Abstract:
An endoscope to obtain an image inside a body cavity is provided. The endoscope includes an image capturing element, a power source, which supplies electric power to the image capturing element, a power shutdown unit, which shuts down the electric power to the image capturing element so that the image capturing element can be prevented from overcurrent, a drive control unit, which outputs control signals to the image capturing element in order to control driving of the image capturing element based on driving signals provided from an external unit connected with the endoscope, and a control restricting unit, which restricts the drive control unit to cease outputting the control signals to the image capturing element in response to activation of the power shutdown unit.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to an electronic endoscope with an image capturing element and an endoscope system having the endoscope and signal processor to process images captured by the image capturing element so that the processed image can be displayed on a monitor to be viewed. 
         [0002]    Conventionally, an endoscope system having an electronic endoscope with an image capturing element in a front end unit thereof and a processor to process signals obtained through the image capturing element and output the processed signals to a monitor is widely used. The front end unit of the electronic endoscope is designed to be smaller in a length and a diameter thereof in consideration of burden on a patient (subject). A drive circuit, for example, to drive the image capturing element is arranged in a proximal end portion of the endoscope rather than in the front end unit so that a size of the front end unit can be minimized. The drive unit and the image capturing element are connected to each other with a signal cable arranged inside a flexible tube of the endoscope, for example, by soldering. 
         [0003]    When the flexible tube of such an endoscope is bent during use, the signal cable inside the flexible tube is bent accordingly. As such a bending operation is repeatedly performed, repeated stress is applied to the connecting portion between the image capturing element and the signal cable, and excessive stress may cause disconnection of the cable from the image capturing element at the connecting portion. Further, external impact applied to the flexible tube may cause conflict and friction between the signal cable and the other component. The signal cable can be thus worn and damaged, and the internal cables can be exposed. 
         [0004]    The disconnected signal cable and the exposed internal cables may cause short-circuiting in the endoscope system including the image capturing element and the drive circuit. Further, the short-circuiting may cause overcurrent in the components, and the components may be overheated. 
         [0005]    In order to prevent the overheating in the components due to the short-circuiting, an electronic power unit having a power shutdown circuit is provided. An example of such power unit is disclosed in Japanese Patent Provisional Publication No. 2005-38281. In this power unit, when overcurrent is caused in the circuit, the electric current is shutdown by one of a fuse arranged at an upstream (input) side of the power unit and the an overcurrent detecting circuit arranged at a downstream (output) side of the power unit. 
         [0006]    Thus, it is considered such an overcurrent detecting circuit may be applied in the endoscope system as described above so that the overheating in the components in the endoscope due to the short-circuiting can be prevented. However, even when the electric current supplied to the image capturing element is shutdown by the power shutdown circuit, the image capturing element remains receiving the driving signals from the driving circuit. Thus, considerably higher voltage than the power supply voltage (e.g., 0 volt when the electric current is shutdown) is applied to the image capturing element. In this situation, a latch-up phenomenon, in which the image capturing element can be overheated and fail, may be easily caused. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the foregoing drawbacks, the present invention is advantageous in that an electronic endoscope and an endoscope system, in which the latch-up phenomenon can be prevented, are provided. 
         [0008]    According to an aspect of the present invention, there is provided an endoscope to obtain an image inside a body cavity. The endoscope includes an image capturing element, a power source, which supplies electric power to the image capturing element, a power shutdown unit, which shuts down the electric power to the image capturing element so that the image capturing element can be prevented from overcurrent, a drive control unit, which outputs control signals to the image capturing element in order to control driving of the image capturing element based on driving signals provided from an external unit connected with the endoscope, and a control restricting unit, which restricts the drive control unit to cease outputting the control signals to the image capturing element in response to activation of the power shutdown unit. 
         [0009]    Optionally, the power shutdown unit may be a fuse provided between the power source and the image capturing element, and activating the power shutdown unit may be blowing the fuse. 
         [0010]    Optionally, the endoscope may further include a fuse status judging system, which judges as to whether the fuse is blown. The control restricting unit may restrict the drive control unit to cease outputting the control signals to the image capturing element when the fuse status judging system judges that the fuse is blown. 
         [0011]    According to another aspect of the present invention, there is provided an endoscope system. The endoscope system includes an endoscope to obtain an image inside a body cavity a monitor, which displays the image obtained by the endoscope, and a processor, which processes the image obtained by the endoscope into a format adaptable to the monitor. The endoscope includes an image capturing element, a power source, which supplies electric power to the image capturing element, a power shutdown unit, which shuts down the electric power to the image capturing element so that the image capturing element can be prevented from overcurrent, a drive control unit, which outputs control signals to the image capturing element in order to control driving of the image capturing element based on driving signals provided from an external unit connected with the endoscope, and a control restricting unit, which restricts the drive control unit to cease outputting the control signals to the image capturing element in response to activation of the power shutdown unit. 
         [0012]    Optionally, the power shutdown unit of the endoscope may be a fuse provided between the power source and the image capturing element, and activating the power shutdown unit may be blowing the fuse. 
         [0013]    Optionally, the endoscope may further include a fuse status judging system, which judges as to whether the fuse is blown. The control restricting unit of the endoscope may restrict the drive control unit to cease outputting the control signals to the image capturing element when the fuse status judging system judges that the fuse is blown. 
         [0014]    Optionally, a reporting signal to report the activation of the power shutdown unit may be transmitted to the processor in response to the activation of the power shutdown unit; and the processor may add a superimposed image over the image obtained by the endoscope on the monitor in response to the reporting signal. 
         [0015]    According to another aspect of the present invention, there is provided an electric power unit for an endoscope with an image capturing element to obtain an image inside a body cavity. The electronic power unit includes a power source, which supplies electric power to the image capturing element, a power shutdown unit, which shuts down the electric power to the image capturing element so that the image capturing element can be prevented from overcurrent, a drive control unit, which outputs control signals to the image capturing element in order to control driving of the image capturing element based on driving signals provided from an external unit connected with the endoscope, and a control restricting unit, which restricts the drive control unit to cease outputting the control signals to the image capturing element in response to activation of the power shutdown unit. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a schematic view of an endoscope system according to an embodiment of the present invention. 
           [0017]      FIG. 2  is a block diagram illustrating a configuration of the endoscope system according to the embodiment of the present invention. 
           [0018]      FIG. 3  is a block diagram illustrating a configuration of a CCD (charge-coupled device) and a DSP (digital signal processor) board of the endoscope system according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0019]    Hereinafter, referring to the accompanying drawings, according to illustrative embodiments of the invention will be described. 
         [0020]      FIG. 1  is a schematic view of an endoscope system  10  according to the embodiment of the present invention.  FIG. 2  is a block diagram illustrating a configuration of the endoscope system  10  according to the embodiment of the present invention. 
         [0021]    The endoscope system  10  includes an electronic endoscope  100 , a processor  200 , and a monitor  300 . The endoscope  100  is provided with a connector unit  100  at a distal end thereof, and the connector unit  100  has a two-prong plug  110   a , which is connectable with a connector  210  of the processor  200 . The connector  210  has two receive portions  210   a , each of which corresponds to one of the two prongs in the two-prong plug  110   a . One of the two prongs  110   a  and a corresponding receive portion  210   a  provide electrical connection between the electronic endoscope  100  and the processor unit  200 , while the other of the two prongs  110   a  and the corresponding receive portion  210   a  provide optical connection. 
         [0022]    The connector unit  110  is connected with one end of a flexible cord  120 , and the other end of the cord  120  is connected with an operation unit  130 . The operation unit  130  receives an operation from a user to manipulate the electronic endoscope  100 . As the user handles the operation unit  130 , for example, by pressing a button (not shown) on the operation unit  130 , fluid such as air and cleaning liquid can be insufflated in a body cavity. The operation unit  130  is connected with one end of a flexible tube  140 . 
         [0023]    The flexible tube  140  is to be inserted in a body cavity and is provided with a front end unit  150  at a distal end thereof. As the user operates the operation unit  130  to bend the flexible tube  140  at a portion where the front end unit  150  is connected with the flexible tube  140 , the front end unit  150  is angled, and an area to be observed transitions accordingly. 
         [0024]    The front end unit  150  is formed with a hard material such as resin and provided with components required for image capturing process, which are a light distributing lens  152 , an objective lens  154 , and a CCD  156 . The light distributing lens  152  and the objective lens  154  are arranged on a front end surface of the front end unit  150 . The CCD  156  is a known color CCD in an arrangement such as Bayer arrangement. 
         [0025]    The electronic endoscope  100  is further provided with a light guide  160 , which is arranged in a longitudinal direction thereof. The light guide  160  is a bundle of optical fibers, of which one end is connected to one of the prongs of the two-prong plug in the connector unit  110 . The other end of the light guide  160  is arranged in vicinity of the light distributing lens  152 . The connector unit  110  is provided with a circuit board having a DSP board  170 , which controls the CCD  156  and processes output signals from the CCD  156 . 
         [0026]    The processor  200  is provided with a power circuit  270 , which converts commercial power source into DC power. The DC power converted in the power circuit  270  is supplied to each component in the processor  200 . In  FIG. 1 , connection between the power circuit  270  and each component in the processor  200  is omitted for explanatory simplicity. 
         [0027]    The processor  200  includes a system control unit  220 , which controls each component in the entire endoscope system  10 . Further, the processor  200  includes a light source  230  to irradiate inside the body cavity, a light source control circuit  232  to control the light source  230 , and a condenser lens  234 . In the present embodiment, a known white light source, such as a metal halide lamp, a xenon lamp, and a halogen lamp, is used as the light source  230 . The light emitted from the light source  230  is collected by the condenser lens  234  which is arranged on a front side of the light source  230  and enters the electronic endoscope  100  (more specifically, a core of the light guide  160 ) through a connector portion  210  of the processor  200 . The light is thus transmitted through the light guide  160  and emitted from the front end thereof through the light distributing lens  152  to irradiate the body cavity. 
         [0028]    The irradiated light is reflected in the body cavity and enters the objective lens  154 . The CCD  156  is substantially arranged in a position in which an image through the objective lens  154  is formed so that the light entering the objective lens  154  is focused on the light receiving surface of the CCD  156 . 
         [0029]      FIG. 3  is a block diagram illustrating a configuration of the CCD  156  and the DSP board  170  of the endoscope system  10  according to the embodiment of the present invention. The DSP board  170  includes a CCD power circuit  171 , a fuse  172 , an FPGA (field programmable gate array)  173 , a CCD drive circuit  174 , a CCD signal process circuit  175 , resistors  176 ,  177 , and a status detecting circuit  178  to detect status of the fuse  172 . 
         [0030]    As the DC power is supplied by the power circuit  270 , the CCD power circuit  171  converts the voltages (DC-to-DC conversion) and supplies the CCD  156  with the driving voltage. The DC voltage from the power circuit  270  is also supplied to the other components in the DSP board  170 . 
         [0031]    The FPGA  173  generates control signals to drive the CCD  156  based on synchronizing pulses, which are transmitted from the system control unit  220  of the processor  200 , and outputs the generated control signals to the CCD drive circuit  174 . The CCD drive circuit  174  outputs drive signals to drive the CCD  156  according to the control signals. 
         [0032]    The CCD  156  driven according to the control signals converts the optical image focused on the light receiving surface into image signals (CCD output signals) and outputs to the DSP board  170 . Then, the CCD signal processing circuit  175  in the DSP board  170  generates image signals including color component signals and brightness signals based on the CCD output signals. The image signals are transmitted to the processor  200 . 
         [0033]    Referring back to  FIG. 2 , signal processing performed in the processor  200  will be described. The processor  200  in the present embodiment includes an insulation circuit  240 , a preliminary signal processing circuit  242 , an image memory  244 , a video signal processing circuit  246 , a superimposition circuit  248 , and an output circuit  250 . The insulation circuit  240  converts the signals transmitted from the electronic endoscope  100  into another transmitting signals such as optical signals by using, for example, a photo-coupler so that the electronic endoscope  100  and the processor  200  are electrically insulated at the insulation circuit  240 . 
         [0034]    The image signals output from the electronic endoscope  100  are inputted through the connector portion  210  and the insulation circuit  240  into the preliminary signal process circuit  242 . The preliminary signal process circuit  242  amplifies and converts the inputted image signals (analog-to-digital conversion), and the output digital image signals are stored in the memory  244  on a frame basis. The stored image signals are output to the video signal process circuit  246  frame by frame based on timing determined with respect to the synchronizing pulses provided from the system control unit  220 . The synchronizing pulses are provided to the FPGA  173  as well in substantially equal timing. Thus, the signal processing in the processor  200  and drive timing of the CCD  156  are synchronized. 
         [0035]    The image signals are thereafter converted into signals adaptable to the monitor  300  (i.e., color component signals and brightness signals) in the video signal process circuit  246 . The converted signals are further output to the output circuit  250 . 
         [0036]    The superimposition circuit  248  processes a predetermined image to be superimposed on the images captured by the electronic endoscope  100  under control of the system control unit  220  in cooperation with the video signal process circuit  246 . 
         [0037]    The output circuit  250  converts the color component signals and the brightness signals transmitted from the video signal processing circuit  246  into video signals in a predetermined format (for example, composite video signals, S-video signals, and RGB video signals) to output to the monitor  300  to be displayed. Thus, the image captured by the electronic endoscope  100  is displayed in the monitor  300  with or without the superimposed image. 
         [0038]    With the above configuration, when one of the signal cables, for example, a cable connecting the CCD  156  and the DSP board  170  is disconnected or exposed to cause short-circuiting between a cable supplying electric power to the CCD  156  and the ground, overcurrent is caused between the CCD power circuit  171  and the CCD  156 . In order to prevent the overcurrent, the fuse  172  arranged between the CCD power circuit  171  and the electric current for the CCD  156  is shutdown. 
         [0039]    The status of the fuse is detected by the status detecting circuit  178 , which monitors potential between the resistor  176  and the resistor  177 . More specifically, in normal status, when the electric power is supplied to the CCD  156 , the voltage is applied to the resistors  176 ,  177 . In this state, resistance ratio of the resistor  176 ,  177  is set such that the potential between the resistor  176  and the resistor  177  is higher than a predetermined threshold. Thus, as the status detecting circuit  178  in the normal state detects the potential between the resistor  176  and the resistor  177  higher than the predetermined threshold, signals indicating the higher potential (hereinafter referred to as H signals) are transmitted to the FPGA  173 . 
         [0040]    The FPGA  173 , which receives the H signals, determines that the fuse  172  is maintained, and the power is normally supplied to generate and output the control signals based on the synchronizing pulses. 
         [0041]    When the overcurrent is caused, and the fuse  172  is blown to cease supplying the power to the CCD  156 , the resistor  176  becomes open, and the resistor  177  serves as a pull-down resistor to lower the potential between the resistor  176  and the resistor  177  than the predetermined threshold. As the status detecting circuit  178  detects the lowered potential, L signals indicating the lower potential are transmitted to the FPGA  173 . 
         [0042]    The FPGA  173 , which receives the L signals, determines that the fuse  172  is blown due to the overcurrent between the CCD  156  and the CCD power circuit  171  and the electric power is shutdown. The FPGA  173  thereafter transmits reporting signals to report the power status to the system control unit  220 . Subsequently, the FPGA  173  transmits signals indicating to cease generating the control signals. Alternatively, signals indicating to cease drive signals for the CCD  156  are transmitted to the CCD drive circuit  174 . Accordingly, drive signals for the CCD  156  are ceased. Therefore, drive signals for the CCD  156  are not inputted in the CCD  156  in connection with the electric power to the CCD  156  being shutdown. Thus, considerably higher voltage than the power supply voltage (e.g., 0 volt) is prevented from being applied to the CCD  156 , and a latch-up phenomenon, in which the CCD  156  can be overheated and fail, can be avoided. 
         [0043]    Further, the system control unit  220  controls the superimposition circuit  248  according to the reporting signals transmitted from the FPGA  173 . The superimposition circuit  248  functions in connection with the video signal process circuit  246  to display an image indicating the failure (i.e., short-circuiting) in the electronic endoscope  100  over the image obtained through the electronic endoscope  100 . Thus, the operator viewing the monitor  50  can recognize the failure in the electronic endoscope  100 . It is noted that the superimposed image can be displayed partially or substantially entirely over the image obtained through the electronic endoscope  100  as long as the superimposed image is recognizable to the operator. 
         [0044]    In the present embodiment, the fuse  172  is configured to be self-recoverable. That is, when the cause of the short-circuiting is removed, the CCD  156  and the DSP board  170  can operate normally. However, the fuse  172  may not necessarily be self-recoverable. In such a configuration, the fuse  172  requires to be exchanged for example when the electronic endoscope  100  is repaired. 
         [0045]    It is noted that, in the power supply unit in the above-referenced publication, the overcurrent in the power supply line is monitored based on electronic current values. If the monitoring system is applied to the endoscope system of the present embodiment, the electric current value to the CCD  156  is monitored. However, in this configuration, individual specificity in, for example, the power supply line, the CCD  156 , and a resistor for monitoring may affect the electric current value to be monitored. On the contrary, in the endoscope system of the present embodiment, the status of the fuse  172  is monitored to detect overcurrent. It is noted that the status of the fuse  172  is rather independent from the individual specificity of each component. Therefore, the overcurrent can be reliably detected. 
         [0046]    Although an example of carrying out the invention has been described above, the present invention is not limited to the above described embodiment. For example, the CCD signal process circuit  175  in the DSP board  170  may be arranged in the processor  200 . In this configuration, the CCD signal process circuit  175  is positioned between the insulation circuit  240  and the preliminary signal processing circuit  242 . Further, the status detecting circuit  178  may be omitted when the resistance values of the resistors  176 ,  177  are properly adjusted, and the FPGA  173  is configured to directly detect the status of the fuse  172 . 
         [0047]    The present disclosure relates to the subject matter contained in Japanese Patent Application No. P2006-205705, filed on Jul. 28, 2006, which is expressly incorporated herein by reference in its entirety.