JP6188384B2 - Shape measuring device - Google Patents

Description

  The present invention relates to a shape measuring apparatus that measures a three-dimensional shape of an object to be measured in a non-contact manner using an optical system.

  Conventionally, various shape measuring apparatuses that measure the three-dimensional shape of an object to be measured in a non-contact manner using an optical system are known. For example, a white interferometer or the like is known as a shape measuring apparatus capable of three-dimensional measurement of an object having a minute step such as a micromachine or LSI (Patent Document 1). In such a shape measuring apparatus, the shape of the measurement object is measured from a series of measurement values obtained at each vertical position by operating the imaging unit in a direction perpendicular to the stage. When the field of view of the imaging unit is narrow with respect to the measurement target, the imaging unit is moved by a predetermined step width in the horizontal direction with respect to the stage, vertical scanning is performed at each position, and finally the image is synthesized and the imaging unit A measurement technique called stitching that enables measurement results in a measurement area wider than the field of view is known.

  However, in the conventional shape measuring apparatus, since measurement is performed in a fixed vertical scanning range at each horizontal position, there is a problem that measurement efficiency is low and measurement takes time. Therefore, the vertical scanning range at the next vertical scanning position is determined based on the average height obtained at the immediately preceding vertical scanning position, thereby narrowing the vertical scanning range and improving the measurement efficiency. A shape measuring device is also known (Patent Document 1).

Japanese Patent Laid-Open No. 10-318729

  However, in the conventional shape measuring apparatus described above, the average height of the measurement range obtained at the immediately previous measurement position, or the average height in each measurement range obtained at the immediately preceding measurement position and the previous measurement position. Thus, since the vertical scanning range at the next measurement position is determined, there is a problem that accurate prediction in consideration of the inclination tendency of the measurement object is difficult and the calculation time is long.

  An object of this invention is to provide the shape measuring apparatus which shortened measurement time further.

  A first shape measuring apparatus according to the present invention includes a stage for placing a measurement object, an imaging unit configured to image the measurement object and be relatively movable with respect to the stage, The imaging unit is moved from a position in a first direction parallel to the stage to dispose the imaging unit at a second position, and a second position perpendicular to the stage at the first position and the second position. A control unit that captures the measurement object in an imaging region by the imaging unit while moving the imaging unit in a direction to obtain a plurality of captured images, and the control unit includes the first position and the first position. The imaging unit is moved so that a part of the imaging region at two positions overlaps in the overlapping region, and the imaging at the second position is based on the average height of the measurement object in the overlapping region at the first position. In front of the department And sets the movement range of the second direction.

  A second shape measuring apparatus according to the present invention includes a stage for placing a measurement object, an imaging unit configured to image the measurement object and be relatively movable with respect to the stage, The imaging unit is moved from a position in a first direction parallel to the stage to dispose the imaging unit at a second position, and a second position perpendicular to the stage at the first position and the second position. A control unit that captures the measurement object in an imaging region by the imaging unit while moving the imaging unit in a direction to obtain a plurality of captured images, and the control unit includes the first position and the first position. Based on a change in the height of the measurement object in the partial area in the imaging region at the first position, the imaging unit is moved so that a part of the imaging region at the two positions overlaps in the first overlapping region. In the second position And sets the moving range of the second direction of the imaging unit.

  A third shape measuring apparatus according to the present invention includes a stage for placing a measurement object, an imaging unit configured to image the measurement object and be relatively movable with respect to the stage, and a first The imaging unit is moved in a first direction parallel to the stage from the position, and the imaging unit is sequentially arranged at the second position and the third position, and the first to third positions are relative to the stage. A control unit that acquires the plurality of captured images by imaging the measurement object in the imaging region by the imaging unit while moving the imaging unit in a second direction perpendicular to the first direction. The imaging region in the first position and the second position overlaps in the first overlapping region, and the imaging region in the second position and the third position overlaps in the second overlapping region. Move the imaging unit to the front A moving range in the second direction of the imaging unit at the third position is set based on a change in height of the measurement object in the first overlapping region and the second overlapping region at a second position. To do.

  According to this invention, the second position of the imaging unit at the second position is based on the average value or inclination of the height of the measurement object in the overlapping area of the first position and the second position or the partial area including the overlapping area. Since the movement range is set, information near the boundary between the first position and the second position is considered, and the number of data to be used for calculation is set to be small. It is possible to provide a shape measuring apparatus that can perform accurate prediction in consideration and can further reduce the measurement time.

It is a perspective view which shows the whole structure of the shape measuring apparatus apparatus which concerns on 1st Embodiment. It is a block diagram which shows the computer main body 21 which concerns on 1st Embodiment. It is a figure which shows the specific structure of the imaging unit 17 which concerns on 1st Embodiment. It is a figure which shows the change of the change of the interference light intensity which concerns on 1st Embodiment. It is a figure for demonstrating an example of the process which calculates | requires the peak position which concerns on 1st Embodiment. It is a figure which shows the outline | summary of the measurement accompanying the movement of the imaging unit 17 which concerns on 1st Embodiment in the Z-axis direction. It is a figure which shows the outline | summary of the measurement accompanying the movement of the X-axis direction of the imaging unit 17 which concerns on 1st Embodiment. It is a flowchart which shows the shape measurement which concerns on 1st Embodiment. It is a figure which shows the effect of 1st Embodiment. It is a flowchart which shows the shape measurement which concerns on 2nd Embodiment. It is a figure which shows Z value data Db1 which concerns on 2nd Embodiment. It is a flowchart which shows the shape measurement which concerns on 3rd Embodiment. It is a figure which shows the Z value data Db2 which concerns on 3rd Embodiment.

[First Embodiment]
FIG. 1 is a perspective view showing the overall configuration of the shape measuring apparatus according to the first embodiment. This shape measuring apparatus is composed of a non-contact type shape measuring machine 10 and a computer 20 that drives and controls the shape measuring machine 10 and executes necessary data processing.

  The shape measuring machine 10 is configured as follows. That is, a stage 13 for mounting a workpiece 12 (measurement object) is mounted on the gantry 11, and the stage 13 is driven in the Y-axis direction. Support arms 14 and 15 extending upward are fixed to the center of both side edges of the gantry 11, and an X-axis guide 16 is fixed so as to connect both upper ends of the support arms 14 and 15. An imaging unit 17 that images the workpiece 12 is supported by the X-axis guide 16. The imaging unit 17 is configured to be movable in the X-axis direction along the X-axis guide 16. The imaging unit 17 is configured to be movable in the Z-axis direction by an actuator 17a. As described above, the imaging unit 17 is configured to be movable relative to the stage 13 in the X, Y, and Z axis directions by the stage 13, the X axis guide 16, and the actuator 17a. The X-axis direction and the Y-axis direction are parallel to the stage 13, and the Z-axis direction is a direction perpendicular to the stage 13. The X, Y, and Z axis directions are orthogonal to each other.

  The computer 20 includes a computer main body 21, a keyboard 22, a joystick box (J / S) 23, a mouse 24 and a display 25. The computer main body 21 is configured, for example, as shown in FIG. That is, the image information of the workpiece 12 input from the imaging unit 17 is stored in the image memory 32 via the interface (I / F) 31.

  The CAD data of the work 12 is input to the CPU 35 via the I / F 33, subjected to predetermined processing by the CPU 35, and stored in the image memory 32. The image information stored in the image memory 32 is displayed on the display 25 via the display control unit 36.

  On the other hand, code information and position information input from the keyboard 22, J / S 23, and mouse 24 are input to the CPU 35 via the I / F 34. The CPU 35 executes various processes according to the macro program stored in the ROM 37 and the program stored in the RAM 40 from the HDD 38 via the I / F 39.

  The CPU 35 controls the shape measuring machine 10 via the I / F 41 according to the program. The HDD 38 is a recording medium for storing various data. The RAM 40 provides a work area for various processes.

  Next, a specific configuration of the imaging unit 17 will be described with reference to FIG. In the example shown in FIG. 3, the imaging unit 17 is a Michelson interferometer. However, the imaging unit 17 may be another equal optical path interferometer such as a Mirau type. Further, the imaging unit 17 may be used in combination with another optical measuring device.

  In the imaging unit 17 shown in FIG. 3, the light source 171 is a white light source having a broadband spectrum such as a halogen lamp, a xenon lamp, a mercury lamp, a metal halide lamp, or an LED. White light emitted from the light source 171 is collimated by a collimator lens 172 and divided in two directions by a beam splitter 173. One split light is applied to the measurement surface of the workpiece 12, and the other split light is applied to the reference surface of the reference plate 175. White light reflected from the measurement surface and the reference surface is combined by the beam splitter 173, and interference light at that time is imaged by the CCD camera 178 via the imaging lens 177.

  The imaging unit 17 as described above is scanned in the Z-axis direction by the actuator 17a, and an interference image at each scanning position is sampled by the CCD camera 178 and stored in the image memory 32 in the computer 20. The computer 20 obtains Z value data of the workpiece 12 based on the intensity of the interference light at each position on the measurement surface of the workpiece 12 and the position (scanning position) in the Z-axis direction of the imaging unit 17 input from the encoder 17b. .

  As shown in FIG. 3, the white light from the light source 171 is reflected by the measurement surface of the workpiece 12 and the reference surface of the reference plate 175 and is combined by the beam splitter 173. The interference light intensity at that time changes by scanning the imaging unit 17 in the Z-axis direction. By using white light with less coherence, the range in which interference fringes are generated can be narrowed. As a result, for example, as shown in FIG. 4, the change in interference light intensity at each position on the measurement surface caused by scanning the reference surface has a phase corresponding to the height of the measurement surface (position in the Z-axis direction). Occur. Therefore, the scanning position of the reference surface where the peak value of the change in interference light intensity at each position on the measurement surface is observed can be obtained as the height of the corresponding portion of the measurement surface.

  FIG. 5 is a diagram for explaining an example of processing for obtaining the peak position from the change in interference light intensity at each position. In this process, a predetermined geometric element (for example, a straight line or a curve) A is applied to the interference light intensity sequence obtained by scanning the reference surface. Alternatively, the geometric element (for example, straight line or curved line) A is obtained by smoothing the obtained interference light intensity sequence. Next, threshold levels B and C are set by shifting the obtained geometric element A in the positive and negative directions of the intensity axis, respectively. Interfering light intensity exceeding the threshold level is obtained as a peak position candidate point. Then, the center of gravity of the region where the peak position candidate points are most dense is obtained as the peak position P. By such processing, the peak position P can be obtained at high speed by reducing the number of processing points. The peak position P obtained as described above corresponds to the height (Z value) at the measurement point. By obtaining the Z value at each position on the measurement surface, the surface data of the workpiece 12 can be obtained. Note that profile data in a certain cross section can be obtained by extracting data in an arbitrary direction from the surface data.

  Next, an outline of measurement associated with movement of the imaging unit 17 in the Z-axis direction will be described with reference to FIG. As shown in FIG. 6, the computer 20 images the work 12 in the imaging region R0 by the imaging unit 17 while moving the imaging unit 17 in the Z-axis direction. Thereby, a plurality of image data D0 are acquired. Each image data D0 is composed of a plurality of pixel data Da arranged in a matrix in the X-axis direction and the Y-axis direction. And the computer 20 calculates | requires Z value data group D1 of the workpiece | work 12 based on several image data D0 with the method demonstrated using FIGS. The Z value data group D1 has Z value data for each pixel data Da.

  Next, with reference to FIG. 7, the outline of the measurement accompanying the movement of the imaging unit 17 in the X-axis direction will be described. As shown in FIG. 7, the computer 20 obtains the Z value data group D1 as shown in FIG. 6 while moving the imaging unit 17 in the X-axis direction. However, the computer 20 moves the imaging unit 17 so that a part of the adjacent imaging region R0 overlaps in the overlapping region R1. The computer 20 then superimposes adjacent Z value data groups D1 in the overlapping region R1 to generate a combined Z value data group D2. The composite Z value data group D2 includes Z value data of the workpiece 12 in the region R2 larger than the imaging region R0. 7 shows an example in which the imaging unit 17 is moved in the X-axis direction, the imaging unit 17 may be moved in the Y-axis direction.

  Next, shape measurement according to the present embodiment will be specifically described with reference to FIG. FIG. 8 is a flowchart showing shape measurement according to the present embodiment. As shown in FIG. 8, first, the computer 20 receives an initial movement range ΔZ0 of the imaging unit 17 in the Z-axis direction (S101). Next, the computer 20 captures an image with the imaging unit 17 while moving the imaging unit 17 over the initial movement range ΔZ0, and acquires a plurality of image data D0 (S102). Subsequently, the computer 20 acquires a Z value data group D1 based on the plurality of image data D0 (S103).

  Next, the computer 20 determines whether or not the measurement is completed (S104). If it is determined that the measurement has not been completed (S104, NO), the computer 20 calculates an average value (average Z value) Zav of the Z value data in the overlapping region R1 (S105). Here, the overlapping area R1 used for calculating the average Z value Zav is an area overlapping with the imaging area R0 where imaging is performed next. Subsequently, the computer 20 calculates a movement range ΔZ in the Z-axis direction based on the average Z value Zav (S106). For example, the center of the movement range ΔZ is an average Z value Zav.

  Next, the computer 20 moves the imaging unit 17 in the X-axis direction (S107). Subsequently, the computer 20 images the workpiece 12 by the imaging unit 17 while moving the imaging unit 17 over the movement range ΔZ, and acquires a plurality of image data D0 (S108). After step S108, the computer 20 executes step S103 again.

  On the other hand, if it is determined in step S104 that the measurement is completed (S104, YES), the computer 20 superimposes adjacent Z value data groups D1 in the overlapping region R1 to generate a combined Z value data group D2 (S109). ). Although FIG. 8 shows an example in which the imaging unit 17 is moved in the X-axis direction, the imaging unit 17 may be moved in the Y-axis direction.

  Next, the effect of the first embodiment will be described with reference to FIG. As shown in FIG. 9A, a range from the minimum height Zmin to the maximum height Zmax of the workpiece 12 is defined as a range ΔZs. A range that includes the range ΔZs and is larger than the range ΔZs is defined as ΔZd. In this case, as shown in FIG. 9A, a comparative example is considered in which the moving range of the imaging unit 17 in the Z-axis direction is a constant range ΔZd regardless of the positions P1 and P2 in the X-axis direction and the Y-axis direction. It is done. However, in such a comparative example, the imaging unit 17 is moved in the Z-axis direction to a region where the workpiece 12 does not exist at a certain position in the X- and Y-axis directions.

  In contrast, in the present embodiment, as shown in FIG. 9B, the movement range ΔZ in the Z-axis direction of the imaging unit 17 is set based on the average Z value Zav in the overlapping region R1 at each of the positions P1 and P2. calculate. Therefore, in the first embodiment, the movement range ΔZ at each of the positions P1 and P2 can be made shorter than the movement range ΔZd of the comparative example, thereby shortening the measurement time.

  Further, according to the present embodiment, since the movement range ΔZ in the Z-axis direction at the next position P2 is set based on the average Z value Zav in the overlapping region R1 at the position P1, the average of all measured values at the position P1 The range close to the actual height of the workpiece 12 can be set as compared with the case where the movement range ΔZ in the Z-axis direction of the next position P2 is obtained based on the height. In addition, since the calculation range is limited to the overlapping region R1, the calculation time is shorter than the method of obtaining the average value of all the measured values. Therefore, there is an effect that the measurement time can be further shortened by the synergistic effect of both.

[Second Embodiment]
Next, a shape measuring apparatus according to the second embodiment will be described. The second embodiment has a configuration similar to that of the first embodiment. On the other hand, the second embodiment differs from the first embodiment in its operation, and this point will be described below.

  In the second embodiment, as shown in FIG. 10, steps S105a and S106a are executed instead of steps S105 and S106 of the first embodiment. The second embodiment is different from the first embodiment only in this point, and otherwise performs the same processing as in the first embodiment.

  In step S105a, the computer 20 calculates a Z value approximate line L (change in the height of the workpiece 12) in the imaging region R0 as shown in FIG. Here, FIG. 11A shows the pixels Db1 arranged in a line in the X-axis direction in the imaging region R0, and FIG. 11B shows changes in the Z value data accompanying changes in the X position in the pixels Db1. In this embodiment, the pixels Db1 arranged in a line are used. However, as long as the data at the boundaries between the positions P1 and P2 are included, only some of the pixels in the horizontal line of data may be used.

  In step S106a following step S105a, the computer 20 calculates the movement range ΔZ in the Z-axis direction based on the Z value approximate line L. For example, the center of the movement range ΔZ is a point on the Z value approximate line L. Even in the above processing, the second embodiment has the same effect as the first embodiment. That is, in the case of the present embodiment, since data (data at the right end portion of Db1) existing in the overlapping region R1 between the position P1 and the position P2 is used for the calculation, the average height of the position P1 and the previous position P0. A range closer to the actual height of the workpiece 12 can be set than when the inclination is estimated using the average height. Further, since the calculation range is limited to the pixels Db1 arranged in a line, the calculation time is shorter than the method of obtaining the inclination from the average value of all the measurement values at the two measurement positions. Therefore, there is an effect that the measurement time can be further shortened by the synergistic effect of both.

[Third Embodiment]
Next, a shape measuring apparatus according to the third embodiment will be described. The third embodiment has a configuration similar to that of the first embodiment. On the other hand, the third embodiment differs from the first embodiment in its operation, and this point will be described below.

  In the third embodiment, as shown in FIG. 12, steps S105b and S106b are executed instead of steps S105 and S106 of the first embodiment. The third embodiment is different from the first embodiment only in this point, and otherwise performs the same processing as that of the first embodiment.

  In step S105b, the computer 20 calculates the Z value approximate line La in the overlapping regions R1a and R1b as shown in FIG. Here, FIG. 13A shows the pixels Db2 arranged in a line in the X-axis direction in the overlapping regions R1a and R1b, and FIG. 13B shows the change in the Z value data accompanying the change in the X position in the pixel Db1. Note that the Z-value data group D1 shown in FIG. 13A overlaps with the adjacent imaging regions R0 in the overlapping regions R1a and R1b.

  In step S106b following step S105b, the computer 20 calculates the movement range ΔZ in the Z-axis direction based on the Z value approximate line La. For example, the center of the movement range ΔZ is a point on the Z value approximate line La. Even if it is the above process, 3rd Embodiment has an effect similar to 1st Embodiment.

  DESCRIPTION OF SYMBOLS 10 ... Shape measuring machine, 20 ... Computer, 11 ... Mount, 12 ... Workpiece, 13 ... Stage, 14, 15 ... Support arm, 16 ... X-axis guide, 17 ... Imaging unit, 21 ... Computer main body, 22 ... Keyboard, 23 ... J / S, 24 ... Mouse, 25 ... Display, 31, 33, 34, 39 ... I / F, 32 ... Image memory, 35 ... CPU, 36 ... Display control unit, 37 ... ROM, 38 ... HDD, 40 ... RAM, 17a ... Actuator, 17b ... Encoder, 171 ... Light source, 172 ... Collimator lens, 173 ... Beam splitter, 175 ... Reference plate, 177 ... Imaging lens, 178 ... CCD camera.

Claims (1)

A stage for placing an object to be measured;
An imaging unit configured to image the measurement object and be relatively movable with respect to the stage;
The imaging unit is moved from a first position in a first direction parallel to the stage, and the imaging unit is sequentially arranged at a second position and a third position, and the stage at the first position to the third position. A control unit that captures the measurement object in the imaging region by the imaging unit while moving the imaging unit in a second direction perpendicular to the image acquisition unit, and acquires a plurality of captured images.
The control unit is configured such that a part of the imaging area at the first position and the second position overlaps in the first overlapping area, and a part of the imaging area at the second position and the third position overlaps the second overlapping area. Move the imaging unit to overlap at
A moving range in the second direction of the imaging unit at the third position is set based on a change in height of the measurement object in the first overlapping region and the second overlapping region at the second position. A shape measuring device.

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