JP2008309652A - Dimension measuring device and dimension measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dimension measuring device and dimension measuring method capable of accurately measuring the measuring object dimension of an object to be measured regardless of the surface roughness thereof. <P>SOLUTION: This dimension measuring device 1 comprises a first interferometer 3 for dividing the light from a white light source 2 into a first light flux and second light flux going to the object to be measured and causing the first optical path difference corresponding to the measuring object dimension of the object between the first light flux and the second light flux, a light receiving element 38 for detecting the light scattered by the object, a second interferometer 4 for dividing the light flux coming from the first interferometer 3 into a third light flux going to a reference mirror 43 and a fourth light flux going to a moving mirror 44 movable along the optical path, and causing the second optical path difference between the third light flux and the fourth light flux, a detector 5 for receiving the third and fourth light fluxes and detecting an interference signal occurring when the first optical path difference is substantially equal to the second optical path difference, and a controller 6 for measuring the measuring object dimension of the object and correcting the acquired measured value based on the light quantity of the scattered light received by the light receiving element 38. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dimension measuring apparatus and a dimension measuring method, and more particularly to a dimension measuring apparatus and a dimension measuring method using white interference.

  Conventionally, a method using the principle of white interference has been proposed as a method for accurately measuring the dimension or surface roughness of a processed part in a non-contact manner. For example, a measuring apparatus that measures the flange back of a digital camera using white light interference is known (see Patent Document 1). In the measuring apparatus described in Patent Document 1, light emitted from a white light source is divided into a first optical path and a second optical path by a beam splitter. And the light which went to the 1st optical path is reflected by the reference mirror for length measurement which can move along a 1st optical path. On the other hand, the light traveling toward the second optical path is reflected by an image sensor of the camera fixedly attached to a reference plane that can come into contact with the flange of the camera. The light reflected by the reference mirror and the image sensor is united by a beam splitter and detected by a detector. Here, by moving the reference mirror along the first optical path, the position of the reference mirror that detects the maximum amount of white interference fringes of the light passing through the first optical path and the light passing through the second optical path is detected. To do. Based on the position of the reference mirror, the length from the flange to the image sensor is detected.

  In addition, in order to detect weak reflected light from the object to be measured with high sensitivity, a measurement method in which an interferometer that scans interference fringes and an interferometer for measurement are separately provided has been developed (see Patent Document 2). .

JP 2005-115149 A JP 2000-65530 A

  In the measurement method using white interference as described above, in order to perform accurate measurement, it is necessary to detect the position of the white interference fringe with the maximum light amount, that is, the peak position of the white interference fringe with high accuracy. . However, the surface of the object to be measured that reflects the measurement light has polishing scratches or the like that are made during processing of the object to be measured, and has a certain degree of surface roughness. Therefore, in actual measurement, the peak position varies depending on the degree of surface roughness of the object to be measured that reflects the measurement light. Specifically, since the measurement light reflection spot on the surface of the object to be measured includes each part of the surface unevenness, the light reflected by the convex part of the surface of the object to be measured and the light reflected by the concave part Thus, the optical path difference generated between the reference light and the reference light is different. Therefore, the peak of the interference fringes spreads depending on the depth of the unevenness. The center position of the peak substantially corresponds to the average value of the surface height. Therefore, the measured value of the measurement target dimension of the object to be measured varies depending on the degree of surface roughness of the object to be measured. However, when a cylinder or ring gauge is an object to be measured and the measurement target dimension is its inner diameter, it is necessary to accurately determine whether or not physical interference with a component inserted into the cylinder or the like occurs. In addition, it is desirable that the measured value of the inner diameter is obtained based on the apex of the convex portion on the surface.

  In view of the above problems, an object of the present invention is to provide a dimension measuring apparatus and a dimension measuring method capable of accurately measuring a dimension to be measured regardless of the degree of surface roughness of an object to be measured in dimension measurement using white interference. Is to provide.

According to one embodiment of the present invention, a dimension measuring device for measuring a dimension of an object to be measured is provided. Such a dimension measuring apparatus splits a white light source and 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 on the object to be measured. A first interferometer that generates a first optical path difference corresponding to the measurement target dimension of the object to be measured between the two light beams and emits the first light beam and the second light beam according to one light beam; , A second interference provided in the first interferometer and having a light receiving element for detecting light scattered by the object to be measured, a reference mirror having a fixed position, and a movable mirror movable along the optical path The light beam emitted from the first interferometer is branched into a third light beam directed toward the reference mirror and a fourth light beam directed toward the movable mirror, and the third light beam and the fourth light beam A second interferometer that causes a second optical path difference between them, a third light flux and a fourth light flux are received, and the first optical path difference and the second optical path difference are approximately Detecting an interference signal which occurs when correct, having a detector for outputting a signal corresponding to the interference signal, the controller to determine the measured dimensions of the object to be measured from the interference signal.
The controller calculates the second optical path difference from the position of the moving mirror measured by the peak position measuring unit and the peak position measuring unit that measures the position of the moving mirror corresponding to the maximum value of the interference signal, The dimension measurement unit for obtaining the measurement value of the measurement target dimension of the object to be measured, and the measurement value obtained by the dimension measurement unit is corrected based on the amount of scattered light received by the light receiving element. A dimension correction unit for obtaining a true value.

According to another embodiment of the present invention, a dimension measuring device for measuring a dimension of an object to be measured is provided. The dimension measuring apparatus is a first interferometer having a white light source, a reference mirror whose position is fixed, and a movable mirror movable along the optical path, and the light emitted from the white light source is converted into the reference mirror. A first interferometer for branching into a first light beam directed toward the second 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; The first light beam and the second light beam emitted from one interferometer are branched into a third light beam and a fourth light beam that are directed to the object to be measured, and the third light beam is reflected by the object to be measured. A second interferometer that causes a second optical path difference corresponding to the measurement target dimension of the object to be measured between the four light beams and emits the third light beam and the fourth light beam according to one light beam. A light receiving element provided in the second interferometer for detecting light scattered by the object to be measured; a third light beam and a fourth light beam; and a first optical path When the second optical path difference detecting an interference signal which occurs when approximately equal, having a detector for outputting a signal corresponding to the interference signal, the controller to determine the measured dimensions of the object to be measured from the interference signal.
The controller calculates the first optical path difference from the position of the moving mirror measured by the peak position measuring unit and the peak position measuring unit that measures the position of the moving mirror corresponding to the maximum value of the interference signal, The dimension measurement unit for obtaining the measurement value of the measurement target dimension of the object to be measured, and the measurement value obtained by the dimension measurement unit is corrected based on the amount of scattered light received by the light receiving element. A dimension correction unit for obtaining a true value.

  Furthermore, according to the other embodiment of this invention, the dimension measuring apparatus which measures the dimension of a to-be-measured object is provided. The dimension measuring apparatus is a first interferometer having a white light source and a movable mirror movable along the optical path, and the light emitted from the white light source is converted into a first light flux directed to the object to be measured. An interferometer for branching into a second light beam directed to the movable mirror and reflecting the first light beam by the object to be measured to generate an optical path difference between the first light beam and the second light beam; A light receiving element provided for detecting light scattered by the object to be measured; a first light beam and a second light beam emitted from the interferometer; and the optical path length and the second light beam for the first light beam. A detector that detects an interference signal that is generated when the optical path lengths of the two are substantially equal to each other and outputs a signal corresponding to the interference signal, and a controller that determines a measurement target dimension of the object to be measured from the interference signal. The controller includes a peak position measurement unit that measures the position of the movable mirror corresponding to the maximum value of the interference signal, a position of the movable mirror measured by the peak position measurement unit, and a predetermined reference position of the movable mirror. By calculating the difference, the dimension measurement unit for obtaining the measurement value of the measurement target dimension of the object to be measured, and the measurement value obtained by the dimension measurement unit are corrected based on the amount of scattered light received by the light receiving element. Thus, there is a dimension correction unit for obtaining a true value of the measurement target dimension.

  Further, according to the present invention, it is preferable that the dimension correction unit corrects so that the true value of the measurement target dimension becomes smaller than the measurement value as the amount of scattered light increases.

  Further, according to the present invention, the controller uses the reference measurement object as the measurement object, and calculates the true value of the measurement target dimension of the reference measurement object and the reference measurement object reflected by the first light flux. The storage unit further stores a reference table that represents the relationship between the amount of scattered light measured by changing the surface roughness and the value of the measurement target dimension of the reference object, and the dimension correction unit includes the reference table. The reference value of the measurement target dimension of the reference measurement object corresponding to the amount of scattered light received by the light receiving element is obtained, and the difference between the measurement value obtained by the dimension measurement unit and the reference value is calculated. It is preferable that a value obtained by adding the difference to the true value of the measurement object dimension of the object to be measured is the true value of the measurement object dimension of the object to be measured.

  Further, according to the present invention, the controller further includes a storage unit that stores a reference table that represents a relationship between the amount of scattered light and a correction amount for the measurement value, and the dimension correction unit receives the scattered light from the reference table. It is preferable that a correction amount corresponding to the amount of light is obtained, and a value obtained by adding the correction amount to the measurement value obtained by the dimension measuring unit is set as a true value of the measurement target dimension of the object to be measured.

According to still another embodiment of the present invention, 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 divided by the object to be measured. A first optical path difference corresponding to the measurement target dimension of the object to be measured is generated between the reflected light and the second light flux, and the first light flux and the second light flux are emitted in accordance with one light flux. Interferometer, a light receiving element provided in the first interferometer for detecting light scattered by the object to be measured, a reference mirror whose position is fixed, and a movable mirror movable along the optical path A second interferometer, which splits the light beam emitted from the first interferometer into a third light beam directed to the reference mirror and a fourth light beam directed to the movable mirror, and the third light beam and the fourth light beam. A second interferometer that generates a second optical path difference between the first optical path difference and the third optical flux difference between the first optical path difference and the second light. Detecting an interference signal caused when the the difference substantially equal, the object to be measured is provided in the measurement system and a detector for outputting a signal corresponding to the interference signal.
According to the dimension measuring method, the difference between the step of measuring the position of the movable mirror corresponding to the maximum value of the interference signal, the position of the movable mirror measured by the peak position measurement unit, and the predetermined reference position of the movable mirror is provided. By calculating the measurement value of the measurement target dimension of the object to be measured, and correcting the measurement value obtained by the dimension measurement unit based on the amount of scattered light received by the light receiving element, And a step of obtaining a true value of the dimension 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 the present invention, it is possible to provide a dimension measuring apparatus and a dimension measuring method capable of accurately measuring a dimension to be measured regardless of the degree of surface roughness of an object to be measured in dimension measurement using white interference. became.

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.
An inner diameter measuring apparatus to which the present invention is applied causes light from a white light source to enter a first interferometer, and the first interferometer generates two light beams having an optical path difference corresponding to the inner diameter of the object to be measured. . The two light beams are incident on the second interferometer, and the light beams are divided and interfered with each other in two optical paths that generate an optical path difference substantially equal to the optical path difference, thereby generating white interference fringes. Then, the inner diameter of the object to be measured is obtained by detecting the maximum signal value of the white interference fringe with a detector and measuring the optical path difference between the two optical paths of the second interferometer. At that time, the inner diameter measuring device is provided in the first interferometer, detects light scattered on the surface of the object to be measured by the light receiving element, and estimates the degree of surface roughness from the amount of the scattered light. Then, the true value of the inner diameter of the measured object is estimated by correcting the measured value of the inner diameter of the measured object according to the degree of surface roughness.

  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, a first interferometer 3 that generates an optical path difference corresponding to twice the inner diameter of the object to be measured, and an optical path difference generated by the first interferometer 3. A second interferometer 4 that generates a white interference fringe by generating an optical path difference, a detector 5 that detects the interference fringe generated by the second interferometer 4, and a control method for each part and detection of the interference fringe. A controller 6 is provided for determining the inner diameter of the measurement object. Further, the inner diameter measuring device 1 includes an optical fiber 7 that transmits light from the white light source 2 to the first interferometer 3 and an optical fiber 8 that transmits light emitted from the first interferometer 3 to the second interferometer. Have.

  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 configuration diagram of the first interferometer 3. In the first interferometer 3, two light beams B 1 and B 2 having an optical path difference corresponding to twice the inner diameter of the DUT 10 arranged on the XYZ stage 36 are generated. For this purpose, in the first interferometer 3, the light incident from the white light source 2 through the first optical fiber 7 is converted into parallel light by the collimator lens 31, and the first position for adjusting the output position with respect to the incident parallel light is adjusted. To the wedge prism 32. Then, the light emitted from the wedge prism 32 is incident on a beam splitter 33 disposed substantially at the center of the inner diameter of the DUT 10. The incident light is reflected by the beam splitter 33 and branched into a light beam traveling toward the inner surface S1 of the DUT 10 and a light beam B2 that passes through the beam splitter 33 and travels straight. The light beam traveling toward the inner surface S1 of the device under test 10 returns to the beam splitter 33 after being reflected by the inner surface S1 of the device under test 10. A part of the light beam returned to the beam splitter 33 passes through the beam splitter 33 and travels to the inner surface S2 opposite to the inner surface S1 of the DUT 10. Then, the light beam directed toward S2 is reflected by the inner surface S2 and returns to the beam splitter 33 again. A part of the light beam returned to the beam splitter 33 is reflected by the beam splitter 33. This light beam is called B1. The light beam B1 and the light beam B2 are emitted together when emitted from the beam splitter 33. The light beams B1 and B2 exit the beam splitter 33, enter the second wedge prism 34 for position adjustment, and are adjusted in position so as to enter the condenser lens 35. Then, the light beam B 1 and the light beam B 2 are collected through the condensing lens 35, exit from the first interferometer, and enter the optical fiber 8.

  At this time, since the light beam B1 emitted from the first interferometer 3 reciprocates between the inner surfaces S1 and S2 of the object to be measured 10, if the inner diameter of the object to be measured 10 is D, the light beam B1 and the light beam B2 2D, a 2D optical path difference occurs. Then, the light beam B 1 and the light beam B 2 having a 2D optical path difference are incident on the second interferometer 4 through the optical fiber 8.

  Further, a light receiving element 38 is installed in the vicinity of the beam splitter 33. In the present embodiment, a photodiode is used as the light receiving element 38. The light receiving element 38 is disposed outside the optical path of the light beams B1 and B2, and the light receiving surface thereof is disposed so as to face the inner surface S1 of the DUT 10. The light receiving element 38 receives the light scattered by the measurement light from the white light source 2 on the inner surface S <b> 1 of the DUT 10. The light receiving element 38 outputs an electrical signal corresponding to the amount of the scattered light. The electric signal is amplified by an amplifier circuit (not shown) and transmitted to a PC (not shown) that controls the light receiving element 38 and the like. The PC transmits the electrical signal to the controller 6 through a communication line or the like. The light receiving element 38 may be arranged such that the light receiving surface thereof faces the inner surface S2 of the object to be measured 10 so as to receive light scattered by the inner surface S2. Further, the light receiving element 38 is not limited to one, and may be configured by a plurality of light receiving elements, and an electric signal corresponding to the average or total of the light amounts detected by the respective light receiving elements may be transmitted to the controller 6.

  The XYZ stage 36 has three directions: an axial direction of the device under test 10 (that is, a direction parallel to the light beam B2), a direction parallel to the light beam B1 and a direction perpendicular to the light beam B1 within the cylindrical surface of the device under test 10. And is driven by the stage controller 37. The stage controller 37 is electrically connected to the controller 6 and is controlled by the controller 6.

  FIG. 3 shows a schematic configuration diagram of the second interferometer 4. The light beams B1 and B2 emitted from the optical fiber 8 pass through the collimator lens 41 of the second 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. A light beam B11 represents a light beam that travels toward the first optical path of the second interferometer 4 among the light beams B1 emitted from the first interferometer 3, and a light beam B21 emitted from the first interferometer 3. Of the light beam B2, the light beam traveling toward the first optical path of the second interferometer 4 is represented. Similarly, a light beam B12 represents a light beam that travels to the second optical path of the second interferometer 4 out of the light beam B1 emitted from the first interferometer 3, and a light beam B22 exits the first interferometer 3. Of the measured light beams B2, the light beams traveling toward the second optical path of the second interferometer 4 are represented.

  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.
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.

  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.

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.

FIG. 4 shows a functional block diagram of the controller 6.
The controller 6 is configured by a so-called PC, and is in accordance with a storage unit 61 including an electrically rewritable nonvolatile memory, a magnetic disk, an optical disk, and a reading device thereof, and communication standards such as RS232C and Ethernet (registered trademark). The communication unit 62 includes software such as the configured electronic circuit and 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 amount and the position of the movable mirror 44. A peak position measuring unit 63 for measuring the position of the movable mirror 44 corresponding to the maximum value of the interference signal, and a dimension measuring unit 64 for obtaining a measured value of the inner diameter D of the DUT 10 from the measured position of the movable mirror 44; , The measurement value is corrected based on the amount of scattered light received by the light receiving element 38, and a dimension correction unit 65 for obtaining a true value of the inner diameter D, each part of the controller 6, a position measurement interferometer 49, a piezo controller 51, And a control unit 66 for controlling devices connected to the controller 6 such as the stage controller 52 and the 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, the distance from the beam splitter 42 to the reference mirror 43 in the first optical path of the second interferometer 4 is L1, and the distance from the beam splitter 42 to the moving mirror 44 in the second optical path is L2. If there is, an optical path difference of 2 (L2−L1) is generated between the third light flux and the fourth light flux (where L2> L1). At this time, if (L2−L1) and D are equal, the first interferometer 3 uses the first interferometer 4 out of the light beams B1 reflected by the inner surfaces S1 and S2 of the DUT 10. The optical path difference between the light beam B11 passing through the optical path and the light beam B2 passing through the beam splitter 33 in the first interferometer 3 and the light beam B22 passing through the second optical path in the second interferometer 4 is 0. It becomes. Therefore, the maximum interference signal can be observed. Then, as the difference between (L2−L1) and D increases, the magnitude of the interference signal decreases rapidly. Therefore, the inner diameter D of the DUT 10 can be obtained by measuring (L2-L1) when the interference signal is maximum.

  Further, when the moving mirror 44 is brought closer to the beam splitter 42, the optical path difference 2 (L1-L2) generated between the third light flux and the fourth light flux is twice the inner diameter D of the DUT 10. Interference fringes can be observed even at equal points (however, L1> L2). In this case, among the light beams B1 reflected by the inner surfaces S1 and S2 of the object to be measured 10 in the first interferometer 3, the light beams B12 that have passed through the second optical path in the second interferometer 4 and the first This is because, in the second interferometer 4, the optical path difference between the light beam B 2 that has passed through the beam splitter 33 in the interferometer 3 and the light beam B 21 that has passed through the first optical path becomes zero. 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. By dividing by 2, the inner diameter D of the DUT 10 can be obtained.

Here, on the surface of the inner surface S1 of the DUT 10, when the light beam B1 is reflected, scattered light corresponding to the surface roughness of the inner surface S1 is generated.
A graph 501 illustrated in FIG. 5 represents an outline of the relationship between the measured value of the inner diameter D and the amount of light (or surface roughness) of scattered light measured by the light receiving element 38. In FIG. 5, the horizontal axis represents the amount of scattered light, and the vertical axis represents the measured value of the inner diameter D. As shown in FIG. 5, since the surface roughness of the inner surface S1 is considered to increase as the amount of scattered light increases, the measured value of the inner diameter D also increases. When the scattered light is not observed, the inner surface S1 is considered to be a substantially ideal mirror surface, and the measured value of the inner diameter D at that time is considered to be the true value of the inner diameter D. Note that the measured value of the inner diameter D increases as the surface roughness of the surface to be measured increases. Matsumoto et al., “The 4th Lightwave Sensing Technology Study Group Lecture Collection” Measurement ", p.109.

Therefore, in order to correct the measurement error of the inner diameter D due to such surface roughness, a master having various surface roughnesses of the inner surfaces S1 and S2 is prepared as a reference product of the object to be measured 10. Then, the inner diameter D of the master and the amount of light received by the light receiving element 38 are measured in advance. Then, a reference table showing the relationship between the measured value of the inner diameter D of the master and the amount of light received by the light receiving element 38 and the true value of the inner diameter D of the master are stored in the storage unit 61. In the created reference table, the measured value of the inner diameter D of each master and the amount of light received by the light receiving element 38 corresponding to the measured value are expressed as a pair of data using, for example, a two-dimensional array.
When the reference table is created, the relationship between the amount of light received by the light receiving element 38 and the measured value of the inner diameter corresponding to the amount of light is extrapolated using a method such as the least square method or spline interpolation, and the amount of received light is zero. The value about the inner diameter D of the master of the DUT 10 is determined. Then, the convergence value is stored in the storage unit 61 in association with the reference table as the true value of the inner diameter D of the master of the DUT 10. Note that the true value of the inner diameter D of the master of the object to be measured 10 may be obtained using another method, for example, a contact type dimension measuring device.

  When measuring the device under test 10, the inner diameter measuring device 1 measures the amount of light received by the light receiving element 38 together with the inner diameter D of the device under test 10. Then, the measurement result is compared with the measured value of the inner diameter of the master recorded in the reference table. Based on the comparison result, the inner diameter measuring device 1 obtains a measured value of the inner diameter D of the object to be measured 10 when there is no scattering on the inner surface S1, that is, a true value of the inner diameter D.

FIG. 6 shows an operation flowchart of the inner diameter measuring apparatus 1 when measuring the inner diameter D of the DUT 10.
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 second interferometer 4 becomes 0 is determined ( Step S101). Therefore, the position where the object to be measured 10 is not installed in the first interferometer 3 of the inner diameter measuring device 1 and the interference fringe is detected by the second interferometer 4 is obtained. At this time, since there is no light beam reflected by the inner surface of the DUT 10, all the light beams emitted from the first interferometer 3 are B2. Therefore, in the second interferometer 4, 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. When the interference signal is maximized. Therefore, the controller 66 of the controller 6 drives the piezo fine movement stage 46 through the piezo controller 51 to move the movable mirror 44. Then, the peak position measurement unit 63 of the controller 6 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. At that time, the peak position measurement unit 63 may obtain a time average value or a moving average value for the output signal from the detector 5 at each measurement point, and use it as the output signal at that measurement point. Then, the maximum value of the output signal value, that is, the maximum value of the interference signal is obtained. The peak position measurement unit 63 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 61 of the controller 6 as a position P1 where L1 = L2. Remember.

  Next, the DUT 10 is installed on the first interferometer 3 of the inner diameter measuring device 1. At this time, as described above, the white interference fringes are observed only at a position where the inner diameter D of the DUT 10 and (L2−L1) are substantially equal. Therefore, the control unit 66 of the controller 6 drives the coarse movement stage 47 through the stage controller 52 to retract the movable mirror 44 of the second interferometer 4 by a distance substantially equal to the inner diameter D of the object to be measured 10. Then, similarly to the above, the control unit 66 of the controller 6 drives the piezo fine movement stage 46 through the piezo controller 51 and moves the movable mirror 44 to increase or decrease the amount of light detected by the detector 5 at a plurality of measurement points. Examine. At that time, the controller 66 of the controller 6 obtains a time average value or a moving average value for the output signal from the detector 5 at each measurement point, and sets it as the output signal at that measurement point (step S102). Then, the peak position measurement unit 63 of the controller 6 obtains the maximum value of the output signal value, that is, the maximum value of the interference signal (step S103). The position P2 of the movable mirror 44 when the output signal becomes maximum is received from the position measurement interferometer 49 (step S104). Then, the dimension measuring unit 64 of the controller 6 reads the position P1 of the movable mirror 44 when L1 = L2 from the storage unit, calculates the value of P2-P1, and obtains the measured value of the inner diameter D of the DUT 10. (Step S105). Moreover, the controller 6 acquires the value of the light quantity received by the light receiving element 38 at this time through the communication unit 62 (step S106).

  Here, the operation of the controller 6 when detecting the position where the interference signal has the maximum value will be described. As described above, in actual measurement, noise is added due to the influence of air turbulence, mechanical vibration of the measurement system, and the amount of light detected by the detector 5 varies with time. Therefore, in this embodiment, the measurement signal acquired while moving the movable mirror 44 within the range in which the interference signal is observed is acquired a plurality of times, and the time average of these is obtained to obtain the interference signal. Since the noise component becomes almost zero by averaging over time, the position where the interference signal is maximized can be accurately detected by obtaining the interference signal as described above.

Next, the controller 6 determines the true value of the inner diameter D by correcting the obtained measurement result in consideration of the surface roughness of the inner surfaces S1 and S2 of the DUT 10.
For this purpose, the dimension correction unit 65 of the controller 6 refers to the reference table to obtain a measured value of the inner diameter D of the master corresponding to the amount of light received by the light receiving element 38 (step S107). At this time, if there is no data corresponding to the value of the received light amount in the reference table, the measured value for the light amount close to the received light amount is interpolated using linear interpolation, spline interpolation, etc. The measured value of the corresponding inner diameter D of the master is obtained.
Next, the dimension correction unit 65 obtains a difference between the above measured value and the measured value of the inner diameter D of the master obtained from the reference table as a correction value (step S108). Finally, the dimension correction unit 65 adds the obtained correction value to the true value of the inner diameter D of the master stored in association with the reference table to obtain the true value of the inner diameter D of the device under test 10 (step S109).

  The measurement value correction method by the dimension correction unit 65 is not limited to the above. For example, you may correct | amend by the method demonstrated below. In this alternative method, instead of recording the measured value of the inner diameter D of the master as a reference table, the correction amount for the amount of scattered light is stored. The dimension correction unit 65 obtains a correction amount by referring to a reference table from the amount of scattered light received by the light receiving element 38 when measuring the DUT 10. Then, the dimension correction unit 65 obtains the true value of the inner diameter D by adding the obtained correction amount to the measured value of the inner diameter D of the DUT 10.

  Further, in the first interferometer 3, when the position of the beam splitter 33 does not exactly coincide with the center of the inner diameter of the device under test 10, the light beam B 1 is shifted from the diameter of the inner diameter of the device under test 10. The measured value is not accurate. In order to solve the problem, the measurement of the inner diameter is repeated by shifting the positional relationship between the beam splitter 33 and the DUT 10 in the direction perpendicular to the light beam B1 within the cylindrical surface of the DUT 10. Then, the value at which the obtained measurement value is maximum is taken as the inner diameter of the DUT 10.

  Therefore, once the controller 6 obtains the measured value of the inner diameter by the above procedure, it stores it in the storage unit 61. Next, the controller 6 transmits a control signal to the stage controller 37 of the first interferometer 3 to drive the XYZ stage 36, and the measured object 10 is changed to the light beam B1 by a predetermined amount (for example, 0.1 μm). It is moved in a direction perpendicular to the direction. Then, the inner diameter is measured again to obtain a measured value. The obtained measurement value is compared with the measurement value stored in the storage unit 61 of the controller 6. If the newly obtained measurement value is larger than the stored measurement value, the measurement value stored in the storage unit 61 is updated with the newly obtained measurement value. Thereafter, the DUT 10 is moved again in the same direction, and the measurement of the inner diameter is repeated. And when the measured value memorize | stored in the memory | storage part 61 becomes more than the newly measured value, let the measured value memorize | stored in the memory | storage part 61 be the internal diameter D of the to-be-measured object 10. FIG.

On the other hand, when the measured value of the inner diameter measured first is equal to or larger than the measured value measured next, the controller 6 moves the DUT 10 in the direction opposite to the direction in which the measured object 10 is first moved. Then, the measurement is repeated in the same manner as described above, and when the measured value stored in the storage unit 61 becomes equal to or greater than the newly measured value, the measured value stored in the storage unit 61 is used as the measured object 10. The inner diameter D of
In this way, by searching for the maximum measured value of the inner diameter D while changing the positional relationship between the object to be measured 10 and the beam splitter 33, the inner diameter measuring apparatus 1 accurately sets the beam splitter 33 to the center of the object to be measured 10. Since the inner diameter measurement result in the state of being placed in the position can be obtained, the inner diameter of the DUT 10 can be measured with high accuracy. Note that once the beam splitter 33 is positioned at the center of the device under test 10, in the subsequent measurement, the positioning procedure of the beam splitter 33 can be omitted unless the device under test 10 is replaced.

  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. And the value of (P2-P3) / 2 is calculated, and the value may be used as the measured value of the inner diameter D of the DUT 10. 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 measured value of the inner diameter of the DUT 10 is obtained based on the difference between the position P2 and the position P3, the detector 5 can be obtained more than when the measured value of the inner diameter is obtained based on the difference between the reference position P1 and the position P2. Since the change in the output signal with respect to the change in the amount of received light can be increased, the position of the movable mirror 44 where the interference signal becomes the maximum value can be specified more accurately.

  As described above, the inner diameter measuring apparatus 1 to which the present invention is applied measures the amount of light scattered on the inner surface S1 of the measurement object 10 reflected by the measurement light when measuring the inner diameter D of the measurement object 10. To do. Then, a correction value is obtained from a reference table representing the relationship between the amount of scattered light, the measured value of the inner diameter D of the master of the object to be measured 10 and the surface roughness, and the measured value of the inner diameter D of the object to be measured 10 is corrected. By doing so, the true value of the inner diameter D of the DUT 10 is obtained. Therefore, the inner diameter D can be measured with high accuracy regardless of the surface roughness of the inner surface S1 of the DUT 10.

  In addition, this invention is not limited to said embodiment. For example, the device under test is not limited to a cylindrical one. The measuring apparatus of the above embodiment can be applied as it is when measuring the distance between two opposing surfaces of an object to be measured. In the measurement apparatus of the above embodiment, the second interferometer may be a Fizeau interferometer.

The present invention can also be applied to a configuration in which only one Michelson interferometer is used as in the measurement apparatus described in Patent Document 1.
FIG. 7 shows a schematic configuration diagram of a configuration of the dimension measuring apparatus 11 that uses only one Michelson interferometer. In this configuration, the measurement light emitted from the white light source 12 is converted into a first light beam directed to the object to be measured 10 ′ by the beam splitter 13 and a second light beam directed to the movable mirror 14 movable along the optical path. To divide. Then, the first light beam reflected by the object to be measured 10 ′ and the second light reflected by the moving mirror 14 are converted into one light beam again by the beam splitter 13, and the interference signal is detected by the detector 15. . The signal output from the detector 15 is transmitted to the controller 16. Then, the controller 16 obtains the position where the interference signal has a peak, and obtains the position of the movable mirror 14 where the optical path difference between the first light flux and the second light flux is zero. Then, by calculating the difference between the reference position of the movable mirror 14 predetermined in relation to the measured object 10 ′ and the obtained position of the movable mirror 14, the dimension of the measured object 10 ′ (for example, the surface Height). Further, a light receiving element 17 is installed in the vicinity of the beam splitter 13. The light receiving element 17 is disposed outside the first and second light beams, and is disposed so that the light receiving surface thereof faces the object to be measured 10 ′. Then, the measurement light receives the light scattered on the surface of the object to be measured 10 ′, and transmits a signal corresponding to the received light amount to the controller 16.

  The controller 16 has the same configuration as the controller 6 in the above embodiment. Then, the true value of the dimension of the DUT 10 ′ is estimated by the same procedure as in the above embodiment. That is, a plurality of masters of the object to be measured 10 ′ whose surface roughness on which the measurement light from the white light source 12 is reflected are prepared in advance, and the measurement values of the measurement target dimensions of the masters and the light receiving element 38 are used. A reference table representing the relationship with the amount of scattered light received and the true value of the master dimensions are stored. In actual measurement, the controller 16 measures the amount of light scattered on the surface of the measurement target 10 ′ together with the measurement value of the measurement target dimension of the measurement target 10 ′. Then, a measurement value of the measurement target dimension of the master corresponding to the amount of the scattered light is obtained. Finally, the controller 16 obtains a difference between the measured value of the measurement target dimension of the object to be measured 10 ′ and the measured dimension value of the master from the reference table as a correction value, and stores it in association with the reference table. Is added to the true value of the dimension, the true value of the measurement target dimension of the object to be measured 10 'is obtained.

Furthermore, in the embodiment using two interferometers, the white light source arranged on the first interferometer 3 side and the detector arranged on the second 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 second interferometer 4 side, and these light beams are sent to the first interferometer 3 side through the optical fiber. In the first interferometer 3, the received two light beams are further divided into a light beam reflected by the inner surfaces S 1 and S 2 of the object to be measured 10 and two light beams traveling straight through the beam splitter 33, and one of them. The white interference fringes are observed by detecting with a detector. Also in this case, the measured value of the inner diameter D of the DUT 10 can be obtained by measuring the optical path difference generated on the second 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 block diagram of the 1st interferometer which comprises an internal diameter measuring apparatus. It is a schematic block diagram of the 2nd interferometer which comprises an internal diameter measuring apparatus. It is a functional block diagram of the controller of an internal diameter measuring device. It is a graph which shows the relationship between the light quantity of the light scattered on the surface of the to-be-measured object, and the dimension measurement value of the to-be-measured object. It is an operation | movement flowchart of an internal diameter measuring apparatus. It is a schematic block diagram of the dimension measuring apparatus by other embodiment to which this invention is applied.

Explanation of symbols

1 Inner Diameter Measuring Device (Dimension Measuring Device)
DESCRIPTION OF SYMBOLS 11 Size measuring apparatus 10, 10 'Measured object 2,12 White light source 3,4 Interferometer 5,15 Detector 6,16 Controller 31,41 Collimator lens 32,34 Wedge prism 33,42,13 Beam splitter 35 Condensing Lens 36 XYZ stage 37 Stage controller 38, 17 Light receiving element 43 Reference mirror 44, 14 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 61 Storage section 62 Communication unit 63 Peak position measuring unit 64 Dimension measuring unit 65 Dimension correcting unit 66 Control unit 7, 8 Optical fiber

Claims (7)

A dimension measuring device for measuring a dimension of an 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 A first interferometer that causes a first optical path difference corresponding to a measurement target dimension of the object to be measured to emit the first light flux and the second light flux in accordance with one light flux;
A light receiving element provided in the first interferometer for detecting light scattered by the object to be measured;
A second interferometer having a reference mirror having a fixed position and a movable mirror movable along the optical path, wherein the light beam emitted from the first interferometer is directed to the reference mirror. A second interferometer for branching into a light beam and a fourth light beam directed to the movable mirror to produce 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 for obtaining a measurement target dimension of the object to be measured,
A peak position measurement unit for measuring the position of the movable mirror corresponding to the maximum value of the interference signal;
From the position of the movable mirror measured by the peak position measurement unit, by calculating the second optical path difference, a dimension measurement unit for obtaining a measurement value of the measurement target dimension of the object to be measured;
A dimension correction unit for obtaining a true value of the measurement target dimension by correcting the measurement value obtained by the dimension measurement unit based on the amount of scattered light received by the light receiving element;
A controller having
A dimension measuring apparatus comprising: A dimension measuring device for measuring a dimension of an object to be measured,
A white light source,
A first 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 reference mirror; A first interferometer for branching into a second light beam directed toward the movable mirror and causing 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 first interferometer 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 divided into the measured light. A second optical path difference corresponding to the measurement object size of the object to be measured is generated between the fourth light flux and the fourth light flux, and the third light flux and the fourth light flux are combined into one light flux. A second interferometer that emits together,
A light receiving element that is provided in the second interferometer and detects light scattered by the object to be measured;
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 for obtaining a measurement target dimension of the object to be measured,
A peak position measurement unit for measuring the position of the movable mirror corresponding to the maximum value of the interference signal;
From the position of the movable mirror measured by the peak position measurement unit, by calculating the first optical path difference, a dimension measurement unit for obtaining a measurement value of the measurement target dimension of the object to be measured;
A dimension correction unit for obtaining a true value of the measurement target dimension by correcting the measurement value obtained by the dimension measurement unit based on the amount of scattered light received by the light receiving element;
A controller having
A dimension measuring apparatus comprising: A dimension measuring device for measuring a dimension of an object to be measured,
A white light source,
A first interferometer having a movable mirror movable along an optical path, wherein the light emitted from the white light source is converted into a first light beam directed toward the object to be measured and a second directed toward the movable mirror. An interferometer that branches into a light beam and reflects the first light beam by the object to be measured to generate an optical path difference between the first light beam and the second light beam;
A light receiving element that is provided in the interferometer and detects light scattered by the object to be measured;
An interference signal generated when the first light flux and the second light flux emitted from the interferometer are received, and an optical path length for the first light flux is substantially equal to an optical path length for the second light flux. A detector for detecting and outputting a signal corresponding to the interference signal;
A controller for obtaining a measurement target dimension of the object to be measured,
A peak position measurement unit for measuring the position of the movable mirror corresponding to the maximum value of the interference signal;
A dimension measuring unit that calculates a measurement value of a measurement target dimension of the object to be measured by calculating a difference between a position of the moving mirror measured by the peak position measuring unit and a predetermined reference position of the moving mirror. When,
A dimension correction unit for obtaining a true value of the measurement target dimension by correcting the measurement value obtained by the dimension measurement unit based on the amount of scattered light received by the light receiving element;
A controller having
A dimension measuring apparatus comprising:   The said dimension correction | amendment part correct | amends so that the true value of the said measuring object dimension may become small with respect to the said measured value, so that there are many light quantities of the said scattered light, The dimension as described in any one of Claims 1-3 measuring device. The controller uses a reference measurement object as the measurement object, the true value of the measurement target dimension of the reference measurement object, and the rough surface of the reference measurement object reflected by the first light flux. A storage unit that stores a reference table that represents the relationship between the amount of scattered light measured by changing the thickness and the value of the measurement target dimension of the reference measurement object;
The dimension correction unit obtains a reference value of the measurement target dimension of the reference measurement object corresponding to the amount of scattered light received by the light receiving element from the reference table, and the measurement value obtained by the dimension measurement unit 2. A difference between the reference value and the reference value is calculated, and a value obtained by adding the difference to a true value of the measurement target dimension of the reference measurement object is defined as a true value of the measurement target dimension of the measurement object. The dimension measuring apparatus as described in any one of -3. The controller further includes a storage unit that stores a reference table representing a relationship between the amount of the scattered light and a correction amount for the measurement value;
The dimension correction unit obtains the correction amount corresponding to the amount of the scattered light from the reference table, and measures the measured value by adding the correction amount to the measurement value obtained by the dimension measurement unit. The dimension measuring apparatus according to any one of claims 1 to 3, wherein the target dimension is a true value. The light emitted from the white light source is branched into a first light beam and a second light beam that are directed to the object to be measured, and the first light beam is reflected by the object to be measured and is between the second light beam and the second light beam. A first interferometer that generates a first optical path difference corresponding to a measurement target dimension of the object to be measured, and emits the first light flux and the second light flux according to one light flux; A second interferometer having a light receiving element for detecting light scattered by the object to be measured, a reference mirror having a fixed position, and a movable mirror movable along the optical path. Then, the light beam emitted from the first interferometer is branched into a third light beam directed to the reference mirror and a fourth light beam directed to the movable mirror, and the third light beam and the fourth light beam A second interferometer that generates a second optical path difference between the first light path, the third light flux, and the fourth light flux, and receives the first optical path difference and the first light path difference. Of the optical path difference detecting an interference signal which occurs when approximately equal to a dimension measuring method of an object to be measured in the measurement system and a detector for outputting a signal corresponding to the interference signal,
Measuring the position of the movable mirror corresponding to the maximum value of the interference signal;
Calculating a measurement value of a measurement target dimension of the object to be measured by calculating a difference between a position of the movable mirror measured by the peak position measurement unit and a predetermined reference position of the movable mirror;
Correcting the measurement value obtained by the dimension measurement unit based on the amount of scattered light received by the light receiving element, thereby obtaining a true value of the measurement target dimension;
A dimension measuring method characterized by comprising:

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