KR100856466B1 - Scanning moire measurement device and method - Google Patents

Abstract

A method and an apparatus for measuring a scanning Moir are provided to measure a height of an object by restoring a 3D shape of the object using a single projection lattice. An apparatus for measuring a scanning Moir includes a projector, an XY-table(50), a line scan camera(58), and a central controller(60). The projector includes an optical source(56) and a projection lattice(54) and forms a shadow of the projection lattice on an object(52). The XY-table moves the object in four directions. The line scan camera pictures the image of projection lattice on the object according to a phase change of the projection lattice. The central controller analyzes a Moir pattern by using the images from the line scan cameras and analyzes a 3D shape of the object. The central controller controls an image interface(62), a projection driver(64), and an XY-table driver(66). The central controller acquires a first image of the object and moves the projection lattice in the same direction as a surface of the object. Then, the central controller acquires a second image and moves the projection lattice on the same direction as the surface of the object. After a third image is acquired, the central controller moves the projection lattice in the same direction as the surface of the object, such that a fourth image is acquired.

Description

Scanning moire measurement device and method

The present invention relates to a moiré pattern acquisition device and a method for measuring the height of an object using the same, and more particularly, the configuration of the object having a small height step by using a projection moire method using only one projection grid with a simple configuration. The present invention relates to a moiré pattern acquisition device capable of restoring a dimensional shape and easily measuring its height, and a method of measuring a height of an object using the same.

In particular, the present invention has been proposed to measure an object with a large measurement area in a short time, and receives a plurality of images again by moving a position after completing a measurement by receiving a plurality of images in a conventional position. It is possible to drastically shorten the measurement time by acquiring a continuous image while moving by measuring a method, as well as a simple and fast measuring device and measuring method by applying a line scan camera to a conventional area camera. It is about.

In general, it is a technique for measuring a three-dimensional shape of a free-form surface, a method of measuring the entire surface shape by measuring a point on the surface by a contact method using a three-dimensional measuring device.

However, this method has a disadvantage in that excessive measurement time is required, and in recent years, a lot of non-contact measuring methods such as the moiré method have been used, which is much larger than the contact method using a three-dimensional measuring instrument. It has advantages

Here, the moiré method, in order to obtain a moire fringe having the three-dimensional shape information of the measurement object, it is necessary to form a straight stripe at regular intervals on the measurement object, and to accurately transfer it. In the conventional method for this purpose, a projection lattice in which a straight line of uniform intervals is engraved on one surface of the glass is projected onto the measurement object using a projection optical system. In addition, the projection grid transfer apparatus is used to transfer the straight stripes formed on the measurement object at regular intervals.

However, in the image obtained by the conventional moiré measuring device, the moiré pattern indicating the height information of the measurement object and the pattern of the reference grating placed in front of the camera are simultaneously displayed. There is a problem in that the configuration is complicated by the need for means.

In addition, the conventional moiré method acquires an image while the camera is stopped, but obtains three or more moiré images by moving the projection grid three or more times, and then obtains a measurement result through an algorithm, and then moves the object to an adjacent position as described above. The measurement is repeated while the measurement area is large. If the area to be measured is large, the projection grid must be moved three times or more at each position where the image is acquired. There is a problem that the measurement accuracy is lowered.

Therefore, the present invention is proposed to use a line scan camera to solve the above-mentioned problems according to the prior art, and to significantly reduce the measurement time when the measurement area is large.

Therefore, the present invention obtains images of all measurement areas in a state in which the projection grid is fixed by applying a line scan camera, and then transfers the projection grids so that the projection grid is completed until the measurement is completed regardless of the measurement area. The present invention provides a measuring apparatus and a measuring method which can reduce the number of times of transferring the projection grid, thereby dramatically reducing the measuring time and increasing the measuring accuracy by transferring only three times.

Assuming 10 measurement points and comparing the moiré method of the present invention with the conventional moiré method,

First, the conventional moiré method

Move to the first point of measurement object (step 1) →

Acquire the first image of the first point (step 2) → Move the projection grid (λ / 4) (step 3) →

Acquire the second image of the first point (step 4) → Move the projection grid (2λ / 4) (step 5) →

Acquiring the third image of the first point (step 6) → Moving the projection grid (3λ / 4) (step 7) →

Acquire the fourth image of the first point (8 steps) → Move the projection grid (4λ / 4) (9 steps) →

Calculation of the measurement result of the first point using the first to fourth images above (step 10) →

Move to the second point of measurement object →

Acquire the first image at the second point → Move the projection grid (λ / 4) →

Acquire the second image at the second point → Move the projection grid (2λ / 4) →

Acquire the third image from the second point → Move the projection grid (3λ / 4) →

Acquire the fourth image at the second point → Move the projection grid (4λ / 4) →

Calculation of the measurement result of the second point using the first to fourth images above →

Calculate the measurement result by the same process as above for points 3-9

Move to the 10th point of measurement object →

Acquire the first image at point 10 → Move the projection grid (λ / 4)

Acquire the second image at point 10 → Move the projection grid (2λ / 4)

Acquire the third image from the tenth point → move the projection grid (3λ / 4)

Acquire the fourth image at point 10 → Move the projection grid (4λ / 4) →

Calculation of the measurement result of the tenth point through the above first to fourth images

The measurement proceeds through the steps of.

At this time, if you look at the total required steps for calculating the measurement results of 10 points, it can be seen that the total takes 100 steps because each step takes 10 steps.

On the contrary, looking at the moiré method of the present invention,

Moving continuously from point 1 to point 10

Acquiring the first image of the first point (step 1) → Acquiring the first image of the second point (step 2) →

Acquiring the first image of the third point (step 3) → Acquiring the first image of the third point (step 4) →

Acquisition of the first image at point 5 (step 5) → Acquisition of the first image at point 5 (step 6) →

Acquisition of the first image at point 7 (step 7) → Acquisition of the first image at point 8 (step 8) →

Acquisition of the first image at point 9 (step 9) → Acquisition of the first image at point 10 (step 10) →

Projection Grid (λ / 4) Shift (11 Steps) →

Moving continuously from point 10 to point 1

Acquisition of the second image at point 10 → Acquisition of the second image at point 9 →

Acquisition of the second image at point 8 → Acquisition of the second image at point 7 →

Acquisition of the second image at point 6 → Acquisition of the second image at point 5 →

Acquisition of the second image at point 4 → Acquisition of the second image at point 3 →

Acquiring the second image at the second point → Acquiring the second image at the first point →

Projection Grid (2λ / 4) Shift →

Moving continuously from point 1 to point 10

Acquire a third image of the first to tenth points

Projection Grid (3λ / 4) Shift →

Moving continuously from point 10 to point 1

Acquire a fourth image of points 10 to 11

Projection Grid (4λ / 4) Shift →

Calculate the measurement result of each point from the first to fourth images of the first to tenth points

The measurement results are calculated through the steps of.

As described in detail above, the moiré measurement method proposed in the present invention acquires images in a batch after moving the projection grid, so that four steps of moving the projection grid and four images for each of 10 points are acquired and the acquisition phase 40 is obtained. The measurement is completed in 10 steps to calculate the measurement results for each of the 10 points.

Therefore, it can be seen that the moiré method of the present invention is measured in only half of the steps compared to the conventional moiré method, assuming 10 points are measured.

However, since the time-consuming step in the moiré method is a step of mechanically transferring the projection grid, in view of the measurement time, the moiré method of the present invention can be reduced by about 1/10 compared to the conventional moire method, so that the measurement time Will be significantly reduced.

That is, in the present invention, the projection grid is only applied until the measurement is completed in such a manner as to obtain an image of each measurement point while continuously moving all the stationary points with the projection grid fixed by applying the line scan camera as described above. Since only three transfers can be made, the number of transfers of the projection grid can be reduced, which significantly shortens the measurement time and increases the measurement accuracy.

Features of the moiré pattern acquisition apparatus according to the present invention for achieving the method described above,

Projection means 12 for projecting a projection grid to the object object 10 using light;

A line scan camera 14 for capturing and scanning images projected from the projection means 12 onto the object 10 according to a phase;

The computer 16 is configured to analyze the three-dimensional shape of the object 10 by analyzing moire fringes using the images transmitted from the line scan camera 14.

In addition, the characteristics of the height measurement method of the object using the moire pattern acquisition apparatus according to the present invention for achieving the above object,

When the lighting unit 12-1 is turned on, light is irradiated onto the object 10;

In order for the light of the lighting unit 12-1 to be irradiated to the target object 10 through the projection grid unit 12-3, the projection grid unit 12-3 is finely adjusted using an actuator to adjust the lens ( Projecting the fine grid to the object object 10 through 12-5);

Photographing, scanning, and acquiring images projected on the object (10) according to a phase through a line scan camera (14), and then transmitting the images obtained by the line scan camera (14) to a computer (16);

And analyzing the three-dimensional shape of the object 10 by analyzing the moire fringes using the images through the scanning moiré analysis module 16-1 of the computer 16.

As described above, the present invention obtains images of all regions through a line scan camera, and can significantly reduce the number of movements of the projection grid compared to the conventional moiré method, so that the measurement time is much higher than that of the conventional moiré method. Fast and excellent measurement accuracy.

That is, the moiré measuring method of the present invention is very useful for obtaining a wide area of three-dimensional shape information, and it is possible to restore the three-dimensional shape of the entire area with only four scanned images obtained by scanning in four times, so that the three-dimensional shape information can be performed at a higher speed. There is an effect that can be obtained.

In particular, the present invention has the effect of restoring the three-dimensional shape of the object having a small height step by using a projection moiré method using only one projection grid and can easily measure the height.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

In addition, the present embodiment is not intended to limit the scope of the present invention, but is presented by way of example only, and various modifications may be made without departing from the technical gist of the present invention.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of the moiré pattern acquisition apparatus according to the present invention and a height measuring method of the object using the same as follows.

1 is a block diagram of a moire fringe obtaining apparatus according to the present invention.

As shown in FIG. 1, the apparatus for acquiring a moire fringe according to the present invention includes projection means 12 for projecting a projection grid to a target object 10 using light; A line scan camera 14 for capturing and scanning images projected from the projection means 12 onto the object 10 according to a phase; The computer 16 is configured to analyze the three-dimensional shape of the object 10 by analyzing moire fringes using the images transmitted from the line scan camera 14.

Here, the projection means 12 includes an illumination unit 12-1 for irradiating light to the object 10; Projection lattice portion 12-installed below the lighting unit 12-1 to project the light irradiated from the lighting unit 12-1, and to shift the phase by a small interval by an actuator (not shown). 3) and; The lens 12-5 is provided below the projection lattice part 12-3 to project the micro lattice onto the target object 10.

In addition, the computer 16 includes a scanning moiré analysis module 16-1 that analyzes a moire fringe using images to analyze a three-dimensional shape of the object 10.

Referring to the method of measuring the height of the object using the moire pattern acquisition device configured as described above are as follows.

First, the object 10 is placed below the moire fringe obtaining apparatus. Here, the object (eg, solder ball) 10 will be described in more detail with reference to FIG. 2. The flip chip has a solder ball grid array having a diameter of about 40μ and a height of about 20-50μ at the center. (8) It is seated on the upper surface.

As described above, when the object 10 is positioned below the moire fringe obtaining apparatus, the lighting unit 12-1 is turned on. As the lighting unit 12-1 is turned on, light is irradiated onto the object 10.

Then, the projection grid unit 12-3 is finely adjusted using an actuator so that the light of the lighting unit 12-1 can be irradiated to the target object 10 through the projection grid unit 12-3. . At this time, according to the adjustment of the actuator, the microlattice of the projection grid portion 12-3 is projected onto the target object 10 through the lens 12-5.

Meanwhile, the line scan camera 14 captures and scans images projected on the object 10 according to phases. At this time, the section obtained by scanning the image is obtained in the same section as 'A' and 'B' section is specified in FIG.

At this time, the projection lattice is moved in the same direction as the target surface as shown in FIG. 4, which is the same in the following description.
Looking at the operation of the line scan camera 14 with reference to Figure 3, the line scan camera 14 is installed so as to move along one line, a total of four scans for the same area in four scans Images are acquired, and when photographing each scanned image, the phase of the projection grids projected on the object 10 is shifted by λ / 4 according to the movement of the projection grid unit 12-3, and then the scanned image is obtained. .

That is, the four scanned images are images in which a projection grid having a phase difference of λ / 4 is projected.

In this case, the first scanned image is an image obtained with the projection grid at the initial position, the second scanned image is an image obtained with the projection grid shifted by λ / 4 from the initial position, and the third scanned image is obtained. The fourth image is obtained when the projection grid is moved by (2λ / 4) from the initial position, and the fourth scanned image is the image obtained when the projection grid is moved by (3λ / 4) from the initial position.

However, if the first scan image is obtained while the projection grid is first moved by [lambda] / 4, the initial position of each scan image becomes [lambda] / 4 and thus is represented as shown in FIG.

The line scan camera 14 then transfers the images obtained in the same way to the computer 16.

In addition, the computer 16 is provided with a scanning moiré analysis module 16-1. The computer 16 analyzes moiré patterns using images through the scanning moiré analysis module 16-1. The three-dimensional shape of the object 10 is analyzed.

Figure 4 shows a schematic measurement flow chart of the moiré meter of the present invention. For ease of explanation, the reference numerals of FIG. 4 indicate that numbers different from those of FIGS. 1 to 3 described above are used.

The measurement method will be described in more detail below.

First, the object 52 is placed on the XY table 50 moving in the left and right and front and rear directions, and above the light source 56, the projection grid 54, and the line scan camera 58 are positioned.

The central control unit 60 on which the moiré measurement algorithm is mounted is connected to the image interface unit 62, the projection lattice drive driver 64, and the XY table drive driver 66 to control them.

The image interface unit 62 acquires and processes an image transmitted from the line scan camera 58, and transmits the result to the central controller 60, and the projection grid driver 64 provides a projection grid driver (not shown). Drive to finely move the projection grid.

At this time, the central controller 60 scans the measurement range of the target object 52 to obtain the first image and then moves the projection grid, and scans the measurement range to acquire the second image and then moves the projection grid. After scanning the measurement range, the projection grid is moved after obtaining the third image, and the projection grid driving driver is controlled to acquire the fourth image by scanning the measurement range.

In addition, the XY table driving driver 66 drives a motor (not shown) that transfers the XY table back, forth, and left and right so that the measurement area of the object 50 is acquired by the line scan camera 58 as an image.

The measurement procedure will be described in detail below.

Step 1: The light of the light source 56 is turned on so that the shadow of the projection grid is reflected on the object 10.

Step 2: The XY table 50 is controlled such that the starting point (see 'A' in FIG. 4) of the object 10 is positioned on the vertical line of the line scan camera 58.

Step 3: Position the projection grid 54 at the initial position.

Step 4: The XY table is driven to continuously move the object 10 to an end point (see point “B” in FIG. 4) while acquiring first images of all positions of the object.

Step 5: The projection grid 54 is moved by λ / 4 from the initial position.

Step 6: Drive the XY table to continuously move the object 10 from the end point (see point “B” in FIG. 4) to the start point (see point “A” in FIG. 4) continuously. Acquire two images. In some cases, an image may be acquired while moving an object from a start point to an end point when an image is acquired.

Step 7: Move the projection grid 54 by (2λ / 4) from the initial position.

Step 8: Drive the XY table to continuously move the object 10 from the start point to the end point and acquire third images of all positions of the object.

Step 9: Move the projection grid 54 by (3λ / 4) from the initial position.

Step 10: drive the XY table to continuously move the object 10 from the end point (see point “B” in FIG. 4) to the start point (see point “A” in FIG. 4) continuously. Acquire 4 images.

Step 11: The first images (images obtained when the projection grid is in the initial position) and the second images (all images obtained when the projection grid is moved by (λ / 4) from the initial position) Image), third images (images obtained when the projection grid was moved by (2λ / 4) from the initial position), and fourth images (images obtained when the projection grid was moved by (3λ / 4) from the initial position) Image) is applied to the moirre analysis module to analyze the 3D image of the object.

Although the projection grid movement distance of the moire measuring method of the present invention described above has been moved by λ / 4, 2λ / 4, 3λ / 4, which are multiples of λ, this is a measurement measured while moving by an arbitrary distance even if the movement distance of the projection grid is not exactly known. Since algorithms are well known, it is natural to apply these algorithms even if the movement distance of the projection grid is shifted by arbitrary distance.

As described above, it can be seen that the moiré measuring method of the present invention only moved the projection lattice three times in order to acquire images of all positions of the object. In the conventional moiré measurement method, since the projection grid is moved at each position of the target object, not only the measurement time is required, but also the vibration caused by the movement of the projection grid causes distortion of the image, thereby reducing the measurement accuracy. Compared with the measurement method, the measurement time is very fast and the measurement accuracy is also excellent.

The following results were obtained by measuring the moiré measuring method and the conventional measuring method of the present invention.

division Conventional moiré measuring technique (area camera applied) Moiré measuring method of the present invention (line scan camera application) Remarks Projection Grid Shifts 240 times 4 times 60x improvement Measuring time 54 seconds 2.7 seconds Approximately 20 times improvement

Data on Application of Conventional Moiré Techniques

Field of View (FOV): 18.432mm X 18.432mm

-Image Acquisition Segmentation Area: Total 60 (Measurement Area: 72mm x 270mm)

-Number of projection grid movements: 240 times (image acquisition area 60 x 4)

-One measurement time: 0.9 seconds (including movement, image acquisition and measurement calculation time)

-Measurement time for all areas: 54 seconds in total (0.9 seconds x 60)

Moire technique application data of the present invention.

X-axis FOV: 73.728mm

Scan speed: 550.8 mm / s

-Number of projection grid movements: 4 times

-Scanning time of the whole area: 0.59 seconds (including 0.1 second of synchronization time, measuring area: 72mm x 270mm)

-Total image acquisition time for all areas: 2.36 seconds (0.59 x 4)

-Measurement time for all areas: less than 2.7 seconds (image acquisition time + calculation time)

As shown in the above table, the moiré measuring method of the present invention was able to obtain the measurement result about 20 times faster than the conventional measuring method for the same measuring area, and it can be seen that the measurement time can be drastically reduced.

1 is a block diagram of a moire fringe obtaining apparatus according to the present invention,

2 is an enlarged view of the object of FIG. 1;

3 is a view showing a moire pattern acquisition of the object in the moire pattern acquisition apparatus according to the present invention.

4 is a control block diagram of a moire fringe obtaining apparatus according to the present invention.

<Description of Symbols for Main Parts of Drawings>

10: object

12: consular means

14: line scan camera

16: computer

Claims (5)

Projection means composed of a light source 56 and a projection grid 54 for forming a shadow of the projection grid 54 on the target object 52; An XY table (50) for moving the object (52) in front, rear, left and right directions; A line scan camera 58 for capturing and scanning in accordance with a phase change caused by the movement of the projection grid projected onto the object 52 from the projection means 12; A central controller 60 for analyzing a three-dimensional shape of the object object 52 by analyzing moire fringes using the images transmitted from the line scan camera 58; The central control unit 60 includes an image interface unit 62, a projection grating driving driver 64, and an XY table driving driver 66; Control the The central control unit 60 acquires the first image by scanning the corresponding measurement range of the target object 52, moves the projection grid in the same direction as the surface of the target object, and scans the corresponding measurement range in the second image. After acquiring, move the projection grid in the same direction as the surface of the object, scan the measurement range and obtain the third image, then move the projection grid in the same direction as the surface of the object, and scan the measurement range. Moiré measuring device characterized in that for controlling the projection grid drive driver to obtain a fourth image. The method of claim 1, The image interface unit 62 acquires and processes an image transmitted from the line scan camera 58, and transmits the result to the central controller 60, and the projection grid driving driver 64 drives the projection grid driving unit. A moiré measuring device characterized in that the projection grating finely moves in the same direction as the target object, and the XY table driving driver (66) drives a motor that transfers the XY table back, forth, and left and right. Projection means composed of a light source 56 and a projection grid 54 for forming a shadow of the projection grid 54 on the target object 52; An XY table (50) for moving the object (52) in front, rear, left and right directions; A line scan camera 58 for acquiring and scanning images according to a phase change (images in phase) due to the phase change caused by the movement of the projection grid projected from the projection means 12 to the object object 52; In the moiré pattern acquisition apparatus consisting of a central control unit 60 for analyzing the three-dimensional shape of the target object 52 by analyzing the moire pattern using the images transmitted from the line scan camera 58, A first step of turning on the light of the light source 56 so that the shadow of the projection grid 54 is reflected on the object 10; A second step of controlling the XY table 50 such that a start point of the object 10 is positioned on a vertical line of the line scan camera 58; A third step of positioning the projection grid 54 in an initial position; A fourth step of driving the XY table to acquire the first image of all positions of the object while continuously moving the object 10 to an end point; A fifth step of moving the projection grid 54 in the same direction as the surface of the object so that the phase difference is greater than the initial position; A sixth step of driving the XY table to continuously move the object 10 from the end point to the start point or to obtain a second image of all positions of the object while continuously moving from the start point to the end point; A seventh step of acquiring third and fourth images of all positions of the object while repeating the fifth and sixth steps; An eighth step of analyzing the three-dimensional image of the object by applying the first image, the second image, the third image, and the fourth image of all positions obtained above to the moire analysis module. Moiré measurement method to use.     The method of claim 3, In the first image, the second image, the third image, and the fourth image of all the positions of the object obtained in the eighth step, the first image is an image obtained when the projection grid is in the initial position. The second image is obtained when the projection grid is shifted to have a phase difference of (λ / 4) from the initial position, and the third image is obtained when the projection grid is shifted to have a phase difference of (2λ / 4) from the initial position. And the fourth image is an image obtained when the projection grid is moved to have a phase difference of (3λ / 4) from the initial position.   In the moiré measurement method        A first step of turning on the light of the light source 56 so that the shadow of the projection grid is reflected on the object 10;  A second step of controlling the XY table 50 such that the start point of the object object 10 (see point 'A' in FIG. 4) is positioned on a vertical line of the line scan camera 58; A third step of positioning the projection grid 54 in an initial position; A fourth step of acquiring first images of all positions of the object while driving the XY table to continuously move the object 10 to an end point (see point “B” in FIG. 4); A fifth step of moving the projection grid 54 to have a phase difference of? / 4 from the initial position; By driving the XY table, the second images of all the positions of the object are continuously moved while continuously moving the object 10 from the end point (see point “B” in FIG. 4) to the start point (see point “A” in FIG. 4). Obtaining a sixth step; Seventh step of shifting the projection grid 54 to have a phase difference of (2λ / 4) from the initial position An eighth step of driving the XY table to acquire the third images of all positions of the object while continuously moving the object 10 from the start point to the end point; A ninth step of moving the projection grid 54 so as to have a phase difference of (3λ / 4) from the initial position; The XY table is driven to continuously move the object 10 from the end point (see point “B” in FIG. 4) to the start point (see point “A” in FIG. 4) while the fourth images of all positions of the object are moved. Obtaining a tenth step; When the first images (all images obtained when the projection lattice is in the initial position) and the second images (the projection lattice has a phase difference of (λ / 4) than the initial position) of all the objects obtained above Acquired images), third images (images obtained when the projection lattice has a phase difference of (2λ / 4) from the initial position), and fourth images (projections lattice (3λ / 4) than the initial position) An eleventh step of analyzing the three-dimensional image of the object by applying the image obtained when the image is moved to have a phase difference as much as the moire analysis module; Moiré measuring method characterized in that consisting of.

Images