Abstract:
A pan and tilt apparatus usable with a camera, and more particularly, a driving mechanism to linearly maintain a tilting angle of the camera relative to a rotating angle of a tilt motor. The pan and tilt apparatus includes a tilting driving mechanism having the tilt motor to induce tilting motion of the camera, a panning driving mechanism to induce panning motion of the camera, and a link device to transmit a driving force of the tilt motor to the camera, such that the tilting angle of the camera varies linearly relative to the rotating angle of the tilt motor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of Korean Patent Application No. 2004-65188, filed on Aug. 18, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present general inventive concept relates to a pan and tilt apparatus usable with a camera, and more particularly, to a driving mechanism to cause panning and tilting motions of a camera. 
   2. Description of the Related Art 
   A pan and tilt apparatus usable with a camera is an apparatus to rotate the camera mounted therein, about both a vertical and a horizontal axes in order to expand a filming region of the camera. The pan and tilt apparatus has two basic motions including a tilting motion (i.e., rotation in a vertical direction) and a panning motion (i.e., rotation in a horizontal direction). 
   As an example of a conventional camera panning and tilting apparatus, Korean Utility Registration No. 273675 discloses a pan and tilt camera comprising a signal input unit having various signal input means for complete scanning of a location of interest, a housing containing a control unit which processes input signals of the signal input unit and a pan motor which rotates upon receiving commands from the control unit, a rotating plate provided with a tilt motor and a monitoring camera using a bracket, and a horizontal rotating device coupled to the housing by means of a shaft and adapted to cause the rotating plate, in a fixed position, to undergo a horizontal rotation under operation of the pan motor. 
   The above described pan and tilt camera, however, experiences a problem in that the pan motor unnecessarily rotates the tilt motor, in addition to the camera, because of an excessive load applied thereto. 
   In an attempt to solve the problem described above, Korean Patent Publication No. 2002-63676 discloses a pan and tilt driving apparatus usable with a camera basically comprising a camera mounting structure, an independent-motion transmission unit for allowing panning and tilting motions of the camera mounting structure to be independently performed relative to each other, a panning motion performing unit usable with the camera mounting structure, a tilting motion performing unit usable with the camera mounting structure, and a fixed plate which supports both the panning motion and tilting motion performing units. 
   The panning motion performing unit includes panning driving means (e.g., an electric motor), a driving gear driven by the pan driving means, and a driven gear that engages and is rotated by the driving gear and is coupled to one end of a fixed frame. The tilting motion performing unit includes tilting driving means (e.g., an electric motor), a pinion rotated by the tilting driving means, and a rack that engages and is vertically moved by the pinion to vertically move the camera mounting structure. 
   The tilting motion in the above described pan and tilt driving apparatus is achieved at a rear end of the camera, which is hingeably coupled to the fixed frame, and rotates about a hinge axis thereof while being vertically shaken when the rack is vertically moved along the pinion rotated by the tilting driving means. With such a structure, however, since a tilting angle of the camera varies in a non-linear pattern relative to a rotating angle of the motor, an algorithm for calculating the relationship between the tilting angle of the camera and the rotating angle of the motor is needed in order to control the tilting angle of the camera to a desired value. This calculation is complex and results in difficult control operations to be performed by a control unit. 
   SUMMARY OF THE INVENTION 
   The present general inventive concept provides a pan and tilt apparatus usable with a camera, which is easily drivable by virtue of a reduced load on a pan motor thereof. 
   The present general inventive concept also provides a pan and tilt apparatus usable with a camera, which is easily controllable by enabling a tilting angle of the camera to vary linearly relative to a rotating angle of a tilt motor that causes a tilting motion. 
   Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
   The foregoing and/or other aspects and advantages of the present general inventive concept are achieved by providing a pan and tilt apparatus usable with a camera comprising a tilting driving mechanism having a tilt motor to induce a tilting motion of the camera, a panning driving mechanism to induce a panning motion of the camera, and a link device to transmit a driving force of the tilt motor to the camera such that a tilting angle of the camera linearly varies relative to a rotating angle of the tilt motor. 
   The tilting driving mechanism may further include a decoupling unit to enable the tilting and panning motions of the camera to be independently performed. 
   The panning driving mechanism may include a main shaft rotatable about a center axis thereof to perform the panning motion, and a pan motor to rotate the main shaft. 
   The panning driving mechanism may further include a belt transmission device to transmit a driving force of the pan motor to the main shaft. 
   The pan and tilt apparatus may further comprise a pan bracket fixed to the main shaft to integrally rotate with the main shaft, and a tilt bracket hingeably coupled to the pan bracket having the camera mounted thereon to perform the tilting motion. 
   The decoupling unit may include a linear guide that vertically moves along the main shaft, and a rotor that vertically moves along with the linear guide and is installed to rotate on the linear guide about the main shaft. 
   The decoupling unit may further include a bearing interposed between the linear guide and the rotor. 
   The link device may include a first tilt link having a rotatable first end at a fixed-position to be rotated by the driving force of the tilt motor, a second tilt link having a first end hingeably coupled to a second free end of the first tilt link and a second end hingeably coupled to the linear guide to vertically move the decoupling unit, and a third tilt link having a first end hingeably coupled to the rotor and a second end hingeably coupled to the tilt bracket to vertically rotate the tilt bracket according to vertical movement of the decoupling unit, thereby causing the tilting motion of the camera. 
   A rotating angle of the first tilt link may coincide with the tilting angle of the camera. 
   A first distance, between a hingeable coupling center of the tilt and pan brackets and a hingeable coupling center of the tilt bracket and the third tilt link, may be equal to a second distance between a rotation center of the first tilt link and a hingeable coupling center of the first and second tilt links, and a first vertical distance between the hingeable coupling center of the tilt and pan brackets and the rotation center of the first tilt link, a second vertical distance between the hingeable coupling center of the tilt bracket and the third tilt link and the hingeable coupling center of the first and second tilt links, and a third vertical distance between a hingeable coupling center of the rotor and the third tilt link and a hingeable coupling center of the linear guide and the second tilt link, may coincide with one another. 
   The tilting driving mechanism may further include a transmission shaft connected to a rotating center of the first tilt link to transmit the driving force of the tilt motor to the first tilt link, and gears to transmit the driving force of the tilt motor to the transmission shaft. 
   The transmission shaft and a driving shaft of the tilt motor may intersect each other, and the gears may be bevel gears. 
   The foregoing and/or other aspects and advantages of the present general inventive concept are also achieved by providing a pan and tilt apparatus usable with a camera, comprising a camera to film an object, brackets to support the camera in a vertically rotatable manner to enable a tilting motion, a main shaft rotatable about a center axis thereof to enable a panning motion, a lifting unit vertically movable on the main shaft, and a link device linked to the brackets and the lifting unit to cause the tilting motion. 
   The lifting unit may include a linear guide that vertically moves along the main shaft, and a rotor that vertically moves along with the linear guide and being installed to rotate on the linear guide about the main shaft. 
   The brackets may include a pan bracket fixed to the main shaft to integrally rotate with the main shaft, and a tilt bracket hingeably coupled to the pan bracket and having the camera mounted thereon to perform the tilting motion. 
   The link device may include a first tilt link having a rotatable first end at a fixed-position to rotate, a second tilt link having a first end hingeably coupled to a second free end of the first tilt link and a second end hingeably coupled to the linear guide to vertically move the lifting unit, and a third tilt link having a first end hingeably coupled to the rotor and a second end hingeably coupled to the tilt bracket to vertically rotate the tilt bracket according to vertical movement of the lifting unit, thereby causing the tilting motion of the camera. 
   The pan and tilt apparatus may further comprise a tilt motor to drive the link device, and a tilting angle of the camera may vary linearly relative to a rotating angle of the tilt motor. 
   The pan and tilt apparatus may further comprise a pan motor to rotate the main shaft, and a transmission device to transmit a driving force of the pan motor to the main shaft. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages of the general inventive concept will become apparent and more easily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a perspective view illustrating a pan and tilt apparatus usable with a camera in accordance with an embodiment of the present general inventive concept; 
       FIG. 2  is an exploded perspective view of the pan and tilt apparatus of  FIG. 1 ; 
       FIG. 3  is a front view of the pan and tilt apparatus of  FIG. 1 ; 
       FIG. 4  is a cross sectional view of the pan and tilt apparatus of  FIG. 1 ; 
       FIG. 5A  is a side view of the pan and tilt apparatus of  FIG. 1 ; 
       FIG. 5B  is an enlarged view illustrating a moving portion of the pan and tilt apparatus of  FIG. 5A ; 
       FIG. 6A  is a side view illustrating an upward tilting motion of the pan and tilt apparatus of  FIG. 1 ; 
       FIG. 6B  is an enlarged view illustrating the moving portion of the pan and tilt apparatus of  FIG. 6A ; 
       FIG. 7A  is a side view illustrating a downward tilting motion of the pan and tilt apparatus of  FIG. 1 ; 
       FIG. 7B  is an enlarged view illustrating the moving portion of the pan and tilt apparatus of  FIG. 7A ; and 
       FIG. 8  is a perspective view illustrating a panning motion of the pan and tilt apparatus of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present general inventive concept by referring to the figures. 
   As described above, a pan and tilt apparatus usable with a camera is an apparatus adapted to rotate in both vertical and horizontal directions in order to expand a filming region of the camera. Here, the horizontal rotation of the camera is referred as a “panning motion” creating a panoramic effect, and the vertical rotation of the camera is referred as a “tilting motion.” 
     FIG. 1  is a perspective view illustrating a pan and tilt apparatus usable with a camera in accordance with an embodiment of the present general inventive concept.  FIGS. 2 to 4  are an exploded perspective view, a front view, and a cross sectional view of the pan and tilt apparatus of  FIG. 1 , respectively. Now, the general structure of the pan and tilt apparatus usable with a camera in accordance with the present general inventive concept will be described with reference to  FIGS. 2 to 4 . 
   The pan and tilt apparatus in accordance with the present general inventive concept comprises a camera  10  to film a desired object, a tilting driving mechanism to cause a tilting motion of the camera  10 , a panning driving mechanism to cause a panning motion of the camera  10 , a pair of brackets  21  and  22  on which the camera  10  is disposed, and a base  90  to support the panning driving and tilting driving mechanisms. 
   The brackets  21  and  22 , on which the camera  10  is disposed, include a tilt bracket  21  and a pan bracket  22 , which are hingeably coupled to each other to rotate in a vertical direction. The body of the camera  10  is fixed at an upper surface of the tilt bracket  21 . The tilt bracket  21  has a pair of first hingeable coupling portions  21   a  and a single second hingeable coupling portion  21   b , which extend downward from opposite lateral sides of a lower surface of the tilt bracket  21 . The first hingeable coupling portions  21   a  are formed with respective protrusions to be hingeably coupled to the pan bracket  22 . The second hingeable coupling portion  21   b , spaced apart from one of the first hingeable coupling portions  21   a  by a predetermined distance, is hingeably coupled to the tilting driving mechanism. A pair of third hingeable coupling portions  22   a  are provided on opposite lateral sides of an upper surface of the pan bracket  22  such that the third hingeable coupling portions  22   a  are hingeably coupled to the first hingeable coupling portions  21   a  of the tilt bracket  21 , respectively. 
   A main shaft  30  is centrally installed on the base  90  so that the main shaft  30  is rotatable about its center axis. The main shaft  30  supports the brackets  21  and  22 . An upper end of the main shaft  30  is fixed to a lower surface of the pan bracket  22 , such that, upon rotation, the main shaft  30  integrally rotates the brackets  21  and  22  and the camera  10 , thereby causing the panning motion. A lower end of the main shaft  30  is surrounded and supported by a main shaft supporting ring  31  provided at the center of the base  90 . A bearing  32  (see  FIGS. 2 and 3 ) is interposed between the main shaft  30  and the main shaft supporting ring  31  to provide smooth rotation of the main shaft  30 . A sensor  34  to detect a rotating angle of the main shaft  30  may be provided at a certain position along the periphery of the main shaft  30 . 
   A pan motor  40  to generate a driving force required to cause the panning motion may be provided on a side of the base  90 . The pan motor  40  is installed on a pan motor supporting structure  41  fixed on the base  90  so that a driving shaft of the pan motor  40  occupies a lower portion of the pan motor  40 . A belt transmission device is provided to transmit the driving force of the pan motor  40  to the main shaft  30 . The belt transmission device comprises a driving pulley  42  provided at the driving shaft of the pan motor  40 , a driven pulley  33  provided at a lower portion of the main shaft  30 , and a belt  43  wound around both the driving pulley  42  and the driven pulley  33 . 
   The pan motor  40 , belt transmission device, and the main shaft  30  constitute the panning driving mechanism to cause the panning motion of the camera  10 . 
   A tilt motor  50  to generate a driving force required to cause the tilting motion may be provided at an opposite side of the base  90  relative to the pan motor  40 . The tilt motor  50  is installed in a tilt motor supporting structure  51  fixed on the base  90  so that a driving shaft of the tilt motor  50  occupies an upper portion of the tilt motor  50 . A transmission shaft  52  to transmit the driving force of the tilt motor  50  to the camera  10  is provided on the tilt motor  50 . The transmission shaft  52  extends perpendicular to a direction along which the driving shaft of the tilt motor  50  extends so that one end thereof faces the main shaft  30 . A transmission shaft supporting structure  53  is coupled to the tilt motor supporting structure  51  to rotatably support opposite end portions of the transmission shaft  52 . A driving gear  54  (see  FIG. 3 ) to transmit the driving force of the tilt motor  50  to the transmission shaft  52  is fixed at the driving shaft of the tilt motor  50 . Additionally, a driven gear  55  that engages the driving gear  54  is fixed at the transmission shaft  52  (see  FIG. 3 ). The driving gear  54  and the driven gear  55  may be bevel gears to transmit the driving force between two intersecting axes. 
   The transmission shaft  52  is connected with a link device to cause the tilting motion of the camera  10 , and a decoupling unit  70  is provided at the middle of the link device. The decoupling unit  70  enables the panning motion and the tilting motion of the camera  10  to be independently conducted. 
   The decoupling unit  70  comprises a linear guide  71 , which vertically moves along the main shaft  30  and a rotor  72 , which vertically moves along with the linear guide  71 . The rotor  72  is also rotatable relative to an axial direction of the main shaft  30 . The linear guide  71  takes a multi-stepped form to have a downwardly increasing outer diameter, and an upper half portion of the linear guide  71  is inserted into the center of the rotor  72 . The rotor  72  rests on the linear guide  71  to provide substantial resistance to relative vertical movement between the rotor  72  and the linear guide  71 . That is, the rotor  72  is only rotatable around the linear guide  71 . A bearing  73  to make rotation of the rotor  72  smooth is interposed between the rotor  72  and the linear guide  70 . 
   The link device comprises first, second, and third tilt links  61 ,  62 , and  63 , respectively. The first tilt link  61  is fixed at one end thereof to the transmission shaft  52  so that it is rotated by the transmission shaft  52 . The second tilt link  62  is hingeably coupled at one end thereof to an opposite free end of the first tilt link  61 , and is also hingeably coupled at an opposite end thereof to an outer peripheral surface of a lower half portion of the linear guide  71 . The third tilt link  63  is hingeably coupled at one end thereof to an outer peripheral surface of the rotor  72 , and is also hingeably coupled at an opposite end thereof to the second hingeable coupling portion  21   b  of the tilt bracket  21 . 
   The tilt motor  50 , the transmission shaft  52 , the link device, and the decoupling unit  70  constitute the tilting driving mechanism. 
   Now, the operation of the pan and tilt apparatus usable with the camera  10  as stated above will be described. Since the pan and tilt apparatus in accordance with the above described embodiment is designed to perform the tilting motion independently of the panning motion, the tilting motion will be described first. 
     FIGS. 5A and 5B  are side views of the pan, and tilt apparatus, in a state wherein the camera  10  faces a front side of the pan and tilt apparatus, and  FIGS. 6A and 6B  are side views illustrating the tilting motion of the pan and tilt apparatus of  FIG. 1 . 
   As the tilt motor  50  is driven, the driving force of the tilt motor  50  is transmitted to the transmission shaft  52  via the driving gear  54  provided at the end of the driving shaft of the tilt motor  50  to rotate the transmission shaft  52 . Then, the first tilt link  61 , fixed to the end of the transmission shaft  52 , is rotated about the transmission shaft  52  by a rotating force of the transmission shaft  52  such that the first tilt link  61  pushes down the second tilt link  62  connected to the opposite end thereof, as illustrated in  FIG. 6A . The opposite end of the second tilt link  62  also pushes down the linear guide  71 , which moves linearly and vertically along the main shaft  30 . Since the rotor  72 , which is coupled to the linear guide  71 , is restricted to provide substantial resistance to relative vertical movement between the rotor  72  and the linear guide  71 , the rotor  72  moves downward along with the linear guide  71 . As a result, the third tilt link  63 , which is connected at one end thereof to the rotor  72  and at the opposite end thereof to the second hingeable coupling portion  21   b  of the tilt bracket  21  pulls down the second hingeable coupling portion  21   b  of the tilt bracket  21  when the third tilt link  63  moves downward following the rotor  72 , thereby causing the tilt bracket  21  to rotate upward about the first hingeable coupling portions  21   a . In this manner, the camera  10  is also rotated upward, resulting in the tilting motion. 
   Hereinafter, the relationship between a rotating angle of the tilt motor  50  and a tilting angle of the camera  10  will be described. 
   In the pan and tilt apparatus usable with the camera  10  according to the present general inventive concept, the driving force of the tilt motor  50  is transmitted to the transmission shaft  52  via the bevel gears  54  and  55 , and the first tilt link  61 , connected at one end thereof to the transmission shaft  52 , rotates in a range of a rotating angle of the transmission shaft  52 . If a gear ratio of the driving gear  54  to the driven gear  55  is 1:1, the rotating angle of the tilt motor  50  coincides with the rotating angle of the transmission shaft  52 , and consequently coincides with a rotating angle (θa) of the first tilt link  61 . 
   The tilting angle (θc) of the camera  10  is equal to a rotating angle (θb) of the tilt bracket  21  on which the camera  10  is fixed. 
   Referring to  FIGS. 6A and 6B , reference alphanumeric character m 1  indicates a distance between a hingeable coupling center (A) of the tilt and pan brackets  21  and  22  and a hingeable coupling center (C) of the tilt bracket  21  and the third tilt link  63 . Reference alphanumeric character m 2  indicates a distance between a rotation center (B) of the first tilt link  61  and a hingeable coupling center (D) of the first and second tilt links  61  and  62 . Here, the distance (m 1 ) is equal to the distance (m 2 ). In addition, reference alphanumeric character I 1  indicates a vertical distance between the hingeable coupling center (A) of the tilt and pan brackets  21  and  22  and the rotation center (B) of the first tilt link  61 , reference alphanumeric character I 2  indicates a vertical distance between the hingeable coupling center (C) of the tilt bracket  21  and the third tilt link  63  and the hingeable coupling center (D) of the first and second tilt links  61  and  62 , and reference alphanumeric character I 3  indicates a vertical distance between a hingeable coupling center (E) of the rotor  72  and the third tilt link  63  and a hingeable coupling center (F) of the linear guide  71  and the second tilt link  62 . Here, the respective vertical distances refer to a height difference on the basis of the base  90 , and are equal to one another. As stated above, the pan and tilt apparatus usable with the camera  10  is configured to fulfill relational expressions of m 1 =m 2  and I 1 =I 2 =I 3 . 
   According to the geometrical relationship described above, a rectangle (ABCD) forms a parallelogram, and the rotating angle (θb) of the tilt bracket  21  is equal to the rotating angle (θa) of the first tilt link  61 . Therefore, when the gear ratio of the driving gear  54  to the driven gear  55  is 1:1, the tilting angle (θc) of the camera  10  coincides with the rotating angle of the tilt motor  50 . Further, even if the gear ratio of the driving gear  54  to the driven gear  55  is not 1:1, the tilting angle (θc) of the camera  10  is equal to the rotating angle (θa) of the first tilt link  61 , and the rotating angle (θa) of the first tilt link  61  varies linearly with respect to the rotating angle of the tilt motor  50 . As a result, the tilting angle (θc) of the camera  10  maintains a linear relationship with the rotating angle of the tilt motor  50 . 
     FIGS. 7A and 7B  are views illustrating another tilting motion of the camera  10 , when the tilt motor  50  rotates in a direction opposite to the direction illustrated in  FIGS. 6A and 6B . By rotation of the tilt motor  50 , the first tilt link  61  pulls up the second tilt link  62 , and thus the third tilt link  63 , connected to the rotor  72 , pushes up the second hingeable coupling portion  21   b  of the tilt bracket  21  as the linear guide  71  and the rotor  72  move upward together, thereby tilting the camera  10  downward. In the same manner as in  FIGS. 6A and 6B , the tilting angle (θc) of the camera  10 , the rotating angle (θb) of the tilt bracket  21 , and the rotating angle (θa) of the first tilt link  61  coincide with one another. The rotating angle (θa) of the first tilt link  61  is equal to the rotating angle of the transmission shaft  52 , and the rotating angle of the transmission shaft  52  maintains the linear relationship described above with the rotating angle of the tilt motor  50 . As a result, the tilting angle (θc) of the camera  10  is in the linear relationship with the rotating angle of the tilt motor  50 . 
   Now, the panning motion of the pan and tilt apparatus usable with the camera  10  according to the above embodiment will be described. 
     FIG. 8  is a perspective view illustrating the panning motion of the pan and tilt apparatus, in a state wherein the camera  10  is tilted upward. In  FIG. 8 , basic components used in the panning motion are represented by solid lines, and other components are represented by dotted lines. 
   As the pan motor  40  is driven, the driving pulley  42  installed at the driving shaft of the pan motor  40  rotates, and the rotating force of the driving pulley  42  is transmitted to the driven pulley  33  provided at the main shaft  30  via the belt  43 . Thereby, the main shaft  30  is rotated, causing the pan bracket  22 , the tilt bracket  21  and the camera  10  connected thereto to rotate altogether. In this manner, the panning motion of the camera  10  is achieved. 
   Since the third tilt link  63  is connected to the second hingeable coupling portion  21   b  of the tilt bracket  21 , the third tilt link  63  rotates along with the tilt bracket  21 , and thus the rotor  72 , connected to the third tilt link  63 , also rotates. Even if the rotor  72  rotates, the linear guide  71  does not correspondingly rotate since the rotor  72  is coupled to the linear guide  71  to rotate independently of the linear guide  71 . In this case, since the third tilt link  63  only rotates in a horizontal direction, rather than additionally moving in a vertical direction, the tilting angle of the camera  10  is maintained during the panning motion. Therefore, the panning motion of the camera  10  is achieved independently of the tilting motion. 
   As is apparent from the above description, a pan and tilt apparatus usable with a camera according to the present general inventive concept is designed in such a fashion that panning and tilting motions of the camera can be independently performed, and that a tilt motor is fixed on a base independently of the camera. This has the effect of minimizing load on a pan motor, and thus enables effective driving of the pan motor. 
   Further, according to the present general inventive concept, since a tilting angle of the camera maintains a linear relationship with a rotating angle of the tilt motor, the rotating angle of the tilt motor can be directly utilized to control the tilting angle of the camera, thereby resulting in easy control thereof. 
   Although an embodiment of the present general inventive concept has been shown and described, it should be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the claims and their equivalents.