Measurement head, and confocal displacement meter

Abstract

To provide a measurement head and confocal displacement meter that can suppress a fall in reliability of a measurement under a high-temperature environment of the confocal displacement meter.SOLUTION: A measurement head 1A is the measurement head for a confocal displacement meter having a white light source. The measurement head 1A has a configuration having a plurality of glass-made lenses 221 to 224 accommodated inside a metal-made head housing 10. Inside of the head housing 10, a female screw part 12j is formed that is in the vicinity of a front end part FE. A ring screw 46 is attached to the female screw part 12j. In this state, a lens 224 is provided so as to abut on the ring screw 46. The ring screw 24 is configured to regulate a movement of the lens 224 to a +x direction. Inside of the head housing 10, a metal-made spring member 43 is provided that urges a plurality of lenses including the lens 224 toward the +x direction in a state where the lens 224 abuts on the ring screw 46.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a measuring head for a confocal displacement meter and to a confocal displacement meter. [Background technology]

[0002] As an apparatus for measuring the displacement of the surface of a measurement object in a non-contact manner, for example, there is a confocal displacement meter equipped with a white light source, an optical fiber, and a measurement head. In the confocal displacement meter, light (white light) in a wide wavelength band generated by a white light source is guided to the measurement head through the optical fiber. The measurement head mainly includes a plurality of lenses and a head housing that houses them, and irradiates the measurement object with the light guided through the optical fiber through the plurality of lenses. At this time, chromatic aberration occurs in the light irradiated to the measurement object by the plurality of lenses. In addition, the measurement head receives the light that is focused and reflected by the surface of the measurement object. The displacement of the surface of the measurement object is measured based on the light received by the measurement head. According to the above confocal displacement meter, the measurement head is disposed at a desired position, thereby expanding the measurable range of the measurement object.

[0003] The accuracy of measuring displacement by a confocal displacement meter decreases due to various factors. Therefore, configurations for suppressing the decrease in measurement accuracy have been proposed. For example, Patent Document 1 proposes a confocal displacement meter equipped with a diffractive lens and a refractive lens with different polarities of spherical aberration in order to suppress the decrease in measurement accuracy caused by the spherical aberration of an optical component (lens of a measuring head). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-02722 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when the measurement object is placed in a high-temperature environment, it is possible to place the measurement head in the high-temperature environment. However, depending on the temperature of the environment in which the measurement head is placed and the linear expansion coefficient of each component of the measurement head, the positional relationship of the multiple lenses may change randomly every time the measurement head is placed in a high-temperature environment. In addition, if any of the multiple lenses contains a resin material, the resin material is likely to deform in a high-temperature environment. In these cases, the reliability of the measurement of the confocal displacement meter in a high-temperature environment decreases.

[0006] An object of the present invention is to provide a measurement head and a confocal displacement meter that are capable of suppressing a decrease in the reliability of measurements of the confocal displacement meter in a high-temperature environment. [Means for solving the problem]

[0007] A measurement head according to one aspect of the present invention is a measurement head for a confocal displacement meter having a white light source, the measurement head including: a metallic housing formed in a cylindrical shape and having a first end and a second end; an optical fiber connected to the first end of the housing and guiding light generated from the white light source to the first end of the housing; and a first lens, which is accommodated inside the housing so as to be aligned in an axial direction of the housing and movable in the axial direction, and which generates chromatic aberration along an optical axis in the light guided to the first end by the optical fiber while converging the light onto a measurement object through the second end. The lens assembly comprises a plurality of glass lenses, a first movement restriction portion provided in a predetermined first portion inside the housing and restricting the first lens from moving in either a first direction from the first end to the second end in the axial direction and a second direction opposite thereto when the first lens abuts against the first movement restriction portion, and a metal biasing member that elastically biases some or all of the plurality of lenses including the first lens toward the one direction when the first lens abuts against the first movement restriction portion.

[0008] A measurement head according to another aspect of the present invention is a measurement head for a confocal displacement meter having a white light source, comprising: a metal housing formed in a cylindrical shape and having a first end and a second end; an optical fiber connected to the first end of the housing and guiding light generated from the white light source to the first end of the housing; a plurality of glass lenses including a first lens, which are accommodated inside the housing so as to be aligned in the axial direction of the housing and movable in the axial direction, and which focus the light guided to the first end by the optical fiber on a measurement object through the second end while generating chromatic aberration along the optical axis; the first movement regulating portion is provided at a predetermined first portion in the housing, and regulates movement of the first lens in either a first direction from the first end to the second end in the axial direction and a second direction opposite thereto, when the first lens abuts against the first movement regulating portion; and a polyimide thermal expansion member is provided inside the housing at a position spaced apart from the movement regulating portion in the axial direction, and some or all of the lenses including the first lens are held between the first movement regulating portion and the fixed member with the first lens abutting against the first movement regulating portion.

[0009] A confocal displacement meter according to yet another aspect of the present invention includes the above-mentioned measurement head, a white light source that generates light that is guided to the measurement head, and a displacement measurement unit that calculates the displacement of the measurement object based on light that is irradiated from the measurement head to the measurement object and reflected by the measurement object. Effect of the Invention

[0010] According to the present invention, it is possible to suppress deterioration in the reliability of measurements by a confocal displacement meter in a high-temperature environment. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing a configuration of a confocal displacement meter according to an embodiment of the present invention. [Diagram 2] 1 is an external perspective view showing an example of a measuring head according to an embodiment of the present invention. [Diagram 3] 3 is a side view of the measurement head of FIG. 2 as viewed in the +Z direction. [Figure 4] 4 is a cross-sectional view of the measuring head taken along an imaginary plane indicated by dotted lines in FIGS. 2 and 3. FIG. [Diagram 5] FIG. 2 is an exploded perspective view of the measurement head of FIG. 1. [Figure 6] 5A and 5B are diagrams for explaining details of the configuration and function of a spring member housed in a head housing. [Figure 7] 11A and 11B are diagrams illustrating a reference example for explaining the function of a spring member. [Figure 8] 6A and 6B are diagrams for explaining a first arrangement condition of the spring members in the head housing. [Figure 9] 4 is a cross-sectional view of the measuring head taken along an imaginary plane indicated by a two-dot chain line in FIGS. 2 and 3. FIG. [Figure 10] FIG. 2 is an external perspective view of a light bending unit and a plurality of distance adjustment members. [Figure 11] 11A and 11B are diagrams illustrating changes in the measurement direction and measurable range of the measuring head caused by the optical bending unit and a plurality of distance adjustment members in FIG. 10. [Figure 12] FIG. 11 is a cross-sectional view showing an example of a measuring head according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a measurement head and a confocal displacement meter including the same according to an embodiment of the present invention will be described with reference to the drawings.

[0013] 1. Basic configuration of the confocal displacement meter Fig. 1 is a schematic diagram showing the configuration of a confocal displacement meter according to an embodiment of the present invention. As shown in Fig. 1, a confocal displacement meter 9 includes measurement heads 1A and 1B, measurement units 100A and 100B, light guiding units 300A and 300B, a control unit 2, and a PC (personal computer) 3. The light guiding unit 300A includes a plurality of optical fibers, and optically connects the measurement head 1A to some of the components (light projecting unit 120 and spectroscopic unit 130 described later) inside the measurement unit 100A.

[0014] The measurement unit 100A includes a unit housing 110, a light projecting section 120, a spectroscopic section 130, a light receiving section 140, a measurement control section 150, and a sub-display section 190. The unit housing 110 accommodates the light projecting section 120, the spectroscopic section 130, the light receiving section 140, and the measurement control section 150. The sub-display section 190 includes a display such as a 7-segment display or a dot matrix display, and is attached to the unit housing 110. The light projecting section 120 has a white light source that generates light in a wide and continuous wavelength band (for example, 500 nm to 700 nm), i.e., light having a plurality of continuous wavelengths (white light), and is configured to be able to emit the light generated from the white light source. The light emitted by the light projecting section 120 is input to an optical fiber 311 (described later) of the light guide section 300A.

[0015] The spectroscopic section 130 includes a diffraction grating 131 and a plurality of (two in this example) lenses 132 and 133. As described later, a part of the light emitted by the light projecting section 120 and reflected by the surface of the measurement target S is output from an optical fiber 312 of the light guiding section 300A, which will be described later. The light output from the optical fiber 312 is approximately parallelized by passing through the lens 132 and is incident on the diffraction grating 131. In this embodiment, the diffraction grating 131 is a reflective diffraction grating. The light incident on the diffraction grating 131 is split so as to be reflected at different angles for each wavelength, and is focused on a one-dimensional position that differs for each wavelength by passing through the lens 133.

[0016] The light receiving unit 140 includes an imaging element (one-dimensional line sensor) in which a plurality of pixels are arranged one-dimensionally. The imaging element may be a multi-segment PD (photodiode), a CCD (charge-coupled device) camera, a CMOS (complementary metal-oxide semiconductor) image sensor, or other elements. The light receiving unit 140 is arranged so that a plurality of pixels of the imaging element receive light at a plurality of focusing positions different for each wavelength formed by the lens 133 of the spectroscopic unit 130. Each pixel of the light receiving unit 140 outputs an analog electrical signal (hereinafter referred to as a light receiving signal) corresponding to the amount of light received. The light receiving signal indicates the intensity of the light received by each pixel.

[0017] The measurement control section 150 includes a CPU (Central Processing Unit) and a memory or a microcomputer. A control program is stored in the measurement control section 150, and various data such as measurement conditions used in displacement measurement are also stored in the measurement control section 150. These data are provided from a control unit 2 described later. The measurement control section 150 controls the light projecting section 120 and the light receiving section 140 based on the stored control program and data, and calculates the displacement of the surface of the measurement target S based on the light receiving signal output by the light receiving section 140. The measurement control section 150 causes the sub-display section 190 to display the displacement calculation result.

[0018] The measurement control section 150 is connected to the control unit 2, and the control unit 2 is further connected to the PC 3. The measurement control section 150 provides the displacement calculation result and the light receiving signal output from the light receiving section 140 to the control unit 2. The configurations and operations of the control unit 2 and the PC 3 will be described later.

[0019] The measurement head 1A includes a head housing 10, a fiber receptacle 30, and a plurality of (four in this example) lenses 221, 222, 223, and 224. The head housing 10 houses the plurality of lenses 221, 222, 223, and 224.

[0020] A fiber receptacle 30 is attached to the head housing 10. A fiber connector 330 (described later) of the light guiding unit 300A is connected to the fiber receptacle 30. The fiber connector 330 holds one end of an optical fiber 319 (described later) of the light guiding unit 300A.

[0021] Light is guided from the measurement unit 100A to the optical fiber 319. The light guided to the optical fiber 319 is output from the optical fiber 319 in the head housing 10 of the measurement head 1A and passes through the lenses 221, 222, 223, and 224 in this order. In this embodiment, each of the lenses 221, 222, 223, and 224 has a circular shape when viewed in the optical axis direction of the lens, and is made of a single glass member. The lens 221 is a magnifying lens that magnifies the light guided from the optical fiber 319. The lenses 222 and 223 are bending lenses that add a predetermined function to the light magnified by the lens 221 and converge the light. The lens 224 is a chromatic aberration lens that generates chromatic aberration in the light guided from the lens 223. The light that has generated chromatic aberration by passing through the lenses 221, 222, 223, and 224 is focused at a position near the surface of the measurement target S.

[0022] The light guiding section 300A includes optical fibers 311, 312, and 319, a fiber coupler 320, and a fiber connector 330. In the example of Fig. 1, the fiber coupler 320 is provided in the unit housing 110 of the measurement unit 100A. The fiber connector 330 is connected to the measurement head 1A as described above.

[0023] The fiber coupler 320 has a so-called 2×2 type configuration, and includes four ports 321 to 323 and a main body 324. In FIG. 1, one of the four ports is not shown. The ports 321, 322 and the port 323 are connected to the main body 324 so as to face each other with the main body 324 in between. Light input to at least one of the ports 321 and 322 is output from the port 323. Light input to the port 323 is output from each of the ports 321 and 322.

[0024] The optical fibers 311 and 312 are connected to ports 321 and 322, respectively, of the fiber coupler 320. The other end of the optical fiber 319 is connected to a port 323 of the fiber coupler 320.

[0025] According to this configuration, light emitted by light-projecting unit 120 of measurement unit 100A is input to port 321 of fiber coupler 320 through optical fiber 311. The light input to port 321 is output from port 323 and guided to measurement head 1A through optical fiber 319. The light guided to measurement head 1A is irradiated onto measurement object S through multiple lenses 221, 222, 223, and 224.

[0026] A portion of the light reflected by the surface of the measurement object S is input to one end of the optical fiber 319 through the multiple lenses 224, 223, 222, and 221. The light input to one end of the optical fiber 319 is input to a port 323 of the fiber coupler 320. The light input to the port 323 is output from the ports 321 and 322. The light output from the port 322 is guided to the spectroscopic section 130 through the optical fiber 312. In this way, the displacement of the measurement object S is calculated based on the light irradiated from the measurement unit 100A to the measurement object S.

[0027] The measurement units 100A and 100B have the same configuration, the measurement heads 1A and 1B have the same configuration, and the light guides 300A and 300B have the same configuration. The measurement head 1B and some of the components inside the measurement unit 100B are optically connected by the light guide 300B, similar to the example of the connection between the measurement head 1A and the measurement unit 100A described above. In addition, the measurement control unit 150 (not shown) of the measurement unit 100B is connected to the control unit 2.

[0028] Light emitted from a light-projecting section 120 (not shown) of the measurement unit 100B is irradiated onto the measurement object S through the measurement head 1B. A part of the light reflected on the surface of the measurement object S is returned to the measurement unit 100B through the measurement head 1B. Thereby, the displacement of the measurement object S is calculated based on the light irradiated onto the measurement object S from the measurement head 1B. In this case, a measurement control section 150 (not shown) provided in the measurement unit 100B provides the displacement calculation result and a light receiving signal output from the light receiving section 140 to the control unit 2.

[0029] The control unit 2 includes a CPU and a memory, or a microcomputer. For example, measurement conditions for displacement in the measurement units 100A and 100B are input to the control unit 2 from the PC 3. The measurement conditions include, for example, the amount of light emitted by the light projector 120, the timing of light emission from the light projector 120, and the amount of exposure in the light receiver 140. The control unit 2 provides the input measurement conditions to the measurement control unit 150 of each of the measurement units 100A and 100B. As a result, each of the measurement units 100A and 100B performs a measurement operation based on the given measurement conditions.

[0030] The PC 3 includes a CPU 3a and a memory 3b. The memory 3b stores various programs related to thickness measurement of the measurement target S, as well as various data used in the thickness measurement. The CPU 3a executes the programs stored in the memory 3b. The displacement calculation results and light receiving signals provided from each of the measurement units 100A, 100B to the control unit 2 are provided from the control unit 2 to the PC 3.

[0031] A main display unit 4a and an operation unit 4b are connected to the PC 3. The main display unit 4a includes a display device such as an organic EL (electroluminescence) panel or a liquid crystal display panel. The operation unit 4b includes a keyboard and a pointing device. The pointing device includes a mouse, a joystick, or the like. A user can give various instructions related to thickness measurement to the PC 3 by operating the operation unit 4b.

[0032] In the above-mentioned confocal displacement meter 9, each of the measurement heads 1A and 1B can be arranged in a space in which one or more measurement objects S are arranged, so that the degree of freedom in measuring the displacement of one or more measurement objects S is high. For example, when the measurement object S is a substrate (wafer) on which a circuit is being formed, the measurement object S is likely to be arranged in a high-temperature environment and a vacuum environment. Even in such a case, by arranging each of the measurement heads 1A and 1B together with the measurement object S in a high-temperature environment, the displacement of the surface of the measurement object S (the height of the substrate surface) can be measured in a high-temperature environment. Also, by arranging each of the measurement heads 1A and 1B together with the measurement object S in a vacuum environment, the displacement of the surface of the measurement object S (the height of the substrate surface) can be measured in a vacuum environment. Here, in this embodiment, the high-temperature environment refers to a temperature environment of, for example, about 100°C to 300°C. Also, the vacuum environment refers to an environment with a vacuum degree of, for example, about 10^(-7) Pa to 10^(-5) Pa.

[0033] The measuring heads 1A and 1B can also measure the thickness of a measuring object S having one surface and the other surface facing in opposite directions. For example, the measuring heads 1A and 1B are arranged to face each other with the measuring object S in between. The measuring heads 1A and 1B also measure the displacement of the one surface and the other surface of the measuring object S. In this case, the thickness of the measuring object S can be measured based on the measurement results of the displacement of the one surface and the other surface of the measuring object S and the distance between the measuring heads 1A and 1B (head-to-head distance).

[0034] 2. Measuring heads 1A and 1B The configuration of the measuring head 1A will be described in detail below as a representative of the measuring heads 1A and 1B in FIG.

[0035] <1> External shape of head housing 10 of measuring head 1A Fig. 2 is an external perspective view showing an example of a measuring head 1A according to an embodiment of the present invention. In Fig. 2 and certain drawings described later, arrows indicating mutually orthogonal x-, y-, and z-directions are added so that the positional relationship between each part of the measuring head 1A and the measuring head 1A and the multiple components housed therein can be easily understood.

[0036] In the following explanation, the x-direction, the direction in which the arrow x points on the drawing, will be referred to as the +x-direction, and the opposite direction will be referred to as the -x-direction. Additionally, the y-direction, the direction in which the arrow y points on the drawing, will be referred to as the +y-direction, and the opposite direction will be referred to as the -y-direction. Additionally, the z-direction, the direction in which the arrow z points on the drawing, will be referred to as the +z-direction, and the opposite direction will be referred to as the -z-direction.

[0037] The head housing 10 of the measurement head 1A is made of a single metal member and has a generally rectangular cylindrical shape extending in the x direction as shown in FIG. 2. In the following description, one end of the head housing 10 facing the +x direction is called the front end FE of the head housing 10, and the other end of the head housing 10 facing the -x direction is called the rear end RE of the head housing 10. The central axis of the head housing 10 extending in the longitudinal direction of the head housing 10 is called the head axis 10a. The metal constituting the head housing 10 is, for example, stainless steel. In this embodiment, SUS304, SUS316, SUS316L, or SUS303 as specified in the Japanese Industrial Standards (JIS) is used as the stainless steel of the head housing 10.

[0038] The head housing 10 includes a first housing part 11 and a second housing part 12 arranged side by side in the x direction. The first housing part 11 has a rear end part RE of the head housing 10, and includes an outer surface 11a facing the -z direction, an outer surface 11b facing the +z direction, an outer surface 11c facing the -y direction, and an outer surface 11d facing the +y direction. The second housing part 12 has a front end part FE of the head housing 10, and includes an outer surface 12a facing the -z direction, an outer surface 12b facing the +z direction, an outer surface 12c facing the -y direction, and an outer surface 12d facing the +y direction. At the boundary between the first housing part 11 and the second housing part 12, each of the two outer surfaces (the outer surface of the first housing part 11 and the outer surface of the second housing part 12) facing in a common direction and adjacent to each other in the x direction are flush with each other.

[0039] With this configuration, the measuring head 1A can easily mount a part of the outer surface of the head housing 10 on a flat installation surface. Furthermore, with the above configuration, when two measuring heads 1A are arranged adjacent to each other, the head housing 10 of one of the two measuring heads 1A can be in surface contact with the head housing 10 of the other measuring head 1A. This makes it possible to stably install multiple measuring heads 1A on a predetermined installation surface, compared to when the head housing 10 has a cylindrical outer circumferential surface.

[0040] Here, two notches 11x, 11y are formed in the first housing part 11. The two notches 11x, 11y are aligned in a circumferential direction based on the head axis 10a. Specifically, one notch 11x is formed so as to cut out a part of the outer surfaces 11b, 11c, and the other notch 11y is formed so as to cut out a part of the outer surfaces 11b, 11d. No notch is formed in the outer surface 11a. As a result, as shown in the third balloon from the left in FIG. 3 described later, the cross section perpendicular to the x direction of the part of the first housing part 11 where the two notches 11x, 11y are formed has a T-shape (an inverted T-shape in FIG. 3).

[0041] In the first housing part 11, two through holes h1 (see FIG. 3 described later) extending in the z direction are formed in a portion located between the space where the notch 11x is formed and a space further in the -z direction than the first housing part 11. In addition, in the first housing part 11, two through holes h1 extending in the z direction are also formed in a portion located between the space where the notch 11y is formed and a space further in the -z direction than the first housing part 11. These multiple through holes h1 are used, for example, to attach the measuring head 1A to a desired member. In this case, a screw member, a binding member, or the like is inserted into any of the multiple through holes h1.

[0042] A circular opening is formed at the front end FE of the head housing 10, through which light is emitted from the measurement head 1A toward the measurement target S and through which light reflected by the measurement target S passes. In the example of FIG. 2, a state in which a part of the lens 224 housed in the head housing 10 is exposed from the opening of the front end FE is shown. Four screw holes h2 are formed at the four corners of the front end FE of the head housing 10 so as to surround the opening at 90° intervals when viewed in the x direction. The four screw holes h2 at the front end FE are used to attach a light bending unit 50 (FIG. 10) or a distance adjustment member 60 (FIG. 10), which will be described later, as necessary, when the measurement head 1A is used.

[0043] A plurality of (four in this example) screw holes h3 extending in the x-direction are formed in the rear end portion RE of the head housing 10. The four screw holes h3 in this example are formed in the four corners of the rear end portion RE of the head housing 10. The four screw holes h3 in the rear end portion RE are used to connect the fiber receptacle 30 to the head housing 10 using four screws SC1. In this embodiment, the fiber receptacle 30 and the fiber connector 330 connected to the head housing 10 are made of the same material as the head housing 10.

[0044] A plurality of through holes h4 that communicate the internal space of the head housing 10 with the external space are formed in some of the multiple outer surfaces (11a to 11d, 12a to 12d) of the head housing 10. Fig. 2 shows a state in which a plurality of through holes h4 are formed in one outer surface 12d of the second housing part 12. These through holes h4 suppress the generation of a large pressure difference between the internal space of the head housing 10 and the external space when, for example, the measurement head 1A is placed in a vacuum environment.

[0045] <2> Internal shape of head housing 10 Fig. 3 is a side view of the measurement head 1A of Fig. 2 as viewed in the +Z direction. The head housing 10 has an internal space that extends from the rear end RE to the front end FE along the head axis 10a. In Fig. 3, the shape of the internal space of the head housing 10 is indicated by a dashed line. Also, in Fig. 3, schematic cross-sectional views (end views) of the head housing 10 taken along lines A1-A1, A2-A2, and A3-A3 that are spaced apart in the x direction are indicated in three balloons, respectively.

[0046] 3, line A1-A1 and line A2-A2 are lines that overlap two portions of first housing portion 11, and line A3-A3 is a line that overlaps a portion of second housing portion 12. Each of first housing portion 11 and second housing portion 12 of head housing 10 has an inner circumferential surface whose cross section perpendicular to head axis 10a is circular.

[0047] 3, the first housing part 11 includes a first inner peripheral surface 11i and a second inner peripheral surface 11j. The first inner peripheral surface 11i has a cylindrical shape with a constant diameter extending from the rear end part RE of the head housing 10 to a position near the boundary part between the first housing part 11 and the second housing part 12. The axis of the first inner peripheral surface 11i coincides with the head axis 10a. The first inner peripheral surface 11i has an inner diameter that is approximately the same as the outer diameter of the optical fiber 319, for example.

[0048] The second inner peripheral surface 11j has a cylindrical shape with a constant diameter extending from the end of the first inner peripheral surface 11i in the +x direction to the boundary between the first housing part 11 and the second housing part 12. The axis of the second inner peripheral surface 11j coincides with the head axis 10a. The second inner peripheral surface 11j has an inner diameter larger than the inner diameter of the first inner peripheral surface 11i. As a result, an annular stepped part (first stepped part st1 in FIG. 4 described later) is formed inside the first housing part 11 when viewed in the -x direction.

[0049] The second housing portion 12 includes a third inner peripheral surface 12i. The third inner peripheral surface 12i has a cylindrical shape with a substantially constant diameter extending from the boundary portion between the first housing portion 11 and the second housing portion 12 to the front end portion FE of the head housing 10. The axis of the third inner peripheral surface 12i coincides with the head axis 10a. The third inner peripheral surface 12i has an inner diameter larger than the inner diameters of the first inner peripheral surface 11i and the second inner peripheral surface 11j of the first housing portion 11. As a result, an annular step portion (a second step portion st2 in FIG. 4 described later) is formed inside the head housing 10 and at the boundary portion between the first housing portion 11 and the second housing portion 12 when viewed in the -x direction.

[0050] <3> Optical Fiber 319 Configuration In FIG. 3, the configuration of the optical fiber 319 held by the fiber connector 330 is further shown in a balloon drawn out from the optical fiber 319. The optical fiber 319 includes a core 319a covered with a cladding 319b. In the fiber receptacle 30, the fiber connector 330 is connected, so that the core 319a at the tip of one end of the optical fiber 319 is held so as to be positioned on the optical axis of the multiple lenses 221 to 224 (FIG. 1). In this embodiment, the head axis 10a of the head housing 10 coincides with the optical axes of the multiple lenses 221 to 224 (FIG. 1) provided in the head housing 10. In this embodiment, the tip of one end of the optical fiber 319 functions as a spatial filter having a minute pinhole.

[0051] A resin coating layer 319c made of polyimide is provided in a portion of the optical fiber 319 located between the measurement head 1A and the measurement unit 100A so as to cover the clad 319b. Furthermore, a stainless steel spiral tube 319d is provided so as to cover the coating layer 319c. The core 319a and the clad 319b are made of quartz and have high heat resistance. Furthermore, the polyimide coating layer 319c and the stainless steel spiral tube 319d have relatively high heat resistance compared to resins other than polyimide. Thus, in the optical fiber 319 according to this embodiment, the core 319a, the clad 319b, the coating layer 319c, and the spiral tube 319d each have relatively high heat resistance. Therefore, even when used in a high-temperature environment, the optical fiber 319 has high reliability in terms of light transmission.

[0052] As described above, the optical fiber 319 according to the present embodiment has a configuration including only one core 319a. The optical fiber 319 is not limited to this example, and may have a configuration including multiple cores 319a. In this case, for example, the bundled multiple cores 319a are covered with the clad 319b, and the clad 319b is further covered with the coating layer 319c and the spiral tube 319d. Alternatively, the multiple cores 319a covered with the clad 319b and the coating layer 319c, respectively, are bundled. The spiral tube 319d is provided to protect the assembly.

[0053] <4> Various components provided inside the head housing 10 Fig. 4 is a cross-sectional view of the measuring head 1A taken along an imaginary plane VS1 indicated by dotted lines in Fig. 2 and Fig. 3. Fig. 5 is an exploded perspective view of the measuring head 1A of Fig. 1.

[0054] As described above, an annular step portion is formed inside the first housing portion 11. Also, a step portion is formed inside the head housing 10 at the boundary portion between the first housing portion 11 and the second housing portion 12. In the following description, the step portion formed inside the first housing portion 11 is called the first step portion st1. Also, the step portion formed inside the head housing 10 at the boundary portion between the first housing portion 11 and the second housing portion 12 is called the second step portion st2. In FIG. 4, the first step portion st1 and the second step portion st2 are each indicated by an outlined arrow.

[0055] 4, the lens 221, spacers 41, 42, spring member 43, lens 222, spacer 44, lens 223, spacer 45, lens 224 and ring screw 46 are accommodated inside head housing 10 between first step portion st1 and front end FE so as to be aligned in this order in the +x direction. The spacers 41, 42, 44, 45, spring member 43 and ring screw 46 are made of the same material as head housing 10.

[0056] The outer diameter of the lens 221 is larger than the inner diameter of the first inner circumferential surface 11i of the first housing part 11 and slightly smaller than the inner diameter of the second inner circumferential surface 11j of the first housing part 11. As a result, the lens 221 is fitted into the second inner circumferential surface 11j of the first housing part 11. In this state, a part (peripheral edge part) of the end face in the -x direction of the lens 221 abuts against the first step part st1. Therefore, the movement of the lens 221 in the -x direction is restricted by the first step part st1.

[0057] In addition, the thickness of the lens 221 (the dimension of the lens 221 in the optical axis direction) is greater than the distance between the first step portion st1 and the second step portion st2 in the x direction. As a result, a part of the lens 221 (a portion including the end face in the +x direction) protrudes into the second housing unit 12.

[0058] The spacer 41 is a substantially disk-shaped member having a diameter slightly smaller than the inner diameter of the third inner circumferential surface 12i. As shown in Fig. 5, a circular opening 41a having an inner diameter smaller than the outer diameter of the lens 221 is formed in the center of the spacer 41. In addition, two through holes 41b are formed in the spacer 41 so as to sandwich the opening 41a.

[0059] As shown in Fig. 4, the spacer 41 is provided in the second housing 12 so as to abut against a part (peripheral edge) of the end face in the +x direction of the lens 221. The spacer 42 is an annular member having the same outer diameter as the spacer 41, and is provided in the second housing 12 so as to abut against the spacer 41. The inner diameter of the spacer 42 is determined so as not to block the two through holes 41b (Fig. 5) of the spacer 41 when the spacer 42 abuts against the spacer 41. In this case, the two through holes 41b (Fig. 5) of the spacer 41 function as a gas flow path to prevent the formation of an airtight space between the spacer 41 and the second step portion st2.

[0060] Since no sealed space is formed between the spacer 41 and the second step portion st2, when the measurement head 1A is placed in a vacuum environment, no significant variation occurs in the pressure distribution inside the head housing 10. This prevents unintended deformation in the measurement head 1A due to significant variation in the pressure distribution.

[0061] The spacers 41 and 42 are used to position the spring member 43 at a predetermined position in the x direction inside the head housing 10. For example, when assembling the measurement head 1A, a plurality of spacers 41 and 42 having a plurality of thicknesses are prepared in advance. Then, appropriate spacers 41 and 42 are selected and used according to the predetermined position of the spring member 43 in the x direction, the dimensions of each part inside the head housing 10, and the dimensions of the lens 221.

[0062] As shown in Fig. 5, the spring member 43 has a flattened, generally cylindrical shape. As shown in Fig. 4, the spring member 43 is provided in the second housing 12 so that the axis of the spring member 43 is aligned with the head axis 10a and is in contact with the spacer 42. The spring member 43 has the same or substantially the same outer diameter as the spacers 41 and 42. The spring member 43 is configured to be expandable and contractible in the axis direction of the spring member 43 by elastic force. The details of the spring member 43 will be described later.

[0063] Lens 222 is provided in second housing portion 12 so as to abut against spring member 43. Furthermore, lens 223 is provided on the +x direction of lens 222 with spacer 44 interposed therebetween. Furthermore, lens 224 is provided on the +x direction of lens 223 with spacer 45 interposed therebetween.

[0064] Each of the three lenses 222, 223, and 224 has the same or approximately the same outer diameter as the spacers 41, 42 and the spring member 43. Each of the spacers 44, 45 is an annular member having a constant thickness, and has the same or approximately the same outer diameter as the spacers 41, 42 and the spring member 43.

[0065] A thread is applied to the third inner peripheral surface 12i of the second housing portion 12 within a certain width range from the front end portion FE in the -x direction. That is, a part of the third inner peripheral surface 12i of the second housing portion 12 forms a female thread portion 12j. The female thread portion 12j is formed so as to be located near the lens 224 when a plurality of components (41-45, 221-224) are housed in the head housing 10 so as to be in contact with each other.

[0066] The ring screw 46 is a male screw that corresponds to the female screw portion 12j of the second housing portion 12. With a plurality of components (41-45, 221-224) housed in the head housing 10 so as to be in contact with one another, the ring screw 46 is attached to the female screw portion 12j of the second housing portion 12. The inner diameter of the ring screw 46 is smaller than the outer diameter of the lens 224. Therefore, when the ring screw 46 is attached to the female screw portion 12j, a part of the ring screw 46 abuts against a part (peripheral part) of the end face of the lens 224 facing the +x direction. In addition, the ring screw 46 is tightened so that a predetermined amount of load in the x direction acts on the spring member 43 while abutting against the lens 224.

[0067] Here, the configuration and function of the spring member 43 will be described in detail. Fig. 6 is a diagram for explaining the configuration and function of the spring member 43 housed in the head housing 10 in detail. As described above, the spring member 43 has a flattened, generally cylindrical shape. Fig. 6(a) shows an external perspective view of the spring member 43. The spring member 43 is composed of a base portion 43a, a small diameter portion 43b, and a flange portion 43c, which are aligned in the direction of the axis ca.

[0068] The base portion 43a and the flange portion 43c have a common outer diameter that is slightly smaller than the third inner peripheral surface 12i of the second housing portion 12. On the other hand, the small diameter portion 43b has an outer diameter smaller than the outer diameters of the base portion 43a and the flange portion 43c (approximately 2 / 3 the outer diameter). In addition, the base portion 43a, the small diameter portion 43b, and the flange portion 43c have a substantially constant inner diameter. Furthermore, the peripheral portion of the flange portion 43c is formed so as to protrude in the opposite direction to the base portion 43a.

[0069] With this configuration, when a load acts between the flange portion 43c and the base portion 43a in the direction of the axis ca, the small diameter portion 43b and the flange portion 43c elastically deform, changing the length of the spring member 43 in the direction of the axis ca. In the following description, the state of the spring member 43 when no or almost no load acts on the spring member 43 in the direction of the axis ca is referred to as the reference state.

[0070] When the measuring head 1A is placed in a high-temperature environment and thermal expansion occurs in the head housing 10, the multiple lenses 221-224 housed in the head housing 10 may be significantly displaced to unintended positions in unintended attitudes. Therefore, in this embodiment, the ring screw 46 is tightened so that a predetermined amount of load in the x direction acts on the spring member 43 when the measuring head 1A is at room temperature (for example, 25°C). In other words, the spring member 43 is provided so that the elastic force of the spring member 43 biases the multiple lenses 221-224 in the x direction in a room-temperature environment.

[0071] 6(b) and (c) show a configuration example for explaining the function of the spring member 43. As shown in FIG. 6(b), assume that a first ring member r1 and a second ring member r2 are fixed to a first portion p1 and a second portion p2, which are different from each other in the x direction, on the third inner circumferential surface 12i of the head housing 10 under a room temperature environment, for example. Furthermore, assume that the spring member 43 and the lens 222 are arranged in this order in the +x direction between the first ring member r1 and the second ring member r2.

[0072] Here, the distance D11 between the first portion p1 and the second portion p2 in the x direction is set so that a predetermined amount of load in the x direction acts on the spring member 43. In other words, the distance D11 is set so that the spring member 43 urges the lens 222 toward the second ring member r2 between the first portion p1 and the second portion p2. As a result, the spring member 43 shown in Fig. 6(b) is contracted in the x direction with respect to the reference state due to the deformation of the small diameter portion 43b and the flange portion 43c.

[0073] Assume that the configuration including the head housing 10 of FIG. 6(b) is placed in a high temperature environment from a normal temperature environment. In this case, as shown in FIG. 6(c), the distance D12 between the first portion p1 and the second portion p2 becomes larger than the distance D11 corresponding to the normal temperature environment due to thermal expansion of the head housing 10. At this time, the spring member 43, which is in a state where it is more compressed than the reference state in the normal temperature environment, continues to urge the lens 222 toward the second ring member r2, and presses the lens 222 against the second ring member r2. This prevents the lens 222 provided in the head housing 10 from shifting to an unintended position in an unintended posture.

[0074] Fig. 7 is a diagram showing a reference example for explaining the function of the spring member 43. As shown in Fig. 7(a), a case is assumed in which the lens 222 is fixed in a state in which it is sandwiched between the first ring member r1 and the second ring member r2 without using the spring member 43 in the head housing 10 under a room temperature environment.

[0075] When such a configuration is placed in a room temperature environment to a high temperature environment, the distance between the first ring member r1 and the second ring member r2 increases due to thermal expansion of the head housing 10, as shown in Fig. 7(b). Therefore, if the linear expansion coefficient of the lens 222 is smaller than that of the head housing 10, a gap occurs between the lens 222 and at least one of the first ring member r1 and the second ring member r2. This may cause the lens 222 to shift to an unintended position in an unintended posture.

[0076] Considering the above, the spring member 43 is held in the head housing 10 in a state where it is contracted in the x direction from a reference state under a normal temperature environment according to the amount of tightening of the ring screw 46. In this case, the spring member 43 urges the lenses 222-224 in the +x direction toward the ring screw 46. The spring member 43 also urges the lens 221 in the -x direction toward the first step portion st1. In this way, the spring member 43 functions as a member that prevents the multiple lenses 221-224 from becoming loose in the head housing 10 due to a change in the temperature environment in which the measuring head 1A is placed.

[0077] <5> Preferred arrangement conditions for the spring member 43 in the head housing 10 (a) A first arrangement condition will be described as a preferable arrangement condition of the spring member 43 in the head housing 10. FIG. 8 is a diagram for explaining the first arrangement condition of the spring member 43 in the head housing 10. In FIG. 8, a cross-sectional view of the measurement head 1A corresponding to FIG. 4 is shown, and the outer edge of the path of light passing through the head housing 10 is indicated by a dotted line. It can be seen from FIG. 8 that the spring member 43 is provided so that the light guided from the optical fiber 319 into the head housing 10 passes through the inside of the spring member 43.

[0078] In the above-described measurement head 1A, the multiple lenses 221-224 housed in the head housing 10 can be regarded as a single synthesized optical system (hereinafter referred to as a synthesized optical system). A first placement condition for the spring member 43 is that the spring member 43 is placed at a position closer to the rear end portion RE than the principal point pp defined in the synthesized optical system when light travels in the +x direction inside the head housing 10, as shown in FIG.

[0079] In a region closer to the rear end RE than the principal point pp in the internal space of the head housing 10, the cross-sectional area of ​​the light traveling inside the head housing 10 gradually expands in the +x direction from the size of the core 319a of the optical fiber 319. Therefore, when the spring member 43 is provided according to the first arrangement condition, even if the size of the head housing 10 is limited, it is easy to arrange the spring member 43 so as not to interfere with the path of the light inside the head housing 10. In addition, since the spring member 43 can be brought closer to the rear end RE, the size of the head housing 10 in the x direction is reduced.

[0080] (b) A second arrangement condition will be described as a preferable arrangement condition for the spring member 43 inside the head housing 10. Some of the multiple lenses 221-224 included in the measurement head 1A have effective diameters larger than the inner diameter of the spring member 43. Specifically, among the multiple lenses 221-224, the lenses 222-224 have effective diameters larger than the inner diameter of the spring member 43. On the other hand, the lens 221 has an effective diameter smaller than the inner diameter of the spring member 43.

[0081] In such a configuration, the second placement condition for the spring member 43 is that the spring member 43 is placed at a position closer to the rear end portion RE than the lenses 222-224 having an effective diameter larger than the inner diameter of the spring member 43. When the spring member 43 is provided in accordance with the second placement condition, even if the size of the head housing 10 is limited, it is easy to place the spring member 43 so as not to interfere with the path of light inside the head housing 10. In addition, since the spring member 43 can be placed closer to the rear end portion RE, the size of the head housing 10 in the x direction is reduced.

[0082] (c) A third arrangement condition will be described as a preferable arrangement condition for the spring member 43 in the head housing 10. Of the multiple lenses 221-224 included in the measurement head 1A, the lens 221 is a magnifying lens, and causes the light guided from the optical fiber 319 to travel in the +x direction while expanding the cross-sectional area of ​​the light. In this manner, a region in the head housing 10 where the cross-sectional area of ​​the light traveling in the +x direction is gradually expanded by at least one of the multiple lenses 221-224 is called a light expanding region. In this case, the third arrangement condition for the spring member 43 is that the spring member 43 is arranged in the light expanding region.

[0083] According to the above configuration, even if the size of the head housing 10 is limited, it is easy to arrange the spring member 43 so as not to interfere with the path of light inside the head housing 10. Also, by bringing the light magnifying region inside the head housing 10 closer to the rear end portion RE, the size of the head housing 10 in the x direction is reduced.

[0084] <6> glue 5, when assembling the measurement head 1A, a ring screw 46 is attached from the front end FE with multiple components (41-45, 221-224) housed inside the head housing 10. Also, a fiber receptacle 30 is connected to the rear end RE of the head housing 10 using multiple screws SC1.

[0085] Here, in the measuring head 1A according to the present embodiment, an adhesive made of an inorganic material is used to further strengthen the fixed state of the fastening portion of the screw. The inorganic material of the adhesive is, for example, ceramic powder.

[0086] Specifically, in this embodiment, as shown by a dashed-dotted rectangular frame ad1 in Fig. 4, when the ring screw 46 is attached to the female thread portion 12j of the second housing portion 12, an adhesive made of an inorganic material is applied between the ring screw 46 and the female thread portion 12j. In this case, since the adhesive does not contain an organic material, outgassing from the adhesive is suppressed even if the measuring head 1A is placed in a vacuum environment. This suppresses a decrease in the degree of vacuum caused by the adhesive.

[0087] Fig. 9 is a cross-sectional view of the measurement head 1A taken along an imaginary plane VS2 indicated by the two-dot chain line in Fig. 2 and Fig. 3. The cross-sectional view of Fig. 9 shows a state in which the fiber receptacle 30 is attached to the rear end portion RE of the head housing 10 using a plurality of screws SC1.

[0088] In this embodiment, as shown by the dashed-dotted rectangular frame ad2 in Fig. 9, when the fiber receptacle 30 is screwed to the head housing 10, an adhesive made of an inorganic material is applied between the screw SC1 and the screw hole h3. In this case, since the adhesive does not contain an organic material, outgassing from the adhesive is suppressed even if the measurement head 1A is placed in a vacuum environment. This suppresses a decrease in the degree of vacuum caused by the adhesive.

[0089] As described above, when an adhesive made of an inorganic material is used to assemble the measuring head 1A, it is preferable that the adhesive is applied so that it is not exposed. This prevents powder of the inorganic material, such as ceramic, from scattering around the measuring head 1A.

[0090] 3. Optical bending unit and distance adjustment member Each of the measurement heads 1A, 1B may further include a light bending unit that is configured to be detachable from the head housing 10 and changes the traveling direction of light emitted from the head housing 10 by a predetermined angle (90° in this example). Each of the measurement heads 1A, 1B may further include a plurality of distance adjustment members that adjust the measurable range of displacement by the measurement heads 1A, 1B when the light bending unit is attached.

[0091] Fig. 10 is an external perspective view of the light bending unit and a plurality of distance adjustment members. Fig. 10 shows an external perspective view of the measuring head 1A in Fig. 2 together with an exploded perspective view of the light bending unit 50 and an external perspective view of a plurality (two in this example) of distance adjustment members 60. Furthermore, Fig. 10 shows a schematic longitudinal sectional view and a schematic end view of the light bending unit 50 in a balloon.

[0092] As shown in FIG. 10, the light bending unit 50 includes a main body MB, a mirror 54, a leaf spring 55, and a fixed plate 56. The mirror 54 is attached to the leaf spring 55. As a result, the mirror 54 and the leaf spring 55 can be handled as a single unit when assembling the light bending unit 50. In the external perspective view of FIG. 10, the mirror 54 and the leaf spring 55 are shown in a state separated from each other so that the shapes and positional relationship of the mirror 54 and the leaf spring 55 can be easily understood. The main body MB has a rear end surface 51, a front end inclined surface 52, and an exit surface 53. The rear end surface 51 is formed so as to be able to come into contact with the front end FE of the head housing 10. The front end inclined surface 52 faces the rear end surface 51 at a position in the +x direction of the rear end surface 51, and is inclined at 45° with respect to the rear end surface 51. The exit surface 53 is perpendicular to the rear end surface 51.

[0093] 10, in the light bending unit 50, a substantially triangular cross section is formed by the rear end face 51, the front end inclined face 52, and the exit face 53. The rear end face 51, the front end inclined face 52, and the exit face 53 have openings 51a, 52a, and 53a formed therein, respectively.

[0094] A mirror 54 is provided on the front end inclined surface 52 so as to cover the opening 52a. The fixed plate 56 is a metal plate-shaped member, and two protrusions 56a are formed on one surface thereof. The fixed plate 56 is attached to the front end inclined surface 52 using screws (not shown) so that the leaf spring 55 is located in the +x direction of the mirror 54 and the two protrusions 56a face the -x direction. Here, the leaf spring 55 is formed with two pressed parts extending in the -z direction and the +z direction. The two protrusions 56a of the fixed plate 56 are formed to correspond to the two pressed parts of the leaf spring 55. Therefore, when the fixed plate 56 is attached to the front end inclined surface 52, the two pressed parts of the leaf spring 55 are pressed by the two protrusions 56a of the fixed plate 56 so as to approach the mirror 54. As a result, the mirror 54 is held in a state in which it is biased toward the front end inclined surface 52 by the leaf spring 55.

[0095] Four through holes 57 are formed in the main body MB of the light bending unit 50, which correspond to the four screw holes h2 (FIG. 2) in the front end FE of the head housing 10. This allows the light bending unit 50 to be easily attached to the head housing 10 by inserting the four screws SC2 into the four screw holes h2 of the head housing 10 through the four through holes 57 of the main body MB, respectively, and tightening the screws SC2.

[0096] The light bending unit 50 may be attached to the head housing 10 using three or two screws SC2. For example, two screws SC2 are inserted through two through holes 57 of the light bending unit 50 into two screw holes h2 of the head housing 10 arranged diagonally across the head axis 10a. In this way, the light bending unit 50 may be attached to the head housing 10.

[0097] With the light bending unit 50 attached to the head housing 10, light emitted from inside the head housing 10 through the opening at the front end FE enters the mirror 54 through the openings 51a and 52a of the main body part MB. The light incident on the mirror 54 is bent 90° by being reflected by the mirror 54, and travels toward the side of the measurement head 1A (in a direction perpendicular to the head axis 10a) through the opening 53a of the main body part MB. Thus, according to the light bending unit 50 in FIG. 10, the measurement direction of the measurement target S with respect to the attitude of the head housing 10 can be changed by 90°.

[0098] The range in which the displacement of the measurement target S can be measured from the front end FE of the head housing 10 in the measurement head 1A (hereinafter referred to as the measurement range) is determined by the lenses 221-224 housed in the head housing 10. Therefore, the measurement range from the emission surface 53 of the light bending unit 50 when the light bending unit 50 is attached to the head housing 10 can be appropriately changed by adjusting the distance between the head housing 10 and the light bending unit 50. Therefore, a plurality of distance adjustment members 60 are used.

[0099] Each of the distance adjustment members 60 has a rear end surface and a front end surface. The rear end surface and the front end surface have a substantially rectangular shape (substantially square shape in this example) corresponding to the front end portion FE of the head housing 10. The rear end surface of the distance adjustment member 60 is formed so as to be able to come into contact with the front end portion FE of the head housing 10. The front end surface of the distance adjustment member 60 is formed so as to be able to come into contact with the rear end surface 51 of the light bending unit 50.

[0100] An opening that passes light emitted from the head housing 10 is formed in the center of the distance adjustment member 60 from the front end surface to the rear end surface. Two through holes 61 and two screw holes 62 are formed in the four corners of the front end surface of the distance adjustment member 60 when viewed in the x direction, surrounding the central opening. The two through holes 61 are located at one diagonal position sandwiching the central opening, and the two screw holes 62 are located at the other diagonal position sandwiching the central opening.

[0101] The two through holes 61 of one distance adjustment member 60 are used for inserting two screws SC3 into two screw holes h2 of the head housing 10 through the two through holes 61, and screwing the one distance adjustment member 60 to the head housing 10. Alternatively, the two through holes 61 of one distance adjustment member 60 are used for inserting two screws SC3 into two screw holes 62 of the other distance adjustment member 60 through the two through holes 61, and screwing the one distance adjustment member 60 to the other distance adjustment member 60.

[0102] As described above, the two screw holes 62 of one distance adjustment member 60 are used to screw another distance adjustment member 60 onto the front end face of the one distance adjustment member 60 with two screws SC3. Alternatively, the two screw holes 62 of one distance adjustment member 60 are used to screw the light bending unit 50 to the one distance adjustment member 60 by inserting two screws SC2 through the two through holes 57 of the light bending unit 50.

[0103] As described above, the distance adjustment member 60 can be inserted between the head housing 10 and the light bending unit 50 when the light bending unit 50 is attached to the head housing 10.

[0104] Fig. 11 is a diagram showing changes in the measurement direction and measurable range of the measurement head 1A due to the light bending unit 50 and the multiple distance adjustment members 60 of Fig. 10. In Fig. 11(a), the path of light of one wavelength (hereinafter referred to as specific wavelength light) emitted from the head housing 10 in a state in which the light bending unit 50 and the multiple distance adjustment members 60 are not attached is shown by a dotted line. According to the example of Fig. 11(a), the specific wavelength light emitted from the head housing 10 travels along the head axis 10a. Therefore, the measurement direction of the displacement coincides with the direction of the head axis 10a.

[0105] In Fig. 11(b), the path of the specific wavelength light emitted from the head housing 10 with the light bending unit 50 attached is shown by a dotted line. According to the example of Fig. 11(b), the specific wavelength light emitted from the head housing 10 travels in a direction bent by 90° from the head axis 10a by the light bending unit 50. Therefore, the displacement measurement direction is perpendicular to the head axis 10a. Also, in the example of Fig. 11(b), the specific wavelength light emitted from the emission surface 53 of the light bending unit 50 is focused at a position separated by a distance D1.

[0106] In Fig. 11(c), a dotted line shows the path of the specific wavelength light emitted from the head housing 10 in a state in which the light bending unit 50 and one distance adjustment member 60 are attached. According to the example of Fig. 11(c), the specific wavelength light emitted from the emission surface 53 of the light bending unit 50 is focused at a position separated by a distance D2 that is shorter than the distance D1 in Fig. 11(b).

[0107] In Fig. 11(d), the path of the specific wavelength light emitted from the head housing 10 in a state in which the light bending unit 50 and the two distance adjustment members 60 are attached is shown by a dotted line. According to the example of Fig. 11(d), the specific wavelength light emitted from the emission surface 53 of the light bending unit 50 is focused at a position separated by a distance D3, which is shorter than the distance D2 in Fig. 11(c).

[0108] In this way, the light bending unit 50 and the multiple distance adjustment members 60 increase the degree of freedom of the position and attitude of the measuring head 1A when measuring the displacement of the measurement target S.

[0109] In the above light bending unit 50, a mirror in which aluminum is evaporated onto one side of glass is used as the mirror 54. As a result, all components of the light bending unit 50 are made of metal or glass. Also, the distance adjustment member 60 is made of a single member made of the same metal as the head housing 10. In these cases, the light bending unit 50 and the multiple distance adjustment members 60 do not contain organic matter. Therefore, even if the measurement head 1A is placed in a vacuum environment with either the light bending unit 50 or the multiple distance adjustment members 60 attached to the head housing 10, outgassing from the measurement head 1A is prevented. Also, a decrease in the degree of vacuum caused by the light bending unit 50 and the multiple distance adjustment members 60 is suppressed.

[0110] 4.Effects (a) In the head housing 10 of the measurement heads 1A and 1B, a plurality of lenses 221, 222, 223, and 224 are housed in a line between the first step portion st1 and the ring screw 46. A spring member 43 is provided between the two lenses 221 and 222.

[0111] The lens 224 is restrained from moving in the +x direction by abutting against the ring screw 46. In this state, the lenses 222, 223, and 224 are biased in the +x direction by the spring member 43. On the other hand, the lens 221 is restrained from moving in the -x direction by abutting against the first step portion st1. In this state, the lens 221 is biased in the -x direction by the spring member 43.

[0112] According to this configuration, even if the dimensions of the components of the measuring heads 1A and 1B change due to thermal expansion as a result of the measuring head 1A being placed in a high-temperature environment, each of the lenses 221-224 is biased in a direction in which movement is restricted. As a result, each of the lenses 221-224 is fixed to a predetermined portion inside the head housing 10 and does not move freely. Therefore, each lens is prevented from significantly shifting to an unintended position in an unintended attitude every time the measuring heads 1A and 1B are placed in a high-temperature environment.

[0113] In addition, in the above-mentioned measuring heads 1A and 1B, the head housing 10, the spacers 41, 42, 44, 45, the spring member 43, the ring screw 46, and the fiber receptacle 30 are made of the same metal material. Furthermore, the plurality of lenses 221 to 224 are made of glass. This improves the heat resistance of the measuring heads 1A and 1B compared to a case in which any of the head housing 10, the spacers 41, 42, 44, 45, the spring member 43, the ring screw 46, the fiber receptacle 30, and the plurality of lenses 221 to 224 is made of an organic material such as resin. In addition, the degree of deformation caused by temperature changes of members made of metal and glass is easier to grasp than that of resin. Therefore, it is also easy to correct the measured value taking temperature changes into account.

[0114] As a result, the measuring heads 1A and 1B according to the present embodiment make it possible to suppress deterioration in the reliability of measurements by the confocal displacement meter 9 in high-temperature environments.

[0115] (b) Furthermore, as described above, in this embodiment, one spring member 43 is used as a common member for biasing the four lenses 221 to 224. This prevents the measurement heads 1A and 1B from increasing in size and number of parts, as compared to a case in which four biasing members are provided individually for biasing the four lenses 221 to 224, respectively.

[0116] (c) Furthermore, according to the above configuration, the materials of the components of the measuring heads 1A and 1B basically do not contain organic materials. As a result, even when the measuring heads 1A and 1B are placed in a vacuum environment, outgassing from the measuring heads 1A and 1B is unlikely to occur. Therefore, when the measuring heads 1A and 1B are placed in a vacuum environment, a decrease in the degree of vacuum of the vacuum environment due to outgassing from the measuring heads 1A and 1B is suppressed. Therefore, a decrease in the reliability of the measurement of the confocal displacement meter 9 in a vacuum environment is also suppressed.

[0117] (d) In the head housing 10, the first housing portion 11 is formed with notches 11x and 11y, and also formed with a plurality of through holes h1 for attaching the measuring heads 1A and 1B to desired locations.

[0118] In the above-described measuring heads 1A and 1B, the cross section of light traveling inside the first housing 11 is smaller than the cross section of light traveling inside the second housing 12. This prevents the measuring heads 1A and 1B from becoming larger than when a structure for attaching the measuring heads 1A and 1B to a desired portion is provided in the second housing 12.

[0119] (e) In the measurement heads 1A and 1B, the head housing 10, the spacers 41, 42, 44, 45, the spring member 43, the ring screw 46, and the fiber receptacle 30 are formed of stainless steel (SUS304, SUS316, SUS316L, or SUS303). Stainless steel is extremely unlikely to generate outgassing in a vacuum environment. As a result, even when the measurement heads 1A and 1B are placed in a vacuum environment, outgassing from the measurement head 1A is even less likely to occur. Therefore, when the measurement heads 1A and 1B are placed in a vacuum environment, a decrease in the degree of vacuum caused by the components of the measurement heads 1A and 1B is suppressed.

[0120] 5. Other embodiments (a) In each of the measuring heads 1A, 1B according to the above-described embodiment, the spring member 43 is housed within the head housing 10 in order to urge each of the multiple lenses 221-224 in the x direction, but the present invention is not limited to this.

[0121] Fig. 12 is a cross-sectional view showing an example of a measuring head 1A according to another embodiment. The cross-sectional view of Fig. 12 corresponds to the cross-sectional view of Fig. 4 of the above embodiment. The measuring head 1A of Fig. 12 will be described below in terms of differences from the measuring head 1A according to the above embodiment.

[0122] 12, a thermal expansion member 49 having a substantially cylindrical shape is provided in the head housing 10 instead of the spring member 43 according to the above embodiment. The thermal expansion member 49 is made of polyimide resin having relatively high heat resistance.

[0123] The thermal expansion member 49 is provided so that the axis of the thermal expansion member 49 extends in the x-direction. In a room temperature environment, both ends of the thermal expansion member 49 in the x-direction are in contact with a part of the spacer 42 and a part of the lens 222, respectively.

[0124] The linear expansion coefficient of polyimide is larger than that of metal. Therefore, in the above-mentioned measuring head 1A, when the dimensions of each component of the measuring head 1A change due to thermal expansion, the thermal expansion member 49 expands more than the lenses 221-224 and the head housing 10. As a result, when the measuring head 1A is placed in a high-temperature environment, each of the lenses 221-224 is urged toward a direction in which the movement is restricted by the expanding thermal expansion member 49. As a result, similar to the example of the above-mentioned embodiment, each lens 221-224 is fixed to a predetermined portion inside the head housing 10 and does not move freely. Therefore, each lens is prevented from being significantly shifted to an unintended position in an unintended posture every time the measuring heads 1A and 1B are placed in a high-temperature environment.

[0125] As a result, by using a highly heat-resistant polyimide as the polyimide used for the thermal expansion member, it is possible to suppress a decrease in the reliability of the measurement of the confocal displacement meter 9 in a high-temperature environment.

[0126] (b) Although four lenses 221-224 are provided in the head housing 10 according to the above embodiment, the present invention is not limited to this. As long as the displacement of the measurement target S can be measured, only two lenses, only three lenses, or five or more lenses may be provided in the head housing 10.

[0127] (c) In the measuring heads 1A and 1B according to the above-described embodiments, one spring member 43 is used as a member for biasing the lenses 221-224 in the x direction, but the present invention is not limited to this. A plurality of spring members may be provided in the head housing 10 so as to correspond to the lenses 221-224, respectively, and each lens may be biased in the x direction by the corresponding spring member.

[0128] (d) In the measurement heads 1A and 1B according to the above-described embodiments, the first step portion st1 in the head housing 10 restricts the movement of the lens 221 in the -x direction, but the present invention is not limited to this. A configuration using a ring screw may be adopted as a configuration for restricting the movement of the lens 221 in the -x direction. In this case, the first step portion st1 and the second step portion st2 may not be formed inside the head housing 10. Also, the lens 221 may be formed so as to abut against the ring screw and not pass through the inside of the ring screw. Therefore, the lens 221 may have an outer diameter larger than the inner diameter of the ring screw, and may have the same outer diameter as the other lenses 222, 223, and 224.

[0129] (e) In the measuring heads 1A and 1B according to the above-described embodiments, the spacers 41, 42, 44, and 45 are provided between each pair of the lenses 221-224 housed in the head housing 10, but the present invention is not limited to this. A spacer need not be provided between any two lenses of the lenses 221-224.

[0130] (f) In the measuring heads 1A, 1B of the above embodiments, the spring member 43 may be provided in the head housing 10 at a position in the +x direction relative to the multiple lenses (221-224), or at a position in the -x direction relative to the multiple lenses (221-224).

[0131] 6. Correspondence between each component of the claims and each part of the embodiment Below, examples of the correspondence between each component of the claims and each part of the embodiment will be described, but the present invention is not limited to the following examples. Various other elements having the configuration or function described in the claims can also be used as each component of the claims.

[0132] In the above embodiment, the white light source possessed by light-projecting unit 120 is an example of a white light source, confocal displacement meter 9 is an example of a confocal displacement meter, measurement heads 1A and 1B are examples of measurement heads, the rear end RE of head housing 10 is an example of a first end, the front end FE of head housing 10 is an example of a second end, head housing 10 is an example of a housing, and optical fiber 319 of light-guiding units 300A and 300B is an example of an optical fiber.

[0133] In addition, lens 224 is an example of a first lens, head axis 10a is an example of an axis of the housing, lenses 221 to 224 are examples of multiple lenses, female thread portion 12j of third inner surface 12i is an example of a first portion, the +x direction is an example of a first direction, the -x direction is an example of a second direction, ring screw 46 is an example of a first movement regulating portion and regulating member, and spring member 43 is an example of a biasing member.

[0134] In addition, spacers 41, 42, 44, and 45 are examples of one or more spacers, lens 221 is an example of a second lens, the first step portion st1 in the head housing 10 is an example of a second portion and a second movement regulating portion, the third inner surface 12i of the second housing portion 12 is an example of an inner surface of a housing, the principal point pp of the composite optical system is an example of a principal point, and outer surfaces 11a, 11b, 11c, 11d, 12a, 12b, 12c, and 12d are examples of outer surfaces.

[0135] In addition, the first housing part 11 is an example of a first housing part, the second housing part 12 is an example of a second housing part, the first inner circumferential surface 11i, the second inner circumferential surface 11j and the third inner circumferential surface 12i are examples of inner circumferential surfaces of the housing, the portion where the multiple through holes h1 are formed in the first housing part 11 is an example of an attachment part, the light bending unit 50 is an example of a light bending unit, and the distance adjustment member 60 is an example of a distance adjustment member.

[0136] Moreover, the fiber receptacle 30 is an example of a fiber connecting member, the screw SC1 is an example of a screw, the thermal expansion member 49 is an example of a thermal expansion member, and the measuring units 100A and 100B are examples of a displacement measuring portion.

[0137] 7. Summary of the embodiment (1) The measuring head according to the first paragraph is A measurement head for a confocal displacement meter having a white light source, comprising: A metal housing formed in a cylindrical shape and having a first end and a second end; an optical fiber connected to the first end of the housing and guiding light generated from the white light source to the first end of the housing; a plurality of glass lenses including a first lens, the lenses being accommodated inside the housing so as to be aligned in an axial direction of the housing and movable in the axial direction, the lenses generating chromatic aberration along an optical axis in the light guided to the first end by the optical fiber and converging the light onto a measurement object through the second end; a first movement restriction portion that is provided in a predetermined first portion inside the housing, and restricts the first lens from moving in any one of a first direction from the first end portion to the second end portion in the axial direction and a second direction opposite thereto, when the first lens comes into contact with the first movement restriction portion; The lens holder includes a metal biasing member that biases some or all of the plurality of lenses, including the first lens, toward the one direction by elastic force when the first lens is in contact with the first movement restricting portion.

[0138] In the measurement head, a plurality of lenses including a first lens are housed in a cylindrical housing so as to be arranged side by side. The first lens is restricted from moving in either a first direction or a second direction by contacting a first movement restricting portion. In a state in which the first lens is in contact with the first movement restricting portion, some or all of the lenses including the first lens among the plurality of lenses are biased in one direction by a biasing member.

[0139] In this case, even if the dimensions of each component of the measurement head change due to thermal expansion when the measurement head is placed in a high-temperature environment, some or all of the lenses including the first lens among the multiple lenses are restricted from moving in one direction. That is, each lens biased by the biasing member is fixed to a predetermined portion inside the housing and does not move freely. Therefore, each lens is prevented from significantly shifting to an unintended position in an unintended attitude every time the measurement head is placed in a high-temperature environment.

[0140] In addition, in the measurement head, the housing and the biasing member are made of metal, and the lenses are made of glass. This improves the heat resistance of the measurement head compared to when any of the housing, the biasing member, and the lenses are made of organic materials. In addition, the degree of deformation caused by temperature changes in members made of metal and glass is easier to grasp compared to resin. Therefore, it is also easy to correct the measured values ​​taking temperature changes into account.

[0141] As a result, it is possible to suppress deterioration in the reliability of measurements by the confocal displacement meter in high-temperature environments.

[0142] Furthermore, according to the above configuration, since the housing and the biasing member are made of metal and the lenses are made of glass, outgassing is unlikely to occur from the housing, the biasing member, and the lenses even when the measurement head is placed in a vacuum environment. Therefore, when the measurement head is placed in a vacuum environment, a decrease in the vacuum level of the vacuum environment due to the housing, the biasing member, and the lenses is suppressed. Therefore, it is possible to suppress a decrease in the reliability of the measurement of the confocal displacement meter in a vacuum environment.

[0143] (2) In the measuring head according to the first aspect, The measuring head includes: Further comprising one or more spacers made of metal and accommodated inside the housing so as to be movable in the axial direction of the housing, Each of the one or more spacers may be provided between two lenses adjacent to each other in the axial direction among the plurality of lenses.

[0144] In this case, the heat resistance of the measurement head is improved compared to when the spacer is made of an organic material. Also, even when the measurement head is placed in a vacuum environment, outgassing from the spacer is prevented, and a decrease in the degree of vacuum caused by the spacer is suppressed.

[0145] (Item 3) In the measuring head according to item 1 or 2, the first movement restricting portion restricts movement of the first lens in the first direction by contacting the first lens; the plurality of lenses includes a second lens disposed within the housing between the first lens and the second end; The measuring head includes: a second movement restricting portion provided in a second portion located between the first portion and the second end portion inside the housing, the second movement restricting portion contacting the second lens of the plurality of lenses to restrict movement of the second lens in the second direction; The biasing member is a first lens and a second lens provided in the housing, In a state in which the first lens abuts against the first movement control portion and the second lens abuts against the second movement control portion, some of the plurality of lenses including the first lens may be urged in the first direction by an elastic force, and the remaining lenses of the plurality of lenses including the second lens may be urged in the second direction by an elastic force.

[0146] In this case, even if the dimensions of each component of the measurement head change due to thermal expansion when the measurement head is placed in a high-temperature environment, some of the lenses, including the first lens, are restricted from moving in the first direction. Also, the remaining lenses, including the second lens, are restricted from moving in the second direction. Therefore, all of the lenses are fixed to a predetermined portion inside the housing and do not move freely. Therefore, each time the measurement head is placed in a high-temperature environment, each of the lenses is prevented from significantly shifting to an unintended position in an unintended attitude.

[0147] In addition, in the above configuration, since the biasing member is disposed between some of the lenses including the first lens and the remaining lenses including the second lens, it is not necessary to prepare multiple biasing members individually to bias multiple lenses, and therefore the increase in the number of parts and size of the measurement head is suppressed.

[0148] (Item 4) In the measuring head according to any one of items 1 to 3, The housing has a cylindrical inner circumferential surface extending in the axial direction, the biasing member is formed in a cylindrical shape extending a certain distance in the axial direction of the housing, and is disposed at a position closer to the first end than a principal point defined in an optical system formed by combining the plurality of lenses when light travels in the first direction within the housing, Light traveling within the housing may pass through an inner side of the biasing member.

[0149] In at least a part of the region inside the housing closer to the first end than the principal point, the cross-sectional area of ​​the light traveling inside the housing from the first end gradually expands in the first direction from the size of the optical fiber. Therefore, according to the above configuration, even if the size of the housing is limited, it is easy to arrange the biasing member so as not to interfere with the path of the light inside the housing. In addition, since the biasing member can be brought closer to the first end, the increase in size of the housing in the axial direction is reduced.

[0150] (Item 5) In the measuring head according to any one of items 1 to 4, The housing has a cylindrical inner circumferential surface extending in the axial direction, The biasing member is formed in a cylindrical shape extending a certain distance in the axial direction of the housing, some of the lenses have an effective diameter larger than an inner diameter of the biasing member; the biasing member is disposed inside the housing at a position closer to the first end than some of the lenses; Light traveling within the housing may pass through an inner side of the biasing member.

[0151] According to the above configuration, even if the size of the housing is limited, it is easy to arrange the biasing member inside the housing so as not to interfere with the path of light. In addition, since the biasing member can be brought close to the first end, the increase in size of the housing in the axial direction is reduced.

[0152] (Item 6) In the measuring head according to item 3, The housing has a cylindrical inner circumferential surface extending in the axial direction, the plurality of lenses are arranged in a partial region inside the housing so as to cause the light guided to the first end to travel in the first direction while expanding a cross-sectional area of ​​the light; the biasing member is formed in a cylindrical shape extending a certain distance in the axial direction of the housing, and is disposed in the partial region within the housing, Light traveling within the housing may pass through an inner side of the biasing member.

[0153] According to the above configuration, even if the size of the housing is limited, it is easy to arrange the biasing member inside the housing so as not to interfere with the path of light. Also, by bringing a part of the inside area of ​​the housing closer to the first end, the increase in size of the housing in the axial direction is reduced.

[0154] (Item 7) In the measuring head according to any one of items 1 to 6, At least a portion of the housing may have an outer surface in the shape of a square tube extending in the axial direction and having a rectangular cross section.

[0155] In this case, it is easier to set up the measurement head on a predetermined installation surface compared to when the housing has a cylindrical outer circumferential surface.

[0156] (Item 8) In the measuring head according to any one of items 1 to 3, The housing includes: a first housing portion and a second housing portion arranged in sequence in the first direction; a cylindrical inner circumferential surface extending in the axial direction from the first housing portion to the second housing portion; an inner diameter of the inner circumferential surface of the first housing portion is smaller than an inner diameter of the inner circumferential surface of the second housing portion; the plurality of lenses are housed within the second housing portion; An attachment portion for attaching the measuring head to another member may be formed on an outer surface of the first housing portion.

[0157] In this case, the size of the measuring head can be prevented from increasing, compared to when the attachment portion is provided on the second housing portion.

[0158] (Item 9) In the measuring head according to any one of items 1 to 8, The measuring head includes: The optical fiber may further include a light bending unit configured to be detachable from the second end portion and bending light emitted from the second end portion in a predetermined direction intersecting with the axial direction.

[0159] In this case, the degree of freedom in the position and orientation of the measuring head when measuring the displacement of the measurement object is increased.

[0160] (Item 10) In the measuring head according to item 9, The measuring head includes: The optical fiber may further include one or more distance adjustment members configured to be detachable between the second end and the optical bending unit, for adjusting the distance between the measurement head and the optical bending unit.

[0161] In this case, the degree of freedom in the position and orientation of the measuring head when measuring the displacement of the measurement object is increased.

[0162] (Item 11) In the measuring head according to any one of items 1 to 10, The metal constituting the housing and the biasing member may be stainless steel.

[0163] In this case, even when the measurement head is placed in a vacuum environment, outgassing is less likely to occur from the housing and the biasing member, and therefore a decrease in the degree of vacuum caused by the housing and the biasing member is suppressed.

[0164] (Item 12) In the measuring head according to any one of items 1 to 11, the first movement restricting portion is configured by connecting a restricting member separate from the housing to the first portion inside the housing, An adhesive made of an inorganic material may be used for a connection portion between the housing and the restricting member.

[0165] In this case, even when the measurement head is placed in a vacuum environment, a decrease in the degree of vacuum caused by the adhesive is suppressed.

[0166] (Item 13) In the measuring head according to any one of items 1 to 12, The measuring head includes: a fiber connecting member for connecting the optical fiber to the first end of the housing; the fiber connection member is connected to the first end of the housing using one or more screws; An adhesive made of an inorganic material may be used in the fastening portion of each of the one or more screws.

[0167] In this case, even when the measurement head is placed in a vacuum environment, a decrease in the degree of vacuum caused by the adhesive is suppressed.

[0168] (14th paragraph) The measuring head according to the 14th paragraph is A measurement head for a confocal displacement meter having a white light source, comprising: A metal housing formed in a cylindrical shape and having a first end and a second end; an optical fiber connected to the first end of the housing and guiding light generated from the white light source to the first end of the housing; a plurality of glass lenses including a first lens, the lenses being accommodated inside the housing so as to be aligned in an axial direction of the housing and movable in the axial direction, the lenses generating chromatic aberration along an optical axis in the light guided to the first end by the optical fiber and converging the light onto a measurement object through the second end; a first movement restriction portion that is provided in a predetermined first portion inside the housing, and restricts the first lens from moving in any one of a first direction from the first end portion to the second end portion in the axial direction and a second direction opposite thereto, when the first lens comes into contact with the first movement restriction portion; a thermal expansion member made of polyimide and provided inside the housing at a position spaced apart from the first movement restricting portion in the axial direction; Some or all of the multiple lenses, including the first lens, are held between the first movement restricting portion and the thermal expansion member with the first lens abutting the first movement restricting portion.

[0169] The linear expansion coefficient of polyimide is larger than that of metal. Therefore, in the above-mentioned measuring head, when the dimensions of each component constituting the measuring head change due to thermal expansion, the thermal expansion member expands more than the lenses and the housing. As a result, when the measuring head is placed in a high-temperature environment from a normal temperature environment, some or all of the lenses including the first lens among the lenses are biased in one direction by the thermal expansion member, and the movement in the one direction is restricted. Therefore, each time the measuring head is placed in a high-temperature environment, each lens is prevented from significantly shifting to an unintended position in an unintended posture.

[0170] In addition, in the measurement head, the housing is made of metal and the lenses are made of glass, so that the heat resistance of the measurement head is improved by using a polyimide having high heat resistance as the polyimide used for the thermal expansion member.

[0171] As a result, it is possible to suppress deterioration in the reliability of measurements by the confocal displacement meter in high-temperature environments.

[0172] (15) The confocal displacement meter according to 15 is A measuring head according to any one of claims 1 to 14, a white light source generating light that is directed to the measurement head; and a displacement measuring unit that calculates the displacement of the measurement object based on light that is irradiated from the measurement head to the measurement object and reflected by the measurement object.

[0173] The confocal displacement meter includes the above-mentioned measurement head, which suppresses deterioration of measurement reliability in a high-temperature environment. [Explanation of symbols]

[0174] 1A, 1B... measuring head, 2... control unit, 3a... CPU, 3b... memory, 4a... main display unit, 4b... operation unit, 9... confocal displacement meter, 10... head housing, 10a... head axis, 11... first housing part, 11a, 11b, 11c, 11d, 12a, 12b, 12c, 12d... outer surface, 11i... first inner surface, 11j... second inner surface, 11x, 11y... notch, 12... second housing part, 12i... third inner surface, 12j... female thread portion, 30... fan Ibara receptacle, 41, 42, 44, 45...spacer, 41a...opening, 41b...through hole, 43...spring member, 43a...base portion, 43b...small diameter portion, 43c...flange portion, 46...ring screw, 49...thermal expansion member, 50...light bending unit, 51...rear end surface, 51a, 52a, 53a...opening, 52...front end inclined surface, 53...emission surface, 54...mirror, 55...leaf spring, 56...fixing plate, 56a...protrusion, 57, 61, h1, h4...through hole, 60...distance Adjustment member, 62, h2, h3...screw holes, 100A, 100B...measurement unit, 110...unit housing, 120...light projecting section, 130...spectroscope section, 131...diffraction grating, 132, 133, 221, 222, 223, 224...lens, 140...light receiving section, 150...measurement control section, 190...sub-display section, 300A, 300B...light guiding section, 311, 312, 319...optical fiber, 319a...core, 319b...clad, 319c...coating layer, 319d...spiral 1, 320...fiber coupler, 321, 322, 323...port, 324, MB...main body, 330...fiber connector, FE...front end, RE...rear end, S...measurement object, SC1, SC2, SC3...screw, VS1, VS2...imaginary surface, ad1, ad2...rectangular frame, ca...axis center, p1...first part, p2...second part, pp...principal point, r1...first ring member, r2...second ring member, st1...first step portion, st2...second step portion

Claims

1. A measurement head for a confocal displacement meter having a white light source, comprising: a metallic housing formed in a cylindrical shape and having a first end and a second end; an optical fiber connected to the first end of the housing and configured to guide light generated from the white light source to the first end of the housing; a plurality of glass lenses including a first lens, the lenses being accommodated inside the housing so as to be aligned in an axial direction of the housing and movable in the axial direction, the lenses converging the light guided to the first end by the optical fiber onto a measurement object through the second end while generating chromatic aberration along an optical axis; a first movement restriction portion that is provided in a predetermined first portion inside the housing, and restricts the first lens from moving in any one of a first direction from the first end portion to the second end portion in the axial direction and a second direction opposite thereto, when the first lens comes into contact with the first movement restriction portion; a metal biasing member that biases some or all of the plurality of lenses, including the first lens, toward the one direction by elastic force when the first lens is in contact with the first movement restricting portion.

2. one or more spacers made of metal and accommodated inside the housing so as to be movable in the axial direction of the housing; The measurement head according to claim 1 , wherein each of the one or more spacers is provided between two lenses that are adjacent to each other in the axial direction among the plurality of lenses.

3. the first movement restricting portion restricts movement of the first lens in the first direction by contacting the first lens; the plurality of lenses includes a second lens disposed within the housing between the first lens and the second end; The measuring head includes: a second movement restriction portion provided in a second portion located between the first portion and the second end portion inside the housing, the second movement restriction portion contacting the second lens of the plurality of lenses to restrict movement of the second lens in the second direction; The biasing member is a first lens and a second lens disposed in the housing, 3. A measuring head as described in claim 1 or 2, wherein, when the first lens is in contact with the first movement regulating portion and the second lens is in contact with the second movement regulating portion, some of the plurality of lenses including the first lens are urged in the first direction by an elastic force, and the remaining lenses of the plurality of lenses including the second lens are urged in the second direction by an elastic force.

4. The housing has a cylindrical inner circumferential surface extending in the axial direction, the biasing member is formed in a cylindrical shape extending a certain distance in the axial direction of the housing, and is disposed at a position closer to the first end than a principal point defined in an optical system in which the plurality of lenses are combined when light travels in the first direction within the housing, The measurement head according to claim 1 , wherein the light traveling inside the housing passes through an inside of the biasing member.

5. The housing has a cylindrical inner circumferential surface extending in the axial direction, The biasing member is formed in a cylindrical shape extending a certain distance in the axial direction of the housing, some of the lenses have an effective diameter larger than an inner diameter of the biasing member; the biasing member is disposed inside the housing at a position closer to the first end than some of the lenses; The measurement head according to claim 1 , wherein the light traveling inside the housing passes through an inside of the biasing member.

6. The housing has a cylindrical inner circumferential surface extending in the axial direction, the plurality of lenses are arranged in a partial region inside the housing so as to cause the light guided to the first end to travel in the first direction while expanding a cross-sectional area of ​​the light; the biasing member is formed in a cylindrical shape extending a certain distance in the axial direction of the housing, and is disposed in the partial region within the housing, The measurement head according to claim 3 , wherein the light traveling within the housing passes through an inside of the biasing member.

7. The measurement head according to claim 1 , wherein at least a portion of the housing has an outer surface in the shape of a square tube extending in the axial direction and having a rectangular cross section.

8. The housing includes: a first housing portion and a second housing portion arranged in sequence in the first direction; a cylindrical inner circumferential surface extending in the axial direction from the first housing portion to the second housing portion; an inner diameter of the inner circumferential surface of the first housing portion is smaller than an inner diameter of the inner circumferential surface of the second housing portion; the plurality of lenses are housed within the second housing portion; 3. The measuring head according to claim 1, wherein an attachment portion for attaching the measuring head to another member is formed on an outer surface of the first housing portion.

9. 3. The measurement head according to claim 1, further comprising a light bending unit configured to be detachable from the second end and bending light emitted from the second end in a predetermined direction intersecting the axial direction.

10. The measurement head according to claim 9 , further comprising one or more distance adjustment members configured to be detachable between the second end and the optical bending unit, for adjusting a distance between the measurement head and the optical bending unit.

11. 3. The measuring head according to claim 1, wherein the metal constituting the housing and the biasing member is stainless steel.

12. the first movement restricting portion is configured by connecting a restricting member separate from the housing to the first portion inside the housing, 3. The measuring head according to claim 1, wherein an adhesive made of an inorganic material is used for a connection between the housing and the regulating member.

13. a fiber connecting member for connecting the optical fiber to the first end of the housing; the fiber connection member is connected to the first end of the housing using one or more screws; 3. The measuring head according to claim 1, wherein an adhesive made of an inorganic material is used for fastening portions of the one or more screws.

14. A measurement head for a confocal displacement meter having a white light source, comprising: a metallic housing formed in a cylindrical shape and having a first end and a second end; an optical fiber connected to the first end of the housing and configured to guide light generated from the white light source to the first end of the housing; a plurality of glass lenses including a first lens, the lenses being accommodated inside the housing so as to be aligned in an axial direction of the housing and movable in the axial direction, the lenses converging the light guided to the first end by the optical fiber onto a measurement object through the second end while generating chromatic aberration along an optical axis; a first movement restriction portion that is provided in a predetermined first portion inside the housing, and restricts the first lens from moving in any one of a first direction from the first end portion to the second end portion in the axial direction and a second direction opposite thereto, when the first lens comes into contact with the first movement restriction portion; a thermal expansion member made of polyimide and provided inside the housing at a position spaced apart from the first movement restricting portion in the axial direction; A measurement head, in which some or all of the multiple lenses including the first lens are held between the first movement regulating portion and the thermal expansion member with the first lens abutting the first movement regulating portion.

15. A measuring head according to any one of claims 1, 2 and 14; a white light source generating light that is directed to the measurement head; a displacement measuring unit that calculates a displacement of the measurement object based on light that is irradiated from the measurement head to the measurement object and reflected by the measurement object.

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