KR20100136588A - Device for measuring 3-d shape using orthogonal fringe patterns and method for the same - Google Patents

Abstract

PURPOSE: A 3-dimensional measuring device using orthogonal fringe patterns and a measuring method thereof are provided to enable 3-dimensional measurement of high precision such as stereo vision using two cameras. CONSTITUTION: A 3-dimensional measuring device using orthogonal fringe patterns comprises a light-transmitting unit, a camera unit, a controller, and an operation unit. The light-transmitting unit projects horizontal patterns and vertical patterns which are vertical to the horizontal patterns. The camera unit is fixed and connected to the light-transmitting unit. The camera unit obtains images of multiple calibration panels. The controller controls the light-transmitting unit and the camera unit.

Description

Three-Dimensional Measurement Apparatus and Measurement Method Using Orthogonal Stripe Pattern {DEVICE FOR MEASURING 3-D SHAPE USING ORTHOGONAL FRINGE PATTERNS AND METHOD FOR THE SAME}

1 is a view showing the configuration of a three-dimensional measuring apparatus using a camera and a light emitter.

2 is a view showing an example of a conventional vertical stripes pattern.

3 is a diagram for calibrating a three-dimensional measuring device using a camera and a light emitter using a multi-calibration panel.

4 is a diagram for obtaining three-dimensional point data using a three-dimensional measuring apparatus using a camera and a light projector.

FIG. 5 is a diagram illustrating a state in which light from a light source passes through a light transmission lens (projection lens).

FIG. 6 is a view showing a three-dimensional measuring apparatus using two conventional cameras and one light emitter (center).

7 is a diagram illustrating an example of horizontal stripe patterns.

8 is a diagram for projecting orthogonal stripe patterns onto a multi-calibration panel.

9 is a diagram for obtaining vertical ID lines and horizontal ID lines that are orthogonal to each other.

10 is a diagram for obtaining three-dimensional intersections of ID lines orthogonal to each other.

FIG. 11 illustrates a combination of vertical stripes patterns and horizontal stripes patterns as an embodiment of the present invention.

12 is a diagram illustrating one embodiment of the present invention as one or more orthogonal stripe patterns (patterns orthogonal to the multiple stripe patterns) of the present invention are added to the multi-stripe pattern.

FIG. 13 is a photograph comparing three-dimensional data applying only conventional vertical stripe patterns and three-dimensional data applying orthogonal stripe patterns of the present invention.

The present invention relates to a three-dimensional measuring apparatus and a measuring method using a camera and one light emitter, a three-dimensional measuring apparatus that can perform a more precise three-dimensional measurement by using an orthogonal stripe pattern in the calibration step of the three-dimensional measurement and It relates to a measuring method.

As an example of the prior art for measuring the shape of a three-dimensional object, there has been proposed a three-dimensional measuring device that combines one or two or more cameras, and a projector that is fixedly or detachably attached to the camera. . 1 is a view showing an example of a general three-dimensional measuring apparatus using a camera. In order to implement a three-dimensional measuring device, a camera and a light emitter must first be calibrated, and the measured object is scanned in three dimensions using the calibration result to obtain three-dimensional point data. . Since the general three-dimensional measurement process is known (see Patent Registration 10-0332995, Publication 10-2006-0118680), a brief look at the process.

(1) Calibration step of three-dimensional measurement

A camera calibration and a projector calibration are performed in two stages, and the present invention will be mainly focused on the projector calibration.

A) Camera calibration is to calculate camera center (CC) coordinates, focal length and lens distortion coefficient (internal variables) from the reference coordinate system.

B) Projector calibration involves the three-dimensional ID plane equation (ax + by + cz = 1) are important results.

FIG. 3 (A) shows a side and top view of calibrating the transmitter while moving a single panel (single calibration panel) back and forth by a predetermined distance, and FIG. 3 (B) is shown in FIG. (A) is a view of the multi-calibration panel in which the vertical stripe pattern is projected from the back of the camera and the light projector as shown in (A), Figure 3 (C) is a single panel in various positions having an arbitrary angle (ex: 5 positions) Shown above is a picture of calibrating the floodlight projector. The single panel is a flat plate for calibration (mainly a rectangular shape) and can be moved in parallel at two or more positions (FIG. 3A) or at any angle at two or more positions (FIG. 3C). This combination of single panels will be referred to as a 'multi calibration panel'.

In addition, the striped pattern described in the present invention means a combination of one or more bright color lines and one or more dark color lines. It can be white (white light source), red (laser light source), green (laser light source), and dark lines are areas where light is not transmitted. Hereinafter, for convenience, bright lines are white and dark lines are indicated by black.

FIG. 2 illustrates a gray code as an example of conventional vertical patterns (VP). As shown in FIG. 11, various vertical stripes patterns VP may be used. The combination of (A) to (F) of FIG. 2 may obtain an ID (ID) of the edge of each stripe or an ID of a center line of each stripe boundary. In the present invention, the stripe ID will be described based on the border of the stripe for convenience. The ID is to identify the stripes of the same spacing from each other, the details of which are known in the expression of correspondence (correspondence) in the patent 10-0332995, the person having ordinary technical knowledge in the field of three-dimensional measurement If you know the meaning of gray code, detailed description is omitted. In addition, the combination of the vertical stripes to obtain the ID, even if only one or two or more selected from (A) to (F) of Figure 2, the number is not limited as long as there is a way to identify each other. FIG. 3B shows the IDs 1 to 5 of the edges of the stripes from FIG. 2B (or a combination of FIG. 2A + B).

Referring to the conventional method of obtaining a single ID plane equation (ax + by + cz = 1) in which only one ID plane exists for one ID, FIG. 2 IDs on the front panel and 2 ID lines on the rear panel of the rear panel One plane equation (ax + by + cz = 1) can be obtained by connecting any two points (R1, R2) on the line, and this single ID plane passes the light source LS, which is 2 This is the single ID plane equation for the streaks.

(2) Scan step of three-dimensional measurement

Three-dimensional point data (X, Y, Z) obtained as a result of the three-dimensional measurement is a three-dimensional vector (Vc) extending from the camera in the three-dimensional space as shown in Figure 4 and a single ID plane (ex) obtained in the calibration step Find the intersection with ID 2). If you perform the same process for all single ID planes, you can get the point data of 3D object surface.

Problems of the prior art will be described with reference to FIGS. 1, 5, and 6. Conventionally, since all the stripes projected from the projector are projected from a single light source, it is assumed that there is only one single light source by ideally simplifying the light source (LS) of the projector. It is assumed that all single ID planes pass through the single light source, and when the three-dimensional position of the single light source is obtained, the horizontal dotted line passing through the camera center (CC) in FIG. Since Y is physically at the same height, the Y coordinate of the three-dimensional light emitter is set to the same Y value as the center of the camera.

However, in FIGS. 5A and 5B, light from a light source (LS) is projected in different directions due to lens refraction when passing through a projection lens, and at each projection angle. Therefore, it can be seen that the positions LS1 and LS2 of the light sources are also different. Even if the position of the light source is different by a few microns, the measurement error occurs in the scanning step of the three-dimensional measurement.

Therefore, the assumption of a single light source and the assumption of the Y-coordinate value of the light emitter in the calibrator calibration stage cause a measurement error in the scan stage of the three-dimensional measurement, and a three-dimensional scanner (three-dimensional measuring instrument, three-dimensional) having high added value according to the precision. The measuring device acts as a fatal defect. Due to the measurement error, the three-dimensional measuring device using one camera and one light emitter cannot be used in the high precision measurement field of micron units, and the high precision measurement field uses two units instead of one camera. In addition, a stereo vision measurement method (see Patent 10-0332995) using two cameras and one light projector is widely used, and the actual photograph is shown in FIG. 6. The stereo vision measuring method using two such cameras has a disadvantage that the system configuration is more complicated than one camera and it is uneconomical because one more expensive industrial camera is used.

An object of the present invention is to provide a high-precision three-dimensional measuring apparatus such as a stereo vision measuring method using two cameras using only one camera. In addition, another object of the present invention is to provide a measuring method for implementing such a three-dimensional measuring apparatus.

The present invention for achieving the above object, in the calibration step of the three-dimensional measurement, the projection unit for projecting the vertical stripe patterns and the horizontal stripe patterns orthogonal to the vertical stripe patterns on the surface of the multi-calibration panel, respectively; A photographing unit fixedly connected to the light transmitting unit and acquiring an image of the multi-calibration panel in which the vertical stripes patterns and the horizontal stripes patterns are projected, a control unit controlling the light transmitting unit and the photographing unit, and the multi-calibration panel And an operation unit for obtaining three-dimensional intersections of the vertical ID lines obtained from the vertical stripe patterns and the horizontal ID lines obtained from the horizontal stripe patterns.

More preferably, the vertical stripe patterns are composed of one or more vertical stripe patterns, the horizontal stripe patterns are composed of one or more horizontal stripe patterns, the multi-calibration panel is a single panel in parallel with a predetermined distance from two or more positions The light transmitting part projects the vertical stripe patterns and the horizontal stripe patterns at each position of the multi-calibration panel.

More preferably, the vertical stripe patterns are composed of one or more vertical stripe patterns, the horizontal stripe patterns are composed of one or more horizontal stripe patterns, the multi-calibration panel is a single panel is located at any angle at two or more positions The light projection part projects the vertical stripe patterns and the horizontal stripe patterns at each position of the multi-calibration panel.

More preferably, the calculator calculates a plurality of ID planes from three-dimensional intersections of the vertical ID lines and the horizontal ID lines.

More preferably, the calculating unit obtains a plurality of light sources from three-dimensional intersections of the vertical ID lines and the horizontal ID lines.

According to another aspect of the present invention, in the calibration step of the three-dimensional measurement, the step of projecting the vertical stripe patterns and the horizontal stripe patterns orthogonal to the vertical stripe patterns on the surface of the multi-calibration panel using a light transmitting unit, respectively; Acquiring an image of the multi-calibration panel on which the vertical stripe patterns and the horizontal stripe patterns are projected by the photographing unit fixedly connected to the light transmitting unit, the control unit controlling the light transmitting unit and the photographing unit, and the calculating unit And obtaining three-dimensional intersections of the vertical ID lines obtained from the vertical stripe patterns and the horizontal ID lines obtained from the horizontal stripe patterns on the surface of the multi-calibration panel.

Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. 7 to 10, and a light transmitting unit, a photographing unit, a control unit, and an operation unit, which are essential components of the present invention, will be described in order.

First, the light transmitting section will be described.

The light transmitting part refers to a device in which stripes generated in the pattern mask are projected to the outside when light from a light source (LS) passes through a pattern mask (pattern mask, pattern film) and passes through a series of lenses. It is used in the same meaning as 'projector'. The light transmitting portion is controlled by a controller to be described below. The light source may be halogen lamps, lasers, LEDs, IR LEDs and other various light sources, and the pattern mask may be an example of generating a stripe pattern (eg, etching) on a semiconductor substrate, and as a substitute for the pattern mask. When the LCD, the DLP, and the slide film are used, the light transmitting unit means a beam projector (LCD projector, a DLP projector) and a slide projector (illuminator), respectively. In the case where the pattern mask is a multi-pattern mask (generally generating a plurality of patterns in a long mask), as described in the Patent 10-0455348, the transfer of the multi-pattern mask by a transfer device is also a pattern of the light projector of the present invention. It will be included in the mask. In one embodiment of the present invention, a diagram of projecting a pattern with a beam projector is shown in Figs. 3B and 8A. For convenience, the light transmitting unit will be described with reference to the beam projector.

In the multi-calibration panel of the present invention, not only two positions of the front and rear panels shown in FIGS. 3A and 3B but also three positions or more can be moved in parallel by a predetermined distance backward. As shown in FIG. 3C, it is also possible to position a single panel at any angle in two or more different positions. In the following description, an example of projecting by moving in parallel at two positions of the front and rear panels having a predetermined distance shown in FIGS. 3A and 3B will be described.

A procedure of projecting a pattern in the present invention using the light transmitting portion will be described. The light-transmitting part projects one or more of the vertical patterns (VP) shown in FIG. 2 at the front position of the multi-calibration panel, respectively, and at the same position (front position), Project one or more of the horizontal patterns (HP), respectively. Next, the same method is performed at the rear position of the multi-calibration panel. However, it is also possible to change the position order of the front and rear panels, the number of projection patterns and the projection order of the patterns. That is, FIG. 8B is a combination of FIG. 3B and FIG. 8A, wherein the light-transmitting portion is arranged in the order of the vertical stripe pattern 81 and the horizontal stripe pattern 82 at the front panel position. And the projection of the same vertical stripe pattern 83 and horizontal stripe pattern 84 in the rear panel position, and the order of the four stripe patterns 81 to 84 is changed. The panel position can also be changed) for projection. This is because the combination can be changed in the original order after all the camera images are acquired. The vertical stripe patterns and the horizontal stripe patterns are generated by orthogonal to each other at a 90-degree angle, and when the vertical stripe pattern is rotated 90 degrees in a horizontal stripe pattern by the rotation of the projector or the camera, the horizontal stripe pattern is also vertical It is rotated 90 degrees in a stripe pattern, and the important thing is to be orthogonal to each other.

In FIG. 11A, vertical patterns (VP) and horizontal patterns (HP) are distinguished by black box lines, and the light-transmitting part first projects one or more of the vertical stripes patterns. Then, one or more of the horizontal stripe patterns are projected. In the present invention, projection of at least one vertical stripe pattern and at least one horizontal stripe pattern at one position of the multi-calibration panel is required. (B), (C), (D) and (E) of FIG. 11 are also the same. In FIG. 11 (A) and (C), four thin stripe patterns 116, 117, 118, and 119 are shown, which are phase shifted by 90 degrees of the same thickness pattern. If the phase difference is 120 degrees, only three thin vertical stripe patterns are used. The vertical stripe patterns of FIG. 11A are known from FIG. 5B of Patent 10-0455348. In the present invention, the stripe pattern is a pattern having a uniform (equal light and dark spacing) or non-uniform (light and dark spacing not equal) spacing, and is generally regular (graycode, binary code). code)) or an irregular pattern (light and dark intervals are not the same). For example, FIGS. 11D and 11E illustrate an irregular vertical stripe pattern and an irregular horizontal stripe pattern. In the case of FIG. 11E, one irregular vertical stripe pattern and one irregular horizontal stripe pattern may be used. The vertical stripes and the horizontal stripes are a combination of (A), (B), (C), (D), and (E) of FIG. 11 (select all or at least one of the vertical stripes and the horizontal stripes) It can be used to select one or more of), and can be implemented in various forms similar to this. In the case of Figure 12 orthogonal stripe pattern (VP: multi-stripe pattern described in the present invention) in the multi-stripe pattern (patterned pattern of the same pattern as the pattern of Figure 11 is a single stripe pattern of the original pattern of a short length) of Patent No. 10-0455348 (A), (B), (C), (D), and (E) of FIG. 12 will also be seen as one embodiment of the present invention. Therefore, even if the embodiment of the stripe pattern, if the resulting pattern is the same as the technical spirit of the present invention will be seen as an embodiment of the present invention.

Although the pattern mask included in the transmitter of the known three-dimensional measuring apparatus has conventionally generated only a vertical stripe pattern or only a horizontal stripe pattern, at least one vertical stripe pattern and at least one horizontal stripe pattern are formed on the stripe patterns generated in the pattern mask. If it exists together, it is presumed that the calibration method of this invention was used. Because the calibration step is made inside the manufacturer of the three-dimensional measuring device, it is difficult to easily demonstrate the implementation of the present invention from the outside, and if one embodiment of the orthogonal stripe patterns is generated in the pattern mask, the practice of the present invention is performed unless there is a valid reason. This can be estimated. 11 and 12 are merely examples and should not be construed as limiting.

Next, the photographing unit will be described.

In the photographing unit, a camera is mainly used as a means for acquiring an image of an object whose pattern is projected from the light transmitting unit, and a CCD camera, a CMOS camera, an image camera, a web camera, a digital camera, and the like are used. The photographing unit is controlled by a controller to be described below. The photographing unit acquires a series of vertical stripe patterns and horizontal stripe patterns projected sequentially (continuously) from the light-transmitting unit for each pattern and one image at each position of the panel. For example, when all of the patterns shown in FIG. 11A are projected and the multi-calibration panel is in two positions, the total acquired images are 30.

(9 vertical stripe patterns + 6 horizontal stripe patterns) * 2 position = 30

In the present invention, only one camera is used. However, even if two or more cameras are used, one of the cameras will be regarded as having the same technical idea if one of the cameras is used as the present invention in relation to the one emitter.

Next, a control part is demonstrated.

As shown in FIG. 1, the controller controls the light projector (projector) to sequentially project each pattern, and controls the photographing unit (camera) to sequentially project the image of the object to which the pattern is sequentially projected. Acquire. In addition, the controller may control an apparatus for automatically transferring the single panel to another position. The controller may be a desktop computer, a notebook computer, a microprocessor, or a device that performs the same function.

Finally, the calculation unit will be described.

As shown in FIG. 1, the operation unit is connected to a control unit, and a desktop computer, a notebook computer, a microprocessor, or a device that performs the same function may be used. Preferably, the operation unit is integrated with the control unit.

Hereinafter, the functions of the calculator will be described with reference to FIGS. 9 and 10. FIG. 9 is a diagram for obtaining vertical ID lines and horizontal ID lines orthogonal to each other. The vertical stripe pattern is shown in FIG. 2B, and the horizontal stripe pattern is shown in FIG. 7. By using (B), the orthogonal ID lines (vertical ID lines + horizontal ID lines) (the edge lines of the vertical stripes and the horizontal stripes in FIG. 9) were obtained by the combination. When the projection part projects the pattern on the multi-calibration panel, since the vertical stripe patterns and the horizontal stripe patterns are successively projected at each single panel position, the orthogonal ID lines are also present at each single panel position. If each single panel position is two positions, orthogonal ID lines should also be obtained for each single panel position.

FIG. 10A shows three-dimensional intersections of ID lines orthogonal to each other, wherein the three-dimensional intersections include five vertical ID lines and horizontal ID lines at front and rear positions of the multi-calibration panel, respectively. Three points of intersection. In FIG. 10B, vertical IDs 2, 3, and horizontal IDs 1 and 2 of the ID lines of FIG. 10A intersect at the front and rear positions of the multi-calibration panel, respectively. As shown in the figure, the position values of the multiple ID plane equations and the multiple light sources are obtained for each cross section of each ID.

As shown in FIG. 5, the light source of the transmitter actually has multiple light sources, and the light emitted from the multiple light sources is projected in various directions by refraction. Since it is consistent with the concept of multiple ID planes rather than single ID planes, more accurate calibration results can be obtained. However, the positions of the plurality of light sources obtained in the present invention will be regarded as ideal positions obtained by reversing the positions of the light sources from the linearly projected light, rather than the positions of the plurality of light sources.

In FIG. 10B, three-dimensional intersection points F1 and F2 of the front panel and three-dimensional intersection points of the rear panel with respect to the vertical ID line 2 and the horizontal ID lines 1 and 2 orthogonal thereto. One ID plane equation (ID plane 12: ax + by + cz = 1) can be obtained by connecting four points of R1 and R2, and a straight line connecting F1 and R1 and a straight line connecting F2 and R2 are obtained. The intersection is the three-dimensional coordinate value of the light source LS12 with respect to the ID plane. In the same way,

F3, F4, R3, R4-> LS34, ID plane 34

F1, F3, R1, R3-> LS13, ID plane 13

F2, F4, R2, R4-> LS24, ID plane 24

It is possible to obtain the position values of the plurality of ID planes (4) and the multiple light sources (4) from two vertical ID lines and two horizontal ID lines. When the vertical stripe patterns and the horizontal stripe patterns are further subdivided as shown in (A) of FIG. 11, the number of ID planes and the plurality of light sources is increased by the number of intersections, so that more precise calibration is possible. You can get the result.

Using these calibration results (multiple ID plane equations, position values of multiple light sources), the intersection of ID planes and 3D vector of the camera for each 3D section of each ID plane is more precise than the conventional 3D point. Data can be obtained.

FIG. 13 is a photograph comparing three-dimensional data applying only conventional vertical stripe patterns and three-dimensional data applying orthogonal stripe patterns of the present invention. As shown in FIG. 13A, three-dimensional data is roughly generated (measurement error occurs) in the neck portion of the plaster, but as a result of applying the calibration method of the present invention, three-dimensional data in the neck portion as shown in FIG. You can see that comes out smoothly.

The present invention described above can be embodied in many different forms without departing from the spirit or main features thereof. Therefore, the above embodiments are merely examples in all respects and should not be interpreted limitedly.

The present invention can be used in the field of high precision three-dimensional measurement in microns by using the orthogonal stripe pattern in the calibration stage of three-dimensional measurement, and compared to the stereo vision measuring method using two expensive cameras by using only one camera. Economical and one camera reduces the size of the entire system, making it light and portable.

Applications include reverse engineering, which applies three-dimensional scanning of real products to product design with three-dimensional measuring device of the present invention, three-dimensional restoration of cultural property for permanent preservation of cultural properties, computer graphics and computer animation, and three of products. Dimensional quality test, face shaping to compare three-dimensional before and after surgery of human face.

Claims (10)

In the calibration phase of three-dimensional measurements, A light projection part projecting the vertical stripe patterns and the horizontal stripe patterns orthogonal to the vertical stripe patterns on the surface of the multi-calibration panel, respectively; A photographing unit fixedly connected to the light transmitting unit and acquiring an image of the multi-calibration panel in which the vertical stripe patterns and the horizontal stripe patterns are projected; A control unit for controlling the light projecting unit and the photographing unit; 3D measurement using an orthogonal stripe pattern, comprising: a calculation unit for calculating three-dimensional intersections of vertical ID lines obtained from the vertical stripe patterns and horizontal ID lines obtained from the horizontal stripe patterns on the surface of the multi-calibration panel. Device. The method of claim 1, The vertical stripe patterns are composed of one or more vertical stripe patterns, the horizontal stripe patterns are composed of one or more horizontal stripe patterns, the multi-calibration panel is a panel in which a single panel is moved in parallel by a predetermined distance from two or more positions 3. The apparatus of claim 3, wherein the light transmitting unit projects the vertical stripes patterns and the horizontal stripes patterns at each position of the multi-calibration panel. The method of claim 1, The vertical stripe patterns are composed of one or more vertical stripe patterns, the horizontal stripe patterns are composed of one or more horizontal stripe patterns, the multi-calibration panel is composed of panels in which a single panel is positioned at any angle from two or more positions And the light transmitting unit projects the vertical stripe patterns and the horizontal stripe patterns at each position of the multi-calibration panel. The method according to any one of claims 1 to 3, And the calculating unit obtains a plurality of ID planes from three-dimensional intersections of the vertical ID lines and the horizontal ID lines. The method according to any one of claims 1 to 3, And the calculating unit obtains a plurality of light sources from three-dimensional intersections of the vertical ID lines and the horizontal ID lines. In the calibration phase of three-dimensional measurements, Projecting vertical stripe patterns and horizontal stripe patterns orthogonal to the vertical stripe patterns on the surface of the multi-calibration panel by using a light transmitting unit, Acquiring an image of the multi-calibration panel through which the vertical stripe patterns and the horizontal stripe patterns are projected by a photographing unit fixedly connected to the light transmitting unit; The control unit controls the light transmitting unit and the photographing unit; The calculating unit may include obtaining three-dimensional intersections of the vertical ID lines obtained from the vertical stripes patterns and the horizontal ID lines obtained from the horizontal stripes patterns on the surface of the multi-calibration panel. Dimensional measurement method. The method of claim 6, The vertical stripe patterns are composed of one or more vertical stripe patterns, the horizontal stripe patterns are composed of one or more horizontal stripe patterns, the multi-calibration panel is a panel in which a single panel is moved in parallel by a predetermined distance from two or more positions 3. The method of claim 3, wherein the light transmitting unit projects the vertical stripe patterns and the horizontal stripe patterns at each position of the multi-calibration panel. The method of claim 6, The vertical stripe patterns are composed of one or more vertical stripe patterns, the horizontal stripe patterns are composed of one or more horizontal stripe patterns, the multi-calibration panel is composed of panels in which a single panel is positioned at any angle from two or more positions And the transmissive part projects the vertical stripes patterns and the horizontal stripes patterns at each position of the multi-calibration panel. The method according to any one of claims 6 to 8, And the calculating part obtains a plurality of ID planes from three-dimensional intersections of the vertical ID lines and the horizontal ID lines. The method according to any one of claims 6 to 8, And the calculating unit obtains a plurality of light sources from three-dimensional intersections of the vertical ID lines and the horizontal ID lines.

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