Patent Publication Number: US-2006017812-A1

Title: Camera link system, camera device and camera link control method

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a camera link system in which a plurality of cameras are linked to shoot the same subject.  
      2. Background  
      Conventionally, in the field of monitor cameras, a camera link system is proposed. In the camera link system, a plurality of cameras are disposed apart. Then, these multiple cameras change the directions thereof by a single trigger to shoot the same subject.  
      In such conventional camera link system, the shooting direction when linked is preset in each of cameras. Then, when a link operation is instructed, cameras turn to the preset directions. Accordingly, multiple cameras shoot the same subject.  
      In the traditional system, a link function is obtained only in the preset direction. Unlike this traditional system, a system has been conventionally proposed, which can obtain a link function with no preset. This type of system is configured of a master camera and a slave camera. When the master camera is rotated, the direction of the master camera is sent to an upper control device. The control device computes the direction of the slave camera to follow the master camera, that is, the direction of the slave camera to shoot the same subject as the master camera. Subsequently, the control device instructs the slave camera about the direction, and the slave camera is rotated in accordance with the instruction. When multiple slave cameras are disposed, the directions of the multiple slave cameras are sequentially computed and instructed.  
      Furthermore, in a camera link system disclosed in JP-A-2003-284050, when a master camera is rotated, the direction of the master camera is sent to slave cameras. Then, the directions of the slave cameras to follow the master camera are computed, and they are rotated so as to turn to the computed direction.  
      In the conventional camera link system described above, a series of processes are conducted in which a master camera is moved, the master camera then sends its direction to a control device, the control device computes the directions of slave cameras to instruct the slave cameras about the directions, and the slave cameras are moved. Also in the configuration in which slave cameras do computations, a similar series of processes are required. Since such a series of processes take time, it is likely to increase a time lag between the operations of the master camera and the slave camera.  
     SUMMARY OF THE INVENTION  
      The invention has been made under the background. An object of the invention is to provide a camera link system in which a slave camera can quickly follow a master camera.  
      An aspect of the invention is a camera link system. The camera link system includes: a plurality of camera devices rotatable; and a control device connected to the plurality of camera devices, wherein the control device provides master camera direction information that instructs a direction of a master camera selected from the plurality of camera devices to the plurality of camera devices including the master camera, and each camera device of the plurality of camera devices includes: a relative position information storing module which stores relative position information about the each camera device and the one or more other camera devices other than the each camera device; a direction information transforming module which transforms the master camera direction information to slave camera direction information that allows the each camera device to follow the master camera as a slave camera based on the relative position information when one of the one or more other camera devices is the master camera; and a rotation control module which controls a rotating mechanism of the each camera device in accordance with the master camera direction information when the each camera device is the master camera, and controls the rotating mechanism of the each camera device in accordance with the slave camera direction information when the each camera device is not the master camera.  
      According to the configuration, the control device provides the master camera direction information to the plurality of cameras. Each of the cameras is rotated in accordance with the master camera direction information when it functions as the master camera. Furthermore, each of the cameras transforms the master camera direction information to the slave camera direction information based on relative position information when it functions as the slave camera, and is rotated in accordance with the slave camera direction information. In this manner, the master camera direction information is sent to the plurality of cameras, and the operations of the master camera and the slave camera are simultaneously conducted. Thus a time lag between the operations of the master camera and the slave camera (delay of the slave camera) is reduced.  
      Moreover, an aspect of the invention is a camera device. The camera device includes: a relative position information storing module which stores relative position information about the camera device and the one or more other camera devices other than the camera device; a communication module which is connected to a control device along with the one or more other camera devices and receives master camera direction information that instructs a direction of a master camera selected from a plurality of camera devices including the camera device and the one or more other camera devices; a direction information transforming module which transforms the master camera direction information to slave camera direction information that allows the camera device to follow the master camera based on the relative position information when one of the one or more other camera devices is the master camera; and a rotation control module which controls a rotating mechanism of the camera device in accordance with the master camera direction information when the camera device is the master camera, and controls the rotating mechanism of the camera device in accordance with the slave camera direction information when the camera device is not the master camera. According to the configuration, similarly to the aspect of the camera link system, a time lag between the operations of the master camera and the slave camera can be reduced.  
      Besides, the camera device may include: a master/slave determining module which determines whether the camera device is the master camera based on the master camera direction information provided by the control device; and a master camera identifying module which identifies a master camera among the other camera devices when the camera device is not the master camera, wherein the direction information transforming module may transform the master camera direction information to the slave camera direction information based on the relative position information of one of the other camera devices identified by the master camera identifying module in relative position information about the other camera devices stored in the relative position information storing module. According to the configuration, the camera device can follow the master camera identified among the plurality of other cameras. Therefore, a preferable link function can be obtained even though the number of cameras is large.  
      Furthermore, in the camera device, the communication module may take in the master camera direction information regardless of whether a destination is for the camera device or one of the one or more other camera devices; and the master/slave determining module and the master camera identifying module may conduct a determination process and a identifying process based on destination information in the master camera direction information. According to the configuration, a preferable link function can be obtained by a simple configuration in which information destined for the other camera is taken by communications.  
      Moreover, an aspect of the invention is a camera link control method. The control method includes: providing master camera direction information that instructs a direction of a master camera to a plurality of cameras including the master camera and a slave camera that follows the master camera; controlling a rotating mechanism of the master camera in accordance with the master camera direction information; and transforming the master camera direction information to slave camera direction information that allows the slave camera to follow the master camera based on relative position information about the master camera and the slave camera to control a rotating mechanism of the slave camera in accordance with the slave camera direction information. In this aspect, the master camera and the slave camera may be changed freely, or they may be decided by a fixed manner (without changing). The advantage described above can also be obtained by this configuration.  
      Besides, an aspect of the invention is a camera link system. The camera link system includes: a plurality of camera devices including a master camera and a slave camera that follows the master camera; and a control device connected to the plurality of camera devices, wherein the control device provides master camera direction information that instructs a direction of a master camera among the plurality of camera devices to the plurality of camera devices, the master camera controls a rotating mechanism in accordance with the master camera direction information, and the slave camera transforms the master camera direction information to slave camera direction information that allows the slave camera to follow the master camera based on relative position information about the master camera and the slave camera to control a rotating mechanism in accordance with the slave camera direction information. Also in this aspect, the master camera and the slave camera may be changed freely, or they may be decided by a fixed manner (without changing). The advantage described above can also be obtained by this configuration.  
      An aspect of the invention is a camera link system. The camera link system includes: a plurality of camera devices rotatable including a first camera device; and a control device connected to the plurality of camera devices, wherein the control device provides master camera direction information that instructs a direction of a master camera selected from the plurality of camera devices to the plurality of camera devices including the master camera, and the first camera device includes: a relative position information storing module which stores relative position information about the first camera device and at least one camera device other than the first camera device, a direction information transforming module which transforms the master camera direction information to slave camera direction information that allows the first camera device to follow the master camera as a slave camera based on the relative position information when the at least one camera device other than the first camera device is the master camera, and a rotation control module which controls a rotating mechanism of the first camera device in accordance with the master camera direction information when the first camera device is the master camera, and controls the rotating mechanism of the first camera device in accordance with the slave camera direction information when the first camera device is not the master camera. The advantage described above can also be obtained by this configuration.  
      As described above, in the invention, the slave camera can quickly follow the master camera, and a time lag between the operations of the master camera and the slave camera can be reduced.  
      As described hereafter, other aspects of the invention exist. Thus, this summary of the invention is intended to provide a few aspects of the invention and is not intended to limit the scope of the invention described and claimed herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings are incorporated in and constitute a part of this specification. The drawings exemplify certain aspects of the invention and, together with the description, serve to explain some principles of the invention.  
       FIG. 1  is a block diagram illustrating a camera link system of an embodiment according to the invention;  
       FIG. 2  is a block diagram illustrating the configuration of a camera device;  
       FIG. 3  is a diagram illustrating an exemplary position information table;  
       FIG. 4  is a diagram illustrating a transformation process of a master camera direction to a slave camera direction;  
       FIG. 5  is a diagram illustrating a transformation process of a master camera direction to a slave camera direction; and  
       FIG. 6  is a flow chart illustrative of the operation of the camera link system. 
    
    
     DETAILED DESCRIPTION  
      The following detailed description refers to the accompanying drawings. Although the description includes exemplary implementations, other implementations are possible and changes may be made to the implementations described without departing from the spirit and scope of the invention. The following detailed description and the accompanying drawings do not limit the invention. Instead, the scope of the invention is defined by the appended claims.  
      Hereinafter, a camera link system of an embodiment according to the invention will be described with reference to the drawings.  
       FIG. 1  depicts a camera link system of the embodiment. In  FIG. 1 , a camera link system  10  has four camera devices  12 . The camera device  12  is a monitor camera device disposed on a ceiling downward. The four monitor camera devices  12 , not shown, are disposed apart. The camera device  12  has a rotating stage or head, which can be rotated in a pan direction and a tilt direction.  
      Four monitor cameras  12  are connected to a four-screen unit  14 , and the four-screen unit  14  is connected to a master monitor  16 . Furthermore, the four monitor cameras  12  are connected to a personal computer  20  through a converter  18  of RS232C or RS485.  
      In the camera link system  10  shown in  FIG. 1 , the four camera devices  12  send video signals to the four-screen unit  14 . The four-screen unit  14  displays images from the four camera devices  12  on the master monitor  16 . As shown in the drawing, the screen of the master monitor  16  is split into four areas, and four camera images are displayed at the same time.  
      Moreover, the personal computer  20  sends control data that instructs camera operations to the four camera devices  12 . The four camera devices  12  are operated in accordance with the control data from the personal computer  20 . The control data is sent in the form of command strings to instruct various operations. The command string also includes a command of camera rotation.  
      As for the command of the rotation instruction, the personal computer  20  selects a master camera from the four camera devices  12 . Then, a command indicating master camera direction information is sent. The master camera direction information is information that indicates a shooting direction of the master camera. The master camera direction information may be the absolute direction of the master camera. The master camera direction information may also be information about the directional variation (rotation angle) such as which direction is oriented at what degrees.  
      To the command of the master camera direction information, an address of the master camera selected from the four camera devices  12  is added. The command is then sent to the master camera. The master camera receives the master camera direction information, and is rotated in accordance with the master camera direction information.  
      Moreover, in the embodiment, the three remaining slave cameras also receive the command of the master camera direction information. A slave camera transforms the master camera direction information to slave camera direction information. The slave camera direction information is the direction of the camera to follow the master camera as the slave camera. More specifically, the slave camera direction information is the direction of that camera to turn to the same subject as the master camera shoots. Similarly to the master camera direction, the slave camera direction may be the absolute direction of the camera, or information about the directional variation (rotation angle) such as which direction is oriented at what degrees. The slave camera is rotated in accordance with the transformed slave camera direction information.  
      In this manner, in the embodiment, a single camera device  12  functions as a master camera, and the remaining camera devices  12  function as slave cameras. In the embodiment, the same camera device  12  is configured to also function as a master camera and a slave camera, as described below.  
       FIG. 2  depicts a block diagram illustrating the configuration of the camera device  12 . The camera device  12  has a control module  30 , an imaging module  32 , a rotating mechanism  34 , a video output module  36 , and a communication module  38 . The control module  30  is configured of a computer to control the entire camera device  12 . The control module  30  may be configured of multiple computers, for example, a computer for imaging or image-pickup control and a computer for rotation control.  
      The imaging module  32  including a lens and an imaging element such as CCD generates a video signal, and supplies it to the control module  30 . In the control module  30 , an imaging control module  40  processes the video signal. Then, the imaging control module  40  controls the video output module  36 , and sends the video signal to the four-screen unit  14 .  
      The rotating mechanism  34  has a pan mechanism and a tilt mechanism, and the pan mechanism and the tilt mechanism have a pan motor and a tilt motor. The rotating mechanism  34  is controlled by the control module  30  to rotate the camera device  12  in the pan direction and the tilt direction.  
      The communication module  38  communicates with the personal computer  20 , receives control data, and supplies it to the control module  30 . As described above, as for camera rotation, the command of master camera direction information is received as control data. The master camera direction information is received even though the command address is that of the other camera.  
      As for camera rotation, the control module  30  has a master/slave determining module  42 , a master camera identifying module  44 , a direction information transforming module  46 , a position information table storing module  48 , and a rotation control module  50 .  
      The master/slave determining module  42  extracts the command address of the master camera direction information, and determines whether the camera itself is a master camera. When the command address is that of the camera, the camera itself is the master camera.  
      The master camera identifying module  44  identifies a master camera among the other cameras when the camera itself is not the master camera. In order to identify a master camera, the command address is checked and a camera indicated by the address is identified as the master camera.  
      The direction information transforming module  46  functions when the camera itself is not the master camera. The direction information transforming module  46  transforms master camera direction information to slave camera direction information based on relative position information about the camera and the master camera. As described above, slave camera direction information is the direction of the camera to follow the master camera as a slave camera. The relative position information about that camera and the master camera is stored in the position information table storing module  48 .  
       FIG. 3  depicts an exemplary position information table. The position information table is a table for relative position between the camera itself and each of the three other cameras. Here, in the embodiment, the height of all the cameras is the same, and the direction of the origin point of horizontal rotation is also set the same. In this case, relative position information is shown by the distance between both cameras.  
      The direction information transforming module  46  reads relative position information of the master camera identified by the master camera identifying module  44  out of three items of relative position information in the position information table. Then, the direction information transforming module  46  transforms the master camera direction information to slave camera direction information based on the relative position information.  
      Return to  FIG. 2 , the rotation control module  50  controls the rotating mechanism  34  to rotate the camera. When the camera is the master camera, the rotation control module  50  rotates the rotating mechanism  32  in accordance with the master camera direction information received from the personal computer  20 . When the camera is the slave camera, the rotation control module  50  operates in accordance with the slave camera direction information transformed by the direction information transforming module  46 .  
       FIGS. 4 and 5  depict exemplary transformation equations from master camera direction information to slave camera direction information. In the drawings, for easy understandings for computation equations, the drawings are turned upside down. In the example shown in  FIG. 4 , as described above, the height of cameras is the same and the direction of the origin point of horizontal rotation is also the same. Since such the arrangement is adapted, projection in a two-dimensional space allows transformation of the master camera direction information to slave camera direction information.  
      In  FIGS. 4 and 5 , the master camera direction is expressed by the master camera tilt angle θt and the master camera pan angle θp. Furthermore, the slave camera direction is expressed by the slave camera tilt angle γt and the slave camera pan angle γp. Besides, the master camera focus Dm is a distance between a master camera and a subject. The slave camera focus Ds is a distance between a slave camera and a subject. Furthermore, the camera distance Dc is a distance between a master camera and a slave camera. The camera distance Dc is equivalent to relative position information. The camera distance Dc is 5 m, for example.  
      Moreover, in  FIGS. 4 and 5 , the point H is the intersection point of the normal from the subject to a horizontal plane and the horizontal plane where the master camera and the slave camera are placed. Then, the triangle A has vertices of the master camera, the subject and the point H. The triangle B has vertices of the master camera, the slave camera and the point H. The triangle C has vertices of the slave camera, the subject and the point H. The triangle B is a projection of a triangle formed of the master camera, the slave camera and the subject toward a horizontal plane.  
       FIG. 5  is a diagram that these triangles are seen from the front. In the drawing, y is a distance between the subject to the point H. x is a distance between the master camera to the point H. z is a distance between the slave camera to the point H. x, y, and z are expressed by the following equations with the master camera tilt angle θt, the master camera pan angle θp, the master camera focus Dm, and the camera distance Dc.
   x =cos(π÷180×θ t )× Dm     y =sin(π÷180×θ t )× Dm     z =( x   2   +Dc   2 −2× x×Dc× cos(π÷180×θ p )) 0.5   
      Then, the slave camera pan angle γp is expressed by the following equations with x, z and the camera distance Dc.  
      “In the case where the tilt angle is an angle of 90 degrees or below and the pan angle is an angle of 180 degrees or below”:
 
γ p= 180−(( a  cos(( Dc   2   +z   2   −x   2 )÷(2× Dc×z )))÷(π÷180))
 
      “In the case where the tilt angle is an angle of 90 degrees or below and the pan angle is an angle above 180 degrees”:
 
γ p= 180+(( a  cos(( Dc   2   +z   2   −x   2 )÷(2× Dc×z )))÷(π÷180))
 
      “In the case where the tilt angle is an angle above 90 degrees and the pan angle is an angle of 180 degrees or below”:
 
γ p =( a  cos(( Dc   2   +z   2   −x   2 )÷(2× Dc×z )))÷(π÷180)
 
      “In the case where the tilt angle is an angle above 90 degrees and the pan angle is an angle above 180 degrees”:
 
γ p =360−(( a  cos(( Dc   2   +z   2   −x   2 )÷(2× Dc×z )))÷(π÷180))
 
      In addition, the slave camera focus Ds and the slave camera tilt angle γt are expressed by the following equations with y and z.
 
 Ds =( z   2   +y   2 −2× z×y× cos(π÷180×90)) 0.5 
 
      “In the case where the tilt angle is an angle of 90 degrees or below”:
 
γ t =( a  cos(( z   2   +Ds   2   −y   2 )÷(2× z×Ds )))÷(π÷180)
 
      “In the case where the tilt angle is an angle above 90 degrees”:
 
γ t =180 −(( a  cos(( z   2   +Ds   2   −y   2 )÷(2× z×Ds )))÷(π÷180)
 
      By doing the transformation process in accordance with the equations, the master camera directions (θp, θt) are transformed to the slave camera directions (γp, γt) based on the relative position (the camera distance Dc) between the master camera and the slave camera. Besides, the slave ZOOM range is determined from Dc with reference to the stored table.  
      Next, the operation of the camera link system of the embodiment will be described. In the personal computer  20 , one of the four camera devices  12  is selected as a master camera in accordance with user&#39;s input operation. Furthermore, in the personal computer  20 , master camera direction information is generated in accordance with user&#39;s input operation. As described above, the master camera direction information is information indicating the shooting direction of the master camera. Then, the personal computer  20  sends a command corresponding to the master camera direction information. To the command, an address of the selected master camera is added.  
      The command of the master camera direction information is sent to the four camera devices  12  through the converter. The individual cameras apparatus  12  receive the command to operate as below.  
       FIG. 6  depicts the operation of a camera device  12  when it receives the command. In the control module  30  of the camera device  12 , the master/slave determining module  42  extracts the command address of the master camera direction information (S 10 ), and determines whether the command is destined for the camera itself (S 12 ). When the command is destined for the camera (YES at S 12 ), the camera itself is a master camera. In this case, the rotation control module  50  controls the rotating mechanism  34  in accordance with the master camera direction information indicated by the command to rotate the camera (S 20 ). Proper coordinate transformation or the like may be conducted for this control. Then, the camera position after rotated is notified to the personal computer  20  through the communication module  38  (S 22 ).  
      On the other hand, when the command is not destined for the camera itself (No at S 12 ), the camera is not the master camera. In this case, the master camera identifying module  44  identifies the master camera among the other cameras (S 14 ). The master camera identifying module  44  identifies one of the other cameras indicated by the command address as the master camera.  
      When the master camera is identified, the direction information transforming module  46  refers to the position information table storing module  48  to read relative position information about the master camera and the camera (S 16 ). Then, the direction information transforming module  46  transforms the master camera direction information to slave camera direction information based on the relative position information (S 18 ). As described above, the slave camera direction is the camera direction (the shooting direction) for the camera to follow the master camera as the slave camera.  
      When the master camera direction information is transformed to the slave camera direction information, the rotation control module  50  controls the rotating mechanism  34  in accordance with the slave camera direction information to rotate the camera (S 20 ). Subsequently, the position of the camera after rotated is notified to the personal computer  20  through the communication module  38  (S 22 ).  
      When the individual camera devices  12  are operated in accordance with the steps shown in  FIG. 6 , the entire camera link system  10  is operated as below. The four camera devices  12  receive the master camera direction information from the personal computer  20  regardless of whether it is the master camera or not. The master camera among the four camera devices  12  is rotated in accordance with the master camera direction information. The three remaining camera devices  12  transform the master camera direction information to slave camera direction and are rotated in accordance with the slave camera direction information. In this manner, a single camera device  12  is rotated as a master camera, and the three remaining camera devices  12  follow the master camera as slave cameras. At this time, since all the cameras simultaneously receive and process the master camera direction information, the master camera and the slave cameras are operated almost at the same time.  
      In addition, although it is not discussed in the description above, the camera device  12  performs a travel limitation process as below when it functions as a slave camera. The shootable range is varied in the slave camera and the master camera. Therefore, when master camera direction is transformed to slave camera direction, the slave camera direction is sometimes deviated from the shooting range of the slave camera. When the slave camera direction is deviated from the shooting range, the slave camera performs the travel limitation process. In this process, for example, the slave camera stays at the same place, not following the master camera. Furthermore, for example, the slave camera may be rotated to the end of the shooting range to follow the master camera within the possible range.  
      Moreover, the tracking area may be limited on the camera side. In the camera arrangement situation that computing error is large, a calibration command may be sent at every time when a proper time period elapses. For example, a command that instructs moving to a home position is sent to the master camera. The slave cameras may stop following the master camera to return in a normal monitor state when this command is sent.  
      Besides, the camera device  12  may be configured to operate automatically in a predetermined time period. The camera device  12  may operate automatically in accordance with the operation instruction by an operator. During the automatic operation, the link operation needs to be limited in order to separately operate the individual cameras. In regard to this point, in the embodiment, the link operation is conducted at the time when a command is sent from the controller (the personal computer), and thus the automatic operation can be conducted easily.  
      Furthermore, in the description, the communication form of RS232C or the like is used. However, the communication form is not necessarily defined. For example, IPv6 may be adapted. In IPv6, multicasting (broadcast communication) is supported. Therefore, the master camera direction information can be distributed to multiple camera devices easily.  
      Moreover, when the embodiment is applied to network cameras, an operation instruction including a master camera identification number and a master camera direction (position coordinates) is sent by using a specific network port. This information is sent to a master camera and multiple slave cameras at the same time. In these data transfer, the transmission forms of the master camera and the slave cameras may be the same or different.  
      Besides, in network cameras, the camera link system may be configured such that the operation by an authorized operator is given preference over automatic operations. Furthermore, a system configurator being an administrator can give preference to automatic operations above, and the setting of this selection can be done on the camera side. Thus, operations can be set in fine steps in each area, that is, at each camera, and flexibility can be provided to access from a global network.  
      Furthermore, in the embodiment, as described with  FIG. 6 , the individual camera devices  12  send information about the camera direction to the personal computer  20 . The camera direction may be sent in a form of coordinate data. In the personal computer  20 , the camera directions are shown on a map such as a control geographical data map or the like (a map of monitor places (for example, a drawing of the inside of a room)). The orientation of the camera horizontal direction (the pan direction) is indicated by arrows, for example. An angle of view is expressed in a fan shape. The orientation of the vertical direction (the tilt direction), the power of lenses, zooming ratio, and the focus distance are expressed in text. These items of information may be shown for a predetermined time period when movement is updated. Moreover, these items of information may be shown in the master monitor  16 .  
      As described above, the camera link system  10  of the embodiment has been described. According to the embodiment, master camera direction information is provided to the master camera and the slave camera simultaneously. The master camera is rotated in accordance with the master camera direction information. The slave camera transforms the master camera direction information to slave camera direction information based on relative position information, and is rotated in accordance with the slave camera direction information. In this manner, master camera direction information is sent to not only the master camera but also the slave camera, and the operations of the master camera and the slave camera are simultaneously conducted. Therefore, a time lag between the operations of the master camera and the slave camera is reduced, and the slave camera quickly follows the master camera.  
      Moreover, in the embodiment, the same camera device  12  is configured to also function as a master camera and a slave camera. Thus, when a master camera is properly selected from multiple camera devices  12 , the remaining camera devices  12  follow the master camera. An operator can manipulate a given camera device  12  as a master camera, and therefore the convenience of operators can be improved.  
      Besides, a camera device  12  of the embodiment determines whether the camera itself is a master camera, it identifies a master camera among the other multiple cameras when the camera itself is not the master camera, and acquires relative position information about the identified master camera and the camera to determine slave camera direction information from relative position information. In this manner, a preferable link function can be obtained even though the number of cameras is large.  
      In addition, the camera device  12  of the embodiment extracts master camera direction information regardless of whether the destination is for the camera itself or the other camera, and conducts determination about the master camera based on the destination of the extracted master camera information. When the destination is for one of the other cameras, this camera indicated by the destination is the master camera. In this manner, a simple configuration in which information destined for one of the other cameras is extracted by communications can obtain a preferable link function of the embodiment.  
      Persons of ordinary skill in the art will realize that many modifications and variations of the above embodiments may be made without departing from the novel and advantageous features of the present invention. Accordingly, all such modifications and variations are intended to be included within the scope of the appended claims. The specification and examples are only exemplary. The following claims define the true scope and spirit of the invention.