KR101311809B1 - Method for inspecting substrate - Google Patents

Abstract

The present invention sequentially divides a substrate into a plurality of observation areas (FOVs) by using a measurement module including at least one projection unit for irradiating pattern illumination with a substrate fixed to a stage and a camera for capturing an image of the substrate. A method for inspecting a substrate, the method comprising: setting a real ROI in which a measurement object is formed and a dummy ROI for confirming a floor trend, for the at least one observation region; Estimating a height displacement amount for a next observation area by using trend information obtained from at least one of the dummy ROIs, and adjusting the height of the measurement module based on the predicted height displacement amount prior to inspection of the next observation area. And adjusting the next observation area using the measurement module having completed the height adjustment. And a step. In this way, by using the floor trend information of the dummy ROI as well as the actual ROI in one observation area, it is possible to more accurately identify the floor trend for the corresponding observation area, thereby predicting the height displacement for the next observation area. Can improve the precision.

Description

Substrate inspection method {METHOD FOR INSPECTING SUBSTRATE}

The present invention relates to a substrate inspection method, and more particularly, to a substrate inspection method for increasing the reliability of the inspection process for inspecting the formation state of the measurement object formed on the substrate.

In general, in order to verify the reliability of a substrate on which an electronic component is mounted, it is necessary to check whether or not the substrate is properly manufactured before and after mounting the electronic component. For example, it is necessary to check whether lead is properly applied to a pad region of a substrate before mounting the electronic component on a substrate, or to inspect whether the electronic component is properly mounted after the electronic component is mounted on the substrate.

Recently, in order to precisely measure the measurement object formed on the substrate, at least one projection unit for irradiating pattern light to the measurement object, including an illumination source and a grid element, and photographing the image of the measurement object through irradiation of the pattern light Techniques for measuring the three-dimensional shape of the measurement object using a measurement module including a camera to be used.

The substrate inspection apparatus may measure the entire area of the substrate in one step. However, when the size of the substrate is larger than the field of view (FOV) of the camera, the substrate inspection apparatus divides the substrate into a plurality of observation regions. Can be measured sequentially over.

On the other hand, the substrate loaded on the substrate inspection apparatus maintains both ends fixed by the stage. Accordingly, as the size of the substrate increases, warpage occurs in the substrate, and a height variation occurs in each of the plurality of observation regions. In general, since the substrate inspection apparatus has a measurable range in which the height can be measured, if the height deviation due to the warpage of the substrate exceeds the height measurable range, the height measurement may not be properly performed. have.

In addition, when height deviation occurs in each observation region according to the warpage of the substrate, the displacement amount of each observation region is measured in advance through a separate laser rangefinder, and the height of the measurement module is reset for each observation region. However, there is a problem that the board inspection time is increased according to the height displacement measurement in advance.

Accordingly, the present invention has been made in view of such a problem, and the present invention adjusts the height of the measurement module for the next observation region to be inspected by using the height trend information of at least one previous observation region that has been inspected. Provided is a substrate inspection method that can shorten measurement time and improve inspection reliability.

In addition, in the present invention, when a region of interest (ROI) in which an object of measurement actually exists in the observation area is biased to one side, a dummy region of interest for confirming the bottom trend is set in the observation area, thereby providing Provides a substrate inspection method that can improve the reliability.

In addition, the present invention provides a substrate inspection method that can increase the measuring range of the height in response to the bending of the substrate by performing the substrate inspection using the first pattern light and the second pattern light having different wavelengths.

According to an aspect of the present invention, a method for inspecting a substrate includes a plurality of substrates using a measurement module including at least one projection unit for irradiating pattern illumination with a substrate fixed to a stage and a camera for capturing an image of the substrate. A method for inspecting a substrate by dividing it into observation areas (FOVs) and sequentially inspecting the same. The at least one observation area includes a real ROI and a dummy ROI for confirming a bottom trend. Setting a DROI), predicting a height displacement amount for a next observation area by using trend information obtained from at least one of the actual ROI and the dummy ROI, and predicting the inspection before the next observation area. Adjusting the height of the measuring module based on the height displacement amount, and the measuring module having completed the height adjustment. Using a step of inspecting the next observation area.

A planar equation of the observation area may be calculated using at least one height information of the actual ROI and the dummy ROI existing in the observation area, and the planar equation may be used as trend information.

The dummy region of interest may be manually set by a user.

Alternatively, the dummy ROI may be automatically set based on the location of the actual ROI. Automatically setting the dummy region of interest may include identifying a position of the actual region of interest in the observation region, and setting the dummy region of interest at a location as far away from the actual region of interest as possible. have.

The measurement module may include at least one first projection unit irradiating a first pattern light having a first wavelength, and at least one second projection unit irradiating a second pattern light having a second wavelength different from the first wavelength. It may include. In contrast, the projection unit may sequentially irradiate the first and second pattern lights having different wavelengths.

As such, by utilizing not only the actual ROI of the observation area FOV but also the bottom trend information of the dummy ROI, the bottom trend of the observation area FOV can be more accurately identified. Through this, the accuracy of height displacement prediction for the next observation area (FOV) can be improved.

1 is a conceptual diagram schematically showing a substrate inspection apparatus according to an embodiment of the present invention.
2 is a plan view illustrating a state in which a substrate is fixed to a stage.
3 is a side view illustrating a state in which a substrate is fixed to a stage.
4 is a flow chart showing a substrate inspection method according to an embodiment of the present invention.
5 is a plan view of one observation area.
6 is a conceptual diagram illustrating a substrate inspection method according to an embodiment of the present invention.
7 and 8 are plan views illustrating first and second pattern lights emitted from the projection unit.
9 is a conceptual diagram illustrating a substrate inspection method according to another embodiment of the present invention.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprising" or "having ", and the like, are intended to specify the presence of stated features, integers, steps, operations, elements, parts, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted as ideal or overly formal in meaning unless explicitly defined in the present application Do not.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

1 is a conceptual view schematically showing a substrate inspection apparatus according to an embodiment of the present invention, Figure 2 is a plan view showing a state in which the substrate is fixed to the stage, Figure 3 is a side view showing a state in which the substrate is fixed to the stage. .

1, 2 and 3, the substrate inspection apparatus 100 according to an embodiment of the present invention is at least one projection unit for irradiating pattern light to the substrate 150 on which the measurement object 152 is formed ( The measurement module 120 includes a camera 130 for capturing an image of the 110 and the substrate 150. In addition, the substrate inspection apparatus 100 may further include a stage 140 for supporting and fixing the substrate 150 on which the measurement object 152 is formed.

The projection unit 110 irradiates the substrate 150 with pattern light to measure the three-dimensional shape of the measurement object 152 formed on the substrate 150. For example, the projection unit 110 includes a light source 112 for generating light, a grating element 114 for converting light from the light source 112 into pattern illumination, and a grating for pitch conveying the grating element 114. And a projection lens 118 for projecting the patterned light converted by the transfer mechanism 116 and the grating element 114 onto the measurement object 152. The grating element 114 may be transferred by 2 [pi] / N by a grating transfer mechanism 116 such as a piezo actuator (PZT) for the phase shift of pattern lighting. Here, N is a natural number of 2 or more. Projection unit 110 having such a configuration may be provided in plurality so as to be spaced apart at a predetermined angle in the circumferential direction with respect to the camera 130 to increase the inspection accuracy. The plurality of projections 110 are installed to be inclined at a predetermined angle with respect to the substrate 150 to irradiate pattern light onto the substrate 150 from a plurality of directions. Meanwhile, the substrate inspecting apparatus 100 may include only one projection unit 110.

The camera 130 captures an image of the substrate 150 through irradiation of the pattern light of the projection unit 110. For example, the camera 130 is installed at an upper portion perpendicular to the substrate 150. The camera 130 may include a CCD camera or a CMOS camera for capturing an image.

The stage 140 is for supporting and fixing the substrate 150, and is configured to support and fix both ends of the substrate 150, for example. To this end, the stage 140 may include a first stage 140a for supporting and fixing one end of the substrate 150 and a second stage 140b for supporting and fixing the other end of the substrate 150. In addition, the first stage 140a and the second stage 140b each include a lower stage 142 in contact with the lower surface of the substrate 150 and an upper stage 144 in contact with the upper surface of the substrate 150. can do. Therefore, when the substrate 150 is carried between the lower stage 142 and the upper stage 144, the gap between the lower stage 142 and the upper stage 144 may be narrowed to fix the substrate 150. For example, the lower stage 142 may be raised to fix the substrate 150.

The substrate inspection apparatus 100 having such a configuration irradiates pattern light using the projection unit 110 to the substrate 150 fixed to the stage 140, and the image of the substrate 150 through the camera 130. By photographing, the three-dimensional shape of the substrate 150 on which the measurement object 152 is formed is inspected. For example, the substrate 150 may be a printed circuit board (PCB) on which conductive wires and pads are formed, and the measurement object 152 is mounted on the solder or substrate 150 formed on the pad. It may be an electronic component.

On the other hand, when the size of the substrate 150 is larger than the measurement area that the camera 130 can measure at one time, the substrate inspection apparatus 100 divides the entire area of the substrate 150 in several steps and measures it. That is, as shown in FIG. 2, the substrate 150 is divided into a plurality of fields of view (FOVs), and the measurement module 120 sequentially views the fields of view according to a predetermined inspection order. By inspecting while moving, the whole area | region of the board | substrate 150 can be inspected. In this case, the size of the observation area (FOV) is preferably substantially the same as the size of the measurement area that the camera 130 can measure at one time, and may be slightly smaller in some cases.

Meanwhile, since the bending of the substrate 150 may occur depending on the size of the substrate 150 or the weight of the mounted electronic component, the upper surface of the substrate 150 may have different heights according to positions. That is, the substrate 150 may have different topography for each observation region FOV due to the warpage phenomenon. Therefore, in order to increase the reliability of the inspection of the substrate 150, it is necessary to adjust the focus of the substrate inspection apparatus 100 for each observation area FOV in response to the bending of the substrate 150. At this time, focus adjustment of the substrate inspection apparatus 100 may be performed by raising or lowering the measurement module 120 in the Z-axis direction.

Hereinafter, a detailed description will be given of a substrate inspection method in which the substrate 150 fixed to the stage 140 is divided into a plurality of observation areas FOV using the measurement module 120 and sequentially inspected.

4 is a flowchart illustrating a substrate inspection method according to an embodiment of the present invention, FIG. 5 is a plan view of one observation area, and FIG. 6 is a conceptual diagram illustrating a substrate inspection method according to an embodiment of the present invention.

2, 4, 5, and 6, when the substrate 150 is divided into a plurality of observation areas FOV and sequentially inspected, first, an inspection order of the plurality of observation areas FOV is examined. Can be set. For example, the inspection order of the plurality of observation areas FOV may be set in a zigzag manner along the length direction of the stage 140. For example, as shown in FIG. 2, when the substrate 150 is divided into nine observation areas FOV1 to FOV9, the stage 150 starts with the first observation area FOV1 adjacent to the stage 140. The inspection order (FOV1-FOV2-FOV3-FOV4-FOV5-FOV6-FOV7-FOV8-FOV9) is set up to the ninth observation area FOV9 along the longitudinal direction of 140.

In the inspection of the plurality of observation areas FOV according to the set inspection order, the height displacement of the target observation area FOV may be predicted using the trend information of the previous observation area FOV. That is, while sequentially examining a plurality of observation areas (FOV), the target observation area by using the trend information on the previous observation area (FOV) that the inspection is completed for the next target observation area (FOV) to be examined next It is possible to predict the height displacement with respect to (FOV).

Specifically, in estimating the height displacement amount for the target observation area FOV, the height displacement amount for the target observation area FOV is determined by using extrapolation from trend information of the previous observation area FOV. Predict. On the other hand, in estimating the amount of height displacement with respect to the target observation area (FOV), interpolation may be used in addition to extrapolation in some cases.

For example, when the target observation area FOV is the fifth observation area FOV5 of FIG. 2, the first observation area FOV, which is located near the fifth observation area FOV5, may include first, There are second, third and fourth viewing areas FOV1, FOV2, FOV3, and FOV4. Accordingly, after estimating the terrain in the fifth observation region FOV5 from the trend information of the first, second, third and fourth observation regions FOV1, FOV2, FOV3, and FOV4 by using the extrapolation method. In addition, the Z-axis transfer position of the measurement module 120 in the fifth viewing area FOV5 may be calculated using the estimated terrain in the fifth viewing area FOV5. Here, although the terrain information for all of the first, second, third and fourth observation areas FOV1, FOV2, FOV3, and FOV4 may be used, the first, second, third and fourth observation areas ( At least one of FOV1, FOV2, FOV3, and FOV4 may be selected and used. That is, before estimating the terrain in the fifth viewing area FOV5, the step of selecting at least one of the first, second, third and fourth viewing areas FOV1, FOV2, FOV3, and FOV4 is performed. May be

In an embodiment, if the previous observation area FOV on which the inspection is completed is present on the same row corresponding to the length direction of the stage 140, the linear trend information may be obtained. The height displacement with respect to the target observation area (FOV) can be estimated. That is, the height displacement of the target observation area FOV is predicted using trend information of at least two or more previous observation areas FOV existing on the same row corresponding to the longitudinal direction of the stage 140. For example, the center of the target observation area FOV using height information of the center point of at least two or more previous observation areas FOV existing on the same row corresponding to the longitudinal direction of the stage 140. Predict the height displacement of the point. For example, when the target observation area FOV is the third observation area FOV3, the third observation area is obtained by using height trend information of the first observation area FOV1 and the second observation area FOV2 that have been inspected. Predict the height displacement of (FOV3).

In another embodiment, if the previous observation area FOV on which the inspection is completed based on the target observation area FOV to be inspected next exists on the same row and the previous row corresponding to the longitudinal direction of the stage 140, Trend information may be used to predict the height displacement of the target observation area (FOV). That is, the height displacement of the target observation area FOV is determined by using trend information of at least three or more previous observation areas FOV on the same row and the previous row corresponding to the longitudinal direction of the stage 140. Predict. For example, the target observation area FOV may be obtained by using height information of a center point of at least three or more previous observation areas FOV on the same row and the previous row corresponding to the longitudinal direction of the stage 140. Predict the height displacement of the center point. In this case, it is preferable to use the trend information of the previous observation areas (FOV) adjacent to the target observation area (FOV). For example, when the target observation area FOV is the fifth observation area FOV5, the height trends of the inspected second observation area FOV2, the third viewing area FOV3, and the fourth viewing area FOV4 are completed. The height displacement of the fifth observation area FOV5 is estimated using the information. In addition, when the target observation area FOV is the sixth observation area FOV5, the first observation area FOV1 and the second observation area FOV2 which are adjacent to the sixth observation area FOV6 among the previous observation areas where the inspection is completed. ) And the height displacement information of the fifth observation area FOV5 is predicted.

The trend information on the previous observation area (FOV) may be a change trend of heights of all areas of the previous observation area (FOV). Here, the change in the height of the entire area may include not only information on the three-dimensional shape of the measurement object 152 but also height information on the upper surface of the substrate 150. Alternatively, the height data may be at some area or at some point of the previous observation area (FOV). For example, the plane equation of the corresponding observation area may be obtained by using height information of at least one Region of Interest (ROI) existing in the previous observation area (FOV). For example, a planar equation is calculated and obtained by using height information of at least one of an entire region of the ROI, a bottom region of the ROI, and an extended ROI, and a center point or at least one of the planar equations. The height of the outer point of can be used as reference data for height displacement measurement. The plane equation for the previous observation area FOV may be calculated using height information of at least three points in the previous observation area FOV.

On the other hand, when setting the observation area (FOV) by dividing the large-sized substrate 150 into a plurality of areas, as shown in Figure 5, the region of interest in which the measurement object 152 is actually formed in the observation area (FOV) (ROI) can be set biased in either direction. That is, in the inspection of the substrate 150, the measurement object 152 that requires substantially inspection is not performed to perform data processing for the entire area of the observation area (FOV) in order to reduce the amount of data to be processed and increase the inspection speed. Only the formed region is set as the region of interest ROI and the substrate 152 is inspected through data processing of only the region of interest ROI. However, when the set ROI is not uniformly distributed in the observation area FOV and is deviated in one direction as shown in FIG. 2, the entire observation area FOV is based on only the data in the ROI. It may be difficult to obtain accurate floor trend information for.

Therefore, in the present exemplary embodiment, the dummy ROI is set up separately in the ROV from the ROI, thereby obtaining more accurate bottom trend information about the ROV. Provide inspection methods.

To this end, first, the ROI in which the measurement object 152 is formed and the dummy ROI for confirming the bottom trend are set for at least one observation area FOV (S100).

The actual ROI is set based on an area in which the measurement object 152 on which the inspection is to be performed is formed. The substrate inspection apparatus 100 automatically sets the actual ROI according to the position of the measurement object 152 existing in the observation area FOV by using the information about the substrate 150 which is previously held. .

The dummy region of interest DROI is set separately from the actual region of interest ROI in order to obtain bottom trend information of the corresponding observation region FOV. The dummy region of interest DROI is preferably set as far from the actual region of interest ROI as possible in order to identify a more accurate bottom trend for the entire area of the field of view. For example, as shown in FIG. 5, when the actual ROI is located in one quadrant of the observation area FOV, the dummy ROI DROI is 3, which is a diagonal direction of the actual ROI. Is set in quadrant.

The dummy ROI may be manually set by a user. That is, when it is determined that the actual ROI existing in the observation area FOV is not evenly distributed in the observation area FOV, the user sets a dummy ROI separately from the actual ROI. Can be. According to the manual setting of the dummy region of interest DROI, the measurement module 120 performs data processing on the actual region of interest ROI and the dummy region of interest DROI in the observation area FOV.

The dummy region of interest DROI may be automatically set based on location information of the actual region of interest ROI. That is, after checking the position of the actual ROI existing in the observation area FOV, the substrate inspection apparatus 100 determines that the actual ROI is not evenly distributed in the observation area FOV. The dummy ROI may be automatically set at a position as far from the ROI as possible.

Subsequently, the height displacement amount for the next observation area FOV is predicted using the bottom trend information acquired from at least one of the actual ROI and the dummy ROI DROI (S110). For example, the trend information of the observation area ROI may be obtained by using at least one height information of the actual ROI and the dummy ROI existing in the observation area FOV. The planar equation of can be calculated, and the planar equation can be used as trend information.

As such, by utilizing not only the actual ROI of the observation area FOV but also the bottom trend information of the dummy ROI, the bottom trend of the observation area FOV can be more accurately identified. Through this, the accuracy of height displacement prediction for the next observation area (FOV) can be improved.

After predicting the height displacement amount for the next observation area FOV, the height of the measurement module 120 is adjusted based on the estimated height displacement amount before the inspection for the next observation area FOV (S120). For example, the height adjustment of the measurement module 120 is made based on the height displacement of the center point of the next observation area (FOV). For example, as shown in FIG. 6, when the next viewing area is the fifth viewing area FOV5, the height of the center point of the fifth viewing area FOV5 is the fourth viewing area FOV4. Compared with the height of the center point of, and as a result of the comparison, if the height of the fifth observation area (FOV5) is lower than the height of the fourth observation area (FOV4), the measurement module 120 is lowered in the Z-axis direction by the height difference, When the height of the fifth viewing area FOV5 is higher than the height of the fourth viewing area FOV4, the measurement module 120 is raised in the Z-axis direction by the height difference. Alternatively, in comparing the height displacement with respect to the next observation area (FOV), it may be compared with the preset initial Z-axis height, not the previous observation area. At this time, the initial Z-axis height for the measurement module 120 is set based on the height of the substrate 150 is fixed to the stage 140, for example, through the Z-axis calibration of the measurement module 120 The data obtained beforehand. Meanwhile, the height adjustment of the measurement module 120 may be performed before, after, or during the transfer of the measurement module 120 to the next observation area FOV.

Thereafter, the next observation area FOV is inspected using the measurement module 120 in which the height adjustment is completed (S130).

As described above, in inspecting the plurality of observation areas according to the inspection order, the height of the measurement module 120 for the next observation area to be inspected is adjusted by using the bottom trend information of the at least one previous observation area. The focus can be adjusted for acquisition of measurement information. In addition, in acquiring the bottom trend information of the observation region, the bottom trend information of the actual ROI and the dummy ROI may be used together, thereby improving reliability of the bottom trend information.

On the other hand, the substrate inspection method according to the present embodiment may use a multi-wavelength inspection method to increase the height measurement range in response to the bending of the substrate 150.

7 and 8 are plan views illustrating first and second pattern lights emitted from the projection unit, and FIG. 9 is a conceptual diagram illustrating a substrate inspection method according to another exemplary embodiment of the present invention.

6, 7 and 8, for the multi-wavelength inspection, the projection unit 110 sequentially irradiates first and second pattern lights having different wavelengths, that is, different pitches between gratings. In an embodiment for the multi-wavelength inspection, the measurement module 120 may include at least one first projection unit 110a that irradiates the first pattern light 210 having the first wavelength λ 1, as shown in FIG. 7. And at least one second projection unit 110b irradiating the second pattern light 220 having a second wavelength λ2 different from the first wavelength λ1 as shown in FIG. 8. . A plurality of first projection unit 110a and second projection unit 110b may be alternately installed at regular intervals along the circumferential direction with respect to the camera 130.

7, 8 and 9, in another embodiment for multi-wavelength inspection, one projection unit 110 and the first pattern light 210 and the second pattern light 220 having different wavelengths Can be examined sequentially. For example, the lattice element 114 included in the projection unit 110 may include a first region having a lattice spacing for the first pattern light 210 and a lattice spacing for the second pattern light 220. By dividing into two areas, multi-wavelength inspection can be performed.

As such, when the substrate inspection is performed using the first pattern light 210 and the second pattern light 220 having different wavelengths, the measurement range of the height is higher than that of the pattern light of the single wavelength. Is increased. At this time, the height measurement range of the substrate inspection apparatus 100 is determined by the least common multiple of the first wavelength λ1 and the second wavelength λ2. Therefore, as the measurement range of the height is increased, even if the substrate 150 is severely bent, it is within the measurement range, thereby improving the reliability of the height measurement.

While the present invention has been described in connection with what is presently considered to be practical and exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100: substrate inspection apparatus 110: projection unit
112 light source 114 grid element
120: measurement module 130: camera
140: stage 150: substrate
152: measuring object

Claims (7)

The substrate is divided into a plurality of observation areas (FOVs) by using a measuring module including at least one projection unit for irradiating pattern light to a substrate fixed to a stage and a camera for capturing an image of the substrate. In the substrate inspection method to inspect,
Setting, for at least one observation area, an actual region of interest (ROI) in which a measurement object is formed and a dummy region of interest (DROI) for identifying a bottom trend;
Predicting a height displacement amount for a next observation area by using bottom trend information of a substrate obtained from at least one of the actual ROI and the dummy ROI;
Adjusting the height of the measurement module based on the predicted height displacement prior to inspecting the next observation area; And
And inspecting the next observation area by using the measurement module whose height has been adjusted. The method of claim 1, wherein the trend information
Calculating a plane equation of the observation area using at least one height information of the actual ROI and the dummy ROI present in the observation area, and using the plane equation as the bottom trend information of the substrate. Substrate inspection method. The method of claim 1,
And said dummy ROI is set manually by a user. The method of claim 1,
And the dummy ROI is automatically set based on a position of the actual ROI. The method of claim 4, wherein automatically setting the dummy ROI includes:
Identifying a location of the actual region of interest in the observation area; And
And setting the dummy region of interest at a location remote from the actual region of interest. The method of claim 1, wherein the measurement module
At least one first projection unit for irradiating first pattern light having a first wavelength; And
And at least one second projection unit for irradiating a second pattern light having a second wavelength different from the first wavelength. The method of claim 1,
And the projection unit sequentially irradiates first and second pattern lights having different wavelengths.

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