Abstract:
A KVM switch including server units that are respectively connected to computers units, user units that are respectively connected to input-output units inputting and outputting a signal to the computer units, and a main unit that connects the server units and the user units selectively. The input-output unit switches between the computer units where the signal is input and output. The server unit has a first reference signal generator that generates a first reference signal used for a distortion control of a picture signal. The main unit has a first controller receiving the first reference signal and controlling the distortion of the picture signal and a second reference signal generator generating a second reference signal used for the distortion control of the picture signal. The user unit has a second controller that receives the second reference signal and controls the distortion of the picture signal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Various embodiments of the present invention generally relate to a keyboard, video, mouse (KVM) switch that controls computers with an input-output unit having a keyboard, a mouse and a display. 
     2. Description of the Related Art 
     A KVM switch is connected between an input-output unit and computers. The KVM switch makes one of the connections between the input-output unit and the computers an active. A user selects and uses one of the computers that is to be connected by using the KVM switch. 
       FIG. 1  illustrates a structure of a conventional KVM switch. The KVM switch has server units  2   a  through  2   n  (“n” is a given value), user units  4   a  through  4   n  (“n” is a given value), and a main unit  3 . Hereinafter, a given one of the server units is referred to as a server unit  2 . A given one of the user units is referred to as a user unit  4 . 
     The server unit  2  is provided on the side of computer units  1   a  through  1   n  (“n” is a given value). Hereinafter, a given one of the computers is referred to as a computer unit  1 . The user unit  4  is provided on the side of input-output units such as monitors  5   a  through  5   n  (“n” is a given value), keyboards  6   a  through  6   n  (“n” is a given value), and mouses  7   a  through  7   n  (“n” is a given value). Hereinafter, a given one of the monitors is referred to as a monitor  5 . A given one of the keyboards is referred to as a keyboard  6 . A given one of the mouses is referred to as a mouse  7 . The main unit  3  is provided between the units, and has a switch that switches connections between the computer unit  1  and the input-output unit. 
     A picture signal is output from the computer unit  1 , and is fed into the main unit  3  via the server unit  2 . In the main unit  3 , a matrix switch  12  selects the user unit  4  to be connected. The picture signal is fed into the monitor  5  via the user unit  4 . 
     There is a case where a cable length between the main unit  3  and the user unit  4  is a few hundreds meters. In this case, there is occurred a high degradation and a delay in the picture signal fed into the user unit. Therefore, there is provided a picture signal controller that controls a picture signal in the user unit. 
       FIG. 2  illustrates a structure of the main unit  3 . The main unit  3  has picture signal input portions  11   a  through  11   n  (“n” is a given value), the matrix switch  12 , switches  13   a  through  13   n  (“n” is a given value), picture signal output portions  14   a  through  14   n  (“n” is a given value), a microcomputer  15 , a reference signal generator  16  and a keyboard/mouse signal generator  17 . 
     Picture signals from the server units  2   a  through  2   n  are fed into the picture signal input portion  11   a  through  11   n . The matrix switch  12  redirects the output of the picture signal. The switches  13   a  through  13   b  output one of the picture signal from the matrix switch  12  and a reference signal from the reference signal generator  16 . The picture signal output portions  14   a  through  14   n  output the picture signals from the switches  13   a  through  13   n  or the reference signal to the user unit  4 . The microcomputer  15  controls the switches  13   a  through  13   n  and the keyboard/mouse signal generator  17 . The reference signal generator  16  generates the reference signal. The keyboard/mouse signal generator  17  generates a control signal of the keyboard/mouse. 
       FIG. 2  shows the picture signal input portions  11   a  and  11   b  of the picture signal input portions  11   a  through  11   n , shows the switches  13   a  and  13   b  of the switches  13   a  through  13   n , and shows the picture signal output portions  14   a  and  14   b  of the picture signal output portions  14   a  through  14   n . 
     The microcomputer  15  controls the switches  13   a  and  13   b  so that the reference signal from the reference signal generator  16  is fed into the picture signal output portions  14   a  and  14   b , at a controlling timing of the picture signal. 
       FIG. 3  illustrates a structure of the user unit  4   a  of the user units  4 . The user unit  4   a  has a picture signal input portion  21   a , a picture signal controller  22   a , a picture signal output portion  23   a , an A/D converter  24   a  and a microcomputer  25   a.    
     When a reference signal is output from the main unit  3 , the user unit  4   a  receives the reference signal with the picture signal input portion  21   a  and outputs the reference signal to the picture signal controller  22   a . The picture signal controller  22   a  outputs the reference signal to the picture signal output portion  23   a.    
     The A/D converter  24   a  A/D converts the reference signal from the picture signal controller  22   a , and outputs the reference signal to the microcomputer  25   a . The microcomputer  25   a  controls the picture signal controller  22   a  so that an output signal from the picture signal controller  22   a  is optimized based on an output level of the reference signal. 
     Japanese Patent Application Publication No. 2005-278085 (hereinafter referred to as Document 1) discloses a system that has a reference signal generator in a transmitter and controls a picture quality automatically in a receiver. 
     Japanese Patent Application Publication No. 9-219803 (hereinafter referred to as Document 2) discloses a cable compensator that has a reference signal generator in a transmitter and controls a gain automatically in a receiver. 
     A distance between the server unit and the main unit is longer or shorter as well as a distance between the main unit and a user unit, in a case where the KVM switch is structured with the server unit, the main unit and the user unit. 
     The KVM switch controls a gain of the picture signal controller  22   a , in view of a given distance between each of the units. A signal voltage level is not reduced to a required level and a halation may be occurred if the distance between the server unit and the user unit is extremely short, even if the gain of the picture signal controller  22   a  is controlled. In contrast, there is a problem that a desirable signal voltage level may not be obtained in a case where the signal voltage level is controlled between the main unit and the user unit in a conventional method, if the distance between the server unit and the main unit is longer. And the arts disclosed in Document 1 and Document 2 do not solve the problem. 
     SUMMARY OF THE INVENTION 
     The present invention provides a KVM switch that optimizes an output signal level in spite of a distance between connected units, and provides a controlling method of the KVM switch. 
     According to an aspect of the present invention, preferably, there is provided a KVM switch including server units that are respectively connected to computers units, user units that are respectively connected to input-output units inputting and outputting a signal to the computer units, and a main unit that connects the server units and the user units selectively. The input-output unit switches between the computer units where the signal is input and output. The server unit has a first reference signal generator that generates a first reference signal used for a distortion control of a picture signal. The main unit has a first controller receiving the first reference signal and controlling the distortion of the picture signal and a second reference signal generator generating a second reference signal used for the distortion control of the picture signal. The user unit has a second controller that receives the second reference signal and controls the distortion of the picture signal. 
     With the structure, the first controller is controlled between the server unit and the main unit, and the second controller is controlled between the main unit and the user unit. The distortion is thus controlled in two steps. It is therefore possible to optimize the output signal level in spite of a distance between the units connected to each other. 
     According to another aspect of the present invention, preferably, there is provided a method of controlling a KVM switch having server units that are respectively connected to computers units, user units that are respectively connected to input-output units, and a main unit that connects the server units and the user units selectively, including: generating a first reference signal used for a distortion control of a picture signal with the server unit; receiving the first reference signal with the main unit; controlling the distortion of the picture signal with the main unit; generating a second reference signal used for the distortion control of the picture signal with the main unit; receiving the second reference signal with the user unit; and controlling the distortion of the picture signal with the user unit. 
     With the method, it is possible to optimize an output signal level in spite of a distance between the units connected to each other 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present invention will be described in detail with reference to the following drawings, wherein: 
         FIG. 1  illustrates a whole structure of a KVM switch; 
         FIG. 2  illustrates a structure of a conventional main unit; 
         FIG. 3  illustrates a structure of a conventional user unit; 
         FIG. 4  illustrates a structure of a server unit; 
         FIG. 5  illustrates a structure of a main unit; 
         FIG. 6  illustrates a structure of a user unit; 
         FIG. 7  illustrates a main unit in accordance with a second embodiment; 
         FIG. 8  illustrates a flowchart showing a procedure of a microcomputer of a main unit; 
         FIG. 9  illustrates a user unit further having a structure in which a picture signal controller of a user unit is manually controlled; 
         FIG. 10  illustrates a main unit further having a structure in which a picture signal controller of a main unit is manually controlled; 
         FIG. 11  illustrates a structure of a user unit in which a picture signal controller of a user unit is controlled only manually; and 
         FIG. 12  illustrates a structure of a main unit in which a picture signal controller of a main unit is controlled only manually. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A description will now be given, with reference to the accompanying drawings, of embodiments of the present invention. 
     (First Embodiment) 
     A KVM switch in accordance with a first embodiment has the server unit  2  provided on the side of the computer unit  1 , the user unit  4  provided on the side of the input-output unit such as the keyboard  6 , the mouse  7 , the monitor  5  and so on, and the main unit  3  that is provided between the units and switches connections between the computer unit  1  and the input-output unit, as shown in  FIG. 1 . 
       FIG. 4  illustrates a structure of the server unit  2   a . The other server units have the same structure as that of the server unit  2   a . An explanation of the other server units is omitted, because a description will be given of an explanation of the server unit  2   a.    
     The server unit  2   a  has a picture signal input portion  31   a , a switch  32   a , a picture signal output portion  33   a , a reference signal generator  34   a , a microcomputer  35   a , and a keyboard/mouse signal divider  36   a.    
     A picture signal from the computer unit  1   a  is fed into the picture signal input portion  31   a  in the server unit  2   a  and is output to the switch  32   a . The switch  32   a  outputs the picture signal to the picture signal output portion  33   a . The picture signal is output to the main unit  3  from the picture signal output portion  33   a.    
     A keyboard/mouse control signal is transmitted between the user unit  4  and the server unit  2  with one cable. The keyboard/mouse control signal fed into the server unit  2   a  is divided into a keyboard control signal and a mouse control signal at the keyboard/mouse signal divider  36   a . The keyboard control signal and the mouse control signal are output to cables different from each other. The keyboard signal is fed into a keyboard signal input terminal. The mouse signal is fed into a mouse signal input terminal. 
     The server unit  2   a  has the reference signal generator  34   a  and the microcomputer  35   a . The reference signal generator  34   a  generates a reference signal in at least one of the main unit  3  and the user unit  4 , the reference signal being used for controlling a distortion of the picture signal. The microcomputer  35   a  controls the switch  32   a  so that a signal fed into the picture signal output portion  33   a  is switched between the picture signal and the reference signal. 
       FIG. 5  illustrates a structure of the main unit  3 . The main unit  3  is structured according to the server units  2   a  through  2   n . The main unit  3  has picture signal input portions  41   a  through  41   n  (“n” is a given value) into which the picture signal from each of the server units is fed, a picture signal matrix switch  44 , picture signal output portions  46   a  through  46   m  (“m” is a given value) that are provided respectively according to each of the user units, and a keyboard/mouse signal matrix switch  48 . 
     Each of the picture signals from the server units  2   a  through  2   n  is fed into each of the picture signal input portions  41   a  through  41   n , and is fed into the picture signal matrix switch  44 . The picture signal matrix switch  44  selects between the picture signal output portions  46   a  through  46   m  to which the picture signal is transmitted. The picture signal output portions  46   a  through  46   m  output the picture signal to the corresponding user units  4   a  through  4   m.    
     The main unit  3  in accordance with the embodiment outputs the reference signals from the server units  2   a  through  2   n  to the user units  4   a  through  4   m , as well as a normal picture signal. 
       FIG. 6  illustrates a structure of the user unit  4   a . The other user units have the same structure as that of the user unit  4   a . An explanation of the other server units is omitted, because a description will be given of an explanation of the user unit  4   a.    
     The user unit  4   a  has a picture signal input portion  51   a , a picture signal controller  52   a , and a picture signal output portion  53   a . The picture signal from the main unit  3  is fed into the picture signal input portion  51   a . The picture signal controller  52   a  controls a signal level of the picture signal. The picture signal output portion  53   a  outputs the picture signal of which signal level is controlled. The user unit  4   a  has an A/D converter  54   a , and a microcomputer  55   a . The A/D converter  54   a  converts a reference signal from the picture signal controller  52   a  into a digital signal. The microcomputer  55   a  controls a signal output level of the picture signal controller  52   a  based on the digitally converted reference signal. 
     The user unit  4   a  has a keyboard/mouse signal generator  56   a . The keyboard/mouse signal generator  56   a  generates a control signal composed of a keyboard control signal and a mouse control signal. The generated signal is transmitted to the main unit  3  and the server unit  2  through one cable. 
     The KVM switch in accordance with the embodiment has a reference signal generator  34  in the server unit  2  as shown in  FIG. 4 , and controls a signal distortion of the picture signal with the user unit  4 . The user unit  4   a  A/D converts the reference signal from the picture signal controller  52   a  in the A/D converter  54   a , and calculates an output voltage level of the reference signal and a distortion amount such as a delay in the microcomputer  55   a . The user unit  4   a  controls the picture signal controller  52   a  based on the calculated distortion amount. 
     It is possible to control the signal distortion such as a picture quality between the server unit  2  and the user unit  4 , if the server unit  2  has the reference signal generator  34 . It is therefore possible to connect the server unit  2  and the user unit  4  directly and to transmit and receive a data therebetween, even if the main unit is out of order because of some reason and is inoperative. 
     (Second Embodiment) 
       FIG. 7  illustrates a structure of the main unit  3  in accordance with a second embodiment. In this embodiment, the main unit  3  receives a reference signal (a first reference signal) from the server unit  2 , and controls a picture signal. The main unit  3  has picture signal controllers  42   a  through  42   n  (“n” is a given value), A/D converters  43   a  through  43   n  (“n” is a given value), and a microcomputer  49 . These components are referred to as a first controller. A method of correcting a signal distortion with the components is described in the first embodiment. 
     The main unit  3  has a reference signal generator  47  in order to control the picture signal between the main unit  3  and the user unit  4 .  FIG. 6  illustrates a structure of the user unit  4 . The user unit  4  receives a reference signal (a second reference signal) and controls the picture signal controller  52   a . The picture signal controller  52   a , the A/D converter  54   a  and a microcomputer  55  correspond to a second controller. 
     When a distance between the server unit  2  and the main unit  3  is long, it is not possible to completely control the picture signal between the main unit and the server unit. In this case, a gain or a delay of a signal is corrected between the server unit  2  and the main unit  3  and between the main unit  3  and the user unit  4 . That is, a picture signal controller  42  in the main unit  3  and a picture signal controller  52  in the user unit  4  are controlled. It is therefore possible to optimize a level of an output signal in spite of a distance between the computer unit  1  to be connected and the input-output unit. 
     In addition, a signal voltage level is set in the KVM switch, in view of a given distance between each of the units. A signal voltage level is not reduced to a required level and a halation may be occurred if the distance between the units is extremely short, even if the gain of the picture signal controller  52  in the user unit  4  is controlled. It is however possible to optimize the signal voltage level and to restrain the halation, when the picture signal controller  42  in the main unit  3  and the picture signal controller  52  in the user unit  4  are controlled. 
     And, a differential is generated between electrical power levels according to the computer unit  1  to be connected, because the server unit  2  receives the electrical power from the computer unit  1 . It is therefore possible to control the picture quality and to obtain a clear picture quality, when the server unit  2  is connected to one of the computer units  1 . However, there is a problem that it is not possible to completely control the gain and the picture quality, when the server unit  2  is connected to another computer unit instead of the computer unit  1 . And so, it is possible to solve the problem, when the gain of the picture signal controller  42  of the main unit  3  is increased and the signal voltage level is increased in a case where the electrical power level is low and the gain is not maintained. 
       FIG. 8  illustrates a determination flow that determines whether the microcomputer  49  of the main unit  3  controls the picture signal controller  42 . 
     The picture signal controller  42   a  (or  42   b ) receives a reference signal from the server unit  2 . The picture signal controller  42   a  (or  42   b ) controls the reference signal and outputs the controlled reference signal to the picture signal matrix switch  44 . 
     The A/D converter  43   a  (or  43   b ) A/D converts the picture signal from the picture signal controller  42   a  (or  42   b ), and outputs the converted signal to the microcomputer  49 . The microcomputer  49  receives the signal that is controlled in the picture signal controller  42   a  (or  42   b ) as a sample (step S 1 ). 
     The microcomputer  49  stores the sampling data, and obtains a minimum value (Vmin) and a maximum value (Vmax) of the signal voltage (step S 2 ). Next, the microcomputer  49  compares the minimum value Vmin with a first threshold (5 min). If the minimum value Vmin is smaller than the first threshold 5 min (step S 3 /YES), the microcomputer  49  determines that the distortion cannot be controlled (step S 6 ) and sets off an alarm. 
     If the minimum value Vmin is larger than the first threshold 5 min (step S 3 /NO), the microcomputer  49  compares the maximum value Vmax with a second threshold (Smax) (step S 4 ). If the maximum value Vmax is larger than the second threshold Smax (step S 4 /YES), the microcomputer  49  determines that the distortion can not be controlled (step S 6 ), and sets off the alarm. If the maximum value Vmax is smaller than the second threshold Smax (step S 4 /NO), the microcomputer  49  calculates the distortion control amount and controls the picture signal controller  42   a  (or  42   b ). 
     The user may manually control the distortion with the mouse  7   a  and the keyboard  6   a , in addition to the control of the picture signal controller  52  with the microcomputer  55  in the user unit  4  and the control of the picture signal controller  42  with the microcomputer  49  in the main unit  3 .  FIG. 9  illustrates a structure of the case. The microcomputer  55   a  receives a control signals from the keyboard  6   a  and the mouse  7   a , and corrects the control amount of the picture signal controller  52   a . And, the microcomputer  49  receives the control signals from the keyboard  6   a  and the mouse  7   a , and corrects the control amount of the picture signal controllers  42   a  through  42   n , as shown in  FIG. 10 . 
     As shown in  FIG. 11  and  FIG. 12 , the microcomputers  55  and  49  may not control the picture signal controllers  52  and  42 , and the picture signal controllers  52  and  42  may be controlled only manually. The microcomputers  55  and  49  receive the control signal from the keyboard  6   a  and the mouse  7   a , and control the picture signal controllers  52  and  42  based on the control signals. 
     While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible of modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims. 
     The present invention is based on Japanese Patent Application No. 2006-315304 filed on Nov. 22, 2006, the entire disclosure of which is hereby incorporated by reference.