JP6073113B2 - Electronic endoscope system - Google Patents

Description

  The present invention relates to an image switching system for switching an image from one method to another method in an electronic endoscope system capable of photographing by different methods, and more particularly to an affected part such as a confocal image in addition to a normal color image. The present invention relates to an image switching system of an electronic endoscope system that employs an imaging method for close-up photography.

  In recent years, endoscope systems using confocal optical systems have been developed. In the confocal endoscope, for example, a biological cell is irradiated with a blue laser, and fluorescence emitted at various depths is detected by a photomultiplier tube (PMT) through a confocal optical system adjusted to a specific depth. Then, a fine and clear fluorescent image of a specific depth is taken by scanning this surface. In addition, the three-dimensional information of the observation site is obtained by scanning in the depth direction.

  On the other hand, since it is necessary to maintain the distance between the confocal optical system and the subject to be constant (usually a close distance), the confocal image is detected by observing the tip of the endoscope insertion part. It is done by pressing against the site. In addition, since the confocal image is a high-magnification image of a subject at a specific distance, the confocal endoscope is also provided with an optical system that captures a normal color image using an imaging element such as a CCD, and a normal color image is provided. An image is also taken (see Patent Document 1).

JP 2005-000640 A

  In the confocal endoscope configured as described above, a confocal image and a normal color image are always captured and displayed on a monitor. However, the confocal image acquired until the distal end of the insertion portion is appropriately pressed against the observation site is mostly composed of noise components and becomes an indefinite image. On the other hand, in a state where the distal end of the insertion portion is pressed against the observation site, the image captured by the image sensor is a substantially red image that is not focused. Display of these images on a monitor generally gives an observer unpleasant feeling. Therefore, it is desired to automatically determine which imaging system is currently appropriate for imaging and switch the display image accordingly.

  An object of the present invention is to provide a system for automatically determining which imaging system is currently appropriate in an endoscope having an appropriate imaging system that differs depending on the distance to the observation site.

  An image determination system for an electronic endoscope according to the present invention includes a first imaging system for photographing a subject from a relatively long distance, a second imaging system for photographing a subject from a relatively short distance, The image processing apparatus includes a determination unit that determines which imaging system is appropriate for imaging based on an image signal obtained by one imaging system and an image signal obtained by the second imaging system.

  The determination means preferably performs the above determination based on a histogram for the image signal from each imaging system. For example, the first imaging system captures a color image, and the second imaging system captures a confocal image, for example. At this time, regarding the color image, it is preferable to use a histogram relating to the luminance signal and a histogram relating to the R signal.

  When determining whether or not shooting by the second imaging system is appropriate, it is preferable to use histograms for image signals from the first and second imaging systems, and shooting by the first imaging system is appropriate. For example, only the histogram for the image signal from the second imaging system is used. It is preferable that the determination means make the above determination based on a value in which the cumulative frequency from one side in each histogram becomes a predetermined number of pixels in one screen.

  It is preferable that the image determination system further includes switching means for switching from shooting from the first or second imaging system to the other shooting based on the above determination, and switching the output to the image display device to the other display. It is also preferable to stop unnecessary functions of the imaging system that are not used by the switching means.

  When the images of the first and second imaging systems are always output to the image display device, it is preferable to perform mask processing on the images of the imaging systems that are not used. A pressure sensor may be provided at the tip of the second imaging system, and the presence or absence of contact with the subject at the tip of the second imaging system detected by the pressure sensor may be used for the above determination.

  An electronic endoscope system according to the present invention includes the image determination system.

  According to the present invention, it is possible to automatically determine which imaging system is currently appropriate in an endoscope in which an appropriate imaging system differs depending on the distance to the observation site.

1 is an external view showing a configuration of an electronic endoscope system to which an image determination system according to an embodiment of the present invention is applied. It is an expansion perspective view of the front-end | tip of an endoscope insertion part. It is a block diagram about the color electronic endoscope system in an electronic endoscope system. It is a block diagram about the confocal electronic endoscope system in an electronic endoscope system. It is a flowchart which shows the outline of the main flow of a system. It is a flowchart of an image switching process. It is an example of the monitor display in this embodiment. It is a histogram which illustrates the relationship between a threshold value and the frequency distribution of a signal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an external view of an electronic endoscope system equipped with an image determination system according to an embodiment of the present invention.

  The electronic endoscope system 10 mainly includes a scope 11 having a flexible tubular insertion portion, a color image processor device 12, a confocal image processor device 13, and a monitor 14. As described later, the scope 11 is provided with two types of imaging systems, a color image imaging system and a confocal image imaging system, and a color image processor device 12 and a confocal image processor via universal codes 15 and 16, respectively. The device 13 is detachably connected. In this embodiment, the monitor 14 is connected only to the confocal image processor device 13, and the video output of the color image processor device 12 is output to the monitor 14 via the confocal image processor device 13.

  The insertion unit 17 of the scope 11 is inserted into, for example, the human body P, and in a color image imaging system, normal color image shooting is performed by an imaging device provided at the distal end of the insertion unit 17. On the other hand, in the confocal imaging system, laser light is emitted from the distal end of the insertion portion 17, and fluorescence excited in the living tissue is detected by a photodetector through the confocal optical system, and this is two-dimensionally scanned at the observation site. By doing so, a monochrome confocal image is acquired. Further, by moving the focal plane in the depth direction, information in the depth direction of the living tissue (three-dimensional information) is also acquired. FIG. 1 shows a state in which the confocal image is displayed on the monitor 14 through the confocal image capturing system, and at this time, the distal end of the insertion portion 17 is pressed against the observation site.

  FIG. 2 is an enlarged perspective view of the distal end of the endoscope insertion portion 17. The color image is irradiated with white illumination light supplied from the color image processor device 13 through the light guide 23 (see FIG. 3) from the tip of the insertion portion 17 through the illumination lens 24, and the reflected light is transmitted through the objective lens 19. The image is picked up by being detected by an image sensor provided in the image sensor 17.

  Further, for example, a protrusion 20 is provided on the distal end surface 17A of the insertion portion 17, and an objective lens 21 of a confocal image capturing system is disposed on the protrusion 20. The objective lens 21 is irradiated with a light beam (for example, a blue laser) such as a laser, and light (for example, fluorescence) from one point of the living tissue is incident on the confocal imaging system through the objective lens 21 and detected by the photodetector. . Thus, the distance from the subject to the objective lens of each imaging system is relatively longer in the objective lens 19 than in the objective lens 21. A two-dimensional confocal image is generated by two-dimensionally operating this. During confocal image capturing, the protrusion 20 is pressed against the observation region, and the distance from the observation region is maintained constant.

  FIG. 3 is a block diagram relating to a color electronic endoscope system in the electronic endoscope system 10, and shows an optical and electrical configuration of the color image imaging system and the color image processor device 12 in the scope 11.

  The color image pickup system provided in the scope 11 includes a light guide 23 and an illumination lens 24 provided at the tip thereof. The base end portion of the light guide 23 is optically connected to a light source unit 26 provided in the color image processor device 12 via a connector 25A. White light is supplied from the light source unit 26 to the light guide 23, and white illumination light is emitted from the distal end of the insertion unit via the illumination lens 24. Under this illumination light, the subject image is detected by an image sensor 27 such as a CCD or CMOS through the objective lens 19.

  The image sensor 27 is connected to the video controller 28 and the preprocess circuit 29 of the color image processor device 12 through the connector 25B. The driving of the image sensor 27 is controlled by a drive signal from the video controller 28, and the image signal detected by the image sensor 27 is converted into a digital signal through the preprocessor circuit 29.

  A color image digital signal output from the preprocessor circuit 29 is sent to the video controller 28 and also input to the luminance histogram circuit 30 and the R signal histogram circuit 31. In the luminance histogram circuit 30 and the R signal histogram circuit 31, histograms relating to the luminance signal and the R signal are created for the input image signal for one screen, and are output to the video controller 28. The image signal input to the video controller 28 is subjected to predetermined image processing as necessary, and is output to the video controller 52 (see FIG. 4) of the confocal image processor device 13.

  On the other hand, the outputs from the histogram circuits 30 and 31 are sent to the system controller 32 via the video controller 28 and then sent to the confocal image processor 13. The system controller 32 controls the entire color image processor device 12 including communication with the confocal image processor device 13 and controls the scope 11 via the front panel 33, the foot switch 34, the keyboard 35, and the connector 25C. An operation button 36 and the like provided on an operation unit (not shown) are also connected. The drive timing of each device in the color image processor unit 12 is controlled by a timing generator 37.

  Next, the configuration of the confocal system in the electronic endoscope system 10 will be described with reference to the block diagram of FIG. FIG. 4 shows the optical and electrical configurations of the confocal image capturing system of the scope 11 and the confocal image processor 13.

  The confocal imaging system provided in the scope 11 includes an objective lens (group) 21, an optical fiber 38, and an optical coupling unit 42, a light source unit 43, and a light receiving unit 44 provided in the confocal image processor device 13. Composed. The optical fiber 38 transmits laser light supplied from the light source unit 43 through the optical coupling unit 42 and emits the laser beam from the distal end of the insertion unit 17. At this time, the fluorescence from the living tissue excited by the laser light is incident on the optical fiber 38, and the fluorescence is transmitted to the light receiving unit 44 through the optical coupling unit 42.

  On the other hand, the two-dimensional scanning of the subject by laser light is performed by driving the tip of the optical fiber 38 by the fiber drive unit 39. For example, the fiber drive unit 39 includes a piezoelectric element 40, and the tip of the optical fiber 38 that is cantilevered by a drive signal sent from the scan driver 53 provided in the confocal image processor device 13 through the connector 41B. For example, two-dimensional scanning is realized by moving in two independent directions perpendicular to the axial direction and bending the tip of the optical fiber 38. The position of the objective lens 21 can be adjusted in the axial direction by a drive signal from the scan driver 53. The position of the focal plane is adjusted by controlling the position of the objective lens 21, and confocal for different distances in the depth direction. An image is acquired.

  The optical fiber 38 is optically connected to the confocal image processor device 13 through the connector 41A, and the light source unit 43 and the light receiving unit 44 through an optical coupling unit 42 provided in the confocal image processor device 13. Connected to. The optical coupling unit 42 is, for example, a two-input, two-output optical directional coupler (optical coupler) 42A. The laser light source 43A of the light source unit 43 is connected to the port P1, and the optical fiber is connected to the port P3 corresponding to the straight port of the port P1. 38 is connected. That is, the light from the laser light source 43A is guided from the port P1 to the port P3 and is emitted from the distal end of the insertion portion 17 through the optical fiber 38. In the present embodiment, the laser beam emitted from the laser light source 43A is, for example, 488 nm.

  For example, a photodiode (PD) 45 is connected to the port P4 corresponding to the cross port of the port P1. That is, the output of the laser light source 43A is monitored by the photodiode (PD) 45, and the laser driver 46 that drives the laser light source 43A is based on the signal from the photodiode (PD) 45 via the PD amplifier 45A. Control the drive.

  On the other hand, the light receiving unit 44 is connected to the port P2 corresponding to the cross port of the port P3, and the light output from the port P2 is received by the photomultiplier tube (PMT) 44B through the confocal optical system 44A of the light receiving unit 44. That is, the fluorescence of the living tissue by the laser light emitted from the optical fiber 38 enters the optical fiber 38 and is received by the photomultiplier tube (PMT) 44B through the ports P3 and P2.

  The gain of the photomultiplier tube (PMT) 44B is controlled by the PMT controller 47 through the PMT amplifier 44C. To the PMT controller 47 and to the histogram circuit 50. The histogram circuit 50 creates a histogram for the input image signal for one screen and outputs it to the PMT controller 47.

  The confocal image input to the PMT controller 47 is input to the image controller 51 of the confocal image processor 13, and the confocal image is further output to the video controller 52. On the other hand, the histogram value input to the PMT controller 47 is sent to the system controller 54 of the confocal image processor 13.

  The image signal input to the video controller 52 is subjected to predetermined image processing and is output to the monitor 14 as necessary. In the present embodiment, as described above, the color image transmitted from the video controller 28 (see FIG. 3) of the color image processor device 12 is also input to the video controller 52, and can be output to the monitor 14, for example. The The image switching process between the color image and the confocal image based on the image determination process of the present embodiment will be described later.

  The system controller 54 controls the entire confocal image processor 13 including communication with the color image processor 12 and controls the scope 11 via the front panel 55, the foot switch 56, the keyboard 57, and the connector 41C. An operation button 58 and the like provided on an operation unit (not shown) are also connected. The drive timing of each device in the confocal image processor 13 is controlled by a timing generator 59.

  Next, image switching processing (including image determination processing) of the present embodiment will be described with reference to FIGS. Note that the image switching process of the present embodiment automatically determines whether an image by a color image capturing system or a confocal image capturing system is currently appropriate, and switches to an appropriate image. Is what you do.

  FIG. 5 is a flowchart showing an outline of the main flow of the system. For example, FIG. 6 executed in the system controller 54 of the confocal image processor 13 is a flowchart of the image switching process of the present embodiment. In this description, only the description related to the image switching process will be given.

  The image switching process of this embodiment is executed as an interrupt task process, for example. When the confocal image processor 13 is powered on and the flow of FIG. 5 is started, the system is initialized in step S100. In the initialization process, various parameters including parameters for the image switching process are initialized. Note that the image switching flag Image_flag is initially set to 0 as a parameter for image switching processing.

  In the present embodiment, Image_flag = 0 indicates that the current observation mode is the color image mode and the image switching process monitors the timing of switching to the confocal image. On the other hand, Image_flag = 1 indicates that the current observation mode is the confocal image mode, and the image switching process monitors the timing of switching to a color image.

  When the system initialization process in step S100 ends, the interrupt task process shown in step S102 is repeatedly executed until the power is turned off, for example. In other words, when an event occurs, a flag is set for the event, and in the interrupt task process in step S102, the flagged process is executed in a steady cycle. In the present embodiment, for example, an image switching process flag is set when an image automatic switching mode is set or when an image signal is received from the color image processor device 12.

  When the image switching process shown in FIG. 6 is started in the interrupt task process in step S102, it is determined in step S200 whether the image switching flag Image_flag is 0 or 1. As described above, the flag Image_flag = 0 indicates that the current observation mode is the normal color image mode, and the image switching flag Image_flag is set to 0 immediately after the initialization process. This is because endoscopic observation is started from observation of a normal color image, and confocal imaging is started only after the distal end of the insertion portion is pressed against the observation site.

  In the present embodiment, for example, as shown in FIG. 7, a color image display area A1 for displaying a normal color image and a confocal image display area A2 for displaying a confocal image are provided on one screen A0. . At the time of color image observation, as shown in FIG. 7A, a normal color image is displayed in the color image display area A1, and a blue background image, for example, is displayed in the confocal image display area A2. On the other hand, at the time of confocal image observation, as shown in FIG. 7B, the confocal image is displayed in the confocal image display region A2, and the blue image is displayed in the color image display region A1.

  If it is determined in step S200 that the image switching flag Image_flag = 0, the image switching processing in steps S202 to S220 in the color image mode is started, and the counter CNT1 is initialized to 0 in step S202. The counter CNT1 counts the number of times that the condition for switching to the confocal image is satisfied. In this embodiment, the counter CNT1 switches to the confocal image when the value of the counter CNT1 reaches a predetermined threshold as described below. Run. At this time, color image observation is performed, and a color image is displayed on the monitor 14 as shown in FIG.

  In step S204, image information of a color image (white light image), that is, a value of a histogram related to the luminance signal and the R signal is acquired. In step S206, the frequency from the higher luminance value (signal level) is accumulated in the luminance histogram. Is obtained as a luminance value (signal level) that becomes a predetermined ratio of the whole (for example, 80% of pixels in one screen), and it is determined whether or not it is equal to or greater than a predetermined threshold value. FIG. 8A shows an example of a histogram when the luminance value (signal level) S at which the frequency accumulation from the higher signal level is 80% of the pixels in one screen is larger than the predetermined threshold T. FIG. 8B shows an example of a histogram when the luminance value (signal level) S obtained is smaller than a predetermined threshold T.

  If it is determined that the threshold value is equal to or greater than the threshold, in step S208, in the histogram of the R signal (R component), the cumulative frequency from the higher R signal value side is a predetermined ratio (for example, 80% in one screen). R signal value is obtained, and it is determined whether or not the value is equal to or greater than a predetermined threshold value. If it is determined in either step S206 or step S208 that the obtained value is less than the threshold value, the current image switching process is terminated, and the process returns to the interrupt task process loop.

  On the other hand, if it is determined in step S206 and step S208 that the obtained value is equal to or larger than the threshold value, the image information of the confocal image, that is, the histogram value of the confocal image is acquired in step S210. In step S212, in the histogram of the confocal image, a gain value is obtained in which the cumulative frequency from the higher gain value side is a predetermined ratio (for example, 50%) of the whole, and whether the value is equal to or greater than a predetermined threshold value. It is determined whether or not. If it is determined that the obtained value is less than the threshold value, the current image switching process is terminated, and the process returns to the interrupt task process loop.

  On the other hand, if it is determined in step S212 that the obtained value is equal to or greater than the threshold value, the value of the counter CNT1 is incremented (+1) in step S214. In other words, the brightness and red component of the color image are high (corresponding to the situation where the endoscope tip seems to be too close to the living tissue to capture a color image) and obtained with a confocal imaging system. When the output from the PMT 44B is sufficiently high (a situation where the endoscope tip is considered to be close enough to the living tissue to capture a confocal image), a counter that prompts switching to the confocal image The value of CNT1 is incremented.

  In the color image mode, since the fiber drive unit 39 is stopped, a histogram related to the confocal image is created with respect to the output obtained from the PMT 44B over a time corresponding to one screen, for example.

  Next, in step S216, it is determined whether or not the value of the counter CNT1 has reached a predetermined threshold value. If the value of the counter CNT1 has not reached the predetermined threshold value, the process returns to step S204, and the above-described process is repeated. On the other hand, if the counter CNT1 has reached the predetermined threshold value in step S216, the image switching flag Image_flag = 1 is set in step S218, and various functions required for confocal image observation are activated in step S220, which are unnecessary. The various functions are stopped. That is, the observation mode is switched from the color image mode to the confocal image mode.

  For example, the color image display area A1 is a blue-back image (see FIG. 7B), the drive of the scan driver 53 is started, and the drive of the optical fiber 38 by the fiber drive unit 39 is started (FIG. 4). reference). Further, the lamp of the light source unit 26 used for photographing the color image is turned off, and the image data scanned by the confocal imaging system is recorded in the recorder 59, and the confocal image is displayed in the confocal image display area A2. Is started. As a result, the current image switching process ends, and the process returns to the interrupt task process loop.

  On the other hand, if it is determined in step S200 that the image switching flag Image_flag = 1, the image switching processing in steps S222 to S234 in the confocal image mode is started, and the counter CNT2 is initialized to 0 in step S222. The counter CNT2 counts the number of times that the condition for switching to a normal color image is satisfied. In this embodiment, when the value of the counter CNT2 reaches a predetermined threshold, switching to a color image is performed as described below. Run. At this time, confocal image observation is performed, and the confocal image is displayed on the monitor 14 as shown in FIG.

  In step S224, the image information of the confocal image, that is, the value of the histogram relating to one confocal image is acquired. In step S226, the cumulative frequency from the higher gain value side in the histogram of the confocal image is Is determined, and it is determined whether the value is equal to or greater than a predetermined threshold. If it is determined that the obtained value is greater than or equal to the threshold value, the current image switching process is terminated, and the process returns to the interrupt task process loop.

  On the other hand, if it is determined in step S226 that the obtained value is less than the threshold value, the value of the counter CNT2 is incremented (+1) in step S228. That is, when the gain value of the confocal image is low as a whole (the situation where the endoscope tip is not close enough to the living tissue to capture the confocal image), switching to the color image is performed. The value of the counter CNT2 to be urged is incremented.

  Next, in step S230, it is determined whether or not the value of the counter CNT2 has reached a predetermined threshold value. If the value of the counter CNT2 has not reached the predetermined threshold value, the process returns to step S222, and the above-described process is repeated. On the other hand, if the counter CNT2 has reached the predetermined threshold value in step S230, the image switching flag Image_flag = 0 is set in step S232, and various functions required for color image observation are activated in step S234. Various functions to be performed are stopped. That is, the observation mode is switched from the confocal image mode to the color image mode.

  That is, the confocal image display area A2 is a blue back image (see FIG. 7A), the drive of the scan driver 53 is stopped, and the drive of the optical fiber 38 by the fiber drive unit 39 is stopped (FIG. 7). 4). In addition, the lamp of the light source unit 26 used for photographing a color image is turned on, and the display of the color image in the color image display area A1 is started. As a result, the current image switching process ends, and the process returns to the interrupt task process loop. Note that when the drive of the fiber drive unit 39 is stopped, the laser emitted from the optical fiber 38 performs a laser pointer function in the color image mode.

  As described above, according to the present embodiment, in an endoscope that has different appropriate imaging systems depending on the distance from an observation site, such as an endoscope that captures a color image and a confocal image, any imaging system is currently used. It is possible to automatically determine whether it is appropriate to use the screen, thereby switching the screen at an appropriate timing. Further, by masking an image inappropriate for observation, it is possible to provide a user-friendly image.

  In this embodiment, the image switching process is executed in the confocal image processor device, but may be performed in the color image processor device. In this case, one monitor is connected to the color image processor device. Also good. In this embodiment, the color image and the confocal image are displayed on one screen. However, the screen may be switched between the color image and the confocal image. Further, this processing can be applied even when each image is displayed on an independent monitor. In the present embodiment, the luminance histogram circuit 30 and the R signal histogram circuit 31 for creating the histogram of the luminance signal and the R signal are provided in the color image processor device 12, but these circuits are used as the confocal image processor. You may provide in the apparatus 13. FIG. In this way, communication between the system controller 32 of the color image processor device 12 and the system controller 54 of the confocal image processor device 13 can be omitted.

  In the present embodiment, an image that is not used for observation is masked with a blue background, but the mask processing may be other than the blue background. Furthermore, in the present embodiment, a color image and a confocal image have been described as examples, but the present invention can also be applied to other images. In the present embodiment, the histogram obtained from the confocal imaging system is also used to determine the switching from the color image to the confocal image (step S212), but this can be omitted. Further, in the confocal image mode, the driving of the image sensor may be stopped.

  In this embodiment, it is determined which imaging system is appropriate based on the image signal obtained by each imaging system. For example, a plurality of pressure-sensitive sensors are provided around the protrusions where the objective lens of the confocal imaging system is provided. The presence / absence of contact by all of the pressure-sensitive sensors may be taken into the above determination (for example, adopted in series with other conditions as one of the conditions for incrementing the counter). Further, in this embodiment, the value at which the frequency accumulation from the higher value side in the histogram is determined to be a predetermined ratio, and the determination is made based on this value. However, the frequency accumulation from the lower value side can also be used. In addition, other statistics such as an average value, median value, and mode value can be used instead, and these can be used in combination.

DESCRIPTION OF SYMBOLS 10 Electronic endoscope system 11 Scope 12 Processor apparatus for color images 13 Processor apparatus for confocal images 14 Monitor 17 Endoscope insertion part 19 Objective lens (color image imaging system)
20 Protrusion 21 Objective lens (confocal imaging system)
DESCRIPTION OF SYMBOLS 23 Light guide 24 Illumination lens 26 Light source part 28, 52 Video controller 30 Luminance histogram circuit 31 R signal histogram circuit 32, 54 System controller 38 Optical fiber 39 Fiber drive unit 40 Piezoelectric element 42 Optical coupling part 42A Optical coupler 43 Light source part 43A Laser Light source 44 Light receiver 44B Photomultiplier tube (PMT)
47 PMT controller 50 Histogram circuit 51 Image controller 53 Scan driver

Claims (8)

A first imaging system for photographing a subject from a relatively long distance;
A second imaging system for photographing the subject from a relatively short distance;
A determination unit that determines which imaging system is appropriate for imaging based on an image signal obtained by the first imaging system and an image signal obtained by the second imaging system ;
Wherein the first and the image of the second imaging system continuously output to the image display device, an electronic endoscope Kagamishi stem, characterized in Rukoto performs masking processing for the image of the imaging system that are not being used. Electronic endoscope Kagamishi stem according to claim 1, characterized in that said determination means wherein the determination on the basis of the histogram for the image signal from the imaging systems. Wherein the first imaging system performs imaging of a color image, the electronic endoscope Kagamishi stem according to claim 2, wherein the second imaging system and performing the imaging confocal image. The regard to color image, the electronic endoscope Kagamishi stem according to claim 3, characterized in that utilizing the histogram of the histogram and R signals relating to the luminance signal. When it is determined whether or not shooting by the second imaging system is appropriate, whether or not shooting by the first imaging system is appropriate using a histogram for the image signals from the first and second imaging systems. when determining the whether the electronic endoscope Kagamishi stem according to any one of claims 2-4, characterized by using only the histogram for the image signal from the second imaging system. 6. The determination unit according to claim 2, wherein the determination unit performs the determination based on a value in which a cumulative frequency from one side in each histogram becomes a predetermined number of pixels in one screen. electronic endoscope Kagamishi stem according to claim. 2. The apparatus according to claim 1, further comprising switching means for switching from shooting from the first or second imaging system to the other shooting based on the determination, and switching the output to the image display device to the other display. electronic endoscope Kagamishi stem according to any one of 6. Electronic endoscope Kagamishi stem according to claim 7, characterized in that stop unnecessary functions of the imaging system which is not used by the switching means.

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