Patent Publication Number: US-11051004-B2

Title: Image processing apparatus, camera apparatus, and image processing method

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an image processing apparatus, a camera apparatus, and an image processing method for processing a captured image obtained during a medical practice, for example. 
     2. Description of the Related Art 
     For example, in microscopic surgery in which a microscope for surgery is used while observing a fine surgical target site (such as an affected part of a human body) or an endoscopic surgical operation in which an endoscope is used while observing a surgical target site in the body, an observation image including the surgical target site is imaged and displayed on a monitor. By displaying the observation image on the monitor, it is possible to easily and finely recognize the surgical target site, and it is possible for a plurality of persons involved in surgery to observe the details of the site, and it is possible to grasp the situation in real time while observing an image of the surgical site. 
     As a related art of the kind of camera apparatus, for example, a stereoscopic endoscope apparatus of Japanese Patent Unexamined Publication No. 2011-206425 (PTL 1) is known. In the stereoscopic endoscope apparatus, an endoscope acquires a wide-angle side captured image (2D image), a stereoscopic viewing image (3D image) and a navigation image (whole image), a 3D image is displayed at a part of a 2D image, and the display region of the 3D image is controlled. Accordingly, it is possible to alleviate fatigue or tension of the reference person of the image. 
     In the above-described medical camera system, in order to ensure a clear field of view of a target site at which surgery or treatment is performed, a display video with high definition and excellent visibility is desired. In addition, since the size or state of an observation target can be grasped more accurately and easily by stereoscopic viewing of a target site, there is an increasing demand for a 3D video that provides a stereoscopic observed video to the observer. Particularly, in a surgical application of a fine site, a high-definition 3D video is required, but in the related art, such as PTL 1, there was a problem that it is difficult to visually recognize the details of the observed video clearly. In addition, in order to generate a high-definition 3D video required in the medical field, it is necessary to use two different cameras for imaging an image for a left eye (hereinafter referred to as “left eye image”) and an image for a right eye (hereinafter referred to as “right eye image”) which have parallax. 
     In addition, for example, in a medical camera system, visibility of video displayed on a monitor is particularly important for a doctor or the like to grasp the details of the situation of a target site (for example, an affected part of a human body). The video displayed on the monitor at the time of surgery or examination is appropriately switched between the 2D video capable of planar viewing and the 3D video capable of stereoscopic viewing. Here, in the related art as in PTL 1, since it is not considered to switch from 2D video to 3D video as the video displayed on the monitor, the following problems are caused when switching from the display of the 2D video to the display of the 3D video. First, in order to improve the image quality (that is, visibility) of the video, various types of signal processing (for example, automatic exposure processing, such as auto exposure (AE)) or adjustment processing of white balance (WB), are performed with respect to the imaged video. However, at the time of switching from the display of 2D video to the display of 3D video, when an area on an imaging surface used for deriving parameters of the signal processing of the 2D video is used as it is as an area used for deriving parameters of the signal processing of the 3D video, there is a case where the 3D video having appropriate image quality cannot be obtained. 
     SUMMARY 
     In view of the above-described conventional circumstances, an object of the disclosure is to provide an image processing apparatus, a camera apparatus, and an image processing method which are capable of adaptively adjusting an area on an imaging surface used for deriving parameters of signal processing with respect to an imaged 3D video when switching from display of a 2D video to display of the 3D video, and imaging and outputting a high-definition 3D video with one camera. 
     The disclosure provides an image processing apparatus which is connected to a camera head capable of imaging a left eye image and a right eye image having parallax on one screen based on light at a target site incident on an optical instrument, the apparatus including: a deriver that derives parameters of signal processing for the left eye image and the right eye image which are imaged by the camera head in accordance with switching from a 2D mode to a 3D mode; an image processor that performs the signal processing of the left eye image and the right eye image which are imaged by the camera head, based on the derived parameters; and an output controller that outputs the left eye image and the right eye image to which the signal processing is performed to a monitor. 
     In addition, the disclosure provides a camera apparatus including: a camera head capable of imaging a left eye image and a right eye image having parallax on one screen based on light at a target site incident on an optical instrument; a deriver that derives parameters of signal processing for the left eye image and the right eye image which are imaged by the camera head in accordance with switching from a 2D mode to a 3D mode; an image processor that performs the signal processing of the left eye image and the right eye image which are imaged by the camera head, based on the derived parameters; and an output controller that outputs the left eye image and the right eye image to which the signal processing is performed to a monitor. 
     Further, the disclosure provides an image processing method in which an image processing apparatus connected to a camera head capable of imaging a left eye image and a right eye image having parallax on one screen based on light at a target site incident on an optical instrument is used, the method including: deriving parameters of signal processing for the left eye image and the right eye image which are imaged by the camera head in accordance with switching from a 2D mode to a 3D mode; performing the signal processing of the left eye image and the right eye image which are imaged by the camera head, based on the derived parameters; and outputting the left eye image and the right eye image to which the signal processing is performed to a monitor. 
     According to the disclosure, when switching from the display of the 2D video to the display of the 3D video, it is possible to adaptively adjust the area on the imaging surface used for deriving the parameters of the signal processing for the imaged 3D video, and to image and output a high-definition 3D video with one camera. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system configuration view illustrating a configuration example in which a medical camera system including a camera apparatus of each embodiment is applied to a surgical microscope system; 
         FIG. 2  is a view illustrating an external appearance example of the surgical microscope system of each of the embodiments; 
         FIG. 3A  is a view illustrating an external appearance example of a front side of a camera head and a CCU of the camera apparatus of each of the embodiments; 
         FIG. 3B  is a view illustrating an external appearance example of a rear side of the CCU of the camera apparatus of each of the embodiments; 
         FIG. 4  is a block diagram illustrating a functional configuration example at the time of imaging a 2D video in the camera apparatus of each of the embodiments; 
         FIG. 5  is a block diagram illustrating a functional configuration example at the time of imaging a 3D video in the camera apparatus of each of the embodiments; 
         FIG. 6  is a block diagram illustrating a functional configuration example of an image processor of the camera apparatus of Embodiment 1; 
         FIG. 7  is an explanatory view illustrating a schematic example of a generation operation of the 2D video in each of the embodiments; 
         FIG. 8  is an explanatory view illustrating a schematic example of a generation operation of the 3D video in each of the embodiments; 
         FIG. 9A  is an explanatory view of one example of extraction positions of a left eye image and a right eye image under an ideal observation optical system; 
         FIG. 9B  is an explanatory view of a first example of default extraction positions of a left eye image and a right eye image under a realistic observation optical system; 
         FIG. 9C  is an explanatory view of an adjustment example of the extraction position based on an operation of a user with respect to an imaging region of the left eye image and the right eye image illustrated in  FIG. 9B ; 
         FIG. 9D  is an explanatory view of a second example of default extraction positions of a left eye image and a right eye image under the realistic observation optical system; 
         FIG. 9E  is an explanatory view of the adjustment example of the extraction position based on the operation of the user with respect to the imaging region of the left eye image and the right eye image illustrated in  FIG. 9D ; 
         FIG. 10  is a block diagram illustrating a first example of a functional configuration of an image processor of a camera apparatus of Embodiment 2; 
         FIG. 11A  is an explanatory view illustrating an adjustment example of a photometric area of automatic exposure with respect to a first subject in accordance with switching from a 2D mode to a 3D mode; 
         FIG. 11B  is an explanatory view illustrating an adjustment example of a photometric area of automatic exposure with respect to a second subject in accordance with switching from the 2D mode to the 3D mode; 
         FIG. 11C  is an explanatory view illustrating an adjustment example of a photometric area of automatic exposure with respect to a third subject in accordance with switching from the 2D mode to the 3D mode; 
         FIG. 11D  is an explanatory view illustrating an adjustment example of a photometric area of automatic exposure with respect to a fourth subject in accordance with switching from the 2D mode to the 3D mode; 
         FIG. 12  is a flowchart for describing an operational procedure example of the camera apparatus of Embodiment 2; 
         FIG. 13  is a flowchart for describing an operational procedure example at the time of interruption processing of mode switching; 
         FIG. 14  is a block diagram illustrating a second example of the functional configuration of the image processor of the camera apparatus of Embodiment 2; 
         FIG. 15  is an explanatory view illustrating an adjustment example of a target area of WB with respect to the subject in accordance with switching from the 2D mode to the 3D mode; 
         FIG. 16  is a block diagram illustrating a functional configuration example of an image processor of a camera apparatus of Embodiment 3; 
         FIG. 17A  is an explanatory view illustrating a transmission example of the left eye image and the right eye image in the 3D mode; 
         FIG. 17B  is an explanatory view illustrating a transmission example of the left eye image and the right eye image after switching from the 3D mode to the 2D mode; 
         FIG. 18  is a flowchart for describing an operational procedure example of the camera apparatus of Embodiment 3; 
         FIG. 19  is a system configuration view illustrating a configuration example in which the medical camera system including the camera apparatus of each of the embodiments is applied to a surgical endoscope system; 
         FIG. 20  is a view illustrating an external appearance example of the surgical endoscope system of each of the embodiments; 
         FIG. 21  is a block diagram illustrating a functional configuration example of an image processor of a camera apparatus of Embodiment 4; 
         FIG. 22  is illustrating each of an arrangement example of an objective lens for a left eye image and an objective lens for a right eye image and an example of a marker designated on the 3D image displayed on a monitor; 
         FIG. 23  is an explanatory view of parallax appearing in the left eye image and the right eye image in accordance with the position of a designated marker; and 
         FIG. 24  is an explanatory view illustrating a display example of a distance from a distal end of a surgical endoscope to the subject. 
     
    
    
     DETAILED DESCRIPTION 
     (Background of Contents of Embodiment 1) 
     In the above-described medical camera system, in order to ensure a clear field of view of a target site at which surgery or treatment is performed, a display video with high definition and excellent visibility is desired. In addition, since the size or state of an observation target can be grasped more accurately and easily by stereoscopic viewing of a target site, there is an increasing demand for a 3D video that provides a stereoscopic observed video to the observer. Particularly, in a surgical application of a fine site, a high-definition 3D video is required, but in the related art, such as PTL 1, there was a problem that it is difficult to visually recognize the details of the observed video clearly. In addition, in order to generate a high-definition 3D video required in the medical field, it is necessary to use two different cameras for imaging an image for a left eye (left eye image) and an image for a right eye (right eye image) which have parallax. 
     In addition, in order to display a highly accurate 3D video on a monitor, it is necessary to generate the left eye image and the right eye image which configure the 3D video with high accuracy. However, it is not always easy to generate the highly accurate left eye image and right eye image due to the design of an actual imaging optical system. For example, due to the positioning (for example, whether lenses are disposed in parallel or the like) of each of a left eye lens for imaging the left eye image and a right eye lens of the right eye image, or manufacturing variations of the lens itself, there is a case where it is difficult to generate the highly accurate left eye image and the right eye image. It is practically difficult to completely eliminate the causes of such positioning and manufacturing variations. In the related art disclosed in the above-described PTL 1, in a case where the left eye lens and the right eye lens are not appropriately disposed due to positioning or manufacturing variations, the image quality of a part of the left eye image and the right eye image deteriorates and influences the image quality of the 3D video, and it is difficult to grasp the detailed target site (for example, an affected part) for an observer. 
     Here, in the following Embodiment 1, in consideration of the above-described situation of the related art, an example of an image processing apparatus, a camera apparatus, and an image processing method which can electronically extract a part with excellent image quality from each of the left eye image and the right eye image which configure the 3D video by a simple user operation, and images and outputs a high-definition 3D video with one camera, will be described. 
     Embodiment 1 
     Hereinafter, each of the embodiments specifically disclosing the image processing apparatus, the camera apparatus, and the image processing method according to the disclosure will be appropriately described in detail with reference to the drawings. However, there is a case where description detailed more than necessary is omitted. For example, there is a case where detailed descriptions of already well-known matters and redundant descriptions on substantially the same configuration is omitted. This is to avoid the unnecessary redundancy of the following description and to make it easy to understand the disclosure for those skilled in the art. In addition, the attached drawings and the following description are provided to enable those skilled in the art to fully understand the disclosure, and are not intended to limit the subject matter described in the claims. 
     In addition, in each of the following embodiments, a configuration example of a medical camera system including the image processing apparatus or the camera apparatus according to each of the embodiments will be described. As a specific application example of each of the embodiments, the configuration of the camera apparatus in the surgical microscope system will be exemplified. However, the embodiments of the camera apparatus according to the disclosure are not limited to the contents of each of the embodiments which will described later. 
     The camera apparatus according to each of the embodiments is configured to be capable of imaging and outputting, for example, an observed video (hereinafter, referred to as “2D video”) capable of planar viewing of 4K resolution (that is, for example, “2160 pixels×3840 pixels” that corresponds to 4K pixels, for example) and an observed video (hereinafter, referred to as “3D video”) capable of stereoscopic viewing of full high definition (FHD) resolution (that is, for example, “1080 pixels×1920 pixels” that corresponds to 2K pixels), as a high-definition observed video. In addition, the resolution equivalent to full high vision (FHD) is referred to as “2K pixels”. 
       FIG. 1  is a system configuration view illustrating a configuration example in which a medical camera system including a camera apparatus of each of the embodiments is applied to a surgical microscope system. The surgical microscope system includes surgical microscope  10  (an example of an optical instrument), camera apparatus  20 , and monitor  30 . Camera apparatus  20  includes: camera head  21  for imaging an observed image of a target site obtained by surgical microscope  10 ; and camera control unit (CCU)  22  for performing signal processing of the observed video imaged by controlling camera head  21 . In camera apparatus  20 , camera head  21  and CCU  22  are connected to each other by signal cable  25 . Camera head  21  is installed in camera installer  15  of surgical microscope  10  and connected thereto. Monitor  30  for displaying the observed video is connected to an output terminal of CCU  22 . 
     Surgical microscope  10  is a binocular microscope and includes objective lens  11 , observation optical system  12  provided so as to correspond to the left and right eyes of the observer, eyepiece portion  13 , optical system  14  for camera imaging, and camera installer  15 . Observation optical system  12  includes zoom optical systems  101 R and  101 L, image forming lenses  102 R and  102 L, and eyepiece lenses  103 R and  103 L so as to correspond to the left and right eyes of the observer. Zoom optical systems  101 R and  101 L, image forming lenses  102 R and  102 L, and eyepiece lenses  103 R and  103 L are respectively disposed with an optical axis of objective lens  11  therebetween. Light from the subject (for example, light from the observation target site) becomes incident on the objective lens  11 , and then guides the left and right observed images having parallax through zoom optical systems  101 R and  101 L, imaging lenses  102 R and  102 L, and eyepiece lenses  103 R and  103 L, to eyepiece portion  13 . The observer can visually recognize subject  40  at the observation target site stereographically by looking at eyepiece portion  13  with both eyes. 
     Camera imaging optical system  14  includes beam splitters  104 R and  104 L and mirrors  105 R and  105 L. Camera imaging optical system  14  deflects and separates the lights of the left and right observed images which passes through observation optical system  12  by beam splitters  104 R and  104 L, reflects left and right observed images by mirrors  105 R and  105 L, and guides the left and right observed images having parallax to camera installer  15 . By installing and imaging camera head  21  of camera apparatus  20  to camera installer  15 , camera apparatus  20  can acquire an observed video capable of stereoscopic viewing for 3D display. 
       FIG. 2  is a view illustrating an external appearance example of the surgical microscope system of each of the embodiments. Surgical microscope  10  includes eyepiece  13  at the top of the microscope main body, a housing of camera imaging optical system  14  extends to the side from a base end portion of eyepiece  13 , camera installer  15  is provided. Camera installer  15  opens upward and is formed such that imaging lens portion  23  of camera head  21  can be installed thereto. Imaging lens portion  23  is attachable to and detachable from the main body of camera head  21  and can be exchanged, and is configured so that an imaging optical system having different optical characteristics can be used depending on the application. Camera head  21  is configured with a three-plate type capture having, for example, a spectral prism that separates a subject image into each color of red green blue (RGB) and three image sensors that respectively image subject images of each color of RGB. In addition, a single plate type capture having one image sensor may be used. 
     The surgical microscope system includes light source device  31  for illuminating a target site, recorder  32  for recording the observed video imaged by camera apparatus  20 , operation unit  33  for operating the surgical microscope system, and foot switch  37  by which the observer performs an operation input with a foot. Operation unit  33 , CCU  22  (one example of the image processing apparatus), light source device  31 , and recorder  32  are stored in control unit housing  35 . Monitor  30  is disposed in the vicinity of control unit housing  35 . Surgical microscope  10  is attached to displaceable support arm  34  and is linked to control unit housing  35  via support arm  34 . 
       FIGS. 3(A) and 3(B)  are views illustrating the external appearance configuration of the camera apparatus of each of the embodiments.  FIG. 3A  is a view illustrating an external appearance example of a front side of the camera head and the CCU of the camera apparatus of each of the embodiments.  FIG. 3B  is a view illustrating an external appearance example of a rear side of the CCU of the camera apparatus of each of the embodiments. Camera head  21  is connected to the rear surface of the housing of CCU  22  via signal cable  25 . Camera head  21  is configured to be capable of imaging a high-definition observed video, and imaging the left eye image and the right eye image which have parallax on one screen, for example, by a three-plate type or a single-plate type capture, in a case of imaging the 3D video. 
     On front panel  221 , CCU  22  is provided with power switch  222 , profile selection switch  223 , menu switch  224 , page changeover switch  225 , upward-and-downward and leftward-and-rightward movement switches  226 , selection switch  227 , and image quality adjustment switch  228 . On rear surface panel  241 , CCU  22  has camera terminal  242 , serial digital interface (SDI) video output terminals  243  and  244 , HDMI (registered trademark) (high-definition multimedia interface) video output terminals  245  and  246 , foot switch terminal  247 , mode switch  248 , and DC power input terminal  249 . 
     CCU  22  (one example of the image processing apparatus) can output the 2D video of 4K pixels or the 3D video of 2K pixels by switching modes. Profile selection switch  223  is a switch for selecting a preset profile in which the mode of CCU  22  is set. A profile is a set value of a parameter related to display of a video displayed on monitors  30  and  130  (refer to the description below), for example, and is provided for each user. The switching setting between a mode in which the 2D video can be output (hereinafter, referred to as “2D mode”) and a mode in which the 3D video can be output (hereinafter, referred to as “3D mode”) is possible, for example, by selecting the profile by profile selection switch  223 , selecting the mode by menu switch  224  and selection switch  227 , or setting the mode by mode switch  248  on the rear surface, by the operation of the user, such as an observer. 
     SDI video output terminals  243  and  244  correspond to the output terminals of two systems of channel CH 1  (one example of a first channel) and channel CH 2  (one example of a second channel) that correspond to the 3G-SDI standard. SDI video output terminal  243  of channel CH 1  has four terminals and can output both 4K video and FHD video. SDI video output terminal  244  of channel CH 2  is capable of outputting the FHD video. HDMI (registered trademark) video output terminals  245  and  246  correspond to the output terminals of two systems of channel CH 1  (one example of the first channel) and channel CH 2  (one example of the second channel). HDMI (registered trademark) video output terminal  245  of the channel CH 1  corresponds to the HDMI (registered trademark) 2.0 standard and can output both 4K video and FHD video. HDMI (registered trademark) video output terminal  246  of channel CH 2  corresponds to the HDMI (registered trademark) 1.4 standard and can output the FHD video. In addition, the video output terminal may be configured to be capable of outputting both the 4K video and the FHD video at any of the output terminals of the two systems. Further, the form and the number of the video output terminals are not limited to that illustrated in the drawing, and the disclosure is equally applicable even when corresponding to other standards. 
     Signal cable  25  of camera head  21  is connected to camera terminal  242 . Monitor  30  is connected to at least one of SDI video output terminals  243  and  244  and HDMI (registered trademark) video output terminals  245  and  246  via a video signal cable (not illustrated). A power supply device for supplying DC power via a power cable (not illustrated) is connected to DC power input terminal  249 . Foot switch  37  is connected to foot switch terminal  247 . 
       FIG. 4  is a block diagram illustrating a functional configuration example at the time of imaging the 2D video in the camera apparatus of each of the embodiments. In a case of imaging the 2D video of 4K pixels by camera apparatus  20 , for example, in a state where monocular lens  211  for forming a subject image is installed in imaging lens portion  23  of camera head  21 , camera head  21  is attached to camera installer  15  of surgical microscope  10 . The light from subject  40  passes through lens  211  and forms an image on the imaging surface of the three image sensors of three-plate type capture  213 , and the RGB subject image is imaged. In other words, camera head  21  includes capture  213  which images the observed image from surgical microscope  10  and obtains the high-definition observed video of high definition (for example, 2K pixels). Capture  213  is capable of acquiring a high-definition captured image and is configured with a three-plate FHD image sensor that images a video of 2 K pixels in each color of RGB. The FHD image sensor is configured with an imaging element, such as a charged-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). In addition, in a case of using a single plate type capture, the capture may be configured with a 4K image sensor capable of imaging a video of 4K pixels and a color filter. The video signal of the imaged video of the subject imaged by camera head  21  is transmitted to CCU  22  via signal cable  25 . 
     CCU  22  (one example of the image processing apparatus) includes: image processor  261  including a signal processing circuit that processes a video signal imaged by camera head  21 ; and central processing unit (CPU)  262  (one example of the processor) that configures the controller that performs setting mode related to the operations of image processor  261  and capture  213  and control of each operation. Image processor  261  is configured using, for example, a field-programmable gate array (FPGA), and can set and change the circuit configuration and operation by a program. Image processor  261  generates high-definition (here, 4K resolution) 2D video (2D video of 4K) from the 2K video R, G, and B (4K video R, G, and B) of each color of R, G, and B transmitted from camera head  21 , and outputs the 2D video to monitor  30  as a video output. 
       FIG. 5  is a block diagram illustrating a functional configuration example at the time of imaging the 3D video in the camera apparatus of each of the embodiments. In a case of imaging the 3D video of 2 K pixels (that is, 2K left parallax video and 2K right parallax video) by camera apparatus  20 , for example, in a state where binocular lens  212  which forms each of left and right subject images having parallax is installed in imaging lens portion  23  of camera head  21 , camera head  21  is attached to camera installer  15  of surgical microscope  10 . In addition, it is possible to image a video of the subject having left and right parallax using the monocular lens. The light from object  40  passes through lens  212  and forms left and right images adjacent to each other respectively on the imaging surfaces of three image sensors of three-plate type capture  213  as two left and right subjects having parallax, and the subject image of the left and right RGB subject images for 3D video are imaged. In other words, camera head  21  includes capture  213  which images left and right observed images having parallax from surgical microscope  10  and obtains a high definition (for example, 2K pixels) observed video including left and right parallax video on one screen. The video signal for 3D video of the subject imaged by camera head  21  is transmitted to CCU  22  via signal cable  25 . 
     In addition, in a case of imaging a 3D video with camera head  21 , instead of exchanging the lens of imaging lens portion  23  for 2D to 3D, an adapter may be provided in camera installer  15  of surgical microscope  10 , and the optical system of the adapter may be exchanged for 2D to 3D and used. Otherwise, the optical instrument itself, such as surgical microscope  10  which connects camera head  21  is replaced and used, the 2D video is imaged by installing the optical instrument in the instrument having an observation optical system for 2D, and the 3D video can also be imaged by installing the optical instrument in the instrument having the observation optical system for 3D. 
     Image processor  261  of CCU  22  generates the high-definition (for example, 2K image) 3D video from left and right 2K video R, G, and B (specifically, the 3D left and 3D right 2K video R, G, and B) for 3D display of each of RGB colors transmitted from camera head  21 , and outputs the 3D video as two left and right video outputs 1 and 2 for 3D display to monitor  30 . Details of the configuration and operation of image processor  261  for generating 2D video of 4K pixels or 3D video of 2K pixels will be described later. In a case of performing stereoscopic viewing of the observed video, for example, in a state where the observer wears 3D observation glasses, the 3D video is displayed on monitor  30  such that the left parallax video and the right parallax video can be observed with respective eyes. 
       FIG. 6  is a block diagram illustrating a functional configuration example of image processor  261  of camera apparatus  20  of Embodiment 1. The image processor  261  includes 4K video processor  264 , 2K left parallax video extractor  265 , 2K right parallax video extractor  266 , and video output switchers  267  and  268 . In addition, when frame buffer FB 1  (memory) and set value storage  262 M are provided in CCU  22 , frame buffer FB 1  (memory) and set value storage  262 M may be provided either on the inside or on the outside of image processor  261 . 
     4K video processor  264  inputs the 2K video R, G, and B of each color of R, G, and B imaged by three-plate camera head  21  as the resolution enhancement processing of the imaged video, and generates the video of 4K pixels. 4K video processor  264  saves the generated video of 4K pixels in frame buffer FB 1  and outputs the video to the video output switchers  267  and  268 . In addition, frame buffer FB 1  outputs the 2K left parallax video and the 2K right parallax video which are extracted from the saved video of 4K pixels by a control signal extracted from 2K left parallax video extractor  265  and 2K right parallax video extractor  266 , to each of video output switchers  267  and  268 , respectively. In addition, the extraction of each of the 2K left parallax video and the 2K right parallax video from the saved video of 4K pixels, is performed similar to 2K left parallax video extractor  265  and 2K right parallax video extractor  266 . As a method of 4K visualization, for example, a known “pixel shifting” processing is used. For each pixel of the 2K image G, 4K video processor  264  performs processing of shifting pixels of 2K video R and 2K video B by ½ in a horizontal and vertical directions, and generates a color video of 4K pixels. In a case of imaging the 2D video of 4K pixels, 4K video of 2D color is generated from the 2K video R, G, and B for 2D display. In a case of capturing the 3D video of 2K pixels, the 4K video (3D left parallax video and 3D right parallax video) including the left and right parallax videos of 2K pixels from the imaged 2K videos R, G, and B for the left eye and the right eye for 3D display which are left and right adjacent to each other in an image sensor, is generated. In addition, in a case of using a single-plate type capture, the 4K video processor  264  is not provided in image processor  261 , and the video signal of the color 4K pixels imaged with camera head  21  is input to image processor  261  and processed. 
     2K left parallax video extractor  265  (one example of the image processor) performs predetermined signal processing with respect to the left eye image which is imaged by camera head  21 . For example, 2K left parallax video extractor  265  extracts a 2K left parallax video that corresponds to a region for half the left eye video from the 4K video including the left and right parallax video of 2K pixels output from 4K video processor  264 , and generates an FHD video (3D left parallax video) for the left eye video for 3D display. Further, 2K left parallax video extractor  265  adjusts an extraction range for extracting the 2K left parallax video (that is, a left eye image on the imaging surface) from the 4K video in accordance with an adjustment signal (refer to the description below) based on the operation of the user by moving in any direction of each of the upward-and-downward and leftward-and-downward directions. 2K left parallax video extractor  265  saves the adjustment result in set value storage  262 M, and also extracts and outputs 2K left parallax image (left eye image) that corresponds to the adjustment result. 
     2K right parallax video extractor  266  (one example of the image processor) performs predetermined signal processing with respect to the right eye image which is imaged by camera head  21 . For example, 2K right parallax video extractor  266  extracts a 2K right parallax video that corresponds to a region for the remaining half the right eye video from the 4K video including the left and right parallax video of 2K pixels output from 4K video processor  264 , and generates an FHD video (3D right parallax video) for the right eye video for 3D display. Further, 2K right parallax video extractor  266  adjusts an extraction range for extracting the 2K right parallax video (that is, a right eye image on the imaging surface) from the 4K video in accordance with an adjustment signal (refer to the description below) based on the operation of the user by moving in any direction of each of the upward-and-downward and leftward-and-downward directions. 2K right parallax video extractor  266  saves the adjustment result of an extraction range in set value storage  262 M, and also extracts and outputs 2K right parallax video (right eye image) that corresponds to the adjustment result. 
     2K left parallax video extractor  265  and 2K right parallax video extractor  266  may respectively move and adjust in a same direction or the extraction ranges of each of the 2K left parallax video (left eye image) and the 2K right parallax video (right eye image) in accordance with an adjustment signal (refer to the description below) based on the operation of the user, and may individually adjust the extraction ranges by moving in different directions. 
     Video output switcher  267  (one example of the output controller) switches the video signal output and outputs the 2D left parallax video of 2K pixels from the 2K left parallax video extractor  265  or the video signal of the 2D video of 4K pixels from 4K video processor  264  via channel CH 1  (one example of the first channel). Video output switcher  268  (one example of the output controller) switches the video signal output and outputs the 2D right parallax video of 2K pixels from the 2K right parallax video extractor  266  or the video signal of the 2D video of 4K pixels from 4K video processor  264  via channel CH 2  (one example of the second channel). In a case of outputting the 2D video of 4K pixels, the video signal may be output to both of video output 1 of channel CH 1  and video output 2 of channel CH 2 , or the video signal may be output to only one of video output 1 and video output 2. Further, the 2D video of 4K pixels may be output to either one of channel CH 1  and channel CH 2 , and 2D video of 2K pixels may be output to the other. 
     Frame buffer FB 1  is configured using a semiconductor memory, such as dynamic random access memory (DRAM) or static random access memory (SRAM), and holds video data. For example, frame buffer FB 1  saves the data of the 2D video of 4K pixels generated by 4K video processor  264 . 
     Set value storage  262 M is configured using a semiconductor memory, such as an electrically erasable programmable read-only memory (EEPROM), and saves the data of the adjustment result of the extraction ranges of the 2K left parallax video and the 2K right parallax video which are adjusted by 2K left parallax video extractor  265  and 2K right parallax video extractor  266 . In addition, 2K left parallax video extractor  265  and 2K right parallax video extractor  266  read out the data of the 2D video of 4K pixels saved in frame buffer FB 1 , and may further adjust the extraction ranges of the 2K left parallax video and the 2K right parallax video by using the adjustment result of the extraction ranges saved in set value storage  262 M. 
       FIG. 7  is an explanatory view showing a schematic example of the generation operation of the 2D video in each of the embodiments, and schematically illustrates processing for generating the 2D video of 4K pixels. In a case of imaging the 2D video of 4K pixels by camera apparatus  20 , 2K video R, G, and B of each of the RGB colors are imaged as videos R, G, and B for 4K of 2D by three-plate camera head  21 . Next, 4K video processor  264  of image processor  261  performs 4K visualization by performing pixel shifting processing with respect to the video signals of the 2K videos R, G, and B to generate the 2D color 4K video. 
       FIG. 8  is an explanatory view illustrating a schematic example of the generation operation of the 3D video in each of the embodiments, and schematically illustrates processing for generating the 3D video of 2K pixels. In a case of imaging the 3D video of 2K pixels by camera apparatus  20 , a three-plate type camera head  21  images the 2K videos R, G, and B (for 3D left eye and 3D right eye) of each of RGB colors for the left eye and the right eye for the 3D display in the ½ regions left and right adjacent to each other of the image sensor. Next, 4K video processor  264  of image processor  261  performs 4K visualization by performing the pixel shifting processing with respect to the video signals of the 2K videos R. G, and B including the left and right parallax video to generate the 3D display color 4K video (the 2K left parallax video for 3D and the 2K right parallax video for 3D). Subsequently, 2K left parallax video extractor  265  and 2K right parallax video extractor  266  respectively perform extraction processing of the 2K parallax video and the 2K right parallax video, and generates the FHD video (2K left parallax video for 3D and 2K right parallax video for 3D) for the 3D display. 
     Here, as described above, in order to display a highly accurate 3D video on monitor  30 , it is necessary to generate the 2K left parallax video (left eye image) and the 2K right parallax video (right eye image) which configure the 3D video with high accuracy. However, it is not always easy to generate a highly accurate 2K left parallax video and a 2K right parallax video due to the design of actual observation optical system  12 . For example, due to the positioning (for example, parallel disposition) of each of zoom optical system  101 R for forming an image of the subject light for obtaining the 2K left parallax video and zoom optical system  101 L for forming an image of the subject light for obtaining the 2K right parallax video and manufacturing variations of the lens itself, there is a case where it is difficult to generate highly accurate 2K left parallax video and 2K right parallax video. It is practically difficult to completely eliminate the causes of such positioning and manufacturing variations. 
     Here, in Embodiment 1, for example, at the time of initial setting of the surgical microscope system, the user (for example, an observer, such as a doctor) reads the 3D video based on the 2K left parallax video and the 2K right parallax video which are displayed (output to a screen) on monitor  30  in a state where the user wears the glasses for 3D observation in the 3D mode (that is, a mode for displaying the 3D video on monitor  30 ). At this time, image processor  261  of CCU  22  adjusts at least one extraction position of the 2K left parallax video (left eye image) and the 2K right parallax video (right eye image) in accordance with the adjustment signal (one example of the adjustment signal based on the operation of the user) generated by the operation of the user (for example, an operation of movement switch  226  by the user) based on the 3D video displayed (output to the screen) on monitor  30 . In addition, the imaging surface (imaging surface at the lower left part of the page of  FIG. 8 ) on which the 4K video of  FIG. 8  is imaged, is an imaging surface of a so-called top view (that is, when the imaging surface side is viewed from an object side). 
     (First Adjustment Example of Extraction Range) 
       FIG. 9A  is an explanatory view of one example of an extraction position of the left eye image and the right eye image under an ideal observation optical system.  FIG. 9B  is an explanatory view of a first example of default extraction positions of the left eye image and the right eye image under realistic observation optical system  12 .  FIG. 9C  is an explanatory view of an adjustment example of the extraction position based on the operation of the user with respect to the imaging region of the left eye image and the right eye image illustrated in  FIG. 9B . 
     In  FIGS. 9A, 9B, and 9C , sensor effective pixel area EFM 1  of the image sensor in camera head  21  is “E pixels×F pixels” (E, F: default value of F&lt;E), the horizontal direction and the vertical direction of sensor effective pixel area EFM 1  are defined as an x-axis direction and a y-axis direction, respectively, and the optical axis direction of the observation optical system is defined as the z-axis direction which is perpendicular to the x-axis direction and the y-axis direction. In addition, sensor effective pixel area EFM 1  illustrated in  FIGS. 9A, 9B, and 9C  is a sensor effective pixel area of a so-called bottom view (that is, when the object side is viewed from the imaging surface side). The definitions of the x-axis direction, the y-axis direction, the z-axis direction and the sensor effective pixel area of the bottom view are similarly applied to the descriptions of  FIGS. 9D and 9E . 
     In  FIG. 9A , an ideal observation optical system is disposed, and each of a zoom optical system for forming an image of the subject light for obtaining the 2K left parallax video and a zoom optical system for forming an image of the subject light for obtaining the 2K right parallax video is appropriately positioned, and there are no manufacturing variations of the lens itself. Therefore, both 2K left parallax video LF 1  (left eye image) and 2K right parallax video RG 1  (right eye image) which are obtained by the imaging of the image sensor are extracted by extracting a video as much as default extraction ranges LFC 1  and RGC 1  which is an initial extraction range. Both default extraction ranges LFC 1  and RGC 1  are “B pixel×C pixel” (B, C: default value of C&lt;B, smaller than E and F). 
     In other words, in  FIG. 9A , 2K left parallax video LF 1  and 2K right parallax video RG 1  having the same size (image area) imaged on sensor effective pixel area EFM 1  based on the same subject light are extracted so as to have an equivalent size (image area) by default extraction ranges LFC 1  and RGC 1 . This is apparent from the viewpoint that a D pixel (D: default value) that corresponds to a distance between the upper end of default extraction ranges LFC 1  and RGC 1  and the upper end of sensor effective pixel area EFM 1  and a D pixel (D: default value) that corresponds to a distance between the lower end of default extraction ranges LFC 1  and RGC 1  and the lower end of sensor effective pixel area EFM 1 , match each other, and that an A pixel (A: default value) that corresponds to a distance between the left end of default extraction range LFC 1  and the left end of sensor effective pixel area EFM 1  and an A pixel that corresponds to a distance between the right end of default extraction range RGC 1  and the right end of sensor effective pixel area EFM 1  match each other. 
     Therefore, the image quality of 2K left parallax video LF 1  and 2K right parallax video RG 1  of the extracted default extraction ranges LFC 1  and RGC 1  becomes excellent, and when the observer reads monitor  30  on which the 3D video is displayed based on 2K left parallax video LF 1  and 2K right parallax video RG 1 , camera apparatus  20  can grasp the detailed situation of the observation target site without giving the observer a feeling of strangeness as a 3D video. 
     Next, in  FIG. 9B , each of zoom optical system  101 L for forming an image of the subject light for obtaining the 2K left parallax video and zoom optical system  101 R for forming an image of the subject light for obtaining the 2K right parallax video is not appropriately positioned, and there are manufacturing variations of the lens itself. Therefore, the 2K left parallax video LF 2  (left eye image) and the 2K right parallax video RG 2  (right eye image) obtained by imaging of the image sensor are somewhat displaced in the upward-and-downward direction (y-axis direction) and the leftward-and-rightward direction (x-axis direction) as illustrated in  FIG. 9B  when comparing each position of 2K left parallax video LF 1  and 2K right parallax video RG 1  which are illustrated in  FIG. 9A . Therefore, when 2K left parallax video LF 2  and 2K right parallax video RG 2  are extracted with default extraction ranges LFC 1  and RGC 1  at the same positions as in  FIG. 9A , extracted 2K left parallax video LF 2  and 2K right parallax video RG 2  are lack of appropriateness as the video of the same subject, the image quality of each of the upper and right portion of the 2K left parallax video LF 2  and the lower portion of the 2K right parallax video RG 2  deteriorates. Therefore, when projected on monitor  30 , a feeling of strangeness as a 3D video is given to the observer, which is inconvenient. 
     Here, as illustrated in  FIG. 9C , CCU  22  of camera apparatus  20  moves in default extraction range LFC 1  in the x-axis direction (horizontal direction) and in the y-axis direction (vertical direction) in accordance with the adjustment signal based on the operation (for example, movement switch  226 ) of the user (for example, an observer, such as a doctor) who reads 2K left parallax video LF 2  and 2K right parallax video RG 2  displayed (output to the screen) on monitor  30 . Accordingly, CCU  22  saves the position information (coordinate information) of post-adjustment extraction range LFC 2  obtained by the movement (adjustment) of the default extraction range LFC 1  in set value storage unit  262 M, and extracts and outputs 2K left parallax video LC 2  of the post-adjustment extraction range LFC 2 . 
     Similarly, CCU  22  of camera apparatus  20  moves in default extraction range RGC 1  in the y-axis direction (vertical direction) in accordance with the adjustment signal based on the operation (for example, movement switch  226 ) of the user (for example, an observer, such as a doctor) who reads 2K left parallax video LF 2  and 2K right parallax video RG 2  displayed (output to the screen) on monitor  30 . Accordingly, CCU  22  saves the position information (coordinate information) of post-adjustment extraction range RGC 2  obtained by the movement (adjustment) of the default extraction range RGC 1  in set value storage unit  262 M, and extracts and outputs 2K right parallax video RG 2  of the post-adjustment extraction range RGC 2 . In addition, CCU  22  saves each piece of the position information (coordinate information) of post-adjustment extraction ranges LFC 2  and RGC 2  in association with each other in set value storage  262 M. Accordingly, even in a case where each of the zoom optical system  101 L and zoom optical system  101 R is not appropriately positioned and there are manufacturing variations of the lens itself, CCU  22  can save the position information of post-adjustment extraction ranges LFC 2  and RGC 2  which are appropriately determined based on the operation of the user, and thus, it is possible to use the position information as a reference of the extraction range of the subsequent imaged video, and to appropriately manage the imaged video of 2K having left and right parallax. 
     (Second Adjustment Example of Extraction Range) 
       FIG. 9D  is an explanatory view of a second example of default extraction positions of the left eye image and the right eye image under realistic observation optical system  12 .  FIG. 9E  is an explanatory view of the adjustment example of the extraction position based on the operation of the user with respect to the imaging region of the left eye image and the right eye image illustrated in  FIG. 9D . 
     Next, in  FIG. 9D , each of zoom optical system  101 L for forming an image of the subject light for obtaining the 2K left parallax video and zoom optical system  101 R for forming an image of the subject light for obtaining the 2K right parallax video is not appropriately positioned, and there are manufacturing variations of the lens itself. Therefore, 2K left parallax video LF 3  (left eye image) and 2K right parallax video RG 3  (right eye image) obtained by imaging of the image sensor are somewhat displaced in the upward-and-downward direction (y-axis direction) and the leftward-and-rightward direction (x-axis direction) as illustrated in  FIG. 9D  when comparing each position of 2K left parallax video LF 1  and 2K right parallax video RG 1  which are illustrated in  FIG. 9A . Therefore, when 2K left parallax video LF 3  and 2K right parallax video RG 3  are extracted with default extraction ranges LFC 1  and RGC 1  at the same positions as in  FIG. 9A , extracted 2K left parallax video LF 3  and 2K right parallax video RG 3  are lack of appropriateness as the video of the same subject, the image quality of each of the upper and right portion of the 2K left parallax video LF 3  and the lower portion of the 2K right parallax video RG 3  deteriorates. Therefore, when projected on monitor  30 , a feeling of strangeness as a 3D video is given to the observer, which is inconvenient. 
     Here, as illustrated in  FIG. 9E , CCU  22  of camera apparatus  20  moves in default extraction range LFC 1  in the y-axis direction (vertical direction) in accordance with the adjustment signal based on the operation (for example, movement switch  226 ) of the user (for example, an observer, such as a doctor) who reads 2K left parallax video LF 3  and 2K right parallax video RG 3  displayed (output to the screen) on monitor  30 . Accordingly, CCU  22  saves the position information (coordinate information) of post-adjustment extraction range LFC 3  obtained by the movement (adjustment) of the default extraction range LFC 1  in set value storage unit  262 M and extracts and outputs 2K left parallax video LC 3  of the post-adjustment extraction range LFC 3 . 
     Similarly, CCU  22  of camera apparatus  20  moves in default extraction range RGC 1  in the y-axis direction (vertical direction) in accordance with the adjustment signal based on the operation (for example, movement switch  226 ) of the user (for example, an observer, such as a doctor) who reads 2K left parallax video LF 3  and 2K right parallax video RG 3  displayed (output to the screen) on monitor  30 . Accordingly, CCU  22  saves the position information (coordinate information) of post-adjustment extraction range RGC 3  obtained by the movement (adjustment) of the default extraction range RGC 1  in set value storage unit  262 M and extracts and outputs 2K right parallax video RG 3  of the post-adjustment extraction range RGC 3 . Further, CCU  22  saves each piece of the position information (coordinate information) of post-adjustment extraction ranges LFC 3  and RGC 3  in association with each other in set value storage unit  262 M. Accordingly, even in a case where each of the zoom optical system  101 L and zoom optical system  101 R is not appropriately positioned and there are manufacturing variations of the lens itself, CCU  22  can save the position information of post-adjustment extraction ranges LFC 3  and RGC 3  which are appropriately determined based on the operation of the user, and thus, it is possible to use the position information as a reference of the extraction range of the subsequent imaged video, and to appropriately manage the imaged video of 2K having left and right parallax. 
     Above, in the medical camera system of Embodiment 1, CCU  22  is connected to the camera head which can perform the imaging on the imaging surface of one screen of the 2K left parallax video (one example of the left eye image) and 2K right parallax video (one example of the right eye image) having parallax based on the light of the target site incident on surgical microscope  10  (one example of the optical instrument). CCU  22  or camera apparatus  20  including CCU  22  performs the signal processing of the left eye image and the right eye image which are imaged by camera head  21 , and outputs the left eye image and the right eye image to which the signal processing is performed to monitor  30 . In addition, CCU  22  or camera apparatus  20  including CCU  22  adjusts the extraction position of at least one of the left eye image and the right eye image in accordance with the operation of the user based on the left eye image and the right eye image displayed on monitor  30 . 
     Accordingly, CCU  22  or camera apparatus  20  including CCU  22  can electronically extract parts having excellent image quality from each of the left eye image and the right eye image which configure the 3D video by a simple operation of the user who reads the left eye image and the right eye image displayed on monitor  30 , and can image and output a high definition 3D video with one camera. In addition, it is possible to image and output a high definition 3D video of 2K pixels with one camera head  21  and CCU  22 , and to project the target site stereographically and with high definition. In particular, for surgical applications, clearer 3D video can be acquired, and operability at the time of surgery and visibility of the target site can be improved. 
     In addition, since one CCU  22  can cope with imaging output of 2D video of 4K pixels and imaging output of 3D video of 2K pixels, the disclosure can be applied to various observation video applications. 
     In addition, CCU  22  or camera apparatus  20  including CCU  22  saves the adjustment result of the extraction position of at least one of the left eye image and the right eye image in set value storage  262 M. Accordingly, even in a case where each of zoom optical system  101 L and zoom optical system  101 R is not appropriately positioned and there are manufacturing variations of the lens itself, CCU  22  or camera apparatus  20  including CCU  22  can save the position information of the post-adjustment extraction range which are appropriately determined based on the operation of the user, and thus, it is possible to use the position information as a reference of the extraction range of the subsequent imaged video, and to appropriately manage the imaged video of 2K having left and right parallax. 
     In addition, CCU  22  or camera apparatus  20  including CCU  22  adjusts the extraction position in the horizontal direction of at least one of the left eye image and the right eye image by camera head  21  in accordance with the operation of the user who reads the left eye image and the right eye image displayed on monitor  30 . Accordingly, CCU  22  or camera apparatus  20  including CCU  22  can extract a video of the post-adjustment extraction range which is appropriately determined based on the operation of the user even in a case where at least one of the 2K left parallax video and the 2K right parallax video is imaged in the horizontal direction being shifted from the default extraction range, can appropriately adjust the depth feeling (stereoscopic feeling) of 3D, and can acquire a video having excellent image quality. 
     In addition, CCU  22  or camera apparatus  20  including CCU  22  adjusts the extraction position in the vertical direction of at least one of the left eye image and the right eye image by camera head  21  in accordance with the operation of the user who reads the left eye image and the right eye image displayed on monitor  30 . Accordingly, CCU  22  or camera apparatus  20  including CCU  22  can extract a video of the post-adjustment extraction range which is appropriately determined based on the operation of the user even in a case where at least one of the 2K left parallax video and the 2K right parallax video is imaged in the vertical direction being shifted from the default extraction range, can appropriately perform adjustment so as to have the qualification as a 3D video, and can acquire a video having excellent image quality. 
     In addition, CCU  22  or camera apparatus  20  including CCU  22  adjusts the extraction position in the horizontal direction or in the vertical direction of both of the left eye image and the right eye image by camera head  21  in accordance with the operation of the user who reads the left eye image and the right eye image displayed on monitor  30 . Accordingly, CCU  22  or camera apparatus  20  including CCU  22  can extract a video of the post-adjustment extraction range which is appropriately determined based on the operation of the user even in a case where both of the 2K left parallax video and the 2K right parallax video are imaged in the horizontal direction or in the vertical direction being shifted from the default extraction range, can appropriately perform adjustment so as to have the depth feeling (stereoscopic feeling) of 3D and the qualification as a 3D video, and can acquire a video having excellent image quality. 
     Further, in the 3D mode. CCU  22  or camera apparatus  20  including CCU  22  includes distance measuring circuit  291  (one example of distance measurer) which measures distance L (refer to  FIG. 19 ) from surgical endoscope  110  (one example of optical instrument) to an observation target site based on the parallax Δ (refer to  FIG. 23 ) appearing in the left eye image and the right eye image which are imaged by camera head  21 . CCU  22  or camera apparatus  20  outputs the result measured by distance measuring circuit  291  (that is, information on the distance) to monitor  130  (refer to  FIG. 19 ) together with the left eye image and the right eye image to which the signal processing is performed. Accordingly, the user (for example, an observer, such as a doctor) can visually grasp the situation of the observation target site projected to monitor  130 , can grasp the specific distance information from surgical endoscope  110  (refer to  FIG. 19 ) to the observation target site, and can support the guidance of the next medical practice by the user at the time of surgery or examination. 
     In addition, in response to the switching from the 3D mode to the 2D mode, CCU  22  or camera apparatus  20  including CCU  22  interrupts the output of the information on the distance to monitor  130 . Accordingly, in the 2D mode, neither the left and right 2K left parallax video having parallax nor the 2K right parallax video is input to distance measuring circuit  291 , and thus, the information on the distance is not displayed on monitor  130 . Therefore, the user (for example, an observer, such as a doctor) can easily recognize that the present is the 2D mode by the fact that the information on the distance is not displayed on monitor  130 , and on the other hand, the user can easily recognize that the present is the 3D mode by the fact that the information on the distance is displayed on monitor  130 . 
     (Background of Contents of Embodiment 2) 
     In the above-described medical camera system, in order to ensure a clear field of view of a target site at which surgery or treatment is performed, a display video with high definition and excellent visibility is desired. In addition, since the size or state of an observation target can be grasped more accurately and easily by stereoscopic viewing of a target site, there is an increasing demand for a 3D video that provides a stereoscopic observed video to the observer. Particularly, in a surgical application of a fine site, a high-definition 3D video is required, but in the related art, such as PTL 1, there was a problem that it is difficult to visually recognize the details of the observed video clearly. In addition, in order to generate a high-definition 3D video required in the medical field, it is necessary to use two different cameras for imaging an image for a left eye (left eye image) and an image for a right eye (right eye image) which have parallax. 
     In addition, for example, in a medical camera system, visibility of video displayed on a monitor is particularly important for a doctor or the like to grasp the details of the situation of a target site (for example, an affected part of a human body). The video displayed on the monitor at the time of surgery or examination is appropriately switched between the 2D video capable of planar viewing and the 3D video capable of stereoscopic viewing. Here, in the related art as in PTL 1, since it is not considered to switch from 2D video to 3D video as the video displayed on the monitor, the following problems are caused when switching from the display of the 2D video to the display of the 3D video. First, in order to improve the image quality (that is, visibility) of the video, various types of signal processing (for example, automatic exposure processing, such as auto exposure (AE)) or adjustment processing of white balance (WB), are performed with respect to the imaged video. However, at the time of switching from the display of 2D video to the display of 3D video, when an area on an imaging surface used for deriving parameters of the signal processing of the 2D video is used as it is as an area used for deriving parameters of the signal processing of the 3D video, there is a case where the 3D video having appropriate image quality cannot be obtained. 
     Here, in Embodiment 2 which will be described below, considering the above-described situation of the related art, an example of the image processing apparatus, the camera apparatus, and the image processing method which are capable of adaptively adjusting the area on the imaging surface used for deriving parameters of signal processing with respect to the imaged 3D video when switching from display of the 2D video to display of the 3D video, and imaging and outputting a high-definition 3D video with one camera will be described. 
     Embodiment 2 
     Since the internal configuration of each of the medical camera system and the camera apparatus or the CCU of Embodiment 2 is the same as the internal configuration of each of the medical camera system and camera apparatus  20  or CCU  22  of Embodiment 1, the same configuration will be given the same reference numerals and the description thereof will be simplified or omitted, and different contents will be described. 
     First, in Embodiment 2, as an example of signal processing performed with respect to an imaged video in order to improve the image quality of the video, an automatic exposure processing, such as auto exposure (AE), is exemplified, and an example in which, in a case of switching from the 2D mode to the 3D mode, an area used for used for deriving parameters (for example, brightness or light amount) of the automatic exposure processing is determined, will be described. In addition, the configuration of the CCU of Embodiment 2 is combined with the configuration of the CCU of Embodiment 1, and after the extraction range of the left eye image and the right eye image is adjusted by the configuration of the CCU of Embodiment 1, it is needless to say that various controls of automatic exposure processing, such as AE and adjustment processing of WB may be performed according to the configuration of the CCU of Embodiment 2. 
       FIG. 10  is a block diagram illustrating a first example of a functional configuration of the image processor of camera apparatus  20  of Embodiment 2. Image processor  261 A includes 4K video processor  264 , photometric area determiner  281 , light exposure calculator  282 , luminance controller  283 , 2K left parallax video extractor  265 , 2K right parallax video extractor  266 , and video output switchers  267  and  268 . In addition, although frame buffer FB 1  (memory) is not illustrated and omitted in  FIG. 10 , when frame buffer FB 1  is provided in CCU  22 , frame buffer FB 1  may be provided either on the inside or on the outside of image processor  261 A. 
     The video data of 4K pixels generated by 4K video processor  264  is input to photometric area determiner  281 . 
     In accordance with a switching signal from the 2D mode to the 3D mode, photometric area determiner  281  (one example of a determiner) determines an area used for deriving parameters (for example, brightness or light amount) of the signal processing (for example, automatic exposure processing, such as AE) with respect to the left eye image and the right eye image (for example, video data of 4K pixels generated by 4K video processor  264 ) which are imaged by camera head  21  (refer to  FIGS. 11A, 11B, 11C, and 11D ). Further, in accordance with a switching signal from the 3D mode to the 2D mode, photometric area determiner  281  determines an area used for deriving parameters (for example, brightness or light amount) of the signal processing (for example, automatic exposure processing, such as AE) with respect to the left eye image and the right eye image (for example, video data of 4K pixels generated by 4K video processor  264 ) which are imaged by camera head  21 . In addition, even when the switching from the 2D mode to the 3D mode or the switching from the 3D mode to the 2D mode does not occur, photometric area determiner  281  determines an area used for deriving parameters (for example, brightness or light amount) of the signal processing (for example, automatic exposure processing, such as AE) with respect to the left eye image and the right eye image (for example, video data of 4K pixels generated by 4K video processor  264 ) which are imaged by camera head  21 . 
       FIG. 11A  is an explanatory view illustrating an adjustment example of a photometric area of automatic exposure with respect to a first subject in accordance with the switching from the 2D mode to the 3D mode.  FIG. 11B  is an explanatory view illustrating an adjustment example of a photometric area of automatic exposure with respect to a second subject in accordance with the switching from the 2D mode to the 3D mode.  FIG. 11C  is an explanatory view illustrating an adjustment example of a photometric area of automatic exposure with respect to a third subject in accordance with the switching from the 2D mode to the 3D mode.  FIG. 11D  is an explanatory view illustrating an adjustment example of a photometric area of automatic exposure with respect to a fourth subject in accordance with the switching from the 2D mode to the 3D mode. 
     In  FIGS. 11A to 11D , in imaging surface CAP 1  of the image sensor in camera head  21  (for example, the size of “2160 pixels×3840 pixels” that corresponds to 4K pixels), sensor effective pixel region EFM 2  which corresponds to the largest pixel region used in imaging the video is provided. In  FIGS. 11A to 11D , imaging surface CAP 1  is an imaging surface of a so-called bottom view (that is, when the object side is viewed from the imaging surface side). In addition, here, in order to simplify the description of  FIGS. 11A  to  11 D, extraction range LFC 4  of the 2D left parallax video which configures the 3D video and extraction range RGC 4  of the 2D right parallax video which configures the same 3D video, are set in a state where there is no shift in the vertical direction of imaging surface CAP 1  and of being horizontally aligned in the horizontal direction. Extraction range LFC 4  is an extraction range of the 2K left parallax video (left eye image) in sensor effective pixel area EFM 3  for the 2K left parallax video (left eye image). Similarly, extraction range RGC 4  is the extraction range of the 2K right parallax video (right eye image) in sensor effective pixel area EFM 4  for the 2K right parallax video (right eye image). In addition, in the description of  FIGS. 11A to 11D , sensor effective pixel region EFM 2  is assumed to be configured with a total of 128 regions divided by 8 in the vertical direction×16 in the horizontal direction. 
     On the left side of the page of  FIG. 11A , a case where the imaging of the 2D video is performed over the entire sensor effective pixel region EFM 2  in the 2D mode, is illustrated. As illustrated in  FIG. 11A , in a case where the imaging of the 2D video is performed over the entire sensor effective pixel region EFM 2 , the entire sensor effective pixel region EFM 2  is used for deriving (calculating) parameters (for example, brightness or light amount) of the automatic exposure processing (one example of the signal processing) of the 2D video (refer to photometric area LAR 1  indicated by the dot hatch in  FIG. 11A ). In accordance with the operation of the user for the switching from the 2D mode to the 3D mode (that is, the switching signal from the 2D mode to the 3D mode), as illustrated on the right side of the page of  FIG. 11A , photometric area determiner  281  determines, for example, the size of extraction range RGC 4  of 2K right parallax video LAR 2  which configures the 3D video as the photometric area used for deriving parameters (for example, brightness or light amount) of the signal processing (for example, automatic exposure processing, such as AE) with respect to the video data (that is, 2K left parallax video and 2K right parallax video) of 4K pixels generated by 4K video processor  264 . In addition, photometric area determiner  281  may determine, for example, the size of extraction range LFC 4  of the 2K left parallax video which configures the 3D video as the photometric area. 
     On the left side of the page of  FIG. 11B , a case where the imaging of 2D video LAR 3  is performed over a small area (for example, 12 squares) including the center of sensor effective pixel region EFM 2  in the 2D mode, is illustrated. As illustrated in  FIG. 11B , in a case where the imaging of 2D video LAR 3  is performed over a small area including the center of sensor effective pixel region EFM 2 , the entire sensor effective pixel region EFM 2  is used for deriving (calculating) the parameters (for example, brightness or light amount) of the automatic exposure processing (one example of the signal processing) of the 2D video (refer to photometric area LAR 1  indicated by the dot hatch of  FIG. 11A ). Here, in accordance with the operation of the user for switching from the 2D mode to the 3D mode (that is, the switching signal from the 2D mode to the 3D mode), as illustrated on the right side of the page of  FIG. 11B , photometric area determiner  281  determines, for example, the size of extraction range RGC 4  of 2K right parallax video LAR 4  which configures the 3D video as the photometric area used for deriving the parameters (for example, brightness or light amount) of the signal processing (for example, automatic exposure processing, such as AE) with respect to the video data (that is, 2K left parallax video and 2K right parallax video) of 4K pixels generated by 4K video processor  264 . In addition, photometric area determiner  281  may determine, for example, the size of extraction range LFC 4  of the 2K left parallax video which configures the 3D video as the photometric area. 
     On the left side of the page of  FIG. 11C , a case where the imaging of 2D video LAR 5  is performed over a medium area (for example, 24 squares) including the center of sensor effective pixel region EFM 2  in the 2D mode, is illustrated. As illustrated in  FIG. 11C , in a case where the imaging of 2D video LAR 5  is performed over a medium area including the center of sensor effective pixel region EFM 2 , the entire sensor effective pixel region EFM 2  is used for deriving (calculating) parameters (for example, brightness or light amount) of the automatic exposure processing (one example of the signal processing) of the 2D video (refer to photometric area LAR 1  indicated by the dot hatch of  FIG. 11A ). Here, in accordance with the operation of the user for switching from the 2D mode to the 3D mode (that is, the switching signal from the 2D mode to the 3D mode), as illustrated on the right side of the page of  FIG. 11C , photometric area determiner  281  determines, for example, the size of extraction range RGC 4  of 2K right parallax video LAR 6  which configures the 3D video as the photometric area used for deriving parameters (for example, brightness or light amount) of the signal processing (for example, automatic exposure processing, such as AE) with respect to the video data (that is, 2K left parallax video and 2K right parallax video) of 4K pixels generated by 4K video processor  264 . In addition, photometric area determiner  281  may determine, for example, the size of extraction range LFC 4  of the 2K left parallax video which configures the 3D video as the photometric area. 
     On the left side of the page of  FIG. 11D , a case where the imaging of 2D video LAR 7  is performed over a large area (for example, 56 squares) including the center of sensor effective pixel region EFM 2  in the 2D mode, is illustrated. As illustrated in  FIG. 11D , in a case where the imaging of 2D video LAR 7  is performed over a medium area including the center of sensor effective pixel region EFM 2 , the entire sensor effective pixel region EFM 2  is used for deriving (calculating) parameters (for example, brightness or light amount) of the automatic exposure processing (one example of the signal processing) of the 2D video (refer to photometric area LAR 1  indicated by the dot hatch of  FIG. 11A ). Here, in accordance with the operation of the user for switching from the 2D mode to the 3D mode (that is, the switching signal from the 2D mode to the 3D mode), as illustrated on the right side of the page of  FIG. 11D , photometric area determiner  281  determines, for example, the size of extraction range RGC 4  of 2K right parallax video LAR 8  which configures the 3D video as the photometric area used for deriving parameters (for example, brightness or light amount) of the signal processing (for example, automatic exposure processing, such as AE) with respect to the video data (that is, 2K left parallax video and 2K right parallax video) of 4K pixels generated by 4K video processor  264 . In addition, photometric area determiner  281  may determine, for example, the size of extraction range LFC 4  of the 2K left parallax video which configures the 3D video as the photometric area. 
     Exposure calculator  282  (one example of a deriver) calculates an exposure amount (that is, brightness or light amount) in the photometric area of the data of the 2D video of 4K pixels generated by 4K video processor  264  considering the photometric area determined by photometric area determiner  281  as a target, and outputs the calculation result to luminance controller  283 . In addition, exposure calculator  282  may not be provided in image processor  261 A, or may be provided in CPU  262 . 
     By using the calculation result of exposure calculator  282 , luminance controller  283  (one example of the image processor) performs the automatic exposure processing, such as AE, with respect to the 2D video of 4K pixels generated by 4K video processor  264 . In other words, luminance controller  283  performs processing of increasing the brightness for setting appropriate brightness in a case where the 2D video of 4K pixels in the photometric area is excessively dark (for example, the exposure amount is less than the predetermined first threshold value, and the first threshold value is the predetermined value). Meanwhile, luminance controller  283  performs processing of reducing the brightness for setting appropriate brightness in a case where the 2D video of 4K pixels in the photometric area is excessively bright (for example, the exposure amount is equal to or greater than the predetermined second threshold value, and the second threshold value is the predetermined value that satisfies first threshold value&lt;second threshold value). In addition, luminance controller  283  may not be provided in image processor  261 A, or may be provided in CPU  262 . Luminance controller  283  outputs data of the 2D video of 4K pixels which is the processing result of the automatic exposure processing, such as AE, to 2K right parallax video extractor  265  and 2K left parallax video extractor  266 , respectively. 
     Since the processing contents of 2K right parallax video extractor  265 , 2K left parallax video extractor  266 , and video output switchers  267  and  268  are the same as those in Embodiment 1, the description thereof will be omitted here. 
       FIG. 12  is a flowchart for describing an operational procedure example of camera apparatus  20  of Embodiment 2. In addition, in the description of  FIG. 12 , during the processing of steps S 11  to S 23 , the processing in steps S 11  and S 12  is performed in camera head  21  of camera apparatus  20 , and the processing after step S 13  is performed in CCU  22  of camera apparatus  20 . Further, it is needless to say that the operation in  FIG. 12  is not the contents dedicated to Embodiment 2, but can be applied as a processing procedure for the video after the extraction range is set in Embodiment 1. 
     In  FIG. 12 , camera apparatus  20  converges the light from subject  40  acquired by surgical microscope  10  with the lens of imaging lens portion  23  (S 11 ). In three-plate type capture  213  of camera head  21 , camera apparatus  20  spectrally disperses the light to the subject image of each color of RGB by a spectroscopic prism, forms an image on the imaging surfaces of the three image sensors of RGB, respectively, and images subject images of RGB of 2K pixels (S 12 ). 
     In image processor  261 A of CCU  22 , camera apparatus  20  generates 4K video (video of 4K pixels) by 4K visualization by the processing of pixel shifting the imaged 2K videos R, G, and B of each color of R, G, and B (S 13 ). In image processor  261 A of the CCU  22 , camera apparatus  20  determines an area used for deriving parameters (for example, brightness or light amount) of the signal processing (for example, automatic exposure processing, such as AE) with respect to the video of 4K pixels generated in step S 13  (S 14 ). 
     In image processor  261 A of CCU  22 , camera apparatus  20  calculates the exposure amount (that is, brightness or light amount) in the photometric area of the data of the 2D video of 4K pixels generated in step S 13 , considering the photometric area determined in step S 14  as a target (S 15 ). In image processor  261 A of CCU  22 , camera apparatus  20  performs the automatic exposure processing, such as AE, with respect to the data of 2D video of 4K pixels generated in step S 13  by using the calculation result of the exposure amount in step S 15  (S 16 ). 
     Camera apparatus  20  determines the output video type in CPU  262  of CCU  22 . In addition, CPU  262  controls the imaging by capture  213  and can determine the output video type of the video imaged by the capture  213 . Camera apparatus  20  sets the operation of image processor  261 A and switches the video output for each output video type of 3D video of 2K pixels (3D (FHD)), 2D video of 4K pixels (2D(4K)), and 3D video of HD resolution (3D (normal)) (S 17 ). 
     In a case of outputting the 3D video (3D (FHD)) of 2K pixels, image processor  261 A of CCU  22  performs the extraction processing of two left and right 2K parallax videos (2K left parallax video and 2K right parallax video) (S 18 ). Image processor  261 A of CCU  22  outputs the 3D left parallax video from channel CH 1  as a 3D video output of 2K pixels for 3D display and outputs the 3D right parallax video from channel CH 2  (S 19 ). 
     In a case of outputting the 2D video (2D (4K)) of 4K pixels, image processor  261 A of CCU  22  outputs the 4K video as a 2D video output of 4K pixels from either or both of channel CH 1  and channel CH 2  (S 20 ). 
     In a case of outputting the 3D video (3D (normal)) of HD resolution, image processor  261 A of CCU  22  performs the extraction processing of two left and right 2K parallax videos (2K left parallax video and 2K right parallax video) (S 21 ). In the processing of the step S 21 , as described in Embodiment 1, at least one extraction region of the 2K left parallax video and the 2K right parallax video may be extracted individually after being adjusted, in accordance with the operation of the user (for example, an observer, such as a doctor). Image processor  261 A combines the two left and right 2K parallax videos and performs video conversion processing (3D image visualization processing) that corresponds to various transmission methods of the 3D video (S 22 ). Image processor  261 A outputs the 3D video (left and right parallax video) as the 3D video output of HD resolution (S 23 ). 
     Here, in a case where the processing of step S 22  is performed, image processor  261 A includes 3D video combiner  272  illustrated in  FIG. 21 . 3D video combiner  272  performs combining processing of the 2D left parallax video from 2K left parallax video extractor  265  and the 2D right parallax video from 2K right parallax video extractor  266 , and generates a 3D video of HD resolution (3D (normal)). The combining processing of the 3D video can be performed by using video conversion processing (3D visualization processing) that corresponds to various transmission methods of the 3D video, such as a side-by-side method in which the left parallax video and the right parallax video are adjacent to each other in the horizontal direction, or a line by line method in which the left parallax video and the right parallax video are disposed for each line. 
       FIG. 13  is a flowchart for describing an operational procedure example at the time of interruption processing of mode switching. The processing in  FIG. 13  is started at the time when the processing of step S 31  (that is, the processing of switching from the 2D mode to the 3D mode or from the 3D mode to the 2D mode) occurs interruptively. 
     In  FIG. 13 , CPU  262  of CCU  22  determines whether or not a switching signal for switching from the 2D mode to the 3D mode or from the 3D mode to the 2D mode has been acquired (S 31 ). In a case where the switching signal has not been acquired (S 31 , NO), the current mode (for example, the 2D mode or the 3D mode) is maintained. CPU  262  determines whether or not the processing of steps S 14  to S 16  of  FIG. 12  has been performed once (S 32 ). In a case where the processing of steps S 14  to S 16  of  FIG. 12  is performed once, CPU  262  holds information (flags and the like) having the effect in the internal memory (not illustrated) or the like, and can determine whether or not the processing of steps S 14  to S 16  in  FIG. 12  has been performed once. In a case where it is determined that the processing of steps S 14  to S 16  of  FIG. 12  has been performed once (S 32 , YES), the processing proceeds to the processing after step S 17  of  FIG. 12 . This means that it is not necessary to change the photometric area since the current mode is not changed and the determination of the photometric area has already been completed and the processing of steps S 14  to S 16  is not necessary, and the processing of image processor  261 A may be ended without proceeding to the processing after step S 17  in  FIG. 12 . 
     Meanwhile, in a case where the switching signal has been acquired (S 31 , YES), or in a case where it is determined that the processing of steps S 14  to S 16  of  FIG. 12  has never been performed (S 32 , NO), image processor  261 A performs the processing of steps S 14  to S 16  illustrated in  FIG. 12  (S 33 ). After step S 33 , the processing of image processor  261 A proceeds to the processing following the step S 17 . 
     Next, in Embodiment 2, as an example of the signal processing performed with respect to the imaged video in order to improve the image quality of the video, an adjustment processing of white balance (WB) is exemplified, and an example in which, in a case of switching from the 2D mode to the 3D mode, an area used for deriving parameters (for example, WB adjustment value) of WB adjustment processing is determined, will be described. 
       FIG. 14  is a block diagram illustrating a second example of a functional configuration of the image processor of camera apparatus  20  of Embodiment 2. Image processor  261 B includes 4K video processor  264 , WB target area determiner  284 , WB controller  285 , 2K left parallax video extractor  265 , 2K right parallax video extractor  266 , and video output switchers  267  and  268 . In addition, although frame buffer FB 1  (memory) is not illustrated and omitted in  FIG. 14 , when frame buffer FB 1  is provided in CCU  22 , frame buffer FB 1  may be provided either on the inside or on the outside of image processor  261 B. In addition, WB target area determiner  284  and WB controller  285  illustrated in  FIG. 14  may be included being combined in image processor  261 A illustrated in  FIG. 10 . 
     Since the internal configuration of image processor  261 B in  FIG. 14  includes the same internal configurations as each of those of the image processor  261 A in  FIG. 10 , the same reference numerals are given to the same configurations and the description is simplified or omitted, and different contents will be described. 
     The video data of 4K pixels generated by 4K video processor  264  is input to WB target area determiner  284 . 
     In accordance with the switching signal from the 2D mode to the 3D mode, WB target area determiner  284  (one example of the determiner) determines an area used for deriving parameters (for example, WB adjustment value) of the signal processing (for example, WB adjustment processing) with respect to the left eye image and the right eye image (for example, video data of 4K pixels generated by 4K video processor  264 ) which are imaged by camera head  21  (refer to  FIG. 15 ). In addition, in accordance with the switching signal from the 3D mode to the 2D mode, WB target area determiner  284  determines an area used for deriving parameters (for example, WB adjustment value) of the signal processing (for example, WB adjustment processing) with respect to the left eye image and the right eye image (for example, video data of 4K pixels generated by 4K video processor  264 ) which are imaged by camera head  21 . In addition, even when the switching from the 2D mode to the 3D mode or the switching from the 3D mode to the 2D mode does not occur, WB target area determiner  284  determines an area used for deriving parameters (for example, WB adjustment value) of the signal processing (for example, WB adjustment processing) with respect to the left eye image and the right eye image (for example, video data of 4K pixels generated by 4K video processor  264 ) which are imaged by camera head  21 . 
       FIG. 15  is an explanatory view illustrating an adjustment example of the target area of WB with respect to the subject in accordance with switching from the 2D mode to the 3D mode. In  FIG. 15 , the imaging surface CAP 1  is the imaging surface of a so-called bottom view (that is, when the object side is viewed from the imaging surface side). In order to simplify the description of  FIG. 15 , extraction range LFC 4  of the 2D left parallax video which configures the 3D video and extraction range RGC 4  of the 2D right parallax video which configures the same 3D video, are set in a state where there is no shift in the vertical direction of imaging surface CAP 1  and of being horizontally aligned in the horizontal direction. Extraction range LFC 4  is the extraction range of the 2K left parallax video (left eye image). Similarly, extraction range RGC 4  is the extraction range of the 2K right parallax video (right eye image). 
     On the left side of the page of  FIG. 15 , in the 2D mode, in imaging surface CAP 1  (for example, the size of “2160 pixels×3840 pixels” that corresponds to 4K pixels) of the image sensor in camera head  21 , as the area used for deriving the WB adjustment value, small area WB 1  including the center of imaging surface CAP 1  is illustrated as an initial position. In other words, based on the WB adjustment value in small area WB 1 , WB target area determiner  284  performs the WB adjustment processing with respect to the left eye image and the right eye image (for example, the video data of 4K pixels generated by 4K video processor  264 ) which are imaged by camera head  21 . Similarly to Embodiment 1, WB target area determiner  284  may move and change the area used for deriving the WB adjustment value to any of other small areas WB 2 , WB 3 , WB 4 , and WB 5  which have the same area as that of small area WB 1  from small area WB 1  in accordance with the operation of the user (for example, an observer, such as a doctor) who reads the 2D left parallax video and the 2D right parallax video which configure the 3D video projected to monitor  30 . 
     Here, it is assumed that the operation (that is, the switching signal from the 2D mode to the 3D mode) of the user for switching from the 2D mode to the 3D mode is performed. In accordance with the operation, as illustrated on the right side of the page of  FIG. 15 , WB target area determiner  284  determines, for example, small area WB 6  including the center of extraction range RGC 4  of the 2K right parallax video which configures the 3D video, as the initial position of the area used for deriving parameters (for example, WB adjustment value) of the WB adjustment processing with respect to the video data of 4K pixels (that is, 2K left parallax video and 2K right parallax video) which are generated by 4K video processor  264 . In addition, WB target area determiner  284  may determine, for example, the small area including the center of extraction range LFC 4  of the 2K left parallax video which configures the 3D video as the area used for deriving the WB adjustment value. Similarly to Embodiment 1, WB target area determiner  284  may move and change the area used for deriving the WB adjustment value to any of other small areas WB 7 , WB 8 , WB 9 , and WB 10  which have the same area as that of small area WB 6  in extraction range RGC 4  from small area WB 6  in accordance with the operation of the user (for example, an observer, such as a doctor) who reads the 2D left parallax video and the 2D right parallax video which configure the 3D video projected to monitor  30 . 
     In addition, WB target area determiner  284  (one example of the deriver) calculates the WB adjustment value in the area of the data of the 2D video of 4K pixels generated by 4K video processor  264  considering the area determined by WB target area determiner  284  as a target, and outputs the calculation result to WB controller  285 . 
     By sampling the color of the area that corresponds to the calculation result of WB target area determiner  284 , WB controller  285  (one example of the image processor) performs the WB adjustment processing with respect to the data of the 2D video of 4K pixels generated by 4K video processor  264 . In addition, WB controller  285  may not be provided in image processor  261 B, or may be provided in CPU  262 . WB controller  285  outputs data of the 2D video of 4K pixels which is the processing result of the WB adjustment processing, to 2K right parallax video extractor  265  and 2K left parallax video extractor  266 , respectively. 
     The flowchart illustrated in  FIG. 12  can be similarly applied in a case where image processor  261 B of CCU  22  is used. For example, instead of steps S 14  to S 16  in  FIG. 12 , processing of determining the parameter (WB adjustment value) of the WB adjustment processing, processing of adjusting the WB using the WB adjustment in the area determined based on the determination processing may be performed. Further, CCU  22  may have a configuration which is combined with image processors  261 A and  261 B, and in this case, between step S 16  and step S 17  in  FIG. 12  or between step S 13  and step S 14 , the processing of determining the parameter (WB adjustment value) of the WB adjustment processing and the WB adjustment processing in which the WB adjustment is used in the area determined based on the determination processing may be performed. Further, in a case where CCU  22  has a configuration which is combined with image processors  261 A and  261 B, the processing of steps S 14  to S 16 , the processing of determining the parameter (WB adjustment value) of the WB adjustment processing, and the WB adjustment processing in which the WB adjustment is used in the area determined based on the determination processing may be performed. 
     Above, in the medical camera system of Embodiment 2, CCU  22  is connected to camera head  21  which can perform the imaging on the imaging surface of one screen of the 2K left parallax video (one example of the left eye image) and 2K right parallax video (one example of the right eye image) having parallax based on the light of the target site incident on surgical microscope  10  (one example of the optical instrument). In accordance with the switching from the 2D mode to the 3D mode, CCU  22  or camera apparatus  20  including CCU  22  derives (for example, calculates) the parameters (for example, brightness or light amount, and WB adjustment value) of the signal processing with respect to the left eye image and the right eye image which are imaged by camera head  21 . In addition, based on the derived parameters (for example, brightness or light amount, and WB adjustment value), CCU  22  or camera apparatus  20  including CCU  22  performs the signal processing of the left eye image and the right eye image which are imaged by camera head  21 , and outputs the left eye image and the right eye image to which the signal processing is performed to monitor  30 . 
     Accordingly, when switching from the display of the 2D video to the display of the 3D video, CCU  22  or camera apparatus  20  including CCU  22  can adaptively adjust the area on the imaging surface used for deriving parameters of the signal processing for the imaged 3D video, and to image and output a high-definition 3D video with one camera. In other words, in the 3D mode, since the parameters of the signal processing are derived considering the extraction range of the 2K left parallax video or the 2K right parallax video which configures the 3D video as a target, it is possible to suppress deterioration of image quality of the 3D video due to the influence of the parameters of a part (for example, a peripheral portion of the imaging surface) of the imaging surface of the image sensor in the 2D mode which is not essentially required in the 3D mode. In addition, it is possible to image and output a high definition 3D video of 2K pixels with one camera head  21  and CCU  22 , and to project the target site stereographically and with high definition. In particular, for surgical applications, clearer 3D video can be acquired, and operability at the time of surgery and visibility of the target site can be improved. 
     In addition, since one CCU  22  can cope with imaging output of 2D video of 4K pixels and imaging output of 3D video of 2K pixels, the disclosure can be applied to various observation video applications. 
     In addition, CCU  22  or camera apparatus  20  including CCU  22  determines an area used for deriving parameters of the signal processing from an imaging area of one of the left eye image and the right eye image which are imaged by camera head  21 . Accordingly, CCU  22  or camera apparatus  20  including CCU  22  can appropriately determine the parameters when performing necessary signal processing with respect to the 2K left parallax video and the 2K right parallax video which configure the 3D video in the 3D mode, and can improve the image quality of the 3D video projected to monitor  30 . 
     In addition, CCU  22  or camera apparatus  20  including CCU  22  determines an area used for deriving parameters of the signal processing based on the shape of the subject appearing in the left eye image and the right eye image which are imaged by camera head  21 . Accordingly, since CCU  22  or camera apparatus  20  including CCU  22  can generate the 2K left parallax video and 2K right parallax video having high image quality that conforms to the shape of the subject imaged in the 3D mode, it is possible to appropriately improve the image quality of the 3D video projected to monitor  30 . 
     In addition, the parameters for the signal processing is the exposure amount of at least one of the left eye image and the right eye image of the area used for deriving the parameters of the signal processing. CCU  22  or camera apparatus  20  including CCU  22  adjusts brightness of the left eye image and the right eye image which are imaged by camera head  21  based on the exposure amount. Accordingly, in the 3D mode, CCU  22  or camera apparatus  20  including CCU  22  can suppress deterioration of the image quality of the 3D video without becoming excessively dark or excessively bright due to the influence of the exposure amount of a part (for example, the peripheral portion of the imaging surface) of the imaging surface of the image sensor in the 2D mode which is not essentially required in the 3D mode. 
     In addition, the parameters for the signal processing is the white balance adjustment value of at least one of the left eye image and the right eye image of the area used for deriving the parameters of the signal processing. CCU  22  or camera apparatus  20  including CCU  22  adjusts white balance of the left eye image and the right eye image which are imaged by camera head  21  based on the white balance adjustment value. Accordingly, in CCU  22  or camera apparatus  20  including CCU  22 , in the 3D mode, the 3D video of which the white balance is appropriately adjusted is obtained without becoming excessively bluish white or excessively reddish white due to the influence of the WB adjustment value of a part (for example, an external peripheral portion of imaging surface CAP 1 ) of the imaging surface of the image sensor in the 2D mode which is not essentially required in the 3D mode. 
     Further, in the 3D mode, CCU  22  or camera apparatus  20  including CCU  22  includes distance measuring circuit  291  (one example of distance measurer) which measures distance L (refer to  FIG. 19 ) from surgical endoscope  110  (one example of optical instrument) to an observation target site based on the parallax Δ (refer to  FIG. 23 ) appearing in the left eye image and the right eye image which are imaged by camera head  21 . CCU  22  or camera apparatus  20  outputs the result measured by distance measuring circuit  291  (that is, information on the distance) to monitor  130  (refer to  FIG. 19 ) together with the left eye image and the right eye image to which the signal processing is performed. Accordingly, the user (for example, an observer, such as a doctor) can visually grasp the situation of the observation target site projected to monitor  130 , can grasp the specific distance information from surgical endoscope  110  (refer to  FIG. 19 ) to the observation target site, and can support the guidance of the next medical practice by the user at the time of surgery or examination. 
     In addition, in response to the switching from the 3D mode to the 2D mode, CCU  22  or camera apparatus  20  including CCU  22  interrupts the output of the information on the distance to monitor  130 . Accordingly, in the 2D mode, neither the left and right 2K left parallax video having parallax nor the 2K right parallax video is input to distance measuring circuit  291 , and thus, the information on the distance is not displayed on monitor  130 . Therefore, the user (for example, an observer, such as a doctor) can easily recognize that the present is the 2D mode by the fact that the information on the distance is not displayed on monitor  130 , and on the other hand, the user can easily recognize that the present is the 3D mode by the fact that the information on the distance is displayed on monitor  130 . 
     (Background of Contents of Embodiment 3) 
     In the above-described medical camera system, in order to ensure a clear field of view of a target site at which surgery or treatment is performed, a display video with high definition and excellent visibility is desired. In addition, since the size or state of an observation target can be grasped more accurately and easily by stereoscopic viewing of a target site, there is an increasing demand for a 3D video that provides a stereoscopic observed video to the observer. Particularly, in a surgical application of a fine site, a high-definition 3D video is required, but in the related art, such as PTL 1, there was a problem that it is difficult to visually recognize the details of the observed video clearly. In addition, in order to generate a high-definition 3D video required in the medical field, it is necessary to use two different cameras for imaging an image for a left eye (left eye image) and an image for a right eye (right eye image) which have parallax. 
     Further, for example, in the medical camera system, when a display mode is switched such that the 2D video is displayed from a state where the 3D video is displayed, it is required that the display of video is smoothly switched such that a doctor or the like continuously grasps the details of the situation of the target site (for example, an affected part of a human body). However, in reality, due to factors, such as the following, delay time (that is, non-display time of the video) in units of several seconds occurs when switching from the display of the 3D video to the display of the 2D video, and there was a case where it is difficult to grasp the details of the situation of the target site (for example, the affected part of the human body) for a certain period of time or more. Specifically, in order to switch from the 3D mode of the video to the 2D mode, an operation for changing the display mode on the monitor side from the 3D mode to the 2D mode was necessary. Since the operation is usually performed by a person, it takes a certain period of time, and in accordance with the transmission format of the 3D video, for example, a delay time (that is, non-display time of the video) in units of several seconds has occurred. Therefore, there was a case where it is difficult to grasp the details of the situation of the target site (for example, the affected part of the human body) for a certain period of time or more, and the convenience of the user (for example, an observer, such as a doctor) is impaired. Factors to switch from the display of the 3D video to the display of the 2D image are, for example, that the eyes become tired when viewing the 3D video all the time during surgery or examination, that the details of the affected part that can be sufficiently grasped by the 2D video without the 3D video during surgery or examination is desired to be seen, and that it is desired to change the setting to 2D rather than 3D after surgery or examination. Even with the related art as in PTL 1, in a case of switching from the display of the 3D video to the display of the 2D video, it is still necessary to change the display mode on the monitor side from the 3D mode to the 2D mode, and there is no consideration for technical measures against the problem of impairing the convenience of the user (for example, an observer, such as a doctor) described above. 
     Here, in Embodiment 3 described below, in view of the above-described situation of the related art, an example of the image processing apparatus, the camera apparatus, and the output control method for suppressing the deterioration of the convenience of the user generated in accordance with the switching from the display of the 3D video to the display of the 2D video and the switching of the display mode of the video in a state of maintaining the display mode of the 3D video without changing the display mode on the monitor side from the 3D mode to the 2D mode, will be described. 
     Embodiment 3 
     Since the internal configuration of each of the medical camera system and the camera apparatus or the CCU of Embodiment 3 is the same as the internal configuration of each of the medical camera system and camera apparatus  20  or CCU  22  of Embodiment 1, the same configuration will be given the same reference numerals and the description thereof will be simplified or omitted, and different contents will be described. 
       FIG. 16  is a block diagram illustrating a functional configuration example of image processor  261 C of camera apparatus  20  of Embodiment 3. Image processor  261 C includes 4K video processor  264 , 2K left parallax video extractor  265 , 2K right parallax video extractor  266 , and video output switchers  267  and  268 . In addition, when frame buffer FB 1  (memory) is provided in CCU  22 , frame buffer FB 1  (memory) may be provided either on the inside or on the outside of image processor  261 . 
     Since the internal configuration of image processor  261 C in  FIG. 16  includes the same internal configurations as each of those of image processor  261  in  FIG. 6 , the same reference numerals are given to the same configurations and the description is simplified or omitted, and different contents will be described. 
     Data of the 2K left parallax video generated by 2K left parallax video extractor  265  is input to both of video output switchers  267  and  268 . In addition, data of the 2K right parallax video generated by 2K right parallax video extractor  266  is input to both of video output switchers  267  and  268 . 
     Here, as described above, when the display mode is switched such that the 2D video is displayed from the state where the 3D image is displayed, it is required that the display of video is smoothly switched such that the user (for example, an observer, such as a doctor) continuously grasps the details of the situation of the target site (for example, an affected part of a human body). However, in reality, delay time (that is, non-display time of the video) in units of several seconds occurs when switching from the display of the 3D video to the display of the 2D video, and there was a case where it is difficult to grasp the details of the situation of the target site (for example, the affected part of the human body) for a certain period of time or more. Specifically, in order to switch from the 3D mode of the video to the 2D mode, an operation for changing the display mode on the monitor side from the 3D mode to the 2D mode was necessary. Since the operation is usually performed by a person, it takes a certain period of time, and in accordance with the transmission format of the 3D video (for example, HDMI (registered trademark) or SDI), for example, a delay time (that is, non-display time of the video) in units of several seconds has occurred. Therefore, there was a case where it is difficult to grasp the details of the situation of the target site (for example, the affected part of the human body) for a certain period of time or more, and the convenience of the user (for example, an observer, such as a doctor) is impaired. Therefore, as a result of the temporary interruption of the display of the video by the user (for example, an observer, such as a doctor) during surgery or examination, there is a time zone in which the state of the affected part cannot be grasped, and since it was necessary to perform the operation of changing the display mode of the monitor, usability is not excellent. 
     Here, in Embodiment 3, for example, when switching from the 3D mode to the 2D mode, image processor  261 C of CCU  22  does not change and maintains the transmission format at the time of transmitting (outputting) the 3D video to monitor  30 , and changes the data of the transmission target from the 2K left parallax video and the 2K right parallax video which configure the 3D video to only one of the 2K left parallax video and the 2K right parallax video that become the 2D video. Accordingly, since there is no need to change the transmission format, it is unnecessary to change the display mode on monitor  30  side from the 3D mode to the 2D mode, and in a state where the display mode on monitor  30  side is maintained in the 3D mode, a pseudo 2D video can be displayed. Therefore, a problem that it becomes impossible to grasp the details of the situation of the target site (for example, the affected part of the human body) for a certain period of time or more, which occurred in accordance with the switching of the display mode of the video, is eliminated, and the above-described usability of the user (for example, an observer, such as a doctor) is improved. 
     Video output switcher  267  (one example of the output controller) switches the video signal output and outputs the 2D left parallax video of 2K pixels from the 2K left parallax video extractor  265 , the 2D right parallax video of 2K pixels from the 2K right parallax video extractor  266 , or the video signal of the 2D video of 4K pixels from 4K video processor  264  via channel CH 1  (one example of the first channel). In a case of switching from the 2D mode to the 3D mode, the video output switcher  267  outputs the 2D left parallax video of 2K pixels from the 2K left parallax video extractor  265 . In a case of switching from the 3D mode to the 2D mode, video output switcher  267  outputs the 2D left parallax video of 2K pixels from the 2K left parallax video extractor  265  or the 2D right parallax video of 2K pixels from 2K right parallax video extractor  266 . In addition, in the output mode of the 2D video of 4K pixels, video output switcher  267  outputs the video signal of the 2D video of 4K pixels from 4K video processor  264 . 
     Video output switcher  268  (one example of the output controller) switches the video signal output and outputs the 2D left parallax video of 2K pixels from the 2K left parallax video extractor  265 , the 2D right parallax video of 2K pixels from the 2K right parallax video extractor  266 , or the video signal of the 2D video of 4K pixels from 4K video processor  264  via channel CH 2  (one example of the second channel). In a case of switching from the 2D mode to the 3D mode, the video output switcher  268  outputs the 2D right parallax video of 2K pixels from the 2K right parallax video extractor  266 . In a case of switching from the 3D mode to the 2D mode, video output switcher  268  outputs the 2D left parallax video of 2K pixels from the 2K left parallax video extractor  265  or the 2D right parallax video of 2K pixels from 2K right parallax video extractor  266 . In addition, in the output mode of the 2D video of 4K pixels, video output switcher  268  outputs the video signal of the 2D video of 4K pixels from 4K video processor  264 . 
     In addition, in a case of outputting the 2D video of 4K pixels in the output mode of the 2D video of 4K pixels, the video signal may be output to both of video output 1 of channel CH 1  and video output 2 of channel CH 2 , or the video signal may be output to only one of video output 1 and video output 2. Further, the 2D video of 4K pixels may be output to either one of channel CH 1  and channel CH 2 , and 2D video of 2K pixels may be output to the other. 
       FIG. 17A  is an explanatory view illustrating a transmission example of the left eye image and the right eye image in the 3D mode.  FIG. 17B  is an explanatory view illustrating a transmission example of the left eye image and the right eye image after switching from the 3D mode to the 2D mode. In  FIGS. 17A and 17B , imaging surface CAP 1  is an imaging surface of a so-called bottom view (that is, when the object side is viewed from the imaging surface side). 
     In  FIG. 17A , image processor  261 C of CCU  22  outputs 2K left parallax video IMGL 1  of extraction range LFC 4  imaged on imaging surface CAP 1  of the image sensor (capture  213 ) of camera head  21  to monitor  30  via channel CH 1 . In addition, image processor  261 C of CCU  22  outputs 2K right parallax video IMGR 1  of extraction range RGC 4  imaged on imaging surface CAP 1  of the image sensor (capture  213 ) of camera head  21  to monitor  30  via channel CH 2 . Accordingly, when 2K left parallax video IMGL 1  and 2K right parallax video IMGR 1  are projected to monitor  30 , the videos are combined with each other and displayed as 3D video IMG 1 . 
     Meanwhile, in  FIG. 17B , when switching from the 3D mode to the 2D mode, image processor  261 C of CCU  22  outputs 2K left parallax video IMGL 2  of extraction range LFC 4  imaged on imaging surface CAP 1  of the image sensor (capture  213 ) of camera head  21  to monitor  30  via both of channel CH 1  and channel CH 2 . Accordingly, both of 2K left parallax video IMGL 2  and 2K right parallax video IMGR 2  having parallax on the left and right sides are not output to monitor  30 , and only one (in this case, 2K left parallax video IMGL 2 ) is projected to monitor  30 , and thus, 2D video IMG 2  is displayed in a pseudo manner while the transmission format of the 3D video is not changed. In addition, in  FIG. 17B , an example in which 2K left parallax video IMGL 2  is output to monitor  30  via both of channel CH 1  and channel CH 2  has been described, but it is needless to say that 2K right parallax video IMGR 2  may be output to monitor  30  via both of channel CH 1  and channel CH 2 . 
       FIG. 18  is a flowchart for describing an operational procedure example of camera apparatus  20  of Embodiment 3. The processing in  FIG. 18  is started at the time when the processing of step S 41  (that is, the processing of switching from the 3D mode to the 2D mode) occurs interruptively. 
     In  FIG. 18 , CPU  262  of CCU  22  determines whether or not the switching signal from the 3D mode to the 2D mode has been acquired (S 41 ). In a case where the switching signal has not been acquired (S 41 , NO), the current mode (for example, the 3D mode) is maintained. In response to the signal that notifies the current mode from CPU  262 , image processor  261 C performs each processing of steps S 18  and S 19  of  FIG. 12  or each processing of steps S 21  to S 23  (S 42 ). 
     Image processor  261 C outputs the 2K left parallax video from channel CH 1  and outputs the 2K right parallax video from channel CH 2  or outputs the 3D video combined in step S 22  from either channel CH 1  or channel CH 2  or from both of channel CH 1  and channel CH 2  (S 43 ). In step S 43 , the video output via each of the channels is projected to monitor  30  (S 44 ), and the 3D video is read by the user (for example, an observer, such as a doctor). 
     Meanwhile, in a case where the switching signal has been acquired (S 41 , YES), by using, for example, the 2K left parallax video (one example of the left eye image), image processor  261 C generates the data (specifically, two 2K left parallax videos) of the 3D video that conforms to the 3D transmission format and be transmitted (S 45 ). Without changing the 3D transmission format, image processor  261 C outputs the data of the 3D video generated in step S 45  to monitor  30  by using both of channel CH 1  and channel CH 2  (S 46 ). In step S 46 , the video output via each of the channels is projected to monitor  30  (S 47 ), and the 3D video that conforms to the 3D transmission format and is sent is read by the user as a pseudo 2D video (for example, an observer, such as a doctor). 
     Above, in the medical camera system of Embodiment 3, CCU  22  is connected to camera head  21  which can perform the imaging on the imaging surface of one screen of the 2K left parallax video (one example of the left eye image) and 2K right parallax video (one example of the right eye image) having parallax based on the light of the target site incident on surgical microscope  10  (one example of the optical instrument). In addition, CCU  22  or camera apparatus  20  including CCU  22  performs the signal processing of the left eye image and the right eye image which are imaged by camera head  21 , and outputs the left eye image and the right eye image to which the signal processing is performed to monitor  30  via each of channel CH 1  (one example of the first channel) and channel CH 2  (one example of the second channel). In addition, in response to the switching from the 3D mode to the 2D mode, CCU  22  or camera apparatus  20  including CCU  22  outputs one of the left eye image and the right eye image to which the signal processing is performed to monitor  30  via each of channel CH 1  and channel CH 2 . 
     Accordingly, when changing from the display of the 3D video to the display of the 2D video, CCU  22  or camera apparatus  20  including CCU  22  does not change and maintains the transmission format of the 3D video, and transmits at least one of the 2K left parallax video and 2K left parallax video which configures the 3D video to monitor  30 . In other words, since there is no need to change the transmission format, it is unnecessary to perform an operation of changing the display mode on monitor  30  side from the 3D mode to the 2D mode, and in a state where the display mode on monitor  30  side is maintained in the 3D mode, a pseudo 2D video can be displayed. Therefore, CCU  22  or camera apparatus  20  including CCU  22  can eliminate a problem that it becomes impossible to grasp the details of the situation of the target site (for example, the affected part of the human body) for a certain period of time or more, which occurred in accordance with the switching of the display mode of the video, and the above-described usability of the user (for example, an observer, such as a doctor) is improved. In addition, it is possible to image and output a high definition 3D video of 2K pixels with one camera head  21  and CCU  22 , and to project the target site stereographically and with high definition. 
     In addition, since one CCU  22  can cope with imaging output of 2D video of 4K pixels and imaging output of 3D video of 2K pixels, the disclosure can be applied to various observation video applications. 
     Further, CCU  22  or camera apparatus  20  including CCU  22  displays the 2D video on monitor  30  in a pseudo manner in the 2D mode based on one of the left eye image and the right eye image output to monitor  30  via both of channel CH 1  and channel CH 2 . Accordingly, only by displaying any one of the 2K left parallax video or the 2K right parallax video on monitor  30 , CCU  22  or camera apparatus  20  including CCU  22  can suppress the generation of display delay time that is supposed to be generated when switching from the 3D mode to the 2D mode as much as possible, and can simply display the 2D video in the 2D mode. 
     In addition, the switching from the 3D mode to the 2D mode is input by the operation of the user. Accordingly, CCU  22  or camera apparatus  20  including CCU  22  can easily detect the switching from the 3D mode to the 2D mode by a simple operation of the user. 
     Further, in the 3D mode, CCU  22  or camera apparatus  20  including CCU  22  includes distance measuring circuit  291  (one example of distance measurer) which measures distance L (refer to  FIG. 19 ) from surgical endoscope  110  (one example of optical instrument) to an observation target site based on the parallax Δ (refer to  FIG. 23 ) appearing in the left eye image and the right eye image which are imaged by camera head  21 . CCU  22  or camera apparatus  20  outputs the result measured by distance measuring circuit  291  (that is, information on the distance) to monitor  130  (refer to  FIG. 19 ) together with the left eye image and the right eye image to which the signal processing is performed. Accordingly, the user (for example, an observer, such as a doctor) can visually grasp the situation of the observation target site projected to monitor  130 , can grasp the specific distance information from surgical endoscope  110  (refer to  FIG. 19 ) to the observation target site, and can support the guidance of the next medical practice by the user at the time of surgery or examination. 
     In addition, in response to the switching from the 3D mode to the 2D mode, CCU  22  or camera apparatus  20  including CCU  22  interrupts the output of the information on the distance to monitor  130 . Accordingly, in the 2D mode, neither the left and right 2K left parallax video having parallax nor the 2K right parallax video is input to distance measuring circuit  291 , and thus, the information on the distance is not displayed on monitor  130 . Therefore, the user (for example, an observer, such as a doctor) can easily recognize that the present is the 2D mode by the fact that the information on the distance is not displayed on monitor  130 , and on the other hand, the user can easily recognize that the present is the 3D mode by the fact that the information on the distance is displayed on monitor  130 . 
     In addition, in the above-described embodiment, surgical microscope  10  is exemplified as an example of the optical instrument, but surgical endoscope  110  may be applied. Next, a configuration of the surgical endoscope system to which operation endoscope  110  is applied will be described as an example of an optical instrument with reference to  FIGS. 19 and 20 . 
       FIG. 19  is a system configuration view illustrating a configuration example in which the medical camera system including the camera apparatus of each of the embodiments is applied to the surgical endoscope system. The surgical endoscope system includes surgical endoscope  110 , camera apparatus  120 , monitor  130 , and light source device  131 . Camera apparatus  120  is similar to camera apparatus  20  illustrated in  FIGS. 1 to 5 , and is configured to include camera head  121  and CCU  122 . 
     Surgical endoscope  110  is a stereoscopic endoscope, and includes objective lenses  201  R and  201  L, relay lenses  202 R and  202 L, and imaging lenses  203 R and  203 L, as an observation optical system provided in elongated insertion portion  111  so as to correspond to the left and right eyes of the observer. Surgical endoscope  110  includes camera installer  115  provided on the proximal side of the observation optical system and light source installer  117 , and is provided with light guide  204  that guides the illumination light from light source installer  117  to the distal end portion of insertion portion  111 . By installing imaging lens portion  123  of camera head  121  to camera installer  115  and performing the imaging, it is possible to acquire an observation video for stereoscopic vision in camera apparatus  120 . Light guide cable  116  is connected to light source installer  117 , and light source device  131  is connected via light guide cable  116 . 
     Camera head  121  and CCU  122  are connected to each other by signal cable  125 , and video signal for the 3D video of the subject imaged by camera head  121  is transmitted to CCU  122  via signal cable  125 . Monitor  130  is connected to the output terminal of CCU  122 , and two left and right video outputs 1 and 2 for the 3D display are output. On monitor  130 , the 3D video of 2K pixels is displayed as an observation video of the target site. 
       FIG. 20  is a view illustrating an external appearance example of the surgical endoscope system of each of the embodiments. In surgical endoscope  110 , camera installer  115  is provided on the proximal side of insertion portion  111 , and imaging lens portion  123  of camera head  121  is installed. Light source installer  117  is provided on the proximal side portion of insertion portion  111 , and light guide cable  116  is connected thereto. An operation switch is provided in camera head  121 , and it is possible to perform an operation (freeze, release, image scan, and the like) of the observed video to be imaged at the hand of the user. The surgical endoscope system includes recorder  132  for recording the observed video imaged by camera apparatus  120 , operation unit  133  for operating the surgical endoscope system, and foot switch  137  for performing the operation input by the foot of the observer, and operation unit  133 , CCU  122 , light source device  131 , and recorder  132  are stored in control unit housing  135 . Monitor  130  is disposed above control unit housing  135 . 
     In this manner, in the configuration of the surgical endoscope system illustrated in  FIGS. 19 and 20 , similar to the configuration of the above-described medical camera system, from the left and right parallax images of the target site acquired by surgical endoscope  110 , it is possible to generate and output each of the left parallax video and the right parallax video of 2K pixels, and to display the 3D video of 2K pixels on monitor  130 . 
     Embodiment 4 
     In Embodiment 4, an example of the surgical endoscope system which is capable of measuring distance L from the optical instrument (for example, the distal end of the insertion portion of surgical endoscope  110  illustrated in  FIG. 19 ) to the observation target site (that is, subject  40 ) and displaying the distance measurement result on monitor  130 , in the 3D mode, will be described. Since the configuration of the surgical endoscope system has been described with reference to  FIGS. 19 and 20 , the description of the same contents will be simplified or omitted, and different contents will be described. 
       FIG. 21  is a block diagram illustrating a functional configuration example of image processor  271  of camera apparatus  20  of Embodiment 4. Similar to image processor  261  illustrated in  FIG. 6 , image processor  271  includes 4K video processor  264 , 2K left parallax video extractor  265 , and 2K right parallax video extractor  266 , and includes 3D video combiner  272 , distance measuring circuit  291 , video output switchers  273  and  274 , display element generator  292 , and superimposition controllers  293  and  294 . 
     In response to the switching signal from the 2D mode to the 3D mode, 2K left parallax video extractor  265  outputs the 2K left parallax video which configures the 3D video to 3D video combiner  272 , video output switcher  273 , and distance measuring circuit  291 , respectively. In response to the switching signal from the 3D mode to the 2D mode, the 2K left parallax video extractor  265  interrupts the output of at least the 2K left parallax video which configures the 3D video to distance measuring circuit  291 . 
     In response to the switching signal from the 2D mode to the 3D mode, 2K right parallax video extractor  266  outputs the 2K right parallax video which configures the 3D video to 3D video combiner  272 , video output switcher  274 , and distance measuring circuit  291 , respectively. In response to the switching signal from the 3D mode to the 2D mode, the 2K right parallax video extractor  266  interrupts the output of at least the 2K right parallax video which configures the 3D video to distance measuring circuit  291 . 
     3D image combiner  272  performs combining processing of the 3D left parallax video from the output of 2K left parallax video extractor  265  and the 3D right parallax video from the output of 2K right parallax video extractor  266 , and generates the 3D video of HD resolution (3D (normal)). The combining processing of the 3D video can be performed by using video conversion processing (3D visualization processing) that corresponds to various transmission methods of the 3D video, such as a side-by-side method in which the left parallax video and the right parallax video are adjacent to each other in the horizontal direction, or a line by line method in which the left parallax video and the right parallax video are disposed for each line. 
     The video output switchers  273  and  274  switch the output of the video signal, and outputs the video signal of the 3D video (3D (FHD)) of 2K pixels, the 3D video of HD resolution (3D (normal)), or the 2D video of 4K pixels (2D (4K)). In a case of outputting the 3D video (3D (FHD)) of 2K pixels, the video signal of the 3D left parallax video is output as video output 1 of channel CH 1  and the video signal of the 3D right parallax video is output as video output 2 of channel CH 2 . In a case of outputting the 2D video (2D (4K)) of 4K pixels or the 3D video (3D (normal)) of HD resolution, the video signal may be output to both of video output 1 of channel CH 1  and video output 2 of channel CH 2 , or the video signal may be output to only one of video output 1 of channel CH 1  and video output 2 of channel CH 2 . 
     In the 3D mode, distance measuring circuit  291  (one example of the distance measurer) measures distance L (refer to  FIG. 19 ) from surgical endoscope  110  to the observation target site based on the parallax Δ (refer to  FIG. 23 ) appearing in the 2K left parallax video from 2K left parallax video extractor  265  and the 2K right parallax video from 2K right parallax video extractor  266 . Distance measuring circuit  291  outputs the measurement result (that is, information on distance L from surgical endoscope  110  to the observation target site) to CPU  262 . 
       FIG. 22  is an explanatory view illustrating each of an arrangement example of objective lens  201 L for the left eye image and objective lens  201 R for the right eye image and an example of marker MK 1  designated on 3D image CPIM 3  displayed on monitor  130 .  FIG. 23  is an explanatory view of the parallax Δ appearing in the left eye image and the right eye image in accordance with the position of designated marker MK 1 . 
     In  FIG. 22 , baseline length D between objective lens  201 L for forming an image of the subject light on imaging surface IGA of the image sensor (capture  213 ) of camera head  121  for imaging the left eye image (that is, the 2K left parallax video) and objective lens  201 R for forming an image of the subject light on the imaging surface of the image sensor (capture  213 ) of camera head  121  for imaging the right eye image (that is, the 2K right parallax video) is a default value. The baseline length D corresponds to the distance between axial line  201 LC that passes through the lens center of objective lens  201 L and axial line  201 RC that passes through the lens center of objective lens  201 R. In addition, in order to simplify the description of Embodiment 4, focal length f of objective lenses  201 L and  201 R will be described as the distance from the principal points (not illustrated) of each of objective lenses  201 L and  201 R to imaging surface IGA. 
     Here, it is assumed that marker MK 1  is displayed at the position designated by the operation of the user (for example, an observer, such as a doctor) on 3D image CPIM 3  which configures the 3D video projected to monitor  130 . Position ZC 1  indicates the center position of marker MK 1 , and dotted line MKC is a line that passes through the center position of marker MK 1  and is provided for describing parallax Δ. 
     In the uppermost stage of  FIG. 23 , 3D image CPIM 3  is illustrated, the middle stage of  FIG. 23  illustrates left eye image LCPIM 2  which configures the 2K left parallax video, and the lowermost stage of  FIG. 23  illustrates right eye image RCPIM 2  which configures the 2K right parallax video. 3D image CPIM 3  is stereoscopically displayed as left eye image LCPIM 2  and right eye image RCPIM 2  which have the parallax Δ and are obtained by the imaging of the same subject are projected to monitor  130 . In addition, dotted lines MKL and MKR are lines that pass through each of the center positions of marker MK 1  on left eye image LCPIM 2  and marker MK 1  on right eye image RCIPM 2 , and are provided for the description of the parallax Δ. 
     Here, in a case where marker MK 1  is displayed at the position designated by the operation of the user (for example, an observer, such as a doctor), the parallax Δ between left eye image LCPIM 2  and right eye image RCPIM 2  corresponds to the sum of distance Δ 1  from position ZC 1  indicating the center of marker MK 1  on 3D image CPIM 3  to position ZL 1  indicating the center of marker MK 1  on left eye image LCPIM 2  and distance Δ 2  from position ZC 1  indicating the center of marker MK 1  on 3D image CPIM 3  and position ZR 1  indicating the center of marker MK 1  on right eye image RCPIM 2 . In other words, the equation (1) is established.
 
Equation 1
 
Δ=Δ1+Δ2  (1)
 
In other words, parallax Δ corresponds to a difference between distance LX from center position ZLC of left eye image LCPIM 2  to the position ZL 1  indicating the center of marker MK 1  and distance RX from center position ZRC of right eye image RCPIM 2  to position ZR 1  indicating the center of marker MK 1 .
 
     Therefore, in the 3D mode, distance measuring circuit  291  derives distance L (refer to  FIG. 19 ) from surgical endoscope  110  to the observation target site based on the parallax Δ (refer to  FIG. 23 ) appearing in the 2K left parallax video from 2K left parallax video extractor  265  and the 2K right parallax video from 2K right parallax video extractor  266 , in accordance with the equation (2).
 
Equation 2
 
 L=f×D/A   (2)
 
     In the 3D mode, when display element generator  292  acquires an instruction to display the measurement result of distance measuring circuit  291  on monitor  130  by CPU  262 , display element generator  292  generates the data of a display element (for example, refer to icon DSI of the distance result illustrated in  FIG. 24 ) that corresponds to the measurement result of distance measuring circuit  291 , and outputs the generated data to superimposition controllers  293  and  294 , respectively. 
     In the 3D mode, superimposition controller  293  (one example of the output controller) outputs the data of the display element from the display element generator  292  on monitor  130  via channel CH 1  after performing superimposition processing with respect to the output video (output image) from video output switcher  273 . 
     In the 3D mode, superimposition controller  294  (one example of the output controller) outputs the data of the display element from display element generator  292  on monitor  130  via channel CH 1  after performing superimposition processing with respect to the output video (output image) from video output switcher  274 . 
       FIG. 24  is an explanatory view illustrating a display example of distance L from the distal end of surgical endoscope  110  to subject  40 . In the upper stage of  FIG. 24 , 3D image CPIM 3  displayed on monitor  130  is illustrated in the 3D mode, and the 2D image (for example, left eye image LCPIM 2 ) displayed on monitor  130  in the 2D mode is illustrated in the lower stage of  FIG. 24 . 
     In the 2D mode, when switching from the 2D mode to the 3D mode by the operation of the user (for example, an observer, such as a doctor), CCU  22  or camera apparatus  20  including CCU  22  measures distance L from surgical endoscope  110  to subject  40  indicated by marker MK 1 . As a result, icon DS 1  indicating the distance measurement result of distance L (for example, L=30 mm) is displayed at a predetermined position on monitor  130  (for example, the upper left end portion of monitor  130 ). 
     Meanwhile, in the 3D mode, when switching from the 2D mode to the 3D mode by the operation of the user (for example, an observer, such as a doctor), CCU  22  or camera apparatus  20  including CCU  22  does not display icon DS 1  indicating the distance measurement result of distance L (for example L=30 mm). This is because, in the 2D mode, since neither left eye image LCPIM 2  nor right eye image is input to distance measuring circuit  291 , it is not possible to derive the distance to subject  40 . 
     Above, in the surgical endoscope system of Embodiment 4, in the 3D mode, CCU  22  or camera apparatus  20  including CCU  22  includes distance measuring circuit  291  (one example of distance measurer) which measures distance L (refer to  FIG. 19 ) from surgical endoscope  110  (one example of optical instrument) to the observation target site based on the parallax Δ (refer to  FIG. 23 ) appearing in the left eye image and the right eye image which are imaged by camera head  21 . CCU  22  or camera apparatus  20  outputs the result measured by distance measuring circuit  291  (that is, information on the distance) to monitor  130  (refer to  FIG. 19 ) together with the left, eye image and the right eye image to which the signal processing is performed. Accordingly, the user (for example, an observer, such as a doctor) can visually grasp the situation of the observation target site projected to monitor  130 , can grasp the specific distance information from surgical endoscope  110  (refer to  FIG. 19 ) to the observation target site, and can support the guidance of the next medical practice by the user at the time of surgery or examination. 
     In addition, in response to the switching from the 3D mode to the 2D mode, CCU  22  or camera apparatus  20  including CCU  22  interrupts the output of the information on the distance to monitor  130 . Accordingly, in the 2D mode, neither the left and right 2K left parallax video having parallax nor the 2K right parallax video is input to distance measuring circuit  291 , and thus, the information on the distance is not displayed on monitor  130 . Therefore, the user (for example, an observer, such as a doctor) can easily recognize that the present is the 2D mode by the fact that the information on the distance is not displayed on monitor  130 , and on the other hand, the user can easily recognize that the present is the 3D mode by the fact that the information on the distance is displayed on monitor  130 . 
     Above, while various embodiments have been described with reference to the drawings, it is needless to say that the disclosure is not limited to the examples. Those skilled in the art will appreciate that various modification examples or modification examples can be conceived within the scope described in the claims and understand that the examples naturally fall within the technical scope of the disclosure. Further, within the scope not departing from the gist of the disclosure, each of the configuration elements in the above-described embodiment may be combined in any manner. 
     In addition, in Embodiment 4, according to the equation (1), regarding distance L from surgical endoscope  110  to the observation target site (that is, subject  40 ), the distance measurement of the same distance L can be realized when fixing and imaging an angle of view (that is, zooming magnification in the observation optical system in surgical endoscope  110 ) of surgical endoscope  110 . Here, the correspondence relationship between the distance to subject  40  that serves as a reference and the angle of view (that is, zoom magnification) of surgical endoscope  110  that serves as a reference is prepared in advance as a table and stored in image processor  271  or CPU  262  in advance. In a case where the value of the distance derived according to the equation (1) is different from the distance that serves as the reference, image processor  271  corrects derived distance L by using a coefficient that corresponds to a ratio between the current zoom magnification and the reference angle of view (zoom magnification that serves as the reference) defined in the table. When the zoom magnification is changed, focal length f is changed, and according to the equation (1), distance L also changes. For example, in a case where the zoom magnification is 1 and distance L is 2 cm, when the zoom magnification is doubled, focal length f doubles and distance L also doubles to 4 cm. However, since distance L measured in Embodiment 4 is the distance from the distal end of the insertion portion of surgical endoscope  110  to subject  40 , practically, distance L becomes wrong when the distance reaches 4 cm. Therefore, in a case where the zoom magnification is changed, it is necessary to correct distance L obtained by the equation (1) by using the coefficient that corresponds to the change ratio of the zoom magnification described above. 
     In addition, in each of the above-described embodiments, a case where the 2K left parallax video and the 2K right parallax video which configure the 3D video are extracted and output from the 2D image having 4K resolution has been described, but it is needless to say that. CCU  22  may extract and output, for example, the 4K left parallax video and the 4K right parallax video which configure the 3D video from the 2D video having the pixel number that corresponds to 8K resolution. 
     The disclosure is effective as the image processing apparatus, the camera apparatus, and the image processing method which are capable of adaptively adjusting the area on the imaging surface used for deriving parameters of signal processing with respect to the imaged 3D video when switching from display of the 2D video to display of the 3D video, and imaging and outputting a high-definition 3D video with one camera.