JP2009022579A - Electronic endoscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic endoscope of a power supply superposition type, even if a power supply voltage is fluctuated, capable of transmitting signals without causing an error. <P>SOLUTION: A signal transmission circuit 153 outputs an image signal to a power supply superposition circuit 18 in a period when a vertical synchronizing signal from a synchronizing signal generation circuit 14 is high and outputs a clock regeneration signal to the power supply superposition circuit 18 in a period when the vertical synchronizing signal is low. Alternatively, an LED 16 is lit only in the period when the vertical synchronizing signal is low. This method transmits no image signal while the LED 16 is lit to transmit the image signal without any skew. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic endoscope, and more particularly, to a power supply superposition type electronic endoscope that superimposes and transmits a video signal on a power supply line.

2. Description of the Related Art In recent years, electronic endoscopes have been widely used in which an elongated insertion portion having an image pickup device disposed at a distal end portion is inserted to observe a body cavity organ or the like. Also in the industrial field, industrial electronic endoscopes are used for inspection of boilers, turbines, engines, and the like. These electronic endoscopes are required to have a thinner insertion portion in order to improve the insertability. As one of the methods for reducing the diameter of the insertion portion, as proposed in Patent Document 1, another signal such as a video signal obtained by the image sensor is superimposed on a power supply line for supplying a power supply voltage. Thus, there is a method of reducing the number of wirings and thereby reducing the diameter of the insertion portion (hereinafter, such a method is referred to as a power supply superposition method).
Japanese Patent Publication No. 3-30365

  In the case of the power supply superposition method as described above, if the power supply voltage fluctuates due to the fluctuation of the load connected to the power supply line, the signal superimposed on the power supply voltage may be distorted to cause an error.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an electronic endoscope that can transmit a signal without causing an error even if a power supply voltage fluctuates.

  In order to achieve the above object, an electronic endoscope according to a first aspect of the present invention includes an imaging unit that captures an image of a subject and obtains a video signal, and at least a period in which a load connected to a power supply line fluctuates. A signal transmission unit for controlling transmission of the video signal so as to transmit a clock reproduction signal instead of the video signal, and a video signal or clock reproduction signal transmitted from the signal transmission unit is superimposed on the power line. And a signal separating means for separating the superimposed video signal or clock reproduction signal from the power supply line.

  According to the present invention, it is possible to provide an electronic endoscope that can transmit a signal without causing an error even if a power supply voltage fluctuates.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, a first embodiment of the present invention will be described. FIG. 1 is a block diagram of an electronic endoscope used in the first embodiment of the present invention. The electronic endoscope shown in FIG. 1 has an in-vivo unit 10 and an extra-corporeal unit 20, and these are configured to be communicably connected via a cable 30. An image display device 40 is connected to the extracorporeal device 20. The in-vivo device 10 includes an image sensor 11, a timing generation circuit 12, a drive circuit 13, a synchronization signal generation circuit 14, and a signal processing circuit (having an internal image processing circuit 151, an LED control circuit 152, and a signal transmission circuit 153). 15, a light emitting diode (LED) 16 serving as a load, an LED drive circuit 17, a power supply superimposing circuit 18, and an internal power supply circuit 19. The extracorporeal device 20 includes a power / signal separation circuit 21, an external power supply circuit 22, and an external image processing circuit 23.

  The imaging device 11 captures a body organ or the like of the subject to acquire a video signal, and outputs the acquired video signal to the internal image processing circuit 151. The timing generation circuit 12 sends a timing signal for controlling the operation timing of the image sensor 11, the LED 16, and the signal transmission circuit 153 to the drive circuit 13, the LED control circuit 152 that controls the LED as a load, and the synchronization signal generation circuit 14. Send each one. The drive circuit 13 drives the image sensor 11 according to the timing signal from the timing generation circuit 12. The synchronization signal generation circuit 14 counts the timing signal from the timing generation circuit 12 to generate a synchronization signal (vertical synchronization signal), and outputs the generated vertical synchronization signal to the signal transmission circuit 153. Here, the synchronization signal may not be a vertical synchronization signal as long as it is a signal that can determine at least a period during which the LED 16 does not emit light. Further, the synchronization signal generation circuit 14 generates a clock reproduction signal from the timing signal from the timing generation circuit 12 and outputs it to the signal transmission circuit 153.

  The signal processing circuit 15 processes a signal generated in each part of the in-vivo device 10. The internal image processing circuit 151 performs various signal processing such as A / D conversion and gain increase on the video signal input from the image sensor 11, and sends the processed video signal to the signal transmission circuit 153. Further, the internal image processing circuit 151 calculates the brightness of the image by, for example, integrating the video signal from the image sensor 11, and outputs a brightness signal indicating the calculated brightness of the image to the LED control circuit 152. The LED control circuit 152 receives the timing signal from the timing generation circuit 12, determines the timing of light emission start, determines the light emission amount (light emission time or current) of the LED 16 from the brightness signal from the internal image processing circuit 151, An LED control signal for controlling the light emission of the LED is generated and output to the LED drive circuit 17. The LED drive circuit 17 causes the LED 16 to emit light when the LED control signal becomes HIGH, and turns off the LED 16 when it becomes LOW.

  Here, the LED control signal becomes HIGH after the vertical synchronization signal becomes LOW, and becomes LOW before becoming HIGH. In order to perform such control, the timing signal from the timing generation circuit 12 is transmitted to the LED control circuit 152 after a certain period of time has elapsed after the vertical synchronization signal becomes LOW. Alternatively, the light emission start timing may be controlled in the LED control circuit 152. That is, the vertical synchronization signal is a waveform with a fixed period, and a period in which the vertical synchronization signal is normally LOW (referred to as a vertical blanking period or the like) is known. Therefore, this period is counted in the LED control circuit 152 and the LED 16 The light emission start timing and the maximum light emission time (high / low switching timing of the LED control signal) may be determined so that the light emission period is within the period when the vertical synchronization signal is LOW.

  The signal transmission circuit 153 outputs the input video signal to the power supply superimposing circuit 18 when the video signal is input while the vertical synchronization signal from the synchronization signal generation circuit 14 is HIGH. That is, since the LED 16 is not caused to emit light during the period when the vertical synchronization signal is HIGH, the power supply voltage fluctuation in the cable 30 on which the video signal is superimposed is small, and the video signal can be superimposed on the cable 30 without being distorted. On the other hand, when a video signal is input while the vertical synchronization signal is LOW, the input video signal is stored in the memory 153a and the clock reproduction signal generated by the synchronization signal generation circuit 14 is output to the power supply superimposing circuit 18. To do. Then, after the vertical synchronization signal becomes HIGH, the video signal stored in the memory 153 a is output to the power supply superimposing circuit 18.

  The power superimposing circuit 18 superimposes the video signal or the clock reproduction signal on the power supply line constituting the cable 30 and outputs the superimposed signal to the power / signal separation circuit 21 of the external unit 20. Further, the power superimposing circuit 18 takes out the power supply voltage supplied from the extracorporeal unit 20 and sends it to the internal power supply circuit 19 of the in-vivo unit 10. The internal power supply circuit 19 generates power for driving each part of the in-vivo device 10 such as the image sensor 11, the signal processing circuit 15, and the LED 16 from the power supply voltage sent from the power supply superimposing circuit 18, and generates the generated power. It supplies to each part of the in-vivo unit 10.

  The power supply / signal separation circuit 21 of the extracorporeal unit 20 separates the video signal or clock reproduction signal from the power supply line constituting the cable 30 and outputs the separated video signal or clock reproduction signal to the external image processing circuit 23. In addition, the power / signal separation circuit 21 sends the power supplied from the external power supply circuit 22 to the in-vivo device 10. The external image processing circuit 23 reads the video signal by reproducing the signal read clock from the video signal or the clock reproduction signal by the PLL 23a. The external image processing circuit 23 performs image processing on the video signal as necessary, and then outputs the image signal to the image display device 40. The image display device 40 displays an image based on the input video signal.

FIG. 2 is a circuit diagram illustrating an example of the power supply superimposing circuit 18 and the power supply / signal separation circuit 21.
The power superimposing circuit 18 uses the LVDS driver 181 to convert the video signal or the clock reproduction signal generated in the in-vivo unit 10 into a differential signal, and the differential signal is supplied to the power line (power supply side, GND) via the capacitors C1 and C2. On the side). Further, the input of the power supply voltage supplied to the power supply line to the LVDS driver 181 by the capacitors C1 and C2 is cut off. In addition, coils L1 and L2 are provided on the power supply line, and the input of the signal superimposed on the power supply line to the internal power supply circuit 19 by the coils L1 and L2 is cut off, and only the power supply voltage is input to the internal power supply circuit 19 is doing.

  Further, the power / signal separation circuit 21 inputs the video signal or the clock reproduction signal superimposed on the power supply line to the LVDS receiver 211 via the capacitors C3 and C4. A termination resistor R1 is connected to the input of the LVDS receiver 211. The LVDS standard voltage is biased by resistors R2 to R5 connected to the LVDS receiver 211, and the differential signal input to the LVDS receiver 211 is restored to the original video signal or clock reproduction signal. ing. In addition, coils L3 and L4 are provided on the power supply line, and the input of the signal superimposed on the power supply line to the external power supply circuit 22 is cut off by the coils L3 and L4.

  FIG. 3 is a diagram illustrating waveforms of various signals related to power supply superposition in the present embodiment. Here, the signals shown in FIG. 3 are, from the top, the LED control signal, the power supply voltage waveform of the power supply line, the vertical synchronization signal, the transmission signal (the hatched portion is a video signal, the white portion is a clock reproduction signal), and the power supply voltage waveform. The superimposition signal of the transmission signal is shown.

  As described above, the LED 16 emits light only while the LED control signal is HIGH. Note that the LED 16 performs control so that the light emission amount varies depending on the brightness of the imaging target of the imaging element 11. FIG. 3 is an example in which the light emission amount of the LED 16 is controlled by varying the period during which the LED control signal is HIGH (that is, the light emission period of the LED 16) depending on the brightness of the imaging target. Specifically, when the imaging target is dark, the HIGH period is set longer than when it is bright. Such LED control signal control is indicated by double-ended arrows in FIG. However, the period during which the LED control signal is HIGH should not exceed the period during which the vertical synchronization signal is LOW (vertical blanking period).

  Here, in the case of an LED driven by receiving a pulsed LED control signal as shown in FIG. 3, the current consumption increases when the LED 16 emits light, so the power supply voltage supplied from the extracorporeal unit 20 is the power supply / signal separation circuit 21. It fluctuates (drops) under the influence of the electromotive force generated in the coil and the winding resistance of the coil. If the video signal is superimposed during such a voltage fluctuation period, the video signal is distorted and causes an error. Therefore, in this embodiment, the video signal is not transmitted at least within the maximum light emission period of the LED 16, but the clock regeneration signal is transmitted so that the PLL 23a of the extracorporeal unit 20 can be correctly synchronized during this period. Specifically, as shown in FIG. 3, when the vertical synchronization signal becomes HIGH, transmission of the video signal is started, and when it becomes LOW, the video signal is not transmitted and a clock reproduction signal is transmitted. As described above, since the LED 16 does not exceed the vertical blanking period even when the light emission period is maximum, it is not possible to affect the image displayed on the image display device 40 by not transmitting a video signal within this period. Absent.

  Here, the relationship between HIGH and LOW of the LED control signal and the vertical synchronization signal shown in FIG. 3 may be reversed.

  By adopting the configuration as described above, it is possible to perform transmission with a simple configuration and no error due to load variation (voltage variation). That is, by transmitting a clock recovery signal for preventing the image processing in the external unit 20 from being out of synchronization without transmitting a video signal during a period of excessive fluctuation, it is possible to transmit an error-free video signal. Is possible.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram of an electronic endoscope used in the second embodiment of the present invention. The electronic endoscope shown in FIG. 4 has an in-vivo unit 10 and an extra-corporeal unit 20, which are configured to be communicably connected via a cable 30. An image display device 40 is connected to the extracorporeal device 20.

  The imaging device 11 captures a body organ or the like of the subject to acquire a video signal, and outputs the acquired video signal to the internal image processing circuit 151. The timing generation circuit 12 is a timing signal for controlling the operation timing of the imaging device 11, the LED 16 serving as a load, and the signal transmission circuit 153, the drive circuit 13, the LED control circuit 152 for controlling the LED serving as a load, and a synchronization signal generation. Each is transmitted to the circuit 14. The drive circuit 13 drives the image sensor 11 according to the timing signal from the timing generation circuit 12. The synchronization signal generation circuit 14 counts the timing signal from the timing generation circuit 12 to generate a synchronization signal (vertical synchronization signal), and outputs the generated vertical synchronization signal to the signal transmission circuit 153. Here, the synchronization signal may not be a vertical synchronization signal as long as it is a signal that can determine at least a period during which the LED 16 does not emit light. Further, the synchronization signal generation circuit 14 generates a clock reproduction signal from the timing signal from the timing generation circuit 12 and outputs it to the signal transmission circuit 153.

  The signal processing circuit 15 processes a signal generated in each part of the in-vivo device 10. The internal image processing circuit 151 performs various signal processing such as A / D conversion and gain increase on the video signal input from the image sensor 11, and sends the processed video signal to the signal transmission circuit 153. Further, the internal image processing circuit 151 calculates the brightness of the image by integrating the video signal from the image sensor 11, and outputs a brightness signal indicating the calculated brightness of the image to the LED control circuit 152. The LED control circuit 152 receives the timing signal from the timing generation circuit 12, determines the timing of light emission start, determines the light emission amount (light emission time or current) of the LED 16 from the brightness signal from the internal image processing circuit 151, An LED control signal for controlling the light emission of the LED is generated and output to the LED drive circuit 17 and the signal transmission circuit 153. The LED drive circuit 17 drives the LED 16 based on the LED control signal.

  Based on the LED control signal, the signal transmission circuit 153 outputs a video signal to the power supply superimposing circuit 18 while avoiding a period in which voltage fluctuation occurs at the start and end of light emission of the LED 16. On the other hand, when a video signal is input during a period in which voltage fluctuation occurs at the start and end of light emission of the LED 16, the input video signal is stored in the memory 153a and used for clock reproduction generated by the synchronization signal generation circuit 14. The signal is output to the power supply superimposing circuit 18. Thereafter, after the voltage is stabilized, the video signal stored in the memory 153 a is output to the power supply superimposing circuit 18. Here, the period in which the voltage fluctuation occurs at the start and end of light emission of the LED 16 is detected by counting by the counter 153b from the input time point of the LED control signal.

  The power superimposing circuit 18 superimposes the video signal or the clock reproduction signal on the power supply line constituting the cable 30 and outputs the superimposed signal to the power / signal separation circuit 21 of the external unit 20. Further, the power superimposing circuit 18 takes out the power supply voltage supplied from the extracorporeal unit 20 and sends it to the internal power supply circuit 19 of the in-vivo unit 10. The internal power supply circuit 19 generates power for driving each part of the in-vivo device 10 such as the image sensor 11, the signal processing circuit 15, and the LED 16 from the power supply voltage sent from the power supply superimposing circuit 18, and generates the generated power. It supplies to each part of the in-vivo unit 10.

  The power supply / signal separation circuit 21 of the extracorporeal unit 20 separates the video signal or clock reproduction signal from the power supply line constituting the cable 30 and outputs the separated video signal or clock reproduction signal to the external image processing circuit 23. In addition, the power / signal separation circuit 21 sends the power supplied from the external power supply circuit 22 to the in-vivo device 10. The external image processing circuit 23 reads the video signal by reproducing the signal read clock from the video signal or the clock reproduction signal by the PLL 23a. The external image processing circuit 23 performs image processing on the video signal as necessary, and then outputs the image signal to the image display device 40. The image display device 40 displays an image based on the input video signal.

  The power superimposing circuit 18 and the power / signal separation circuit 21 are the same as those in the first embodiment shown in FIG.

  FIG. 5 is a diagram illustrating waveforms of various signals related to power supply superposition in the present embodiment. Here, from the top, the signals shown in FIG. 5 are the LED control signal, the power supply voltage waveform of the power supply line, the transmission signal (the hatched portion is the video signal, the white portion is the clock reproduction signal), and the power supply voltage waveform and the transmission signal are superimposed. The signal is shown.

  As described above, the LED 16 emits light only while the LED control signal is HIGH. Note that the LED 16 performs control so that the light emission amount varies depending on the brightness of the imaging target of the imaging element 11. Such LED control signal control is indicated by double-ended arrows in FIG.

  Here, in the case of an LED that is driven by receiving a pulsed LED control signal as shown in FIG. 5, the current consumption increases when the LED 16 emits light. Therefore, the power supply voltage supplied from the extracorporeal unit 20 is the power supply / signal separation circuit 21. It fluctuates (drops) under the influence of the electromotive force generated in the coil and the winding resistance of the coil. If the video signal is superimposed during such a voltage fluctuation period, the video signal is distorted and causes an error. Therefore, in the present embodiment, a video signal is not transmitted at least within a period in which the power supply voltage is not stable, which is a period immediately after the LED control signal changes from HIGH to LOW and a period immediately after the LED control signal changes from LOW to HIGH. Also during this period, a clock regeneration signal is transmitted so that the PLL 23a of the extracorporeal unit 20 can be correctly synchronized.

  Here, the time from the start of voltage fluctuation to the stabilization of the voltage (rise time and fall time in the voltage waveform of FIG. 5) is constant. Therefore, the signal transmission circuit 153 starts counting by the counter 153b when the LED control signal becomes HIGH, and starts transmission of the video signal again after the counter 153b measures a certain rise time. In this way, even when the LED 16 is emitting light, the video signal is transmitted within a period in which the voltage is stable. Next, when the LED control signal becomes LOW, the light emission of the LED 16 ends and the power supply voltage rises. At that time, the transmission of the video signal is stopped and the clock reproduction signal is transmitted. At this time, the counter 153b starts counting, and after the counter 153b measures a certain falling time, transmission of the video signal is started again.

  Here, the relationship between the HIGH and LOW of the LED control signal and the vertical synchronization signal shown in FIG. 5 may be reversed.

  By adopting the configuration as described above, it is possible to transmit a video signal while the LED is emitting light, and to transmit without causing an error due to load fluctuation.

  In FIG. 5, the video signal is transmitted except for the timing of the rise and fall of the LED control signal from when the power supply voltage drops until it returns to the original state. However, as shown in FIG. Only the clock reproduction signal may be transmitted during the light emission period. This is a period after the LED control signal becomes HIGH and the LED 16 starts to emit light, then becomes LOW and after a certain time has elapsed, and within the period from the start to the end of the fluctuation of the voltage waveform of the power supply line, This means that no signal is transmitted. As a result, the processing can be simplified by reducing the number of times of switching between transmission of the video signal and transmission of the clock recovery signal.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention. For example, in the above-described embodiment, the LED 16 that emits a pulse as the load connected to the power supply line is cited. However, an illumination element other than the LED, various sensors such as a temperature sensor, the image sensor 11 and the like are also considered as the load. The method of this embodiment can be applied to these loads. That is, only the clock recovery signal is transmitted within a period in which the power supply voltage variation due to the load is large, and the video signal is transmitted within a period during which the power supply voltage variation due to the load is small. An effect can be obtained.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, the above-described problem can be solved, and this configuration requirement is deleted when the above-described effects can be obtained. The configuration can also be extracted as an invention.

1 is a block diagram of an electronic endoscope used in a first embodiment of the present invention. It is a circuit diagram which shows an example of a power supply superimposition circuit and a power supply / signal separation circuit. It is a figure which shows the waveform of the various signals which concern on the power supply superposition in 1st Embodiment. It is a block diagram of the electronic endoscope used for the 2nd Embodiment of this invention. It is a figure which shows the waveform of the various signals which concern on the power supply superposition in 2nd Embodiment. It is a figure shown about the modification of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal organs, 11 ... Image sensor, 12 ... Timing generation circuit, 13 ... Drive circuit, 14 ... Synchronization signal generation circuit, 15 ... Signal processing circuit, 16 ... Light emitting diode (LED), 17 ... LED drive circuit, 18 ... Power superimposition circuit, 19 ... internal power supply circuit, 20 ... external unit, 21 ... power supply / signal separation circuit, 22 ... external power supply circuit, 23 ... external image processing circuit, 30 ... cable, 40 ... image display device, 151 ... internal image Processing circuit 152 ... LED control circuit 153 ... Signal transmission circuit

Claims (6)

Imaging means for imaging a subject to obtain a video signal;
Signal transmission means for controlling transmission of the video signal so as to transmit a clock reproduction signal instead of the video signal in a period when the load connected to the power supply line fluctuates at least;
Signal superimposing means for superimposing the video signal or clock reproduction signal transmitted from the signal transmitting means on the power supply line;
Signal separating means for separating the superimposed video signal or clock reproduction signal from the power supply line;
An electronic endoscope comprising: A load control unit configured to set a period for changing the load based on the timing signal and to control the load to change within the set period;
The signal transmission means determines a period during which the load fluctuates based on the timing signal, transmits the clock regeneration signal to the signal superimposing means within the period during which the load fluctuates, and is outside the period during which the load fluctuates. The electronic endoscope according to claim 1, wherein the video signal is transmitted to the signal superimposing unit. Load control means for transmitting to the load a load control signal for controlling a load connected to the power line;
The electronic endoscope according to claim 1, wherein the signal transmission unit transmits the video signal or the clock reproduction signal to the signal superimposing unit based on the load control signal.   The signal transmission means transmits the clock regeneration signal when a load control signal for changing the load is transmitted from the load control means, and considers that the load has become constant after a predetermined time has elapsed. The electronic endoscope according to claim 3, wherein a video signal is transmitted.   The signal transmission means transmits the clock regeneration signal during a period from when the load starts to fluctuate until it returns to the original state by a load control signal from the load control means. 3. An electronic endoscope according to 3.   The electronic endoscope according to claim 1, wherein the load includes a light emitting diode that illuminates the subject by pulsed light emission.

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