JP2016151566A - Motion tracker device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motion tracker device capable of performing highly accurate three-dimensional measurement by reducing a measurement error.SOLUTION: A motion tracker device 1 includes: a first camera 11; a second camera 12; a moving mechanism 14 for moving the first camera 11 and the second camera 12 respectively, to adjust a camera-to-camera distance Dc between the first camera 11 and the second camera 12; position calculation means 15 for calculating the three-dimensional position coordinate of an object OB on the basis of the two-dimensional images of the first camera 11 and the second camera 12; and camera position control means 16 for performing control to adjust the camera-to-camera distance Dc, so that a first distance D1 between the first camera 11 and the object OB, a second distance D2 between the second camera 12 and the object OB, and the camera-to-camera distance Dc have a predetermined relation on the basis of the three-dimensional position coordinate of the object OB.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a motion tracker device.

  Conventionally, a motion tracker device that measures a three-dimensional position of an object using a plurality of cameras is known (see, for example, Patent Document 1).

  Patent Document 1 discloses a motion tracker device including two cameras (stereo cameras) fixed at a predetermined interval and a control device. This motion tracker device acquires three-dimensional position information of an object from the two-dimensional position information of the object photographed by two cameras by applying the principle of triangulation.

JP 2014-95557 A

  In principle, the measurement accuracy of a three-dimensional position using a stereo camera is affected by the relative positional relationship between each camera and an object. Especially in the depth direction, the error increases when the distance between cameras (inter-camera distance) is small. On the other hand, if the distance between the cameras is too large, the object will be more likely to be out of the field of view (view angle) of the camera, or the distance between the camera and the object will be too large, causing a decrease in accuracy. There is. Therefore, it is desired to reduce the measurement error and enable more accurate three-dimensional measurement.

  The present invention has been made in order to solve the above-described problems, and one object of the present invention is to provide a motion tracker device capable of performing highly accurate three-dimensional measurement by reducing measurement errors. Is to provide.

  In order to achieve the above object, a motion tracker device according to one aspect of the present invention acquires a two-dimensional image of a target object from a first camera that acquires a two-dimensional image of the target object and a direction different from the first camera. A second camera, a moving mechanism for adjusting the distance between the first camera and the second camera by moving the first camera and the second camera, and two of the first camera and the second camera, respectively. A position calculating means for calculating the three-dimensional position coordinates of the object based on the three-dimensional image; a first distance between the first camera and the object based on the three-dimensional position coordinates of the object; Camera position control means for performing control to adjust the inter-camera distance so that the second distance between the object and the object and the inter-camera distance have a predetermined relationship.

  In the motion tracker device according to one aspect of the present invention, as described above, the moving mechanism for adjusting the inter-camera distance between the first camera and the second camera by moving the first camera and the second camera, respectively. And a first distance between the first camera and the object, a second distance between the second camera and the object, and the inter-camera distance based on the three-dimensional position coordinates of the object. Camera position control means for performing control for adjusting the inter-camera distance so as to be in a relationship is provided. Thus, by adjusting the inter-camera distance, the relative positional relationship between the object, the first camera, and the second camera can be adjusted so as to be a predetermined relationship that allows more accurate measurement. it can. That is, with respect to the distance between the object and each camera (first distance, second distance), the distance between the cameras is adjusted so as not to be relatively small or too large. The relative positional relationship between the camera and the second camera can be adjusted to an appropriate positional relationship suitable for highly accurate measurement. As a result, according to the present invention, measurement errors can be reduced and highly accurate three-dimensional measurement can be performed.

  In the motion tracker device according to the above aspect, the camera position control unit is preferably configured to perform control to bring the inter-camera distance, the first distance, and the second distance closer to each other. If comprised in this way, it can suppress that the distance between cameras becomes small too much and the error of a depth direction becomes large, and the distance (1st distance and 2nd distance) between a camera and a target object is large. It is possible to adjust the inter-camera distance so as to obtain an appropriate relative positional relationship that can suppress the occurrence of a decrease in accuracy due to becoming too much. As a result, measurement errors due to the relative positional relationship between the object and the camera can be effectively reduced.

  In this case, preferably, the camera position control means is configured to perform control so that the inter-camera distance, the first distance, and the second distance coincide with each other within a predetermined allowable range. If comprised in this way, a three-dimensional measurement can be performed by the relative positional relationship by which a target object and a 1st and 2nd camera are arrange | positioned at each vertex of a substantially equilateral triangle. As a result, it is possible to suppress an excessive increase in size of the apparatus and to further effectively reduce measurement errors. In addition, unlike the case where control is performed so that the distances are exactly the same, it is also possible that the distances are different from each other within an allowable range, so position control of the first camera and the second camera (inter-camera distance control) It is possible to suppress complication.

  In the configuration in which the camera position control unit matches the inter-camera distance, the first distance, and the second distance within a predetermined allowable range, preferably, the camera position control unit includes the inter-camera distance, the first distance, and the second distance. When any of the distances falls outside the allowable range, the inter-camera distance is adjusted by moving the first camera and the second camera every predetermined unit distance. If comprised in this way, when either distance becomes outside an allowable range, the distance between cameras can be adjusted, and a target object and the 1st and 2nd camera can be adjusted to appropriate relative positional relationship. At this time, the first and second cameras are not moved completely to arbitrary positions, but are moved every predetermined unit distance, so that calibration for three-dimensional measurement is predetermined. Just go for every unit distance. As a result, even in the configuration in which the first and second cameras are moved, three-dimensional measurement at each position after the movement can be easily performed.

  In the motion tracker device according to the above aspect, preferably, the position calculation unit calculates the three-dimensional position coordinates of the object at predetermined time intervals, and the camera position control unit calculates the three-dimensional position calculated by the position calculation unit. By performing feedback control using the position coordinates, the inter-camera distance is adjusted according to the movement of the object. If comprised in this way, even if a target object moves, the relative positional relationship of a target object and a 1st and 2nd camera can be maintained. Therefore, even when the relative positional relationship changes due to the movement of the object, the three-dimensional measurement accuracy can be maintained.

  In the motion tracker device according to the above aspect, preferably, the moving mechanism includes a linear rail, a plurality of pedestals that respectively support the first camera and the second camera on the rail, and a plurality of pedestals along the rails. And a plurality of motors for movement. If comprised in this way, the distance between cameras can be adjusted with the simple structure which moves a 1st camera and a 2nd camera along a rail. As a result, it is possible to prevent the device configuration and control for adjusting the inter-camera distance from becoming complicated.

  In the motion tracker device according to the above aspect, preferably, the first camera, the second camera, and the moving mechanism are provided in a moving body on which the user is boarded, and the object is a head of the user on the moving body. It is a helmet to be attached to. Here, a motion tracker technique is used when a user of a mobile body wears a helmet equipped with an HMD (head mounted display) and changes the image of the HMD in accordance with the current angle of the helmet. In such a field, it is required to measure the current angle of the helmet with high accuracy. Therefore, according to the present invention, it is possible to provide a motion tracker device (head motion tracker) capable of measuring the current angle of the helmet with high accuracy by reducing the measurement error by configuring as described above.

  According to the present invention, as described above, highly accurate three-dimensional measurement can be performed while reducing measurement errors.

It is the schematic diagram which showed the whole structure of the head mounted display system. It is a typical back view for demonstrating the structure of the motion tracker apparatus by one Embodiment of this invention. It is a typical top view for explaining a motion tracker device by one embodiment of the present invention. It is a schematic diagram for demonstrating operation | movement of the motion tracker apparatus when a target object moves in FIG. It is a flowchart for demonstrating the adjustment process of the distance between cameras of the motion tracker apparatus by one Embodiment of this invention. It is the schematic which showed the relative positional relationship (A) in case the distance between cameras is small, and the relative positional relationship (A) of the target object, 1st camera, and 2nd camera by this embodiment. It is a figure for demonstrating the experimental result which changed the distance between cameras and measured the three-dimensional position of the target object. It is the schematic diagram which showed the modification of the predetermined relative positional relationship of a target object, a 1st camera, and a 2nd camera.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

  With reference to FIGS. 1-4, the motion tracker apparatus 1 by one Embodiment of this invention is demonstrated. In the present embodiment, an example in which the motion tracker device 1 is applied to a head mounted display system (hereinafter referred to as “HMD system”) mounted on a moving body that carries a person such as an automobile, an aircraft, and a ship. explain. More specifically, as shown in FIG. 1, in a HMD system 100 mounted on a moving body 4 that moves in the sky (in the air) such as an aircraft (airplane or helicopter), a helmet worn by a pilot who is a user. An example in which the present invention is applied to a motion tracker device for measuring the direction of 23 (the direction of the pilot's head) will be described.

(Overall configuration of head-mounted display system)
As shown in FIG. 1, the HMD system 100 includes a motion tracker device 1, a head mounted display (hereinafter referred to as “HMD”) 2 having a photographing device 21 and a display screen 22, and an image photographed by the photographing device 21. Is displayed on the display screen 22.

  The HMD system 100 displays a moving image captured by the image capturing device 21 on the display screen 22 of the HMD 2, thereby allowing a scene to be viewed through the display screen 22 and a moving image displayed on the display screen 22. It is possible to make a user visually recognize by overlapping. As a result, the HMD system 100 supplements the field of view with a moving image of the photographing device 21 having higher sensitivity than the naked eye or transmits the display screen 22 in a low-light environment where it is difficult to grasp the outside world with the naked eye, such as in the evening or at night. Various information can be displayed on the object that is visually recognized.

  The HMD 2 is a head-mounted display device that includes a photographing device 21 and a display screen 22. FIG. 1 shows an example of a helmet-shaped HMD2. The HMD 2 includes a helmet 23 to which a visor-like display screen 22 and a photographing device 21 are attached. The HMD 2 includes a display element 24 and an optical system 25 for projecting an image on the display screen 22.

  The display screen 22 has translucency so that the user can see the scene in front of the line of sight through the display screen 22. The imaging device 21 includes a lens and an imaging device (not shown), and is fixed to the helmet 23 so that the imaging optical axis direction is directed forward in the direction of the user's line of sight. The display element 24 is configured to collimate the left-eye image and the right-eye image by the optical system 25 and project the image on the display screen 22. The left-eye image and the right-eye image reflected by the display screen 22 are visually recognized by the user's left eye and right eye, together with external light transmitted through the display screen 22 from the outside. In addition, the marker 23a for the detection by the motion tracker apparatus 1 is attached to the helmet 23 shown in FIG.

  The image processing device 3 is incorporated in the helmet 23 as a video signal processing device of the HMD 2. The image processing device 3 has a function of displaying a moving image on the display screen 22 by receiving a moving image captured by the imaging device 21, performing image processing, and outputting the processed image to the display element 24. The image processing device 3 is configured to display an image on the display screen 22 in accordance with the movement of the user's head 5 measured by the motion tracker device 1.

  The motion tracker device 1 according to the present embodiment is provided on the moving body 4 and detects the orientation of the helmet 23 attached to the user's head 5 to thereby detect the orientation (orientation) of the imaging device 21 fixed to the helmet 23. ) Is detected.

  The motion tracker device 1 includes a first camera 11, a second camera 12, and a control unit 13. The motion tracker device 1 measures the three-dimensional position of the helmet 23 (marker 23a) using the helmet 23 (marker 23a) mounted on the head 5 of the user (pilot) who is riding on the moving body 4 as an object OB. It is configured as follows.

  The motion tracker device 1 photographs the marker 23 a provided on the helmet 23 with the first camera 11 and the second camera 12. The markers 23 a are light emitting elements such as LEDs, for example, and three or more markers 23 a are provided so that the three-dimensional posture of the helmet 23 can be determined. Each marker 23 a is fixedly attached to a position on the surface of the helmet 23 that can be photographed by the first camera 11 and the second camera 12.

  The motion tracker device 1 calculates the spatial position coordinates (three-dimensional position coordinates) of each marker 23 a from the two-dimensional images captured by the first camera 11 and the second camera 12. Since each marker 23a is fixed to the helmet 23 at a predetermined relative position coordinate, the motion tracker device 1 is based on the spatial position coordinates of the three or more markers 23a and the relative position coordinates between the markers 23. Calculate the current angle (orientation).

  The motion tracker device 1 is configured to send a detection signal of the detected current angle (posture) of the helmet 23 to the image processing device 3. As a result, the HMD system 100 displays various images on the display screen 22 of the HMD 2 in accordance with the direction (line-of-sight direction) of the head 5 of the user (pilot) measured by the motion tracker device 1.

(Configuration of motion tracker device)
Next, the configuration of the motion tracker device 1 will be described in detail.

  Each of the first camera 11 and the second camera 12 includes a CCD camera or the like, and is configured to acquire a two-dimensional image of the object OB (helmet 23). The second camera 12 is configured to photograph the object OB from a direction different from that of the first camera 11.

  The motion tracker device 1 includes a moving mechanism 14 for the first camera 11 and the second camera 12. The 1st camera 11, the 2nd camera 12, and the moving mechanism 14 are provided in the mobile body 4 on which a user (pilot) gets on. The moving mechanism 14 can adjust the inter-camera distance Dc between the first camera 11 and the second camera 12 by moving the first camera 11 and the second camera 12, respectively. The inter-camera distance Dc is an interval between the first camera 11 and the second camera 12.

  In the present embodiment, as shown in FIG. 2, the moving mechanism 14 is a uniaxial moving mechanism that linearly moves the first camera 11 and the second camera 12 along a common moving axis (rail 14a). Specifically, the moving mechanism 14 includes a linear rail 14a, a plurality (two) of pedestals 14b that respectively support the first camera 11 and the second camera 12 on the rail 14a, and a plurality (two). A plurality of (two) motors 14c for moving the base 14b along the rails 14a are included.

  The rail 14a is attached to the moving body 4 via a support member 14d (see FIG. 1). The rail 14a supports the pedestal 14b so as to be linearly movable along the rail 14a. Hereinafter, the direction in which the rail 14a extends is referred to as the X direction (see FIG. 3), and the depth direction orthogonal to the X direction is referred to as the Y direction (see FIG. 3).

  The base 14b is a slider that can move along the rail 14a. Each pedestal 14b supports the first camera 11 and the second camera 12, respectively. The first camera 11 and the second camera 12 are fixed to the respective bases 14b, and the first camera 11 (second camera 12) does not have a so-called swing (pan or tilt) function. In the present embodiment, the first camera 11 and the second camera 12 are attached to the pedestal 14b so that the camera optical axes are at angles α1 and α2 (see FIG. 1) with respect to the rail 14a, respectively. In the present embodiment, the magnitudes of α1 and α2 are each about 60 °, and the camera optical axes of the first camera 11 and the second camera 12 are inclined toward each other.

  The motor 14c is built in or externally attached to the pedestal 14b, and is configured to move the pedestal 14b in accordance with the drive amount. Each motor 14c is configured to be independently driven and controlled by the control unit 13. Therefore, the 1st camera 11 and the 2nd camera 12 can move independently, respectively. The motor 14c is formed of, for example, a stepping motor or a servo motor, and the position of the first camera 11 and the second camera 12 can be controlled by controlling the driving amount of the motor 14c. That is, the inter-camera distance Dc between the first camera 11 and the second camera 12 is adjusted by driving control of the respective motors 14c.

  As shown in FIG. 1, the control unit 13 is a computer including a CPU 13a and a memory 13b.

  In the present embodiment, the CPU 13a executes a program stored in the memory 13b to calculate the three-dimensional position coordinates of the object OB based on the two-dimensional images of the first camera 11 and the second camera 12. It is configured to function as the calculation means 15.

  The position calculation means 15 extracts each marker 23a from the two-dimensional image imaged by the first camera 11 and the second camera 12, and uses the two-dimensional coordinates (position coordinates of the marker 23a in the image) of each extracted marker 23a. get. And the position calculation means 15 calculates the three-dimensional position coordinate of each marker 23a by the DLT method (Direct Liner Transformation Method) based on the principle of triangulation using the two-dimensional coordinate of the marker 23a in each two-dimensional image. . The position calculating means 15 is configured to calculate the three-dimensional position coordinates of the object OB at every predetermined time interval (measurement timing).

  In the present embodiment, the CPU 13a executes a program stored in the memory 13b to perform control for adjusting the inter-camera distance Dc based on the three-dimensional position coordinates of the object OB. Is configured to function as

  As shown in FIG. 3, the camera position control means 16 controls the movement mechanism 14 based on the three-dimensional position coordinates of the object OB, and the first distance D1 between the first camera 11 and the object OB. The inter-camera distance Dc is adjusted so that the second distance D2 between the second camera 12 and the object OB and the inter-camera distance Dc have a predetermined relationship. In other words, the camera position control means 16 controls the moving mechanism 14 to move the first camera 11 and the second camera 12, so that the object OB, the first camera 11, and the second camera 12 are relative to each other. Adjust the positional relationship. The camera position control means 16 adjusts the inter-camera distance Dc according to the movement of the object OB by performing feedback control using the three-dimensional position coordinates calculated by the position calculation means 15 (camera and object). To maintain a relative positional relationship with the

  In the present embodiment, the camera position control means 16 controls the inter-camera distance Dc, the first distance D1, and the control to obtain a predetermined relationship among the first distance D1, the second distance D2, and the inter-camera distance Dc. Control is performed to bring the second distance D2 closer to each other. More specifically, the camera position control means 16 is configured to perform control to make the inter-camera distance Dc, the first distance D1, and the second distance D2 coincide with each other within a predetermined allowable range RA. Yes. In the most typical case, the camera position control means 16 makes the inter-camera distance Dc, the first distance D1, and the second distance D2 coincide with each other (Dc = D1 = D2). In this case, in the camera position control means 16, the object OB, the first camera 11, and the second camera 12 form an equilateral triangle as shown in FIG. 3 (the object OB, the first camera 11, and the second camera 12). The first camera 11 and the second camera 12 are moved so that the camera 12 is positioned at each vertex of the equilateral triangle. Even if the inter-camera distance Dc, the first distance D1, and the second distance D2 do not coincide with each other, the inter-camera distance Dc is maintained as long as the difference (residual) between the distances is within the allowable range RA. Is done.

  The camera position control means 16 is configured to adjust the inter-camera distance Dc when any of the inter-camera distance Dc, the first distance D1, and the second distance D2 is outside the allowable range RA. For example, in FIG. 3, when the object OB moves in the Y2 direction and approaches the first camera 11 (second camera 12), the camera position control means 16 moves the first camera 11 and the second camera 12 in the X direction. It moves so that it may mutually approach, and distance Dc between cameras is made small. Conversely, when the object OB moves away in the Y1 direction, the camera position control means 16 moves the first camera 11 and the second camera 12 away from each other in the X direction to increase the inter-camera distance Dc.

  In the present embodiment, the camera position control means 16 adjusts the inter-camera distance Dc by moving the first camera 11 and the second camera 12 every predetermined unit distance D3. Therefore, the size of the allowable range RA for determining whether or not to adjust the inter-camera distance Dc is determined according to the size of the unit distance D3. That is, the allowable range RA is the same as or larger than the unit distance D3.

  The camera position control means 16 is configured to adjust the first distance D1 by moving the first camera 11 and adjust the second distance D2 by moving the second camera 12. . In FIG. 3, when the object OB moves only in the X direction, the camera position control means 16 moves the first camera 11 and the second camera 12 so that the magnitudes of the first distance D1 and the second distance D2 are close to each other. Move in the X direction. That is, the first camera 11 and the second camera 12 are moved so that the intermediate position between the X direction positions of the first camera 11 and the second camera 12 approaches the X direction position of the object OB.

  Since the actual movement of the object OB is random, as shown in FIG. 4, the camera position control means 16 increases or decreases the inter-camera distance Dc in accordance with the movement of the object OB in the Y direction. The intermediate position of the first camera 11 and the second camera 12 is moved in the X direction according to the movement in the X direction. Thereby, the camera position control means 16 maintains the positional relationship in which the object OB, the first camera 11 and the second camera 12 form a substantially equilateral triangle.

  Note that the 3D position measurement of the object OB by the DLT method requires camera constants for coordinate conversion between the 2D coordinate system of the 2D image of each camera and the 3D spatial coordinate system. The constant includes parameters related to the positions of the first camera 11 and the second camera 12 (inter-camera distance Dc) in the spatial coordinate system. Therefore, calibration is performed in advance at each position where the first camera 11 and the second camera 12 can move (each position for each unit distance D3), so that camera constants at the respective positions are stored in the memory 13b in advance. ing. At the time of three-dimensional position measurement, camera constants corresponding to the positions of the first camera 11 and the second camera 12 are read from the memory 13b by the position calculation means 15, so that the three-dimensional position measurement using the corresponding camera constants is performed. Is done.

(Camera distance adjustment process)
Next, with reference to FIG. 2, FIG. 3, and FIG. 5, the adjustment process of the inter-camera distance Dc of the motion tracker device 1 will be described. The adjustment process of the inter-camera distance Dc is performed by the CPU 13a (camera position control means 16, position calculation means 15) of the control unit 13. Below, it demonstrates as a process which CPU13a performs, without distinguishing the camera position control means 16 and the position calculation means 15. FIG.

  In step S <b> 1 of FIG. 5, the CPU 13 a acquires a two-dimensional image obtained by photographing the object OB from each of the first camera 11 and the second camera 12.

  In step S2, the CPU 13a reads camera constants corresponding to the current positions of the first camera 11 and the second camera 12 from the memory 13b. The current positions of the first camera 11 and the second camera 12 are always grasped by the position control of each motor 14c (see FIG. 2) of the moving mechanism 14 by the CPU 13a.

  In step S3, the CPU 13a uses the two-dimensional images obtained in step S1 and the camera constants to change the object OB in the three-dimensional spatial coordinate system from the two-dimensional coordinates of the object OB in the two-dimensional image. Perform coordinate conversion to position coordinates. Thereby, the three-dimensional position of the object OB is acquired.

  In step S4, the CPU 13a determines the first distance D1 and the second distance D2 based on the current positions of the first camera 11 and the second camera 12 and the three-dimensional position of the object OB acquired in step S3. calculate. Further, the CPU 13a acquires the inter-camera distance Dc (see FIG. 3) from the current positions of the first camera 11 and the second camera 12.

  In step S5, the CPU 13a determines whether or not the inter-camera distance Dc, the first distance D1, and the second distance D2 are within the allowable range RA (see FIG. 3). That is, the CPU 13a determines whether or not the respective differences (residuals) between the inter-camera distance Dc, the first distance D1, and the second distance D2 are less than or equal to the allowable range RA (threshold). When all the differences are less than or equal to the allowable range RA, the CPU 13a returns the process to step S1. As a result, the relative positional relationship in which the inter-camera distance Dc, the first distance D1, and the second distance D2 match within the allowable range RA is maintained.

  If any difference is larger than the allowable range RA (threshold) in step S5, the CPU 13a advances the process to step S6. In step S6, the CPU 13a moves the first camera 11 and the second camera 12 so that the inter-camera distance Dc, the first distance D1, and the second distance D2 coincide within the allowable range RA, and sets the inter-camera distance Dc. adjust. After adjusting the inter-camera distance Dc, the CPU 13a returns the process to step S1.

  By repeating the above processing every predetermined time interval (measurement timing), the CPU 13a determines whether or not the inter-camera distance Dc, the first distance D1, and the second distance D2 are within the allowable range RA. Monitor. And when the difference of each distance becomes larger than the threshold value corresponding to the allowable range RA, the CPU 13a performs feedback control for adjusting the inter-camera distance Dc, whereby the inter-camera distance Dc, the first distance D1, and the second The distance D2 is maintained in a predetermined relationship (in this embodiment, a relationship in which Dc≈D1≈D2).

(Operation of this embodiment)
The operation of this embodiment will be described with reference to FIG. As shown in FIG. 6, when the object OB is reflected on the corresponding pixel Px of the two-dimensional image, the range of light passing through the corresponding pixel Px becomes the measurement error range. Therefore, as shown in FIG. 6A, when the inter-camera distance Dc, the first distance D1, and the second distance D2 are close (match), the error range in the depth direction is E1. On the other hand, as shown in FIG. 6B, when the inter-camera distance Dc is smaller than the first distance D1 and the second distance D2, the error range in the depth direction is E2. Thus, by appropriately adjusting the inter-camera distance Dc with respect to the first distance D1 and the second distance D2, the error range becomes smaller (measurement error is reduced).

  If the inter-camera distance Dc is excessively increased, as shown in FIG. 3, the overlapping area (measurable range) of the field of view (view angle) A1 of the first camera 11 and the field of view (view angle) A2 of the second camera 12 is understood. ) Goes away in the Y1 direction and becomes narrower. Further, as the inter-camera distance Dc is increased, the first distance D1 and the second distance D2 are increased, which is an obstacle to accuracy improvement. Furthermore, it is necessary to increase the moving range for moving the first camera 11 and the second camera 12 with the movement of the object OB, and the motion tracker device 1 including the moving mechanism 14 is enlarged. Therefore, as the relative positional relationship between the object OB and the first camera 11 and the second camera 12, the inter-camera distance Dc, the first distance D1, and the second distance D2 are close to each other (close to an equilateral triangle). Is preferable from the viewpoint of balance between measurement accuracy, measurable range, and apparatus size.

(Effect of this embodiment)
In the present embodiment, the following effects can be obtained.

  In the present embodiment, as described above, the moving mechanism 14 for adjusting the inter-camera distance Dc between the first camera 11 and the second camera 12 by moving the first camera 11 and the second camera 12 respectively. Based on the three-dimensional position coordinates of the object OB, the first distance D1 between the first camera 11 and the object OB, the second distance D2 between the second camera 12 and the object OB, and the camera Camera position control means 16 is provided for performing control for adjusting the inter-camera distance Dc so that the inter-distance Dc has a predetermined relationship. Thus, by adjusting the inter-camera distance Dc, the relative positional relationship between the object OB, the first camera 11, and the second camera 12 is set to a predetermined relationship that enables more accurate measurement. Can be adjusted. In other words, the inter-camera distance Dc is adjusted so as not to be relatively small or too large with respect to the first distance D1 and the second distance D2, and an appropriate positional relationship suitable for high-accuracy measurement is obtained. it can. As a result, according to the motion tracker device 1 of the present embodiment, it is possible to reduce the measurement error and perform highly accurate three-dimensional measurement.

  In the present embodiment, as described above, the camera position control unit 16 is configured to perform control so that the inter-camera distance Dc, the first distance D1, and the second distance D2 are close to each other. As a result, it is possible to suppress the inter-camera distance Dc from becoming too small and increasing the error in the depth direction, and it is also possible to prevent the first distance D1 and the second distance D2 from becoming too large and causing a decrease in accuracy. The inter-camera distance Dc can be adjusted so that an appropriate relative positional relationship is possible. As a result, measurement errors can be effectively reduced.

  In the present embodiment, as described above, the camera position control means performs control so that the inter-camera distance Dc, the first distance D1, and the second distance D2 coincide with each other within a predetermined allowable range RA. 16 is configured. Thereby, three-dimensional measurement can be performed with the relative positional relationship in which the object OB and the first camera 11 and the second camera 12 are arranged at the vertices of a substantially equilateral triangle. As a result, it is possible to suppress an excessive increase in size of the apparatus and to further effectively reduce measurement errors. In addition, unlike the case where control is performed so that each distance (the inter-camera distance Dc, the first distance D1, and the second distance D2) is exactly the same, it is allowed that the distances are different from each other within the allowable range RA. It is possible to prevent the position control of the first camera 11 and the second camera 12 (control of the inter-camera distance Dc) from becoming complicated.

  Further, in the present embodiment, as described above, when any of the inter-camera distance Dc, the first distance D1, and the second distance D2 is outside the allowable range RA, the first camera 11 and the unit camera D for each unit distance D3. The camera position control means 16 is configured to adjust the inter-camera distance Dc by moving the second camera 12. Thereby, when any one of the distances is outside the allowable range RA (when accuracy deterioration is large), the object OB and the first camera 11 and the second camera 12 can be adjusted to an appropriate relative positional relationship. it can. At this time, since the first camera 11 and the second camera 12 are moved for each unit distance D3, it is only necessary to perform calibration in advance at a plurality of locations for each unit distance D3. As a result, three-dimensional measurement at each position after movement can be easily performed.

  In the present embodiment, as described above, the inter-camera distance Dc is adjusted according to the movement of the object OB by performing feedback control using the three-dimensional position coordinates calculated by the position calculation unit 15. Thus, the camera position control means 16 is configured. Thereby, since the relative positional relationship between the object OB and the first camera 11 and the second camera 12 can be maintained, even when the relative positional relationship changes due to the movement of the object OB, the three-dimensional measurement accuracy is maintained. can do.

  In the present embodiment, as described above, the linear rail 14a, the plurality of pedestals 14b that respectively support the first camera 11 and the second camera 12 on the rail 14a, and the plurality of pedestals 14b are respectively connected to the rail 14a. A moving mechanism 14 including a plurality of motors 14c for moving along the direction is provided. Accordingly, the inter-camera distance Dc can be adjusted with a simple configuration in which the first camera 11 and the second camera 12 are moved along the rail 14a. As a result, it is possible to prevent the apparatus configuration and control for adjusting the inter-camera distance Dc from becoming complicated.

  In the present embodiment, as described above, the first camera 11, the second camera 12, and the moving mechanism 14 are provided in the moving body 4 on which the user rides, and the user's head 5 that gets on the moving body 4. Let the helmet 23 (marker 23a) with which it is mounted | worn is set as the target object OB. Thereby, the motion tracker apparatus 1 (head motion tracker) which can measure the present angle of the helmet 23 with high accuracy can be provided.

(Explanation of experimental results)
Next, with reference to FIG. 7, the results of experiments conducted to confirm the effects of the present invention will be described.

  As shown in FIG. 7, the experiment was performed by measuring the three-dimensional position of the object OB under a plurality of measurement conditions in which the inter-camera distance Dc was changed with respect to the first distance D1 and the second distance D2. The magnitude of the error between the three-dimensional position (measured value) of the object OB and the measured value was evaluated. The three-dimensional position measurement of the object OB was performed 15 times by changing the position of the object OB, and the average value of errors in each measurement was evaluated.

  There are the following three types of measurement conditions. In each measurement, the first distance D1 and the second distance D2 were fixed values (500 mm). First, as a measurement condition of the present embodiment, the inter-camera distance Dc is set to 500 mm, and the first distance D1, the second distance D2, and the inter-camera distance Dc are matched.

  As Comparative Example 1, the inter-camera distance Dc was set to 200 mm. Further, as Comparative Example 2, the inter-camera distance Dc was set to 350 mm. In Comparative Examples 1 and 2, the inter-camera distance Dc is relatively small with respect to the first distance D1 and the second distance D2. In Comparative Example 1, the size of the inter-camera distance Dc with respect to the first distance D1 and the second distance D2 is the smallest.

  The average measurement error obtained was 1.47 in Comparative Example 1 and 1.13 in Comparative Example 2 when the error average in this embodiment was 1.00, and the error was large in the Comparative Example. . Thereby, according to this embodiment, it was confirmed that a measurement error can be reduced effectively and highly accurate three-dimensional measurement can be performed.

(Modification)
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above-described embodiment, an example in which the present invention is applied to a motion tracker device used in an HMD system has been described, but the present invention is not limited to this. The present invention may be applied to a motion tracker device used for purposes other than the HMD system. The present invention may be applied to a motion capture application for recording a motion of an object (change in a three-dimensional position) as data.

  Moreover, although the example which applied this invention to the HMD system mounted in moving bodies, such as an aircraft (an airplane and a helicopter) was shown in the said embodiment, this invention is not limited to this. In the present invention, for example, the present invention may be applied to an HMD system mounted on a land mobile body such as an automobile or a water mobile body such as a ship. Further, the present invention may be applied to, for example, an HMD system used for a game application or an HMD system used by being worn by a user in daily life.

  Moreover, in the said embodiment, although the example of the motion tracker apparatus 1 which optically measures the three-dimensional position of a target object with the 1st camera 11 and the 2nd camera 12 was shown, this invention is not limited to this. In the present invention, the motion tracker device may measure the three-dimensional position of the object using a sensor such as an acceleration sensor and a gyro sensor attached to the object in addition to the camera. Three or more cameras may be provided.

  Moreover, although the example which provided the uniaxial moving mechanism 14 which linearly moves the 1st camera 11 and the 2nd camera 12 was shown in the said embodiment, this invention is not limited to this. In the present invention, the moving mechanism may be a two-axis moving mechanism that moves the camera in a predetermined plane, or may be a three-axis or more moving mechanism that moves the camera three-dimensionally. Further, the first camera and the second camera may be moved independently of each other by separate moving mechanisms.

  In the above embodiment, as an example of the predetermined relationship between the inter-camera distance Dc, the first distance D1, and the second distance D2, the inter-camera distance Dc, the first distance D1, and the second distance D2 are set as follows. Although the example (object OB, the 1st camera 11, and the 2nd camera 12 are arrange | positioned so that an equilateral triangle may be formed) matched with each other was shown, this invention is not limited to this. In the present invention, the first distance D1 and the second distance D2 may be different from the inter-camera distance Dc. For example, as shown in FIG. 8, the object OB, the first camera 11, and the second camera 12 may form a right isosceles triangle. In this case, the relationship is Dc: D1: D2 = √2: 1: 1. However, in this case, since the moving mechanism becomes larger as compared with the above embodiment, it is preferable that the inter-camera distance Dc, the first distance D1, and the second distance D2 are close to each other.

  Moreover, although the example which makes the 1st distance D1 and the 2nd distance D2 approach mutually was shown in the said embodiment, this invention is not limited to this. In the present invention, the first distance D1 and the second distance D2 may be different.

  Moreover, although the example which fixed the 1st camera 11 and the 2nd camera 12 on the base 14b was shown in the said embodiment, this invention is not limited to this. In the present invention, the first camera and the second camera may be configured to swing on the pedestal, and the camera orientation may be adjusted following the position of the object.

  Moreover, in the said embodiment, although the example of the structure which moves the 1st camera 11 and the 2nd camera 12 for every unit distance D3 was shown, this invention is not limited to this. In the present invention, the first camera 11 and the second camera 12 may be moved by an arbitrary distance without setting the unit distance. In this case, the calibration of each camera may be performed in real time according to the position after movement. That is, a gyro sensor or the like is provided on the helmet 23 of the HMD 2 so that the orientation of the helmet 23 (marker 23a) can be detected. Then, calibration can be performed based on the three-dimensional position measurement result of the object OB after the movement of the first camera 11 and the second camera 12 and the detection result (actual measurement value) of the sensor.

DESCRIPTION OF SYMBOLS 1 Motion tracker apparatus 4 Moving body 5 Head 11 1st camera 12 2nd camera 14 Moving mechanism 14a Rail 14b Base 14c Motor 15 Position calculation means 16 Camera position control means 23 Helmet D1 1st distance D2 2nd distance D3 Unit distance Dc Inter-camera distance OB Object RA Tolerable range

Claims (7)

A first camera that acquires a two-dimensional image of the object;
A second camera that acquires a two-dimensional image of the object from a different direction from the first camera;
A moving mechanism for adjusting the distance between the first camera and the second camera by moving the first camera and the second camera, respectively;
Position calculating means for calculating three-dimensional position coordinates of the object based on two-dimensional images of the first camera and the second camera;
Based on the three-dimensional position coordinates of the object, a first distance between the first camera and the object, a second distance between the second camera and the object, and the inter-camera distance And a camera position control unit that performs control to adjust the inter-camera distance so that a predetermined relationship is established.   2. The motion tracker device according to claim 1, wherein the camera position control unit is configured to control the inter-camera distance, the first distance, and the second distance to be close to each other.   The said camera position control means is comprised so that the control which makes the said inter-camera distance, the said 1st distance, and the said 2nd distance mutually correspond within a predetermined | prescribed allowance range may be performed. Motion tracker device.   The camera position control means is configured to provide the first camera and the second camera for each predetermined unit distance when any of the inter-camera distance, the first distance, and the second distance is out of the allowable range. The motion tracker device according to claim 3, wherein the motion tracker device is configured to adjust the inter-camera distance by moving the camera. The position calculation means calculates a three-dimensional position coordinate of the object at predetermined time intervals,
The camera position control means is configured to adjust the inter-camera distance according to the movement of the object by performing feedback control using the three-dimensional position coordinates calculated by the position calculation means. The motion tracker device according to any one of claims 1 to 4.   The moving mechanism includes a linear rail, a plurality of pedestals that respectively support the first camera and the second camera on the rail, and a plurality of pedestals for moving the pedestals along the rails. The motion tracker device according to claim 1, comprising a motor. The first camera, the second camera, and the moving mechanism are provided on a moving body on which a user rides,
The motion tracker device according to any one of claims 1 to 6, wherein the object is a helmet mounted on a head of a user who rides on the moving body.

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