JP2018119817A - Shape measurement device and shape measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape measurement device and a shape measurement method capable of highly accurately connecting a plurality of pieces of data and acquiring the whole shape with high accuracy.SOLUTION: A surface shape measurement device 1 for measuring a surface shape of a measurement object P from the intensity information of interference light acquired by a photographing unit 16 while changing the optical path length of the measuring light emitted to each point of a surface S to be measured, comprises a sensor 11 on a supporting part 10 for supporting the measurement object P. The shape measurement device is provided with a correction data unit 18A which obtains a direction and a method of correcting a base line of the supporting part on the basis of the load applied to the supporting part measured by the sensor, the barycenter, and the distribution of load and a calculation unit 18 which corrects and combines the measured surface shape data using the obtained correction direction and correction method.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a shape measuring apparatus and a shape measuring method, and more particularly, to a shape measuring apparatus and a shape measuring method for measuring the shape of the surface of a measurement object in a non-contact manner using a scanning white interferometer.

  In a non-contact shape measuring instrument using light, there are many limitations on the range that can be measured in one measurement due to limitations on the field of view of the objective lens used. As a technique to avoid this limitation, a measurement object is placed on a stage that can be moved horizontally, multiple measurements are performed so that the measurement ranges overlap at a certain rate, and these measurement data are connected later (stitch) Ng) is known.

  When such a method is used, a relative position error at the time of connecting a plurality of data has been a problem. For example, in Patent Document 1 below, the amount of deviation in the height direction of measurement data is set as an overlap region. It is described that a cumulative error caused by optical distortion is suppressed by obtaining measurement from the height direction and translating the measurement data in the height direction.

Patent No. 5698963

  In the surface shape measuring method described in Patent Document 1, it is necessary to add a separate height measuring device in order to measure the height. Further, when the object to be measured is heavy or when an unbalanced load is applied, the straightness of the stage deteriorates and correction including spatial rotation cannot be performed. In addition, the non-contact shape measuring machine using light can measure with higher sensitivity when the object to be measured is a flat object, and in the case of a high waviness shape, there are problems such as collision with the objective lens. In general, he was good at measuring a shape close to a plane. In recent years, a non-contact shape measuring machine having a long working distance has been developed, and application to a measuring object having a high waviness shape or a large size is expected.

  The present invention has been made in view of such circumstances, and a shape measuring apparatus and a shape measuring method capable of connecting a plurality of data with high accuracy and acquiring the entire shape of a measurement object with high accuracy. The purpose is to provide.

  In order to achieve the above object, a shape measuring apparatus according to the present invention includes a support unit that supports a measurement object, a light source unit that emits white light, and white light from the light source unit as measurement light and reference light. Divide and irradiate the measurement surface with the measurement light and irradiate the reference surface with the reference light to generate interference light that interferes with the measurement light returning from the measurement surface and the reference light returning from the reference surface An optical unit having an interference unit, and a surface shape acquisition unit that acquires surface shape data of the measurement object from the luminance information of the interference light of the measurement light and the reference light irradiated to each point of the measurement surface; An XY-direction moving unit that relatively moves the positions of the support unit and the optical unit, a sensor that measures the distribution of the load applied to the support unit, and the support unit based on the load distribution measured by the sensor A baseline correction value is obtained, and a plurality of correction values are calculated based on the correction value. Combining serial surface shape data, and a processing unit for acquiring the entire surface shape data of the measurement object.

  According to the shape measuring apparatus of the present invention, the sensor is provided, and the correction value of the base line of the support part is obtained based on the distribution of the load applied to the support part by the measurement object. And when connecting a plurality of surface shape data of the measurement object, it is possible to correct the baseline of the support part due to the load of the measurement object by performing correction with the correction value of the base line of the support part, which is high The surface shape of the measurement object can be measured with high accuracy.

  In one aspect of the shape measuring apparatus according to the present invention, the sensor is a force sensor that measures a load applied to the support portion, and the baseline correction direction and the correction amount are measured for a reference workpiece under each load condition. It is preferable to obtain by

  According to this aspect, by using the force sensor as the sensor and measuring the reference workpiece under the load condition measured by the force sensor, the displacement amount of the support portion under the load condition can be obtained. Therefore, the correction direction and the correction method under the load condition can be obtained from the amount of displacement, and correction data under various load conditions can be created by measuring using the reference workpiece under a plurality of load conditions.

  In one aspect of the shape measuring apparatus according to the present invention, the sensor is preferably a displacement sensor that measures the displacement of the support portion.

  This embodiment defines another specific example of the sensor. By measuring the displacement of the support portion using a displacement sensor, the displacement amount of the support portion under the load condition can be obtained, and the correction direction and A correction method can be obtained.

  In one aspect of the shape measuring apparatus according to the present invention, the reference workpiece is preferably at least one of an optical flat and a grid chart.

  This aspect shows a specific example of the reference workpiece, and the correction amount in the height direction can be obtained by using the optical flat, and the correction amount in the in-plane direction can be obtained by using the grid chart.

  In one aspect of the shape measuring apparatus according to the present invention, the baseline correction direction and the correction amount are preferably a lookup table or a function model.

  According to this aspect, the correction direction of the baseline and the correction amount obtained in the correction data part can be easily corrected by creating a lookup table or modeling the function, and the calculation cost can be reduced. Can be reduced.

  In order to achieve the above object, the shape measuring method according to the present invention uses a load distribution measured by a force sensor to obtain a correction amount for a base line of a support part, and a correction amount acquisition step on the support part. A surface shape measurement process for placing a measurement object, measuring the surface shape of the measurement object, obtaining surface shape data, measuring the load distribution with a force sensor, and recording the position of the support, and the surface shape The correction process for correcting the surface shape data measured in the measurement process using the correction amount of the base line of the support part, the surface shape measurement process, and the correction process are performed within the measurement range of the measurement object, and the support part is moved. And a step of creating a plurality of surface shape data and a connection step of connecting the plurality of surface shape data and acquiring a wide range surface shape data of the measurement object.

  According to the shape measuring method of the present invention, first, the correction amount of the base line of the support portion is obtained under the load condition measured using the force sensor in the range where the load of the measurement object is applied and the range of the center of gravity. Then, after acquiring the surface shape data of the measurement object, the surface shape data is corrected by using the obtained baseline correction amount of the support portion. Thus, since correction is performed according to the load condition of the measurement object, the surface shape of the measurement object can be measured with high accuracy.

  In one aspect of the shape measuring method according to the present invention, the correction amount acquisition step includes placing a heavy object within a range where the load of the measurement object is applied to the support portion and a range of the center of gravity position, and A load measurement process for measuring the load distribution, a displacement acquisition process for determining the displacement of the base line of the support part under the load condition measured in the load measurement process by placing a reference workpiece on the support part, and a measurement Within the range where the load of the object is applied and within the range of the center of gravity position, the correction amount acquisition repetition process which repeats the load measurement process and the displacement acquisition process, the range where the load of the measurement object is applied, and the range of the center of gravity position It is preferable to have a correction data creation step of creating correction data from the position of the support portion under the conditions and the correlation between the displacements.

  This aspect shows an example of the correction amount acquisition process, and creates correction data from the displacement of the reference workpiece under a plurality of load conditions within the range where the load of the measurement object is applied and the position of the center of gravity. Thus, the correction amount in the load condition of the measurement object can be easily obtained.

  In one aspect of the shape measuring method according to the present invention, the displacement acquisition step uses an optical flat as a reference workpiece, and uses a height direction correction amount acquisition step for acquiring a correction amount in the height direction, and uses a grid chart as a reference workpiece. And an in-plane direction correction amount acquisition step of acquiring an in-plane direction correction amount.

  According to this aspect, in the displacement acquisition step, the correction amounts in the height direction and the in-plane direction can be acquired by separately obtaining the correction amounts using the optical flat and the grid chart.

  In order to achieve the above object, a shape measurement method according to the present invention includes a surface shape measurement step of placing a measurement object on a support, measuring a surface shape of the measurement object, and acquiring surface shape data. In the surface shape measurement process, a displacement measurement process for measuring displacement due to a load applied to the support portion of the measurement object with a displacement sensor, a surface shape measurement process, and a displacement measurement within a range for measuring the surface shape of the measurement object Repeat the process to acquire multiple surface shape data, correct the correction data creation step to create correction data using the displacement of the support part measured in the displacement measurement process, and correct the multiple surface shape data A correction step of correcting with data, and a connection step of connecting a plurality of surface shape data after the correction step and acquiring a wide range surface shape data of the measurement object.

  According to the shape measuring method of the present invention, the displacement of the support portion displaced by the load of the measurement object is measured using the displacement sensor, and the acquired surface shape data is corrected. The displacement of the support portion can be corrected, and the surface shape of the measurement object can be measured with high accuracy. Moreover, the error at the time of combining the measured surface shapes can be suppressed.

  According to the shape measuring apparatus and the shape measuring method of the present invention, before the measurement, the displacement of the support part due to the weight of the measurement object is measured, and after measuring the surface of the measurement object, the displacement of the support part is corrected. Thus, the entire shape of the measurement object can be obtained with high accuracy.

It is a whole block diagram of the surface shape measuring apparatus (scanning white interferometer) of embodiment of this invention. It is the figure which showed the pixel arrangement | sequence of the interference fringe on the xy coordinate of the imaging surface of an image pick-up element. It is the figure which illustrated the relationship between z position of an interference part, and a luminance value, and an interference fringe curve. It is the figure which illustrated the relationship between the different z coordinate value of the different point of a to-be-measured surface, and an interference fringe curve. It is a figure explaining the overlapping part of the imaging surface to measure. It is a figure explaining the load applied to a stage. It is a figure explaining the example of a correction example. It is a figure which shows the flowchart which produces correction data. It is a figure which shows the flowchart of an optical flat measurement. It is a figure which shows the flowchart of a grid chart measurement. It is a figure which shows the flowchart of correction implementation of the measured surface shape data. It is the schematic of the stage vicinity of the shape measuring apparatus which concerns on other embodiment.

  Hereinafter, preferred embodiments of a shape measuring apparatus and a shape measuring method of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram showing the overall configuration of a shape measuring apparatus to which the present invention is applied.

  The surface shape measuring apparatus 1 in FIG. 1 is a so-called mirrow-type scanning white interferometer (microscope) that measures a surface shape of a measurement object in a non-contact manner using a mirrow-type interferometer. An optical unit 2 that acquires an interference image of the object P, a stage 10 on which the measurement object P is placed, various controls of the optical unit 2, and various arithmetic processes based on the interference image acquired by the optical unit 2. A processing unit 18 including an arithmetic processing device such as a personal computer is provided.

  In the measurement space in which the measurement object P is arranged, two coordinate axes in the horizontal direction orthogonal to each other are an x axis (axis orthogonal to the paper surface) and a y axis (axis parallel to the paper surface), and the x axis and the y axis. A vertical coordinate axis orthogonal to the z axis is defined as z-axis.

  The stage 10 is a flat upper surface substantially parallel to the x-axis and the y-axis and is a support unit that supports the measurement object P, and has a stage surface 10S on which the measurement object P is placed.

  A force sensor 11 is provided on the opposite side of the stage surface 10S of the stage 10, and the load applied to the stage 10, the position of the center of gravity, and the distribution of the load are measured. By correcting the baseline based on the data measured using the force sensor 11, the surface shape of the measurement object P can be measured with high accuracy. Creation of correction data for correcting the baseline and a correction method will be described later.

  At a position facing the stage surface 10S, that is, above the stage 10, the optical unit 2 that is integrally accommodated and held by a housing (not shown) is disposed.

  The optical unit 2 includes a light source unit 12 having an optical axis Z-1 parallel to the x axis and an interference unit having an optical axis Z-0 parallel to the z axis (hereinafter referred to as “measurement optical axis Z-0”). 14 and the photographing unit 16. The optical axis Z-1 of the light source unit 12 is orthogonal to the optical axis Z-0 of the interference unit 14 and the imaging unit 16, and intersects the optical axis Z-0 between the interference unit 14 and the imaging unit 16. The optical axis Z-1 does not necessarily have to be parallel to the x axis.

  The light source unit 12 emits white light having a wide wavelength range (low coherence light with low coherence) as illumination light for illuminating the measurement object P, and illumination light emitted after being diffused from the light source 40. And a collector lens 42 that converts the light into a substantially parallel light beam. The center axis of each of the light source 40 and the collector lens 42 is coaxially arranged as the optical axis Z-1 of the light source unit 12.

  Further, as the light source 40, any type of light emitter such as a light emitting diode, a semiconductor laser, a halogen lamp, and a high-intensity discharge lamp can be used.

  The illumination light emitted from the light source unit 12 is disposed between the interference unit 14 and the imaging unit 16, and is a half mirror disposed at a position where the optical axis Z-1 and the measurement optical axis Z-0 intersect. Is incident on the beam splitter 44. The illumination light reflected by the beam splitter 44 (the flat light splitting surface (reflecting surface) of the beam splitter 44) travels along the measurement optical axis Z-0 and enters the interference unit 14.

  The interference unit 14 is configured by a Michelson interferometer, and divides illumination light incident from the light source unit 12 into measurement light and reference light. Then, while irradiating the measurement object P with the measurement light and irradiating the reference mirror 52 with the reference light, interference light in which the measurement light returning from the measurement object P interferes with the reference light returning from the reference mirror 52 is generated. .

  The interference unit 14 includes an objective lens 50 having a condensing function, a reference mirror 52 that is a reference surface that reflects light and has a flat reflection surface, and a flat beam splitter 54 that divides light. The center axes of the objective lens 50, the reference mirror 52, and the beam splitter 54 are arranged coaxially as the optical axis Z-0 of the interference unit 14. The reflection surface of the reference mirror 52 is disposed at a side position of the beam splitter 54 in parallel with the measurement optical axis Z-0.

The illumination light incident on the interference unit 14 from the light source unit 12 is focused on the objective lens 50 and then enters the beam splitter 54.

  The beam splitter 54 is, for example, a half mirror, and the illumination light incident on the beam splitter 54 is split into measurement light that passes through the beam splitter 54 and reference light that is reflected by the light splitting surface of the beam splitter 54.

  The measurement light transmitted through the beam splitter 54 is irradiated onto the measurement surface S of the measurement object P, returns from the measurement surface S to the interference unit 14, and is incident on the beam splitter 54 again. Then, the measurement light transmitted through the beam splitter 54 enters the objective lens 50.

  On the other hand, the reference light reflected by the beam splitter 54 is reflected by the light reflecting surface of the reference mirror 52 and then enters the beam splitter 54 again. Then, the reference light reflected by the beam splitter 54 enters the objective lens 50.

  As a result, interference light is generated by superimposing the measurement light that is irradiated from the interference unit 14 onto the measurement target surface S of the measurement object P and returns to the interference unit 14 and the reference light reflected by the reference mirror 52, and the interference is generated. After the light is focused by the objective lens 50, the light is emitted from the interference unit 14 toward the photographing unit 16.

  Further, after the illumination light is divided into the measurement light and the reference light, the optical distance of the optical path through which each of the measurement light and the reference light passes until the measurement light and the reference light are superimposed is expressed as an optical path of the measurement light. The length and the optical path length of the reference light are referred to as the optical path length difference between the measurement light and the reference light.

  The interference unit 14 is provided so as to be linearly movable in the z-axis direction in the optical unit 2. Then, the objective lens 50 and the beam splitter 54 are moved in the z-axis direction by driving the interference unit actuator 56. As a result, the position (height) of the focal plane of the objective lens 50 moves in the z-axis direction, and the optical path length of the measurement light changes as the distance between the measured surface S and the beam splitter 54 changes. The optical path length difference between the light and the reference light changes.

  The imaging unit 16 is a surface shape acquisition unit that acquires surface shape data of the measurement object P from luminance information of interference light between the measurement light and the reference light irradiated to each point on the surface S to be measured. It corresponds to a Charge Coupled Device) camera and has a CCD type image pickup device 60 and an imaging lens 62. The center axes of the image sensor 60 and the imaging lens 62 are arranged coaxially as the optical axis Z-0 of the imaging unit 16. The imaging device 60 can be any imaging means such as a CMOS (Complementary Metal Oxide Semiconductor) type imaging device.

  The interference light emitted from the interference unit 14 enters the beam splitter 44 described above, and the interference light transmitted through the beam splitter 44 enters the imaging unit 16.

  The interference light incident on the imaging unit 16 forms an interference image on the imaging surface 60S of the imaging element 60 by the imaging lens 62. Here, the imaging lens 62 enlarges an interference image with respect to a region around the optical axis Z-0 of the measurement target surface S of the measurement target P, and forms an image on the imaging surface 60S of the imaging element 60 with a high magnification.

  In addition, the imaging lens 62 images a point on the focal plane of the objective lens 50 of the interference unit 14 as an image point on the imaging surface of the imaging element 60. In other words, the photographing unit 16 is designed so that it is focused (focused) on the position of the focal plane of the objective lens 50.

  In the following, the position of the focal plane of the measurement object P in the z-axis direction is simply referred to as “focus position” or “focus position of the imaging unit 16”.

  The interference image formed on the imaging surface 60S of the imaging device 60 is converted into an electrical signal by the imaging device 60 and acquired as an interference image. Then, the interference image is given to the processing unit 18.

  As described above, the optical unit 2 including the light source unit 12, the interference unit 14, the imaging unit 16, and the like is provided as a whole so as to be linearly movable in the z-axis direction. For example, the optical unit 2 is supported by a z-axis guide unit (not shown) provided upright along the z-axis direction so as to be able to move straight. The entire optical unit 2 moves straight in the z-axis direction by driving the z actuator 70. Thereby, the focus position of the imaging unit 16 can be moved more in the z-axis direction than when the interference unit 14 is moved in the z-axis direction. For example, the imaging unit can be used according to the thickness of the measurement object P or the like. The 16 focus positions can be adjusted to appropriate positions.

  The optical unit 2 or the stage 10 includes XY direction moving means (not shown) that relatively moves the positions of the optical unit 2 and the stage 10. By relatively moving the positions of the optical unit 2 and the stage 10, the measurement position of the measurement object P is changed, and a plurality of surface shape data is acquired.

  When the processing unit 18 measures the surface shape of the measurement target surface S of the measurement object P, the processing unit 18 controls the interference unit actuator 56 to move the interference unit 14 of the optical unit 2 in the z-axis direction while moving the interference unit 14 in the z-axis direction. Interference images are sequentially acquired from the image sensor 60. Then, the three-dimensional shape data of the measurement surface S is acquired as data indicating the surface shape of the measurement surface S based on the acquired interference image.

  Here, a process in which the processing unit 18 acquires the three-dimensional shape data of the measurement surface S based on the interference fringes will be described.

  The imaging device 60 of the imaging unit 16 includes a large number of light receiving elements (pixels) arranged two-dimensionally along an xy plane (horizontal plane) composed of the x axis and the y axis, and an interference image received at each pixel. The luminance value, that is, the luminance value of each pixel of the interference image acquired by the image sensor 60 depends on the optical path length difference between the measurement light reflected at each point of the measurement target surface S corresponding to each pixel and the reference light. Indicates the intensity (luminance information) of the interference light.

  Here, as shown in FIG. 2, the pixels in the m-th column and the n-th column of the interference image (the imaging surface of the imaging device 60) are expressed as (m, n). An x coordinate value indicating the position of the pixel (m, n) in the x-axis direction (hereinafter, the position in the x-axis direction is referred to as “x position”) is represented by x (m, n), and the position in the y-axis direction ( Hereinafter, a y coordinate value indicating a position in the y-axis direction is referred to as “y position”) is represented as y (m, n).

  Further, the x coordinate value indicating the x position of the point on the measured surface S of the measurement object P corresponding to the pixel (m, n) is represented as X (m, n), and the y coordinate value indicating the y position is represented as Y. It is assumed that (m, n) is represented, and the point is represented by (X (m, n), Y (m, n)) by an xy coordinate value. The point on the measured surface S corresponding to the pixel (m, n) is on the measured surface S where the image point is formed at the position of the pixel (m, n) in the focused state. Means a point.

  At this time, the luminance value of the pixel (m, n) of the interference image acquired by the image sensor 60 is a point (X (m, n), Y () on the measured surface S corresponding to the pixel (m, n). m, n)) shows the magnitude according to the optical path length difference between the measurement light and the reference light irradiated.

  That is, the interference unit actuator 56 of FIG. 1 moves the interference unit 14 in the z-axis direction, and the relative position of the interference unit 14 with respect to the optical unit 2 (imaging unit 16) (hereinafter referred to as “z position”). ) Is moved, the focus position of the imaging unit 16 (focal plane of the objective lens 50) is also moved in the z-axis direction, and the focus position is also displaced by the same displacement amount as the interference unit 14. Further, when the focus position is displaced, the optical path length of the measurement light applied to each point of the measurement surface S also changes.

  Then, while moving the interference unit 14 in the z-axis direction and displacing the focus position, that is, while changing the optical path length of the measurement light, the interference image is sequentially acquired from the image sensor 60 and any pixel ( The luminance value of m, n) is detected.

  Here, the processing unit 18 can detect the amount of displacement of the interference unit 14 from the predetermined reference position (z position of the interference unit 14) by a detection signal from a position detection unit (not shown) such as a potentiometer or an encoder. it can. Alternatively, when the z position of the interference unit 14 is controlled without using position detection means, for example, when the interference unit 14 is moved by a certain amount of displacement by a drive signal applied to the interference unit actuator 56, the total displacement amount Can be detected.

  Then, the z position of the focus position when the interference unit 14 is the reference position is set as the reference position (origin position) of the z coordinate in the measurement space, and the displacement amount from the reference position of the interference unit 14 is the z coordinate value of the focus position. Can be obtained as For the z coordinate value, a position higher than the origin position (position approaching the imaging unit 16) is set as a positive side, and a position lower than (position approaching the stage surface 10S) is set as a negative side. In addition, the reference position of the interference unit 14, that is, the origin position of the z coordinate can be set and changed to an arbitrary z position.

  3A to 3C show an image acquired from the image sensor 60 of the imaging unit 16 while being raised in the z-axis direction from a position close to the measurement surface S of the measurement target P of the interference unit 14. It is the figure which showed the relationship between z position of the interference part 14, and a luminance value.

  As shown in FIG. 3A, when the optical path length L1 of the measurement light is smaller than the optical path length L2 of the reference light, the interference is small and the luminance value is substantially constant. Then, as shown in FIG. 3B, when the optical path length L1 of the measurement light and the optical path length L2 of the reference light are the same, that is, when the optical path length difference is 0, the interference becomes large and shows the largest luminance value. . Further, as shown in FIG. 3C, when the optical path length L1 of the measurement light is larger than the optical path length L2 of the reference light, the interference is reduced again, and the luminance value becomes substantially constant. Thereby, the luminance value along the interference fringe curve Q shown in FIG.

  That is, the interference fringe curve Q at an arbitrary pixel (m, n) is at a point (X (m, n), Y (m, n)) on the measured surface S corresponding to that pixel (m, n). When the optical path length difference between the irradiated measurement light and the reference light is larger than a predetermined value, it shows a substantially constant luminance value. When the optical path length difference is smaller than the predetermined value, the luminance value decreases as the optical path length difference decreases. As it vibrates, its amplitude increases.

  Therefore, as shown in FIG. 3D, the interference fringe curve Q shows the maximum value when the optical path lengths of the measurement light and the reference light match (when the optical path length difference is 0), and The maximum value in the envelope of the interference fringe curve Q is shown.

  Further, the optical path length between the measurement light and the reference light irradiated to the point (X (m, n), Y (m, n)) on the surface S to be measured is such that the focus position of the photographing unit 16 is the surface S to be measured. When the upper point (X (m, n), Y (m, n)) coincides with the z position, it matches.

  Therefore, when the interference fringe curve Q shows the maximum value (or when the envelope of the interference fringe curve Q shows the maximum value), the focus position is a point (X (m, n), Y ( The z coordinate value of the focus position at that time is the z coordinate of the point (X (m, n), Y (m, n)) on the measured surface S. Indicates the value.

  From the above, the processing unit 18 moves the interference unit 14 in the z-axis direction by the interference unit actuator 56 and moves the focus position in the z-axis direction (while changing the optical path length of the measurement light), and the imaging device. The interference image is sequentially acquired from 60, and the luminance value of each pixel (m, n) is acquired in association with the z coordinate value of the focus position. That is, the brightness value of each pixel (m, n) of the interference image is acquired while scanning the focus position in the z-axis direction. Then, for each pixel (m, n), the z coordinate value of the focus position when the luminance value of the interference fringe curve Q as shown in FIG. 3D shows the maximum value corresponds to each pixel (m, n). It is detected as the z coordinate value Z (m, n) of the point (X (m, n), Y (m, n)) on the surface S to be measured.

  Z (m, n) represents the z coordinate value of the point (X (m, n), Y (m, n)) on the measured surface S corresponding to the pixel (m, n).

  Also, a method of detecting the z coordinate value of the focus position when the luminance value of the interference fringe curve Q shows the maximum value is well known, and any method may be adopted. For example, an interference fringe curve Q as shown in FIG. 3D can be actually drawn for each pixel (m, n) by acquiring an interference image at z coordinate values at minute intervals at the focus position. The focus position when the brightness value of the interference fringe curve Q shows the maximum value by detecting the z-coordinate value of the focus position when the acquired brightness value shows the maximum value. The z-coordinate value of can be detected.

  Alternatively, the interference fringe curve Q is estimated by the least square method or the like based on the luminance value acquired at each z coordinate value of the focus position, or the envelope of the interference fringe curve Q is estimated, and the estimated interference fringe curve Q Alternatively, the z coordinate value of the focus position when the luminance value of the interference fringe curve Q shows the maximum value is detected by detecting the z coordinate value of the focus position when the luminance value shows the maximum value based on the envelope. be able to.

  As described above, the processing unit 18 uses the points (X (m, n), Y) on the measured surface S corresponding to the pixels (m, n) of the interference image (the imaging surface 60S of the imaging device 60). By detecting the z coordinate value Z (m, n) of (m, n)), the relative height of each point (X (m, n), Y (m, n)) on the surface S to be measured. Can be detected.

  Then, the x coordinate value X (m, n), the y coordinate value Y (m, n), and the z coordinate value Z (m, n) of each point on the measured surface S are converted into a three-dimensional shape of the measured surface S. It can be acquired as data (data indicating the surface shape).

  For example, as shown in FIG. 4, when z coordinate values Z1, Z2, and Z3 at three points on the measured surface S corresponding to three pixels arranged in the x-axis direction are different, the focus position is scanned in the z-axis direction. When the luminance values of the pixels of the interference image are acquired while the interference position is the z-coordinate value Z1, Z2, and Z3 with respect to each of the pixels, the interference fringe curves Q1, Q2, and Q3 that indicate the maximum luminance values are obtained. Is acquired. Therefore, by detecting the z coordinate value of the focus position when the luminance values of the interference fringe curves Q1, Q2, and Q3 show the maximum values, z at three points on the measured surface S corresponding to those pixels is detected. Coordinate values Z1, Z2, and Z3 can be detected. In this way, the surface shape of the measurement object P is measured by acquiring the three-dimensional shape data of the measurement surface S.

  The processing unit 18 includes a correction data unit 18A and a calculation unit 18B. The correction data unit 18A is a measurement target based on the load applied to the stage 10 acquired from the force sensor 11, the load distribution and the center of gravity position, the position information of the stage 10, and the shape data of the reference workpiece imaged by the imaging unit 16. Create correction data for connecting object shape data. In the correction data, a correction direction (translation, rotation, and distortion) and a correction amount necessary for connection are measured under a plurality of load conditions, and stored as a lookup table or a function model. The calculation unit 18B corrects the surface shape data of the measurement object P imaged by the imaging unit 16 using the correction data created by the correction data unit 18A, and performs connection calculation of a plurality of surface shape data.

  Next, a method for measuring the surface shape of an object to be measured by stitching using a surface shape measuring apparatus will be described.

  When measuring a wide range by measuring the non-contact shape, as shown in FIG. 5A, the surface shape is measured by providing an overlapping portion 60A where the measurement ranges overlap at a certain rate on the imaging surface 60S. And as shown in FIG.5 (B), it connects so that the overlapping part 60A of adjacent surface shape data may overlap, and the whole surface shape of a measuring object is measured. At this time, as shown in FIG. 6A, a load is applied to the stage 10, and the stage 10 may fluctuate in the z-axis direction. In addition, as shown in FIG. 6B, a load may not be evenly applied on the stage 10, and there may be an unbalanced load in which a large load is applied only to one side. If the connection is made by simply translating each measured surface shape data in the z-axis direction, errors will be stacked if the amount of surface shape data to be connected increases, so one end of the obtained surface shape The error increases between the side and the other end side. Further, in the case of an unbalanced load, the stage 10 is tilted and the measurement object is also tilted. However, if the parallel movement is performed in the z-axis direction, the measurement object may be processed as being tilted. The surface shape cannot be measured. In this embodiment, the load applied to the stage by the measurement object, the position of the center of gravity, and the distribution of the load are measured, and the reference workpiece is placed on the stage under the condition that the load is applied in advance, and the correction value in each load condition And using this correction value to correct the surface shape data of the measurement object, a plurality of measurement data can be connected with high accuracy, and the surface shape can be measured.

  First, an example of performing correction will be described with reference to FIG. FIG. 7A is a diagram illustrating an example of a stage position and a change in the height direction under a specific load condition. When the measurement object P is placed on the stage 10, a load is applied to the stage 10 by the measurement object P, and when the stage 10 is moved, for example, as shown in FIG. 10 may swell.

  FIG. 7B is a diagram showing a state when the measurement object P is placed on the stage 10 for measurement, and when the swell as shown in FIG. As shown in FIG. 7 (B), it is recognized as an oblique shape with respect to the horizontal plane, although it is originally a flat shape due to the undulation. In addition, a difference occurs in the height direction. If it is recognized as an oblique shape with respect to the horizontal direction, it will be recognized to be shorter than the actual width when the measurement object P is viewed in plan view. FIG. 7C is a diagram in which the shape measured in FIG. 7B is plotted without correction. If plotting is performed without correction, the positions in the height direction are different, so that adjacent measurement surfaces cannot be connected. Moreover, since the shape is inclined simply by connecting, an accurate shape cannot be measured. In this embodiment, the correction amount in the z direction is obtained from the correction amount in the height direction, the correction amount in the xy direction is obtained from the correction amount in the in-plane direction, and correction data is created from the load condition and the position of the stage. By performing correction using the correction data, an accurate surface shape can be acquired.

  FIG. 7D shows a correction model under the same load condition. A correction model under the load condition shown in (A) of FIG. 7 or a condition close to the load condition is obtained before the measurement of the surface shape of the measurement object P along the flowchart shown in FIG. A model function is created or a lookup table is created as the correction data for the obtained correction model, and the correction model is stored in the correction data section 18A in the processing section 18 shown in FIG. When the correction amount under the load condition shown in FIG. 7A is calculated by using this correction data, the correction amount shown in FIG. 7E is obtained.

  FIG. 7 (C) plotted without correction is corrected by calculation (E) of FIG. 7 which is a correction amount obtained by calculation, and the respective measurement data are combined to show (F) of FIG. A surface shape can be obtained. According to the present embodiment, since the data of the measured surface shape is corrected in consideration of the load applied to the stage 10, the surface shape of the measurement object P can be measured with high accuracy.

  8 to 10 are flowcharts for creating correction data.

  The correction data includes the load within the range to be corrected and the range of the gravity center position condition (hereinafter also referred to as “the range of the load to be corrected”), that is, the measurement object P is placed on the stage 10. It is created so that the load applied at the time of the correction and the range of the center of gravity position can be corrected.

  First, as the process of step S10 in FIG. 8, a heavy object within the range of the load to be corrected is placed on the stage 10, and the load and the gravity center position are measured by the force sensor 11 (step S12: load measurement). Process).

  Next, in a state where the load condition measured in step S12 is applied to the stage 10, a reference work is placed, and a displacement acquisition process for obtaining the displacement of the stage 10 under this load condition is performed. For example, first, as a process of step S14, optical flat measurement (height direction correction amount acquisition process) is performed. The optical flat measurement in step S14 will be described with reference to FIG.

  The optical flat measurement is a step of determining the correction amount in the height direction by placing the optical flat on the stage 10 and measuring the surface shape of the optical flat while moving the stage 10. In the optical flat measurement, an optical flat is first installed on the stage 10 as a process of step S30. Next, the stage 10 is moved (step S32), and the optical flat position information on the stage 10 is measured (step S34). Further, the surface shape of the optical flat is acquired (step S36). When measuring the position information of the stage 10 and acquiring the optical flat surface shape, the load measured in the step S12 is applied to the stage 10, and the load condition is set so that the center of gravity is also the same position. Set. Depending on the distribution of the load applied to the stage 10, the stage 10 may be inclined, and the change in the height direction can be measured by measuring the optical flat surface shape with the load applied.

  In step S36, after measuring the surface shape of the optical flat, if the surface shape of the entire range of the movable range of the stage 10 or the range where the measurement object P is placed is not acquired (step S38), Returning to step S32, the stage 10 is moved, the position information of the stage 10 is measured (step S34), and the optical flat surface shape is acquired (step S36). The movement of the stage 10 in step S32 is repeated within the movable range of the stage 10 or in the range where the measurement object P is placed so as to cover these ranges, and the process from step S32 to step S36. I do. When the measurement of the optical flat surface shape in these ranges is completed (step S38), the correction amount in the height direction corresponding to the position of each stage 10 under the load condition measured in step S12 is determined (step S40). End the optical flat measurement.

  Returning to FIG. 8, after optical flat measurement is performed in step S <b> 14, grid chart measurement (in-plane direction correction amount acquisition step) is performed as step S <b> 16. The grid chart measurement in step S16 will be described with reference to FIG.

  The grid chart measurement is a process of determining the correction amount in the in-plane direction by placing the grid chart on the stage 10 and measuring the grid chart while moving the stage 10. In the grid chart measurement, first, a grid chart is set on the stage 10 as a process of step S50. Next, the stage 10 is moved (step S54), and the position information of the grid chart is measured (step S54). Further, the surface shape of the grid chart is acquired (step S56). Note that when measuring the surface shape of the grid chart, the load condition is set so that the load measured in the step S12 is applied to the stage 10 and the center of gravity is the same position. Depending on the distribution of the load applied to the stage 10, the stage 10 may be inclined, and the change in the in-plane direction can be measured by measuring the surface shape of the grid chart with the load applied.

  In step S56, after measuring the surface shape of the grid chart, if the surface shape of the entire range of the range in which the stage 10 can be moved or the measurement object P is placed has not been acquired (step S58). Returning to step S52, the stage 10 is moved, the position information of the stage 10 is measured (step S54), and the surface shape of the grid chart is acquired (step S56). Regarding the movement of the stage 10 in step S52 as well as the optical flat measurement, in the movable range of the stage 10, or in the range where the measurement object P is placed, the movement is repeated so as to cover these ranges, Steps S52 to S56 are performed. When the measurement of the surface shape of the grid chart in these ranges is completed (step S58), the correction amount in the in-plane direction corresponding to the position of each stage 10 under the load condition measured in step S12 is determined (step S60). End grid chart measurement.

  Returning to FIG. 8, after determining the correction amount in the height direction in the step S14 and determining the correction amount in the in-plane direction in the step S16, these data are combined in the step S18. Thus, a three-dimensional correction amount (translation, rotation, distortion) under the load condition measured in step S12 is determined (step S18).

In step S18, after determining the correction amount in the load condition measured in step S12,
When the measurement is not performed under a load condition sufficient to create correction data (step S20), the process returns to step S10, the installation position of the heavy object on the stage 10 is changed, and the load and the load are within the range of the load to be corrected. The center of gravity position is changed (step S12). Hereinafter, similarly, the three-dimensional correction amount under the load condition measured in step S12 is determined by repeating step S12 to step S18 (correction amount acquisition repeating step). It is preferable to obtain the three-dimensional correction amount under various load conditions by performing the load and the change of the center of gravity position in step S10 discretely a plurality of times within the range of the load to be corrected.

  After determining Steps S10 to S18 to determine the three-dimensional correction amounts for a plurality of load conditions, as the process of Step S22, each load condition (load, center of gravity position), each stage position, and the corresponding three-dimensional correction amount From this correlation, a model function or a lookup table is created and the process ends (correction data creation step). By using the model function or the lookup table created in step S22, the three-dimensional correction amount can be obtained from the load condition of the measurement object P (the numerical value of the force sensor 11) and the stage position, and high accuracy. The surface shape can be measured.

[Correction method]
FIG. 11 is a diagram illustrating a flowchart for correcting the measured surface shape data using the generated correction data (model function or lookup table).

  First, as the process of step S70, the measurement object P is placed on the stage 10. Next, while moving the stage 10 (step S72), the force sensor 11 measures the load applied to the stage 10 of the measurement object P (step S74), records the position information of the stage 10 (step S76), and the measurement target. The surface shape of the object P is measured (step S78: surface shape measuring step).

  Next, as the process of step S80, three-dimensional correction is performed using the load measured in the process of step S74, the position information of the stage measured in the process of step S76, and the model function or the lookup table. The amount is calculated (correction process). This three-dimensional correction amount is applied to the surface shape measured in step S78. Thereby, a highly accurate surface shape can be measured without being affected by the load of the measurement object and the position of the center of gravity.

  After measuring the surface shape at the stage position, if the surface shape of the entire surface of the measuring object P has not been acquired (step S82), the process returns to step S72, and the steps S72 to S80 are all measured. The movement of the stage 10 is repeated so as to cover the entire area of the measurement object (repetition process). As shown in FIG. 5, the stage 10 is moved in the step S72 so that the measurement ranges overlap at a constant rate.

  After measuring the entire area of the measurement object P (step S82), as a process of step S84, wide area surface shape data is output by connecting the areas of the corrected shape that overlap the measurement ranges (connection process). . According to the present embodiment, before measuring the measurement object, correction data is created, and each image is acquired with high accuracy by correcting the data after measuring the surface shape of the measurement object. Can do. Therefore, even if the images are connected, since the error of each image is small, the error can be reduced as a whole, and the surface shape of the measurement object can be measured with high accuracy.

<< Other Embodiments >>
FIG. 12 is an enlarged schematic view of the vicinity of the stage of the shape measuring apparatus according to another embodiment. The shape measuring apparatus shown in FIG. 12 is different from the shape measuring apparatus shown in FIG. 1 in that a displacement sensor 111 is provided on the stage 10 and that the displacement due to the load applied to the stage 10 is corrected by the displacement sensor 111.

  In the shape measuring apparatus shown in FIG. 12, the stage 10 is provided on the surface plate 120 having high flatness, and the stage 10 is measured when measuring the surface shape of the measurement object P by the displacement sensor provided on the surface plate side of the stage 10. Measure the displacement.

  In the present embodiment, the surface shape of the measuring object P is measured (surface shape measuring step) as in the surface shape measuring apparatus 1 shown in FIG. When measuring the surface shape, the displacement of the stage 10 is measured using the displacement sensor 111 (displacement measuring step). By repeating the measurement of the surface shape of the measurement object P and the measurement of the displacement sensor, the surface shape of the entire measurement object P is measured.

  A baseline is calculated using the displacement of the stage 10 measured by the displacement sensor 111, a correction method and a correction amount are determined, and correction data is generated (correction data generation step). By correcting the surface shape data of the measurement object P using the correction data (correction process), the surface shape of the measurement object P can be measured with high accuracy. Further, in the connecting step, a plurality of surface shape data can be accurately connected, and a wide range of surface shape data can be acquired with high accuracy.

  DESCRIPTION OF SYMBOLS 1 ... Surface shape measuring apparatus, 2 ... Optical part, 10 ... Stage, 10S ... Stage surface, 11 ... Force sensor, 12 ... Light source part, 14 ... Interference part, 16 ... Imaging | photography part, 18 ... Processing part, 18A ... Correction data , 18B ... calculation unit, 40 ... light source, 42 ... collect lens, 44,54 ... beam splitter, 50 ... objective lens, 52 ... reference mirror, 56 ... interference part actuator, 60 ... imaging device, 60A ... overlapping part, 60S DESCRIPTION OF SYMBOLS ... Imaging surface, 62 ... Imaging lens, 70 ... z actuator, 111 ... Displacement sensor, 120 ... Surface plate, L1, L2 ... Optical path length, P ... Measurement object, Q ... Interference fringe curve, S ... Measurement surface, Z-0, Z-1 ... Optical axis

Claims (9)

A support for supporting the measurement object;
A light source unit that emits white light; and white light from the light source unit is divided into measurement light and reference light to irradiate the measurement light on the surface to be measured of the measurement object; And an interference unit that generates interference light that causes the measurement light returning from the measurement surface and the reference light returning from the reference surface to interfere with each other, and the measurement light applied to each point of the measurement surface; A surface shape acquisition unit that acquires surface shape data of the measurement object from luminance information of interference light with the reference light, and an optical unit,
XY direction moving means for relatively moving the positions of the support part and the optical part;
A sensor for measuring a distribution of a load applied to the support part;
Based on the distribution of the load measured by the sensor, a correction value for the baseline of the support portion is obtained, and based on the correction value, a plurality of the surface shape data are combined, and the total surface shape data of the measurement object A shape measuring apparatus comprising: a processing unit that acquires   The shape according to claim 1, wherein the sensor is a force sensor that measures a load applied to the support portion, and the correction direction and the correction amount of the baseline are obtained by measuring a reference workpiece under each load condition. measuring device.   The shape measuring apparatus according to claim 1, wherein the sensor is a displacement sensor that measures a displacement of the support portion.   The shape measuring apparatus according to claim 2, wherein the reference workpiece is at least one of an optical flat and a grid chart.   The shape measuring apparatus according to claim 1, wherein the correction direction and the correction amount of the baseline are a look-up table or a function model. Using the load distribution measured by the force sensor, a correction amount acquisition step for obtaining the correction amount of the base line of the support part;
A measurement object is placed on the support, the surface shape of the measurement object is measured, surface shape data is acquired, load distribution is measured by the force sensor, and the position of the support is recorded. A surface shape measuring step to perform,
A correction step of correcting the surface shape data measured in the surface shape measurement step using a correction amount of a baseline of the support;
The step of measuring the surface shape, and the correction step, the step of moving the support in the measurement range of the measurement object, and creating a plurality of surface shape data,
A connecting step of connecting the plurality of surface shape data to obtain a wide range surface shape data of the measurement object. In the correction amount acquisition step, a heavy object is placed within a range where the load of the measurement object is applied on the support part and a range of the center of gravity, and the load distribution is measured by the force sensor. Load measurement process;
A displacement acquisition step of placing a reference workpiece on the support and obtaining a baseline displacement of the support under the load conditions measured in the load measurement step;
A correction amount acquisition repeating step that repeats the load measurement step and the displacement acquisition step within the range where the load of the measurement object is applied and the range of the center of gravity position,
The correction data creation process which creates correction data from the range where the load of the measurement object is applied, and the position of the support part under the condition within the range of the center of gravity position and the displacement. Shape measurement method. The displacement acquisition step includes
A height direction correction amount acquisition step for acquiring a correction amount in the height direction using an optical flat for the reference workpiece,
The shape measuring method according to claim 7, further comprising: an in-plane direction correction amount acquisition step of acquiring a correction amount in an in-plane direction using a grid chart as the reference workpiece. A surface shape measurement step of placing a measurement object on the support, measuring the surface shape of the measurement object, and acquiring surface shape data;
In the surface shape measurement step, a displacement measurement step of measuring a displacement due to a load applied to the support portion of the measurement object with a displacement sensor;
Within the range of measuring the surface shape of the measurement object, the surface shape measurement step and the displacement measurement step are repeated, and a repetition step of acquiring a plurality of surface shape data,
A correction data creating step for creating correction data using the displacement of the support portion measured in the displacement measuring step;
A correction step of correcting the plurality of surface shape data with the correction data;
A shape measuring method comprising: connecting a plurality of surface shape data after the correcting step, and acquiring a wide range surface shape data of the measurement object.

Images