JP2019032180A - Shape measurement device and shape measurement method - Google Patents

Abstract

To provide a shape measurement device capable of measuring a shape of a measurement object with high accuracy.SOLUTION: The shape measurement device for measuring a shape of a measurement object by causing a first probe and a second probe to scan the measurement object subtracts a noise component which is determined on the basis of shape measurement data measured by the first probe and the second probe and is included in the shape measurement data of the measurement object, from the shape measurement data of the measurement object.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a shape measuring apparatus and a shape measuring method for measuring the shape of an optical element or the like.

  As an apparatus for measuring the surface shape of an optical element such as a lens or a mirror, a probe scanning type shape measuring apparatus that acquires shape information by scanning a probe along the surface shape is known. In a probe scanning type shape measuring apparatus, noise components are likely to be included in measurement data due to disturbance vibrations during probe scanning.

  As a method for reducing such a noise component, Patent Document 1 discloses a method for calculating a vibration component of a measurement object.

JP 2002-365041 A

  In the shape measurement method disclosed in Patent Document 1, two distance meters are moved relative to each other along the longitudinal direction of the measurement object, and the difference between the measurement results of the two distance meters at the same measurement point is integrated. The vibration component of the object is calculated. Then, the shape of the measurement object is measured by subtracting the vibration component from the shape data of the measurement object measured by the distance meter.

  As described above, in the shape measuring method disclosed in Patent Document 1, the variation amount of the vibration component generated until the other distance meter reaches the point where the shape data is measured by one of the two distance meters is integrated. Yes. That is, since the approximate value of the vibration component at the specific measurement point is calculated, there is a possibility that the measurement accuracy is not sufficient.

  An object of this invention is to provide the shape measuring apparatus which can measure the shape of a measuring object with high precision.

  The shape measuring apparatus of the present invention is a shape measuring apparatus that performs shape measurement by scanning a measurement object with a first probe and a second probe, and the first probe and the second probe. Are arranged along the scanning direction, and are included in the shape measurement data of the measurement object determined based on the shape measurement data measured by the first probe and the second probe, respectively. The shape measurement is performed by subtracting a noise component from the shape measurement data of the measurement object.

  ADVANTAGE OF THE INVENTION According to this invention, the shape measuring apparatus which can measure the shape of a measuring object with high precision is obtained.

It is the figure which showed the shape measuring apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the shape measurement data acquired from the output data of a probe. It is a figure which shows the structure for acquiring the positional information on a probe. It is the figure which showed the modification of the shape measuring apparatus which concerns on 1st Embodiment of this invention. It is the figure which showed the shape measuring apparatus which concerns on 2nd Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a diagram showing a configuration of a shape measuring apparatus 100 according to the first embodiment of the present invention. The configuration of the shape measuring apparatus 100 will be described with reference to FIG. Here, each axis is determined as shown in FIG. 1, assuming that the plane on which the measurement object 102 is arranged is the XY plane and the direction perpendicular to the XY plane is the Z direction. The shape measuring apparatus 100 measures the surface shape of the measurement object 102.

  The shape measuring apparatus 100 includes a plurality of probes. In the first embodiment, two probes, a probe 101a (first probe) and a probe 101b (second probe), are arranged along the scanning direction as probes used for shape measurement. In addition, the probe 101a and the probe 101b are arranged at a predetermined interval.

  Shape measurement data is acquired by scanning the probe 101 a and the probe 101 b along the surface shape of the measurement object 102. The probe 101a and the probe 101b are driven integrally, and the shape measurement data by the probe 101a and the shape measurement data by the probe 101b are acquired simultaneously. The measurement object 102 is disposed on the holding unit 103.

  At the timing when the probe 101a measures the surface shape of the measurement object 102 at the measurement point A, the probe 101b measures the surface shape of the measurement object 102 at the measurement point B. The relative positional relationship between the measurement point A and the measurement point B is determined by the positional relationship between the probe 101a and the probe 101b, and this probe interval is dx.

The shape measurement data acquired from the output data of the probe 101a and the probe 101b is assumed to be Fa (t) and Fb (t), respectively. At this time, Fa (t) and Fb (t) are respectively expressed as the following formulas (1) and (2).
Fa (t) = f (t) + g (t) (1)
Fb (t) = f (t + dt) + g (t) (2)

  f (t) is true surface shape data indicating the surface shape of the measurement object 102, and g (t) is a noise component caused by vibration disturbance of the measurement object. The noise component g (t) can be determined by solving the simultaneous equations of the equations (1) and (2). In the present invention, g (t) is calculated by inclination correction using the least square method.

  The shape measurement data Fa (t) and Fb (t) will be described with reference to FIG. As shown in FIG. 1, the surface shape is measured from the left side to the right side of the measurement object 102. Since the probe 101a is arranged on the left side of the probe 101b, the surface shape measurement by the probe 101b at the measurement point A is performed before the timing when the probe 101a performs the surface shape measurement at the measurement point A. become.

The time dt from when the probe 101b performs the surface shape measurement at the measurement point A to when the probe 101b performs the surface shape measurement at the measurement point B is:
dt = dx / V
It can be expressed as.

  Here, dx is an interval between the probe 101a and the probe 101b, and V is a scanning speed of the probe 101a and the probe 101b.

  As shown in the above formulas (1) and (2), there is a phase shift caused by the distance dx between the probe 101a and the probe 101b between Fb (t) and Fa (t). The calculation accuracy of the noise component g (t) may be reduced due to this phase shift.

In this embodiment, the calculation accuracy of the noise component g (t) is increased by appropriately setting the distance dx between the probe 101a and the probe 101b. Specifically, when the spatial frequency of the shape measurement data is fs and the scanning speed of the probe 101a and the probe 101b is V,
V / dx ≧ fs
That means
dx ≦ V / fs
The distance dx between the probe 101a and the probe 101b is determined so as to satisfy the above. For example, when the scanning speed V of the probe 101a and the probe 101b is 20 mm / s and the spatial frequency fs of the shape measurement data is 1 Hz, the interval dx is set to 20 mm or less.

  Next, a specific configuration of the shape measuring apparatus 100 will be described with reference to FIG. The probe 101a and the probe 101b shown in FIG. 1 are attached to the driven unit 104, and the driven unit 104 is driven by an actuator (not shown), thereby driving the probe 101a and the probe 101b.

  The position information of the driven unit 104 is acquired based on information from an interferometer provided in the driven unit 104. The information acquired in the driven unit 104 is transmitted to the processing unit 105, and the processing unit 105 measures the shape of the measurement object 102.

  The driven unit 104 includes an interferometer 300x for detecting the position of the driven unit 104 in the X-axis direction and an interferometer 300z for detecting the position of the driven unit 104 in the Z-axis direction. . Although not shown in FIG. 3, an interferometer 300y for detecting the position of the driven unit 104 in the Y-axis direction may be provided. Interferometer 300x is driven by irradiating laser light toward mirror 301x and detecting the laser light reflected by mirror 301x and the laser light reflected by the reference surface included in interferometer 300x. The position information of the unit 104 in the X-axis direction is acquired. Similarly, the interferometer 300z emits laser light toward the mirror 301z, and detects the laser light reflected by the mirror 301z and the laser light reflected by the reference surface included in the interferometer 300z. The position information of the driven unit 104 in the Z-axis direction is acquired.

  The processing unit 105 acquires the shape measurement data Fa (t) and Fb (t) based on the output data of the probes 101a and 101b and the position information obtained from each interferometer.

  Although FIG. 1 shows an example in which the shape measurement is performed by bringing the probe 101a and the probe 101b into contact with the measurement surface of the measurement object 102, the measurement of the probe 101a and the probe 101b and the measurement object 102 is performed as shown in FIG. The shape measurement may be performed without contacting the surfaces. Of course, one of the probe 101a and the probe 101b may be in contact with the measurement surface of the measurement object 102 and the other may not be in contact with the measurement surface of the measurement object 102.

(Second Embodiment)
FIG. 5 is a diagram showing a configuration of a shape measuring apparatus 100 according to the second embodiment of the present invention. In the shape measuring apparatus according to the first embodiment, the embodiment has been described in which the shape of the measurement object 102 is measured using the two probes 101a and 101b. In the present embodiment, the configuration of the shape measuring apparatus 100 that performs shape measurement using the probe 101c (third probe) in addition to the probe 101a and the probe 101b will be described.

  In FIG. 5, the probe 101c is arranged on the right side of the probe 101b. Here, the distance dx2 between the probe 101b and the probe 101c is different from the distance dx1 between the probe 101a and the probe 101b.

  Thereby, it becomes possible to subtract each frequency component of V / dx1, V / dx2, and V / (dx1 + dx2) from the shape measurement data, and the shape of the measurement object 102 can be measured with high accuracy. The number of probes is not limited to three, and shape measurement may be performed using four or more probes. At this time, it is preferable that the intervals between the probes are different from each other.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 100 Shape measuring apparatus 101a 1st probe 101b 2nd probe 102 Measuring object

Claims (6)

A shape measuring apparatus for measuring a shape by scanning a measurement object with a first probe and a second probe,
The first probe and the second probe are arranged along the scanning direction,
The noise component included in the shape measurement data of the measurement object determined based on the shape measurement data respectively measured by the first probe and the second probe is subtracted from the shape measurement data of the measurement object. Thus, the shape measurement apparatus performs the shape measurement.   The shape measuring apparatus according to claim 1, wherein the noise component is determined from the shape measurement data by inclination correction using a least square method.   The first probe and the second probe are arranged at a predetermined interval, and the predetermined interval includes a spatial frequency of the shape measurement data and scanning speeds of the first probe and the second probe. The shape measuring device according to claim 1, wherein the shape measuring device is determined based on   The shape measuring apparatus according to claim 1, wherein the first probe and the second probe are driven integrally.   A third probe different from the first probe and the second probe; and a distance between the first probe and the second probe; the second probe and the third probe; 5. The shape measuring apparatus according to claim 1, wherein an interval between the first probe and the third probe is different from each other. A shape measurement method for measuring a shape of the measurement object by causing the measurement object to scan a first probe and a second probe arranged along a scanning direction,
Obtaining shape measurement data respectively by the first probe and the second probe;
Determining a noise component included in the shape measurement data of the measurement object based on the acquired shape measurement data;
A shape measuring method comprising the step of subtracting the noise component from the shape measurement data of the measurement object.

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