JP4858753B2 - Two-dimensional scale manufacturing method and encoder - Google Patents

Description

  The present invention relates to a manufacturing method and an encoder for a two-dimensional scale, and more particularly, to a manufacturing method for manufacturing a two-dimensional scale suitable for an optical encoder and an encoder including a two-dimensional scale manufactured by the manufacturing method.

  Conventionally, an optical scale having a periodic structure such as a phase diffraction grating is irradiated with a light beam from the detection head, and the reflected light is processed, whereby the relative position between the detection head and the optical scale is processed. Methods for measuring the relationship and the relative direction of motion of both are well known and commonly used.

  Recently, the most commonly used method is to irradiate the optical scale with two light beams that can produce periodic reflected signals that are 90 ° out of phase with each other, and the amplitude and phase of the two reflected signals. From this relationship, the relative positional relationship between the detection head and the optical scale and the relative movement direction of both are measured.

  Based on the relationship between the amplitude and phase of the two reflected signals, the relative positional relationship between the detection head and the optical scale is obtained. Further, in this method, the method described in Patent Document 1 can be used in order to eliminate a decrease in detection resolution caused by a decrease in the S / N ratio of the reflected signal due to the influence of noise.

  As an optical scale, a two-dimensional scale having a plurality of linear lattices arranged in a uniaxial direction and a plurality of linear lattices arranged in a direction orthogonal to the uniaxial direction in order to perform measurement in a two-dimensional direction Can be adopted. In order to manufacture this two-dimensional scale, a first plate member having a plurality of linear lattices arranged in a uniaxial direction and a plurality of linear lattices arranged in a direction orthogonal to the uniaxial direction are used. In general, the second plate-shaped member having the second plate-shaped member is overlapped (bonded). In this case, it is necessary to set the lattices so as to intersect with each other at an angle of 90 degrees.

  Conventionally, the angle adjustment between the lattices (adjustment of the positional relationship between the plate-like members) is performed by observing the lattice with a microscope or the like, measuring the angle, performing automatic alignment using image recognition, or manually. It was supposed to be combined with. However, in automatic adjustment, expensive equipment such as a microscope and an image recognition device has to be used, and in manual adjustment, considerable adjustment time is required.

US Pat. No. 6,639,686

The present invention has been made under the circumstances described above. From the first viewpoint, the present invention is a manufacturing method for manufacturing a two-dimensional scale, and includes a first pattern, the first pattern, and a predetermined positional relationship. Providing a transparent first plate-like member having a first alignment grid arranged at a position; a second pattern, and a position that is in a predetermined positional relationship with the second pattern; Providing a second plate-like member having a second alignment grid; and overlapping the first plate-like member and the second plate-like member to form the first alignment. use grid before SL based on the moire fringes due lattice for the second alignment, the step of adjusting the positional relationship between said first plate member second plate-like member; and wherein the first pattern The first plate-like member having the first alignment grid is the The second plate member disposed on one side of the two-dimensional scale and having the second pattern and the second alignment grid is disposed on the other side of the two-dimensional scale, and the two-dimensional scale. A step of bonding the first plate-like member and the second plate-like member to each other.

According to this, the first plate-like member and the second plate-like member are based on the moire fringes formed by the first alignment lattice and the second alignment lattice (for example, by visual observation). By adjusting the positional relationship between the first pattern and the second pattern, it is possible to set the first pattern and the second pattern in a desired relationship. Scales can be manufactured.

  According to a second aspect of the present invention, there is provided an encoder for measuring the position of the scale by irradiating the scale on which the pattern is formed and receiving the light through the scale, The encoder includes a two-dimensional scale manufactured by the manufacturing method of the present invention.

  According to this, since a highly accurate two-dimensional scale manufactured in a short time without using expensive equipment is provided, highly accurate position measurement can be realized and an inexpensive encoder can be realized. It is possible.

  Hereinafter, an encoder capable of simultaneously measuring two axial directions according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 schematically shows the configuration of the encoder 100 of the present embodiment. As can be seen from FIG. 1, the encoder 100 includes a two-dimensional scale 30, and a first detection device 10 and a second detection device 20 that project detection light onto the two-dimensional scale.

  The first detection device 10 includes a first light source 11, a first collimator lens 12, a first beam splitter 13, a first projection lens 14, a first condenser lens 15, a first light receiving element 16, and The first CCD 18 is included. The second detection device 20 includes a second light source 21, a second collimator lens 22, a second beam splitter 23, a second projection lens 24, a second condenser lens 25, and a second light receiving element 26. The second CCD 28 is included.

  The first light source 11 is a laser light source that emits laser light having a wavelength of 850 nm, for example, and a piezo element 17 is fixed to the first light source 11. The piezoelectric element 17 causes the first light source 11 to periodically vibrate in the Y-axis direction, for example.

  The second light source 21 is also composed of the same laser light source, and a piezo element 27 is fixed to the second light source. The piezo element 27 causes the second light source 21 to periodically vibrate in the X-axis direction, for example.

  The two-dimensional scale 30 includes a first plate member 32A having a first scale on the lower surface side, a second plate member 32B having a second scale on the upper surface side, and both plate members 32A. , 32B in the vicinity of the + X side end, and in the vicinity of the −X side end, and a pair of spacer members 38 provided in a state of being sandwiched between both plate-like members 32A, 32B.

  The first plate-like member 32A is made of, for example, a 30 mm square glass member, and the back surface (the surface on the −Z side) has a length of about 25 mm as shown in FIG. 2 (A). A first pattern 36 made of a reflective phase diffraction grating including the engraved lines is formed. The plurality of engraving lines each extend in the Y-axis direction and are arranged at intervals of, for example, about 1 to 4 μm pitch along the X-axis direction orthogonal to the Y-axis, and the first pattern 36 as a whole is about 25 mm square. The size is set.

  A pair of alignment patterns 34 a and 34 b are formed on the + Y side and the −Y side of the first pattern 36. Each of the alignment patterns 34a and 34b includes a plurality of engraved lines extending in the X-axis direction, and each engraved line is arranged at a pitch of, for example, about 10 μm along the Y-axis direction. Each of the first pattern 36 and the alignment patterns 34a and 34b is transferred and formed on a glass member by using a semiconductor exposure apparatus (stepper or the like).

  The second plate-like member 32B is made of, for example, a 30 mm square glass member, and the surface (+ Z side surface) has a plurality of lengths of about 25 mm as shown in FIG. A second pattern 36 'made of a reflective phase diffraction grating including a score line is formed. The plurality of engraved lines extend in the X-axis direction and are arranged at intervals of, for example, about 1 to 4 μm pitch along the Y-axis direction orthogonal to the X-axis, and the second pattern 36 ′ as a whole is about 25 mm square. Is set to the size of

  A pair of alignment patterns 34a 'and 34b' are formed on the + Y side and the -Y side of the second pattern 36 '. The positional relationship between the alignment patterns 34a 'and 34b' and the second pattern 36 'is set to be the same as the positional relationship between the first pattern 36 and the alignment patterns 34a and 34b. That is, the positional relationship between the center of the first pattern 36 (the center of gravity when the pattern is regarded as a rectangular figure) and the center of the alignment patterns 34a and 34b (the center of gravity when the pattern is regarded as a rectangular figure) is The positional relationship between the center of the second pattern 36 ′ (the center of gravity when the pattern is regarded as a rectangular figure) and the center of the alignment patterns 34a ′ and 34b ′ (the center of gravity when the pattern is regarded as a rectangular figure) Set to match.

  Each of the alignment patterns 34a 'and 34b' includes a plurality of score lines extending in the X-axis direction, and each score line is arranged along the Y-axis direction. Each of the alignment patterns 34a ′ and 34b ′ is composed of engraving lines having the same length as the alignment patterns 34a and 34b provided on the first plate-like member 32A described above, and the pitch of each engraving line is also set. It is set to be the same as the alignment patterns 34a and 34b.

  When these first plate-like member 32A and second plate-like member 32B are bonded together via a pair of spacer members 38 as shown in FIG.

  That is, after the first plate-like member 32A and the second plate-like member 32B are brought close to each other via the spacer member 38, the operator visually observes the alignment pattern 34a and the alignment pattern 34a ′ from the + Z side. The positional relationship between the first plate member 32A and the second plate member 32B is adjusted by visually observing the alignment pattern 34b and the alignment pattern 34b ′ from the + Z side.

  Here, as shown in FIG. 4A, when the angular relationship between the two plate-like members 32A and 32B is ideal, that is, the engraving lines constituting the first pattern 36 and the second pattern 36 ′. When the engraving lines constituting the pattern are orthogonal to each other, no moire fringes are generated by the alignment pattern 34a and the alignment pattern 34a ′, and the moire pattern is also generated by the alignment pattern 34b and the alignment pattern 34b ′. No stripes are generated.

  On the other hand, when the angular relationship is not ideal, that is, when the engraved lines constituting the first pattern 36 and the engraved lines constituting the second pattern 36 ′ are not orthogonal to each other, it is shown in FIG. As described above, moire fringes are generated by the alignment pattern 34a and the alignment pattern 34a ′, and moire fringes are also generated by the alignment pattern 34b and the alignment pattern 34b ′.

  Therefore, the operator checks the positional relationship (angular relationship) between the two plate-like members 32A and 32B so that the moire fringes are not generated while visually confirming whether the moire fringes are generated by the alignment pattern. By adjusting and bonding the first plate-like member 32A and the second plate-like member 32B through the pair of spacer members 38, the engraving lines constituting the first pattern 36 and the second pattern 36 ′ are formed. It is possible to manufacture a two-dimensional scale in a state in which the engraved lines that intersect constitute a perpendicular line.

  Returning to FIG. 1, the encoder configured as described above performs measurement as follows.

  First, in the first detection device 10, the light emitted from the first light source 11 is converted into a parallel light beam by the collimator lens 12 and enters the first beam splitter 13. The first light source 11 is periodically vibrated in the Y-axis direction by the piezoelectric element 17. The light transmitted through the first beam splitter 13 is collected on the surface (upper surface) of the second plate member 32B of the two-dimensional scale 30 by the first projection lens 14. The reflection type phase diffraction grating formed on the surface of the second plate-like member 32B of the two-dimensional scale 30 emits reflected light having a periodic (sine curve) amplitude according to the position of the two-dimensional scale 30. It is like that.

  The reflected light is converted into a parallel light beam by the first projection lens 14, reflected by the first beam splitter, condensed on the photoelectric detection surface of the first light receiving element 16 by the first condenser lens 15, and converted into an electric signal. Changed and processed. The moving distance and moving direction of the two-dimensional scale 30 in the Y-axis direction are the amplitude and phase of the reflected light from the two-dimensional scale 30 detected by the first light receiving element 16 and the first light source vibrated by the piezo element 17. 11 is calculated by a control device (not shown) based on the amplitude and phase of the vibration of the light emitted from 11 (vibration of the piezo element 17).

  On the other hand, of the light transmitted through the first collimating lens 12, the light reflected by the first beam splitter 13 is condensed on the light receiving surface of the first CCD 18 through a condensing lens (not shown). If the position of the light beam changes as the first light source 11 vibrates, the position of the light beam incident on the first CCD 18 changes, so that the vibration center of the light beam can be known from the output fluctuation of the first CCD 18. The control device detects the vibration center and controls the voltage applied to the piezo element 17 that vibrates the first light source 11 so that the vibration center becomes a predetermined position. In this way, the vibration center position of the light beam, which serves as a reference for position measurement, is always kept constant with respect to the first CCD 18. Therefore, even if the ambient temperature or humidity changes, the vibration center position of the light beam can be changed. Measurement errors due to fluctuations do not occur, and deterioration of measurement accuracy can be prevented. In this embodiment, the center of vibration of the light beam is made constant by controlling the piezo element 17, but the position of the center of vibration of the light beam is adjusted by inserting a parallel plate or the like in the optical path and adjusting the angle. It may be constant.

  The same applies to the second detection device 20, and the light emitted from the second light source 21 is converted into a parallel light beam by the collimator lens 22 and enters the second beam splitter 23. The second light source 21 is periodically oscillated by the piezo element 27 in the X-axis direction. The light transmitted through the second beam splitter 23 is condensed on the back surface (lower surface) of the first plate-like member 32 </ b> A of the two-dimensional scale 30 by the second projection lens 24. The reflection type phase diffraction grating formed on the back surface of the first plate member 32A of the two-dimensional scale 30 emits reflected light having a periodic (sine curve) amplitude according to the position of the two-dimensional scale 30. It is like that.

  The reflected light is converted into a parallel light beam by the second projection lens 24, reflected by the second beam splitter 23, and condensed on the photoelectric detection surface of the second light receiving element 26 by the second condenser lens 25, and an electric signal. It is changed to be processed. The moving distance and moving direction of the two-dimensional scale 30 in the X-axis direction are the amplitude and phase of the reflected light from the two-dimensional scale 30 detected by the second light receiving element 26 and the second light source vibrated by the piezo element 27. Based on the amplitude and phase of the vibration of the light emitted from 21 (vibration of the piezo element 27), it is calculated by a control device (not shown).

  On the other hand, of the light transmitted through the second collimating lens 22, the light reflected by the second beam splitter 23 is condensed on the light receiving surface of the second CCD 28 through a condensing lens (not shown). According to the second CCD 28, as in the first CCD 18, the vibration center of the light beam can be known.

  As described above, the first detection device 10 and the second detection device 20 can detect the movement distance and the movement direction of the two-dimensional scale 30 in the X-axis direction and the Y-axis direction. .

  As described in detail above, according to the present embodiment, the transparent first plate-like member 32A having the first pattern 36 and the second plate-like member 32B having the second pattern 36 ′ are replaced with the first plate member 32B. Alignment pattern 34a (and 34b ') arranged at a position having a predetermined positional relationship with the pattern 36 and alignment pattern 34a' (and 34b ') disposed at a position having a predetermined positional relationship with the second pattern 36'. The first pattern 36 and the second pattern 36 ′ can be set in a desired relationship by superimposing them on the basis of the moiré fringes (ie, by visually observing the moire fringes, for example). Thereby, a highly accurate two-dimensional scale can be manufactured in a short time without using expensive equipment as in the prior art.

  In addition, the encoder of this embodiment having such a two-dimensional scale can realize highly accurate position measurement without incurring high costs.

  In the above embodiment, the case where the operator visually observes the occurrence state of moire fringes and bonds the first plate member 32A and the second plate member 32B together is described. Not limited to this, it is also possible to observe the state of occurrence of moire fringes by performing image processing or the like. Even in this case, the plate-like members 32A and 32B can be bonded in a state in which the positional relationship is adjusted in a short time, rather than detecting and adjusting the angular relationship between the first pattern 36 and the second pattern 36 ′. It becomes possible.

  In the above embodiment, the alignment patterns 34a, 34b, 34a ′, 34b ′ having the same pitch are used. However, the present invention is not limited to this, and FIGS. 5A and 5B are used. The first plate member 132A having the alignment patterns 134a and 134b and the second plate member 132B having the alignment patterns 134a ′ and 134b ′ can be used.

  As in the first embodiment, the first plate-like member 132A shown in FIG. 5A has a first pattern 36, and the first pattern member 132A has a predetermined positional relationship with the first pattern 36. Matching patterns 134a and 134b are formed. The alignment patterns 134a and 134b have a plurality of score lines extending in the Y-axis direction and arranged at a predetermined pitch (for example, 10 μm here) in the X-axis direction.

  As in the first embodiment, the second plate-like member 132B in FIG. 5B has a second pattern 36 ′ formed therein, and at a position that has a predetermined positional relationship with the second pattern 36 ′. , Alignment patterns 134a ′ and 134b ′ are formed. The alignment patterns 134a 'and 134b' have a plurality of score lines extending in the Y-axis direction and arranged at a predetermined pitch (here, for example, 9.8 μm) in the X-axis direction. In other words, the alignment pitch is slightly different between the alignment patterns 134a and 134b and the alignment patterns 134a 'and 134b'.

  By using such an alignment pattern, when the angular relationship when the first plate member 132A and the second plate member 132B are superposed is in an ideal state (that is, the first pattern 36 is As shown in FIG. 6 (A), moire fringes appear as gradations along the X axis when the engraved lines and the engraved lines forming the second pattern 36 ′ intersect each other vertically. To do.

  On the other hand, when the first plate-like member 132A and the second plate-like member 132B are misaligned (that is, the engraved line constituting the first pattern 36 and the engraved line constituting the second pattern 36 ′ are 6 (B), the moire fringes appear as gradations along the direction inclined with respect to the X axis and the Y axis.

  Therefore, the operator bonds the first plate-like member 132A and the second plate-like member 132B together while observing the formation state of the stripes, and thereby the engraving line of the first pattern 36 and the second pattern 36 ′. It is possible to make a state where the engraving line intersects perpendicularly.

  For example, when the pitch of the alignment patterns 134a and 134b is 100 μm, the pitch of the alignment patterns 134a ′ and 134b ′ may be 98 μm or 99.8 μm. However, these pitches are not limited to the numerical values described above, and any pitch can be selected as long as moire fringes are formed.

  In the above-described embodiment and modification, the case where only one type of alignment pattern is provided on one plate-like member has been described. However, the present invention is not limited to this, and a single plate-like member is provided. Two types of alignment patterns may be provided.

  In the above embodiment, the case where the two plate-like members are bonded together while adjusting the positional relationship between the first plate-like member and the second plate-like member according to the state of occurrence of the stripes by the alignment mark is described. However, the present invention is not limited to this, and the positional relationship between the two plate-like members after bonding the stripe occurrence state (understanding the angle between the first pattern and the second pattern) It is good also as using for. For example, before performing measurement using a two-dimensional scale, the number and angle of moire fringes generated by the first and second patterns are detected using an image processing device or the like, and the first pattern and The angle formed by the second pattern can be detected, and the control device can correct the measurement result using the two-dimensional scale in consideration of the detection result.

  In the above embodiment, the case where the alignment marks are provided on the + Y side and the −Y side of the first pattern 36 (second pattern 36 ′) has been described. However, the present invention is not limited to this, and the alignment marks are provided only on one of them. It is also good. Further, the position is not limited to the + Y side and the −Y side, and the positions to be provided such as the + X side and the −X side are not limited. Further, the alignment direction of the alignment marks is not limited.

  In the above embodiment, the spacer member arranged between the two plate-like members is prepared separately from the two plate-like members. However, the present invention is not limited to this. A spacer member may be attached in advance to the surface of the plate member, or a step may be formed on one plate member, and the step portion may have the same function as the spacer member. Moreover, you may attach a spacer member to each of the surface where two plate-shaped members oppose.

  In addition, although the said embodiment demonstrated the case where the apparatus of the structure which irradiates a condensed beam on a two-dimensional scale was employ | adopted as a 1st detection apparatus and a 2nd detection apparatus, it is not restricted to this, From a light source A diffraction interference detection device that separates the emitted light into two lights by a beam splitter or a diffractive optical element and superimposes the separated lights on a two-dimensional scale may be employed.

  In the encoder of the above embodiment, the case where the two axial directions to be measured are the X axis and the Y axis orthogonal to each other has been described. However, the measurement axes are not limited to these. For example, the X axis and an axis that intersects the X axis at 45 ° may be set as a measurement axis (two axes to be measured).

  As described above, the two-dimensional scale manufacturing method of the present invention is suitable for manufacturing a two-dimensional scale having a two-dimensional pattern in which two patterns are superimposed. The encoder of the present invention is suitable for scale position measurement.

It is the schematic which shows the encoder which concerns on one Embodiment. FIG. 2A is a plan view showing the first plate member, and FIG. 2B is a plan view showing the second plate member. It is a perspective view which shows the state which bonds a 1st plate-shaped member and a 2nd plate-shaped member through a spacer member. FIG. 4A is a diagram illustrating a state of the alignment mark when the first pattern and the second pattern are in an ideal state, and FIG. 4B is a diagram illustrating the first pattern and the second pattern. It is a figure which shows the state of the mark for position alignment when and have deviated from the ideal state. FIG. 5A is a plan view showing a first plate-like member according to a modification, and FIG. 5B is a plan view showing a second plate-like member according to the modification. FIG. 6A is a diagram showing a state of the alignment mark when the first pattern and the second pattern are in the ideal state in the modification, and FIG. 6B is a diagram in the modification. FIG. 10 is a diagram showing a state of alignment marks when the first pattern and the second pattern are deviated from the ideal state.

Explanation of symbols

  30 ... Two-dimensional scale, 32A, 132A ... First plate member, 32B, 132B ... Second plate member, 34a, 34a '134a, 134a' ... Alignment mark (first alignment grid) , 34b, 34b ′, 134b, 134b ′,... Alignment mark (second alignment grid), 36, first pattern, 36 ′, second pattern, 100, encoder.

Claims (9)

A manufacturing method for manufacturing a two-dimensional scale,
Providing a transparent first plate member having a first pattern and a first alignment grid disposed at a position having a predetermined positional relationship with the first pattern;
Providing a second plate-like member having a second pattern and a second alignment grid disposed at a position having a predetermined positional relationship with the second pattern;
The first of the plate-like member overlapped with the second plate-like member, on the basis of the moire fringes by a lattice for the first alignment grating and the front Stories second alignment, the first Adjusting the positional relationship between the plate member and the second plate member ;
The first plate-like member having the first pattern and the first alignment grating is disposed on one side of the two-dimensional scale, and the second pattern and the second alignment grating are The first plate-like member and the second plate-like member are bonded so that the second plate-like member having the second plate-like member is disposed on the other surface side of the two-dimensional scale to constitute the two-dimensional scale. And a step of combining .   2. The manufacturing method according to claim 1, wherein the first alignment grating and the second alignment grating have a plurality of linear engraving lines arranged in the same direction. . Wherein the first alignment grating and the second alignment grating, the arrangement pitch of the rulings are the same,
3. The method according to claim 2, wherein in the step of adjusting the positional relationship, the first plate-like member and the second plate-like member are overlapped so that the moire fringes are not generated. Production method. Wherein the first alignment grating and the second alignment grid, different arrangement pitch of the score line,
In the step of adjusting the positional relationship, the first plate member and the second plate member are overlapped so that the arrangement direction of the moire fringes is in the same state as the arrangement direction of the engraving lines. The manufacturing method of Claim 2 characterized by these. The first pattern and the second pattern have a plurality of linear patterns,
The linear patterns constituting the first pattern and the second pattern are orthogonal to each other in a state where the first and second plate-shaped members are overlapped in the bonding step. The manufacturing method as described in any one of 1-4. The first pattern and the second pattern have a plurality of linear patterns,
The linear pattern constituting the first pattern and the second pattern intersect with each other in a state where the first and second plate-shaped members are overlapped in the bonding step. The manufacturing method as described in any one of 1-4. In the step of adjusting the positional relationship, the first and second plate members are overlapped with a spacer member interposed between the first plate member and the second plate member. The manufacturing method as described in any one of Claims 1-6 characterized by the above-mentioned.   The manufacturing method according to claim 7, wherein the spacer member is formed on at least one of the first plate-like member and the second plate-like member. An encoder that measures the position of the scale by irradiating the scale on which the pattern is formed and receiving the light through the scale,
An encoder provided with the two-dimensional scale manufactured by the manufacturing method as described in any one of Claims 1-8 as the said scale.

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