KR101981533B1 - Calibration method of 3 dimensional shape detection system - Google Patents

Abstract

The present invention relates to a calibration method of a three-dimensional shape measurement system having a plurality of pattern projecting parts and one or more cameras. Provided is an efficient calibration method comprising: precision calibration using a high resolution pattern for each region of a circuit board which is already known for a position or an accurate depth value of a circuit component which is a target object for calibration; and simple calibration using a low resolution pattern.

Description

[0001] CALIBRATION METHOD OF 3 DIMENSIONAL SHAPE DETECTION SYSTEM [0002]

Circuit boards with electronic integrated circuits and discrete electronic components are well known. The circuit board is provided with certain conductive paths and pads for receiving leads of electronic components such as integrated circuit chips, resistors or capacitors. During the assembly process of the circuit board, solder paste deposits are placed at the appropriate locations on the circuit board. Solder paste deposits are usually applied by placing a stencil screen over the substrate, applying the solder paste through the stencil openings, and removing the stencil from the substrate.

 The electronic components of the circuit board are then placed on the substrate with a pick and place machine with the leads of the electronic components placed on each solder paste deposit. After all the components have been placed on the substrate, the circuit board passes through an oven to melt the solder paste deposits to form electrical and / or mechanical connections between the components and the substrate.

As miniaturization has become more and more emphasized in the electronics industry, the size of solder paste deposits and electronic components and the accuracy with which they must be placed on a substrate has become smaller and more stringent. The height of the solder paste precipitate can be as small as 50 microns, and the depth of the solder paste brick is usually measured within 1% of the design depth and size.

Discrete electronic components such as resistors and capacitors can be as small as 200x400 microns and leads on the microball grid array components can have a center-to-center spacing of less than 300 microns. The center-to-center spacing between solder bricks can sometimes be as small as 200 microns.

If the amount of the solder paste is too small, electrical connection between the lead of the electronic component and the pad of the circuit board may not be made. Too much paste may cause bridging and short-circuiting between the leads of the part. After placement, it is also important to inspect the parts to ensure that they are properly positioned. Owing parts, missing parts, or low solder joints are typical defects that occur during part placement and solder paste reflow processes. After the reflow process, an automated optical inspection system can be used to inspect the proper placement of components and the quality of reflowed solder joints to ensure that all components are properly soldered and connected to the circuit board. Current optical inspection systems use 2D video images of circuit boards to detect defects. However, optical inspection systems that detect 3D depth images of circuit boards may enable detection of placement defects such as lifted leads, package coplanarity and component tombstones and billboards, Or improved.

Structured optical systems are well known for detecting 3D depth images. The structured optical system projects a specially designed optical pattern onto an object for generating depth information, and then acquires image information on which the optical pattern is projected through the camera. The projected optical pattern decoding is performed on the acquired image to find a corresponding point between the image and the projected structural light pattern. After finding the corresponding points, depth information is calculated by triangulation method.

 FIG. 1C shows an image obtained by irradiating a structured light pattern of the type shown in FIG. 1A onto a target object 100 as shown in FIG. 1B. As shown in FIG. 1C, distortion occurs in a portion of the target object 100 where the depth changes, so that the same line pattern (pattern D and pattern D ', pattern E and pattern E') is separated, And the pattern D ', and the parallax occurred between the pattern E and the pattern E'. Also, the number of pixels corresponding to the parallax size can be determined through the captured image. For example, it can be seen that the pattern is separated by 20 pixels between the pattern D and the pattern D 'and between the pattern E and the pattern E'.

2, b denotes a baseline, which is the distance between the infrared light 210 and the lens 220 in the monochrome sensor.

The reference plane 230 refers to any plane that is defined as a reference in measuring the depth of a specific object. ZO corresponds to the distance between the sensor and the reference plane 230 and can be predetermined.

f is the focal length and corresponds to the distance between the lens 220 in the monochrome sensor and the image plane 250 of the imaging device.

The reference image, which is a specific reference in the measurement of the three-dimensional depth, is configured to project the structured light in the infrared light 210 to an arbitrary reference plane 230, detect the structured light reflected from the reference plane in a monochrome sensor, . ≪ / RTI >

In order to obtain a reference image, the structured light is projected onto a reference plane 230, which is a predetermined distance ZO away from the infrared light 210. The projected structured light is reflected from the reference surface 230 and is detected by the monochrome sensor.

An image of the pattern of the structured light projected on the reference surface 230 becomes the reference image. In this case, the reference image may be generated in advance and stored in a memory.

In order to measure the three-dimensional depth of the object 240, structured light having the same pattern as that used in acquiring the reference image may be projected onto the object 240. In FIG. 2, the object 240 is shown as a single surface, but this is for convenience of explanation. In fact, the structured light will be projected on each surface of the object 240.

When the structured light reflected by the object 240 is obtained from the monochrome sensor, the positional shift of the corresponding patterns in the obtained image can be measured based on the reference image. The movement of the pattern corresponds to d in Fig. 2, which means disparity corresponding to k points of the object 240 with reference to the reference image.

According to an example, it can be seen that the relationship of D / b = (ZO-ZK) / ZO, d / f = D / ZK is obtained by using the resemblance of triangle in FIG.

The above two formulas can be summarized by the following equations.

Z k = Z 0 / (1 + (Z 0 x d) / (f x b))

In the above equation, f is a focal length, b is a base line, and ZO is a distance to the reference plane 230. Thus, if the parallax d for an arbitrary point k of the object 240 is measured in the acquired image, the 3D depth ZK, which is the distance to the object 240, can be calculated.

In order to apply the three-dimensional depth measurement technique of the structured light method to an object having a small size such as an optical inspection system, it is necessary to increase the pattern resolution by densely spacing the patterns, It is necessary to have a way to investigate the pattern of.

In order to shorten the processing time, it is necessary to check the position of the circuit component, which is a region of interest, in order to shorten the processing time, to move the region of interest for precise measurement and to determine the optimal high- It is necessary to select a measurement method.

In addition, in order to improve the precision of the three-dimensional shape measurement, it becomes more important to compensate for various causes of small system failures. Therefore, the correction for the three-dimensional shape measuring system is becoming more and more important.

The correction method of the three-dimensional shape measurement system is based on the general optical ratio of the projector and the camera including the geometric distortion of the lens, the obliquity / keystone effect, the vertical movement error, and the line of sight error Optical non-idealities must be compensated. Some of this non-ideality will not change noticeably over time to affect measurement accuracy. Other non-idealities, however, can drift noticeably over a few minutes to several days, affecting measurement performance. For example, the visual distance may change noticeably due to thermal expansion due to environmental changes.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of correcting a three-dimensional shape measuring system having a plurality of pattern projecting units and at least one camera.

Also, it is an object of the present invention to provide an efficient correction method including a precise correction using a high-resolution pattern and a simple correction using a low-resolution pattern for each area of a circuit board, do.

According to an aspect of the present invention, there is provided an image processing method including the steps of projecting a low-resolution first optical pattern onto a target object for correction with a first pattern projection unit, acquiring a first pattern image of the first pattern projection unit with a camera Generating a second pattern image by performing coordinate transformation on the first pattern image based on the position information of the second pattern projection unit that knows a relative position of the first pattern image, The method comprising the steps of projecting an optical pattern, acquiring a third pattern image of the second pattern projection section with the camera, generating a first correction value by comparing the second pattern image and the third pattern image, 1 correction value to a threshold value to determine whether or not precise correction is to be performed; Generating a depth map by projecting a high resolution second optical pattern for each of at least one region of interest, generating a second correction value by comparing the depth value of the target object with an already known depth map; And a step of correcting the system by utilizing the three-dimensional shape measuring system.

The target object for correction is a circuit board, the target object is a circuit part, and the camera is an infrared camera.

The step of projecting the low-resolution first optical pattern on the object to be corrected may project the optical pattern by vertically moving the plurality of pattern projecting units to predetermined measurement positions.

Wherein the generating of the first correction value is performed by sequentially designating the remaining pattern projecting units other than the first pattern projecting unit as the second pattern projecting unit to repeatedly generate the first correction values, You can create a matrix.

The first pattern projection unit may be sequentially changed to generate a correction value matrix of each pattern projection unit, and the optimal correction value matrix may be designated as the first correction value.

The pattern projection unit can be moved up and down to change the measurement position to correct the system at various measurement positions.

Wherein the step of comparing the first correction value with a threshold value includes a step of performing simple correction of the pattern projecting unit by utilizing the first correction value when the first correction value is smaller than a threshold value, Precision correction can be performed.

The precision correction may further include performing a precision correction of the camera.

The number of times of performing the precision correction or the simple correction may be different from each other.

The region of interest may be specified by the size of the target object.

The region of interest of the object for correction to which the simple correction and the precision correction are performed may be designated differently.

At least one first optical filter unit for projecting a first low-resolution optical pattern onto the target object for correction, a second high-resolution projection unit for projecting the high-resolution first optical pattern onto the target object for correction, At least one second optical filter unit for generating a second optical pattern and controlling the projection area so that the high-resolution second optical pattern is projected onto the ROI, a camera for acquiring an optical pattern image projected on the object for correction, And a control unit for controlling the pattern projection unit and the camera to calculate a correction value, wherein the control unit controls the coordinate transformation unit to perform coordinate transformation on the basis of the position information of the second pattern projection unit that knows the pattern image of the first pattern projection unit, And comparing the pattern image of the second pattern projecting unit with the pattern image of the second pattern projecting unit to calculate a first correction value, A second correction value is compared with a threshold value to determine whether or not precise correction is to be performed, and a depth map calculated by projecting the second high-resolution optical pattern in the projection area is compared with a depth value of the target object that is already known, And correcting the system by utilizing the second correction value.

The target object for correction is a circuit board, the target object is a circuit part, and the camera is an infrared camera.

Wherein the control unit compares the first correction value with a threshold value to perform a simple correction of the pattern projection unit using the first correction value when the first correction value is smaller than a threshold value and if the second correction value is larger than the threshold value, The above-described precision correction can be performed.

The control unit may perform accurate correction of the camera when performing the precision correction.

The control unit may control the number of times of the precision correction and the simple correction differently.

The control unit may designate the region of interest in which the simple correction and the precision correction are performed differently.

According to the present invention, a correction value is generated by utilizing a low-resolution pattern and a high-resolution pattern for each region of a target object for correction, thereby correcting the system, shortening the processing time and improving the correction accuracy.

Further, the present invention can improve the accuracy of correction by calculating the correction value for each pattern projection unit and correcting it using the optimal optimal correction value.

1A is a prior art structured light projection pattern.
1B is a target object for depth measurement of the prior art.
1C is an image obtained for depth measurement of the prior art.
2 is a conceptual diagram for explaining a depth measurement method using the structured light of the prior art.
3 is a block diagram of a three-dimensional shape measuring system according to an embodiment of the present invention,
4 is an image projecting a first light pattern according to an embodiment of the present invention.
5 is an image projecting a second optical pattern according to an embodiment of the present invention.
6 is an example of a lant speckle pattern, which is an example of a second optical pattern according to an embodiment of the present invention.
7 is a block diagram of an optical filter for generating and controlling a second optical pattern in accordance with an embodiment of the present invention.
8 is a flowchart illustrating a method of measuring a three-dimensional shape according to an embodiment of the present invention.
Fig. 9 is a movable prism for generating a first optical pattern according to an embodiment of the present invention.
10 is a micro-mirror for generating a first optical pattern according to an embodiment of the present invention.
11 is a flowchart of a method of correcting a three-dimensional shape measurement system utilizing pattern image coordinate transformation according to an embodiment of the present invention.
12 is a flowchart illustrating a method of calibrating a 3D shape measuring system using a depth value using a high-resolution pattern and a low-resolution pattern according to an exemplary embodiment of the present invention.
13 is a conceptual diagram for explaining the 7 parameter coordinate transformation.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals are used to designate identical or similar elements, and redundant description thereof will be omitted. The suffix " module " and " part " for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role. In the following description of the embodiments of the present invention, a detailed description of related arts will be omitted when it is determined that the gist of the embodiments disclosed herein may be blurred. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , ≪ / RTI > equivalents, and alternatives.

Terms including ordinals, such as first, second, etc., may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Referring to FIG. 3, FIG. 3 is a block diagram illustrating a three-dimensional measurement system related to the present invention

The system 300 may include an infrared camera 301, an RGB camera 302, a pattern projection unit 303, an optical filter unit 304, a circuit board 305, and the like. The components shown in FIG. 3 are not essential for implementing a three-dimensional measurement system, so that the three-dimensional measurement system described herein may have more or fewer components than the components listed above.

The pattern projection unit 303 can generate various patterns according to the object through the optical filter unit 304 and project the pattern onto the circuit board 305 by using the light emitted from the infrared laser light source, And controls the area irradiated with the pattern in accordance with the vertical movement.

The infrared (IR) camera 301 images the image of the first optical pattern 401 projected on the circuit board 305, which is a measurement object, and generates a depth information by measuring a change amount of the pattern in the control unit 306.

The RGB camera 302 measures the image of the circuit board 305 as a measurement object and determines the edge of the circuit part 402 on the image in the control unit 306 and determines the position of the circuit part 402 do.

4 is a view for explaining an image in which a first optical pattern is irradiated on a circuit board which is a measurement object of a three-dimensional measurement system related to the present invention. Referring to FIG. 4, a plurality of circuit components 402 are disposed on a circuit board 305, and a first optical pattern 401 for three-dimensional depth measurement is irradiated.

The first optical pattern 401 corresponds to the infrared region, and the pattern can be projected onto the entire circuit board 305, but there is a limitation in increasing the spatial resolution with a periodic pattern such as a lattice pattern. Therefore, accurate depth information of the accurate edge portion of the circuit component 402 can not be obtained.

Referring to FIG. 5, FIG. 5 is a view for explaining an image in which a second optimal optical pattern is irradiated onto a circuit board, which is a measurement object of the three-dimensional measurement system related to the present invention.

Is an image in which a plurality of circuit components 402 are arranged on a circuit board 305 and a second optical pattern 501 for three-dimensional depth measurement is irradiated.

The second optical pattern 501 corresponds to the infrared region and can control the progress of the light by the optical filter unit 304 to project an optimal pattern for each position of the circuit component 402, Spatial pattern can be increased with Random Speckle Pattern. Thus, accurate depth information of the precise edge portion of the circuit component 402 can be obtained.

6 is an example of a random speckle pattern projected onto an object in a second optical pattern.

Fig. 7 is a detailed configuration diagram of the optical filter unit 304. Fig. Referring to FIG. 7, the optical filter unit 304 includes a diffuser 701 and an electronically controlled diffractive lens 702.

The diffuser plate 701 diffuses the laser light from the infrared laser light source to generate a random speckle pattern. In addition, the pattern size of the random speckle pattern can be adjusted by adjusting the spot size of the laser light source. Therefore, the optimum pattern can be selected according to the position and shape of the circuit component.

The diffraction lens 702 can change the traveling direction of the random speckle pattern and electrically control the liquid crystal elements included therein to control the projection area so that the pattern is projected only in a necessary projection area.

8 is a flowchart illustrating a method of measuring a three-dimensional shape of a three-dimensional shape measuring system according to an embodiment of the present invention. The RGB camera 302 can be used to obtain a 2D image of a circuit board that is an object (801). In one embodiment, the processes illustrated in FIG. 8 may be performed by the control unit controlling other objects.

An object candidate group can be derived through image processing for edge detection using the acquired 2D image (802).

At least one pattern projection unit projects the first optical pattern 401 onto the object (803). Although the first optical pattern 401 can be projected onto the entire circuit board 305 in the infrared region, there is a limit to increase the spatial resolution with a periodic pattern such as a lattice pattern. Projection of the first pattern is performed by using any one of a micro mirror (see FIG. 10) and a movable prism (see FIG. 9) provided in the optical filter unit and advancing the light incident from the infrared laser light source Direction to scan the first optical pattern 401 on the object.

The image obtained by projecting the first optical pattern onto the circuit board is obtained by using the IR camera 301, and the distance traveled by the pattern on the acquired image relative to the projected pattern is measured, and depth information of the corresponding region is included by the triangulation method (804). ≪ / RTI >

The position of the circuit components can be determined by using the object candidate group and the depth map (805). Some of the object candidates obtained by edge detection may not have a height due to a mark or the like formed on the substrate. Accordingly, it is possible to determine whether the circuit component 402 is provided with the depth information of the object candidate region, and to obtain the position information on the 2D image.

The optimum second optical pattern is selected for each circuit component 402 (806). The necessary spatial resolution is selected according to at least one of the position, size and shape of the circuit components, and the spot size of the laser light source is controlled to adjust the size of the random speckle pattern to secure the required spatial resolution. In one embodiment, the resolution of the second optical pattern may be higher than the resolution of the first optical pattern.

The pattern projection section 303 is moved up and down to move the pattern projection area around the circuit component 402 (807). The at least one pattern projection unit 303 installed at a specific angle is moved up and down to move the region where the pattern is projected. At this time, the projection regions of the plurality of pattern projecting portions 303 can be moved so as to overlap the periphery of the circuit component 402.

The optical filter unit 304 is controlled to match the projection area of the pattern with the position of the circuit component 402 (808). It is possible to electrically control the liquid crystal portion of the diffraction lens 702 in the optical filter portion 304 so that the pattern is irradiated only to the position of the circuit component 402. [ The optimal second optical pattern selected by the circuit part 402 is projected to the designated projection area according to the position of the circuit component 402 (809).

A precision depth map is calculated from the image obtained by the IR camera 301 (810). The relative random pattern variation is determined by comparing the projected random speckle pattern with the acquired image, and the depth information is calculated. When the projection area of the plurality of pattern projecting parts 303 is moved so as to overlap the periphery of the circuit part 402, the projection time of the pattern is synchronized with the image acquiring time for each pattern projecting part 303, The accuracy of the shape measurement can be improved. In this case, in the case of the pattern projection unit 303 having a distance from the circuit component 402, the depth resolution is higher than that of the other pattern adverbs, so that the depth information can be generated by reflecting it preferentially.

The precision depth map is compared with the information of the normal circuit board 305 having the reference depth information to check whether the circuit board 305 is defective (811).

11 is a flowchart illustrating a method of correcting a three-dimensional shape measurement system utilizing coordinate transformation of an image pattern according to an embodiment of the present invention. This is an embodiment, and the processes illustrated in FIG. 11 can be performed by the control unit controlling other objects.

The plurality of pattern projecting units 303 are moved up and down to the measurement position for correction (1101). At this time, the respective pattern projection units 303 may be at the same height, or the pattern projection unit 303 designated by the first pattern projection unit 303 may be positioned at a relatively low height to increase the depth resolution.

The first optical pattern is projected onto the circuit board 305 on which the arbitrary pattern projecting unit 303 is designated as the first pattern projecting unit 303 and an accurate depth value for each circuit component 402 as the target object for correction is known 1102), and acquires a first pattern image through an infrared camera (1103). In one embodiment, the first optical pattern may be a low-resolution pattern in a periodic lattice form, and various other types of patterns may be utilized.

(1104) a second pattern image obtained by performing coordinate transformation on the pattern image by the first pattern projecting unit using the position information of the designated second pattern projecting unit that knows the relative position information with respect to the first pattern projecting unit. The coordinates of the image are transformed into a matrix including delta X, delta Y, delta Z, X Rotation, Y Rotation, Z Rotation, and Scale, which are seven parameters of the first pattern projection part and the second pattern projection part.

The seven-parameter coordinate transformation matrix is defined as shown in the following equation when the (X2, Y2, Z2) coordinate system is shifted by a (X1, Y1, Z1)

Where R (?,?,?) Is a rotation matrix,? Is a scale factor, and (Tx, Ty, Tz) is a translation.

A first optical pattern is projected from a designated second pattern projection unit to a target object for correction (1105), and a third pattern image is acquired using an infrared camera (1106).

The second pattern image that is image-converted by the known relative position information is compared with the third pattern image obtained by the actual pattern projection, and the correction value between the first pattern projection unit and the second pattern projection unit is calculated 1107 ). At this time, the correction value may be any one of the position between the pattern projection units, the characteristic value of the pattern projection optical system, the characteristic value of the image acquisition optical system, and the characteristic value of the image sensor. The correction value corresponding to the position between the pattern projection units is a matrix including the delta X, delta Y, delta Z, X Rotation, Y Rotation, Z Rotation, and Scale, which are seven parameters identified in the compared image.

In order to obtain the correction value for the pattern projection unit other than the second pattern projection unit obtained by obtaining the correction value for the first pattern projection unit, a pattern projection unit other than the first and second pattern projection units is designated as the second pattern projection unit 1108 (Step 1109). If the correction value has not been generated, steps 1104 to 1107 are repeated to determine whether or not the first pattern is projected, (1110) a correction value matrix for the first pattern projection unit is generated by obtaining correction values between the projection unit and other pattern projection units and obtaining correction values for all the remaining pattern projection units.

When a correction value matrix for the first pattern projection unit is generated, the first pattern projection unit is designated as another pattern projection unit 1111, and the steps from 1102 to 1109 are repeated to obtain a newly designated first pattern projection unit- Create a matrix.

When generation of the correction value matrix for all the pattern projection units is completed, the optimal pattern projection unit having the minimum correction value is selected (1113). In this case, the minimum correction value may be an optimum correction value in various conditions.

The optimum correction value is designated as the first correction value and the pattern projection unit and the camera are corrected (1114). In one embodiment, it is easy to correct the position of the pattern projection unit that is normally movable. However, if the correction value is difficult to be corrected only by the pattern projection unit, the related characteristic values such as the camera position, optical characteristics, sensor characteristics, and image processing can be corrected. In another embodiment, correction may be possible only by image processing of the camera without mechanical movement of the pattern projection unit. The position correction of the pattern projection section uses the seven parameters delta X, delta Y, delta Z, X Rotation, Y Rotation, Z Rotation, and Scale.

If the correction is completed at the measurement position designated at the step 1101, the pattern projection unit is moved to another measurement position (1116), and it is determined whether or not the correction at the designated measurement position is completed (1117) Steps 1101 to 1116 are repeated after shifting to the changed measurement position, and if the correction is completed at all the designated measurement positions, the correction step of the pattern image is completed (1118).

FIG. 12 is a detailed flowchart of the correction method of step 1114 of FIG. 11 for performing accurate correction using a high-resolution second optical pattern when the optimum correction value matrix according to the embodiment of the present invention is larger than a threshold value. In one embodiment, the processes illustrated in FIG. 12 may be performed by the control unit controlling other objects.

If the first correction value is smaller than the threshold value in step 1201, the pattern projection unit is simply corrected using the first correction value selected in step 1113 using the first low-resolution optical pattern. If the first correction value is larger than the threshold value, the second correction value is selected using the high-resolution second optical pattern to precisely correct the pattern projection unit and the camera unit.

When the optimum correction value matrix is larger than the threshold value, the position of the circuit component capable of high resolution measurement among the circuit components, which is the target object of the target object for correction, which knows the pattern projection part in advance, is selected as the region of interest and the pattern projection portion is moved up and down , Controls the optical filter to control the projection area (1202), and projects the second optical pattern of high resolution (1203).

A depth map is generated 1204 using an infrared camera, and a second correction value 1206 is generated by comparing 1205 a depth value of a circuit component, which is a known object, to a known correction value. At this time, the second correction value may be any one of a pattern projection unit, a position of a camera, a characteristic value of a pattern projection optical system, a characteristic value of an image acquisition optical system, and a characteristic value of an image sensor. The second correction value corresponding to the position of the pattern projection unit or the camera includes seven parameters, delta X, delta Y, delta Z, X Rotation, Y Rotation, Z Rotation, and Scale, which are seven parameters identified in the compared image. Also, the second correction value may be composed of a matrix including seven parameters as in the above equation.

The pattern projection unit is precisely corrected with high resolution according to the generated second correction value (1207). Since the first correction value is larger than the threshold value, the camera also performs precision correction with high resolution (1208).

If the first correction value is smaller than the threshold value, the position of each pattern projection unit is corrected using the first correction value (1215). At this time, the correction value may be any one of a pattern projection unit, a position of a camera, a characteristic value of a pattern projection optical system, a characteristic value of an image acquisition optical system, and a characteristic value of an image sensor. The position correction of the pattern projection section includes seven parameters delta X, delta Y, delta Z, X Rotation, Y Rotation, Z Rotation, and Scale.

The high-resolution precise correction region and the low-resolution simple correction region can be different. For example, if the size of the circuit component is relatively small compared to the size of the pattern, it can be designated as a high resolution precision correction area,

The repetition period of the correction can be carried out more often than the number of times of performing the simple correction with a relatively small amount of calculation compared to the number of times of the precise correction.

   The present invention described above can be embodied as computer-readable codes on a medium on which a program is recorded. The computer readable medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the computer readable medium include a hard disk drive (HDD), a solid state disk (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, , And may also be implemented in the form of a carrier wave (e.g., transmission over the Internet). In addition, the computer may include a control unit.

Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. It is intended that the scope of the invention be determined by rational interpretation of the appended claims and that all changes which come within the meaning and range of equivalency of the invention are intended to be embraced therein

100: Target object 210: Infrared illumination
220: Lens 220 in a monochrome sensor 230: Reference plane
240: Object 250: Image plane of the imaging device
300: Three-dimensional shape measuring system 301: Color camera
302: infrared camera 303: pattern projection unit
304: Optical filter unit 305: Circuit board
306: control unit 401: first optical pattern
402: circuit component 501: second optical pattern
701: diffusion plate 702: diffraction lens

Claims (17)

Projecting a low-resolution first optical pattern onto a target object for correction with a first pattern projection unit;
Obtaining a first pattern image of the first pattern projection unit with a camera;
Generating a second pattern image by performing coordinate transformation on the first pattern image based on positional information of a second pattern projection unit having a known relative position;
Projecting the first low-resolution optical pattern onto the object to be corrected with the second pattern projection unit;
Obtaining a third pattern image of the second pattern projection unit with the camera;
Comparing the second pattern image and the third pattern image to generate a first correction value, and
Comparing the first correction value with a threshold value to determine whether the correction is precise,
Generating a depth map by projecting a high-resolution second optical pattern for each of at least one ROI in which the target object in the target object for correction is located;
Comparing the depth value of the target object already known with the depth map to generate a second correction value; and
And correcting the system using a second correction value. The method of claim 1, wherein
Wherein the correction target object is a circuit board, the target object is a circuit component, and the camera is an infrared camera. The method of claim 1, wherein
Wherein projecting the first low-resolution optical pattern onto the object to be corrected comprises projecting the optical pattern by vertically moving the plurality of pattern projecting portions to a predetermined measurement position. The method of claim 1, wherein
Wherein the generating of the first correction value is performed by sequentially designating the remaining pattern projecting units other than the first pattern projecting unit as the second pattern projecting unit to repeatedly generate the first correction values, A method for calibrating a three-dimensional shape measuring system for generating a matrix. 5. The method of claim 4,
Wherein the generating the first correction value comprises:
Wherein the first pattern projection unit is sequentially changed to generate a correction value matrix of each pattern projection unit, and the optimum correction value matrix is designated as the first correction value. The method of claim 3, wherein
And correcting the system at different measurement positions by changing the measurement position by moving the pattern projection unit up and down. The method of claim 1, wherein
Wherein the step of comparing the first correction value with a threshold value includes a step of performing simple correction of the pattern projecting unit by utilizing the first correction value when the first correction value is smaller than a threshold value, A method of correcting a three-dimensional shape measurement system that performs precision correction. The method of claim 7, wherein
Wherein the precision correction further comprises performing a precision correction of the camera. The method of claim 7, wherein
Wherein the number of times of performing the precision correction or the simple correction is different from each other. The method of claim 1, wherein
Wherein the region of interest is specified by the size of the target object. The method of claim 7, wherein
Wherein the region of interest of the object for correction to be subjected to the simple correction and the precision correction is differently specified. One or more pattern projecting units for controlling a region of interest corresponding to a position of a target object included in a target object for correction by up-and-down movement;
At least one first optical filter unit for projecting a low-resolution first optical pattern onto the object to be corrected;
At least one second optical filter unit for generating a high-resolution second optical pattern and controlling the projection area so that the high-resolution second optical pattern is projected onto the area of interest;
A camera for acquiring an optical pattern image projected on the object for correction;
And a control unit for controlling the pattern projection unit and the camera and calculating a correction value, wherein the control unit
Calculating a first correction value by comparing the pattern image of the second pattern projecting unit with the pattern image of the second pattern projecting unit, the pattern image being coordinate-converted by the position information of the second pattern projecting unit that knows the pattern image of the designated first pattern projecting unit among the pattern projecting units, Comparing the first correction value with a threshold value to determine whether or not precise correction is to be performed, comparing a depth map calculated by projecting the second high-resolution optical pattern to the projection area, and a depth value of the target object, And correcting the system by utilizing the second correction value. The method of claim 12, wherein
Wherein the object to be corrected is a circuit board, the target object is a circuit component, and the camera is an infrared camera. The method of claim 12, wherein
Wherein the control unit compares the first correction value with a threshold value to perform a simple correction of the pattern projection unit using the first correction value when the first correction value is smaller than a threshold value and if the second correction value is larger than the threshold value, Dimensional shape measurement system for performing the above-mentioned precision correction. The method of claim 14, wherein
Wherein the controller performs precision correction of the camera when performing the precision correction. The method of claim 14, wherein
Wherein the control unit controls the number of times of the precision correction and the simple correction differently. The method of claim 14, wherein
Wherein the control unit specifies the region of interest in which the simple correction and the precision correction are performed differently.

Images