JPS63184013A - Optical displacement detector - Google Patents

Abstract

PURPOSE:To increase an allowance degree from a structural planning aspect and to specify an arbitrary absolute origin, by providing separate optical lattices different in a pitch and making it possible to generate a reference pulse signal on the basis of the phase difference between sets from the relation of both optical lattices. CONSTITUTION:A main scale 10 having a measuring optical lattice 13 and an origin detecting optical lattice 15 different from said lattice 13 in a pitch provided thereto and an index scale 20 provided with measuring and origin detecting reference optical lattices 23(23A, 23B), 25(25A, 25B) opposed to each other are moved relatively. Whereupon, by the irradiation of the non-parallel beam from a non-parallel illumination system 40, electric signals having phase differences theta1, theta2 are respectively outputted to the optical lattices 23, 25 from the corresponding photoelectric converter 30. A reference signal generating circuit 70 inputs the electric signals having the phase differences theta1, theta2 and generates a reference signal when the phase difference (theta1-theta2) between sets becomes a specific value. Therefore, by utilizing this signal, the absolute origins of both scales 10, 20 can be arbitrarily specified. The relative moving displacement quantity of both scales 10, 20 is detected by the processing of the signal from the converter 30.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention has a relatively movable measuring optical grating, and transmits reflected light from a main scale through a measuring reference optical grating of an index scale. This invention relates to an optical displacement detection device that detects the amount of relative movement through predetermined processing, and in particular, it is capable of detecting the absolute origin of both scales by providing other optical gratings with different pitches in addition to the measurement optical grating. be.

[Background technology and its problems]

2. Description of the Related Art Reflection-type optical displacement detection devices are known that are used as one means for determining physical specifications (length, pressure, weight) by detecting relative displacement between independent objects.

Such a conventional reflective optical displacement detection device will be explained with reference to FIG. 6. The displacement detection device, which is generally referred to as a moiré stripe method, includes a main scale 10 on which optical gratings 13 for measurement are aligned and a reference optical grating 3A for measurement that corresponds to the main scale 10.
, 3B is displaceable relative to the index scale 20 provided with the index scale 20, and a light source 1 (
A photoelectric converter 2 (
2A, 2B), and the electric signal output from the photoelectric converter 2 is processed in a predetermined manner by the displacement detection circuit 50.
It was configured to obtain a relative displacement amount of 0.20. Note that the reason why two sets of each of the reference optical gratings 3A and 3B and the photoelectric converters 2A and 2B are provided is for the purpose of directional discrimination and improvement of resolution.

The conventional optical displacement detection device configured in this way uses a so-called incremental method in which the amount of displacement is detected in increments, and has a structural problem in that it must have a sophisticated structure to ensure the desired operation. There was a problem with the method.

That is, the structural problem is that the mechanical mutual positional relationship between the optical grating 13 and the reference optical gratings 3A and 3B (main scale 10 and index scale 20) must be strictly established and maintained. In particular, the inter-plane clearance C between both scales 10 and 20 must be more than 10 μm, which not only makes assembly and adjustment extremely difficult.
If the S/N ratio fluctuates in the direction of increasing during operation, the S/N deteriorates significantly, and if it fluctuates in the direction of decreasing, relative movement becomes difficult and detection becomes impossible.

On the other hand, as a problem with the method, if there is a miscount due to noise etc., subsequent counted values (detected values) will become meaningless, and if the power is cut off midway through, the origin alignment work will have to be done again when the power is restored. I had to.

Thus, in the past, to solve the problem with the above method, for example, a random pattern of 80.81 was applied to both scales of 10.20 as shown in FIG. 6, mainly from the viewpoint of facilitating origin alignment.
A so-called absolute origin detecting means is provided for specifying the origin on the main scale 10 by detecting that both random patterns 80 and 81 match. Therefore, the trouble of setting the absolute origin at one end of the main scale 10, for example, is eliminated, but it is difficult to attach the random pattern 80 continuously due to its form, so it is difficult to say that it is a perfect solution. There was a problem in that if the clearance C varied between 10 and 20, the detection origin would be displaced.

In addition, for the above structural problem, both scales are 10.2.
An optical displacement detection device using three optical gratings as shown in FIG. 5 has been proposed, which can greatly expand the clearance C between zero and the permissible variation thereof. Fifth
In the figure, the displacement detection device includes an optical grating 13 for measurement provided on the main scale 10 and an optical grating 1 on the optical system.
3, an index scale 20 that also serves as a second scale having a reference optical grating 3 placed in front of it and a third scale having a reference optical grating 3 placed after it, and diffusion to the main scale 10 through this index scale 20. A condensing lens 42 whose purpose is simply to condense light for irradiation.
and a half mirror 45 for guiding reflected light from the main scale 10 to the photoelectric converter 2 via the index scale 20. Therefore, if the pitch of the optical grating 13 of the main scale 10 is P, the pitch of the reference optical grating 3 of the index scale 20 is q (=2P), and the wavelength of the non-parallel illumination system 40 is λ, then the distance between both scales 10.20 The clearance C can be set as C"-nP"/λ (n is an integer of 1 or more), so the clearance C can be set several times to several tens of times as much as the above moiré stripe method, and the processing ,
It is easy to assemble and adjust, which improves the productivity of the machines used, and further improves ease of handling through long-term stable operation.

However, although it was possible to increase the clearance C, this created a new problem in that it hindered the function of the absolute origin detection means for solving the above-mentioned system problem. In other words, increasing the clearance C itself makes the image of the random pattern 80 or 81 that specifies one point unclear, and since it uses non-parallel light that includes all or part of the diffused light, there is basically no difference. This was due to a technical issue that could not be used by customers.

Thus, no conventional optical displacement detection device has been realized that can solve both the above-mentioned structural and methodical problems.

[Purpose of the invention]

The present invention was made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an optical displacement detection device that has a large margin in structural design and is capable of specifying an arbitrary absolute origin. . [Means and effects for solving the problem] The present invention provides a separate optical grating with a pitch different from that of the optical grating for measurement on the main scale, and utilizes the phase difference between the sets resulting from the relationship between the two optical gratings. This invention solves the above-mentioned conventional problems by making it possible to generate a reference pulse signal that can specify the absolute origin.

For this reason, a main scale is provided with an optical grating for measurement and an optical grating for origin detection whose pitch is different from that of the optical grating for measurement, and an optical grating for measurement and an optical grating for origin detection of the main scale. an index scale that is provided with a reference optical grating for measurement and an optical grating for detecting the origin and that serves as a second scale placed in front of the main scale and a third scale placed after the main scale on the optical system; , a non-parallel illumination system for irradiating non-parallel light to the main scale via the index scale, and a non-parallel illumination system for irradiating non-parallel light to the main scale, and a non-parallel illumination system disposed corresponding to each of the measurement optical grating and the origin detection optical grating of the main scale. Two sets of photoelectric converters receive the reflected light reflected from the main scale and output electric signals with a phase shift of 90 degrees, and the electric signals from the photoelectric converters corresponding to the optical grating for measurement are output. A displacement detection circuit for detecting the amount of relative displacement of both scales through predetermined processing, and determining the inter-group phase difference between the electric signals output from each of the photoelectric converters, and detecting this inter-group phase difference. and a reference signal generation circuit configured to generate a reference signal when the reference signal reaches a specific value, and the absolute difference between the main scale and the index scale is determined using the reference signal output from the reference signal generation circuit. The above purpose is achieved by configuring the system so that the origin can be specified.

Therefore, it is necessary to relatively move the main scale, which is provided with an optical grating for measurement and an optical grating for origin detection with a different pitch from the optical grating, and the index scale, which is provided with a reference optical grating for measurement and for origin detection, which faces the main scale. For example, a photoelectric converter corresponding to a reference optical grating for measurement has a phase difference θ1.
Similarly, the photoelectric converter corresponding to the reference optical grating for origin detection outputs an electrical signal having a phase difference θ2. Here, the reference signal generating circuit receives electrical signals having a phase difference θ1 and 02 as input, and generates a reference signal when the phase difference between pairs (θ1-θ2) reaches a specific value. Therefore, it is possible to arbitrarily specify the absolute origin of both scales using this reference signal, and absolute use is also possible. Note that the amount of relative displacement of both scales can be detected with high precision as in the past by performing predetermined processing on the output signal from the photoelectric converter that corresponds to the reference optical grating for measurement.

Originally, three scales (optical gratings) were provided on the optical system, including an index scale that served as a second scale placed before the main scale and a third scale placed after it, and were irradiated with non-parallel light. Since it is a method in which the reflected light from the main scale is photoelectrically converted after passing through the index scale, the structural and operational effects of increasing the clearance C between the main scale and the index scale are guaranteed. .

〔Example〕

An embodiment of the optical displacement detection device of the present invention will be described in detail with reference to the drawings.

This embodiment is shown in FIGS. 1 to 4, and the apparatus includes a main scale 10 provided with two rows of optical gratings, and second and third scales provided with corresponding reference optical gratings. Index scale 20 that also serves as both scales 10.
A non-parallel irradiation system 40 for irradiating the '20 with light, two sets of photoelectric converters 30 that receive reflected light from both scales 10.
A) Both scales 10.2
A displacement detection circuit 50 capable of detecting a relative displacement amount of 0 and an electric signal from a 2 m photoelectric converter 30 (30A, 30B) are input to calculate the inter-group phase difference, and the inter-group phase difference is determined to a specific value. A reference signal generation circuit 70 generates a reference signal when and an absolute origin setting means 80 for holding and setting the value of .

As shown in FIG. 2, the main scale 10 is in the form of an elongated thin plate made of a glass material 11 with a rectangular cross section, and a measuring light beam with a pitch P of 100 μm is mounted on the lower side (right side in FIG. 1). , the first optical grating 13, which is an optical grating, has a second optical grating 15, which is an optical grating for origin detection, and has a pitch P-ΔP of 99.8 μm on the upper stage side (left side in FIG. 1).
is provided.

Here, the first optical grating 13 has a detection range of 50 m>
is divided into N (=500) equal parts, and the second optical grating 15 is divided into N (=500) equal parts.
Since it is formed to divide into +1 equal parts, L=NP= (N+1)(P-ΔP)...fl
) ΔP = −, L # P ” / ΔP...
(2)(N+1) holds true. The above values were chosen for this relationship.

On the other hand, the index scale 20 is made of a glass material having a rectangular cross section like the main scale 10 and serves as a second scale placed in front of the main scale 10 and a third scale placed after the main scale 10 in the optical system. As shown in FIG. 2, a first reference optical grating 23A (23B), which is a measurement optical grating corresponding to the first optical grating 13 of the main scale 10, is provided on the lower side as shown in FIG. A second reference optical grating 25A (25B), which is an optical grating for detecting the origin and corresponds to the second optical grating 15, is provided on the upper stage side.

The pitch of the first reference optical grating 23A (23B) is q, the pitch of the second reference optical grating 25A (25B) is q-Δq, and the corresponding first and second optical gratings in the longitudinal direction are Two sets of reference optical gratings 23A, 23B, 25A, 2 whose phase is shifted by 90 degrees with respect to the optical grating 13°15
5B is provided. Note that in this example, q=2P
, Δq=Δ2P (However, in FIGS. 1 and 2, for convenience, q#P is drawn.)Next, the photoelectric converter 30 (consisting of two sets of 30A and 30B) is 4 Each photoelectric element 33A, 33B, 3
5A, 35B have preamplifiers 37A, 37B, 38A,
38B are connected to each other. Also, both scales 1
On the opposite side of the photoelectric converter 30 with 0.20 in between, there is a light a that emits not a perfectly parallel ray but a ray that includes at least a diffused component.
4tA, 4tB, condenser lens 4 for simple purpose of condensing light
A non-parallel illumination system 40 is provided for irradiating non-parallel light to both scales 10 and 20 consisting of scales 2A and 42B (optional). The main scale 10 can be moved relative to the main scale 10 in the X direction in the figure in a predetermined relationship.

Then, the index scale 20 and the non-parallel illumination system 40
A half mirror 45 is interposed between the two. Therefore, the non-collimated light irradiated from the non-collimated illumination system 40 first passes through the half mirror 45 and the index scale 20 as the second scale and is irradiated onto the main scale 10, and the reflected light from the main scale 10 is reflected from the main scale 10. After passing through an index scale 20 as a scale of No. 3, the beam is refracted in a 45 degree direction by a half mirror 45 and is incident on a photoelectric converter 30. Further, as described above, the pitch of the first optical grating 13 of the main scale 10 is P, and the pitch of the first reference optical grating 23A (23B) of the index scale (second and third scale) 20 is q (=2
P), and if the wavelength of the light from the non-parallel illumination system 40 is λ, then the clearance C between both scales 10.20 is C#
Since it is determined by npZ/λ (n is an integer greater than or equal to 1), it can be made extremely large, such as several tens of μm.

Here (as seen in FIG. 2, the first optical grating 13
If the origin is the point T where the second optical grating 15 and the second optical grating 15 coincide with each other, and the coordinate in the right direction in the figure, that is, the relative displacement amount of the index scale 20 with respect to the main scale 10 is set as X, the photoelectric elements 33A and 33B Reference optical grating 2
3A and 23B are arranged with a phase difference of 90 degrees, so the output of photoelectric element 33A is
If the output of 3B is bl, both photoelectric elements 33A, 33
The phase difference θ1 of the electrical signal from B can be approximated as follows. Note that □ in the second term on the right side of equation (3) is introduced as a correction term because the amount of transmitted light is maximum at the origin T.

Similarly, the outputs of the photoelectric elements 35A and 35B are at
+bl, the phase difference θ2 between the electrical signals from the photoelectric elements 35A and 35B can be approximated as follows.

The displacement detection circuit 50 also includes a first
It receives electrical signals from the photoelectric elements 33A, 33B of the photoelectric converter 30A corresponding to the reference optical gratings 23A, 23B, and includes a pulsing circuit of 1 μm/1 pulse and a reversible counter. It is also said to have waveform shaping, division, direction discrimination, and precent functions.

Now, as shown in FIGS. 3 and 4, the reference signal generation circuit 70 generates the signal al (A sin θ1) and the signal b2 (
a multiplier 71 that multiplies the signal a2 (Bcos θ2) and the signal bl (A sin θ, );
The output signals of the multiplier 72 and both multipliers 71 and 72 are subtracted and the signal I (AB (cos θ.

sin19g −sinθ, conθt ) =A
A subtracter 73 for outputting B sin (θ1-02)), and a comparator 7 for comparing the output signal I of the subtracter 73 with the reference value of the reference value setting device 76 and outputting the signal J.
4, and a reference pulse generating circuit 75 that generates a specific reference signal K from the output No. 13 J of the comparator 74 (in this embodiment, it is generated at the rising edge of the signal J).

Therefore, if the reference value is set to zero by the reference value setter 76, the reference signal K is set at each detection range length when the signal I becomes zero in the rising direction, as shown in FIG.
can occur.

The absolute origin setting means 80 receives a hold switch 83, a set switch 84, and a reference signal K, and is also connected to a hold switch 81 and a set switch 84, and sends a hold signal H2 and a set signal ST to the displacement detection circuit 50.
2 and a hold circuit 82 connected to the displacement detection circuit 50. Here, the control circuit 81 holds the count value of the counter of the displacement detection circuit 50 in the hold circuit 82 when the hold switch 83 is closed, the signal H1 is set to low level (LL), and the reference signal K is input. It functions to make In this case, the value displayed on the display means 60 is also held.

Further, when the detection work is restarted, the cent switch 84 is closed, the signal STI is set to low level (LL), and the reference signal K
When inputted, the count value previously held in the hold circuit 82 is presented to the displacement detection circuit 50 (a display buffer not shown in detail), and the measurement function is restarted.

Next, the operation of this embodiment will be explained.

For example, main scale 1 is installed on a stationary object such as a machine tool vent.
0 is fixed, the index scale 20 is integrated with the non-parallel illumination system 40 and the photoelectric converter 30, and the index scale 20 is fixed to a movable body such as a slider. Therefore, by operating the machine tool, the main scale 10 and the index scale 20
When these move relative to each other, each photoelectric element 33A, 33B, 35
Electrical signals al + bl + a from A and 35B
m + b2 is output, and the signals al+ bl and a2. b, whose cycle differs by an amount equivalent to the pitch difference of the optical grating 13.15, and the signals a, and bl and a2
and bt each produce a phase difference of 90 degrees.

Here, the displacement detection circuit 50 is a first
optical grating 11, and a photoelectric element 33A corresponding to the first reference optical gratings 23A and 23B, which are reference optical gratings for measurement.
, 33B (amplifiers 37A, 37B) output signal a
1. Using bl as an input, the relative movement variables of both scales 10 and 20 are detected and displayed on the display means 60 as in the case of the conventional optical displacement detecting device shown in FIG. In this case, the displacement detection circuit 50 starts counting with the absolute position set by the reference value setter 76 of the reference signal generation circuit 70 and immediately after closing the cent switch 84 of the absolute origin setting means 80 as the absolute origin. It is formed with what you do.

Next, when the work is interrupted during a lunch break or the like, the hold switch 83 in the absolute origin setting means 80 is closed. Thereafter, the reference signal K is output from the reference signal generation circuit 70 (the setting value of the reference value setter 76 is assumed to be set to "zero" for ease of explanation) (see Fig. 4). Instantaneously, the control circuit 81 outputs a hold signal H2 and holds the count value of the counter (specifically, the display buffer) of the displacement detection circuit 50 in the hold circuit 82. Here, the absolute position at the time of interruption of the work is held in the hold circuit 82 and its value is displayed on the display means 60.

Note that the hold circuit 82 is configured to be able to store the held contents even if the power to the entire apparatus is cut off.

Next, when resuming work, the seven-node switch 84 is closed. Main scale 1 when work is interrupted immediately after that
When the reference signal K is output from the reference signal generation circuit 70 by slightly moving the index scale 20 so as to pass through the relative position between 0 and the index scale 20 once, the control circuit 81 detects the displacement of the contents stored in the hold circuit 82. present to circuit 50.

Therefore, the work can be resumed at the same position as when the work was interrupted and with the same value displayed on the display means.

Therefore, according to this embodiment, the main scale 10
An optical grating for origin detection with a pitch different from that of the optical grating for measurement is provided on the index scale 20, and reference optical gratings for measurement and origin detection are also provided in the index scale 20. Since a reference signal generation circuit 70 is provided that calculates the inter-group phase difference based on the electrical signal and generates a reference pulse signal when the inter-group phase difference reaches a specific value, the reference signal K can be used to generate a reference pulse signal. The absolute positional relationship between both scales 10 and 20, that is, the absolute origin can be detected.

Therefore, even in the case of an incremental type displacement detection device, semi-absolute operation can be achieved by restarting from the set absolute origin without having to perform complicated origin adjustment work when work is interrupted. In addition, since the reference signal is generated based on the phase difference between the sets based on the optical gratings provided on both scales 10 and 20, it has higher accuracy and deteriorates over time compared to absolute origin detection means using, for example, an electromagnetic switch. There is no.

The displacement detection circuit 50 also includes an optical grating 13.2 for measurement.
A photoelectric element 33A corresponding to 3A and 23B.

Both scales 10.
20 relative movement displacements can be detected, so there is no difference from the conventional method in terms of accuracy and handling. In particular, in this embodiment, the index scale 20 is placed in front of the main scale 10 on the optical system, and the index scale 20 is placed after the main scale 10 in the optical system. The irradiation is performed by a non-parallel illumination system 40, and the clearance C between both scales of 10° and 20° can be expanded, and there is a large margin in the structural design of the device, and it is easy to process, assemble, adjust, and operate the device. The actual situation can be dramatically improved. Of course, even if the clearance C is enlarged, the reference signal K is generated based on the phase difference between the pairs, so that highly accurate detection of the absolute origin can be guaranteed. Here, the conventional structural problems and system problems can be solved at once.

Furthermore, since the reference signal generation circuit 70 is configured to compare the periodic function output signal related to the inter-group phase difference of the subtracter 73 with the set value signal of the reference value setter 76 using a comparator 74, the setting By changing the value settings, it is possible to set the absolute origin anywhere on the main scale 10. This is equivalent to using conventional absolute origin detection means such as an electromagnetic switch or a random pattern that is continuously installed, and it is practical to match the mechanical characteristics of the machine tool etc. in which the device is used, simplify the absolute origin alignment work, etc. The above profits can be further improved.

Furthermore, absolute origin setting means 80 is provided to prevent work interruption,
If a switch such as the hold switch 83 is operated to cancel or restart, the absolute relative movement amount from the absolute origin is stored (held) using the reference signal K from the reference signal generation circuit 70, and the work is resumed from this value. Since the displacement detection circuit 50 is matched with the displacement detection circuit 50 so that the displacement detection circuit 50 can perform .

In this embodiment, the first optical grating 13, which is the measurement optical grating of the main scale 10, is shown in FIG.

The pitch P is 100 μm, the pitch P-ΔP of the second optical grating 15, which is the optical grating for origin detection, is 99.8 μm, and the length of the detection range is 50 Tsuru, but the length of the detection range is 51 Otori. You can also do that.

Further, the reference signal generation circuit 70 is formed from multipliers 71, 72, a subtracter 73, etc., but the point is that the 2Mi photoelectric converter 3
The four signals al, bl, a2, and b2 from 0 are input to calculate the inter-set phase difference (θ2-θ1), and when the inter-set phase difference reaches a specific value, the absolute origin between both scales 10.20 is determined. Since it is sufficient to generate the reference signal K for specifying the reference signal K, the reference signal K is not limited to the scope disclosed above, and may be generated from a computer or the like. The same applies to the absolute origin setting means 80.

Further, the absolute origin setting means 80 is configured to operate the hold switch 83 when interrupting or canceling the work, but this is not done manually, but by, for example, reducing the power supply of the non-parallel illumination system 40 or using the op speed from the displacement detection circuit 50. is detected by known means, and the control circuit 81 is automatically activated by these signals.
It may be formed so that it is activated and held.

Furthermore, it is also possible to count the reference signals K from the reference signal generation circuit 70, determine the number of the reference signals, and set a plurality of absolute origins.

Although the detection device itself is a reflective linear type using the non-parallel illumination system 40, the present invention is also applicable to a rotary type instead of a linear type. Furthermore, the detection range length is the length in the direction of relative movement between the main scale 10 and the index scale 20, but since this detection device detects displacement, the measurement target is limited to length, width, etc. Not, but
It may be pressure, weight, etc.

〔Effect of the invention〕

The present invention has the advantage that it is possible to provide an optical displacement detection device that has a large margin in structural design and can specify an arbitrary absolute origin.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the optical displacement detection device according to the present invention, FIG. 2 is an enlarged view of the main parts, FIG. 3 is a configuration diagram of the reference signal generation circuit, and FIG. 4 5 is a schematic diagram showing a conventional reflective displacement detection device, and FIG. 6 is a schematic configuration diagram of an optical displacement detection device equipped with a conventional absolute origin detection means. DESCRIPTION OF SYMBOLS 10... Main scale, 13... First optical grating which is an optical grating for measurement, 15... Second optical grating which is an optical grating for origin detection, 20... Second and third optical gratings An index scale that also serves as a scale, 23... A first reference optical grating that is a measurement reference optical grating, 25...
a second reference optical grating, 3, which is a reference optical grating for origin detection;
0... Photoelectric converter, 40... Non-parallel illumination system, 50...
...Displacement detection circuit, 70...Reference signal generation circuit, 80
...Absolute origin setting means.

Claims (5)

[Claims] (1) A main scale provided with a measurement optical grating and an origin detection optical grating having a pitch different from that of the measurement optical grating, and a measurement optical grating and an origin detection optical grating of the main scale. an index scale that is provided with a reference optical grating for measurement and an optical grating for detecting the origin and that serves as a second scale placed in front of the main scale and a third scale placed after the main scale on the optical system; , a non-parallel illumination system for irradiating non-parallel light onto the main scale via the index scale; Two sets of photoelectric converters receive the reflected light reflected from the main scale and output electric signals with a phase shift of 90 degrees, and the electric signals from the photoelectric converters corresponding to the optical grating for measurement are output. a displacement detection circuit for detecting the amount of relative displacement of both scales through predetermined processing; and a displacement detection circuit for detecting the amount of relative displacement of both scales; and a reference signal generation circuit configured to generate a reference signal when the reference signal reaches a specific value, and the absolute difference between the main scale and the index scale is determined using the reference signal output from the reference signal generation circuit. Optical displacement detection device configured to identify the origin. (2) In claim 1, the optical system is configured such that the reference signal generation circuit receives output signals from the two sets of photoelectric converters and generates a periodic function of the phase difference between the sets. Displacement detection device. (3) In claim 1 or 2, the reference signal generation circuit calculates two sets of multipliers and the output signals from both multipliers to generate a phase difference between the photoelectric converters on one side. is θ_1 and the phase difference of the other set of photoelectric converters is θ_2, a subtracter outputs a periodic function of Sin(θ_1-θ_2), a comparator compares the output signal of this subtracter with a reference setting signal, and this and a reference pulse generator that generates a reference signal of a constant width based on the output signal of the comparator. (4) In claims 1 to 3, the reference optical grating of the index scale has a pitch of the optical grating of the main scale P_1, P_2, .
..., an optical displacement detection device formed with a pitch of 2P_1, 2P_2... (5) An optical displacement detection device according to any one of claims 1 to 3, wherein the reference optical grating of the index scale is formed with a pitch equivalent to that of the optical grating of the main scale. .