KR101766468B1 - Method for 3D shape measuring using of Triple Frequency Pattern - Google Patents

Method for 3D shape measuring using of Triple Frequency Pattern Download PDF

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KR101766468B1
KR101766468B1 KR1020150123927A KR20150123927A KR101766468B1 KR 101766468 B1 KR101766468 B1 KR 101766468B1 KR 1020150123927 A KR1020150123927 A KR 1020150123927A KR 20150123927 A KR20150123927 A KR 20150123927A KR 101766468 B1 KR101766468 B1 KR 101766468B1
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reference pattern
pattern data
pattern
inspected
phase
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KR1020150123927A
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Korean (ko)
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KR20170027893A (en
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박찬화
한영진
최경진
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주식회사 미르기술
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • G01B11/2513—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object with several lines being projected in more than one direction, e.g. grids, patterns
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0608—Height gauges
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • G01B11/2531—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object using several gratings, projected with variable angle of incidence on the object, and one detection device
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/0002—Inspection of images, e.g. flaw detection
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10004—Still image; Photographic image
    • G06T2207/10012—Stereo images

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Quality & Reliability (AREA)
  • Theoretical Computer Science (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

The present invention relates to a three-dimensional shape measuring method using a triple frequency pattern, in which at least one projector irradiates a pattern illumination on an object to be inspected, and then, using the reflected pattern image, A three-dimensional shape measuring method using a triple frequency pattern performed by a measuring apparatus, the method comprising: generating first to third reference pattern data having different periods; The first to third reference pattern data corresponding to the loaded first to third reference pattern data are loaded on the surface of the inspected object, ; Capturing a plurality of first through third pattern images by photographing a surface of the inspection object irradiated with the first through third reference pattern lights in at least one camera; Selecting two pattern images having different periods from the first through third pattern images according to the measurement range of the inspection object; And extracting phase information from the two selected pattern images and calculating height information for the inspected object by a phase-height calculation equation. Accordingly, the present invention solves the ambiguity of 2? With respect to the inspection object having various heights, and simultaneously calculates the height information of the inspection object by selecting two pattern images having different periods according to the inspection area or property information of the inspection object The measurement accuracy can be improved and the inspection speed can be improved compared to the conventional method.

Description

TECHNICAL FIELD [0001] The present invention relates to a three-dimensional shape measuring method using a triple frequency pattern,

The present invention relates to a method for measuring a three-dimensional shape using a triple frequency pattern, and more particularly, to a method for measuring a three-dimensional shape using three frequency patterns, Dimensional shape measuring method using a triple frequency pattern capable of measuring a three-dimensional shape of an object to be inspected using an image selectively.

Three-dimensional shape measurement technology has been developed by using laser triangulation method, stereo measurement method, and moiré principle measurement method. Since this measurement method uses optical, it is possible to obtain a fast and accurate three-dimensional shape.

A three-dimensional shape measurement method using a moire is to measure a three-dimensional shape of an object to be inspected using a pattern image reflected after irradiating the pattern illumination to the object to be inspected. There is a phase shift method as an analysis method.

The phase shift method obtains a pattern image according to a plurality of interference signals while moving the reference plane of the object to be inspected and analyzes the mathematical relationship between the shape and the height of the interference signal at each measurement point of the obtained pattern image, .

The 3-D shape measurement method using the phase shift method has a problem that 2? Ambiguity occurs when a height difference between adjacent two measurement points is equal to or more than an integral multiple of the equivalent wavelength of light source, and the measurement of the object to be inspected There is a problem that the range is limited.

In the past, when the phase shift of the point to be measured deviates by more than 2? From the surrounding point, the problem of 2? Ambiguity is solved by correcting 2? To the height value of the measuring point and reflecting it to the resultant value.

However, in the three-dimensional shape measuring method using the phase shift method according to the related art, when two measurement objects are located apart from each other by 2? Or more, whether the measurement result is a result of 2? Ambiguity or a measurement object having a depth of 2? It is difficult to distinguish the recognition, and there still exists a problem that an inaccurate result may occur. That is, 2π ambiguity can be obtained to obtain relative three-dimensional information, but it is impossible to obtain accurate three-dimensional information.

Accordingly, Korean Patent No. 10-0558325 has proposed a 3D inspection method and apparatus using stereo vision and moire as a technique for solving the 2? Ambiguity.

In the conventional three dimensional inspection method and apparatus using stereo vision and moire, when the light projection part scans a certain pattern several times and phase shifts the measurement object with the motor, two cameras measure each object to be measured at each time point, Dimensional shape information of the object to be measured is finally measured by comparing the three-dimensional shape information.

However, conventional stereoscopic vision and moire-based three-dimensional inspection methods and devices have not completely solved the 2? Ambiguity. In other words, 2π ambiguity occurs again at a position that is a multiple of the left and right phase information, and the problem of finding the matching point can not be solved.

In order to improve the problem of 2? Ambiguity in the case of measuring an object to be inspected having a different measurement range in a three-dimensional shape measuring apparatus using one projection moire, a method of replacing the lattice corresponding to the measurement range of each object to be inspected However, in this case, since it takes time to replace the lattice, the inspection speed is lowered.

As a technique for improving this, a pattern illumination having a different equivalent wavelength is generated for each of a plurality of projectors, and the height information is calculated using the phase information obtained by irradiating the pattern illumination to the object to be inspected, A three-dimensional shape measuring apparatus and a measuring method using multiple wavelengths have been proposed in Korean Patent No. 10-1190122.

Conventionally, the apparatus and method for measuring three-dimensional shape using multi-wavelengths are characterized by projecting pattern lights having different equivalent wavelengths respectively to a plurality of projectors and calculating height information using the acquired phase information, So that the maximum measurement height of the object to be inspected can be increased. In this case, although the 2? Ambiguity is partially solved, there is a problem that the accuracy is poor with respect to the height deviation of the object to be inspected and it is difficult to apply it to various parts / products inspection.

That is, in the conventional apparatus and method for measuring three-dimensional shape using multiple wavelengths, two projectors in the vicinity of the camera project a grating pattern light having a similar period, i.e., a first period and a grating pattern light having a second period, To obtain a pattern image having a third period corresponding to the second period.

Specifically, a first phase is calculated using a plurality of first pattern images obtained by irradiating the surface of the object to be inspected with a grating pattern light having a first period using an N-bucket algorithm, and a first phase is calculated using a grid pattern light having a second period Is applied to the surface of the object to be inspected, and a second phase is calculated using a plurality of second pattern images obtained by using the N-bucket algorithm.

When the first and second phases are calculated, the third phase is calculated according to the beating phenomenon caused by the lattice pattern light having the first period and the lattice pattern light having the second period. (X, y) = 2? H /? 1 + M? 2? To calculate a first order of the first phase and a second order of the second phase using the calculated third phase, And the second order N is calculated using? 1 (x, y) = 2? H /? 1 + N? 2?, And the first and second orders and the first and second phases are calculated using the calculated first and second orders, The second height information is calculated

However, in this case, if all of the patterns are not accurately projected, accurate measurement is difficult. That is, when an obstacle having a height is located in the vicinity of the object to be inspected, shadows may be generated on a pattern projected from one of the projectors.

For example, a pattern having the first frequency component f1 projected from the first projector is accurately photographed through the camera, but a pattern having the second frequency component f2 projected from the second projector is generated by the inspected object There is a problem in that the third frequency component due to the beat components of the two wavelengths can not be accurately obtained.

Korean Patent No. 10-0901537 has proposed a three-dimensional measuring method using a color grating in a different form from Korean Patent No. 10-1190122.

A conventional three-dimensional measuring method using a color lattice includes a step of synthesizing a red color lattice, a green color lattice, and a blue color lattice having a cycle corresponding to the moiré technique into a single composite pattern, , Obtaining an image, and separating the red, green, and blue color gratings from the image of the composite pattern to measure the three-dimensional shape.

The conventional three-dimensional measurement method using a color grid solves the ambiguity of 2?, But there is a problem that it can not cope with various heights by making a pattern synthesized with three color color gratings.

As described above, in general, a three-dimensional shape measurement technique using a phase shift projection type moire is to take four images in one cycle because the shape of the object is measured while shifting the lattice by a quarter cycle. In this case, when the gratings of different periods are used, four times of image capturing is performed in a large period lattice and four times of images are taken in a small period lattice. Therefore, a total of 8 images .

In the case of applying a double frequency pattern using a large period and a small period, it is necessary to increase the pattern period ratio between a large period and a small period in order to increase the measurement range, but a phase unwrapping error There is a disadvantage that the possibility is high.

In a 3D shape measurement technique using a dual frequency pattern, the measurement range is determined by a large period, that is, a low frequency pattern, but it is difficult to set a large size arbitrarily according to a pattern period ratio limit with a high frequency pattern The measurement range is limited. For example, when the pattern period ratio is set to 9 when the measurement range of the high frequency pattern is 900 mu m (8 pixels), the measurement range of the low frequency pattern is limited to 8 mm (72 pixels).

In order to solve this disadvantage, when the height of the object to be inspected is measured by applying the triple frequency pattern to the three-dimensional shape measuring technique, eight pattern images are obtained in the case of the double frequency pattern, but 12 Since the pattern image of the field is required to be acquired, the number of times of image capturing and the photographing time are long, and the calculation time for the inspection increases at least 1.5 times the triple frequency pattern compared with the double frequency pattern. .

Korean Patent No. 10-0558325 entitled " 3-D Inspection Method and Apparatus Using Stereo Vision and Moire " Korean Patent No. 10-1190122 entitled " Apparatus and method for measuring three-dimensional shape using multi-wavelength " Korean Patent No. 10-0901537 "Three-Dimensional Measurement Method Using Color Grid"

In the present invention, a plurality of pattern images for each cycle are obtained by using three frequency pattern lights having different cycles, and two pattern images having different cycles are selected according to the inspection area or characteristic information of the inspection object, A three-dimensional shape measuring method using a triple frequency pattern for calculating the height of a three-dimensional shape is provided.

In addition, the present invention can set a pattern period ratio between two selected pattern images to an integral multiple of 7 or less, thereby minimizing the possibility of occurrence of errors in the phase conversion process, thereby enabling a triple frequency pattern capable of maximizing the measurement range and improving the measurement accuracy Dimensional shape measuring method using the same.

Among the embodiments, a three-dimensional shape measuring method using a triple frequency pattern is a three-dimensional shape measuring method of measuring a three-dimensional shape of the inspected object by using a pattern image reflected after irradiating a pattern illumination on an object to be inspected by at least one projector, A three-dimensional shape measuring method using a triple frequency pattern performed by a measuring apparatus, the method comprising: generating first to third reference pattern data having different periods; The first to third reference pattern data corresponding to the loaded first to third reference pattern data are loaded on the surface of the inspected object, ; Capturing a plurality of first through third pattern images by photographing a surface of the inspection object irradiated with the first through third reference pattern lights in at least one camera; Selecting two pattern images having different periods from the first through third pattern images according to the measurement range of the inspection object; And calculating height information for the inspected object by extracting phase information from the selected two pattern images and calculating the phase-height equation.

The generating of the first to third reference pattern data having the different periods may include configuring the first reference pattern data to have N number of pixels per cycle, <N) number of pixels, and the third reference pattern data has L (L <M) number of pixels.

The number of pixels of the first reference pattern data is an integral multiple of the number of pixels of the second reference pattern data and the number of pixels of the second reference pattern data is an integral multiple of the number of pixels of the third reference pattern data.

 The first to third reference pattern data corresponding to the loaded first to third reference pattern data are loaded on the surface of the inspected object, , The first to third reference pattern lights are projected on the surface of the object to be inspected by a predetermined number of times while being phase shifted by a predetermined phase value.

Wherein the measurement range of the inspection object is inspection area or characteristic information, and the characteristic information is any one of a type, a height, a size, a manufacturer, parts information, a model name, a color, and an identification code of the inspection object.

The step of calculating the height information of the three-dimensional shape by extracting the phase information from the selected two pattern images and calculating the height information of the three-dimensional shape by the phase-height calculation equation may include calculating a reference phase value at the reference height for each of the first to third reference pattern data Respectively; Determining a calibration constant value by performing calibration while moving the unit pattern data by a unit step in units of the first to third reference pattern data; Calculating a phase value of the inspected object using the selected two pattern images after setting an inspection area of the inspected object; Calculating a difference between the reference phase value and a phase value of the inspected object, and calculating a height by using a phase-height calculation formula using the calibration constant value.

Wherein the step of generating and storing the reference phase values at the reference height for each of the first to third reference pattern data comprises the steps of phase shifting each of the first to third reference pattern lights by a preset phase value, A plurality of first to third reference pattern images are obtained by projecting the plurality of reference pattern images onto the surface of the object, respectively, and the reference phase values are respectively calculated using the plurality of first to third reference pattern images.

Wherein the step of calibrating the first to third reference pattern data by unit steps while determining the calibration constant value comprises the steps of: 1 calibration constant value and determines a second calibration constant value for the second reference pattern data and the third reference pattern data.

Wherein the pattern period ratio of the first reference pattern data is set to an integral multiple of a set value of the pattern period ratio of the second reference pattern data and the pattern period ratio of the second reference pattern data is set to a pattern period ratio And the measurement range of the object to be inspected is adjusted.

The present invention can solve the ambiguity of 2? For the inspection object having various heights and simultaneously calculate the height information of the inspection object by selecting two pattern images having different periods according to the inspection area or characteristic information of the inspection object Compared with the conventional method, the measurement accuracy can be increased and the test speed can be improved.

In addition, the present invention can set the pattern period ratio between two selected pattern images to an integral multiple of 7 or less, thereby minimizing the possibility of occurrence of errors in the phase conversion process, thereby maximizing the measurement range and improving the measurement accuracy and repeatability .

1 is a front view illustrating a configuration of a three-dimensional shape measuring apparatus according to an embodiment of the present invention;
2 is a flowchart illustrating a method of measuring a three-dimensional shape using a triple frequency pattern according to an embodiment of the present invention
3 is a view for explaining a first reference pattern image and a first pattern image according to the first reference pattern data of FIG. 2;
Fig. 4 is a view for explaining a second reference pattern image and a second pattern image according to the second reference pattern data of Fig. 2
FIG. 5 is a view for explaining a third reference pattern image and a third pattern image according to the third reference pattern data of FIG. 2;
6 is a view for explaining a process of measuring a height of a stepped specimen by a three-dimensional shape measuring method using a triple frequency pattern according to an embodiment of the present invention

The description of the present invention is merely an example for structural or functional explanation, and the scope of the present invention should not be construed as being limited by the embodiments described in the text. That is, the embodiments are to be construed as being variously embodied and having various forms, so that the scope of the present invention should be understood to include equivalents capable of realizing technical ideas. Also, the purpose or effect of the present invention should not be construed as limiting the scope of the present invention, since it does not mean that a specific embodiment should include all or only such effect.

Meanwhile, the meaning of the terms described in the present invention should be understood as follows.

The terms "first "," second ", and the like are intended to distinguish one element from another, and the scope of the right should not be limited by these terms. For example, 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.

It is to be understood that when an element is referred to as being "connected" to another element, it may be directly connected to the other element, but there may be other elements in between. On the other hand, when an element is referred to as being "directly connected" to another element, it should be understood that there are no other elements in between. On the other hand, other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

It should be understood that the singular " include "or" have "are to be construed as including a stated feature, number, step, operation, component, It is to be understood that the combination is intended to specify that it does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

In each step, the identification code (e.g., a, b, c, etc.) is used for convenience of explanation, the identification code does not describe the order of each step, Unless otherwise stated, it may occur differently from the stated order. That is, each step may occur in the same order as described, may be performed substantially concurrently, or may be performed in reverse order.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used predefined terms should be interpreted to be consistent with the meanings in the context of the related art and can not be interpreted as having ideal or overly formal meaning unless explicitly defined in the present invention.

1 is a front view for explaining a configuration of a three-dimensional shape measuring apparatus according to an embodiment of the present invention.

1, a three-dimensional shape measuring apparatus 100 includes a stage 110, a plurality of lights (not shown), an LED driving unit 120, a vertical camera 130, a plurality of projectors 140, A driving unit 145, a grabber 150, an image processing unit 160, and an interface unit 170.

The stage 110 supports the object to be inspected, and moves the object to be inspected to the inspection position while moving under the control of the image processor 160.

The illumination is arranged on the object to be inspected in such a manner that a plurality of LEDs for R, G, B color illumination or white illumination are set in a predetermined manner. Such illumination may include various numbers and types of illumination, such as two, three, or six.

The LED driving unit 120 may control the LEDs of the plurality of projectors 140 or the LEDs of the plurality of projectors 140 for a predetermined period of time according to the lighting control signal, Adjust the brightness of each LED according to it.

The vertical camera 130 is installed on the stage 110 to capture an image of the object to be inspected and output a video signal. The vertical camera 130 is a camera for acquiring a two-dimensional image in a state in which the color illumination is on, and performs a two-dimensional inspection using the captured color image. Here, a color image is used to shape a three-dimensional image through texturing of three-dimensional data.

The vertical camera 130 acquires a pattern image in a state in which an illumination pattern of a vertical pattern or a horizontal pattern is irradiated by the projector 140, and calculates a three-dimensional shape of the object to be inspected Perform dimension checking.

At least one of the projectors 140 may project the specific illumination pattern to the object to be inspected by loading the illumination pattern data for the illumination pattern in accordance with the purpose of the digital vision inspection, The period and direction can be set. The projector 140 may be a 3D optical system for irradiating a vertical pattern or a horizontal pattern onto the surface of the object to be inspected, and the period of the pattern may be determined according to the pattern data provided by the image processor 160.

A plurality of such projectors 140 are disposed around the vertical camera 130 so as to face each other. For example, two projectors 140 are installed on the right and left sides of the vertical camera 130, and the remaining two projectors 140 are installed on the upper and lower sides of the vertical camera 130 so as to face each other. The four projectors 140 may be disposed on the same concentric circle centering on the vertical camera 130.

The projector driving unit 145 operates the projector 140 in accordance with the illumination control signal when the trigger signal of the image processing unit 160 is transmitted and outputs the image acquisition signal And transmits it to the grabber 150. In addition, the projector driving unit 145 loads and stores pattern data for a pattern that meets the purpose of the vision inspection in a digital manner.

The grabber 150 instructs the photographing of the vertical camera 130 according to the image acquisition signal and converts the image signal of the pattern image transmitted through the connection line of the vertical camera 130 into a digital signal, To the processing unit 160.

The image processor 160 processes the digital image signal transmitted from the grabber 150 and outputs the digital image signal. The image processing unit 160 controls the operation of the stage 110, the illumination, the LED driving unit 120, the vertical camera 130, the projector 140, and the grabber 150 as a whole.

The image processing unit 160 can output the inspection image or the inspection result data of the inspection object to the display means (not shown) by using the image signals picked up by the vertical camera 130, It is possible to check the shape of the object to be inspected or to judge whether the object is defective through the image or the inspection result data.

Here, the image processing unit 160 may be a communication device capable of connecting to the network such as a desktop computer, a laptop computer, a smart phone, a tablet PC, and the like. The image processing unit 160 may include image processing and vision inspection There is no limit to the type of terminal that can be used.

The interface unit 170 receives the trigger signal generated by the image processor 160 and transmits the trigger signal to the projector driver 145.

2 is a flowchart illustrating a method of measuring a three-dimensional shape using a triple frequency pattern according to an embodiment of the present invention.

Referring to FIG. 2, a method of measuring a three-dimensional shape using a triple frequency pattern performed by a three-dimensional shape measuring device generates first to third reference pattern data having different periods T1, T2, and T3 (S1). The first reference pattern data has a low frequency (f1 = 1 / T1), the second reference pattern data has an intermediate frequency (f2 = 1 / T2) (f3 = 1 / T3).

At this time, each reference pattern data is generated as an image, and the frequency in the image is expressed by the number of pixels. That is, the number of pixels constituting the pattern of one period in the low frequency reference pattern becomes larger than the number of pixels constituting the pattern of one period in the reference pattern of high frequency. For example, the first reference pattern image of low frequency may be composed of 96 pixels, the second reference pattern image of intermediate frequency may be composed of 24 pixels, the third reference pattern image of high frequency may be composed of 8 pixels, And the number of pixels of the second reference pattern image is an integer multiple K1 and the number of pixels of the second reference pattern image and the third reference pattern image is an integral multiple K2.

The projector driver 145 loads and stores reference pattern data of a specific period to be projected according to a predetermined reference. The image processor 160 determines a brightness setting value of the illumination according to the reference pattern data, And outputs a trigger signal for photographing the camera 130. (S2)

The projector driver 145 receives the trigger signal, operates the projector 140 in accordance with the illumination control signal, synchronizes with the illumination control signal, and the vertical camera 130 generates an image acquisition signal for imaging the image, (150).

The illumination of the projector 140 is turned on for a predetermined time according to the illumination control signal to project the reference pattern illumination based on any one of the first to third reference pattern data onto the surface of the object to be inspected (S3)

The projector 140 projects the first to third reference pattern lights on the surface of the object to be inspected four times while shifting the phase by π / 2, which is a predetermined phase value. That is, the first reference pattern illumination is projected four times, the second reference pattern illumination is projected four times, and the third reference pattern illumination is projected four times to perform a total of 12 projecting operations.

At least one camera 130 captures a plurality of pattern images by photographing the surface of the inspected object irradiated with the reference pattern illumination of a specific period (S4). That is, when the first reference pattern illumination is irradiated four times, 130 irradiates the surface of the object to be inspected with the first reference pattern illumination four times to acquire four first pattern images. When the second reference pattern illumination is irradiated four times, the camera 130 acquires the second reference pattern illumination When the third reference pattern illumination is irradiated four times, the camera 130 irradiates the surface of the inspected object irradiated with the third pattern illumination with 4 So as to acquire four third pattern images.

When the three-dimensional shape measuring apparatus acquires all the pattern images by the first reference pattern illumination, the second reference pattern illumination, and the third reference pattern illumination, the three-dimensional shape measuring apparatus acquires different cycles from the first through third pattern images according to the measurement range of the object to be inspected (S5, S6).

At this time, the measurement range of the object to be inspected may be either the inspection area or the characteristic information, and the characteristic information may be any of the type, height, size, manufacturer, part information, model name, color and identification code of the object to be inspected.

For example, when the object to be inspected is a PCB on which a plurality of chips are mounted, the three-dimensional shape measuring apparatus selects the first pattern image and the second pattern image in the case of a high chip, Select an image and a third pattern image.

The three-dimensional shape measuring apparatus selects the first pattern image and the second pattern image when measuring the surface height of the chip, and selects the second pattern image and the third pattern image when measuring the height of the solder.

The image processing unit 160 may extract the phase information from the selected two pattern images and calculate the height information of the object to be inspected by using the phase-

FIG. 3 is a view for explaining a first reference pattern image and a first pattern image according to the first reference pattern data of FIG. 2, FIG. 4 is a diagram illustrating a second reference pattern image according to the second reference pattern data of FIG. FIG. 5 is a view for explaining a third reference pattern image and a third pattern image according to the third reference pattern data of FIG. 2; FIG.

Referring to FIGS. 3 and 5, the image processor 160 performs a reference phase calculation process and a calibration process before calculating the height information of the object to be inspected.

First, in the reference phase calculation process, a flat plate is placed on the stage, and a total of four first reference pattern images are obtained while shifting the first reference pattern illumination according to the first reference pattern data by π / 2 from the reference height do. Likewise, four second reference pattern images and third reference pattern images corresponding to the second reference pattern data and the third reference pattern data are obtained, respectively.

The three-dimensional shape measuring apparatus calculates and stores a reference phase value using the first reference pattern image, the second reference pattern image, and the third reference pattern image.

Thereafter, the three-dimensional shape measuring apparatus carries out a calibration process while moving the first to third reference pattern images by unit steps, thereby obtaining a first calibration constant for the first reference pattern image and the second reference pattern image And determines a second calibration constant value for the second reference pattern image and the third reference pattern image.

At this time, the calibration constant value can be calculated by using the difference between the reference phase value at the reference height and the phase value at each unit step height.

The image processor 160 calculates the phase values of the object to be inspected based on the first pattern image, the second pattern image, and the third pattern image of the surface of the object to be inspected, And then calculates the difference between the reference phase value for each cycle and the phase value of the inspected object and converts the height information by a phase-height calculation formula using the calibration constant value.

The image processing unit 160 calculates the height information calculated using the pattern images obtained from the reference pattern illumination projected from the four projectors 140 in accordance with the integrated rule, And constructs the final height values for the object to be inspected.

FIG. 6 is a view for explaining a process of measuring a height of a stepped specimen by a three-dimensional shape measuring method using a triple frequency pattern according to an embodiment of the present invention.

Referring to FIG. 6, at the time of teaching, pattern images of different periods to be used are set based on the inspection area and characteristic information of the inspection object.

When the third pattern image using the third reference pattern data having a high frequency and the second pattern image using the second reference pattern data having the intermediate frequency are selected in the three-dimensional shape measuring apparatus, the height of the stepped specimen is 100 mu m to 2000 mu m And when the first pattern image using the first reference pattern data having the frequency lower than the second pattern image is selected, the height of the stepped specimen can be measured from 100 mu m to 5000 mu m.

In this case, when the height of the object to be inspected is measured by applying the triple frequency pattern, the height of the stepped specimen can be measured as in the case of measuring the height of the object to be inspected by applying the double frequency pattern. However, And the phase-height calculation process for the 12 pattern images to which the pattern image is applied. Therefore, it takes a long time for the inspection.

However, in the present invention, it is only required to perform the phase-height calculation process for two pattern images, i.e., eight pattern images, which have different periods depending on the inspection area and characteristic information of the inspection object, It is possible to maximize the height of the stepped specimen which can be measured at a shorter inspection time than the conventional method.

E.g. When the height of the top surface of the chip component is measured, the second pattern image using the second reference pattern data and the third pattern image using the third reference pattern data are selected and inspected. When the chip solder region is measured, A first pattern image using the reference pattern data and a second pattern image using the second reference pattern data are selected and inspected. In this case, although the number of image capturing times can not be reduced, the pattern image having two frequencies is selectively used instead of using all the pattern images having the triple frequency for the inspection region. Thus, And as the pattern period ratio between the two selected pattern images becomes smaller, the height calculation by phase becomes accurate, which can improve the measurement accuracy.

As described above, according to the present invention, a triple frequency moire pattern having different cycles is used, and each pattern period ratio can be set to an integral multiple of 7 or less, so that the phase conversion process can be more accurately performed. Repeatability can also contribute to improvement.

In addition, the present invention can minimize the pattern period ratio (PPR1) between the first reference pattern data and the second reference pattern data, the pattern period ratio (PPR2) between the first reference pattern data and the third reference pattern data, , Thereby eliminating errors in the phase conversion process (ase unwrapping).

If the third reference pattern data is set to 8 pixels (measurement range 900um) per cycle and PPR2 = 3 is set, the second reference pattern data is set to 1 (Measurement range 2.7 mm) per cycle, and when PPR1 = 4, the first reference pattern data is 96 pixels per measurement cycle (measurement range 10.8 mm), and the measurement range determined by the lower frequency of the first reference pattern data is set to Can be enlarged.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

110: stage 120: LED driver
130: vertical camera 140: plural projectors
145: Projector driving part 150: Grabber
160: image processor 170:

Claims (9)

A three-dimensional shape measuring method using a triple frequency pattern, which is performed by a three-dimensional shape measuring apparatus for measuring a three-dimensional shape of the object to be inspected by irradiating pattern light on an object to be inspected in at least one projector, As a result,
Generating first to third reference pattern data having different periods, respectively;
The first to third reference pattern data corresponding to the loaded first to third reference pattern data are loaded on the surface of the inspected object, ;
Capturing a plurality of first through third pattern images by photographing a surface of the inspection object irradiated with the first through third reference pattern lights in at least one camera;
Selecting two pattern images having different periods from the first through third pattern images according to the measurement range of the inspection object; And
Extracting phase information from the two selected pattern images and calculating height information for the inspected object by a phase-height calculation equation,
The step of extracting the phase information from the two selected pattern images and calculating the height information of the three-dimensional shape by the phase-
Generating and storing a reference phase value at a reference height for each of the first to third reference pattern data; Determining a calibration constant value by performing calibration while moving the unit pattern data by a unit step in units of the first to third reference pattern data; Calculating a phase value of the inspected object using the selected two pattern images after setting an inspection area of the inspected object; And calculating a difference between the reference phase value and a phase value of the inspected object and calculating a height by using a phase-height calculation formula using the calibration constant value. Shape measuring method.
The method according to claim 1,
The generating of the first to third reference pattern data having the different periods, respectively,
Wherein the first reference pattern data is configured to have N number of pixels per cycle and the second reference pattern data has M (M <N) number of pixels, and the third reference pattern data is set to L ( L &lt; M) number of pixels. The three-dimensional shape measuring method using the triple frequency pattern.
3. The method of claim 2,
Wherein the number of pixels of the first reference pattern data is an integral multiple of the number of pixels of the second reference pattern data and the number of pixels of the second reference pattern data is an integral multiple of the number of pixels of the third reference pattern data. A method for measuring three - dimensional shape using.
The method according to claim 1,
The first to third reference pattern data corresponding to the loaded first to third reference pattern data are loaded on the surface of the inspected object, Wherein the step of projecting,
So that the first to third reference pattern lights are projected on the surface of the object to be inspected by a preset number of times while being phase-shifted by a predetermined phase value, respectively.
The method according to claim 1,
Wherein the measurement range of the inspection object is inspection area or characteristic information,
Wherein the characteristic information is any one of a type, a height, a size, a manufacturer, part information, a model name, a color, and an identification code of the inspected object.
delete The method according to claim 1,
And generating and storing reference phase values at a reference height for each of the first through third reference pattern data,
Projecting each of the first to third reference pattern lights onto the surface of the object to be inspected by a predetermined number of times while phase-shifting the predetermined number of first to third reference pattern lights to obtain a plurality of first to third reference pattern images, And the third reference pattern image is used to calculate the reference phase value, respectively.
The method according to claim 1,
The step of calibrating the first to third reference pattern data while moving the unit step by a unit step to determine a calibration constant value comprises:
And a second calibration constant value for the second reference pattern data and the third reference pattern data is determined by determining a first calibration constant value for the first reference pattern data and the second reference pattern data, 3 - D shape measurement method using frequency pattern.
The method according to claim 1,
Wherein the pattern period ratio of the first reference pattern data is set to an integral multiple of a set value of the pattern period ratio of the second reference pattern data and the pattern period ratio of the second reference pattern data is set to a pattern period ratio And the measurement range of the object to be inspected is adjusted by setting an integral multiple of the set value of the three-dimensional shape.
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