Optical motion capture system of movable camera

Abstract

The utility model relates to an optical motion capture system of a movable camera, which comprises a plurality of motion capture cameras, the motion capture cameras are arranged on a movable tripod, and each motion capture camera is provided with a group of positioning equipment; the positioning equipment comprises a tracking camera and a gyroscope sensor; a reflective mark is pasted in the site space of the optical motion capture system; the system further comprises a hand-eye calibration device. Compared with the prior art, the position and posture tracking device can track the position and posture of the mobile motion capture camera in a motion capture coordinate system, so that the mobile work of the motion capture camera is realized, the capture range of the camera is greatly increased, the field shape can be flexibly adjusted, and the position and posture tracking device is suitable for shooting of different scenes in a short time.

Description

Technical Field

[0001] The utility model relates to the technical field of optical motion capture, in particular to an optical motion capture system of a movable camera. Background Art

[0002] The general optical motion capture system uses a camera to capture some wearable marker balls, and calculates the 3D position of the balls in space to solve the skeletal posture of the actor wearing these markers. Motion capture technology has been widely used in animation production, sports medicine, virtual shooting and other fields.

[0003] Traditional optical motion capture systems use an outside-in tracking method, that is, a number of stationary cameras form a tracking device, and the tracked marker ball moves in space. Before tracking, the camera group will be calibrated in advance to determine the internal parameters (focal length, etc.) and external parameters (relative position and orientation between cameras) of each camera. Once the calibration is completed, the position and direction of the camera cannot be moved during the entire tracking process. The reason is that after the relative posture of the cameras changes, the mathematical relationship between the projection of the 3D marker onto the 2D camera plane changes. Using the previously calibrated camera external parameters will cause the 3D reconstruction of the marker to fail, which will cause the subsequent motion solution to be wrong accordingly.

[0004] R&D personnel and users have accepted the fact that they cannot move the motion capture camera while it is working. However, such a motion capture system is limited by the tracking range. If a larger space needs to be captured, without being able to rotate or move the camera, people can only increase the number of cameras and enhance the camera's resolution and field of view, which greatly increases the cost of the system.

[0005] On the other hand, in order to obtain a larger tracking range and considering the need for a suitable public viewing area between cameras, users can only hang the camera farther away from the actual captured object. A common practice is that when it is necessary to capture the movements of motion capture actors performing on the ground, the camera needs to be hung on a truss more than ten meters high. In fact, the farther the camera is from the tracked object, the worse the tracking accuracy will be. Utility Model Content

[0006] The purpose of the utility model is to overcome the defects of limited tracking range and limited tracking accuracy in the above-mentioned prior art and to provide a novel optical motion capture system with a movable camera.

[0007] The purpose of the utility model can be achieved through the following technical solutions:

[0008] An optical motion capture system with a movable camera, the system comprising:

[0009] Multiple motion capture cameras, each of which is mounted on a mobile tripod, and each of which is equipped with a set of positioning equipment; the positioning equipment includes a tracking camera and a gyroscope sensor;

[0010] Reflective markers are posted in the venue space of the optical motion capture system;

[0011] The system also includes a device for performing hand-eye calibration.

[0012] As a preferred technical solution, the tracking camera lens is directed toward the reflective markers posted in the venue space.

[0013] As a preferred technical solution, the reflective mark is posted on the ceiling of the venue space.

[0014] As a preferred technical solution, the reflective mark is a disc that reflects 850nm infrared light signals in the original light path.

[0015] As a preferred technical solution, the tracking camera is an infrared camera.

[0016] As a preferred technical solution, the hand-eye calibration device is provided with a set of marker balls with known three-dimensional structures.

[0017] As a preferred technical solution, the hand-eye calibration device is a two-dimensional calibration plate provided with a set of marker balls with known three-dimensional structures.

[0018] As a preferred technical solution, the hand-eye calibration device is an L-shaped marker rod having a set of marker balls with known three-dimensional structures.

[0019] As a preferred technical solution, the tracking camera is a camera with high resolution and wide field of view.

[0020] As a preferred technical solution, the motion capture camera is a camera with a long focal length and a small field of view.

[0021] Compared with the prior art, the utility model has the following beneficial effects:

[0022] The utility model provides a set of device systems, which sets a motion capture camera on a movable tripod, and configures a set of positioning equipment for each motion capture camera. Among them, the positioning equipment includes a tracking camera and a 6-axis gyroscope IMU, and reflective markers for positioning are arranged in the venue space. Through the tracking camera and IMU, the position tracking of the mobile motion capture camera in the motion capture coordinate system can be achieved, and then the movement tracking of the camera in the motion capture system can be achieved, which greatly increases the capture range of the camera, and can flexibly adjust the shape of the venue to adapt to the shooting of different scenes in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The utility model is a schematic diagram of the structure of an optical motion capture system of a movable camera. DETAILED DESCRIPTION

[0024] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0025] Example 1

[0026] The utility model proposes an optical motion capture system with a movable camera, such as Figure 1 As shown, the system mounts a motion capture camera on a mobile tripod.

[0027] In order to obtain the 6-DOF position of the motion capture camera in real time, each motion capture camera is equipped with a set of positioning equipment, including a tracking camera and a 6-axis gyroscope (IMU) sensor. The newly added tracking camera is an infrared camera similar to ordinary motion capture cameras, which can identify and track small balls made of special materials (which can reflect 850nm infrared light signals from the original optical path).

[0028] In this embodiment, the tracking camera is bound to the top of the original motion capture camera, and the lens is pointed toward the ceiling. Then, many small discs of special materials are arbitrarily attached to the ceiling of the venue. The tracking camera calculates the 6-DOF posture of the tracking camera in real time by shooting the small disc markers on the ceiling. The points on the ceiling are chosen because there are few objects, especially moving objects, blocking the light path between the camera and the ceiling, which can increase the stability of camera tracking. Of course, the points are not limited to the ceiling, and the direction of the tracking camera can theoretically be any direction. The posture of the motion capture camera is obtained in real time by locating the posture of the tracking camera in an inside-out tracking manner, so that the motion capture camera can be moved arbitrarily in the venue, so as to achieve the purpose of motion capture shooting in a moving camera array.

[0029] In order to obtain the scale information of the tracking camera position and improve the positioning accuracy of the tracking camera, the utility model is also equipped with a 6-axis IMU (three-axis angular velocity, three-axis acceleration) on each tracking camera.

[0030] The utility model is also provided with a hand-eye calibration device, and a set of marker balls with known 3D structures are placed on the ground of the motion capture space, such as a two-dimensional calibration plate or an L-shaped marker rod for setting the motion capture coordinate system. The hand-eye calibration device is used to calibrate the motion capture camera and the tracking camera, and the conversion between the field space coordinate system and the motion capture coordinate system, as well as the relative position and posture of the tracking camera and the motion capture camera can be obtained.

[0031] The working principle of the device system provided by the utility model is as follows: by tracking the markers on the ceiling with a tracking camera and the 6-DOF posture data collected by the IMU, the posture of the tracking camera in the space coordinate system S of the venue where the marker group on the ceiling is located can be obtained; since the relative posture of the tracking camera and the motion capture camera is fixed, the coordinate transformation between the two and the conversion between the motion capture coordinate system and the ceiling coordinate system are obtained, and the posture of the motion capture camera in the motion capture coordinate system where the motion capture actor is located can be derived through the posture of the tracking camera. Then, the hand-eye calibration device provided by the utility model is used to perform hand-eye calibration, and the relative posture between the tracking camera and the motion capture camera and the conversion relationship between the motion capture coordinate system and the ceiling coordinate system can be obtained. The posture of the motion capture camera in the motion capture coordinate system can be derived. Then, the mobile tracking and capture of the motion capture camera can be realized.

[0032] In addition, due to the different functions of tracking cameras and motion capture cameras, different parameters of lenses and chips can be used for these two cameras. Tracking cameras need to be accurately positioned and can see as many marker discs as possible on the ceiling of the venue as tracking feature points. Cameras with high resolution and wide field of view can be selected. As for motion capture cameras, since we can move to adjust the shooting position and angle, cameras with longer focal lengths and smaller field of view can be selected.

[0033] The preferred specific embodiments of the utility model are described in detail above. It should be understood that ordinary technicians in this field can make many modifications and changes based on the concept of the utility model without creative work. Therefore, all technical solutions that can be obtained by technicians in this technical field based on the concept of the utility model through logical analysis, reasoning or limited experiments on the basis of the existing technology should be within the scope of protection determined by the claims.

Claims

1. An optical motion capture system with a movable camera, characterized in that: The system comprises: Multiple motion capture cameras, each of which is mounted on a mobile tripod, and each of which is equipped with a set of positioning equipment; the positioning equipment includes a tracking camera and a gyroscope sensor; Reflective markers are posted in the venue space of the optical motion capture system; The system also includes a device for performing hand-eye calibration.

2. The optical motion capture system of a movable camera according to claim 1, characterized in that: The tracking camera lens is directed toward the reflective markers posted in the venue space.

3. The optical motion capture system of a movable camera according to claim 1, characterized in that: The reflective mark is posted on the ceiling of the venue space.

4. The optical motion capture system of a movable camera according to claim 3, characterized in that: The reflective mark is a disc that reflects 850nm infrared light signals in the original light path.

5. The optical motion capture system of a movable camera according to claim 1, characterized in that: The tracking camera is an infrared camera.

6. The optical motion capture system of a movable camera according to claim 1, characterized in that: The hand-eye calibration device is provided with a set of marker balls with known three-dimensional structures.

7. The optical motion capture system of a movable camera according to claim 6, characterized in that: The hand-eye calibration device is a two-dimensional calibration plate provided with a set of marker balls with known three-dimensional structures.

8. The optical motion capture system of a movable camera according to claim 6, characterized in that: The hand-eye calibration device is an L-shaped marker rod having a set of marker balls with known three-dimensional structures.

9. The optical motion capture system of a movable camera according to claim 1, characterized in that: The tracking camera is a camera with high resolution and wide field of view.

10. The optical motion capture system of a movable camera according to claim 1, characterized in that: The motion capture camera is a camera with a long focal length and a small field of view.

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