Laser Interference Device

Abstract

To provide a laser interference device that can reduce an influence caused by thermal expansion.SOLUTION: A laser interference device 1 comprises: a slider 3 that is movable in a predetermined measuring direction; a photoelectric microscope 5 that executes measurement processing on an object W arranged on the slider 3; a measurement reflection body 65 that is fixed to the slider 3; a reference reflection body 67 that is fixed to the photoelectric microscope 5; and a laser interferometer 63 that divides a laser beam output from a laser source into a measuring beam and a reference beam, causes the measuring beam to be emitted toward the measurement reflection body 65 along the measuring direction, causes the reference beam to be emitted toward the reference reflection body 67 along the measuring direction, and measures the interference light between the measuring beam reflected on the measurement reflection body 65 and the reference beam reflected on the reference reflection body 67.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laser interference device. [Background technology]

[0002] BACKGROUND ART Conventionally, laser interference devices have been used as means for measuring the displacement of a moving body with high precision in measuring instruments, ultra-precision machining devices, and the like (see, for example, Patent Document 1). For example, Fig. 6 is a plan view showing a laser interferometer described in Patent Document 1. In the laser interferometer 100 shown in Fig. 6, a laser beam emitted from a laser source 101 is split by a beam splitter 102 into a measurement beam and a reference beam. The measurement light is light that passes through the beam splitter 102 and travels in the X direction, and is reflected by a measurement reflector 104 that is fixed to a slider 103 that is movable in the X direction. The reference light is light that is reflected by beam splitter 102 and travels in the Y direction, is reflected by reflecting mirror 105 and travels along the X direction, and is reflected by reference reflector 107 provided on bridge structure 106 fixed to the base. In Patent Document 1, an object placed on slider 103 is measured by photoelectric microscope 108 fixed to bridge structure 106. Reference reflector 107 is placed on straight line 109 connecting photoelectric microscope 108 and the measurement center where measurement by photoelectric microscope 108 is performed. The measurement light and reference light reflected by the reflectors 104 and 107 are superimposed by the beam splitter 102 to generate interference light. The brightness of this interference light changes depending on the difference in optical path length between the measurement light and the reference light. Therefore, the interference light generated when the slider 103 moves is detected by the photodetector 110, and the amount of displacement of the slider 103 can be measured by counting the interference fringes of the interference light based on the output signal of the photodetector 110. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3400393 Summary of the Invention [Problem to be solved by the invention]

[0004] In a laser interference device such as that disclosed in Patent Document 1, the amount of movement of the slider is measured using the position of the reference reflector 107 as a reference. The position that should be used as the reference is the processing center, and when measurement is performed using a photoelectric microscope 108 as in Patent Document 1, the processing center is a measurement center 109 where measurement is performed by the photoelectric microscope 108. Therefore, in Patent Document 1, the reference reflector 107 is provided in a part of the bridge structure 106 that is coincident with the measurement center 109 in the X direction. Therefore, it is desirable that the bridge structure 106 on which the photoelectric microscope 108 and the reference reflector 107 are provided be a rigid body that is immobile and does not deform. However, there is a problem in that if temperature fluctuations occur during operation of the laser interferometer, thermal expansion of the bridge structure 106 occurs, causing a misalignment in the X direction between the measurement center 109 and the reference reflector 107, resulting in a measurement error. In order to suppress such thermal expansion, it is conceivable to use a constant temperature booth capable of high-performance temperature control or to use a material with a small thermal expansion coefficient for the bridge structure 106, but in either case, an increase in the cost of the device is unavoidable.

[0005] SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a laser interference device capable of reducing the influence of thermal expansion. [Means for solving the problem]

[0006] A first aspect of the present invention provides a laser interference device comprising: a slider that can move in a predetermined length measurement direction; a processing unit that performs a predetermined process on an object placed on the slider; a measurement reflector fixed to the slider; a reference reflector fixed to the processing unit; and a laser measurement unit that splits laser light output from a laser light source into measurement light and reference light, emits the measurement light toward the measurement reflector along the length measurement direction, emits the reference light toward the reference reflector along the length measurement direction, and measures interference light between the measurement light reflected by the measurement reflector and the reference light reflected by the reference reflector.

[0007] In the present invention, the measurement reflector is fixed to the slider, and the reference reflector is fixed to the processing section. In this configuration, the reference reflector can be located closer to the processing center where a predetermined process is performed on the object, compared to a case where the reference reflector is provided at a position distant from the processing section, such as a bridge structure. This reduces the influence of thermal expansion caused by temperature changes during processing. In other words, even if a temperature change occurs, the change in the distance between the reference reflector and the processing center is suppressed, making it possible to properly adjust the position of the slider relative to the processing center.

[0008] A second aspect of the present invention provides a laser interference device comprising: a slider movable in a predetermined length measurement direction relative to a base; a measurement reflector fixed to the slider; a processing section that performs predetermined processing on an object placed on the slider; a holding section that is fixed to the base and holds the processing section; an arm section that extends from the holding section to a position opposite the processing section; a reference reflector that is fixed to the arm section at a position opposite the processing section; and a laser measurement section that splits laser light output from a laser light source into measurement light and reference light, emits the measurement light toward the measurement reflector along the length measurement direction, emits the reference light toward the reference reflector along the length measurement direction, and measures interference light between the measurement light reflected by the measurement reflector and the reference light reflected by the reference reflector.

[0009] In this aspect, the measurement reflector is fixed to the slider, and the reference reflector is fixed to an arm portion that extends from a holder to which the processing portion is attached to a position facing the processing portion. When the processing section is held movably (positionally adjustable) relative to the holder, if the reference reflector is fixed to the processing section as in the first embodiment, the optical path of the reference light may change due to positional fluctuations of the reference reflector, and interference light between the measurement light and the reference light may not be obtained. In contrast, in this embodiment, even if the position of the processing section relative to the holder fluctuates, the position of the reference reflector is fixed, so the optical path of the reference light does not change. Therefore, interference light between the measurement light and the reference light can be properly obtained, and the position of the slider can be measured based on this interference light.

[0010] The laser interference device of this aspect further includes a distance measuring unit that measures the distance between the reference reflector and the processing unit. When the reference reflector is fixed to the arm, it is necessary to correctly grasp the positional relationship between the reference reflector and the processing section. In contrast, in this aspect, the distance between the reference reflector and the processing section can be detected by the distance measurement section, and thus the distance between the reference reflector and the processing section can be detected even if the position of the processing section relative to the holding section changes. By detecting the distance between the reference reflector and the processing section, the processing section can correctly detect the position of the processing center, and it is also possible to properly adjust the position of the slider relative to the processing center based on the interference light between the measurement light and the reference light.

[0011] In the laser interference device of this embodiment, the holding portion comprises a first holding portion fixed to the base or integral with the base, a second holding portion to which the processing portion is fixed, and a position adjustment portion that holds the second holding portion movably relative to the first holding portion, and the arm portion is connected to the first holding portion. As described above, in this aspect, even if a position adjustment unit that adjusts the position of the processing unit relative to the holder is provided, the position of the second reference object remains unchanged, and it is possible to properly obtain interference light between the measurement light and the reference light. That is, when, for example, a touch probe that comes into contact with the object is used as the processing unit, or a processing tool that comes into contact with the object and processes it is used, the position of the processing unit changes when it comes into contact with the object, but in this aspect, because the reference reflector is provided on the arm unit, the position of the reference reflector does not change even if the position of the processing unit changes.

[0012] In the laser interference devices of the first and second aspects, the laser measurement unit includes a light splitting unit that splits the laser light into measurement light and reference light, a first light guiding unit that guides the measurement light incident from the light splitting unit and emits the measurement light toward the measurement reflector in the length measurement direction, and a second light guiding unit that guides the reference light incident from the light splitting unit and emits the reference light toward the reference reflector in the length measurement direction, and the first distribution path that is the path of the measurement light from the light splitting unit to the light exit surface of the first light guiding unit and the second distribution path that is the path of the reference light from the light splitting unit to the light exit surface of the second light guiding unit have equal mechanical path lengths and equal optical path lengths.

[0013] In this aspect, the first distribution path and the second distribution path have the same mechanical path length and the same optical path length. Therefore, even if thermal expansion or the like occurs in the laser interferometer, causing a misalignment between the first and second light guiding sections, the amount of change in the optical path length occurring in the first distribution path and the amount of change in the optical path length occurring in the second distribution path can be made approximately the same. As a result, errors occurring in the optical path length difference can be further reduced, and the measurement accuracy of the laser interferometer can be improved. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a plan view showing a laser interference device according to an embodiment of the present invention; [Figure 2] 2 is a cross-sectional view of the laser interference device shown in FIG. 1 taken along line II-II. [Figure 3] FIG. 2 is a schematic diagram showing a first light guiding section and a second light guiding section of the first embodiment. [Figure 4] FIG. 10 is a plan view showing a laser interference device according to a second embodiment. [Figure 5] FIG. 10 is a plan view showing a laser interference device according to a first modified example. [Figure 6] FIG. 1 is a plan view showing a prior art laser interference device. DETAILED DESCRIPTION OF THE INVENTION

[0015] First Embodiment A first embodiment of the present invention will be described below with reference to FIGS. Fig. 1 is a plan view showing a schematic configuration of a laser interference device 1 according to a first embodiment. In Fig. 1, the upper portions of some elements of the laser interference device 1 are shown cut away in order to illustrate the optical path of the laser light.

[0016] The laser interference device 1 of this embodiment is a device that can detect the amount of displacement of the slider 3 that moves in one direction (length measurement direction) while observing the object W placed on the slider 3. Specifically, in this embodiment, a line standard is placed on the slider 3 as the object W, and the laser interference device 1 is configured as a device for evaluating the accuracy of the line standard by calculating the deviation of the scale line spacing of the line standard detected by the photoelectric microscope 5 based on the displacement amount of the slider 3 detected by the laser interferometer 6.

[0017] (Laser interference device 1) First, the overall configuration of the laser interference device 1 will be described. FIG. 2 is a cross-sectional view taken along line II-II in FIG. The laser interference device 1 includes a base 2, a slider 3 movable relative to the base 2, a drive mechanism 4 for driving the slider 3, a photoelectric microscope 5 for observing an object W placed on the slider 3, and a laser interferometer 6 for detecting the displacement of the slider 3.

[0018] The base 2 has a horizontally disposed upper surface 21, and the slider 3, laser interferometer 6, etc. are mounted on this upper surface 21. The base 2 also has a bridge structure 22 disposed so as to straddle the slider 3. Both legs of the bridge structure 22 are fixed to the base 2.

[0019] The slider 3 is movable in one direction (hereinafter referred to as the X direction) parallel to the upper surface 21 of the base 2. The X direction corresponds to the length measurement direction in the present invention. An object W is set on the slider 3. This object W is preferably arranged on the same line as the center of a measurement optical path tube 66, which will be described later.

[0020] The driving mechanism 4 is configured by, for example, a feed screw mechanism, and drives the slider 3 in the X direction. The driving mechanism 4 is also connected not only to the slider 3 but also to the carriage 668 of the laser interferometer 6, and drives the carriage 668 together with the slider 3 in the X direction.

[0021] The photoelectric microscope 5 is supported by a bridge structure 22 above the slider 3. This photoelectric microscope 5 corresponds to the processing section of the present invention, and performs measurement (observation) processing on the object W placed on the slider 3. In this embodiment, the observation optical axis A of the photoelectric microscope 5 is arranged parallel to the upper surface 21 of the base 2 and along an orthogonal direction (hereinafter referred to as the Y direction) that is orthogonal to the X direction. The laser interferometer 6, the details of which will be described later, utilizes the principle of interferometry to output interference light for detecting the displacement of the slider 3.

[0022] (Laser interferometer 6) Next, the configuration of the laser interferometer 6 will be described. The laser interferometer 6 is the laser measurement unit of the present invention, and includes a laser light source 61, a half-wave plate 62, a vacuum chamber 63, a beam splitting / combining member 64, a first light guiding unit 71, a second light guiding unit 72, a measurement reflector 65, a measurement optical path tube 66, a reference reflector 67, a reference optical path tube 68, and a detection unit 69.

[0023] The laser light source 61 is, for example, a helium-neon laser, and emits laser light with a stable frequency. The half-wave plate 62 adjusts the polarization state of the laser light emitted from the laser light source 61. Furthermore, a rotating means for rotating the half-wave plate 62 around the optical axis may be provided.

[0024] The vacuum chamber 63 is a container that houses the light beam splitting / combining member 64, the first light guiding section 71, and the second light guiding section 72, and the space inside the vacuum chamber 63 is maintained in a vacuum state or a reduced pressure state that is almost a vacuum. The vacuum chamber 63 also has a window 631 through which the laser light emitted from the laser light source 61 and transmitted through the half-wave plate 62 passes.

[0025] The beam splitting / combining member 64 corresponds to the light splitting section of the present invention and has a splitting surface 641 that splits incident light into transmitted light and reflected light (see FIG. 3). The beam splitting / combining member 64 of this embodiment is configured with a polarizing beam splitter, and of the laser light emitted from the laser light source 61 and transmitted through the half-wave plate 62, it transmits P-polarized light to be output as measurement light and reflects S-polarized light to be output as reference light. As described above, the half-wave plate 62 may be configured to be rotatable, in which case it is possible to adjust the light intensity ratio between the measurement light and the reference light. Furthermore, the beam splitting / combining member 64 combines the measurement light reflected by the measurement reflector 65 and returned thereto and the reference light reflected by the reference reflector 67 and returned thereto.

[0026] The first light guiding unit 71 is composed of a group of optical elements. The first light guiding unit 71 guides the measurement light emitted from the light beam splitting / combining member 64 and emits the measurement light in the length measurement direction (X direction), thereby forming a linear measurement light path Lp1 between itself and the measurement reflector 65. The first light guiding unit 71 also guides, to the light beam splitting / combining member 64, the measurement light that is reflected by the measurement reflector 65 and returns along the measurement light path Lp1.

[0027] The second light guiding unit 72 is composed of a group of optical elements having the same content as the first light guiding unit 71. This second light guiding unit 72 guides the reference light emitted from the light beam splitting / combining member 64 and emits the reference light in the length measurement direction (X direction), thereby forming a reference light path Lp2 parallel to the measurement light path Lp1 between itself and the reference reflector 67. In addition, the second light guiding unit 72 guides the reference light that is reflected by the reference reflector 67 and returns along the reference light path Lp2 to the light beam splitting / combining member 64.

[0028] The measurement reflector 65 is attached to the slider 3 and is movable in the X direction together with the slider 3. The measurement reflector 65 is a retroreflector such as a corner cube prism, and retroreflects the measurement light emitted from the first light guiding section 71.

[0029] The measurement optical path cylinder 66 is arranged along the X direction so as to surround the measurement optical path Lp1. One end of the measurement optical path cylinder 66 is connected to the vacuum chamber 63, and the other end of the measurement optical path cylinder 66 is fixed to the measurement reflector 65. The measurement optical path cylinder 66 is configured to expand and contract in the X direction as the measurement reflector 65 moves in the X direction.

[0030] Specifically, measurement optical path tube 66 is configured by connecting bellows 661 (bellows tube), double bellows 662, 663, and intermediate tubes 664, 665. Double bellows 662, 663 have a double structure that separates an inner space from an outer space, and maintains the inner space in a vacuum state while maintaining the outer space at atmospheric pressure, thereby achieving pressure balance. Intermediate tube 664 is supported by carriage 668 that is movable in the X direction, and is driven in the X direction by drive mechanism 4.

[0031] The reference reflector 67 is fixed to the photoelectric microscope 5, and specifically, is arranged on the observation optical axis A in plan view seen from the Z direction. That is, in this embodiment, the observation center of the object W observed by the photoelectric microscope 5, which is the processing section, becomes the processing center of the present invention, and the reference reflector 67 is fixed to the photoelectric microscope 5. Preferably, as shown in FIG. 1, the reference reflector 67 is positioned in the same position in the X direction as the processing center of the photoelectric microscope 5, which is the processing section, that is, on the observation optical axis A in the XY plan view seen from the Z direction. The reference reflector 67 is a retroreflector such as a corner cube prism, and retroreflects the reference light emitted from the second light guiding section 72 .

[0032] The reference optical path cylinder 68 is disposed along the X direction so as to surround the reference optical path Lp2. One end of the reference optical path cylinder 68 is connected to the vacuum chamber 63, and the other end of the reference optical path cylinder 68 is fixed to the reference reflector 67.

[0033] Specifically, the reference optical path tube 68 has a pipe structure 681 and double bellows 682, 683 arranged on both sides of the pipe structure 681. The double bellows 682, 683 have a double structure similar to the above-mentioned double bellows 662, 663. The reference optical path tube 68 is not designed to expand and contract, but by having the double bellows 682, 683, it is possible to prevent a load from occurring in the X direction when each element of the laser interference device 1 thermally expands.

[0034] The detector 69 generates interference light by causing the measurement light and reference light that are converged on the same axis by the beam splitting / combining member 64 to interfere with each other, and outputs a detection signal by photoelectrically converting the interference light. The detector 69 is connected to an external signal processing device, and the signal processing device processes the detection signal to calculate the displacement amount of the measurement reflector 65, etc. The specific detection method and configuration of the detector 69 are not particularly limited, and known techniques can be used. For example, the detector 69 splits the beam of measurement light and reference light that are converged on the same axis by the beam splitting / combining member 64 into multiple beams, and generates multiple interference light beams with arbitrary phase differences from these multiple beams. Each interference light beam is then received by a light-receiving element and photoelectrically converted to obtain multiple detection signals that can detect displacement in each direction.

[0035] (First light guiding section 71 and second light guiding section 72) Next, the configurations of the first light guiding section 71 and the second light guiding section 72 will be described with reference to Fig. 3. Fig. 3 shows the light beam splitting / combining member 64, the first light guiding section 71, and the second light guiding section 72 arranged in the vacuum chamber 63.

[0036] In this embodiment, the first light guiding section 71 and the second light guiding section 72 are each made up of a plurality of optical elements arranged on the same XY plane. Specifically, the first light guiding unit 71 has, in order from the light beam splitting / combining member 64 side, a right-angle prism 711, a polarizing beam splitter 712, and a right-angle prism 713. The second light guiding unit 72 has, in order from the light beam splitting / combining member 64 side, a polarizing beam splitter 721, and right-angle prisms 722 and 723. The polarizing beam splitters 712 and 721 are equal in size and are made of materials with the same refractive index, while the rectangular prisms 711, 713, 722, and 723 are equal in size and are made of materials with the same refractive index. That is, the optical element group constituting the first light guiding section 71 and the optical element group constituting the second light guiding section 72 are the same in number, material, and size of the optical elements.

[0037] In this configuration, the measurement light L1 that passes through the beam splitting / combining member 64 is reflected by the rectangular prism 711 in the first light guiding section 71, passes through the polarizing beam splitter 712, and is reflected by the rectangular prism 713, and is thereby emitted in the measurement direction (X direction). On the other hand, the reference light L2 reflected by the beam splitting / combining member 64 is reflected by the polarizing beam splitter 721 in the second light guiding section 72, and then reflected by the right-angle prism 722 and the right-angle prism 723, and is emitted in the measurement direction (X direction).

[0038] Here, when the path of the measurement light from the splitting surface 641 of the light beam splitting / combining member 64 to the exit surface 71A of the first light guiding section 71 is defined as the first distribution path Dp1, and the path of the reference light from the splitting surface 641 to the exit surface 72A of the second light guiding section 72 is defined as the second distribution path Dp2, the first distribution path Dp1 and the second distribution path Dp2 have the same mechanical path length and the same optical path length. The optical path length is the length obtained by multiplying the mechanical path length of the path along which light travels by the refractive index of the medium forming the path.

[0039] Furthermore, the beam splitting / combining member 64 is disposed on a temporary line Lt that equally divides the distance between the path of the measurement light L1 emitted from the emission surface 71A of the first light guiding section 71 (measurement light path Lp1 in FIG. 1) and the path of the reference light L2 emitted from the emission surface 72A of the second light guiding section 72 (reference light path Lp2 in FIG. 1). As a result, the first distribution path Dp1 and the second distribution path Dp2 are formed so that the mechanical path lengths W1 and W2 in the X direction are equal to each other and the mechanical path lengths D1 and D2 in the Y direction are equal to each other.

[0040] In the first light guiding section 71, the rectangular prisms 711 and 713 are configured so that their attitudes can be adjusted in both pitching and yawing. Similarly, in the second light guiding section 72, the rectangular prisms 722 and 723 are configured so that their attitudes can be adjusted in both pitching and yawing.

[0041] [Effects of this embodiment] The laser interference device 1 of this embodiment includes a slider 3 that is movable in the X direction, a photoelectric microscope 5 (processing unit) that performs measurement processing on an object W placed on the slider 3, a measurement reflector 65 fixed to the slider 3, a reference reflector 67 fixed to the photoelectric microscope 5, and a laser interferometer 6. The laser interferometer 6 splits a laser beam output from a laser light source 61 into measurement beam and reference beam, emits the measurement beam along the X direction toward the measurement reflector 65, and emits the reference beam along the X direction toward the reference reflector 67, and measures interference beams of the measurement beam and the reference beam reflected by the measurement reflector 65 and the reference reflector 67. In this configuration, the reference reflector 67 is fixed to the photoelectric microscope 5 that performs the measurement process (observation process), so the positional relationship between the reference reflector 67 and the processing center does not change even if a temperature change or the like occurs during measurement. In other words, if the reference reflector 67 is fixed to the bridge structure 22 as in the conventional case, even if the reference reflector 67 is positioned on the observation optical axis A at the start of measurement, the bridge structure 22 may be deformed due to thermal expansion when the temperature changes during measurement. In this case, if the reference reflector 67 is provided on the bridge structure 22, the distance from the position where the reference reflector 67 on the bridge structure 22 is provided to the photoelectric microscope 5 becomes longer, so that it is more susceptible to the influence of thermal expansion, and the position of the reference reflector 67 in the X direction is shifted from the observation optical axis A (i.e., the position of the processing center in the X direction), resulting in larger measurement errors. In contrast, in this embodiment, the reference reflector 67 is fixed directly to the photoelectric microscope 5, which is the processing section, rather than to the bridge structure 22, so that the position of the reference reflector 67 in the X direction relative to the observation optical axis A hardly moves even if a temperature change occurs during measurement. Therefore, measurement errors due to temperature changes during processing are suppressed, the position of the slider 3 relative to the measurement center can be properly controlled, and highly accurate measurements can be performed. In addition, since there is no need to use expensive materials with low thermal expansion coefficients for the bridge structure 22, etc., or to store the entire device in a constant temperature bath, the cost of the laser interference device 1 can be reduced.

[0042] In this embodiment, the laser interferometer 6 includes a beam splitting / combining member 64 that splits the laser beam into measurement light and reference light, a first light guiding unit 71 that guides the measurement light, and a second light guiding unit 72 that guides the reference light. A first distribution path Dp1, which is a path of the measurement light from the beam splitting / combining member 64 to the light exit surface of the first light guiding unit 71 in the first light guiding unit 71, and a second distribution path Dp2, which is a path of the reference light from the beam splitting / combining member 64 to the light exit surface of the second light guiding unit 72 in the second light guiding unit 72, have the same mechanical path length and the same optical path length. Therefore, even if the vacuum chamber 63 thermally expands and misalignment occurs in the optical elements of the first light guiding section 71 and the second light guiding section 72, the amount of change in the optical path length occurring in the first distribution path Dp1 and the amount of change in the optical path length occurring in the second distribution path Dp2 can be made to be approximately the same. As a result, the error occurring in the difference in optical path length can be further reduced, and the measurement accuracy of the laser interferometer 1 can be improved.

[0043] In this embodiment, due to the arrangement of the light beam splitting / combining member 64, the first distribution path Dp1 and the second distribution path Dp2 are configured to be equal in both the X direction and the Y direction. Therefore, regardless of whether thermal expansion occurs in the X direction or the Y direction, the amount of change in the optical path length occurring in the first distribution path Dp1 and the amount of change in the optical path length occurring in the second distribution path Dp2 can be made to be approximately the same. As a result, the error occurring in the optical path length difference can be further reduced, and the measurement accuracy of the laser interferometer 1 can be further improved.

[0044] Furthermore, in this embodiment, by using the same materials for the optical elements in the optical element group constituting the first light guide section 71 and the optical element group constituting the second light guide section 72, it is possible to match the thermal expansion coefficients, which affect the mechanical path length, and the refractive index and temperature characteristics of the refractive index, which affect the optical path length. Furthermore, by matching the number and size of optical elements in the optical element group constituting the first light guide section 71 and the optical element group constituting the second light guide section 72, the total optical paths within the optical elements are equal. Therefore, even if the component dimensions of the optical elements or the refractive index within the optical elements change due to heat transmitted to the first light guide section 71 and the second light guide section 72, the amount of change in the optical path length occurring in the first distribution path Dp1 and the amount of change in the optical path length occurring in the second distribution path Dp2 can be made approximately equal. This allows for improved measurement accuracy using the laser interferometer 1 while using optical elements other than mirrors as the optical elements constituting the first light guide section 71 and the second light guide section 72.

[0045] Second Embodiment Next, a second embodiment will be described. In the first embodiment, the reference reflector 67 is directly fixed to the photoelectric microscope 5, which is the processing section, but there are cases where the processing section is not fixed to the bridge structure 22 but is attached so as to be displaceable within a certain range. In such cases, it is not possible to fix the reference reflector 67 to the processing section. In contrast, in the second embodiment, the above problem is solved by fixing a reference reflector at a position facing the processing section. In the following description, the same reference numerals will be used to designate components that have already been described, and the description thereof will be omitted or simplified.

[0046] FIG. 4 is a plan view showing the laser interference device of the second embodiment. The laser interference device 1A of this embodiment includes a base 2, a slider 3, a bridge structure 22, a photoelectric microscope 5 as a processing unit, and a laser interferometer 6, similar to the first embodiment. In this embodiment, the photoelectric microscope 5 is held by a holder 23 fixed to the bridge structure 22. More specifically, the holding unit 23 includes a first holding unit 231 that is fixed to the bridge structure 22 or configured integrally with the bridge structure 22, and a second holding unit 232 to which the photoelectric microscope 5 is fixed, and the first holding unit 231 and second holding unit 232 are connected via a position adjustment unit 233. The position adjustment unit 233 holds the position of the second holding unit 232 relative to the first holding unit 231 so that it can move in the X direction, and thus, in this embodiment, the position of the photoelectric microscope 5 held by the second holding unit 232 can be finely adjusted within a predetermined range. Here, a configuration is shown in which the position adjustment unit 233 allows fine adjustment of the second holding unit 232 in the X direction relative to the first holding unit 231, but the position may also be adjustable in the Y and Z directions.

[0047] Moreover, in this embodiment, an arm unit 24 is fixed to the first holding unit 231. The arm unit 24 is connected to a side (for example, the -X side) of the first holding unit 231, and extends in the direction toward the photoelectric microscope 5 along the Y direction to a position facing the photoelectric microscope 5. A reference reflector 67 is fixed to the tip side of the arm unit 24, and as a result, in this embodiment, the reference reflector 67 is disposed at a position facing the photoelectric microscope 5 in the X direction.

[0048] Furthermore, in this embodiment, a distance measurement unit 25 is provided that measures the distance between the photoelectric microscope 5 and the reference reflector 67. The distance measurement unit 25 is not particularly limited, and may be, for example, a capacitance sensor that detects the distance based on a change in capacitance, or a configuration in which a separate interferometer is provided. When an interferometer is used as the distance measurement unit 25, the influence of air fluctuations on the measurement optical path can be ignored by setting the gap between the photoelectric microscope 5 and the reference reflector 67 as narrow as possible within a range that allows the measurement stroke to be secured. Furthermore, when the position adjustment unit 233 is configured to be movable not only in the X direction but also in the Y and Z directions as described above, a distance measurement unit 25 may be provided corresponding to each axial direction (XYZ).

[0049] The laser interferometer 1A of this embodiment adjusts the position of the slider 3 using both the detection signal output from the detector 69 of the laser interferometer 6 and the signal output from the distance measurement unit 25. That is, the laser interferometer 1A of this embodiment calculates the position of the slider 3 relative to the reference reflector 67 based on the detection signal output from the detector 69. Furthermore, based on the signal output from the distance measurement unit 25, the laser interferometer 1A calculates the distance (offset amount) in the X direction between the photoelectric microscope 5 (observation optical axis A) and the reference reflector 67, and corrects the position of the slider 3 relative to the reference reflector 67.

[0050] [Effects of this embodiment] The laser interference device 1A of this embodiment is provided with a holding section 23 that is provided on a bridge structure 22 fixed to the base 2 and that holds a photoelectric microscope 5, which is a processing section, and the holding section 23 is provided with an arm section 24 that extends to a position facing the photoelectric microscope 5. The reference reflector 67 is fixed at the tip of the arm section 24 in a position facing the photoelectric microscope 5.

[0051] With this configuration, the same effects as in the first embodiment can be obtained, and even if a temperature change occurs during measurement, the distance between the reference reflector 67 and the photoelectric microscope 5 is short, making it possible to suppress measurement errors due to thermal expansion. Furthermore, in this embodiment, it is possible to use a processing unit (such as the photoelectric microscope 5) whose position relative to the holder 23 is adjustable. That is, in the first embodiment described above, the reference optical path Lp2 of the laser interferometer 6 is fixed, and therefore, when adjusting the position of the photoelectric microscope 5, which is the processing unit, it is necessary to also adjust the reference optical path Lp2 (specifically, adjust the positions of the optical members arranged in the second light guiding unit 72). In contrast, in this embodiment, the reference reflector 67 is arranged with a predetermined gap between it and the photoelectric microscope 5, and therefore, the position of the photoelectric microscope 5 can be finely adjusted, and replacement and maintenance of the photoelectric microscope 5 can also be easily performed.

[0052] In addition, this embodiment further includes a distance measurement unit 25 that measures the distance between the reference reflector 67 and the photoelectric microscope 5 . As a result, even when there is a gap between the reference reflector 67 and the photoelectric microscope 5 as described above, the distance of the gap can be measured by the distance measuring unit 25. This makes it possible to calculate the distance from the reference reflector 67 to the observation optical axis A, which is the processing center, and by correcting the position of the slider 3 measured by the laser interferometer 6 using this distance, the position of the slider 3 with respect to the observation optical axis A can be adjusted with high precision.

[0053] In this embodiment, the holder 23 includes a first holder 231 fixed to the bridge structure 22 and a second holder 232 to which the photoelectric microscope 5 is fixed, and the second holder 232 is attached to the first holder 231 via a position adjustment part 233. In other words, the position adjustment part 233 makes it possible to adjust the position of the second holder 232 relative to the first holder 231, thereby enabling the observation optical axis A of the photoelectric microscope 5 to be accurately aligned with a desired measurement point on the object W. Furthermore, in this embodiment, the photoelectric microscope 5, which does not come into contact with the object W, has been exemplified as the processing unit, but it is also possible to use, for example, a contact-type measuring means such as a touch probe, or a processing tool that comes into contact with the object W to process it. When such a contact-type processing unit is used, the attitude of the processing unit may change or the position of the processing unit may fluctuate due to contact between the processing unit and the object W. In response to this, by providing a distance measurement unit 25 as in this embodiment, the amount of positional fluctuation of the processing unit can be measured, and the processing center relative to the object W can be accurately determined.

[0054] [Modification] The present invention is not limited to the above-described embodiments, and includes modifications within the scope of achieving the object of the present invention.

[0055] (Variation 1) In the laser interference device 1 of the first embodiment, the position of the reference reflector 67 and the observation optical axis A of the photoelectric microscope 5, which is the processing unit, are configured to coincide with each other in the X direction, but the present invention is not limited to this. Fig. 5 is a plan view of a laser interference apparatus 1B according to Modification 1. For example, as shown in Fig. 5, a configuration may be adopted in which a reference reflector 67 is fixed to a side surface of a photoelectric microscope 5 in the X direction. In this case, the positions of the observation optical axis A and the reference reflector 67 are shifted by the width of the photoelectric microscope 5 in the X direction. However, the dimension from the observation optical axis A to the side surface of the photoelectric microscope 5 is known, and the position of the slider 3 measured by the laser interferometer 6 is corrected using this dimension as an offset amount, thereby making it possible to properly calculate the position of the observation optical axis A.

[0056] Furthermore, in the second embodiment, a configuration has been exemplified in which the reference reflector 67 fixed to the tip of the arm unit 24 is arranged on the -X side of the photoelectric microscope 5 with a predetermined distance therebetween, but the present invention is not limited to this. For example, a configuration may be adopted in which the arm unit 24 extends from the +Z side or the -Z side of the holder 23 to the +Y side, and the reference reflector 67 fixed to the tip of the arm unit 24 is arranged on the +Z side or the -Z side of the photoelectric microscope 5.

[0057] (Variation 2) In the second embodiment, the first holding portion 231 is fixed to the bridge structure 22, but the bridge structure 22 and the first holding portion 231 may be integrally formed. Similarly, although the configuration in which the arm portion 24 is fixed to the first holding portion 231 has been exemplified, the first holding portion 231 and the arm portion 24 may be integrally formed.

[0058] (Variation 3) In the above embodiment, the laser interferometer 6 is configured such that the first distribution path Dp1 in the first light guiding section 71 and the second distribution path Dp2 in the second light guiding section 72 have the same mechanical path length and the same optical path length, but is not limited to this. For example, the first distribution path Dp1 and the second distribution path Dp2 may have different mechanical path lengths or optical path lengths.

[0059] (Variation 4) Although the laser interference devices 1, 1A of the above embodiments are provided with the vacuum chamber 63, this vacuum chamber 63 may be omitted. In this case, the double bellows 663, 683 of the measurement optical path tube 66 and the reference optical path tube 68 connected to the vacuum chamber 63 are also omitted. In this case, it is preferable to use a cover to prevent air fluctuations instead of the vacuum chamber 63. In this configuration, since a large, heavy object such as the vacuum chamber 63 is not used, the laser interference device 1 can be made smaller and lighter.

[0060] (Variation 5) In the above embodiment, a polarizing beam splitter is used as an example of the light splitting unit of the present invention, but this is not limiting. For example, the function of splitting the laser light into the measurement light and the reference light and the function of combining the measurement light and the reference light may be realized by separate components.

[0061] Furthermore, although the measurement reflector 65 and the reference reflector 67 are each corner cubes, the present invention is not limited to this. For example, the measurement reflector 65 and the reference reflector 67 may each be a plane mirror, and the laser interferometer 6 may be configured not to use polarized light.

[0062] (Variation 6) In each of the above embodiments, the photoelectric microscope 5 is exemplified as the processing unit, but as mentioned above, the processing unit may be any device that performs processing such as measurement or processing on the object W. For example, the processing unit may be a contact-type touch probe sensor, a non-contact-type laser probe sensor, a contact-type processing tool such as a drill or a grinder, an exposure optical system that irradiates a laser beam of a predetermined wavelength onto the resist that is the object W, or a non-contact processing tool such as a laser cutter. Additionally, the present invention can be applied to various laser interference devices that measure the amount of displacement of a moving object. [Explanation of symbols]

[0063] 1, 1A...laser interference device, 2...base, 21...upper surface, 22...bridge structure, 3...slider, 4...driving mechanism, 5...photoelectric microscope, 6...laser interferometer, 61...laser light source, 62...two wavelength plates, 63...vacuum chamber, 631...window portion, 64...beam splitting / combining member, 641...splitting surface, 65...measurement reflector, 66...measurement optical path tube, 661...bellows, 662, 663...double bellows, 664, 665...intermediate tube, 668...carriage, 67...reference reflector, 68...reference optical path Cylinder, 681...pipe structure, 682, 683...double bellows, 69...detection unit, 71...first light guiding unit, 711, 713...right-angle prism, 712...polarizing beam splitter, 71A...exit surface, 72...second light guiding unit, 721...polarizing beam splitter, 722, 723...right-angle prism, 72A...exit surface, A...observation optical axis, Dp1...first distribution path, Dp2...second distribution path, L1...measurement light, L2...reference light, Lp1...measurement optical path, Lp2...reference optical path, Lt...temporary line, W...object.

Claims

1. a slider provided so as to be movable in a predetermined length measurement direction relative to the base; a measurement reflector fixed to the slider; a processing unit that performs a predetermined process on the object placed on the slider; a holding part fixed to the base and holding the processing part; an arm portion extending from the holding portion to a position facing the processing portion; a reference reflector fixed to the arm at a position facing the processing section; a laser measurement unit that splits a laser beam output from a laser light source into a measurement beam and a reference beam, emits the measurement beam toward the measurement reflector along the length measurement direction, emits the reference beam toward the reference reflector along the length measurement direction, and measures interference light between the measurement beam reflected by the measurement reflector and the reference beam reflected by the reference reflector; a distance measuring unit for measuring a distance between the reference reflector and the processing unit; A laser interference device comprising:

2. the holding unit includes a first holding unit fixed to the base or integrated with the base, a second holding unit to which the processing unit is fixed, and a position adjustment unit that holds the second holding unit movably relative to the first holding unit, The arm portion is connected to the first holding portion.

2. The laser interference device according to claim 1.

3. The laser measurement unit a light splitting unit that splits the laser light into measurement light and reference light; a first light guiding unit that guides the measurement light incident from the light splitting unit and emits the measurement light toward the measurement reflector in the length measurement direction; a second light guiding unit that guides the reference light incident from the light splitting unit and emits the reference light in the length measurement direction toward the reference reflector, a first distribution path, which is a path of the measurement light from the light splitting unit to the light exit surface of the first light guiding unit, and a second distribution path, which is a path of the reference light from the light splitting unit to the light exit surface of the second light guiding unit, have the same mechanical path length and the same optical path length; 3. The laser interference device according to claim 1.

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