Medical observation system, filter, and optical viewing tube

Abstract

A medical observation system 1 comprises: a light source device 3 that emits first excitation light; an imaging element 512 for imaging first fluorescence emitted from a substance contained in an observation object OB, the emission caused by irradiation with the first excitation light; and a filter 11 that is disposed on an observation light path P1 on which the first fluorescence propagates from the observation object OB to the imaging element 512, and that suppresses light in a first wavelength band, which is at least a partial wavelength band of the first fluorescence wavelength band, so that a first output signal value from the imaging element 512 that received the first fluorescence approaches a prescribed signal value.

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 excitation light, which is narrow-band 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 that are difficult to recognize through the observation target fluorescence. Therefore, fluorescence observation can be used for various purposes and applications, such as identifying lesions.

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

[0004] Furthermore, there is a demand for improved performance in 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 can improve performance in fluorescence observation.

[0006] In order to solve the above-mentioned problems and achieve the object, the medical observation system according to the present disclosure includes a light source device that emits first excitation light, an image sensor that captures an image of first fluorescence emitted from a substance contained in an observation object when irradiated with the first excitation light, and a filter that is disposed on an observation optical path along which the first fluorescence propagates from the observation object to the image sensor, and that suppresses light of a first wavelength band that is at least a part of the wavelength band of the first fluorescence so that a first output signal value from the image sensor that has received the first fluorescence approaches a predetermined signal value.

[0007] Furthermore, the filter according to the present disclosure is disposed on an observation optical path along which the first fluorescence propagates from an observation object irradiated with first excitation light to an image sensor that images the first fluorescence emitted from a substance contained in the observation object in response to the irradiation of the first excitation light, and suppresses light in a first wavelength band that is at least a part of the wavelength band of the first fluorescence so that a first output signal value from the image sensor that receives the first fluorescence approaches a predetermined signal value.

[0008] Furthermore, the optical scope according to the present disclosure is an optical scope that irradiates an observation object with first excitation light and captures first fluorescence emitted from a substance contained in the observation object as a result of the irradiation of the first excitation light, and is equipped with a filter that is arranged on an observation optical path along which the first fluorescence propagates and that suppresses light in a first wavelength band that is at least a part of the wavelength band of the first fluorescence so that a first output signal value from an imaging element that receives the first fluorescence approaches a predetermined signal value.

[0009] The medical observation system, filter, and optical endoscope according to the present disclosure can improve performance in fluorescence observation.

[0010] FIG. 1 is a diagram illustrating the configuration of a medical observation system according to an embodiment. FIG. 2 is a diagram illustrating the function of a filter. FIG. 3 is a diagram illustrating the effects of the embodiment. FIG. 4 is a diagram illustrating a first modification of the embodiment. FIG. 5 is a diagram illustrating a second modification of the embodiment. FIG. 6 is a diagram illustrating a third modification of the embodiment. FIG. 7 is a diagram illustrating a fourth modification of the embodiment. FIG. 8 is a diagram illustrating a fourth modification of the embodiment. FIG. 9 is a diagram illustrating a fifth modification of the embodiment. FIG. 10 is a diagram illustrating a sixth modification of the embodiment. FIG. 11 is a diagram illustrating a seventh modification of the embodiment. FIG. 12 is a diagram illustrating an eighth modification of the embodiment. FIG. 13 is a diagram illustrating a ninth modification of the embodiment. FIG. 14 is a diagram illustrating a tenth modification of the embodiment. FIG. 15 is a diagram illustrating an eleventh modification of the embodiment. FIG. 16 is a diagram illustrating a twelfth modification of the embodiment. FIG. 17 is a diagram illustrating a twelfth modification of the embodiment.

[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] [Configuration of Medical Observation System] Fig. 1 is a diagram showing the configuration of a medical observation system 1 according to an embodiment. In this embodiment, the medical observation system 1 is a medical endoscope system that uses an endoscope to observe an observation object OB (inside a living 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] In this embodiment, the insertion section 2 is configured as a rigid endoscope and corresponds to the optical endoscope according to the present disclosure. That is, the insertion section 2 has an elongated shape that is rigid as a whole or has a flexible portion and a rigid portion, and is inserted into the observation object OB. The insertion section 2 includes an optical system configured using one or more lenses that focuses the return light (subject image) from the observation object OB.

[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 excitation light to one end of the light guide 4 and a second light source 32 ( FIG. 1 ) that supplies second excitation light to one end of the light guide 4 under the control of a control device 9. The first excitation light may be visible light or invisible light. Similarly, the second excitation light may be visible light or invisible light. The first light source 31 may be configured with an LED (Light Emitting Diode) or a semiconductor laser. Similarly, the second light source 32 may be configured with an LED or a semiconductor laser. The number of first light sources 31 that emit the first excitation light may be one or more. Similarly, the number of second light sources 32 that emit the second excitation light may be one or more.

[0015] Here, examples of substances contained in the observation object OB that are excited by the first and second excitation lights 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 that can be applied to the observation target OB include "coumarine," "Cy3," "DyLight547," "GE3126," "metal nanoclusters," "oxacarbocyanine," "rhodamine," "riboflavin," "fluorescein," "AlexaFluor 488," "AlexaFluor 660," "AlexaFluor 680," "AlexaFluor 700," "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," and "cyanine." Examples of such dyes include "IRDye 800CW", "IRDye 800RS", "IRDye 800BK", "Nervelight", "OTL-38 (Pafolacianine)", "Polymethine", "VivoTag-S750", "ASP5354", "Xanthene", and "LUM-015".

[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, 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 and second excitation light beams supplied from the light source device 3 (first and second light sources 31, 32) from one end to the other end, supplying the first and second excitation light beams to the insertion section 2. The first and second excitation light beams supplied to the insertion section 2 are each emitted from the tip of the insertion section 2 and irradiated onto the observation object OB. The first and second excitation light beams irradiated onto the observation object OB and returned from the observation object OB (subject images) are each collected by an optical system within the insertion section 2. The returned light of the first excitation light includes not only the first excitation light reflected by the observation object OB, but also fluorescence (hereinafter referred to as first fluorescence) emitted from a substance contained in the observation object OB when the first excitation light is irradiated onto the observation object OB and the substance is excited. In addition, the return light of the second excitation light includes not only the second excitation light reflected by the observation object OB, but also fluorescence (hereinafter referred to as second fluorescence) emitted from a substance contained in the observation object OB when the second excitation light is irradiated onto the observation object OB and the substance is excited.

[0021] The camera head 5 is detachably connected to the base 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 a lens unit 511 and an imaging element 512.

[0022] The lens unit 511 forms an image of the return light (subject image) of the first and second excitation light condensed by the insertion portion 2 on the light receiving surface of the image sensor 512 .

[0023] The image sensor 512 is composed of a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) that receives the return light (subject image) of the first and second excitation light formed by the lens unit 511 and converts it into an electrical signal.

[0024] Then, under the control of the control device 9, the imaging unit 51 outputs pixel signals obtained by imaging.

[0025] One end CN1 of the first transmission cable 6 is detachably connected to the control device 9. The other end CN2 of the first transmission cable 6 is detachably connected to the camera head 5. The other end CN2 is not limited to being detachably connected to the camera head 5, but may also be fixed to the camera head 5. The first transmission cable 6 transmits 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.

[0026] 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.

[0027] 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 .

[0028] 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.

[0029] 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).

[0030] Specifically, the control device 9 generates a video signal by performing various processes 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.

[0031] 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.

[0032] Generally, in the medical observation system 1, it is difficult to adjust the signal value based on the fluorescence (first and second fluorescence) generated by the image sensor 512 that receives the fluorescence, due to the influence of the following factors (1) to (4):

[0033] (1) Drugs Generally, the intensity of fluorescent light emitted from a drug varies depending on the type and dosage of the drug. The type of drug administered to the observation target OB is selected according to the observation target OB (cancer, blood, lymph, etc.). Furthermore, in order to image the fluorescence emitted from the drug in the medical observation system 1, drugs are selected that allow the wavelength of the excitation light that excites the drug to be separated from the wavelength of the fluorescence emitted by the drug. Drugs selected in this manner emit different amounts of fluorescent light. Furthermore, while the amount of fluorescent light 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 amount of fluorescent light by selecting the type of drug and adjusting the dosage. As a result, it is difficult to adjust the signal value based on the fluorescence imaged by the image sensor 512 by selecting the type of drug and adjusting the dosage.

[0034] (2) Observation Object The amount of fluorescent light 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 fluorescent light 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 fluorescent light 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 fluorescent light received by the image sensor 512 changes depending on its spread, size, and depth. In other words, it is difficult to adjust the amount of fluorescent light 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 fluorescence imaged by the image sensor 512 depending on the type and condition of the observation object OB.

[0035] (3) Light Source Device The intensity of the fluorescence varies depending on the intensity of the excitation light emitted from the light source device 3. Increasing the intensity of the excitation light may require adjusting the power supplied to the light source device 3. However, the power that can be supplied to the light source device 3 is limited by the upper limit of the power required to operate the entire medical observation system 1. Furthermore, the adjustment of the intensity of the excitation light must take into account factors such as heat generation in components constituting the optical path of the excitation light (e.g., heat generation between the light guide 4 and the insertion section 2), compatibility with the laser class, the amount of light energy received by the observation target OB or surrounding living tissue (high light energy levels pose a risk of burns), and the rate of fading of the fluorescence emitted from the pharmaceutical. Furthermore, the intensity of the excitation light can also be adjusted by changing the number of excitation light sources installed in the light source device 3. However, the number of light sources may affect the size of the light source device 3. The size of the light source device 3 may be limited by the size of a cart used to transport the light source device 3. In other words, it is difficult to adjust the intensity of the fluorescence by adjusting the intensity of the excitation light. As a result, it is difficult to adjust the signal value based on the fluorescence imaged by the image sensor 512 by adjusting the amount of excitation light.

[0036] (4) Image Sensor The fluorescence-based signal value generated by the image sensor 512 varies depending on the amount of fluorescence received by the image sensor 512. To adjust the fluorescence-based signal value, it is desirable to select an image sensor 512 with optimal sensitivity and configuration for capturing the fluorescence. However, the image sensor 512 may be required not only to output an image for fluorescence observation based on receiving fluorescence in a specific wavelength band, but also to output an image for normal light observation based on receiving visible light, such as white light. Furthermore, the image sensor 512 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 and invisible light. Furthermore, even when the same drug is used, the amount of fluorescence may change depending on the procedure or the observation target OB, and the image sensor 512 may be required to output an image for fluorescence observation that corresponds to such changes in the amount of fluorescence. In such cases, the image sensor 512 must be selected to accommodate these observations, and it may not be possible to use an image sensor with optimal characteristics for capturing fluorescence in a specific wavelength band. Furthermore, the image sensor 512 is disposed inside the camera head 5, but because the size and weight of the camera head 5 are appropriate for observation, the type of image sensor 512, including its size, may be limited. Note that the image sensor 512 is not limited to being disposed inside the camera head 5, and even when disposed at the tip of a rigid endoscope or a flexible endoscope, the size and weight are appropriate for observation, and the type of image sensor 512, including its size, may be limited. In other words, it is difficult to adjust the signal value based on the fluorescence captured by the image sensor 512 by selecting the type of image sensor 512.

[0037] As described above, the signal value based on the fluorescence imaged by the image sensor 512 is determined within the above-mentioned constraints and cannot be easily adjusted.

[0038] Further, suppose that first and second drugs are administered to the observation object OB. The second drug is a drug that emits a weak amount of fluorescence. The first drug is a drug that emits a strong amount of fluorescence. For the second drug, which has poor fluorescence efficiency, the signal value based on the fluorescence captured by the image capture element 512 is adjusted by combining parameters and measures such as increasing the amount of emitted excitation light, increasing the emission time of the excitation light, lengthening the exposure time of the image capture element 512, and increasing the electrical gain that amplifies the output signal from the image capture element 512 through signal processing. On the other hand, for the first drug, which has good fluorescence efficiency, the signal value based on the fluorescence captured by the image capture element 512 is adjusted by combining parameters and measures such as decreasing the emission amount of the excitation light, decreasing the emission time of the excitation light, shortening the exposure time of the image capture element 512, and decreasing the electrical gain that amplifies the output signal from the image capture element 512 through signal processing. However, there are limitations to the means and parameters that can be realized using the light source device 3, the image sensor 512, and the signal processing, and there is a problem in that it is not always possible to realize the optimal means and parameters for the first and second drugs using a single device.

[0039] In this embodiment, in order to address the above-mentioned problem, a filter 11 is employed. This filter 11 is disposed on the observation optical path P1 (FIG. 1) along which the return light (subject image) of the first and second excitation light propagates from the observation object OB to the image sensor 512. More specifically, the filter 11 is disposed between the eyepiece 21 and the camera head 5 (FIG. 1). The filter 11 is detachably connected to the eyepiece 21.

[0040] The filter 11 has a structure in which an inorganic material is optically deposited on a substrate that emits little autofluorescence, such as synthetic quartz, and has a bandpass function, a shortpass function, or a longpass function. The function of the filter 11 will be described in detail in the section "Function of the Filter" below.

[0041] [Regarding Filter Function] Next, the function of the above-mentioned filter 11 will be described. Fig. 2 is a diagram illustrating the function of the filter 11. Specifically, Fig. 2 is a diagram illustrating the spectra of the first excitation light LE1, the second excitation light LE2, the first fluorescence LF1, and the second fluorescence LF2. The line LI indicates the transmission characteristics (filter characteristics) of the filter 11. In Fig. 2, the horizontal axis indicates wavelength [nm], and the vertical axis indicates light density [W / nm].

[0042] FIG. 2 illustrates a case where the light density of the first fluorescence LF1 is greater than the light density of the second fluorescence LF2. In this embodiment, the filter 11 has an excitation light cutting function that cuts off the first and second excitation lights LE1 and LE2 contained in the return light (subject image) of the first and second excitation lights LE1 and LE2, and a fluorescence suppression function that suppresses the first fluorescence LF1 contained in the return light. Here, the term "cut" refers to partially, substantially, or completely suppressing light. The same meaning applies to the "cut" described below. Note that (a) of FIG. 2 illustrates a case where the filter 11 has only the excitation light cutting function out of the excitation light cutting function and the fluorescence suppression function. (b) of FIG. 2 illustrates a case where the filter 11 has both the excitation light cutting function and the fluorescence suppression function.

[0043] Specifically, the pumping light cutting function is as follows: As shown by line LI in Fig. 2, the filter 11 has the pumping light cutting function of cutting light of wavelengths λa to λb, which is the wavelength band of the first pumping light LE1, and cutting light of wavelengths λc to λd, which is the wavelength band of the second pumping light LE2.

[0044] The filter 11 has the following fluorescence suppression function: As indicated by the line LI in Fig. 2(b) , the filter 11 has a fluorescence suppression function of suppressing light in a first wavelength band (wavelength λe or greater), which is a part of the wavelength band of the first fluorescence LF1.

[0045] As shown by the line LI in FIG. 2B, the filter 11 transmits substantially or completely all light other than the wavelength bands of wavelengths λa to λb, wavelengths λc to λd, and wavelengths equal to or greater than λe.

[0046] When the filter 11 does not have a fluorescence suppression function (FIG. 2(a)), the signal value of the output signal from the image sensor 512 that receives the first fluorescence LF1 (hereinafter referred to as the first output signal S1) is greater than the signal value of the output signal from the image sensor 512 that receives the second fluorescence LF2 (hereinafter referred to as the second output signal S2). On the other hand, when the filter 11 has a fluorescence suppression function (FIG. 2(b)), the signal value of the first output signal S1 approaches the signal value of the second output signal S2. Note that the signal value of the first output signal S1 only needs to approach the signal value of the second output signal S2, and it does not matter whether the two signal values ​​are the same or not. That is, the filter 11 suppresses light in a first wavelength band, which is at least a part of the wavelength band of the first fluorescence LF1, by using its fluorescence suppression function so that the signal value of the first output signal S1 approaches a predetermined signal value (the signal value of the second output signal S2).

[0047] The present embodiment described above has the following advantages. The medical observation system 1 according to the first embodiment is provided with a filter 11 that is disposed on the observation optical path P1 and that suppresses light of a first wavelength band, which is at least a part of the wavelength band of the first fluorescence LF1, so that the signal value of the first output signal S1 approaches a predetermined signal value (the signal value of the second output signal S2). That is, when fluorescence observation using the first fluorescence LF1 and fluorescence observation using the second fluorescence LF2 are performed using the same system, the signal values ​​of the first and second output signals S1 and S2 can be made to be approximately the same, which simplifies the control process in the control device 9 and improves performance in fluorescence observation.

[0048] FIG. 3 is a diagram illustrating the effects of the embodiment. Specifically, FIG. 3(a) 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). FIG. 3(b) 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. 3, the horizontal axis represents wavelength [nm], and the vertical axis represents optical density (OD value). For ease of explanation, FIG. 3 focuses only on the wavelength band from wavelength λa to λb as the transmission characteristics of the filter 11.

[0049] The transmission 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 return light of the first and second excitation light LE1, LE2 enters the filter 11 as approximately parallel light. When the return light enters as approximately parallel light in this manner, the transmission characteristics of the filter 11 become substantially the transmission characteristics of the design value, as shown in FIG. 3( a).

[0050] 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. 3B. 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. 3A) to a gradual rise and fall (FIG. 3B). Furthermore, the OD value of the cut wavelength band may also decrease.

[0051] 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 the first fluorescence LF1 can be suppressed according to the design value.

[0052] Furthermore, the filter 11 may be detachably connected to the eyepiece 21. In this detachable configuration, if a plurality of filters 11 with different wavelength bands or light levels to be cut are prepared according to the drug or fluorescent dye applied to the observation object OB, the filter 11 according to the drug, fluorescent dye, or other observation object substance to be used can be selected and used.

[0053] Incidentally, when the first and second excitation light beams LE1 and LE2 propagate through the optical path P2 ( FIG. 1 ), and when the return light beams of the first and second excitation light beams LE1 and LE2 propagate through the observation optical path P1, the components forming the optical paths P1 and P2 (hereinafter referred to as autofluorescence-generating components) may be irradiated with the first and second excitation light beams LE1 and LE2 or the return light beams, causing autofluorescence to be generated from the autofluorescence-generating components. The optical path P2 is an optical path that traces a path from the light source device 3 to the light guide 4 to the insertion portion 2 to the observation object OB. Examples of the 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. Such autofluorescence has a wavelength band that includes the wavelength band of the observation target fluorescence (first and second fluorescence LF1, LF2) in fluorescence observation, and becomes noise during the fluorescence observation. Note that such autofluorescence may also be generated by irradiating the observation target OB with the first and second excitation light LE1, LE2. In response to this, the filter 11 has a fluorescence suppression function that suppresses light with wavelengths λe or greater. Therefore, the filter 11 can suppress autofluorescence with wavelengths λe or greater, which is part of the autofluorescence described above that becomes noise during fluorescence observation, thereby enabling the fluorescence observation to be performed satisfactorily.

[0054] 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 embodiments, the number of filters according to the present disclosure is not limited to one, but may be two or more. For example, in the above-described embodiments, only one filter 11 (hybrid filter) is provided for the first and second fluorescence LF1 and LF2. However, a filter may be provided for each of the first and second fluorescence LF1 and LF2. If the filter 11 is a hybrid filter, the number of filters can be reduced, thereby achieving a smaller and lighter overall system. Furthermore, the location of the filter according to the present disclosure is not limited to the location described in the above-described embodiments, as long as it is on the observation optical path P1. As long as it is on the observation optical path P1, the filter according to the present disclosure may be provided, for example, in the insertion section 2 or in the camera head 5 (such as the imaging surface of the image sensor 512). Furthermore, when the number of filters according to the present disclosure is two or more, all of the filters may be disposed in the same position, or each filter may be disposed in a different position.

[0055] In the above-described embodiment, the predetermined signal value according to the present disclosure is not limited to the signal value of the second output signal S2. For example, the predetermined signal value according to the present disclosure may be a signal value that can suppress the fluorescence intensity of the agent within the imageable range of the image sensor 512. In other words, a value smaller than the signal value at which the pixels of the image sensor 512 saturate may be the predetermined signal value according to the present disclosure. Furthermore, while multiple agents are used in the above-described embodiment, a configuration using only one agent may also be used. Furthermore, for example, the predetermined signal value according to the present disclosure may be a signal value set based on brightness-related information that specifies the brightness during fluorescence observation. The brightness-related information includes at least one or more of the type of observation target OB (cancer, blood, lymph, etc.), the type of agent, the surgical procedure, and the equipment constituting the system. In other words, even when the same agent is used, the fluorescence intensity will vary depending on, for example, the type of observation target OB or the surgical procedure. Therefore, the predetermined signal value according to the present disclosure may be a signal value that matches the need to perform fluorescence observation at a specific brightness. Furthermore, for example, a signal value obtained with the same drug and under the same conditions using a previous model or a different model may be used as the predetermined signal value according to the present disclosure.

[0056] In the above-described embodiment, the following modifications 1 to 10 may be adopted.

[0057] (Variation 1) Fig. 4 is a diagram illustrating Variation 1 of the embodiment. Specifically, Fig. 4 is a diagram corresponding to Fig. 2. More specifically, Fig. 4(a) is a diagram showing the spectra of the first and second fluorescence LF1, LF2 immediately before passing through the filter 11 according to Variation 1. Fig. 4(b) is a diagram showing the spectra of the first and second fluorescence LF1, LF2 after passing through the filter 11 according to Variation 1.

[0058] In the above-described embodiment, the filter 11 has both the excitation light cutting function and the fluorescence suppression function, but this is not limiting. For example, as in the filter 11 according to the first modification shown by line LI in Fig. 4(b), a configuration having only the fluorescence suppression function of both the excitation light cutting function and the fluorescence suppression function may be employed. That is, in the first modification, a filter having the excitation light cutting function is separately provided on the upstream side of the optical path of the filter 11 according to the first modification.

[0059] Even when the filter 11 according to the first modified example described above is employed, the same effects as those of the above-described embodiment are achieved.

[0060] (Variation 2) Fig. 5 is a diagram illustrating Variation 2 of the embodiment. Specifically, Fig. 5 is a diagram corresponding to Fig. 2. Variation 2 is a variation of the above-described embodiment in that an ND (Neutral Density) filter is used as the filter 11. Note that the filter 11 may also be an electronic ND filter that is electrically adjusted. Specifically, as shown by line LI in Fig. 5(b), the filter 11 according to Variation 2 has the same excitation light cutting function as the above-described embodiment, and also has the following fluorescence suppression function.

[0061] The filter 11 according to the second modification has a fluorescence suppression function, as indicated by the line LI in FIG. 5B , that reduces the transmittance of light in a first wavelength band (wavelengths λb to λf) that includes the entire wavelength band of the first fluorescence LF1, thereby producing first fluorescence LF1'. In this case, the hue of the first fluorescence LF1' is maintained relative to that of the first fluorescence LF1. Note that the state in which the hue is maintained means that the hue difference in a uniform color space such as L*a*b* is approximately 5 or less.

[0062] In the filter 11 according to the second modification, the signal value of the first output signal S1 approaches the signal value of the second output signal S2, as in the above-described embodiment.

[0063] Even when the filter 11 according to the second modified example described above is employed, the same effects as those of the above-described embodiment are achieved.

[0064] (Variation 3) Fig. 6 is a diagram illustrating Variation 3 of the embodiment. Specifically, Fig. 6 is a diagram corresponding to Fig. 2. More specifically, Fig. 6(a) is a diagram showing the spectra of the first and second fluorescence LF1, LF2 immediately before passing through the filter 11 according to Variation 3. Fig. 6(b) is a diagram showing the spectra of the first and second fluorescence LF1, LF2 after passing through the filter 11 according to Variation 3.

[0065] In the above-described second modification, the filter 11 has both an excitation light cutting function and a fluorescence suppression function, but this is not limiting. For example, as in the filter 11 according to the third modification shown by line LI in (b) of Fig. 6, a configuration having only the fluorescence suppression function of both the excitation light cutting function and the fluorescence suppression function may be employed. That is, in the third modification, a filter having an excitation light cutting function is separately provided on the upstream side of the optical path of the filter 11 according to the third modification.

[0066] Even when the filter 11 according to the third modification described above is employed, the same effects as those of the second modification described above can be achieved.

[0067] (Modification 4) Modification 4 changes the configurations of the imaging unit 51 and the imaging element 512, and the function of the filter 11, compared to the embodiment described above. For ease of explanation, the imaging unit 51, the imaging element 512, and the filter 11 according to Modification 4 will be referred to below as the imaging unit 51A, the imaging element 512A, and the filter 11A, respectively.

[0068] 7 and 8 are diagrams illustrating a fourth modification of the embodiment. Specifically, FIG. 7 is a diagram illustrating the configuration of an image capturing unit 51A according to the fourth modification. For ease of explanation, the lens unit 511 is not illustrated in FIG. 7 . (a) and (c) of FIG. 8 are diagrams illustrating the spectra of the second excitation light LE2 and the second fluorescence LF2. (b) and (d) of FIG. 8 are diagrams illustrating the spectra of the first excitation light LE1 and the first fluorescence LF1. Line LI1 indicates the transmission characteristics (filter characteristics) of the filter 11A. Line LI2 indicates the transmission characteristics (filter characteristics) of the excitation light cut filter 514. In FIG. 8 , the horizontal axis represents wavelength [nm], and the vertical axis represents light density [W / nm].

[0069] FIG. 8 illustrates a case where the light density of the first fluorescent light LF1 is greater than the light density of the second fluorescent light LF2, as in the above-described embodiment.

[0070] The image capturing section 51A according to the fourth modification includes a lens unit 511, a prism 513, an excitation light cut filter 514, and an image capturing element 512A, as shown in FIG.

[0071] The prism 513 is disposed on the observation optical path P1 and separates the return light of the first and second excitation light LE1, LE2 that propagates along the observation optical path P1 and passes through the lens unit 511 into light of two wavelength bands. In the fourth modification, the prism 513 separates the return light into visible light and infrared light (invisible light). Also, Fig. 7 illustrates a case in which the first excitation light LE1 and the first fluorescence LF1 are included in infrared light, and the second excitation light LE2 and the second fluorescence LF2 are included in visible light.

[0072] The excitation light cut filter 514 cuts out the second excitation light LE2 from the visible light that has passed through the lens unit 511 and then separated by the prism 513. Specifically, the excitation light cut filter 514 cuts out light of wavelengths λc to λd, which is the wavelength band of the second excitation light LE2, as shown by the line LI2 in Figures 8(a) and 8(c). Note that the excitation light cut filter 514 transmits substantially or completely all light outside the wavelength band of wavelengths λc to λd, as shown by the line LI2 in Figures 8(a) and 8(c).

[0073] The image sensor 512A according to the fourth modification includes first and second image sensors 5121 and 5122. The image sensor 512A is not limited to two image sensors, and may include three or more image sensors. The types (sensitivity, size, resolution, etc.) of these image sensors may be the same or different.

[0074] The first image pickup element 5121 is configured by a CCD or CMOS, and picks up an image of the infrared light separated by the prism 513 .

[0075] The second image sensor 5122 is configured by a CCD, a CMOS, or the like, and captures an image of the second fluorescence LF2 that is part of the visible light separated by the prism 513 and passes through the excitation light cut filter 514 .

[0076] As shown in FIG. 7 , the filter 11A according to the fourth modification is disposed between the prism 513 and the first image sensor 5121. The filter 11A has a configuration in which an inorganic material is optically deposited on a substrate, such as synthetic quartz, that emits little autofluorescence, and has a bandpass function, a shortpass function, or a longpass function. The filter 11A has an excitation light cutting function that cuts out the first excitation light LE1 contained in the infrared light separated by the prism 513, and a fluorescence suppression function that suppresses the first fluorescence LF1 contained in the returned light. Note that (b) of FIG. 8 illustrates a case in which the filter 11A has only the excitation light cutting function, out of the excitation light cutting function and the fluorescence suppression function. (d) of FIG. 8 illustrates a case in which the filter 11A has both the excitation light cutting function and the fluorescence suppression function.

[0077] Specifically, the pumping light cutting function is as follows: As shown by the line LI1 in Figures 8(b) and 8(d), the filter 11A has the pumping light cutting function of cutting light of wavelengths λa to λb, which is the wavelength band of the first pumping light LE1, and cutting light of wavelengths λc to λd, which is the wavelength band of the second pumping light LE2.

[0078] The filter 11A has the following fluorescence suppression function: As indicated by a line LI1 in (d) of Fig. 8, the filter 11A has a fluorescence suppression function of suppressing light in a first wavelength band (wavelength λe or greater), which is a part of the wavelength band of the first fluorescence LF1.

[0079] As indicated by the line LI1 in FIG. 8(d), the filter 11A transmits substantially or completely all light other than the wavelength bands of wavelengths λa to λb and wavelengths equal to or greater than λe.

[0080] When the filter 11A does not have a fluorescence suppression function (FIGS. 8A and 8B), the signal value of the first output signal S1 from the first image sensor 5121 that receives the first fluorescence LF1 is greater than the signal value of the second output signal S2 from the second image sensor 5122 that receives the second fluorescence LF2. On the other hand, when the filter 11A has a fluorescence suppression function (FIGS. 8C and 8D), the signal value of the first output signal S1 approaches the signal value of the second output signal S2. Note that the signal value of the first output signal S1 only needs to approach the signal value of the second output signal S2, and it does not matter whether the two signal values ​​are the same or not. That is, the filter 11A suppresses light in a first wavelength band, which is at least a part of the wavelength band of the first fluorescence LF1, by using its fluorescence suppression function so that the signal value of the first output signal S1 approaches a predetermined signal value (the signal value of the second output signal S2).

[0081] Even when the configuration of the fourth modified example described above is adopted, the same effects as those of the above-described embodiment are achieved.

[0082] In the above-described fourth modification, the first excitation light LE1 and the first fluorescence LF1 are included in infrared light, and the second excitation light LE2 and the second fluorescence LF2 are included in visible light. However, this is not limiting. The first and second excitation lights LE1, LE2 and the first and second fluorescence LF1, LF2 may be invisible light. When observing the observation target OB using visible light such as white light, an image sensor that captures visible light may be provided in addition to the two image sensors that capture invisible light described above.

[0083] Furthermore, in the fourth modification example described above, the imaging unit 51A may function as a stereo camera. In this case, for example, the first imaging element 5121 that captures the first fluorescence LF1 functions as an imaging element for the left eye, and the second imaging element 5122 that captures the second fluorescence LF2 functions as an imaging element for the right eye. Then, in a two-dimensional mode that displays two-dimensional images, an image captured by one of the first and second imaging elements 5121 and 5122 is displayed. In this configuration, by disposing a filter according to the present disclosure on the upstream side of the optical path of at least one of the first and second imaging elements 5121 and 5122, it is possible to obtain the same effects as in the above-described embodiment, and also to correct the difference in sensitivity between the first and second imaging elements 5121 and 5122 using the filter.

[0084] (Variation 5) Fig. 9 is a diagram illustrating Variation 5 of the embodiment. Specifically, Fig. 9 is a diagram corresponding to Fig. 8. More specifically, (a) of Fig. 9 and (c) of Fig. 9 are diagrams illustrating the spectrum of the second fluorescence LF2 after passing through the excitation light cut filter 514. (b) of Fig. 9 is a diagram illustrating the spectrum of the first fluorescence LF1 immediately before passing through the filter 11A according to Variation 5. (d) of Fig. 9 is a diagram illustrating the spectrum of the first fluorescence LF1 after passing through the filter 11A according to Variation 5.

[0085] In the above-described fourth modification, the filter 11A has both the excitation light cutting function and the fluorescence suppression function, but this is not limited thereto. For example, as in the filter 11A according to the fifth modification shown by the line LI1 in (d) of Fig. 9, a configuration having only the fluorescence suppression function of both the excitation light cutting function and the fluorescence suppression function may be adopted. That is, in the fifth modification, a filter having the excitation light cutting function is separately provided on the upstream side of the optical path of the filter 11A according to the fifth modification.

[0086] Even when the filter 11A according to the fifth modification described above is employed, the same effects as those of the fourth modification described above can be achieved.

[0087] (Variation 6) Fig. 10 is a diagram illustrating Variation 6 of the embodiment. Specifically, Fig. 10 is a diagram corresponding to Fig. 8. Variation 6 is a variation of Variation 4 described above in which an ND filter is used as filter 11A. Specifically, as shown by line LI1 in Fig. 10(d), filter 11A according to Variation 6 has the same excitation light cutting function as in Variation 4 described above, and also has the following fluorescence suppression function.

[0088] The filter 11A according to the sixth modification has a fluorescence suppression function, as indicated by the line LI1 in (d) of Fig. 10, in which the transmittance of light in a first wavelength band (wavelengths λb to λf) that includes the entire wavelength band of the first fluorescence LF1 is reduced to produce first fluorescence LF1'. In this case, the hue of the first fluorescence LF1' is maintained relative to that of the first fluorescence LF1. Note that the state in which the hue is maintained means that the hue difference in a uniform color space such as L*a*b* is approximately 5 or less.

[0089] In the filter 11A according to the sixth modification, as in the fourth modification, the signal value of the first output signal S1 approaches the signal value of the second output signal S2.

[0090] Even when the filter 11A according to the sixth modification described above is employed, the same effects as those of the fourth modification described above can be achieved.

[0091] (Variation 7) Fig. 11 is a diagram illustrating Variation 7 of the embodiment. Specifically, Fig. 11 is a diagram corresponding to Fig. 8. More specifically, (a) of Fig. 11 and (c) of Fig. 11 are diagrams illustrating the spectrum of the second fluorescence LF2 after passing through the excitation light cut filter 514. (b) of Fig. 11 is a diagram illustrating the spectrum of the first fluorescence LF1 immediately before passing through the filter 11A according to Variation 7. (d) of Fig. 11 is a diagram illustrating the spectrum of the first fluorescence LF1 after passing through the filter 11A according to Variation 7.

[0092] In the sixth modification, the filter 11A has both the excitation light blocking function and the fluorescence suppression function, but this is not limiting. For example, as in the filter 11A according to the seventh modification shown by the line LI1 in (d) of Fig. 11, a configuration having only the fluorescence suppression function of both the excitation light blocking function and the fluorescence suppression function may be adopted. That is, in the seventh modification, a filter having the excitation light blocking function is separately provided on the upstream side of the optical path of the filter 11A according to the seventh modification.

[0093] Even when the filter 11A according to the seventh modification described above is employed, the same effects as those of the sixth modification described above can be achieved.

[0094] (Variation 8) Fig. 12 is a diagram illustrating Variation 8 of the embodiment. Specifically, Fig. 12 is a diagram corresponding to Fig. 1. The configuration described in the above embodiment may be applied to surgery using multiple drugs as shown in Table 1 below. In Table 1, drugs that are used are marked with "O" and drugs that are not used are marked with "X".

[0095]

[0096] Here, fluorescein emits fluorescence in a wavelength band of approximately 520 nm when irradiated with excitation light in a wavelength band of approximately 470-480 nm. Furthermore, ALM-488 emits fluorescence in a wavelength band of approximately 530 nm when irradiated with excitation light in a wavelength band of approximately 488 nm. Furthermore, LUM-015 emits fluorescence L2 in a wavelength band of approximately 675 nm when irradiated with excitation light in a wavelength band of approximately 650 nm. Furthermore, 5-ALA emits fluorescence in a wavelength band of approximately 530-630 nm when irradiated with excitation light in a wavelength band of approximately 405 nm. Furthermore, ICG emits fluorescence L2 in a wavelength band of approximately 830 nm when irradiated with excitation light in a wavelength band of approximately 805 nm.

[0097] 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. In this case, one of the two drugs, ALM-488 and ICG, is excited by one of the first and second excitation lights. The other of the two drugs, ALM-488 and ICG, is excited by the other of the first and second excitation lights. Note that filter 11 transmits the fluorescence from the one of the two drugs, ALM-488 and ICG, which emits weaker fluorescence (corresponding to the second fluorescence according to the present disclosure). Furthermore, the filter 11 suppresses at least a part of the wavelength band of the fluorescence (corresponding to the first fluorescence according to the present disclosure) from the other drug (corresponding to the first drug according to the present disclosure) so that the output signal value from the image sensor 512 that receives the fluorescence approaches a predetermined signal value. The doctor performing the lobectomy can then ascertain the positions of the left recurrent laryngeal nerve and lymph nodes from the image displayed on the display device 7.

[0098] Furthermore, for example, when performing lateral 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. Visualization of the neurovascular bundle and lymph nodes allows differentiation between the neurovascular bundle and lymph nodes, thereby reducing urinary disorders, defecation disorders, male sexual dysfunction, motor dysfunction, and the like, caused by nerve damage during rectal resection. In this case, one of the two agents, ALM-488 and ICG, is excited by one of the first and second excitation lights. The other of the two agents, ALM-488 and ICG, is excited by the other of the first and second excitation lights. The filter 11 transmits the fluorescence from one of the two drugs, ALM-488 and ICG, which emits weaker fluorescence (corresponding to the second fluorescence according to the present disclosure). The filter 11 also suppresses at least a portion of the wavelength band of the fluorescence from the other drug (corresponding to the first drug according to the present disclosure) so that the output signal value from the image sensor 512 that receives the received light approaches a predetermined signal value. The physician performing the rectal resection can then determine the locations of the nerve and vascular bundles and lymph nodes from the image displayed on the display device 7.

[0099] 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). Visualization of nerves and blood vessels in this manner allows 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. In this case, one of the two agents, ALM-488 and ICG, is excited by one of the first and second excitation lights. The other of the two agents, ALM-488 and ICG, is excited by the other of the first and second excitation lights. Note that filter 11 transmits the fluorescence from the agent with weaker fluorescence (corresponding to the second fluorescence according to the present disclosure) between ALM-488 and ICG. Furthermore, the filter 11 suppresses at least a part of the wavelength band of the fluorescence (corresponding to the first fluorescence according to the present disclosure) from the other drug (corresponding to the first drug according to the present disclosure) so that the output signal value from the image sensor 512 that receives the fluorescence approaches a predetermined signal value. The doctor performing the malignant tumor resection can then ascertain the positions of nerves and blood vessels from the image displayed on the display device 7.

[0100] For example, when performing a mastectomy for breast cancer to remove a malignant tumor and perform axillary lymph node dissection, ALM-488, LUM-015, and ICG are used, as shown in Table 1. Specifically, ALM-488 is used to visualize nerves such as the intercostobrachial nerves and thoracodorsal nerves, LUM-015 is used to visualize the malignant tumor, and ICG is used to visualize the lymph nodes. Visualizing the nerves, malignant tumor, and lymph nodes in this manner allows for differentiation between the malignant tumor, nerves, and lymph nodes, thereby reducing nerve damage during mastectomy. Because three agents, ALM-488, LUM-015, and ICG, are used in this procedure, a medical observation system 1B is required, as shown in FIG. 12, which includes first to third light sources 31 to 33 that emit excitation light for each of the three agents. The filter 11 transmits fluorescence from at least one of the three drugs, ALM-488, LUM-015, and ICG, which emits weak fluorescence (corresponding to the second fluorescence according to the present disclosure). The filter 11 also suppresses at least a portion of the wavelength band of the fluorescence from the other drugs (corresponding to the first fluorescence according to the present disclosure) so that the output signal value from the image sensor 512 that receives the received fluorescence approaches a predetermined signal value. The physician performing the mastectomy can then determine the locations of nerves, malignant tumors, and lymph nodes from the image displayed on the display device 7.

[0101] 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 area near the tumor is visualized using fluorescein, the fluorescent dye of ALM-488, and tumor cells are visualized using protoporphyrin (PpIX), which is biosynthesized from 5-ALA. This visualization of tumor cells, including those near the tumor, allows for safe tumor removal and prevents damage during brain tumor treatment. In this case, one of the two drugs, ALM-488 and 5-ALA, is excited by one of the first and second excitation lights. The other of the two drugs, ALM-488 and 5-ALA, is excited by the other of the first and second excitation lights. Of the two drugs, ALM-488 and 5-ALA, filter 11 transmits the fluorescence from 5-ALA (corresponding to the second fluorescence according to the present disclosure), which is the weaker fluorescence. Furthermore, filter 11 suppresses at least a portion of the wavelength band of the fluorescence from ALM-488 (corresponding to the first drug according to the present disclosure) (corresponding to the first fluorescence according to the present disclosure) so that the output signal value from the image sensor 512 that receives the fluorescence approaches a predetermined signal value. Thus, a physician treating a brain tumor can determine the location of tumor cells and the vicinity of the tumor from the image displayed on display device 7.

[0102] 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, one of the two agents, fluorescein and 5-ALA, is excited by one of the first and second excitation lights. The other of the two agents, fluorescein and 5-ALA, is excited by the other of the first and second excitation lights. Note that filter 11 transmits the fluorescence from 5-ALA, which has the weakest fluorescence (corresponding to the second fluorescence according to the present disclosure). Furthermore, filter 11 suppresses at least a portion of the wavelength band of the fluorescence (corresponding to the first fluorescence according to the present disclosure) from fluorescein (corresponding to the first drug according to the present disclosure) so that the output signal value from image sensor 512 that receives the fluorescence approaches a predetermined signal value. The physician performing the transurethral cystectomy can then ascertain the location of the tumor and any false positives of hypermetabolic inflammatory tissue due to PpIX from the image displayed on display device 7.

[0103] 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.

[0104] (Modification 9) Fig. 13 is a diagram illustrating Modification 9 of the embodiment. In the above-described embodiment, the camera head 5 may function as a stereo camera. For ease of explanation, the camera head 5 according to Modification 9 will be referred to as camera head 5C below. That is, the camera head 5C captures right-eye observation light (right-eye subject image) and left-eye observation light (left-eye subject image) that have parallax with each other.

[0105] Here, as the insertion section 2, in addition to a general scope (a scope in which one optical path is set within the scope), a twin-eye relay type or monocular split-pupil type scope as shown below may be used.

[0106] A twin-lens relay scope has two parallel optical paths within the scope. Each optical path is provided with its own optical system. The twin-lens relay scope captures and emits observation light for the right and left eyes, each with a parallax between them, through the two optical systems (see, for example, Japanese Patent Laid-Open Publication No. 6-160731).

[0107] Furthermore, a monocular split-pupil scope has a single optical path within the scope. An optical system is disposed along this optical path. A pupil division unit is disposed at the pupil position of the optical system, dividing the light beam within the pupil into two regions. A monocular split-pupil scope takes in observation light through the optical system, and then separates the observation light into right-eye and left-eye observation light having a parallax therebetween and emits the separated light (see, for example, Japanese Patent Application Laid-Open No. 6-59199).

[0108] As shown in FIG. 13, the camera head 5C includes a right-eye lens unit 511R, a right-eye imaging module 512CR, a left-eye lens unit 511L, and a left-eye imaging module 512CL.

[0109] As shown in FIG. 13, the right-eye lens unit 511R and the right-eye imaging module 512CR are each disposed on an observation optical path P1R along which right-eye observation light propagates.

[0110] As shown in FIG. 13, the right-eye lens unit 511R is composed of a plurality of lenses, prisms, etc., and captures a right-eye subject image via the insertion portion 2 and guides the right-eye subject image to the right-eye imaging module 512CR.

[0111] The right-eye imaging module 512CR includes at least one imaging element configured by a CCD, a CMOS, or the like, and captures a right-eye subject image guided by the right-eye lens unit 511R.

[0112] As shown in FIG. 13, the left-eye lens unit 511L and the left-eye imaging module 512CL are each disposed on an observation optical path P1L along which left-eye observation light propagates.

[0113] As shown in FIG. 13, the left-eye lens unit 511L is composed of a plurality of lenses, prisms, etc., and captures a left-eye subject image via the insertion portion 2 and guides the left-eye subject image to the left-eye imaging module 512CL.

[0114] The left-eye imaging module 512CL includes at least one imaging element configured by a CCD, a CMOS, or the like, and captures a subject image for the right eye guided by the left-eye lens unit 511L.

[0115] In the ninth modification, the right- and left-eye imaging modules 512CR, 512CL are configured differently from each other. Specifically, the right- and left-eye imaging modules 512CR, 512CL are configured to capture different wavelength bands at least in part. For example, the right-eye imaging module 512CR is capable of capturing fluorescence (corresponding to the first fluorescence according to the present disclosure) from a drug that emits non-weak fluorescence (corresponding to the first drug according to the present disclosure). On the other hand, the left-eye imaging module 512CL is capable of capturing fluorescence (corresponding to the second fluorescence according to the present disclosure) from a drug that emits weak fluorescence. In a two-dimensional mode that displays two-dimensional images, an image captured by one of the right- and left-eye imaging modules 512CR, 512CL is displayed. 13 , a filter 11R for non-weak fluorescence is disposed on the observation optical path P1R through which the right-eye observation light propagates, and a filter 11L for weak fluorescence is disposed on the observation optical path P1L through which the left-eye observation light propagates. For example, when the OD value of the filter 11R in the wavelength band of non-weak fluorescence is compared with the OD value of the filter 11L in the wavelength band of weak fluorescence, the former OD value is set higher. In other words, the filter 11R suppresses at least a portion of the wavelength band of non-weak fluorescence so that the output signal value from the right-eye imaging module 512CR that receives the light approaches a predetermined signal value.

[0116] Even when the configuration of the present modified example 9 described above is adopted, the same effects as those of the above-described embodiment are achieved.

[0117] (Modification 10) The medical observation system according to Modification 10 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 Modification 10 will be referred to as medical observation system 1D below.

[0118] Fig. 14 is a diagram illustrating a modified example 10 of the embodiment. As shown in Fig. 14, the medical observation system 1D includes an endoscope 100D that captures in-vivo images of an observation site by inserting an insertion section 2D into a living body and outputs the captured images, a light source device 3 that emits first and second excitation light LE1 and LE2 from the tip of the endoscope 100D, a control device 9 that processes the captured images output from the endoscope 100D, 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.

[0119] 14, the endoscope 100D includes a flexible, elongated insertion section 2D, an operation section 101 connected to the base end side of the insertion section 2D 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 2D extends and incorporating various cables connecting to the light source device 3 and the control device 9. As shown in Fig. 14, the insertion section 2D 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.

[0120] 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 embodiment. 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.

[0121] Furthermore, in the medical observation system 1D, although not specifically shown in the drawings, a filter similar to the filter 11 described in the above embodiment is disposed on the observation optical path along which the return light of the first and second excitation light LE1 and LE2 propagates from the observation subject to the image sensor.

[0122] Even when the configuration of the present modified example 10 described above is adopted, the same effects as those of the above-described embodiment are achieved.

[0123] (Modification 11) The medical observation system according to Modification 11 is a medical observation system that uses a surgical microscope to magnify and capture images of a predetermined field of view of the inside of a subject (inside a living body) or the surface of a subject (surface of a living body), which is the observation target. For ease of explanation, the medical observation system 1 according to Modification 11 will be referred to as medical observation system 1E below.

[0124] Fig. 15 is a diagram illustrating Modification 11 of the embodiment. As shown in Fig. 15, the medical observation system 1E includes 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.

[0125] As shown in Fig. 15 , the surgical microscope 14 includes a microscope unit 141 that magnifies and captures an image of 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. 15 . Although not specifically shown, the base unit 143 also has installed thereon a light source device 3 that emits first and second excitation light LE1 and LE2 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.

[0126] Although not specifically shown in the drawings, the microscope unit 141 has a built-in configuration substantially similar to that of the camera head 5 described in the above-described embodiment. An image captured by the microscope unit 141 (image capture element) is output to the control device 9 via a first transmission cable 6 wired along the support unit 142.

[0127] Furthermore, in the medical observation system 1E, although not specifically shown in the drawings, a filter similar to the filter 11 described in the above embodiment is disposed on the observation optical path along which the return light of the first and second excitation light LE1 and LE2 propagates from the observation subject to the image sensor.

[0128] Even when the configuration of the present modified example 11 described above is adopted, the same effects as those of the above-described embodiment are achieved.

[0129] (Modification 12) Figures 16 and 17 are diagrams illustrating Modification 12 of the embodiment. Specifically, Figure 16 is a view of the ring light 15 as seen from the side. Figure 17 is a view of the ring light 15 as seen from the front side (left side in Figure 16). In this modification 12, in addition to the insertion section 2 described in the above embodiment, the ring light 15 shown in Figures 16 and 17 is detachably connected to the camera head 5. That is, depending on the usage state of the user, the insertion section 2 may be connected to the camera head 5 in some cases, or the ring light 15 may be connected in other cases, as shown in Figure 16.

[0130] The ring light 15 is not inserted into the observation object OB like the insertion section 2, but supplies the first and second excitation lights LE1 and LE2 to the surgical site and captures the return light of the first and second excitation lights LE1 and LE2 from the surgical site. As shown in Figures 16 and 17, the ring light 15 includes an illumination section 151 and a subject image capture section 152 that captures a subject image.

[0131] 16 and 17 , 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.

[0132] 17, the multiple illumination lenses 1512 are arranged at predetermined intervals along the circumferential direction centered on the optical axis Ax on the front end surface of the housing 1511. The multiple illumination lenses 1512 irradiate the first and second excitation light LE1, LE2, which is supplied from the light source device 3 and introduced into the housing 1511 via the light guide 4, toward the surgical site.

[0133] The subject image capture unit 152 extends along the optical axis Ax. An optical system configured using one or more lenses is provided within the subject image capture unit 152, and focuses the return light of the first and second excitation light LE1, LE2 that is irradiated from 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. 16 ) 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.

[0134] Although not specifically shown in the drawings, in this modification 12, a filter similar to the filter 11 described in the above embodiment is disposed on the observation optical path along which the return light of the first and second excitation light LE1 and LE2 propagates from the observation object to the image sensor. More specifically, the filter is provided on the front surface of the subject image capture unit 152 (the front surface on the upstream side of the optical path).

[0135] Even when the configuration of the present modified example 12 described above is adopted, the same effects as those of the above-described embodiment are achieved.

[0136] 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 excitation light; an image sensor that captures first fluorescence emitted from a substance contained in an observation object in response to irradiation with the first excitation light; and a filter that is arranged on an observation optical path along which the first fluorescence propagates from the observation object to the image sensor, and that suppresses light in a first wavelength band that is at least a part of the wavelength band of the first fluorescence so that a first output signal value from the image sensor that receives the first fluorescence approaches a predetermined signal value. (2) The medical observation system described in (1) above, further comprising an insertion section that includes a part of the observation optical path and guides the first fluorescence to the image sensor, the filter being arranged on the observation optical path of the insertion section. (3) The medical observation system described in (1) or (2) above, further comprising a camera head including the image sensor, and the filter being arranged on the observation optical path of the camera head. (4) The medical observation system according to any one of (1) to (3), further comprising an insertion section that includes a part of the observation optical path and guides the first fluorescence to the image sensor, and a camera head including the image sensor, wherein the filter is disposed on the observation optical path between the eyepiece of the telescope and the camera head. (5) The medical observation system according to any one of (1) to (4), wherein the filter is configured to be detachable from a member that configures the observation optical path. (6) The medical observation system according to any one of (1) to (5), wherein the filter adjusts the transmittance of light in the first wavelength band. (7) The medical observation system according to any one of (1) to (6), wherein the filter is a long-pass filter or a short-pass filter. (8) The medical observation system according to any one of (1) to (6), wherein the filter is an ND filter. (9) The medical observation system according to any one of (1) to (8), wherein the filter has an excitation light cutting function that partially, substantially, or completely suppresses the first excitation light. (10) The medical observation system according to any one of (1) to (9), wherein the first fluorescence is fluorescence emitted from a first drug administered to the observation subject.(11) The medical observation system according to any one of (1) to (10), wherein the predetermined signal value is a value smaller than a signal value at which pixels of the image sensor are saturated. (12) The medical observation system according to any one of (1) to (11), wherein the light source device emits the first excitation light and the second excitation light, the image sensor captures the first fluorescence and the second fluorescence emitted from a substance contained in the observation object by irradiation with the second excitation light, and the predetermined signal value is a second output signal value from the image sensor that receives the second fluorescence. (13) The medical observation system according to any one of (1) to (11), wherein the light source device emits the first excitation light and the second excitation light, the image capture element includes a first image capture element that captures the first fluorescence and a second image capture element that captures the second fluorescence emitted from a substance contained in the observation object when irradiated with the second excitation light, the first output signal value being an output signal value from the first image capture element that receives the first fluorescence, and the predetermined signal value being a second output signal value from the second image capture element that receives the second fluorescence. (14) The medical observation system according to any one of (1) to (11), wherein the predetermined signal value is a signal value set based on brightness-related information that defines the brightness when performing fluorescence observation. (15) The medical observation system according to (14), wherein the brightness-related information is information including at least one or more of the type of the observation object, the type of medication, the surgical procedure, and equipment constituting the system. (16) The medical observation system according to any one of (1) to (12), (14), and (15), wherein only one image sensor is provided. (17) The medical observation system according to any one of (1) to (11), and (13) to (15), wherein a plurality of image sensors are provided. (18) The medical observation system according to any one of (1) to (17), wherein the light source device includes a first light source that emits the first excitation light, and wherein the first light source is composed of one or more light sources. (19) The medical observation system according to any one of (1) to (18), wherein the light source device includes a first light source that emits the first excitation light, and wherein the first light source is composed of an LED or a semiconductor laser.(20) A filter that is arranged on an observation optical path along which the first fluorescence propagates from an observation object irradiated with first excitation light to an image sensor that captures an image of first fluorescence emitted from a substance contained in the observation object in response to irradiation with the first excitation light, and that suppresses light in a first wavelength band that is at least a part of the wavelength band of the first fluorescence so that a first output signal value from the image sensor that receives the first fluorescence approaches a predetermined signal value. (21) An optical scope that irradiates an observation object with first excitation light and captures first fluorescence emitted from a substance contained in the observation object in response to irradiation with the first excitation light, comprising: a filter that is arranged on the observation optical path along which the first fluorescence propagates and that suppresses light in a first wavelength band that is at least a part of the wavelength band of the first fluorescence so that a first output signal value from the image sensor that receives the first fluorescence approaches a predetermined signal value. (22) A camera head including an image sensor that captures an image of first fluorescence emitted from a substance contained in an observation target when irradiated with first excitation light, the camera head including a filter that is disposed on an observation optical path along which the first fluorescence propagates and that suppresses light in a first wavelength band that is at least a portion of the wavelength band of the first fluorescence so that a first output signal value from the image sensor approaches a predetermined signal value.

[0137] DESCRIPTION OF SYMBOLS 1, 1B, 1D, 1E Medical observation system 2, 2D Insertion section 3 Light source device 4 Light guide 5, 5C Camera head 6 First transmission cable 7 Display device 8 Second transmission cable 9 Control device 10 Third transmission cable 11, 11A Filter 14 Surgical microscope 15 Ring light 21 Eyepiece 22 Tip 23 Bending section 24 Flexible tube section 31 First light source 32 Second light source 33 Third light source 51, 51A Imaging section 100D Endoscope 101 Operation section 102 Universal cord 141 Microscope section 142 Support section 143 Base section 151 Illumination section 152 Subject image capture section 511 Lens unit 511L Lens unit for left eye 512R Lens unit for right eye 512, 512A Image pickup element 512CL Left eye image pickup module 512CR Right eye image pickup module 513 Prism 514 Excitation light cut filter 1511 Housing 1512 Illumination lens 1521 Connection part 5121 First image pickup element 5122 Second image pickup element Ax Optical axis LI, LI1, LI2 Line LE1 First excitation light LE2 Second excitation light LF1, LF1' First fluorescence LF2 Second fluorescence OB Observation object P1, P1L, P1R Observation light path P2 Light path

Claims

1. A medical observation system comprising: a light source device that emits a first excitation light; an image sensor that images a first fluorescence emitted from a substance contained in an observation target by irradiation with the first excitation light; and a filter disposed on an observation optical path through which the first fluorescence propagates from the observation target to the image sensor, the filter suppressing light in a first wavelength band that is at least a part of a wavelength band of the first fluorescence so that a first output signal value from the image sensor that has received the first fluorescence approaches a predetermined signal value.

2. The medical observation system according to claim 1, further comprising an insertion portion that includes a part of the observation optical path and guides the first fluorescence to the image sensor, wherein the filter is disposed on the observation optical path of the insertion portion.

3. The medical observation system according to claim 1, further comprising a camera head that includes the image sensor, wherein the filter is disposed on the observation optical path of the camera head.

4. The medical observation system according to claim 1, further comprising an insertion portion that includes a part of the observation optical path and guides the first fluorescence to the image sensor, and a camera head that includes the image sensor, wherein the filter is disposed on the observation optical path between an eyepiece portion of the optical viewing tube and the camera head.

5. The medical observation system according to claim 1, wherein the filter is configured to be detachable from a member constituting the observation optical path.

6. The medical observation system according to claim 1, wherein the filter adjusts a transmittance of light in the first wavelength band.

7. The medical observation system according to claim 1, wherein the filter is a long-pass filter or a short-pass filter.

8. The medical observation system according to claim 1, wherein the filter is an ND filter.

9. The medical observation system according to claim 1, wherein the filter has an excitation light cut function of partially, substantially, or completely suppressing the first excitation light.

10. The medical observation system according to claim 1, wherein the first fluorescence is fluorescence emitted from a first drug administered to the observation target.

11. The medical observation system according to claim 1, wherein the predetermined signal value is a value smaller than a signal value at which pixels of the image sensor are saturated.

12. The light source device emits the first excitation light and the second excitation light respectively, the imaging device images the first fluorescence and the second fluorescence emitted from the substance contained in the observation target by the irradiation of the second excitation light respectively, and the predetermined signal value is the second output signal value from the imaging device that has received the second fluorescence. The medical observation system according to claim 1.

13. The light source device emits the first excitation light and the second excitation light respectively, the imaging device includes a first imaging device that images the first fluorescence and a second imaging device that images the second fluorescence emitted from the substance contained in the observation target by the irradiation of the second excitation light, the first output signal value is the output signal value from the first imaging device that has received the first fluorescence, and the predetermined signal value is the second output signal value from the second imaging device that has received the second fluorescence. The medical observation system according to claim 1.

14. The predetermined signal value is a signal value set based on brightness-related information that defines the brightness when performing fluorescence observation. The medical observation system according to claim 1.

15. The brightness-related information is information including at least one or more of the type of the observation target, the type of the drug, the surgical procedure, and the devices constituting the system. The medical observation system according to claim 14.

16. Only one imaging device is provided. The medical observation system according to claim 1.

17. A plurality of imaging devices are provided. The medical observation system according to claim 1.

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

19. The light source device includes a first light source that emits the first excitation light, and the first light source is composed of an LED or a semiconductor laser. The medical observation system according to claim 1.

20. A filter disposed on an observation optical path through which first fluorescence emitted from a substance contained in an observation target irradiated with a first excitation light propagates from the observation target irradiated with the first excitation light to an image sensor that images the first fluorescence, the filter suppressing light in a first wavelength band that is at least a part of a wavelength band of the first fluorescence so that a first output signal value from the image sensor that has received the first fluorescence approaches a predetermined signal value.

21. An optical viewing tube that irradiates an observation target with a first excitation light and captures first fluorescence emitted from a substance contained in the observation target by the irradiation with the first excitation light, the optical viewing tube including a filter disposed on an observation optical path through which the first fluorescence propagates, the filter suppressing light in a first wavelength band that is at least a part of a wavelength band of the first fluorescence so that a first output signal value from an image sensor that has received the first fluorescence approaches a predetermined signal value.

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