Patent Publication Number: US-10764506-B2

Title: Medical observation device and medical observation system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Japanese Priority Patent Application JP 2017-171680 filed Sep. 7, 2017, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a medical observation device and a medical observation system. 
     Technologies for controlling surgical devices through a plurality of types of contactless input have been developed. As one of the technologies, for example, the technology disclosed in JP 2017-70636A described below is exemplified. 
     SUMMARY 
     In recent years, medical observation devices which enlarge observation targets such as lesions for observation, for example, in order to support microsurgery like neurosurgical operations and to perform endoscopic surgery are used in the medical field. As medical observation devices, for example, medical observation devices with optical microscopes and medical observation devices with imaging devices functioning as electronic imaging-type microscopes are exemplified. Such a medical observation device with an optical microscope will be referred to as an “optical medical observation device” below. In addition, such a medical observation device with an imaging device will be referred to as an “electronic imaging-type medical observation device” or may be referred to simply as a “medical observation device” below. In addition, an image obtained by capturing an observation target using an imaging device included in a medical observation device will be referred to as a “medical captured image” below. 
     Electronic imaging-type medical observation devices are designed to obtain image quality equal to or higher than that of optical medical observation devices accompanied by high image quality of imaging devices and high resolution of display devices on which captured images are displayed. In addition, it is not necessary for users who use such electronic imaging-type medical observation devices (e.g., medical staff including operators, assistants of operators, etc.) to look into eyepieces of optical microscopes as in cases in which they use optical medical observation devices, and thus the users can move positions of imaging devices more freely. Thus, using electronic imaging-type medical observation devices is advantageous in that microsurgery and the like can be supported more flexibly, and thus use of electronic imaging-type medical observation devices has been progressing in the medical field. 
     In surgery in which an electronic imaging-type medical observation device is used, an operator performs various kinds of treatments such as a surgical procedure on an operative site in accordance with a surgical technique, for example, while observing the operative site with reference to a medical captured image displayed on a display screen. In addition, in surgery in which a medical observation device is used, there are cases in which the medical observation device is operated by a person other than an operator, for example, a scopist (an endoscope (an example of a medical observation device) operator). Thus, a medical captured image displayed on a display screen may not be an “image in which an operative site that an operator desires to observe can be easily viewed.” In addition, in order to make a “medical captured image in which an operative site that an operator desires to observe is easily viewed,” a separate operation for making an image having a favorable signal-noise ratio (S/N) by, for example, adjusting intensity of illumination or the like is necessary. Thus, there is concern of convenience of medical staff including operators, assistants of operators, scopists, and the like being impaired in a medical observation system of the related art. In addition, in the medical field, there is a potential need for medical observation devices with higher convenience. 
     The present disclosure proposes a novel and improved medical observation device and medical observation system that can improve convenience. 
     According to an embodiment of the present disclosure, there is provided a medical observation device including: an imaging control unit configured to control an imaging function of an imaging device. The imaging control unit controls an exposure function of the imaging device on a basis of a detection result of a line of sight of a recognition target so that luminance of a predetermined region in a medical captured image obtained by the imaging device capturing an observation target is changed. 
     In addition, according to an embodiment of the present disclosure, there is provided a medical observation system including: a medical observation device including an imaging control unit configured to control an imaging function of an imaging device; and a display device configured to display a medical captured image captured by the imaging device on a display screen. The imaging control unit of the medical observation device controls the exposure function of the imaging device on a basis of a detection result of a line of sight of a recognition target so that luminance of a predetermined region in the medical captured image is changed. 
     According to an embodiment of the present disclosure, convenience can be improved. 
     Note that the effects described above are not necessarily limitative. With or in the place of the above effects, there may be achieved any one of the effects described in this specification or other effects that may be grasped from this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory diagram illustrating a first example of a configuration of a medical observation system according to an embodiment of the present disclosure; 
         FIG. 2  is an explanatory diagram illustrating a second example of the configuration of the medical observation system according to an embodiment of the present disclosure 
         FIG. 3  shows explanatory diagrams for describing an example of a configuration of an imaging device included in the medical observation device illustrated in  FIG. 2 ; 
         FIG. 4  is a functional block diagram illustrating an example of a configuration of a medical observation device according to an embodiment of the present disclosure; 
         FIG. 5  shows explanatory diagrams for describing a control method according to an embodiment of the present disclosure; 
         FIG. 6  is an explanatory diagram for describing the control method according to an embodiment of the present disclosure; 
         FIG. 7  is an explanatory diagram for describing the control method according to an embodiment of the present disclosure; 
         FIG. 8  is an explanatory diagram for describing an example of a hardware configuration of the medical observation device that can perform a process according to the control method according to an embodiment of the present disclosure; and 
         FIG. 9  is an explanatory diagram illustrating an example of a hardware configuration of a display device having both a function of detecting a line of sight and a function of causing the line of sight to be displayed on a display screen on the basis of the detection result of the line of sight. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     Hereinafter, (a) preferred embodiment(s) of the present disclosure will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
     In addition, description will be provided below in the following order. 
     1. Medical observation system according to present embodiment and control method according to present embodiment 
     2. Program according to present embodiment 
     (Medical Observation System According to Present Embodiment and Control Method According to Present Embodiment) 
     An example of a medical observation system according to the present embodiment will be described, and then a control method according to the present embodiment that can be applied to the medical observation system according to the present embodiment will be described below. 
     [1] Configuration of Medical Observation System 
     [1-1] Medical Observation System According to First Example 
       FIG. 1  is an explanatory diagram illustrating a first example of a configuration of a medical observation system  1000  according to the present embodiment, showing an example of a medical observation system having a medical observation device  100  that functions as an endoscope device that is an example of an electronic imaging-type medical observation device. The medical observation system  1000  illustrated in  FIG. 1  has, for example, the medical observation device  100  and a display device  200 . 
     Note that the medical observation system according to the first example is not limited to the example illustrated in  FIG. 1 . 
     The medical observation system according to the first example may further have a control device (not illustrated) that controls various operations of the medical observation device  100 . An example in which the medical observation device  100  has the function of the control device (not illustrated) in the medical observation system  1000  illustrated in  FIG. 1  when the medical observation device  100  has the control unit (which will be described below) that performs a process relating to the control method according to the present embodiment as will be described below is shown. 
     As the control device (not illustrated), for example, an arbitrary apparatus that can perform the process related to the control method according to the present embodiment such as a “medical controller,” or a “computer such as a server” is exemplified. In addition, the control device (not illustrated) may be, for example, an integrated circuit (IC) that can be incorporated into the above-described apparatus. 
     In addition, the medical observation system according to the first example may have a plurality of medical observation devices  100  and display devices  200 . In a case in which a plurality of medical observation devices  100  are provided, each of the medical observation devices  100  performs the process related to the control method of the medical observation device  100  which will be described below. In addition, in the case in which the medical observation system according to the first example has a plurality of medical observation devices  100  and display devices  200 , the medical observation devices  100  and the display devices  200  correspond to each other one to one, or the plurality of medical observation devices  100  may correspond to one display device  200 . In the case in which the plurality of medical observation devices  100  correspond to one display device  200 , for example, a switching operation is performed in the display device  200  to switch images captured by the medical observation devices  100  to be displayed on the display screen. 
     In addition, the medical observation system according to the first example may also have, for example, a line-of-sight detection sensor that can detect lines of sight. As the line-of-sight detection sensor, for example, a “sensor unit that has a stereo camera and a processor and detects a line of sight from an image captured by the stereo camera” is exemplified. In addition, the line-of-sight detection sensor may be a sensor of an arbitrary type that can detect a line of sight, for example, a “sensor which is provided in a wearable device worn on a head for use, such as an eyewear type device, and detects a line of sight in a corneal reflection method using infrared rays or the like.” 
     In the case in which the medical observation system according to the first example has the line-of-sight detection sensor, the medical observation device  100  can perform the process relating to the control method according to the present embodiment using the detection result of the line-of-sight detection sensor as will be described below. Note that the line-of-sight detection sensor may be an external sensor of the medical observation system according to the first example. 
     [1-1-1] Display Device  200   
     The display device  200  is a display section of the medical observation system  1000 , and corresponds to an external display device with respect to the medical observation device  100 . The display device  200  displays various images, for example, medical captured images (moving images or a plurality of still images; the same applies below) captured by the medical observation device  100 , images relating to a user interface, and the like. In addition, the display device  200  may be capable of performing  3 D display. Display by the display device  200  is controlled by, for example, the medical observation device  100  or the control device (not illustrated). 
     The display device  200  of the medical observation system  1000  is installed in an arbitrary place at which the display device can be visually recognized by a person relating to surgery such as an operator within an operating room, for example, a wall surface, a ceiling, a floor of the operating room. As the display device  200 , for example, a liquid crystal display, an organic electro-luminescence (EL) display, a cathode ray tube (CRT) display, or the like is exemplified. 
     Note that the display device  200  is not limited to the above-described example. 
     The display device  200  may be an arbitrary wearable device worn on the body of an operator or the like for use, for example, a head-mounted display, an eyewear-type device, or the like. 
     The display device  200  is driven by, for example, power supplied from an internal power supply included in the display device  200  such as a battery, power supplied from a connected external power supply, or the like. An example of a configuration of the display device  200  will be described below. 
     [1-1-2] Medical Observation Device  100   
     The medical observation device  100  constituting the medical observation system  1000  according to the first example is an endoscope device. In a case in which the medical observation device  100  illustrated in  FIG. 1  is used during surgery, for example, an operator (an example of a user of the medical observation device  100 ) observes an operative site with reference to a medical captured image captured by the medical observation device  100  and displayed on the display screen of the display device  200 , and performs various treatments such as a procedure on the operative site in accordance with a surgical technique. 
     The medical observation device  100  illustrated in  FIG. 1  includes, for example, an insertion member  102 , a light source unit  104 , a light guide  106 , a camera head  108 , a cable  110 , and a control unit  112 . The medical observation device  100  is driven by, for example, power supplied from an internal power supply included in the medical observation device  100  such as a battery, power supplied from a connected external power supply, or the like. 
     The insertion member  102  has an elongated shape and has an optical system that collects incident light therein. A tip of the insertion member  102  is inserted into, for example, a body cavity of a patient. A rear end of the insertion member  102  is connected to a tip of the camera head  108  to be detachable therefrom. In addition, the insertion member  102  is connected to the light source unit  104  via the light guide  106  and thus receives supply of light from the light source unit  104 . 
     The insertion member  102  may have, for example, a material having no flexibility or of a material having flexibility. The medical observation device  100  can be called a rigid endoscope or a flexible endoscope depending on a material forming the insertion member  102 . 
     The light source unit  104  is connected to the insertion member  102  via the light guide  106 . The light source unit  104  supplies light to the insertion member  102  via the light guide  106 . In addition, the light source unit  104  is connected by wire or wirelessly to the control unit  112 , and light emitted from the light source unit  104  is controlled by the control unit  112 . 
     Light supplied to the insertion member  102  is injected from the tip of the insertion member  102  and radiated to an observation target such as a tissue in a body cavity of a patient. In addition, light reflected from the observation target is collected by the optical system inside the insertion member  102 . 
     The camera head  108  has a function of imaging an observation target. The camera head  108  is connected to the control unit  112  via the cable  110  that is a signal transmission member. The camera head  108  captures the observation target by photoelectrically converting reflected light from the observation target collected by the insertion member  102 , and outputs an image signal (a signal indicating a medical captured image) obtained from the imaging to the control unit  112  via the cable  110 . Note that an example of a configuration of the camera head  108  will be described below. 
     In the medical observation device  100  functioning as an endoscope device, for example, the insertion member  102 , the light source unit  104 , and the camera head  108  play a role of an “imaging device that is inserted into the inside of the body of a patient and images the inside of the body.” 
     The control unit  112  plays a role of performing the process related to the control method according to the present embodiment and controls the imaging function of the imaging device. More specifically, the control unit  112  controls each of the light source unit  104  and the camera head  108 . 
     In addition, the control unit  112  includes a communication device (not illustrated), and transmits an image signal output from the camera head  108  to the display device  200  in arbitrary wireless communication or arbitrary wired communication. The control unit  112  may transmit an image signal and a display control signal to the display device  200 . 
     As the communication device (not illustrated) included in the control unit  112 , for example, an IEEE 802.15.1 port and a transmission/reception circuit (wireless communication), an IEEE 802.11 port and a transmission/reception circuit (wireless communication), a communication antenna and an RF circuit (wireless communication), an optical communication device (wired communication or wireless communication), a LAN terminal and a transmission/reception circuit (wired communication), or the like are exemplified. The communication device (not illustrated) may be capable of communicating with one or two or more external devices using a plurality of communication methods. 
     In addition, the control unit  112  may perform a predetermined process on the image signal output from the camera head  108  and transmit the image signal that has undergone the predetermined process to the display device  200 . Examples of the predetermined process with respect to the image signal include one or two or more processes among various kinds of processes including gamma correction, adjustment of white balance, image enlargement or reduction in accordance with an electronic zoom function, and inter-pixel correction. 
     Note that the control unit  112  may store the medical captured image on the basis of the image signal. 
     As the control unit  112 , for example, a camera control unit (CCU) is exemplified. 
     The medical observation device  100  functioning as an endoscope device has, for example, a hardware configuration illustrated with reference to  FIG. 1 . In the medical observation device  100  functioning as an endoscope device, for example, the insertion member  102 , the light source unit  104 , and the camera head  108  play the role of an imaging device, and the control unit  112  controls imaging of the imaging device. 
     Note that the medical observation system  1000  according to the present embodiment is not limited to the configuration with the medical observation device  100  functioning as an endoscope device. 
     [1-2] Medical Observation System According to Second Example 
       FIG. 2  is an explanatory diagram illustrating a second example of the configuration of the medical observation system  1000  according to the present embodiment, showing an example of the medical observation system having a medical observation device  100  functioning as an electronic imaging-type medical observation device according to another example. The medical observation system  1000  illustrated in  FIG. 2  has, for example, the medical observation device  100  and a display device  200 . 
     Note that the medical observation system according to the second example is not limited to the example illustrated in  FIG. 2 . 
     The medical observation system according to the second example may further have, for example, a control device (not illustrated) that controls various operations of the medical observation device  100 , similarly to the medical observation system according to the first example. 
     In addition, the medical observation system according to the second example may have a plurality of medical observation devices  100  and a plurality of display devices  200 , similarly to the medical observation system according to the first example. 
     In addition, the medical observation system according to the second example may also have a line-of-sight detection sensor, similarly to the medical observation system according to the first example. In the case in which the medical observation system according to the second example has a line-of-sight detection sensor, the medical observation device  100  can perform the process relating to the control method according to the present embodiment using a detection result of the line-of-sight detection sensor as will be described below. Note that the line-of-sight detection sensor may be an external sensor of the medical observation system according to the second example. 
     [1-2-1] Display Device  200   
     The display device  200  constituting the medical observation system according to the second example has a similar function and configuration to the display device  200  constituting the medical observation system according to the first example. 
     [1-2-2] Medical Observation Device  100   
     The medical observation device  100  constituting the medical observation system  1000  according to the second example is an electronic imaging-type medical observation device according to another example. An example of a hardware configuration of the medical observation device  100  functioning as an electronic imaging-type medical observation device will be described with reference to  FIG. 2 . 
     The medical observation device  100  functioning as an electronic imaging-type medical observation device includes, for example, a base  120 , an arm  122 , and an imaging device  124 . 
     In addition, although not illustrated in  FIG. 2 , the medical observation device  100  may also include, for example, one or two or more processors (not illustrated) constituted by an arithmetic circuit such as a micro-processing unit (MPU), a read only memory (ROM; not illustrated), a random access memory (RAM; not illustrated), and a recording medium (not illustrated), and a communication device (not illustrated). The medical observation device  100  is driven by, for example, power supplied from an internal power supply included in the medical observation device  100  such as a battery, power supplied from a connected external power supply, or the like. 
     The processors (not illustrated) function as a control unit which will be described below. The ROM (not illustrated) stores control data such as programs and arithmetic parameters to be used by the processors (not illustrated). The RAM (not illustrated) temporarily stores programs executed by the processors (not illustrated) and the like. 
     The recording medium (not illustrated) functions as a storage unit. The recording medium (not illustrated) stores, for example, various kinds of data such as data relating to the control method according to the present embodiment and various applications. Here, as the recording medium (not illustrated), for example, a magnetic recording medium such as a hard disk, a non-volatile memory such as a flash memory, or the like is exemplified. In addition, the recording medium (not illustrated) may be detachable from the medical observation device  100 . 
     The communication device (not illustrated) is a communication section included in the medical observation device  100 , and plays a role of performing wireless or wired communication with an external device such as the display device  200 . Here, as the communication device (not illustrated), for example, an IEEE 802.15.1 port and a transmission/reception circuit, an IEEE 802.11 port and a transmission/reception circuit, a communication antenna and an RF circuit, an optical communication device, a LAN terminal and a transmission/reception circuit, or the like are exemplified. The communication device (not illustrated) may be capable of communicating with one or two or more external devices in a plurality of communication methods. 
     [1-2-2-1] Base  120   
     The base  120  is the base of the medical observation device  100 , and is connected to one end of the arm  122  to support the arm  122  and the imaging device  124 . 
     In addition, the base  120  has, for example, casters, and the medical observation device  100  stands on the floor via the casters. By having the casters, the medical observation device  100  can be easily moved on the floor with the casters. 
     [1-2-2-2] Arm  122   
     The arm  122  is constituted by a plurality of links connected to each other by joints. 
     In addition, the arm  122  supports the imaging device  124 . The imaging device  124  supported by the arm  122  is three-dimensionally movable, and the arm  122  helps the imaging device  124  to maintain a position and a posture after movement. 
     More specifically, the arm  122  is constituted by, for example, a plurality of joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  and a plurality of links  132   a ,  132   b ,  132   c ,  132   d ,  132   e , and  132   f  that are connected by the joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  to revolve. A rotatable range of each of the joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  is arbitrarily set in the design stage, the manufacturing stage, or the like so that desired movement of the arm  122  is realized. 
     That is, in the medical observation device  100  illustrated in  FIG. 2 , six degrees of freedom with respect to movement of the imaging device  124  are realized by six rotation axes (a first axis O 1 , a second axis O 2 , a third axis O 3 , a fourth axis O 4 , a fifth axis O 5 , and a sixth axis O 6 ) corresponding to the six joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  constituting the arm  122 . More specifically, in the medical observation device  100  illustrated in  FIG. 2 , movement of six degrees of freedom including three translational degrees of freedom and three rotational degrees of freedom is realized. 
     Each of the joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  has an actuator (not illustrated), and each of the joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  rotates at a corresponding rotational axis by driving of the actuator (not illustrated). Driving of the actuator (not illustrated) is controlled by, for example, a processor functioning as a control unit which will be described below or an external control device (not illustrated). 
     Since each of the joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  rotates at a corresponding rotational axis by driving of the actuator (not illustrated), various kinds of operations of the arm  122 , for example, stretching, shrinking (folding), and the like of the arm  122 , are realized. 
     The joint  130   a  has a substantially cylindrical shape, and supports the imaging device  124  (an upper end portion of the imaging device  124  in  FIG. 2 ) to be revolvable around a rotation axis (the first axis O 1 ) parallel to a central axis of the imaging device  124  at a tip portion of the joints  130   a  (a lower end part thereof in  FIG. 2 ). Here, the medical observation device  100  is configured such that the first axis O 1  matches the optical axis of the imaging device  124 . That is, by causing the imaging device  124  to revolve around the first axis O 1  illustrated in  FIG. 2 , a medical captured image captured by the imaging device  124  becomes an image in which a line of sight is changed to rotate. 
     The link  132   a  is a substantially rod-shaped member, and fixedly supports the joint  130   a . The link  132   a  extends, for example, in a direction orthogonal to the first axis O 1  and is connected to the joint  130   b.    
     The joint  130   b  has a substantially cylindrical shape and supports the link  132   a  to be revolvable around the rotation axis (the second axis O 2 ) orthogonal to the first axis O 1 . In addition, the link  132   b  is fixedly connected to the joint  130   b.    
     The link  132   b  is a substantially rod-shaped member and extends in a direction orthogonal to the second axis O 2 . In addition, the joint  130   b  and the joint  130   c  are respectively connected to the link  132   b.    
     The joint  130   c  has a substantially cylindrical shape and supports the link  132   b  to be revolvable around the rotation axis (the third axis O 3 ) orthogonal to the first axis O 1  and the second axis O 2 . In addition, one end of the link  132   c  is fixedly connected to the joint  130   c.    
     Here, by causing the tip side of the arm  122  (the side on which the imaging device  124  is provided) to revolve around the second axis O 2  and the third axis O 3 , the imaging device  124  can be moved so that a position of the imaging device  124  is changed within a horizontal plane. That is, since rotation around the second axis O 2  and the third axis O 3  is controlled in the medical observation device  100 , a line of sight of a medical captured image can be moved within a plane. 
     The link  132   c  has a member having one end in a substantially cylindrical shape and the other end in substantially a rod shape. The one end of the link  132   c  is fixedly connected to the joint  130   c  such that the central axis thereof and the central axis of the substantially cylindrical shape are the same. In addition, the other end of the link  132   c  is connected to the joint  130   d.    
     The joint  130   d  has a substantially cylindrical shape and supports the link  132   c  to be revolvable around a rotational axis (the fourth axis O 4 ) orthogonal to the third axis O 3 . The link  132   d  is fixedly connected to the joint  130   d.    
     The link  132   d  is a substantially rod-shaped member and extends to be orthogonal to the fourth axis O 4 . One end of the link  132   d  is fixedly connected to the joints  130   d  to abut against a side face of the substantially cylindrical shape of the joint  130   d . In addition, the other end of the link  132   d  (the end on the opposite side to the side on which the joint  130   d  is connected) is connected to the joint  130   e.    
     The joint  130   e  has a substantially cylindrical shape and supports one end of the link  132   d  to be revolvable around the rotational axis (the fifth axis O 5 ) parallel to the fourth axis O 4 . In addition, the joint  130   e  is connected to one end of the link  132   e.    
     Here, the fourth axis O 4  and the fifth axis O 5  are rotational axis that can move the imaging device  124  in the vertical direction. By causing the tip side of the arm  122  (the side on which the imaging device  124  is provided) to revolve around the fourth axis O 4  and the fifth axis O 5 , a position of the imaging device  124  in the vertical direction is changed. Thus, by causing the tip side of the arm  122  (the side on which the imaging device  124  is provided) to revolve around the fourth axis O 4  and the fifth axis O 5 , a distance between the imaging device  124  and an observation target such as an operative site of a patient or the like can be changed. 
     The link  132   e  is a member constituted by a combination of a first member having a substantially L shape with one side extending in the vertical direction and the other side extending in the horizontal direction and a rod-shaped second member extending vertically downward from a portion of the first member extending in the horizontal direction. A portion of the first member of the link  132   e  extending in the vertical direction is fixedly connected to the joint  130   e . In addition, the second member of the link  132   e  is connected to the joint  130   f.    
     The joint  130   f  has a substantially cylindrical shape and supports the link  132   e  to be revolvable around a rotational axis (the sixth axis O 6 ) parallel to the vertical direction. In addition, the joint  130   f  is fixedly connected to the link  132   f.    
     The link  132   f  is a substantially rod-shaped member and extends in the vertical direction. One end of the link  132   f  is connected to the joint  130   f . In addition, the other end of the link  132   f  (the end on the opposite side to the side on which the joints  130   f  is connected) is fixedly connected to the base  120 . 
     Since the arm  122  has the above-described configuration, six degrees of freedom with respect to movement of the imaging device  124  are realized in the medical observation device  100 . 
     Note that a configuration of the arm  122  is not limited to the above-described example. 
     For example, a brake that regulates rotation of each of the joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  may be provided in each of the joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f  of the arm  122 . As a brake according to the present embodiment, for example, an arbitrary type of brake such as a mechanically driven brake or an electrically driven electromagnetic brake is exemplified. 
     Driving of the brake is controlled by, for example, a processor that functions as a control unit which will be described below or an external control device (not illustrated). Since driving of the brake is controlled, an operation mode of the arm  122  is set in the medical observation device  100 . As operation modes of the arm  122 , for example, a fixed mode and a free mode are exemplified. 
     Here, the fixed mode according to the present embodiment is an operation mode in which, for example, a position and a posture of the imaging device  124  are fixed by a brake regulating rotation at each rotational axis provided in the arm  122 . When the arm  122  is the fixed mode, an operation state of the medical observation device  100  is a fixed state in which a position and a posture of the imaging device  124  are fixed. 
     In addition, the free mode according to the present embodiment is an operation mode in which, when the brake is released, each rotational axis provided in the arm  122  is freely rotatable. In the free mode, for example, a position and a posture of the imaging device  124  can be adjusted through a direct operation by an operator. Here, a direct operation according to the present embodiment means, for example, an operation in which an operator grabs the imaging device  124  with his or her hand and moves the imaging device  124  in person. 
     [1-2-2-3] Imaging Device  124   
     The imaging device  124  is supported by the arm  122  and captures an observation target, for example, an operative site of a patient, or the like. Imaging by the imaging device  124  is controlled by, for example, a processor that functions as a control unit, which will be described below, or an external control device (not illustrated). 
     The imaging device  124  has a configuration corresponding to, for example, an electronic imaging-type microscope. 
       FIG. 3  shows explanatory diagrams for describing an example of a configuration of the imaging device  124  included in the medical observation device  100  illustrated in  FIG. 2 . 
     The imaging device  124  has, for example, an imaging member  134  and a tubular member  136  having a substantially cylindrical shape, and the imaging member  134  is provided in the tubular member  136 . 
     Cover glass (not illustrated) for protecting the imaging member  134 , for example, is provided on an opening surface of a lower end (an end on a lower side in  FIG. 3 ) of the tubular member  136 . 
     In addition, a light source (not illustrated) is provided, for example, inside of the tubular member  136 , and during imaging, illumination light from the light source is radiated to a subject through the cover glass. Since reflected light (observation light) from the subject irradiated with the illumination light is incident on the imaging member  134  through the cover glass (not illustrated), an image signal (an image signal indicating a captured image) representing the subject is obtained by the imaging member  134 . 
     As the imaging member  134 , a configuration used in any of various known electronic imaging-type microscope unit can be applied. 
     To give an example, the imaging member  134  is constituted by, for example, an optical system  134   a  and an image sensor  134   b  including an image sensor that captures image of an observation target using light that has passed through the optical system  134   a . The optical system  134   a  includes optical elements, for example, one or two or more lenses such as an objective lens, a zoom lens, and a focus lens, a mirror, and the like. As the image sensor  134   b , for example, an image sensor using a plurality of image sensors such as complementary metal oxide semiconductors (CMOS), charge coupled devices (CCDs), and the like is exemplified. 
     The imaging member  134  may have a pair of image sensors, that is, may function as a so-called stereo camera. The imaging member  134  may have one or two or more functions included in a general electronic imaging type microscope unit, such as a zoom function (one or both of an optical zoom function and an electronic zoom function), a focus function such as auto focus (AF), and the like. 
     In addition, the imaging member  134  may be capable of perform imaging at so-called high resolution of, for example, 4K, 8K, or the like. When the imaging member  134  can perform imaging at high resolution, it is possible to display an image on the display device  200  having a large display screen of, for example, 50 inches or greater while predetermined resolution (e.g., full HD image quality, etc.) is secured, and thus visibility of an operator viewing the display screen is improved. In addition, when the imaging member  134  can perform imaging at high resolution, even if a captured image is enlarged using the electronic zoom function and displayed on the display screen of the display device  200 , predetermined resolution can be secured. Furthermore, in a case in which predetermined resolution is secured by using the electronic zoom function, performance of the optical zoom function of the imaging device  124  can be suppressed, and thus the optical system of the imaging device  124  can be made simpler and thus the imaging device  124  can be further miniaturized. 
     The imaging device  124  has, for example, various operation devices for controlling operations of the imaging device  124 . In  FIG. 3 , for example, a zoom switch  138 , a focus switch  140 , and an operation mode change switch  142  are provided in the imaging device  124 . Note that it is a matter of course that a position at which the zoom switch  138 , the focus switch  140 , and the operation mode change switch  142  are provided and shapes thereof are not limited to the example illustrated in  FIG. 3 . 
     The zoom switch  138  and the focus switch  140  are an example of an operation device for adjusting imaging conditions of the imaging device  124 . 
     The zoom switch  138  is constituted by, for example, a zoom-in switch  124   a  for increasing zoom magnifications (enlargement magnifications) and a zoom-out switch  124   b  for decreasing zoom magnifications. A zoom magnification is adjusted by performing an operation on the zoom switch  138 , and thereby zoom is adjusted. Increasing a zoom magnification may be referred to as “zoom in” and decreasing a zoom magnification may be referred to as “zoom out” below. 
     The focus switch  140  is constituted by, for example, a distant view focus switch  140   a  for lengthening a focal distance to an observation target (subject) and a near-view focus switch  140   b  for shortening a focal distance to an observation target. By adjusting a focal distance by performing an operation on the focus switch  140 , focus is adjusted. Lengthening a focal distance to an observation target may be called “focus out,” and shortening a focal distance to an observation target may be called “focus in.” 
     The operation mode change switch  142  is an example of an operation device of the imaging device  124  for changing an operation mode of the arm  122 . When an operation is performed on the operation mode change switch  142 , the operation mode of the arm  122  is changed. As the operation mode of the arm  122 , for example, there are the fixed mode and the free mode as described above. 
     As an example of an operation with respect to the operation mode change switch  142 , an operation of pressing the operation mode change switch  142  is exemplified. For example, while an operator presses the operation mode change switch  142 , the operation mode of the arm  122  shifts to the free mode, and when the operator does not press the operation mode change switch  142 , the operation mode of the arm  122  shifts to the fixed mode. 
     In addition, in the imaging device  124 , a non-slip member  144  and a projecting member  146 , for example, are provided to improve operability, convenience, and the like during operations by an operator who performs an operation with respect to the various operation devices. 
     The non-slip member  144  is a member provided to prevent an operating body from slipping when, for example, an operator performs an operation on the tubular member  136  using an operating body such as his or her hand. The non-slip member  144  has, for example, a material having a high friction factor, and thus has a structure which makes it difficult for an operating body to slip due to unevenness. 
     The projecting member  146  is a member provided to prevent an operating body from blocking a visual field of the optical system  134   a  when an operator operates the tubular member  136  with the operating body such as his or her hand or to prevent the cover glass (not illustrated) from becoming dirty due to contact of the cover glass with an operating body when performing an operation with the operating body. 
     Note that it is a matter of course that a position at which each of the non-slip member  144  and the projecting member  146  is provided and a shape thereof are not limited to the example illustrated in  FIG. 3 . In addition, in the imaging device  124 , one or both of the non-slip member  144  and the projecting member  146  may not be provided. 
     An image signal (image data) generated from imaging by the imaging device  124  is subject to, for example, image processing by a processor that functions as a control unit, which will be described below. As image processing according to the present embodiment, for example, one or two or more processes among various kinds of processes including gamma correction, adjustment of white balance, image enlargement or reduction in accordance with the electronic zoom function, inter-pixel correction, and the like are exemplified. Note that, in a case in which the medical observation system according to the second example has a control device (not illustrated) that controls various operations of the medical observation device  100 , image processing according to the present embodiment may be performed by the control device (not illustrated). 
     The medical observation device  100  transmits, for example, a display control signal and an image signal that has undergone the above-described image processing to the display device  200 . 
     When a display control signal and an image signal are transmitted to the display device  200 , the display screen of the display device  200  displays a medical captured image obtained by capturing an observation target (e.g., a captured image in which an operative site is captured) enlarged or reduced to a desired magnification using one or both of the optical zoom function and the electronic zoom function. 
     The medical observation device  100  that functions as the electronic imaging-type medical observation device according to the other example has, for example, the hardware configuration illustrated with reference to  FIGS. 2 and 3 . 
     Note that a hardware configuration of the medical observation device that functions as the electronic imaging-type medical observation device according to the other example is not limited to the configuration illustrated with reference to  FIGS. 2 and 3 . 
     For example, the medical observation device according to the present embodiment may have the arm  122  that is directly installed on a ceiling, a wall surface, or the like of an operating room or the like, without having the base  120 . For example, in a case in which the arm  122  is installed on a ceiling, the arm  122  of the medical observation device according to the present embodiment is hung from the ceiling. 
     In addition, although the example in which the arm  122  realizes six degrees of freedom with respect to driving of the imaging device  124  is illustrated in  FIG. 2 , a configuration of the arm  122  is not limited to the configuration in which driving of the imaging device  124  has six degrees of freedom. For example, the arm  122  may appropriately move the imaging device  124  in accordance with an application, and the number and disposition of the joints and links, directions of driving axes of the joints, and the like can be appropriately set so that the arm  122  has a desired degree of freedom. To give an example, the medical observation device according to the present embodiment may have a simpler configuration of controlling an X axis and a Y axis, like an ophthalmology microscope. 
     In addition, although the example in which various operation devices for controlling operations of the imaging device  124  are provided in the imaging device  124  is illustrated in  FIGS. 2 and 3 , some or all of the operation devices illustrated in  FIGS. 2 and 3  may not be provided in the imaging device  124 . To give an example, various operation devices for controlling operations of the imaging device  124  may be provided in a part other than the imaging device  124  constituting the medical observation device according to the present embodiment. In addition, to give another example, various operation device for controlling operations of the imaging device  124  may be external operation devices such as a foot switch and a remote controller. 
     As the medical observation device  100  constituting the medical observation system  1000  according to the present embodiment, for example, a medical observation device that functions as the endoscope device illustrated in  FIG. 1 , a medical observation device that functions as the electronic imaging-type medical observation device according to the other example illustrated in  FIG. 2 , or the like is exemplified. 
     [2] Control Method According to the Present Embodiment 
     [2-1] Overview of Control Method According to the Present Embodiment 
     In an existing medical observation system in which a medical observation device such as an existing endoscope is used as described above, a medical captured image displayed on a display screen may not be an image in which an operative site that an operator desires to observe can be easily viewed. In addition, in order to gain a medical captured image in which an operative site that an operator desires to observe can be easily viewed, for example, an operation of making an image with a favorable S/N is necessary by adjusting intensity of illumination. Thus, with regard to an existing medical observation system, there is concern of convenience of medical staff such an operator, an assistant of the operator, or a scopist being impaired. 
     Therefore, in the medical observation system  1000 , the medical observation device  100  controls at least an exposure function of an imaging device (the process relating to the control method according to the present embodiment) using, for example, a line of sight detected having a specific person such as an operator as a recognition target. 
     Detection of a line of a sight of a recognition target is performed by, for example, a line-of-sight detection sensor of the medical observation system  1000 . For example, in a case in which the line-of-sight detection sensor is a sensor unit having a stereo camera, the line-of-sight detection sensor is provided to perform imaging in the front direction of the display screen (e.g., a perpendicular direction to the plane corresponding to the display screen) on which a medical captured image is displayed. 
     In the medical observation system  1000 , a recognition target is specified by performing a face detection process of detecting a face set in an image captured by the line-of-sight detection sensor. In addition, in the medical observation system  1000 , by performing a line-of-sight detection process of detecting a line-of-sight on the specified recognition target on the basis of the image captured by the line-of-sight detection sensor, the detection result of the line of sight of the recognition target is obtained. 
     As a detection result of a line of sight of a recognition target, for example, a line-of-sight vector indicating a line of sight of a recognition target is exemplified. In addition, a detection result of a line of sight of a recognition target may be, for example, a position of the line of sight of the recognition target on a display screen on which a medical captured image is displayed. A position of a line of sight of a recognition target on a display screen is specified by, for example, obtaining an intersection of a line-of-sight vector with a plane corresponding to the display screen and expressed by two-dimensional coordinates having an arbitrary position of the display screen as the origin. 
     One or both of the face detection process and the line-of-sight detection process in the medical observation system  1000  may be performed by the line-of-sight detection sensor, or by the medical observation device  100 , the control device (not illustrated), or the display device  200 . Note that it is a matter of course that a method of detecting a line of sight of a recognition target according to the present embodiment is not limited to the above-described example. 
     In addition, detection of a line of sight of a recognition target in the medical observation system  1000  may be stopped by an operation of a user of the medical observation system  1000 , and the stop may be cancelled by an operation of a user of the medical observation system  1000 . As an operation relating to detection of a line of sight of a recognition target, for example, an operation with respect to an operation device such as a foot switch, an operation using a motion such as a gesture, an operation using a voice, or the like is exemplified. 
     By enabling detection of a line of sight of a recognition target to be stopped, a state in which the line of sight of the recognition target is fixed can be realized without imposing a strain on the recognition target. 
     Since the medical observation device  100  controls the exposure function of the imaging device on the basis of a detection result of a line of sight of a recognition target, a medical captured image displayed on the display screen can be automatically made into an “image in which an operative site that a specific person who is a recognition target desires to observe can be easily viewed.” 
     Therefore, since the medical observation device  100  controls the exposure function of the imaging device on the basis of the detection result of the line of sight of the specific person, the medical observation system  1000  that can achieve enhancement in convenience is realized. 
     The medical observation system  1000  to which the control method according to the present embodiment is applied will be described along with description of functions of respective devices constituting the medical observation system  1000 . In addition, a case in which the medical observation system  1000  according to the present embodiment is the medical observation system  1000  according to the first example illustrated in  FIG. 1  will be mainly described below. 
     [2-2] Medical Observation Device  100   
       FIG. 4  is a functional block diagram illustrating an example of a configuration of the medical observation device  100  according to the present embodiment. The medical observation device  100  includes, for example, an imaging unit  150 , a communication unit  152 , and a control unit  154 . 
     [2-2-1] Imaging Unit  150   
     The imaging unit  150  captures observation targets. In a case in which the medical observation device  100  has the configuration illustrated in  FIG. 1 , the imaging unit  150  is constituted by the insertion member  102 , the light source unit  104 , and the camera head  108  (members playing the role of an imaging device in the medical observation device  100  illustrated in  FIG. 1 ). In addition, in a case in which the medical observation device  100  has the configuration illustrated in  FIG. 2 , the imaging unit  150  is constituted by the imaging device  124 . Imaging performed by the imaging unit  150  is controlled by, for example, the control unit  154 . 
     [2-2-2] Communication Unit  152   
     The communication unit  152  is a communication section of the medical observation device  100 , and plays the role of performing wireless or wired communication with an external device such as the display device  200 . The communication unit  152  is constituted by, for example, the above-described communication device (not illustrated). Communication performed by the communication unit  152  is controlled by, for example, the control unit  154 . 
     [2-2-3] Control Unit  154   
     The control unit  154  plays a role of controlling the entire medical observation device  100 . In addition, the control unit  154  plays the leading role of performing the process relating to the control method according to the present embodiment. 
     In the case in which the medical observation device  100  has the configuration illustrated in  FIG. 1 , the control unit  154  is constituted by, for example, the control unit  112 . In addition, in the case in which the medical observation device  100  has the configuration illustrated in  FIG. 2 , the control unit  154  is constituted by, for example, the above-described processor (not illustrated). Note that the process relating to the control method by the control unit  154  may be distributed to be performed by a plurality of processing circuits (e.g., a plurality of processors and the like). 
     More specifically, the control unit  154  has, for example, an imaging control unit  156  and a display control unit  158 . 
     [2-2-3-1] Imaging Control Unit  156   
     The imaging control unit  156  controls the imaging device constituting the imaging unit  150 . As control over the imaging device  124 , for example, control of one or two or more imaging functions through which imaging of the imaging device can be controlled, such as control of the zoom function (one or both of the optical zoom function and the electronic zoom function) including at least the exposure function, control of the focus function such as AF, control of a shutter speed function to control a refresh rate of an image sensor, and the like are exemplified. 
     The imaging control unit  156  controls, for example, a light source such as the light source unit  104  and the exposure function by controlling illumination light radiated to an observation target such as a lesion. In addition, the imaging control unit  156  may control the exposure function by, for example, controlling a gain with respect to an image signal indicating a medical captured image. As an example of a process relating to control of a gain with respect to an image signal, for example, signal processing of averaging luminance of a medical captured image is exemplified. 
     More specifically, the imaging control unit  156  controls the exposure function of the imaging device on the basis of a detection result of a line of sight of a recognition target so that luminance of a predetermined region of a medical captured image is changed. The imaging control unit  156  controls the exposure function of the imaging device on the basis of, for example, a position of a line of sight of recognition target (an example of a detection result of a line of sight of a recognition target or an example of information specified from a detection result of a line of sight of a recognition target) on the display screen on which a medical captured image is displayed so that luminance of a predetermined region of the medical captured image is changed. 
     The imaging control unit  156  changes luminance of a predetermined region by controlling the exposure function of the imaging device so that, for example, luminance of the predetermined region of the medical captured image increases or luminance of the predetermined region is decreased. The predetermined region becomes brighter by increasing the luminance of the predetermined region of the medical captured image, or the predetermined region becomes darker by decreasing the luminance of the predetermined region. The imaging control unit  156  controls the exposure function of the imaging device so that the luminance of the predetermined region in the medical captured image increases in a case in which a line of sight of a recognition target moves from a bright operative site to a dark operative site, for example, a case in which the line of sight of the recognition target moves from a front operative site to a deep operative site. In addition, the imaging control unit  156  controls the exposure function of the imaging device so that luminance of a predetermined region of a medical captured image is decreased in a case in which a line of sight of a recognition target moves from a dark operative site to a bright operative site, for example, a case in which the line of sight of the recognition target moves from a deep operative site to a front operative site. Since the imaging control unit  156  controls the exposure function of the imaging device as described above, for example, it is possible to make it easier to view a predetermined region of a medical captured image. 
     The imaging control unit  156  controls the exposure function of the imaging device by controlling intensity of illumination light so that, for example, the average of brightness of a predetermined region of a medical captured image is uniform and averaging luminance through signal processing. 
     Readiness for control of the exposure function based on a detection result of a line of sight of a recognition target is determined using, for example, calibration performed on the recognition target or a value set in a statistical method, or the like. 
     As a predetermined region according to the present embodiment, for example, a “region in which a position in a medical captured image corresponding to a position of a light of sight on a display screen is included” is exemplified. A position of a line of sight on a display screen is expressed by, for example, two-dimensional coordinates having an arbitrary position on the display screen as the origin as described above. In addition, a position in a medical captured image corresponding to a position of a line of sight on a display screen is expressed by, for example, two-dimensional coordinates having an arbitrary position on a medical captured image as the origin. Hereinbelow, a “position in a medical captured image corresponding to a position of a line of sight on a display screen” may be referred to simply as a “position in a medical captured image.” 
     The imaging control unit  156  transforms a position of a line of sight on the display screen into a position in a medical captured image and sets a predetermined region to include the position in the medical captured obtained from the transform. The imaging control unit  156  transforms the position of the line of sight on the display screen into the position in the medical captured image, for example, by using a transformation matrix stored in the recording medium (not illustrated). Note that the imaging control unit  156  may transform the position of the line of sight on the display screen into the position in the medical captured image by performing an arithmetic operation of an arbitrary algorithm in which a coordinate transformation can be performed. 
     In addition, as a predetermined region, for example, regions introduced in the following examples are exemplified.
         Region of which shape and size are set in advance   Region of which shape and size are set for each recognition target   Region of which one or both of shape and size are changed in accordance with a movement of a line of sight       

     The imaging control unit  156  specifies a shape and a size of a predetermined region set in advance with reference to, for example, “region data of a region of which a shape and a size are set in advance” stored in the recording medium (not illustrated). In addition, the imaging control unit  156  specifies a shape and a size of a predetermined region corresponding to a recognition target with reference to, for example, a “table (or database) in which data indicating the recognition target (e.g., a user ID or the like) is associated with region data” stored in the recording medium (not illustrated). In addition, the imaging control unit  156  specifies a shape and a size of a predetermined region corresponding to a movement of a line of sight with reference to, for example, a “table (or database) in which a movement amount of the line of sight is associated with region data” stored in the recording medium (not illustrated). A movement amount of a line of sight is determined on the basis of, for example, a Euclidean distance between a “position of the line of sight on the display screen at a first time point” and a “position of the line of sight on the display screen at a second time point (a time point later than the first time point).” 
     Note that a predetermined region according to the present embodiment is not limited to the above-described examples. The imaging control unit  156  may set a predetermined region by, for example, performing an arithmetic operation of an arbitrary algorithm in which a region can be set every time. 
     As control of the exposure function by the imaging control unit  156 , for example, one or both of control of illumination light radiated from a light source such as the light source unit  104  and control of a gain with respect to an image signal indicating a medical captured image are exemplified. In addition, as control of illumination light, for example, one or two or more of control of illuminance of illumination light, control of a type of illumination light, and control of a radiation time of illumination light (an example of control of an exposure time) are exemplified. 
     To give an example, as control of the exposure function by the imaging control unit  156 , for example, one or both of a first example introduced in (A) and a second example introduced in (B) below are exemplified. Note that an example of control of the exposure function according to the present embodiment is not limited to the following examples, and arbitrary control by which exposure can be changed so that luminance of a predetermined region in a medical captured image is changed is possible. 
     (A) First example of Control of Exposure Function 
     The imaging control unit  156  controls the exposure function so that luminance of a region other than a predetermined region in a medical captured image is decreased. The imaging control unit  156  decreases luminance of the region other than the predetermined region through control of a gain with respect to an image signal indicating the medical captured image. 
     To give an example, the imaging control unit  156  decreases luminance of the region other than the predetermined region so that the luminance of the region other than the predetermined region has a value equal to or smaller than a set threshold value (or the luminance of the region other than the predetermined region has a value smaller than the threshold value). In addition, to give another example, the imaging control unit  156  decreases luminance of the region other than the predetermined region so that the luminance of the region other than the predetermined region has a value smaller than an average value of luminance of the predetermined region. 
     The imaging control unit  156  performs control of the exposure function according to the first example on the basis of, for example, a detection result of a line of sight of a recognition target. To give an example, the imaging control unit  156  performs the control of the exposure function according to the first example in a case in which a “state in which a change of a position of a line of sight on the display screen in a set first period is smaller than a set threshold value (or a state in which the change of the position of the line of sight on the display screen in the first period is equal to or smaller than the threshold value)” continues for a set second period or longer (or continues longer than the second period). For example, by performing the control of the exposure function according to the first example on the basis of the detection result of the line of sight of the recognition target as described above, a visual effect as if an operative site is irradiated with spot illumination light when an operator (an example of the recognition target) gazes the operative site is realized. 
     Note that a trigger for the control of the exposure function according to the first example is not limited to a detection result of a line of sight of a recognition target. For example, the imaging control unit  156  may perform the control of the exposure function according to the first example on the basis of a predetermined operation such as an operation performed on an operation device such as a foot switch, a gesture operation, or a voice operation. In addition, the imaging control unit  156  may switch from the control of the exposure function according to the first example to other control of the exposure function such as control of the exposure function according to the second example, which will be described below, on the basis of a predetermined operation such as an operation with respect to the operation device. 
     In addition, the imaging control unit  156  may control the zoom function of the imaging device so that electronic zoom is performed with respect to a predetermined region in conjunction with the control of the exposure function according to the first example. The control of the zoom function in conjunction with the control of the exposure function according to the first example may be automatically performed, or performed on the basis of a predetermined operation such as an operation performed on an operation device such as a foot switch, a gesture operation, or a voice operation. In addition, the control of the zoom function in conjunction with the control of the exposure function according to the first example, for example, can be cancelled on the basis of a predetermined operation such as an operation performed on an operation device. 
     To exemplify a case in which an operator is a line-of-sight recognition target, by performing the control of the zoom function in conjunction with the control of the exposure function according to the first example, a medical staff member such as the operator or an assistant of the operator can conduct medical practice viewing an “enlarged medical captured image that seems to be captured as if an operative site that the operator desires to observe was irradiated with spot illumination.” Thus, by performing the control of the zoom function in conjunction with the control of the exposure function according to the first example, the medical captured image in which the operative site that the operator desires to observe can be viewed more easily can be displayed on the display screen, and thus convenience of medical staff can be further improved. 
     (B) Second Example of Control of Exposure Function 
     The imaging control unit  156  controls the exposure function such that diffused illumination light is radiated to a position of an observation target corresponding to a position in a medical captured image. 
     The imaging control unit  156  controls the imaging device so that, for example, the center of an optical axis of diffused illumination light comes at an estimated position of an observation target. In the case in which the medical observation device  100  has the configuration illustrated in  FIG. 1 , the imaging control unit  156  causes diffused illumination light to be radiated to the position of the observation target by controlling, for example, a mechanism (not illustrated) that adjusts an incidence angle of illumination light to a diffuser constituting the light source unit  104  and the light guide  106 . In a case in which the medical observation device  100  has the configuration illustrated in  FIG. 1  and the insertion member  102  has a material having flexibility (i.e., a flexible mirror), diffused illumination light may be radiated to the position of the observation target by moving the center of the optical axis of the diffused illumination light. In addition, in the case in which the medical observation device  100  has the configuration illustrated in  FIG. 2 , the imaging control unit  156  causes diffused illumination light to be radiated to the position of the observation target by, for example, controlling the diffuser constituting the light source (not illustrated) and the arm  122 . Note that it is a matter of course that a method of controlling the exposure function such that diffused illumination light is radiated to a position of an observation target is not limited to the above-described example. 
     The imaging control unit  156  performs the control of the exposure function according to the second example on the basis of, for example, a predetermined operation such as an operation performed on an operation device such as a foot switch, a gesture operation, or a voice operation. In addition, the imaging control unit  156  may automatically perform the control of the exposure function according to the second example and switch to the above-described control of the exposure function according to the first example on the basis of a detection result of a line of sight of a recognition target, or the like. 
     Here, switching between the above-described control of the exposure function according to the first example and control of the exposure function according to the second example can be realized on the basis of the fact that, for example, “the light source unit  104  has a diffuser insertion/removal mechanism.” 
       FIG. 5  shows explanatory diagrams for describing the control method according to the present embodiment. A of  FIG. 5  schematically illustrates a diffuser insertion/removal mechanism included in the light source unit  104  illustrated in  FIG. 1 , and B of  FIG. 5  shows differences in radiation angles depending on the presence or absence of a diffuser. 
     As shown in B of  FIG. 5 , a radiation angle changes from X[° ] to Y[° ] (Y&gt;X) and an illuminated region is widened since a diffuser has been inserted. In addition, illumination light with higher illuminance can be radiated to the illuminated region as shown in B of  FIG. 5  without changing illuminance of the illumination light radiated from the light source unit  104  since the diffuser has been inserted. 
     [2-2-3-2] Display Control Unit  158   
     The display control unit  158  controls display of the display device  200  by, for example, transferring a display control signal and an image signal to the communication device (not illustrated) constituting the communication unit  152  and causing the display control signal and the image signal to be transmitted to the display device  200 . Note that control over communication of the communication unit  152  may be performed by a communication control unit (not illustrated) constituting the control unit  154 . 
     In addition, the display control unit  158  may perform, for example, one or two or more kinds of display control among display control introduced in a first example of (a) below to a fourth example of (d) below. 
     (a) First Example of Display Control 
     The display control unit  158  causes a position in a medical captured image corresponding to a position of a line of sight on the display screen to be displayed on the display screen on the basis of a detection result of the line of sight of a recognition target. 
     The display control unit  158  causes the position in the medical captured image to be displayed on the display screen by, for example, causing a predetermined region in which the position in the medical captured image is included to be displayed on the display screen. 
       FIG. 6  is an explanatory diagram for describing the control method according to the present embodiment, showing an example in which a predetermined region in which a position in a medical captured image is included is displayed on the display screen of the display device  200 . In  FIG. 6 , a line-of-sight detection sensor  300  serving as a sensor unit having a stereo camera is also shown. In addition, reference sign O shown in  FIG. 6  represents the predetermined region in which the position in the medical captured image is included, and an example in which the predetermined region is a circular region having the position in the medical captured image as the center. Note that it is a matter of course that a shape and a size of the predetermined region is not limited to the example shown in  FIG. 6 . 
     In a case in which the position of the line of sight on the display screen is changed from a position A to a position B shown in  FIG. 6 , the display control unit  158  moves display of the predetermined region in which the position in the medical captured image is included to match the change of the position of the line of sight on the display screen. 
     Here, in a case in which an observation target faces the imaging device and illumination light and is a uniform plane, intensity of the illumination light does not change and a change in luminance caused by signal processing does not occur even the line of sight of the recognition target moves. 
     In addition, since the region other than the predetermined region in the medical captured image is not subject to the control of the exposure function, halation is likely to occur in a case in which illumination is excessively strong, and an image thereof becomes dark in a case in which illumination is weak. However, since the region other than the predetermined region does not includes a position of a line of sight of a recognition target, there is no concern of control of the region affecting medical practice conducted by an operator (an example of a recognition target). 
     Note that an example of causing a position in a medical captured image to be displayed on a display screen is not limited to displaying a predetermined region in which a position in a medical captured image is included on the display screen as illustrated in  FIG. 6 . For example, the display control unit  158  may cause a position in a medical captured image to be displayed on the display screen by, for example, causing an image signal indicating a “medical captured image on which an object indicating a position in the medical captured image (e.g., an object indicating a position in the medical captured image like an arrow, etc.) is superimposed” to be transmitted to the display device  200 . 
     To give an example of a case in which an operator is a recognition target of a line of sight, by performing the display control according to the first example described above, other medical staff members, for example, an assistant of the operator, a scopist, a nurse, and the like can visually recognize an operative site that the operator is viewing. Thus, by performing the display control according to the first example described above, the effect of more smooth communication between the medical staff members using the medical observation system  1000  is expected. 
     In addition, to give another example of the case in which an operator is a recognition target of a line of sight, by performing the display control according to the first example described above, a preceptor who instructs the operator, for example, can visually recognize the operative site that the operator is viewing. Thus, by performing the display control according to the first example described above, the effect that the operator can be effectively educated by the preceptor is expected. 
     (b) Second Example of Display Control 
     The display control unit  158  causes a user interface image for controlling the imaging functions of the imaging device to be displayed on the display screen. 
     As a user interface image for controlling the imaging functions of the imaging device, an image for operating one or two or more imaging functions of the imaging device such as the zoom function (one or both of the optical zoom function and the electronic zoom function), the focus function, the exposure function, and a shutter speed function is exemplified. In the user interface image for controlling the imaging functions of the imaging device, each of the imaging functions may be displayed using an icon or a letter. 
       FIG. 7  is an explanatory diagram for describing the control method according to the present embodiment, showing an example in which a user interface image for controlling the imaging functions of the imaging device is displayed on the display screen of the display device  200  in addition to similar display to  FIG. 6 . In  FIG. 7 , the line-of-sight detection sensor  300  serving as a sensor unit having a stereo camera is also shown as in  FIG. 6 . Reference sign O 1  shown in  FIG. 7  represents a predetermined region in which a position in a medical captured image is included, similarly to reference sign O shown in  FIG. 6 . In addition, reference sign O 2  shown in  FIG. 7  represents an example of the user interface image for controlling the imaging functions of the imaging device. Note that it is a matter of course that a user interface image for controlling the imaging functions of the imaging device is not limited to the example illustrated in  FIG. 7 . 
     In a case in which a position of a line of sight on the display screen is changed from a position C to a position D shown in  FIG. 7 , the display control unit  158  moves display of the predetermined region in which the position in the medical captured image is included to correspond to the change of the position of the line of sight on the display screen. 
     In addition, in a case in which an operation is performed on the user interface image for controlling the imaging functions of the imaging device, for example, an operation of an operation device, a gesture operation, a voice operation, or the like, the display control unit  158  changes display of the user interface image to correspond to the operation. In addition, the imaging control unit  156  controls an imaging function corresponding to an operation performed on the user interface image for controlling the imaging functions of the imaging device. 
     Note that display control according to the second example is not limited to the above-described examples. 
     For example, the display control unit  158  may cause a position of a line of sight of a recognition target on the user interface image to be displayed on the display screen on the basis of a detection result of the line of sight of the recognition target. 
     To give an example of the case in which an operator is a recognition target of a line of sight, by displaying a position of a line of sight of the operator on the user interface image on the display screen, other medical staff members such as an assistant of the operator can notice intention of the operator and perform an operation on the user interface image. 
     In addition, the display control unit  158  may cause a user interface image for controlling the function other than the imaging functions of the imaging device of the medical observation device  100  and a user interface image for controlling a function of an apparatus other than the medical observation device  100  to be displayed on the display screen. 
     (c) Third Example of Display Control 
     The display control unit  158  causes a state of the imaging functions of the imaging device to be displayed on the display screen. 
     As display of a state of the imaging functions of the imaging device, for example, display of a value indicating a zoom magnification, display of an F number (aperture value), display of an exposure value (EV), display of a shutter speed value, or the like is exemplified. 
     Note that display control according to the third example is not limited to the above-described example. 
     For example, the display control unit  158  may cause a position of a line of sight of a recognition target on the display screen on which a state of the imaging functions of the display device has been displayed to be displayed on the display screen on the basis of a detection result of a line of sight of a recognition target. 
     (d) Fourth Example of Display Control 
     The display control unit  158  may cause a “vital sign of a patient,” an “image output from a navigation device,” an “image showing a setting of a treatment device among various treatment devices such as an electric scalpel, bipolar forceps, an ultrasonic aspirator,” or the like to be displayed on the display screen. The display control unit  158  causes a value or an image acquired from an external device such as a device that measures vital conditions to be displayed on the display screen. 
     Note that display control according to the fourth example is not limited to the above-described example. 
     For example, the display control unit  158  may cause a position of a line of sight of a recognition target on the display screen on which a “vital sign of a patient” or the like is displayed to be displayed on the display screen on the basis of a detection result of the line of sight of the recognition target. 
     To give an example of the case in which an operator is a recognition target of a line of sight, a mechanism that helps another medical staff member transfer new information regarding information at the tip of the line of sight of the operator to the operator when a line of sight of the operator is at a position on the display screen on which a vital condition of patient or the like is displayed can be realized. 
     The control unit  154  has a leading role of performing the process relating to the control method according to the present embodiment, for example, having the imaging control unit  156  and the display control unit  158 . 
     Note that a configuration of the control unit  154  is not limited to the example illustrated in  FIG. 4 . 
     In the case in which the medical observation device  100  has the configuration illustrated in  FIG. 1 , for example, the control unit  154  may have a processing unit (not illustrated) that causes a robot that operates the medical observation device  100  (a rigid endoscope or a flexible endoscope) to move on the basis of a detection result of a line of sight of a recognition target. When the processing unit (not illustrated) transmits a control signal corresponding to the detection result of the line of sight of the recognition target to the robot, an operation of a rigid endoscope or an operation of a flexible endoscope by the robot is realized. 
     In addition, in the case in which the medical observation device  100  has the configuration illustrated in  FIG. 2 , for example, the control unit  154  may have an arm control unit (not illustrated) that controls driving of the arm  122 . As an example of control of driving of the arm  122 , for example, “application of a control signal for controlling driving to the actuator (not illustrated) corresponding to each of the joints  130   a ,  130   b ,  130   c ,  130   d ,  130   e , and  130   f ” or the like is exemplified. 
     In addition, the control unit  154  can have an arbitrary configuration corresponding to a method of dividing the functions of the medical observation device  100 , such as a configuration corresponding to a method of dividing the process relating to the control method according to the present embodiment, or the like. 
     By having the functions illustrated in, for example,  FIG. 4 , the medical observation device  100  performs the process relating to the control method according to the present embodiment. 
     Note that a configuration of the medical observation device according to the present embodiment is not limited to the configuration illustrated in  FIG. 4 . 
     For example, the medical observation device according to the present embodiment can have one or both of the imaging control unit  156  and the display control unit  158  illustrated in  FIG. 4  separately from the control unit  154  (e.g., the imaging control unit  156  and the display control unit  158  can be realized as a separate processing circuit). 
     In addition, a configuration of the medical observation device according to the present embodiment for realizing the process relating to the control method according to the present embodiment is not limited to the configuration illustrated in  FIG. 4 , for example, and the medical observation device according to the present embodiment can have a configuration corresponding to a method of dividing the process relating to the control method according to the present embodiment. 
     In addition, in a case in which communication is performed with an external device via an external communication device having a similar function and configuration to the communication unit  152 , for example, the medical observation device according to the present embodiment may not include the communication unit  152 . 
     In addition, in a case in which the medical observation system according to the present embodiment has a control device (not illustrated) and the medical observation device according to the present embodiment is controlled by the control device (not illustrated), the medical observation device according to the present embodiment may not include the control unit  154 . 
     Here, when the control device (not illustrated) includes a control unit having a similar function and configuration to the control unit  154 , for example, the control device performs the process relating to the control method according to the present embodiment, which will be described below, and controls operations of each constituent element such as the imaging unit  150  or an arm unit (not illustrated) included in the medical observation device according to the present embodiment. When the control device (not illustrated) communicates with the medical observation device according to the present embodiment via the included communication device or a connected external communication device, the control device controls operations of each constituent element included in the medical observation device according to the present embodiment. 
     Furthermore, in a case in which the medical observation system according to the present embodiment has a control device (not illustrated) and the medical observation device according to the present embodiment is controlled by the control device (not illustrated), the medical observation device according to the present embodiment can also have a configuration without some of the functions of the control unit  154 . 
     [2-2-4] Example of Hardware Configuration of Medical Observation Device  100   
     Next, an example of a hardware configuration of the medical observation device  100  that can perform the process relating to the control method according to the present embodiment will be described.  FIG. 8  is an explanatory diagram for describing an example of a hardware configuration of the medical observation device  100  that can perform the process according to the control method according to the present embodiment, showing an example of a configuration of the control unit  112  illustrated in  FIG. 1 . 
     The control unit  112  has, for example, a signal input interface  160 , an AGC circuit  162 , a white balance circuit  164 , a transmission device  166 , and a processor  168 . In  FIG. 8 , the signal input interface  160  is denoted by “signal input I/F,” the AGC circuit  162  is denoted by “AGC (Automatic Gain Control),” and the white balance circuit  164  is denoted by “W/B.” 
     The signal input interface  160  is a communication interface to which signals are input, and image signals obtained from imaging by the camera head  108  are transferred to the signal input interface  160 . As an image signal transferred from the camera head  108 , for example, a signal indicating a raw image is exemplified. 
     An image signal input to the signal input interface  160  is subject to gain control in the AGC circuit  162  and to adjustment of white balance in the white balance circuit  164 . 
     The transmission device  166  transmits, for example, the image signal that has undergone various kinds of signal processing in the AGC circuit  162  and the white balance circuit  164  and a display control signal to the display device  200 . The transmission device  166 , for example, performs signal processing on the image signal in accordance with an output format and transmits the signal-processed image signal. 
     In addition, the transmission device  166  may transmit, for example, data indicating a state of an imaging function of the imaging device such as a value indicating a zoom magnification, an F number, an EV, or a shutter speed value to the display device  200 . Transmission by the transmission device  166  is controlled by the processor  168 . 
     The processor  168  is constituted by an arithmetic circuit such as an MPU and various processing circuits, and plays a leading role of performing the process relating to the control method according to the present embodiment. 
     The processor  168  has, for example, an analysis unit  170 , an AE detection unit  172 , an illumination control light unit  174 , an output gain adjustment unit  176 , and a control command generation unit  178 . 
     The analysis unit  170  analyzes data indicating a detection result of a line of sight acquired from an external device such as the line-of-sight detection sensor  300  or the display device  200 , and transfers a control signal corresponding to the analysis result to each of the AE detection unit  172  and the control command generation unit  178 . In a case in which it is necessary to change an exposure detection range of as a result of the analysis, for example, the analysis unit  170  transfers a control signal for changing the exposure detection range to the AE detection unit  172 . In addition, in a case in which it is necessary to control various imaging functions of the camera head  108  as a result of the analysis, for example, the analysis unit  170  transfers a control signal for controlling the imaging functions to the control command generation unit  178 . 
     The AE detection unit  172  acquires an exposure detection value on the basis of an image signal input to the signal input interface  160 . The exposure detection value is calculated on the basis of, for example, a luminance value acquired from the image signal. The exposure detection range of the AE detection unit  172  can be changed in accordance with a control signal transferred from the analysis unit  170 . The AE detection unit  172  transfers the acquired exposure detection value to each of the illumination control light unit  174  and the output gain adjustment unit  176 . 
     The illumination control light unit  174  controls the light source unit  104  on the basis of the exposure detection value transferred from the AE detection unit  172  to adjust radiated illumination light from the light source unit  104 . 
     The output gain adjustment unit  176  changes an output gain of the image sensor on the basis of the exposure detection value transferred from the AE detection unit  172 . 
     The control command generation unit  178  generates a command for controlling the camera head  108  on the basis of each of the control signal transferred from the analysis unit  170  and the result of the changed output gain transferred from the output gain adjustment unit  176  and outputs the generated command to the camera head  108 . 
     With the configuration of the control unit  112  illustrated in  FIG. 8 , for example, the process relating to the control method according to the present embodiment can be realized. Note that it is a matter of course that a configuration that makes it possible to perform the process relating to the control method according to the present embodiment is not limited to the configuration illustrated in  FIG. 8 . 
     [2-3] Display Device  200   
     The display device  200  displays a medical captured image indicated by an image signal transmitted from the medical observation device  100  on the display screen. 
     In addition, the display device  200  may have, for example, one or both of the function of detecting a line of sight on the basis of a detection result of the line-of-sight detection sensor  300  and the function of causing the line of sight to be displayed on the display screen on the basis of the detection result of the line of sight. 
     An example of a hardware configuration of the display device  200  having both the function of detecting a line of sight and the function of causing the line of sight to be displayed on the display screen on the basis of the detection result of the line of sight will be shown below. 
       FIG. 9  is an explanatory diagram illustrating an example of a hardware configuration of the display device  200  having both the function of detecting a line of sight and the function of causing the line of sight to be displayed on the display screen on the basis of the detection result of the line of sight. In  FIG. 9 , the control unit  112  illustrated in  FIG. 1  and the line-of-sight detection sensor  300  serving as a sensor unit having a stereo camera are shown together. 
     The display device  200  has, for example, an image signal input interface  250 , processors  252 ,  256 , and  264 , an information input interface  254 , a user interface  258 , a combiner  260 , and a display member  262 . In  FIG. 9 , the image signal input interface  250  is denoted by “image signal input I/F,” the information input interface  254  is denoted by “information input I/F,” and the user interface  258  is denoted by “user I/F.” 
     The image signal input interface  250  is a communication interface to which signals are input, and the image signal input interface  250  receives image signals transmitted from the control unit  112  of the medical observation device  100 . In addition, the image signal input interface  250  can receive display control signals along with image signals. An image signal received on the image signal input interface  250  is subject to arbitrary signal processing in the processor  252 . 
     The information input interface  254  is another communication interface to which signals are input, and the information input interface  254  receives data indicating a state of an imaging function of the imaging device (e.g., data indicating a value indicating a zoom magnification, an F number, an EV, or a shutter speed value) transmitted from the control unit  112  of the medical observation device  100 . The data indicating the state of the imaging function of the imaging device received by the information input interface  254  is subject to arbitrary data processing in the processor  256 . 
     The user interface  258  is constituted by an operation device that can be operated by a user using the display device  200 , and a combining method of the combiner  260  is switched through an operation on the user interface  258 . As an operation device constituting the user interface  258 , for example, a button, an arrow key, a rotary-type selector such as a jog dial, or a combination thereof is exemplified. In addition, in a case in which the display member  262  functions as a touch panel, the display member  262  and the user interface  258  may be integrated. 
     The combiner  260  selectively combines an image signal processed in the processor  252  and the data indicating the state of the imaging function of the imaging device processed in the processor  256 . Combining or non-combining by the combiner  260  and a combining method are switched, for example, through an operation with respect to the user interface  258 . In a case in which the combiner  260  does not perform combining, the combiner  260  outputs the image signal processed in the processor  252  to the display member  262 . 
     The display member  262  is constituted by, for example, a display panel and various drivers, and displays an image corresponding to the transferred image signal on a display screen. In addition, on the display screen of the display member  262 , one or both of the state of the imaging function of the imaging device and the position of the line of sight of the recognition target can be displayed. 
     The processor  264  has, for example, a line-of-sight detection unit  266  and an image generation unit  268 , and plays a role of performing a line-of-sight detection process. 
     The line-of-sight detection unit  266  performs the line-of-sight detection process on a captured image acquired from the line-of-sight detection sensor  300  to detect a line of sight of a recognition target. The line-of-sight detection unit  266  transmits, for example, data indicating the detection result of the line of sight to the medical observation device  100 . In addition, the line-of-sight detection unit  266  transfers the data indicating the detection result of the line of sight to the image generation unit  268 . 
     The image generation unit  268  generates an image indicating a position of the line of sight of the recognition target (e.g., the circular image having the position of the line of sight denoted by reference sign O as the center in  FIG. 6 ) on the basis of the data indicating the detection result of the line of sight transferred from the line-of-sight detection unit  266 . Then, the image generation unit  268  transfers the generated image indicating the position of the line of sight of the recognition target to the display member  262 , and thereby the position of the line of sight of the recognition target is displayed on the display screen of the display member  262 . 
     With the hardware configuration illustrated in  FIG. 9 , for example, the display device  200  having both the function of detecting a line of sight and the function of displaying the line of sight on the display screen on the basis of the detection result of the line of sight is realized. Note that it is a matter of course that a hardware configuration of the display device  200  having both the function of detecting a line of sight and the function of displaying the line of sight on the display screen on the basis of the detection result of the line of sight is not limited to the example illustrated in  FIG. 9 . 
     [3] Example of Effects Exhibited By Using Medical Observation System According to Present Embodiment 
     The following effects, for example, are exhibited by using the medical observation system according to the present embodiment. Note that it is a matter of course that an effect exhibited by using the medical observation system according to the present embodiment is not limited to the following examples.
         Brightness of a part (an example of a predetermined region) of a medical captured image including an operative site being observed by an operator can be optimized. Thus, even in a case in which an inside of an abdominal cavity of a patient with varying complex unevenness is imaged, a medical captured image with a higher S/N can be displayed on the display screen. In addition, the operator can concentrate on observing the medical captured image, and thus stress caused by surgery can be reduced.   Since surgery (an example of medical practice) is performed on a predetermined region in which an operative site that an operator is observing is included, even if the display device has made progress in high resolution such as 4K or 8K, it rarely affects a size of the predetermined region. Thus, even if the display device makes progress in high resolution, the effect of reducing stress caused by the surgery is exhibited.   By displaying a position of a line of sight of an operator on the display screen on which a medical captured image is being displayed, an intention of the operator can be shared with the surgery team.   In a case in which a user interface image for controlling various apparatuses such as the medical observation device  100  is displayed on the display screen and a position of a line of sight of an operator is displayed on the display screen, the apparatuses can be controlled on the basis of the position of the line of sight of the operator.       

     (Program According to the Present Embodiment) 
     Usability can be improved by a processor and the like executing a program (e.g., a program that can execute the process relating to the control method according to the present embodiment) for causing a computer system to function as the medical observation device according to the present embodiment (or the control device according to the present embodiment) in the computer system. Here, as the computer system according to the present embodiment, a single computer or a plurality of computers are exemplified. A series of processes relating to the control method according to the present embodiment are performed by the computer system according to the present embodiment. 
     In addition, when the program for causing the computer system to function as the medical observation device according to the present embodiment (or the control device according to the present embodiment) is executed by the processor and the like in the computer system, an effect to be produced from display that is realized by the process relating to the above-descried control method according to the present embodiment can be exhibited. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. 
     Although it has been described above that, for example, the program (computer program) for causing the computer system to function as the medical observation device according to the present embodiment is provided, the present embodiment can also provide a recording medium in which the program is stored therealong. 
     The above-described configuration is an example of the present embodiment, and of course belongs to the technical scope of the present disclosure. 
     Further, the effects described in this specification are merely illustrative or exemplified effects, and are not limitative. That is, with or in the place of the above effects, the technology according to the present disclosure may achieve other effects that are clear to those skilled in the art from the description of this specification. 
     Additionally, the present technology may also be configured as below. 
     (1) A medical observation device including: 
     an imaging control unit configured to control an imaging function of an imaging device, 
     in which the imaging control unit controls an exposure function of the imaging device on a basis of a detection result of a line of sight of a recognition target so that luminance of a predetermined region in a medical captured image obtained by the imaging device capturing an observation target is changed. 
     (2) The medical observation device according to (1), in which the imaging control unit controls the exposure function of the imaging device on a basis of a position of a line of sight of a recognition target specified from the detection result of the line of sight of the recognition target on a display screen on which the medical captured image is displayed so that the luminance of the predetermined region is changed.
 
(3) The medical observation device according to (2), in which the predetermined region is a region in which a position in the medical captured image corresponding to the position of the line of sight on the display screen is included.
 
(4) The medical observation device according to (3), in which the imaging control unit controls the exposure function so that luminance of a region other than the predetermined region in the medical captured image is decreased.
 
(5) The medical observation device according to (4), in which the imaging control unit controls a zoom function of the imaging device so that electronic zoom is performed on the predetermined region in conjunction with control of the exposure function.
 
(6) The medical observation device according to (3), in which the imaging control unit controls the exposure function so that diffused illumination light is radiated to a position of the observation target corresponding to the position in the medical captured image.
 
(7) The medical observation device according to (3), in which the imaging control unit controls the exposure function so that illuminance of the predetermined region in the medical captured image is increased.
 
(8) The medical observation device according to any one of (2) to (7), further including:
 
     a display control unit configured to cause a position in the medical captured image corresponding to the position of the line of sight on the display screen to be displayed on the display screen on the basis of the detection result of the line of sight of the recognition target. 
     (9) The medical observation device according to (8), in which the display control unit causes the predetermined region in which the position in the medical captured image is included to be displayed on the display screen. 
     (10) The medical observation device according to (8) or (9), in which the display control unit further causes a user interface image for controlling the imaging function of the imaging device to be displayed on the display screen. 
     (11) The medical observation device according to any one of (8) to (10), in which the display control unit further causes a state of the imaging function of the imaging device to be displayed on the display screen. 
     (12) The medical observation device according to any one of (1) to (11), in which the imaging control unit controls the exposure function of the imaging device so that the luminance of the predetermined region is increased or luminance of the predetermined region is decreased.
 
(13) The medical observation device according to any one of (1) to (12), including:
 
     the imaging device configured to be inserted into an inside of a body of a patient and image the inside of the body. 
     (14) The medical observation device according to any one of (1) to (12), including: 
     an arm including a plurality of links connected to each other by a joint; and 
     the imaging device supported by the arm. 
     (15) A medical observation system including: 
     a medical observation device including an imaging control unit configured to control an imaging function of an imaging device; and 
     a display device configured to display a medical captured image captured by the imaging device on a display screen, 
     in which the imaging control unit of the medical observation device controls the exposure function of the imaging device on a basis of a detection result of a line of sight of a recognition target so that luminance of a predetermined region in the medical captured image is changed.