Shape measurement device and shape measurement method

Abstract

To precisely measure a shape of an object by inhibiting occurrence of measurement noise.SOLUTION: A probe has an optical path switching element for switching an optical path of measurement light, the optical path switching element has a first surface that the measurement light entering from an optical element enters, a second surface for reflecting the measurement light entering from the first surface, a third surface for emitting the measurement light reflected by the second surface to an object, a fourth surface in contact with the second surface, and a fifth surface for emitting measurement light through the second surface to the object, and an angle to the axis of rotation of the probe is larger than 45 degrees in a normal line of the second surface, an angle to the axis of rotation is less than 90 degrees in a normal line of the third surface, and a normal line of the fifth surface is not parallel with the axis of rotation.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to a shape measurement device and a shape measurement method. [Background technology]

[0002] As a technology for measuring the shape of the bottom or side of a hole in an object, for example, Patent Document 1 describes "a distance measuring device comprising: a light-emitting unit that outputs measurement light; a polarization state control unit that controls the polarization of the measurement light output from the light-emitting unit; and an optical path switching element that selectively emits the measurement light controlled by the polarization state control unit, wherein the polarization state control unit controls the polarization so that the measurement light is emitted from the optical path switching element in multiple directions, and the optical path switching element captures reflected light used to measure the distance to the object of the measurement light emitted from the optical path switching element." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6513846 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, when the distance between the exit surface of the optical element and the surface of the object is close and the normal directions of the surfaces are close, multiple reflections that cause measurement noise can occur when measurement light is output inside the hole in the object, which can reduce the accuracy of shape measurement. Also, reflections from the exit surface of the optical element can cause measurement noise, which can reduce the accuracy of shape measurement.

[0005] The present invention has been made in view of the above points, and has as its object to measure the shape of an object with high accuracy by suppressing the occurrence of measurement noise. [Means for solving the problem]

[0006] The present application includes a number of means for solving at least part of the above problems, examples of which are as follows.

[0007] In order to solve the above-described problems, a shape measurement device according to one aspect of the present invention is a shape measurement device including a measurement head, the measurement head including a probe engaged with a tip of the measurement head, a rotating unit that rotates the engaged probe, and an optical element that emits measurement light to the probe, the probe including an optical path switching element that switches an optical path of the measurement light incident from the optical element, the optical path switching element having a first surface onto which the measurement light incident from the optical element is incident, a second surface that reflects the measurement light incident from the first surface, and a second surface that reflects the measurement light reflected from the second surface. the probe has a third surface that emits the measurement light to an object, a fourth surface that is in contact with the second surface, and a fifth surface that emits the measurement light that has passed through the second surface to the object, the optical path switching element is capable of controlling the reflection rate of the measurement light at the second surface, and has a first light-transmitting member that has the first surface, the second surface, and the third surface, and a second light-transmitting member that has the fourth surface and the fifth surface, the angle between the normal to the second surface and the rotation axis of the probe is greater than 45 degrees, the angle between the normal to the third surface and the rotation axis is less than 90 degrees, and the normal to the fifth surface is not parallel to the rotation axis. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress the occurrence of measurement noise and measure the shape of an object with high accuracy.

[0009] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a shape measuring device according to a first embodiment of the present invention. [Figure 2]Figures 2(A) and (B) are diagrams for explaining the function of a polarizing beam splitter. Figure 2(A) shows a state in which the vibration direction of the linearly polarized measurement light is in the left-to-right direction of the drawing, and Figure 2(B) shows a state in which the vibration direction of the linearly polarized measurement light is in the depth direction of the drawing. [Figure 3] FIG. 3 is a diagram for explaining the relationship between the first polarization state control unit, the second polarization state control unit, and the optical path switching element. [Figure 4] FIG. 4 is a diagram for explaining the relationship between the first polarization state control unit, the second polarization state control unit, and the optical path switching element. [Figure 5] FIG. 5 is a diagram showing a first configuration example of the distance measurement control mechanism. [Figure 6] FIG. 6 is a diagram for explaining an example of a method for determining the reflection position on the surface of the object T from the reflection intensity profile. [Figure 7] FIG. 7 is a diagram showing a second configuration example of the distance measurement control mechanism. [Figure 8] FIG. 8 is a diagram showing a third example of the configuration of the distance measurement control mechanism. [Figure 9] FIG. 9 is a diagram for explaining the relationship between the first polarization state control unit, the second polarization state control unit, and the optical path switching element in the third exemplary configuration of the distance measurement control mechanism. [Figure 10] FIG. 10 is a schematic diagram showing an example of the configuration of a shape measurement device that employs a distance measurement device. [Figure 11] FIG. 11 is a schematic diagram showing another example of the configuration of a shape measurement device that employs a distance measurement device. [Figure 12] FIG. 12 is a diagram illustrating an example of the functional block configuration of the shape measurement device. [Figure 13] FIG. 13 is a perspective view showing a first configuration example of the optical path switching element. [Figure 14] FIG. 14 is a view of the tip portion of the first configuration example of the optical path switching element as seen from the arrow. [Figure 15] FIG. 15 is a view of the tip portion of the first configuration example of the optical path switching element as seen from the arrow. [Figure 16] FIG. 16 is a perspective view showing a modification of the first configuration example of the optical path switching element. [Figure 17] FIG. 17 is a diagram for explaining the optical path in the first configuration example of the optical path switching element. [Figure 18] FIG. 18 is a perspective view showing a second configuration example of the optical path switching element. [Figure 19] FIG. 19 is a view of the tip portion of the second configuration example of the optical path switching element as seen from the arrow. [Figure 20] FIG. 20 is a view of the tip portion of the second configuration example of the optical path switching element as seen from the arrow. [Figure 21] FIG. 21 is a perspective view showing a third configuration example of the optical path switching element. [Figure 22] FIG. 22 is a perspective view showing a fourth configuration example of the optical path switching element. [Figure 23] FIG. 23 is a diagram for explaining coordinate calculation in the first direction. [Figure 24] FIG. 24 is a flowchart illustrating a three-dimensional shape measurement process performed by the shape measurement system. [Figure 25] FIG. 25 is a diagram showing an example of an output screen displaying the measurement results. [Figure 26] FIG. 26 is a diagram showing an example of an output screen displaying the measurement results. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present invention will be described with reference to the drawings. In all drawings used to explain each embodiment, the same components are generally designated by the same reference numerals, and repeated explanations will be omitted. Furthermore, in the following embodiments, the components (including element steps, etc.) are not necessarily essential unless otherwise specified or considered to be clearly essential in principle. Furthermore, when the terms "consisting of A," "composed of A," "having A," and "including A" are used, other elements are not excluded unless otherwise specified to include only the element. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of components, etc., these terms include those that are substantially similar or similar to the shape, etc., unless otherwise specified or considered to be clearly essential in principle.

[0012] <Distance measuring device 10 according to the first embodiment of the present invention> 1 is a schematic diagram showing an example of the configuration of a distance measurement device 10 according to a first embodiment of the present invention. The distance measurement device 10 includes a distance measurement control mechanism 110, a measurement head 160, and an information processing device 210.

[0013] The distance measurement control mechanism 110 is connected to the measurement head 160 via a connection cable 150. The distance measurement control mechanism 110 generates measurement light and outputs it to the measurement head 160 via the connection cable 150. The distance measurement control mechanism 110 also converts the measurement light (reflected light) returned from the measurement head 160 into a predetermined electrical signal and outputs it to the information processing device 210.

[0014] The connection cable 150 is made of, for example, an optical fiber, and guides the measurement light output from the distance measurement control mechanism 110 to the measurement head 160 .

[0015] The measurement head 160 irradiates the object T with measurement light, receives the measurement light (reflected light) reflected by the object T, and outputs the received reflected light to the distance measurement control mechanism 110 via the connection cable 150.

[0016] The distance measurement control mechanism 110 is also connected to an information processing device 210. The information processing device 210 is formed, for example, by a general computer such as a personal computer. The information processing device 210 includes a distance calculation unit 261 ( FIG. 12 ) that calculates the distance to the object T using a predetermined electrical signal input from the distance measurement control mechanism 110. The distance calculation unit 261 may be included in the distance measurement control mechanism 110. The information processing device 210 displays the calculation result of the distance to the object T on a display unit 250. The information processing device 210 may also be connected to the measurement head 160 so as to be able to communicate directly with the measurement head 160 without going through the distance measurement control mechanism 110.

[0017] The measurement head 160 has a lens unit 161, a rotation unit 162, an optical path switching element 163, a measurement head tip unit 164, a first polarization state control unit 165, and a second polarization state control unit 166. The lens unit 161, the first polarization state control unit 165, and the second polarization state control unit 166 correspond to the optical elements of the present invention.

[0018] The lens unit 161 narrows the measurement light input from the distance measurement control mechanism 110 and guides it to the first polarization state control unit 165. The rotation unit 162 is made up of a motor and the like. The rotation unit 162 drives the motor and the like to rotate under the control of the distance calculation unit 261 (FIG. 12) of the information processing device 210, and simultaneously rotates the second polarization state control unit 166 and the optical path switching element 163 around a rotation axis parallel to the measurement light output from the lens unit 161.

[0019] The optical path switching element 163 is composed of, for example, a polarizing beam splitter. The optical path switching element 163 selectively outputs the measurement light, the circular polarization direction of which has been controlled by the linear polarization switching element 302 (FIG. 5) and the first polarization state control unit 165, in accordance with the polarization direction of the measurement light. Specifically, the optical path switching element 163 outputs the measurement light in at least one of a first direction 300a inclined at an angle of 90 degrees or less with respect to the traveling direction of the measurement light output from the lens unit 161, and a second direction 300b that is approximately parallel to the xy plane.

[0020] The measurement head tip 164 engages the second polarization state control unit 166 and the optical path switching element 163. The measurement head tip 164 also passes measurement light traveling from the second polarization state control unit 166 toward the optical path switching element 163 and reflected light traveling from the optical path switching element 163 toward the second polarization state control unit 166.

[0021] The measurement head tip 164 has a structure that allows light to pass through, and is formed, for example, in a hollow cylindrical shape, with an opening in the first direction 300a. The measurement head tip 164 may be formed, for example, in a cylindrical shape using a material with sufficient transmittance (for example, 90% or more) for the wavelength of the measurement light. As the rotating unit 162 rotates, the measurement head tip 164 rotates around a rotation axis parallel to the measurement light output from the lens unit 161. As a result, the second polarization state control unit 166, to which the measurement head tip 164 is engaged, and the light path switching element 163 also rotate together with the measurement head tip 164. Note that the measurement head tip 164 refers to the portion from the rotation point of the rotating unit 162 to the point where the light path switching element 163 is engaged. Hereinafter, the light path switching element 163 and the measurement head tip 164 will collectively be referred to as a probe.

[0022] The structure of the measurement head tip portion 164 is not limited to the above example. For example, the measurement head tip portion 164 may be configured such that the second polarization state control unit 166 and the optical path switching element 163 are secured by one or more support pillars, and the optical path switching element 163 rotates as the support pillars are driven. Alternatively, the measurement head tip portion 164 may be formed of, for example, a transparent two-layered cylinder, and the second polarization state control unit 166 and the optical path switching element 163 may be secured by the innermost cylinder, allowing the second polarization state control unit 166 and the optical path switching element 163 to rotate. Alternatively, the second polarization state control unit 166 and the optical path switching element 163 may be directly bonded and secured to the measurement head tip portion 164. Alternatively, the second polarization state control unit 166 and the optical path switching element 163 may be secured to the measurement head tip portion 164 separately.

[0023] The first polarization state control unit 165 is fixed inside the measurement head 160 and does not rotate. The first polarization state control unit 165 controls the polarization of the measurement light output from the distance measurement control mechanism 110, for example, by changing the circular polarization direction of the measurement light. When a fiber-type polarization control element is used for the first polarization state control unit 165, it may be mounted in a stage before the lens unit 161. An example configuration and detailed operation of the first polarization state control unit 165 will be described later with reference to FIG. 3.

[0024] The second polarization state control unit 166 is made of, for example, a quarter-wave plate. As described above, the second polarization state control unit 166 is rotated together with the optical path switching element 163 as the rotation unit 162 rotates the measurement head tip unit 164. The second polarization state control unit 166 outputs the polarization state of the measurement light controlled by the first polarization state control unit 165 to the optical path switching element 163 while keeping the polarization state constant with respect to the optical path switching element 163.

[0025] In the distance measurement device 10, the measurement light generated by the distance measurement control mechanism 110 is output to the measurement head 160. In the measurement head 160, the polarization of the measurement light is controlled by the first polarization state control unit 165, and the polarization of the measurement light is again controlled by the second polarization state control unit 166, and the measurement light is emitted in the first direction 300a or the second direction 300b by the optical path switching element 163 depending on the polarization.

[0026] The measurement light emitted from the optical path switching element 163 is reflected or scattered by the object T. Then, the reflected or scattered light travels in the reverse direction of the path taken when the measurement light was emitted, i.e., travels through the optical path switching element 163, the second polarization state control unit 166, the first polarization state control unit 165, the lens unit 161, and the connection cable 150, in this order, and returns to the distance measurement control mechanism 110.

[0027] The distance measurement control mechanism 110 converts the returned reflected light into a predetermined electrical signal and outputs it to the information processing device 210. The information processing device 210 calculates the distance to the target object T based on the predetermined electrical signal from the distance measurement control mechanism 110.

[0028] For example, when measuring the shape of a cylindrical hole drilled in the object T, the depth to the bottom of the hole can be measured by using the measurement light emitted in the first direction 300a, and the distance to the side of the hole can be measured by using the measurement light emitted in the second direction 300b.

[0029] <Function of the optical path switching element 163> Next, we will explain the operation of the optical path switching element 163. Figure 2 is a diagram for explaining the operation when a polarizing beam splitter 180 is used as the optical path switching element 163.

[0030] 1A shows a state in which the linearly polarized measurement light is oscillating in the left-right direction of the drawing. In this state, the measurement light incident on the polarizing beam splitter 180 passes through the reflecting surface of the polarizing beam splitter 180 and travels in the first direction 300a. The reflected light from the object T travels back along the same path to the distance measurement control mechanism 110.

[0031] 1B shows a state in which the linearly polarized measurement light is vibrating in the depth direction of the drawing (the direction perpendicular to the drawing). In this state, the measurement light incident on the polarizing beam splitter 180 is reflected by the reflecting surface of the polarizing beam splitter 180 and travels in the second direction 300b. The reflected light reflected by the object T travels back along the same path to the distance measurement control mechanism 110.

[0032] By utilizing the properties of the linearly polarized light and the optical path switching element 163 as shown in the figure, it is possible to maintain the traveling direction of the measurement light in the first direction 300a or the second direction 300b by controlling the polarization state of the measurement light so as to maintain a predetermined angle with respect to the optical path switching element 163. In other words, by controlling the polarization of the measurement light, it is possible to switch the traveling direction of the measurement light to the first direction 300a or the second direction 300b.

[0033] The polarization of the measurement light can be controlled by the polarization stabilizing unit 301 (FIG. 5), the linear polarization switching element 302 (FIG. 5), the first polarization state control unit 165 (FIG. 1), and the second polarization state control unit 166 (FIG. 1).

[0034] 3 and 4 are diagrams for explaining the relationship between the first polarization state control unit 165, the second polarization state control unit 166, and the optical path switching element 163. However, in Fig. 3 and Fig. 4, the first polarization state control unit 165 employs a quarter wave plate 305, the second polarization state control unit 166 employs a quarter wave plate 311, and the optical path switching element 163 employs a polarizing beam splitter 180.

[0035] When the optical axis of the quarter-wave plate 305 is used as a reference, as shown in FIG. 3, when the angle α of the vibration direction of the linearly polarized measurement light incident on the quarter-wave plate 305 is π / 4, the measurement light exiting the quarter-wave plate 305 becomes a circularly polarized state (left-handed circularly polarized light) 307a that rotates clockwise when viewed in the direction of propagation.

[0036] Also, as shown in Figure 4, when the angle α of the vibration direction of the linearly polarized measurement light incident on the quarter-wave plate 305 is 3π / 4, the measurement light exiting the quarter-wave plate 305 becomes a circularly polarized state (right-handed circularly polarized) 307b that rotates counterclockwise when viewed in the direction of propagation.

[0037] Generally, when circularly polarized light is incident on a quarter-wave plate, the plate emits linearly polarized light that oscillates in a direction corresponding to the rotation direction of the circularly polarized light. Therefore, as shown in Fig. 3, when left-handed circularly polarized light 307a is incident on quarter-wave plate 311, linearly polarized light having an angle of π / 4 with respect to the optical axis of quarter-wave plate 311 is emitted. Furthermore, as shown in Fig. 4, when right-handed circularly polarized light 307b is incident on quarter-wave plate 311, linearly polarized light having an angle of 3π / 4 with respect to the optical axis of quarter-wave plate 311 is emitted.

[0038] The polarizing beam splitter 180, which is disposed after the quarter-wave plate 311, transmits linearly polarized light whose vibration direction is parallel to the incident surface 309. That is, it outputs linearly polarized light whose vibration direction is parallel to the incident surface 309 in a first direction 300a. The polarizing beam splitter 180 also reflects linearly polarized light whose vibration direction forms an angle of π / 2 with respect to the incident surface 309. That is, it outputs linearly polarized light whose vibration direction forms an angle of π / 2 with respect to the incident surface 309 in a second direction 300b.

[0039] The quarter-wave plate 311 (second polarization state control unit 166) and the polarizing beam splitter 180 (optical path switching element 163) are rotated by the rotation unit 162. Therefore, by rotating the quarter-wave plate 311 and the polarizing beam splitter 180 while they are respectively engaged with the measurement head tip unit 164 so that the angle between the optical axis of the quarter-wave plate 311 and the incident surface of the polarizing beam splitter 180 is π / 4, it is possible to achieve distance measurement using measurement light traveling in the first direction 300a and distance measurement using measurement light traveling in the second direction 300b.

[0040] The vibration direction of the linearly polarized measurement light incident on the quarter-wave plate 305 is switched by the linear polarization switching element 302 (FIG. 5). When no voltage is applied to the linear polarization switching element 302, the element 302 adjusts the vibration direction of the linearly polarized measurement light incident on the quarter-wave plate 305 to a first measurement light vibration direction 306a, as shown in FIG. 3. When a voltage is applied to the element 302, the element 302 adjusts the vibration direction of the linearly polarized measurement light incident on the quarter-wave plate 305 to a second measurement light vibration direction 306b, as shown in FIG. 4. That is, by electrically controlling the linear polarization switching element 302, the measurement light can be emitted from the measurement head tip 164 in either a first direction 300a or a second direction 300b.

[0041] 3, when the measurement light is irradiated in the first direction 300a, the voltage application to the linear polarization switching element 302 is stopped so that the linear polarization oscillation direction of the measurement light becomes the first measurement light oscillation direction 306a inclined at an angle of π / 4 with respect to the main axis 308 of the quarter-wave plate A. As a result, the measurement light is converted into a left-handed circularly polarized state by the quarter-wave plate A 305, and then converted into linearly polarized light oscillating parallel to the incident surface 309 of the polarizing beam splitter 180 by the quarter-wave plate 311, and is output in the first direction 300a.

[0042] 4, for example, when the measurement light is irradiated in the second direction 300b, a voltage may be applied to the linear polarization switching element 302 so that the linear polarization oscillation direction of the measurement light becomes the second measurement light oscillation direction 306b inclined at an angle of 3π / 4 with respect to the main axis 308 of the quarter-wave plate A. As a result, the measurement light is converted into a right-handed circularly polarized state by the quarter-wave plate A 305, and then converted into linearly polarized light oscillating perpendicularly to the incident surface 309 of the polarizing beam splitter 180 by the quarter-wave plate 311, and is output in the second direction 300b.

[0043] 3 and 4 show an example in which the quarter-wave plate 305 is used in the first polarization state control unit 165, but a liquid crystal element may be used in the first polarization state control unit 165. In this case, the first polarization state control unit 165 can change the polarization direction of the measurement light to be output by controlling the voltage applied to the liquid crystal element serving as the first polarization state control unit 165 and controlling the optical rotation of the liquid crystal element.

[0044] Furthermore, a fiber-type polarization control element may be adopted as the first polarization state control unit 165. In this case, by applying twist or pressure to the fiber-type polarization control element as the first polarization state control unit 165, birefringence is induced, thereby making it possible to control the polarization direction of the measurement light output from the first polarization state control unit 165.

[0045] <First Configuration Example of Distance Measurement Control Mechanism 110> Next, FIG. 5 shows a first configuration example of the distance measurement control mechanism 110. As shown in FIG.

[0046] The first configuration example employs frequency modulated continuous waves (FMCW) or swept-source optical coherence tomography (SS-OCT) (or swept-wavelength OCT) as a distance measurement method to measure the distance to the object T.

[0047] The basic principles of FMCW and SS-OCT are the same. FMCW is primarily used for long-distance measurements using a light source with a long coherence length. SS-OCT is primarily used for measuring fine structures using a light source with a short coherence length.

[0048] The first configuration example includes an oscillator 101, a light emitter 102, optical fiber couplers 103, 104, 106, and 114, an optical fiber 105, light receivers 107 and 109, an optical circulator 108, a reference mirror 112, optical switches 113a and 113b, a ranging control mechanism control unit 111, a polarization stabilization unit 301, and a linear polarization switching element 302.

[0049] The oscillator 101 injects a triangular wave current into the light emitting unit 102 based on a sweep waveform signal from the ranging control mechanism controller 111, thereby modulating the drive current. The light emitting unit 102 generates FM (Frequency Modulated) light whose frequency is swept over time at a constant modulation rate using the modulated drive current, and outputs the FM light to the polarization stabilizing unit 301. Note that the light emitting unit 102 may be configured as a semiconductor laser device with an external resonator, and the resonant wavelength of the light emitting unit 102 may be changed by a triangular wave control signal from the oscillator 101. In this case as well, the light emitting unit 102 can generate FM light whose frequency is swept over time.

[0050] The polarization stabilizing unit 301 stabilizes the polarization state of the FM light input from the light emitting unit 102 to a linearly polarized state in a constant direction and outputs it to the linear polarization switching element 302. By applying a voltage to a liquid crystal element contained within the linear polarization switching element 302, the linear polarization switching element 302 either outputs the linearly polarized light direction of the FM light input from the polarization stabilizing unit 301 to the subsequent stage as is, or rotates it by π / 2 and outputs it to the subsequent stage. Note that because the polarization stabilizing unit 301 and the linear polarization switching element 302 are used to output linearly polarized light having a desired vibration direction, a combination of a general polarization state analyzer and polarization state generator can be used.

[0051] The light (linearly polarized light) output from the linear polarization switching element 302 is incident on the optical fiber coupler 103. The optical fiber coupler 103 splits the incident light into two. One of the split lights is incident on the optical fiber coupler 104 of the reference optical system. Note that the optical fiber couplers 103, 104, and 114 may be, for example, polarized beam splitters.

[0052] The light incident on the optical fiber coupler 104 is split into two, one of which is provided with a predetermined optical path difference, and then combined by the optical fiber coupler 106 and received by the light receiving unit 107. The light receiving unit 107 functions as a Mach-Zehnder interferometer and detects a constant reference beat signal proportional to the optical path difference.

[0053] The other of the two beams split by the optical fiber coupler 103 is input to the optical fiber coupler 114 by the optical circulator 108. The optical fiber coupler 114 splits the input beam into two beams. One of the beams split by the optical fiber coupler 114 is reflected by the reference mirror 112 to become reference beam. The other of the beams split by the optical fiber coupler 114 is output to the measurement head 160 via the optical switches 113a and 113b, and is irradiated onto the object T. The functions of the optical switches 113a and 113b will be described later. The reflected beam (measurement beam) reflected by the object T is returned to the distance measurement control mechanism 110 via the connection cable 150.

[0054] The measurement light returned to the distance measurement control mechanism 110 passes through optical switches 113a and 113b, is combined with the reference light reflected by the reference mirror 112 in the optical fiber coupler 114, and is guided to the light receiving unit 109 by the optical circulator 108. The light receiving unit 109 detects a measurement beat signal generated by interference between the reference light and the measurement light.

[0055] The ranging control mechanism control unit 111 performs A / D conversion of the measurement beat signal detected by the light receiving unit 109, using the reference beat signal detected by the light receiving unit 107 as a sampling clock. Alternatively, the ranging control mechanism control unit 111 samples the reference beat signal and the measurement beat signal using a constant sampling clock.

[0056] More specifically, the ranging control mechanism control unit 111 performs a Hilbert transform on the reference beat signal to create a signal with a phase shift of π / 2, calculates the local phase of the signal from the reference signal before and after the Hilbert transform, and interpolates this phase to determine the timing at which the reference signal has a constant phase. Furthermore, the ranging control mechanism control unit 111 performs interpolated sampling of the measurement beat signal to match this timing, thereby resampling the measurement signal using the reference signal as a reference.

[0057] The distance measurement control mechanism control unit 111 can obtain similar results by sampling the measurement signal using the reference beat signal as a sampling clock in a built-in AD / DA converter and performing A / D conversion.

[0058] Regarding the analysis of the beat signal, there is a time difference Δt between the timing at which the measurement light and the reference light arrive at the light receiving unit 109. During this time, the frequency of the light source changes, so the beat frequency f is equal to the resulting frequency difference. b If the frequency sweep width is Δν and the time required to modulate the frequency by the frequency sweep width Δν is T, the following equation (1) holds: Δt=(T / 2Δν)f b (1)

[0059] The distance L to the target object is half the distance light travels during the time difference Δt, so it can be calculated using the following equation (2) using the speed of light c in the atmosphere. As is clear from equation (2), the distance L and the beat frequency f b are linearly related. L=(cT / 2Δν)f b (2)

[0060] Note that by performing a fast Fourier transform (FFT) on the measurement signal obtained in the distance measurement control mechanism control unit 111 and determining the peak position and magnitude, the reflection position and amount of reflected light from the object T can be determined. For example, in an OCT device, it is desirable to visualize the scattering position and scattering magnitude of a semitransparent body such as a living body, so the FFT amplitude spectrum can be used as is. In this embodiment, in order to accurately determine the position of the surface of the object T, interpolation is performed as described with reference to FIG. 6 to improve the distance detection resolution.

[0061] 6 is a diagram for explaining an example of a method for determining the reflection position on the surface of the object T from the reflection intensity profile. In the diagram, the horizontal axis represents the FFT frequency, and the vertical axis represents the reflection intensity.

[0062] As shown in the figure, the data near the peak of the reflection intensity is discrete. The spacing between points, i.e., the distance resolution, is c / 2Δν. In the case of SS-OCT, the typical wavelength is 1300 nm, the sweep width is 100 nm, and the frequency sweep width Δν is 17.8 THz, so the distance resolution c / 2Δν is 8.4 μm. In the case of FMCW, the typical wavelength is 1500 nm, the sweep width is 2 nm, and the frequency sweep width Δν is 267 GHz, so the distance resolution c / 2Δν is 0.56 mm.

[0063] In contrast, as shown in Figure 6, by fitting a function such as a quadratic function or Gaussian function to three or more points near the peak and then interpolating using values ​​near the peak of the fitted function, it is possible to increase the resolution to about 1 / 10.

[0064] Returning to Fig. 5, the following describes the optical switches 113a and 113b that make up the distance measurement control mechanism 110. The optical switches 113a and 113b perform switching under the control of the distance measurement control mechanism control unit 111.

[0065] To obtain a beat signal due to the interference between the reference light and the measurement light, the difference between the optical path length from the optical fiber coupler 114 to the reference mirror 112 and the optical path length from the optical fiber coupler 114 to the object T must be equal to or less than the coherence length of the light-emitting unit 102. To meet this condition, the optical switches 113a and 113b are simultaneously switched depending on the distance from the optical fiber coupler 114 to the object T, thereby changing the length of the optical fiber between each switch.

[0066] Also, when the difference between the optical path length from the optical fiber coupler 114 to the reference mirror 112 and the optical path length from the optical fiber coupler 114 to the target T is too long, that is, when the coherence length is long, the beat frequency f b becomes too high to be detected by the light receiving unit 109. b The optical switches 113a and 113b are switched simultaneously to change the length of the optical fiber between the switches so that the frequency becomes detectable by the light receiving unit 109.

[0067] In the first configuration example, the optical switches 113a and 113b switch between two optical fibers of different lengths, but they may switch between three or more optical fibers of different lengths depending on the range of the object. Furthermore, the timing at which the optical switches 113a and 113b switch the optical fibers may be constant or may be changed depending on conditions such as the distance of the object T from the optical path switching element 163. For example, the optical switches 113a and 113b may be switched for each rotation in synchronization with the rotation of the optical path switching element 163.

[0068] Furthermore, although the optical path has been described as using an optical fiber, it is also possible to first use an optical fiber collimator or the like to convert the light into light that propagates through free space, and then change the optical path length by switching the light with a mirror or by moving the mirror.

[0069] Furthermore, an optical switch similar to the optical switches 113a and 113b may be provided in the optical path between the optical fiber coupler 114 used for branching and the reference mirror 112 to switch the length of the optical fiber.

[0070] In the first configuration example, the optical path from the optical fiber coupler 114 to the optical switch 113b is installed inside the distance measurement control mechanism 110, but these optical paths may also be installed inside the measurement head 160 instead of inside the distance measurement control mechanism 110.

[0071] Furthermore, the distance measurement method performed using the ranging control mechanism 110 is not limited to the above-mentioned examples. For example, a method such as the TOF (Time Of Flight) method, in which pulsed or burst-shaped light is irradiated onto the object T and the time until the pulse or burst is received can be used, or a method such as the Phase Shift method or the optical comb ranging method, in which continuously intensity-modulated light is irradiated onto the object T and the phase of the received signal can be measured. Furthermore, the distance can be measured by measuring the defocus, or a white light confocal method, an astigmatism method, a knife-edge method, or a conoscopic holography method can also be used.

[0072] <Second Configuration Example of Distance Measurement Control Mechanism 110> 7 shows a second configuration example of the distance measurement control mechanism 110. The second configuration example employs Spectral Domain-Optical Coherence Tomography (SD-OCT) (or Frequency Domain OCT) as a distance measurement method to measure the distance to the object T.

[0073] The second configuration example includes an optical circulator 108, an optical fiber coupler 114, a reference mirror 112, a distance measurement control mechanism control unit 111, a broadband light emitting unit 115, a spectrometer 116, a polarization stabilization unit 301, and a linear polarization switching element 302. Among the components of the second configuration example, those that are common to the components of the first configuration example (FIG. 5) are given the same reference numerals, and therefore, description thereof will be omitted as appropriate.

[0074] The broadband light emitting unit 115 generates broadband light as measurement light under control of the distance measurement control mechanism control unit 111. The generated measurement light reaches the optical circulator 108 via the polarization stabilizing unit 301 and the linear polarization switching element 302, and is guided by the optical circulator 108 to the optical fiber coupler 114 where it is split into two. One of the split measurement light beams is emitted to the object T via the measurement head 160. The other split measurement light beam is reflected by the reference mirror 112 and becomes reference light.

[0075] The measurement light reflected by the object T returns to the distance measurement control mechanism 110 via the measurement head 160, is combined with the reference light by the optical fiber coupler 114, and is guided to the spectrometer 116 by the optical circulator 108, where the spectrum is analyzed.

[0076] This spectrum exhibits oscillations at a frequency proportional to the difference in optical path length between the object T and the reference mirror 112. Therefore, the distance measurement control mechanism control unit 111 in the second configuration example realizes distance measurement of the object T by analyzing this frequency.

[0077] <Third Configuration Example of Distance Measurement Control Mechanism 110> 8 shows a third configuration example of the distance measurement control mechanism 110. In this third configuration example, measurement light can be emitted simultaneously from the measurement head tip 164 of the measurement head 160 in both the first direction 300a and the second direction 300b without switching between them.

[0078] In the third configuration example, similar to the first configuration example (FIG. 5), FMCW or SS-OCT (or swept wavelength OCT) is employed as the distance measurement method to measure the distance to the object T.

[0079] Of the components of the third configuration example, those that are common to the components of the first configuration example (FIG. 5) are given the same reference numerals, and the description thereof will be omitted as appropriate.

[0080] In the third configuration example, the linear polarization switching element 302 is omitted from the first configuration example (FIG. 5), optical fiber couplers 314 and 315 and optical fibers 316a and 316b are added between the optical fiber coupler 103 and the optical circulator 108, and a light receiving unit 117 and an optical fiber coupler 118 are added after the optical circulator 108.

[0081] The optical fiber coupler 314 splits the light, which is output from the polarization stabilizing unit 301 and input via the optical fiber coupler 103 and whose linearly polarized state in a certain direction is stabilized, into two beams.

[0082] The optical fiber 316a outputs one of the two beams split by the optical fiber coupler 314 to the optical fiber coupler 315 while maintaining its linear polarization state.

[0083] The length of the optical fiber 316b is adjusted so that the difference between the length of the optical fiber 316b and the length of the optical fiber 316a is longer than the coherence length of the measurement light, thereby preventing interference between the left-handed circularly polarized light 307a and the right-handed circularly polarized light 307b (FIG. 9) that are simultaneously output from the first polarization state controller 165.

[0084] Furthermore, the optical fiber 316b is connected to the optical fiber coupler 315 in a state where it is physically twisted by π / 2 compared to the optical fiber 316a. As a result, light beams whose linear polarization states are orthogonal to each other enter the optical fiber coupler 315 via the optical fibers 316a and 316b.

[0085] The optical fiber coupler 315 combines the light beams having orthogonal linear polarization states and outputs the combined light beam to the optical circulator 108. The optical fiber coupler 118 splits the combined light beam of the reference light and the measurement light beam incident from the optical circulator 108 into two beams, and outputs one beam to the light receiving unit 109 and the other beam to the light receiving unit 117.

[0086] The light receiving unit 109 detects a constant reference beat signal proportional to the optical path difference in response to the light reflected from the first direction 300a (FIG. 1), and the light receiving unit 117 detects a constant reference beat signal proportional to the optical path difference in response to the light reflected from the second direction 300b (FIG. 1).

[0087] 9 is a diagram for explaining the relationship between the first polarization state control unit 165, the second polarization state control unit 166, and the optical path switching element 163 in the third configuration example of the distance measurement control mechanism 110. However, in this figure, similar to FIGS. 3 and 4, the first polarization state control unit 165 employs a quarter-wave plate 305, the second polarization state control unit 166 employs a quarter-wave plate 311, and the optical path switching element 163 employs a polarizing beam splitter 180.

[0088] When the optical axis of the quarter-wave plate 305 is used as a reference, as shown in the same figure, when measurement light having linear polarization states that are orthogonal to each other is incident on the quarter-wave plate 305, a circular polarization state (left-handed circular polarization) 307a that rotates clockwise when viewed in the direction of travel from the quarter-wave plate 305 and a circular polarization state (right-handed circular polarization) 307b that rotates counterclockwise are simultaneously emitted.

[0089] Next, in response to the incident left-handed circularly polarized light 307a, the quarter-wave plate 311 emits linearly polarized light having an angle of π / 4 with respect to the optical axis of the quarter-wave plate 311. In response to the incident right-handed circularly polarized light 307b at the same time, the quarter-wave plate 311 emits linearly polarized light having an angle of 3π / 4 with respect to the optical axis.

[0090] Polarizing beam splitter 180, which is disposed after quarter-wave plate 311, transmits linearly polarized light whose vibration direction is parallel to incident surface 309, i.e., emits it in first direction 300a. Polarizing beam splitter 180 also reflects linearly polarized light that is incident at the same time and whose vibration direction forms an angle of π / 2 with respect to incident surface 309, i.e., emits it in second direction 300b.

[0091] Therefore, the third configuration example of the distance measurement control mechanism 110 can emit measurement light in both the first direction 300a and the second direction 300b simultaneously from the measurement head tip 164 of the measurement head 160 without switching between them. The distance measurement control mechanism control unit 111 can then calculate the distance to the target T in both the first direction 300a and the second direction 300b approximately simultaneously.

[0092] <Other Configuration Examples of Distance Measurement Control Mechanism 110> The first configuration example (FIG. 5) and the third configuration example (FIG. 8) of the distance measurement control mechanism 110 described above use FMCW or SS-OCT as the distance measurement method, and the second configuration example (FIG. 7) uses SD-OCT as the distance measurement method.

[0093] Another distance measurement method that can be adopted by the distance measurement control mechanism 110 is, for example, the white light confocal method.

[0094] Although not shown in the figure, an example configuration of a distance measurement control mechanism 110 that adopts the white light confocal method omits the reference mirror 112 and optical fiber coupler 114 from the second example configuration (Figure 7), and instead adopts a configuration in which chromatic aberration is intentionally generated in the lens section 161 of the measurement head 160, and uses a measurement head 160 in which the focal position varies depending on the wavelength of the measurement light.

[0095] In this configuration example, when the light reflected or scattered by the object T is re-focused by the lens unit 161 and returns to the distance measurement control mechanism 110, only the wavelength that is in focus at the distance to the object T is captured. In other words, by detecting this light with the spectrometer 116 and calculating the wavelength at which the spectrum peaks with the distance measurement control mechanism control unit 111, distance measurement of the object T can be realized. According to this configuration example, the detected spectral data itself can be obtained as the data shown in Fig. 6 without performing an FFT on the measurement light.

[0096] <Configuration example of shape measurement device 20 employing distance measurement device 10> 10 is a schematic diagram showing an example of the configuration of a shape measuring device 20 that employs the distance measuring device 10. The shape measuring device 20 measures the three-dimensional shape of an object T.

[0097] The shape measurement device 20 has a movement mechanism 280 (FIG. 12) including an xz-axis movement mechanism 251 and a y-axis movement mechanism 252.

[0098] The distance measurement device 10 having the measurement head 160 is installed on the xz-axis moving mechanism 251. The xz-axis moving mechanism 251 can move in the x-axis direction and the z-axis direction. As the xz-axis moving mechanism 251 moves, the measurement head tip 164 of the measurement head 160 also moves.

[0099] The y-axis moving mechanism 252 is a gate-shaped structure that can move in the y-axis direction. The y-axis moving mechanism 252 supports the xz-axis moving mechanism 251, and as the y-axis moving mechanism 252 moves, the measuring head tip 164 of the measuring head 160 supported by the xz-axis moving mechanism 251 also moves. Therefore, the xz-axis moving mechanism 251 and the y-axis moving mechanism 252 can control the attitude of the target T with three degrees of freedom.

[0100] The configuration of the movement mechanism is not limited to that described above, and may be any mechanism capable of moving the measurement head tip 164 in three axial directions. For example, the distance measurement control mechanism 110 may not be installed in the xz-axis movement mechanism 251, and only the measurement head 160 may be installed in the xz-axis movement mechanism 251, thereby allowing the measurement head tip 164 to be moved in three axial directions.

[0101] The shape measurement device 20 has a typical axis configuration used in three-dimensional measuring devices, but by installing the measurement head 160 of the distance measurement device 10 instead of the measurement head of the three-dimensional measuring device, it is possible to achieve highly functional non-contact shape measurement.

[0102] Furthermore, in a typical three-axis machining tool, the Z axis is often provided on the tool side and the x and y axes are provided on the object T side, and this configuration differs from the shape measuring device 20 in Fig. 10. However, if a measuring head 160 is installed on the three-axis machining tool, it becomes possible to realize on-machine measurement on the machining tool.

[0103] Furthermore, if the measuring head 160 is installed on a multi-degree-of-freedom robot and the measuring head tip 164 is made movable, a shape measuring device 20 that allows measurements with a higher degree of freedom can be realized.

[0104] <Another configuration example of a shape measurement device employing the distance measurement device 10> 11 is a schematic diagram showing another example of the configuration of a shape measurement device 20 that employs the distance measurement device 10. In this example of the configuration, a rotation mechanism 256 is added to the example of the configuration in FIG. 10. That is, in this example of the configuration, the shape measurement device 20 has a movement mechanism 280 that includes an xz-axis movement mechanism 251, a y-axis movement mechanism 252, and a rotation mechanism 256.

[0105] The rotation mechanism 256 is engaged by a rotation axis 253 supported by a structure 254, and rotates around the rotation axis 253 parallel to the xy plane. The rotation mechanism 256 also rotates around a rotation axis (not shown) that is perpendicular to the rotation axis 253 and parallel to the z axis.

[0106] A sample stage 255 is installed on the rotation mechanism 256, and the sample stage 255 rotates in accordance with the rotation of the rotation mechanism 256. This causes the object T placed on the sample stage 255 to also rotate. Therefore, the rotation mechanism 256 makes it possible to control the attitude of the object T with two degrees of freedom.

[0107] That is, this other configuration example allows for control of three degrees of freedom of the relative position between the measurement head 160 and the object T using the xz-axis movement mechanism 251 and the y-axis movement mechanism 252, and also allows for control of two degrees of freedom of the relative position using the rotation mechanism 256, making it possible to control five degrees of freedom in total. This allows measurement of any location on the object T from any direction.

[0108] In addition, in a general five-axis processing machine, it is possible to realize on-machine measurement on the processing machine by installing the measuring head 160. In addition, since the number of degrees of freedom and the configuration differ depending on the processing machine, the configuration example of the shape measuring device 20 is not limited to those illustrated in Fig. 10 and Fig. 11.

[0109] <Configuration example of functional blocks of shape measurement device 20> 12 shows an example of the functional block configuration of the shape measurement device 20. The shape measurement device 20 includes a calculation unit 260, a distance measurement control mechanism 110, a measuring head 160, a display unit 250, and a movement mechanism 280.

[0110] The distance measurement control mechanism 110 and the measurement head 160 correspond to the distance measurement device 10. The calculation unit 260 corresponds to the information processing device 210.

[0111] The calculation unit 260 comprehensively controls the entire shape measurement device 20. The calculation unit 260 includes a distance calculation unit 261, a shape calculation unit 262, and a movement mechanism control unit 263.

[0112] The distance calculation unit 261 analyzes the measurement beat signal and the reference beat signal received by the distance measurement control mechanism 110, converts them into distance, and outputs them together with the emission direction of the measurement light to the shape calculation unit 262. The distance calculation unit 261 also controls the measurement head 160, and controls the rotation angle of the measurement head tip 164.

[0113] The shape calculation unit 262 measures the shape of the object T based on the distance input from the distance calculation unit 261 and the emission direction of the measurement light. The shape calculation unit 262 causes the display unit 250 to display the measured shape of the object T.

[0114] The movement mechanism control unit 263 controls the movement mechanism 280 and controls the relative position between the measurement head 160 and the object T. The position and orientation of the object T controlled by the movement mechanism control unit 263 are notified to the distance calculation unit 261. The calculation unit 260 may be installed in the distance measurement control mechanism 110 or the measurement head 160. The display unit 250 is made up of a display device and displays the measurement results.

[0115] <First Configuration Example of Optical Path Switching Element 163> Next, Fig. 13 shows a first configuration example of the optical path switching element 163. In this first configuration example, a polarized beam splitter 180 is used for the optical path switching element 163. Fig. 14 is a diagram showing the tip portion of the optical path switching element 163 (polarized beam splitter 180) as seen from the direction of arrow A shown in Fig. 13. Fig. 15 is a diagram showing the tip portion of the optical path switching element 163 (polarized beam splitter 180) as seen from the direction of arrow B shown in Fig. 13. Figs. 14 and 15 show the angular relationship of the surfaces that make up the polarized beam splitter 180 as the optical path switching element 163.

[0116] 13, the polarizing beam splitter 180 has a first surface P1 at its upper end which is engaged by the measurement head tip portion 164, a fifth surface P5 on the tip side, a second surface P2 above the fifth surface P5 on the tip side, and a third surface P3 on a side surface on the tip side. The polarizing beam splitter 180 is made up of a first light-transmissive member having the first surface P1, the second surface P2, and the third surface P3, and a second light-transmissive member having the fourth surface P4 and the fifth surface P5, and is formed so that the second surface of the first light-transmissive member and the fourth surface of the second light-transmissive member are in contact with each other.

[0117] The polarizing beam splitter 180 in the first configuration example is engaged with the hollow measurement head tip portion 164 so that the fifth surface P5 and the third surface P3 are exposed.

[0118] 14, the fifth surface P5 of the polarizing beam splitter 180 is an exit surface for the measurement light in the first direction 300a (FIG. 1). A normal vector N5 of the fifth surface P5 is not parallel to the rotation axis R. The angle θ5 between the normal vector N5 and the rotation axis R is greater than 0 degrees and less than 45 degrees, for example, 1 degree.

[0119] The third surface P3 of the polarizing beam splitter 180 is formed in a partial elliptical shape. The third surface P3 is an exit surface for the measurement light in the second direction 300b (FIG. 1). The angle θ3 between the normal vector N3 of the third surface P3 and the rotation axis R is greater than 0 degrees and less than 90 degrees, for example, 84 degrees.

[0120] The second surface P2, which serves as a deposition surface that reflects the measurement light toward the third surface P3 in the polarizing beam splitter 180, is also referred to as the fourth surface P4. The angle θ2 between the normal vector N2 of the second surface P2 and the rotation axis R is in the range of greater than 45 degrees and less than 90 degrees, for example, 46 degrees.

[0121] The polarized beam splitter 180 of the first configuration example may be circular when viewed from the direction of arrow B (Fig. 13), or may have a shape with a part of a circle missing as shown in Fig. 15. The polarized beam splitter 180 serving as the optical path switching element 163 shown in Figs. 13 to 15 is smaller than a typical optical path switching element configured as a substantially hexahedron, and can accommodate measurement of holes with smaller diameters.

[0122] Furthermore, the surfaces other than the first surface P1 to the fifth surface P5 that make up the polarizing beam splitter 180 may have any shape, and may be cylindrical, for example, as shown in FIG.

[0123] 16 shows a modified example of the first configuration example of the optical path switching element 163. For example, in order to ensure manufacturing precision, all surfaces of the optical path switching element 163 may be configured to be approximately flat, as shown in the figure.

[0124] Furthermore, if the measurement head tip 164 can be inserted and measured while maintaining a sufficient distance from the internal shape of the hole in the object T, the dimension between the first surface P1 and the second surface P2 of the optical path switching element 163 can be further shortened, as shown in the same figure, and an opening 168 can be provided in the measurement head tip 164 to engage the optical path switching element 163 and measure the second direction 300b (Figure 1), and the measurement head tip 164 can be inserted into the hole in the object T.

[0125] In this modified example, the optical path switching element 163 is shown to be engaged so as to be covered by the measurement head tip 164 having the opening 168, but it may also be engaged so that at least a portion of the third surface P3 of the optical path switching element 163 is exposed to the measurement head tip 164 that does not have the opening 168, or the optical path switching element 163 may be covered by a cap-shaped translucent part.

[0126] Next, FIG. 17 shows the optical paths in a first configuration example of the optical path switching element 163.

[0127] In the first configuration example, by controlling the linear polarization switching element 302, the measurement light traveling in the first direction 300a is emitted in an inclined state with respect to the rotation axis R depending on the inclination θ5 of the fifth surface P5 and the relative refractive index of the optical path switching element 163.

[0128] The reflected light that passes through the second surface P2, is reflected by the fifth surface P5, and returns upward, and is tilted at an angle twice the angle θ5 (2 degrees in this case) with respect to the rotation axis R. Therefore, the amount of detected reflected light generated by the fifth surface P5 is reduced compared to when the fifth surface P5 is not tilted, and measurement noise can be reduced.

[0129] On the other hand, by controlling the linear polarization switching element 302, the measurement light traveling in the second direction 300b is emitted at an angle according to the relative refractive index of the optical path switching element 163 and the angle of incidence on the third surface P3. At this time, the second direction 300b can be made approximately perpendicular to the rotation axis R by maintaining the relationship of the following equation (3) for the angles θ2 and θ3 based on Snell's law, the relative refractive index n of the region of the optical path switching element 163 composed of the first surface P1, the second surface P2, and the third surface P3, and a geometric relationship. (90-θ3)=(2n / n-1)(θ2-45) (3)

[0130] However, even when the linear polarization switching element 302 is controlled to output the measurement light in the second direction 300b, part of the measurement light may travel in the direction of the fifth surface P5 and be reflected by the fifth surface P5 due to the polarization extinction ratio of the optical element used. Even in this case, the amount of detected light is reduced, similar to when the measurement light traveling in the first direction 300a is reflected by the fifth surface P5, and therefore measurement noise can be reduced.

[0131] Furthermore, the direction of the reflected light that is reflected laterally by the second surface (film-forming surface) P2 and then reflected by the third surface P3 also maintains an angle of 360-4×θ2-2×θ3 with respect to the rotation axis R, i.e., when θ2=46 and θ3=84, it has an angle of 8 degrees. Therefore, compared to when the third surface P3 is not tilted, the detected amount of reflected light generated by the third surface P3 is reduced, making it possible to reduce measurement noise.

[0132] Generally, to accurately measure the inner diameter of a precisely machined hole, it is desirable to align the axis of the hole with the rotation axis R and to align the normal vector of the surface of the object T with the direction of the measurement light traveling in the second direction 300b. However, when doing so, the normal vectors of the third surface P3 of the optical path switching element 163 and the surface of the object T tend to coincide, which raises the concern that multiple reflections may occur between the third surface P3 and the surface of the object T, resulting in measurement noise.

[0133] Therefore, in this embodiment, the angular relationship shown in formula (3) is maintained. This allows the normal vector of the surface of the object T to be aligned with the direction of the measurement light traveling in the second direction 300b, while allowing the normal vector of the third plane P3 and the normal vector of the surface of the object T to be tilted without being aligned with each other.

[0134] The multiple-reflected light generated between the third surface P3 and the surface of the object T re-enters the optical path switching element 163 at an angle relative to the optical axis of the measurement light input from the lens portion 161 and reflected laterally at the film formation surface P2, thereby enabling the measurement light to be appropriately irradiated onto the surface of the object T while reducing measurement noise caused by the multiple-reflected light.

[0135] At this time, in order to further reduce measurement noise that may occur when light reflected from the surface of the object T is reflected on the outer surface of the optical path switching element 163, the cylindrical outer surface of the optical path switching element 163 and the inner surface of the measurement head tip 164 may be processed into a sand-polished surface or painted black.

[0136] Each component surface of the optical path switching element 163 may be subjected to an anti-reflection coating treatment in order to reduce loss of irradiated light intensity and measurement noise. Also, each component surface of the optical path switching element 163 may be subjected to a water-repellent coating treatment in order to prevent an increase in reflectance due to contamination of the surface.

[0137] Furthermore, by measuring the distance from a predetermined origin Op to the first surface P1 by detecting the reflected light of the measurement light on the first surface P1 at the same time as measuring the distance to the surface of the object T, it is possible to grasp fluctuations in the optical path length of the measurement head tip 164 and the optical system in the preceding stage and correct the results of the distance measurement of the surface of the object T. In this case, the first surface P1 may be subjected to a partial reflection coating treatment in order to obtain a desired reflected light intensity.

[0138] <Second Configuration Example of Optical Path Switching Element 163> Next, Fig. 18 shows a second configuration example of the optical path switching element 163. Similar to the first configuration example (Fig. 13), this second configuration example employs a polarized beam splitter 180 as the optical path switching element 163. This second configuration example differs from the first configuration example (Fig. 13) in the shape of the third surface P3. The third surface of the polarized beam splitter 180 in the second configuration example is formed in a rectangular shape.

[0139] Fig. 19 is a view of the tip portion of the optical path switching element 163 as seen from the direction of arrow A shown in Fig. 18. Fig. 20 is a view of the tip portion of the optical path switching element 163 as seen from the direction of arrow B shown in Fig. 18. Figs. 19 and 20 show the angular relationship of the surfaces that make up the polarized beam splitter 180 as the optical path switching element 163.

[0140] 19, the fifth surface P5 of the polarizing beam splitter 180 is the output surface in the first direction 300a. A normal vector N5 of the fifth surface P5 is not parallel to the rotation axis R. An angle θ5 between the normal vector N5 and the rotation axis R is greater than 0 degrees and in the range of 90 degrees, for example, 1 degree.

[0141] The third surface P3 of the polarizing beam splitter 180 is an exit surface in the second direction 300b, and the angle θ3 between the normal vector N3 of the third surface P3 and the rotation axis R is approximately 90 degrees.

[0142] Moreover, the angle θ2 between the normal vector N2 of the second surface (film formation surface) P2 of the polarizing beam splitter 180 and the rotation axis R is, for example, 45 degrees.

[0143] 20, the normal vector N3 of the third surface P3 of the polarizing beam splitter 180 and the normal vector N2 of the second surface P2 are not parallel to each other. The angle θ23 between the normal vector N2 and the normal vector N3 is, for example, 0.5 degrees.

[0144] In the second configuration example, by controlling the linear polarization switching element 302, the measurement light traveling in the first direction 300a is emitted in an inclined state with respect to the rotation axis R depending on the inclination θ5 of the fifth surface P5 and the relative refractive index of the optical path switching element 163.

[0145] Furthermore, by controlling the linear polarization switching element 302, the measurement light traveling in the second direction 300b is emitted at an angle according to the relative refractive index of the optical path switching element 163 and the angle of incidence on the third surface P3. More specifically, in the case of the second configuration example, the angle of incidence on the third surface P3 of the measurement light reflected by the second surface (film formation surface) P2 and traveling toward the third surface P3 is angle θ23 (0.5 in this case).

[0146] Furthermore, assuming that the relative refractive index n of the optical path switching element 163 at the optical wavelength used is 1.5, the emission angle of the measurement light emitted from the third surface P3 is approximately 0.75 degrees according to Snell's law, and the light emitted from the third surface P3 is tilted by 0.25 degrees on the XY plane with respect to the light incident on the third surface P3, so the surface coordinates are corrected to take this tilt into account when determining the coordinates.

[0147] In the second configuration example, the same effect as in the first configuration example can be obtained. Furthermore, in the second configuration example, the normal vector between the normal N3 of the third surface P3 and the surface of the object T is tilted around the rotation axis R. As a result, the multiple-reflected light generated between the third surface P3 and the surface of the object T re-enters the optical path switching element 163 at an angle with respect to the optical axis input from the lens unit 161, so that the measurement light can be appropriately irradiated onto the surface of the object T while reducing distance measurement noise caused by the multiple-reflected light.

[0148] <Third Configuration Example of Optical Path Switching Element 163> Next, FIG. 21 shows a third configuration example of the optical path switching element 163. In FIG.

[0149] The third configuration example is obtained by adding a partially reflective surface P11 between the first surface P1 and the second surface P2 of the first configuration example (FIG. 13). The partially reflective surface P11 can be generated, for example, by irradiating the inside of the optical path switching element 163 with an ultrashort pulse laser beam to change the refractive index.

[0150] In the third configuration example, the reflected light of the measurement light reflected by the partially reflecting surface P11 is detected to measure the distance from a predetermined origin Op to the partially reflecting surface P11, simultaneously with measuring the distance to the surface of the object T. This makes it possible to detect not only fluctuations in the measurement distance of the measurement head tip 164 and the upstream optical system, but also changes in the optical path length from the first surface P1 to the partially reflecting surface P11 due to temperature changes in the optical path switching element 163, and correct the measurement result of the distance to the surface of the object T.

[0151] Furthermore, by detecting the fluctuation in the distance between the first surface P1 and the partially reflecting surface P11, it is possible to predict the change in the optical path length of the entire optical path switching element 163 and correct the optical path length from the partially reflecting surface P11 to the third surface P3 and the fifth surface P5.

[0152] <Fourth Configuration Example of Optical Path Switching Element 163> Next, FIG. 22 shows a fourth configuration example of the optical path switching element 163. In FIG.

[0153] In the fourth configuration example, a glass rod 183 that transmits measurement light is added between the measurement head tip 164 and the optical path switching element 163. One upper end of the glass rod 183, which has a first surface P21, is engaged with the measurement head tip 164. In addition, the glass rod 183 has a second surface P22 at the other lower end connected to the first surface P1 of the optical path switching element 163 by optical contact, adhesive, or the like.

[0154] In the fourth configuration example, while measuring the distance to the surface of the target object T, the reflected light of the measurement light reflected on the first surface P21 of the glass rod 183 is detected to measure the distance from the predetermined origin Op to the first surface P21. At the same time, the reflected light of the measurement light reflected on the second surface P22 of the glass rod 183 is detected to measure the distance from the predetermined origin Op to the second surface P22. By understanding the fluctuation in the distance between the first surface P21 and the second surface P22 of the glass rod 183, it is possible to predict the change in the optical path length between the optical path switching element 163 and the glass rod 183 and to correct the optical path length from the first surface P1 to the third surface P3 and the optical path length from the first surface P1 to the fifth surface P5.

[0155] In addition, the first surface P1 of the optical path switching element 163 and the first surface P21 of the glass rod 183 may be subjected to a partial reflection coating treatment to obtain a desired reflected light intensity, and by providing a difference in refractive index between the optical path switching element 163 and the glass rod 183, the reflection at the interface between the first surface P1 of the optical path switching element 163 and the first surface P21 of the glass rod 183 may be controlled.

[0156] <Method of Calculating Coordinates in the First Direction 300a> 23 is a diagram for explaining a method for calculating the surface coordinates of the target T using the measurement light emitted in the first direction 300a from the light path switching element 163. Note that while the figure shows a case where the first configuration example of the light path switching element 163 is used, the coordinate calculation method in the first direction 300a is basically the same in the second to fourth configuration examples, and therefore the description thereof will be omitted.

[0157] As shown in the figure, the measurement light traveling in the first direction 300a is irradiated onto the surface of the target T at an angle θ6 with respect to the rotation axis R, depending on the inclination of the fifth surface P5. The angle θ6 and the inclination angle θ5 between the normal N5 of the fifth surface P5 and the rotation axis R have the following relationship (4) according to Snell's law: n·sinθ5=sinθ6 (4)

[0158] Furthermore, if the rotation angle Φ in the first direction 300a by the rotation unit 162 is defined as D1, and the relative distance measurement value from the coordinate P = (Xp, Yp, Zp) of the exit end surface of the fifth surface P5, determined by design values ​​and calibration, to the surface Q of the object T, the coordinate QP = (Qx, Qy, Qz) of the surface in the first direction 300a can be determined by the following equation (5). Qx=Xp+D1·sinθ6·cosΦ Qy=Yp+D1·sinθ6·cosΦ Qz=Zp-D1·cosθ6 (5)

[0159] Here, by changing the rotation angle Φ by rotating the rotating unit 162, the measurement light is scanned so as to trace a conical trajectory with the apex at point P, thereby making it possible to measure multiple points on the shape in the first direction 300a without moving the measurement head 160 in the horizontal direction. Furthermore, by changing the Z coordinate of the measurement head 160 and performing rotational scanning at the rotation angle Φ, it is possible to concentrically measure multiple points on the shape in the first direction.

[0160] Therefore, for example, when measuring the axial shape of a hole that is narrow relative to the outer diameter of the optical path switching element 163, the horizontal scanning amount of the measurement head 160 is limited, but in this embodiment, the shape of the target T in the first direction 300a can be measured without moving the measurement head 160 horizontally. Note that this measurement method is not limited to measuring the internal shape of a hole, and can be used for any shape measurement in the first direction 300a without being affected by motion error in the horizontal movement axis.

[0161] <Three-dimensional shape measurement processing by shape measurement device 20> Next, FIG. 24 is a flowchart illustrating a three-dimensional shape measurement process by the shape measurement device 20 (FIG. 12).

[0162] The three-dimensional shape measurement process is started in response to a predetermined operation by the user on the calculation unit 260 of the shape measurement device 20, for example.

[0163] First, the distance measurement control mechanism 110 switches the measurement direction to the first direction 300a (step S1) under the control of the distance calculation unit 261. Note that if the measurement direction is already the first direction 300a as the initial state, step S1 can be omitted.

[0164] Next, under the control of distance calculation unit 261, measurement head 160 irradiates measurement light while rotating a specified number of times around the z-axis as rotation axis R, and receives the reflected light. Then, the rotation angle Φ of measurement head tip 164 and the corresponding optical path length in first direction 300a are obtained and output to distance calculation unit 261 (step S2).

[0165] Next, the distance calculation unit 261 calculates the coordinates of the object T based on the optical path length in the first direction 300a at each rotation angle Φ of the measurement head tip 164 input from the measurement head 160, the actual length H1 in the first direction 300a of the measurement head tip 164, and the angle θ6 at which the measurement light is irradiated in the first direction 300a, and outputs the calculation results to the shape calculation unit 262 (step S3).

[0166] Here, the effective length H1 in the first direction 330a refers to the distance from a predetermined origin Op to a point P on the fifth surface P5 of the optical path switching element 163 in the case of the measurement head tip 164 (FIG. 23).

[0167] Next, the shape calculation unit 262 measures the shape of the object T using the calculation result input from the distance calculation unit 261, and displays an output screen 700 (FIG. 25) including a three-dimensional image of the object T on the display unit 250 (step S4).

[0168] FIG. 25 shows an example of an output screen 700 displayed on the display unit 250. On the output screen 700, an image 702a of the bottom of the object T is displayed as a result of the processing of steps S1 to S6. Also, an image 702b of the side of the object T is displayed as a result of the processing of steps S7 to S12 (described below).

[0169] Returning to Fig. 24, the calculation unit 260 then determines whether or not to terminate the three-dimensional shape measurement process (step S5). Specifically, it determines to terminate the three-dimensional shape measurement process when, for example, a predetermined operation is performed by the user, when it is detected that the measuring head 160 has come into contact with the object T, or when a predetermined number of repeated measurements has been reached.

[0170] Here, if the calculation unit 260 determines not to terminate the three-dimensional shape measurement process (NO in step S5), the movement mechanism 280 moves the measurement head 160 in the z direction by a predetermined distance ΔZ1 according to control from the movement mechanism control unit 263 (step S6).

[0171] Thereafter, the process returns to step S2, and steps S2 to S6 are repeated. As a result, the three-dimensional image of the object T in the first direction 300a displayed on the output screen 700 is accumulated concentrically if the surface of the object T that can be measured in the first direction 300a is substantially flat (image 702a in FIG. 25).

[0172] Thereafter, if the calculation unit 260 determines to end the three-dimensional shape measurement process (YES in step S5), then the distance measurement control mechanism 110 switches the measurement direction to the second direction 300b under the control of the distance calculation unit 261 (step S7).

[0173] Next, under the control of the distance calculation unit 261, the measurement head 160 irradiates the measurement light while rotating a specified number of rotations around the z-axis as the rotation axis R, and receives the reflected light. Then, the measurement head 160 obtains the rotation angle Φ of the measurement head tip 164 and the corresponding optical path length in the second direction 300b, and outputs them to the distance calculation unit 261 (step S8).

[0174] Next, the distance calculation unit 261 calculates the surface coordinates of the object T based on the optical path length in the second direction at each rotation angle Φ input from the measurement head 160 and the actual length H2 in the second direction 300b of the measurement head tip 164, and outputs the calculation results to the shape calculation unit 262 (step S9).

[0175] Here, the effective length H2 in the second direction refers to the distance from a predetermined origin Op to a point (hereinafter referred to as a direction change point) where the direction of the measurement light changes on the second surface P2 of the optical path switching element 163. Note that the reason why the direction of the measurement light changes may be reflection or refraction, but other reasons may also be possible.

[0176] Next, the shape calculation unit 262 measures the shape of the target object T using the calculation result input from the distance calculation unit 261, and updates the three-dimensional image of the output screen 700 displayed on the display unit 250 (step S10).

[0177] Next, the calculation unit 260 determines whether or not to end the three-dimensional shape measurement process, similar to step S5 (step S11). If the calculation unit 260 determines not to end the three-dimensional shape measurement process (NO in step S11), the movement mechanism 280 moves the measuring head 160 in the z direction by a predetermined distance Δz2 under the control of the movement mechanism control unit 263 (step S12).

[0178] Regarding the movement of the measurement head 160, for example, when measuring the internal shape of a hole in the object T, by reversing the signs of the movement amounts in the z direction (i.e., distance Δz1 and distance Δz2) between steps S6 and S12, it is possible to efficiently measure the first direction 300a on the outbound path and the second direction on the return path.

[0179] Thereafter, the process returns to step S8, and steps S8 to S12 are repeated. As a result, the three-dimensional image of the object T in the second direction 300b displayed on the output screen 700 is accumulated concentrically if the surface of the object T that can be measured in the second direction 300b is substantially cylindrical (image 702b in FIG. 25).

[0180] Thereafter, when the calculation unit 260 determines that the three-dimensional shape measurement process should be ended (YES in step S11), the three-dimensional shape measurement process is ended.

[0181] In the above-described three-dimensional shape measurement process, the coordinates of the object T are calculated in real time, and a three-dimensional image is displayed based on the calculation results. However, it is also possible to calculate the coordinates of the object T after the measurement head 160 has finished moving in the z direction, and display a three-dimensional image based on the calculation results.

[0182] Furthermore, the process of step S4 and the process of step S6 may be executed simultaneously. Similarly, the process of step S8 and the process of step S12 may be executed simultaneously.

[0183] 26 shows an example of the display on the output screen 700 when the processes of steps S4 and S6 are executed simultaneously, and when the processes of steps S8 and S12 are executed simultaneously. In this case, spiral images 700a and 700b are displayed on the output screen 700.

[0184] Furthermore, the order of the processes of steps S1 to S6 and the processes of steps S7 to S12 may be reversed.Furthermore, only one of the processes of steps S1 to S6 or the processes of steps S7 to S12 may be executed.

[0185] Furthermore, in the above-described three-dimensional shape measurement process, the movement direction of the measurement head 160 (including relative movement) is the z direction, but the movement direction is not limited to the z direction and may be along the rotation axis R of the measurement head tip 164.

[0186] However, in order to prevent elastic bending of the measuring head tip 164, it is preferable that the rotation axis R of the measuring head tip 164, which is roughly cylindrical, coincides with the direction of gravity.

[0187] Alternatively, the measuring head 160 may be fixed and not moved, and the object T may be moved to change the relative position between the measuring head 160 and the object T. In this case, since the measuring head 160 is not moved, bending of the measuring head tip 164 due to acceleration and deceleration when moving or stopping can be avoided. Even when the measuring head 160 is moved, it is preferable to move the direction of movement along the rotation axis R of the measuring head tip 164. However, this is not necessary when moving the measuring head 160 relatively.

[0188] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with or add to the configuration of another embodiment.

[0189] Furthermore, some or all of the above-described configurations, functions, processing units, processing means, etc. may be implemented in hardware, for example, by designing them as integrated circuits. Furthermore, the above-described configurations, functions, etc. may be implemented in software by a processor interpreting and executing a program that implements each function. Information such as programs, tables, and files that implement each function may be stored in memory, a storage device such as a hard disk or SSD, or a storage medium such as an IC card, SD card, or DVD. Furthermore, the control lines and information lines shown are those considered necessary for explanation, and do not necessarily represent all control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected. [Explanation of symbols]

[0190] 10 Distance measurement device, 20 Shape measurement device, 110 Distance measurement control mechanism, 111 Distance measurement control mechanism control section, 150 Connection cable, 160 Measurement head, 161 Lens section, 162 Rotation section, 163 Optical path switching element, 164 Measurement head tip section, 165 First polarization state control section, 166 Second polarization state control section, 168 Aperture, 180 Polarizing beam splitter, 183 Glass rod, 300a First direction, 300b Second direction

Claims

1. A shape measurement device including a measurement head, The measuring head a probe engaged with the tip of the measuring head; a rotating part that rotates the locked probe; an optical element that emits measurement light to the probe, The probe is an optical path switching element that switches the optical path of the measurement light incident from the optical element; The optical path switching element is a first surface onto which the measurement light incident from the optical element is incident; a second surface that reflects the measurement light incident from the first surface; a third surface that emits the measurement light reflected by the second surface to an object; a fourth surface in contact with the second surface; a fifth surface that emits the measurement light that has passed through the second surface to the object, The optical path switching element is a reflection ratio of the measurement light on the second surface is controllable; a first light-transmitting member having the first surface, the second surface, and the third surface, and a second light-transmitting member having the fourth surface and the fifth surface, the angle between the normal to the second surface and the rotation axis of the probe is greater than 45 degrees; a normal to the third surface has an angle of less than 90 degrees with the rotation axis; a normal to the fifth surface is not parallel to the rotation axis; The angle θ2 between the normal to the second surface and the rotation axis, and the angle θ3 between the normal to the third surface and the rotation axis satisfy the following formula: (90-θ3)=(2n / n-1)(θ2-45) Here, n is the relative refractive index of the optical path switching element. Shape measurement device.

2. The shape measurement device according to claim 1, When the normal line to the second surface and the normal line to the third surface are viewed in the direction of the rotation axis from the fifth surface side or the first surface side, the normal line to the second surface and the normal line to the third surface are not parallel to each other. Shape measurement device.

3. 3. The shape measurement device according to claim 1 or 2, When the optical path switching element is viewed in the direction of the rotation axis from the fifth surface side or the first surface side, the shape of the optical path switching element is a circle or a shape with a part of a circle missing. Shape measurement device.

4. 3. The shape measurement device according to claim 1 or 2, the measurement head has a measurement head tip portion that engages the optical path switching element and has a space therein through which the measurement light from the optical element passes, At least a portion of the third surface of the optical path switching element is exposed in the direction of the rotation axis beyond the tip of the measurement head. Shape measurement device.

5. 3. The shape measurement device according to claim 1 or 2, The optical path switching element is a partially reflecting surface between the first surface and the second surface that reflects a part of the measurement light toward the first surface; Shape measurement device.

6. 3. The shape measurement device according to claim 1 or 2, The probe is a glass rod between the optical element and the optical path switching element, the glass rod transmitting the measurement light incident from the optical element; The glass rod has partially reflecting surfaces at both ends that reflect a portion of the measurement light. Shape measurement device.

7. A shape measurement method using a shape measurement device including a calculation unit and a measurement head, The measuring head a probe engaged with the tip of the measuring head; a rotating part that rotates the locked probe; an optical element that emits measurement light to the probe, The probe is an optical path switching element that switches the optical path of the measurement light incident from the optical element; The optical path switching element is a first surface onto which the measurement light incident from the optical element is incident; a second surface that reflects the measurement light incident from the first surface; a third surface that emits the measurement light reflected by the second surface to an object; a fourth surface in contact with the second surface; a fifth surface that emits the measurement light that has passed through the second surface to the object, The optical path switching element is a reflection ratio of the measurement light on the second surface is controllable; a first light-transmitting member having the first surface, the second surface, and the third surface, and a second light-transmitting member having the fourth surface and the fifth surface, the angle between the normal to the second surface and the rotation axis of the probe is greater than 45 degrees; a normal to the third surface has an angle of less than 90 degrees with the rotation axis; a normal to the fifth surface is not parallel to the rotation axis; An angle θ2 between the normal to the second surface and the rotation axis, and an angle θ3 between the normal to the third surface and the rotation axis satisfy the following formula: (90-θ3)=(2n / n-1)(θ2-45) where n is the relative refractive index of the optical path switching element, switching the optical path of the measurement light incident from the optical element toward the fifth surface by the optical path switching element; scanning the object with the measurement light emitted from the fifth surface at an angle that is not parallel to the rotation axis while rotating the probe by the rotation unit; measuring, by the calculation unit, a shape of the object present in a direction of the rotation axis based on reflected light from the object; A shape measurement method including:

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