JP2015102339A - Surface shape measuring apparatus, and machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the surface shape of a measurement object with a laser displacement sensor more accurately than in a conventional way.SOLUTION: In s surface shape measuring apparatus 40A, a data processor 52 subjects to data processing of the surface shape data of an object measured with a laser displacement sensor in a measuring head 42. More specifically, the data processor 52 figures out, by subjecting the surface shape data to moving average processing, the moving average of each of measurement points along the scanning direction of laser beams and, at the same time, calculates the standard deviations of displacement data used for calculating the moving averages for each of the measurement points where the moving average was figured out. The data processor 52 determines whether or not each of the calculated standard deviations surpasses a threshold, and specifies as singular points the measurement points where the standard deviation surpasses the threshold. The data processor 52 corrects the data of the moving averages on the basis of the information on the singular points thereby acquired.

Description

  The present invention relates to a surface shape measuring device that measures a surface shape using a laser displacement sensor and a machine tool including the surface shape measuring device.

  The laser displacement sensor usually measures the distance to the measurement object using a triangulation method. The two-dimensional shape of the surface of the measurement object is obtained by scanning the irradiation position of the laser beam on the surface of the measurement object. It is known that the two-dimensional shape data measured by the laser displacement sensor includes noise due to random irregularities on the surface.

  In order to remove such noise, for example, a measurement apparatus described in Japanese Patent Application Laid-Open No. 2004-12430 (Patent Document 1) irradiates a laser beam along a predetermined path in a predetermined region including a measurement target point. Then, an average value of the displacement amounts measured at a plurality of locations on the predetermined path is calculated, and the average value is set as the displacement amount of the measurement target point.

JP 2004-12430 A

  Even when the surface shape of a block gauge (which is of poor grade but its surface roughness is within ± 0.2μm), which is considered to have a very flat surface, is measured with a laser displacement sensor, the measurement data is about ± 20μm. Of random noise. However, with this level of noise, the noise can be reduced to a level that does not cause a problem in practice by calculating the moving average value of the measurement data as in the above-mentioned patent document.

  However, the measurement data obtained by the laser displacement sensor often includes impulsive noise having a size of about 100 μm. Such impulse noise is detected even when the surface shape of the block gauge is measured by a laser displacement sensor. Impulsive noise cannot be removed by simply averaging the measurement data, so that it is misrecognized as a protrusion or depression on the surface.

  The present invention has been made in consideration of the above-mentioned problems, and its main object is to provide a surface shape measuring apparatus capable of measuring the surface shape of a measurement object with higher accuracy than before by using a laser displacement sensor. Is to provide.

  In one aspect, the present invention is a surface shape measuring device, and includes a displacement sensor and a data processing unit. The displacement sensor irradiates the surface of the measurement object with laser light, and measures the displacement in the height direction of the surface of the measurement object at the irradiation position of the laser light based on the reflected light of the laser light. The data processing unit performs data processing on the surface shape data of the measurement object. The above surface shape data is the displacement data in the height direction at each measurement point along the scanning direction of the laser beam, which is obtained when the relative positional relationship between the displacement sensor and the measurement object changes continuously. is there. The data processing unit includes a moving average processing unit, an index value calculation unit, a singularity determination unit, and a data correction unit. The moving average processing unit obtains a moving average value for each of at least some measurement points along the scanning direction by performing a moving average process on the surface shape data using a predetermined first moving average section. The index value calculation unit calculates an index value indicating the degree of variation of the displacement data used for calculating the moving average value for each measurement point for which the moving average value is obtained. The singular point determination unit determines whether or not each calculated index value exceeds a threshold value, and specifies a measurement point whose index value exceeds the threshold value as a singular point. The data correction unit corrects the data of the moving average value obtained by the moving average processing unit based on the determination result of the singular point determination unit.

  According to the above configuration, when performing the moving average processing of the surface shape data, the index value (for example, standard deviation) indicating the degree of variation of the displacement data used for calculating each moving average value is calculated and calculated. A measurement point whose index value exceeds the threshold is specified as a singular point. Since the moving average value data (that is, the surface shape data after the moving average process) is corrected based on the information on the singular point, the influence of noise is suppressed more accurately than in the past, and the measurement object is accurately measured. The surface shape can be measured.

  Here, within the range of the beam diameter of the laser beam irradiated on the surface of the measurement object, the displacement data changes exceeding the threshold value, so the length of the first moving average section is measured. It is desirable to set the value to be substantially equal to the beam diameter of the laser beam irradiated on the surface of the object.

  According to a preferred embodiment, the data correction unit corrects the data of the moving average value obtained by the moving average processing unit by removing the moving average value at each singular point.

  Preferably, the threshold value is equal to an average value of at least a part of the plurality of index values calculated by the index value calculation unit. Alternatively, the threshold value is equal to a value in a predetermined order when at least a part of the plurality of index values calculated by the index value calculation unit is arranged in order of size.

  According to another preferred embodiment, the data processing unit further determines whether or not the surface shape of the measurement object has changed near each singular point specified by the singular point determination unit, and the surface shape Includes a shape change determining unit that identifies a singular point where the change is a shape change point. In this case, the data correction unit corrects the data of the moving average value obtained by the moving average processing unit based on the determination results of the singular point determination unit and the shape change determination unit.

  According to the above configuration, the case where the index value exceeds the threshold value due to the change in the surface shape can be distinguished from the case where the index value exceeds the threshold value due to noise, so the surface shape can be measured more accurately. Can do.

  In the other embodiment described above, the data correction unit uses the second moving average section that is narrower than the first moving average section at each shape change point specified by the shape change determination unit to generate a new moving average. Calculate the value. In this case, the data correction unit removes the moving average value at each singular point and adds the above-described new moving average value calculated at each shape change point, thereby moving the moving average value obtained by the moving average processing unit. The data may be modified.

  In the other embodiment described above, the data correction unit removes the moving average value at each singular point and adds the surface shape data at each shape change point to thereby calculate the moving average value obtained by the moving average processing unit. Data may be corrected.

  This invention is a machine tool provided with said surface shape measuring apparatus in another situation.

  According to the present invention, it is possible to provide a surface shape measuring apparatus capable of measuring the surface shape of a measurement object with higher accuracy than before using a laser displacement sensor.

1 is a perspective view schematically showing a configuration of a machine tool 10 provided with a surface shape measuring device 40A according to Embodiment 1. FIG. It is a block diagram which shows the functional structure of the surface shape measuring apparatus 40A of FIG. 4 is a diagram for explaining the principle of a laser displacement sensor provided in a measurement head 42. FIG. It is a figure which shows typically an example of the data detected by the light receiving element 76 of FIG. It is a figure which shows an example of the surface shape data detected by the laser displacement sensor provided in the measurement head. It is a flowchart which shows the procedure of the data processing by the data processing part 52 of FIG. It is a figure which shows the moving average data after correction | amendment by the data correction part 60 of FIG. It is a block diagram which shows the functional structure of the surface shape measuring apparatus 40B by Embodiment 2. FIG. It is a figure which shows typically an example of the calculation result of surface shape data in the presence of impulse noise, its moving average data, and standard deviation. It is a figure which shows typically an example of the calculation result of the surface shape data in case a level | step difference exists in the surface of a measuring object, its moving average data, and a standard deviation. 10 is a flowchart showing a procedure for correcting moving average data in the case of the second embodiment. In the surface shape data shown in FIG. 10, it is a figure which shows an example of the moving average data at the time of narrowing a moving average area. It is a flowchart which shows the other example of the procedure which determines whether the surface shape is changing.

  Hereinafter, each embodiment will be described in detail with reference to the drawings. In each of the following embodiments, the case where the machine tool is a vertical machining center is described, but the machine tool may be of other types such as a horizontal machining center or a lathe. In the following description, the same or corresponding parts are denoted by the same reference symbols, and the description thereof may not be repeated.

<Embodiment 1>
[Configuration of machine tool and surface shape measuring device]
FIG. 1 is a perspective view schematically showing a configuration of a machine tool 10 provided with a surface shape measuring apparatus 40A according to the first embodiment. FIG. 1 shows an NC (Numerical Control) device 24 and an ATC (Automatic Tool Changer) 28 in addition to the machine tool 10 and the surface shape measuring device 40A.

  Referring to FIG. 1, a machine tool 10 includes a bed 12, a column 14 installed on the bed 12, a spindle head 20 having a spindle 22, and a saddle 16 having a table 18.

  The spindle head 20 is supported on the front surface of the column 14 and is movable in the vertical direction (Z-axis direction). A tool (not shown) or a measurement head 42 is detachably attached to the tip of the main shaft 22. The main shaft 22 is supported by the main shaft head 20 so that its central axis (CL in FIG. 2) is parallel to the Z axis and is rotatable about the central axis.

  The saddle 16 is disposed on the bed 12 and is movable in the front-rear horizontal direction (Y-axis direction). A table 18 is disposed on the saddle 16. The table 18 is movable in the left and right horizontal direction (X-axis direction). The workpiece 2 is placed on the table 18.

  Three orthogonal axes are constituted by the X, Y, and Z axes orthogonal to each other. The machine tool 10 is a machining center that performs three-axis control in which the measuring head 42 and the workpiece 2 are linearly moved relatively in the three orthogonal directions of the X, Y, and Z axes. Unlike the configuration of FIG. 1, the machine tool 10 may be configured to move the spindle head 20 that supports the measurement head 42 in the X-axis and Y-axis directions with respect to the workpiece 2.

  The NC device 24 controls the overall operation of the machine tool 10 including the above three-axis control. An ATC (automatic tool changer) 28 automatically changes the tool and the measuring head 42 with respect to the spindle 22. The ATC 28 is controlled by the NC device 24.

  FIG. 2 is a block diagram showing a functional configuration of the surface shape measuring apparatus 40A of FIG. 2 also shows the machine tool 10, the NC device 24, the ATC 28, and the Z-axis feed mechanism 34, the Y-axis feed mechanism 32, and the X-axis feed mechanism 30 provided in the machine tool 10.

  Referring to FIG. 2, the Z-axis feed mechanism 34 drives the spindle head 20 supported by the column 14 to move in the Z-axis direction. The Y-axis feed mechanism 32 drives the saddle 16 disposed on the bed 12 to move in the Y-axis direction. The X-axis feed mechanism 30 drives the table 18 that is placed on the saddle 16 and supports the workpiece 2 to move in the X-axis direction. A PLC (Programmable Logic Controller) 26 provided in the NC device 24 controls the Z-axis feed mechanism 34, the Y-axis feed mechanism 32, and the X-axis feed mechanism 30, respectively.

  The surface shape measuring device 40 </ b> A includes a measuring head 42 that is detachably attached to the main shaft 22 of the machine tool 10, and a measurement control unit 44. The measurement head 42 includes a laser displacement sensor. The laser displacement sensor irradiates the surface of the workpiece 2 with the laser beam L, and measures the displacement in the height direction (Z-axis direction) of the workpiece 2 at the irradiation position of the laser beam L based on the reflected light of the laser beam L. To do.

  The measurement control unit 44 is configured based on a computer, and includes a processor 46, a memory 48, an input / output interface (not shown) with the NC device 24, and a communication device 50 that performs wireless communication with the measurement head 42. Etc. The measurement control unit 44 continuously changes the relative positional relationship between the measurement head 42 and the workpiece 2 by cooperating with the PLC 26 of the NC device 24, and a plurality of laser beams L obtained as a result of the measurement control unit 44 in the scanning direction. Displacement data in the height direction (Z-axis direction) at the measurement point is acquired as surface shape data of the workpiece 2. The specific procedure is as follows.

  First, based on the control from the processor 46 of the measurement control unit 44, the PLC 26 performs either one of the X-axis feed mechanism 30 and the Y-axis feed mechanism 32, or the X-axis feed mechanism 30, the Y-axis feed mechanism 32, and the Z-axis feed mechanism 32. By driving at least two axes of the axis feed mechanism 34, the relative positional relationship between the measuring head 42 and the workpiece 2 is continuously changed.

  The PLC 26 outputs a trigger signal to the communication device 50 at a predetermined cycle along with the driving of the feeding mechanism. Upon receiving the trigger signal, the communication device 50 transmits a measurement command f to the measurement head 42, and the measurement head 42 distances the measurement head 42 to the workpiece 2 according to the measurement command f (ie, displacement of the surface of the workpiece 2). Measure. Data F of the measured distance D is transmitted from the measurement head 42 to the processor 46 of the measurement control unit 44 via the communication device 50.

  The PLC 26 further acquires positional information of the X-axis feed mechanism 30, the Y-axis feed mechanism 32, and the Z-axis feed mechanism 34 in accordance with the timing of distance measurement by the measurement head 42, so that the measurement head 42 Detect position data. The PLC 26 transmits the detected position data of the measurement head 42 to the processor 46 of the measurement control unit 44.

  Based on the position data of the measurement head 42 acquired from the PLC 26 and the data F of the distance D acquired from the measurement head 42, the processor 46 determines the height direction (Z at each measurement point along the scanning direction of the laser light L). The displacement data in the axial direction is stored in the memory 48 as the surface shape data 62.

  The measurement control unit 44 further functions as a data processing unit 52 that performs data processing for removing noise included in the surface shape data 62 described above. The function of the data processing unit 52 is realized by the data processing program being executed by the processor 46. As shown in FIG. 2, the data processing unit 52 includes a moving average processing unit 54, a standard deviation calculation unit 56, a singular point determination unit 58, and a data correction unit 60. The function of each of these elements will be described later with reference to FIGS.

[Principle of laser displacement sensor and measurement example of surface shape data]
FIG. 3 is a diagram for explaining the principle of the laser displacement sensor provided in the measurement head 42. The laser displacement sensor 70 detects the distance to the measurement object 80 (80A, 80B, 80C) by so-called triangulation.

  Referring to FIG. 3, a laser displacement sensor 70 includes a laser element 72 for irradiating a measurement target with laser light, and a lens 74 that collects scattered light from the measurement target 80 (80A, 80B, 80C). And a light receiving element 76 for detecting the positions DP1, DP2 and DP3 of the condensed light spot. The distance from the laser displacement sensor 70 to the measurement object 80 can be calculated based on the detected light spot positions DP1, DP2, DP3.

  FIG. 4 is a diagram schematically showing an example of data detected by the light receiving element 76 of FIG. Referring to FIGS. 3 and 4, profiles of detection data 82A, 82B, and 82C shown in FIG. 4 are obtained corresponding to positions 80A, 80B, and 80C of measurement object 80 shown in FIG. The positions DP1, DP2, DP3 of the light spots collected by the lens 74 are given as the peak positions or the positions of the center of gravity of the detection data 82A, 82B, 82C, respectively.

  Here, the problem is that the peak position or barycentric position of the detection data 82A, 82B, 82C changes randomly due to random irregularities on the surface of the measurement object. As a result, the distance data from the laser displacement sensor 70 to the measurement object 80 (that is, the displacement of the measurement object 80 in the height direction) changes randomly according to the irradiation position of the laser light.

  FIG. 5 is a diagram illustrating an example of surface shape data detected by a laser displacement sensor provided in the measurement head 42. The upper graph in FIG. 5 represents an example of the surface shape data, and the lower graph in FIG. 5 is obtained by applying a moving average to the surface shape data. The moving average section is set to 200 μm.

  As shown in FIG. 5, overall noise of about ± 20 μm (much larger than the actual unevenness of the surface of the object to be measured) is observed, and in some places (around the scanning position of 19 mm and 25.5 mm) A larger impulse noise is observed. Such impulsive noise cannot be removed even if moving average is performed, so that it is erroneously recognized that there is a protrusion or a depression.

  The surface shape measuring apparatus 40A according to the first embodiment performs data processing for removing the impulse-like noise in consideration of the above problems.

[Procedure for data processing (noise removal)]
FIG. 6 is a flowchart showing a data processing procedure by the data processing unit 52 of FIG. Hereinafter, the function of each element of the data processing unit 52 in FIG. 2 will be described with reference to FIGS. 2 and 6.

  First, the data processing unit 52 reads the surface shape data 62 stored in the memory 48 (step S100). The moving average processing unit 54 of the data processing unit 52 performs a moving average process on the surface shape data 62 using a predetermined moving average section, thereby at least a part of measurement points along the scanning direction of the laser beam. The moving average value is obtained for (step S105).

  Usually, the above-mentioned impulse displacement is observed within the range of the beam diameter (diameter) of the laser beam irradiated on the surface of the measurement object (workpiece 2). It is desirable to set it substantially equal to the beam diameter.

  There are various definitions of the beam diameter of laser light. For example, in the case of a laser beam having a symmetric beam profile as in the TEM00 mode, in a plane orthogonal to the optical axis, 1 / e 2 of the peak value (where e is the base of natural logarithm) ( The beam diameter is defined by the width of the intensity distribution (13.5%). When the beam profile is broken, for example, a circle including 86.5% of the total power of the beam is calculated based on the peak power, and the diameter of this circle is defined as the beam diameter. Therefore, in this specification, a range larger than the diameter of the circle including 50% of the total power and smaller than the diameter of the circle including 95% of the total power is assumed to be substantially equal to the beam diameter.

  Accompanying the calculation of the moving average value, the standard deviation calculating unit 56 of the data processing unit 52 calculates the standard deviation of the displacement data used for calculating the moving average value for each measurement point at which the moving average value is obtained. Calculate (step S110). The standard deviation is used as an index value indicating the degree of variation in the displacement data. Instead of the standard deviation, other statistics such as variance, average absolute deviation, and interquartile range are used. May be.

  Next, the singular point determination unit 58 of the data processing unit 52 determines whether or not the calculated standard deviation exceeds the threshold value TH1 (step S115), and the standard deviation corresponding to a certain measurement point exceeds the threshold value TH1. If it is present (YES in step S115), the measurement point is specified as a singular point (step S120). The determination as to whether or not it is a singular point is executed for each measurement point for which the moving average value is obtained (until NO in step S125).

  The threshold value TH1 used for determining the singularity may be set to an average value of at least a part of the plurality of standard deviations calculated by the standard deviation calculation unit 56. Alternatively, the threshold value TH1 may be set to a value (for example, a median value) in a predetermined order when at least some of the calculated standard deviations are arranged in order of size.

  Next, the data correction unit 60 of the data processing unit 52 uses a plurality of moving average value data (referred to as moving average data) obtained by the moving average processing unit 54 based on the determination result of the singular point determination unit 58. Correct it. Specifically, the moving average data obtained by the moving average processing unit 54 (that is, the surface shape data after the moving average processing) is corrected by removing the moving average value at each singular point from the moving average data.

  FIG. 7 is a diagram showing the moving average data after correction by the data correction unit 60 of FIG. The graph of FIG. 7 shows, in order from the top, surface shape data (raw data), moving average data corrected by the data correction unit 60, and standard deviation values calculated for each measurement point. The threshold value for determining the singularity is set to the median value of the standard deviation calculated corresponding to all the measurement points in FIG. Therefore, the corrected moving average data excludes measurement points whose standard deviation exceeds the median value. The values corresponding to the excluded measurement points can be interpolated by an appropriate method (for example, linear interpolation, n-order interpolation, polynomial interpolation, etc.).

[Effect of Embodiment 1]
According to the surface shape measuring apparatus 40A of the first embodiment, when performing the moving average process of the surface shape data 62, the standard deviation of the displacement data used for calculating each moving average value is calculated, and the calculated standard deviation is calculated. A measurement point that exceeds the threshold is identified as a singular point. Since the surface shape data after the moving average process is corrected based on the information on the singular point, the surface shape can be measured with higher accuracy while suppressing the influence of noise than in the past.

<Embodiment 2>
In the second embodiment, a case where the surface shape of the measurement object (workpiece 2) is changed will be described. Since the standard deviation value corresponding to each measurement point exceeds the threshold even when the surface shape actually changes, it is necessary to distinguish from the case where the standard deviation exceeds the threshold due to impulsive noise. . Hereinafter, specific description will be given with reference to the drawings.

[Configuration of surface shape measuring device]
FIG. 8 is a block diagram showing a functional configuration of the surface shape measuring apparatus 40B according to the second embodiment. Referring to FIG. 8, surface shape measuring apparatus 40B is different from surface shape measuring apparatus 40A in FIG. 2 in that data processing unit 52 further includes a shape change determining unit 64. The shape change determination unit 64 determines whether or not the surface shape of the measurement object has changed in the vicinity of each singular point specified by the singular point determination unit 58, and shapes the singular points whose surface shape has changed. Identifies as a change point. The data correction unit 60 corrects the data of the moving average value obtained by the moving average processing unit 54 based on the determination results of the singular point determination unit 58 and the shape change determination unit 64. Since the other points of FIG. 8 are the same as those of FIG. 2, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Specific example of shape change]
FIG. 9 is a diagram schematically illustrating an example of surface shape data, moving average data, and standard deviation calculation results when there is impulse noise. In FIG. 9, the surface shape data (raw data) 90 measured by the laser displacement sensor is indicated by a solid line, the moving average data 92 is indicated by a broken line, and the standard deviation of the surface shape data used for calculating the moving average value at each measurement point. 94 is indicated by a dotted line. In FIG. 9, the moving average process is performed with the moving average section set to 200 μm.

  As shown in FIG. 9, since there is an impulse-like noise in the vicinity of the scanning position of 400 μm, the standard deviation 94 increases in the vicinity thereof. For example, if the threshold value for determining whether or not it is a singular point is 13 μm, a measurement point between the scanning position 250 μm and 540 μm is determined as a singular point, and moving average data in this section is removed. become.

  FIG. 10 is a diagram schematically illustrating an example of the calculation result of the surface shape data, the moving average data, and the standard deviation when there is a step on the surface of the measurement object. In FIG. 10, as in the case of FIG. 9, the surface shape data (raw data) 90 measured by the laser displacement sensor is indicated by a solid line, the moving average data 92 is indicated by a broken line, and the moving average value at each measurement point is calculated. The standard deviation 94 of the used surface shape data is indicated by a dotted line. The length of the moving average section is 200 μm.

  As shown in FIG. 10, since there is a step near the scanning position of 400 μm, the standard deviation 94 increases in the vicinity thereof. For example, if the threshold value for determining whether or not it is a singular point is 13 μm, a measurement point between the scanning positions 300 μm and 500 μm is determined as a singular point. In the case of the first embodiment, the moving average during this time Value data will be removed. For this reason, the surface shape change (step) is not accurately reflected in the moving average data. In the surface shape measurement apparatus 40B of the second embodiment, the processing content (step S130 in FIG. 6) executed by the data correction unit 60 is changed in consideration of the above-described problems.

[Correction procedure for moving average data]
FIG. 11 is a flowchart showing a procedure for correcting the moving average data in the second embodiment. The processing procedure in FIG. 11 replaces step S130 in FIG. Steps S100 to S125 in FIG. 6 are not changed in the second embodiment. That is, at the time when the processing shown in FIG. 11 is started, the determination as to whether or not each measurement point along the scanning direction is a singular point has been completed.

  Referring to FIGS. 8 and 11, the shape change determination unit 64 of the data processing unit 52 determines whether or not the surface shape has changed in the vicinity of each singular point (step S200).

  There are various methods for determining whether or not the surface shape has actually changed. For example, the shape change determination unit 64 compares the surface shape data measured at both the measurement point in the scanning direction and the measurement point in the scanning direction with respect to the singular point, and the surface shape data changes beyond the threshold value. It is determined that the surface shape has actually changed.

  If the shape change determination unit 64 determines that the surface shape has changed in the vicinity of a certain singular point, the shape change determination unit 64 identifies the singular point as a shape change point (step S205). The determination of whether or not it is a shape change point is executed for each measurement point determined as a singular point in step S120 of FIG. 6 (until NO in step S210).

  Next, the data correction unit 60 of the data processing unit 52 calculates the moving average value again for each shape change point specified in step S205, narrowing the moving average section (step S215). As the moving average section is narrowed, the moving average data comes closer to the surface shape data (raw data).

  Next, the data correction unit 60 removes the moving average value corresponding to each measurement point determined to be a singular point in step S120 in FIG. 6 from the moving average data, and determines each shape change point determined in step S205. The moving average value newly calculated in step S215 with respect to the measurement point is added to the moving average data (step S220). Thus, it is possible to obtain moving average data that more accurately reflects the shape change of the surface of the measurement object (workpiece 2) while suppressing the influence of noise as much as possible.

  In step S220, surface shape data (raw data) can be added to each measurement point determined as a shape change point in step S205. This makes it possible to obtain moving average data that more faithfully reflects the actual shape change of the surface of the measurement object (workpiece 2), but noise near the shape change point remains without being removed. .

  FIG. 12 is a diagram showing an example of moving average data when the moving average section is narrowed in the surface shape data shown in FIG. In FIG. 12, similarly to the case of FIG. 10, the surface shape data (raw data) 90 measured by the laser displacement sensor is indicated by a solid line, and the moving average data 92 is indicated by a broken line. FIG. 12 shows the result when the moving average processing is performed with the moving average section being 100 μm (half the value in the case of FIG. 10).

  Referring to FIGS. 10 and 12, the moving average data 92 of FIG. 12 in which the moving average section is narrower than the moving average data 92 of FIG. It can be seen that the shape data 90 is close to the shape change.

  When the moving average data 92 shown in FIG. 10 is corrected according to the correction procedure of FIG. 11, a section (scanning position 300 μm to 500 μm) where the standard deviation exceeds the threshold (13 μm) in the moving average data 92 of FIG. Each measurement point is identified as a singular point and a shape change point. Then, the moving average data 92 in this section in FIG. 10 is replaced with the moving average data 92 in FIG.

[Surface shape change judgment method]
FIG. 13 is a flowchart illustrating another example of a procedure for determining whether or not the surface shape has changed. The flowchart in FIG. 13 corresponds to steps S200 and S205 in FIG. 11, and shows a procedure for determining whether or not the surface shape has changed using the moving average data and the standard deviation.

  With reference to FIGS. 8 and 13, shape change determination unit 64 executes the following steps for each singular point specified in step S <b> 120 of FIG. 6. First, the shape change determination unit 64 specifies the first measurement point and the second measurement point in the vicinity of the singular point (steps S300 and S305). Here, the first measurement point is a measurement point ahead of the singular point in the scanning direction with a standard deviation equal to or less than a threshold value and closest to the singular point. The second measurement point is the measurement point behind the singular point in the scanning direction, the standard deviation of which is equal to or smaller than the threshold value, and the closest to the singular point.

  Next, the shape change determination unit 64 determines whether or not the difference between the moving average values exceeds the threshold value TH2 between the identified first measurement point and second measurement point (step S310). The threshold value TH2 is determined in consideration of actual machining accuracy. When the absolute value of the difference between the moving average value at the first measurement point and the moving average value at the second measurement point exceeds the threshold value TH2 (YES in step S310), the shape change determination unit 64 The surface shape of the measurement object (workpiece 2) has changed near the point, and it is determined that the singular point is a shape change point (step S315).

[Effect of Embodiment 2]
According to the surface shape measuring apparatus 40B of the second embodiment, the shape change determination unit 64 that determines whether or not the surface shape of the measurement object (workpiece 2) has changed is further provided. The shape change determination unit 64 identifies, as the shape change point, a singular point whose standard deviation exceeds the threshold value because the surface shape has changed among the singular points determined by the singular point determination unit 58, and noise Distinguish from singularities due to The data correction unit 60 removes the moving average value at the singular point caused by noise, but the shape moving point is a value that more accurately reflects the change in the surface shape of the original moving average value (for example, the moving average section). (Removed moving average value). Thus, it is possible to provide the surface shape measuring apparatus 40B that suppresses the influence of noise and further improves the surface shape measurement accuracy.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2 Workpieces, 10 Machine tools, 12 Beds, 14 Columns, 16 Saddles, 18 Tables, 20 Spindle heads, 22 Spindles, 24 NC units, 30 X-axis feed mechanisms, 32 Y-axis feed mechanisms, 34 Z-axis feed mechanisms, 40A , 40B Surface shape measuring device, 42 Measuring head, 44 Measurement control unit, 46 Processor, 48 Memory, 50 Communication device, 52 Data processing unit, 54 Moving average processing unit, 56 Standard deviation calculation unit, 58 Singularity determination unit, 60 Data correction unit, 64 shape change determination unit, 70 laser displacement sensor.

Claims (9)

A displacement sensor that irradiates the surface of the measurement object with laser light, and measures a displacement in the height direction of the surface of the measurement object at the irradiation position of the laser light based on the reflected light of the laser light;
A data processing unit that performs data processing on the surface shape data of the measurement object;
The surface shape data is obtained when the relative positional relationship between the displacement sensor and the measurement object continuously changes, and the displacement in the height direction at each measurement point along the scanning direction of the laser beam. Data,
The data processing unit
A moving average processing unit that obtains a moving average value for each of at least some measurement points along the scanning direction by performing a moving average process on the surface shape data using a predetermined first moving average section; ,
An index value calculation unit that calculates an index value indicating the degree of variation in displacement data used for calculating the moving average value for each measurement point for which the moving average value was obtained;
It is determined whether each of the calculated index values exceeds a threshold, and a singularity determination unit that identifies a measurement point where the index value exceeds the threshold as a singularity;
A surface shape measuring apparatus, comprising: a data correction unit that corrects data of a moving average value obtained by the moving average processing unit based on a determination result of the singular point determination unit.   The surface shape measuring apparatus according to claim 1, wherein a length of the first moving average section is substantially equal to a beam diameter of the laser light irradiated on a surface of the measurement object.   The surface shape measurement apparatus according to claim 1, wherein the data correction unit corrects the data of the moving average value obtained by the moving average processing unit by removing the moving average value at each of the singular points.   The surface shape measuring apparatus according to claim 1, wherein the threshold value is equal to an average value of at least a part of the plurality of index values calculated by the index value calculation unit.   The threshold value is equal to a value in a predetermined order when at least a part of the plurality of index values calculated by the index value calculation unit is arranged in order of size. The surface shape measuring apparatus according to item. The data processing unit further determines whether or not the surface shape of the measurement object has changed in the vicinity of each of the singular points identified by the singular point determination unit, and the surface shape has changed. Including a shape change determination unit that identifies a point as a shape change point;
The data correction unit corrects the data of the moving average value obtained by the moving average processing unit based on the determination results of the singular point determination unit and the shape change determination unit. The surface shape measuring apparatus according to item 1. The data correction unit
At each of the shape change points specified by the shape change determination unit, a new moving average value is calculated by using a second moving average section that is narrower than the first moving average section,
The moving average value obtained by the moving average processing unit is corrected by removing the moving average value at each singular point and adding the new moving average value calculated at each shape change point. The surface shape measuring apparatus according to claim 6, which is configured as follows.   The data correction unit corrects the data of the moving average value obtained by the moving average processing unit by removing the moving average value at each singular point and adding the surface shape data at each shape change point. The surface shape measuring apparatus according to claim 6.   A machine tool comprising the surface shape measuring device according to any one of claims 1 to 8.

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