Fluorescence endoscope device

Abstract

A fluorescence endoscope device (1) comprises: a WLI light source (31) that emits WLI light; excitation light sources (32, 33) that emit excitation light for exciting a fluorescent reagent; a first imaging element (522) that images return light, which is the WLI light from an object being observed; a second imaging element (523) that images fluorescence emitted from the fluorescent reagent contained in the object being observed; and a processor (93). The processor (93) can switch between a superimposed fluorescence mode for outputting a superimposed image in which a fluorescence image obtained through imaging by the second imaging element (523) is superimposed on a WLI light image obtained through imaging by the first imaging element (522), and a single fluorescence mode for only outputting the fluorescence image. The processor (93) sets the amount of WLI light that is emitted by the WLI light source (31) for each exposure time per frame in the second imaging element (523) to be smaller in the single fluorescence mode than in the superimposed fluorescence mode.

Description

Fluorescence endoscope device

[0001] The present invention relates to a fluorescence endoscope device.

[0002] Conventionally, a fluorescence endoscope device is known that irradiates a subject to be observed (such as a human subject) with WLI light including a wavelength band of visible light such as excitation light or white light emitted from a light source device, and fluorescence emitted from a fluorescent reagent contained in the subject to be observed by the irradiation of the excitation light (hereinafter referred to as observed subject fluorescence) is observed (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2002-291682

[0004] By the way, a fluorescence endoscope device has an observation optical path including a first optical path through which WLI light and excitation light propagate from a light source device to an observation target, return light of the WLI light from the observation target irradiated with the WLI light, and an observation target fluorescence emitted from the observation target (fluorescent reagent) by the irradiation of the excitation light. When the WLI light, the return light of the WLI light, and the excitation light propagate through the observation optical path, autofluorescence may be generated from the member forming the observation optical path when the WLI light, the return light of the WLI light, and the excitation light are irradiated to the member. Such autofluorescence has a wavelength band including the wavelength band of the observed subject fluorescence that is the object of fluorescence observation, and can be noise in performing the fluorescence observation.

[0005] Therefore, a technique that can perform fluorescence observation well is desired.

[0006] The present invention has been made in view of the above, and an object thereof is to provide a fluorescence endoscope device that can perform fluorescence observation well.

[0007] To solve the above-mentioned problems and achieve the objective, the fluorescence endoscope apparatus according to the present invention comprises a WLI light source that emits WLI light including the wavelength band of visible light, an excitation light source that emits excitation light for exciting a fluorescent reagent, a first image sensor that images the reflected light of the WLI light from the observation target when the WLI light is irradiated onto the observation target, a second image sensor that images the fluorescence emitted from the fluorescent reagent contained in the observation target when the excitation light is irradiated onto the observation target, and the WLI light source, the excitation light source, and the The system comprises an image sensor and a processor that controls the operation of the second image sensor. The processor is switchable between a fluorescence superposition mode, which outputs a superimposed image obtained by superimposing a fluorescence image obtained by imaging with the second image sensor onto a WLI light image obtained by imaging with the first image sensor, and a fluorescence-only mode, which outputs only the fluorescence image. In the fluorescence-only mode, the amount of WLI light irradiated by the WLI light source for each exposure time of one frame on the second image sensor is reduced compared to the fluorescence superposition mode.

[0008] According to the imaging device and fluorescence endoscope device of the present invention, fluorescence observation can be performed with good results.

[0009] Figure 1 is a diagram showing the configuration of a fluorescence endoscope device according to an embodiment. Figure 2 is a diagram showing the absorption spectrum of the first fluorescent reagent. Figure 3 is a diagram showing the absorption spectrum of the second fluorescent reagent. Figure 4 is a diagram illustrating the wavelengths of the first and second excitation light. Figure 5 is a block diagram showing the configuration of the camera head and control device. Figure 6 is a diagram showing the configuration of the imaging unit. Figure 7 is a diagram illustrating the operation of the fluorescence endoscope device in fluorescence superposition mode. Figure 8 is a diagram illustrating the operation of the fluorescence endoscope device in fluorescence alone mode. Figure 9 is a diagram illustrating the effects of the embodiment. Figure 10 is a diagram illustrating a modification 1 of the embodiment. Figure 11 is a diagram illustrating a modification 1 of the embodiment.

[0010] The embodiments for carrying out the present invention (hereinafter referred to as "embodiments") will be described below with reference to the drawings. However, the present invention is not limited to the embodiments described below. Furthermore, in the drawings, the same parts are denoted by the same reference numerals.

[0011] [Configuration of the Fluorescence Endoscope Device] Figure 1 shows the configuration of the fluorescence endoscope device 1 according to an embodiment. The fluorescence endoscope device 1 is an endoscope device that uses an endoscope to observe an object (in vivo) using fluorescence. As shown in Figure 1, the fluorescence endoscope device 1 comprises an insertion unit 2, a light source device 3, a light guide 4, a camera head 5, a first transmission cable 6, a display device 7, a second transmission cable 8, a control device 9, and a third transmission cable 10.

[0012] In this embodiment, the insertion section 2 is composed of a rigid endoscope. That is, the insertion section 2 has an elongated shape that is entirely rigid, or partially flexible with other parts rigid, and is inserted into the object to be observed. Inside the insertion section 2, there is an optical system (not shown) composed of one or more lenses that collects the WLI light and the first and second excitation light reflected by the object to be observed, as well as the first and second fluorescence emitted from the first and second fluorescent reagents contained in the object to be observed. For the sake of explanation, the WLI light and the first and second excitation light reflected by the object to be observed, as well as the first and second fluorescence emitted from the first and second fluorescent reagents contained in the object to be observed, will be referred to as the subject image below.

[0013] Furthermore, an excitation light cut filter 22 (Figure 1) is provided at the base end (eyepiece 21) of the insertion section 2 to remove the first and second excitation lights contained in the focused subject image. Note that the excitation light cut filter 22 is not limited to the insertion section 2, but may also be provided inside the camera head 5.

[0014] One end of the light guide 4 is connected to the light source device 3. As shown in Figure 1, the light source device 3 includes first to third light sources 31 to 33. The first light source 31 corresponds to the WLI light source according to the present invention. Under the control of the control device 9, this first light source 31 supplies WLI light (white light) including the visible light wavelength band to one end of the light guide 4. The second light source 32 corresponds to the excitation light source according to the present invention. Under the control of the control device 9, this second light source 32 supplies first excitation light to one end of the light guide 4 to excite first fluorescent reagent contained in the object being observed. The third light source 33 corresponds to the excitation light source according to the present invention. Under the control of the control device 9, this third light source 33 supplies second excitation light to one end of the light guide 4 to excite second fluorescent reagent contained in the object being observed.

[0015] The first to third light sources 31 to 33 may be composed of LEDs (Light Emitting Diodes) or semiconductor lasers.

[0016] Figure 2 shows the absorption spectrum of the first fluorescent reagent. Figure 3 shows the absorption spectrum of the second fluorescent reagent. In Figures 2 and 3, the horizontal axis shows Wavelength [nm] and the vertical axis shows Absorbance of the absorption spectrum. Figure 4 is a diagram illustrating the wavelengths of the first and second excitation lights. Specifically, Figure 4 shows the wavelengths of the first and second excitation lights in relation to the absorption spectra of the first and second fluorescent reagents shown in Figures 2 and 3. In Figure 4, the curve indicated by the symbol "CL1" shows the absorption spectrum of the first fluorescent reagent. The curve indicated by the symbol "CL2" shows the absorption spectrum of the second fluorescent reagent. The wavelength indicated by the symbol "P1" shows the wavelength of the first excitation light. The wavelength indicated by the symbol "P2" shows the wavelength of the second excitation light.

[0017] Here, the first fluorescent reagent has the following characteristics. The peak wavelength of the absorption spectrum of the first fluorescent reagent is around 680 nm, as shown in Figure 2. Therefore, as the first excitation light, as shown in Figure 4, it is preferable to use excitation light with a wavelength around 680 nm in order to increase the intensity of the first fluorescence emitted from the first fluorescent reagent. Furthermore, when the first fluorescent reagent is excited by the first excitation light, it emits a first fluorescence with a wavelength around 700 nm.

[0018] Furthermore, the second fluorescent reagent has the following characteristics. The peak wavelength of the absorption spectrum of the second fluorescent reagent is around 800 nm, as shown in Figure 3. For this reason, as shown in Figure 4, it is preferable to use excitation light with a wavelength around 800 nm to increase the intensity of the second fluorescence emitted from the second fluorescent reagent. When the second fluorescent reagent is excited by the second excitation light, it emits a second fluorescence with a wavelength around 800 nm.

[0019] In this embodiment, the light source device 3 is configured separately from the control device 9, but it is not limited to this configuration, and it may also be configured to be housed in the same enclosure as the control device 9.

[0020] One end of the light guide 4 is detachably connected to the light source device 3. The other end of the light guide 4 is detachably connected to the insertion section 2. The light guide 4 propagates the WLI light and the first and second excitation light supplied from the light source device 3 (first to third light sources 31 to 33) from one end to the other, and supplies them to the insertion section 2. The WLI light and the first and second excitation light supplied to the insertion section 2 are emitted from the tip of the insertion section 2 and irradiate the object to be observed. The WLI light and the first and second excitation light that are irradiated onto the object to be observed and reflected by the object, as well as the first and second fluorescence (object image) emitted from the first and second fluorescent reagents contained in the object to be observed, are focused by the optical system within the insertion section 2.

[0021] The camera head 5 is detachably connected to the base end of the insertion section 2 (eyepiece section 21 (Figure 1)). The camera head 5 captures an image of the subject after the light has been focused by the insertion section 2 and the first and second excitation lights have been removed by the excitation light cut filter 22. For the sake of explanation, the image signals obtained by imaging with the camera head 5 will be collectively referred to as the captured image. The image of the subject after the first and second excitation lights have been removed by the excitation light cut filter 22 will be referred to as the subject image with the excitation light removed. The detailed configuration of the camera head 5 will be explained later in "Camera Head Configuration".

[0022] One end of the first transmission cable 6 is detachably connected to the control device 9. The other end of the first transmission cable 6 is detachably connected to the camera head 5. The first transmission cable 6 transmits the captured image output from the camera head 5 to the control device 9, and also transmits control signals, synchronization signals, clock signals, and power signals transmitted from the control device 9 to the camera head 5.

[0023] Furthermore, the captured images and other data transmitted from the camera head 5 to the control device 9 via the first transmission cable 6 may be transmitted as optical signals or as electrical signals. The same applies to the transmission of control signals, synchronization signals, and clock signals from the control device 9 to the camera head 5 via the first transmission cable 6.

[0024] The display device 7 is composed of a display using liquid crystal or organic EL (Electro Luminescence), and under the control of the control device 9, it displays an image based on a video signal from the control device 9.

[0025] One end of the second transmission cable 8 is detachably connected to the display device 7. The other end of the second transmission cable 8 is detachably connected to the control device 9. The second transmission cable 8 transmits the video signal processed by the control device 9 to the display device 7.

[0026] The control unit 9 includes controllers such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit), and comprehensively controls the operation of the light source device 3, the camera head 5, and the display device 7. The control unit 9 is not limited to a CPU or MPU; it may also include an ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or GPU (Graphics Processing Unit). The detailed configuration of the control unit 9 will be explained later in the section "Control Unit Configuration".

[0027] One end of the third transmission cable 10 is detachably connected to the light source device 3. The other end of the third transmission cable 10 is detachably connected to the control device 9. The third transmission cable 10 transmits control signals from the control device 9 to the light source device 3.

[0028] [Camera Head Configuration] Next, the configuration of the camera head 5 will be described. Figure 5 is a block diagram showing the configuration of the camera head 5 and the control device 9. As shown in Figure 5, the camera head 5 comprises a lens unit 51, an imaging unit 52, and a communication unit 53.

[0029] The lens unit 51 is composed of one or more lenses. The lens unit 51 then forms an image of the subject, after the excitation light has been removed, onto the imaging surfaces of the first and second image sensors 522 and 523, respectively.

[0030] Figure 5 shows the configuration of the imaging unit 52. The imaging unit 52 is the part that generates an image by capturing an image of the subject after the excitation light has been removed. As shown in Figures 4 and 5, the imaging unit 52 includes a prism 521, first and second image sensors 522 and 523, and a signal processing unit 524.

[0031] The prism 521 has a roughly cubic shape, formed by combining two triangular prism-shaped light-transmitting members 521a (Figure 5). A dichroic filter 521b is provided at the interface between the two light-transmitting members 521a.

[0032] The dichroic filter 521b has the characteristic of transmitting light in the wavelength band of approximately 700 nm or more and reflecting light in other wavelength bands (light in the wavelength band of less than approximately 700 nm). Therefore, of the subject image after the excitation light has been removed from the prism 521, most of the reflected light WL of the WLI light (Figure 5), after the first and second excitation lights have been removed by the excitation light cut filter 22, is reflected by the dichroic filter 521b. Then, as shown in Figure 5, the reflected light WL of the WLI light travels towards the first image sensor 522. On the other hand, of the subject image after the excitation light has been removed from the prism 521, most of the first and second fluorescence FL1 and FL2 (Figure 5), after the first and second excitation lights have been removed by the excitation light cut filter 22, is transmitted through the dichroic filter 521b (prism 521). Then, the first and second fluorescent FL1 and FL2 propagate toward the second image sensor 523.

[0033] The first and second image sensors 522 and 523 receive incident light and convert it into an electrical signal (analog signal). Examples of these first and second image sensors 522 and 523 include CMOS (Complementary Metal Oxide Semiconductor), which is a rolling shutter type image sensor in which multiple pixels are arranged in a two-dimensional manner in units of horizontal lines, or CCD (Charge Coupled Device), which is a global shutter type image sensor.

[0034] The first image sensor 522 then captures the light reflected by the dichroic filter 521b under the control of the control device 9. For the sake of explanation, the image generated by the first image sensor 522 will be referred to as the WLI light image below.

[0035] Here, as shown in Figures 4 and 5, a color filter 522a is provided on the light-receiving surface of the first image sensor 522. In other words, the first image sensor 522 provided with the color filter 522a is a so-called color image sensor. Note that the first image sensor according to the present invention is not limited to the first image sensor 522 provided with the color filter 522a, but may also be configured as a three-chip image sensor with three monochrome image sensors that capture light in three wavelength bands: R (red), G (green), and B (blue).

[0036] The color filter 522a is a color filter in which three filter groups, each grouped according to the wavelength band of light (red, green, blue) to be transmitted, are arranged in a specific format (e.g., a Bayer array).

[0037] Specifically, the color filter 522a includes an R filter group that mainly transmits light in the red wavelength band, a B filter group that mainly transmits light in the blue wavelength band, and a G filter group that mainly transmits light in the green wavelength band.

[0038] Furthermore, the second image sensor 523 captures light transmitted through the prism 521 under the control of the control device 9. For the sake of explanation, the image generated by the second image sensor 523 will be referred to as a fluorescence image below. Note that the light-receiving surface of the second image sensor 523 does not have a color filter 522a like the first image sensor 522. In other words, the second image sensor 523 is a so-called monochrome image sensor.

[0039] Furthermore, the number of pixels in the WLI optical image and the number of pixels in the fluorescence image may be different, or they may be the same.

[0040] The signal processing unit 524, under the control of the control device 9, performs signal processing on the captured images (analog signals) generated by the first and second image sensors 522 and 523, and outputs the captured images (digital signals).

[0041] For example, the signal processing unit 524 performs processing to remove reset noise, multiplies an analog gain for amplifying the analog signal (hereinafter referred to as analog gain adjustment), and performs signal processing such as A / D conversion on the captured images (analog signals) generated by the first and second imaging elements 522 and 523.

[0042] The communication unit 53 functions as a transmitter that sequentially transmits the captured images output from the imaging unit 52 to the control device 9 via the first transmission cable 6.

[0043] Note that the communication unit 53 may sequentially transmit the WLI optical image and the fluorescence image to the control device 9, or may transmit these WLI optical image and fluorescence image simultaneously.

[0044] [Configuration of Control Device] Next, the configuration of the control device 9 will be described while referring to FIG. 5. The control device 9 corresponds to the processor according to the present invention. As shown in FIG. 5, the control device 9 includes a communication unit 91, a processing module 92, a control unit 93, an input unit 94, an output unit 95, and a storage unit 96.

[0045] The communication unit 91 functions as a receiver that sequentially receives the captured images transmitted from the camera head 5 (communication unit 53) via the first transmission cable 6.

[0046] The processing module 92 processes the captured images sequentially transmitted from the camera head 5 (communication unit 53) and received by the communication unit 91 under the control of the control unit 93. As shown in FIG. 5, the processing module 92 includes an image processing unit 921 and a display control unit 922.

[0047] The image processing unit 921 executes image processing on the input captured image (the captured image received by the communication unit 91). Examples of such image processing include optical black subtraction processing (clamp processing), white balance adjustment processing, demosaic processing, color correction matrix processing, gamma correction processing, YC processing for converting RGB signals into luminance chrominance signals (Y, Cb / Cr signals), digital gain adjustment for multiplying a digital gain, noise removal, filter processing for enhancing the structure, and the like.

[0048] Note that the image processing performed on the WLI optical image and the fluorescence image may be different from each other or may be the same image processing.

[0049] The display control unit 922 generates a video signal for displaying the captured image after the image processing is performed by the image processing unit 921 under the control of the control unit 93. Then, the display control unit 922 outputs the video signal to the display device 7 via the second transmission cable 8.

[0050] The control unit 93 corresponds to the processor according to the present invention. This control unit 93 is realized by executing various programs stored in the storage unit 96 by a controller such as a CPU or an MPU, controls the operations of the light source device 3, the camera head 5, and the display device 7, and controls the operation of the entire control device 9. Note that the control unit 93 is not limited to a CPU or an MPU and may include an ASIC, an FPGA, or a GPU.

[0051] The input unit 94 is configured using an operation device such as a mouse, a keyboard, and a touch panel, and receives a user operation by a user such as a surgeon. Then, the input unit 94 outputs an operation signal corresponding to the user operation to the control unit 93.

[0052] The output unit 95 is configured using a speaker, a printer, etc., and outputs various information.

[0053] The storage unit 96 stores programs executed by the control unit 93, information necessary for the processing of the control unit 93, and the like. [[ID=十六]] [[ID=十七]]

[0054] [Operation of Fluorescence Endoscope Device] Next, the operation of the fluorescence endoscope device 1 described above will be described. In the present embodiment, the control unit 93 sets the fluorescence endoscope device 1 to the fluorescence superimposition mode or the fluorescence single mode according to, for example, a user operation on the input unit 94. The fluorescence superimposition mode is a mode in which a superimposed image obtained by superimposing a fluorescence image on a WLI optical image is output (displayed on the display device 7). The fluorescence single mode is a mode in which only a fluorescence image is output (displayed on the display device 7). Hereinafter, the operation of the fluorescence endoscope device 1 will be described for each of the fluorescence superimposition mode and the fluorescence single mode.

[0055] The observation sample shall contain both the first and second fluorescent reagents.

[0056] Furthermore, the "fluorescence image" described in the fluorescence superimposed mode and fluorescence alone mode described below is one of the following fluorescence images (1) to (3).

[0057] (1) The fluorescence image is an image obtained by imaging with the second image sensor 523 when the excitation light (first excitation light) is irradiated onto the object of observation only from the second light source 32 of the second and third light sources 32 and 33.

[0058] (2) The fluorescence image is an image obtained by imaging with the second image sensor 523 when the excitation light (second excitation light) is irradiated onto the object of observation only from the third light source 33 of the second and third light sources 32 and 33.

[0059] (3) The fluorescence image is an image obtained by imaging with the second image sensor 523 when the observation target is irradiated with excitation light (first and second excitation light) from both the second and third light sources 32 and 33.

[0060] In the following, the first and second excitation lights will be collectively referred to as excitation light.

[0061] [Operation of the Fluorescence Endoscope in Fluorescence Overlay Mode] Figure 7 is a diagram illustrating the operation of the fluorescence endoscope 1 in fluorescence overlay mode. Specifically, Figure 7(a) is a time chart showing the operating state of the light source device 3, with the vertical axis showing the irradiation intensity of light (WLI light and excitation light) (corresponding to the power value supplied to the first to third light sources 31 to 33), and the horizontal axis showing time (power supply time to the first to third light sources 31 to 33). In Figure 7(a), WLI light is represented by the letters "WLI" and excitation light is represented by the letters "EL". Figure 7(b) is a time chart showing the operating state of the first image sensor 522. Furthermore, Figure 7(c) is a time chart showing the operating state of the second image sensor 523. In Figures 7(b) and 7(c), examples are shown where CMOS image sensors are used as the first and second image sensors 522 and 523. The vertical axis shows the horizontal lines of the first and second image sensors 522 and 523 (the top row shows the uppermost horizontal line (the first horizontal line), and the bottom row shows the lowermost horizontal line (the final line)), and the horizontal axis shows time. The parallelogram region is the region that contributes to the generation of the WLI optical image and the fluorescence image in one frame. In Figures 7(b) and 7(c), the WLI optical image is represented by the letters "WLI," and the fluorescence image is represented by the letters "fluorescence."

[0062] In fluorescence superposition mode, the control unit 93 controls the operation of the light source device 3 and the first and second image sensors 522 and 523 as shown below.

[0063] The control unit 93 causes the first and second image sensors 522 and 523 to take images at a first frame rate. Specifically, as shown in Figures 7(b) and 7(c), the control unit 93 performs imaging control using a so-called rolling shutter method, which involves sequentially starting exposure for each horizontal line during one frame period of the first and second image sensors 522 and 523, and sequentially reading out each horizontal line after a predetermined period has elapsed since the start of exposure. In the case of the NTSC system, the exposure time T1 for one frame of the first and second image sensors 522 and 523 in this imaging control (hereinafter referred to as the first exposure time T1) is 1 / 60 [s] (Figures 7(b) and 7(c)).

[0064] Furthermore, the control unit 93 controls the operation of the light source device 3 and intermittently irradiates the WLI light from the light source device 3 with a first duty cycle for a first exposure time T1, as shown in Figure 7(a). This first duty cycle is, for example, about 50%. Here, the control unit 93 performs dimming control to adjust the irradiation intensity of the WLI light from the light source device 3 in order to adjust the WLI light image to a reference brightness based on the brightness (average value of luminance, etc.) of a specific area (detection area) in the WLI light image.

[0065] Furthermore, the control unit 93 controls the operation of the light source device 3 and, as shown in Figure 7(a), continuously irradiates excitation light from the light source device 3 at a constant irradiation intensity. Here, the control unit 93 performs dimming control to adjust the irradiation intensity of the excitation light from the light source device 3 in order to adjust the fluorescence image to a reference brightness based on the brightness (average value of luminance, etc.) of a specific region (detection region) in the WLI light image.

[0066] The first image sensor 522 then captures the reflected light WL of the WLI light separated by the prism 521 from the subject image after the excitation light has been removed, at each first exposure time T1, and generates a WLI light image. Similarly, the second image sensor 523 then captures the fluorescence (at least one of the first and second fluorescence FL1 and FL2) separated by the prism 521 from the subject image after the excitation light has been removed, at each first exposure time T1, and generates a fluorescence image. The image processing unit 921, under the control of the control unit 93, performs image processing on the WLI light image and the fluorescence image received by the communication unit 91, respectively. Furthermore, the image processing unit 921 superimposes the WLI light image and the fluorescence image using a known alpha blending process or additive blending process to generate a superimposed image in which the regions where fluorescence (first and second fluorescence) was emitted can be identified. The display control unit 922, under the control of the control unit 93, generates a video signal corresponding to the superimposed image and outputs it to the display device 7. As a result, the superimposed image is displayed on the display device 7.

[0067] [Operation of the Fluorescence Endoscope in Fluorescence-Only Mode] Figure 8 is a diagram illustrating the operation of the fluorescence endoscope 1 in fluorescence-only mode. Specifically, Figures 8(a) to 8(c) correspond to Figures 7(a) to 7(c), respectively. In fluorescence-only mode, the control unit 93 controls the operation of the light source device 3 and the first and second image sensors 522 and 523 as shown below.

[0068] The control unit 93 performs imaging control to cause the first and second image sensors 522 and 523 to capture images at a first frame rate, as shown in Figures 8(b) and 8(c), similar to the fluorescence superposition mode described above.

[0069] Furthermore, the control unit 93 controls the operation of the light source device 3 and intermittently irradiates WLI light from the light source device 3 with a second duty cycle smaller than the first duty cycle for the first exposure time T1, as shown in Figure 8(a). This second duty cycle is a value corresponding to the minimum amount of WLI light irradiation that the first image sensor 522 can receive, according to the specifications of the first image sensor 522, and is, for example, about 5 to 10%. Here, the control unit 93 performs dimming control to adjust the irradiation intensity of the WLI light from the light source device 3 in order to adjust the WLI light image to a reference brightness based on the brightness (average value of luminance, etc.) of a specific area (detection area) in the WLI light image.

[0070] Furthermore, the control unit 93 controls the operation of the light source device 3, as shown in Figure 8(a), in the same manner as the fluorescence superposition mode described above, and continuously irradiates excitation light from the light source device 3 at a constant irradiation intensity. Here, the control unit 93 performs dimming control to adjust the irradiation intensity of the excitation light from the light source device 3 in order to adjust the fluorescence image to a reference brightness based on the brightness (average value of luminance, etc.) of a specific region (detection region) in the WLI light image.

[0071] Then, at each first exposure time T1, the first image sensor 522 captures the reflected light WL of the WLI light separated by the prism 521 from the subject image after the excitation light has been removed, and generates a WLI light image. Similarly, at each first exposure time T1, the second image sensor 523 captures the fluorescence (at least one of the first and second fluorescence FL1 and FL2) separated by the prism 521 from the subject image after the excitation light has been removed, and generates a fluorescence image. Furthermore, the image processing unit 921, under the control of the control unit 93, performs image processing on the WLI light image and the fluorescence image received by the communication unit 91, respectively. Then, the display control unit 922, under the control of the control unit 93, generates a video signal corresponding to the fluorescence image and outputs it to the display device 7. As a result, the fluorescence image is displayed on the display device 7.

[0072] As described above, in the fluorescence-only mode, the control unit 93 reduces the amount of WLI light irradiated for each first exposure time T1 compared to the fluorescence-supervised mode. The amount of WLI light irradiated corresponds to the product of the WLI light irradiation intensity and the WLI light emission time (the power supply time to the first light source 31). In this embodiment, in the fluorescence-only mode, the control unit 93 shortens the WLI light irradiation time for each first exposure time T1 compared to the fluorescence-supervised mode.

[0073] The embodiment described above provides the following effects. Figure 9 is a diagram illustrating the effects of the embodiment. Specifically, Figure 9 is a graph showing the total amount of autofluorescence on the vertical axis, with the total amount of autofluorescence generated due to WLI light and the total amount of autofluorescence generated due to excitation light side by side. Hereinafter, the path from the light source device 3 to the light guide 4 to the insertion unit 2 to the object of observation, followed by the WLI light and excitation light, will be referred to as the first optical path. The path from the object of observation to the insertion unit 2 to the second image sensor 523, followed by the reflected light WL of the WLI light and the excitation light, will be referred to as the second optical path. When the WLI light, the reflected light WL of the WLI light, and the excitation light propagate through the first and second optical paths, the WLI light, the reflected light WL of the WLI light, and the excitation light are irradiated onto the member forming the observation optical path (hereinafter referred to as the autofluorescence generating member), causing autofluorescence to be generated from the autofluorescence generating member (Figure 9(a)). Examples of autofluorescence generating components include components contained in lenses and adhesives used to join lenses together. Such autofluorescence has a wavelength band that includes the wavelength band of the fluorescence (at least one of the first and second fluorescence FL1 and FL2) which is the light to be observed in fluorescence observation, and thus becomes noise when performing the fluorescence observation.

[0074] In the fluorescence endoscope device 1 according to this embodiment, the control unit 93 reduces the amount of WLI light irradiated for each first exposure time T1 of one frame on the second image sensor 523 in fluorescence-only mode compared to fluorescence-supervised mode. As a result, in fluorescence-only mode, the amount of WLI light irradiated to generate the WLI light image used for dimming control can be reduced, and the autofluorescence generated due to the WLI light included in the fluorescence image can be reduced (Figure 9(b)). In other words, fluorescence generated from the fluorescent reagent can be clearly identified in the fluorescence image. Therefore, fluorescence observation can be performed well with the fluorescence endoscope device 1 according to this embodiment.

[0075] (Other Embodiments) While embodiments for carrying out the present invention have been described so far, the present invention should not be limited to the embodiments described above. In the embodiments described above, the fluorescent reagent according to the present invention is not limited to the fluorescent reagent described in the embodiments described above, but other fluorescent reagents may be used. In this case, the light source device 3 should be a light source that emits excitation light corresponding to the fluorescent reagent.

[0076] In the embodiment described above, the control unit 93 shortened the irradiation time of WLI light for each first exposure time T1 in the fluorescence-only mode compared to the fluorescence-supervised mode. However, it is not limited to this, and the irradiation intensity of WLI light for each first exposure time T1 may be reduced, as shown by the dashed line in Figure 8(a).

[0077] In the embodiment described above, the first image sensor 522 may be, for example, a high-sensitivity image sensor with HD resolution. When such a high-sensitivity image sensor is used, compared to, for example, a high-resolution image sensor with 4K resolution is used, the amount of WLI light irradiation required to generate the WLI light image used for dimming control can be further reduced in the fluorescence-only mode because of its high sensitivity. Therefore, unwanted light contained in the fluorescence image can be further reduced. Similarly, when adopting the configuration of Modification 1 shown in Figures 10 and 11 below, the first image sensor 522 may be, for example, a high-sensitivity image sensor with HD resolution.

[0078] Figures 10 and 11 illustrate a modified example 1 of the embodiment. Specifically, Figures 10(a) to 10(c) correspond to Figures 7(a) to 7(c), respectively, and illustrate the operation of the fluorescence endoscope device 1 in fluorescence superposition mode. Figures 11(a) to 11(c) correspond to Figures 8(a) to 8(c), respectively, and illustrate the operation of the fluorescence endoscope device 1 in fluorescence alone mode.

[0079] In the above-described embodiment, in the fluorescence superimposed mode and the fluorescence alone mode, the control unit 93 may control the operation of the light source device 3 and the first and second image sensors 522 and 523 as shown below.

[0080] [Fluorescence Overlay Mode] In fluorescence overlay mode, the control unit 93 controls the operation of the light source device 3 and the first and second image sensors 522 and 523, as shown in Figure 10.

[0081] Specifically, the control unit 93 performs imaging control to cause the first and second image sensors 522 and 523 to capture images at a first frame rate, as shown in Figures 10(b) and 10(c), similar to the fluorescence superposition mode described in the above-described embodiment.

[0082] Furthermore, the control unit 93 controls the operation of the light source device 3 and intermittently irradiates the WLI light from the light source device 3 with a third duty cycle for a first exposure time T1, as shown in Figure 10(a). This third duty cycle is, for example, about 20%. Here, the control unit 93 performs dimming control to adjust the irradiation intensity of the WLI light from the light source device 3 in order to adjust the WLI light image to a reference brightness based on the brightness (average value of luminance, etc.) of a specific area (detection area) in the WLI light image.

[0083] Furthermore, the control unit 93 controls the operation of the light source device 3 and, as shown in Figure 10(a), continuously irradiates excitation light from the light source device 3 at a constant irradiation intensity. Here, the control unit 93 performs dimming control to adjust the irradiation intensity of the excitation light from the light source device 3 in order to adjust the fluorescence image to a reference brightness based on the brightness (average value of luminance, etc.) of a specific region (detection region) in the WLI optical image.

[0084] The first image sensor 522 then captures the reflected light WL of the WLI light separated by the prism 521 from the subject image after the excitation light has been removed, at each first exposure time T1, and generates a WLI light image. Similarly, the second image sensor 523 then captures the fluorescence (at least one of the first and second fluorescence FL1 and FL2) separated by the prism 521 from the subject image after the excitation light has been removed, at each first exposure time T1, and generates a fluorescence image. The image processing unit 921, under the control of the control unit 93, performs image processing on the WLI light image and the fluorescence image received by the communication unit 91, respectively. Furthermore, the image processing unit 921 superimposes the WLI light image and the fluorescence image using a known alpha blending process or additive blending process to generate a superimposed image in which the regions where fluorescence (first and second fluorescence) was emitted can be identified. The display control unit 922, under the control of the control unit 93, generates a video signal corresponding to the superimposed image and outputs it to the display device 7. As a result, the superimposed image is displayed on the display device 7.

[0085] [Fluorescence-only mode] In fluorescence-only mode, the control unit 93 controls the operation of the light source device 3 and the first and second image sensors 522 and 523, as shown in Figure 11.

[0086] Specifically, the control unit 93 performs imaging control to cause the first image sensor 522 to take images at a first frame rate, similar to the fluorescence superposition mode described above, as shown in Figure 11(b).

[0087] Furthermore, as shown in Figure 11(c), the control unit 93 performs imaging control to cause the second image sensor 523 to capture images at a second frame rate smaller than the first frame rate. In other words, the control unit 93 performs long exposure (imaging control) of the second image sensor 523. In the case of the NTSC system, the exposure time T2 for one frame on the second image sensor 523 in this imaging control (hereinafter referred to as the second exposure time T2) is 1 / 30 [s] (Figure 11(c)).

[0088] Furthermore, the control unit 93 controls the operation of the light source device 3 and intermittently irradiates WLI light from the light source device 3 with a fourth duty cycle smaller than the third duty cycle for the second exposure time T2, as shown in Figure 11(a). This fourth duty cycle is a value corresponding to the minimum amount of WLI light irradiation that the first image sensor 522 can receive, according to the specifications of the first image sensor 522, and is, for example, about 5 to 10%. Here, the control unit 93 performs dimming control to adjust the irradiation intensity of the WLI light from the light source device 3 in order to adjust the WLI light image to a reference brightness based on the brightness (average value of luminance, etc.) of a specific area (detection area) in the WLI light image.

[0089] Furthermore, the control unit 93 controls the operation of the light source device 3, as shown in Figure 11(a), similar to the fluorescence superposition mode described above, and continuously irradiates excitation light from the light source device 3 at a constant irradiation intensity. Here, the control unit 93 performs dimming control to adjust the irradiation intensity of the excitation light from the light source device 3 in order to adjust the fluorescence image to a reference brightness based on the brightness (average value of luminance, etc.) of a specific region (detection region) in the WLI light image.

[0090] Then, at each first exposure time T1, the first image sensor 522 captures the reflected light WL of the WLI light separated by the prism 521 from the subject image after the excitation light has been removed, and generates a WLI light image. Similarly, at each second exposure time T2, the second image sensor 523 captures the fluorescence (at least one of the first and second fluorescence FL1 and FL2) separated by the prism 521 from the subject image after the excitation light has been removed, and generates a fluorescence image. Furthermore, the image processing unit 921, under the control of the control unit 93, performs image processing on the WLI light image and the fluorescence image received by the communication unit 91, respectively. Then, the display control unit 922, under the control of the control unit 93, generates a video signal corresponding to the fluorescence image and outputs it to the display device 7. As a result, the fluorescence image is displayed on the display device 7.

[0091] Even when configured as in the modified example 1 described above, the same effects as those of the embodiment described above are achieved.

[0092] 1 Fluorescence endoscope device 2 Insertion section 3 Light source device 4 Light guide 5 Camera head 6 First transmission cable 7 Display device 8 Second transmission cable 9 Control device 10 Third transmission cable 21 Eyepiece section 22 Excitation light cut filter 31 First light source 32 Second light source 33 Third light source 51 Lens unit 52 Imaging unit 53 Communication unit 91 Communication unit 92 Processing module 93 Control unit 94 Input unit 95 Output unit 96 Memory unit 521 Prism 521a Light-transmitting member 521b Dichroic filter 522 First image sensor 522a Color filter 523 Second image sensor 524 Signal processing unit 921 Image processing unit 922 Display control unit CL1, CL2 Curves P1, P2 Wavelength T1 First exposure time T2 Second exposure time WL Reflected light of WLI FL1 First fluorescence FL2 Second fluorescence

Claims

1. A fluorescence endoscope comprising: a WLI light source that emits WLI light including the wavelength band of visible light; an excitation light source that emits excitation light for exciting a fluorescent reagent; a first image sensor that images the reflected light of the WLI light from an object when the WLI light is irradiated onto the object; a second image sensor that images the fluorescence emitted from the fluorescent reagent contained in the object when the excitation light is irradiated onto the object; and a processor that controls the operation of the WLI light source, the excitation light source, the first image sensor, and the second image sensor, wherein the processor can be switched between a fluorescence superposition mode that outputs a superimposed image obtained by superimposing a fluorescence image obtained by imaging with the second image sensor onto a WLI light image obtained by imaging with the first image sensor, and a fluorescence-only mode that outputs only the fluorescence image, wherein in the fluorescence-only mode, the amount of WLI light irradiated by the WLI light source for each exposure time of one frame on the second image sensor is reduced compared to the fluorescence superposition mode.

2. The fluorescence endoscope apparatus according to claim 1, wherein the processor controls the operation of the excitation light source and adjusts the amount of excitation light based on the WLI light image.

3. The fluorescence endoscope apparatus according to claim 1, wherein the processor, in the fluorescence-only mode, shortens the irradiation time of the WLI light source by the WLI light source for each exposure time of one frame in the second image sensor compared to the fluorescence-supervised mode.

4. The fluorescence endoscope apparatus according to claim 1, wherein the processor reduces the irradiation intensity of the WLI light source by the WLI light source for each exposure time of one frame in the second image sensor compared to the fluorescence superimposed mode in the fluorescence-only mode.

5. The fluorescence endoscope apparatus according to claim 1, wherein the processor, in the fluorescence superposition mode, continuously irradiates the excitation light source with a constant irradiation intensity and causes the second image sensor to take images at a first frame rate, intermittently irradiates the WLI light source with a first duty cycle with respect to the exposure time of one frame on the second image sensor and causes the first image sensor to take images at a first frame rate, and in the fluorescence alone mode, continuously irradiates the excitation light source with a constant irradiation intensity and causes the second image sensor to take images at a first frame rate, and intermittently irradiates the WLI light source with a second duty cycle smaller than the first duty cycle with respect to the exposure time of one frame on the second image sensor and causes the first image sensor to take images at a first frame rate.

6. The fluorescence endoscope apparatus according to claim 1, wherein the processor, in the fluorescence superposition mode, continuously irradiates the excitation light source with a constant irradiation intensity and causes the second image sensor to take images at a first frame rate, intermittently irradiates the second image sensor with WLI light from the WLI light source with a third duty cycle with respect to the exposure time of one frame and causes the first image sensor to take images at a first frame rate, and in the fluorescence alone mode, continuously irradiates the excitation light source with a constant irradiation intensity and causes the second image sensor to take images at a second frame rate smaller than the first frame rate, and intermittently irradiates the second image sensor with WLI light from the WLI light source with a fourth duty cycle smaller than the third duty cycle with respect to the exposure time of one frame and causes the first image sensor to take images at a first frame rate.

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