JPWO2020067385A1 - Endoscope - Google Patents

Abstract

The endoscope has a plurality of optical components constituting the optical path, and images are formed by incidenting light from the subject into the optical path, including fluorescence based on excitation light for fluorescing the fluorescent agent administered to the subject. An imaging optical system that performs photoelectric conversion of light from a subject imaged by the imaging optical system, and only one image sensor is arranged inside the imaging optical system, and at least a part of the excitation light from the subject. It is provided with an excitation light cut filter that blocks the transmission of light.

Description

The present disclosure relates to an endoscope that captures fluorescence generated based on excitation light applied to an observation target.

When imaging the fluorescence generated in the observation target (for example, the patient's body) into which the endoscope is inserted, the transmission of the excitation light is transmitted in order to minimize the incident of the excitation light emitted to the imaging target (for example, the affected area). An excitation light cut filter for blocking is arranged in the imaging optical system of the endoscope. For example, in Patent Document 1, an endoscope in which at least two excitation light cut filters are arranged in an imaging optical system is known. Each of these excitation light cut filters has the same transmittance characteristics, has a transmittance in the red to near infrared light region, has a transmittance of 0.1% or less in the wavelength band of excitation light, and has an incident angle of 25 degrees. The wavelength at which the transmittance of the light beam is 0.1% or more and the transmittance of the light beam having an incident angle of 0 degree is 50% or more is 680 nm or more.

Japanese Patent No. 5380690

However, in the configuration of Patent Document 1, a plurality of (for example, two) excitation light cut filters are arranged in the optical system, and further, the objective side of the first excitation light cut filter, the first excitation light cut filter, and the second excitation light cut filter. An optical element having power (for example, a biconvex lens) is arranged between the excitation light cut filter and the light cut filter. Therefore, it is difficult to shorten the total optical length of the imaging optical system, and there is a problem that the manufacturing is not easy.

The present disclosure has been devised in view of the above-mentioned conventional situation, and has a simple structure using one excitation light cut filter, effectively reducing the passage of excitation light unnecessary for fluorescence imaging, and imaging optics. An object of the present invention is to provide an endoscope that suppresses deterioration of the image quality of a fluorescent image while shortening the optical length of the system.

The present disclosure concludes by incidenting light from the subject into the optical path, including a plurality of optical components constituting the optical path and fluorescence based on excitation light for causing the fluorescent agent administered to the subject to emit fluorescent light. Only one image sensor is arranged inside the imaging optical system, the imaging optical system to image, an image sensor that photoelectrically converts the light from the subject imaged by the imaging optical system, and the light from the subject. Provided is an endoscope comprising an excitation light cut filter that blocks the transmission of at least a part of the excitation light.

Further, the present disclosure has a plurality of optical components constituting an optical path, and causes light from the subject to enter the optical path, including fluorescence based on excitation light for fluorescing the fluorescent agent administered to the subject. The imaging optical system that forms an image, an image sensor that photoelectrically converts the light from the subject imaged by the imaging optical system, and blocks the transmission of at least a part of the excitation light from the subject. With an excitation light cut filter, the plurality of optical components include a first lens and a second lens arranged on the rear end side of the first lens, and after the first lens adjacent to each other. The end face and the tip surface of the second lens are flat, and the excitation light cut filter is inserted between the rear end face of the first lens and the tip face of the second lens adjacent to each other. Provide an optics.

According to the present invention, with a simple structure using one excitation light cut filter, the passage of excitation light unnecessary for fluorescence imaging can be effectively reduced, and the optical length of the imaging optical system can be shortened. Above, the deterioration of the image quality of the fluorescent image can be suppressed.

Perspective view showing an external example of the endoscope system according to the first embodiment. Perspective view showing an example of the appearance of the tip side of the endoscope Cross-sectional view showing an example of a rigid part of an endoscope Graph showing an example of the characteristics of the band cut filter and the characteristics of excitation light and fluorescence Enlarged view of the main part of the characteristics in the wavelength region of 700 to 900 nm in FIG. The figure which shows the configuration arrangement of the 1st imaging optical system, and an example of the incident optical path of a light ray. The figure which shows the configuration arrangement of the 2nd imaging optical system, and an example of the incident optical path of a light ray. The figure which shows the configuration arrangement of the 3rd imaging optical system, and an example of the incident optical path of a light ray. The figure which shows the configuration arrangement of the 4th imaging optical system, and an example of the incident optical path of a light ray. The figure which shows an example of the maximum incident angle (air conversion) corresponding to the generated light ray in each of the 1st to 4th imaging optical systems.

(Background to obtain one form according to this disclosure)
First, in order to shorten the total optical length of the imaging optical system as compared with the imaging optical system including a plurality of excitation light cut filters disclosed in Patent Document 1, an excitation light cut filter (for example, a band cut filter (BCF:): Consider placing only one Band Cut Filter)). The excitation light fluoresces a fluorescent agent (eg, ICG (Indocyanine Green)) that has been pre-administered to the subject (that is, the observation target into which the insertion part of the endoscope is inserted, for example, the body of the patient). Therefore, the subject is irradiated.

If only one band cut filter is arranged and the angle of incidence of the excitation light (for example, 690 nmm to 820 nm) incident on the band cut filter is large, the band cut filter will sufficiently reflect the excitation light (in other words, block it). It cannot be done, and the excitation light passes through the band cut filter. In this case, the excitation light passes through the band cut filter and enters the image sensor side of the imaging optical system, so that it is unnecessary light (in other words, light that causes deterioration of the image quality of the captured image) during imaging. Is more likely to occur.

On the other hand, when the angle of incidence of the excitation light on the band cut filter is less than a predetermined threshold value (for example, 25 degrees), the band cut filter can sufficiently block the incident excitation light. In this case, since the amount of excitation light imaged on the image sensor is reduced, it is expected that deterioration of the image quality of the image captured by the image sensor can be suppressed.

Therefore, in the following embodiment, a simple structure using one band cut filter is used so that the angle of incidence of the excitation light on the band cut filter is less than a predetermined threshold value (for example, 25 degrees). The transmission of excitation light (690 nmm to 820 nm), which is unnecessary for fluorescence imaging, can be sufficiently blocked.

Hereinafter, embodiments in which the configuration and operation of the endoscope according to the present disclosure are specifically disclosed will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art. It should be noted that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

FIG. 1 is a perspective view showing an external example of the endoscope system 11 according to the first embodiment. In the following description, the directions used in the description follow the description of the directions in FIG. Specifically, the upward and downward directions of the housing 27 of the video processor 13 mounted on the horizontal plane are referred to as "upper" and "lower", respectively. Further, the side where the endoscope 15 images the observation target is referred to as "front (front)", and the side connected to the video processor 13 is referred to as "rear". Further, the right-hand side in the direction in which the endoscope 15 is inserted is referred to as "right", and the left-hand side in the direction in which the endoscope 15 is inserted is referred to as "left".

The endoscope system 11 includes an endoscope 15, a video processor 13, and a monitor 17. The endoscope 15 is, for example, a medical flexible mirror. The video processor 13 captures an image (including, for example, a still image and a moving image) obtained by the endoscope 15 taking an image of an observation target (for example, a human body such as a patient or an affected part inside the human body). Image processing is performed on the surface. The video processor 13 sends the image signal obtained by the image processing to the monitor 17 as an image signal for display. The monitor 17 displays the captured image of the endoscope 15 image-processed by the video processor 13 according to the display image signal output from the video processor 13. Image processing includes, but is not limited to, for example, color correction, gradation correction, and gain adjustment.

The endoscope 15 is inserted into an observation target (an example of a subject) of a human body such as a patient, and images the observation target. The endoscope 15 includes a scope 19 inserted inside the observation target and a plug portion 21 to which the rear end portion of the scope 19 is connected. Further, the scope 19 has a configuration including a soft portion 23 having a relatively long flexibility and a rigid portion 25 having rigidity provided at the tip of the soft portion 23. The structure of the scope 19 will be described later.

The video processor 13 has a housing 27, performs image processing on the captured image captured by the endoscope 15, and outputs the image signal after the image processing as an image signal for display. On the front surface of the housing 27, a socket portion 31 into which the base end portion 29 of the plug portion 21 is inserted is arranged. By inserting the plug portion 21 into the socket portion 31 and electrically connecting the endoscope 15 and the video processor 13, power and various signals (for example, video signals) are provided between the endoscope 15 and the video processor 13. , Control signal) can be transmitted and received. These electric powers and various signals are guided from the plug portion 21 to the flexible portion 23 via a transmission cable 231 (see FIG. 3) inserted inside the scope 19. Further, the image signal of the captured image output from the image sensor 33 (see FIG. 3) provided inside the rigid portion 25 is transmitted from the plug portion 21 to the video processor 13 via the transmission cable 231.

Further, the housing 27 includes a visible light source (not shown) for irradiating visible light (white light) and an IR excitation light source (not shown) for irradiating excitation light (for example, excitation light in the IR band). Is built-in.

The visible light source emits (irradiates) visible light (white light) when operated by a doctor or the like (including a person who assists the doctor or the like; the same applies hereinafter). This visible light (white light) is guided to the tip of the endoscope 15 in the insertion direction via optical fibers 49, 49 (an example of a light guide) and illuminated toward an observation target.

Similarly, the IR excitation light source emits (irradiates) excitation light in the IR band when operated by a doctor or the like. This excitation light is guided to the tip of the endoscope 15 in the insertion direction via optical fibers 39, 41 (an example of a light guide) and is illuminated toward the observation target.

The video processor 13 performs image processing on the image signal transmitted from the endoscope 15 via the transmission cable 231, converts the image signal after the image processing into an image signal for display, and outputs the image signal to the monitor 17. do.

The monitor 17 is composed of a display device such as an LCD (Liquid Crystal Display), a CRT (Cathode Ray Tube), or an organic EL (Electroluminescence) display. The monitor 17 displays an captured image of an observation target captured by the endoscope 15. Specifically, the monitor 17 displays a visible light image acquired by imaging visible light and a fluorescence image generated by imaging fluorescence based on excitation light.

FIG. 2 is a perspective view showing an example of the appearance of the distal end side of the endoscope 15. An imaging window 35 is arranged on the tip surface of the rigid portion 25. The image pickup window 35 is formed including, for example, an optical material such as optical glass or optical plastic, and receives light from an observation target (an example of a subject). The light from the observation target is, for example, the light reflected by the observation target when irradiated with white light (that is, visible light), or the light reflected by the observation target when irradiated with excitation light in the IR band. Fluorescence generated by light (ie, excitation light) and excitation light.

The endoscope 15 irradiates the observation target of the subject with excitation light for fluorescence observation, and emits fluorescence emitted from a fluorescent agent (for example, ICG) previously administered by injection or the like into the subject based on the irradiation of the excitation light. It can be imaged and a fluorescent image can be obtained. In such fluorescence observation, for example, ultraviolet rays having a wavelength band of 380 nm to 450 nm or excitation light in the IR band having a wavelength band of 690 to 820 nm are used. Hereinafter, in the first embodiment, an example in which IR (Infrared) excitation light is used as the excitation light for fluorescence observation will be described, but the excitation light is not limited to this.

Illumination windows 43, 45 in which the tips of a pair of optical fibers 39, 41 for transmitting (light guiding) the excitation light from the IR excitation light source are exposed are arranged on the tip surface of the rigid portion 25. On the tip surface of the rigid portion 25, a pair of illumination windows 51 in which the tips of a pair of optical fibers 49 and 50 for transmitting (light guiding) visible light from a visible light source are exposed are arranged. The pair of illumination windows 43 and 45 for IR are arranged on both ends in the radial direction of the circular tip flange 53 provided at the tip of the rigid portion 25. Further, the pair of illumination windows 51, 51 for visible light are similarly arranged on both ends in the diameter direction of the tip flange 53. The pair of illumination windows 43 and 45 for IR and the pair of illumination windows 51 and 51 for visible light are arranged at equal intervals in the circumferential direction, for example. The number of the pair of optical fibers 39, 41 for IR and the pair of optical fibers 49, 49 for visible light may be other than the above.

FIG. 3 is a cross-sectional view showing an example of the rigid portion 25 of the endoscope 15. The cross section of FIG. 3 may be represented as, for example, a cross section cut by a plane passing through the centers of the illumination window 43, the imaging window 35, and the illumination window 45 of FIG. 2, or the illumination window 51 of FIG. , The cross section cut by a plane passing through the centers of the imaging window 35 and the illumination window 51 may be represented.

The endoscope 15 includes a lens unit 235 that accommodates an imaging optical system by a lens supporting member 239, an image sensor 33 in which an imaging surface 241 is covered with an element cover glass 243, and a lens light at the center of the imaging surface 241. Adhesive resin 37 for fixing the lens unit 235 with the same axis and the element cover glass 243 (an example of the sensor glass) is provided on the surface of the image sensor 33 opposite to the imaging surface (that is, the rear side). A transmission cable 231 having four electric wires 245 connected to each of the four conductor connecting portions 249 is provided.

The lens support member 239 is formed on a plurality of (three in the illustrated example) plano-convex lens L1, biconvex lens L2, biconcave lens L3, and the front surface of the plano-convex lens L1 formed of an optical material (for example, glass, resin, etc.). The aperture AP1 and the aperture AP1 are incorporated in a state of being close to each other in the direction of the optical axis. The diaphragm AP1 is provided for adjusting the amount of light incident on the plano-convex lens L1, and only the light that has passed through the diaphragm AP1 can be incident on the plano-convex lens L1. The plano-convex lens L1, the biconvex lens L2, and the biconcave lens L3 are fixed to the inner peripheral surface of the lens support member 239 with an adhesive over the entire circumference. In the following description, a concave flat lens may be provided instead of the biconcave lens L3.

As the metal material constituting the lens support member 239, for example, nickel is used. Nickel has a relatively high rigidity and high corrosion resistance, and is suitable as a material for forming the hard portion 25. In addition, the periphery of the lens support member 239 before the examination or the operation so that the nickel constituting the lens support member 239 is not directly exposed from the rigid portion 25 during the examination using the endoscope 15 or the operation. Is preferably coated evenly with the mold resin 217, and the rigid portion 25 is preferably biocompatible coated. For example, a copper-nickel alloy may be used instead of nickel. Copper-nickel alloy also has high corrosion resistance and is suitable as a material constituting the hard portion 25. Further, as the metal material constituting the lens support member 239, a material that can be manufactured by electroplating is preferably selected.

The image sensor 33 is composed of, for example, a small CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) imaging device having a square shape when viewed from the front-rear direction. In the image sensor 33, the light incident from the outside is collected by the optical lens group in the lens support member 239 and imaged on the image pickup surface 241. Further, in the image sensor 33, the imaging surface 241 is covered so as to be protected by the element cover glass 243 (for example, the sensor glass SG2 described later).

Four conductor connecting portions 249 are provided at the rear portion on the back surface side of the image sensor 33. The conductor connection portion 249 can be formed by, for example, an LGA (Land grid array). The four conductor connection portions 249 include a pair of power connection portions and a pair of signal connection portions. The four conductor connection portions 249 are electrically connected to the four electric wires 245 of the transmission cable 231. The transmission cable 231 includes a pair of power lines which are electric wires 245 and a pair of signal lines which are electric wires 245. That is, a pair of power lines of the transmission cable 231 are connected to the pair of power connection portions of the conductor connection portion 249. A pair of signal lines of the transmission cable 231 are connected to the pair of signal connection portions of the conductor connection portion 249.

According to the endoscope 15, the lens unit 235 and the image sensor 33 are fixed by the adhesive resin 37 while being held at a predetermined distance. The fixed lens unit 235 and the image sensor 33 are aligned with the optical axis of the lens unit 235 and the center of the imaging surface 241. The distance between the lens unit 235 and the image sensor 33 is such that the incident light from the subject passing through the lens unit 235 is focused on the image pickup surface 241 of the image sensor 33. The lens unit 235 and the image sensor 33 are fixed after being aligned.

A separation portion is formed between the fixed lens unit 235 and the image sensor 33. The shape of the separated portion is determined by the lens unit 235 and the image sensor 33 being relatively aligned and being fixed to each other by the adhesive resin 37. That is, the separation portion is an adjustment gap for positioning the lens unit 235 and the image sensor 33.

FIG. 4 is a graph showing an example of the characteristics of the band cut filter and the characteristics of excitation light and fluorescence. In the endoscope 15, a band cut filter (an example of an IR excitation light cut filter) can be configured by a reflection type cut filter. In this case, since the band cut filter is a non-absorbent filter, it is called a dielectric filter (that is, a reflective cut filter) and can be distinguished from a metal filter exhibiting absorption.

The band cut filter is an edge filter in which the boundary 89 (edge) between the transmission band and the blocking band and the boundary 91 are steep. What is required of this type of edge filter is that the change from the blocking band to the transmission band is generally as sharp as possible, and the transmission band is as close to 100% as possible. In the band cut filter according to the first embodiment, the wavelength of the excitation light is substantially in the center of the blocking band.

FIG. 5 is an enlarged view of a main part of the characteristics in the wavelength region of 700 to 900 nm in FIG. Here, the fluorescence due to the excitation light is a few percent weaker than that of the excitation light. Indocyanine green (ICG), which is a medical fluorescent drug that is harmless to the human body, is administered around the affected area in the body, and the observation site (for example, the affected area where ICG accumulates) is irradiated with excitation light in the IR band to generate fluorescence. It is conceivable that the affected area is illuminated to take an image. Therefore, the video processor 13 adjusts the gain so as to increase the gain of the fluorescence emission image (fluorescence image). Therefore, the image quality is deteriorated even by the intrusion of weak excitation light. Under these circumstances, it is desirable to secure a sufficient range for the blocking band with respect to the wavelength of the excitation light.

On the other hand, the fluorescence due to the excitation light peaks in a gentle wavelength range continuously in the wavelength band of the excitation light. Therefore, the boundary 91 between the blocking band and the transmission band of the band cut filter is important. That is, there is a request that the boundary 91 should take in the fluorescence wavelength Wk as much as possible while keeping it away from the excitation light wavelength. Band cut filter, inhibition zone (transmission prohibition zone) comprises a wavelength of the peak intensity of the excitation light, the intensity of the excitation light is a peak 1 / Exp2 (i.e., e ²⁾ and a wavelength to be less, and , The wavelength does not include all of the generated fluorescence wavelength Wk (or the wavelength includes a part of the generated fluorescence wavelength Wk). e is 2.71828 ... (hereinafter abbreviated), which is the base of the natural logarithm. That is, the band cut filter is cut off by including a wavelength region close to the excitation light in the blocking band, which is particularly weak among the fluorescence wavelengths Wk. As a result, it is possible to efficiently capture the effective effective fluorescence wavelength Wka among the weak fluorescence wavelength Wk while suppressing the intrusion of excitation light as much as possible.

As this reflection type band cut filter, it is preferable to use one having a high optical density (OD value). It is desirable that the OD value is, for example, 5 or more. The band cut filter can more easily block the passage of excitation light by setting the OD value higher.

Further, in the endoscope 15, the band cut filter can be configured by an absorption type cut filter. As the absorption type cut filter, a filter glass (absorption type) having little dependence on the angle of the incident light beam can be used. In the case of the band-cut filter of the absorption type, inhibition zone (transmission prohibition zone) is the wavelength of the peak intensity of the excitation light, the excitation light intensity is peak 1 / Exp2 (i.e., e ²⁾ less than or equal to It can be a wavelength that includes a wavelength and does not include all of the generated fluorescence wavelength Wk (or a wavelength that includes a part of the generated fluorescence wavelength Wk). As a result, it has the same effect as described above. That is, the absorption type band cut filter is cut off by including the wavelength region close to the excitation light in the blocking band, which is particularly weak among the fluorescence wavelengths Wk. As a result, it is possible to efficiently capture the effective effective fluorescence wavelength Wka among the weak fluorescence wavelength Wk while suppressing the intrusion of excitation light as much as possible.

Next, an example of the configuration arrangement of the imaging optical system of the endoscope 15 including the band cut filter will be described with reference to FIGS. 6 to 9.

(Structure arrangement of the first imaging optical system)
FIG. 6 is a diagram showing an example of the configuration arrangement of the first imaging optical system 55 and the incident optical path of the light beam. The first imaging optical system 55 has an objective cover glass CG1, an aperture AP1, a plano-convex lens L1, and a flat plate along the optical axis from the tip side (in other words, the objective side or the incident side of the excitation light) of the endoscope 15. The glass FG1, the biconvex lens L2, the biconcave lens L3, and the sensor glass SG2 are arranged in this order.

In the first imaging optical system 55, a thin-film film of the band cut filter 111 is formed on the front end side surface of the flat glass FG1 (that is, the surface on the plano-convex lens L1 side). In the first imaging optical system 55, the vapor deposition film of the band cut filter 111 is formed on the imaging side surface of the flat glass FG1 (that is, the surface on the biconvex lens L2 side) or on both side surfaces of the flat glass FG1. May be done. The thickness of the flat glass FG1 is, for example, 0.30 mm.

Further, between the biconvex lens L2 and the biconcave lens L3, for example, an adhesive having a refractive index larger than that of air is filled, and an adhesive layer between the biconvex lens L2 and the biconcave lens L3 is formed. Since the biconvex lens L2 is brought into close contact with the biconcave lens L3 by this adhesive layer, no air layer is interposed between the biconvex lens L2 and the biconcave lens L3. Further, an image sensor 33 is arranged on the back surface (rear surface) of the sensor glass SG2.

The diaphragm AP1 acts as an aperture stop (Aperture Stop) that narrows the passage of incident light by limiting the angle of incidence, and corresponds to an F number. The diaphragm AP1 allows only the light rays of the portion of the light from the observation target (see above) to be imaged to pass through. The main ray passes through the center of the aperture even when the aperture stop is sufficiently closed. In the endoscope 15, the light rays that have passed through the diaphragm AP1 are focused by the first imaging optical system 55 and imaged by the image sensor 33.

In the first imaging optical system 55, the incident light b1 including the excitation light enters the plano-convex lens L1 through the diaphragm AP1, converges in the optical axis direction with the plano-convex lens L1, and forms a vapor-deposited film on the surface of the flat glass FG1. It is incident on the formed band cut filter 111. In this case, the angle of incidence on the band cut filter 111 (that is, the angle from the direction perpendicular to the band cut filter 111) is reduced by the plano-convex lens L1 having the power to refract the light beam. That is, the incident light b1 is incident on the band cut filter 111 with an inclination close to vertical (in other words, an incident angle close to 0 degrees). The band cut filter 111 can efficiently reflect the excitation light contained in the incident light b1 and sufficiently block the transmission thereof.

For example, the image height FA, which is considered to have the largest incident angle, is incident at a position having a value of 1.0 (that is, the position farthest from the center of the band cut filter 111 among the incident light on the band cut filter 111). It simulates the case where a light beam enters the band cut filter 111. In this case, according to the configuration arrangement of the first imaging optical system 55, the angle of incidence on the band cut filter 111 (that is, the maximum ray angle) is 24.9 degrees in terms of air, and a predetermined threshold value (for example, 25 degrees). ) (See FIG. 10). A predetermined threshold value indicates an incident angle of light that is sufficiently reflective (that is, difficult to pass) light incident on the band cut filter.

The incident light b2 transmitted through the band cut filter 111 passes through the biconvex lens L2 and the biconcave lens L3 and converges, and is imaged on the image sensor 33 arranged on the back surface (rear surface) of the sensor glass SG2.

Here, Table 1 shows various lenses constituting the first imaging optical system 55 and lens data related to the band cut filter 111 (BCF). Here, BF represents the back focus (distance from the rear end of the lens to the image sensor), and the same applies hereinafter.

As described above, in the first imaging optical system 55, a thin-film film of the band cut filter 111 is formed on one side (for example, the surface on the objective side) of the flat glass FG1 so that the band cut filter 111 faces the plano-convex lens L1. By arranging the flat glass FG1 between the plano-convex lens L1 and the biconvex lens L2, the configuration can be easily arranged. Therefore, the first imaging optical system 55 and the endoscope 15 in which only one band cut filter 111 is arranged can be easily manufactured.

The surface of the band cut filter 111 on which the vapor deposition film is formed may be the back surface of the flat glass FG1 (the surface on the image sensor side). Further, a thin-film film of the band cut filter 111 may be formed on both the front surface (objective side surface) and the back surface (imaging side surface) of the flat glass FG1. In any of these cases, the same effect as when the band cut filter 111 is formed on the surface of the flat glass FG1 (that is, the angle of incidence of the upper light beam having an image height FA of 1.0 on the band cut filter 111). Is less than 25 degrees, and the effect of properly blocking the excitation light) is obtained.

(Structure arrangement of the second imaging optical system)
FIG. 7 is a diagram showing an example of the configuration arrangement of the second imaging optical system 56 and the incident optical path of the light beam. In the description of the second imaging optical system 56, the same components as those of the first imaging optical system 55 are designated by the same reference numerals to simplify or omit the description of their configurations and operations, and different contents will be described. ..

In the second imaging optical system 56, the flat glass FG1 on which the vapor-deposited film of the band cut filter 111 is formed is omitted from the configuration of the first imaging optical system 55. That is, a thin-film film of the band cut filter 112 is formed on the lens surface (specifically, the curved surface of the convex lens) on the exit side of the plano-convex lens L1. The second imaging optical system 56 has an objective cover glass CG1, an aperture AP1, a plano-convex lens L1, and a band along the optical axis from the tip side (in other words, the objective side or the incident side of the excitation light) of the endoscope 15. The cut filter 112, the biconvex lens L2, the biconcave lens L3, and the sensor glass SG2 are arranged in this order.

In the second imaging optical system 56, the incident light b1 including the excitation light enters the plano-convex lens L1 through the diaphragm AP1 and converges in the optical axis direction at the plano-convex lens L1. The incident light in the plano-convex lens L1 is incident on the band cut filter 112 formed on the curved surface of the lens on the exit side.

In this case, the incident light b1 is emitted at an inclination close to perpendicular to the curved surface of the lens on the exit side of the plano-convex lens L1. That is, the angle of incidence on the band cut filter 112 formed on the curved surface of the lens on the exit side (the angle of the band cut filter 112 from the normal direction) is small, and the incident light b1 is similar to the first imaging optical system 55. It is incident on the band cut filter 112 with an inclination close to vertical (in other words, an incident angle close to 0 degrees). The band cut filter 112 can reflect the excitation light contained in the incident light b1 and sufficiently block the transmission thereof.

For example, the case where the upper and lower rays incident on the position where the image height FA considered to have the largest incident angle has a value of 0.0 (that is, the center position of the band cut filter 112) is incident on the band cut filter 112 is simulated. In this case, according to the arrangement configuration of the second imaging optical system 56, the angle of incidence on the band cut filter 112 (that is, the maximum ray angle) is 13.7 degrees in terms of air, which is a predetermined threshold value (25 degrees). It was less than (see FIG. 10).

The incident light b2 transmitted through the band cut filter 112 passes through the biconvex lens L2 and the biconcave lens L3 and converges, and is imaged on the image sensor 33 arranged on the back surface (rear surface) of the sensor glass SG2.

Here, Table 2 shows various lenses constituting the second imaging optical system 56 and lens data related to the band cut filter 112 (BCF).

As described above, in the second imaging optical system 56, the vapor deposition film of the band cut filter 112 is formed on the lens curved surface of the plano-convex lens L1. Therefore, the configuration of the flat glass FG1 on which the vapor-deposited film of the band cut filter 111 of the first imaging optical system 55 is formed can be omitted. As a result, the total optical length of the second imaging optical system 56 can be further shortened as compared with the first imaging optical system 55, the second imaging optical system 56 can be designed into a compact shape, and the second imaging can be performed. The optical system 56 and the endoscope 15 can be manufactured more easily.

(Structure arrangement of the third imaging optical system)
FIG. 8 is a diagram showing an example of the configuration arrangement of the third imaging optical system 57 and the incident optical path of the light beam. In the description of the third imaging optical system 57, the same components as those of the first imaging optical system 55 are designated by the same reference numerals to simplify or omit the description of their configurations and operations, and different contents will be described. ..

In the third imaging optical system 57, as in the second imaging optical system 56, the flat glass FG1 on which the vapor-deposited film of the band cut filter 111 is formed is omitted. Specifically, the biconvex lens L2 is composed of a convex flat lens L2f on the incident side and a plano-convex lens L2b on the exit side whose cross section perpendicular to the optical axis is a flat surface. A thin-film film of the band cut filter 113 is formed on either the back surface (rear surface) of the convex flat lens L2f or the front surface of the plano-convex lens L2b.

After the thin-film deposition film is formed, the back surface of the convex flat lens L2f and the front surface of the plano-convex lens L2b are bonded to each other with an adhesive or the like with the vapor deposition film of the band cut filter 113 interposed therebetween. This adhesive has a higher refractive index than air. As a result, the biconvex lens L2 in which the band cut filter 113 is arranged is formed. The inside of the biconvex lens L2 is a region having the smallest ray angle in the third imaging optical system 57. Therefore, the light beam can be incident on the band cut filter 113 from a direction close to vertical (in other words, an incident angle close to 0 degrees). The third imaging optical system 57 includes an objective cover glass CG1, an aperture AP1, a plano-convex lens L1 from the tip side of the endoscope 15 (in other words, the objective side or the incident side of the excitation light) along the optical axis. The convex lens L2 (specifically, the convex flat lens L2f, the band cut filter 113, the plano-convex lens L2b), the biconcave lens L3, and the sensor glass SG2 are arranged in this order.

In the third imaging optical system 57, the incident light b1 including the excitation light enters the plano-convex lens L1 through the diaphragm AP1 and converges in the optical axis direction with the plano-convex lens L1 to the convex flat lens L2f of the biconvex lens L2. Incident. Inside the convex flat lens L2f, the inclination of the ray angle is small, and the direction is close to perpendicular to the band cut filter 113 interposed between the convex flat lens L2f and the plano-convex lens L2b (in other words, the incident angle close to 0 degrees). Light rays are incident from. The band cut filter 113 can efficiently reflect the excitation light contained in the incident light b1 and sufficiently block the transmission thereof.

For example, below where the image height FA, which is considered to have the largest incident angle, is incident at a position with a value of 1.0 (that is, the position farthest from the center of the band cut filter 113 among the incident light on the band cut filter 113). It simulates the case where a light beam enters the band cut filter 113. In this case, the angle of incidence on the band cut filter 113 (that is, the maximum ray angle) was 17.1 degrees in terms of air, which was less than a predetermined threshold value (25 degrees) (see FIG. 10).

Here, when the band cut filter 113 is arranged inside the biconvex lens L2, the incident light on the band cut filter 113 is incident from the lens medium, not from the air. Therefore, in the lens medium, the angle of incidence θ2 on the band cut filter can be calculated according to the mathematical formula (1) according to Snell's law.

In the mathematical formula (1), nd1 is the refractive index of air and has a value of 1. nd2 is the refractive index of the lens medium and has a value of 1.77. θ11 is the angle of incidence on the air, which is 17.1 degrees. θ2 is the angle of incidence on the lens medium.

As a result of the calculation, θ2 was 9.6 degrees in terms of lens medium. Therefore, the angle of incidence on the band cut filter 113 is closer to the vertical direction (that is, the angle of incidence is closer to 0 degrees) according to the configuration arrangement of the third imaging optical system 57.

The incident light b2 transmitted through the band cut filter 112 passes through the plano-convex lens L2b and the biconcave lens L3 of the biconvex lens L2, converges, and forms an image on the image sensor 33 arranged on the back surface (rear surface) of the sensor glass SG2. ..

Here, various lenses constituting the third imaging optical system 57 and lens data related to the band cut filter 111 (BCF) are shown.

As described above, in the third imaging optical system 57, similarly to the second imaging optical system 56, the total optical length of the third imaging optical system 57 can be further shortened as compared with the first imaging optical system 55. The third imaging optical system 57 can be designed in a compact shape, and the third imaging optical system 57 and the endoscope 15 can be manufactured more easily. Moreover, since the excitation light is reflected inside the lens, the angle of incidence inside the lens is smaller than the angle of incidence from the air. As a result, the light beam is incident on the band cut filter from a direction close to vertical. Further, in the region of the biconvex lens L2, in the third imaging optical system 57, the light beam is closest to the optical axis direction, so that the light ray can be incident on the band cut filter 113 from a direction closer to perpendicular to the band cut filter 113. Therefore, the excitation light can be efficiently reflected by the band cut filter 113.

(Structure arrangement of the 4th imaging optical system)
FIG. 9 is a diagram showing an example of the configuration arrangement of the fourth imaging optical system 58 and the incident optical path of the light beam. In the fourth imaging optical system 58, the same components as those of the first imaging optical system 55 are designated by the same reference numerals to simplify or omit the description of their configurations and operations, and different contents will be described.

In the fourth image pickup optical system 58, as in the second image pickup optical system 56 and the third image pickup optical system 57, the flat glass FG1 on which the vapor deposition film of the band cut filter 111 is formed is omitted. Specifically, the two lenses L10 in the front stage (objective side) are configured as lenses for reducing the chromatic aberration of the incident light, and are combined with the concave-convex lens L11 and the concave-convex lens L12. The two lenses for reducing chromatic aberration are not limited to the example shown in FIG. 9, and a biconcave lens and a biconvex lens may be combined.

The rear lens L20 is composed of a convex flat lens L21 and a plano-concave lens L22 whose cross section perpendicular to the optical axis is a flat surface. A thin-film film of the band cut filter 114 is formed on either the back surface (rear surface) of the convex flat lens L21 or the front surface of the plano-concave lens L22.

After the thin-film deposition film is formed, the back surface of the convex flat lens L21 and the front surface of the plano-concave lens L22 are bonded to each other with an adhesive or the like with the vapor deposition film of the band cut filter 114 interposed therebetween. This adhesive has a higher refractive index than air. As a result, the rear lens L20 is formed into a concave-convex lens in which the band cut filter 114 is arranged. The inside of this concave-convex lens is the region where the inclination of the ray angle is the smallest. Therefore, the light beam can be incident on the band cut filter 114 from a direction close to vertical (in other words, an incident angle close to 0 degrees). The fourth imaging optical system 58 includes an objective cover glass CG1, an aperture AP1, and a lens L10 (specifically, from the tip side of the endoscope 15 (in other words, the objective side or the incident side of the excitation light) along the optical axis. The concave-convex lens L11, the concave-convex lens L12), the lens L20 (specifically, the convex flat lens L21, the band cut filter 114, the flat concave lens L22), and the sensor glass SG2 are arranged in this order.

In the fourth imaging optical system 58, the incident light b1 including the excitation light passes through the diaphragm AP1 and is incident on the front lens L10, converges on the front lens L10 in the optical axis direction, and is incident on the rear lens L20. .. At this time, in the lens L10 in the previous stage, chromatic aberration is reduced by the concave-convex lens L11 and the concave-convex lens L12 with respect to the incident light. Examples of the combination of lenses that reduce chromatic aberration include an achromatic lens that cancels (cancels) color shift (chromatic aberration) by combining a convex lens made of crown glass and a concave lens made of flint glass.

The light beam emitted from the front lens L10 is incident on the rear lens L20. Inside the lens L20 in the subsequent stage, the inclination of the ray angle is small, and the direction is close to vertical with respect to the band cut filter 114 interposed between the convex flat lens L21 and the plano-concave lens L22 (in other words, the incident angle close to 0 degrees). Light rays are incident from. The band cut filter 114 can efficiently reflect the excitation light contained in the incident light b1 and sufficiently block the transmission thereof.

For example, the position where the image height FA, which is considered to have the largest incident angle, has a value of 0.6 (that is, the distance from the center to the upper end of the band cut filter 114 in the incident light to the band cut filter 114 is 60% apart. The case where the upper light beam incident on the position) is incident on the band cut filter 114 is simulated. In this case, the angle of incidence on the band cut filter 114 (that is, the maximum ray angle) was 9.5 degrees in terms of air, which was smaller than the predetermined threshold value (25 degrees) (see FIG. 10).

The incident light b2 transmitted through the band cut filter 114 converges through the plano-concave lens L22 and forms an image on the image sensor 33 arranged on the back surface of the sensor glass SG2.

Here, various lenses constituting the third imaging optical system 57 and lens data related to the band cut filter 111 (BCF) are shown.

As described above, in the fourth imaging optical system 58, as with the second imaging optical system 56 and the third imaging optical system 57, all of the fourth imaging optical system 58 is compared with the first imaging optical system 55. The optical length can be further shortened, the fourth imaging optical system 58 can be designed into a compact shape, and the fourth imaging optical system 58 and the endoscope 15 can be manufactured more easily. Moreover, since the excitation light is reflected inside the lens, the incident angle inside the lens is smaller than the incident angle when converted to air. Further, in the region of the lens L20 in the subsequent stage, in the fourth imaging optical system 58, the light rays are in the direction closest to the optical axis, so that the light rays can be incident on the band cut filter from a direction closer to perpendicular to the band cut filter. Therefore, the excitation light can be efficiently reflected by the band cut filter, and the transmission of the excitation light can be blocked.

FIG. 10 is a diagram showing an example of the maximum incident angle (air conversion) corresponding to the generated light rays in each of the first to fourth imaging optical systems. As described above, in any of the first imaging optical system 55 to the fourth imaging optical system 58, the maximum ray angle is less than a predetermined threshold value (25 °).

As described above, in the first imaging optical system 55 to the fourth imaging optical system 58, only one band cut filter is arranged as compared with the case where two or more band cut filters are conventionally arranged. The total optical length of the imaging optical system can be shortened.

Further, particularly limited to the second imaging optical system 56 to the fourth imaging optical system 58, the band cut filter is formed as a thin-film deposition film inside or outside the lens, so that the first imaging optical system 55 can be used. Compared with the case of forming a thin-film deposition film on the flat glass FG1, the thickness (0.3 mm) of the flat glass can be omitted, and the total optical length of the imaging optical system can be further shortened by that amount. Further, in the case of a single band cut filter, when the excitation light is incident at an incident angle close to the plane perpendicular to the surface, the reflectance of the excitation light is increased, but when the incident angle is large, the excitation light is excited by stray light. It cannot reflect light completely. Therefore, by forming the band cut filter by vapor deposition in the region where the incident angle becomes small, the band cut filter can efficiently reflect the excitation light.

As described above, the endoscope 15 according to the first embodiment receives light from the subject into the optical path, including fluorescence based on visible light from the subject or excitation light for fluorescing the fluorescent agent administered to the subject. It has an imaging optical system (for example, a first imaging optical system 55) for forming an image. The endoscope 15 has an image sensor 33 that photoelectrically converts the light from the subject imaged by the first imaging optical system 55. Only one endoscope 15 is arranged inside the first imaging optical system 55, and a band cut filter 111 (an example of an excitation light cut filter) that blocks the transmission of at least a part of the excitation light from the subject. ).

In the first imaging optical system 55, the objective cover glass CG1, the aperture AP1, the plano-convex lens L1, the flat plate glass FG1, the biconvex lens L2, the biconcave lens L3, and the sensor glass SG2 (optical path) along the optical axis from the tip side. An example of a plurality of constituent optical components) is arranged in order. As a result, the endoscope 15 has a simple structure using a single band cut filter, and can effectively reduce the passage of excitation light unnecessary for fluorescence imaging, so that the optical length can be shortened. It is possible to suppress the deterioration of the image quality of the captured image due to the excitation light.

Further, in the first imaging optical system 55, the band cut filter 111 (an example of an excitation light cut filter) is the objective side and the imaging of the flat glass FG1 adjacent to the plano-convex lens L1 (an example of the optical component on the most objective side). Formed on either or both sides. The band cut filter 111 may be formed between the plurality of optical components or in the flat glass FG1 closest to the objective side of the plurality of optical components. Thereby, the imaging optical system of the endoscope 15 including the band cut filter 111 can be easily manufactured.

Further, in the third and fourth imaging optical systems 57 and 58, the band cut filters 113 and 114 (an example of the excitation light cut filter) are any of the optical components inserted among the plurality of optical components (for example, both). It is formed by flat-depositing on a convex lens L2 and a lens L20). As a result, light rays can be incident from a direction close to the optical axis (in other words, an incident angle close to 0 degrees), and the amount of excitation light received by the image sensor 33 is reduced. In addition, the total optical length of the imaging optical system can be shortened.

Further, in the third and fourth imaging optical systems 57 and 58, the surfaces of the band cut filters 113 and 114 are surfaced by any of the adjacent optical components of the biconvex lens L2 and the lens L20 (for example, the convex flat lens L2f or the plano-convex lens). It is adhered to L2b, or a convex flat lens L21 or a plano-concave lens L22), and the adhesion is filled with an adhesive having a refractive index higher than that of air. As a result, light rays can be incident from a direction close to the optical axis (in other words, an incident angle close to 0 degrees), and the amount of excitation light received by the image sensor 33 is reduced.

Further, in the first imaging optical system 55, the surface of the band cut filter 111 has a gap (that is, an air layer) with any adjacent optical component (for example, the plano-convex lens L1). As a result, the light rays can be incident from a direction close to the optical axis without spreading the light rays due to the voids, and the amount of the excitation light received by the image sensor 33 is reduced.

Further, in the second imaging optical system 56, the band cut filter 112 is formed by being vapor-deposited on the curved surface of any of the adjacent optical components (for example, the plano-convex lens L1). As a result, even if the light rays are diffused rather than in the direction close to the optical axis, they can be incident at an incident angle close to the normal direction of the band cut filter 112, and the amount of the excitation light received by the image sensor 33 is reduced. In addition, the total optical length of the imaging optical system can be shortened.

Further, in the fourth imaging optical system 58, the optical components other than any of the optical components (for example, the lens L10 in the previous stage) are two or more lenses (for example, the concavo-convex lens L11 and the concavo-convex lens L11) capable of reducing chromatic aberration. It is composed of a combination of lenses L12). As a result, the chromatic aberration can be reduced, the transmission of the excitation light can be blocked regardless of the color difference, and the amount of the excitation light received by the image sensor 33 can be reduced.

Further, the band cut filter is formed by vapor deposition on any of a plurality of optical components constituting the imaging optical system. As the angle dependence of the band cut filter, the ^{ray angle at which the intensity of the excitation light is 1 / e 2} or less of the peak is θL, the refractive index of the optical component on which the band cut filter is formed is nL, and the light to the band cut filter is When the angle of incidence is θF, ^{the excitation light in which θF = sin -1} (nL * sin θL) is formed on another part (that is, another optical part) or inserted into another part (that is, another optical part). Satisfies a relationship smaller than the angle of incidence on the cut filter (* indicates the multiplication operator). As a result, the excitation light having a peak intensity of 1 / e ² or more can be reflected and its transmission can be blocked, and the amount of the excitation light received by the image sensor 33 is reduced.

Further, the band cut filters 111, 112, 113, 114 are composed of a reflection type cut filter, and have a wavelength corresponding to the peak intensity of the excitation light and an excitation light intensity of 1 / e ² or less of the peak as a transmission prohibition band. It is a wavelength that includes a wavelength that becomes, and includes a part of the wavelength band of fluorescence generated based on the excitation light, or does not include all of the wavelength band of fluorescence. As a result, the transmission of the excitation light can be reliably blocked, and the fluorescence can be transmitted. That is, it is possible to efficiently capture the effective effective fluorescence wavelength among the weak fluorescence wavelengths while suppressing the invasion of the excitation light as much as possible.

Further, the band cut filters 111, 112, 113, 114 are composed of an absorption type cut filter, and have a wavelength corresponding to the peak intensity of the excitation light and an excitation light intensity of 1 / e ² or less of the peak as a transmission prohibition band. It is a wavelength that includes a wavelength that becomes, and includes a part of the wavelength band of fluorescence generated based on the excitation light, or does not include all of the wavelength band of fluorescence. As a result, the transmission of the excitation light can be reliably blocked, and the fluorescence can be transmitted. That is, it is possible to efficiently capture the effective effective fluorescence wavelength among the weak fluorescence wavelengths while suppressing the invasion of the excitation light as much as possible.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications, modifications, substitutions, additions, deletions, and equality within the scope of the claims. It is understood that it naturally belongs to the technical scope of the present disclosure. Further, each component in the various embodiments described above may be arbitrarily combined as long as the gist of the invention is not deviated.

For example, in the above-described embodiment, the band cut filter has been described by exemplifying a reflection type band cut filter that blocks the transmission of the excitation light by reflecting the excitation light, but is excited by absorbing the excitation light. The present disclosure is similarly applicable even when an absorption type band cut filter that blocks light transmission is used.

This application is based on a Japanese patent application filed on September 28, 2018 (Japanese Patent Application No. 2018-185223), the contents of which are incorporated herein by reference.

The present disclosure has a simple structure using a single excitation light cut filter, effectively reducing the passage of excitation light unnecessary for fluorescence imaging, and shortening the optical length of the imaging optical system. It is useful as an endoscope that suppresses deterioration of the image quality of fluorescent images.

15 Endoscope 25 Rigid part 33 Image sensor 53 Tip flange 55 First image pickup optical system 56 Second image pickup optical system 57 Third image pickup optical system 58 Fourth image pickup optical system 111, 112, 113, 114 Band cut Filter AP1 Aperture CG1 Objective cover glass FG1 Flat plate glass L1 Plano-convex lens L2 Bi-convex lens L2f Convex flat lens L2b Plano-convex lens L20 Lens L21 Convex flat lens L22 Plano-concave lens SG2 Sensor glass

The present disclosure concludes that light from the subject is incident on the optical path, including a plurality of optical components constituting the optical path and fluorescence based on excitation light for causing the fluorescent agent administered to the subject to emit fluorescent light. Only one image sensor is arranged inside the imaging optical system, the imaging optical system to image, an image sensor that photoelectrically converts the light from the subject imaged by the imaging optical system, and the light from the subject. The excitation light cut filter includes an excitation light cut filter that blocks the transmission of at least a part of the excitation light, and the excitation light cut filter is formed by vapor deposition on any one of the plurality of optical components to cut the excitation light. As the angle dependence of the filter, the ray angle at which the intensity of the excitation light is 1 / e ² or less of the peak is θL, the refractive index of any of the optical components on which the excitation light cut filter is formed is nL, and the excitation is performed. When the angle of incidence of light on the optical cut filter is θF, θF = sin ^-1 (nL * sinθL) is smaller than the angle of incidence on the excitation light cut filter inserted in another portion, satisfying the relationship ( * Indicates the multiplication operator), providing an endoscope.

Further, the present disclosure has a plurality of optical components constituting an optical path, and causes light from the subject to enter the optical path, including fluorescence based on excitation light for fluorescing the fluorescent agent administered to the subject. The imaging optical system that forms an image, an image sensor that photoelectrically converts the light from the subject imaged by the imaging optical system, and blocks the transmission of at least a part of the excitation light from the subject. comprising an excitation light cut filter, wherein the includes a plurality of optical components and the second lens disposed on the rear end side of the first lens and the first lens, before Symbol excitation light cut filter adjacent to each other Provided is an endoscope inserted between the rear end surface of the first lens and the front end surface of the second lens.

Claims (15)

Imaging optics that have a plurality of optical components constituting an optical path and include fluorescence based on excitation light for fluorescing a fluorescent agent administered to the subject to form an image by incident light from the subject into the optical path. System and
An image sensor that photoelectrically converts the light from the subject imaged by the imaging optical system,
It is provided with an excitation light cut filter, which is arranged inside the imaging optical system and blocks the transmission of at least a part of the excitation light from the light from the subject.
Endoscope. The excitation light cut filter may be used between the plurality of optical components, or either or both of the objective side and the imaging side of the flat glass adjacent to the most objective side or the most imaging side optical component of the plurality of optical components. Formed in
The endoscope according to claim 1. The excitation light cut filter is formed by plane-depositing on any of the plurality of optical components to be inserted.
The endoscope according to claim 1. The surface of the excitation light cut filter is adhered to any of the adjacent optics, the adhesion of which is filled with an adhesive having a higher refractive index than air.
The endoscope according to claim 1. The surface of the excitation light cut filter has a gap between it and any of the adjacent optical components.
The endoscope according to claim 1. The excitation light cut filter is formed by being vapor-deposited on a curved surface of any of adjacent optical components.
The endoscope according to claim 1. Other optical components other than any of the above optical components are composed of a combination of two or more lenses capable of reducing chromatic aberration.
The endoscope according to claim 3. The excitation light cut filter is formed by vapor deposition on any of the plurality of optical components.
As the angle dependence of the excitation light cut filter, the ^{ray angle at which the intensity of the excitation light is 1 / e 2} or less of the peak is θL, and the refractive index of any of the optical components on which the excitation light cut filter is formed is defined. nL, when the angle of incidence of light on the excitation light cut filter is θF
θF = sin ^-1 (nL * sin θL) is smaller than the angle of incidence on the excitation light cut filter inserted at another site, satisfying the relationship (* indicates the multiplication operator),
The endoscope according to any one of claims 1 to 7. The excitation light cut filter is composed of a reflection type cut filter, and has a wavelength corresponding to the peak intensity of the excitation light and a wavelength at which the intensity of the excitation light is 1 / e ² or less of the peak as a transmission prohibition band. A wavelength that includes a part of the wavelength band of fluorescence generated based on the excitation light, or does not include all of the wavelength band of fluorescence.
The endoscope according to any one of claims 1 to 8. The excitation light cut filter is composed of an absorption type cut filter, and has a wavelength corresponding to the peak intensity of the excitation light and a wavelength at which the intensity of the excitation light is 1 / e ² or less of the peak as a transmission prohibition band. A wavelength that includes a part of the wavelength band of fluorescence generated based on the excitation light, or does not include all of the wavelength band of fluorescence.
The endoscope according to any one of claims 1 to 8. Imaging optics that have a plurality of optical components constituting an optical path and include fluorescence based on excitation light for fluorescing a fluorescent agent administered to the subject to form an image by incident light from the subject into the optical path. System and
An image sensor that photoelectrically converts the light from the subject imaged by the imaging optical system,
An excitation light cut filter that blocks the transmission of at least a part of the excitation light among the light from the subject is provided.
The plurality of optical components include a first lens and a second lens arranged on the rear end side of the first lens.
The rear end surface of the first lens and the front end surface of the second lens adjacent to each other are flat surfaces.
The excitation light cut filter is inserted between the rear end surface of the first lens and the front end surface of the second lens adjacent to each other.
Endoscope. The excitation light cut filter is formed by vapor deposition on at least one of the rear end surface of the first lens and the front end surface of the second lens.
The endoscope according to claim 11. The first lens is a convex flat lens, and the second lens is a plano-convex lens.
The endoscope according to claim 11. The first lens is a convex flat lens, and the second lens is a plano-concave lens.
The endoscope according to claim 11. The region between the rear end surface of the first lens and the front end surface of the second lens is the region having the smallest ray angle in the imaging optical system.
The endoscope according to claim 11.

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