CROSS REFERENCE TO RELATED APPLICATIONS
[0001]
This application claims the benefit of Japanese Priority Patent Application JP 2015-175569 filed September 7, 2015, the entire contents of which are incorporated herein by reference.
Technical Field
[0002]
The present disclosure relates to an image pickup device, a microscope image pickup system, and an endoscope image pickup system.
Background Art
[0003]
There is known a technology (photodynamic diagnosis/treatment technology) for administering any of various fluorescent probes to a patient, emitting excitation light for exciting the fluorescent probe when the fluorescent probe is accumulated on a cancer tissue or the like, observing near-infrared fluorescence having a predetermined wavelength emitted from the fluorescent probe to specify a position of an affected part (that is, the cancer tissue) to thereby perform diagnosis and treatment. A wavelength of the excitation light for exciting the fluorescent probe and a wavelength of the near-infrared fluorescence emitted from the fluorescent probe are inherent to a fluorescent probe to be used, and, in the case where, for example, indocyanine green is used as a fluorescent probe, light having a wavelength of about 769 nm is used as excitation light, and fluorescence having a wavelength of about 832 nm is emitted from indocyanine green.
[0004]
In the above photodynamic diagnosis/treatment technology, fluorescence is observed in a dark state in which indoor lighting is off because obtainable fluorescence intensity is weak. Thus, a doctor recognizes an image in which a fluorescence part is luminous in a dark field of vision, and therefore it is difficult to specify a position of the fluorescence part in the whole affected part. As a result, the doctor recognizes the affected part while switching observation with visible light and observation with fluorescence and then implements diagnosis or treatment. Thus, processing is complicated. In order to solve such a circumstance, various matters of an image pickup system for performing superimposed display of a fluorescence image and a visible light image in real time have been studied.
[0005]
For example, PTL 1 cited below discloses a microscope system including: branch optical mechanism for dividing, into two parts, an observed luminous flux extracted to the outside from an affected part to which a fluorescent probe has been administered; fluorescence image pickup mechanism connected to one end of the branch optical mechanism; and visible light image pickup mechanism connected to the other end of the branch optical mechanism; and display mechanism for displaying a fluorescence image captured by the fluorescence image pickup mechanism and a visible light image captured by the visible light image pickup mechanism so that the fluorescence image and the visible light image are superimposed, in which the branch optical mechanism is an optical block having an interface for coaxially separating only fluorescence having a predetermined wavelength from visible light in the observed luminous flux.
[0006]
PTL 2 described below discloses a near-infrared fluorescence detection device for detecting near-infrared fluorescence from a fluorescent material accumulated on a sentinel lymph node inside a body. More specifically, the near-infrared fluorescence detection device splits reflected light and near-infrared fluorescence from an observation target into visible-light reflected light and near-infrared fluorescence by using a beam splitter such as a dichroic prism, then detects the visible reflection light and the near-infrared fluorescence to thereby form a visible reflection light image signal and a near-infrared fluorescence signal, and outputs a composite image obtained by combining the visible-light video signal and the near-infrared fluorescence signal. Herein, PTL 2 cited below discloses that visible reflection light is detected by a color image sensor, whereas near-infrared fluorescence is detected by a monochrome image sensor, and the monochrome image sensor is disposed to be isolated from the beam splitter at a predetermined distance (Δ), as compared with the color image sensor, in order to correct axial chromatic aberration.
Citation List
Patent Literature
[0007]
patcit 1 : JP 2013-3495A
patcit 2 : JP 2015-16332A
Summary
Technical Problem
[0008]
However, in PTL 1 cited above, because only a fluorescence component is attempted to be extracted from an incident observed luminous flux by using only an optical multilayer film having a characteristic that "the branch optical mechanism is an optical block having an interface for coaxially separating only fluorescence having a predetermined wavelength from visible light in the observed luminous flux", costs for manufacturing the optical multilayer film are increased and a desired spectral characteristic is not achieved.
[0009]
PTL 2 cited above neither discloses a condition that is necessary for a spectral characteristic of the beam splitter for splitting near-infrared fluorescence nor a method of achieving an isolation distance Δ. Therefore, depending on a spectral characteristic of fluorescence from the observation target, axial chromatic aberration is not completely corrected and a favorable superimposed image is not obtained.
[0010]
As described above, in the technologies disclosed in PTL 1 and PTL 2 cited above, light from an observation target is not split into a visible light component and a fluorescence component with high accuracy, and a favorable superimposed image obtained by superimposing a visible light image and a fluorescence image is not obtained.
[0011]
In view of the above circumstances, embodiments of the present disclosure propose an image pickup device, a microscope image pickup system, and an endoscope image pickup system, each of which is capable of splitting light from an observation target into a visible light component and a fluorescence component with high accuracy and is capable of obtaining a favorable superimposed image by superimposing a visible light image and a fluorescence image on each other.
Solution to Problem
[0012]
According to an embodiment of the present disclosure, there is provided
medical imaging device including a color separation prism that has a dichroic film configured to split light into first light belonging to a visible light wavelength band and second light belonging to a fluorescence wavelength band, a fluorescence image sensor that is provided at an output side of the color separation prism and that is configured to image at least part of the second light belonging to the fluorescence wavelength band separated by the dichroic film, a visible light image sensor that is provided at the output side of the color separation prism and that is configured to image at least part of the first light belonging to the visible light wavelength band separated by the dichroic film, and a bandpass filter that is disposed between the color separation prism and the fluorescence image sensor. The fluorescence image sensor and the visible light image sensor are arranged such that an optical path difference between an optical path length of a fluorescence optical path for the second light imaged on the fluorescence image sensor via the color separation prism and an optical path length of a visible light optical path for the first light imaged on the visible light image sensor via the color separation prism corresponds to an amount of a shift between a fluorescence imaging position and a visible light imaging position, the shift being generated by an imaging lens positioned at an input side of the color separation prism. The fluorescence imaging position is an imaging position of filtered second light, which results from passing the second light through the bandpass filter, such that the amount of shift is based on the filtered second light.
[0013]
According to an embodiment of the present disclosure, there is provided a medical microscopic system including a microscopic optical lens assembly including at least an objective lens and an imaging lens, and an imaging device configured to capture a magnified image of an object. The imaging device includes a color separation prism that has a dichroic film configured to split light into first light belonging to the visible light wavelength band and second light belonging to the fluorescence wavelength band, a fluorescence image sensor that is provided at an output side of the color separation prism and that is configured to image at least part of the second light belonging to the fluorescence wavelength band separated by the dichroic film, a visible light image sensor that is provided at the output side of the color separation prism and that is configured to image at least part of the first light belonging to the visible light wavelength band separated by the dichroic film, and a bandpass filter that is disposed between the color separation prism and the fluorescence image sensor. The fluorescence image sensor and the visible light image sensor are arranged such that an optical path difference between an optical path length of a fluorescence optical path for the second light imaged on the fluorescence image sensor via the color separation prism and an optical path length of a visible light optical path for the first light imaged on the visible light image sensor via the color separation prism corresponds to an amount of a shift between a fluorescence imaging position and a visible light imaging position, the shift being generated by an imaging lens positioned at an input side of the color separation prism. The fluorescence imaging position is an imaging position of filtered second light, which results from passing the second light through the bandpass filter, such that the amount of shift is based on the filtered second light.
[0014]
According to an embodiment of the present disclosure, there is provided an endoscopic system including an endoscopic optical lens assembly, an imaging device configured to capture an image of an object, and an coupler optical lens assembly that is provided between the endoscopic optical lens assembly and the imaging device. The imaging device includes a color separation prism that has a dichroic film configured to split light into first light belonging to the visible light wavelength band and second light belonging to the fluorescence wavelength band, a fluorescence image sensor that is provided at an output side of the color separation prism and that is configured to image at least part of the second light belonging to the fluorescence wavelength band separated by the dichroic film, a visible light image sensor that is provided at the output side of the color separation prism and that is configured to image at least part of the first light belonging to the visible light wavelength band separated by the dichroic film, and a bandpass filter that is disposed between the color separation prism and the fluorescence image sensor. The fluorescence image sensor and the visible light image sensor are arranged such that an optical path difference between an optical path length of a fluorescence optical path for the second light imaged on the fluorescence image sensor via the color separation prism and an optical path length of a visible light optical path for the first light imaged on the visible light image sensor via the color separation prism corresponds to an amount of a shift between a fluorescence imaging position and a visible light imaging position, the shift being generated by an imaging lens positioned at an input side of the color separation prism. The fluorescence imaging position is an imaging position of filtered second light, which results from passing the second light through the bandpass filter, such that the amount of shift is based on the filtered second light.
[0015]
Accordingly in the present embodiments, axial chromatic aberration contained in fluorescence imaged by the fluorescence image sensor is completely corrected by setting arrangement positions of the fluorescence image sensor and the visible light image sensor as described above.
Advantageous Effects of Invention
[0016]
As described above, according to an embodiment of the present disclosure, it is possible to split light from an observation target into a visible light component and a fluorescence component with high accuracy and to obtain a favorable superimposed image by superimposing a visible light image and a fluorescence image on each other.
[0017]
Note that the effects described above are not necessarily limited, and along with or instead of the effects, any effect that is desired to be introduced in the present specification or other effects that can be expected from the present specification may be exhibited.
Brief Description of Drawings
[0018]
[fig. 1A] FIG. 1A is an explanatory diagram schematically illustrating an example of a configuration of an image pickup device according to an embodiment of the present disclosure.
[fig. 1B] FIG. 1B is an explanatory diagram schematically illustrating an example of the configuration of the image pickup device according to the embodiment.
[fig. 2] FIG. 2 is a graph showing an example of a spectral transmittance characteristic of a dichroic film provided in the image pickup device according to the embodiment.
[fig. 3] FIG. 3 is a graph showing an example of a spectral transmittance characteristic of a bandpass filter provided in the image pickup device according to the embodiment.
[fig. 4] FIG. 4 is an explanatory diagram schematically illustrating an example of a configuration of a 2-piece camera system including the image pickup device according to the embodiment.
[fig. 5] FIG. 5 is a block diagram showing an example of a configuration of a camera control unit that can be used for the image pickup device according to the embodiment.
[fig. 6] FIG. 6 is an explanatory diagram schematically illustrating an example of a configuration of a microscope image pickup system including the image pickup device according to the embodiment.
[fig. 7A] FIG. 7A is an explanatory diagram schematically illustrating another example of the configuration of the image pickup device according to the embodiment.
[fig. 7B] FIG. 7B is an explanatory diagram schematically illustrating another example of the configuration of the image pickup device according to the embodiment.
[fig. 8] FIG. 8 is an explanatory diagram schematically illustrating an example of a configuration of an endoscope image pickup system including the image pickup device according to the embodiment.
[fig. 9] FIG. 9 is a block diagram showing an example of a hardware configuration of the camera control unit that can be used for the image pickup device according to the embodiment.
Description of Embodiments
[0019]
Hereinafter, (a) preferred embodiment(s) of the present disclosure will be described in detail with reference to the appended drawings. In this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted.
[0020]
Note that the following description is given in the order indicated below.
1. Study by Inventor of the Present Disclosure
2. First Embodiment
2.1 Example of Configuration of Image Pickup Device
2.2 2-piece Camera System Including Image Pickup Device
2.3 Configuration of Camera Control Unit That Can Be Used for Image Pickup Device
2.4 Microscope Image Pickup System Including Image Pickup Device
2.5 Another Example of Configuration of Image Pickup Device
2.6 Endoscope Image Pickup System Including Image Pickup Device
3. Hardware Configuration of Camera Control Unit
[0021]
(Study by Inventor of the Present Disclosure)
Prior to description of an image pickup device, a microscope image pickup system, and an endoscope image pickup system according to an embodiment of the present disclosure, the content of study performed by the inventor of the present disclosure regarding an image pickup system for performing superimposed display of a fluorescence image and a visible light image in real time will be briefly described, and what the embodiment of the present disclosure aims at will be briefly described.
[0022]
Prior to study of the image pickup device according to the embodiment of the present disclosure, the inventor of the present disclosure first studied a technology disclosed in PTL 1 cited above. As a result, the inventor found that it was important to further study the technology disclosed in PTL 1 cited above regarding the following points. That is, in PTL 1 cited above, only a fluorescence component is attempted to be extracted from an incident observed luminous flux by using only an optical multilayer film having a characteristic that "the branch optical mechanism is an optical block having an interface for coaxially separating only fluorescence having a predetermined wavelength from visible light in the observed luminous flux". However, the inventor of the present disclosure found that there were problems described below in order to extract only the fluorescence component.
[0023]
First, in PTL 1 cited above, the above optical block functioning as the branch optical mechanism is attempted to be achieved by adhering two prisms to each other and providing the optical multilayer film having the above characteristic between adhered surfaces. At this time, in order to split an optical path into an optical path of visible light and an optical path of near-infrared fluorescence, the adhered surfaces of the prisms (in other words, an interface between the two prisms) of the optical block are inclined with respect to an optical axis, and an angle of incidence of beams of light to the interface is increased.
[0024]
Herein, it is known that the characteristic of the optical multilayer film is changed in accordance with an angle of incidence of beams of light to be incident thereon. That is, a spectral characteristic of the optical multilayer film is originally designed assuming that beams of light are vertically incident on the multilayer film. However, as described in PTL 1 cited above, in the case where an angle of incidence of beams of light is increased, and, as a result, the beams of the light are not vertically incident on the optical multilayer film, it is important to increase the number of optical thin films included in the optical multilayer film in order to achieve the same spectral characteristic as a spectral characteristic obtained when beams of light are vertically incident thereon. As a result, it is difficult to reduce a size of an optical prism and costs are increased. In the case where beams of light having a bright f-number are incident on the optical prism disclosed in PTL 1 cited above, a change in spectral characteristic caused by a difference in angle of incidence between upper beams of light and lower beams of light is not suppressed. Thus, a desired spectral characteristic is not achieved.
[0025]
That is, in the technology disclosed in PTL 1 cited above, the following matter for study exists: the characteristic of the optical multilayer film for dividing beams of light into two parts, the number of arranged optical multilayer films, and a positional relationship with the optical multilayer film are not preferable.
[0026]
It can also be considered that axial chromatic aberration is greatly generated in a fluorescence wavelength band depending on a spectral characteristic of a fluorescence image to be focused on. Regarding this point, the technology disclosed in PTL 2 cited above attempts to correct axial chromatic aberration by disposing the monochrome image sensor so that the monochrome image sensor is isolated from the beam splitter at a distance Δ, as compared with the color image sensor. However, as a result of study performed by the inventor of the present disclosure, it is found that, even in the case where a difference in the center of chromatic aberration between a visible light wavelength band and the fluorescence wavelength band is corrected by providing the isolation distance Δ, components of wavelengths other than a central wavelength in the fluorescence wavelength band form a blur image and a contrast is reduced. That is, it is found that the effect of the isolation distance Δ is not satisfactorily exerted in some cases in the technology disclosed in PTL 2 cited above. Because PTL 2 cited above neither discloses a condition that is necessary for a spectral characteristic of an optical filter nor a method of achieving the isolation distance Δ, PTL 2 cited above discloses no method of completely correcting axial chromatic aberration. Therefore, the method of completely correcting axial chromatic aberration is a matter for study.
[0027]
The inventor of the present disclosure found the above matters for study and then focused on an image pickup system capable of performing superimposed display of a visible light image and a fluorescence image in real time. Such an image pickup system can be achieved by using an image pickup device capable of separating a visible light image and a fluorescence image with high accuracy and a control unit that controls the image pickup device.
[0028]
An example of the image pickup system is a medical CMOS full HD video camera including a camera head unit (CHU) and a camera control unit (CCU) (Hereinafter, such an image pickup system including a CHU and a CCU will be also referred to as "2-piece camera".). In the image pickup system, the CHU includes a single-plate image pickup element having an RGB color filter or a 3-color separation prism module, and a user can capture a full-HD image with high color reproducibility by attaching an arbitrary imaging lens (various kinds of optical systems such as a microscope and an endoscope) to the CHU.
[0029]
An example of the similar image pickup system is a CHU for a rigid endoscope. The CHU for a rigid endoscope includes a coupler optical system, and an eyepiece unit of the rigid endoscope is detachable from the CHU. In the CHU, the coupler optical system images a substantially afocal luminous flux from the eyepiece unit on an image pickup element.
[0030]
In the above image pickup system, depending on an optical system (imaging lens or rigid endoscope) to be used by a user, axial chromatic aberration is generated between the visible light wavelength band and the fluorescence wavelength band, and imaging positions thereof are different in an optical axis direction. As a result, when a visible light image is focused in the CHU, a fluorescence image is not focused, whereas, when the fluorescence image is focused, the visible light image is not focused. That is, both the images are not simultaneously captured with the best pint. Therefore, in related arts, observation is performed on an average image surface while a balance is being kept between visible light and fluorescence. In particular, even in the case where the optical system to be used by the user has an MTF of full-HD resolution, the CHU does not satisfactorily exert resolution performance when the CHU has the matters for study in the technologies disclosed in PTL 1 and PTL 2 cited above.
[0031]
In view of this, the inventor of the present disclosure has diligently studied to solve the above matters for study and achieve an image pickup device (CHU) capable of splitting light into visible light and fluorescence with high accuracy even in the case where a user uses an arbitrary optical system. As a result, the inventor has arrived at a method of solving the above matters for study and have arrived at an image pickup device capable of splitting light into visible light and fluorescence with high accuracy. When the image pickup device is used, it is possible to superimpose visible light and fluorescence in a state in which both the visible light and the fluorescence are focused. Therefore, it is possible to achieve an image pickup system capable of generating a better superimposed image.
[0032]
Hereinafter, the image pickup device that has been completed as a result of diligent study by the inventor of the present disclosure and a microscope image pickup system and an endoscope image pickup system each of which includes the image pickup device will be described in detail.
[0033]
(First Embodiment)
Hereinafter, an image pickup device, a microscope image pickup system, and an endoscope image pickup system according to a first embodiment of the present disclosure will be described in detail with reference to the drawings.
[0034]
Note that, hereinafter, there will be described an example where fluorescence having a wavelength of 832 nm belonging to a near-infrared band, the fluorescence being emitted from indocyanine green (excitation wavelength: about 769 nm), is focused on. However, even in the case where fluorescence belonging to another wavelength band is focused on, it is possible to similarly apply a technical idea of an embodiment of the present disclosure by changing spectral characteristics of a dichroic film and a bandpass filter described below to spectral characteristics thereof suitable for fluorescence to be focused on.
[0035]

An example of a configuration of an image pickup device according to the embodiment will be described in detail with reference to FIG. 1A to FIG. 3. FIG. 1A and FIG. 1B are explanatory diagrams each of which schematically illustrates an example of the configuration of the image pickup device according to the embodiment. FIG. 2 is a graph showing an example of a spectral transmittance characteristic of a dichroic film provided in the image pickup device according to the embodiment. FIG. 3 is a graph showing an example of a spectral transmittance characteristic of a bandpass filter provided in the image pickup device according to the embodiment.
[0036]
In the case where incident light containing both light belonging to the visible light wavelength band and light belonging to the fluorescence wavelength band is incident on the image pickup device according to the embodiment, the image pickup device splits the incident light into the light belonging to the visible light wavelength band and the light belonging to the fluorescence wavelength band with high accuracy and then independently captures images of the light belonging to the respective wavelength bands to generate a visible light captured image (hereinafter, also simply referred to as "visible light image") and a fluorescence captured image (hereinafter, also simply referred to as "fluorescence image").
[0037]
As schematically illustrated in, for example, FIG. 1A, such an image pickup device 10 includes at least a color separation prism 101, a visible light image pickup element 111, a bandpass filter 115, and a fluorescence image pickup element 117.
[0038]
The color separation prism 101 is an optical member that splits incident light incident on the image pickup device 10 into light belonging to the visible light wavelength band and light belonging to the fluorescence wavelength band. The color separation prism 101 includes a dichroic film 103 for splitting light into light belonging to the visible light wavelength band and light belonging to the fluorescence wavelength band.
[0039]
The dichroic film 103 is an optical film that splits incident light incident on the color separation prism 101, the incident light containing light belonging to the visible light wavelength band and light belonging to the fluorescence wavelength band, into the light belonging to the visible light wavelength band and the light belonging to the fluorescence wavelength band. FIG. 2 shows an example of a spectral transmittance characteristic of the dichroic film 103 according to the embodiment. In FIG. 2, a horizontal axis indicates a wavelength of light (unit: nm) incident on the dichroic film 103, whereas a vertical axis indicates spectral transmittance (unit: %).
[0040]
In the case where fluorescence having a wavelength of 832 nm belonging to the near-infrared band, the fluorescence being emitted from indocyanine green, is focused on, as shown in FIG. 2, the spectral transmittance of the dichroic film 103 preferably has a characteristic that reflects light in the visible light wavelength band and allows light in a near-infrared wavelength band to transmit therethrough. More specifically, as shown in FIG. 2, the dichroic film 103 preferably has transmittance of 90% or more in a wavelength band from 780 nm to 880 nm and transmittance of 10% or less in a wavelength band from 400 nm to 720 nm.
[0041]
The transmittance of less than 90% in the wavelength band from 780 nm to 880 nm is not preferable because a ratio of fluorescence that is not transmitted through the dichroic film 103 is increased and brightness of a fluorescence image is reduced. Such a case is also not preferable in terms of image quality of a visible light image because fluorescence leaks into the visible light image pickup element 111 to thereby reduce a contrast of the visible light image.
[0042]
The transmittance exceeding 10% in the wavelength band from 400 nm to 720 nm is not preferable because a ratio of visible light that is not reflected by the dichroic film 103 but is transmitted therethrough is increased and brightness of a visible light image is reduced. Such a case is also not preferable in terms of image quality of a fluorescence image because visible light leaks into the fluorescence image pickup element 117 to thereby reduce a contrast of the fluorescence image.
[0043]
As is clear from FIG. 2 and the above description, the dichroic film 103 according to the embodiment splits incident light into two colors, i.e., light belonging to a predetermined fluorescence wavelength band and a band of longer wavelengths than the predetermined fluorescence wavelength band and light belonging to a band of shorter wavelengths than the predetermined fluorescence wavelength band. More specifically, the dichroic film 103 having the characteristic shown in FIG. 2 is a film functioning like a low-pass filter that splits incident light into two groups by setting a boundary to 750 nm which is a boundary between the visible light wavelength band and the fluorescence wavelength band.
[0044]
Accordingly, the spectral characteristic of the dichroic film 103 according to the embodiment is comparatively broad as shown in FIG. 2, and, in the case where the dichroic film 103 is achieved as an optical multilayer film, the number of layers of the film can be reduced to about several tens of layers and a general vacuum deposition method can be used as a manufacturing method thereof. In the optical multilayer film disclosed in PTL 1 cited above, it is necessary to have an extraordinarily large number of layers of the film to achieve a function of extracting only fluorescence that is focused on by using only the optical multilayer film. Instead of extracting only fluorescence that is focused on by using only the dichroic film 103, the dichroic film 103 according to the embodiment only separates light in a long-wavelength band containing fluorescence that is focused on from incident light. Therefore, it is possible to obtain an optical multilayer film that is less expensive and more accurate than the optical multilayer film disclosed in PTL 1 cited above.
[0045]
Note that the image pickup device 10 according to the embodiment includes the bandpass filter 115 described below in order to extract fluorescence that is focused on from light in the long-wavelength band containing fluorescence, the light having been separated by the dichroic film 103. When the bandpass filter 115 is used, light other than fluorescence is removed from light to be imaged on the fluorescence image pickup element 117, and a contrast of a fluorescence image is therefore improved.
[0046]
A structure of the color separation prism 101 having the dichroic film 103 is not limited, and, in particular, the structure may have an arbitrary shape in the case where a size of the whole image pickup device 10 is not limited. However, in the case where the image pickup device 10 according to the embodiment is attached to various kinds of optical systems described above, such as a microscope and an endoscope, and functions as a camera head unit (CHU), the size of the image pickup device 10 is preferably reduced as much as possible. In order to reduce the size of the image pickup device 10, the color separation prism 101 preferably has a structure illustrated in FIG. 1A.
[0047]
For example, the color separation prism 101 illustrated in FIG. 1A is a prism obtained by joining a first prism 105 and a second prism 107 to each other, and the first prism 105 and the second prism 107 are joined to each other via the dichroic film 103. That is, the dichroic film 103 is provided on an interface between the first prism 105 and the second prism 107.
[0048]
Light belonging to the visible light wavelength band and light belonging to the fluorescence wavelength band (that is, incident light) are incident on the first prism 105, and the first prism 105 functions as a visible light optical path through which the light belonging to the visible light wavelength band is guided. The second prism 107 functions as a fluorescence optical path through which the light belonging to the fluorescence wavelength band is guided.
[0049]
The incident light incident on the first prism 105 moves straight in the first prism 105 and is split by the dichroic film 103 that is obliquely provided on the optical axis into the light belonging to the visible light wavelength band and the light belonging to the fluorescence wavelength band.
[0050]
The light belonging to the visible light wavelength band is reflected by the dichroic film 103 to be guided in the first prism 105. Herein, the reflected and split light belonging to the visible light wavelength band (that is, visible light rays) is totally reflected at a position A illustrated in FIG. 1A only once and is transmitted to the outside of the first prism 105. With this, an angle formed by a film deposition surface of the dichroic film 103 and the optical axis can be close to a right angle. Conversely, an installation angle of the dichroic film 103 according to the embodiment on the optical axis is set to satisfy a total reflection condition of visible light rays at the position A. Because the dichroic film 103 is disposed as described above, it is possible to suppress a change in spectral characteristic of the dichroic film 103 caused by a difference in angle of incidence between upper beams of light and lower beams of light even in the case where beams of light having a bright f-number are incident on the first prism 105. Therefore, it is possible to split wavelengths with high accuracy.
[0051]
The visible light rays transmitted through the first prism 105 are guided to the visible light image pickup element 111. At this time, an infrared cut-off filter 113 may be provided between an emission surface of the first prism 105 and the visible light image pickup element 111. When the infrared cut-off filter 113 is provided, it is possible to remove infrared light contained in the visible light rays transmitted through the first prism 105, and therefore color reproducibility of a visible light image can be further improved. As the infrared cut-off filter 113, for example, a publicly-known absorption filter such as C5000 manufactured by HOYA CORPORATION can be used.

Claims
[Claim 1]
A medical imaging device comprising:
a color separation prism that has a dichroic film configured to split light into first light belonging to a visible light wavelength band and second light belonging to a fluorescence wavelength band;
a fluorescence image sensor that is provided at an output side of the color separation prism and that is configured to image at least part of the second light belonging to the fluorescence wavelength band separated by the dichroic film;
a visible light image sensor that is provided at the output side of the color separation prism and that is configured to image at least part of the first light belonging to the visible light wavelength band separated by the dichroic film; and
a bandpass filter that is disposed between the color separation prism and the fluorescence image sensor,
wherein the fluorescence image sensor and the visible light image sensor are arranged such that an optical path difference between an optical path length of a fluorescence optical path for the second light imaged on the fluorescence image sensor via the color separation prism and an optical path length of a visible light optical path for the first light imaged on the visible light image sensor via the color separation prism corresponds to an amount of a shift between a fluorescence imaging position and a visible light imaging position, the shift being generated by an imaging lens positioned at an input side of the color separation prism, and
wherein the fluorescence imaging position is an imaging position of filtered second light, which results from passing the second light through the bandpass filter, such that the amount of shift is based on the filtered second light.
[Claim 2]
The medical imaging device according to claim 1,
wherein each of the fluorescence image sensor and the visible light image sensor is fixed such that the optical path difference corresponds to the amount of the shift.
[Claim 3]
The medical imaging device according to claim 1,
wherein the fluorescence image sensor is provided such that an isolation distance from the bandpass filter is changeable,
further comprising:
a fluorescence image focusing actuator configured to focus the second light belonging to the fluorescence wavelength band separated by the dichroic film on the fluorescence image sensor, and
wherein the fluorescence image focusing actuator controls the isolation distance in accordance with the imaging lens attached at the input side of the color separation prism such that the optical path difference corresponds to the amount of the shift.
[Claim 4]
The medical imaging device according to claim 3,
wherein a coupler optical lens assembly, in which axial chromatic aberration has been corrected at least in the visible light wavelength band, is provided as the imaging lens at the input side of the color separation prism,
wherein the fluorescence image sensor is provided such that the isolation distance from the bandpass filter is changeable,
wherein the image sensor further includes a visible light image focusing actuator configured to focus the first light belonging to the visible light wavelength band separated by the dichroic film on the visible light image sensor,
wherein the visible light image focusing actuator moves the coupler optical lens assembly in an optical axis direction to focus the first light belonging to the visible light wavelength band separated by the dichroic film on the visible light image sensor, and
wherein the fluorescence image focusing actuator controls the isolation distance such that the optical path difference, obtained when the first light belonging to the visible light wavelength band is focused on the visible light image sensor, corresponds to the amount of the shift.
[Claim 5]
The medical imaging device according to claim 3,
wherein the fluorescence image focusing actuator controls the isolation distance by moving the bandpass filter in an optical axis direction with respect to the fluorescence image sensor.
[Claim 6]
The medical imaging device according to claim 3,
wherein the fluorescence image focusing actuator controls the isolation distance by moving the fluorescence image sensor in an optical axis direction with respect to the bandpass filter.
[Claim 7]
The medical imaging device according to claim 1,
wherein the dichroic film splits incident light into the second light belonging to a predetermined fluorescence wavelength band, light of a band of longer wavelengths than the predetermined fluorescence wavelength band, and light belonging to a band of shorter wavelengths than the predetermined fluorescence wavelength band.
[Claim 8]
The medical imaging device according to claim 1,
wherein the color separation prism is a prism comprising a first prism on which the first light belonging to the visible light wavelength band and the second light belonging to the fluorescence wavelength band are incident, the first prism functioning as the visible light optical path through which the first light belonging to the visible light wavelength band is guided, and
a second prism functioning as the fluorescence optical path through which the second light belonging to the fluorescence wavelength band is guided, to each other,
wherein the first prism and the second prism are joined to each other via the dichroic film,
wherein the second light belonging to the fluorescence wavelength band separated by the dichroic film moves straight in the second prism to be vertically incident on the bandpass filter, and
wherein the first light belonging to the visible light wavelength band separated by the dichroic film is totally reflected in the first prism and is then imaged on the visible light image sensor.
[Claim 9]
The medical imaging device according to claim 1, further comprising a 3-color separation prism configured to split the first light belonging to the visible light wavelength band emitted from the color separation prism into three colors of an R component, a G component, and a B component.
[Claim 10]
The medical imaging device according to claim 1,
wherein the dichroic film has transmittance of 90% or more in a wavelength band from 780 nm to 880 nm and has transmittance of 10% or less in a wavelength band from 400 nm to 720 nm.
[Claim 11]
The medical imaging device according to claim 1,
wherein the bandpass filter has transmittance of 90% or more in a wavelength band from 820 nm to 850 nm and has transmittance of 10% or less in a wavelength band from 400 nm to 805 nm and in a wavelength band from 860 nm to 1000 nm.
[Claim 12]
A medical microscopic system comprising:
a microscopic optical lens assembly including at least an objective lens and an imaging lens; and
an imaging device configured to capture a magnified image of an object,
wherein the imaging device includes
a color separation prism that has a dichroic film configured to split light into first light belonging to the visible light wavelength band and second light belonging to the fluorescence wavelength band,
a fluorescence image sensor that is provided at an output side of the color separation prism and that is configured to image at least part of the second light belonging to the fluorescence wavelength band separated by the dichroic film,
a visible light image sensor that is provided at the output side of the color separation prism and that is configured to image at least part of the first light belonging to the visible light wavelength band separated by the dichroic film, and
a bandpass filter that is disposed between the color separation prism and the fluorescence image sensor,
wherein the fluorescence image sensor and the visible light image sensor are arranged such that an optical path difference between an optical path length of a fluorescence optical path for the second light imaged on the fluorescence image sensor via the color separation prism and an optical path length of a visible light optical path for the first light imaged on the visible light image sensor via the color separation prism corresponds to an amount of a shift between a fluorescence imaging position and a visible light imaging position, the shift being generated by an imaging lens positioned at an input side of the color separation prism, and
wherein the fluorescence imaging position is an imaging position of filtered second light, which results from passing the second light through the bandpass filter, such that the amount of shift is based on the filtered second light.
[Claim 13]
The medical microscope imaging system according to claim 12,
wherein each of the fluorescence image sensor and the visible light image sensor is fixed such that the optical path difference corresponds to the amount of the shift.
[Claim 14]
The medical microscope imaging system according to claim 12,
wherein the fluorescence image sensor is provided such that an isolation distance from the bandpass filter is changeable,
wherein the imaging device further includes a fluorescence image focusing actuator configured to focus the second light belonging to the fluorescence wavelength band separated by the dichroic film on the fluorescence image sensor, and
wherein the fluorescence image focusing actuator controls the isolation distance in accordance with the imaging lens attached at the input side of the color separation prism such that the optical path difference corresponds to the amount of the shift.
[Claim 15]
The medical microscope imaging system according to claim 14,
wherein a coupler optical lens assembly, in which axial chromatic aberration has been corrected at least in the visible light wavelength band, is provided as the imaging lens at the input side of the color separation prism,
wherein the fluorescence image sensor is provided such that the isolation distance from the bandpass filter is changeable,
wherein the image sensor further includes a visible light image focusing actuator configured to focus the first light belonging to the visible light wavelength band separated by the dichroic film on the visible light image sensor,
wherein the visible light image focusing actuator moves the coupler optical lens assembly in an optical axis direction to focus the first light belonging to the visible light wavelength band separated by the dichroic film on the visible light image sensor, and
wherein the fluorescence image focusing actuator controls the isolation distance such that the optical path difference, obtained when the first light belonging to the visible light wavelength band is focused on the visible light image sensor, corresponds to the amount of the shift.
[Claim 16]
The medical microscope imaging system according to claim 14,
wherein the fluorescence image focusing actuator controls the isolation distance by moving the bandpass filter in an optical axis direction with respect to the fluorescence image sensor or moving the fluorescence image sensor in an optical axis direction with respect to the bandpass filter.
[Claim 17]
The medical microscope imaging system according to claim 12,
wherein the color separation prism is a prism comprising
a first prism on which the first light belonging to the visible light wavelength band and the second light belonging to the fluorescence wavelength band are incident, the first prism functioning as the visible light optical path through which the first light belonging to the visible light wavelength band is guided, and
a second prism functioning as the fluorescence optical path through which the second light belonging to the fluorescence wavelength band is guided, to each other,
wherein the first prism and the second prism are joined to each other via the dichroic film,
wherein the second light belonging to the fluorescence wavelength band separated by the dichroic film moves straight in the second prism to be vertically incident on the bandpass filter, and
wherein the first light belonging to the visible light wavelength band separated by the dichroic film is totally reflected in the first prism and is then imaged on the visible light image sensor.
[Claim 18]
The medical microscope imaging system according to claim 12,
wherein the dichroic film has transmittance of 90% or more in a wavelength band from 780 nm to 880 nm and has transmittance of 10% or less in a wavelength band from 400 nm to 720 nm.
[Claim 19]
The medical microscope imaging system according to claim 12,
wherein the bandpass filter has transmittance of 90% or more in a wavelength band from 820 nm to 850 nm and has transmittance of 10% or less in a wavelength band from 400 nm to 805 nm and in a wavelength band from 860 nm to 1000 nm.
[Claim 20]
An endoscopic system comprising:
an endoscopic optical lens assembly;
an imaging device configured to capture an image of an object; and
an coupler optical lens assembly that is provided between the endoscopic optical lens assembly and the imaging device,
wherein the imaging device includes
a color separation prism that has a dichroic film configured to split light into first light belonging to the visible light wavelength band and second light belonging to the fluorescence wavelength band,
a fluorescence image sensor that is provided at an output side of the color separation prism and that is configured to image at least part of the second light belonging to the fluorescence wavelength band separated by the dichroic film,
a visible light image sensor that is provided at the output side of the color separation prism and that is configured to image at least part of the first light belonging to the visible light wavelength band separated by the dichroic film, and
a bandpass filter that is disposed between the color separation prism and the fluorescence image sensor, and
wherein the fluorescence image sensor and the visible light image sensor are arranged such that an optical path difference between an optical path length of a fluorescence optical path for the second light imaged on the fluorescence image sensor via the color separation prism and an optical path length of a visible light optical path for the first light imaged on the visible light image sensor via the color separation prism corresponds to an amount of a shift between a fluorescence imaging position and a visible light imaging position, the shift being generated by an imaging lens positioned at an input side of the color separation prism, and
wherein the fluorescence imaging position is an imaging position of filtered second light, which results from passing the second light through the bandpass filter, such that the amount of shift is based on the filtered second light.