Endoscope and image capturing unit provided therein

Abstract

An endoscope and an image capture unit disposed therein, the endoscope comprising an observation lens and an image capture unit housed within the observation lens. The image capture unit comprises: first and second prisms; a reflective film disposed between the inclined surfaces of the first and second prisms; a first fine-tuning filter, upon which visible light transmitted through the first prism is incident via the reflective film; a first image sensor facing the first fine-tuning filter; a second fine-tuning filter, upon which near-infrared light transmitted through the second prism is incident via the reflective film; and a second image sensor facing the second fine-tuning filter. The first prism is fixed to the second prism, the first fine-tuning filter is fixed to the first prism, and the second fine-tuning filter is fixed to the second prism.

Description

Technical Field

[0001] The present disclosure relates to an endoscope and an image capturing unit provided in the endoscope. Background Art

[0002] Patent document 1 discloses an endoscope in which a single image sensor including an RGB color filter and an infrared light (IR) filter is arranged near the tip end of the endoscope. In the endoscope of patent document 1, the patient's biological tissue is alternately irradiated with visible light and excitation light, and thus visible light image data and near-infrared light image data are alternately collected on the time axis by a single image sensor. In this regard, the endoscope of patent document 1 has a problem that visible light image data and near-infrared light image data cannot be collected at the same timing. Further, four types of pixels are provided in a single image sensor, including red pixels, green pixels, blue pixels and IR pixels. Therefore, there is a problem that noise may appear in the infrared light image signal output from each IR pixel of the image sensor, and the image quality of the near-infrared light image data finally generated may deteriorate.

[0003] Meanwhile, Patent Document 2 discloses an endoscope in which a four-color separation prism and four image sensors are arranged in a camera head. In the endoscope of Patent Document 2, the light emitted from the relay lens is separated by the four-color separation prism into four light components including red light, green light, blue light, and near-infrared light, and each of the four light components is then received by a corresponding image sensor among the four image sensors. The endoscope of Patent Document 2 can simultaneously collect visible light image data and near-infrared light image data. On the other hand, since the four image sensors are arranged at a position away from the tip end of the observation mirror (optical tube), the light intensity (light amount) of the visible light and near-infrared light (particularly the near-infrared light) decreases during the period before the visible light and near-infrared light associated with the patient's biological tissue reaches the four image sensors. As a result, there is a problem of deterioration in the image quality of the visible light image data and the near-infrared light image data. Furthermore, since the overall size of the four-color separation prism is large, it is necessary to arrange the four-color separation prism, for example, in the camera head. For this reason, in order to guide visible light and near-infrared light reflected by the patient's biological tissue from the tip end of the observation scope to the four-color separation prism, expensive optical components (such as relay lenses) need to be provided in the endoscope, and the manufacturing cost of the entire endoscope may increase.

[0004] Patent Document 1: JP-A-2016-209143

[0005] Patent Document 2: JP-A-2019-000339 Summary of the Invention

[0006] From the above viewpoint, the object of the present disclosure is to provide an endoscope capable of improving the image quality of visible light image data and near-infrared light image data indicating a patient's biological tissue while reducing manufacturing costs; and an image capture unit set in the endoscope.

[0007] One aspect of the present disclosure may provide an endoscope including: an observation scope to be inserted into a patient's body; and an image capture unit housed inside the observation scope and configured to receive light associated with the patient's biological tissue so as to capture an image of the biological tissue. The image capture unit includes: a first prism; a second prism facing the first prism; a reflective film, which is arranged between the oblique surface of the first prism and the oblique surface of the second prism and is configured to separate light associated with biological tissue into visible light and near-infrared light; a first fine-tuning filter, which is configured to transmit light in the visible region and shield light in the near-infrared region, and the visible light transmitted through the first prism is incident on the first fine-tuning filter via the reflective film; a first image sensor, which faces the first fine-tuning filter so as to receive the visible light transmitted through the first fine-tuning filter and is configured to convert the received visible light into an electrical signal; a second fine-tuning filter, which is configured to transmit light in the near-infrared region and shield light in the visible region, and the near-infrared light transmitted through the second prism is incident on the second fine-tuning filter via the reflective film; and a second image sensor, which faces the second fine-tuning filter so as to receive the near-infrared light transmitted through the second fine-tuning filter and is configured to convert the received near-infrared light into an electrical signal. The first prism is fixed to the second prism, the first fine tuning filter is fixed to the first prism, and the second fine tuning filter is fixed to the second prism.

[0008] According to the above configuration, the first prism and the second prism are fixed to each other. Furthermore, the first fine-tuning filter is fixed to the first prism, and the second fine-tuning filter is fixed to the second prism. With this configuration, the size of the entire image capture unit can be reduced, and the image capture unit can be accommodated inside the observation scope. Since the image capture unit is accommodated inside the observation scope, the visible light and near-infrared light associated with the patient's biological tissue are effectively received by the first image sensor and the second image sensor, respectively. As described above, since the electrical signal (visible light image signal) indicating the biological tissue is collected by the first image sensor without reducing the SN ratio (signal-to-noise ratio), the image quality of the visible light image data indicating the biological tissue is improved. Further, since the electrical signal (near-infrared light image signal) indicating the biological tissue is collected by the second image sensor without reducing the SN ratio, the image quality of the near-infrared image data indicating the biological tissue is improved. Since the visible light image signal and the near-infrared light image signal are collected at the same timing, the time axis of each frame of the visible light image data and the time axis of each frame of the near-infrared light image data match each other. Therefore, because the time axis of the visible light image data frames matches the time axis of the near-infrared light image data frames, the accuracy of the composite image data generated by synthesizing the visible light image data and the near-infrared light image data is improved. Furthermore, because the image capture unit is housed within the scope, there is no need to provide the scope with expensive relay lenses, etc., for guiding visible light and near-infrared light from the patient's biological tissue to the image capture unit, thereby reducing the manufacturing cost of the entire endoscope. Therefore, an endoscope can be provided that can improve the image quality of the visible light image data and near-infrared light image data indicating the patient's biological tissue while reducing the manufacturing cost.

[0009] In the endoscope, the first image sensor may be fixed to the first fine tuning filter, and the second image sensor may be fixed to the second fine tuning filter.

[0010] According to the above configuration, the size of the entire image capture unit can be reduced, and the image capture unit can be accommodated inside the observation mirror. In this regard, for example, the image capture unit can be accommodated inside the observation mirror having a small inner diameter.

[0011] In the endoscope, the image capturing unit may be arranged near a tip end surface of the endoscope that faces the biological tissue.

[0012] According to the above configuration, since the image capture unit is arranged near the tip end surface of the endoscope facing the biological tissue, the first image sensor and the second image sensor can effectively receive visible light and near-infrared light associated with the patient's biological tissue. As a result, the image quality of the visible light image data and near-infrared light image data collected by the endoscope is improved.

[0013] In the endoscope, the image capture unit may further include: an infrared light-shielding film disposed between the first fine-tuning filter and the first image sensor and configured to transmit light in the visible region and shield light in the near-infrared region; and a visible light-shielding film disposed between the second fine-tuning filter and the second image sensor and configured to transmit light in the near-infrared region and shield light in the visible region. The infrared light-shielding film and the visible light-shielding film may be configured to shield excitation light emitted into biological tissue and included in a wavelength band having a central wavelength of 700 nm to 800 nm.

[0014] According to the above configuration, since the excitation light in the wavelength band of 700nm to 800nm ​​at the center emitted to the biological tissue is shielded by the infrared light shielding film and the visible light shielding film, it is possible to appropriately prevent the excitation light from adversely affecting the image quality of the visible light image data and the near-infrared light image data.

[0015] In the endoscope, the image capturing unit may further include: a lens unit fixed to the first prism so as to guide light associated with the biological tissue toward the first prism.

[0016] According to the above configuration, the lens unit allows visible light and near-infrared light associated with biological tissue to be effectively incident on the first prism, and an appropriate viewing angle of the image capture unit can be ensured. Furthermore, since there is no gap between the lens unit and the first prism, dust and the like can be appropriately prevented from entering the gap, and the burden required for maintenance of the endoscope can be reduced.

[0017] In the endoscope, a distance between a tip end portion of the lens unit and a tip end surface of the endoscope facing biological tissue may be in a range of 0.5 mm to 5 mm.

[0018] According to the above configuration, since the distance between the tip end of the lens unit and the tip end surface of the endoscope facing the biological tissue is within the range of 0.5 mm to 5 mm, the first image sensor and the second image sensor can effectively receive visible light and near-infrared light reflected by the patient's biological tissue. Furthermore, an appropriate viewing angle of the image capture unit can be ensured.

[0019] The endoscope may further include a first support member configured to support the lens unit, the first prism, and the second prism and housed inside the viewing scope. The first support member may be fixed to the lens unit, the first prism, and the second prism.

[0020] According to the above configuration, since the lens unit, the first prism, and the second prism are supported and fixed by the first supporting member, the strength of the entire image capturing unit can be improved by the first supporting member.

[0021] The endoscope may further include a second support member fixed to the first support member and the viewing scope and housed inside the viewing scope.

[0022] According to the above configuration, the first support member fixed to the image capture unit is fixed to the observation mirror via the second support member. In this way, the image capture unit can be reliably fixed to the observation mirror via the first support member and the second support member.

[0023] In the endoscope, the first image sensor may include a CMOS image sensor configured to generate a visible light image signal indicating a normal image of the biological tissue based on visible light forming an inverted image of the biological tissue.

[0024] According to the above configuration, since the first image sensor is a CMOS image sensor configured to generate a visible light image signal indicating a normal image of biological tissue, visible light image data and near-infrared light image data can be acquired at the same timing. Specifically, if the first image sensor is a CCD image sensor, it is necessary to separately perform image inversion processing on the image processing circuit side to generate visible light image data indicating a normal image of biological tissue based on the visible light image signal indicating an inverted image of the biological tissue. For this reason, situations may arise where the timing of generating the visible light image data is later than the timing of generating the near-infrared light image data, making it difficult for the image processing circuit side to acquire the visible light image data and near-infrared light image data at the same timing. Meanwhile, if the first image sensor is a CMOS image sensor, since image inversion processing is not required on the image processing circuit side, the visible light image data and near-infrared light image data can be acquired at the same timing on the image processing circuit side.

[0025] In the endoscope, the first image sensor and the second image sensor may have the same configuration.

[0026] According to the above configuration, since it is not necessary to prepare different types of image sensors for the first image sensor and the second image sensor, the manufacturing cost of the endoscope can be reduced. For example, a CMOS image sensor including a Bayer pattern color filter array can be applied to both the first image sensor and the second image sensor.

[0027] In the endoscope, an imaging surface of the first image sensor and an imaging surface of the second image sensor may be perpendicular to each other.

[0028] According to the above configuration, since the imaging surface of the first image sensor and the imaging surface of the second image sensor are perpendicular to each other, the size of the entire image capturing unit can be reduced and the image capturing unit can be successfully accommodated inside the observation mirror.

[0029] In the endoscope, the visible light channel formed by the combination of the reflective film, the first fine-tuning filter and the infrared light shielding film can have a spectral characteristic such that the transmittance of light in the wavelength band of 720nm to 1050nm is 0.1% or less, and the near-infrared light channel formed by the combination of the reflective film, the second fine-tuning filter and the visible light shielding film can have a spectral characteristic such that the transmittance of light in the wavelength band of 400nm to 798nm is 0.5% or less.

[0030] According to the above configuration, the visible light channel formed by the combination of the reflective film, the first fine-tuning filter, and the infrared light-shielding film has spectral characteristics such that the transmittance of light in the wavelength band of 720nm to 1050nm is 0.1% or less. Therefore, it is possible to appropriately prevent situations in which both the excitation light in the wavelength band of 700nm to 800nm ​​and the near-infrared light emitted into biological tissue adversely affect the image quality of visible light image data. Furthermore, the near-infrared light channel formed by the combination of the reflective film, the second fine-tuning filter, and the visible light-shielding film has spectral characteristics such that the transmittance of light in the wavelength band of 400nm to 798nm is 0.5% or less. Therefore, it is possible to appropriately prevent situations in which both the excitation light in the wavelength band of 700nm to 800nm ​​and the visible light emitted into biological tissue adversely affect the image quality of near-infrared light image data.

[0031] An aspect of the present disclosure may provide an image capturing unit that is housed inside a viewing scope of an endoscope and is configured to receive light associated with biological tissue of a patient so as to capture an image of the biological tissue. The image capture unit includes: a first prism; a second prism facing the first prism; a reflective film, which is arranged between the oblique surface of the first prism and the oblique surface of the second prism and is configured to separate light associated with biological tissue into visible light and near-infrared light; a first fine-tuning filter, which is configured to transmit light in the visible region and shield light in the near-infrared region, and the visible light transmitted through the first prism is incident on the first fine-tuning filter via the reflective film; a first image sensor, which faces the first fine-tuning filter so as to receive the visible light transmitted through the first fine-tuning filter and is configured to convert the received visible light into an electrical signal; a second fine-tuning filter, which is configured to transmit light in the near-infrared region and shield light in the visible region, and the near-infrared light transmitted through the second prism is incident on the second fine-tuning filter via the reflective film; and a second image sensor, which faces the second fine-tuning filter so as to receive the near-infrared light transmitted through the second fine-tuning filter and is configured to convert the received near-infrared light into an electrical signal. The first prism is fixed to the second prism, the first fine tuning filter is fixed to the first prism, and the second fine tuning filter is fixed to the second prism.

[0032] According to the present disclosure, it is possible to provide an endoscope capable of improving the image quality of visible light image data and near-infrared light image data indicating biological tissue of a patient while reducing manufacturing costs; and an image capturing unit provided in the endoscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is an exploded perspective view showing the endoscope according to the present embodiment.

[0034] Figure 2 is a cross-sectional view showing the endoscope according to the present embodiment.

[0035] Figure 3 : is a diagram showing an example of the reflection characteristics of a visible light reflecting film with respect to visible light and the transmission characteristics of the visible light reflecting film with respect to near-infrared light.

[0036] Figure 4 is a diagram showing an example of the transmission characteristics of the first fine tuning filter and the transmission characteristics of the second fine tuning filter.

[0037] Figure 5 is a graph showing an example of the transmission characteristics of an infrared light-shielding film and the transmission characteristics of a visible light-shielding film.

[0038] Figure 6is a diagram showing an example of the spectral transmittance characteristics of a visible light channel and the spectral transmittance characteristics of a near-infrared light channel.

[0039] Figure 7 Graphs showing transmission characteristics of RGB color filters on a visible light channel and transmission characteristics of RGB color filters on a near-infrared light channel.

[0040] Figure 8 is a diagram schematically showing a CMOS image sensor including a Bayer pattern RGB color filter.

[0041] Figure 9 is a diagram showing the configuration of an endoscope system.

[0042] Figure 10 is a diagram illustrating an example of synthesized image data obtained by synthesizing visible light image data and near-infrared light image data. DETAILED DESCRIPTION

[0043] Hereinafter, an endoscope 1 according to an embodiment of the present disclosure (hereinafter, simply referred to as "this embodiment") will be described with reference to the drawings. For convenience of description, the size of each component shown in the drawings may be different from the actual size of each component.

[0044] In the description of this embodiment, for the convenience of description, the X-axis, Y-axis and Z-axis directions of the endoscope 1 may be appropriately mentioned. These directions are Figure 1 The relative direction of the endoscope 1 shown in FIG. It is defined that one of the X-axis, Y-axis, and Z-axis is orthogonal to the other two axes. The Z-axis corresponds to the direction in which the scope 3 of the endoscope 1 extends.

[0045] First, we will refer to Figure 1 and Figure 2 The configuration of the endoscope 1 according to the present embodiment will be described. Figure 1 is an exploded perspective view showing the endoscope 1 according to the present embodiment. Figure 2 is a cross-sectional view showing the endoscope 1 in a state in which the image capturing unit 2 is accommodated inside the observation scope 3 .

[0046] like Figure 1 and Figure 2 As shown, endoscope 1 includes a viewing lens 3, an image capture unit 2, a light guide 4, a first support member 5, a second support member 6, and a lens cover 7. By inserting endoscope 1 into a patient's body, a healthcare worker can observe biological tissue, such as within the patient's body, in real time. Endoscope 1 may be, for example, a rigid endoscope used in laparoscopic surgery. Endoscope 1 is not limited to a rigid endoscope.

[0047] Both visible light image data and near-infrared light image data of the patient's biological tissue can be collected simultaneously by the endoscope 1. In this regard, in laparoscopic surgery, a fluorescent contrast agent that emits near-infrared light (such as indocyanine green (ICG)) is used. When ICG is irradiated with excitation light (laser), ICG emits near-infrared light. The central wavelength λ of the laser as the excitation light is, for example, in the range of 700nm to 800nm, more specifically, in the range of 785nm to 795nm. After ICG is injected into the patient's vein, a health care worker can visually specify the diseased part in which the ICG resides by visually identifying the near-infrared light image data collected by the endoscope 1. In this way, a health care worker such as a surgeon can perform surgical treatment (such as resection of the diseased part) on the diseased part specified by the ICG.

[0048] The observation scope 3 is a portion of the endoscope 1 to be inserted into the patient's body. The observation scope 3 is configured as a rigid tube having a space S, for example. The outer diameter of the observation scope 3 is, for example, approximately 10 mm, and the inner diameter of the observation scope 3 is, for example, approximately 9 mm. The image capture unit 2 is configured to receive visible light and near-infrared light associated with the patient's biological tissue so as to capture an image of the biological tissue. Specifically, the image capture unit 2 is configured to receive visible light reflected by the patient's biological tissue and near-infrared light emitted from a fluorescent contrast agent (ICG, etc.) residing in the biological tissue so as to capture an image of the biological tissue. In the present embodiment, the image capture unit 2 is accommodated inside the space S of the observation scope 3. In this regard, the image capture unit 2 is reduced to such an extent that the image capture unit 2 can be accommodated inside the observation scope 3 having an inner diameter of approximately 9 mm. Further, the image capture unit 2 is provided at the tip end 3a of the observation scope 3 (see Figure 2 ) vicinity. In a state in which the endoscope 1 is inserted into the patient's body interior, the tip end portion 3a of the viewing scope 3 faces the patient's biological tissue. A specific configuration of the image capturing unit 2 will be described later.

[0049] The light guide 4 is configured to guide the visible light emitted from the visible light source (not shown) and the excitation light emitted from the excitation light source (not shown) toward the biological tissue of the patient. The light guide 4 includes a plurality of optical fibers through which the visible light and the excitation light are propagated. Figure 1 In the figure, only a portion of the light guide 4 is shown for simplified illustration. However, the light guide 4 is housed within the space S of the observation scope 3 and extends along the Z-axis direction to the visible light source and the excitation light source. Visible light emitted from the light guide 4 is reflected by biological tissue and then received by the image capture unit 2. Furthermore, the excitation light emitted from the light guide 4 is transmitted to a fluorescent contrast agent (such as ICG) residing in the biological tissue. Thereafter, near-infrared light (fluorescence) emitted from the fluorescent contrast agent by irradiation with the excitation light is received by the image capture unit 2.

[0050] like Figure 2 As shown, the first support member 5 is housed within the space S of the viewing mirror 3 and is configured to support the image capture unit 2. Specifically, the first support member 5 is secured to the image capture unit 2 via an adhesive. More specifically, the first support member 5 is configured to support the lens unit 20, first prism 21, and second prism 22 provided in the image capture unit 2, and is secured to the lens unit 20, first prism 21, and second prism 22 via an adhesive. In this manner, the strength of the entire image capture unit 2 can be enhanced by the first support member 5.

[0051] The second support member 6 is housed within the space S of the observation scope 3 and is secured to the first support member 5 and the observation scope 3 by an adhesive. The second support member 6 includes an insertion hole 62 into which the light guide 4 is inserted, an insertion hole 63 into which the lens unit 20 is inserted, and an insertion hole 64 into which the lens cover 7 is inserted. With the light guide 4 inserted into the insertion hole 62, the light guide 4 is supported by the second support member 6. The insertion hole 63 and the insertion hole 64 communicate with each other. With the lens cover 7 inserted into the insertion hole 64, the lens cover 7 is secured and supported by the second support member 6. The front surface 65 of the second support member 6, the front surface 7a of the lens cover 7, and the end surface 4a of the light guide 4 form the tip end surface 1a of the endoscope 1 that faces biological tissue.

[0052] As described above, since the first support member 5 is fixed to the image capturing unit 2 and the second support member 6 is fixed to the first support member 5 and the observation mirror 3 , the image capturing unit 2 can be reliably fixed to the observation mirror 3 through the first support member 5 and the second support member 6 .

[0053] (Specific Configuration of Image Capturing Unit 2)

[0054] Next, we will refer to Figure 2 The specific configuration of the image capturing unit 2 is described below. Figure 2 As shown, the image capture unit 2 includes a lens unit 20, a first prism 21, a second prism 22, and a visible light reflecting film 27 (an example of a reflecting film). The image capture unit 2 also includes a first fine-tuning filter 23, an infrared light shielding film 28, a first image sensor 24, and a first circuit board 32. The image capture unit 2 also includes a second fine-tuning filter 25, a visible light shielding film 29, a second image sensor 26, and a second circuit board 33.

[0055] The lens unit 20 is configured to guide visible light and near-infrared light from biological tissue toward the first prism 21. In order to widen the image angle (viewing angle) of the image capture unit 2 and more efficiently acquire visible light and near-infrared light from biological tissue, it is preferable to set the lens unit 20 near the tip end 3a of the observation mirror 3 or near the tip end face 1a of the endoscope 1. In the present embodiment, the distance in the Z-axis direction between the incident surface 20a of the lens unit 20, which is the tip end of the lens unit 20, and the tip end face 1a of the endoscope 1 is in the range of 0.5 mm to 5 mm. Preferably, the distance in the Z-axis direction between the incident surface 20a and the tip end face 1a is in the range of 0.5 mm to 2 mm. More preferably, the distance in the Z-axis direction between the incident surface 20a and the tip end face 1a is in the range of 0.5 mm to 1 mm.

[0056] The lens unit 20 and the first prism 21 are fixed to each other via the first supporting member 5. At this point, the emission surface 20b of the lens unit 20 and the incident surface 21b of the first prism 21 are in contact with each other, and there is no gap between the lens unit 20 and the first prism 21. Therefore, dust and the like can be appropriately prevented from entering the gap, and the burden required for maintenance of the endoscope 1 can be reduced.

[0057] The first prism 21 and the second prism 22 are configured as right-angle prisms. The first prism 21 and the second prism 22 are formed of, for example, a transparent glass material or a transparent plastic material. The first prism 21 and the second prism 22 face each other and are fixed to each other by an adhesive. In particular, the first prism 21 and the second prism 22 are fixed to each other in a state in which the inclined surface 21a of the first prism 21 and the inclined surface 22a of the second prism 22 face each other. Therefore, since the shape of the first prism 21 and the second prism 22 fixed to each other is a rectangular parallelepiped, the size of the entire image capture unit 2 can be reduced, and the image capture unit 2 can be accommodated inside the observation mirror 3.

[0058] A visible light reflecting film 27 (an example of a reflecting film) is provided between the inclined surface 21a of the first prism 21 and the inclined surface 22a of the second prism 22. In this embodiment, after the visible light reflecting film 27 is formed on either the inclined surface 21a or the inclined surface 22a, the first prism 21 and the second prism 22 are fixed to each other via an adhesive. The visible light reflecting film 27 is configured to separate visible light and near-infrared light from biological tissue. More specifically, the visible light reflecting film 27 is configured to reflect visible light emitted from biological tissue and transmitted through the lens unit 20 and the first prism 21 toward the first fine-tuning filter 23. Further, the visible light reflecting film 27 is configured to transmit near-infrared light emitted from biological tissue and transmitted through the lens unit 20 and the first prism 21 toward the second fine-tuning filter 25.

[0059] Since the inclined surface 21a of the first prism 21 and the inclined surface 22a of the second prism 22 are inclined at 45 degrees relative to the Z-axis, the visible light reflective film 27 is also inclined at 45 degrees relative to the Z-axis. Therefore, the visible light reflective film 27 reflects visible light, changing its propagation direction by 90 degrees, while transmitting near-infrared light without changing its propagation direction. As described above, the propagation direction of visible light is converted from the Z-axis direction to the Y-axis direction by the visible light reflective film 27, while the propagation direction of near-infrared light traveling in the Z-axis direction is not changed by the visible light reflective film 27.

[0060] The visible light reflecting film 27 is a dichroic mirror made of a dielectric multilayer film formed by alternately stacking dielectric thin films having a high refractive index (high refractive index layer) and dielectric thin films having a low refractive index (low refractive index layer). As a material of the high refractive index layer, for example, TiO2 (refractive index n H =2.35). As the material of the low refractive index layer, for example, SiO2 (refractive index n L =1.47). Both the number of high-refractive-index layers and the number of low-refractive-index layers are, for example, 80.

[0061] Figure 3 2 shows an example of the reflection characteristics of the visible light reflecting film 27 with respect to visible light and the transmission characteristics of the visible light reflecting film 27 with respect to near infrared light. Figure 3 As shown, the visible light reflecting film 27 reflects visible light with a reflectivity of 90% or higher relative to visible light in the wavelength range of 400 nm to 650 nm. On the other hand, the visible light reflecting film 27 reflects almost no near-infrared light in the wavelength range of 800 nm to 1050 nm. In other words, the visible light reflecting film 27 transmits visible light with a transmittance of 10% or lower relative to visible light in the wavelength range of 400 nm to 650 nm. Furthermore, the visible light reflecting film 27 transmits most of the near-infrared light in the wavelength range of 800 nm to 1050 nm.

[0062] The first fine-tuning filter 23 is fixed to the first prism 21 with an adhesive. The incident surface 23b of the first fine-tuning filter 23 and the emitting surface 21c of the first prism 21 are in contact with each other through the adhesive. The first fine-tuning filter 23 is configured to transmit light in the visible region (visible light) and shield light in the near-infrared region (near-infrared light). Light reflected by the visible light reflecting film 27 and transmitted through the first prism 21 is incident on the first fine-tuning filter 23. The first fine-tuning filter 23 transmits the visible light component of the incident light on the first fine-tuning filter 23 and shields the near-infrared light component of the incident light. Figure 4 2 shows an example of the transmission characteristics of the first fine-tuning filter 23. Figure 4As shown, the transmittance of the first fine-tuning filter 23 with respect to visible light in the wavelength band of 400 nm to 600 nm is 90% or higher, while the transmittance of the first fine-tuning filter 23 with respect to near-infrared light at a wavelength of 800 nm or higher is 20% or lower. The first fine-tuning filter 23 is formed of colored glass that shields infrared light.

[0063] The infrared light shielding film 28 is provided between the first fine-tuning filter 23 and the first image sensor 24 in the Y-axis direction. In the present embodiment, after the infrared light shielding film 28 is formed on the emission surface 23a of the first fine-tuning filter 23, the first fine-tuning filter 23 and the first image sensor 24 are fixed to each other via an adhesive. The infrared light shielding film 28 is configured to transmit light in the visible region (visible light) and shield light in the near-infrared region (near-infrared light) and excitation light emitted to biological tissue and included in a band having a central wavelength of 700nm to 800nm. The infrared light shielding film 28 transmits the visible light component in the incident light, the incident light is transmitted through the first fine-tuning filter 23 and incident on the infrared light shielding film 28, and shields the near-infrared light component in the incident light. Figure 5 An example of the transmission characteristics of the infrared light shielding film 28 is shown. Figure 5 As shown, the transmittance of the infrared light shielding film 28 with respect to visible light in the wavelength band of 400 nm to 650 nm is 95% or higher, and the transmittance with respect to light of a wavelength of 700 nm or higher is 1% or lower.

[0064] The infrared light shielding film 28 is a dichroic mirror made of a dielectric multilayer film formed by alternately stacking high refractive index layers and low refractive index layers. As a material of the high refractive index layer, for example, TiO2 (refractive index n H =2.35). As the material of the low refractive index layer, for example, SiO2 (refractive index n L =1.47). Both the number of high refractive index layers and the number of low refractive index layers are, for example, 50.

[0065] Therefore, visible light reflected by the biological tissue of the patient is incident on the first image sensor 24 through a visible light channel formed by a combination of the visible light reflecting film 27 , the first fine tuning filter 23 , and the infrared light shielding film 28 . Figure 6 An example of the spectral transmission characteristics of the visible light channel formed by the combination of the visible light reflecting film 27, the first fine tuning filter 23 and the infrared light shielding film 28 is shown. Figure 6As shown, the transmittance of the visible light channel with respect to visible light in the wavelength band of 400 nm to 600 nm is 80% or higher, while the transmittance of light in the wavelength band of 720 nm to 1050 nm is 0.1% or lower. In this regard, the visible light channel preferably has spectral characteristics such that the transmittance of light in the wavelength band of 720 nm to 1050 nm is 0.01% or lower.

[0066] The first image sensor 24 is mounted on the first circuit board 32 and is arranged so that its imaging surface faces the first fine-tuning filter 23 and the infrared light shielding film 28 in the Y-axis direction. The first image sensor 24 is fixed to the first fine-tuning filter 23 by an adhesive, with the infrared light shielding film 28 interposed therebetween. The first image sensor 24 is configured to receive visible light transmitted through the visible light channel formed by the combination of the visible light reflecting film 27, the first fine-tuning filter 23, and the infrared light shielding film 28, and convert the received visible light into an electrical signal.

[0067] The first image sensor 24 is a complementary metal oxide semiconductor (CMOS) image sensor or a charge coupled device (CCD) image sensor. In this regard, since the visible light incident on the image capture unit 2 is incident on the first image sensor 24 after being reflected once by the visible light reflecting film 27, the image of the biological tissue incident on the first image sensor 24 is an inverted image. On the other hand, the first image sensor 24 is preferably a CMOS image sensor because the CMOS image sensor can generate a visible light image signal indicating a normal image of the biological tissue based on the visible light that forms the inverted image of the biological tissue. In this regard, by adjusting the order of reading the charges accumulated in the photodiodes of the CMOS image sensor, a visible light image signal indicating a normal image of the biological tissue can be generated.

[0068] like Figure 8As shown, the first image sensor 24 includes a Bayer pattern color filter array and a photodiode array having a plurality of photodiodes arranged in a matrix. The color filter array includes a plurality of red filters, a plurality of green filters, and a plurality of blue filters. In the Bayer pattern color filter array, the number of green filters is twice the number of red filters and the number of blue filters. Each photodiode included in the photodiode array faces one of the plurality of color filters (red filter, green filter, and blue filter). Therefore, the first image sensor 24 converts the received visible light into an electrical signal to generate a visible light image signal (raw data) indicating an image of biological tissue, and then transmits the generated visible light image signal to the visible light image data generation circuit 41 (see FIG. 4 ) via the electrical wire 35. Figure 9 ). Thereafter, the visible light image data generation circuit 41 generates visible light image data by performing image data conversion processing (raw data -> RGB data) on the visible light image signal (raw data). In the following description, the red filter, green filter, and blue filter in the color filter array may be collectively referred to as "RGB filters."

[0069] Figure 7 1 shows the transmission characteristics of the RGB color filter on the visible light channel. The visible light from the biological tissue passes through the visible light channel of the image capture unit 2 and then passes through the RGB color filter of the first image sensor 24. Thereafter, the visible light passing through the RGB color filter is received by the photodiode. Figure 7 As shown, regarding the transmission characteristics of the red filter on the visible light channel, the transmittance of light at a wavelength of 720 nm or greater is 0.1% or less. Regarding the transmission characteristics of the green filter on the visible light channel, the transmittance of light at a wavelength of 720 nm or greater is 0.1% or less. Regarding the transmission characteristics of the blue filter on the visible light channel, the transmittance of light at a wavelength of 720 nm or greater is 0.1% or less.

[0070] In this manner, excitation light having a central wavelength of 700 nm to 800 nm (more specifically, excitation laser light having a central wavelength of 785 nm to 795 nm) is emitted toward biological tissue, while near-infrared light is appropriately prevented from passing through the RGB color filters. As a result, the excitation light and near-infrared light are appropriately prevented from being received by the photodiode of first image sensor 24, and the accuracy or reliability of visible light image data indicating biological tissue is improved.

[0071] The second fine-tuning filter 25 is fixed to the second prism 22 with an adhesive. The incident surface 25b of the second fine-tuning filter 25 and the emission surface 22b of the second prism 22 are in contact with each other via the adhesive. The second fine-tuning filter 25 is configured to transmit light in the near-infrared region (near-infrared light) and shield light in the visible region (visible light). Light transmitted through the visible light reflecting film 27 and the second prism 22 is incident on the second fine-tuning filter 25. The second fine-tuning filter 25 transmits the near-infrared light component of the incident light on the second fine-tuning filter 25 and shields the visible light component of the incident light. Figure 4 2 shows an example of the transmission characteristics of the second fine-tuning filter 25. Figure 4 As shown, the second fine-tuning filter 25 has a transmittance of 90% or more for near-infrared light having a wavelength of 850 nm or more, and a transmittance of 1% or less for visible light in the wavelength band of 400 nm to 750 nm. The second fine-tuning filter 25 is formed of colored glass that shields visible light.

[0072] The visible light shielding film 29 is provided between the second fine-tuning filter 25 and the second image sensor 26 in the Z-axis direction. In the present embodiment, after the visible light shielding film 29 is formed on the emission surface 25a of the second fine-tuning filter 25, the second fine-tuning filter 25 and the second image sensor 26 are fixed to each other via an adhesive. The visible light shielding film 29 is configured to transmit light in the near-infrared region (near-infrared light) and shield light in the visible region (visible light) and excitation light emitted to biological tissue and included in a wavelength band having a central wavelength of 700nm to 800nm. The visible light shielding film 29 transmits the near-infrared light component in the incident light, the incident light is transmitted through the second fine-tuning filter 25 and incident on the visible light shielding film 29, and shields the visible light component in the incident light. Figure 5 An example of the transmission characteristics of the visible light shielding film 29 is shown. Figure 5 As shown, the transmittance of the visible light shielding film 29 with respect to near infrared light having a wavelength of 850 nm or more is 95% or more, while the transmittance of the visible light shielding film 29 with respect to light in a wavelength band of 700 nm to 800 nm is 1% or less.

[0073] The visible light shielding film 29 is a dichroic mirror made of a dielectric multilayer film formed by alternately stacking high refractive index layers and low refractive index layers. As a material of the high refractive index layer, for example, TiO2 (refractive index n H =2.35). As the material of the low refractive index layer, for example, SiO2 (refractive index n L =1.47). Both the number of high refractive index layers and the number of low refractive index layers are, for example, 50.

[0074] Therefore, near infrared light emitted from the fluorescent contrast agent present in biological tissue is incident on the second image sensor 26 through a near infrared light channel formed by a combination of the visible light reflecting film 27 , the second fine tuning filter 25 , and the visible light shielding film 29 . Figure 6 An example of the spectral transmission characteristics of the near-infrared light channel formed by the combination of the visible light reflecting film 27, the second fine tuning filter 25 and the visible light shielding film 29 is shown. Figure 6 As shown, the transmittance of the near-infrared light channel with respect to near-infrared light having a wavelength of 870 nm or greater is 90% or greater, and the transmittance of the near-infrared light channel with respect to light in the wavelength band of 400 nm to 798 nm is 0.5% or less. In this regard, the near-infrared light channel preferably has spectral characteristics such that the transmittance of light in the wavelength band of 400 nm to 798 nm is 0.01% or less.

[0075] The second image sensor 26 is mounted on the second circuit board 33 and is arranged so that its imaging surface faces the second fine-tuning filter 25 and the visible light shielding film 29 in the Z-axis direction. The second image sensor 26 is fixed to the second fine-tuning filter 25 by an adhesive, with the visible light shielding film 29 interposed therebetween. The imaging surface of the second image sensor 26 and the imaging surface of the first image sensor 24 are perpendicular to each other. The second image sensor 26 is configured to receive near-infrared light that has been transmitted through the near-infrared light channel formed by the combination of the visible light reflecting film 27, the second fine-tuning filter 25, and the visible light shielding film 29, and convert the received near-infrared light into an electrical signal.

[0076] The second image sensor 26 converts the received near-infrared light into an electrical signal to generate a near-infrared light image signal indicating an image of the biological tissue, and then transmits the generated near-infrared light image signal to the near-infrared light image data generating circuit 42 (see FIG. Figure 9 ). Thereafter, the near-infrared light image data generation circuit 42 generates near-infrared light image data by performing predetermined processing on the near-infrared light image signal.

[0077] The second image sensor 26 is a CMOS image sensor or a CCD image sensor. From the perspective of manufacturing costs for the endoscope 1, the second image sensor 26 and the first image sensor 24 preferably have the same configuration. In this case, there is no need to prepare different types of image sensors for the first image sensor 24 and the second image sensor 26, thereby reducing the manufacturing costs of the endoscope 1. For example, similar to the first image sensor 24, the second image sensor 26 may include a Bayer pattern color filter array and a photodiode array having a plurality of photodiodes arranged in a matrix. In the following description, it is assumed that the second image sensor 26 includes a Bayer pattern color filter array.

[0078] Figure 7 : shows the transmission characteristics of the RGB color filter on the near-infrared light channel. The near-infrared light emitted from the fluorescent contrast agent present on the biological tissue passes through the near-infrared light channel of the image capture unit 2 and then passes through the RGB color filter of the second image sensor 26. Thereafter, the near-infrared light passing through the RGB color filter is received by the photodiode. Figure 7 As shown, regarding the transmission characteristics of the blue filter on the near-infrared light channel, the transmittance of light in the band of 400nm to 798nm is 0.5% or less, and the transmittance of light near the wavelength of 850nm is the highest. Similarly, regarding the transmission characteristics of the green filter on the near-infrared light channel, the transmittance of light in the band of 400nm to 798nm is 0.5% or less, and the transmittance of light near the wavelength of 850nm is the highest. Similarly, regarding the transmission characteristics of the red filter on the near-infrared light channel, the transmittance of light in the band of 400nm to 798nm is 0.5% or less, and the transmittance of light near the wavelength of 850nm is the highest. Further, as Figure 7 As shown, according to the spectral characteristics of the fluorescence (near-infrared light) output from the fluorescent contrast agent, the center wavelength of the near-infrared light exists near a wavelength of 830 nm.

[0079] Therefore, even if the second image sensor 26 includes a Bayer pattern filter array, the near-infrared light output from the fluorescent contrast agent can be converted into an electrical signal, and the visible light and the excitation light can be appropriately prevented from being received by the photodiode of the second image sensor 26. Therefore, the manufacturing cost of the endoscope 1 is reduced, and the accuracy or reliability of the near-infrared light image data indicating the biological tissue is improved.

[0080] Furthermore, in the single image sensor disclosed in Patent Document 1, there are four types of pixels, including blue pixels, green pixels, red pixels, and infrared pixels. Therefore, there are problems such as low pixel values ​​of IR pixels, the possibility of noise appearing in the near-infrared image signal output from a single IR pixel of the image sensor, and the possibility of deterioration in the image quality of the near-infrared image data. Meanwhile, in the second image sensor 26, since all pixels are IR pixels, the pixel value of each IR pixel can be increased through H / V pixel addition processing, which is a process of adding the pixel values ​​of adjacent pixels in the horizontal (H) and vertical (V) directions. In this way, in the second image sensor 26, the pixel value of each IR pixel is increased through H / V pixel addition processing, making it less likely that noise will appear in the near-infrared image signal output from the second image sensor 26, and improving the accuracy or reliability of the near-infrared image data indicating biological tissue.

[0081] Next, we will refer to Figure 9 Endoscopic system 100 is described. Figure 9 is a diagram showing the configuration of the endoscope system 100. Figure 9 As shown, the endoscope system 100 includes an endoscope 1, which includes an image capturing unit 2, an image processing circuit 40, and a display unit 50. Figure 9 , for convenience of description, only a portion of the configuration of the endoscope 1 and the image processing circuit 40 is shown. The image processing circuit 40 includes a visible light image data generating circuit 41, a near infrared light image data generating circuit 42, a synthetic image data generating circuit 43, and an output interface 44.

[0082] The image processing circuit 40 is configured to generate image data indicating biological tissue based on the image signal (digital signal) transmitted from the image capture unit 2, and then transmit the generated image data to the display unit 50. The image processing circuit 40 generates image data at a predetermined frame rate (e.g., 60 fps). The frame rate of the image data is not particularly limited. In this embodiment, the image processing circuit 40 can generate visible light image data and near-infrared light image data at the same timing and at the same frame rate.

[0083] The image processing circuit 40 may include: a microcomputer including one or more processors and one or more memories; and an electronic circuit including passive components and active components (such as transistors). The processor is, for example, at least one of a central processing unit (CPU), a micro processing unit (MPU), and a graphics processing unit (GPU). The memory includes a read-only memory (ROM) and a random access memory (RAM). In addition to or instead of the microcomputer, the image processing circuit 40 may be a non-von Neumann computer, such as an application specific integrated circuit (ASIC) or a field-programmable gate array (FPGA).

[0084] As described above, the visible light image data generation circuit 41 is configured to receive the visible light image signal (RAW data) from the first image sensor 24 and then generate visible light image data based on the visible light image signal. The visible light image data generation circuit 41 transmits the visible light image data to the synthetic image data generation circuit 43 and the output interface 44.

[0085] The near-infrared image data generation circuit 42 is configured to receive the near-infrared image signal from the second image sensor 26 and then generate near-infrared image data based on the near-infrared image signal. The near-infrared image data generation circuit 42 transmits the near-infrared image data to the synthetic image data generation circuit 43 and the output interface 44.

[0086] The synthetic image data generating circuit 43 is configured to generate synthetic image data by synthesizing the received visible light image data and near-infrared light image data. The synthetic image data generating circuit 43 can generate synthetic image data after coloring the near-infrared light image data with a predetermined color (fluorescent color). Since the near-infrared light image data shows biological tissue in which a fluorescent contrast agent such as ICG exists, when the near-infrared light image data is colored with a predetermined color, the biological tissue (diseased portion) in which the fluorescent contrast agent exists is highlighted and displayed on the synthetic image data (for example, see Figure 10 ). Therefore, a health care worker such as a surgeon can clearly grasp the diseased part by visually recognizing the synthesized image data displayed on the display unit 50.

[0087] The visible light image data, the near-infrared light image data, and the synthesized image data are transmitted to the display unit 50 via the output interface 44. The display unit 50 is configured to display at least one of the visible light image data, the near-infrared light image data, and the synthesized image data. The image data transmitted to the display unit 50 can be appropriately changed according to the healthcare worker's operation of the endoscope system 100. The display unit 50 can be a liquid crystal display or an organic EL display, or can be a transmissive or non-transmissive head-mounted display mounted on the healthcare worker's head.

[0088] According to this embodiment, first prism 21 and second prism 22, which are right-angle prisms, are fixed to each other. First fine-tuning filter 23 is fixed to first prism 21 and first image sensor 24, and second fine-tuning filter 25 is fixed to second prism 22 and second image sensor 26. Furthermore, the imaging surfaces of first image sensor 24 and second image sensor 26 are perpendicular to each other. This configuration reduces the size of the entire image capture unit 2 and allows it to be accommodated within the space S of observation scope 3, which has a small inner diameter. Since image capture unit 2 is accommodated within space S near the tip end face 1a of endoscope 1, visible light and near-infrared light associated with the patient's biological tissue are efficiently received by first image sensor 24 and second image sensor 26, respectively. In this way, since visible light image signals indicating the biological tissue are captured by first image sensor 24 without reducing the signal-to-noise ratio (SN ratio), the image quality of the visible light image data indicating the biological tissue is improved. Furthermore, since near-infrared light image signals indicating the biological tissue are captured by second image sensor 26, the image quality of the near-infrared light image data indicating the biological tissue is also improved. Since the visible light image signal and the near-infrared light image signal are acquired at the same timing, the time axis of each frame of the visible light image data and the time axis of each frame of the near-infrared light image data match each other. Therefore, since the time axis of the frames of the visible light image data and the time axis of the frames of the near-infrared light image data match, the accuracy of the composite image data generated by synthesizing the visible light image data and the near-infrared light image data is improved. Furthermore, since the image capture unit 2 is housed within the space S of the observation scope 3, there is no need to provide an expensive relay lens or the like on the observation scope 3 for guiding visible light and near-infrared light from the patient's biological tissue to the image capture unit 2, so that the manufacturing cost of the entire endoscope 1 can be reduced. Therefore, an endoscope 1 can be provided that can improve the image quality of visible light image data, near-infrared light image data, and composite image data indicating the patient's biological tissue while reducing the manufacturing cost.

[0089] According to this embodiment, when the first image sensor 24 is a CMOS image sensor configured to generate a visible light image signal indicating a normal image of biological tissue, visible light image data and near-infrared light image data can be acquired at the same timing. Specifically, when the first image sensor 24 is a CCD image sensor, image processing circuit 40 must separately perform image inversion processing to generate visible light image data indicating a normal image of biological tissue based on the visible light image signal indicating an inverted image of the biological tissue. For this reason, the visible light image data may be generated later than the near-infrared light image data, making it difficult for image processing circuit 40 to acquire the visible light image data and near-infrared light image data at the same timing. Meanwhile, when the first image sensor 24 is a CMOS image sensor, image processing circuit 40 does not need to perform image inversion processing, so visible light image data and near-infrared light image data can be acquired at the same timing.

[0090] According to this embodiment, the visible light channel formed by the combination of visible light reflecting film 27, first fine-tuning filter 23, and infrared light shielding film 28 has spectral characteristics such that the transmittance of light in the wavelength band of 720 nm to 1050 nm is 0.1% or less. Therefore, it is possible to appropriately prevent situations in which both excitation light in the wavelength band of 700 nm to 800 nm and near-infrared light emitted into biological tissue adversely affect the accuracy or reliability of visible light image data. Furthermore, the near-infrared light channel formed by the combination of visible light reflecting film 27, second fine-tuning filter 25, and visible light shielding film 29 has spectral characteristics such that the transmittance of light in the wavelength band of 400 nm to 798 nm is 0.5% or less. Therefore, it is possible to appropriately prevent situations in which excitation light and visible light emitted into biological tissue adversely affect the accuracy or reliability of near-infrared light image data. Further, in the second image sensor 26, the pixel value of each IR pixel is increased by H / V pixel addition processing, so that noise is less likely to appear in the near-infrared light image signal output from the second image sensor 26, and the accuracy or reliability of the near-infrared light image data is improved.

[0091] Although the embodiment of the present invention has been described above, it goes without saying that the technical scope of the present invention should not be interpreted as being limited to the description of the present embodiment. It should be understood by those skilled in the art that the present embodiment is merely an example and that various modifications of the embodiment can be made within the scope of the present invention described in the claims. The technical scope of the present invention should be determined based on the scope of the present invention described in the claims and its equivalent scope.

[0092] In the present embodiment, the visible light reflecting film 27 has been described as an example of a reflecting film that separates visible light and near-infrared light from biological tissue, but the reflecting film is not limited to a visible light reflecting film. For example, the reflecting film that separates visible light and near-infrared light may be a near-infrared light reflecting film configured to transmit visible light and reflect near-infrared light. In this case, the position of the first prism 21 and the position of the second prism 22 are interchanged with each other, and the position of the first fine-tuning filter 23 on which the infrared light shielding film 28 is formed and the position of the second fine-tuning filter 25 on which the visible light shielding film 29 is formed are interchanged with each other. Further, the position of the first image sensor 24 and the position of the second image sensor 26 are interchanged with each other. Similarly, the near-infrared light reflecting film is also a dichroic mirror made of a dielectric multilayer film formed by alternately stacking a dielectric film having a high refractive index (high refractive index layer) and a dielectric film having a low refractive index (low refractive index layer).

[0093] In the present embodiment, the first prism 21 and the second prism 22 are configured as right-angle prisms, but the shape of the first prism 21 or the second prism 22 is not limited to a right-angle triangular prism.

[0094] The first image sensor 24 and the second image sensor 26 may have different configurations. For example, the second image sensor 26 may not include a color filter array. In this case, since the near-infrared light channel arranged in front of the second image sensor 26 transmits the near-infrared light while shielding the visible light and the excitation light, only the near-infrared light can be incident on the photodiode of the second image sensor 26.

Claims

1. An endoscope comprising: a scope, to be inserted into the patient's body; as well as an image capturing unit housed inside the scope and configured to receive light associated with the patient's biological tissue so as to capture an image of the biological tissue, The image capturing unit comprises: First Prism; a second prism facing the first prism; a reflective film disposed between the oblique surface of the first prism and the oblique surface of the second prism and configured to separate light associated with the biological tissue into visible light and near-infrared light; a first fine tuning filter configured to transmit light in a visible region and shield light in a near-infrared region, the visible light transmitted through the first prism being incident on the first fine tuning filter via the reflective film; a first image sensor facing the first fine tuning filter so as to receive the visible light transmitted through the first fine tuning filter and configured to convert the received visible light into an electrical signal; a second fine tuning filter configured to transmit light in a near-infrared region and shield light in a visible region, the near-infrared light transmitted through the second prism being incident on the second fine tuning filter via the reflective film; and a second image sensor facing the second fine tuning filter so as to receive the near-infrared light transmitted through the second fine tuning filter and configured to convert the received near-infrared light into an electrical signal, wherein the first prism is fixed to the second prism, wherein the first fine-tuning filter is fixed to the first prism, and wherein the second fine tuning filter is fixed to the second prism, The image capturing unit further comprises: an infrared light shielding film provided between the first fine tuning filter and the first image sensor and configured to transmit light in the visible region and shield light in the near-infrared region; and a visible light shielding film provided between the second fine tuning filter and the second image sensor and configured to transmit light in the near-infrared region and shield light in the visible region, and wherein the infrared light shielding film and the visible light shielding film are configured to shield excitation light emitted to the biological tissue and included in a wavelength band having a central wavelength of 700 nm to 800 nm.

2. The endoscope according to claim 1, wherein the first image sensor is fixed to the first fine-tuning filter, and Wherein the second image sensor is fixed to the second fine tuning filter.

3. The endoscope according to claim 1 or 2, The image capturing unit is arranged near a tip end surface of the endoscope facing the biological tissue.

4. The endoscope according to claim 1 or 2, The image capturing unit further comprises: A lens unit is fixed to the first prism so as to guide light associated with the biological tissue toward the first prism.

5. The endoscope according to claim 4, The distance between the tip end portion of the lens unit and the tip end surface of the endoscope facing the biological tissue is within a range of 0.5 mm to 5 mm.

6. The endoscope according to claim 4, further comprising: a first supporting member configured to support the lens unit, the first prism, and the second prism, and housed inside the observation mirror, The first supporting member is fixed to the lens unit, the first prism, and the second prism.

7. The endoscope according to claim 6, further comprising: A second support member is fixed to the first support member and the sight glass and is accommodated inside the sight glass.

8. The endoscope according to claim 1 or 2, The first image sensor includes a CMOS image sensor configured to generate a visible light image signal indicating a normal image of the biological tissue based on visible light that forms an inverted image of the biological tissue.

9. The endoscope according to claim 1 or 2, The first image sensor and the second image sensor have the same configuration.

10. The endoscope according to claim 1 or 2, The imaging surface of the first image sensor and the imaging surface of the second image sensor are perpendicular to each other.

11. The endoscope according to claim 1, wherein a visible light channel formed by a combination of the reflective film, the first fine tuning filter, and the infrared light shielding film has spectral characteristics such that a transmittance of light in a wavelength band of 720 nm to 1050 nm is 0.1% or less, and wherein the near-infrared light channel formed by a combination of the reflective film, the second fine tuning filter, and the visible light shielding film has spectral characteristics such that a transmittance of light in a wavelength band of 400 nm to 798 nm is 0.5% or less.

12. The endoscope according to claim 1 or 2, wherein the viewing scope is the portion of the endoscope to be inserted into the patient's body, wherein the first fine-tuning filter is attached to the first prism, wherein the second fine tuning filter is attached to the second prism, wherein the first image sensor is attached to the first fine-tuning filter, and Wherein the second image sensor is attached to the second fine tuning filter.

13. An image capture unit housed inside a viewing scope of an endoscope according to any one of claims 1 to 12 and configured to receive light associated with a patient's biological tissue so as to capture an image of the biological tissue, the image capture unit comprising: First Prism; a second prism facing the first prism; a reflective film disposed between the oblique surface of the first prism and the oblique surface of the second prism and configured to separate light associated with biological tissue into visible light and near-infrared light; a first fine tuning filter configured to transmit light in a visible region and shield light in a near-infrared region, the visible light transmitted through the first prism being incident on the first fine tuning filter via the reflective film; a first image sensor facing the first fine tuning filter so as to receive the visible light transmitted through the first fine tuning filter and configured to convert the received visible light into an electrical signal; a second fine tuning filter configured to transmit light in a near-infrared region and shield light in a visible region, the near-infrared light transmitted through the second prism being incident on the second fine tuning filter via the reflective film; as well as a second image sensor facing the second fine tuning filter so as to receive the near infrared light transmitted through the second fine tuning filter and configured to convert the received near infrared light into an electrical signal, wherein the first prism is fixed to the second prism, wherein the first fine-tuning filter is fixed to the first prism, and wherein the second fine tuning filter is fixed to the second prism.

Images