JP5319478B2 - Method for calculating position of camera device - Google Patents

Description

  The present invention relates to a position calculation method and a position calculation apparatus for a camera device used when shooting on a movie, a television or the like, and in particular, a position calculation method for a camera device suitable for combining a computer graphic (CG) image and a real map. About.

  For example, in a virtual studio, a three-dimensional positional relationship of a live-action image captured by a camera in a studio and computer graphics (CG) generated as a background or production as viewed from the camera position. When interlocking while maintaining, it is necessary to calculate the position of the camera in the CG coordinate system. That is, if the camera position is determined in the CG coordinate system, the mutual positional relationship between the camera, the subject, and the CG can be calculated, and the camera subject and the CG are linked while maintaining the three-dimensional positional relationship. Can be made.

  As a technique in consideration of such a situation, in Patent Document 1, a reference position is set on the floor surface, and first and second lines are formed on the floor surface so as to be orthogonal to each other from the reference position. When two first sensors that detect a line and one second sensor that detects a second line are attached to the moving frame of the camera, the two first sensors pass through the first line, respectively. There is disclosed a technique for performing alignment by calculating a camera position and a rotation angle based on a movement amount and a movement amount when a second sensor passes a second line.

JP 2002-204378 A

  By using the technique of the above-mentioned Patent Document 1, it is possible to accurately grasp and calibrate the position of the camera device in the CG coordinate system, but there are the following problems.

  That is, in order to accurately form the first and second lines on the floor so as to be orthogonal to each other from the reference position, it is necessary to install a special sheet (origin sheet), and a space where such a sheet can be installed. However, the application is limited to a certain place, and it is necessary to consider the installation of the origin sheet so that it does not enter the field of view of the camera when the program is recorded.

  Also, it is necessary to move the camera device base to the position where the origin sheet is installed at every calibration. When aligning multiple camera devices, the origin sheet is installed on all camera devices. It must be moved to a certain position, which is complicated. Although it is possible to install a plurality of origin sheets, matching the coordinate systems of the origin sheets takes time and effort. Further, the technique of Patent Document 1 cannot be applied to a camera device that cannot move.

  The present invention has been made in view of such circumstances, and can easily calculate the position of the camera device in the CG coordinate system without using a special jig, and can also be applied to a camera device that cannot move. An object of the present invention is to provide a position calculation method for a camera device.

In order to solve the above-described problem, the present invention relates to a position of a camera device that calculates a position of the camera device in a CG coordinate system when a live-action image and a computer graphic (CG) image are synthesized by a camera device having a television camera. A calculation method, the step of setting two points whose positions in the CG coordinate system are known, the step of imaging the first point of the two points by the camera device, and the case of imaging the first point Detecting a pan angle, a tilt angle, and a height of the television camera of the camera device, and obtaining a position of the first point in the camera device coordinate system based on the detected pan angle, a tilt angle, and a second point of the two points. The step of imaging by the camera device, and the pan angle, tilt angle, and height of the television camera when the second point is imaged are detected, and based on these, the camera device coordinate system is detected. Obtaining a position of the second point; obtaining a rotation angle of a CG coordinate system with respect to the camera apparatus coordinate system from positions of the first point and the second point in the camera apparatus coordinate system; and And a step of calculating the position of the camera device in the CG coordinate system.

  According to the present invention, two points whose positions in the CG coordinate system are known are set, and based on these, the position of the camera device in the CG coordinate system is calculated. There is no need to use it, and calibration can be easily performed anywhere where an image can be captured by the camera device. It is not necessary to move the camera device to the position where the origin sheet is installed each time calibration is performed, and if two points in the CG coordinate system can be imaged, any number of camera devices can be calibrated at that location at any time can do. Furthermore, since it is sufficient that two points can be imaged, the present invention can be applied to a camera device that cannot move.

It is a block diagram which shows schematic structure of the CG synthetic | combination system with which the position calculation method of the camera apparatus which concerns on one Embodiment of this invention is applied. It is a side view which shows an example of the camera apparatus used for the position calculation method of the camera apparatus which concerns on one Embodiment of this invention. It is a top view which shows an example of the camera apparatus used for the position calculation method of the camera apparatus which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the position calculation method of the camera apparatus which concerns on one Embodiment of this invention. It is a figure for demonstrating the relationship between the position of A point in a camera apparatus coordinate system when a point A is imaged with a camera apparatus, pan angle (alpha), tilt angle (beta), and camera height h. It is a figure for demonstrating the method of calculating | requiring rotation angle (theta) of the CG coordinate system with respect to a camera apparatus coordinate system from the position of A point and B point in a camera apparatus coordinate system. It is a figure which shows the position of the camera apparatus in CG coordinate system.

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.
Here, a CG synthesis system to which the camera apparatus position calculation method according to an embodiment of the present invention is applied will be described.

FIG. 1 is a block diagram showing a schematic configuration of such a CG synthesis system. The CG synthesis system includes a camera device 1 that captures a real image, a parameter detection unit 2 that detects parameters (pan angle, tilt angle, camera height) of the camera device 1, and a CG coordinate system of the camera device 1. The camera includes a position calculation unit 3 that calculates a position, a control unit 4, and an image composition unit 5 that includes a monitor that synthesizes a real map and CG. The camera device 1 captures an object 7 in the CG coordinate system. Then, an image obtained by synthesizing the actual image and the CG image arranged in the CG coordinate system is output.

  As shown in FIGS. 2 and 3, the camera device 1 includes a pedestal 12 as a moving base that travels on the floor of a studio, a pan head 13 provided on the pedestal 12, and a TV mounted on the pan head 13. The TV camera 14 can be turned and tilted by the camera platform 13. Reference numeral 15 is a handle for changing the moving direction of the pedestal, and 16 is a lever for tilting or turning the TV camera 14. The pedestal 12 is provided with three traveling wheels 17 at the bottom thereof.

  In such a CG synthesis system, the camera device 1 is placed at a position input from the outside in advance. However, a real image captured by the camera device 1 and a CG are viewed in three dimensions from the position of the camera device 1. When interlocking while maintaining the target positional relationship, it is necessary to calculate the position of the camera device 1 in the CG coordinate system. Therefore, in the present embodiment, the position calculation unit 3 calculates the position of the camera device 1 in the CG coordinate system based on the image captured by the camera device 1 and the parameters of the camera device 1 detected by the parameter detection unit 2. Perform calibration. Specifically, as will be described later, the position calculation unit 3 detects the points A and B2 whose positions in the CG coordinate system are captured by the camera device 1 at a predetermined position. The position of the camera device 1 in the CG coordinate system is calculated based on the parameter information thus obtained and the position information in the CG coordinate system of the points A and B.

  The control unit 4 receives a command from the outside and controls the camera device 1 and the image composition unit 5. Further, a calibration execution command is output to the position calculation unit 3 by an external command at the start of shooting or during shooting. Specifically, the position and angle of the camera device 1 are controlled based on the parameter detected by the parameter detection unit 2 or the video monitored by the image synthesis unit 5, and the image synthesis in the image synthesis unit 5 is controlled. The received detection information of the parameter detection unit 2 is sent to the position calculation unit 3.

  Next, a method for calculating the position of the camera device 1 in the CG composition system configured as described above will be described with reference to the flowchart of FIG.

  First, two points of points A and B whose positions in the CG coordinate system are known are set (step 1). At this time, it is preferable to take the first point A as the origin (0, 0) of the CG coordinate system and the second point B as the point (0, x) of the CG coordinate system. Specifically, these points A and B are taken, for example, on the floor of a studio, and marks are placed on the surface of the P tile with tape or the like.

  Next, the camera unit 1 controls the parameters (pan angle, tilt angle, camera height) of the camera device 1 by the control unit 4 or positions the point A in the center of the TV camera 14 by the operation of the cameraman. To image point A (step 2).

  The parameters (pan angle α, tilt angle β, camera height h) obtained at that time are detected and calculated by the position detection unit 3 based on these parameters, and point A in the coordinate system (camera device coordinate system) of the movable platform 12 Is determined (step 3).

Specifically, assuming that the position of the camera device 1 is the origin of the camera device coordinate system, the point A (x, y) in the camera device coordinate system can be obtained as follows. That is, as shown in FIG. 5A, since the pan angle of point A is α, the point A in the camera apparatus coordinate system is a position of a length L on a straight line passing through the origin inclined at an angle α from the Y axis. As shown in FIG. 5B, the length L can be calculated as L = h / tan β from the camera height h and the tilt angle β. Accordingly, x and y of the point A (x, y) in the camera device coordinate system are as follows.
x = L · sin α / tan β
y = L · cos α / tan β

  Next, the control unit 4 controls the parameters (pan angle, tilt angle, camera height) of the camera device 1, or the B point is set so that the B point is located at the center of the TV camera 14 by the operation of the cameraman. An image is taken (step 4).

  Parameters (pan angle α ′, tilt angle β ′, camera height h ′) obtained at that time are detected, and based on these, the position detection unit 3 calculates and obtains the position of point B in the camera device coordinate system ( Step 5).

At this time, the length from the origin to the point B in the camera device coordinate system is L ′, and the point B (x ′, y ′) in the camera device coordinate system is obtained in the same manner as in the case of the point A. , X ′, y ′ are as follows.
x ′ = L ′ · sin α ′ / tan β ′
y ′ = L ′ · cos α ′ / tan β ′

Next, the rotation angle θ of the CG coordinate system with respect to the camera device coordinate system is obtained from the positions of the points A and B in the camera device coordinate system (step 6). That is, by obtaining the points A and B in the camera device coordinate system, as shown in FIG. 6, the x axis of the CG coordinate system is drawn in the camera device coordinate system, and the rotation angle of the CG coordinate system with respect to the camera device coordinate system θ is calculated from the following equation.
tan θ = (y′−y) / (x′−x)

  Then, the planar position of the camera device 1 in the CG coordinate system is as shown in FIG. 7, and the position C (Cx, Cy) of the camera device 1 in the CG coordinate system is obtained from the rotation angle θ and the calculation result (step 7). ).

Cx and Cy at this time can be calculated from the following equations, as is apparent from FIG.
Cx = −L · sin (α + θ) = − h · sin (α + θ) / tan β
Cy = −L · cos (α + θ) = − h · cos (α + θ) / tan β

  As described above, the position C of the camera device 1 in the CG coordinate system can be grasped.

  Then, calibration is performed based on the position calculation result of the camera device 1 in the CG coordinate system, and the photographed image by the camera device 1 and the CG are synthesized by the control by the control unit 4 or the operation of the cameraman. At this time, since the position of the camera device 1 in the CG coordinate system is obtained, it is possible to synthesize these without causing the real image and the CG to shift.

  In the present embodiment, calibration is performed by calculating the position of the camera device 1 in the CG coordinate system using the image of the camera device 1 as described above, and thus the origin sheet as in the technique of Patent Document 1 described above. It is not necessary to use a jig or a sensor such as that described above, and calibration can be easily performed anywhere where an image can be captured by the camera device 1. Further, as in the present embodiment, the calibration can be performed with the CG origin position as the first point, and thereby, the reference position on the origin sheet and the CG origin, which are necessary in the technique of Patent Document 1, are obtained. It is possible to eliminate the work of combining the two.

  In the present embodiment, unlike the technique of Patent Document 1, it is not necessary to move the frame of the camera device to the position where the origin sheet is installed each time calibration is performed, and two points in the CG coordinate system are imaged. If possible, any number of camera devices can be calibrated at that location. Furthermore, in Patent Document 1, since the camera device is assumed to move, a camera device that cannot move cannot be used. However, in this embodiment, it is sufficient that two points can be imaged. Applicable.

Conventionally, calibration has been performed by matching the three-dimensional positional relationship between the coordinates of the CG and the live-action image by operating the image composition unit. However, according to the present invention, the calibration of the image composition unit requiring specialized knowledge is performed. In addition to the need for operation, surveying of the positional relationship between the origin of the camera device coordinate system and the origin of the CG coordinate system is also unnecessary.

  The present invention is not limited to the above embodiment and can be variously modified. For example, in the above embodiment, the floor surface point is used as two reference points of the CG coordinate system. However, when the subject moves and the floor reference point cannot be captured by the camera, the present invention is not limited to this. It is good also considering the point with a set as two reference points.

  Further, in the above embodiment, the case where the CG image of the CG coordinate system of the virtual studio is synthesized is exemplified. However, the present invention is not limited to this. Even in operations where it is difficult to survey the position of the camera device, if two points with known dimensions are set as reference points in the stadium, the position of the camera device in the CG coordinates can be calculated, and it is easy and accurate. It is possible to calibrate.

DESCRIPTION OF SYMBOLS 1 ... Camera apparatus 2 ... Parameter detection part 3 ... Position calculation part 4 ... Control part 5 ... Image composition part 12 ... Pedestal (moving stand)
14 ... TV camera

Claims (4)

A position calculation method for a camera device that calculates a position of the camera device in a CG coordinate system when a live-action image and a computer graphic (CG) image are combined by a camera device having a television camera.
Setting two points whose positions in the CG coordinate system are known;
Imaging the first point of the two points with the camera device;
Detecting a pan angle, a tilt angle, and a height of a television camera when the first point is imaged, and determining a position of the first point in a camera device coordinate system based on these,
Imaging the second point of the two points with the camera device;
Detecting a pan angle, a tilt angle, and a height of a television camera of the camera device when the second point is imaged, and obtaining a position of the second point in the camera device coordinate system based on these,
Obtaining a rotation angle of the CG coordinate system relative to the camera device coordinate system from the positions of the first point and the second point in the camera device coordinate system;
And a step of calculating a position of the camera device in the CG coordinate system based on the rotation angle.   The method of claim 1, wherein the first point is an origin of a CG coordinate system.   3. The position calculation method for a camera device according to claim 2, wherein the second point is an arbitrary point on the X axis of a CG coordinate system.   4. The method according to claim 1, wherein when the first point or the second point is imaged, the first point or the second point is positioned at the center of the television camera. 5. A position calculation method for the camera device according to claim 1.

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