JPH0650718A - Optical displacement measuring apparatus and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a laser scale type optical displacement measuring apparatus in which a scale having a flaw on the diffraction grating can be used as it is without causing any measurement error. CONSTITUTION:The optical displacement measuring apparatus includes a detecting optical system comprising a scale 32 having diffraction grating 30 and a light source which can be-displaced relatively to the scale 32 and irradiates the diffraction grating 30 with interfering light, wherein the light diffracted through the diffraction grating 30 is detected in order to measure relative displacement between the detection optical system and the diffraction grating 30. The detection optical system is disposed such that the interfering light is irradiated along predetermined tracks T1, T2, or T3 of the diffraction grating which is set based on a detection value of diffraction light produced by irradiating the diffraction grating with interfering light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement measuring apparatus suitable for use in, for example, an NC machine tool or a semiconductor manufacturing apparatus and a manufacturing method thereof, and more particularly to a laser scale type displacement measuring apparatus and a manufacturing method thereof. Regarding

[0002]

2. Description of the Related Art A laser scale, which is a combination of a semiconductor laser and a hologram scale, has been put into practical use as a highly accurate optical displacement measuring device because it has a resolution of about 0.01 μm and has very few errors.

The laser scale includes a hologram scale and detection optics that are displaced relative to the scale. A hologram used for a laser scale is manufactured by superimposing two plane waves having extremely high precision and causing them to interfere with each other, and printing the interference fringes on a photographic plate, which is called a volume phase hologram.

The period of such interference fringes is determined by the wavelength of the plane wave and its crossing angle, and is about 0.55 μm, for example.
The period of the interference fringes constitutes the wavelength of the scale, and such a value is as large as the wavelength of light, and cannot be achieved by general lithography technology or writing by electron beam.

The holographic scale formed by recording the scale holographically in this manner has a characteristic that a high resolution that cannot be achieved by other scales can be obtained.

The detection optical device forms a detection head portion for reading the displacement of the hologram scale, and is configured to measure the displacement in a wave-optical manner by utilizing the diffraction and interference of light. The period of the interference light measured by the photodetector has a wavelength of 1/4 of the scale wavelength, and is about 0.14 μm when the scale wavelength is 0.55 μm. Therefore, if the waveform of such interference light is divided by 1/16, it becomes about 0.
A resolution of 01 μm can be obtained.

Details of the measuring principle of the laser scale and its characteristics are described, for example, in “Measurement Control” Vol. 38,
NO. 7,1989, P15 [771] to 23 [77
9].

FIG. 7 shows an example of a laser scale type optical displacement measuring device disclosed in Japanese Patent Publication No. 2-34848 by the same applicant as the present applicant. The optical displacement measuring device is a coherent light source 1 such as a semiconductor laser generator.
0, a beam splitter 14, a diffraction grating 30 such as a hologram scale, reflectors 18, 20, and a photodetector 26. The coherent light generated by the coherent light source 10 travels along the optical path 40 along the beam splitter 14
And is split into two directions by the beam splitter 14.

The first branched light passes through the beam splitter 14 and reaches the irradiation point 30a of the diffraction grating 30 along the optical path 46, and the second branched light is incident on the beam splitter 14 at an incident angle with respect to the normal 30n. The light is reflected at the same reflection angle, is guided along the optical path 44, and reaches the irradiation point 30b of the diffraction grating 30. The first branched light is diffracted by the diffraction grating 30 to change its direction and travel toward the reflector 18. The diffracted light is reflected by the reflector 18 and reaches the irradiation point 30a of the diffraction grating 30 again along the same path 50. The light beam is diffracted again by the diffraction grating 30 and redirected to reach the beam splitter 14 again along the same optical path 46.

Similarly to the first branched light, the second branched light is also diffracted at the point 30b of the diffraction grating 30 and the direction thereof is changed to the optical path 4.
8 travels toward the reflector 20 and is reflected by the reflector 20 before being diffracted again by the diffraction grating 30 and redirected to reach the beam splitter 14.

The first branched light that has reached the beam splitter 14 through the optical path 46 and the beam splitter 14 through the optical path 44
The second branched light that has arrived at is guided along the optical path 42 and reaches the photodetector 26. The two split lights are configured to interfere with each other by the beam splitter 14, thereby generating interference light. The intensity of such interference light is detected by the photodetector 26. Since the amplitude wave of the interference light detected by the photodetector 26 includes the phase displacement amount of the scale, the displacement of the scale can be obtained by detecting the interference light.

Similar to FIG. 7, FIG. 8 shows another example of the laser scale type optical displacement measuring device disclosed in Japanese Patent Publication No. 2-35248 by the same applicant as the present applicant.
According to this example, the optical displacement measurement device includes a coherent light source 10, a beam splitter 14, a diffraction grating 30, reflectors 18, 20, 22, 24, and a photodetector 26.

The coherent light generated by the coherent light source 10 reaches the beam splitter 14 via the optical path 40, and is split into two light beams by the beam splitter 14. The first branched light reaches the diffraction grating 30 via the optical path 46, the reflector 22, and the optical path 50. Such a light beam is diffracted at the irradiation point 30g of the diffraction grating 30 and guided along the optical path 54.

Further, such a light ray is reflected by the reflector 18 and reaches the beam splitter 14 via the optical path 54, the optical path 50 and the optical path 46. The second split light reaches the reflector 20 from the beam splitter 14 via the optical path 44, the optical path 48, and the optical path 52, and is reflected by the reflector 20.
The beam splitter 14 is reached via the same path, that is, the optical path 52, the optical path 48, and the optical path 44. The first branched light and the second branched light are incident on the beam splitter 14 to generate interference light, and the interference light is detected by the photodetector 26 via the optical path 42.

[0015]

However, in such an optical displacement measuring device, when the surface of the diffraction grating 30 is scratched or the material of the diffraction grating 30 is partially defective, the output of the photodetector 26 is output. It has the disadvantage that it affects the value, which can cause errors.

FIG. 9 is drawn on the assumption that the scale 32 on which the diffraction grating 30 is formed is observed from the direction of arrow AA in FIG. The state where the coherent light is incident on the diffraction grating 30 having the scratch 80 at the irradiation points 30a and 30b is shown.

When the detection optical device travels to the right in FIG. 7 relative to the diffraction grating 30 constituting the scale 32, the coherent light irradiation points 30a, 3 shown by circles are shown.
0b moves to the right. The X-axis is the moving direction of the irradiation points 30a and 30b, and the Y-axis is the direction perpendicular thereto, that is, the direction in which the diffraction grating 30 is formed.

The irradiation point 30a corresponds to the irradiation point of the first branched light incident via the optical path 46, and the irradiation point 30b.
Corresponds to the irradiation point of the incident second branched light that has passed through the optical path 44. FIG. 9A shows the first area where the scratch 80 exists.
9B shows a state in which the irradiation points 30a and 30b of the coherent light are moved to the right and the irradiation point 30b of the second branched light is present in a portion where the flaw 80 exists. .

FIG. 10 shows a diffraction grating 30 as shown in FIG.
When the scratch 80 is present on the upper surface of which the coherent light is irradiated and the irradiation points 30a and 30b are scanned, the photodetector 2
6 represents the output of the interference light detected by 6. The horizontal axis of the graph represents the relative displacement amount x of the detection optical device with respect to the diffraction grating 30, and the vertical axis represents the output y of the photodetector 26. The curve in the figure is the envelope of the sine wave signal and represents the intensity of the interference light detected.

The displacement amount of the detection optical device is x = x ₁ and x = x
_{When 2} , the output value is decreasing. This is because the displacement is x
This is because when x = ₁ , the coherent light at the irradiation point 30a is blocked by the scratch 80 and the intensity of the interference light generated by the two branched lights decreases as shown in FIG. This is because when x = ₂ , the coherent light at the irradiation point 30b is blocked by the scratch 80 as shown in FIG. 9B, and the intensity of the interference light generated by the two branched lights is reduced.

Such a reduction in output may cause a miscount and cause a measurement error by the optical displacement measuring device. Therefore, conventionally, the scale diffraction grating 30 is used.
If there were scratches 80 on the top, the scale was discarded as defective.

However, the portion where the flaw 80 exists on the diffraction grating 30 of the scale is only a part, and the flaw 8
Parts other than 0 can be used as a scale.

In view of the above, the present invention is directed to a laser scale type optical displacement measuring apparatus, in which the scale 32 is provided even when the flaw 80 exists on the diffraction grating 30.
Is used without being discarded, and a measurement error due to such a scratch does not occur.

[0024]

The present invention is a diffraction grating 30.
And a detection optical device having a light source for irradiating the diffraction grating 30 with coherent light, and detects the diffracted light generated by the diffraction grating 30 to detect the diffracted light between the diffraction grating 30 and the detection optical device. In the optical displacement measuring device for measuring the relative displacement of the diffraction grating 30, the detection optical device is arranged so that the coherent light is irradiated along a predetermined track of the diffraction grating 30, and the predetermined track interferes with the diffraction grating 30. It is characterized in that the light is irradiated to detect the diffracted light and the diffracted light is set based on the detected value.

The present invention includes a scale 32 having a diffraction grating 30 and a detection optical device having a light source for irradiating the diffraction grating 30 with coherent light, and detects diffraction light generated by the diffraction grating 30 to detect the diffraction grating. In a method of manufacturing an optical displacement measuring device that measures relative displacement between a detection optical device 30 and a detection optical device, a track position setting step of defining a plurality of tracks on the diffraction grating 30 and a coherent light beam along the tracks. The irradiation step of irradiating, the detection step of detecting the diffracted light generated by the irradiation of the coherent light, the track selection step of determining a predetermined track from the plurality of tracks based on the detection value of the diffracted light, and the predetermined track Arranging the detection optical device so that the coherent light is emitted.

According to the present invention, in the method for manufacturing an optical displacement measuring apparatus, a rank setting step of prioritizing a plurality of tracks, and the irradiation step and the detection step according to the rank are carried out to determine whether a defect exists on the track. It includes a determination step of determining whether or not there is a defect, and a track selection step of determining a predetermined track according to the order assigned to the track when a track having no defect is found in the determination step.

According to the present invention, in a method of manufacturing an optical displacement measuring apparatus, a light source for irradiating coherent light is arranged for each track of the diffraction grating 30, and a coherent light for each track of the diffraction grating 30 is arranged. Arranging detection means for detecting the diffracted light generated by irradiation, selecting a predetermined track from a plurality of tracks on the diffraction grating 30 based on the detected value of the diffracted light, and detecting the predetermined track with respect to the predetermined track. Disposing an optical device.

[0028]

According to the present invention, in the laser scale type optical displacement measuring apparatus, the scale 3 having the diffraction grating 30 is used.
A plurality of tracks are defined on 2 and coherent light is emitted sequentially or simultaneously along this track, and the diffracted light generated by the irradiation of the coherent light is detected, and a flaw is detected from the detected value of the diffracted light. Select a track that has no defects such as
A light source is arranged to illuminate such selected tracks with coherent light.

According to the present invention, in the method of manufacturing a laser scale type optical displacement measuring apparatus, a plurality of tracks are defined on the scale 32 having the diffraction grating 30, and coherent light is irradiated along the tracks. Then, the diffracted light generated by irradiating this coherent light is detected for each track, and the track without defects such as scratches is selected based on the detected value of the diffracted light, and the coherence is applied to the selected track. Since the light source is arranged so as to be irradiated with light, the scale 32 having the diffraction grating 30 having scratches can be used without being discarded.

[0030]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 6, corresponding parts in FIGS. 7 to 10 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, a method and apparatus for detecting whether or not the diffraction grating 30 of the scale 32 has a flaw 80 will be described, and then an optical displacement measuring apparatus, a method for manufacturing the same, and an example of the manufacturing apparatus will be described. .

FIG. 1 shows a state in which the diffraction grating 30 of the scale 32 is irradiated with coherent light. As shown, the moving direction of the detection optical device with respect to the scale 32 is the X axis, and the direction in which the diffraction grating 30 is formed is the Y axis.

According to this example, the diffraction grating 3 of the scale 32 is
For example, three tracks T1, T2, and T3 are set in 0. These three tracks T1, T2, T3 may be set so as to be arranged in each of the three regions A1, A2, A3 extending along the X-axis direction.

For example, the tracks T1, T2, T3 are arranged in the approximate center of the areas A1, A2, A3, and the areas A1,
The widths of A2 and A3 may be substantially equal to each other, so that the intervals between two adjacent tracks of the three tracks T1, T2, and T3 may be substantially equal.
Alternatively, a plurality of tracks may be set in each of the three areas A1, A2, A3 so that the intervals between two adjacent tracks are substantially the same.

Next, the surface of the diffraction grating 30 of the scale 32 is irradiated with the coherent light so that the irradiation point of each of the tracks T1 ,.
Scan along T2 and T3. That is, the first area A1
Irradiation points 30a-1, 30a along the first track T1 of
b-1 is moved to move the second track T of the second area A2.
Move irradiation points 30a-2 and 30b-2 along 2
Irradiation point 3 along the third track T3 in the third area A3
0a-3 and 30b-3 are scanned.

Such coherent light is detected by the photodetector 26 as diffracted light as described with reference to FIGS. 7 and 8. Such work is performed over the entire length of the scale 32. As shown in the figure, the surface of the diffraction grating 30 has a scratch 80.
If there is a mark, it appears as a decrease in the output of the photodetector 26, so that it can be known on which track in which region the flaw exists.

FIG. 1 shows an example in which three areas are set on the scale 32 and coherent light is simultaneously radiated along the three tracks T1, T2 and T3 to detect the diffracted light by the photodetector 26. However, the scale 32 may have four or more areas and tracks, or one area may have two or more tracks.

FIG. 2 shows an example of a detection device for detecting the flaw 80 used when the settings are made as shown in FIG.

The detecting device is constructed to have three channels corresponding to the set number of tracks. That is, the detection device includes photodetectors 62A, 62B, 62C and photodetectors 62A, 62B, 6 provided for each track.
Amplifiers 64A, 64B, 64 for amplifying the output from 2C
C, level comparators 66A, 66B and 66C for detecting whether or not the outputs from the amplifiers 64A, 64B and 64C are above a predetermined level, and a level comparator 66.
Monostable multivibrators 68A, 68B and 68C, which generate pulse signals indicating that the output of the photodetectors 62A, 62B and 62C are lower than the pulse signals output from A, 66B and 66C, and the monostable multivibrator 68A. D-type flip-flop circuits 70A, 70 for inputting the pulse signals from the C, 68B, 68C as trigger signals
B and 70C may be included.

FIG. 3 shows a signal waveform in each channel of the detection device of FIG. FIG. 3A shows photodetectors 62A and 62A.
B and 62C represent the output signal S0, and the portions indicated by the symbols P1 and P2 are dense sine waves, and the portion indicated by the symbol Q is an enlargement thereof. FIG. 3B is an enlarged view of the portion Q of the signal S0 of FIG. 3A, and the output signal S1 of the amplifiers 64A, 64B and 64C is the diffraction grating 30.
A sine wave having a period corresponding to the period lambda, for example, a reduction of the output signal S1 to the sign x ₁ is attached position.
This indicates that the irradiation point has passed through the scratch 80 on the surface of the diffraction grating 30. Level comparators 66A, 66B, 6
The output signal S2 of 6C is maintained at the H level corresponding to the position of the output signal S1 designated by the symbol x ₁ , as indicated by the symbol N.

Monostable multivibrator 68A, 68
The output signals S3 of B and 68C have a waveform that becomes H level at the fall of the input signal S2 and stabilizes at L level after the time constant τ has elapsed. The time constant τ may be set to, for example, 1.5 times the time corresponding to the lattice constant λ. Therefore,
Since there is no fall of the input signal S2 within the range of the time constant τ corresponding to the position of the output signal S1 indicated by the symbol x _1, L
Become a level.

D-type flip-flop circuits 70A and 70
The output signal S4 of B and 70C becomes H level at the fall of the input signal S3. In this way, it is detected that the output signal S4 has become H level, and the flaw 80 of the diffraction grating 30 is detected. Incidentally, for example, a D-type flip-flop circuit 70A,
A suitable light emitting diode is connected to the output terminals 72A, 72B, 72C of the 70B, 70C, and the scratches 80 are made for each track.
Of the diffraction grating 30 for each track by connecting a suitable counter circuit to the output side of the monostable multivibrator 68A, 68B, 68C.
The number of the scratches 80 may be counted.

Another example of the method and apparatus for detecting the flaw 80 of the diffraction grating 30 will be described with reference to FIGS. 4 and 5. In this example, as shown in FIG. 4, a detected non-defective scale 32A having no flaw 80 other than the scale 32B for detecting the flaw 80 is prepared. Next, as shown in FIG. 5, a detection device having two channels is prepared. The first channel corresponds to the first scale 32A, and the second channel corresponds to the second scale 32B.

Each channel has a photodetector 62A or 62A.
B and an amplifier 64A or 64B for amplifying the output from the photodetector 62A or 62B, a level comparator 66A or 66B for detecting whether or not the output from each amplifier 64A or 64B is above a predetermined level, and a level comparator 66A. Or an n-ary counter 74A or 74B for counting the number of pulses of the pulse signal output from 66B. Further, it has a comparison circuit 76 for comparing the output signals from the two n-ary counters 74A or 74B.

In this example, the first channel is arranged with respect to the non-defective scale 32A having no scratch 80, and the second channel is
Channel of scale 3 which will detect scratch 80 from now on
It is arranged for one track of 2B. The output signal of the level comparator 16A of the first channel has the same waveform as the output signal S2 of FIG. 3, but since the first scale 32A has no flaw 80, a pulse having a large width indicated by the symbol N is Not included.

However, the output signal of the level comparator 66B of the second channel includes a pulse having a large width indicated by a symbol N in the scratch 80 portion of the second scale 32B, as in the output signal S2 of FIG. Therefore, the first
The first pulse number counted by the n-ary counter 74A of the second channel and the n-ary counter 74 of the second channel
Comparing with the second number of pulses counted by B,
The second pulse number is smaller corresponding to the number of scratches 80 present on the second scale 32B.

Therefore, by comparing the second pulse number with the first pulse number in the comparison circuit 76 and obtaining the difference, the number of scratches 80 existing in the track measured by the second scale 32B is clarified. Becomes If such a measurement is performed along the track of each area of the first scale 32B, it can be known in which area of the first scale 32B the flaw 80 exists.

FIG. 6 shows an example of the result of detecting the flaw 80 of the diffraction grating 30 by the detection apparatus and method of this example. Here, the three tracks T1 on the scale 32,
By setting T2 and T3 and scanning the irradiation point along each track, the presence or absence of scratches on the track is detected. A circle indicates that the diffraction grating 30 has no scratch 80,
The cross mark indicates that the diffraction grating 30 has a flaw 80. There are eight cases depending on the presence or absence of the scratch 80.

Here, the priority order is set according to the position of the scratch 80. For example, the priority order is set in the order of the second track T2, the first track T1, and the third track T3.
Therefore, those having no defects in the second track T2 are group B, those having defects in the second track T2 but no defects in the first track T1 are group A, and those having the second track T2 and the first track T2. The tracks T1 of which are both defective and the third track T3 is not defective are group C, and the defective products in which all the tracks are defective are group D.

This grouping work may be carried out by providing a detection optical device corresponding to each track as shown in FIG. 2, or by carrying out one detection optical device sequentially arranged on each track. You may. In the former example, it is necessary to prepare as many detection optical devices as the number of tracks, but there is an advantage that grouping can be performed by one measurement.

In the latter example, the detection optical device must be sequentially arranged on each track, but there is an advantage that one detection optical device may be prepared for one scale 32. The order of the tracks on which the detection optics are arranged may be defined by any suitable method, but preferably the order of priority described above is followed.

In the above example, the second track T2, the first track
Since the priorities are set in the order of the track T1 and the third track T3, the irradiation point of the coherent light beam is first scanned along the second track T2 to inspect whether there is any defect. If it is determined that there is no defect in the second track T2, the inspection is ended there and this scale is classified into group B. This corresponds to the first to third cases or the fifth case of FIG.

If it is determined that there is a defect on the second track T2, then the irradiation point is scanned along the first track T1 to inspect for the presence or absence of a defect. If it is determined that there is no defect in the first track T1, the inspection is ended there and this scale is classified into group A. This corresponds to the fourth and sixth cases of FIG.

If it is determined that the first track T1 has a defect, then the irradiation point is scanned along the third track T3 to inspect the presence or absence of the defect. If it is determined that there is no defect in the third track T3, the inspection is ended there and this scale is classified into group C. This corresponds to the seventh case in FIG. If it is determined that the third track T3 also has a defect, this scale is classified into group D. This corresponds to the eighth case in FIG.

In this way, by using the above-mentioned priority order of grouping as the order of inspecting for the presence or absence of defects, it is possible to minimize the number of times the irradiation points are scanned and the presence or absence of defects is inspected. With such a method, the table as shown in FIG. 6 cannot be obtained, but only the result of the grouping in the rightmost column of the table of FIG. 6 is obtained.

According to this example, first, an appropriate number of tracks are set on the diffraction grating 30 at appropriate positions. Then, prioritize such tracks in order to group them.

For example, in the case of inspecting a defect of the diffraction grating 30 by using a plurality of detection optical devices as shown in FIG. 2, a table as shown in FIG. 6 is prepared and divided into groups. If one detection optic is used to inspect the diffraction grating 30 for defects, the detection optics are sequentially arranged in the tracks according to such a priority, whereby the tracks are grouped.

Next, examples of the optical displacement measuring device, the manufacturing method thereof and the manufacturing device thereof according to the present invention will be shown.

In the optical displacement measuring device of the present invention, the detection optical devices are arranged corresponding to the above groups. For example, a scale 32 having a B group diffraction grating 30
In the optical displacement measuring device incorporating the above, the detection optical device is arranged so that the irradiation points 30a and 30b by the coherent light source are scanned along the second track T2. Similarly,
In the optical displacement measuring device including the diffraction grating 30 of the A group, the detecting optical device is the irradiation points 30a, 3 and 3 by the coherent light source.
0b is arranged so as to be scanned along the first track T1, and in the optical displacement measuring device including the diffraction grating 30 of the C group, the detecting optical device is the irradiation point 3 by the coherent light source.
0a and 30b are arranged to be scanned along the third track T3.

Next, an example of a method of manufacturing the optical displacement measuring device of the present invention will be described. The manufacturing method of this example includes a step of first grouping the scales 32 having the diffraction grating 30 as described above, prior to the assembling step of the optical displacement measuring device. After this grouping process, the optical displacement measuring device is assembled. In this assembly operation, the detection optics are placed as a result of the grouping of scales 32. The grouping work may use a detection optical system incorporated in the optical displacement measuring device, or may use a separate grouping device described below.

Next, an example of the manufacturing apparatus of the optical displacement measuring apparatus of the present invention will be shown. The manufacturing apparatus of this example includes an apparatus for grouping the scales 32 as described above. A device for performing such grouping includes the detection optical device shown in FIG. 7 or 8. The device for this grouping may be configured to include as many detection optics as there are channels, as shown in FIG. 2, one detection optic being arranged per channel, or one detection optic. The detection optical device including the optical device may be sequentially arranged on a plurality of tracks.

Although the embodiments of the present invention have been described in detail above, those skilled in the art will understand that the present invention is not limited to the above-mentioned embodiments and various other configurations can be adopted without departing from the gist of the present invention. Easy to understand.

Although the above example describes the optical displacement detecting device using the linear scale, the present invention can be applied to the optical displacement detecting device and the angular displacement measuring device using the rotary scale. Further, the diffraction grating 30 of the scale 32 includes a transmission type and a reflection type.

[0064]

According to the present invention, it is detected whether or not defects such as scratches are present in the diffraction grating 30 of the scale 32 before assembling the optical displacement measuring device. There is the advantage that errors in the displacement measurements due to their presence can be eliminated.

According to the present invention, since the scale is divided into a plurality of areas and the presence or absence of a flaw is detected for each area, there is an advantage that even a scale with a flaw can be used without being discarded. is there.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a method of detecting a flaw or the like on a scale.

FIG. 2 is a configuration diagram showing an example of an apparatus for detecting scale flaws and the like.

FIG. 3 is an explanatory diagram explaining an operation of the apparatus of FIG.

FIG. 4 is an explanatory diagram illustrating another method for detecting a flaw or the like on the scale.

FIG. 5 is a configuration diagram showing another example of an apparatus for detecting scratches and the like on the scale.

FIG. 6 is an explanatory diagram illustrating a result of detecting a flaw or the like on a scale.

FIG. 7 is a configuration diagram showing an example of a conventional optical displacement measuring device.

FIG. 8 is a configuration diagram showing another example of a conventional optical displacement measuring device.

FIG. 9 is an explanatory diagram illustrating irradiation points that scan over the scale.

FIG. 10 is an explanatory diagram showing changes in the output value of the photodetector.

[Explanation of symbols]

10 Coherent light source 14 Beam splitter 18, 20, 22, 24 Reflector 26 Photodetector 30 Diffraction grating 30a, 30b, 30g Irradiation point 30n Normal 32 Scale 40, 42, 44, 46, 48, 50, 52, 54 optical path 62A, 62B photodetector 64A, 64B amplifier 66A, 66B, 66C level comparator 68A, 68B, 68C monostable multivibrator 70A, 70B, 70C D-type flip-flop circuit 72A, 72B, 72C output terminal 74A, 74B n-ary Counter 76 Comparison circuit 76A Output terminal 80 Scratches

Claims (4)

[Claims] 1. A scale having a diffraction grating, and a detection optical device having a light source for irradiating the diffraction grating with coherent light, the diffracted light generated by the diffraction grating is detected to detect the diffraction grating and the diffraction grating. In the optical displacement measuring device for measuring relative displacement between the detection optical device and the detection optical device, the detection optical device is arranged so that the coherent light is irradiated along a predetermined track of the diffraction grating. An optical displacement measuring device characterized in that the track is set on the basis of the detected value by detecting diffracted light by irradiating the diffraction grating with coherent light. 2. The diffracted light generated by the diffractive grating is detected by including a scale having a diffractive grating and a detection optical device having a light source for irradiating the diffractive grating with coherent light. In a method of manufacturing an optical displacement measuring device for measuring relative displacement with an optical device, a track position setting step of defining a plurality of tracks on the diffraction grating, and irradiating coherent light along the tracks. An irradiation step, a detection step of detecting diffracted light generated by the irradiation of the coherent light, a track selection step of determining a predetermined track from the plurality of tracks based on the detection value of the diffracted light, and the predetermined track An arranging step of arranging the detection optical device so that the coherent light is radiated onto the substrate. 3. The method for manufacturing an optical displacement measuring device according to claim 2, wherein a ranking setting step of ranking the plurality of tracks in advance,
A determination step of performing the irradiation step and the detection step according to the above order to determine whether or not there is a defect on the track, and the order given to the track when a track having no defect is found by the determination step A method of manufacturing an optical displacement measuring device, the method including: 4. The method of manufacturing an optical displacement measuring device according to claim 2, wherein a light source for irradiating coherent light is arranged on each track of the diffraction grating, and the light source is arranged on each track of the diffraction grating. Arranging detection means for detecting diffracted light generated by irradiation of coherent light; selecting a predetermined track from a plurality of tracks on the diffraction grating based on the detection value of the diffracted light; A method of manufacturing an optical displacement measuring device, comprising: disposing the detection optical device on a track.