Abstract:
Systems for videoconferencing are designed for where people are seated around a video conferencing system. The systems include a camera so the far site can see the local participants and the systems include displays that show the far site. The displays are properly aligned with the cameras so that when people at the far site view the displayed images of the near site, it looks like they have eye contact with the near site. Obtaining the alignments of the camera and the displays to provide this apparent eye contact result requires meeting a series of different constraints relating to the various sizes and angles of the components and the locations of the participants.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/872,817, entitled “Method and Design for Optimum Camera and Display Alignment of Center of the Room Video Conferencing Systems,” filed Oct. 1, 2015, which is hereby incorporated by reference. 
         [0002]    This is application is related to U.S. patent application Ser. No. 29/539,282, entitled “Videoconferencing Unit,” filed Sep. 11, 2015, which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to videoconferencing units. 
         [0005]    2. Description of the Related Art 
         [0006]    Today&#39;s video conferencing systems do not allow for a conversation-like video conference where people are seated in a circle or around a system that is in the middle of the space or table. There are systems today that place a 360 degree camera in the center of a table and the far site is displayed on a wall at one end of the room. The participants are seated on three sides of the table and naturally face the wall display. This results in each participant facing the far site at a different angle, with most participants not facing the camera but instead having at least a portion of the side of their head being seen by the camera. Further, this portion varies with each participant so that it is clear that the participants are not looking at the camera but looking at the display on the wall. This results in a videoconference that is completely different from a normal conversation held in person, where the participants look at each other, and reduces the value of the videoconference. 
         [0007]    There have been attempts to address this problem by the use of “presence” systems. However, most presence systems are very expensive and very difficult to set up properly and require significant bandwidth for their communications. This has limited the use of “presence” systems to only the most demanding environments. 
       SUMMARY OF THE INVENTION 
       [0008]    According the embodiments of the present invention, systems for videoconferencing are designed where people are seated around a video conferencing system. The systems include a camera so the far site can see the local participants and the systems include displays that show the far site. The displays are properly aligned with the cameras and the local participants so that when people at the far site view the displayed images of the near site, it looks like they have eye contact with the near site. The reverse is also true if the far site has a similar system, so that both groups of participants can have a much more conversational videoconference without the expense and bandwidth of presence systems. 
         [0009]    The embodiments allow for participants to sit in a circle or in a geometry where participants see each other around a space and they are all seen by the far site equally well. This is done by placing a surround camera in the center of the space along with the displays that show the far site. When the near site participants look at the far site on the displays, the near site camera provides a near eye-to-eye view to the far site since the camera is placed appropriately with the image of the far site. 
         [0010]    Obtaining the alignments of the camera and the displays to provide this apparent eye contact result requires meeting a series of different constraints relating to the various sizes and angles of the components and the locations of the participants. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which: 
           [0012]      FIG. 1  is a diagram illustrating relationships of various variables relevant to developing an embodiment according to the present invention. 
           [0013]      FIG. 2  is a diagram illustrating relationships of various variables relevant to developing an embodiment according to the present invention. 
           [0014]      FIG. 3  is a perspective view of a first embodiment according to the present invention. 
           [0015]      FIG. 4A  is a side view of a second embodiment according to the present invention illustrating a location for the videoconferencing unit and a participant. 
           [0016]      FIG. 4B  is a side view of the first embodiment according to the present invention illustrating various locations of participants with respect to the videoconferencing unit. 
           [0017]      FIG. 5A  is a top view of the second embodiment according to the present invention illustrating a central location for the videoconferencing unit on an office table surrounded by chairs. 
           [0018]      FIG. 5B  is a top view of the first embodiment according to the present invention illustrating a central location for videoconferencing unit in a setting with love seats. 
           [0019]      FIG. 6  is a block diagram of an exemplary videoconferencing unit according to the present invention. 
           [0020]      FIG. 7  is a block diagram of interconnected videoconferencing units. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    Embodiments according to the present invention allow for participants to sit in a circle or in a geometry where participants see each other around a space and they are all seen by the far site equally well. This is done by placing a surround camera in the center of the space along with the displays that show the far site. When participants look at the far site, the near site camera provides near eye-to-eye view to the far site since the camera is placed as close as possible to the image of the far site. 
         [0022]    A number of variables are relevant to this description and many are shown graphically in  FIGS. 1 and 2 : 
         [0023]    Desired camera height for eye contact—H cam    
         [0024]    Display size width—D w    
         [0025]    Display size height—D h    
         [0026]    Vertical field of view (FOV) of the camera below horizontal axis-FOV −v    
         [0027]    Vertical field of view of the camera above horizontal axis—FOV +v    
         [0028]    Occlusion of the local participants from each other by the centrally located camera 
         [0029]    How far people sit from the camera 
         [0030]    Height of the 360° camera relative to top edge of the display so it does not see the top of the displays.—H disp    
         [0031]    For optimum eye contact with the far site, the camera needs to be positioned close to the display where the far site is shown. 
         [0032]    Display angle from vertical, participant&#39;s eye is perpendicular to the display—α disp    
         [0033]    The most important fact is the desired camera height H cam . This can be derived by placing the camera at about an average eye level of an average person. 
         [0034]    In practical embodiments, all of these factors come into play. With these factors in mind, it is then best to find the optimum camera height, display height and display tilt angle. Once these quantities are determined, the dimensions of an actual videoconferencing system can be determined. Because of the interrelationships, it is preferred to not allow a user to adjust these alignments so as to provide a “plug and play” experience. 
         [0035]    With reference to  FIGS. 1 and 2 , it is then necessary to determine H cam , H disp , and α disp , based on display size, eye contact and user experience considerations, and sitting arrangements. 
         [0036]    To simplify the problem, the following factors were selected to be “known quantities”. These are factors either determined through experiment or left with limited variation or choices due to practical considerations. 
         [0037]    Eye level—H eye    
         [0038]    This is the eye level of an average person in a sitting position. This is derived through experiment and statistics. It is best to err on the lower end of the eye level distribution to ensure the vast majority of people will not see the camera as an obstruction to the view of the person sitting across the videoconferencing system. 
         [0039]    Camera field of view—FOV +v , FOV −v    
         [0040]    Generally a particular camera is chosen for other reasons, so that the FOV of the camera is fixed by the choice. 
         [0041]    Display dimension—D w , D h    
         [0042]    Based on view angle, weight, cost, and other practical considerations, these factors usually limit the display choice to a few options, such as a display size of 27 inches or 23 inches (diagonal). An optimal set of (H cam , H disp , α disp ) should best fit the selected display sizes. Note that the physical dimensions vary, even for a given diagonal size, from model to model due to bezel size variations. 
         [0043]    Optimum sitting distance—D 
         [0044]    This is how far from the display most people will sit. This is determined by target room size, view angle, social considerations (how close people can comfortably sit together), etc. 
         [0045]    To solve the unknown quantities based on the known quantities, the following constrains are applied: 
         [0046]    Constrain 1. The camera should be as close to eye level as possible (to maintain good eye contact), though if the camera FOV +v  is sufficiently large, the camera cab readily be below eye level. 
         [0000]      H cam ≈H eye    (Eq. 1)
 
         [0047]    Constrain 2. Camera should be lower than eye level (to avoid obstruction of people by the camera). As mentioned with regard to Constrain 1, if the camera has a large FOV +v , the camera can be lowered additional amounts as compared to cameras with less FOV +v . This lower position is advantageous because it reduces the angle between the line of sight to the camera and line of sight to the center of the display as discussed in Constrain 3. 
         [0000]      H cam &lt;H eye    (Eq. 2)
 
         [0048]    Constrain 3. The angle between the line of sight to the camera and line of sight to the center of the display should be less than 20 degrees, with smaller angles such as 15°-16° or 10° being advantageous. 
         [0000]      θ&lt;20°  (Eq. 3)
 
         [0049]    This constrain is to maintain a good eye contact. A study by Milton Chen, “Leveraging the Asymmetric Sensitivity of Eye Contact for Videoconferencing”, Proceedings of the CHI 2002 Conference on Human Factors in Computing Systems, pp. 49-56, Apr. 20-25, 2002, which is hereby incorporated by reference, suggest that the angle separation between the camera and monitor should be less than 10 degrees before people start to notice eye contact issues. The inventors experience based on testing of units according to the present invention indicates that 20° is a more practical upper bound, with designs often employing angles in the 15°-16° range. 
         [0050]    Constrain 4. The line of sight to the center of the display should be perpendicular to the display. If the display is purely vertical, this results in a less pleasing experience as the display is effectively canted with respect to the participant, which causes distortions in the displayed items. 
         [0000]      φ=90°  (Eq. 4)
 
         [0051]    Constrain 5. The display&#39;s edge should not be seen by the camera. 
         [0052]    As shown in the following diagram, this means the angle of the display&#39;s outer edge should be outside of the camera field of view as shown in  FIG. 2 . 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       tan 
                       
                         - 
                         1 
                       
                     
                      
                     
                       ( 
                       
                         
                           H 
                           disp 
                         
                         
                           D 
                           d 
                         
                       
                       ) 
                     
                   
                   &gt; 
                   
                     F 
                      
                     
                         
                     
                      
                     O 
                      
                     
                         
                     
                      
                     
                       V 
                       
                         - 
                         v 
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     Eq 
                     . 
                     
                         
                     
                      
                     5 
                   
                   ) 
                 
               
             
           
         
       
     
         [0053]      FIG. 2  illustrates a 4 display configuration. The top edges of the four displays are arranged end to end to form a square if looked down from above. D d  in Eq. 4 is half of the diagonal length of that square. 
         [0000]    
       
         
           
             
               
                 
                   
                     D 
                     d 
                   
                   = 
                   
                     
                       
                         2 
                       
                       2 
                     
                      
                     
                       D 
                       w 
                     
                   
                 
               
               
                 
                   ( 
                   
                     Eq 
                     . 
                     
                         
                     
                      
                     6 
                   
                   ) 
                 
               
             
           
         
       
     
         [0054]    A similar equation could be derived if 3 or 5 monitors are used to form the center of the room displays. 
         [0055]    Given the constrain equations Eq. 1-5, and taking proper approximations considering 
         [0000]    
       
         
           
             
               
                 
                   
                     H 
                     eye 
                   
                   - 
                   
                     H 
                     cam 
                   
                 
                 
                   H 
                   eye 
                 
               
                
               • 
                
               
                   
               
                
               1 
             
             , 
           
         
       
       
         
           
             sin α disp □ 1, 
           
         
       
     
         [0057]    we can solve the unknown quantities as follows 
         [0000]      H cam =H eye    (Eq. 6)
 
         [0000]    
       
         
           
             
               
                 
                   
                     H 
                     disp 
                   
                   &gt; 
                   
                     
                       
                         2 
                       
                       2 
                     
                      
                     
                       D 
                       w 
                     
                      
                     tan 
                      
                     
                         
                     
                      
                     F 
                      
                     
                         
                     
                      
                     O 
                      
                     
                         
                     
                      
                     
                       V 
                       
                         - 
                         v 
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     Eq 
                     . 
                     
                         
                     
                      
                     7 
                   
                   ) 
                 
               
             
             
               
                 
                   
                     H 
                     disp 
                   
                   &lt; 
                   
                     
                       sin 
                        
                       
                           
                       
                        
                       20 
                        
                       
                         ° 
                         · 
                         D 
                       
                     
                     - 
                     
                       
                         D 
                         h 
                       
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   
                     Eq 
                     . 
                     
                         
                     
                      
                     8 
                   
                   ) 
                 
               
             
             
               
                 
                   
                     α 
                     disp 
                   
                   = 
                   
                     
                       sin 
                       
                         - 
                         1 
                       
                     
                      
                     
                       ( 
                       
                         
                           
                             H 
                             disp 
                           
                           + 
                           
                             
                               D 
                               h 
                             
                             / 
                             2 
                           
                         
                         D 
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   
                     Eq 
                     . 
                     
                         
                     
                      
                     9 
                   
                   ) 
                 
               
             
           
         
       
     
         [0058]    Eq. 6 basically says place the camera right below eye level. The most important factor is the height of camera relative to the top edge of the display, H disp . 
         [0059]    Eq. 7 gives the lower bound of H disp  based on constrain 5 (edge of the display not in camera view). 
         [0060]    Eq. 8 gives the upper bound of H disp  based on constrain 3 (eye contact). Note that the larger D w  and D h  are, the narrower the range of acceptable H disp  becomes. Therefore it is generally preferred to use a display with a thinner bezel to minimize D w  and D h  for the same viewing area. 
         [0061]    Eq. 9 shows that the display tilt angle is a function of H disp , D h  and D. Once H disp  is determined from the range given by Eq. 7-8, the tilt angle can be easily derived. 
         [0062]      FIG. 3  illustrates an exemplary embodiment of a videoconferencing system  300  according to the present embodiment. Four displays  302 A-D are located around a central column  304 . Arms  306 A-D ( 306 C and  306 D not shown) are provided to mount the displays  302 A-D to the central column  304 . The arms  306 A-D are configured to place the displays  302 A-D at the desired tilt or α disp . Each display  302 A-D has a height of D h  and a width of D w . The optical center of the camera  308  is the distance H disp  above the top edge of the displays  302 A-D. The central column  304  is mounted to a base  310 . The base  310  preferably includes the electronics of the videoconferencing system  300 , such as shown in  FIG. 6 . This includes the electronics for the camera  308 , to drive the displays  302 A-D, to communicate with a far site and the like. The base  310  may be mounted on wheels or casters  312  for mobility. 
         [0063]    As can be seen, the video displays  302 A-D generally form the sides of an equilateral polyhedron. Four displays are shown but other numbers could be used if desired, with the video displays still generally forming the sides of an equilateral polyhedron. A 360° panoramic camera is preferred to allow full flexibility in the location of the participants, but in other embodiments the camera could just receive images from an axis aligned with the video displays. In the illustrated case the camera would then get four different images, one for each video display, to capture participants looking at the respective video display. 
         [0064]    The central column  304  and arms  306 A-D over a separate base  310  are preferred, but other configurations can be used. For example, a sheet metal chassis that is in the shape of the equilateral polyhedron could be used, the video displays mounted to the faces or sides of the chassis and the camera mounted to the top. The chassis could sit on a table or be floor standing, as desired. Numerous other structures could be used to hold the video displays and camera in the determined locations, as dictated by the aesthetics desired by the designers. 
         [0065]    In a preferred embodiment of a floor mounted or standing videoconferencing system  300  the camera height is 1062 mm from the ground, the screen dimensions are 655 mm by 435 mm at a α disp  of 15°, with the H disp  value being 225 mm and the participant seated 1800 mm away from the display with his eye at 1240 mm above the ground. With this embodiment the camera height from the ground can vary by 10 mm, from 1057 mm to 1067 mm and the user distance from the screen can vary from 450 mm to 2500 mm, with the eye height varying between 1140 mm and 1340 mm and still provide acceptable results. 
         [0066]      FIG. 4A  illustrates a second embodiment where the videoconferencing unit  300 ′ is reduced in size for table top  402  installation. In a preferred embodiment the camera height is 1142 mm, the screen dimensions are 350 mm by 200 mm at a α disp  of 15°, with the H disp  value being 80 mm and the participant  404  seated 780 mm away from the display with his eye at 1240 mm. With this embodiment the camera height from the ground can vary by 50 mm, from 1090 mm to 1190 mm and the user distance from the screen can vary from 560 mm to 700 mm, with the eye height varying between 1140 mm and 1340 mm and still provide acceptable results. 
         [0067]      FIG. 4B  is an illustration of the floor standing videoconferencing system  300  with three different participant positions. In a standing position  422  the participant&#39;s eye is 1690 mm from the camera and 1725 mm above the ground. This results in a θ angle of approximately 18°, an acceptable angle so that the participant appears to have eye contact with the far site. In a seated position  424  the participant&#39;s eye is 1830 mm from the camera and 1240 mm above the ground, resulting in a θ angle of approximately 16°, a very acceptable angle so that the participant appears to have eye contact with the far site. In a seated position  426  the participant is seated much closer to the videoconferencing system  300 , the eye 900 mm from the camera and 1205 mm above the ground. This position  426  results in a θ angle of approximately 38°, well above the point where the participant no longer appears to have eye contact with the far site. The participant needs to move from position  426  to a position farther from the videoconferencing unit  300 , such as position  424 l where the participant appears to have eye contact with the far site. 
         [0068]      FIG. 5A  is top view of a table top videoconferencing unit  300 ′ on a typical meeting room table  502  surrounded by chairs  504 . The dimensions of the illustrated table  502  is 1800 mm or 6 feet in diameter so that the chairs  504  are at approximately the preferred 780 mm from the display. A five foot diameter table can be used, though the participants are a little closer so that the θ angle is approaching the 20° limit.  FIG. 5B  is a top view of a room containing the floor standing videoconferencing unit  300  surrounded by four normal sized love seats  520 , the love seats  520  placed so that the participants are approximately the desired 1800 mm from the display. In testing systems according to the present invention, it has been found that a floor standing videoconferencing unit  300  having the preferred dimensions provided above can work satisfactorily in room sizes from n feet square to 30 feet square, with the seating adjusted according to the room size, not merely to optimize eye contact. 
         [0069]      FIG. 6  is a block diagram of an exemplary videoconferencing unit  600 . A camera  602  is formed by a series of camera imagers  604 . In the illustrated embodiment five imagers  604  are shown to allow for a full 360° panoramic image to be developed. Different numbers of imagers can be used in either a panoramic camera or a camera having views only over the video displays. The camera  602  is connected to a CPU/DSP complex  606 . The included CPUs and DSPs provide the processing components to form the panoramic image from the images, encode the image and any audio for transmission using industry standard formats, decode any received image for display, encode any local audio and decode any audio from the far site. A memory  618  holds the necessary software programs and working memory needed for the CPUs and DSPs. A microphone  608  is used to receive the local speech signals. A simple microphone is shown for explanatory purposes, it being understood that many different microphone arrangements could be used, such as liner arrays, circular arrays and the like. An amplifier  610  receives the analog audio output developed by encoding the far site audio and drives a speaker  612  so that participants can hear the audio of the far site. A network adapter  614  is connected to the CPU/DSP complex  606  to provide the interface to connect to a far site videoconferencing unit. Typically the network adapter  614  is an Ethernet adapter configured to use a TCP/IP connection but other types can be used as is well known. The CPU/DSP complex  606  is connected to video displays  616 A-D to provide the images from the far site. In preferred embodiments the video displays  616 A-D are touch screens to allow easier participant control, though it is noted that when a participant is actually using the touch screen, the participant may be too close to the video display to allow eye contact at the far site. When the participant returns to a normal position after completing operations on the touch screen, the participant will have returned to a position providing eye contact. The images can be presented in various formats. For example, each video display  616 A-D could show a panoramic strip and a single large window for the current speaker. Alternatively, each video display  616 A-D could show a composite of the four images directly in front of the far site video displays, if a similar videoconferencing unit is present at the far site. Other arrangements and formats can be done if desired and are familiar to those skilled in the art. 
         [0070]      FIG. 7  illustrates the connection of two videoconferencing units  700  and  702  through the Internet  704 . It is understood that the Internet is an exemplary network and other private and public networks, or a combination thereof, can be used to connect the videoconferencing units  700  and  702 . Typical industry standard formats such as H.263, H.264 and H.265 can be used for the video codecs, with signaling done using H.323 or SIP. Normal audio codecs such as G.729, G.711 and the like can be used as the audio codecs. One skilled in the art will be familiar with the various audio and video codecs and signaling industry standards used for videoconferencing, as well as various proprietary formats. 
         [0071]    With this it is shown that both table top and floor standing videoconference units can be developed that provide eye contact to the far site by following the described procedures. 
         [0072]    The above description is illustrative and not restrictive. Many variations of the invention will become apparent to those skilled in the art upon review of this disclosure. The scope of the invention should therefore be determined not with reference to the above description, but instead with reference to the appended claims along with their full scope of equivalents.