Position detection method and computer

Abstract

The present invention provides a position detection method wherein, in detecting three-dimensional coordinates and / or a three-dimensional direction vector of an object marker (11) attached to an object (10), information on three-dimensional coordinates and a three-dimensional direction vector of a reference marker (14) is acquired. Next, an image of the object marker (11) and the reference marker (14) is captured by an image capture device (3). Next, the captured image containing the object marker (11) and the reference marker (14) is used as a basis for calculating relative three-dimensional coordinates and / or a relative three-dimensional direction vector of the object marker (11) with respect to the reference marker (14).

Description

Position detection method and computer

[0001] The present invention relates to a location sensing method and a computer.

[0002] Conventionally, a technique has been known in which a marker is attached to an object, the marker is captured by a camera, and the position and orientation of the object are measured from the image of the marker. Markers that can be attached to objects are disclosed, for example, in Japanese Patent Application Publication No. 2012-145559 (JP2012-145559A). A typical marker is a planar pattern that can be attached to an object. A typical marker includes a square black frame and a two-dimensional pattern code printed within it. Then, by capturing an image of the marker with a camera, the relative position and orientation of the marker and the camera can be recognized, and the position and orientation of the object to which the marker is attached can be recognized. Furthermore, the camera can also read information recorded in the marker.

[0003] There is a demand for a technique that can accurately detect at least one of the three-dimensional coordinates and the three-dimensional direction vector of a marker.

[0004] The present disclosure has been made in consideration of these points, and aims to provide a new position detection method and computer that can accurately detect at least one of the three-dimensional coordinates and three-dimensional direction vector of a marker.

[0005] The position detection method disclosed herein is a position detection method for detecting at least one of the three-dimensional coordinates and three-dimensional direction vector of a target marker attached to an object, and includes the steps of: acquiring information on the three-dimensional coordinates and three-dimensional direction vector of a reference marker; capturing images of the target marker and the reference marker using an imaging device; and calculating at least one of the three-dimensional coordinates and three-dimensional direction vector of the target marker relative to the reference marker based on the captured image including the target marker and the reference marker.

[0006] The position detection method disclosed herein further includes the steps of: placing an origin marker at an origin, and acquiring information on three-dimensional coordinates and three-dimensional direction vectors of the origin marker; capturing an image of the origin marker and the reference marker; and calculating, based on the captured image including the origin marker and the reference marker, the relative three-dimensional coordinates and three-dimensional direction vector of the reference marker with respect to the origin marker, wherein, in the step of acquiring the information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker, the acquired information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker is information on the relative three-dimensional coordinates and three-dimensional direction vector of the reference marker with respect to the origin marker; and, in the step of calculating the relative three-dimensional coordinates and three-dimensional direction vector of the target marker with respect to the reference marker, at least any one of the relative three-dimensional coordinates and three-dimensional direction vector of the target marker with respect to the origin marker may also be calculated.

[0007] In the position detection method of the present disclosure, the origin marker may be arranged on the same plane as the reference marker.

[0008] a position detection method according to the present disclosure for detecting the three-dimensional coordinates and three-dimensional direction vector of a target marker attached to an object, the position detection method comprising the steps of: acquiring information on the three-dimensional coordinates of an origin; placing a reference marker at the origin; capturing an image of the reference marker using an imaging device at a fixed position; acquiring information on the three-dimensional coordinates of the imaging device relative to the origin by calculating information on the three-dimensional coordinates of the imaging device relative to the reference marker based on the captured image including the reference marker; capturing an image of the target marker using the imaging device; calculating the relative three-dimensional coordinates of the target marker with respect to the imaging device based on the captured image including the target marker, and detecting the three-dimensional coordinates of the target marker with respect to the origin based on the calculated relative three-dimensional coordinates of the target marker with respect to the imaging device.

[0009] In the position detection method of the present disclosure, the imaging device may be capable of changing the imaging direction.

[0010] In the position detection method disclosed herein, in the step of capturing an image of the reference marker with the imaging device, the same reference marker is captured by a plurality of imaging devices that are fixed in different positions; in the step of acquiring information on the three-dimensional coordinates of the imaging devices relative to the origin, information on the three-dimensional coordinates of each of the imaging devices relative to the reference marker is calculated based on images including the reference marker captured by each of the imaging devices, thereby acquiring information on the three-dimensional coordinates of each of the imaging devices relative to the origin; in the step of capturing an image of the target marker with the imaging device, the target marker is captured by each of the imaging devices; and in the step of detecting the three-dimensional coordinates of the target marker relative to the origin, relative three-dimensional coordinates of the target marker with each of the imaging devices are calculated based on images including the target marker captured by each of the imaging devices, and the three-dimensional coordinates of the target marker with respect to the origin may be detected based on the calculated relative three-dimensional coordinates of the target marker with each of the imaging devices.

[0011] In the position detection method of the present disclosure, each of the imaging devices may be capable of changing its imaging direction.

[0012] In the computer of the present disclosure, the control unit executes a program to acquire information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker, and calculates the relative three-dimensional coordinates and three-dimensional direction vector of the target marker with respect to the reference marker based on the received image including the target marker and the reference marker captured by an imaging device.

[0013] The computer of the present disclosure has a control unit that executes a program to acquire information on the three-dimensional coordinates of the origin, calculate information on the three-dimensional coordinates of the imaging device relative to the reference marker based on an image captured by the imaging device and including the reference marker placed at the accepted origin, thereby acquiring information on the three-dimensional coordinates of the imaging device relative to the origin, calculate the relative three-dimensional coordinates of the target marker with respect to the imaging device based on an image captured by the imaging device and including the accepted target marker, and detect the three-dimensional coordinates of the target marker with respect to the origin based on the calculated relative three-dimensional coordinates of the target marker with respect to the imaging device.

[0014] FIG. 1 is a schematic diagram showing a configuration of a position detection system according to an embodiment of the present disclosure; FIG. 2 is a schematic diagram showing the principle of detection processing of the position detection system according to an embodiment of the present disclosure; FIG. 3 is a schematic diagram showing one usage form of the position detection system according to an embodiment of the present disclosure; FIG. 4 is a flowchart showing a processing flow in the position detection system according to an embodiment of the present disclosure; FIG. 5 is a schematic diagram showing a modified example of the position detection system according to an embodiment of the present disclosure, which is a form of a position detection system including an imaging device capable of changing the imaging direction; FIG. 6 is a schematic diagram showing another embodiment of the position detection system according to an embodiment of the present disclosure, which is a form of a position detection system in which a mounting body or the like is used as an object and in which a plurality of imaging devices are used; FIG. 7 is a schematic diagram showing a modified example of the position detection system according to an embodiment of the present disclosure, which is a form in which various markers are respectively arranged on one surface of an object having a step; and FIG. 8 is a schematic diagram showing a modified example of the position detection system according to an embodiment of the present disclosure, which is a form of use in which the number of reference markers used is reduced.

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Figs. 1 to 4 are diagrams showing a portion of a position detection system according to an embodiment of the present disclosure. Of these, Fig. 1 is a schematic diagram showing the configuration of the position detection system according to this embodiment, and Fig. 2 is a schematic diagram showing the principle of detection processing of the position detection system according to this embodiment. Fig. 3 is a schematic diagram showing one usage form of the position detection system according to this embodiment. Fig. 4 is a flowchart showing the processing flow in the position detection system according to this embodiment.

[0016] 1 is a block diagram showing the configuration of a position detection system 1 according to this embodiment. The position detection system 1 according to this embodiment includes a computer 2 and an imaging device 3.

[0017] The imaging device 3 captures an image of a target marker 11 attached to the object 10 and a reference marker 14 placed on the placement surface 7 and used to measure the position of the target marker 11. The three-dimensional coordinates and three-dimensional direction vector of the reference marker 14 relative to an origin on the placement surface 7 are measured in advance, and the position detection system 1 acquires information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker 14 relative to the origin. The position detection system 1 also captures images of the target marker 11 and the reference marker 14 using the imaging device 3. The position detection system 1 also calculates at least one of the three-dimensional coordinates and three-dimensional direction vector of the target marker 11 relative to the reference marker 14 based on an image including the captured target marker 11 and reference marker 14. For example, the computer 2 is communicatively connected to the imaging device 3. The imaging device 3 and the computer 2 may also be communicatively connected to each other via a communication network such as the Internet. In this specification, three-dimensional coordinates refer to the coordinates at the center position of the marker, and the three-dimensional direction vector of the marker refers to the direction in which a straight line perpendicular to the plane of the marker extends.

[0018] 2, the target marker 11 is one or more AR markers, and the target marker 11 is attached to the target object 10. The target marker 11 is used to grasp the positional relationship of a predetermined position (point m1) on the target object 10. The size of the target marker 11 is such that it can be imaged by the imaging device 3 when attached to the predetermined position on the target object 10.

[0019] As shown in FIG. 2, the reference marker 14 is an AR marker and is placed on the placement surface 7 .

[0020] As shown in FIG. 2, the image capturing device 3 is a camera device that is provided in one or more (one in the embodiment shown in FIG. 2) in the position detection system 1.

[0021] In the position detection system 1 configured as described above, by capturing images of the target marker 11 and the reference marker 14 using the imaging device 3, information regarding the position and orientation of the reference marker 14 and the target marker 11 relative to a predetermined position (origin O) can be obtained.

[0022] Next, a description will be given of an example of one usage form of the position detection system 1. In this embodiment, as shown in Fig. 3, an example is also given in which an origin marker 71 is placed at the above-mentioned predetermined position (origin).

[0023] The imaging device 3 also captures an image of an origin marker 71, which is used to position an object (target object 10) to be detected and is attached to the origin (point m0) of the placement surface 7 of the target object 10. The imaging device 3 also captures an image of a reference marker 14, which is placed separately from the origin marker 71 on the placement surface 7. For example, the imaging device 3 is placed on the ground, suspended, or held by a person on the placement surface 7. The imaging device 3 is placed in a position where it can capture images of the reference marker 14 and target marker 11, captures images of them, and acquires image data.

[0024] Furthermore, multiple reference markers 14 may be placed on the placement surface 7. When the reference marker 14 is placed on the placement surface 7, the reference marker 14 is placed at a position different from the origin marker 71. In this way, one or multiple reference markers 14 are placed on the placement surface 7, and at least one reference marker 14 is imaged by the imaging device 3 due to the movement of the target object 10. The predetermined position on the placement surface 7 where the reference marker 14 is attached is represented as point mk.

[0025] The origin marker 71 is an AR marker attached to an origin (point m0) set at a predetermined position on the placement surface 7, and is used for calibration together with the target marker 11 or the reference marker 14. When measuring the coordinate of the predetermined position (point m1) where the target marker 11 is attached from the predetermined position (point m0) where the origin marker 71 is attached, the position of point m1 may be obtained by further measuring the coordinate of the predetermined position (point m1) where the target marker 11 is attached from the predetermined position (point m0) where the origin marker 71 is attached using the predetermined position (point m0) where the origin marker 71 is attached. The predetermined position where the origin marker 71 is attached is represented as point m0. The origin marker 71 is placed on the same plane as the reference marker 14.

[0026] The placement surface 7 is a surface used to define a predetermined position (point m1) of the object 10, and is a plane on which the reference marker 14 is attached. Here, the predetermined position (point m1) refers to a specific location where the object 10 is located, and in the case of a humanoid robot, for example, it may be the center point of the object marker 11 attached to the humanoid robot. The placement surface 7 is also defined by the range that can be imaged by the imaging device 3. Note that in the present disclosure, an example will be described in which the object marker 11 is attached to a location corresponding to the head of a self-propelled humanoid robot.

[0027] The above function is achieved by capturing an image of the target marker 11 and the reference marker 14 or the origin marker 71 using the imaging device 3. The above function is also achieved by capturing an image of the target marker 11 and the reference marker 14 and the origin marker 71 using the imaging device 3.

[0028] <Configuration of Computer 2> The computer 2 can be used via a communication network such as the Internet. As shown in Fig. 1, the computer 2 has a control unit 4, a storage unit 5, and a communication unit 6. The control unit 4 is configured as a microcomputer including a CPU and semiconductor memory, and controls the operation of the computer 2. More specifically, the control unit 4 functions as a receiving unit 41, a calculating unit 42, and a detecting unit 43 by executing a program stored in the storage unit 5.

[0029] -Preliminary Information Acquisition Process and Imaging Process- The reception means 41 receives three-dimensional coordinates and three-dimensional direction vectors of the reference marker 14 and the origin marker 71 that have been acquired in advance. By using such a coordinate system that has been acquired in advance, it becomes easier to handle the movement and positioning of the humanoid robot as the target object 10. The reception means 41 also receives images captured by the imaging device 3. For example, the reception means 41 receives image data of the origin marker 71, the target marker 11, and the reference marker 14 that have been captured in advance by the imaging device 3.

[0030] 3, the calculation means 42 calculates the relative three-dimensional coordinates of a predetermined position (point m1) on the object 10 relative to the attachment position of the target marker 11 attached to the object 10, based on image data including at least the target marker 11 and the reference marker 14, selected from a group including image data of the origin marker 71, the target marker 11, and the reference marker 14 received by the reception means 41. This makes it possible to continue to acquire the relative coordinates and vector of the predetermined position (point m1) on the object 10, for example, without continuously positioning the origin marker 71 at point m0.

[0031] First, the calculation means 42 calculates a homogeneous transformation matrix θk based on the matrices at the positions of the image capturing device 3 (point C) and the reference marker 14 (point mk) from the image data captured by the image capturing device 3. ｃ H ｍｋ －１ Furthermore, based on the respective positions of the image capture device 3 (point C) and the target marker 11 (point m1), the homogeneous transformation matrix ｃ H ｍ１ And then,ｃ H ｍ１ and ｃ H ｍｋ －１ Based on ｍｋ H ｍ１ ( ｃ H ｍｋ －１ ｃ H ｍ１ ) is calculated. The homogeneous transformation matrix is ​​used to efficiently calculate coordinate transformation and rigid body transformation by matrix calculation, and is expressed in three-dimensional space by the following equation.

[0032] (In Equation 1, r represents a rotation matrix, and t represents a translation vector.)

[0033] Furthermore, when measuring the coordinates of the predetermined position (point m1) where the target marker 11 is attached from the predetermined position (point m0) where the origin marker 71 is attached, the calculation means 42 calculates a homogeneous transformation matrix mk based on the matrices at the predetermined position (point m0) of the origin marker 71 and the predetermined position (point mk) of the reference marker 14. ｍ０ H ｍｋ Then, the calculation means 42 calculates the calculated ｍ０ H ｍｋ and ｍｋ H ｍ１ Based on ｍ０ H ｍ１ ( ｍ０ H ｍｋｍｋ H ｍ１ ) is calculated. By measuring the reference marker 14 and the target marker 11 in this manner, the predetermined position of the target marker 11 from the predetermined position of the origin marker 71 can be calculated.

[0034] More specifically, the calculation means 42 calculates the relative three-dimensional coordinates and three-dimensional direction vector of the predetermined position (point mk) of the reference marker 14 relative to the predetermined position (point m0) of the origin marker 71 based on the image including the coordinates of the predetermined position (point mk) of the reference marker 14 and the coordinates of the predetermined position (point m0) of the origin marker 71 received by the reception means 41 ( ｍ０ H ｍｋ). This calibrates the predetermined position (point mk) of the reference marker 14 with respect to the predetermined position (point m0) on the placement surface 7. Furthermore, the calculation means 42 calculates the relative three-dimensional coordinates and three-dimensional direction vector of the predetermined position (point m1) of the target marker 11 with respect to the predetermined position (point mk) of the reference marker 14 based on the image including the coordinates of the predetermined position (point mk) of the reference marker 14 and the coordinates of the predetermined position (point m1) of the target marker 11 received by the reception means 41 ( ｍｋ H ｍ１ ).

[0035] Then, the origin marker 71, the reference marker 14, and the target marker 11 are photographed over time by the imaging device 3, and the detection means 43 ｍ０ H ｍ１ ( ｍ０ H ｍｋｍｋ H ｍ１ By continuously detecting the target marker 11, it is possible to continuously obtain the coordinates of the predetermined position (point m1) of the target marker 11 in more detail as the target marker 11 moves.

[0036] The programs executed by the control unit 4 are not limited to those stored in the storage unit 5. The programs executed by the control unit 4 may be those transmitted from an external device to the control unit 4 via the communication unit 6, those stored in a storage medium such as a USB memory attached to the computer 2, or those stored in a server (for example, a cloud server) separate from the computer 2.

[0037] The storage unit 5 is composed of a hard disk drive (HDD), random access memory (RAM), read only memory (ROM), solid state drive (SSD), etc. Various programs including programs executed by the control unit 4 are stored in the storage unit 5. The storage unit 5 also stores images captured by the imaging device 3. Details of the information stored in the storage unit 5 will be described later.

[0038] The communication unit 6 is, for example, a wired LAN (Local Area Network) module, a wireless LAN module, etc., and includes an interface for performing wired or wireless communication. That is, the communication unit 6 is configured from a communication interface configured to communicate with other devices via a communication network.

[0039] Next, various processes in this embodiment will be described with reference to the usage form of the position detection system 1 shown in Fig. 3 and the flowchart shown in Fig. 4. The operations of the position detection system 1 described below are performed by the control unit 4 of the computer 2 executing a program stored in the storage unit 5.

[0040] <Calibration Process> First, the user attaches the reference marker 14 and the origin marker 71 to the placement surface 7 .

[0041] Next, the user captures an image of the reference marker 14 using the imaging device 3, thereby acquiring information on the three-dimensional coordinates and three-dimensional direction vectors of the predetermined position (point mk) of the reference marker 14, using a predetermined position (point C) or the like of the imaging device 3 as a reference point (step S10). The acquired data is accepted by the accepting means 41.

[0042] <Detection Process> Next, the image capturing device 3 captures an image of the target marker 11 and the reference marker 14 attached to the target object 10 (step S11). At this time, the coordinates of a predetermined position (point m1) of the target marker 11 and a predetermined position (point mk) of the reference marker 14 are acquired from the captured image, with the predetermined position (point C) of the image capturing device 3 as a reference, and are accepted by the accepting means 41.

[0043] Next, the calculation means 42 calculates the relative three-dimensional coordinates and three-dimensional direction vector of the predetermined position (point m1) of the target marker 11 relative to the predetermined position (point mk) of the reference marker 14 based on the image including the coordinates of the predetermined position (point mk) of the reference marker 14 and the coordinates of the predetermined position (point m1) of the target marker 11 received by the reception means 41 (step S12).

[0044] After step S12, the image capturing device 3 captures images of the reference marker 14 and the target marker 11 over time, and the detecting means 43 ｍｋ H ｍ１ By continuously detecting the target marker 11, the coordinates of the predetermined position (point m1) of the target marker 11 are continuously acquired as the target 10 moves.

[0045] According to the position detection method of the present embodiment configured as described above, the position detection method of the present disclosure acquires information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker 14 when detecting at least one of the three-dimensional coordinates and three-dimensional direction vector of the target marker 11 attached to the object 10. Next, the target marker 11 and the reference marker 14 are imaged by the imaging device 3. Next, based on the image including the captured target marker 11 and the reference marker 14, at least one of the three-dimensional coordinates and three-dimensional direction vector of the target marker 11 relative to the reference marker 14 is calculated.

[0046] According to this position detection method, by continuously capturing images of the target marker 11 using the imaging device 3, coordinates of the target marker 11 can be acquired over time as the target marker 10 moves. More specifically, a technique has been known in the past in which a marker is attached to an object and captured using a camera to measure the position and orientation of the object from the image of the marker. A technique for accurately detecting at least one of the marker's three-dimensional coordinates and three-dimensional directional vector has been desired. According to the position detection method configured as described above, by calculating the three-dimensional coordinates and three-dimensional directional vector of the target marker 11 relative to the reference marker 14, the three-dimensional coordinates of a predetermined position (point m1) on the target marker 10 to which the target marker 11 is attached can be detected from the image of the target marker 11, thereby solving the above-mentioned problem.

[0047] Furthermore, in the detection method of this embodiment, as described above, the origin marker 71 is placed at the origin, and information on the three-dimensional coordinates and three-dimensional direction vector of the origin marker 71 is acquired. Next, the origin marker 71 and the reference marker 14 are imaged. Next, based on the image including the captured origin marker 71 and the reference marker 14, the three-dimensional coordinates and three-dimensional direction vector of the reference marker 14 relative to the origin marker 71 are calculated. Here, when acquiring the information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker 14, the acquired information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker 14 is information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker 14 relative to the origin marker 71. Furthermore, when calculating the three-dimensional coordinates and three-dimensional direction vector of the target marker 11 relative to the reference marker 14, at least one of the three-dimensional coordinates and three-dimensional direction vector of the target marker 11 relative to the origin marker 71 may also be calculated. In this case, by measuring the relative position of the reference marker 14 with respect to the origin marker 71 in advance, the position of the target marker 11 with respect to the origin marker 71 can be detected, and the target can be imaged even if the angle of view of the imaging device 3 is small.

[0048] Furthermore, in the detection method of this embodiment, as described above, the origin marker 71 may be arranged on the same plane as the reference marker 14. In this case, by arranging the origin marker 71 on the same plane as the reference marker 14, the coordinate systems in the surface directions of the origin marker 71 and the reference marker 14 can be handled together.

[0049] Furthermore, in the computer 2 of this embodiment, the control unit 4 executes a program to acquire information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker 14. Furthermore, based on the received image including the target marker 11 and the reference marker 14 captured by the imaging device 3, the computer 2 calculates the three-dimensional coordinates and three-dimensional direction vector of the target marker 11 relative to the reference marker 14. In this case, by calculating the three-dimensional coordinates and three-dimensional direction vector of the target marker 11 relative to the reference marker 14, the computer 2 can detect the three-dimensional coordinates of a predetermined position (point m1) on the object 10 to which the target marker 11 is attached from the image of the target marker 11.

[0050] In the computer 2 of this embodiment, the control unit 4 executes a program to acquire information about the three-dimensional coordinates of the origin. Furthermore, based on an image captured by the imaging device 3 and including the reference marker 14 positioned at the accepted origin, information about the three-dimensional coordinates of the imaging device 3 relative to the reference marker 14 is calculated to acquire information about the three-dimensional coordinates of the imaging device 3 relative to the origin. Furthermore, based on an image captured by the imaging device 3 and including the accepted target marker 11, the relative three-dimensional coordinates of the target marker 11 relative to the imaging device 3 are calculated, and the three-dimensional coordinates of the target marker 11 relative to the origin are detected based on the calculated relative three-dimensional coordinates of the target marker 11 relative to the imaging device 3. In this case, the computer 2 can acquire coordinates related to the movement of the target marker 10 by measuring the target marker 10 using the imaging device 3.

[0051] The position detection method and computer 2 according to the present disclosure are not limited to the above-described aspects, and various modifications can be made.

[0052] In the present embodiment, an example in which the target marker 11 is placed on a humanoid robot has been described, but this is not limiting. For example, as shown in FIG. 6 , after acquiring the self-position of the imaging device 3, the self-position measurement and self-position estimation of the target 10, such as a moving object such as a rock, robot, drone, or AGV, may be performed. In this case, a fixed-position camera is used as the imaging device 3. This allows relative positional deviations at multiple points on the target 10 to be measured. For example, in a position detection method, first, information on the three-dimensional coordinates of the origin is acquired. Next, a reference marker 14 is placed at the origin as a predetermined position on the placement surface 7. At this time, the coordinates of the reference marker 14 are acquired in advance. The reference marker 14 is then imaged by the fixed-position camera. Based on an image including the captured reference marker 14, information on the three-dimensional coordinates of the fixed-position camera relative to the reference marker 14 is calculated, thereby acquiring information on the three-dimensional coordinates of the fixed-position camera relative to the origin. Then, the fixed-position camera images the target marker 11 placed on the target 10. Furthermore, based on the captured image including the target marker 11, the three-dimensional coordinates of the target marker 11 relative to the fixed-position camera are calculated. Then, based on the calculated three-dimensional coordinates of the target marker 11 relative to the fixed-position camera, the three-dimensional coordinates of the target marker 11 relative to the origin are detected. At this time, after the coordinates of the reference marker 14 are acquired, the reference marker 14 may be removed. In this way, by measuring the target 10 with the imaging device 3, it is possible to acquire coordinates related to the movement of the target 10. Furthermore, in cases where the target 10 does not move much, such as in civil engineering management, the measurement accuracy can be improved by measuring the coordinates multiple times and performing statistical processing.

[0053] The position detection system 1 may also include a plurality of imaging devices 3. In this case, the reference marker 14 and the target marker 11 are imaged by the plurality of imaging devices 3, and the three-dimensional coordinates of the target marker 11 relative to the origin are detected based on the captured images.

[0054] 5, the imaging device 3 may be configured to change its imaging direction. In this case, first, information on the three-dimensional coordinates of the origin (point m0) is acquired in advance. A reference marker 14 is placed at the origin (point m0), and the reference marker 14 is imaged by the fixed-position imaging device 3. Then, based on the image containing the captured reference marker 14, information on the three-dimensional coordinates of the fixed-position imaging device 3 relative to the reference marker 14 is calculated. This makes it possible to acquire information on the three-dimensional coordinates of the fixed-position imaging device 3 relative to the origin (point m0) (information on point C0). Then, the fixed-position imaging device 3 images the target marker 11. Based on the image containing the captured target marker 11, the relative three-dimensional coordinates of the target marker 11 relative to the fixed-position imaging device 3 are calculated. In other words, since information on the three-dimensional coordinates of the fixed-position imaging device 3 relative to the origin (point m0) (information on point C0) is acquired in advance, even if the imaging direction of the fixed-position imaging device 3 changes (the fixed-position imaging device 3 rotates), the relative three-dimensional coordinates of the target marker 11 with respect to the fixed-position imaging device 3 can be calculated based on the image including the captured target marker 11, and the three-dimensional coordinates of the target marker 11 with respect to the origin (point m0) can be detected based on the calculated relative three-dimensional coordinates of the target marker 11 with respect to the fixed-position imaging device 3. More specifically, the reference marker 14 is captured by the imaging device 3 whose imaging direction has changed (it has rotated to a position corresponding to C1), and the captured image is received by the receiving means 41. Based on the image received by the receiving means 41, the calculating means 42 ｃ１ H ｍ０ －１ , ｃ０ H ｃ１ －１ respectively, ｍ０ H ｃ０ ( ｃ１ H ｍ０ －１ ｃ０ H ｃ１ －１ ) and measure the coordinates of a predetermined position (point C0) of the image capturing device 3 relative to a predetermined position (point m0) of the reference marker 14. Next, the image capturing device 3 is rotated, and the target marker 11 is photographed from position C2 after the rotation. ｃ０ H ｃ２ ,ｃ２ H ｍ１ , respectively, ｍ０ H ｍ１ ( ｍ０ H ｃ０ｃ０ H ｃ２ｃ２ H ｍ１ ), the coordinates of the predetermined position (point m1) of the target marker 11 relative to the predetermined position (point m0) of the reference marker 14 are measured.

[0055] After the above, at least the target marker 11 is imaged over time by the fixed-position image capturing device 3, and the detecting means 43 ｍ０ H ｍ１ ( ｍ０ H ｃ０ｃ０ H ｃ２ｃ２ H ｍ１ By continuously detecting the target marker 11, it is possible to continuously obtain the coordinates of the predetermined position (point m1) of the target marker 11 in more detail as the target marker 11 moves.

[0056] Furthermore, although the origin marker 71 has been described as being placed on the same plane as the reference marker 14, this is not limiting. For example, the origin marker 71 does not have to be placed on the same plane as the reference marker 14 as long as calibration and detection processing are possible. Furthermore, as shown in Fig. 7 , the origin marker 71 and the reference marker 14 may each be placed on one surface of an object that has steps such as stairs.

[0057] 8, two of the reference markers 14 placed on an object such as a wall may be imaged, and then the reference markers 14 may be thinned out. In this case, the calculation means 42 calculates a homogeneous transformation matrix ｃ１ H ｍ０ －１ Furthermore, based on the respective positions of the image capture device 3 (point C1) and the reference marker 14 (point mk1), the homogeneous transformation matrix ｃ１ H ｍｋ１ And then, ｃ１ H ｍ０ －１ and ｃ１ Hｍｋ１ Based on ｍ０ H ｍｋ１ ( ｃ１ H ｍ０ －１ ｃ１ H ｍｋ１ ) is calculated. This calibrates the predetermined position (point mk1) of the reference marker 14 with the predetermined position (point m0) of the origin marker 71 as a reference. Furthermore, the calculation means 42 calculates a homogeneous transformation matrix θ based on the matrices at the predetermined position (point C2) of the imaging device 3 and the predetermined position (point mk1) of the reference marker 14 from the image data captured by the imaging device 3. ｃ２ H ｍｋ１ －１ Furthermore, based on the predetermined position (point C2) of the image capturing device 3 and the predetermined position (point mk2) of the reference marker 14, the homogeneous transformation matrix ｃ２ H ｍｋ２ And then, ｃ２ H ｍｋ１ －１ and ｃ２ H ｍｋ２ Based on ｍｋ１ H ｍｋ２ ( ｃ２ H ｍｋ１ －１ ｃ２ H ｍｋ２ ) is calculated. In this way, the predetermined position (point mk2) of the reference marker 14 is calibrated using the predetermined position (point mk1) of the reference marker 14 as a reference. Then, the calculation means 42 calculates ｍ０ H ｍｋ１ and ｍｋ１ H ｍｋ２ Based on the homogeneous transformation matrix ｍ０ H ｍｋ２ ( ｍ０ H ｍｋ１ｍｋ１ H ｍｋ２ ) is calculated. By repeating this calculation, it is possible to obtain position and orientation information, i.e., three-dimensional coordinates and three-dimensional direction vectors, at predetermined positions (points mk1, mk2, ..., mkn (n is a natural number)) of the reference marker 14 from a predetermined position (point m0) of the origin marker 71. As a result, it is possible to reduce the number of locations where the reference marker 14 is placed, as shown on the right side of FIG. 8.

Claims

1. A position detection method for detecting at least one of the three-dimensional coordinates and three-dimensional direction vector of a target marker attached to an object, comprising the steps of: acquiring information on the three-dimensional coordinates and three-dimensional direction vector of a reference marker; capturing images of the target marker and the reference marker using an imaging device; and calculating at least one of the relative three-dimensional coordinates and three-dimensional direction vector of the target marker with respect to the reference marker based on an image including the captured target marker and the reference marker.

2. A position detection method as described in claim 1, further comprising the steps of: placing an origin marker at an origin and acquiring information on three-dimensional coordinates and three-dimensional direction vector of the origin marker; capturing an image of the origin marker and the reference marker; and calculating relative three-dimensional coordinates and three-dimensional direction vector of the reference marker with respect to the origin marker based on the captured image including the origin marker and the reference marker, wherein in the step of acquiring information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker, the acquired information on the three-dimensional coordinates and three-dimensional direction vector of the reference marker is information on the relative three-dimensional coordinates and three-dimensional direction vector of the reference marker with respect to the origin marker, and in the step of calculating the relative three-dimensional coordinates and three-dimensional direction vector of the target marker with respect to the reference marker, at least any of the relative three-dimensional coordinates and three-dimensional direction vector of the target marker with respect to the origin marker is also calculated.

3. The position detection method according to claim 2, wherein the origin marker is disposed on the same plane as the reference marker.

4. A position detection method for detecting three-dimensional coordinates and three-dimensional direction vectors of a target marker attached to an object, comprising the steps of: acquiring information on the three-dimensional coordinates of an origin; placing a reference marker at the origin; capturing an image of the reference marker with an imaging device at a fixed position; acquiring information on the three-dimensional coordinates of the imaging device relative to the origin by calculating information on the three-dimensional coordinates of the imaging device relative to the reference marker based on the captured image including the reference marker; imaging the target marker with the imaging device; calculating the relative three-dimensional coordinates of the target marker with the imaging device based on the captured image including the target marker, and detecting the three-dimensional coordinates of the target marker with respect to the origin based on the calculated relative three-dimensional coordinates of the target marker with respect to the imaging device.

5. A position detection method according to claim 4, wherein said imaging device is adapted to be capable of changing an imaging direction.

6. A position detection method as claimed in claim 4, wherein in the step of imaging the reference marker with the imaging device, the same reference marker is imaged by a plurality of imaging devices with fixed positions arranged at different positions; in the step of acquiring information of the three-dimensional coordinates of the imaging devices relative to the origin, information of the three-dimensional coordinates of each of the imaging devices relative to the reference marker is calculated based on an image including the reference marker imaged by each of the imaging devices, thereby acquiring information of the three-dimensional coordinates of each of the imaging devices relative to the origin; in the step of imaging the target marker with the imaging device, the target marker is imaged by each of the imaging devices; and in the step of detecting the three-dimensional coordinates of the target marker relative to the origin, relative three-dimensional coordinates of the target marker with respect to each of the imaging devices are calculated based on an image including the target marker imaged by each of the imaging devices, and the three-dimensional coordinates of the target marker with respect to the origin are detected based on the calculated relative three-dimensional coordinates of the target marker with respect to each of the imaging devices.

7. A position detection method according to claim 6, wherein each of said imaging devices is capable of changing its imaging direction.

8. A computer in which the control unit executes a program to acquire information on the three-dimensional coordinates and three-dimensional directional vector of a reference marker, and calculates the relative three-dimensional coordinates and three-dimensional directional vector of the target marker with respect to the reference marker based on an image including the target marker and the reference marker captured by an imaging device.

9. A computer having a control unit executing a program, which performs the following steps: acquiring information on the three-dimensional coordinates of an origin; acquiring information on the three-dimensional coordinates of the imaging device relative to the origin by calculating information on the three-dimensional coordinates of the imaging device relative to the reference marker based on an image captured by the imaging device and including the reference marker placed at the accepted origin; calculating the relative three-dimensional coordinates of the target marker with respect to the imaging device based on an image captured by the imaging device and including the accepted target marker; and detecting the three-dimensional coordinates of the target marker with respect to the origin based on the calculated relative three-dimensional coordinates of the target marker with respect to the imaging device.

Images