JP2016166873A - Shape measurement apparatus, processing device and calibration method of shape measurement apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape measurement apparatus capable of easily executing calibration of a fitting position of a displacement gauge, and capable of highly accurately measuring a surface shape of a measurement object.SOLUTION: A shape measurement apparatus scans a measurement object by a detector with three displacement gauges arranged in line, and measures a surface shape of the measurement object. The detector includes: off-set amount calculation means configured to calculate an off-set amount at a fixing position of the three displacement gauges from data obtained by scanning a sample for calibration; and calibration means configured to compensate, with the off-set amount, data obtained by scanning the measurement object by the detector and calibrate positional deviation of the displacement gauges.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a shape measuring device, a processing device, and a calibration method for the shape measuring device.

  There is known a method of obtaining a straight shape of a measurement object by a sequential three-point method using three displacement meters. In order to obtain a straight shape with high accuracy by such a method, it is necessary to calibrate variations in the mounting positions of the three displacement meters.

  Therefore, the three displacement meters and the three discs are arranged opposite to each other, the measured value of the displacement meter at a predetermined rotational position of the disc, and the measured value of the displacement meter at a position rotated 180 degrees from the predetermined rotational position of the disc, Based on the above, a method for calibrating the mutual position of the displacement meter is disclosed (for example, see Patent Document 1).

JP 2010-286430 A

  However, in the method according to Patent Document 1, the installation position, rotation angle, and the like of the disk need to be calibrated with high accuracy. Moreover, in order to adjust the position of the displacement meter based on the obtained positional deviation amount, a very complicated operation may be required. In particular, when performing high-precision measurement by increasing the resolution of shape measurement, it is necessary to calibrate more strictly, and further complicated work may be required.

  The present invention has been made in view of the above, and provides a shape measuring device that can easily calibrate the mounting position of a displacement meter and can measure the surface shape of a measurement object with high accuracy. Objective.

  According to an aspect of the present invention, there is provided a shape measuring apparatus that scans a measurement object with a detector in which three displacement meters are arranged in a row and measures a surface shape of the measurement object, the detector Offset amount calculating means for calculating the offset amount of the mounting position of the three displacement gauges from data obtained by scanning the calibration sample, and the offset obtained by scanning the measurement object by the detector Correction means for correcting by a quantity and calibrating the displacement of the displacement meter.

  According to the embodiment of the present invention, there is provided a shape measuring apparatus that can easily calibrate the mounting position of a displacement meter and can measure the surface shape of a measurement object with high accuracy.

It is a figure which illustrates the processing apparatus in an embodiment. It is a figure which illustrates the composition of the shape measuring device in an embodiment. It is a figure which illustrates the composition of the sensor head in an embodiment. It is a figure for demonstrating the shape measurement in embodiment. It is a figure for demonstrating the mounting position dispersion | variation of a displacement sensor and the unevenness | corrugation of the sample surface for a calibration. It is a figure which illustrates the flowchart of the offset amount calculation process in embodiment. It is a figure which illustrates the gap data of the sample for calibration in an embodiment. It is a figure which illustrates the flowchart of the shape measurement process in embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

(Configuration of processing equipment)
FIG. 1 is a diagram illustrating a configuration of a processing apparatus 200 on which a shape measuring apparatus according to this embodiment is mounted.

  As shown in FIG. 1, the processing device 200 includes a movable table 10, a table guide mechanism 11, a grindstone head 15, a grindstone 16, a guide rail 18, a control device 20, and a display device 40. In the following drawings, the X direction is the moving direction of the movable table 10, the Y direction is the moving direction of the grindstone head 15 orthogonal to the X direction, and the Z direction is the height direction orthogonal to the X and Y directions.

  The movable table 10 is provided so as to be movable in the X direction by a table guide mechanism 11, and an object 12 to be processed and a measurement target is placed thereon. The table guide mechanism 11 moves the movable table 10 in the X direction.

  The grindstone head 15 is provided with a grindstone 16 at the lower end, and is provided on the guide rail 18 so as to be movable in the X direction and movable up and down in the Z direction. The guide rail 18 moves the grindstone head 15 in the X direction and the Z direction. The grindstone 16 has a cylindrical shape and is rotatably provided at the lower end of the grindstone head 15 so that the central axis thereof is parallel to the Y direction. The grindstone 16 moves in the X and Z directions together with the grindstone head 15 and rotates to grind the surface of the object 12.

  The control device 20 controls the positions of the movable table 10 and the grindstone head 15 and rotates the grindstone 16 to control each part of the processing device 200 so as to grind the surface of the object 12.

  The display device 40 is, for example, a liquid crystal display. The display device 40 is controlled by the control device 20, and displays, for example, processing conditions of the object 12.

(Configuration of shape measuring device)
FIG. 2 is a diagram illustrating the configuration of the shape measuring apparatus 100 mounted on the processing apparatus 200. As shown in FIG. 2, the shape measuring apparatus 100 includes a control device 20, a sensor head 30, and a display device 40.

  As described above, the control device 20 controls each part of the processing device 200 so as to grind the surface of the object 12, and based on the measurement values output from the displacement sensors 31a, 31b, and 31c of the sensor head 30. The surface shape of the object 12 is obtained.

  The control device 20 includes a sensor data acquisition unit 21, a gap data calculation unit 23, an offset amount calculation unit 25, a calibration unit 27, and a shape calculation unit 29. The control device 20 includes, for example, a CPU, a ROM, a RAM, and the like, and the functions of each unit are realized by the CPU executing a control program stored in the ROM in cooperation with the RAM.

  The sensor data acquisition unit 21 is an example of an acquisition unit, and acquires sensor data from the displacement sensors 31a, 31b, and 31c provided in the sensor head 30. The gap data calculation unit 23 is an example of a gap calculation unit, and calculates gap data from the sensor data acquired by the sensor data acquisition unit 21. The offset amount calculation unit 25 is an example of an offset amount calculation unit, obtains an average value of gap data obtained using a calibration sample, and uses the obtained average value as an offset amount of the attachment position of the displacement sensors 31a, 31b, 31c. And The calibration unit 27 calibrates the displacement of the displacement sensors 31a, 31b, and 31c by correcting the gap data using the calculated offset amount. The shape calculation unit 29 is an example of a shape calculation unit, and calculates the surface shape of the object 12 based on the gap data calibrated by the calibration unit 27. Processing executed in each unit of the control device 20 will be described later.

  The sensor head 30 is an example of a detector, includes a first displacement sensor 31a, a second displacement sensor 31b, and a third displacement sensor 31c, and is provided at the lower end of the grindstone head 15 of the processing apparatus 200. FIG. 3 is a diagram illustrating the configuration of the sensor head 30 according to the embodiment.

  As shown in FIG. 3, the sensor head 30 includes a first displacement sensor 31a, a second displacement sensor 31b, and a third displacement sensor 31c arranged in a row in the X direction.

  The first displacement sensor 31a, the second displacement sensor 31b, and the third displacement sensor 31c are examples of a displacement meter, for example, a laser displacement meter. The first displacement sensor 31a, the second displacement sensor 31b, and the third displacement sensor 31c are arranged so that the measurement points are arranged in a straight line parallel to the X direction on the surface of the object 12 at equal intervals. Measure the distance between the measuring points on the surface. When the object 12 is placed on the movable table 10 and moves in the X direction, the sensor head 30 moves relative to the object 12, and each displacement sensor 31a, 31b, 31c scans the surface of the object 12 and outputs a measurement value. To do.

  The display device 40 is controlled by the control device 20 and displays, for example, a measurement result of the surface shape obtained by the shape calculation unit 29.

  In the present embodiment, the shape measuring device 100 and the processing device 200 are configured to share the control device 20 and the display device 40. However, the shape measuring device 100 and the processing device 200 each have a control device and a display. A device may be provided. Further, although the movable table 10 is configured to move in the X direction together with the object 12, the sensor head 30 may be configured to move in the X direction with respect to the object 12.

(Basic principle of shape measurement)
Next, a method for obtaining the surface shape of the object 12 in the shape measuring apparatus 100 will be described. FIG. 4 is a diagram for explaining a surface shape measurement method.

  As shown in FIG. 4, the displacement sensors 31a, 31b, and 31c are arranged in a line in the X direction at intervals P, and measure the distances from points a, b, and c on the surface of the object 12, respectively. Assuming that the distances between the displacement sensors 31a, 31b, and 31c obtained by the displacement sensors 31a, 31b, and 31c and the surface of the object 12 are A, B, and C, respectively, from the point b in the Z direction shown in FIG. A distance g (gap) between a line connecting point a and point c is obtained by the following equation (1).

次に、物体１２表面のｂ点における変位ｚの２階微分（ｄ^２ｚ／ｄｘ^２）は、ｂ点の曲率（１／ｒ）であり、図４（Ｂ）に示されるように、ａ点とｂ点とを結ぶ直線の傾き（ｄｚ_ａｂ／ｄｘ）と、ｂ点とｃ点とを結ぶ直線の傾き（ｄｚ_ｂｃ／ｄｘ）とを用いて、以下の式（２）により表される。

Next, the second derivative (d ² z / dx ² ) of the displacement z at the point b on the surface of the object 12 is the curvature (1 / r) of the point b, and as shown in FIG. Using the slope of the straight line connecting the point b and the point b (dz _ab / dx) and the slope of the straight line connecting the point b and the point c (dz _bc / dx), the following equation (2) is used. .

式（２）に、以下の式（３），（４）を代入し、さらに式（１）を用いると、式（５）で表されるように、変位ｚの２階微分である曲率をギャップｇ及びセンサ間の距離Ｐから求められることが分かる。

Substituting the following formulas (3) and (4) into the formula (2) and further using the formula (1), the curvature, which is the second derivative of the displacement z, is expressed as expressed by the formula (5). It can be seen from the gap g and the distance P between the sensors.

センサ間の距離Ｐは予め定められているため、各変位センサ３１ａ，３１ｂ，３１ｃによるセンサデータから式（１）に基づいてギャップｇを求め、式（５）により求められる曲率を積分ピッチで２階積分することで、任意のｘ点における変位ｚを求めることができる。積分ピッチは、例えば走査時におけるＸ方向の各変位センサ３１ａ，３１ｂ，３１ｃのデータ取得間隔等である。

Since the distance P between the sensors is determined in advance, the gap g is obtained from the sensor data by the displacement sensors 31a, 31b, and 31c based on the equation (1), and the curvature obtained by the equation (5) is 2 with an integral pitch. The displacement z at an arbitrary x point can be obtained by the step integration. The integration pitch is, for example, a data acquisition interval of each displacement sensor 31a, 31b, 31c in the X direction during scanning.

  Here, it is very difficult to attach the three displacement sensors 31a, 31b, and 31c to the sensor head 30 by adjusting the height so as to be strictly aligned in a range of several tens of nanometers, for example. Therefore, the displacement sensors 31a, 31b, and 31c have slight variations in the Z direction at the attachment positions to the sensor head 30, as shown in FIG. In FIG. 5, the variation in the attachment position is shown enlarged for the sake of explanation.

In the example shown in FIG. 5, the attachment position of the second displacement sensor 31b and the straight line connecting the attachment position of the first displacement sensor 31a and the attachment position of the third displacement sensor 31c are offset by g _{0 in} the Z direction. ing.

Thus displacement sensors 31a, 31b, when there is variation in the mounting position of 31c, the gap g obtained by the equation (1) becomes a value including the offset amount g ₀ on the basis of the measured values, so-called the surface shape of the object 12 A parabolic shape error occurs.

Therefore, in the shape measuring apparatus 100 according to the present embodiment, the offset amount g ₀ of the displacement sensors 31a, 31b, and 31c is obtained by the offset amount calculation process described below, and the offset amount g ₀ is used when measuring the surface shape. Perform calibration.

(Offset amount calculation process)
FIG. 6 is a diagram illustrating a flowchart of offset amount calculation processing in the embodiment.

  As shown in FIG. 6, when performing the offset amount calculation process, first, in step S <b> 101, the calibration sample 13 is placed on the movable table 10, and the sensor head 30 is caused to scan the surface of the calibration sample 13. . As the calibration sample 13, a sample having a flatness close to zero and a small surface roughness such as an optical flat can be preferably used. A sample with a constant curvature and known shape data can also be used. The scanning distance by the sensor head 30 is set, for example, between 10 mm and 100 mm, but is not limited thereto.

  Next, in step S102, the sensor data acquisition unit 21 acquires sensor data from each of the displacement sensors 31a, 31b, 31c. Here, the interval at which the sensor data acquisition unit 21 acquires the sensor data is the period of the maximum spatial frequency included in the surface roughness waveform in the scanning direction (X direction) of the surface of the calibration sample 13 shown in FIG. It is preferable that it is 1/2 or less.

  For example, the sensor data acquisition unit 21 can appropriately adjust the sensor data acquisition interval by appropriately setting the sensor data acquisition time interval based on the scanning speed of the sensor head 30. For example, the sensor data acquisition unit 21 is set to acquire sensor data at intervals of 10 μm in the scanning direction of the sensor head 30, and the sensor data acquisition interval is appropriately set according to measurement conditions and the like.

By setting the sensor data acquisition interval of the sensor data acquisition unit 21 to ½ or less of the period of the maximum spatial frequency included in the waveform of the surface roughness (in the X direction) of the surface of the calibration sample 13, an offset amount to be described later the g ₀ it is possible to determine accurately.

  Next, in step S103, the gap data calculation unit 23 calculates gap data from the sensor data acquired by the sensor data acquisition unit 21 based on Expression (1). FIG. 7 is a diagram illustrating gap data obtained from the calibration sample 13.

Gap g obtained from the calibration sample 13, sensor 31a, 31b, is substantially equal to the offset amount _{g 0} of 31c. However, the gap data obtained from the calibration sample 13 varies around the average value as shown in FIG. 7 due to the influence of the surface roughness. Thus, when employing the measurement result of any one point as the offset amount g _0, the offset amount g ₀ varies within a variation width, variations reliability straightness measurements of object 12 as determined using the value May result in low results.

Therefore, in step S104, the offset amount calculation unit 25 calculates the average value of the gap data calculated by the gap data calculation unit 23. By setting the average value of the gap data to the offset amount g ₀ , the influence of the surface roughness of the calibration sample 13 can be reduced, and the offset amount g ₀ of the displacement sensors 31 a, 31 b, 31 c can be obtained with high accuracy. Become. However, the offset amount g ₀ obtained since also includes curvature component g _0r calibration sample 13, it is necessary to advance the curvature of the calibration sample 13 is measured by another means subtraction.

By correcting the gap data using this way the offset amount g ₀ determined by the offset amount calculating section 25, for measuring the surface shape of the object 12 is the measurement object by calibrating the sensor positional deviation with high accuracy It becomes possible.

  Note that the offset amount calculation process described above may be executed, for example, every time the shape measurement apparatus 100 measures the surface shape of the object 12, and is set when the shape measurement apparatus 100 is started or after the offset amount calculation process. It may be executed as appropriate after the elapse of time.

  As described above, the offset amount calculation unit 25 calculates the offset amounts of the attachment positions of the sensors 31a, 31b, and 31c from the data obtained by the sensors 31a, 31b, and 31c scanning the calibration sample 13. Note that the method by which the offset amount calculation unit 25 calculates the offset amount is not limited to the method exemplified in this embodiment.

(Shape measurement process)
FIG. 8 is a diagram illustrating a flowchart of the shape measurement process in the embodiment.

  As shown in FIG. 8, when measuring the surface shape of the object 12, first, in step S <b> 201, the sensor head 30 is placed in a state where the object 12 as the measurement target is placed on the movable table 10. The surface of the object 12 is scanned. Next, in step S202, the sensor data acquisition unit 21 acquires sensor data from the displacement sensors 31a, 31b, and 31c that scan the surface of the object 12 together with the sensor head 30 at a set sampling cycle. Subsequently, in step S203, the gap data calculation unit 23 calculates the gap g from the sensor data acquired by the sensor data acquisition unit 21 based on the formula (1), and the gap g at a plurality of measurement points in the scanning range. Gap data including

In step S204, the calibration unit 27 corrects the gap data using the offset amount g ₀ determined in offset amount calculation processing. Specifically, the offset amount g ₀ is subtracted from each value of the gap g included in the gap data.

In step S205, the shape calculating unit 29 calculates the second-order differential value from the calibrated gap data offset amount g ₀ by equation (5) by the calibration unit 27, to second-order integration of the value in the integral pitch Thus, the Z displacement is obtained, and the straight shape of the object 12 is calculated from the scatter diagram of Z and X. By correcting the gap data with the offset amount g _0, calibrated displacement sensors 31a, 31b, the mounting position variations of 31c, it becomes possible to measure the surface shape of the object 12 with high accuracy. In addition, the surface shape of the object 12 calculated by the shape calculation unit 29 is displayed on the display device 40.

  As described above, the calibration unit 27 corrects the data obtained by the sensors 31a, 31b, and 31c scanning the object 12 with the offset amount, and calibrates the positional deviation of the sensors 31a, 31b, and 31c. Note that the method by which the calibration unit 27 corrects the data of the sensors 31a, 31b, and 31c using the offset amount is not limited to the method exemplified in this embodiment.

As explained above, according to the shape measuring apparatus 100 according to the present embodiment, by calculating the average value of the gap data of the calibration sample 13, the displacement sensors 31a, 31b, the offset amount g ₀ of 31c accuracy You can ask well. Also, this way, by correcting the gap data of the object 12 is a measurement object by using the offset amount g ₀ obtained with high accuracy, the displacement sensors 31a, 31b, easily and highly accurately mounting position variations of 31c The surface shape of the object 12 can be accurately measured.

  Further, the processing apparatus 200 equipped with the shape measuring apparatus 100 according to the present embodiment grinds the surface of the object 12 and then performs surface shape measurement performed by the shape measuring apparatus 100 while the object 12 is placed on the movable table 10. Correction processing or the like can be performed based on the result. Therefore, the object 12 can be processed efficiently and with high accuracy.

  As described above, the shape measuring device, the processing device, and the calibration method for the shape measuring device according to the embodiment have been described. Is possible.

  For example, the shape measuring apparatus 100 may be mounted on a processing apparatus that performs processing such as grinding of the object 12 with a configuration different from that of the present embodiment.

12 objects (objects to be measured)
13 Calibration Sample 20 Control Device 21 Sensor Data Acquisition Unit (Acquisition Means)
23 Gap data calculation unit (gap calculation means)
25 Offset amount calculation unit (offset amount calculation means)
27 Calibration section (calibration means)
29 Shape calculation unit (shape calculation means)
30 Sensor head (detector)
31a First displacement sensor (displacement meter)
31b Second displacement sensor (displacement meter)
31c Third displacement sensor (displacement meter)
100 shape measuring device 200 processing device

Claims (5)

A shape measuring device that scans a measurement object with a detector in which three displacement meters are arranged in a row and measures a surface shape of the measurement object,
An offset amount calculating means for calculating an offset amount of the attachment positions of the three displacement meters from data obtained by scanning the calibration sample by the detector;
A shape measuring apparatus comprising: calibration means for correcting data obtained by the detector scanning the measurement object with the offset amount and calibrating a displacement of the displacement meter. Obtaining means for obtaining respective measured values from the three displacement meters;
Gap calculating means for obtaining gap data based on a difference between a measured value by a central displacement meter and a measured value by another displacement meter among the three displacement meters,
The offset amount calculating means calculates an average value of the gap data obtained by scanning the calibration sample by the detector as the offset amount,
2. The calibration unit according to claim 1, wherein the detector corrects the gap data obtained by scanning the measurement object by the detector using the offset amount, and calibrates the displacement of the displacement meter. Shape measuring device. When the detector scans the calibration sample, the acquisition means includes an interval of acquiring each measurement value from the three displacement meters in the surface roughness waveform in the scanning direction of the calibration sample surface. The shape measuring apparatus according to claim 2, wherein the shape measuring apparatus is ½ or less of a period of a maximum spatial frequency.   A processing apparatus comprising the shape measuring apparatus according to claim 1. A method for calibrating a shape measuring apparatus that scans a measurement object with a detector in which three displacement meters are arranged in a row and measures the surface shape of the measurement object,
An offset amount calculating step of calculating an offset amount of the attachment position of the three displacement meters from data obtained by scanning the calibration sample by the detector;
A calibration step of correcting the gap data obtained by scanning the measurement object by the detector with the offset amount and calibrating the displacement of the displacement meter, Method.

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