Medical observation system, filter, and optical viewing tube

Abstract

A medical observation system 1 comprises: a light source device 3 that emits first light; an imaging element 513 that images second light, which is the first light returning from an object OB under observation irradiated with the first light; and a filter 11 that is disposed on an observation optical path P0 including a first optical path P1 through which the first light propagates from the light source device 3 to the object OB under observation and a second optical path P2 through which the second light propagates from the object OB under observation to the imaging element 513, and partially, substantially, or completely suppresses unnecessary light including autofluorescence generated from a member forming the observation optical path P0 due to at least one of the first and second light.

Description

Medical observation system, filter, and optical endoscope

[0001] The present disclosure relates to medical observation systems, filters, and optical scopes.

[0002] Conventionally, a medical observation system has been known that irradiates an observation target (such as a human subject) 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 in response to the irradiation of the excitation light (see, for example, Patent Document 1). This type of fluorescence observation makes it possible to grasp tissue conditions, which are difficult to recognize using white light, through the observation target fluorescence. Therefore, fluorescence observation can be used for various purposes and applications, such as identifying lesions.

[0003] Japanese Patent Application Laid-Open No. 2021-132695

[0004] A medical observation system has an observation optical path including a first optical path along which first light propagates from a light source device to an observation object, and a second optical path along which second light propagates, the second light being return light (including observation object fluorescence) of the first light from the observation object irradiated with the first light. As the first and second lights propagate through the observation optical path, the first and second lights irradiate components forming the observation optical path, causing autofluorescence to be generated from the components. Such autofluorescence has a wavelength band that includes the wavelength band of the observation object fluorescence that is the target of fluorescence observation, and causes noise in the fluorescence observation. Therefore, there is a demand for technology that enables satisfactory fluorescence observation.

[0005] The present disclosure has been made in view of the above, and aims to provide a medical observation system, a filter, and an optical endoscope that are capable of performing satisfactory fluorescence observation.

[0006] In order to solve the above-mentioned problems and achieve the object, the medical observation system according to the present disclosure comprises: a light source device that emits first light; an image sensor that captures second light, which is return light of the first light from an observation object irradiated with the first light; and a filter that is disposed on an observation optical path that includes a first optical path along which the first light propagates from the light source device to the observation object and a second optical path along which the second light propagates from the observation object to the image sensor, and that partially, substantially, or completely suppresses unnecessary light, including autofluorescence, generated from a member that forms the observation optical path by at least one of the first light and the second light.

[0007] Furthermore, the filter according to the present disclosure is disposed on an observation optical path including a first optical path along which the first light propagates from a light source device that emits the first light to an observation object, and a second optical path along which second light, which is return light of the first light from the observation object irradiated with the first light, propagates, and partially, substantially, or completely suppresses unwanted light, including autofluorescence, generated from a component that forms the observation optical path by at least one of the first light and the second light.

[0008] In addition, the optical scope according to the present disclosure is an optical scope that irradiates an object to be observed with first light and captures second light, which is return light of the first light from the object to be observed onto which the first light has been irradiated, and has a part of a first optical path along which the first light propagates from a light source device that emits the first light to the object to be observed, and a part of a second optical path along which the second light propagates, and is equipped with a filter that partially, substantially, or completely suppresses unnecessary light, including autofluorescence, generated by at least one of the first light and the second light from components that form an observation optical path including the first optical path and the second optical path.

[0009] The medical observation system, filter, and optical endoscope according to the present disclosure enable satisfactory fluorescence observation.

[0010] FIG. 1 is a diagram illustrating the configuration of a medical observation system according to a first embodiment. FIG. 2 is a diagram illustrating the shape of a filter. FIG. 3 is a diagram illustrating the function of a filter. FIG. 4 is a diagram illustrating the function of a filter. FIG. 5 is a diagram illustrating the function of a filter. FIG. 6 is a diagram illustrating a method for calculating an S / N ratio. FIG. 7 is a diagram illustrating the effects of the first embodiment. FIG. 8 is a diagram illustrating the configuration of a medical observation system according to a second embodiment. FIG. 9 is a diagram illustrating the function of a second filter in the case of short-wave excitation. FIG. 10 is a diagram illustrating the function of a second filter in the case of short-wave excitation. FIG. 11 is a diagram illustrating the function of a second filter in the case of short-wave excitation. FIG. 12 is a diagram illustrating the function of a second filter in the case of long-wave excitation. FIG. 13 is a diagram illustrating the function of a second filter in the case of long-wave excitation. FIG. 14 is a diagram illustrating the function of a second filter in the case of long-wave excitation. FIG. 15 is a diagram illustrating a first modification of the first and second embodiments. FIG. 16 is a diagram illustrating a first modification of the first and second embodiments. FIG. 17 is a diagram illustrating a first modification of the first and second embodiments. FIG. 18 is a diagram illustrating a second modification of the first and second embodiments. FIG. 19 is a diagram illustrating a third modification of the first and second embodiments. FIG. 20 is a diagram illustrating a fourth modification of the first and second embodiments. FIG. 21 is a diagram illustrating a fourth modification of the first and second embodiments. FIG. 22 is a diagram illustrating a fifth modification of the first and second embodiments. FIG. 23 is a diagram illustrating a fifth modification of the first and second embodiments. FIG. 24 is a diagram illustrating a sixth modification of the first and second embodiments. FIG. 25 is a diagram illustrating a seventh modification of the first and second embodiments. FIG. 26 is a diagram illustrating an eighth modification of the first and second embodiments. FIG. 27 is a diagram illustrating an eighth modification of the first and second embodiments.

[0011] 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.

[0012] (Embodiment 1) [Configuration of Medical Observation System] Fig. 1 is a diagram showing the configuration of a medical observation system 1 according to embodiment 1. In this embodiment 1, the medical observation system 1 is a medical endoscope system that uses an endoscope to observe an observation object OB (inside a living organism). 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, a third transmission cable 10, and a filter 11.

[0013] The insertion section 2 corresponds to an optical endoscope according to the present disclosure. In the first embodiment, the insertion section 2 is configured as a rigid endoscope. That is, the insertion section 2 has an elongated shape that is rigid as a whole or has a soft portion and a rigid portion, and is inserted into the observation object OB. The insertion section 2 includes an optical system configured using one or more lenses that focuses second light (subject image) from the observation object OB, which will be described later.

[0014] One end of the light guide 4 is connected to the light source device 3. The light source device 3 includes a first light source 31 ( FIG. 1 ) that supplies first light to one end of the light guide 4 under the control of the control device 9. In this embodiment, excitation light that excites a substance contained in the observation object OB is used as the first light. 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 that emit the first light may be one or more.

[0015] 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.

[0016] 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".

[0017] The above-mentioned fluorescent dyes 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.

[0018] Furthermore, examples of fluorescent substances derived from the observation object OB that constitute the observation object OB itself include "collagen," "elastin," and "NADH."

[0019] In this embodiment 1, 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.

[0020] 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 first light supplied from the light source device 3 (first light source 31) from one end to the other end, and supplies the first light to the insertion section 2. The first 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 second light (subject image), which is the return light of the first light irradiated onto the observation object OB and returned from the observation object OB, is collected by the optical system within the insertion section 2. The second light includes, in addition to 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 OB and the substance is excited.

[0021] The camera head 5 is detachably connected to the proximal end (eyepiece 21 (FIG. 1)) of the insertion section 2 via a filter 11. As shown in FIG. 1, the camera head 5 includes an imaging section 51. As shown in FIG. 1, the imaging section 51 includes an excitation light cut filter 511, a lens unit 512, and an imaging element 513.

[0022] The excitation light cut filter 511 is a filter that partially, substantially, or completely suppresses the excitation light contained in the second light (subject image) collected by the insertion portion 2. The excitation light cut filter 511 is not limited to being disposed in the camera head 5, but may also be disposed in the insertion portion 2 (for example, the eyepiece 21).

[0023] The lens unit 512 focuses the second light (subject image) that is collected by the insertion portion 2 and passes through the excitation light cut filter 511 , and forms an image on the light receiving surface (imaging surface) of the image sensor 513 .

[0024] The image sensor 513 is composed of a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), which receives the second light (subject image) formed by the lens unit 512 after passing through the excitation light cut filter 511 and converts it into an electrical signal.

[0025] Then, under the control of the control device 9, the imaging unit 51 outputs pixel signals obtained by imaging.

[0026] One end of the first transmission cable 6 is detachably connected to the control device 9. The other end of the first transmission cable 6 is detachably connected to the camera head 5. The first transmission cable 6 transmits pixel signals output from the imaging unit 51 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.

[0027] The pixel signals and the like transmitted from the camera head 5 to the control device 9 via the first transmission cable 6 may be transmitted as optical signals or as electrical signals. 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.

[0028] 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 .

[0029] 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.

[0030] 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. Note that the control device 9 is not limited to a CPU or an MPU, and may include integrated circuits such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit).

[0031] Specifically, the control device 9 generates a video signal by performing various image processing on the pixel signal acquired from the camera head 5 via the first transmission cable 6, and outputs the video signal to the display device 7 via the second transmission cable 8. The display device 7 then displays an image based on the video signal. The control device 9 also outputs control signals and the like to the camera head 5 and the light source device 3 via the first and third transmission cables 6 and 10.

[0032] 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.

[0033] FIG. 2 is a diagram showing the shape of the filter 11. Specifically, FIG. 2 is a diagram showing the filter 11 as viewed along the optical axis Ax of light incident on the filter 11. The filter 11 has a circular shape in a plan view ( FIG. 2 ) and is disposed between the eyepiece 21 and the camera head 5 so that the optical axis Ax is located at the center of the circle ( FIG. 1 ). Specifically, the filter 11 is detachably connected to the eyepiece 21. Note that the planar shape of the filter 11 is not limited to a circular shape and may be other planar shapes. For example, the planar shape of the filter 11 may be a rectangle whose inscribed circle is a circle centered on the optical axis Ax.

[0034] This filter 11 has a configuration in which an inorganic material is optically deposited on a substrate that emits little autofluorescence, such as synthetic quartz, and has a bandpass function, or a shortpass function or a longpass function. The filter 11 partially, substantially, or completely suppresses unwanted light, including autofluorescence L3 (see FIGS. 4 and 5), which will be described later. The function of the filter 11 will be described in detail in the section "Function of the Filter" below.

[0035] [Regarding Filter Function] Next, the function of the filter 11 described above will be described. FIGS. 3 to 5 are diagrams illustrating the function of the filter 11. Specifically, FIG. 3 is a diagram illustrating an ideal state in which no autofluorescence L3 that becomes noise is generated. FIG. 4 is a diagram illustrating an actual state in which autofluorescence L3 that becomes noise is generated. FIG. 5 is a diagram illustrating the function of the filter 11. Note that FIGS. 3(a), 4(a), and 5(a) are diagrams illustrating the spectrum of the second light L2. Note that FIGS. 3(b), 4(b), and 5(b) are diagrams schematically illustrating a signal value S1 based on the observation target fluorescence LF and a signal value S2 based on unnecessary light including autofluorescence L3. Note that in FIGS. 3 to 5, the horizontal axis represents wavelength [nm], and the vertical axis represents signal density [intensity / nm].

[0036] First, referring to FIG. 3 , an ideal state in which noise-causing autofluorescence L3 is not generated will be described. Excitation light L1 ( FIG. 3 ) is irradiated from the light source device 3 onto the observation object OB via a first optical path P1 ( FIG. 1 ). The first optical path P1 is an optical path that traces a path from the light source device 3 to the light guide 4 to the insertion section 2 to the observation object OB. When the excitation light L1 is irradiated onto the observation object OB, substances contained in the observation object OB are excited, and the observation object fluorescence LF ( FIG. 3 ) is emitted from the substances. The observation object fluorescence LF is the observation object light in fluorescence observation. Then, second light L2 ( FIG. 3 ), which is return light of the excitation light L1 containing the observation object fluorescence LF ( FIG. 3 ), propagates to the image sensor 513 via a second optical path P2 ( FIG. 1 ). The second optical path P2 is an optical path that traces a path from the observation object OB to the insertion section 2 to the image sensor 513. The excitation light L1 contained in the second light L2 is partially, substantially, or completely suppressed by the excitation light cut filter 511 when propagating through the second optical path P2. Note that in FIG. 3A, the wavelength band Ar1 marked with a dot is the wavelength band cut by the excitation light cut filter 511. Here, the term "cut" means that light is partially, substantially, or completely suppressed. The same meaning applies to "cut" described below. The image sensor 513 then captures an image of the subject including the observation target fluorescence LF.

[0037] The S / N ratio of the signal value based on the observation target fluorescence LF in the pixel signal obtained by imaging with the imaging unit 51 is S1 / S2, which is a relatively large value as shown in FIG. 3B, where S1 is the signal value based on the observation target fluorescence LF and S2 is the signal value based on the noise component. The signal values ​​S1 and S2 are each generated by the following equation (1). In equation (1), the wavelengths λa to λb are a wavelength band that includes the wavelength band of the observation target fluorescence LF.

[0038]

[0039] Next, referring to FIG. 4 , we will explain the actual state in which autofluorescence L3, which becomes noise, is generated. When excitation light L1 propagates through the first optical path P1 and second light L2 propagates through the second optical path P2, the excitation light L1 and second light L2 are irradiated onto a component (hereinafter referred to as an autofluorescence-generating component) that forms the observation optical path P0 ( FIG. 1 ) of the first and second optical paths P1 and P2, respectively, causing autofluorescence L3 ( FIG. 4 ) to be generated from the autofluorescence-generating component. Examples of such autofluorescence-generating components include components contained in multi-component glass such as lenses, material components contained in color filters, adhesives used to bond lenses or other optical components together, and oil adhering to optical components such as lenses. As shown in FIG. 4 , such autofluorescence L3 has a wavelength band that includes the wavelength band of observation object fluorescence LF, which is the light to be observed in fluorescence observation, and becomes noise during fluorescence observation. Incidentally, such autofluorescence L3 can also be generated by irradiating excitation light L1 onto the observation object OB.

[0040] That is, the S / N ratio (S1 / S2) of the signal value based on the fluorescence LF of the object to be observed in the pixel signal obtained by imaging with the imaging unit 51 becomes smaller than the value shown in FIG. 3(b) described above, because the signal value S2 based on the noise component including the autofluorescence L3 increases, as shown in FIG. 4(b).

[0041] In particular, when the observation object fluorescence LF from the observation object OB is weak, in order to separate the observation object fluorescence LF from the above-mentioned autofluorescence L3 and perform good fluorescence observation, it is necessary to adjust the signal value based on the observation object fluorescence LF imaged by the image sensor 513. However, adjusting the signal value based on the observation object fluorescence LF is difficult due to the influence of the following (1) to (4).

[0042] (1) Drugs Generally, the intensity of the observation object fluorescence LF emitted from a drug 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 observation object fluorescence LF 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 observation object fluorescence LF emitted by the drug. Drugs selected in this manner emit different intensities of the observation object fluorescence LF. Furthermore, while the intensity of the observation object fluorescence LF 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 the observation object fluorescence LF by selecting the type of drug and adjusting the dosage. As a result, it is difficult to adjust the signal value based on the observation object fluorescence LF imaged by the image sensor 513 by selecting the type of drug and adjusting the dosage.

[0043] (2) Observation Object The amount of observation object fluorescence LF emitted from the observation object OB varies depending on the location and condition of the observation object OB. Specifically, if the observation object OB is located in a location or condition where the drug is likely to remain, the amount of observation object fluorescence LF emitted from the observation object OB increases. On the other hand, if the observation object OB is located in a location or condition where the drug is likely to flow and not remain, the amount of observation object fluorescence LF emitted from the observation object OB decreases, and the afterglow time also becomes shorter. Furthermore, if the observation object OB is a tumor, the amount of observation object fluorescence LF received by the image sensor 513 changes depending on its spread, size, and depth. In other words, it is difficult to adjust the amount of observation object fluorescence LF depending on the type and condition of the observation object OB. As a result, it is difficult to adjust the signal value based on the observation object fluorescence LF imaged by the image sensor 513 depending on the type and condition of the observation object OB.

[0044] (3) Light Source Device The intensity of the observation object fluorescence LF varies depending on the intensity of the excitation light L1 emitted from the light source device 3. Increasing the intensity of the excitation light L1 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 L1 needs to be adjusted taking into account factors such as heat generation in components constituting the optical path of the excitation light L1 (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 organisms (high light energy levels pose a risk of burns), and the rate of fading of the observation object fluorescence LF emitted by the pharmaceutical. Furthermore, the intensity of the excitation light L1 can also be adjusted by changing the number of light sources for the excitation light L1 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. That is, it is difficult to adjust the amount of the observation object fluorescence LF by adjusting the amount of the excitation light L1. As a result, it is difficult to adjust the signal value based on the observation object fluorescence LF imaged by the image sensor 513 by adjusting the amount of the excitation light L1.

[0045] (4) Imager The signal value based on the observation target fluorescence LF generated by the imager 513 varies depending on the amount of the observation target fluorescence LF received by the imager 513. To adjust the signal value based on the observation target fluorescence LF, it is desirable to select an imager 513 with optimal sensitivity, configuration, etc. for capturing the observation target fluorescence LF. However, the imager 513 may be required not only to output an image for fluorescence observation based on receiving observation target fluorescence LF 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 imager 513 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 the observation target fluorescence LF may change depending on the procedure or the observation target OB. Therefore, the imager 513 may be required to output an image for fluorescence observation that corresponds to such changes in the amount of the observation target fluorescence LF. In this case, an element compatible with such observations must be selected for the imaging element 513, and it may not be possible to use an imaging element with optimal characteristics for imaging fluorescence in a predetermined wavelength band. Furthermore, although the imaging element 513 is disposed inside the camera head 5, the size and weight of the camera head 5 must be appropriate for the observation, which may limit the type of imaging element 513, including its size. Even in cases where the imaging element 513 is disposed at the tip of a rigid endoscope or a flexible endoscope, rather than being disposed inside the camera head 5, the size and weight must be appropriate for the observation, which may limit the type of imaging element 513, including its size. In other words, it is difficult to adjust the signal value based on the observation target fluorescence LF captured by the imaging element 513 by selecting the type of imaging element 513.

[0046] As described above, the signal value based on the observation object fluorescence LF captured by the image capturing element 513 is determined within the above-mentioned constraints, and therefore cannot be easily adjusted.

[0047] Therefore, in the first embodiment, a filter 11 is provided between the eyepiece 21 and the camera head 5 on the second optical path P2 in the observation optical path P0, so that the S / N ratio (S1 / S2) of the signal value based on the observation object fluorescence LF in the pixel signal obtained by imaging with the imaging unit 51 is set to a value greater than 1. If the S / N ratio (S1 / S2) is greater than 1, the control device 9 amplifies the S / N ratio by clamping, gain processing, gamma correction processing, or the like, making it possible to generate an image that allows the user to easily distinguish between the signal of the observation object fluorescence LF and the signal of noise components including the autofluorescence L3.

[0048] More specifically, the filter 11 cuts light in the wavelength band λc to λb from the wavelength band λa to λb, excluding the wavelength band of the observation target fluorescence LF. In other words, the filter 11 partially, substantially, or completely suppresses light other than the observation target fluorescence LF, which is the light to be observed during fluorescence observation. Note that in FIG. 5A, the dotted wavelength band Ar2 is the wavelength band cut by the filter 11. As a result, the S / N ratio (S1 / S2) of the signal value of the pixel signal obtained by image capture by the image capture unit 51 is greater than 1 because the signal value in the wavelength band λc to λb in the signal value S2 based on noise components including the autofluorescence L3 is reduced (FIG. 5B). The optical density (OD) value of the wavelength band cut by the filter 11 must be 1 or greater, and preferably 4 or greater. Here, the higher the OD value, the greater the cutting effect, resulting in a greater effect on improving image quality. However, filters with high OD values ​​require film formation using dedicated equipment, which tends to increase costs. An OD value of around 4 is within the range that can be produced using general-purpose film formation equipment. Therefore, in terms of practicality, it is preferable to select an OD value of 4, taking into account the balance between performance and cost.

[0049] In the wavelength band of wavelengths λc to λb, the S / N ratio (S1 / S2) may be set to a value greater than 1 by adjusting the OD value of the wavelength band to be cut by the filter 11. Furthermore, the filter 11 may cut light in a part of the wavelength band of the observation target fluorescence LF, as long as the S / N ratio (S1 / S2) of the signal value of the pixel signal obtained by imaging by the imaging unit 51 is set to a value greater than 1.

[0050] [Method of calculating S / N ratio] Fig. 6 is a diagram for explaining a method of calculating the S / N ratio. Specifically, Fig. 6 is a diagram corresponding to Fig. 1. The method of calculating the S / N ratio according to this embodiment is a method that refers to "2.D.8. Excitation light crosstalk" and "3.G. Excitation light crosstalk" in the title "Performance test methods for near-infrared fluorescence imaging" of the following document A. (Document A) "MEDICAL PHYSICS" Volume 47, Issue 8, August 2020, Pages 3389-3401

[0051] The method for calculating the S / N ratio uses first and second objects (phantoms) F1 and F2, as shown in Fig. 6. The first object F1 is a phantom that does not contain any drug and contains only scattering particles. The second object F2 is a phantom that contains a drug at a concentration appropriate for the living body to be observed.

[0052] The S / N ratio is calculated by the following equation (2): S / N ratio=((c)-(a)) / ((b)-(a)) (2)

[0053] Here, (a) in equation (2) is the luminance level based on the pixel signal output from the image sensor 513 in a state where no external light enters the camera head 5 and the first light source 31 is turned off in the medical observation system 1 shown in Fig. 6. Note that (a) may also be the luminance level based on the pixel signal output from the image sensor 513 in a state where a mechanical shutter is provided between the camera head 5 and the eyepiece 21 and the mechanical shutter prevents light from entering the camera head 5. Furthermore, (b) is the luminance level based on the pixel signal output from the image sensor 513 when the first light source 31 is turned on, the first subject F1 is irradiated with excitation light L1, and the second light L2 is imaged by the image sensor 513 in the medical observation system 1 shown in Fig. 6. Furthermore, (c) is the luminance level based on the pixel signal output from the image sensor 513 when the first light source 31 is turned on, the excitation light L1 is irradiated onto the second subject F2, and the second light L2 is imaged by the image sensor 513 in the medical observation system 1 shown in FIG. 6 .

[0054] In the filter 11 according to the present disclosure, the wavelength band to be cut and the OD value of the wavelength band are adjusted so that the S / N ratio calculated by equation (2) using the pixel signal (RAW signal) output from the image sensor 513 before image processing is performed on the pixel signal is greater than 1. More preferably, in the filter 11 according to the present disclosure, the wavelength band to be cut and the OD value of the wavelength band are adjusted so that the S / N ratio calculated by equation (2) using the pixel signal after image processing is performed on the pixel signal output from the image sensor 513 is 4 or greater.

[0055] The first embodiment described above provides the following advantages. The medical observation system 1 according to the first embodiment includes a filter 11 disposed on the observation optical path P0 that partially, substantially, or completely suppresses unwanted light, including autofluorescence L3, generated by components forming the observation optical path P0 due to at least one of the excitation light L1 and the second light L2. The filter 11 ensures that the S / N ratio (S1 / S2) of the signal value based on the observation object fluorescence LF in the pixel signal obtained by imaging with the imaging unit 51 is greater than 1. This enables the control device 9 to generate an image that allows the user to easily distinguish between the signal of the observation object fluorescence LF and the signal of noise components, including the autofluorescence L3. The medical observation system 1 according to the first embodiment therefore enables satisfactory fluorescence observation.

[0056] 7A and 7B are diagrams illustrating the effects of the first embodiment. Specifically, (a) of Fig. 7A shows the transmission characteristics (filter characteristics) of the filter 11 when the filter 11 is disposed in a specific position (between the eyepiece 21 and the camera head 5). (b) of Fig. 7A shows the transmission characteristics (filter characteristics) of the filter 11 when the filter 11 is disposed in a position other than the specific position. In Fig. 7A, the horizontal axis represents wavelength [nm], and the vertical axis represents OD value.

[0057] The transmission characteristics (filter characteristics) of the filter 11 change depending on the angle of incidence of light. The light emitted from the eyepiece 21 is approximately parallel light. Therefore, when the filter 11 is disposed between the eyepiece 21 and the camera head 5, the second light L2 enters the filter 11 as approximately parallel light. When the second light L2 enters as approximately parallel light in this manner, the transmission characteristics of the filter 11 become the transmission characteristics of the design value, as shown in FIG. 7A.

[0058] On the other hand, when there is a light distribution such as an NA of 0.2 or more (light of ±12 degrees or more), the transmission characteristics of the filter 11 may deteriorate from the transmission characteristics of the designed value, as shown in FIG. 7B. Specifically, the wavelength band to be cut may shift to the short wavelength side, and the cut wavelength band may no longer be the optimal wavelength band. Furthermore, the rise and fall of the OD value in the filter characteristics may change from the designed steep rise and fall (FIG. 7A) to a gradual rise and fall (FIG. 7B). Furthermore, the OD value of the cut wavelength band may also decrease.

[0059] As described above, by disposing the filter 11 between the eyepiece 21 and the camera head 5, the transmission characteristics of the filter 11 can be maintained at the transmission characteristics of the design value, and unwanted light including autofluorescence L3 can be partially, substantially, or completely suppressed according to the design value.

[0060] The filter 11 may also be detachably connected to the eyepiece 21. In this detachable configuration, multiple filters 11 with different wavelength bands or light levels to be cut are prepared depending on the observation target substance, such as a drug or fluorescent dye, applied to the observation target OB. This allows the user to select and use the filter 11 appropriate for the drug, fluorescent dye, or other observation target substance being used. The filter 11 may be a filter corresponding to multiple observation target substances that require simultaneous observation (e.g., the drug and another drug, or the drug and the autofluorescence of the subject), or a filter corresponding to a single observation target substance (the drug or the autofluorescence of the subject). Alternatively, multiple filters with the same or different wavelength bands or light levels to be cut may be stacked on the eyepiece 21.

[0061] The filter 11 according to the present disclosure allows for satisfactory fluorescence observation in the following scenes 1 to 6. Note that, although ICG is used as the drug in the following scenes 1 to 6, satisfactory fluorescence observation can also be performed in scenes using other drugs.

[0062] [Scene 1] An example of a scenario in which the fluorescence LF of the object to be observed is weak when using ICG is surgery on a pediatric patient. The dose of ICG administered per session must be set according to the patient's weight. Therefore, compared to adult patients, when administering ICG to a pediatric patient, the dose of ICG must be reduced in proportion to the patient's weight. That is, when ICG is administered to a pediatric patient, the concentration of ICG may be low, resulting in weak fluorescence LF of the object to be observed. Even when the fluorescence LF of the object to be observed is weak during surgery on a pediatric patient, the filter 11 can partially, substantially, or completely suppress unwanted light, including autofluorescence L3, allowing for satisfactory fluorescence observation.

[0063] [Second Scene] An example of a scene in which the fluorescence LF of the observation target is weak when using ICG is a scene in which intrabronchial injection is performed. The intrabronchial injection is a technique for identifying segments during lung segmental resection. Specifically, with the intrabronchial injection method, ICG is sprayed into the segmental bronchi using a bronchoscope, and the lung segment to be resected is identified through fluorescence observation. That is, with the intrabronchial injection method, it is more difficult to achieve a high ICG concentration than when identifying the lung segment to be resected using intravenous injection of ICG (hereinafter referred to as ICG intravenous injection), and the fluorescence LF of the observation target may be weak. Even when the fluorescence LF of the observation target is weak during the intrabronchial injection method, the filter 11 can partially, substantially, or completely suppress unwanted light, including autofluorescence L3, allowing for good fluorescence observation.

[0064] [Third Scene] A scene in which the fluorescence LF of the observation target is weak when ICG is used includes a scene in which a thin-diameter endoscope with a narrower outer diameter of the insertion section 2 is used. As fluorescence observation using ICG in the lower gastrointestinal tract becomes more common, there is a growing need for less invasive surgical procedures. Furthermore, in cases with spatial constraints, such as transanal total mesorectal excision and single-port surgery, thin-diameter endoscopes are often used to improve the operability of forceps and other instruments. However, compared to standard endoscopes and thick-diameter endoscopes with a thicker outer diameter of the insertion section 2, the light guide path of the excitation light in thin-diameter endoscopes is narrower, which can reduce the energy of the emitted excitation light and result in weak fluorescence LF of the observation target. Even when the fluorescence LF of the observation target is weak when using a thin-diameter endoscope, the filter 11 can partially, substantially, or completely suppress unwanted light, including autofluorescence L3, allowing for good fluorescence observation.

[0065] [Scene 4] An example of a scenario in which the fluorescence LF of the target of observation becomes weak when using ICG is identified through multiple fluorescence observations using intravenous ICG injection, for example, when a low concentration of ICG is used the first time. A challenge with intravenous ICG injection is that once ICG is intravenously injected, it remains in the bloodstream and continues to glow until it is metabolized in the liver, making it difficult to observe again. For example, during lobectomy, if incorrect hemostasis or loose ligation causes areas other than the target of observation, such as the entire lung, to glow, making it difficult to identify the target of observation again using intravenous ICG injection. Furthermore, because of the upper limit on the dose of ICG administered to adults, it is also difficult to identify the target of observation again using intravenous ICG injection after the ICG has been metabolized. Therefore, when identifying the lung region the first time, a low concentration of ICG (e.g., 1 / 10 of the normal concentration) is intravenously injected, and fluorescence observation is performed. If the appropriate area cannot be identified through the fluorescence observation, the ICG concentration is adjusted to the normal concentration, the ICG is intravenously injected again, and fluorescence observation is performed. When identifying the lung area for the first time, the ICG concentration is set to a low concentration, which may result in weaker observation target fluorescence LF than when the ICG concentration is set to a normal concentration. Even if the observation target fluorescence LF is weak when performing fluorescence observation with a low ICG concentration, the filter 11 can partially, substantially, or completely suppress unwanted light, including autofluorescence L3, allowing for satisfactory fluorescence observation. After this, the ICG concentration is set to the normal concentration and fluorescence observation is performed. In this way, performing fluorescence observation on the same area multiple times allows for more accurate identification of the lung area.

[0066] [Scene 5] An example of a scene in which the fluorescence LF of the observation target becomes weak when using ICG is when blood flow in an intestinal anastomotic failure is confirmed by multiple fluorescence observations using intravenous ICG injection, for example, using a low concentration of ICG the first time. When confirming blood flow in an intestinal anastomotic failure by fluorescence observation, if the blood flow cannot be properly confirmed due to incorrect instrument settings or the subject being buried in tissue such as fat, it takes time for the ICG to be metabolized, making it difficult to confirm the blood flow again by ICG injection. Therefore, as in the fourth scene described above, when confirming blood flow for the first time, a low concentration of ICG (e.g., 1 / 10 of the normal concentration) is intravenously injected, and fluorescence observation is performed. If the blood flow cannot be properly confirmed by fluorescence observation, the ICG concentration is increased to the normal concentration and intravenously injected again, and fluorescence observation is performed. When blood flow is first confirmed, the ICG concentration is set to a low concentration, which may result in weaker fluorescence LF of the object being observed than when the ICG concentration is set to a normal concentration. Even if the fluorescence LF of the object being observed is weak when performing fluorescence observation with a low ICG concentration, the filter 11 partially, substantially, or completely suppresses unnecessary light, including autofluorescence L3, allowing for satisfactory fluorescence observation. After this, the ICG concentration is set to the normal concentration and fluorescence observation is performed. In this way, performing fluorescence observation at the same site multiple times can reduce complications such as peritonitis due to anastomotic failure.

[0067] [Sixth Scene] When using ICG, the fluorescence LF of the observation object may be weak when a 3D fluorescence image is used for fluorescence observation (hereinafter referred to as 3D fluorescence observation). When performing 3D fluorescence observation, a twin-lens relay scope may be used as the insertion section 2. In this twin-lens relay scope, two parallel optical paths are arranged within the scope. Each of the two optical paths is provided with an optical system. The twin-lens relay scope captures observation light for the right and left eyes, which have a parallax between them, using the two optical systems and guides the light to the image sensor 513 (see, for example, Japanese Patent Application Laid-Open No. 6-160731). In this twin-lens relay scope, as with the thin-diameter endoscope described in the third scene above, the two optical paths narrow the light guide path of the excitation light compared to a normal endoscope. This reduces the energy of the emitted excitation light, and the fluorescence LF of the observation object may be weak. Furthermore, when performing 3D fluorescence observation, two image capturing elements, one for capturing the observation light for the right eye and one for the left eye, may be used as the image capturing element 513. When two image capturing elements are used as the image capturing element 513 in this manner, the size is smaller than when a single image capturing element is used, and therefore the received energy of the observation-target fluorescence LF may be lower, and the signal value based on the observation-target fluorescence LF may be weak. Note that the above example illustrates the use of a rigid endoscope for 3D fluorescence observation. However, even when a flexible endoscope for 3D fluorescence observation is used, the observation-target fluorescence LF and the signal value based on the observation-target fluorescence LF may also be weak. Furthermore, even when the observation-target fluorescence LF is weak during surgery using an endoscope for 3D fluorescence observation, the filter 11 can partially, substantially, or completely suppress unwanted light, including autofluorescence L3, allowing for satisfactory 3D fluorescence observation.

[0068] (Embodiment 2) Next, embodiment 2 will be described. Below, the same components as those in embodiment 1 described above will be assigned the same reference numerals, and detailed description thereof will be omitted or simplified. FIG. 8 is a diagram showing the configuration of a medical observation system 1A according to embodiment 2. Specifically, FIG. 8 corresponds to FIG. 1. As shown in FIG. 8, the medical observation system 1A according to embodiment 2 employs a filter 12 in addition to a filter 11 as a filter for partially, substantially, or completely suppressing unwanted light including autofluorescence L3. Hereinafter, for convenience of explanation, filter 11 will be referred to as the first filter 11, and filter 12 will be referred to as the second filter 12.

[0069] As shown in FIG. 8 , the second filter 12 is disposed on the first optical path P1 between the light guide 4 and the insertion section 2 (the exit end 41 of the light guide 4) or at the exit end 211 of the insertion section 2 from which the excitation light L1 is emitted. For ease of explanation, FIG. 8 illustrates the second filter 12 at two positions: the exit end 41 of the light guide 4 and the exit end 211 of the insertion section 2. The second filter 12 partially, substantially, or completely suppresses light other than the excitation light L1. More specifically, when the excitation light L1 is short-wavelength light (hereinafter referred to as the case of short-wavelength excitation), the second filter 12 is disposed at the exit end 211 of the insertion section 2. Examples of the short-wavelength light include visible light and ultraviolet light. On the other hand, when the excitation light L1 is light with a long wavelength (hereinafter referred to as the case of long-wave excitation), the second filter 12 is disposed at the exit end 41 of the light guide 4. An example of such long-wavelength light is infrared light. Below, we will explain the difference in effect depending on the location of the second filter 12 between the case of short-wave excitation and the case of long-wave excitation.

[0070] First, the case of short-wave excitation will be described. Figures 9 to 11 are diagrams illustrating the function of the second filter 12 in the case of short-wave excitation. Specifically, Figure 9 shows the spectrum of light immediately before it is emitted from the exit end 41 of the light guide 4 when the second filter 12 is not provided (Figure 9(a)), the spectrum of light immediately before it is emitted from the exit end 211 of the insertion section 2 (Figure 9(b)), and the spectrum of return light immediately before it is taken in by the insertion section 2 from the observation object OB (Figure 9(c)). Figure 10 shows the spectrum of light immediately before it is emitted from the exit end 41 of the light guide 4 when the second filter 12 is provided (Figure 10(a)), the spectrum of light immediately before it is emitted from the exit end 211 of the insertion section 2 (Figure 10(b)), and the spectrum of return light immediately before it is taken in by the insertion section 2 from the observation object OB (Figure 10(c)). 11 shows the spectrum of light immediately before it is emitted from the exit end 41 of the light guide 4 when the second filter 12 is disposed at the exit end 211 of the insertion portion 2 ((a) of FIG. 11), the spectrum of light immediately before it is emitted from the exit end 211 ((b) of FIG. 11), and the spectrum of returned light immediately before it is taken in by the insertion portion 2 from the observation object OB ((c) of FIG. 11). Note that in (a) of FIG. 10 and (b) of FIG. 11, the wavelength band Ar3 marked with dots is the wavelength band cut by the second filter 12. Note that in FIGS. 9 to 11, the horizontal axis represents wavelength [nm] and the vertical axis represents signal density [intensity / nm].

[0071] As shown in Figures 9(a), 10(a), and 11(a), when the excitation light L1 propagates through the light guide 4, autofluorescence L3 is generated from the autofluorescence generating material included in the light guide 4.

[0072] 9(b) and 11(b), when the excitation light L1 propagates through the insertion portion 2, autofluorescence L3 is generated from the autofluorescence generating member included in the insertion portion 2. Therefore, when the second filter 12 is not provided or when the second filter 12 is disposed at the exit end 211 of the insertion portion 2, the intensity of the autofluorescence L3 is greater immediately before the light is emitted from the exit end 211 of the insertion portion 2 than immediately before the light is emitted from the exit end 41 of the light guide 4.

[0073] On the other hand, when the second filter 12 is disposed at the exit end 41 of the light guide 4, the autofluorescence L3 generated from the autofluorescence generating member included in the light guide 4 is partially, substantially, or completely suppressed by the second filter 12. Therefore, as shown in Fig. 10(b), the intensity of the autofluorescence L3 included in the light immediately before being emitted from the exit end 211 of the insertion portion 2 is smaller than in Fig. 9(b) and Fig. 11(b).

[0074] 9(c) and 10(c), when the excitation light L1 is irradiated onto the observation object OB, autofluorescence L3 may also be generated from the observation object OB. In this case, the intensity of the autofluorescence L3 is greater immediately before the returning light is taken in by the exit end 211 of the insertion portion 2 than immediately before the light is emitted from the exit end 211 of the insertion portion 2.

[0075] On the other hand, when the second filter 12 is disposed at the exit end 211 of the insertion portion 2, the autofluorescence L3 generated from both the autofluorescence generating member included in the light guide 4 and the autofluorescence generating member included in the insertion portion 2 is partially, substantially, or completely suppressed by the second filter 12. Therefore, as shown in (c) of Fig. 11, the intensity of the autofluorescence L3 contained in the returned light immediately before being taken into the exit end 211 of the insertion portion 2 is smaller than in (c) of Fig. 9 and (c) of Fig. 11.

[0076] In the case of short-wave excitation, the energy of the excitation light L1 irradiated onto the autofluorescence generating member is high, resulting in the generation of a large amount of autofluorescence L3. Furthermore, as can be seen by comparing (c) of Figure 10 with (c) of Figure 11, it is effective to provide the second filter 12 at a later stage in the first optical path P1. Therefore, in the case of short-wave excitation, the second filter 12 is disposed at the exit end 211 of the insertion section 2.

[0077] Next, the case of long-wave excitation will be described. Figures 12 to 14 are diagrams illustrating the function of the second filter 12 in the case of long-wave excitation. Specifically, Figure 12 is a diagram illustrating a case where the second filter 12 is not provided, and corresponds to Figure 9. Figure 13 is a diagram illustrating a case where the second filter 12 is provided at the output end 41 of the light guide 4, and corresponds to Figure 10. Figure 14 is a diagram illustrating a case where the second filter 12 is provided at the output end 211 of the insertion section 2, and corresponds to Figure 11. In Figures 12 to 14, the horizontal axis represents wavelength [nm], and the vertical axis represents signal density [intensity / nm].

[0078] In the case of long-wave excitation, the behavior of the autofluorescence L3 is similar to that in the case of short-wave excitation described above, as shown in FIGS.

[0079] In the case of long-wave excitation, the energy of the excitation light L1 irradiated onto the autofluorescence generating member is small, and therefore, as can be seen by comparing Figures 12 to 14 with Figures 9 to 11, the amount of autofluorescence L3 generated is relatively small. Furthermore, as can be seen by comparing Figures 13(c) and 14(c), the intensity of the autofluorescence L3 contained in the return light immediately before being taken into the exit end 211 of the insertion portion 2 is substantially the same whether the second filter 12 is provided at the exit end 41 of the light guide 4 or at the exit end 211 of the insertion portion 2. The exit end 211 of the insertion portion 2 is the portion inserted into the observation object OB (inside the living body), and its design is relatively difficult. For this reason, in the case of long-wave excitation, the second filter 12 is provided at the exit end 41 of the light guide 4.

[0080] The second embodiment described above provides the same effects as the first embodiment, as well as the following effects. The medical observation system 1 according to the second embodiment is equipped with the first and second filters 11 and 12, and therefore can effectively, partially, substantially, or completely suppress unwanted light, including autofluorescence L3. The second filter 12 may also be fixed to the output end 41 of the light guide 4 or the output end 211 of the insertion section 2. In this case, compared to a detachable configuration such as the first filter 11, no additional parts are required, making it easier for the user to handle.

[0081] Other Embodiments Although the embodiments for implementing the present disclosure have been described above, the present disclosure should not be limited to the above-described embodiments. In the above-described first and second embodiments, the number of filters according to the present disclosure is not limited to one or two, but may be three or more. Furthermore, the arrangement position of the filter according to the present disclosure is not limited to the arrangement position described in the above-described first and second embodiments, as long as it is on the observation optical path P0. As long as it is on the observation optical path PO, the filter according to the present disclosure may be arranged, for example, in the light source device 3, the light guide 4, the insertion portion 2, or the camera head 5 (such as the imaging surface of the image sensor 513). Furthermore, the filter according to the present disclosure may be disposable. Furthermore, an ND (Neutral Density) filter may be used as the filter according to the present disclosure.

[0082] In the first and second embodiments described above, excitation light L1 is used as the first light according to the present disclosure, but this is not limiting. In addition to excitation light L1, normal observation light such as visible light (broadband light such as white light, or narrowband light such as red light, green light, or blue light) may also be used as the first light according to the present disclosure. Examples of the configuration of the light source device that emits the normal observation light include a configuration including a white LED and 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.

[0083] Furthermore, when two types of first light, excitation light L1 and normal observation light, are used according to the present disclosure, the number of image capture elements 513 may be one, two, or more. For example, when only one image capture element 513 is provided, the excitation light L1 and normal observation light are turned on in a time-division manner, and the image capture element 513 captures images in a time-division manner in accordance with the turn-on timing of the excitation light L1 and the normal observation light. Furthermore, when two image capture elements 513 are provided, a color separation optical device such as a prism is used. Specifically, the color separation optical device is disposed on the second optical path P2 and separates the return light of the normal observation light from the observation target OB that has propagated along the second optical path P2 from the return light of the excitation light L1 (observation target fluorescence LF) from the observation target OB. One of the two image capture elements 513 captures the return light of the normal observation light. The other image sensor 513 captures the return light (observation target fluorescence LF) of the excitation light L1. When the color separation optical device is used, a filter according to the present disclosure may be provided in the color separation optical device. As described above, when the excitation light L1 and normal observation light are used as the first light according to the present disclosure, the filter according to the present disclosure needs to be configured to cut out all light except for the return light of the normal observation light from the subject and the observation target fluorescence LF.

[0084] In the above, we have described a case where two types of light, excitation light L1 and normal observation light, are used as the first light according to the present disclosure. However, even if only excitation light L1 or only normal observation light is used as the first light according to the present disclosure, the number of image sensors 513 may be one, two, or more.

[0085] In the above-described first and second embodiments, the following modifications 1 to 3 may be adopted.

[0086] (Modification 1) Figures 15 to 17 are diagrams illustrating Modification 1 of Embodiments 1 and 2. Specifically, Figure 15 is a diagram showing the shape of filter 13 according to Modification 1, and is a diagram of filter 13 viewed along the optical axis Ax of light incident on filter 13. Figures 16 and 17 correspond to Figure 1. The filter 11 described in Embodiments 1 and 2 above has the same transmission characteristics over the entire surface, but this is not limited to this.

[0087] As shown in FIG. 15 , the filter 13 according to this first modification has a wheel shape that can rotate around a rotation axis RAx and is divided into multiple regions 13A-13D with different transmission characteristics. While this first modification is divided into four regions 13A-13D, any number greater than two may be used. The transmission characteristics of the four regions 13A-13D are set according to the agent or fluorescent dye applied to the observation object OB. The filter 13 is rotated so that the region corresponding to the agent or fluorescent dye applied to the observation object OB is positioned on the optical axis Ax. These regions partially, substantially, or completely suppress light other than the observation object fluorescence LF corresponding to the agent or fluorescent dye applied to the observation object OB.

[0088] The above-described first modification provides the same effects as those of the first and second embodiments, as well as the following effects. The filter 13 according to the first modification has a wheel shape that is rotatable about the rotation axis RAx, and includes the above-described multiple regions 13A to 13D. This allows a single filter 13 to be used with a variety of drugs and fluorescent dyes, improving convenience.

[0089] The configuration of the filter 13 is not limited to the above-described configuration. For example, the four regions 13A to 13D may have different OD values.

[0090] Furthermore, the filter 13 according to this first modification can be applied to surgeries and the like using a plurality of drugs shown in the following Table 1. In Table 1, drugs that are used are marked with "◯" and drugs that are not used are marked with "X".

[0091]

[0092] Here, when fluorescein is irradiated with excitation light L1 in a wavelength band of approximately 470 to 480 nm, it emits fluorescence LF of approximately 520 nm. When ALM-488 is irradiated with excitation light L1 in a wavelength band of approximately 488 nm, it emits fluorescence LF of approximately 530 nm. When LUM-015 is irradiated with excitation light L1 in a wavelength band of approximately 650 nm, it emits fluorescence LF of approximately 675 nm. When 5-ALA is irradiated with excitation light L1 in a wavelength band of approximately 405 nm, it emits fluorescence LF of approximately 530 to 630 nm. When ICG is irradiated with excitation light L1 in a wavelength band of approximately 805 nm, it emits fluorescence LF of approximately 830 nm.

[0093] For example, when performing lymph node dissection during lobectomy for lung cancer, ALM-488 and ICG are used, as shown in Table 1. Specifically, ALM-488 is used to visualize the left recurrent laryngeal nerve, and ICG is used to visualize the lymph nodes. Visualizing the left recurrent laryngeal nerve and lymph nodes in this manner allows for differentiation between the left recurrent laryngeal nerve and lymph nodes, thereby reducing recurrent laryngeal nerve paralysis during lobectomy. Because two drugs, ALM-488 and ICG, are used in this procedure, the medical observation system 1 must be configured to include a first light source 31 that emits excitation light L1 to excite one of the two drugs, and a second light source 32 that emits excitation light L1 to excite the other drug, as shown in FIG. 16 . The first and second light sources 31 and 32 correspond to the first light source according to the present disclosure. Furthermore, when using one of the two drugs, ALM-488 or ICG, which produces a weak observation target fluorescence LF, the medical observation system 1 positions one of the multiple regions 13A-13D in the filter 13 on the optical axis Ax (hereinafter referred to as the first mode), and when using the other drug, positions another of the multiple regions 13A-13D on the optical axis Ax (hereinafter referred to as the second mode).The physician performing the lobectomy can determine the position of either the left recurrent laryngeal nerve or the lymph nodes from the image displayed on the display device 7 in the first mode, and can determine the position of the other of the left recurrent laryngeal nerve and the lymph nodes from the image displayed on the display device 7 in the second mode.

[0094] Furthermore, for example, when performing lateral lymph node dissection in rectal resection for colorectal cancer, ALM-488 and ICG are used, as shown in Table 1. Specifically, ALM-488 is used to visualize the neurovascular bundle, and ICG is used to visualize the lymph nodes. Visualizing the neurovascular bundle and lymph nodes in this manner allows differentiation between the neurovascular bundle and lymph nodes, thereby reducing urinary disorders, defecation disorders, male sexual dysfunction, and motor dysfunction due to nerve damage during rectal resection. Because two drugs, ALM-488 and ICG, are used in this case, the medical observation system 1 must be configured to include a first light source 31 that emits excitation light L1 to excite one of the two drugs, and a second light source 32 that emits excitation light to excite the other drug, as shown in FIG. 16 . The first and second light sources 31 and 32 correspond to the first light source according to the present disclosure. Furthermore, when using one of the two drugs, ALM-488 or ICG, which produces a weak fluorescence LF to be observed, the medical observation system 1 positions one of the multiple regions 13A-13D in the filter 13 on the optical axis Ax (hereinafter referred to as the first mode), and when using the other drug, positions another of the multiple regions 13A-13D on the optical axis Ax (hereinafter referred to as the second mode).The physician performing the rectal resection can determine the position of one of the nerve bundle vascular bundle and lymph node from the image displayed on the display device 7 in the first mode, and can determine the position of the other of the nerve bundle vascular bundle and lymph node from the image displayed on the display device 7 in the second mode.

[0095] Furthermore, for example, in pediatric brain tumor resection, ALM-488 and ICG are used when performing malignant tumor resection, as shown in Table 1. Specifically, ALM-488 is used to visualize nerves, and ICG is used to visualize blood vessels (blood flow). Visualizing nerves and blood vessels in this manner allows for differentiation between malignant tumors, nerves, and blood vessels, preventing cancer recurrence after malignant tumor resection, and preventing damage to nerves and blood vessels during malignant tumor resection. Because two drugs, ALM-488 and ICG, are used in this procedure, a medical observation system 1 must be configured, as shown in FIG. 16 , including a first light source 31 that emits excitation light L1 to excite one of the two drugs, and a second light source 32 that emits excitation light L1 to excite the other drug. The first and second light sources 31 and 32 correspond to the first light source in the present disclosure. Furthermore, when using one of the two drugs, ALM-488 or ICG, which produces a weak fluorescence LF of the object to be observed, the medical observation system 1 positions one of the multiple regions 13A-13D in the filter 13 on the optical axis Ax (hereinafter referred to as the first mode), and when using the other drug, positions another of the multiple regions 13A-13D on the optical axis Ax (hereinafter referred to as the second mode).The physician performing the malignant tumor resection can determine the position of one of the nerves and blood vessels from the image displayed on the display device 7 in the first mode, and can determine the position of the other of the nerves and blood vessels from the image displayed on the display device 7 in the second mode.

[0096] For example, in mastectomy for breast cancer, when removing a malignant tumor and performing axillary lymph node dissection, ALM-488, LUM-015, and ICG are used, as shown in Table 1. That is, nerves such as the intercostobrachial nerves and thoracodorsal nerves are visualized using ALM-488, the malignant tumor is visualized using LUM-015, and the lymph nodes are visualized using ICG. Visualization of nerves, malignant tumors, and lymph nodes in this way makes it possible to distinguish between malignant tumors, nerves, and lymph nodes, thereby reducing nerve damage during mastectomy. In this case, since three drugs, ALM-488, LUM-015, and ICG, are used, the medical observation system 1 must be configured to include a first light source 31 that emits excitation light L1 to excite one of the three drugs, a second light source 32 that emits excitation light L1 to excite one of the other two drugs, and a third light source 33 that emits excitation light L1 to excite the other of the other two drugs, as shown in Fig. 17. The first to third light sources 31 to 33 correspond to the first light source according to the present disclosure. Furthermore, the medical observation system 1 positions one of the multiple regions 13A-13D in the filter 13 on the optical axis Ax when using one of the three drugs, ALM-488, LUM-015, and ICG, which produces a weak fluorescence LF as the observation target (hereinafter referred to as the first mode), and positions two other regions of the multiple regions 13A-13D on the optical axis Ax when using another drug (hereinafter referred to as the second mode).The physician performing the mastectomy can determine the location of at least one of the nerves, malignant tumors, and lymph nodes from the image displayed on the display device 7 in the first mode, and can determine the locations of the other nerves, malignant tumors, and lymph nodes from the image displayed on the display device 7 in the second mode.

[0097] Furthermore, for example, when treating brain tumors using photodynamic diagnosis (PDD), ALM-488 and 5-ALA (5-aminolevulinic acid) are used, as shown in Table 1. Specifically, the tumor vicinity is visualized using fluorescein, the fluorescent dye of ALM-488, and tumor cells are visualized using protoporphyrin (PpIX), which is biosynthesized from 5-ALA. Visualizing tumor cells, including those near the tumor, in this manner allows for safe tumor removal while preventing damage during brain tumor treatment. Because two drugs, ALM-488 and 5-ALA, are used in this case, a medical observation system 1 must be configured, as shown in FIG. 16 , including a first light source 31 that emits excitation light L1 to excite one of the two drugs, and a second light source 32 that emits excitation light L1 to excite the other drug. The first and second light sources 31 and 32 correspond to the first light source in the present disclosure. Furthermore, when using 5-ALA, which of the two drugs, ALM-488 and 5-ALA, produces a weak fluorescence LF, the medical observation system 1 positions one of the multiple regions 13A-13D in the filter 13 on the optical axis Ax (hereinafter referred to as the first mode), and when using ALM-488, positions another of the multiple regions 13A-13D on the optical axis Ax (hereinafter referred to as the second mode).The physician treating the brain tumor can then determine the location of tumor cells from the image displayed on the display device 7 in the first mode, and can determine the location of the area near the tumor from the image displayed on the display device 7 in the second mode.

[0098] Furthermore, for example, when performing transurethral cystectomy in the surgical treatment of superficial urothelial cell carcinoma using photodynamic diagnosis, fluorescein and 5-ALA are used, as shown in Table 1. Specifically, tumors are visualized using PpIX, which is biosynthesized from 5-ALA. However, PpIX has the drawback of visualizing not only tumors but also hypermetabolic inflammatory tissue present in the bladder. Therefore, false positives due to PpIX in hypermetabolic inflammatory tissue are reduced by using fluorescein. In this case, because two drugs, fluorescein and 5-ALA, are used, a medical observation system 1 must be configured, as shown in FIG. 16 , including a first light source 31 that emits excitation light L1 to excite one of the two drugs, and a second light source 32 that emits excitation light L1 to excite the other drug. The first and second light sources 31 and 32 correspond to the first light source in the present disclosure. Furthermore, when using 5-ALA, which of the two drugs, fluorescein and 5-ALA, produces a weak fluorescence LF to be observed, the medical observation system 1 positions one of the multiple regions 13A-13D in the filter 13 on the optical axis Ax (hereinafter referred to as the first mode), and when using fluorescein, positions another of the multiple regions 13A-13D on the optical axis Ax (hereinafter referred to as the second mode).The physician performing the transurethral cystectomy can determine the location of the tumor from the image displayed on the display device 7 in the first mode, and can determine false positives of hypermetabolic inflammatory tissue due to PpIX from the image displayed on the display device 7 in the second mode.

[0099] (Modification 2) FIG. 18 is a diagram illustrating Modification 2 of Embodiments 1 and 2. Specifically, FIG. 18 is a diagram illustrating positions to which the filter 11 according to Modification 2 moves. In Modification 1 described above, the mode (first and second modes) is switched by rotating the filter 13 around the rotation axis RAx, but this is not limited thereto. For example, as in Modification 2 shown in FIG. 18 , by operating a movement mechanism (not shown), the filter 11 is positioned at a first position on the observation optical path P0 (the position where the filter 11 is indicated by a solid line in FIG. 18 ) or at a second position off the observation optical path P0 (the position where the filter 11 is indicated by a dashed-dotted line in FIG. 18 ). Note that in Modification 2, the filter 11 moves between the first and second positions while maintaining an orientation in which the light incident surface of the filter 11 intersects (orthogonal to) the observation optical path P0. The medical observation system 1 then sets the first mode by positioning the filter 11 at the first position. Moreover, the medical observation system 1 is set to the second mode by positioning the filter 11 at the second position.

[0100] According to the second modification described above, the same effects as those of the first and second embodiments described above can be achieved.

[0101] (Variation 3) FIG. 19 is a diagram illustrating Variation 3 of Embodiments 1 and 2. FIG. 19 is a diagram showing positions to which the filter 11 according to Variation 3 moves. In Variation 1 described above, the mode (first and second modes) is switched by rotating the filter 13 around the rotation axis RAx, but this is not limited thereto. For example, as in Variation 3 shown in FIG. 19 , by operating a movement mechanism (not shown), the filter 11 is positioned at a first position on the observation optical path P0 (the position where the filter 11 is indicated by a solid line in FIG. 19 ) or at a second position off the observation optical path P0 (the position where the filter 11 is indicated by a dashed-dotted line in FIG. 19 ). Note that in Variation 3, the filter 11 moves between the first and second positions by rotating around one end side as the rotation center. The medical observation system 1 then sets the first mode by positioning the filter 11 at the first position. Moreover, the medical observation system 1 is set to the second mode by positioning the filter 11 at the second position.

[0102] According to the third modification described above, the same effects as those of the first and second embodiments described above can be achieved.

[0103] (Variation 4) FIGS. 20 and 21 are diagrams illustrating Variation 4 of Embodiments 1 and 2. Specifically, FIG. 20 illustrates the location of the filter 11 according to Variation 4. FIG. 21 illustrates the absorption and emission spectra of LUM-015, the spectrum of excitation light L1, and the wavelength range in which autofluorescence L3 can be generated when the excitation light L1 propagates through the first optical path P1. In FIG. 21 , the horizontal axis represents wavelength [nm], and the vertical axis represents light intensity such as absorbance and fluorescence intensity. In FIG. 21 , the absorption spectrum of LUM-015 is indicated by a dashed line, the emission spectrum of LUM-015 is indicated by a solid line, the spectrum of excitation light L1 is indicated by a dashed line, and the wavelength range in which autofluorescence L3 can be generated is indicated by a two-dot chain line. In this fourth variant, the preferred wavelength of the excitation light L1 and the preferred characteristics of the filter 11 when the filter 11 is arranged on the first optical path P1 as shown in Figure 20 will be explained using the example of using LUM-015 as the drug.

[0104] In order to increase the intensity of the observation target fluorescence LF emitted from the drug, it is preferable that the excitation light L1 has a wavelength that is highly absorbed by the drug. Furthermore, it is preferable that the wavelength of the excitation light L1 includes a wavelength range in which the intensity is at least half of the peak wavelength of the drug's absorption spectrum. Furthermore, it is efficient to set the excitation light L1 to a wavelength between -10 nm and +10 nm from the peak wavelength of the drug's absorption spectrum. Here, the peak wavelength of the absorption spectrum of LUM-015 is approximately 650 nm, as shown in FIG. 21 . Therefore, it is preferable that the wavelength of the excitation light L1 be in the range of 640 to 660 nm.

[0105] Furthermore, as shown in FIG. 21 , the autofluorescence L3 generated when the excitation light L1 propagates through the first optical path P1 is generated at wavelengths longer than the wavelength band of the excitation light L1. Therefore, it is preferable to design the filter 11 to cut off the wavelength band from the peak wavelength of the excitation light L1 +10 nm to the peak wavelength +310 nm. That is, when using LUM-015, it is preferable to design the filter 11 to cut off the wavelength band from 660 to 960 nm. Here, the intensity of the autofluorescence L3 is greater closer to the peak wavelength of the excitation light L1. Therefore, the OD value of the wavelength band cut by the filter 11 may be changed depending on the intensity. For example, the filter 11 is designed so that the OD value from the peak wavelength of the excitation light L1 +10 nm to the peak wavelength +150 nm is greater than the OD value from the peak wavelength +150 nm to the peak wavelength +310 nm. Generally, maintaining a constant OD value within the wavelength band to be cut increases the difficulty of manufacturing, so by changing the OD value within the wavelength band to be cut as described above, the filter 11 can be manufactured more easily and at a lower cost.

[0106] When the filter 11 is disposed on the first optical path P1, it is preferable to design the wavelength bands that are transmitted and cut by the filter 11 as shown in Table 2 below, regardless of whether the drug is LUM-015 or not.

[0107]

[0108] Specifically, the case where only the observation object fluorescence LF is used as the observation object light is as described above. Furthermore, when only white light for normal light observation is used as the observation object light, it is preferable to design the filter 11 to have a wavelength band that transmits a wavelength band that does not impair discrimination in clinical use (for example, a wavelength band of approximately 400 to 700 nm) and a wavelength band that cuts off the wavelength band from the long wavelength end +10 nm to the long wavelength end +310 nm of that wavelength band. Furthermore, when white light for normal light observation and observation object fluorescence LF, which is visible light, are used as the observation object light, it is preferable to design the filter 11 so that the wavelength band that transmits and the band that cuts off are similar to those when only the white light is used as the observation object light. Furthermore, when the observation target light is white light for normal light observation and invisible observation target fluorescence LF, it is preferable to design the filter 11 to have a wavelength band that transmits the peak wavelength of the excitation light and a wavelength band that does not deteriorate discrimination in clinical use (for example, a wavelength band of approximately 400 to 700 [nm]), and to have a wavelength band that cuts off a wavelength band from the peak wavelength of the excitation light +10 [nm] to the peak wavelength +310 [nm]. Note that, if necessary, the filter may be designed to have a wavelength band that cuts off a wavelength band between the peak wavelength of the excitation light -10 [nm] and the long wavelength end +10 [nm] of the wavelength band that does not deteriorate discrimination in clinical use.

[0109] (Variation 5) FIGS. 22 and 23 are diagrams illustrating Variation 5 of Embodiments 1 and 2. Specifically, FIG. 22 illustrates the location of the filter 11 according to Variation 5. FIG. 23 illustrates the absorption and emission spectra of LUM-015 and the wavelength range in which autofluorescence L3 can be generated when second light L2 propagates through the second optical path P2. In FIG. 23, the horizontal axis represents wavelength [nm], and the vertical axis represents absorbance and fluorescence intensity. In FIG. 23, the absorption spectrum of LUM-015 is indicated by a dashed line, the emission spectrum of LUM-015 is indicated by a solid line, and the wavelength range in which autofluorescence L3 can be generated is indicated by a two-dot chain line. In Variation 5, the preferable characteristics of the filter 11 when the filter 11 is disposed on the second optical path P2 as shown in FIG. 22 are described using LUM-015 as a drug. The filter 11 is disposed downstream in the optical path from the excitation light cut filter 511. When the excitation light cut filter 511 is disposed in the insertion section 2, the filter 11 only needs to be disposed downstream in the optical path from the excitation light cut filter 511, and can be disposed inside the insertion section 2, the eyepiece section 21, the camera head 5, or the like.

[0110] As shown in Figure 23, the autofluorescence L3 generated when the second light L2 propagates through the second optical path P2 occurs at wavelengths longer than the peak wavelength of the drug's emission spectrum. Therefore, the filter 11 is preferably designed to cut the wavelength range from the peak wavelength +10 nm to the peak wavelength +310 nm. Furthermore, if the intensity of the target fluorescence L3 is not high, the filter is preferably designed to cut the wavelength range where the intensity is less than half the peak wavelength of the drug's emission spectrum. Furthermore, the OD value is preferably 4 or 5.

[0111] Here, the peak wavelength of the emission spectrum of LUM-015 is approximately 660 [nm], as shown in FIG. 23 . Therefore, it is preferable to design the filter 11 to cut the wavelength band from 670 to 970 [nm]. The OD value of the excitation light cut filter 511 is preferably 3 or higher, with 4 or 5 being more preferable. The OD value of the filter 11 is preferably 1 or higher, with 2 or 3 being more preferable. In this modification 5, the excitation light cut filter 511 and the filter 11 are configured as separate bodies, but it is also possible to have a single filter that has the function of cutting both the excitation light L1 and the autofluorescence L3.

[0112] When the filter 11 is disposed on the second optical path P2, it is preferable to design the wavelength bands that are transmitted and cut by the filter 11 as shown in Table 3 below, regardless of whether the drug is LUM-015 or not.

[0113]

[0114] Specifically, the case where only the observation object fluorescence LF is used as the observation object light is as described above. Furthermore, when only white light for normal light observation is used as the observation object light, it is preferable to design the filter 11 to have a wavelength band that transmits a wavelength band that does not impair discrimination in clinical use (for example, a wavelength band of approximately 400 to 700 nm) and a wavelength band that cuts off the wavelength band from the long wavelength end +10 nm to the long wavelength end +310 nm of that wavelength band. Furthermore, when white light for normal light observation and observation object fluorescence LF, which is visible light, are used as the observation object light, it is preferable to design the filter 11 so that its transmission band and cutoff band are similar to those when only the white light is used as the observation object light. Furthermore, when the observation target light is white light for normal light observation and invisible observation target fluorescence LF, it is preferable to design the filter 11 to have a wavelength band that transmits the peak wavelength of the drug's emission spectrum and a wavelength band that does not deteriorate discrimination in clinical use (e.g., a wavelength band of approximately 400 to 700 [nm]), and to have a wavelength band that cuts off a wavelength band from the peak wavelength of the drug's emission spectrum +10 [nm] to the peak wavelength +310 [nm]. Note that, if necessary, the filter may be designed to have a wavelength band that cuts off a wavelength band between the peak wavelength of the drug's emission spectrum -10 [nm] and the long wavelength end +10 [nm] of the wavelength band that does not deteriorate discrimination in clinical use.

[0115] In the above-described modifications 4 and 5, the absorption spectrum and emission spectrum of the drug measured in an experiment using ethanol as a solvent differ from the spectrum in, for example, blood in the body, and therefore the wavelength band and OD value cut off by the filter 11 must be set in consideration of the clinical situation.

[0116] (Variation 6) The medical observation system according to Variation 6 is a medical observation system that uses a so-called videoscope (flexible endoscope) that has an imaging unit at the tip of an insertion section. For ease of explanation, the medical observation system 1 according to Variation 6 will be referred to as medical observation system 1B below.

[0117] Fig. 24 is a diagram illustrating a sixth modification of embodiments 1 and 2. As shown in Fig. 24 , the medical observation system 1B includes an endoscope 100B 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, a light source device 3 that emits a first light such as excitation light L1 from the tip of the endoscope 100B, a control device 9 that processes the captured image output from the endoscope 100B, 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.

[0118] 24, the endoscope 100B includes a flexible, elongated insertion section 2B, an operation section 101 connected to the base end side of the insertion section 2B and accepting various operations, and a universal cord 102 extending from the operation section 101 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. 24, the insertion section 2B includes a tip section 22, a freely bendable bending section 23 connected to the base end side of the tip section 22 and made up of a plurality of bending pieces, and a flexible, elongated flexible tube section 24 connected to the base end side of the bending section 23.

[0119] Although not specifically shown in the drawings, the tip portion 22 has a built-in configuration substantially similar to that of the camera head 5 described in the above-mentioned first and second embodiments. An image captured by the tip portion 22 (image pickup element) is output to the control device 9 via the operation unit 101 and the universal cord 102.

[0120] Furthermore, in the medical observation system 1B, although not specifically shown in the drawings, filters similar to the filters 11 and 12 described in the first and second embodiments are disposed on the observation optical paths, which include a first optical path along which first light such as excitation light L1 propagates from the light source device 3 to the observation object, and a second optical path along which second light, which is return light of the first light, propagates from the observation object to the image sensor.

[0121] Even when the configuration of the sixth modification described above is adopted, the same effects as those of the first and second embodiments described above can be achieved.

[0122] (Variation 7) The medical observation system according to Variation 7 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 organism) or the surface of a subject (surface of a living organism), which is the observation target. For ease of explanation, the medical observation system 1 according to Variation 7 will be referred to as medical observation system 1C below.

[0123] Fig. 25 is a diagram illustrating a seventh modification of the first and second embodiments. As shown in Fig. 25, the medical observation system 1C comprises a surgical microscope 14 that captures images for observing a subject and outputs the captured images, a control device 9 that processes the captured images output from the surgical microscope 14, and a display device 7 that is connected to the control device 9 via a second transmission cable 8 and displays images based on video signals processed by the control device 9.

[0124] As shown in Fig. 25 , the surgical microscope 14 includes a microscope unit 141 that magnifies and captures a minute portion of a subject and outputs the captured image, a support unit 142 that is connected to the base end of the microscope unit 141 and includes an arm that rotatably supports the microscope unit 141, and a base unit 143 that rotatably holds the base end of the support unit 142 and is movable on the floor. The control device 9 is also installed on the base unit 143 as shown in Fig. 25 . Although not specifically shown, the base unit 143 also has installed thereon a light source device 3 that emits a first light, such as excitation light L1, from the surgical microscope 14 to the object of observation. The base unit 143 may be configured to support the support unit 142 by being fixed to a ceiling, wall, or the like, rather than being movable on the floor.

[0125] Although not specifically shown in the drawings, the microscope unit 141 has a built-in configuration that is substantially the same as that of the camera head 5 described in the above-mentioned Embodiments 1 and 2. The image captured by the microscope unit 141 (image capture element) is output to the control device 9 via a first transmission cable 6 wired along the support unit 142.

[0126] Furthermore, in the medical observation system 1C, although not specifically shown in the drawings, filters similar to the filters 11 and 12 described in the first and second embodiments are disposed on the observation optical paths, which include a first optical path along which first light such as excitation light L1 propagates from the light source device 3 to the observation object, and a second optical path along which second light, which is return light of the first light, propagates from the observation object to the image sensor.

[0127] Even when the configuration of the seventh modified example described above is adopted, the same effects as those of the above-described embodiment are achieved.

[0128] (Variation 8) FIGS. 26 and 27 are diagrams illustrating Variation 8 of the embodiment. Specifically, FIG. 26 is a side view of the ring light 15. The ring light 15 corresponds to an open-field observation device for observing biological tissue. The open-field observation device is a device used in open surgery. FIG. 27 is a front view of the ring light 15 (left side in FIG. 26). In Variation 8, in addition to the insertion section 2 described in the above-mentioned embodiments 1 and 2, the ring light 15 shown in FIGS. 26 and 27 is detachably connected to the camera head 5. That is, depending on the user's usage state, as shown in FIG. 26, the insertion section 2 or the ring light 15 may be connected to the camera head 5.

[0129] The ring light 15 is not inserted into the observation object OB like the insertion section 2, but supplies a first light to the surgical site and captures a second light (subject image) that is a return light of the first light from the surgical site. As shown in Figures 26 and 27, the ring light 15 includes an illumination section 151 and a subject image capture section 152 that captures the subject image.

[0130] 26 and 27 , 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.

[0131] 27 , 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 each irradiate the first 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.

[0132] The subject image capture unit 152 extends along the optical axis Ax. An optical system configured with one or more lenses is provided within the subject image capture unit 152, and focuses second light (subject image) that is irradiated from the multiple illumination lenses 1512 and passes through the surgical site. A connector 1521 is provided at the end on the proximal side (right side in FIG. 26 ) 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.

[0133] Although not specifically shown in the drawings, in Modification 8, filters similar to the filters 11 and 12 described in the above-mentioned Embodiments 1 and 2 are disposed on an observation optical path that includes a first optical path along which first light such as excitation light L1 propagates from the light source device 3 to the observation object, and a second optical path along which second light, which is return light of the first light, propagates from the observation object to the image sensor. More specifically, the filters are provided at a connection between the light guide 4 and the ring light 15, or on the front surface of the subject image capture unit 152 (front surface on the upstream side of the optical path).

[0134] Even when the configuration of the eighth modified example described above is adopted, the same effects as those of the above-described embodiment are achieved.

[0135] Note that the following configurations also fall within the technical scope of the present disclosure: (1) A medical observation system comprising: a light source device that emits first light; an image sensor that captures second light, which is return light of the first light from an observation object irradiated with the first light; and a filter that is disposed on an observation optical path that includes a first optical path along which the first light propagates from the light source device to the observation object and a second optical path along which the second light propagates from the observation object to the image sensor, and that partially, substantially, or completely suppresses unnecessary light, including autofluorescence, generated by a member that forms the observation optical path by at least one of the first light and the second light. (2) The medical observation system described in (1), in which the filter is disposed on the first optical path and partially, substantially, or completely suppresses light other than the first light emitted from the light source device. (3) The medical observation system according to (2), further comprising: an optical endoscope that includes a portion of the first optical path and a portion of the second optical path, and that irradiates the first light onto the observation target and takes in the second light; and a light guide that includes a portion of the first optical path and that propagates the first light emitted from the light source device to the optical endoscope, wherein the filter is disposed at an end of the light source device from which the first light is emitted, an end of the light guide from which the first light is emitted, or an end of the optical endoscope from which the first light is emitted. (4) The medical observation system according to any one of (1) to (3), wherein the filter is disposed on the second optical path and partially, substantially, or completely suppresses light other than light for the observation target that is included in the second light. (5) The medical observation system according to (4), wherein the filter is disposed on the second optical path at a position where the second light becomes approximately parallel light. (6) The medical observation system described in (4) further includes an optical scope including a portion of the first optical path and a portion of the second optical path, irradiating the first light onto the object of observation and capturing the second light, and a camera head including a portion of the second optical path, capturing the second light emitted from the eyepiece of the optical scope and including the image sensor, wherein the filter is disposed at the entrance end of the second light in the optical scope, the entrance end of the second light in the camera head, or the image sensor.(7) The medical observation system according to any one of (1) to (6), wherein the filter partially, substantially, or completely suppresses unnecessary light, including the autofluorescence, thereby making the S / N ratio of the signal value of the light under observation in the pixel signal obtained by imaging with the image sensor greater than 1. (8) The medical observation system according to any one of (1) to (7), wherein the first light includes excitation light that excites a substance contained in the object of observation, and the second light includes light under observation that is fluorescence emitted from the substance contained in the object of observation in response to irradiation with the excitation light. (9) The medical observation system according to any one of (1) to (8), wherein the filter is configured to be detachable from a member that constitutes the observation optical path. (10) The medical observation system according to any one of (1) to (9), further comprising: an optical scope including a portion of the first optical path and a portion of the second optical path, irradiating the observation target with the first light and capturing the second light; and a camera head including a portion of the second optical path, capturing the second light emitted from an eyepiece of the optical scope and including the image sensor, wherein the filter is disposed on the second optical path between the eyepiece of the optical scope and the camera head. (11) The medical observation system according to any one of (1) to (10), further comprising: an optical scope including a portion of the first optical path and a portion of the second optical path, irradiating the observation target with the first light and capturing the second light; and a light guide including a portion of the first optical path, transmitting the first light emitted from the light source device to the optical scope, wherein the filter is disposed on the first optical path between the optical scope and the light guide. (12) A medical observation system according to any one of (1) to (11), further comprising an optical scope that includes a portion of the first optical path and a portion of the second optical path, irradiates the first light onto the observation object, and takes in the second light, and the filter is disposed on the first optical path at an exit end of the optical scope that irradiates the first light onto the observation object.(13) The medical observation system according to any one of (1) to (9), further comprising: an optical scope that includes a portion of the first optical path and a portion of the second optical path, and that irradiates the first light onto the observation object and takes in the second light; a light guide that includes a portion of the first optical path and propagates the first light emitted from the light source device to the optical scope; and a camera head that includes a portion of the second optical path, that takes in the second light emitted from the eyepiece of the optical scope and includes the image sensor, wherein the filters comprise a first filter disposed on the second optical path between the eyepiece of the optical scope and the camera head, and a second filter disposed on the first optical path between the optical scope and the light guide, or at the exit end of the optical scope that irradiates the first light onto the observation object. (14) The medical observation system according to any one of (1) to (13), wherein the light source device includes a first light source that emits the first light, and the first light source is composed of one or more light sources. (15) The medical observation system according to any one of (1) to (14), wherein the light source device includes a first light source that emits the first light, and the first light source is composed of an LED or a semiconductor laser. (16) A filter disposed on an observation optical path including a first optical path along which the first light propagates from the light source device that emits the first light to an observation object, and a second optical path along which second light, which is return light of the first light from the observation object irradiated with the first light, propagates, and which partially, substantially, or completely suppresses unnecessary light, including autofluorescence, generated from a member forming the observation optical path by at least one of the first light and the second light. (17) The filter described in (16) is arranged on the first optical path and partially, substantially, or completely suppresses light other than the first light emitted from the light source device.(18) The filter according to (17), wherein the filter is disposed at the first light exit end of the light source device, a portion of the first optical path, and a portion of the second optical path, at the first light exit end of an optical scope that irradiates the first light onto the observation target and takes in the second light, or at the first light exit end of a light guide that includes a portion of the first optical path and propagates the first light emitted from the light source device to the optical scope. (19) The filter according to any one of (16) to (18), wherein the filter is disposed on the second optical path and partially, substantially, or completely suppresses light other than light for the observation target that is contained in the second light. (20) The filter according to (19), wherein the filter is disposed on the second optical path at a position where the second light becomes approximately parallel light. (21) The filter according to (19), wherein the filter is disposed at an entrance end of the second light in an optical scope that includes a part of the first optical path and a part of the second optical path and irradiates the observation target with the first light and takes in the second light, at an entrance end of the second light in a camera head that includes a part of the second optical path and takes in the second light emitted from an eyepiece of the optical scope and includes an image sensor that captures the second light, or at an image capturing surface of the image sensor. (22) The filter according to any one of (16) to (21), wherein the filter partially, substantially, or completely suppresses unnecessary light including the autofluorescence, thereby increasing the S / N ratio of the signal value of the observation target light in a pixel signal obtained by image capturing by the image sensor that captures the second light to be greater than 1. (23) The filter according to any one of (16) to (22), wherein the first light includes excitation light that excites a substance contained in the observation object, and the second light includes observation object light that is fluorescence emitted from the substance contained in the observation object by irradiation with the excitation light. (24) The filter according to any one of (16) to (23), wherein the filter is configured to be detachable from a member that constitutes the observation optical path.(25) The filter according to any one of (16) to (24), wherein the filter is disposed on the second optical path between an eyepiece of an optical scope that includes a part of the first optical path and a part of the second optical path, and that irradiates the observation target with the first light and takes in the second light, and a camera head that includes a part of the second optical path, and that takes in the second light emitted from the eyepiece of the optical scope and includes an image sensor that captures the second light. (26) The filter according to any one of (16) to (25), wherein the filter is disposed on the first optical path between an optical scope that includes a part of the first optical path and a part of the second optical path, and that irradiates the observation target with the first light and takes in the second light, and a light guide that includes a part of the first optical path and that propagates the first light emitted from the light source device to the optical scope. (27) The filter is a filter described in any one of (16) to (26), which includes a part of the first optical path and a part of the second optical path on the first optical path, and is disposed at an exit end of an optical scope that irradiates the first light onto the object of observation and takes in the second light, thereby irradiating the first light onto the object of observation. (28) The filter described in any one of (16) to (24) includes a first filter arranged on the second optical path between an eyepiece of an optical scope that includes a part of the first optical path and a part of the second optical path, and that irradiates the first light onto the object of observation and takes in the second light, and a camera head that includes a part of the second optical path, that takes in the second light emitted from the eyepiece of the optical scope and includes an image sensor that images the second light; and a second filter arranged on the first optical path between the optical scope and a light guide that includes a part of the first optical path and propagates the first light emitted from the light source device to the optical scope, or at the exit end of the optical scope that irradiates the first light onto the object of observation.(29) An optical scope that irradiates an observation target with first light and captures second light, which is return light of the first light from the observation target irradiated with the first light, the optical scope having a portion of a first optical path along which the first light propagates from a light source device that emits the first light to the observation target and a portion of a second optical path along which the second light propagates, and is equipped with a filter that partially, substantially, or completely suppresses unnecessary light, including autofluorescence, generated by at least one of the first light and the second light from components that form an observation optical path including the first optical path and the second optical path. (30) The optical scope described in (29) above, wherein the filter is disposed on the first optical path and partially, substantially, or completely suppresses light other than the first light emitted from the light source device. (31) The optical scope described in (30) above, wherein the filter is disposed at an end of the optical scope from which the first light exits. (32) The telescope according to any one of (29) to (31), wherein the filter is disposed on the second optical path and partially, substantially, or completely suppresses light other than light to be observed that is contained in the second light. (33) The telescope according to (32), wherein the filter is disposed on the second optical path at a position where the second light becomes approximately parallel light. (34) The telescope according to (32), wherein the filter is disposed at an end of the telescope where the second light is incident. (35) The telescope according to any one of (29) to (34), wherein the filter partially, substantially, or completely suppresses unnecessary light including the autofluorescence, thereby increasing the S / N ratio of the signal value of the light to be observed in the pixel signal obtained by imaging with an image sensor that captures the second light to greater than 1. (36) The telescope according to any one of (29) to (35), wherein the first light includes excitation light that excites a substance contained in the observation target, and the second light includes observation target light that is fluorescence emitted from the substance contained in the observation target when irradiated with the excitation light. (37) The telescope according to any one of (29) to (36), wherein the filter is configured to be detachable from the telescope. (38) The telescope according to any one of (29) to (37), wherein the filter is disposed in an eyepiece of the telescope on the second optical path.(39) The telescope according to any one of (29) to (37), wherein the filter comprises a first filter disposed on the second optical path in an eyepiece of the telescope, and a second filter disposed on the first optical path at an exit end of the telescope that irradiates the first light onto the observation target. (40) A light source device that emits first light, the light source device having a first optical path along which the first light propagates, and comprising a filter that partially, substantially, or completely suppresses unwanted light, including autofluorescence, generated by the first light from a component that forms the first optical path. (41) The light source device according to (40), wherein the filter is disposed at the exit end of the light source device from which the first light is emitted. (42) The light source device according to (40) or (41), wherein the filter partially, substantially, or completely suppresses unnecessary light including the autofluorescence, thereby making the S / N ratio of the signal value of the light under observation in the pixel signal obtained by imaging with an imaging element that captures second light, which is return light of the first light from the object of observation irradiated with the first light, greater than 1. (43) The light source device according to any one of (40) to (42), wherein the first light includes excitation light that excites a substance contained in the object of observation, and the second light, which is return light of the first light from the object of observation irradiated with the first light, includes light under observation that is fluorescence emitted from the substance contained in the object of observation by irradiation with the excitation light. (44) The light source device according to any one of (40) to (43), wherein the filter is configured to be detachable from the light source device. (45) The light source device according to any one of (40) to (44), including a first light source that emits the first light, wherein the first light source is composed of one or more light sources. (46) The light source device according to any one of (40) to (45), including a first light source that emits the first light, wherein the first light source is composed of an LED or a semiconductor laser. (47) A light guide that propagates the first light emitted from a light source device, the light guide having a part of a first optical path along which the first light propagates from the light source device to an observation object, and including a filter that partially, substantially, or completely suppresses unnecessary light including autofluorescence generated from a member that forms the first optical path by the first light.(48) The light guide according to (47), wherein the filter is disposed at an output end of the light guide from which the first light is emitted. (49) The light guide according to (47) or (48), wherein the filter partially, substantially, or completely suppresses unnecessary light including the autofluorescence, thereby increasing the S / N ratio of the signal value of the observation target light in a pixel signal obtained by imaging with an image sensor that captures second light, which is return light of the first light from the observation target irradiated with the first light, to greater than 1. (50) The light guide according to any one of (47) to (49), wherein the first light includes excitation light that excites a substance contained in the observation target, and the second light, which is return light of the first light from the observation target irradiated with the first light, includes observation target light that is fluorescence emitted from a substance contained in the observation target by irradiation with the excitation light. (51) The light guide according to any one of (47) to (50), wherein the filter is configured to be detachable from the light guide. (52) A camera head having an insertion section connected to the insertion section that is inserted into an observation target and that captures second light, which is return light of the first light from the observation target irradiated with the first light, and an image sensor that captures the second light, the camera head having a part of a second optical path along which the second light propagates from the observation target to the image sensor, and a filter that partially, substantially, or completely suppresses unnecessary light, including autofluorescence, generated from components that form an observation optical path including the first optical path and the second optical path along which the first light propagates from a light source device that emits the first light to the observation target. (53) The camera head according to (52), wherein the filter is disposed on the second optical path at a position where the second light becomes approximately parallel light. (54) The camera head according to (52) or (53), wherein the filter is disposed at an end of the camera head where the second light enters. (55) A camera head described in any one of (52) to (54), wherein the filter partially, substantially, or completely suppresses unnecessary light, including the autofluorescence, thereby increasing the S / N ratio of the signal value of the light to be observed in the pixel signal obtained by imaging with the imaging element to greater than 1.(56) The camera head according to any one of (52) to (55), wherein the first light includes excitation light that excites a substance contained in the observation target, and the second light includes observation target light that is fluorescence emitted from the substance contained in the observation target when irradiated with the excitation light. (57) The camera head according to any one of (52) to (56), wherein the filter is configured to be detachable from the camera head. (58) A color separation optical device that separates incident light into light of different wavelength bands, the color separation optical device comprising a filter that partially, substantially, or completely suppresses unnecessary light, including autofluorescence, generated from members that form observation optical paths, the observation optical paths including a first optical path along which the first light propagates from a light source device that emits first light to an observation target, and a second optical path along which second light, which is return light of the first light from the observation target irradiated with the first light, propagates. (59) The color separation optical device according to (58), wherein the filter partially, substantially, or completely suppresses unnecessary light including the autofluorescence, thereby making the S / N ratio of the signal value of the light under observation in the pixel signal obtained by imaging by an image sensor that captures the second light greater than 1. (60) The color separation optical device according to (58) or (59), wherein the first light includes excitation light that excites a substance contained in the object of observation, and the second light includes light under observation that is fluorescence emitted from the substance contained in the object of observation when irradiated with the excitation light. (61) An image sensor in which a filter is provided on an imaging surface that partially, substantially, or completely suppresses unnecessary light including autofluorescence generated from members that form an observation optical path, including a first optical path along which the first light propagates from a light source device that emits the first light to the object of observation, and a second optical path along which second light that is return light of the first light from the object of observation irradiated with the first light propagates. (62) The image sensor described in (61) in which the filter partially, substantially, or completely suppresses unnecessary light including the autofluorescence, thereby increasing the S / N ratio of the signal value of the light to be observed in the pixel signal obtained by imaging with the image sensor to greater than 1.(63) The imaging element described in (61) or (62), wherein the first light includes excitation light that excites a substance contained in the object of observation, and the second light includes observation object light, which is fluorescence emitted from the substance contained in the object of observation when irradiated with the excitation light.

[0136] DESCRIPTION OF SYMBOLS 1, 1A to 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 11 Filter (first filter) 12 Second filter 13 Filter 13A to 13D Area 14 Surgical microscope 15 Ring light 21 Eyepiece 22 Tip 23 Bending section 24 Flexible tube section 31 First light source 41 Emission end 51 Imaging section 100B Endoscope 101 Operation section 102 Universal cord 141 Microscope section 142 Support section 143 Base section 151 Illumination section 152 Subject image capture section 211 Emission end 511 Excitation light cut filter 512 Lens unit 513 Image pickup element 1511 Housing 1512 Illumination lens Ar1 to Ar3 Wavelength band Ax Optical axis L1 Excitation light L2 Second light L3 Autofluorescence LF Observation object fluorescence OB Observation object P0 Observation optical path P1 First optical path P2 Second optical path

Claims

1. A medical observation system comprising: a light source device that emits a first light; an image sensor that captures a second light which is a return light of the first light from an observation object irradiated with the first light; and a filter that is disposed on an observation optical path including a first optical path along which the first light propagates from the light source device to the observation object, and a second optical path along which the second light propagates from the observation object to the image sensor, and that partially, substantially, or completely suppresses unnecessary light including autofluorescence generated from a member forming the observation optical path by at least one of the first light and the second light.

2. The medical observation system according to claim 1, wherein the filter is disposed on the first optical path and partially, substantially, or completely suppresses light other than the first light emitted from the light source device.

3. A medical observation system as described in claim 2, further comprising: an optical scope including a portion of the first optical path and a portion of the second optical path, irradiating the first light onto the observation object and taking in the second light; and a light guide including a portion of the first optical path, transmitting the first light emitted from the light source device to the optical scope, wherein the filter is disposed at the first light emission end of the light source device, the first light emission end of the light guide, or the first light emission end of the optical scope.

4. The medical observation system according to claim 1, wherein the filter is disposed on the second optical path and partially, substantially, or completely suppresses light other than the light to be observed that is contained in the second light.

5. A medical observation system according to claim 4, wherein the filter is disposed on the second optical path at a position where the second light becomes substantially parallel light.

6. A medical observation system as described in claim 4, further comprising: an optical scope including a portion of the first optical path and a portion of the second optical path, irradiating the first light onto the object to be observed and capturing the second light; and a camera head including a portion of the second optical path, capturing the second light emitted from an eyepiece of the optical scope and including the image sensor, wherein the filter is disposed at an entrance end of the second light in the optical scope, an entrance end of the second light in the camera head, or an imaging surface of the image sensor.

7. A medical observation system as described in claim 1, wherein the filter partially, substantially, or completely suppresses unnecessary light including the autofluorescence, thereby making the S / N ratio of the signal value of the light under observation in the pixel signal obtained by imaging with the image sensor greater than 1.

8. A medical observation system as described in claim 1, wherein the first light includes excitation light that excites a substance contained in the observation object, and the second light includes observation object light which is fluorescence emitted from the substance contained in the observation object when irradiated with the excitation light.

9. A medical observation system according to claim 1, wherein the filter is configured to be freely attached and detached to a member that constitutes the observation optical path.

10. A medical observation system as described in claim 1, further comprising: an optical scope including a portion of the first optical path and a portion of the second optical path, irradiating the first light onto the object to be observed and capturing the second light; and a camera head including a portion of the second optical path, capturing the second light emitted from an eyepiece of the optical scope and including the image sensor, wherein the filter is disposed on the second optical path between the eyepiece of the optical scope and the camera head.

11. A medical observation system as described in claim 1, further comprising: an optical scope including a portion of the first optical path and a portion of the second optical path, irradiating the first light onto the object of observation and taking in the second light; and a light guide including a portion of the first optical path, transmitting the first light emitted from the light source device to the optical scope, wherein the filter is disposed on the first optical path between the optical scope and the light guide.

12. A medical observation system as described in claim 1, further comprising an optical scope that includes a portion of the first optical path and a portion of the second optical path, irradiates the first light onto the object to be observed and takes in the second light, wherein the filter is disposed on the first optical path at an exit end of the optical scope that irradiates the first light onto the object to be observed.

13. The medical observation system of claim 1, further comprising: an optical scope including a portion of the first optical path and a portion of the second optical path, irradiating the first light onto the observation object and taking in the second light; a light guide including a portion of the first optical path, transmitting the first light emitted from the light source device to the optical scope; and a camera head including a portion of the second optical path, taking in the second light emitted from an eyepiece of the optical scope and including the image sensor, wherein the filters comprise: a first filter disposed on the second optical path between the eyepiece of the optical scope and the camera head; and a second filter disposed on the first optical path, between the optical scope and the light guide, or at the emission end of the optical scope that irradiates the first light onto the observation object.

14. The medical observation system according to claim 1, wherein the light source device includes a first light source that emits the first light, and the first light source is composed of one or more light sources.

15. The medical observation system according to claim 1, wherein the light source device includes a first light source that emits the first light, and the first light source is configured with an LED or a semiconductor laser.

16. A filter that is disposed on an observation optical path including a first optical path along which the first light propagates from a light source device that emits first light to an object of observation, and a second optical path along which second light, which is return light of the first light from the object of observation irradiated with the first light, propagates, and that partially, substantially, or completely suppresses unnecessary light, including autofluorescence, generated from a component that forms the observation optical path by at least one of the first light and the second light.

17. An optical scope that irradiates an observation object with a first light and captures a second light which is a return light of the first light from the observation object irradiated with the first light, the optical scope having a part of a first optical path along which the first light propagates from a light source device that emits the first light to the observation object, and a part of a second optical path along which the second light propagates, and is equipped with a filter that partially, substantially, or completely suppresses unnecessary light including autofluorescence generated by at least one of the first light and the second light from a component that forms an observation optical path including the first optical path and the second optical path.

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