JP4936286B2 - Inner diameter measuring device - Google Patents

Description

  The present invention relates to an inner diameter measuring apparatus that measures the inner diameter of a cylindrical object to be measured, and more particularly to an inner diameter measuring apparatus that uses white interference.

  Conventionally, a method using the principle of white interference has been proposed as a method for accurately measuring a cylindrical part in a non-contact manner. For example, an interferometer for measuring the inner diameter of a cylinder using white interference is known (see Non-Patent Document 1). In the interferometer described in Non-Patent Document 1, light emitted from a white light source is converted into parallel light by a collimator and divided into two light beams by a half mirror arranged in a cylinder. Then, the light beams are reflected by the inner surface of the cylinder or the plane mirror, and then, for example, an optical path difference corresponding to twice the inner diameter of the cylinder is generated, coupled again by the half mirror, and emitted from the cylinder. Then, the light beam emitted from the cylinder is again divided into two light beams by an interferometer provided separately, and an optical path difference substantially equal to the optical path difference generated in the cylinder is generated, thereby generating white interference fringes. Since the white interference fringe has the maximum amplitude when the optical path difference generated in the cylinder is equal to the optical path difference generated on the interferometer side, measure the optical path difference between the two light beams generated on the interferometer side. Thus, the inner diameter of the cylinder can be accurately measured.

Ueki, Oiwa, "Interferometer for measuring inner diameter of cylinder", Report of Metrology Institute, January 1988, Vol. 37, No. 1, p.53-57

  By the way, due to the recent progress in microfabrication technology, parts having an extremely small inner diameter, and in some cases having an inner diameter of only 1 mm or less have been used for various products. For such parts, there is a demand for measuring the inner diameter with high accuracy in order to confirm processing accuracy. In order to meet such a demand, if it is going to measure the internal diameter of a cylindrical component using said interferometer, it will be necessary to use a half mirror smaller than the internal diameter. Furthermore, in order to fix the position of the half mirror inside the cylinder of the component, it is necessary to arrange the holding member of the half mirror inside the cylinder. However, since there is a limit to downsizing the half mirror and its holding member, if the inner diameter becomes too small, it becomes difficult to dispose the half mirror and its holding member inside the cylinder. For this reason, it has been difficult to accurately measure the inner diameter of a component having such a small inner diameter.

  In view of the above problems, an object of the present invention is to provide an inner diameter measuring apparatus capable of measuring an inner diameter of a measured object having a small inner diameter in measuring the inner diameter of a cylindrical measured object using white interference. There is.

  According to one embodiment of the present invention, an inner diameter measuring device for measuring an inner diameter dimension of a cylindrical object to be measured is provided. The inner diameter measuring apparatus splits the white light source and the light emitted from the white light source into a first light beam and a second light beam directed to the object to be measured, and reflects the first light beam by the object to be measured. An optical waveguide element that causes a first optical path difference corresponding to the inner diameter of the object to be measured between the second light flux and emits the first light flux and the second light flux according to one light flux; An interferometer having a fixed mirror that is fixed and a movable mirror that is movable along the optical path, wherein the light beam emitted from the optical waveguide element is converted into a third light beam that is directed to the fixed mirror and a fourth beam that is directed to the movable mirror. An interferometer that branches into a first light beam and causes a second light path difference between the third light beam and the fourth light beam, and receives the third light beam and the fourth light beam, and receives the first light path difference. And a detector for detecting an interference signal generated when the second optical path difference is substantially equal to the second optical path difference and outputting a signal corresponding to the interference signal; A controller for measuring the inner diameter of the object to be measured by measuring the position of the movable mirror corresponding to the maximum value of the interference signal and calculating the second optical path difference from the position. .

  According to the invention, the optical waveguide element is provided in the vicinity of the first waveguide through which the first light flux passes, the second waveguide through which the second light flux passes, and the optical waveguide element. A reference mirror provided, and the first waveguide is formed of a waveguide formed to guide the light emitted from the white light source to the first inner surface of the object to be measured, and the first inner surface of the waveguide. A waveguide formed so as to guide the reflected light to the second inner surface of the object to be measured facing the first inner surface, and the light reflected by the second inner surface as the exit port of the optical waveguide element The second waveguide is preferably formed to guide the light emitted from the white light source to the reference mirror.

  Furthermore, according to the present invention, the optical waveguide element is preferably a photonic crystal waveguide element.

  Further, according to the present invention, the optical waveguide element is arranged such that a part thereof is located outside the cylinder of the object to be measured, and the inner diameter measuring device is an optical waveguide element located outside the cylinder of the object to be measured. It is preferable to have a holding member for holding a part and fixing the optical waveguide element.

Furthermore, the inner diameter measuring apparatus according to the present invention includes a reference optical path difference that is a second optical path difference corresponding to the maximum value of the interference signal obtained by using the object to be measured as a reference object to be measured, and the inner diameter of the reference object to be measured. And the controller obtains a difference between the second optical path difference corresponding to the maximum value of the interference signal measured for the object to be measured and the reference optical path difference, and calculates half of the difference. The value added to the inner diameter of the reference object is preferably the inner diameter of the object to be measured.
In each of the above embodiments, the white light source is not limited to a light source that emits light in a broad band in the visible light range, but a light source that emits light in a certain wavelength band with a predetermined wavelength as a center wavelength.

  According to another embodiment of the present invention, an inner diameter measuring device for measuring an inner diameter dimension of a cylindrical object to be measured is provided. The inner diameter measuring apparatus is an interferometer having a white light source, a reference mirror whose position is fixed, and a movable mirror that can move along the optical path. The inner diameter measuring device transmits light emitted from the white light source toward the reference mirror. An interferometer for branching into a first light beam and a second light beam directed toward the movable mirror to produce a first optical path difference between the first light beam and the second light beam, and a first light beam emitted from the interferometer The first light beam and the second light beam are branched into a third light beam and a fourth light beam that are directed toward the object to be measured, and the third light beam is reflected by the object to be measured and is measured between the fourth light beam and the fourth light beam. An optical waveguide element that generates a second optical path difference corresponding to the inner diameter of the object and emits the first and second luminous fluxes in accordance with one luminous flux, and receives the third and fourth luminous fluxes. Detecting an interference signal generated when the first optical path difference and the second optical path difference are substantially equal, and outputting a signal corresponding to the interference signal When the position of the moving mirror corresponding to the maximum value of the interference signal is measured by calculating the first optical path difference from that position, and a controller for determining the inner diameter of the object.

  ADVANTAGE OF THE INVENTION According to this invention, it became possible to provide the internal diameter measuring apparatus which can measure an internal diameter also about the to-be-measured object which has a small internal diameter in the internal-diameter dimension measurement of the cylindrical to-be-measured object using white interference.

Hereinafter, embodiments in which the present invention is applied to an inner diameter measuring device that measures the inner diameter of a cylindrical object to be measured, such as a ring gauge and a cylinder, will be described with reference to the drawings.
The inner diameter measuring apparatus to which the present invention is applied causes light from a white light source to enter an optical waveguide element disposed substantially at the center of the object to be measured. The optical waveguide element has two waveguides that branch incident light so as to generate two light beams having optical path differences determined according to the inner diameter of the object to be measured. One of the waveguides is formed to face the inner surface of the object to be measured, and the other of the waveguides is formed to face the reference mirror. Then, the light beams that have passed through the respective waveguides are emitted together and incident on the interferometer. In the interferometer, white interference fringes are generated by splitting the light beam into two optical paths that cause an optical path difference substantially equal to the optical path difference to cause interference. Then, the maximum signal value of the white interference fringes is detected by the detector, the optical path difference between the two optical paths of the interferometer is measured, and compared with the optical path difference obtained for the master whose inner diameter is known in advance. Obtain the inner diameter of the workpiece.

  FIG. 1 is a diagram showing a schematic configuration of an inner diameter measuring apparatus 1 to which the present invention is applied. The inner diameter measuring device 1 includes a white light source 2, an optical waveguide element 3 that generates two light fluxes having an optical path difference determined according to the inner diameter of the object to be measured, and an optical path that is similar to the optical path difference generated in the optical waveguide element 3. An interferometer 4 that generates a white interference fringe by generating a difference, a detector 5 that detects the interference fringe generated by the interferometer 4, and a controller that determines the inner diameter of the object to be measured from the control of each part and the detected interference fringe 6. Further, the inner diameter measuring apparatus 1 includes an optical fiber 7 that transmits light from the white light source 2 to the optical waveguide element 3, and an optical fiber 8 that transmits light emitted from the optical waveguide element 3 to the interferometer 4.

  The white light source 2 is a light source that has a short coherence length and can emit light having a broad wavelength. As the white light source 2, for example, an LED, an SLD (super luminescent diode), an SOA (Semiconductor Optical Amplifier) light source, an ASE (Amplified Spontaneous Emission) light source, or the like can be used. The center wavelength of the light emitted from the white light source 2 can be set to 750 nm, 1300 nm, 1550 nm, and the like, for example. In the present embodiment, an infrared LED having a center wavelength of 1550 nm is used as the white light source 2.

  FIG. 2 shows a schematic side cross-sectional view of the optical waveguide element 3. In the optical waveguide element 3, two light beams B1 and B2 having an optical path difference determined according to the inner diameter of the DUT 10 arranged on the XYZ stage 14 are generated. For this purpose, the light emitted from the white light source 2 is guided to the optical waveguide element 3 through the first optical fiber 7, the collimator lens 11 and the wedge prism 12. The collimator lens 11 makes incident light parallel light. The wedge prism 12 adjusts the position of the parallel light incident through the collimator lens 11 and emits it. Then, the light emitted from the wedge prism 12 is incident on the optical waveguide element 3 disposed at the approximate center of the inner diameter of the DUT 10.

  Hereinafter, the optical waveguide element 3 will be described in detail with reference to FIG. The optical waveguide element 3 includes first to third waveguides 31 to 33 that guide the light beam B1 to the DUT 10 and a fourth guide that guides the light beam B2 to the reference mirror 38 provided on the side surface of the optical waveguide element 3. A waveguide 34 and a fifth waveguide 35 that guides the light beam B 1 reflected by the DUT 10 and the light beam B 2 reflected by the reference mirror 38 to the outside of the optical waveguide element 3 are provided. The first waveguide 31 guides the light incident on the incident port 30 provided on the upper surface of the optical waveguide element 3 to the inner surface S <b> 1 of the DUT 10. For this purpose, the first waveguide 31 is formed downward substantially perpendicularly from the entrance 30. Then, it is curved at the lower part of the optical waveguide element 3, is directed substantially in the horizontal direction, and is connected to the first entrance / exit port 36 provided on the lower side surface of the optical waveguide element 3. The second waveguide 32 guides the light reflected by the inner surface S1 and re-entered through the first entrance / exit port 36 of the optical waveguide element 3 to the inner surface S2 opposite to the inner surface S1 of the object to be measured 10. Therefore, the second waveguide 32 is formed substantially horizontally, branches in the middle of the first waveguide 31, and on the side surface opposite to the optical waveguide element 3 with respect to the first entrance / exit port 36. It is connected to the provided second exit / incident port 37. The third waveguide 33 guides the light reflected by the inner surface S <b> 2 and incident three times through the second exit / incident port 37 of the optical waveguide element 3 to the first waveguide 31. Therefore, the third waveguide 33 is branched and curved in the middle of the second waveguide 32, and merges with the first waveguide 31 when it is substantially perpendicular.

  The fourth waveguide 34 generates the reference light beam B2 having an optical path difference from the light beam B1 reflected by the inner surfaces S1 and S2 of the DUT 10, so that the third waveguide 33 is the first waveguide. Branches downward from the first waveguide 31 at a position closer to the entrance 30 than where it joins 31, and travels toward a reference mirror 38 provided close to the side surface of the optical waveguide element 3. Further, the fifth waveguide 35 guides the light beams B1 and B2 to the emission port 39 together. Therefore, the fifth waveguide 35 branches upward from the first waveguide 31 at a position closer to the entrance 30 than the point where the third waveguide 33 branches from the first waveguide 31. The optical waveguide element 3 is connected to an emission port 39 provided on the side surface.

Here, the path of the light beam B1 reflected by the inner surfaces S1 and S2 of the DUT 10 and emitted from the emission port 39 and the path of the light beam B2 reflected by the reference mirror 38 and emitted from the emission port 39 will be summarized. The light beam B <b> 1 enters the incident port 30, and then exits from the first exit / incident port 36 through the first waveguide 31. Then, the light is reflected by the inner surface S1 of the DUT 10. The light beam B <b> 1 reflected by the inner surface S <b> 1 enters the optical waveguide device 3 again through the first exit / incident port 36, and travels straight through the second waveguide 32. Thereafter, the light exits from the second exit / incident port 37 and is reflected again by the inner surface S <b> 2 of the DUT 10. After the reflection, the light enters the optical waveguide element 3 three times through the second exit / incident port 37, returns to the first waveguide 31 through the third waveguide 33, and proceeds upward. Then, it branches to the fifth waveguide 35 and proceeds to the emission port 39.
On the other hand, the light beam B <b> 2 enters the incident port 30, passes through the first waveguide 31, branches in the middle, and travels through the fourth waveguide 34. Then, the light is reflected by the reference mirror 38 and proceeds through the fourth waveguide 34 in the reverse direction. Thereafter, the first waveguide 31 passes through the fifth waveguide 35 and reaches the emission port 39.
The light beam B1 and the light beam B2 are combined in the fifth waveguide 35 and emitted from the optical waveguide element 3. The light beams B <b> 1 and B <b> 2 are emitted from the optical waveguide element 3, condensed through the condenser lens 13, and enter the optical fiber 8.

  At this time, the optical path difference generated between the light beams B1 and B2 is determined according to the inner diameter D of the DUT 10. This means that in the optical waveguide element 3, the length of the waveguide through which the light beam B1 passes and the length of the waveguide through which the light beam B2 passes are determined at the time of manufacturing the optical waveguide element 3, and the optical path difference between the light beams B1 and B2 is Depending on the distance between the first entrance / exit port 36 of the optical waveguide element 3 and the inner surface S1 of the object to be measured 10 and the distance between the second exit / incident port 37 of the optical waveguide element 3 and the inner surface S2 of the object 10 to be measured. It is clear from the change.

As shown in FIG. 2, in order to suppress the diffusion of the light beams emitted from the first exit / incident port 36 and the second exit / incident port 37, the light collection efficiency of the light incident on the optical waveguide element 3 again is increased. In addition, convex lenses L1 and L2 may be provided at the exit and entrance.
Further, the optical waveguide element 3 was fabricated such that the length in the vertical direction in FIG. 2 was larger than the length in the same direction (that is, the axial direction) of the DUT 10. Then, the optical waveguide element 3 was arranged so that the upper part of the optical waveguide element 3 protruded from the inside of the cylinder of the DUT 10. Then, the optical waveguide element 3 was fixed by a holding member 16 configured to hold the optical waveguide element 3 at a portion protruding from the inside of the cylinder of the DUT 10. By producing and arranging the optical waveguide element 3 in this way, it is not necessary to insert anything other than the optical waveguide element 3 inside the cylinder of the DUT 10. Therefore, the inner diameter measuring apparatus 1 according to the present invention can measure the inner diameter dimension even when the inner diameter of the DUT 10 is small.

  In the present embodiment, the optical waveguide element 3 is made of an optical plastic or the like, and is formed as an optical waveguide element that propagates in the waveguide using total reflection. However, the optical waveguide element 3 may be formed of another optical material such as quartz glass. Further, the optical waveguide element 3 may be formed using a photonic crystal. By using a photonic crystal in which the wall surface of the waveguide is formed so as to have a photonic band gap with respect to the light from the white light source 2, compared with an optical waveguide device using general total reflection, Since the curvature radius of the curved portion can be reduced, the optical waveguide element 3 can be further reduced.

  Note that the XYZ stage 14 has an axial direction of the device under test 10 (that is, a vertical direction in FIG. 2), a direction parallel to the second waveguide 32 in the cylindrical cross section perpendicular to the axial direction of the device under test 10 and the first direction. It can move in three directions perpendicular to the two waveguides 32 and is driven by the stage controller 15. The stage controller 15 is electrically connected to the controller 6 and controlled by the controller 6. Then, the stage controller 15 drives the XYZ stage 14 based on the control signal from the controller 6 to adjust the positional relationship between the optical waveguide element 3 and the device under test 10.

  FIG. 3 shows a schematic configuration diagram of the interferometer 4. The light beams B1 and B2 emitted from the optical fiber 8 pass through the collimator lens 41 of the interferometer 4 and become parallel light. Then, the light enters the beam splitter 42. The light beams B1 and B2 are reflected by the beam splitter 42 and branched into light beams B11 and B21 that travel toward the first optical path, and light beams B12 and B22 that pass through the beam splitter 42 and travel toward the second optical path. The light beam B11 represents the light beam B1 emitted from the optical waveguide element 3 and travels toward the first optical path of the interferometer 4, and the light beam B21 represents the interferometer among the light beam B2 emitted from the optical waveguide element 3. 4 represents a light beam traveling toward the first optical path 4. Similarly, the light beam B12 represents the light beam B1 emitted from the optical waveguide element 3 and directed to the second optical path of the interferometer 4, and the light beam B22 represents the interference light beam B2 emitted from the optical waveguide element 3. This represents the light flux toward the second optical path in total.

  A reference mirror 43 whose position is fixed is installed in the first optical path. The light beams B <b> 11 and B <b> 21 going to the first optical path are reflected by the reference mirror 43 and return to the beam splitter 42, and part of the light passes through the beam splitter 42 and goes to the detector 5. On the other hand, a movable mirror 44 that is movable along the optical path is provided in the second optical path. Then, the light beams B12 and B22 traveling toward the second optical path are reflected by the moving mirror 44 and returned to the beam splitter 42. A part of the light beams B12 and B22 are reflected by the beam splitter 42 and travel to the detector 5 together with B11 and B21.

  The movable mirror 44 is attached to the support member 45. The movable mirror 44 and the support member 45 are installed on a piezo fine movement stage 46 that can finely adjust the position of the movable mirror 44 although the movement range is narrow. The movable mirror 44 and the support member 45 are installed on a coarse movement stage 47 that, together with the piezo fine movement stage 46, has a relatively large movement range and roughly determines the position of the movement mirror 44. The piezo fine movement stage 46 and the coarse movement stage 47 are electrically connected to the piezo controller 51 and the stage controller 52, respectively. Then, the piezo fine movement stage 46 and the coarse movement stage 47 move the movable mirror 44 along the second optical path based on control signals from the piezo controller 51 and the stage controller 52.

A corner cube 48 is attached to the back surface of the support member 45. Further, an interferometer 49 for measuring the position of the movable mirror 44 is installed behind the support member 45 (that is, on the opposite side of the beam splitter 42 with the support member 45 as the center). The position measurement interferometer 49 is irradiated to the corner cube 48, reflected by the corner cube 48 and returned to the position measurement interferometer 49, and interference observed between the reference light and the reference light. The amount of movement of the movable mirror 44 can be measured by counting the number of moving stripes.
If the interference signal is continuously measured during the movement while moving the movable mirror 44, the piezo fine movement stage 46 and the piezo controller 51 may be omitted.

The detector 5 outputs the detected light quantity as an electrical signal. As the detector 5, for example, a semiconductor detection element such as a photodiode, CCD, or C-MOS can be used. In this embodiment, a detector in which CCD elements are arranged in a two-dimensional array is used as the detector 5.
The detector 5 is electrically connected to the controller 6 and transmits an electrical signal corresponding to the detected light amount to the controller 6.

The controller 6 is configured by a so-called PC, and is configured in accordance with a communication unit such as RS232C and Ethernet (registered trademark), and a storage unit including an electrically rewritable nonvolatile memory, a magnetic disk, an optical disk, and a reading device thereof. A communication unit including software such as an electronic circuit and a device driver.
Further, the controller 6 is a functional module realized by a CPU, ROM, RAM and its peripheral circuits (not shown) and a computer program executed on the CPU, based on the detected light quantity and the position of the movable mirror 44. It has a control unit for obtaining an inner diameter D of the device under test 10 and for controlling devices connected to the controller 6 such as a position measuring interferometer 49, a piezo controller 51, a stage controller 52, and a detector 5.

Hereinafter, an operation for measuring the inner diameter of the DUT 10 by the inner diameter measuring apparatus 1 will be described.
Since the light from the white light source 2 has a short coherence length, interference fringes are generated only when the optical path differences are substantially equal. Here, it is assumed that the distance from the beam splitter 42 to the reference mirror 43 in the first optical path of the interferometer 4 is L1, and the distance from the beam splitter 42 to the moving mirror 44 in the second optical path is L2. An optical path difference ΔL = 2 (L2−L1) occurs between the third light flux and the fourth light flux (where L2> L1). At this time, if the optical path difference ΔL and the optical path difference generated between the light beams B1 and B2 are equal, the interferometer 4 out of the light beams B1 reflected by the inner surfaces S1 and S2 of the DUT 10 in the optical waveguide element 3. In the interferometer 4, the optical path difference between the light beam B11 passing through the first optical path and the light beam B2 reflected by the reference mirror 38 in the optical waveguide element 3 is 0. It becomes. Therefore, the maximum interference signal can be observed. Then, as the difference between the optical path difference ΔL generated in the interferometer 4 and the optical path difference generated between the light beams B1 and B2 increases, the magnitude of the interference signal rapidly decreases. In addition, regarding the optical path difference generated between the light beams B1 and B2, as described above, since the optical path difference generated in the waveguide in the optical waveguide element 3 is always constant, the first output of the optical waveguide element 3 is constant. It fluctuates in proportion to twice the distance between the entrance 36 and the inner surface S1 of the object to be measured 10 and the distance between the second exit / incident port 37 of the optical waveguide element 3 and the inner surface S2 of the object to be measured 10 (note that (Because the light beam B1 reciprocates between the exit / injection port 36 and the inner surface S1 and between the exit / injection port 37 and the inner surface S2). Therefore, a reference product whose inner diameter is known in advance is used as a master (whose inner diameter is Dm), and the optical path difference ΔLm between the light beams B1 and B2 (hereinafter referred to as a reference optical path difference) is obtained for the master. At this time, for an arbitrary object to be measured 10, ½ of the difference between the optical path difference ΔL generated in the interferometer 4 when the interference signal is maximum and the reference optical path difference ΔLm is the inner diameter D of the object 10 to be measured. It becomes a difference from the inner diameter Dm of the master. Therefore, the inner diameter D of the object to be measured 10 can be obtained by measuring the optical path difference ΔL and adding ½ of the difference from the reference optical path difference ΔLm to the inner diameter Dm of the master.

  When the moving mirror 44 is moved closer to the beam splitter 42, the optical path difference ΔL = 2 (L1−L2) generated between the third light flux and the fourth light flux is the second interference in the light flux B1. Even when the optical path difference between the light beam B12 passing through the second optical path in the total 4 and the light beam B21 passing through the first optical path in the second interferometer 4 among the light beams B2 is 0, interference fringes are generated. Can be observed (where L1> L2). Therefore, the difference between the position of the moving mirror 44 at which the interference signal generated between the light beams B11 and B22 is maximized and the position of the moving mirror 44 at which the interference signal generated between the light beams B12 and B21 is maximized. The value divided by 2 can be used as the above ΔL.

FIG. 4 shows an operation flowchart of the inner diameter measuring apparatus 1 when measuring the inner diameter D of the DUT 10.
As an advance preparation, the inner diameter Dm of the master and the optical path difference (that is, the reference optical path) generated in the interferometer 4 when the master is installed in the inner diameter measuring apparatus 1 and the maximum amplitude of the white interference signal is measured by the interferometer 4. The difference ΔLm) is obtained and stored in the storage unit of the controller. The master may have a relatively large inner diameter, for example, an inner diameter of about several mm to several tens mm. Therefore, the inner diameter Dm of the master may be measured using a known contact-type inner diameter dimension measuring device or the interferometer described in Non-Patent Document 1 above.
When the measurement is started, first, as an initialization procedure, the reference position of the movable mirror 44, that is, the position of the movable mirror 44 at which the optical path difference between the first optical path and the second optical path of the interferometer 4 becomes 0 is determined ( Step S101). Therefore, the position where the interference fringes are detected by the interferometer 4 is obtained without installing the DUT 10 in the inner diameter measuring device 1. At this time, since there is no light beam reflected from the inner surface of the DUT 10, all the light beams emitted from the optical waveguide element 3 are B2. Therefore, in the interferometer 4, when the difference between the distance L1 from the beam splitter 42 to the reference mirror 43 in the first optical path and the distance L2 from the beam splitter 42 to the moving mirror 44 in the second optical path is zero, the interferometer 4 The signal is maximized. Therefore, the controller 6 moves the movable mirror 44, observes the light amount detected by the detector 5 at a plurality of measurement points, and finds the position where the detected light amount is maximum, that is, the interference signal is maximum. The controller 6 receives the position of the movable mirror 44 when the interference signal reaches the maximum value from the position measurement interferometer 49 and stores it in the storage unit of the controller 6 as a position P1 where L1 = L2. .

  Next, the device under test 10 is installed in the inner diameter measuring device 1, and the optical waveguide element 3 is placed inside the cylinder of the device under test 10. At this time, as described above, the white interference fringes are observed only at a position where ΔL = 2 (L2−L1) is substantially equal to the optical path difference generated between the light beams B1 and B2. Therefore, the controller 6 drives the coarse movement stage 47 through the stage controller 52 and moves the moving mirror 44 of the interferometer 4 backward until white interference fringes are observed. Then, similarly to the above, the controller 6 moves the movable mirror 44 to check increase / decrease in the amount of light detected by the detector 5 at a plurality of measurement points, and the maximum value of the output signal value, that is, the maximum value of the interference signal. Is obtained (step S102). The position P2 of the movable mirror 44 when the output signal becomes maximum is received from the position measurement interferometer 49 (step S103). Then, the controller 6 reads the position P1 of the movable mirror 44 when L1 = L2 from the storage unit, calculates the value P2-P1, and obtains the optical path difference ΔL = 2 (L2-L1) (step S104). When the optical path difference generated in the interferometer 4 is obtained, the controller 6 reads out the reference optical path difference ΔLm measured for the master and the inner diameter Dm of the master from the storage unit (step S105). Then, a difference (ΔL−ΔLm) between the optical path difference ΔL obtained for the DUT 10 and the reference optical path difference ΔLm is obtained (step S106). Finally, the controller 6 adds a value obtained by adding 1/2 of the difference, that is, (ΔL−ΔLm) / 2 to the inner diameter Dm of the master, to the inner diameter D (= Dm + (ΔL−ΔLm) / 2) (step S107).

  Instead of measuring the reference position P1 of the movable mirror 44 in step S101, as described above, the movable mirror 44 is moved closer to the beam splitter 42 than the reference mirror 43, and interference occurs between the light beams B12 and B21. The position P3 of the movable mirror 44 that maximizes the signal may be obtained. Then, the value of (P2−P3) / 2 is calculated, and the value may be ΔL. The intensity of the interference signal observed at the reference position P1 is greatly different from the intensity of the interference signal observed at the position P2. On the other hand, the interference signal observed at the position P2 and the interference signal observed at the position P3 have substantially the same intensity. Therefore, when the inner diameter D of the DUT 10 is determined based on the difference between the position P2 and the position P3, the change in the amount of light received by the detector 5 is greater than when the inner diameter D is determined based on the difference between the reference position P1 and the position P2. Therefore, the position of the movable mirror 44 where the interference signal becomes the maximum value can be specified more accurately.

  As described above, in the inner diameter measuring apparatus 1 to which the present invention is applied, the light flux passing through the inner surfaces S1 and S2 positioned at both ends of the diameter inside the cylinder of the object to be measured 10 is present inside the cylinder of the object to be measured 10. By arranging only the optical waveguide element 3 having the waveguide formed so as to pass through and the waveguide formed so that the light beam reflected by the reference mirror 38 can pass therethrough, it corresponds to the inner diameter of the object to be measured 10. Two light fluxes having an optical path difference are generated. Therefore, the inner diameter measuring device 1 can accurately measure the inner diameter dimension even when the inner diameter of the DUT 10 is small.

In addition, this invention is not limited to said embodiment.
FIG. 5 shows a schematic side cross-sectional view of an optical waveguide element 3 ′ that can be used in place of the optical waveguide element 3 in the inner diameter measuring apparatus of the present invention. In FIG. 5, for simplification, the XYZ stage 14 on which the device under test 10 is arranged is omitted, and only the optical waveguide element 3 ′ and the device under test 10 are illustrated. As shown in FIG. 5, in this optical waveguide element 3 ′, a waveguide 31 that guides light from the white light source 2 to the inner surface S1 of the device under test 10 and a waveguide 32 that connects the inner surfaces S1 and S2 of the device under test 10 are shown. And are formed to be completely separate paths. Similarly, the waveguide 33 and the waveguide 33 that guides the light reflected by the inner surface S2 of the DUT 10 and incident on the optical waveguide element 3 again are formed to be completely separate paths. Since the light emitted from the waveguide 31 or the waveguide 32 is not completely parallel light but diffused light, even if the waveguide is formed in this way, a part of the light reflected by the inner surface S1 or S2 is The light enters the waveguide 32 or the waveguide 33. Therefore, such an optical waveguide element 3 ′ can also generate two light beams having an optical path difference corresponding to the inner diameter D of the DUT 10. In this case, the diameter of the entrance that faces the inner surface S1 of the waveguide 32 is larger than that of the exit of the waveguide 31 so that more light reflected by the inner surface S1 of the DUT 10 can be collected. May be. Similarly, the diameter of the entrance facing the inner surface S2 of the waveguide 33 is made larger than that of the exit of the waveguide 32 so that more light reflected by the inner surface S2 of the device under test 10 can be collected. Also good.

  Further, FIG. 6 shows a schematic side cross-sectional view of another optical waveguide element 3 ″ that can be used in the inner diameter measuring apparatus of the present invention. In FIG. 6 as well, for the sake of simplification, an XYZ stage in which the DUT 10 is arranged. 14 and the like are omitted, and only the optical waveguide element 3 ″ and the DUT 10 are shown. The optical waveguide element 3 ″ shown in FIG. 6 is obtained by providing an isolator I in the middle of the waveguide 32 and eliminating the reference mirror 38 and the waveguide 34 directed to the reference mirror 38. Here, the isolator I is a device under test. Only light in the direction from the inner surface S1 to S2 of the object 10 is allowed to pass, in this case, instead of the light beam reflected by the reference mirror 38, it passes through the waveguide 31 and passes through the first entrance / exit port 36. Thus, the light beam reflected by the end face and emitted from the waveguide 35 via the waveguide 31 again can be used as the light beam B2.

In the measurement apparatus of the above embodiment, the interferometer may be a Fizeau interferometer.
Furthermore, the white light source arranged on the optical waveguide element 3 side and the detector arranged on the interferometer 4 side may be interchanged. In this case, two light beams having an optical path difference corresponding to the measurement target dimension of the object to be measured are generated in advance on the interferometer 4 side, and these light beams are sent to the optical waveguide element 3 side through the optical fiber. In the optical waveguide element 3, the two received light beams are further divided into a light beam reflected by the inner surfaces S1 and S2 of the object to be measured 10 and a two light beams reflected by the reference mirror, and these are combined into one. The white interference fringes are observed by detecting with a detector. Also in this case, the inner diameter D of the DUT 10 can be obtained by measuring the optical path difference generated on the interferometer 4 side.
As described above, various modifications can be made within the scope of the present invention according to the embodiment to be implemented.

It is a schematic block diagram of the internal diameter measuring apparatus to which this invention is applied. It is a schematic sectional side view of the optical waveguide element which comprises an internal diameter measuring apparatus. It is a schematic block diagram of the interferometer which comprises an internal diameter measuring apparatus. It is an operation | movement flowchart of an internal diameter measuring apparatus. It is a schematic sectional side view of other embodiment of an optical waveguide device. It is a schematic sectional side view of other embodiment of an optical waveguide device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner diameter measuring apparatus 10 Object to be measured 2 White light source 3, 3 ', 3 "Optical waveguide element 4 Interferometer 5 Detector 6 Controller 11 Collimator lens 12 Wedge prism 13 Condensing lens 14 XYZ stage 15 Stage controller 16 Holding member 30 Entrance 31-35 Waveguide 36, 37 Exit entrance 38, 43 Reference mirror 39 Exit 44 Moving mirror 45 Support member 46 Piezo fine movement stage 47 Coarse movement stage 48 Corner cube 49 Position measurement interferometer 51 Piezo controller 52 Stage controller 7,8 Optical fiber

Claims (6)

An inner diameter measuring device for measuring an inner diameter dimension of a cylindrical object to be measured,
A white light source,
The light emitted from the white light source is branched into a first light beam and a second light beam that are directed toward the object to be measured, and the first light beam is reflected by the object to be measured, and the second light beam An optical waveguide element that causes a first optical path difference corresponding to the inner diameter of the object to be measured between them, and emits the first light flux and the second light flux according to one light flux;
An interferometer having a fixed mirror whose position is fixed and a movable mirror movable along the optical path, wherein the light beam emitted from the optical waveguide element is converted into a third light beam directed to the fixed mirror and the movement An interferometer that diverges into a fourth light beam directed to the mirror and produces a second optical path difference between the third light beam and the fourth light beam;
The third light beam and the fourth light beam are received, an interference signal generated when the first optical path difference and the second optical path difference are substantially equal is detected, and a signal corresponding to the interference signal is output. A detector to
A controller that determines the inner diameter of the object to be measured by measuring the position of the movable mirror corresponding to the maximum value of the interference signal and calculating the second optical path difference from the position;
An inner diameter measuring device comprising: The optical waveguide element includes a first waveguide through which the first light flux passes, a second waveguide through which the second light flux passes, and a reference mirror provided in the vicinity of the optical waveguide element. And
The first waveguide includes a waveguide formed to guide the light emitted from the white light source to the first inner surface of the object to be measured, and the light reflected by the first inner surface. A waveguide formed to guide the second inner surface of the object to be measured facing the first inner surface, and the light reflected by the second inner surface to guide the output port of the optical waveguide element. Consisting of a formed waveguide,
The inner diameter measuring apparatus according to claim 1, wherein the second waveguide is formed to guide light emitted from the white light source to the reference mirror.   The inner diameter measuring apparatus according to claim 1, wherein the optical waveguide element is a photonic crystal waveguide element.   The optical waveguide element is arranged so that a part thereof is located outside the cylinder of the object to be measured, and the inner diameter measuring device grips a part of the optical waveguide element located outside the cylinder of the object to be measured. The inner diameter measuring device according to claim 1, further comprising a holding member that fixes the optical waveguide element. A storage unit that stores a reference optical path difference that is the second optical path difference corresponding to the maximum value of the interference signal obtained by using the measurement object as a reference measurement object, and an inner diameter of the reference measurement object; And have
The controller obtains a difference between the second optical path difference corresponding to the maximum value of the interference signal measured for the measurement object and the reference optical path difference, and halves the difference of the reference measurement object. The inner diameter measuring device according to any one of claims 1 to 4, wherein a value added to the inner diameter is an inner diameter of the object to be measured. An inner diameter measuring device for measuring an inner diameter dimension of a cylindrical object to be measured,
A white light source,
An interferometer having a reference mirror having a fixed position and a movable mirror movable along an optical path, wherein the light emitted from the white light source is directed to the first light flux toward the reference mirror, and the movement An interferometer that branches into a second light beam directed to the mirror to produce a first optical path difference between the first light beam and the second light beam;
The first light beam and the second light beam emitted from the interferometer are branched into a third light beam and a fourth light beam directed to the object to be measured, and the third light beam is reflected by the object to be measured. Then, a second optical path difference corresponding to the inner diameter of the object to be measured is generated between the fourth light flux and the first light flux and the second light flux are emitted in accordance with one light flux. A waveguide element;
The third light beam and the fourth light beam are received, an interference signal generated when the first optical path difference and the second optical path difference are substantially equal is detected, and a signal corresponding to the interference signal is output. A detector to
A controller that determines the inner diameter of the object to be measured by measuring the position of the movable mirror corresponding to the maximum value of the interference signal and calculating the first optical path difference from the position;
An inner diameter measuring device comprising:

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