Medical control device and medical observation system

Abstract

A medical control device 9 comprises a control unit 94 for executing each of first and second controls. The first control is a control for changing at least one of: the light emission energy of light emitted from a light source 31; the exposure time of an imaging element 52 for imaging return light from an observation target based on irradiation of the light emitted from the light source 31 and outputting pixel signals; an analog gain for adjusting the brightness of an image based on the pixel signals; and a digital gain for adjusting the brightness of the image based on the pixel signals. The second control is a control for changing the transmittance of light in a light amount adjustment optical element 33 disposed on an optical path through which the light emitted from the light source 31 propagates from the light source 31 to the observation target. The control unit 94 executes the first and second controls in a specific order as the brightness of the image based on the pixel signals becomes brighter.

Description

Medical control device and medical observation system

[0001] The present disclosure relates to a medical control device and a medical observation system.

[0002] Conventionally, a medical observation system has been known that irradiates an observation target (a subject such as a human) with a first light including visible light, such as narrow-band excitation light or broad-band white light, emitted from a light source device, and observes the fluorescence (hereinafter referred to as "observation target fluorescence") emitted from a substance contained in the observation target by the irradiation of the excitation light (see, for example, Patent Document 1). This type of fluorescence observation makes it possible to grasp tissue conditions that are difficult to recognize through the observation target fluorescence. Therefore, fluorescence observation can be used for various purposes and applications, such as identifying lesions.

[0003] JP 2009-66121 A

[0004] In the medical observation system described in Patent Document 1, the brightness of an image is adjusted by changing the light emission intensity of a light source. However, there are problems such as the inability to appropriately set the image brightness due to the narrow dynamic range over which the light emission intensity of the light source can be adjusted, and further improvements in the performance of adjusting the image brightness are desired.

[0005] The present disclosure has been made in view of the above, and aims to provide a medical control device and a medical observation system that can further improve the performance for adjusting the brightness of an image.

[0006] In order to solve the above-mentioned problems and achieve the object, the medical control device according to the present disclosure includes a control unit that executes a first control and a second control, wherein the first control is a control that changes at least one of the luminous energy of light emitted from a light source, the exposure time of an image sensor that captures returned light from an object of observation based on the irradiation of light emitted from the light source and outputs a pixel signal, an analog gain that adjusts the brightness of an image based on the pixel signal, and a digital gain that adjusts the brightness of an image based on the pixel signal, and the second control is a control that changes the transmittance of light in a light intensity adjusting optical element that is arranged on the optical path along which the light emitted from the light source propagates from the light source to the object of observation and that enables the transmittance of the light to be adjusted, and the control unit executes the first control and the second control in a specific order as the brightness of the image based on the pixel signal becomes brighter.

[0007] Furthermore, a medical observation system according to the present disclosure includes a light source that emits light, an image sensor that captures returned light from an observation target based on irradiation with the light emitted from the light source and outputs a pixel signal, a light intensity adjusting optical element that is disposed on an optical path along which the light emitted from the light source propagates from the light source to the observation target and that is capable of adjusting the transmittance of the light, and a medical control device having a control unit that executes first control and second control, respectively, wherein the first control is control that changes at least one of the emission energy of the light emitted from the light source, the exposure time of the image sensor, the analog gain that adjusts the brightness of an image based on the pixel signal, and the digital gain that adjusts the brightness of the image based on the pixel signal, and the second control is control that changes the light transmittance of the light intensity adjusting optical element, and the control unit executes the first control and the second control in a specific order as the brightness of the image based on the pixel signal increases.

[0008] According to the medical control device and medical observation system according to the present disclosure, it is possible to further improve the performance for adjusting the brightness of an image.

[0009] FIG. 1 is a diagram illustrating the configuration of a medical observation system according to an embodiment. FIG. 2 is a block diagram illustrating the configuration of a camera head and a control device. FIG. 3 is a diagram illustrating a problem associated with simultaneously executing PWM control and electronic shutter control. FIG. 4 is a diagram illustrating a problem associated with simultaneously executing PWM control and electronic shutter control. FIG. 5 is a diagram illustrating conventional gain control, current control, and PWM control. FIG. 6 is a diagram illustrating gain control, electronic shutter control, and ND filter control according to an embodiment. FIG. 7 is a diagram illustrating a first modification of the embodiment. FIG. 8 is a diagram illustrating a second modification of the embodiment. FIG. 9 is a diagram illustrating a second modification of the embodiment. FIG. 10 is a diagram illustrating a third modification of the embodiment. FIG. 11 is a diagram illustrating a third modification of the embodiment. FIG. 12 is a diagram illustrating a fourth modification of the embodiment. FIG. 13 is a diagram illustrating a fourth modification of the embodiment. FIG. 14 is a diagram illustrating a fourth modification of the embodiment. FIG. 15 is a diagram illustrating a fifth modification of the embodiment. FIG. 16 is a diagram illustrating a sixth modification of the embodiment. FIG. 17 is a diagram illustrating a seventh modification of the embodiment. FIG. 18 is a diagram illustrating a seventh modification of the embodiment.

[0010] Hereinafter, modes for carrying out the present disclosure (hereinafter, referred to as embodiments) will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiments described below. Furthermore, in the description of the drawings, the same parts are assigned the same reference numerals.

[0011] [Configuration of Medical Observation System] Fig. 1 is a diagram showing the configuration of a medical observation system 1 according to an embodiment. In this embodiment, the medical observation system 1 is a medical endoscope system that uses an endoscope to observe an observation object OB (inside a living body). As shown in Fig. 1, this medical observation system 1 includes an insertion section 2, a light source device 3, a light guide 4, a camera head 5, a first transmission cable 6, a display device 7, a second transmission cable 8, a control device 9, and a third transmission cable 10.

[0012] In this embodiment, the insertion section 2 is a rigid endoscope. That is, the insertion section 2 has an elongated shape that is rigid as a whole or has a flexible portion and a rigid portion, and is inserted into the observation object OB. The insertion section 2 includes an optical system that includes one or more lenses and focuses return light (subject image) from the observation object OB.

[0013] An excitation light cut filter 22 (FIG. 1) that partially, substantially, or completely suppresses excitation light (described later) contained in the collected return light (subject image) is disposed at the proximal end (eyepiece 21) of the insertion portion 2. The excitation light cut filter 22 is not limited to being disposed in the insertion portion 2, but may also be disposed in the camera head 5.

[0014] One end of the light guide 4 is connected to the light source device 3. The light source device 3 supplies light to the one end of the light guide 4 under the control of the control device 9. The light source device 3 includes a first light source 31, a first collimator lens 32, a first ND (Neutral Density) filter 33, and a lens unit 34 (see FIGS. 1 and 2).

[0015] The first light source 31 corresponds to the light source according to the present disclosure. This first light source 31 emits excitation light that excites a substance contained in the observation object OB. The first light source 31 may be configured with an LED (Light Emitting Diode) or a semiconductor laser. The number of first light sources 31 may be one or more. Furthermore, the wavelength band of the excitation light may include a visible wavelength band, or may be an infrared wavelength band or an ultraviolet wavelength band excluding the visible wavelength band.

[0016] Here, examples of substances contained in the observation object OB that are excited by the excitation light include drugs or fluorescent dyes attached to the observation object OB, or fluorescent substances derived from the observation object OB that constitute the observation object OB itself.

[0017] Examples of the above-mentioned drugs administered to the observation subject OB include "5-ALA (PP-IX)", "ADS780WS", "ADS830WS", "aggregation-induced emission dots allophycocyanin (APC)", "boron-dipyrromethane (BODIPY)", "CLR 1502", "Flavins", "fluorescamine", "Fluorescein", "fluoro-gold", "green fluorescence protein", "ICG (indocyanine green)", "IRDye 78", "IR-PEG nanoparticles", "Isothiocyanate", "rose Bengal", "SGM-101", and "trypan blue".

[0018] The above-mentioned fluorescent dyes that can be applied to the observation target OB include "coumarine," "Cy3," "DyLight547," "GE3126," "metal nanoclusters," "oxacarbocyanine," "rhodamine," "riboflavin," "fluorescein," "AlexaFluor660," "AlexaFluor680," "AlexaFluor700," "Cy5," "Cy5.5," "Dy677," "Dy682," "Dy752," "DyLight647," "HiLyte Fluor 647," "HiLyte Fluor 680," "IRDye 700DX," "methylene blue," "Porphyrins," "Porphysomes," "VivoTag-680," "VivoTag-S680," "AlexaFluor750," "AlexaFluor790," "carbocyanine," "conjugated copolymers," "CW800-CA," "Cy7," "Cy7.5," "cyanine dyes," "Dy780," and "HiLyte Fluor 750," "Indocarbocyanine," "IR-786," ​​"IRDye 800CW," "IRDye 800RS," "IRDye 800BK," "Nervelight," "OTL-38 (Pafolacianine)," "Polymethine," "VivoTag-S750," "Xanthene," and "LUM-015" can be cited as examples.

[0019] Furthermore, examples of fluorescent substances derived from the observation object OB that constitute the observation object OB itself include "collagen," "elastin," and "NADH."

[0020] In this embodiment, the light source device 3 is configured as a separate entity from the control device 9, but this is not limited to this, and a configuration in which the light source device 3 and the control device 9 are provided in the same housing may also be adopted.

[0021] The first collimator lens 32 is disposed downstream of the first light source 31 in the optical path. The first collimator lens 32 converts the excitation light emitted from the first light source 31 into substantially parallel light.

[0022] The first ND filter 33 corresponds to the light intensity adjusting optical element and the first light intensity adjusting optical element according to the present disclosure. This first ND filter 33 is disposed downstream of the first collimating lens 32 in the optical path. Note that the first ND filter 33 may be disposed not only within the light source device 3 but also at other locations as long as it is disposed on the optical path P1 ( FIG. 1 ) along which the excitation light propagates from the first light source 31 to the observation object OB. Under the control of the control device 9, the first ND filter 33 transmits the excitation light converted into substantially parallel light by the first collimating lens 32 at a specific transmittance. That is, the first ND filter 33 is disposed at a position on the optical path P1 where the excitation light emitted from the first light source 31 becomes substantially parallel light.

[0023] The first ND filter 33 can be, for example, an absorption type ND filter or a reflection type ND filter. An example of the absorption type ND filter is an electronic variable ND filter, in which a light-absorbing dimming material is mixed into liquid crystal, so that the density can be changed under the control of the control device 9. The absorption type ND filter is not limited to the electronic variable ND filter, and a variable ND filter arranged on a turret, an ND filter that rotates two ND filters with gradation, or an ND filter that stacks two circular polarizing filters may also be used.

[0024] An example of a reflective ND filter is an ND filter that is formed in a round or rectangular shape with gradation and that can be varied by rotation or horizontal movement.

[0025] The lens unit 34 guides the excitation light emitted from the first light source 31 and passed through the first collimator lens 32 and the first ND filter 33 to the incident end of the light guide 4 .

[0026] One end of the light guide 4 is detachably connected to the light source device 3. The other end of the light guide 4 is detachably connected to the insertion section 2. The light guide 4 propagates light (excitation light) supplied from the light source device 3 from one end to the other end, and supplies the light to the insertion section 2. The light (excitation light) supplied to the insertion section 2 is emitted from the tip of the insertion section 2 and irradiated onto the observation object OB. The light irradiated onto the observation object OB and returned (subject image) from the observation object OB is collected by an optical system within the insertion section 2. The returned light includes, in addition to the excitation light reflected by the observation object OB, fluorescence (hereinafter referred to as observation object fluorescence) emitted from a substance contained in the observation object OB when the excitation light is irradiated onto the observation object and the substance is excited.

[0027] The camera head 5 is detachably connected to the eyepiece 21 of the insertion section 2. Under the control of the control device 9, the camera head 5 captures light that is collected by the insertion section 2 and returns via the excitation light cut filter 22, generating a pixel signal. For ease of explanation, the pixel signal generated by capturing the returned light will be referred to as a captured image or a fluorescent image below. The detailed configuration of the camera head 5 will be described later in the section "Configuration of the Camera Head."

[0028] One end of the first transmission cable 6 is detachably connected to the control device 9 via a connector CN1 (FIG. 1). The other end of the first transmission cable 6 is detachably connected to the camera head 5 via a connector CN2 (FIG. 1). The connector CN2 is not limited to being detachably connected to the camera head 5, but may also be fixed to the camera head 5. The first transmission cable 6 transmits captured images (fluorescence images) and the like output from the camera head 5 to the control device 9, and also transmits control signals, synchronization signals, clocks, power, and the like sent from the control device 9 to the camera head 5.

[0029] The captured image (fluorescence image) and the like transmitted from the camera head 5 to the control device 9 via the first transmission cable 6 may be transmitted as an optical signal or as an electrical signal. The same applies to the transmission of control signals, synchronization signals, and clocks from the control device 9 to the camera head 5 via the first transmission cable 6.

[0030] The display device 7 is configured with a display using a liquid crystal or organic EL (Electro Luminescence) display, etc., and displays an image based on a video signal from the control device 9 under the control of the control device 9 .

[0031] One end of the second transmission cable 8 is detachably connected to the display device 7. The other end of the second transmission cable 8 is detachably connected to the control device 9. The second transmission cable 8 transmits the video signal processed by the control device 9 to the display device 7.

[0032] The control device 9 corresponds to a medical control device according to the present disclosure. The control device 9 includes controllers such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit), and comprehensively controls the operations of the light source device 3, the camera head 5, and the display device 7. The control device 9 is not limited to a CPU or an MPU, and may include an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), a GPU (Graphics Processing Unit), or the like. The detailed configuration of the control device 9 will be described later in the section "Configuration of the Control Device."

[0033] One end of the third transmission cable 10 is detachably connected to the light source device 3. The other end of the third transmission cable 10 is detachably connected to the control device 9. The third transmission cable 10 transmits a control signal from the control device 9 to the light source device 3.

[0034] [Configuration of Camera Head] Next, we will explain the configuration of the camera head 5. Fig. 2 is a block diagram showing the configuration of the camera head 5 and the control device 9. As shown in Fig. 2, the camera head 5 includes a lens unit 51, a first image sensor 52, a signal processing unit 53, and a communication unit 54.

[0035] The lens unit 51 is configured using one or more lenses. The lens unit 51 focuses light in the insertion portion 2 and forms an image of the return light that has passed through the excitation light cut filter 22 on the imaging surface of the first imaging element 52.

[0036] The first imaging element 52 corresponds to the imaging element according to the present disclosure. This first imaging element 52 receives a subject image and converts it into an electrical signal (analog signal). In this embodiment, the first imaging element 52 is configured as a CMOS (Complementary Metal Oxide Semiconductor), which is a rolling shutter imaging element in which a plurality of pixels are two-dimensionally arranged in horizontal line units. Note that the first imaging element 52 is not limited to a CMOS, and may also be configured as a CCD (Charge Coupled Device).

[0037] Here, although not specifically shown, the first image sensor 52 is composed of an invalid area in which the output signal is not used to generate the captured image (fluorescence image), an optical black area (OB area), and an effective pixel area in which the subject image formed by the lens unit 51 is converted into pixel signals and output.

[0038] The signal processing unit 53, under the control of the control device 9, performs signal processing on the captured image (fluorescence image) of an analog signal generated by the first image sensor 52, and outputs the captured image (fluorescence image) of a digital signal. For example, the signal processing unit 53 performs signal processing on the captured image (analog signal) generated by the first image sensor 52, such as processing to remove reset noise, processing to multiply the analog signal by an analog gain that amplifies the analog signal, and A / D conversion.

[0039] The communication unit 54 functions as a transmitter that transmits the captured images (fluorescence images) sequentially output from the signal processing unit 53 to the control device 9 via the first transmission cable 6. The communication unit 54 is configured, for example, with a high-speed serial interface that communicates the captured images (fluorescence images) with the control device 9 via the first transmission cable 6 at a transmission rate of 1 Gbps or more.

[0040] [Configuration of Control Device] Next, the configuration of the control device 9 will be described with reference to Fig. 2. As shown in Fig. 2, the control device 9 includes a communication unit 91, an image memory 92, a processing module 93, a control unit 94, an input unit 95, an output unit 96, and a storage unit 97.

[0041] The communication unit 91 functions as a receiver that receives captured images (fluorescence images) sequentially transmitted from the camera head 5 (communication unit 54) via the first transmission cable 6. This communication unit 91 is configured, for example, with a high-speed serial interface that communicates captured images (fluorescence images) with the communication unit 54 at a transmission rate of 1 Gbps or more.

[0042] The image memory 92 is configured, for example, by a dynamic random access memory (DRAM), etc. This image memory 92 is capable of temporarily storing multiple frames of captured images (fluorescence images) sequentially output from the camera head 5 (communication unit 54).

[0043] Under the control of the control unit 94, the processing module 93 processes the captured images (fluorescence images) that are sequentially transmitted from the camera head 5 (communication unit 54) and received by the communication unit 91. As shown in FIG. 2 , the processing module 93 includes a memory controller 931, a first image processing unit 932, and a display control unit 933.

[0044] The memory controller 931 controls the writing of captured images (fluorescence images) to the image memory 92 and the reading of the captured images (fluorescence images) from the image memory 92. More specifically, the memory controller 931 writes the captured images (fluorescence images) received by the communication unit 91 to the image memory 92, reads the captured images (fluorescence images) from the image memory 92 at specific times, and inputs them to the first image processing unit 932.

[0045] The first image processing unit 932 performs first image processing on the input captured image (fluorescence image), such as optical black subtraction (clamping), white balance adjustment, demosaic processing, color correction matrix processing, gamma correction, YC processing for converting RGB signals into luminance color difference signals (Y, Cb / Cr signals), digital gain adjustment for multiplying by a digital gain, noise removal, and filtering for enhancing structure.

[0046] Under the control of the control unit 94, the display control unit 933 generates a video signal for displaying the captured image (fluorescence image) after the first image processing has been performed by the first image processing unit 932. Then, the display control unit 933 outputs the video signal to the display device 7 via the second transmission cable 8.

[0047] The control unit 94 is realized by a controller such as a CPU or an MPU executing various programs stored in the storage unit 97, and controls the operations of the light source device 3, the camera head 5, and the display device 7, as well as the operation of the entire control device 9. The control unit 94 is not limited to being a CPU or an MPU, and may be configured using an ASIC, an FPGA, a GPU, or the like. The functions of the control unit 94 will be described later in "Regarding conventional problems" and "Regarding gain control, electronic shutter control, and ND filter control."

[0048] The input unit 95 corresponds to an operation reception unit according to the present disclosure. The input unit 95 is configured using operation devices such as a mouse, a keyboard, and a touch panel, and receives user operations from a user such as a surgeon. The input unit 95 then outputs an operation signal corresponding to the user operation to the control unit 94. Note that the operation reception unit according to the present disclosure is not limited to a configuration provided in the control device 9 like the input unit 95, and may also be a configuration provided in the camera head 5, for example.

[0049] The output unit 96 is configured using a speaker, a printer, etc., and outputs various information.

[0050] The storage unit 97 stores programs executed by the control unit 94, information necessary for the processing of the control unit 94, and the like.

[0051] Generally, in the medical observation system 1, it is difficult to adjust the signal value of the fluorescence image generated by the first image sensor 52 that receives the returning light (subject image) (the signal value based on the fluorescence of the observation object imaged by the first image sensor 52) because of the influences of the following factors (1) to (4):

[0052] (1) Drugs Generally, the intensity of the fluorescence emitted from the observation object OB varies depending on the type and dosage of the drug. The type of drug administered to the observation object OB is selected according to the observation object OB (cancer, blood, lymph, etc.). Furthermore, in order to image the fluorescence emitted from the drug in the medical observation system 1, drugs are selected that can separate the wavelength of the excitation light that excites the drug from the wavelength of the fluorescence emitted from the drug. Drugs selected in this manner emit different intensities of fluorescence from the observation object. Furthermore, while the intensity of fluorescence from the observation object can be adjusted by the dosage of the drug, it is difficult to increase the dosage more than necessary to achieve minimally invasive treatment. In other words, it is difficult to adjust the intensity of fluorescence from the observation object by selecting the type of drug and adjusting the dosage. As a result, it is difficult to adjust the signal value based on the fluorescence from the observation object imaged by the first image sensor 52 by selecting the type of drug and adjusting the dosage.

[0053] (2) The amount of observation target fluorescence emitted from the observation target OB varies depending on the location and condition of the observation target OB. Specifically, if the observation target OB is located in a location or condition where the drug is likely to remain, the amount of observation target fluorescence emitted from the observation target OB increases. On the other hand, if the observation target OB is located in a location or condition where the drug is likely to flow and not remain, the amount of observation target fluorescence emitted from the observation target OB decreases and the afterglow time also becomes shorter. Furthermore, if the observation target OB is a tumor, the amount of observation target fluorescence received by the first image sensor 52 changes depending on its spread, size, and depth. In other words, it is difficult to adjust the amount of observation target fluorescence depending on the type and condition of the observation target OB. As a result, it is difficult to adjust the signal value based on the observation target fluorescence imaged by the first image sensor 52 depending on the type and condition of the observation target OB.

[0054] (3) Light Source Device: The intensity of the fluorescence emitted from the light source device 3 varies depending on the intensity of the excitation light. Increasing the intensity of the excitation light may require adjusting the power supplied to the light source device 3. However, the power that can be supplied to the light source device 3 is limited by the upper limit of the power required to operate the entire medical observation system 1. Furthermore, the intensity of the excitation light must be adjusted taking into account factors such as heat generation in components constituting the optical path of the excitation light (e.g., heat generation between the light guide 4 and the insertion section 2), compatibility with the laser class, the amount of light energy received by the observation object OB and surrounding living tissue (high light energy levels pose a risk of burns), and the rate of fading of the fluorescence emitted from the drug. Furthermore, the intensity of the excitation light can also be adjusted by changing the number of excitation light sources installed in the light source device 3. However, the number of light sources may affect the size of the light source device 3. The size of the light source device 3 may be limited by the size of a cart used to transport the light source device 3. In other words, it is difficult to adjust the intensity of the fluorescence emitted from the observation object by adjusting the intensity of the excitation light. As a result, it is difficult to adjust the signal value based on the fluorescence from the object of observation imaged by the first image sensor 52 by adjusting the amount of excitation light.

[0055] (4) The signal value based on the observation target fluorescence generated by the first imaging element 52 varies depending on the amount of the observation target fluorescence received by the imaging element 52. To adjust the signal value based on the observation target fluorescence, it is desirable to select a first imaging element 52 with optimal sensitivity, configuration, etc. for imaging the observation target fluorescence. However, the first imaging element 52 may be required not only to output an image for fluorescence observation based on receiving observation target fluorescence in a predetermined wavelength band, but also to output an image for normal light observation based on receiving visible light, such as white light. Furthermore, the first imaging element 52 may be required to output an image for fluorescence observation corresponding to a wide wavelength band or multiple wavelength bands within a wavelength band including visible light and invisible light. Furthermore, even when the same drug is used, the amount of observation target fluorescence may change depending on the procedure or the observation target OB. Therefore, the first imaging element 52 may be required to output an image for fluorescence observation that corresponds to such changes in the amount of observation target fluorescence. In such cases, the first imaging element 52 must be selected to accommodate such observations, and it may not be possible to use an imaging element with optimal characteristics for imaging fluorescence in a predetermined wavelength band. Furthermore, the first imaging element 52 is disposed inside the camera head 5, but because the size and weight of the camera head 5 are appropriate for observation, the type of the first imaging element 52, including its size, may be limited. Note that the first imaging element 52 is not limited to a configuration in which it is disposed inside the camera head 5, and even when it is disposed at the tip of a rigid endoscope or a flexible endoscope, the size and weight are appropriate for observation, and the type of the first imaging element 52, including its size, may be limited. In other words, it is difficult to adjust the signal value based on the fluorescence of the observation object imaged by the first imaging element 52 by selecting the type of first imaging element 52.

[0056] As described above, the signal value based on the fluorescence from the object of observation captured by the first image capturing element 52 is determined within the above-mentioned constraints, and therefore cannot be easily adjusted.

[0057] [Regarding the Problems of the Related Art] The fluorescence of the object of observation input to the first image sensor 52 is generated due to the administered drug. Therefore, users who use fluorescence observation require a function to adjust the brightness of the captured image (fluorescence image). To adjust the brightness, it is common to control the operation of the first light source 31 to control the current value supplied to the first light source 31 (hereinafter referred to as current control) or the PWM (Pulse Width Modulation) value (hereinafter referred to as PWM control). However, in order to control the brightness from a bright area to a dark area, the following problems (5) to (8) arise.

[0058] (5) Limits on Current Values ​​and PWM Values ​​Semiconductor devices, including LEDs and laser diodes (LDs), have set limits on rated current values ​​and minimum pulse inputs. Therefore, even if you want to control the brightness from very bright to very dark, the device's constraints limit the dynamic range of brightness. Specifically, when controlling a light-emitting device using PWM control, the device repeatedly turns on and off, causing overshoots and undershoots that distort the pulse waveform, making it difficult to achieve proper control. Furthermore, setting a current value or PWM value that exceeds the rated current value or minimum pulse input limit can lead to failure of the light-emitting device.

[0059] (6) Problems of Spectral Changes In semiconductor light-emitting devices, including LEDs and LDs, current control or PWM control can cause the spectrum of light emitted from the light-emitting device to change depending on the temperature of the light-emitting device. When excitation light is emitted from the first light source 31, as in the present embodiment, if the spectrum of the excitation light changes, it becomes difficult to obtain fluorescence of the target object with the desired intensity. Furthermore, for example, when white light is emitted from the first light source 31, if the spectrum of the white light changes, it becomes difficult to perform treatment or diagnosis based on the color reproduction of the affected area. While a method of combining multiple LEDs or multiple LDs to create white light and correct the color balance is conceivable, this method would result in the above-mentioned problem (5) occurring for each of the multiple LEDs or multiple LDs, further reducing the effective dynamic range.

[0060] (7) Restrictions on Emitted Light Amount: To ensure a dynamic range, one method is to install multiple identical LEDs or LDs and combine the light emitted from these LEDs or LDs to increase the brightness on the maximum light intensity side. However, due to the characteristics of the medical observation system 1, this method increases the risk of burns if the emitted light intensity is increased more than necessary, as it is used close to the affected area. Furthermore, for LDs, increasing the light emission energy too much increases the laser class. Furthermore, this method does not provide a measure to further reduce the brightness on the minimum light intensity side.

[0061] (8) Issues with Simultaneous PWM Control and Electronic Shutter Control Figures 3 and 4 are diagrams illustrating issues with simultaneous PWM control and electronic shutter control. Specifically, in Figures 3(a) and 4(a), the vertical axis indicates the horizontal line of the first image sensor 52 (the top row indicates the uppermost horizontal line (the first horizontal line) and the bottom row indicates the lowermost horizontal line (the final line)), and the horizontal axis indicates time. The parallelogram area is the area that contributes to the generation of a fluorescence image in one field. In Figures 3(b) and 4(b), the vertical axis indicates the current value supplied to the first light source 31, and the horizontal axis indicates time (the supply time of current supplied to the first light source 31). Figure 4(c) is a schematic diagram showing the generated fluorescence image FG.

[0062] One method for ensuring the dynamic range is to use electronic shutter control that discards the charge received by the first image sensor 52. Here, for example, as shown in Figure 3, if PWM control is performed with the opening amount (exposure time) of the electronic shutter of the first image sensor 52 fixed to a specific opening amount, the following problem occurs. Note that in Figures 3(a) and 4(a), the hatched parallelogram regions indicate the area where charge is swept away by the electronic shutter. Furthermore, the unhatched parallelogram regions indicate the area where the exposure period is valid.

[0063] Specifically, as shown in Fig. 4, when the emission time of the excitation light is narrowed by PWM control, within the region indicating the effective exposure period (the unshaded parallelogram region), the fluorescence from the object to be observed does not strike the upper and lower horizontal lines of the first image sensor 52. This poses a problem, as shown in Fig. 4(c), in that the generated fluorescence image FG has dark upper and lower portions, resulting in an image with uneven brightness.

[0064] FIG. 5 is a diagram illustrating conventional gain control, current control, and PWM control. Specifically, FIG. 5(a) shows the subject luminance (image brightness) of a fluorescent image. In FIG. 5, the subject luminance increases toward the right side of the figure, and decreases toward the left side of the figure. FIG. 5(b) shows gain control (changes in analog gain and digital gain), which is signal processing. FIG. 5(c) shows current control of the first light source 31. FIG. 5(d) shows PWM control of the first light source 31.

[0065] The control unit 94 calculates the brightness (subject luminance) of the fluorescence image. For example, the control unit 94 calculates the subject luminance (average luminance value, etc.) within the detection region, which is at least a portion of the entire image region of the fluorescence image, based on the luminance signal (Y signal) within the detection region, which is at least a portion of the entire image region of the fluorescence image, out of the luminance and color difference signals (Y, Cb / Cr signals) that are the fluorescence image after YC processing has been performed by the first image processing unit 932. Then, the control unit 94 executes dimming control to adjust the fluorescence image to a specific brightness based on the calculated subject luminance.

[0066] In the past, as shown in FIG. 5B, when the calculated subject brightness is darker than a specific reference subject brightness (the subject brightness indicated by the arrow Ar in FIG. 5), the control unit 94 brightens the subject brightness by gain control (changing the analog gain and digital gain), which is a signal processing. Note that the reference subject brightness is set to a subject brightness with a high occurrence rate and corresponds to the reference brightness according to the present disclosure. Furthermore, when the calculated subject brightness is brighter than the specific reference subject brightness, the control unit 94 first reduces the current value supplied to the first light source 31 to reduce the amount of excitation light emitted from the first light source 31 (current control (FIG. 5C)). Next, the control unit 94 reduces the PWM value of the first light source 31 to reduce the amount of excitation light emitted from the first light source 31 (PWM control (FIG. 5D)).

[0067] However, the conventional control shown in Fig. 5 involves current control or PWM control, which results in the above-mentioned problem of spectrum change (6). Therefore, in this embodiment, in order to address the above-mentioned problem of spectrum change (6), a dimming control different from the conventional one is adopted.

[0068] [Regarding Gain Control, Electronic Shutter Control, and ND Filter Control] FIG. 6 is a diagram illustrating gain control, electronic shutter control, and ND filter control according to an embodiment. Specifically, FIGS. 6A and 6B correspond to FIGS. 5A and 5B, respectively. FIG. 6C illustrates electronic shutter control. FIG. 6D illustrates ND filter control of the first ND filter 33. The control unit 94 calculates the brightness (subject luminance) of the fluorescence image. For example, the control unit 94 calculates the subject luminance (e.g., the average luminance value) within a detection region, which is at least a portion of the entire image region of the fluorescence image, based on the luminance signal (Y signal) within the detection region, which is at least a portion of the entire image region of the fluorescence image, from the luminance and color-difference signals (Y, Cb / Cr signals) of the fluorescence image after YC processing by the first image processing unit 932. Then, the control unit 94 performs dimming control to adjust the fluorescence image to a specific brightness based on the calculated subject luminance.

[0069] Specifically, as shown in (b) of Fig. 6, when the calculated subject brightness is darker than a specific reference subject brightness (the subject brightness indicated by the arrow Ar in Fig. 6 (the same as the arrow Ar in Fig. 5)), the control unit 94 brightens the subject brightness by gain control (changing the analog gain and digital gain), which is signal processing. Also, when the calculated subject brightness is brighter than the specific reference subject brightness, the control unit 94 first reduces the opening amount of the electronic shutter in the first image sensor 52 (electronic shutter control ((c) of Fig. 6)). Next, the control unit 94 reduces the transmittance of excitation light in the first ND filter 33 (ND filter control ((d) of Fig. 6)).

[0070] Here, the electronic shutter control is control for changing the exposure time of the first image sensor 52. That is, the gain control and the electronic shutter control correspond to the first control according to the present disclosure. The electronic shutter control corresponds to the imaging control according to the present disclosure. The ND filter control corresponds to the second control according to the present disclosure.

[0071] As described above, in this embodiment, the control unit 94 executes the first control and the second control in a specific order as the calculated subject brightness increases. More specifically, the control unit 94 executes the first control and then the second control as the calculated subject brightness increases. In other words, the control unit 94 executes the second control and then the first control as the calculated subject brightness decreases. Furthermore, the control unit 94 executes the second control within a predetermined brightness range that does not include the reference subject brightness (the subject brightness indicated by the arrow Ar in FIG. 6 ). In other words, the control unit 94 executes the second control within a brightness range that is far from the reference subject brightness. Furthermore, the control unit 94 executes the gain control and then the imaging control as the calculated subject brightness increases.

[0072] The present embodiment described above provides the following advantages. In the control device 9 according to this embodiment, the control unit 94 executes the first control and the second control in a specific order as the calculated subject brightness increases. Here, the first control is gain control and electronic shutter control. The second control is ND filter control. That is, in the dimming control according to this embodiment, the current value and PWM value supplied to the first light source 31 are fixed. This solves the problem of spectral change described in (6) above. In other words, spectral change of the excitation light can be avoided, making it possible to obtain fluorescence from the observation object of a desired intensity. Therefore, the control device 9 according to this embodiment can further improve the performance for adjusting the brightness of the captured image (fluorescence image).

[0073] In particular, the control unit 94 executes the first control and then the second control as the calculated subject brightness increases. The control unit 94 also executes the second control in a brightness range that is far from the reference subject brightness (the subject brightness indicated by the arrow Ar in FIG. 6 ). Therefore, since the ND filter control is executed in a brightness range where the incidence of subject brightness is low, deterioration of the first ND filter 33 can be avoided.

[0074] Furthermore, in this embodiment, the first ND filter 33 is disposed on the optical path P1 at a position where the excitation light emitted from the first light source 31 becomes substantially parallel light. This makes it possible to reduce the amount of light per unit area incident on the first ND filter 33, thereby suppressing deterioration of the first ND filter 33. Furthermore, because the excitation light enters the first ND filter 33 as substantially parallel light, the characteristics of the first ND filter 33 can function at the design value characteristics.

[0075] In this embodiment, the control unit 94 executes the first control and then the second control as the calculated subject brightness increases, but conversely, the control unit 94 may execute the second control and then the first control. Also, as long as the first control is executed first and then the second control is executed as the calculated subject brightness increases, the first control and the second control may be executed simultaneously at the same subject brightness.

[0076] Furthermore, in this embodiment, the light source device 3 is configured to emit excitation light, but this is not limited to this, and it may also be configured to emit light including a visible wavelength band (for example, white light) instead of excitation light.

[0077] Other Embodiments Although the embodiments for carrying out the present disclosure have been described above, the present disclosure should not be limited to only the above-described embodiments. In the above-described embodiments, the following modified examples 1 to 7 may be adopted.

[0078] (Variation 1) Fig. 7 is a diagram illustrating Variation 1 of the embodiment. Specifically, (a) of Fig. 7 and (b) of Fig. 7 correspond to (a) of Fig. 5 and (b) of Fig. 5, respectively. (c) of Fig. 7 is a diagram illustrating current control of the first light source 31. (d) of Fig. 7 is a diagram illustrating PWM control of the first light source 31. (e) of Fig. 7 is a diagram illustrating ND filter control of the first ND filter 33. In the above-described embodiment, the control unit 94 may execute dimming control according to Variation 1 shown in Fig. 7, which is different from the dimming control shown in Fig. 6.

[0079] Specifically, as shown in FIG. 7B , when the calculated subject brightness is darker than a specific reference subject brightness (the subject brightness indicated by the arrow Ar in FIG. 7 (the same as the arrow Ar in FIG. 5 )), the control unit 94 according to this first modification brightens the subject brightness by gain control (changing the analog gain and digital gain), which is a signal processing. Furthermore, when the calculated subject brightness is brighter than the specific reference subject brightness, the control unit 94 first reduces the current value supplied to the first light source 31 to reduce the amount of excitation light emitted from the first light source 31 (current control (FIG. 7C)). Next, the control unit 94 reduces the PWM value of the first light source 31 to reduce the amount of excitation light emitted from the first light source 31 (PWM control (FIG. 7D)). Finally, the control unit 94 reduces the transmittance of the excitation light through the first ND filter 33 (ND filter control (FIG. 7E)).

[0080] Here, the gain control, current control, and PWM control correspond to the first control according to the present disclosure. Furthermore, the current control and PWM control correspond to the illumination light control according to the present disclosure. That is, the light emission energy according to the present disclosure corresponds to the current value supplied to the first light source 31 (the light intensity of the light emitted from the first light source 31) and the PWM value (light emission time) of the first light source 31. Furthermore, the ND filter control corresponds to the second control according to the present disclosure.

[0081] As described above, in this first modification, as in the above-described embodiment, the control unit 94 executes the first control and the second control in a specific order as the calculated subject brightness increases. More specifically, the control unit 94 executes the first control and then the second control as the calculated subject brightness increases. In other words, the control unit 94 executes the second control and then the first control as the calculated subject brightness decreases. Furthermore, the control unit 94 executes the second control within a brightness range away from the reference subject brightness (the subject brightness indicated by the arrow Ar in FIG. 7 ). Furthermore, the control unit 94 executes the gain control and then the illumination light control as the calculated subject brightness increases.

[0082] The above-described first modification provides the same effects as the above-described embodiment, as well as the following effects. In the first modification, the first control is gain control, current control, and PWM control. The second control is ND filter control. That is, the dimming control according to the first modification combines conventional current control and PWM control with ND filter control. This solves the problem of the limits on the current value and PWM value in (5) above. That is, the dynamic range of brightness can be increased.

[0083] Furthermore, as in the above-described embodiment, the control unit 94 executes the first control and then the second control as the calculated subject brightness increases. That is, ND filter control can be performed with the amount of excitation light reduced by current control and PWM control. Here, an absorption-type ND filter absorbs excitation light to reduce the amount of light and may deteriorate due to heat generated when absorbing the excitation light. Therefore, if the first ND filter 33 is configured as an absorption-type ND filter, performing ND filter control with the amount of excitation light reduced can suppress thermal deterioration of the first ND filter 33. On the other hand, a reflective ND filter reflects excitation light to reduce the amount of light and is less susceptible to thermal deterioration, unlike the absorption-type ND filter described above. However, the reflected light may scatter within the housing of the light source device 3 and have adverse effects (such as affecting the detection value of the sensor that detects the light amount). Therefore, it is preferable to perform ND filter control with the amount of excitation light reduced.

[0084] In the present modified example 1, the control unit 94 executes the first control and then the second control as the calculated subject brightness increases, but conversely, the control unit 94 may execute the second control and then the first control. Also, as long as the first control is executed first and then the second control is executed as the calculated subject brightness increases, the first control and the second control may be executed simultaneously at the same subject brightness.

[0085] Furthermore, in this second variant, the light source device 3 is configured to emit excitation light, but this is not limited to this, and it may also be configured to emit light including a visible wavelength band (e.g., white light) instead of excitation light.

[0086] (Variation 2) FIGS. 8 and 9 are diagrams illustrating Variation 2 of the embodiment. Specifically, FIG. 8 is a diagram corresponding to FIG. 2. (a) of FIG. 9 is a diagram corresponding to (a) of FIG. 7. (b) of FIG. 9 is a diagram illustrating gain control in a normal light image, which will be described later. (c) of FIG. 9 is a diagram corresponding to (b) of FIG. 7. (d) of FIG. 9 is a diagram illustrating current control of a second light source 35, which will be described later. (e) of FIG. 9 is a diagram corresponding to (c) of FIG. 7. (f) of FIG. 9 is a diagram illustrating PWM control of the second light source 35, which will be described later. (g) of FIG. 9 is a diagram corresponding to (d) of FIG. 7. (h) of FIG. 9 is a diagram illustrating ND filter control of a second ND filter 37, which will be described later. (i) of FIG. 9 is a diagram corresponding to (e) of FIG. 7. In the above-described embodiment, the number of light sources and the number of image pickup elements according to the present disclosure may be changed as in Variation 2 shown in FIG. 8.

[0087] 8 , in the light source device 3 according to the present modification 2, a second light source 35, a second collimator lens 36, and a second ND filter 37 are added to the light source device 3 described in the above embodiment. That is, in the present modification 2, the number of light sources according to the present disclosure is two, that is, the first and second light sources 31 and 35. Note that the number of light sources according to the present disclosure may be three or more.

[0088] The second light source 35 corresponds to the light source according to the present disclosure. This second light source 35 emits light including a visible wavelength band (broadband light such as white light or narrowband light such as red light, green light, or blue light). In this second modification, the light including the visible wavelength band will be described as white light. Examples of the configuration of this second light source 35 include a configuration including a white LED, or a configuration including three light sources that respectively emit red light, green light, and blue light, and an optical element that combines the red light, the green light, and the blue light. Note that the second light source 35 may be configured using an LED or a semiconductor laser. The number of second light sources 35 may be one or more.

[0089] The second collimator lens 36 is disposed downstream of the second light source 35 in the optical path. The second collimator lens 36 converts the white light emitted from the second light source 35 into substantially parallel light.

[0090] The second ND filter 37 corresponds to the light intensity adjusting optical element and second light intensity adjusting optical element according to the present disclosure. This second ND filter 37 is disposed downstream of the second collimating lens 36 in the optical path. The second ND filter 37 may be disposed in any location other than within the light source device 3, as long as it is disposed on the optical path P1 along which the white light propagates from the second light source 35 to the observation object OB. The second ND filter 37 transmits the white light converted into substantially parallel light by the second collimating lens 36 at a specific transmittance under the control of the control unit 94. That is, the second ND filter 37 is disposed at a position on the optical path P1 where the white light emitted from the second light source 35 becomes substantially parallel light. The white light passing through the second ND filter 37 enters the lens unit 34 and is guided to the incident end of the light guide 4 via the lens unit 34. When the observation object OB is irradiated with white light via the light guide 4 and the insertion portion 2 , return light (reflected white light) from the observation object OB is collected by the optical system in the insertion portion 2 .

[0091] The second ND filter 37 may be, for example, an absorption type ND filter or a reflection type ND filter as described in the above-described embodiment.

[0092] In addition, in the camera head 5 according to this modified example 2, in addition to the addition of the second light source 35, a prism 55 and a second image sensor 56 are added to the camera head 5 described in the above-mentioned embodiment, as shown in FIG.

[0093] The prism 55 separates the light (subject image) incident through the lens unit 51 into light of first and second wavelength bands that are different from each other. The light of the first wavelength band is light of a wavelength band that excludes at least a portion of the visible wavelength band and includes at least a portion of the wavelength band of the fluorescence of the object to be observed. Hereinafter, the light of the first wavelength band will be referred to as the first subject image. The light of the second wavelength band is light of a wavelength band that excludes at least a portion of the wavelength band of the fluorescence of the object to be observed and includes at least a portion of the visible wavelength band. Hereinafter, the light of the second wavelength band will be referred to as the second subject image. The prism 55 then causes the first subject image to travel toward the first image sensor 52. The prism 55 also causes the second subject image to travel toward the second image sensor 56.

[0094] The second imaging element 56 corresponds to the imaging element according to the present disclosure. The second imaging element 56 is configured with a CMOS, similar to the first imaging element 52. Note that the second imaging element 56 is not limited to a CMOS, and may be configured with a CCD (Charge Coupled Device).

[0095] The first image sensor 52 then captures a first subject image via the prism 55 under the control of the control device 9. That is, the first image sensor 52 captures light that includes at least a part of the wavelength band of the fluorescence of the object of observation. Hereinafter, as in the above-described embodiment, the captured image generated by capturing the first subject image with the first image sensor 52 will be referred to as a fluorescence image.

[0096] Furthermore, the second image sensor 56 captures a second subject image via the prism 55 under the control of the control device 9. That is, the second image sensor 56 captures light that includes at least a part of the visible wavelength band. For ease of explanation, the captured image generated by capturing the second subject image with the second image sensor 56 will be referred to as a normal light image below.

[0097] The number of pixels in the fluorescent light image and the number of pixels in the normal light image may be different or the same.

[0098] The signal processing unit 53 in this modification 2, under the control of the control device 9, performs signal processing on the analog signal captured images (fluorescence image and normal light image) generated by the first and second image sensors 52 and 56, respectively, and outputs digital signal captured images (fluorescence image and normal light image).

[0099] The communication unit 54 according to the present second modification transmits the captured images (fluorescence image and normal light image) sequentially output from the signal processing unit 53 to the control device 9. The communication unit 54 may alternately transmit the normal light image and the fluorescence image to the control device 9 in different frames, or may transmit them simultaneously in the same frame.

[0100] Furthermore, in the processing module 93 according to this second modification, in addition to the second light source 35 and the second image sensor 56, a second image processing unit 934 is added to the processing module 93 described in the above-mentioned embodiment, as shown in FIG. 8.

[0101] The memory controller 931 according to the present second modification writes the fluorescence image received by the communication unit 91 into the image memory 92, reads out the fluorescence image from the image memory 92 at a specific timing, and inputs it to the first image processing unit 932. The memory controller 931 also writes the normal light image received by the communication unit 91 into the image memory 92, and reads out the normal light image from the image memory 92 at a specific timing, and inputs it to the second image processing unit 934.

[0102] The second image processing unit 934 performs second image processing on the input normal light image. Examples of the second image processing include optical black subtraction processing (clamping processing), white balance adjustment processing, demosaic processing, color correction matrix processing, gamma correction processing, YC processing for converting RGB signals into luminance color difference signals (Y, Cb / Cr signals), digital gain adjustment for multiplying by digital gain, noise removal, and filter processing for structure enhancement. Note that the first and second image processing may be different from each other or may be the same.

[0103] The display control unit 933 according to the second modification generates, under the control of the control unit 94, a video signal for displaying the fluorescence image after the first image processing has been performed by the first image processing unit 932 and the normal light image after the second image processing has been performed by the second image processing unit 934. The display control unit 933 then outputs the video signal to the display device 7 via the second transmission cable 8.

[0104] The control unit 94 according to the second modification then executes the following dimming control. The control unit 94 calculates the brightness (subject luminance) of the fluorescence image or normal light image. For example, the control unit 94 calculates the subject luminance (average luminance) within a detection region, which is at least a portion of the entire image region of the normal light image, based on the luminance signal (Y signal) within the detection region, which is at least a portion of the entire image region of the normal light image, from the luminance and color difference signals (Y, Cb / Cr signals) that constitute the normal light image after YC processing has been performed by the second image processing unit 934. The control unit 94 then executes dimming control to adjust the captured images (fluorescence image and normal light image) to a specific brightness based on the calculated subject luminance.

[0105] Specifically, as shown in (b) and (c) of Figure 9, if the calculated subject brightness is darker than a specific reference subject brightness (the subject brightness indicated by arrow Ar in Figure 9 (the same as arrow Ar in Figure 5)), the control unit 94 brightens it by gain control (changing the analog gain and digital gain), which is signal processing. Furthermore, if the calculated subject brightness is brighter than a specific reference subject brightness, the control unit 94 first reduces the current values ​​supplied to the first and second light sources 31, 35, respectively, thereby reducing the amount of excitation light and white light emitted from the first and second light sources 31, 35 (current control ((d) and (e) of Figures 9A and 9B)). Next, the control unit 94 reduces the PWM values ​​of the first and second light sources 31, 35, respectively, thereby reducing the amount of excitation light and white light emitted from the first and second light sources 31, 35 (PWM control ((f) and (g) of Figures 9A and 9B)). Finally, the control unit 94 reduces the transmittance of the excitation light and white light in the first and second ND filters 33, 37, respectively (ND filter control ((h) and (i) of Figures 9A and 9B)).

[0106] In the second modification, gain control involves multiplying the same gain (analog gain and digital gain) in the white field (the field in which a normal light image is generated) and the fluorescent field (the field in which a fluorescent image is generated). Current control involves changing the current values ​​supplied to the first and second light sources 31, 35 at the same ratio in the white field and the fluorescent field. PWM control involves changing the PWM values ​​of the first and second light sources 31, 35 at the same ratio in the white field and the fluorescent field. ND filter control involves changing the transmittance of the first and second ND filters 33, 37 at the same ratio in the white field and the fluorescent field.

[0107] Here, the gain control, current control, and PWM control correspond to the first control according to the present disclosure. Furthermore, the current control and PWM control correspond to the illumination light control according to the present disclosure. That is, the light emission energy according to the present disclosure corresponds to the current value (light intensity of light emitted from the first light source 31 (second light source 35)) supplied to the first light source 31 (second light source 35) and the PWM value (light emission time) of the first light source 31 (second light source 35). The gain control, current control, and PWM control in the fluorescent field correspond to the third control according to the present disclosure. Meanwhile, the gain control, current control, and PWM control in the white field correspond to the fourth control according to the present disclosure. Furthermore, the ND filter control corresponds to the second control according to the present disclosure. Meanwhile, the ND filter control in the fluorescent field corresponds to the fifth control according to the present disclosure. Meanwhile, the ND filter control in the white field corresponds to the sixth control according to the present disclosure.

[0108] As described above, in the second modification, as in the above-described embodiment, the control unit 94 executes the first control and the second control in a specific order as the calculated subject brightness increases. More specifically, the control unit 94 executes the first control and then the second control as the calculated subject brightness increases. In other words, the control unit 94 executes the second control and then the first control as the calculated subject brightness decreases. The control unit 94 also executes the second control within a brightness range away from the reference subject brightness (the subject brightness indicated by the arrow Ar in FIG. 9 ). Furthermore, the control unit 94 executes the gain control and then the illumination light control as the calculated subject brightness increases.

[0109] Even when the configuration of the present modified example 2 described above is adopted, the same effects as those of the above-described embodiment are achieved.

[0110] In the second modification, the control unit 94 executes the first control and then the second control as the calculated subject brightness increases, but the control unit 94 may execute the second control and then the first control. Also, as long as the first control is executed first and then the second control is executed as the calculated subject brightness increases, the first control and the second control may be executed simultaneously at the same subject brightness.

[0111] In the second modification, either one of the first and second ND filters 33 and 37 may be omitted.

[0112] (Variation 3) FIGS. 10 and 11 are diagrams illustrating Variation 3 of the embodiment. Specifically, FIG. 10 corresponds to FIG. 9 . FIG. 11 illustrates the fluorescence gain set by the user. As mentioned above, various types of drugs can be administered to the observation target OB, ranging from those that emit bright fluorescence to those that emit only dim fluorescence. Furthermore, depending on the location of the observation target OB, there are various regions, from areas where the drug accumulates and emits bright fluorescence to areas where the drug concentration is low due to reflux and metabolism of the observation target OB, resulting in weak fluorescence. Therefore, users performing fluorescence observation require a function to adjust brightness. This function is generally implemented using gain control. However, when a high-sensitivity imager is used as the first imaging element 52, the image may become bright even without multiplication by gain (analog gain and digital gain). In this case, a negative gain is multiplied in signal processing, but if the signal value of the fluorescence image is saturated, the gradation adjustment of the signal value cannot be restored. In this third modification, in order to address this problem, the control unit 94 executes dimming control according to the third modification shown in FIG. 10, which is different from the dimming control described in the second modification above.

[0113] The control unit 94 calculates the brightness (subject luminance) of the fluorescence image or normal light image. For example, the control unit 94 calculates the subject luminance (average luminance) within a detection region, which is at least a portion of the entire image region of the normal light image, based on the luminance signal (Y signal) within the detection region, which is at least a portion of the entire image region of the normal light image, from the luminance and color difference signals (Y, Cb / Cr signals) that are the normal light image after YC processing has been performed by the second image processing unit 934. Then, the control unit 94 executes dimming control to adjust the captured images (fluorescence image and normal light image) to a specific brightness based on the calculated subject luminance.

[0114] Specifically, as shown in (b) and (c) of Figure 10, if the calculated subject brightness is darker than a specific reference subject brightness (the subject brightness indicated by arrow Ar in Figure 10 (the same as arrow Ar in Figure 5)), the control unit 94 brightens it by gain control (changing the analog gain and digital gain), which is signal processing. Furthermore, if the calculated subject brightness is brighter than a specific reference subject brightness, the control unit 94 first reduces the current values ​​supplied to the first and second light sources 31, 35, respectively, thereby reducing the amount of excitation light and white light emitted from the first and second light sources 31, 35 (current control ((d) and (e) of Figures 10A and 10B)). Next, the control unit 94 reduces the PWM values ​​of the first and second light sources 31, 35, respectively, thereby reducing the amount of excitation light and white light emitted from the first and second light sources 31, 35 (PWM control ((f) and (g) of Figures 10A and 10B)).

[0115] Unlike the gain control according to the second modification, the gain control according to the third modification does not multiply the white field and the fluorescence field by the same amount of gain (analog gain and digital gain). More specifically, the control unit 94 multiplies the gain for the white field, as in the second modification. Meanwhile, for the fluorescence field, the control unit 94 sets a minimum gain corresponding to the fluorescence gain ( FIG. 11 ) selected by a user operation on the input unit 95, and adjusts the gain. As shown in FIG. 11 , the fluorescence gain is information that associates the gain (analog gain and digital gain) with the transmittance of the first ND filter 33 according to a numerical value (+3 to −3), and is stored in the storage unit 97. For example, if a fluorescence gain of +2 is selected by a user operation, the control unit 94 sets a minimum gain four times the reference gain (analog gain and digital gain) and adjusts the gain.

[0116] Furthermore, in the current control and PWM control according to the present modified example 3, similar to the current control and PWM control according to the modified example 2 described above, the current values ​​supplied to the first and second light sources 31, 35 are changed at the same ratio in the white field and the fluorescent field, and the PWM values ​​of the first and second light sources 31, 35 are changed at the same ratio.

[0117] Furthermore, for the white field, the control unit 94 always sets the transmittance of the second ND filter 37 to the maximum value, regardless of the calculated subject luminance, as shown in (h) of Fig. 10. On the other hand, for the fluorescent field, the control unit 94 always sets the transmittance to a value corresponding to the fluorescent gain (Fig. 11) selected by user operation on the input unit 95, regardless of the calculated subject luminance, as shown in (i) of Fig. 10. For example, if a fluorescent gain of -2 is selected by user operation, the control unit 94 sets the transmittance to ¼ of the reference transmittance (reference transmittance).

[0118] The above-described third modification provides the same effects as those of the above-described embodiment and second modification, as well as the following effect. In the third modification, the control unit 94 changes the transmittance of the first ND filter 33 to the transmittance set by a user operation during the second control. Therefore, even in cases where the signal value related to the fluorescence image would be saturated if the ND filter control were not executed, such as when a drug that emits bright fluorescence is used, the brightness of the fluorescence image can be adjusted to an appropriate brightness without losing the gradation adjustment of the fluorescence image.

[0119] 12 to 14 are diagrams illustrating a fourth modification of the embodiment. In the above-described embodiment, a configuration may be adopted that allows switching between normal dimming control without ND filter control (e.g., the dimming control in FIG. 5 ) and dimming control including ND filter control (e.g., the dimming control in FIG. 6 ). Examples of the switching method include a method performed by a user operation, and a method in which the control device 9 detects the type of the insertion portion 2, light source device 3, or camera head 5 being used and switches depending on the type.

[0120] For example, when a camera head 5 equipped with a normal-sensitivity image sensor 52 is used, the control unit 94 executes normal dimming control that does not reduce brightness. On the other hand, when a camera head 5 equipped with a high-sensitivity image sensor 52 is used, the control unit 94 executes dimming control that includes ND filter control, since it may be necessary to reduce brightness. In this way, dimming control may be switched depending on the type of camera head 5 used. Note that this is not limited to the camera head 5, and the same applies when a flexible endoscope equipped with an image sensor 52 is used.

[0121] Furthermore, when a xenon lamp is used as the light source, it takes time for the light to stabilize after lighting. For this reason, it is difficult to dim the light source using PWM control. In such cases, the control unit 94 prioritizes light intensity adjustment using ND filter control. In this way, dimming control may be switched depending on the type of light source used.

[0122] Furthermore, the insertion section 2 (endoscope) is available in various outer diameters. As the outer diameter becomes smaller, the light guide path in the endoscope becomes narrower, and the brightness of the captured image tends to become darker. Even with a small-diameter endoscope, it is required to observe bright captured images, but some endoscopes have a limit to the amount of light energy that can be input (the amount of light emitted from the light source) due to heat generation. The dimming control may be switched depending on the type (outer diameter) of the endoscope used.

[0123] Furthermore, the dimming control may be switched depending on what is connected to the camera head 5. In addition to rigid endoscopes with normal outer diameters, thin-diameter endoscopes with smaller outer diameters than normal, fiberscopes, ring lights, etc. may be connected to the camera head 5. The brightness requirements for each of these devices connected to the camera head 5 are different. Therefore, the dimming control may be switched depending on what is connected to the camera head 5. For example, when a ring light for observing a distant point is connected to the camera head 5, the control unit 94 performs normal dimming control because there is little need to narrow the light. On the other hand, when a thin-diameter endoscope for observing a near point is connected to the camera head 5, the control unit 94 performs dimming control including ND filter control.

[0124] When normal light adjustment control is performed, the first ND filter 33 is positioned at a first position that is off the optical axis Ax (optical path P1) of the excitation light emitted from the first light source 31. On the other hand, when light adjustment control including ND filter control is performed, the first ND filter 33 is positioned at a second position on the optical axis Ax (optical path P1). Examples of methods for positioning the first ND filter 33 at the first and second positions include the methods shown in Figures 12 to 14.

[0125] 12 , the first ND filter 33 is attached to a wheel 38 that is rotatable about a rotation axis RAx. This wheel 38 has a circular hole 381 that penetrates from the front to the back. When normal light control is performed, the first ND filter 33 is positioned at a first position by rotating the wheel 38 about the rotation axis RAx. At this time, the circular hole 381 is positioned on the optical axis Ax. On the other hand, when light control including ND filter control is performed, the first ND filter 33 is positioned at a second position by rotating the wheel 38 about the rotation axis RAx.

[0126] 13, the first ND filter 33 is positioned at a first position (the position where the first ND filter 33 is indicated by the dashed line in FIG. 13) or a second position (the position where the first ND filter 33 is indicated by the solid line in FIG. 13) by operating a movement mechanism (not shown). Note that in the example shown in FIG. 13, the first ND filter 33 moves between the first position and the second position while maintaining an attitude where the light incident surface of the first ND filter 33 intersects with the optical path P1 (orthogonal in FIG. 13).

[0127] 14, the first ND filter 33 is positioned at a first position (the position where the first ND filter 33 is indicated by the dashed line in FIG. 14) or a second position (the position where the first ND filter 33 is indicated by the solid line in FIG. 14) by operating a movement mechanism (not shown). Note that in the example shown in FIG. 14, the first ND filter 33 moves between the first position and the second position by rotating around one end side.

[0128] The same effects as those of the above-described embodiment can be achieved even when the configuration of the present modified example 4 described above is adopted. Note that the configuration of the present modified example 4 may also be adopted in the configurations of the above-described modified examples 1 to 3.

[0129] (Variation 5) The medical observation system according to Variation 2 is a medical observation system that uses a so-called videoscope (flexible endoscope) equipped with an imaging element at the tip of the insertion section. For ease of explanation, the medical observation system 1 according to Variation 5 will be referred to as medical observation system 1B below.

[0130] 15 is a diagram illustrating a fifth modified example of the embodiment. As shown in Fig. 15, the medical observation system 1B includes an endoscope 300B that captures an in-vivo image of an observation site by inserting an insertion section 2B into a living body and outputs the captured image (fluorescence image), a light source device 3 that emits excitation light from the tip of the endoscope 300B, a control device 9 that processes the captured image output from the endoscope 300B, and a display device 7 that is connected to the control device 9 via a second transmission cable 8 and displays an image based on a video signal processed by the control device 9.

[0131] 15, the endoscope 300B includes a flexible, elongated insertion section 2B, an operation section 301 connected to the base end side of the insertion section 2B and accepting various operations, and a universal cord 302 extending from the operation section 301 in a direction different from the direction in which the insertion section 2B extends and incorporating various cables connecting to the light source device 3 and the control device 9. As shown in Fig. 15, the insertion section 2B includes a tip section 24, a freely bendable bending section 25 connected to the base end side of the tip section 24 and made up of a plurality of bending pieces, and a flexible, long flexible tube section 26 connected to the base end side of the bending section 25.

[0132] Although not specifically shown in the drawings, the tip portion 24 has a built-in configuration substantially similar to that of the camera head 5 described in the above embodiment. An image captured by the tip portion 24 (first image sensor 52) is output to the control device 9 via the operation unit 301 and the universal cord 302.

[0133] The same effects as those of the above-described embodiment can be achieved even when the configuration of the present modified example 5 described above is adopted. Note that the configuration of the present modified example 5 may also be adopted in the configurations of the above-described modified examples 1 to 4.

[0134] (Variation 6) The medical observation system according to Variation 3 is a medical observation system that uses a surgical microscope to magnify and capture images of a predetermined field of view of the inside of a subject (inside a living body) or the surface of a subject (surface of a living body), which is the observation target. For ease of explanation, the medical observation system 1 according to Variation 6 will be referred to as medical observation system 1C below.

[0135] Fig. 16 is a diagram illustrating a sixth modification of the embodiment. As shown in Fig. 16, the medical observation system 1C includes a surgical microscope 12 that captures an image for observing a subject and outputs the captured image (fluorescence image), a control device 9 that processes the captured image output from the surgical microscope 12, and a display device 7 that is connected to the control device 9 via a second transmission cable 8 and displays an image based on a video signal processed by the control device 9.

[0136] As shown in Fig. 16, the surgical microscope 12 includes a microscope unit 121 that magnifies and captures a minute portion of a subject and outputs the captured image, a support unit 122 that is connected to the base end of the microscope unit 121 and includes an arm that rotatably supports the microscope unit 121, and a base unit 123 that rotatably holds the base end of the support unit 122 and is movable on the floor. The control device 9 is mounted on the base unit 123 as shown in Fig. 13. Although not specifically shown, the light source device 3 that emits excitation light from the surgical microscope 12 to the observation target is also mounted on the base unit 123. The base unit 123 may be configured to support the support unit 122 by being fixed to a ceiling, wall, or the like, rather than being movable on the floor.

[0137] Although not specifically shown in the drawings, the microscope unit 121 has a built-in configuration substantially similar to that of the camera head 5 described in the above-described embodiment. An image captured by the microscope unit 121 (first image sensor 52) is output to the control device 9 via a first transmission cable 6 wired along the support unit 122.

[0138] The same effects as those of the above-described embodiment can be achieved even when the configuration of the present modified example 6 described above is adopted. Note that the configuration of the present modified example 6 may also be adopted in the configurations of the above-described modified examples 1 to 4.

[0139] (Variation 7) Figures 17 and 18 are diagrams illustrating Variation 7 of the embodiment. Specifically, Figure 17 is a view of the ring light 15 as seen from the side. Figure 18 is a view of the ring light 15 as seen from the front side (left side in Figure 17). In this Variation 7, in addition to the insertion section 2 described in the above embodiment, the ring light 15 shown in Figures 17 and 18 is detachably connected to the camera head 5. That is, depending on the usage state of the user, as shown in Figure 17, there are cases where the insertion section 2 is connected to the camera head 5, and cases where the ring light 15 is connected.

[0140] The ring light 15 is not inserted into the observation target like the insertion section 2, but supplies excitation light to the surgical site and captures the return light (subject image) of the excitation light from the surgical site. As shown in Figures 17 and 18, the ring light 15 includes an illumination section 151 and a subject image capture section 152 that captures the subject image.

[0141] 17 and 18 , the illumination unit 151 includes a housing 1511 and a plurality of illumination lenses 1512. The housing 1511 has an annular shape centered on the optical axis Ax. The other end of the light guide 4 is detachably connected to the housing 1511.

[0142] 18, the multiple illumination lenses 1512 are arranged at predetermined intervals along the circumferential direction centered on the optical axis Ax on the front end surface of the housing 1511. The multiple illumination lenses 1512 irradiate the excitation light, which is supplied from the light source device 3 and introduced into the housing 1511 via the light guide 4, toward the surgical site.

[0143] The subject image capture unit 152 extends along the optical axis Ax. The subject image capture unit 152 includes an optical system configured using one or more lenses that focuses the return light (observation target fluorescence) of the excitation light irradiated from the multiple illumination lenses 1512 and passing through the surgical site. Furthermore, a connector 1521 is provided at the end on the proximal side (right side in FIG. 17 ) of the subject image capture unit 152. This connector 1521 has a design (shape) compatible with the eyepiece 21 of the insertion unit 2 and is detachably connected to the camera head 5.

[0144] The same effects as those of the above-described embodiment can be achieved even when the configuration of the present modified example 7 described above is adopted. Note that the configuration of the present modified example 7 may also be adopted in the configurations of the above-described modified examples 1 to 4.

[0145] The following configurations also fall within the technical scope of the present disclosure: (1) A medical control device including a control unit that executes a first control and a second control, wherein the first control changes at least one of the emission energy of light emitted from a light source, the exposure time of an image sensor that captures returned light from an observation object based on irradiation with the light emitted from the light source and outputs a pixel signal, an analog gain that adjusts brightness of an image based on the pixel signal, and a digital gain that adjusts brightness of the image based on the pixel signal, and the second control changes the light transmittance of a light intensity adjusting optical element that is disposed on an optical path along which the light emitted from the light source propagates from the light source to the observation object and that adjusts the transmittance of the light, and the control unit executes the first control and the second control in a specific order as the brightness of the image based on the pixel signal increases. (2) The medical control device according to (1), wherein the control unit changes the emission energy by changing at least one of the light intensity and the emission time of the light emitted from the light source. (3) The medical control device according to (1) or (2), wherein the control unit executes the first control and then the second control as the brightness of the image based on the pixel signals becomes brighter. (4) The medical control device according to (1) or (2), wherein the control unit executes the second control and then the first control as the brightness of the image based on the pixel signals becomes darker. (5) The medical control device according to any one of (1) to (4), wherein the control unit executes the second control within a predetermined brightness range in which the brightness of the image based on the pixel signals does not include a reference brightness. (6) The medical control device according to any one of (1) to (5), wherein the first control includes imaging control that changes the exposure time and gain control that changes at least one of the analog gain and the digital gain. (7) The medical control device according to (6), wherein the control unit executes the gain control and then the imaging control as the brightness of the image based on the pixel signals becomes brighter.(8) The medical control device according to any one of (1) to (5), wherein the first control includes illumination light control that changes the light emission energy and gain control that changes at least one of the analog gain and the digital gain. (9) The medical control device according to (8), wherein the control unit executes the illumination light control after executing the gain control as the brightness of an image based on the pixel signals increases. (10) The light source includes a first light source that emits excitation light and a second light source that emits light including a visible wavelength band, and the image capture device includes a first image capture device that captures fluorescence, which is return light from the observation object based on irradiation with the excitation light, and outputs a first pixel signal, and a second image capture device that captures return light from the observation object based on irradiation with light including the visible wavelength band, and outputs a second pixel signal, and the first control includes a third control and a fourth control, and the third control is control that changes at least one of a first emission energy of the excitation light emitted from the first light source, a first exposure time of the first image capture device, a first analog gain that adjusts brightness of an image based on the first pixel signal, and a first digital gain that adjusts brightness of an image based on the first pixel signal, and the fourth control is control that changes the second light source The medical control device of any one of (1) to (9) is a control that changes at least one of a second emission energy of light including the visible wavelength band emitted from the second imaging element, a second exposure time of the second imaging element, a second analog gain that adjusts the brightness of an image based on the second pixel signal, and a second digital gain that adjusts the brightness of an image based on the second pixel signal, wherein the control unit executes the third control and the fourth control so that a ratio between at least one of the first emission energy, the first exposure time, the first analog gain, and the first digital gain that is changed in the third control and at least one of the second emission energy, the second exposure time, the second analog gain, and the second digital gain that is changed in the fourth control becomes a specific ratio.(11) The light amount adjusting optical element includes a first light amount adjusting optical element that is disposed on an optical path along which the excitation light propagates from the first light source to the observation object and that can adjust the transmittance of the excitation light, and a second light amount adjusting optical element that is disposed on an optical path along which light including the visible wavelength band propagates from the second light source to the observation object and that can adjust the transmittance of light including the visible wavelength band, and the second control includes a fifth control and a sixth control, and the fifth control is a control for adjusting the transmittance of the first light amount adjusting optical element. The medical control device described in (10) is a control that changes the transmittance of the excitation light, and the sixth control is a control that changes the transmittance of light including the visible wavelength band in the second light-intensity adjusting optical element, and the control unit executes the fifth control and the sixth control so that the ratio between the transmittance of the excitation light in the first light-intensity adjusting optical element that is changed in the fifth control and the transmittance of light including the visible wavelength band in the second light-intensity adjusting optical element that is changed in the sixth control becomes a specific ratio. (12) The medical control device according to any one of (1) to (11), wherein the light source includes a first light source that emits excitation light, the light intensity adjusting optical element is disposed on an optical path along which the excitation light propagates from the first light source to the observation object and is capable of adjusting a transmittance of the excitation light, the medical control device further includes an operation receiving unit that receives a user operation to set a transmittance of the excitation light in the light intensity adjusting optical element, and the control unit changes the transmittance of the excitation light in the light intensity adjusting optical element to the transmittance of the excitation light set by the user operation in the second control. (13) The medical control device according to any one of (1) to (12), wherein the light source includes a first light source that emits excitation light, the light intensity adjusting optical element is disposed on the optical path along which the light emitted from the light source becomes approximately parallel light.(14) A medical observation system comprising: a light source that emits light; an image sensor that captures light returned from an observation target based on irradiation with the light emitted from the light source and outputs a pixel signal; a light intensity adjusting optical element that is arranged on an optical path along which the light emitted from the light source propagates from the light source to the observation target and that adjusts the transmittance of the light; and a medical control device having a control unit that executes first and second controls, respectively, wherein the first control changes at least one of the emission energy of the light emitted from the light source, the exposure time of the image sensor, an analog gain that adjusts the brightness of an image based on the pixel signal, and a digital gain that adjusts the brightness of the image based on the pixel signal, and the second control changes the light transmittance of the light intensity adjusting optical element, and the control unit executes the first and second controls in a specific order as the brightness of the image based on the pixel signal increases. (15) The medical observation system according to (14), wherein the light source emits broadband light or narrowband light. (16) The medical observation system according to (14) or (15), wherein the light source includes a first light source that emits excitation light, and wherein the first light source is composed of one or more light sources. (17) The medical observation system according to any one of (14) to (16), wherein the light source includes a first light source that emits excitation light, and wherein the first light source is composed of an LED or a semiconductor laser. (18) The medical observation system according to (16) or (17), wherein the excitation light is narrowband light. (19) The medical observation system according to any one of (14) to (18), wherein the light source includes a second light source that emits light including a visible wavelength band, and wherein the second light source is composed of one or more light sources. (20) The medical observation system according to any one of (14) to (19), wherein the light source includes a second light source that emits light including a visible wavelength band, and wherein the second light source is composed of an LED or a semiconductor laser.

[0146] DESCRIPTION OF SYMBOLS 1, 1B, 1C Medical observation system 2, 2B Insertion section 3 Light source device 4 Light guide 5 Camera head 6 First transmission cable 7 Display device 8 Second transmission cable 9 Control device 10 Third transmission cable 12 Surgical microscope 15 Ring light 21 Eyepiece 22 Excitation light cut filter 24 Tip 25 Bending section 26 Flexible tube section 31 First light source 32 First collimating lens 33 First ND filter 34 Lens unit 35 Second light source 36 Second collimating lens 37 Second ND filter 38 Wheel 51 Lens unit 52 First image sensor 53 Signal processing section 54 Communication section 55 Prism 56 Second image sensor 91 Communication section 92 Image memory 93 Processing module 94 Control section 95 Input section 96 Output section 97 Memory section 121 Microscope section 122 Support section 123 Base section 151 Illumination section 152 Subject image capture section 300B Endoscope 301 Operation section 302 Universal cord 381 Circular hole 931 Memory controller 932 First image processing section 933 Display control section 934 Second image processing section 1511 Housing 1512 Illumination lens 1521 Connection section Ar Arrow Ax Optical axis CN1, CN2 Connectors OB Observation object P1 Optical path RAx Rotation axis

Claims

1. A medical control device comprising a control unit that executes a first control and a second control, wherein the first control is a control that changes at least one of the luminous energy of light emitted from a light source, the exposure time of an image sensor that captures returned light from an object of observation based on the irradiation of light emitted from the light source and outputs a pixel signal, an analog gain that adjusts the brightness of an image based on the pixel signal, and a digital gain that adjusts the brightness of an image based on the pixel signal, and the second control is a control that changes the light transmittance of a light intensity adjusting optical element that is arranged on an optical path along which the light emitted from the light source propagates from the light source to the object of observation and that enables adjustment of the transmittance of the light, and the control unit executes the first control and the second control in a specific order as the brightness of the image based on the pixel signal becomes brighter.

2. A medical control device according to claim 1, wherein the control unit changes the light emission energy by changing at least one of the light intensity and light emission time of the light emitted from the light source.

3. A medical control device as described in claim 1, wherein the control unit executes the first control and then the second control as the brightness of the image based on the pixel signal becomes brighter.

4. A medical control device as described in claim 1, wherein the control unit executes the second control and then the first control as the brightness of the image based on the pixel signal becomes darker.

5. A medical control device as described in claim 1, wherein the control unit executes the second control within a predetermined brightness range in which the brightness of the image based on the pixel signal does not include a reference brightness.

6. A medical control device according to claim 1, wherein the first control includes imaging control for changing the exposure time, and gain control for changing at least one of the analog gain and the digital gain.

7. The medical control device according to claim 6, wherein the control unit executes the gain control and then the imaging control as the brightness of the image based on the pixel signals increases.

8. A medical control device according to claim 1, wherein the first control includes illumination light control for changing the light emission energy, and gain control for changing at least one of the analog gain and the digital gain.

9. The medical control device according to claim 8, wherein the control unit executes the gain control and then the illumination light control as the brightness of the image based on the pixel signals increases.

10. The light source includes a first light source that emits excitation light and a second light source that emits light including a visible wavelength band, and the image capture device includes a first image capture device that captures fluorescence that is return light from the object of observation based on irradiation with the excitation light and outputs a first pixel signal, and a second image capture device that captures return light from the object of observation based on irradiation with light including the visible wavelength band and outputs a second pixel signal, and the first control includes a third control and a fourth control, and the third control is control that changes at least one of a first emission energy of the excitation light emitted from the first light source, a first exposure time of the first image capture device, a first analog gain that adjusts brightness of an image based on the first pixel signal, and a first digital gain that adjusts brightness of an image based on the first pixel signal, and the fourth control is control that changes a second emission energy of the light including the visible wavelength band emitted from the second light source, a second exposure time of the second image capture device, The medical control device of claim 1, wherein the control unit executes the third control and the fourth control so that a ratio between at least one of the first light-emitting energy, the first exposure time, the first analog gain, and the first digital gain changed in the third control and at least one of the second light-emitting energy, the second exposure time, the second analog gain, and the second digital gain changed in the fourth control becomes a specific ratio.

11. The light intensity adjusting optical element includes: a first light intensity adjusting optical element that is arranged on an optical path along which the excitation light propagates from the first light source to the object of observation, and that is capable of adjusting the transmittance of the excitation light; and a second light intensity adjusting optical element that is arranged on an optical path along which light including the visible wavelength band propagates from the second light source to the object of observation, and that is capable of adjusting the transmittance of the light including the visible wavelength band; the second control includes a fifth control and a sixth control; the fifth control is a control that changes the transmittance of the excitation light in the first light intensity adjusting optical element; and the sixth control is a control that changes the transmittance of the light including the visible wavelength band in the second light intensity adjusting optical element; and the control unit is A medical control device as described in claim 10, wherein the fifth control and the sixth control are executed so that the ratio between the transmittance of the excitation light in the first light-intensity adjusting optical element, which is changed in the fifth control, and the transmittance of light including the visible wavelength band in the second light-intensity adjusting optical element, which is changed in the sixth control, becomes a specific ratio.

12. The medical control device according to claim 1, wherein the light source includes a first light source that emits excitation light, the light intensity adjusting optical element is arranged on an optical path along which the excitation light propagates from the first light source to the object of observation and is capable of adjusting the transmittance of the excitation light, the medical control device further includes an operation receiving unit that receives a user operation to set the transmittance of the excitation light in the light intensity adjusting optical element, and the control unit, in the second control, changes the transmittance of the excitation light in the light intensity adjusting optical element to the transmittance of the excitation light set by the user operation.

13. A medical control device according to claim 1, wherein the light intensity adjusting optical element is disposed at a position on the optical path where the light emitted from the light source becomes substantially parallel.

14. A medical observation system comprising: a light source that emits light; an imaging element that captures returned light from an observation object based on the irradiation of the light emitted from the light source and outputs a pixel signal; a light intensity adjusting optical element that is arranged on an optical path along which the light emitted from the light source propagates from the light source to the observation object and that can adjust the transmittance of the light; and a medical control device having a control unit that executes first control and second control, respectively, wherein the first control is control that changes at least one of the emission energy of the light emitted from the light source, the exposure time of the imaging element, an analog gain that adjusts the brightness of an image based on the pixel signal, and a digital gain that adjusts the brightness of an image based on the pixel signal; and the second control is control that changes the light transmittance of the light intensity adjusting optical element, and the control unit executes the first control and the second control in a specific order as the brightness of the image based on the pixel signal becomes brighter.

15. The medical observation system according to claim 14, wherein the light source emits broadband light or narrowband light.

16. A medical observation system according to claim 14, wherein the light source includes a first light source that emits excitation light, and the first light source is configured to include one or more light sources.

17. A medical observation system according to claim 14, wherein the light source includes a first light source that emits excitation light, and the first light source is configured as an LED or a semiconductor laser.

18. A medical observation system according to claim 16, wherein the excitation light is narrowband light.

19. The medical observation system according to claim 14, wherein the light source includes a second light source that emits light including a visible wavelength band, and the second light source is configured to include one or more light sources.

20. A medical observation system according to claim 14, wherein the light source includes a second light source that emits light including a visible wavelength band, and the second light source is configured as an LED or a semiconductor laser.