KR101988630B1 - Camera calibration method for time slice shooting and apparatus for the same - Google Patents

Abstract

According to one embodiment of the present invention, a camera calibration method for time slice shooting comprises the following steps: (a) generating a first marker by irradiating a laser beam to a first position; (b) performing primary calibration of cameras using first images shooting the first marker; (c) generating a second marker by irradiating the laser beam to a second position different from the first position; and (d) performing secondary calibration of the cameras using second images shooting the second marker.

Description

Camera calibration method for time slice shooting and apparatus for same {CAMERA CALIBRATION METHOD FOR TIME SLICE SHOOTING AND APPARATUS FOR THE SAME}

The present invention relates to a camera calibration method for time slice photography and an apparatus therefor.

A time slice photographing technique is a photographing technique in which three cameras of different directions are installed on one subject, photographed at the same time, attached to an image frame, and three-dimensionally depicting the stationary state of the subject.

Conventional time slice imaging systems typically use expensive equipment, such as a digital single-lens reflex camera (DSLR), as each camera.

In this case, the time-slice shooting requires a high cost and a large installation space, there is a problem that requires a professional manpower to control the camera equipment.

In addition, for time slice photographing, a process of calibrating camera apparatuses such that a plurality of camera apparatuses form a viewpoint rotation axis is required.

Korea Patent Registration No. 10-1619478 (name of the invention: time slice controller)

An object of the present invention is to provide a time slice photographing system capable of aligning the viewpoint rotation axis of the cameras without a separate object by performing calibration using a laser beam for the cameras used in the time slice photographing system.

According to an aspect of the present invention, there is provided a camera calibration method for time slice photographing, the method comprising: (a) generating a first marker by irradiating a laser beam to a first position; (b) performing primary calibration of the cameras using the first images of the first markers; (c) generating a second marker by irradiating a laser beam to a second position different from the first position; And (d) performing secondary calibration of the cameras by using second images photographing the second marker.

In addition, the camera calibration apparatus for time slice photographing according to another embodiment of the present invention comprises a laser beam irradiation apparatus for generating a marker; And a processor configured to control the beam irradiation apparatus to generate a plurality of markers, and to perform calibration of cameras by using the images of the markers, wherein the processor controls the beam irradiation apparatus to irradiate a laser beam to a first position. Generate a first marker, perform first calibration of the cameras using the first images of the first marker, and generate a second marker by irradiating a laser beam to a second position different from the first position; The second calibration of the cameras may be performed using the second images photographing the second marker.

In addition, a time slice photographing system according to another embodiment of the present invention includes a plurality of cameras arranged to surround a subject; A camera control unit performing a synchronization process of the plurality of cameras and obtaining an image from the cameras; And a laser beam irradiation apparatus, generating a first marker by irradiating a laser beam to a first position, receiving first images of photographing the first marker from a camera control unit, and performing primary calibration of the cameras. A camera calibration apparatus for generating a second marker by irradiating a laser beam to a second position different from the first position, and receiving second images photographing the second marker from the camera control unit to perform secondary calibration of the cameras; It includes.

According to the time-slice photographing system according to an embodiment of the present invention, by performing calibration on the cameras using a laser beam, it is possible to provide a time-slice photographing system capable of aligning the viewpoint rotation axis of the cameras without a separate object. have.

1 is a view schematically showing the configuration of a time slice photographing system according to an embodiment of the present invention.
2 is a diagram illustrating a process of generating a first marker by a camera calibration apparatus according to an embodiment of the present invention.
3 is a view showing a first calibration result image according to an embodiment of the present invention.
4 is a diagram illustrating a process of generating a second marker by a camera calibration apparatus according to an embodiment of the present invention.
5 is a view showing a secondary calibration result image according to an embodiment of the present invention.
6 is a flowchart illustrating a camera calibration method for time slice photography according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components, unless specifically stated otherwise, one or more other features It is to be understood that the present disclosure does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, parts, or combinations thereof.

The following examples are detailed description to aid in understanding the present invention, and do not limit the scope of the present invention. Therefore, the same range of inventions that perform the same functions as the present invention will also fall within the scope of the present invention.

1 is a view schematically showing the configuration of a time slice photographing system according to an embodiment of the present invention.

Referring to FIG. 1, the time slice photographing system 1 according to an embodiment of the present invention includes a camera calibration apparatus 100, a camera control unit 200, and a camera 300.

The camera calibration apparatus 100 includes a communication module, a memory, a processor, and a database.

In addition, the camera calibration apparatus 100 further includes a laser beam irradiation apparatus 110 for generating a marker used to perform calibration.

In detail, the communication module provides a communication interface necessary to provide a transmission / reception signal between the camera calibration device 100 and the camera control unit 200. Furthermore, the communication module may perform a role of receiving a data request from the camera control unit 200 and transmitting data as a response thereto.

Here, the communication module may be a device including hardware and software necessary for transmitting and receiving a signal such as a control signal or a data signal through a wired or wireless connection with another network device.

Here, an interface such as RS485 that supports a multi-drop method may be used as an interface to which the camera calibration device 100 and the camera control unit 200 are connected, but the present invention is limited to such an interface. no.

In the memory, a program for performing a camera calibration method for time slice photography is recorded. It also performs the function of temporarily or permanently storing data processed by the processor. Here, the memory may include a magnetic storage media or a flash storage media, but the scope of the present invention is not limited thereto.

The processor serves as a central processing unit to transmit a capture command to the camera control unit 200.

Here, the processor may include all kinds of devices capable of processing data, such as a processor. Here, the 'processor' may refer to a data processing apparatus embedded in hardware having, for example, a circuit physically structured to perform a function represented by code or instructions included in a program. As an example of a data processing device embedded in hardware, a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, and an application-specific integrated device (ASIC) It may include a processing device such as a circuit, a field programmable gate array (FPGA), etc., but the scope of the present invention is not limited thereto.

The database stores captured images collected from the camera control units 200.

The camera control units 200 are connected to the plurality of cameras 300 to transmit a capture start signal to the plurality of cameras 300, and capture captured images obtained from the cameras 300 to the camera calibration device 100. It serves to transmit.

Here, a plurality of camera control units 200 may be connected to one camera calibration device 100, and the number of camera control units 200 connected to the camera calibration device 100 is limited to the embodiment of FIG. 1. It is not.

In addition, although the camera control units 200 are illustrated as being arranged in an arc shape in FIG. 1, the camera control units 200 may be arranged in a straight line, and the arrangement of the camera control units 200 according to the present invention may be arranged. It is not limited to any particular arrangement.

In addition, each of the camera control units 200 performs an automatic synchronization process to generate a captured image synchronized with other camera control units 200.

To this end, the camera control units 200 are composed of one master camera control unit and slave camera control units except the master camera control unit, so that the entire camera control units 200 can be synchronized by the control of the master camera control unit. have.

The camera 300 may include an image sensor such as a complementary metal-oxide-semiconductor (CMOS) sensor or a charge-coupled device (CCD) sensor.

The camera 300 receives a capture start signal from the camera control unit 200, obtains an image, and transmits the image to the camera control unit 200 as a captured image.

Here, a plurality of cameras 300 may be connected to one camera control unit 200, and the number of cameras 300 connected to the camera control unit 200 is not limited to the embodiment of FIG. 1.

Although not shown in FIG. 1, the camera calibration apparatus 100 may be configured to be embedded in a kiosk.

The user can input a camera calibration signal through the kiosk, time-slice the shots in front of the camera modules after the camera calibration is completed, and check the time-slice photographing results through the kiosk again.

2 to 5 are diagrams illustrating a camera calibration method for time slice photographing according to an embodiment of the present invention.

In particular, FIG. 2 is a diagram illustrating a process of generating a first marker by the camera calibration apparatus 100 according to an embodiment of the present invention, and FIG. 3 is a diagram illustrating a first calibration result image according to an embodiment of the present invention. Drawing.

First, referring to FIG. 2, it can be seen that the camera calibration apparatus 100 generates a first marker 115 at a first position by irradiating a laser at an initial angle.

Here, the first position may be a point at which the viewpoint rotation axis shown in the time slice photographing result intersects with the ground or the background surface.

Here, the viewpoint rotation axis refers to a rotation axis corresponding to the effect of rotating the viewpoint in the time slice photographing result.

In addition, the background surface refers to a background plate installed so that a marker is formed by the laser beam irradiation apparatus in front of the cameras 300 when the cameras 300 do not photograph the ground.

For example, the first position of the ground may be a position on the ground having the same distance as the viewpoints of each of the cameras 300. This may be a point at which the line passing in the direction perpendicular to the circle and the ground intersecting the center of the circle passing through each viewpoint of the cameras 300 cross each other.

Here, when the cameras 300 are ideally arranged, it can be seen that the first marker 115 is present at the same coordinates 311 on the image 310 obtained by the cameras 300 as shown in FIG. 3.

The camera calibration apparatus 100 identifies the first marker 115 on the image 310 obtained by the cameras 300, and when the coordinate values of the first marker 115 are different from each other, the camera calibration apparatus 100 may be aligned with reference coordinates. Primary calibration may be performed on the cameras 300.

For example, when the coordinates of the first marker 115 are 10 pixels (px) in the x-axis direction and 0 pixels in the y-axis direction on the image 310 acquired by one camera, the camera calibration apparatus ( 100 may set an offset value of the first camera to (-10, 0).

Here, the offset value (-10, 0) means that the camera is aligned when it moves by 10 pixels in the -x axis direction with respect to the acquired image.

Here, the reference coordinate may be a coordinate such that the sum of offset values set in the cameras 300 through the first calibration is minimized.

That is, the reference coordinate may be a coordinate such that the sum of distances from the reference coordinate to the coordinates of the first marker on the image acquired by the cameras 300 is minimized.

In some embodiments, the camera calibration apparatus 100 may first calculate all coordinates of the first marker from the cameras 300, set reference coordinates, and calculate offset values of the cameras 300. .

4 is a diagram illustrating a process of generating a second marker by the camera calibration apparatus 100 according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating a second calibration result image according to an embodiment of the present invention. .

Referring to FIG. 4, it can be seen that the camera calibration device 100 generates a second marker 116 at a second position by irradiating a laser with a changed irradiation angle at an initial angle.

Here, the second position may be determined to be separated from the first position by a predetermined distance.

In detail, the second position may be a point at which the coordinates 311 of the first marker and the coordinates of the second marker 312 on the image of the camera 300 are separated by a reference distance.

Through this, an elliptic trajectory connecting the second markers 312 can be calculated more accurately, and a second calibration can be performed more precisely using the elliptic trajectory.

Here, when the cameras 300 are ideally arranged, it can be seen that the second marker 312 on the image 310 obtained by the cameras 300 forms an elliptic trajectory 315 as shown in FIG. 5. .

The camera calibration apparatus 100 may identify the second marker 116 on the image 310 obtained by the cameras 300, and calculate an elliptic trajectory around the coordinates 311 of the aligned first marker. .

Here, the camera calibration apparatus 100 calculates the positions of the ideal second markers 312 as mapping points on the ideal elliptic trajectory, and the sum of the distances between the mapping point and the coordinate value at which the second marker 116 is identified is calculated. The long and short axis values of the ideal elliptic trajectory can be adjusted to be minimal.

When the elliptic trajectory is determined, the camera calibration apparatus 100 changes the four corner coordinates of the image 310 so that the coordinate values of the second marker 116 coincide with the mapping point, thereby performing secondary calibration with respect to the cameras 300. Can be done.

For example, when the coordinates of the second marker 116 are separated from the mapping point on the image 310 acquired by one camera, the coordinates of the second marker 116 are mapped while the position of the first marker 115 is fixed. It can be seen that the four corner coordinates of the image 310 must be changed or rotated to move to a point.

Camera 300 according to an embodiment of the present invention is a module form having a plurality of image sensors, roll distortion can be ignored.

Accordingly, in order to move the coordinates of the second marker 116 to the mapping point while fixing the position of the first marker 115, the rotation of the image 310 for roll correction is excluded, Pan, tilt and zoom corrections can be made by changing the corner coordinates.

That is, it can be seen that the change value of the four corner coordinates of the image 310 corresponds to the pan value, the tilt value, and the zoom value of the camera 300.

6 is a flowchart illustrating a camera calibration method for time slice photography according to an embodiment of the present invention.

Referring to FIG. 6, in the camera calibration method for time slice photographing according to an embodiment of the present invention, the camera calibration apparatus first generates a first marker by irradiating a laser at an initial angle (S610).

In operation S610, the camera calibrating apparatus may irradiate a laser beam at an initial angle so that the laser beam is irradiated to the first position.

Here, the first position may be a position corresponding to an intersection point at which the viewpoint rotation axes of the cameras and the ground or the background surface intersect.

Next, the camera calibration apparatus performs first calibration of the cameras using the first images photographing the first marker (S620).

In operation S620, the apparatus for calibrating the camera may identify the first marker in the first images to obtain coordinates of the first marker, calculate a reference coordinate based on the coordinates of the first marker, and determine the first marker of the reference coordinate. The primary calibration may be performed by calculating relative coordinates of each of the coordinates as an offset value of the camera photographing each of the first images.

Here, the reference coordinate may be a coordinate such that the sum of distances from the reference coordinate to the coordinates of the first marker is minimized.

Next, the camera calibration device generates a second marker by changing the irradiation angle of the laser (S630).

In operation S630, the camera calibration apparatus may cause the laser beam to be irradiated to a second position different from the first position.

In operation S630, the apparatus for calibrating the camera identifies the second marker in any one second image of the second marker to obtain sample coordinates of the second marker, and the distance from the sample coordinates to the coordinates of the first marker is determined. The second position may be adjusted to exceed the preset reference distance.

Through this, in operation S640, the first marker and the second marker may be easily distinguished from each other so that the elliptic trajectory may be more accurately calculated.

Next, the camera calibration apparatus performs secondary calibration of the cameras by using the second images photographing the second marker (S640).

In operation S640, the apparatus for calibrating the camera identifies the second marker in the second images, obtains coordinates of the second marker to correspond to the order of the camera, and places mapping points on an elliptic trajectory having the reference coordinate as a center point. And a pan value, a tilt value and a zoom value of the camera photographing each of the second images based on an amount of change in the corner coordinates of each of the second images for mapping the coordinates of the second marker to the mapping points in the order of the cameras. Can be calculated.

Here, the elliptic trajectory may be a trajectory for minimizing the sum of the distances between the mapping points and the coordinates of the second marker.

One embodiment of the present invention can also be implemented in the form of a recording medium containing instructions executable by a computer, such as a program module executed by the computer. Computer readable recording media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, the computer readable recording medium may include a computer storage medium. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data.

Although the methods and systems of the present invention have been described in connection with specific embodiments, some or all of their components or operations may be implemented using a computer system having a general purpose hardware architecture.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

1: Time Slice Shooting System
100: camera calibration device 110: laser beam irradiation device
115: first marker 116: second marker
200: camera control unit 300: image sensor

Claims (10)

In the camera calibration method for time slice photography,
(a) irradiating a laser beam to the first position to generate a first marker;
(b) performing primary calibration of cameras using first images of the first marker;
(c) generating a second marker by irradiating a laser beam to a second position different from the first position; And
(d) performing secondary calibration of the cameras by using second images of the second marker;
And the first position is a position corresponding to an intersection point at which a viewpoint rotation axis of the cameras intersects a ground or a background surface of the cameras. delete The method of claim 1,
Step (b) is
(b1) identifying the first marker in the first images to obtain coordinates of the first marker;
(b2) calculating reference coordinates based on the coordinates of the first marker; And
(b3) calculating a relative coordinate of each of the coordinates of the first marker of the reference coordinates as an offset value of a camera photographing each of the first images;
That will include, the camera calibration method for time slice photography. The method of claim 3, wherein
The reference coordinate is
And coordinates such that the sum of distances from the reference coordinates to the coordinates of the first marker is minimized. The method of claim 1,
Step (c) is
(c1) acquiring the sample coordinates of the second marker by identifying the second marker in any one second image of the second marker; And
(c2) adjusting the second position such that a distance from the sample coordinates to the coordinates of the first marker exceeds a preset reference distance;
That will include, the camera calibration method for time slice photography. The method of claim 1,
Step (d)
(d1) identifying the second marker in the second images and obtaining coordinates of the second marker to correspond to the order of the camera;
(d2) arranging mapping points on an elliptic trajectory having a reference point as a center point; And
(d3) a pan value of a camera photographing each of the second images based on an amount of change in corner coordinates of each of the second images for mapping the coordinates of the second marker to the mapping points in the order of the camera; Calculating a tilt value and a zoom value;
That will include, the camera calibration method for time slice photography. The method of claim 6,
The elliptic trajectory is
And a trajectory for minimizing the sum of the distances between the mapping points and the coordinates of the second marker. A laser beam irradiation apparatus for generating a marker; And
And a processor configured to control the beam irradiation apparatus to generate a plurality of markers, and to calibrate cameras by using the images of the markers.
The processor is
The beam irradiation apparatus is controlled to irradiate a laser beam to a first position to generate a first marker, to perform first calibration of the cameras by using the first images photographing the first marker, and to perform the first position. And generating a second marker by irradiating a laser beam to a second position different from each other, and performing second calibration of the cameras by using second images photographing the second marker.
The first position is a position corresponding to the intersection of the viewpoint rotation axis and the ground plane or the background surface of the cameras, camera calibration apparatus for time slice photographing. A plurality of cameras arranged to surround the subject;
A camera control unit performing a synchronization process of the plurality of cameras and obtaining an image from the cameras; And
A laser beam irradiation apparatus, irradiating a laser beam to a first position to generate a first marker, receiving first images of the first marker photographed from the camera control unit, and performing primary calibration of the cameras; And generating a second marker by irradiating a laser beam to a second position different from the first position, and receiving second images photographing the second marker from the camera control unit to perform secondary calibration of the cameras. Including a camera calibration device;
And the first position is a position corresponding to an intersection point at which a viewpoint rotation axis of the cameras intersects a ground or a background surface. A computer-readable recording medium having recorded thereon a program for performing the camera calibration method for time slice photographing according to any one of claims 1 and 3.

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