section as the first address section is (n + 1) λa (λa is the second wavelength). A first address track is formed adjacent to the main track or the first address track, and the same address section as the first address section forms a third scale of n (λa + (n ² −1) λ) + λa. A scale unit (20) having at least a second address track, a detection unit (30) for detecting scales of the plurality of tracks, and a signal detecting the scales of the plurality of tracks. Phase difference detection means (40) for detecting each phase difference, and processing means (50, 60, 70) for performing address determination based on the detected plurality of phase differences and calculating the position or angle of the measurement target. 80).
[Selection] Figure 1

Description

The present invention relates to an encoder used for measuring a moving distance, length, or angle of a measurement object, for example.
In particular, the present invention uses at least three scales (tracks) in which a plurality of sections divided by different wavelengths are defined adjacent to each other, and uses the phase difference of the phase modulation signals detected from the plurality of tracks. The present invention relates to an absolute encoder that outputs a moving distance, length, angle, and the like of a measurement target as absolute values.

  In machine tools, semiconductor manufacturing equipment, robots, etc., high precision, high speed, high reliability, and safety are required.

  In order to achieve high accuracy, high speed, and high reliability in length measurement and angle measurement, an absolute type measurement device is more appropriate than a so-called incremental type length (or angle) measurement device. Although it is considered, an incremental type position (angle) measuring device is mostly used in terms of price and required specifications.

  In recent years, high-resolution and high-precision encoders using M-sequence codes and the like have been put into practical use in absolute measuring devices of length and angle, but they are extremely expensive.

  For cost-sensitive fields, for example, rotary encoders using code plates, differential transformers, and magnetostrictive linear encoders are available on the market. Can't fully meet the needs of

Therefore, as disclosed in Patent Documents 1 to 3, a second track (hereinafter referred to as an address track) having a wavelength λa different from the wavelength λ of the main track for incremental measurement is provided, and the wavelength λ and the wavelength λa are set. By setting an appropriate relationship, a method has been proposed for absolute detection over an interval n times the incremental track wavelength.
In these methods, the main track wavelength λ and the address track wavelength λa are set to a relation nλ = (n−1) λa or nλ = (n + 1) λa with respect to the integer n, so that The phase difference between the phase modulation signal output corresponding to the position x and the phase modulation signal output corresponding to the position x in the address track changes by 2π (rad) every n-fold intervals of the wavelength λ. Take advantage of what you do. That is, the quotient when this phase difference is divided by 2π = n (rad) corresponds to the position in λ unit (hereinafter referred to as address) in the nλ section, and the remainder at that time corresponds to the position in the wavelength λ. When the remainder is close to 0 or 2π = n, it is determined that the remainder belongs to the vicinity of address switching, and a correct address is obtained by comparing with a predetermined position within the main track wavelength λ. I am doing so.

Japanese Patent Laid-Open No. 2003-83766 JP 2003-83767 A JP 2003-83768 A

However, there are several problems with the prior art.
First, there was no clear solution for determining how close the remainder is to 0 or 2π / n as the vicinity of the address switching position. There was a possibility that it was not implemented. That is, in an actual system, there is an interpolation error due to imperfectness of the scale and head, performance of the circuit system, and imperfection of the traveling system, so that the phase difference is 0 or Even at 2π / n, it does not coincide with the switching position in units of the main track wavelength λ. In order to avoid the influence of different interpolation errors for each encoder, the area where the remainder is close to 0 or 2π / n must be expanded, and as a result, the phase difference when divided by 2π / n The area where the address in the nλ section can be unconditionally determined using the quotient is narrowed and overlaps with the central position in the wavelength λ which is a reference for determination at the time of address correction, and the address correction work itself becomes impossible. There was a technical problem.
If this problem is to be addressed at the encoder production stage, this area must be set in accordance with the encoder-specific interpolation error, and the interpolation error in all address switching units within the nλ interval is measured. After setting an optimal area that is not affected by this, it may be necessary to re-verify that it operates correctly, leading to an increase in production cost.

  In addition, it is difficult to expand the absolute measurable area. As a method for expanding the absolute measurable region in the prior art, an integer n (hereinafter referred to as an expansion number n) relating the wavelengths of these two tracks may be selected as large as possible. However, the larger the extension number n is selected, the smaller the difference between the main track wavelength λ and the address track wavelength λa. As a result, the phase difference between the main track and the address track decreases, and the address switching unit is accurately detected. This is not only difficult, but also a slight misalignment between the main track and the address track leads to an address detection error in units of the main track wavelength λ.

  Furthermore, a method of selecting a small extension number n and increasing the number of address tracks to expand the absolute measurable range is conceivable, but this method also has a similar problem.

  Therefore, it is desired to provide an absolute encoder that solves the above-described problems.

In the present invention, the relationship between the size of the interpolation error in each track and the expansion number n is set appropriately, and the behavior of the interpolation error between these two tracks in the address switching unit in units of wavelength λ is appropriately set. Use.
That is, address discrimination in units of wavelength λ uses the phase difference between these two tracks, and the phase difference is affected by the combination of interpolation errors in each track, but the address switching unit in units of wavelength λ. The phase difference output in is referred to a position including an interpolation error in the first address track wavelength λa with reference to a fixed position (or length) for each main track wavelength λ. It utilizes the corresponding phase difference.

  In other words, the length of the main track wavelength λ unit is always constant regardless of the presence or absence of the interpolation error, and only the interpolation error within the first address track wavelength λa is reflected in the address switching unit. Then, the position in the wavelength referred to changes corresponding to the change of the address switching position, and the reference position makes a round corresponding to the movement in the section expanded n times.

  Therefore, in the present invention, the relationship of 2Ie <λ / 2n is assumed, where Ie is the amplitude of the interpolation error of the track having the largest interpolation error among the plurality of tracks, and n is the number of expansions by the plurality of address tracks. Manage to be satisfied. Furthermore, the interpolation error due to any factor is a signal that repeats sinusoidally in one or two cycles with respect to the wavelength λ, and the deviation from the theoretical value is superimposed before and after the address switching unit. The problem is solved by making the area corresponding to the amplitude corresponding to the insertion error, that is, the width corresponding to Ie, and the area added with the influence of the quantization error associated with these processes as an area that generates uncertainty in address determination.

In the present invention, in addition to the main track, at least two or more address tracks are provided, and the first address track (hereinafter referred to as address track 1) having a wavelength λa different from the main track wavelength λ is an expansion coefficient. Is a scale having a relationship of nλ = (n + 1) λa, and a second address track (hereinafter referred to as address track 2) has an nλ section (nλ section expanded by n times with the main track wavelength λ as a unit). Hereinafter, of the n ² λ intervals (hereinafter referred to as the second address interval) which is n times the first address interval), the nλ interval is replaced with (n + 1) λa, and the wavelength λa of the address track 1 is set to one wavelength and the main track wavelength λ After arranging n sets of (n-1) wavelengths as one set, the wavelength λa of the address track 1 is further formed as one wavelength.

Similarly, the third address track (hereinafter referred to as address track 3) includes an nλ interval (n + 1) within an n ³ λ interval (hereinafter referred to as the third address interval) further expanded n times in units of the second address interval. ) Replace with λa, and after arranging n sets of the wavelength λa of the address track 1 as one set and the (n ² −1) wavelength of the main track wavelength λ, one wavelength λa of the address track 1 is formed. . In the following, the address track is expanded according to the same rule so that the absolute measurable range can be expanded.

  Then, a difference in position within the wavelength between the main track and the address track 1 (hereinafter referred to as a phase difference) is compared to obtain a phase difference signal that continuously changes in the first address section, and the phase difference signal The phase difference between the main track and the address track 2 is compared with the means for identifying the first address section using the main track phase difference as n addresses (hereinafter referred to as the first address) with the main track wavelength λ as a unit. After tentatively determining n addresses (hereinafter referred to as second addresses) in the second address section in units of nλ, the phase difference between the address track 1 and the address track 2 is compared, and the address switching of nλ is performed. At the position, n second addresses in the second address section are used by using signals having different phases by 2π / n (rad) and the already determined first address. Means for identifying the third address and the fourth address by the same means, and the phase difference corresponding to the identified address and the position within the wavelength within the main track. The position within the wavelength λ detected based on the weight is combined in consideration of the weight, and the (n × n ×...) Section of the main track wavelength λ is made into absolute position information according to the number of addresses. By converting, it is configured to solve the problem.

In other words, the absolute encoder of the present invention includes a main track having first graduations formed at equal intervals at the first wavelength (λ), and a first address section (nλ, where n is an extension number) n times the first wavelength λ. ) Are arranged adjacent to these first address tracks on which the second graduations are formed at equal intervals with the second wavelength (λa) so that nλ = (n + 1) λa, and the first address section is defined as n A scale unit having at least one extended address track having an extended scale formed by a combination of the first wavelength and the second wavelength in which the nλ section is replaced with (n + 1) λa among the address sections expanded in units of multiples When,
A detection unit for detecting scales of the plurality of tracks; a phase difference detection unit for detecting phase differences of signals indicating the scales of the plurality of tracks detected by the detection unit; and a plurality of units detected by the phase difference detection unit And processing means for performing address determination based on the phase difference and calculating the position or angle of the object to be measured.

  In the present invention, the main track in which the first graduations are formed at equal intervals at the first wavelength (λ) and the first address section (nλ, where n is an expansion number) n times the first wavelength λ A first address track having a second graduation at equal intervals of two wavelengths (λa) such that nλ = (n + 1) λa, or in addition to these tracks, the first address section is in units of n times A scale having an extended address track formed of at least one extended scale formed by a combination of the first wavelength and the second wavelength in which the nλ section is replaced with (n + 1) λa among the address sections expanded in (1). A phase difference detection means for detecting a phase difference of each of the signals indicating the scales of the plurality of tracks detected by the detection section, and a phase difference detection means. Detected Interpolating due to imperfection of the two-phase sine wave signals detected from these tracks, having processing means for performing address determination based on the phase difference of the number and calculating the position or angle of the object to be measured When the amplitude of the interpolation error of the track with the largest error is Ie, the relationship between the extension number n and the first wavelength λ in each address track is set to be 2Ie <λ / 2n, and the phase difference detection The means detects a difference between a position in the first wavelength (λ) and a position in the second wavelength (λa) as a phase difference, and continues from 0 to 2π (rad) in an n-fold section of the first wavelength λ. And the processing means divides the phase difference detected at time (t) by 2π / n, and uses the quotient to address in the first wavelength λ unit. Tentatively determine the remainder in the operation to 0 or The zone is divided into three zones, the vicinity of the maximum value and the central portion, and the phase difference corresponding to the quantization error generated in the process of the calculation is set to the phase difference corresponding to λ / 2n with the size of the area near 0 or the maximum value. When the remainder belongs to a central zone, the tentatively determined address is unconditionally set. When the remainder belongs to a zone near 0 or the maximum value, the first wavelength (λ) is set. An address in units of λ is determined by comparison with a predetermined position.

  According to the present invention, the position within the first track wavelength λ and the position within the second track wavelength λa are detected as a phase difference, and the movement in the section expanded to nλ times the first track wavelength λ is supported. The quotient when the phase difference signal continuously changing from 0 to 2π (rad) is divided by λ / 2n (rad) is uniquely determined within the nλ interval. The influence of the interpolation error generated in the first address switching unit in units of λ wavelengths can be set uniquely and quantitatively based on a predetermined management level in production.

Therefore, the uncertainty related to the determination of the first address can be reliably avoided, and the encoder quality can be stabilized and the production cost can be reduced.
According to the present invention, the second track has a scale formed only with the same wavelength λa, whereas the third track and subsequent tracks have the first track wavelength λ and the second track wavelength λa predetermined. It is characterized by being formed in combination with each other.

  The phase difference signal output by detecting the difference between the position within the first track wavelength λ and the position within the third track wavelength is the switching position of the second address in units of nλ where the second track wavelength λa is formed. In the center portion where the first track wavelength λ is formed, a flat phase difference signal is obtained. The phase difference generated at these positions has almost the same rate of change as that of the second track, and identification near the address switching position becomes extremely easy.

ADVANTAGE OF THE INVENTION According to this invention, an address determination can be performed correctly and an encoder with high precision can be provided.
According to the present invention, identification near the address switching position is facilitated.
According to the present invention, a small and inexpensive encoder can be provided.

It is a block diagram of the absolute encoder of 1st Embodiment. FIG. 2 is a configuration diagram of a track illustrated in FIG. 1. It is a detailed block diagram of the encoder illustrated in FIG. FIG. 4 is a diagram showing a phase relationship between a main track and an address track 1; It is a figure which shows an interpolation error. FIG. 5 is a diagram showing a state in which the interpolation error of the address track 1 is assumed to have Ie and has the same period as the wavelength λa, and this interpolation error is reflected in the first address section. It is a flowchart which shows the determination process of a 1st address. It is a diagram showing the relationship between the phase difference of the ideal state in the phase modulation signal e _{pm (M)} and e _{pm (A 2)} over a second address period. It is a flowchart which shows the process of the zone discrimination | determination for 2nd address confirmation. (A) is a figure which shows the phase difference of an e _pm (A ₁ ) signal and an e _pm (A ₂ ) signal. (B) is a figure which shows the phase change in the both ends of a 2nd address area. It is a flowchart which shows the process regarding determination of a 2nd address. It is a block diagram of the encoder of 2nd Embodiment. It is a block diagram of a 3rd address track. FIG. 13 is a detailed view of FIG. 12. e _pm (M) and _e pm _{(A 3)} is a diagram showing the phase difference between the signals. It is a flowchart which shows the process which fixes a 3rd address. It is a block diagram of a displacement detection circuit of a phase detection type. It is a block diagram of a coordinate conversion type displacement amount detection circuit.

  An embodiment of an absolute encoder (hereinafter abbreviated as an encoder) of the present invention will be described with reference to the accompanying drawings.

First embodiment

  A first embodiment will be described with reference to FIGS.

Overall Configuration FIG. 1A is a diagram illustrating the overall configuration when the present invention is applied to a rotary encoder. The encoder includes a scale unit (20) fixed to the rotating shaft (1), a detection circuit (30), and a signal processing unit (100).

  As illustrated in FIG. 1B, the scale portion (20) has an annular main track (201), an address track 1 (202), and an address track 2 (203) concentrically from the outer periphery toward the inner periphery. ) Is formed. These tracks (201 to 203) are provided with a plurality of scales along the circumference of the scale portion (20). The plurality of scales are provided as magnetic scales on which an alternating magnetic field is formed, for example.

  As shown in FIG. 3, the scale unit (20) includes a main track (201) and a two-channel detection head (211) for detecting a magnetic signal indicating the scale, an address track 1 (202) and the scale. And a 2-channel detection head (213) for detecting a magnetic signal indicating the address track 2 (203) and its scale.

  2A to 2C are diagrams in which tracks 201, 202, and 203 formed in an annular shape are expanded in a straight line for convenience. FIG. 2D shows an enlarged view of the intensity of the magnetic signal recorded on one scale of the wavelength λ of the main track. A magnetic signal indicating a sinusoidal intensity distribution is recorded in one scale of wavelength λ. A magnetic signal is recorded on one scale of the wavelength λa of the address track 1 as in FIG. 2D (where λ> λa).

  The scale unit (20) rotates with the rotation of the rotary shaft 1, and the tracks 201 to 203 output a signal corresponding to the rotational position, for example, a magnetic signal. Detection heads installed in the vicinity of the tracks 201 to 203, for example, MR sensors (211) to (213) detect the magnetic field.

The detection circuit (30) includes first to third displacement amount detection circuits (301 to 303) illustrated in FIG. From these detection circuits (301 to 303), phase modulation signals corresponding to the detection signals of the MR sensors (211 to 213) are e _pm (A ₂ ) of the e _pm (M) and e _pm (A ₁ ) signals. Is output as 4A and 4B show changes in the phase of the e _pm (M) signal and the e _pm (A ₁ ) signal with respect to the displacement nλ, and FIG. 4C shows the e _pm (M) signal and e _pm. (A ₁ ) Changes in the phase difference from the signal are shown.

Based on the detection signals e _pm (M), e _pm (A ₁ ), e _pm (A ₂ ) of the detection circuits (301 to 303), the signal processing unit (100) ) Rotation position or angle is output as an absolute value.

  The signal processing unit (100) includes the phase comparison circuit 40 including the first to third phase comparison circuits (401 to 403), the determination signal generation unit 50, the address determination circuit 60, and the absolute position synthesis circuit illustrated in FIG. 70 and a reference signal generation circuit 80.

Configuration of Each Track As illustrated in FIG. 2, the main track 201 is formed with a scale such that a signal having a constant pitch of, for example, 256 μm is output as the wavelength λ. On the address track 1 (202), a scale is formed so that a signal of λa = 254.9 μm satisfying 17 × λa = 16 × λ is output.

In the address track 2, for example, an extension number n = 16, and for 16 ² λ, one set of one wavelength λa and 15 wavelengths λ is set so as to satisfy the following relationship in a section 256 times the wavelength λ. Then, a scale is formed so that one wavelength of the wavelength λa is output.

16 ² λ = 16 × (16−1) λ + 16λ
= 16 × 15λ + 17λa = 16 × 15λ + (16λa + λa)
= 16 × (λa + 15λ) + λa

In the present invention, a relationship of 2Ie <λ / 2n between the amplitude Ie of the interpolation error of the track having the maximum interpolation error among the plurality of tracks, the main track wavelength λ, and the expansion number n. In addition to satisfying the above, after the address track 2, the signal from the scale in which the main track wavelength λ and the first address track wavelength λa are formed in a predetermined combination must be reproduced by a single detection head. Has constraints.

  The detection head (211 to 213) for detecting the signal of each scale track is composed of a two-channel head so as to have an electrical phase difference of 90 ° with respect to the wavelength of the track as illustrated in FIG. Thus, when detecting a signal of a scale track in which two types of wavelengths are formed, a deviation from 90 ° in the ideal state occurs, and an interpolation error accompanying this deviation occurs.

A case will be described in which a signal of a scale track on which a single wavelength λ is formed is detected by an ideal head set correctly in accordance with the wavelength λ. For convenience, a detection head that outputs a sin x signal when a positive displacement x occurs is channel 1 (CH1), and a detection head that outputs a cosx signal is channel 2 (CH2). The relative movement between the scale (20) and the detection head is x, the balanced modulation wave signal output from the CH1 detection head is e ₁ , and the balanced modulation wave signal output from the CH2 head is e _2. The balanced modulation signal obtained by adjusting the amplitude of 1 to 1 can be expressed as follows.

When e ₁ and e ₂ are added, a phase modulation signal e _pm whose phase changes in accordance with the position x in the wavelength is obtained.

Here, the reference signal e _ref having the same frequency f as e _pm can be expressed as follows.

Therefore, the position x within the wavelength can be detected as the phase difference φ (x) between the e _pm and e _ref signals.

If replaced with ωt = T, 2πx / λ = X, the phase modulation signal e _pm can be expressed by the following equation.

The phase modulation signal e _pm in the ideal state shown in the equation (5) can also be expressed as follows when the phase when two orthogonal sine waves are combined is Φ.

Here, since the deflection angle Φ can be expressed as follows, the phase modulation signal e _pm is expressed by the following equation.

  Therefore, from the equations (5) and (7), the phase X is given as follows.

Next, consider a case where signals of different wavelengths are detected by one detection head. The above equation is for when the wavelength is λ and a detection head designed for that wavelength is used, and the signal of wavelength λ _a is detected using the detection head manufactured for the main track wavelength λ. In this case, it is considered that a phase shift ΔZ occurs in any head, for example, the cos output on the CH2 side, and the position X is detected as (X + ΔZ), and the output e ₂ ′ on the CH2 side can be expressed as follows: it can.

The phase modulation signal e ′ _pm at this time can be expressed as follows.

  Further, if the above equation is transformed into a monomial form and the phase component is X ′, the following equation is obtained.

  Therefore, from the equation (11), the phase X ′ at this time can be expressed as follows.

  As a result, the phase error ΔX when signals of different wavelengths are detected by one head is expressed as the difference between the phase X ′ expressed by the equation (12) and the phase X expressed by the equation (8) as follows: Can be represented.

  Applying the tangent addition theorem, the following equation is obtained.

  In consideration of the fact that ΔZ is sufficiently small in the above equation, cos ΔZ = 1 can be approximated, and the following equation is obtained.

  Further, when ΔZ is sufficiently small, tanΔX = ΔX, so ΔX can be approximated as follows.

Applying the double angle formula (1-cosΔZ) = 2 × sin ² (ΔZ / 2) and considering that ΔΔ << 1, sin ΔZ / = ΔZ, the above equation can be approximated as follows.

Therefore, when the phase error ΔX is converted into the interpolation error ΔI _Er normalized by the wavelength, the following equation is obtained.

As is clear from the equation (18), the phase error ΔI _Er when a signal having a different wavelength is detected by a single head is ¼π of the magnitude of the deviation sin ΔZ, and the period is twice the phase X. It can be seen that it has an error pattern that repeats.

  For example, if the number of expansions is n = 16 and the main track wavelength λ = 256 μm, it is necessary to detect a signal having a wavelength of 256 μm and a signal having a wavelength of 240.94 μm (hereinafter abbreviated as 240.9 μm) with a single head. The deviation ΔZ with respect to the detection head for 256 μm is about 5.9%, and the deviation v with respect to the detection head for 240.9 μm is about 6.3. % And an intermediate wavelength between them, for example, a deviation ΔZ based on a detection head for 248 μm, corresponds to about 3% of the wavelength.

FIG. 5 shows the interpolation error ΔI _Er normalized with the wavelength given by the equation (18) when the deviation ΔZ is changed from 1% to 3% to 7%. Even when shifted to the maximum of 7%, the total amplitude of interpolation error 2I _e = 0.018λ, and the total amplitude of interpolation error allowed when the number of expansions n = 16 is 0.031λ (= λ / 2 × 16) is not exceeded. In order to reduce this influence, the total amplitude 2I _e = 0.0075λ of the interpolation error when the intermediate wavelength 248 μm is used as a reference, which is about 1 / of the allowable error with respect to the set expansion number. Corresponds to 4.

  This is the same even when the expansion number n = 32, and the influence of the interpolation error when detecting signals of different wavelengths with a single head is not the limitation of the present invention, and the wavelength of the detection head is optimized. This indicates that there is a possibility that the expansion number n can be selected large.

Specific Circuit Configuration In the first embodiment, a displacement amount detection device that extracts a position within a wavelength in each track in the form of a phase modulation signal is used.

  The signal generation circuit (80) uses a carrier signal to obtain a reference signal (hereinafter referred to as a REF signal) having the same frequency as the carrier frequency f of the phase modulation signal and a resolution of 1 μm by dividing the wavelength λ into 1/256. A rectangular wave clock signal (hereinafter referred to as a CKI signal) having a frequency 256 times the frequency f is generated.

Here, the reference signal REF is a rectangular wave signal corresponding to the sine wave signal e _ref having the frequency f and the phase 0 shown in Expression (3), and is used as a reference signal in phase detection in the phase comparison circuit (401). It is done.

The displacement detection circuit 1 (301) converts the phase modulation signal e _pm shown in Expression (2) whose phase is displaced according to the relative displacement x between the main track (201) and the detection head (211) into a rectangular wave. A phase modulation signal (hereinafter, e _pm (M) signal) is output.
The displacement amount detection circuit 2 (302) is a rectangular wave phase modulation signal (hereinafter referred to as e _pm (A ₁ ) signal) whose phase changes in accordance with the relative displacement amount between the address track 1 (202) and the detection head (212). ) Is output.
The displacement detection circuit 3 (303) is a rectangular wave phase modulation signal (hereinafter referred to as an e _pm (A ₂ ) signal) whose phase changes in accordance with the relative movement amount between the address track 2 (203) and the detection head (213). ) Is output.

The phase comparison circuit 1 (401) compares the phases of the e _pm (M) signal and the REF signal, and a pulse corresponding to the phase difference 2πx = λ shown in Expression (3), that is, the position x within the main track wavelength λ. A width signal (hereinafter PW (M)) is output.
The phase comparison circuit 2 (402) compares the phases of the e _pm (M) signal and e _pm (A ₁ ), and outputs a signal having a pulse width corresponding to the phase difference (hereinafter, PW (MA ₁ )). .
The phase comparison circuit 3 (403) compares the phases of the e _pm (M) signal and the e _pm (A ₂ ) signal, and outputs a pulse width signal corresponding to the phase difference (hereinafter, PW (MA ₂ )). Output.

The determination signal generation circuit (50) compares the phases of the e _pm (A ₁ ) signal and the e _pm (A ₂ ) signal, and a signal having a pulse width corresponding to the phase difference (hereinafter referred to as PW (A ₁ A _2). )) Is output.

The address determination circuit (60) includes signals PW (M) and PW (MA ₁ ) having pulse widths corresponding to the phase differences output from the three phase comparison circuits (401 to 403) and the determination signal generation circuit (50). , PW (MA ₂ ) and PW (A ₁ A ₂ ), the CKI signal and the REF signal output from the signal generation circuit (80), the 16 first addresses A 1 in the first address section, The 16 second addresses A2 in the 2-address section are determined.

The absolute position combining circuit (70) converts the position of the main track wavelength lambda, the absolute position of the addition to the resolution 1μm addresses A ₁ and A _2, which is determined in consideration of the weights.

It describes a method of determining the first address A ₁ of the λ unit in the first address confirmation process first address in section.

A signal PW (M) having a pulse width corresponding to a position within the main track wavelength λ output from the phase comparison circuit 1 (401), an e _pm (M) signal output from the phase comparison circuit 2 (402), and e A signal PW (MA ₁ ) having a pulse width corresponding to the phase difference from the _pm (A ₁ ) signal is interpolated with a CKI signal having a frequency 256 times the carrier frequency f in the address determination circuit (60). The number of pulses varies from 0 to 255 corresponding to the position in λ, and the number of pulses depends on the phase difference between the pulse train signal PS (M) and e _pm (M) and e _pm (A ₁ ) (not shown). Generates a pulse train signal PS (MA ₁ ) (not shown) in which changes from 0 to 255.

As shown in FIG. 4, the e _pm (M) signal causes a phase change of 16 × 2π (rad) and the e _pm (A ₁ ) signal is 17 × 2π (rad) with respect to movement within the first address period. Therefore, the pulse train signal PS (MA ₁ ) is a pulse train whose number of pulses changes from 0 to 255 corresponding to the phase difference 2π (rad), and is 16 for each address in the first address section. It changes every pulse.
Therefore, the number of pulses 16 can be considered the number of pulses identifying the address A ₁ of the λ unit of the first address in section. If the first address measured every reciprocal of the carrier frequency f of the phase modulation signal, that is, every period T = 1 / f, is expressed as A ₁ (t), the pulse train signal PS (MA _{1 at} time t ) Is obtained by counting the number of pulses (ie, D (MA ₁ )), and the quotient when performing a congruent operation modulo 16 is 16 addresses A ₁ (in the first address section). t), and the remainder corresponds to the position in address A ₁ (t).

Conventionally, there is a possibility of misjudgment as an adjacent address A ₁ (t) in an area where the remainder is close to the minimum value of 0 and an area close to the maximum value of 15. Therefore, the remainder is divided into three areas depending on the value of the remainder, In the area where the remainder is close to 0, it is considered that it belongs to the previous address, and in the area where the remainder is close to 15, it may belong to the next address. When the address A ₁ (t) is tentatively determined based on the quotient by determining which side is a predetermined position within the wavelength λ, specifically, which side is compared with the median value within the wavelength λ. ) And a method for obtaining a correct address has been proposed.

However, in an actual system, interpolation errors included in the e _pm (M) signal and the epm (A ₁ ) signal are independent of each other, and can affect both the addition direction and the subtraction direction. Therefore, if the influence of the expansion number n and the interpolation error I _e in each track is appropriately evaluated and not reflected in the above zone setting, the phase difference corresponding to the movement in the first address section is changed to the movement in the wavelength λ unit. In addition to the possibility that a unique quotient cannot be obtained when dividing by the corresponding phase 2π / n, the adjacent address A _{1 is} not corrected because it is originally an area that needs to be corrected. There is a possibility of erroneous determination as (t).

  Further, if an attempt is made to provide a margin for the area that needs to be corrected, the maximum value in the area where the remainder is close to 0 competes with the minimum value in the area where the remainder is close to 15, and is compared with the median of the wavelength λ. Thus, the correction operation itself of determining which side belongs and determining the correct address A1 based on the determination result itself has a problem.

Therefore, in accordance with the first embodiment, the amplitude Ie of interpolation error in all of the tracks that make up the system between the extension number n, by managing to satisfy 2I e _<λ / 2n condition: It is guaranteed that the maximum fluctuation range due to the combination of interpolation errors does not exceed 2Ie, and that a unique quotient is obtained in the above congruent operation.

The phase difference information for address discrimination is obtained by referring to the position in the address track 1 wavelength λa when the main track wavelength λ is used as a reference, and in an actual system having an interpolation error. In consideration of the fact that the scale pitch of the main track wavelength λ is always constant and the symmetry of the interpolation error is taken into account, four pulses corresponding to the amplitude I _{e of the} interpolation error (= I _e <λ / 4n = 256). / 64) affects the remainder when the pulse train signal PS (MA ₁ ) is divided by the number of reference pulses in an additive or subtractive manner, and adds the influence of quantization errors generated in a series of determination operations. The remaining 5 pulses are set in a region where the remainder requiring correction for address determination is close to 0 and two regions close to 15.

FIG. 6 assumes that the amplitude of the interpolation error of the address track 1 is _Ie and has the same period as the wavelength λa, and this interpolation error is reflected in an enlarged manner in the first address section. FIG. Interpolation error IEr (1) at 1/16 position of address rack 1 wavelength λa in the first address section, and interpolation error IEr (2) at 2/16 position of wavelength λa in the next address switching unit, In the same manner, it can be seen that the deviation accompanying the amplitude _Ie of the interpolation error within the wavelength λa is superimposed in an additive or subtractive manner.

That is, when the data D (MA ₁ ) obtained by counting the pulse train PS (MA ₁ ) at time t is divided by modulo the reference pulse number 16, the remainders are 0 to 4 and 11 to 15 When it becomes, it is determined that this is a region that causes uncertainty in address determination, and a predetermined value of data (hereinafter referred to as D (M)) obtained by counting the pulse train signal PS (M) at time t is determined. The first address A ₁ (t), which is provisionally determined by collating with the value, is corrected. Then, when the remainder becomes 0 to 4 and 11 to 15, it is only necessary to determine whether the remainder is on the smaller side or the larger side with respect to the center position of the wavelength λ. M) = 128 is used as the determination value.

  FIG. 7 is a flowchart showing a processing process related to the determination of the first address by the address determination circuit (40) applying this determination condition.

Second address confirmation process will now be described how to determine sixteen of the second address A ₂ of the second address in a section which is enlarged 16 times the first address period as a unit.

FIG. 8 shows the relationship of the phase difference between the phase modulation signal e _pm (M) output from the displacement detection circuit 301 and the e _pm (A ₂ ) signal output from the displacement detection circuit 303 in an ideal state. It is the figure shown over the 2nd address area. In the second address section, the wavelength λ is formed for 256 wavelengths in the main track (201), and the main track wavelength λ and the first address track wavelength λa are formed for a total of 257 wavelengths in the address track 2 (203). Therefore, a phase difference of 2π (rad) corresponding to the wave number difference 1 is generated in the entire second address section. The change occurs in 17 regions where a wavelength λa different from the main track wavelength λ is formed, in a region where the phase changes sharply by 2π / 17 (rad), and in 16 15λ sections which are substantially equal to the first address section. It can be seen that there is a region where the phase is flat.

The phase comparison circuit 3 (303) is a circuit that generates a signal having a pulse width corresponding to the phase difference. The phase comparison circuit 3 (303) compares the phase difference between the e _pm (M) signal and the e _pm (A ₂ ) signal. The pulse width changes sharply in the λa sections, and is converted into a PW (MA ₂ ) signal having a constant pulse width in the 16 λ sections.

This PW (MA2) signal is guided to the address determination circuit (60), and the CKI signal is interpolated, and the number of pulses changes sharply by 0 to 256/17 in the above 17 λa intervals, and 16 15λ intervals. Is converted to a pulse train signal PS (MA ₂ ) (not shown) having a pulse number n × 256/17 (n = 1 to 16) which is n times the pulse number 256/17 corresponding to the position.

Therefore, in the first embodiment, the second address section is divided as follows.
(A) Subtraction and addition of pulse numbers corresponding to ½ width of the number of pulses 256/17 changing in the λa interval before and after the 16 15λ intervals for obtaining a constant number of pulses so as not to overlap each other. 16 zones {(n + 1) × 256 / 17− (128/17) ≦ Z _n (A ₂ ) <(n + 1) × 256/17 + (128/17)) (where n = 0 to 15) ).
(B) A zone {0 ≦ Z _L (A ₂ ) obtained by adding the number of pulses corresponding to ½ width of 256/17 to the number of pulses output at the origin side position in the second address section. {256/16 (128/17) obtained by subtracting the number of pulses corresponding to ½ width of the number of pulses 256/17 from <128/17} and the number of pulses 256 output at the maximum measurement position side. ≦ Z _u (A ₂ ) <256}, plus a total of 18 zones.
Then, using the relationship between the data D (MA2) obtained by counting the PS (MA ₂ ) at the time t and the number of pulses 256/17, the 18 zones in the second address section are discriminated. .

Here, out of the above 18 zones, the zone Z _L (A ₂ ) on the origin position side determines the zone Z _U (max measurement position side) by determining {0 ≦ D (MA ₂ ) <128/17}. A ₂ ) can be determined according to the condition {256-16 (128/17) ≦ D (MA ₂ ) <256}, and data D (MA ₂ ) is broadly defined by the number of pulses 256/17 for the other zones. quotient joint when calculating the conducted in, specifically data D (MA ₂₎ from using either the pulse number 256/17 times can subtract zone _{Z 0 (a 2) ~Z 15} (a 2) As can be seen from FIG. 8, the zones Z ₀ (A ₂ ) to Z ₁₅ (A ₂ ) have almost the second addresses A ₂ = 0 (H) to F except for both ends. It matches (H).

However, since the number of pulses 256/17 is not an integer, determination by the congruent calculation is not realistic. Therefore, the zone _{Z 0 (A 2) ~Z 15} (A 2) and the maximum measurement position side zone _Z U _{(A 2)} the number of pulses _P n _(A 2) to the number of pulses was rounded to an integer in the beginning of = ( It is convenient to set n + 1) × 256/17 (n = 0 to 16) and determine the zone Z _n (A ₂ ) based on the number of pulses.

Table 1 shows the relationship between the number of pulses P _n (A ₂ ) (where n = 0 to 16) corresponding to each zone and the second address A ₂ (t) provisionally determined by the discrimination of the zone. 9 is a flowchart showing the procedure for zone discrimination of the 18 locations using the number of pulses P _n (A ₂ ).

Next, a procedure for determining the second address A ₂ using the determined 18 zones and the temporarily determined address A ₂ (t) will be described.

Table 2 shows the zone switching positions in the 18 zones Z _L (A ₂ ), Z ₀ (A ₂ ) to Z ₁₅ (A ₂ ), and Z _U (A ₂ ) in an ideal state, that is, A value obtained by rounding the position in the main track wavelength λ corresponding to the start and end of each zone to the unit of 1 μm of resolution in this embodiment, and the theoretical address to which the position belongs is a 4-bit second address A _2. And an 8-bit address A ₂ A ₁ obtained by concatenating the 4-bit first address A ₁ in consideration of the weight, 2 hexadecimal digits (00 (H) to FF (H), where (H) is a hexadecimal number. It shows that there is).

As is apparent from Table 2, in the zone Z _L (A ₂ ) on the origin position side, both the start and end parts are set to A ₂ A ₁ = 00 (H), and the zone Z _U (A ₂ ) on the maximum measurement position side. In FIG. _2, both the start part and the end part correspond to the correct address as A ₂ A ₁ = FF (H). In the central zones Z ₇ (A ₂ ) and Z ₈ (A ₂ ), A ₂ A ₁ = 70 (H) and A ₂ A ₁ = 80 (H) at the start, and A ₂ at the end. ₂ A ₁ = 7F (H) and A ₂ A ₁ = 8F (H) correspond to correct addresses. In addition, in Z ₀ (A ₂ ) to Z ₆ (A ₂ ), the start portion corresponds to the correct address as A ₂ A ₁ = 00 (H) to A ₂ A ₁ = 60 (H). The end part belongs to the next second address adjacent to A ₂ A ₁ = 10 (H) to A ₂ A ₁ = 70 (H). In Z ₉ (A ₂ ) to Z ₁₅ (A ₂ ), A ₂ A ₁ = 9F (H) and A ₂ A ₁ = FF (H) correspond to correct addresses at the end portion, whereas The start part belongs to the second address immediately before A ₂ A ₁ = 8F (H) and A ₂ A ₁ = EF (H).

In other words, when it is determined that the zone is Z ₀ (A ₂ ) to Z ₆ (A ₂ ) and the first address that has already been determined is A ₁ = 0 (H), it is determined temporarily from that zone. 2 addresses may belong to the next adjacent second address at the end of A ₂ (t) = 0 (H) to 6 (H), and zones Z ₉ (A ₂ ) to Z ₁₅ (A ₂ ) and when the first address is A ₁ = F (H), the second address temporarily determined from the zone is A ₂ (t) = 9 (H) to F (H This indicates that there is a possibility that it belongs to the adjacent second address at the beginning of the above.

However, the actual system has an interpolation error corresponding to the management level of the system, and a shift occurs between the zone switching unit and the position within the main track wavelength λ. As a result, the first address A ₁ and the first address 2 address a ₂ would produce displacement. As already described, in the first embodiment, the interpolation error in each track is managed so that 2Ie <λ / 2n (where Ie is the amplitude of the interpolation error and n is the expansion number). Therefore, the maximum amplitude of the interpolation error determined by the combination of the interpolation errors of the two tracks does not exceed λ / 2n. Also, considering that the interpolation error changes sinusoidally with a constant period with respect to the wavelength λ, in an actual system having the interpolation error, the position within the main track wavelength λ at the zone switching unit is the origin side. Alternatively, it can be considered as a parallel movement to the maximum measurement position side within the range of the deflection width.

Table 3 considers that the number of pulses 256/32 corresponding to the deflection width λ / 2n is not exceeded, and the above when the deviation is made to the origin side and the maximum measurement position side by 4 pulses corresponding to 1/2 of that. The position within the main track wavelength λ corresponding to the start and end of the 18 zones Z ₀ (A ₂ ) to Z ₁₅ (A ₂ ) and the 8-bit address A ₂ A ₁ to which the position belongs are expressed in hexadecimal. This is indicated by two digits (00 (H) to FF (H)).

As is clear from Table 3, in the zones Z _L (A ₂ ) and Z _u (A ₂ ) at both ends of the second address interval, the context in the second address interval is inverted, and the center Part Z ₇ (A ₂ ) includes the next second address A ₂ A ₁ = 80 (H) that is adjacent at the end part, and Z ₈ (A ₂ ) also includes the second address immediately before the adjacent part at the start part. It can be seen that two addresses A ₂ A ₁ = 7F (H) may be included.

When these are arranged, in an actual system having an interpolation error managed at a predetermined level, the already determined first address is A ₁ = F (H) and the zone start side Z _L ( A ₂ ), and when it is temporarily determined as A ₂ (t) = 0 (H) from the determination result, the first address already determined is A ₁ = 0 (H), and the zone When it is determined that Z _u (A ₂ ) on the end side and A ₂ = F (H) is tentatively determined from the determination result, it may be determined that the second address section has been deviated. The determined first address is A ₁ = F (H), and from the determined zones Z ₀ (A ₂ ) to Z ₇ (A ₂ ), the second addresses A ₂ = 0 (H) to 7 (H ) Is temporarily determined, whether or not the end address belongs to the next adjacent second address The first address that has already been determined is A ₁ = F (H) and the second address A is determined from the determined zones Z ₈ (A ₂ ) to Z ₁₅ (A ₂ ). ₂ = When 8 (H) to F (H) are tentatively determined, if the problem of determining whether the address of the start part belongs within the adjacent second address section is correct, It can be seen that the second address can be determined.

Therefore, in the first embodiment, the phase modulation signal e _pm (A ₁ ) output by detecting the signal of the address track 1 (202) and the signal of the address track 2 (203) are detected and output. The above-described problem is solved by using the phase difference with the phase modulation signal e _pm (A ₂ ).

  In this example, the wavelength λa is formed for 272 (= 17 × 16) wavelengths in the second address section, and the address track 2 has a total of 257 wavelengths of 240 wavelengths and 17 wavelengths of λa. Since the wavelength component is formed, a phase change of 2π × 15 (rad) corresponding to the wave number difference 272−257 = 15 occurs for the movement in the second address section.

In addition, since one section of the second address in the second address section corresponds to λa + 15λ + λa / 16 = (17/16) λa + 15λ, 2π corresponding to λ / 16 for each address in the second address section. A phase difference of / 16 (rad) occurs. In other words, the first address A ₁ = 0 (H) on the start side in the second address section or the first address A ₁ = F (H) on the end side corresponds to λ / 16. The above-described problem is solved by utilizing the fact that the phase difference of 2π / 16 (rad) is different.

FIG. 10A shows a flat phase difference between e _pm (A ₁ ) output from address track ₁ and e _pm (A ₂ ) output from address track 2 in 17 λa sections in address track 2. Ignoring the above, an outline of the phase difference between the e _pm (A ₁ ) signal and e _pm (A ₂ ) in the movement in the second address section will be shown. FIG. 10B shows a detailed phase change including changes between λa at both ends of the second address interval, that is, in the vicinity of A ₂ = 0 (H) and A ₂ = 0 (H). Is.

Table 4 shows a zone determined by the pulse train signal PS (MA ₁ ), a second address A ₂ (t) temporarily determined corresponding to the zone, and a determination value CPn (A ₂ ).
Table 4 shows a signal PW (A ₁ A ₂ ) having a pulse width corresponding to the theoretical value of the phase difference at the second address switching position in the second address section, and CKI that is 256 times the carrier frequency f. The relationship between the number of pulses of the pulse train signal PS (A ₁ A ₂ ) obtained by interpolating the signal is shown, and the second address increases in the number of pulses output from the PS (A ₁ A ₂ ) signal. It can be seen that 16 pulses increase every time.

The number of pulses corresponding to the address switching position is provisionally determined by the pulse train signal PS (MA ₁ ), considering that it corresponds to the end position of the corresponding second address and the start position of the next second address. In the first half A ₂ (t) = 0 (H) to A ₂ = 7 (H) of the second address A ₂ (t), the already determined first address is A ₁ = 0 (H), and When the number of pulses exceeds the above value, it belongs to the next second address, and in A ₂ (t) = 8 (H) to A ₂ = FH in the _second half of the second address period, If the determined first address is A ₁ = F (H) and the number of pulses is equal to or less than the above value, it can be determined that the provisionally determined second address A ₂ (t) is correct.

However, in an actual system, it is affected by the interpolation error, and in the λa section at the start and end of the second address section, this interpolation error causes a constant value relative to the theoretical value (phase difference = 0). A phase difference output with an offset can be obtained. Then, there is a possibility that the maximum phase fluctuation width when interpolation errors of a plurality of tracks are additively superimposed is 2π / 32 (= 2π / 2 × n). The maximum change amount of PS (A ₁ A ₂ ) at this time corresponds to 8 (= 256/32), but the second address switching unit, that is, A ₁ = 0 (H) and A ₁ = F ( Considering that H) occurs every 17 wavelengths of the address track wavelength λa, the influence of the interpolation error of the address track 1 can be ignored, so the maximum change amount of the pulse train signal PS (A ₁ A ₂ ) is 4 It can be estimated to be about the number of pulses, and even if the influence of quantization error related to pulsing is taken into consideration, the fluctuation width does not exceed 5 pulses, and 16 pulses per address in the second address section In consideration of the above difference, a value obtained by subtracting 8 pulses corresponding to the substantially intermediate position of the address can be used as the determination value CPn (A ₂ ) for determining the second address.

When these are rearranged, when it is temporarily determined that A ₂ (t) = 0 (H) at the start of the second address section, the second address section is determined at the start A ₁ = 0 (H) in the address. Similarly, when it is temporarily determined that A ₂ (t) = F (H) at the end of the second address section, it deviates from the second address section at the end A ₁ = F (H) in the address. When the determination taking into account that there is a possibility to be performed is tentatively determined as A ₂ (t) = 0 (H) to A ₂ (t) = 7 (H) in the first half of the second address period excluding the above, By comparing the start portion in the address, that is, the pulse train signal PS (A ₁ A ₂ ) at the first address A ₁ = 0 (H), which has already been determined, with the determination value CPn (A ₂ ). , that does not belong to the next adjacent second address, the second half of _{a 2 (t) = 8 (} H) ~A (T) = F (H) and when it is tentatively determined, the end portion in the address, i.e., already pulse train signal PS _(A 1 A when the confirmation to that first address _A 1 = F (H) ₂ ) may be compared with the determination value CPn (A ₂ ) to determine that it does not belong to the adjacent previous address.

FIG. 11 shows, as a flow, an example of a procedure for determining the second address A ₂ after determining the zone in the second address section as 18 zones Z ₀ (A ₂ ) to Z ₁₇ (A ₂ ). It is a thing. The address determination circuit (60) compares the data D (MA ₁ ) obtained by counting the pulse train signal PS (MA ₁ ) at time t with a predetermined number of pulses Pn (A ₂ ) and sets the second address section to 18 zones. Based on the determined zone, the second address A ₂ (t) is provisionally determined and stored in a predetermined area, and at the same time, the determination value CPn (A ₂ ) corresponding to the zone and the time t After the data D (A ₁ A ₂ ) obtained by counting the pulse train signal PS (A ₁ A ₂ ) is stored in a predetermined area, it is already determined as the stored data according to the determined zone in the second address section. a second address using the first address a ₁ is configured to determine. Hereinafter, each determination condition will be briefly supplemented.

In the zone Z _{L (A 2)} corresponding to the maximum position side as zone Z _{L (A 2)} corresponding to the start position side in the second address period, that zone is a switching position of the second address period . In an ideal state with no interpolation error, the zone Z _o (A ₂ ) is A ₂ = 0 (H) and the zone Z _u (A ₂ ) is A ₂ = F (H). Deviates from the zone, and it is necessary to determine that Z _o (A ₂ ) is A ₂ = F (H) and Z _u (A ₂ ) is A ₂ = 0 (H). Therefore, in this zone, the correct second address A ₂ may be determined by correcting the second address A ₂ (t) provisionally determined according to the already determined state of the first address A ₁ .

Next, a procedure for determining the second address in the zones Z _o (A ₂ ) and Z ₁₅ (A ₂ ) close to both ends of the second address section will be described. This area may belong to the next adjacent second address when the first address already determined in the former is A ₁ = 0 (H), and in the latter when A ₁ = F (H). May belong to the previous address adjacent to. Further, in this region, as shown in FIG. 10, there is a region where the phase change is flat because the signal of wavelength λa is formed. The pulse train signal PS (A ₁ A ₂ ) in an ideal state is 0, but changes in the vicinity of 0 in an actual system, and as described above, a fluctuation of about 0 ± 5 pulses occurs.

Therefore, in the zone Z _o (A ₂ ), the data D (A ₁ A ₂ ) obtained by counting the pulse train signal PS (A ₁ A ₂ ) when the already determined first address A ₁ = 0 (H). ) Is the number of determination pulses CPo (A ₂ ) = 8 or more corresponding to the zone Z _o (A ₂ ) and less than the number of determination pulses CP ₁ (A ₂ ) = 24 in the next zone Z ₁ (A ₂ ) When the condition is satisfied, the second address A ₂ (t) provisionally determined by determining that it belongs to the next second address is corrected, and when the condition is not satisfied, the second address A ₂ (t ) Belong to the correct second address.

In the zone Z ₁₅ (A ₂ ), when the first address A ₁ = F (H) that has already been determined, the data D (A ₁ A ₂ ) has the number of determination pulses CP ₁₅ (A ₂ ) = less than 248, and when the condition of the determination pulse number CP ₁₄ (A2) = 232 or more in the zone Z ₁₄ (A ₂ ) corresponding to the previous zone belongs to the second address before one If the second address A ₂ (t) determined to be temporary and corrected and the condition is not satisfied, the second address A ₂ (t) temporarily determined belongs to the correct second address. Just judge.

Then, in Z ₁ (A2) to Z ₇ (A2) in the first half of the second address section, there is a possibility that the next adjacent second address belongs when the already determined first address is A ₁ = 0 (H). In the latter half of Z ₈ (A2) to Z ₁₄ (A2), when A ₁ = F (H), there is a possibility that it belongs to the previous second address adjacent thereto. However, in these areas, the pulse train signal PS (A ₁ A ₂ ) output at the address switching position is a signal that increases monotonously with an increase in address, so in the former case, A ₁ = 0 (H). When the data D (A ₁ A ₂ ) exceeds the determination value CP _n (A ₂ ) corresponding to the zone, it is assumed that it belongs to the next adjacent second address. In the latter case, A ₁ = F ( H), if the data D (A ₁ A ₂ ) does not exceed the zoned determination value CP _n (A ₂ ), the second address A ₂ (t ) Should be corrected.

Synthesis of absolute position Next, from these results, the section which is enlarged to n ² times the main track wavelength lambda, the steps to convert the absolute value data resolution 1μm units described. The absolute position synthesizing circuit (70) counts a pulse train PS (M) (not shown) output at time t, and as a data D (M) in units of 1 μm, the maximum is 256 μm, that is, 8-bit absolute data and an address track. 1 and 16 first addresses A ₁ and 16 second addresses A ₂ identified using the address track 2, and n ² (= 256) times section of the main track wavelength λ based on the following equation The absolute value data DT (AB) having a resolution of 1 μm is synthesized.

  As exemplified above, when the main track wavelength λ = 256 μm, two address tracks are used in addition to the main track, and the extension number n = 16, a 16-bit encoder with 1 μm resolution can be realized. Indicated. This indicates that, for example, when applied to a rotary encoder, a small rotary encoder having a diameter of about 21 mm can be realized. Whereas a conventional absolute type encoder of the same size using a code plate or the like generally has a resolution of about 8 to 10 bits, this embodiment can realize a small and high resolution rotary encoder. . Further, since the rotary encoder is excellent in the reproducibility of the traveling system, the number of expansions can be selected as large as n = 32 = 32 to 64. For example, if the main track wavelength λa = 64 μm is divided into 1/256 and the expansion number is n = 32, a rotary encoder having a resolution of 18 bits can be realized with a disk having a diameter of 20 mm, and higher accuracy is required. It can also be used in other fields.

Second Embodiment FIG. 12 shows the overall configuration of an encoder according to the second embodiment. Assuming an encoder with a wide measurement range, a third address track (hereinafter referred to as address track 3) is added to the configuration of the first embodiment as illustrated in FIGS. A 20-bit encoder that detects a section of 16 ³ = 4,096 times the main track wavelength λ with a resolution of 1 μm is realized with 256 μm and an extension number n = 16.

Configuration of Each Track FIG. 13 shows the configuration of the address track 3 added in the second embodiment. In the section of 16 × 256 = 4,096 times the main track wavelength λ, the extension number n = 16. Then, the address track 3 is added so as to satisfy the following relationship, and 16 sets of one wavelength λa of the address track 1 and 255 wavelengths of the main track wavelength λ are formed, and then one wavelength of the address track 1 wavelength λa. A scale is formed to output the minute.

16 ³ λ = 16 × (16 ² −1) λ + 16λ
= 16 × 255λ + 17λa
= 16 × (λa + 255λ) + λa

Circuit Configuration FIG. 14 shows an example of a specific circuit configuration in the second embodiment. In addition to the addition of the portion related to the extension of the address track 3, the circuit portion for comparing the phase of the phase modulation signal output from each track is different from that in the first embodiment. Here, only parts that have been changed and added to the first embodiment will be described.

In the scale section (20A), a signal of λ = 256 μm and a signal of λa = 240.9 μm are formed in a predetermined relationship with an address track 3 (204) and a two-channel detection head for detecting the signal ( 214) and a displacement amount detection circuit 4 (404) for outputting the detection signal as a rectangular wave phase modulation signal e _pm (A ₃ ).

The phase comparison circuit 2 (401) compares the e _pm (A ₁ ) signal with the REF signal and compares the phase difference 2πx / λa, that is, PW (A with a pulse width corresponding to the position x in the address track 1 wavelength λa. ₁ ), the phase comparison circuit 3 (402) compares the e _pm (A ₂ ) signal with the REF signal, and compares the phase difference, that is, PW (A of the pulse width corresponding to the position in the address track 2) ₂ ), and the phase comparison circuit 4 (403) compares the e _pm (A ₃ ) signal and the REF signal to compare the phase difference, that is, PW (A of the pulse width corresponding to the position in the address track 3) ₂ ) It is configured to output a signal.

In the first embodiment, the phase difference between the e _pm (M) signal and the e _pm (A ₁ ) signal is determined. In the phase comparison circuit 3, the level between the e _pm (M) signal and the e _pm (A ₂ ) signal is determined. Whereas the phase difference is directly compared, in the second embodiment, the comparison is made with the reference signal REF having the same frequency f as the phase modulation signal and the phase of 0, and the final address of the second address A ₂ is changed. The determination signal generation circuit (50) that has generated a signal for determination is omitted.

The address determination circuit (60A) outputs the PW (M) signal, the PW (A ₁ ) signal, the PW (A ₂ ) signal, the PW (A ₃ ) signal and the signal output from the phase comparison circuits (401 to 404). Addresses A _{1 to} A ₃ are determined from the CKI signal and REF signal from the generation circuit (80), added to the position within the main track wavelength λ in consideration of the weight, and converted to an absolute position of 20 bits with a resolution of 1 μm. Circuit.

Third Address Determination Process First, the address determination circuit (60A) outputs a PW (M) signal output from the phase comparison circuit 1 (401), and a PW (A ₁ ) signal output from the phase comparison circuit 2 (402). Using the PW (A ₂ ) signal output from the phase comparison circuit 3 and the PW (A ₃ ) signal output from the phase comparison circuit 4 and the CKI signal and REF signal output from the signal generation circuit, the first implementation is performed. A procedure for generating a signal group similar to that in the embodiment will be described.

The address determination circuit (60A) interpolates the CKI signal into the PW (M) signal output from the phase comparison circuit 1, and the phase difference 2πx / λ between the phase modulation signal e _pm (M) and the reference signal REF, that is, A CKI signal is interpolated into a pulse train signal PS (M) (not shown) having a pulse number corresponding to a position x within the main track wavelength λ, and a CKI signal is added to a PW (A ₁ ) signal output from the phase comparison circuit 2. Is converted into a PS (A ₁ ) signal (not shown) having a phase difference between the phase modulation signal e _pm (A ₁ ) and the reference signal REF, that is, a pulse number corresponding to a position within the address 1 track wavelength λa. To do. After that, by calculating (specifically subtracting) the pulse train, a pulse train signal PS (MA _{1 not} shown) having a pulse train corresponding to the phase difference between the e _pm (M) signal and the e _pm (A ₁ ) signal. ).

Similarly, the address determination circuit (60) converts the PW (A ₂ ) signal and the PW (A ₃ ) signal into pulse train signals PS (A ₂ ) and PS (A ₃ ) (not shown), and then PS (M) And PS (A ₂ ) are used to calculate a pulse train signal PS (MA ₂ ) (not shown) having a pulse train corresponding to the phase difference, and to the PS (M ₃ ) signal and PS (A ₃ ) signal. The pulse train signal PS (MA ₃ ) (not shown) is further converted into a pulse train signal PS (A ₁ A ₃ ) corresponding to the phase difference by calculation of the PS (A ₁ ) signal and the PS (A ₃ ) signal.

  In the second embodiment, the main track in the third address section has a main track wavelength λ of 4,096 wavelengths, and the address track 3 has a main track wavelength λ of 4,080 wavelengths. Since one wavelength λa is a total of 4,097 wavelengths corresponding to 17 wavelengths, a phase difference 2π corresponding to one wavelength is generated for movement in the third address section.

FIG. 15 shows the relationship of the phase difference between the e _pm (M) signal and the e _pm (A ₃ ) signal. The e _pm (M) signal and the e _pm (A ₁ ) signal in the _first embodiment. It can be seen that the configuration has the same configuration except that the interval between the zone switching portions is increased from λa + 15λ to λa + 255λ by 240λ of the main track wavelength.

That is, the PS (MA ₃ ) newly generated in the second embodiment is pulsed in the 17 λa intervals of the third address interval in the same manner as the pulse train signal PS (MA ₂ ) in the first embodiment. The number changes steeply from 0 to 256/17, and in 16 255λ sections, the pulse train signal has a constant number of pulses n × 256/17 (where n = 1 to 16) corresponding to the position, Using the number of pulses P _n (A ₃ ) (not shown) having the same value as in the first embodiment, the zone Z _L (A ₃ ) on the start position side and the zone Z on the end side in the third address section _U (A ₃ ) and 16 zones Z ₀ (A ₃ ) to Z ₁₆ (A ₃ ) in the central part are determined, and based on the determination result, the third address A ₃ (t) = 0 (H) ~ F (H) can be provisionally determined.

Table 6 is expanded to 12 bits in the main track wavelength λ at the start and end points of the 18 zones in the third address section in an ideal state according to the first embodiment. is a table showing the relationship between the address _{a 3 a 2 a 1 (H} ). It can be seen that the address is the same as that of the first embodiment except that the number of digits is increased to A ₃ A ₂ A ₁ (H).

That is, both ends Z _L (A ₃ ) and Z _U (A ₃ ) of the third address section and Z ₇ (A ₃ ) in the middle part have the same third address, whereas in other zones, the zone starts And the zone end portion have different third addresses A _3, and the lower address in a zone having different third addresses A ₃ may be A ₂ A ₁ = 00 (H) or FF (H) Recognize.

Furthermore, both the PS (MA ₂ ) signal and the PS (MA ₃ ) signal have a region in which the number of pulses changes in one section of the address track 1 wavelength λa. Considering that the insertion error has the same tendency, in the actual system having the interpolation error, it is determined as Z _L (A ₃ ) of the zone start portion as in the first embodiment, and When the already determined address is A ₂ A ₁ = FF (H), it is determined as Z _U (A ₃ ) on the zone end side, and the already determined address is A ₂ A ₁ = 00. In the case of (H), there is a possibility of deviating from the second address section, and it is necessary to make a determination based on the already determined state of the _second address A ₂ A ₁ .

When it is determined that Z ₀ (A ₃ ) to Z ₁₇ (A ₃ ) and the already determined address is A ₂ A ₁ = 00 (H), there is a possibility that the address belongs to the next adjacent third address. When it is determined that there are Z ₈ (A ₃ ) to Z ₁₅ (A ₃ ) and the already determined address is A ₂ A ₁ = FF (H), the third address before the adjacent one is set. When there is a possibility of belonging, that is, when A ₂ A ₁ = 00 (H) or A ₂ A ₁ = FF (H) as in the first embodiment, it belongs to which side of the adjacent third address It can be seen that it is sufficient to solve the problem.

Therefore, the second embodiment is also configured to solve the above problem using the phase difference between the phase modulation signal e _pm (A ₁ ) and the e _pm (A ₃ ) signal. As described above, in the third address section, the wavelength λa of the address track 1 is 4,352 (= 17 × 16 ² ) wavelengths, and the address track 3 is a combination of the main track wavelength and the address track 1 wavelength 4. , 097 wavelengths are formed, and the phase difference changes by 2π × 255 (rad) corresponding to the difference in wave number with respect to the movement of the third address section. Since one address section in the third address section corresponds to λa + 255λ + λa / 16, the phase difference generated for each address in the third address section is 2π / 16 (rad) corresponding to λa / 16. As in the first embodiment, the phase difference of 2π / 16 (rad) differs when the positions of adjacent third address switching units in the third address section are compared with each other.

Accordingly, also in the determination of the third address, the data D (MA ₃ ) obtained by counting the pulse train PS (MA ₃ ) at time t is used as the number of pulses as in the second address determination in the first embodiment. Compared with Pn (A ₃ ), 18 zones Z _L (A ₃ ), Z _U (A ₃ ) and Z ₀ (A ₃ ) to Z ₁₅ (A ₃ ) are determined, and the determined zones are Data D obtained by tentatively determining the third address A ₃ (t) based on the selected zone and selecting the discrimination condition according to the determined zone and counting the pulse train PS (A ₁ A ₃ ) at the same time t (A ₁ A ₃ ) is compared with the third address determination pulse number CP _n (A ₃ ) having the same value as in the first embodiment to correct the temporarily determined address A ₃ (t) and correct it is possible to determine the third address a _3.

Figure 16 is a diagram showing the procedure up to determine the third address A ₃ in the third address period by utilizing the results of the zone Z ₀ to Z ₁₇ of the 18 sites were detected in the flow chart.

The absolute position composition is also the same as that of the first embodiment. The absolute position generation circuit (70A) combines the determined addresses A _{1 to} A ₃ and the data D (M) corresponding to the position within the main track wavelength λ read at time t in consideration of the weight. The absolute value data DT (AB) in units of 1 μm is synthesized.

In the second embodiment, it has been shown that an encoder having a resolution of 20 bits with three address tracks can be realized. This indicates that a section of 4,096 times the main track wavelength λ can be detected absolutely, and when applied to a linear encoder, a section of 1,048 mm can be detected absolutely, It can be used as a linear absolute positioning device in combination with a linear slide with a drive mechanism.
In the present invention, it is easy to increase the number of interpolations and further divide the main track wavelength more finely to realize high resolution, and the address track can be extended as necessary. Further, in a system in which the traveling system is stable and excellent in reproducibility, the expansion number n can be set to a larger value, and a high-resolution rotary encoder or a linear encoder with a long measurement range can be realized.

Third embodiment (expansion of measurement range)
1 μm resolution encoder with 16-bit resolution by expanding the address track to 2 according to the first embodiment, 1 μm resolution with 20-bit resolution by expanding the address track to 3 according to the second embodiment An example of application to an encoder has been described. In the address expansion, the abrupt phase difference 2π / (n + 1) generated within one section of the address track 1 wavelength λa by the phase comparison between the main track, the address track 2 and the address track 3 is used to expand the address. After determining a zone that is substantially equal to the address section, the phase comparison between the address track 1, the address track 2, and the address track 3 utilizes the fact that the phase changes by 2π / n for each address switching section. It was shown that the address and the third address were correctly determined.

  According to the present embodiment, even when the address track 4 is expanded, the section in which the steep phase is obtained is the (n + 1) section in which the wavelength of λa is formed, and the address track 1 and the address track 4 The basic characteristic that the signal obtained by the phase comparison is changed by 2π / n in the adjacent address section does not change. In other words, the address track can be expanded as much as necessary to expand the absolute measurable range. In the first embodiment and the second embodiment, the extension number n is a binary sequence value, but a decimal sequence value or an M-ary sequence (where M is a natural number) may be selected. .

Fourth embodiment (track position deviation correction)
In the first and second embodiments, the scale start positions in the plurality of main tracks and the plurality of address tracks are formed in an ideal state, and the phase relationship between the scale and the head is in an ideal state. It has been described on the assumption that it is arranged in the above. However, in an actual system, even if the start positions of the scales on the respective tracks on the scale can be matched, it is inevitable that the positional relationship between the scale track and the detection head facing the shift will occur. As a result, an address shift in units of the main track wavelength λ may occur, and there may be a shift at the intended origin position on the scale as an encoder.

In some cases, it is desirable to match the origin positions as encoders in order to maintain compatibility between encoders. Therefore, a memory area of a non-volatile storage unit (not shown) is secured in the address determination circuit, and the position difference within the main track wavelength λ and the address track wavelength λa are stored in the memory for the first embodiment. The correction amount that gives an offset to the pulse train signal PS (MA ₁ ) corresponding to the difference between the two and the pulse train signal PS (MA ₂ ) corresponding to the difference between the position within the main track wavelength λ and the position within the wavelength of the address track 2 A correction amount that gives an offset and a correction amount that gives an offset to the pulse train signal PS (A ₁ A ₂ ) corresponding to the difference between the position of the address track 2 in the wavelength λa and the position of the address track 2 in the wavelength are given. Further, for the second embodiment, the correction amount for giving an offset to the pulse train signal PS (MA ₃ ) corresponding to the position in the main track wavelength λ and the position in the address track 3 and the wavelength λa of the address track 1 A correction amount that gives an offset to the pulse train signal PS (A ₁ A ₃ ) corresponding to the difference between the position in the address track 3 and the position in the wavelength of the address track 3 is stored in the nonvolatile storage unit, and this is calculated from the data counted at time t. If the correction amount is configured to be added or subtracted, a predetermined offset is given to a position within a wavelength reproduced from a plurality of tracks, and the main track wavelength λ unit due to an unintended shift between tracks in each encoder is provided. It is possible to maintain compatibility between encoders by correcting misalignment or by intentionally shifting the origin position on the scale. Come.

  In this embodiment, the correction amount for giving an offset to the pulse train signal accompanying the position difference between the tracks is stored, but the offset is given to the in-wavelength positions of the main track and the plurality of address tracks. Even if configured in this way, the same effect can be obtained.

Fifth embodiment (selection of displacement detection circuit)
In the present invention, the position in each track is detected as a phase, and a section multiple times the main track wavelength λ is detected absolutely by using the phase difference between these tracks. Therefore, as the displacement detection circuits (301 to 304), as illustrated in FIG. 17, a phase detection type displacement amount detection circuit is suitable.

  Further, in the present invention, when the main track has a scale with an equal interval of wavelength λ, and the address track has an extension number n, nλ = (n + 1) λa, and the equally spaced wavelength λ has a relationship of nλ = (n + 1) λa. For the subsequent address tracks, it is necessary to form the main track wavelength λ and the address track 1 wavelength λa in a predetermined combination. Therefore, in order to cope with various applications, it is preferable to adopt a magnetic recording system. As a displacement amount detection circuit in the first embodiment and the embodiment, as shown in FIG. It is preferable to use a magnetoresistive effect element and modulate a quadrature signal obtained from two channels with a signal orthogonal to the carrier frequency f, and add these signals to output a position modulation signal. is there.

Progress in mixed signal technology in recent years is often more convenient when analog signals are converted into digital signals and processed, and in the case of detecting a position within a wavelength in the present invention, a phase displacement type displacement amount is not necessarily required. It need not be a detection device. Figure 18 is configured to convert the quadrature signal of the signal e ₂ which is output from the signal e _1, CH2 side detection head output from the CH1-side detection head to a position within the wavelength by polar coordinate transformation (phase) "coordinates 3 shows a configuration example of a “conversion-type displacement amount detection circuit”.

In the circuit shown in FIG. 18, if the displacement is x, the output signal e ₂ from the output signals e ₁ and CH2 detection head from CH1 detection head can be expressed as follows.

If the phase corresponding to the position in the wavelength is X (= 2πx / λ), e ₁ and e ₂ can be rewritten as follows.

A / D conversion circuit is a circuit for converting the output e ₂ of the output e ₁ and CH2 side detection head CH1 side detection head into digital data, the resolution required to obtain a predetermined resolution by interpolating the main track wavelength For example, if the main track wavelength is divided into 1/256, it is preferable to use an A / D converter having a resolution of about 12 bits.

  These signals are guided to an absolute value generation circuit and a coordinate conversion circuit, and are configured to obtain a phase X (= 2πx / λ) corresponding to a position within the wavelength. The phase X can also be obtained by the inverse tangent calculation (arc tangent), but in this calculation, the denominator becomes 0 in some areas and an indefinite calculation occurs. Therefore, in the configuration example shown in FIG. 18, an absolute value generation circuit that generates an absolute value | R | from outputs output from two sets of detection heads is provided, and the absolute value is used to correspond to a position in the wavelength. The phase X is obtained.

  Although the actual calculation is processed as a digital signal, for convenience, the analog signal will be described as it is, and the absolute value | R | and the position X within the wavelength can be obtained by the following calculation.

Next, the influence when a track on which signals of different wavelengths are formed using a coordinate conversion type displacement amount detection circuit will be described.
'When ₂ to, e' CH2-side detection head the CH2 side output when deviated ΔZ from the ideal state e ₂ can be expressed as follows.

  Therefore, if the position in the wavelength at this time is X ′,

  The phase X in the ideal state can also be expressed as follows using an inverse function of tangent.

  Thus, the phase error ΔX (X′−X) at this time is approximately

  Furthermore, since sinΔZ << 1 + cosΔZ and tanX = X at a small angle,

  Thus, exactly the same result as that obtained when the phase modulation signal is used can be obtained. As the displacement amount detection circuit in the present invention, not only a phase detection type displacement amount detection circuit but also a displacement amount detection device that generates a position within a wavelength by coordinate conversion from orthogonal two-phase signals can be used.

In the present invention, it is easy to increase the number of interpolations and further divide the main track wavelength more finely to realize high resolution, and the address track can be extended as necessary.
Further, in a system in which the traveling system is stable and excellent in reproducibility, the expansion number n can be set to a larger value, and a high-resolution rotary encoder and a linear encoder with a long measurement range can be realized.

  The absolute encoder of the present invention is a machine tool, a robot, etc., a manufacturing processing industry that requires precise position measurement for precision parts processing, an industrial machine field that requires liquid level measurement, stroke measurement, etc. It can be used in all industrial fields that require high speed, high accuracy, and high reliability.

  DESCRIPTION OF SYMBOLS 1 ... Rotary shaft, 20 ... Scale part, 201-203 ... Track, 211-213 ... Detection head, 30, 301-303 ... Displacement amount detection circuit, 40, 401-403 ..Phase comparison circuit, 50... Determination signal generation circuit, 60, 60A... Address determination circuit, 70, 70A.

Claims (7)

A main track in which first graduations are formed at equal intervals at the first wavelength (λ), and a first address section (nλ, where n is an extension number) that is n times the first wavelength λ at the second wavelength (λa). a first address track in which a second graduation having equal intervals of nλ = (n + 1) λa is formed, and an address section that is arranged adjacent to these tracks and extends the first address section in units of n times , A scale portion having at least one extended address track having an extended scale formed by a combination of the first wavelength and the second wavelength in which nλ sections are replaced by (n + 1) λa,
A detection unit for detecting scales of the plurality of tracks;
Phase difference detection means for detecting a phase difference of each of the signals indicating the scales of the plurality of tracks detected by the detection unit;
An absolute encoder comprising: processing means for performing address determination based on a plurality of phase differences detected by the phase difference detection means and calculating a position or angle of the measurement target. A main track in which first graduations are formed at equal intervals at the first wavelength (λ), and a first address section (nλ, where n is an extension number) that is n times the first wavelength λ at the second wavelength (λa). a first address track in which second graduations with equal intervals of nλ = (n + 1) λa are formed, or in addition to these tracks, an address section obtained by extending the first address section in units of n times A scale portion having an extended address track formed of at least one extended scale formed by a combination of the first wavelength and the second wavelength in which nλ sections are replaced by (n + 1) λa;
A detection unit for detecting scales of the plurality of tracks;
Phase difference detection means for detecting a phase difference of each of the signals indicating the scales of the plurality of tracks detected by the detection unit;
Processing means for performing address determination based on a plurality of phase differences detected by the phase difference detection means, and calculating the position or angle of the measurement object;
When the amplitude of the interpolation error of the track having the largest interpolation error due to the incompleteness of the two-phase sine wave signal detected from these tracks is Ie, the extension number n and the first wavelength λ in each address track Is set so that 2Ie <λ / 2n.
The phase difference detecting means detects a difference between a position in the first wavelength (λ) and a position in the second wavelength (λa) as a phase difference, and 0 to 2π (in the n-fold section of the first wavelength λ). rad) to obtain a phase difference signal that continuously changes until
The processing means includes
After the phase difference detected at time (t) is divided by 2π / n and the quotient is used to temporarily determine the address of the first wavelength λ unit in the nλ section,
Divide the remainder in the calculation into three zones of 0 or near the maximum value and the center,
The size of the region in the vicinity of 0 or the maximum value is set as a region obtained by adding a phase difference corresponding to a quantization error generated in the calculation process to a phase difference corresponding to λ / 2n,
When the remainder belongs to a central zone, the tentatively determined address is unconditionally. When the remainder belongs to a zone near 0 or the maximum value, the predetermined position within the first wavelength (λ) is An absolute encoder that is configured to determine addresses in λ by comparison. The second address track applied first among the extended address tracks is formed adjacent to the main track or the first address track, and is a second address interval (n) n times the first address interval (nλ). ² λ), a third graduation of n ² λ = n (λa + (n−1) λ) + λa is formed, and the third address track to be applied next is a third number n times the second address interval. In the address section (n ³ λ), a fourth scale of n ³ λ = n (λa + (n ² −1) λ) + λa is formed, and the fourth address track and the fifth address track expanded according to the same rule. The absolute encoder according to claim 1, wherein the absolute encoder is formed as follows. The phase difference detecting means is configured to detect a position in the first scale of the main track and a third position of the second address track in a second address interval (n ² λ) that is n times the first address interval (nλ). Detecting a difference in position within the graduation and a difference between a position within the second graduation of the first address track and a position within the third graduation of the second address track as a phase difference;
The processing means has a sudden phase change at the (n + 1) positions where the second wavelength (λa) is formed for each section substantially equal to the first address section (nλ), and the first wavelength λ is ( n-1) A signal having a flat phase difference is used in n sections formed for the wavelength, and a correct address is obtained in an area excluding the address switching area in the first address section (nλ), and the first address It is configured to identify n addresses in nλ units using a phase difference of 2π / n (rad) by 2π / n (rad) at an address switching position in a section (nλ) unit and an already determined λ unit address. Yes,
The absolute encoder according to claim 1. The phase difference detecting means is configured to detect a position in the first scale of the main track and the position of the third address track in a third address interval (n ³ λ) that is n times the second address interval (n ² λ). Detecting a difference in position in a fourth scale and a difference in position in the second scale of the first address track and a position in the fourth scale of the third address track as a phase difference;
The processing means has a steep phase change at the (n + 1) positions where the second wavelength (λa) is formed for each section substantially equal to the second address section (n ² λ), and the first wavelength λ is (N ² −1) n-number of sections formed for the wavelength are used to obtain a correct address in the area excluding the address switching position in the second address section (n ² λ) using a signal having a flat phase difference. Using the difference in phase by 2π / n (rad) at the address switching position in the second address interval (n ² λ), and using the determined address in λ and the address in nλ, n ² It is configured to identify n addresses in units of λ,
Hereinafter, for the fourth address track and the fifth address track, a phase difference signal similar to the above is obtained, and using the phase difference and the identified address, a higher order address in units of the expanded section is obtained. Configured to be identified,
The absolute encoder according to claim 1. Means for determining an address in units of a first wavelength λ using a position difference within a wavelength of a plurality of tracks; and a correction amount for giving a predetermined offset to a position difference within the wavelength between the plurality of tracks or the plurality of the plurality of tracks Non-volatile storage means for storing a correction amount that gives a predetermined offset to a difference in position within a wavelength between tracks;
The calculation is performed on the data corresponding to the position within the wavelength of the plurality of tracks measured at time (t) or the difference between the positions within the wavelength and the corresponding correction amount stored in the nonvolatile storage means. Configured to correct a positional shift in units of the first wavelength (λ) due to an unintended positional shift between the plurality of tracks, or to make it possible to intentionally adjust the origin position on the scale.
The absolute encoder according to claim 1. The phase difference detection means is a phase detection type displacement amount detection circuit that outputs a phase corresponding to a position in the plurality of tracks as a phase modulation signal, or two orthogonal sine waves output from each track. It is configured by a coordinate conversion type displacement amount detection circuit configured to extract a signal as a phase corresponding to a position within a wavelength by coordinate conversion.
The absolute encoder according to claim 1.

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