Endoscope system

Abstract

To provide an endoscope system capable of obtaining illumination light having a target emission spectrum by easy control even when a fluorescence type semiconductor light source is used.SOLUTION: A third dichroic mirror 81 integrates a light path through which light integrated by a second dichroic mirror 80 passes and a light path through which green fluorescent light passes, and does not integrate a light path of blue excitation light. When a normal observation mode is set, a drive current pulse to be given to a blue semiconductor light source 35 is adjusted on the basis of light volume received by a blue light volume measuring sensor 101, a drive current pulse to be given to a green semiconductor light source 36 is adjusted on the basis of the light volume received by a green light volume measuring sensor 103, and a drive current pulse to be given to a red semiconductor light source 37 is adjusted on the basis of the light volume received by a red light volume measuring sensor 103.SELECTED DRAWING: Figure 26

Description

[Technical field]

[0001] The present invention relates to an endoscope system. [Background technology]

[0002] In the medical field, endoscopic diagnosis using an endoscope system is widespread. The endoscope system includes an endoscope, an endoscope light source device (hereinafter simply referred to as a light source device) for supplying illumination light to the endoscope, and a processor device for processing image signals output by the endoscope. The endoscope has an insertion section that is inserted into a living body, and at the tip of the insertion section, an illumination window for irradiating an observation site (subject) with illumination light and an observation window for photographing the observation site are arranged. The endoscope has a built-in light guide made of a fiber bundle in which optical fibers are bundled. The light guide guides the illumination light supplied from the light source device to the illumination window. An imaging element such as a CCD is arranged behind the observation window. The observation site irradiated with the illumination light is imaged by the imaging element, and a display image for observation is generated by the processor device based on the image signal output by the imaging element. The display image is displayed on a monitor, thereby observing the inside of the living body.

[0003] Conventionally, light source devices have used xenon lamps or halogen lamps that emit white light as light sources. Recently, however, instead of these, proposals have been made to use semiconductor light sources having light emitting elements such as laser diodes (LDs: Laser Diodes) and light emitting diodes (LEDs: Light Emitting Diodes) (see Patent Documents 1 and 2).

[0004] Patent document 1 describes a light source device that uses three semiconductor light sources of blue, green, and red, each composed of three LEDs that emit light of the respective colors blue (B), green (G), and red (R), and generates white light by combining the three colors of light emitted from the three LEDs.

[0005] Xenon lamps and halogen lamps contain a fixed ratio of blue, green, and red components in their white light, and the ratio of each color component cannot be changed.In contrast, semiconductor light sources with three colors (blue, green, and red) can independently control the amount of light for each color, and can freely change the ratio of the amount of light for each color, making it easy to generate multiple types of illumination light with diverse emission spectra.

[0006] As the green and red semiconductor light sources, in addition to semiconductor light sources having light emitting elements that emit light of each color of green and red, there are fluorescent semiconductor light sources having an excitation light emitting element that emits excitation light and a phosphor that is excited by the excitation light and emits either green or red fluorescence. For example, paragraph

[0040] of Patent Document 2 describes a fluorescent green semiconductor light source that is composed of a blue excitation light LED that emits excitation light in the violet to blue wavelength band and a green phosphor that emits green fluorescence in the green wavelength band by the blue excitation light.

[0007] Many of the currently commercialized LEDs that emit light in the violet to blue wavelength band have higher luminous efficiency and are cheaper than LEDs that emit green light. Therefore, a fluorescent green semiconductor light source as described in Patent Document 2 may be used as the green semiconductor light source of a light source device, rather than a semiconductor light source having an LED that emits green light. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2007-068699 A [Patent Document 2] JP 2009-297290 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, for example, when the fluorescent green semiconductor light source described in Patent Document 2 is used as the green semiconductor light source of the light source device of Patent Document 1, a problem occurs in that illumination light with a target emission spectrum cannot be obtained stably. This is because, in the fluorescent green semiconductor light source, most of the blue excitation light is absorbed by the phosphor, but a part of it is not absorbed by the phosphor and passes through the phosphor to be irradiated to the observation site together with the fluorescence, so that changing the amount of green light means that the amount of blue excitation light also changes accordingly. Since the wavelength band of the blue excitation light overlaps with the wavelength band of the blue light emitted by the blue semiconductor light source, a change in the amount of green light affects the amount of blue light.

[0010] In endoscopic diagnosis, illumination light with a target emission spectrum may be generated by setting the light amounts of blue, green, and red lights to specific ratios depending on the purpose of observation. On the other hand, exposure control is performed to increase the light amount of illumination light when the light amount of the entire displayed image is insufficient (underexposure), and to decrease the light amount of illumination light when the light amount is too high (overexposure).

[0011] In the case of exposure control in which the ratio of the light amount of each color light is determined to generate illumination light with a target emission spectrum, if the exposure control is performed based on an image signal based on the amount of light received by an image sensor, the exposure control should be performed according to the amount of illumination light, excluding the amount of excitation light received by the image sensor, and the overall amount of light should be increased or decreased without changing the emission spectrum of the illumination light. However, when a fluorescent semiconductor light source is used, when the output of the fluorescent semiconductor light source is increased to change the amount of fluorescence, the amount of light whose wavelength band overlaps with the excitation light is affected by the excitation light as described above, and the emission spectrum of the illumination light changes. For these reasons, when a fluorescent semiconductor light source is used, illumination light with a target emission spectrum cannot be obtained stably. As a solution to this problem, it is possible to increase or decrease the amount of light whose wavelength band overlaps with the excitation light by taking into account the change in the excitation light caused by the change in the amount of fluorescence, but this is difficult to adopt because the control becomes complicated.

[0012] Patent documents 1 and 2 do not mention the problem that illumination light with a target emission spectrum cannot be stably obtained when using a fluorescent semiconductor light source, and naturally do not mention a solution to this problem.

[0013] The present invention has been made in consideration of the above problems, and has an object to provide an endoscope system that can stably obtain illumination light having a target emission spectrum with simple control, even when a fluorescent semiconductor light source is used. [Means for solving the problem]

[0014] The present invention relates to an endoscope system including an endoscope and an endoscope light source device that supplies illumination light to a light guide of the endoscope, the endoscope system including a purple LED light source that emits purple light, a blue LED light source that emits blue light, an excitation light LED that emits blue excitation light having a wavelength band that at least partially overlaps with the wavelength band of the blue light, a substrate on which the excitation light LED is mounted, sealing resin, and a green phosphor that is excited by the blue excitation light and emits green fluorescence in a green wavelength band, the green phosphor being diffused in the sealing resin, a red LED light source that emits red light, and the excitation light LED that emits blue excitation light having a wavelength band that at least partially overlaps with the wavelength band of the blue light. a first dichroic mirror that combines an optical path through which the purple light passes and an optical path through which the blue light emitted from the blue LED light source passes; a second dichroic mirror that combines an optical path through which the light combined by the first dichroic mirror passes and an optical path through which the green fluorescent light emitted from the green LED light source passes, and prevents the optical path of the blue excitation light from being combined; a condensing lens that collects the light combined by the second dichroic mirror onto an incident end of a light guide; a purple light quantity measuring sensor that is provided between the purple LED light source and the second dichroic mirror and that receives a portion of the purple light emitted by the purple LED light source; and a blue LED light source. a blue light amount measuring sensor provided between the first dichroic mirror and the green LED light source, receiving a portion of the green fluorescence emitted by the green LED light source; a red light amount measuring sensor provided between the red LED light source and the second dichroic mirror, receiving a portion of the red light emitted by the red LED light source; an image sensor mounted in the insertion section of the endoscope, receiving reflected light from an observation site irradiated with illumination light and outputting an image signal; and a light source control section, wherein the light source control section: When determining a drive current pulse to be given to a purple LED light source, a blue LED light source, an excitation light LED light source, or a red LED light source based on an exposure control signal corresponding to an exposure value calculated from an image signal, when a normal observation mode in which white light is irradiated is set, the drive current pulse to be given to the blue LED light source is adjusted based on the amount of light received by the blue light quantity measuring sensor, the drive current pulse to be given to the excitation light LED is adjusted based on the amount of light received by the green light quantity measuring sensor, and the drive current pulse to be given to the red LED light source is adjusted based on the amount of light received by the red light quantity measuring sensor.

[0015] It is preferable that the central wavelength of the blue excitation light is between the central wavelength of the violet light and the central wavelength of the blue light.When the vessel enhancement observation mode in which the violet LED light source and the green LED light source are turned on is set, it is preferable that the light source control unit adjusts the drive current pulse to be given to the violet LED light source based on the amount of light received by the violet light amount measurement sensor, and adjusts the drive current pulse to be given to the excitation light LED based on the amount of light received by the green light amount measurement sensor.It is preferable that the proportion of the amount of blue light is reduced in the vessel enhancement observation mode compared to the normal observation mode.

[0016] It is preferable that the imaging element is a monochrome imaging element, and the light source control unit sequentially turns on the blue LED light source, the excitation light LED, or the red LED light source on a frame-by-frame basis to sequentially irradiate blue light, green fluorescent light, or red light.

[0017] It is preferable to include a collimator lens for purple light provided between the purple LED light source and the first dichroic mirror, a collimator lens for blue light provided between the blue LED light source and the first dichroic mirror, a collimator lens for green fluorescence provided between the green LED light source and the first dichroic mirror, and a collimator lens for red light provided between the red LED light source and the first dichroic mirror.It is preferable to have a third dichroic mirror that integrates the optical path through which the green fluorescence passes and the optical path through which the red light passes.

[0018] Of the image signals, it is preferable to assign the image signal B to the B and G channels of the monitor, and the image signal G to the R channel of the monitor, thereby displaying the observed area in pseudo-color on the monitor. It is preferable that the imaging element sequentially outputs the image signal B, the image signal G, or the image signal R. Effect of the Invention

[0019] According to the present invention, even when a fluorescent semiconductor light source is used, illumination light having a desired emission spectrum can be obtained stably with simple control. [Brief description of the drawings]

[0020] [Figure 1] 1 is an external view of an endoscope system according to the present invention. [Diagram 2] FIG. 2 is a front view of the tip portion of the endoscope. [Diagram 3] 2 is a block diagram showing the electrical configuration of the endoscope system. FIG. [Figure 4] FIG. 2 is a diagram showing a blue semiconductor light source. [Diagram 5] FIG. 2 illustrates a green semiconductor light source. [Figure 6] 4 is a graph showing an emission spectrum of blue light emitted by a blue semiconductor light source. [Figure 7] 4 is a graph showing an emission spectrum of red light emitted by a red semiconductor light source. [Figure 8] 4 is a graph showing an emission spectrum of purple light emitted by a purple semiconductor light source. [Figure 9] 4 is a graph showing emission spectra of blue excitation light and green fluorescence emitted by a green semiconductor light source. [Figure 10] 1 is a graph showing the absorption spectrum of hemoglobin. [Figure 11] 1 is a graph showing the scattering coefficient of biological tissue. [Figure 12] 1 is a graph showing an emission spectrum of white light composed of blue light, green fluorescent light, and red light. [Figure 13] 1 is a graph showing the spectral characteristics of a micro color filter of an imaging element. [Figure 14] 11 is an explanatory diagram showing the irradiation timing of illumination light and the operation timing of the image sensor in a normal observation mode. FIG. [Figure 15] 11 is an explanatory diagram showing the irradiation timing of illumination light and the operation timing of the image sensor in a vessel enhancement observation mode. FIG. [Figure 16] FIG. 11 is an explanatory diagram showing an image processing procedure in a normal observation mode. [Figure 17] FIG. 11 is an explanatory diagram showing an image processing procedure in a vessel enhancement observation mode. [Figure 18] 3 is a diagram showing an arrangement of semiconductor light sources and a detailed configuration of an optical path combining unit; FIG. [Figure 19] 4 is a graph showing the transmission characteristics of a dichroic filter of the first dichroic mirror. [Figure 20] 13 is a graph showing the transmission characteristics of a dichroic filter of the second dichroic mirror. [Figure 21] 13 is a graph showing the transmission characteristics of a dichroic filter of the third dichroic mirror. [Figure 22] 13 is a diagram showing an optical path combining section provided with a first dichroic mirror on which a dichroic filter having a function of an excitation light cut filter is formed in the second embodiment. FIG. [Diagram 23] 4 is a graph showing the transmission characteristics of a dichroic filter of the first dichroic mirror. [Figure 24] 13 is a diagram showing an optical path integrating section provided with an excitation light cut filter according to a third embodiment. FIG. [Diagram 25] 1 is a graph showing the transmission characteristics of an excitation light cut filter. [Figure 26] 13 is a diagram showing a light path integration section provided with a light quantity measurement sensor according to a fourth embodiment; FIG. [Figure 27] 13 is a graph showing the transmission characteristics of a filter placed in front of a green light quantity measuring sensor. [Figure 28] 11 is a graph showing the transmission characteristics of a filter placed in front of a red light quantity measuring sensor. [Figure 29] FIG. 11 is a configuration diagram for performing light amount control using a light amount measurement sensor. [Diagram 30] FIG. 13 is a diagram showing a light path integrating section provided with an excitation light cut filter and a light quantity measuring sensor. [Diagram 31] FIG. 13 is a diagram showing a light source section provided with a white semiconductor light source according to a fifth embodiment. [Diagram 32] FIG. 13 is a diagram illustrating another example of a green semiconductor light source according to the sixth embodiment. [Diagram 33] FIG. 13 is a diagram illustrating another example of the white semiconductor light source according to the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [First embodiment] 1, an endoscope system 10 includes an endoscope 11 that captures an image of an observation site in a living body, a processor device 12 that generates a display image of the observation site based on an image signal obtained by capturing the image, a light source device 13 that supplies illumination light for irradiating the observation site to the endoscope 11, and a monitor 14 that displays the display image. An operation input unit 15 such as a keyboard and a mouse is connected to the processor device 12.

[0022] The endoscope system 10 has a normal observation mode for observing the observation site, and a vessel enhancement observation mode for emphasizing and observing blood vessels present inside the mucosa of the observation site. The vessel enhancement observation mode is a mode for acquiring a blood vessel pattern as blood vessel information and performing a diagnosis such as distinguishing between benign and malignant tumors. In the vessel enhancement observation mode, the observation site is irradiated with illumination light containing a large amount of light components in a specific wavelength band that has a high absorbance to hemoglobin in blood. In the normal observation mode, a normal observation image suitable for observing the overall characteristics of the observation site is generated as a display image, and in the vessel enhancement observation mode, a vessel enhancement observation image suitable for observing the blood vessel pattern is generated as a display image.

[0023] The endoscope 11 comprises an insertion portion 16 that is inserted into the digestive tract of a living body, an operating portion 17 provided at the base end portion of the insertion portion 16, and a universal cord 18 that connects the endoscope 11 to the processor device 12 and the light source device 13.

[0024] The insertion section 16 is composed of a tip section 19, a bending section 20, and a flexible tube section 21, which are arranged in sequence from the tip. As shown in Fig. 2, the tip surface of the tip section 19 is provided with an illumination window 22 for irradiating the observation site with illumination light, an observation window 23 for capturing an image of the observation site, an air / water nozzle 24 for supplying air / water to clean the observation window 23, and a forceps outlet 25 for protruding treatment tools such as forceps and an electric scalpel to perform various treatments. An image sensor 56 and an objective optical system 60 for forming an image (both see Fig. 3) are built in behind the observation window 23.

[0025] The bending section 20 is made up of multiple linked bending pieces, and is bent in the up, down, left and right directions by operating the angle knob 26 of the operation section 17. The bending section 20 is bent so that the tip 19 is oriented in a desired direction. The flexible tube section 21 is flexible so that it can be inserted into a winding duct such as the esophagus or intestines. A communication cable for communicating a drive signal for driving the image sensor 56 and an image signal output by the image sensor 56, a light guide 55 (see FIG. 3) for guiding illumination light supplied from the light source device 13 to the illumination window 22, and the like are inserted into the insertion section 16.

[0026] In addition to the angle knob 26, the operation unit 17 is provided with a forceps port 27 for inserting a treatment tool, an air / water supply button 28 which is operated when supplying air / water from the air / water supply nozzle 24, and a release button (not shown) for taking still images.

[0027] A communication cable and a light guide 55 extending from the insertion portion 16 are inserted into the universal cord 18, and a connector 29 is attached to one end of the universal cord 18 on the side of the processor device 12 and the light source device 13. The connector 29 is a composite connector consisting of a communication connector 29a and a light source connector 29b. The communication connector 29a and the light source connector 29b are detachably connected to the processor device 12 and the light source device 13, respectively. One end of the communication cable is disposed in the communication connector 29a, and an entrance end 55a (see FIG. 3) of a light guide 55 is disposed in the light source connector 29b.

[0028] In FIG. 3, light source device 13 includes a light source section 40 consisting of four semiconductor light sources 35, 36, 37, and 38 of blue, green, red, and purple, an optical path integration section 41 that integrates the optical paths of each color light of each of the semiconductor light sources 35 to 38, and a light source control section 42 that controls the driving of each of the semiconductor light sources 35 to 38.

[0029] The blue, red and purple semiconductor light sources 35, 37 and 38 each have, as light emitting elements, a blue LED 43 that emits light in a blue wavelength band, a red LED 45 that emits light in a red wavelength band and a purple LED 46 that emits light in a purple wavelength band. On the other hand, the green semiconductor light source 36 has a blue excitation light LED (hereinafter simply referred to as excitation light LED) 44 that emits blue excitation light in a wavelength band from purple to blue, and a green phosphor 47 that is excited by the blue excitation light and emits green fluorescence in a green wavelength band.

[0030] As is well known, each of the LEDs 43-46 is a junction of a P-type semiconductor and an N-type semiconductor. When a voltage is applied, electrons and holes recombine beyond the band gap near the PN junction, causing a current to flow, and at the time of recombination, energy equivalent to the band gap is emitted as light. When the value of the supplied power is increased, each of the LEDs 43-46 increases the amount of light emitted. In the green semiconductor light source 36, which is a fluorescent semiconductor light source combining an excitation light LED 44 and a green phosphor 47, the amount of green fluorescence from the green phosphor 47 also increases as the amount of blue excitation light from the excitation light LED 44 increases.

[0031] As shown in FIG. 4, the blue semiconductor light source 35 is composed of a substrate 35a on which the blue LED 43 is mounted, a mold 35b formed on the substrate 35a and having a cavity for accommodating the blue LED 43, and a resin 35c sealed in the cavity. The inner surface of the cavity functions as a reflector that reflects light. A diffusing material that diffuses light is dispersed in the resin 35c. The blue LED 43 is electrically connected to the substrate 35a by a wiring 35d. Such a mounting form of the blue semiconductor light source 35 is generally called a surface mount type. Since the semiconductor light sources 35, 37, and 38 except for the green semiconductor light source 36 are basically the same in configuration, the blue semiconductor light source 35 will be described as an example, and the description of the red and purple semiconductor light sources 37 and 38 will be omitted.

[0032] As shown in Fig. 5, the green semiconductor light source 36 has a substrate 36a and a mold 36b, similar to the other semiconductor light sources 35, 37, and 38, and is packaged with an excitation light LED 44 in a surface-mounted manner. The difference between the green semiconductor light source 36 and the other semiconductor light sources 35, 37, and 38 is that a green phosphor 47 is sealed in the cavity of the mold 36b. The green phosphor 47 is a phosphor and a diffusing agent dispersed in a sealing resin that seals the excitation light LED 44. Reference numeral 36d denotes a wire that connects the substrate 36a and the excitation light LED 44.

[0033] As shown in Fig. 6, the blue LED 43 has wavelength components in the blue wavelength band of 440 nm to 470 nm, for example, and emits blue light LB with a central wavelength of 455 ± 10 nm. As shown in Fig. 7, the red LED 45 has wavelength components in the red wavelength band of 615 nm to 635 nm, for example, and emits red light LR with a central wavelength of 620 ± 10 nm. As shown in Fig. 8, the purple LED 46 has wavelength components in the purple wavelength band of 395 nm to 415 nm, for example, and emits purple light LV with a central wavelength of 405 ± 10 nm.

[0034] 9, the green semiconductor light source 36 emits mixed light (LBe+LGf) of blue excitation light LBe emitted by the excitation light LED 44 and green fluorescence LGf excited by the blue excitation light LBe and emitted by the green phosphor 47. The blue excitation light LBe has wavelength components in the vicinity of 420 nm to 440 nm, which is a wavelength band from violet to blue, and is light with a central wavelength of 430±10 nm. The green fluorescence LGf has wavelength components in the vicinity of 500 nm to 600 nm, which is a wavelength band of green, and is light with a central wavelength of 520±10 nm. The wavelength band of the blue excitation light LBe partially overlaps with the wavelength band of the blue light LB emitted by the blue semiconductor light source 35 and the wavelength band of the purple light LV emitted by the purple semiconductor light source 38 (see also FIG. 19, etc.).

[0035] The green phosphor 47 absorbs most of the blue excitation light LBe and emits green fluorescence LGf, but a portion of the blue excitation light LBe is not absorbed by the green phosphor 47 and passes through the green phosphor 47. For this reason, the emission spectrum of the light emitted by the green semiconductor light source 36 contains two color components, the portion of the blue excitation light LBe that has passed through the green phosphor 47, and the green fluorescence LGf, as shown in the figure.

[0036] The purple semiconductor light source 38 is a light source for blood vessel enhancement observation (semiconductor light source for acquiring blood vessel information). In FIG. 10 showing the absorption spectrum of blood hemoglobin, the absorption coefficient μa of blood hemoglobin has wavelength dependency, increases sharply in the wavelength band of 450 nm or less, and has a peak near 405 nm. In addition, although it is a lower value compared to the wavelength band of 450 nm or less, it also has a peak in the wavelength band of 530 nm to 560 nm. When light in a wavelength band with a large absorption coefficient μa is irradiated to an observation site, absorption is high in blood vessels, and an image with a difference in contrast between blood vessels and other parts is obtained.

[0037] Furthermore, as shown in Figure 11, the light scattering characteristics of biological tissue are also wavelength-dependent, with the shorter the wavelength, the larger the scattering coefficient μS. Scattering affects the depth of light penetration into biological tissue. In other words, the greater the scattering, the more light is reflected near the mucosal surface layer of the biological tissue, and the less light reaches the mid-to-deep layers. Therefore, the shorter the wavelength, the lower the depth of penetration, and the longer the wavelength, the deeper the depth of penetration. The wavelength of light for blood vessel enhancement is selected taking into account the light absorption characteristics of hemoglobin and the light scattering characteristics of biological tissue.

[0038] The purple light LV with a central wavelength of 405±10 nm emitted by the purple LED 46 is relatively short in wavelength and has a low penetration depth, and is therefore absorbed by superficial blood vessels. For this reason, the purple light LV is used as light for highlighting superficial blood vessels. By using the purple light LV, a vessel-enhanced observation image in which the superficial blood vessels are depicted with high contrast can be obtained. In addition, light in the green wavelength band of the white light LW (see FIG. 12) is used as light for highlighting mid- and deep blood vessels. In the absorption spectrum shown in FIG. 10, the absorption coefficient changes gradually in the green wavelength band of 530 nm to 560 nm compared to the blue wavelength band of 450 nm or less, so the light for highlighting mid- and deep blood vessels is not required to have a narrow band like the purple light LV. For this reason, as described later, a green image signal color-separated from the white light by a G-color micro color filter of the image sensor 56 is used for highlighting mid- and deep blood vessels.

[0039] 3, drivers 50, 51, 52, and 53 are connected to the LEDs 43 to 46, respectively. The light source control unit 42 controls the turning on and off and light amount of the LEDs 43 to 46 via the drivers 50 to 53. The light amount is controlled by changing the power supplied to the LEDs 43 to 46 based on an exposure control signal received from the processor device 12.

[0040] Each driver 50-53, under the control of the light source control unit 42, continuously supplies a driving current to each LED 43-46 to light up each LED 43-46. Then, in response to an exposure control signal received from the processor device 12, the driver 50-53 changes the power supplied to each LED 43-46 by changing the value of the driving current to be supplied, thereby controlling the light intensities of the blue light LB, the green fluorescent light LGf, the red light LR, and the violet light LV. The light intensity of the green fluorescent light LGf is controlled by controlling the light intensity of the blue excitation light LBe of the excitation light LED 44. Therefore, when the light intensity of the green fluorescent light LGf is to be increased, the driving current value supplied from the driver 51 to the excitation light LED 44 is increased in order to increase the light intensity of the blue excitation light LBe. Note that the driving current may be supplied in a pulsed manner, not continuously, and PAM (Pulse Amplitude Modulation) control for changing the amplitude of the driving current pulse or PWM (Pulse Width Modulation) control for changing the duty ratio of the driving current pulse may be performed.

[0041] The optical path combining unit 41 combines the optical paths of the color lights emitted by the semiconductor light sources 35-38 into one optical path. The light output unit of the optical path combining unit 41 is disposed in the vicinity of the receptacle connector 54 to which the light source connector 29b is connected. The optical path combining unit 41 outputs the light incident from each of the semiconductor light sources 35-38 to the incident end 55a of the light guide 55 of the endoscope 11. Although not shown in the figure, the light source connector 29b and the receptacle connector 54 are each provided with protective glass.

[0042] FIG. 12 shows the emission spectrum of the mixed light of the blue light LB, the green fluorescent light LGf, and the red light LR from the blue, green, and red semiconductor light sources 35-37 combined by the optical path combining unit 41. This mixed light is used as white light LW. Since the blue excitation light LBe is cut by the third dichroic mirror 81 (see FIG. 18) as described later, the emission spectrum of the blue excitation light LBe is not superimposed on the emission spectrum of the white light LW. Note that the emission spectrum of the white light LW shown in FIG. 12 is an example, and the emission spectrum of the target white light LW may be changed in various ways depending on the color tone of the desired display image. Specifically, the ratio of the light amounts of the blue light LB, the green fluorescent light LGf, and the red light LR (the ratio of the driving current values ​​of the LEDs 43-45) is changed to generate the white light LW with the target emission spectrum.

[0043] The light source control unit 42 controls the exposure of the illumination light while maintaining a target emission spectrum. If the ratio of the light intensity of each color light constituting the illumination light changes, the emission spectrum of the illumination light changes, and the color of the displayed image changes. For this reason, the light source control unit 42 independently changes the drive current value given to each LED 43-46 through each driver 50-53 to increase or decrease the light intensity of each color light so that the ratio of the light intensity of each color light is constant.

[0044] Furthermore, the light source control unit 42 changes the emission spectrum of the illumination light between the normal observation mode and the vessel enhancement observation mode. In the vessel enhancement observation mode, in addition to the white light LW, purple light LV for enhancing superficial blood vessels is irradiated, so that the emission spectrum of the illumination light is the white light LW plus the purple light LV. In the emission spectrum of the mixed light of the white light LW and the purple light LV, the light source control unit 42 reduces the proportion of the amount of blue light LB compared to the normal observation mode so that the purple light LV becomes dominant compared to the blue light LB.

[0045] 3, the endoscope 11 includes a light guide 55, an imaging element 56, an analog processing circuit 57 (AFE: Analog Front End), and an imaging control unit 58. The light guide 55 is a fiber bundle in which a plurality of optical fibers are bundled. When the light source connector 29b is connected to the light source device 13, an incident end 55a of the light guide 55 disposed in the light source connector 29b faces an exit end of the optical path integration unit 41. The exit end of the light guide 55 located at the tip portion 19 branches into two before the illumination window 22 so that light is guided to the two illumination windows 22.

[0046] An illumination lens 59 is disposed behind the illumination window 22. The illumination light supplied from the light source device 13 is guided to the illumination lens 59 by the light guide 55 and is irradiated from the illumination window 22 towards the observation site. The illumination lens 59 is made of a concave lens, and widens the divergence angle of the light emitted from the light guide 55. This allows the illumination light to be irradiated over a wide range of the observation site.

[0047] An objective optical system 60 and an image sensor 56 are disposed behind the observation window 23. An image of the observation site is incident on the objective optical system 60 through the observation window 23 and is formed on an image sensor surface 56a of the image sensor 56 by the objective optical system 60.

[0048] The imaging element 56 is composed of a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and a plurality of photoelectric conversion elements constituting pixels such as photodiodes are arranged in a matrix on its imaging surface 56a. The imaging element 56 photoelectrically converts light received on the imaging surface 56a, and accumulates signal charges in each pixel according to the amount of light received. The signal charges are converted into voltage signals by an amplifier and read out. The voltage signals are output from the imaging element 56 to the AFE 57 as image signals.

[0049] The AFE (Analog Front End) 57 is composed of a correlated double sampling circuit (CDS), an automatic gain control circuit (AGC), and an analog / digital converter (A / D (Analog / Digital)) (all not shown). The CDS performs correlated double sampling on the analog image signal from the image sensor 56 and removes noise caused by resetting the signal charge. The AGC amplifies the image signal from which noise has been removed by the CDS. The A / D converts the image signal amplified by the AGC into a digital image signal having a gradation value according to a predetermined number of bits and inputs it to the processor device 12.

[0050] The imaging control unit 58 is connected to the controller 65 in the processor device 12, and inputs a drive signal to the imaging element 56 in synchronization with a reference clock signal input from the controller 65. The imaging element 56 outputs an image signal to the AFE 57 at a predetermined frame rate based on the drive signal from the imaging control unit 58.

[0051] The imaging element 56 is a color imaging element, and on the imaging surface 56a, micro color filters of three colors, B, G, and R, having the spectral characteristics as shown in Fig. 13, are assigned to each pixel. The arrangement of the micro color filters is, for example, a Bayer arrangement.

[0052] The B pixel to which the B filter is assigned is sensitive to light in a wavelength band of about 380 nm to 560 nm, and the G pixel to which the G filter is assigned is sensitive to light in a wavelength band of about 450 nm to 630 nm. The R pixel to which the R filter is assigned is sensitive to light in a wavelength band of about 580 nm to 800 nm. The blue light LB, the green fluorescence LGf, and the red light LR constituting the white light LW are received mainly by the B pixel in the reflected light corresponding to the blue light LB, mainly by the G pixel in the reflected light corresponding to the green fluorescence LGf, and mainly by the R pixel in the reflected light corresponding to the red light LR. The reflected light corresponding to the purple light LV for blood vessel enhancement observation is received by the B pixel. The blue excitation light LBe is cut by the third dichroic mirror 81 and is not irradiated to the observation site, but if the blue excitation light LBe is irradiated, the B pixel is sensitive to the reflected light corresponding to the blue excitation light LBe.

[0053] As shown in Figs. 14 and 15, the image sensor 56 performs an accumulation operation for accumulating signal charges in pixels and a readout operation for reading out the accumulated signal charges during an acquisition period of one frame. In Fig. 14, in the normal observation mode, the semiconductor light sources 35 to 37 except the purple semiconductor light source 38 are turned on in accordance with the timing of the accumulation operation of the image sensor 56, and white light LW (LB+LGf+LR) consisting of a mixture of blue light LB, green fluorescent light LGf, and red light LR is irradiated onto the observation site as illumination light, and the reflected light is incident on the image sensor 56. The image sensor 56 separates the reflected light of the white light LW by a micro color filter. The B pixel receives the reflected light corresponding to the blue light LB, the G pixel receives the reflected light corresponding to the green fluorescent light LGf, and the R pixel receives the reflected light corresponding to the red light LR. The image sensor 56 sequentially outputs one frame's worth of image signals B, G, and R, in which the pixel values ​​of the B, G, and R pixels are mixed, according to the frame rate in accordance with the readout timing. This imaging operation is repeated while the normal observation mode is set.

[0054] 15, in the vessel enhancement observation mode, in addition to the semiconductor light sources 35-37, the purple semiconductor light source 38 is turned on in synchronization with the accumulation operation of the image sensor 56. When the semiconductor light sources 35-38 are turned on, purple light LV is added to the white light LW, which is the same as in the normal observation mode, and the mixed light (LW+LV) is irradiated onto the observation area as illumination light.

[0055] As in the normal observation mode, the illumination light, which is white light LW plus violet light LV, is dispersed by the micro color filter of the image sensor 56. The B pixels receive reflected light corresponding to the violet light LV in addition to reflected light corresponding to the blue light LB. As in the normal observation mode, the G pixels and R pixels receive reflected light corresponding to the green fluorescence LGf and red light LR, respectively. Even in the vessel enhancement observation mode, the image sensor 56 sequentially outputs image signals B, G, and R according to the frame rate in accordance with the readout timing. This imaging operation is repeated while the vessel enhancement observation mode is set.

[0056] 3, the processor device 12 includes a controller 65, as well as a DSP (Digital Signal Processor) 66, an image processing unit 67, a frame memory 68, and a display control circuit 69. The controller 65 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a control program and setting data required for control, a RAM (Random Access Memory) that loads a program and functions as a working memory, and the like, and the CPU executes the control program to control each part of the processor device 12.

[0057] The DSP 66 acquires the image signal output by the imaging element 56. The DSP 66 separates the image signal, which is a mixture of signals corresponding to each of the B, G, and R pixels, into B, G, and R image signals, and performs pixel interpolation processing on the image signals of each color. In addition, the DSP 66 performs signal processing such as gamma correction and white balance correction on each of the B, G, and R image signals.

[0058] The DSP 66 also calculates an exposure value based on the image signals B, G, and R, and outputs an exposure control signal to the controller 65 so as to increase the amount of illumination light when the amount of light in the entire image is insufficient (underexposure), and to decrease the amount of illumination light when the amount of light is too high (overexposure). The controller 65 transmits the exposure control signal to the light source control unit 42 of the light source device 13.

[0059] The frame memory 68 stores image data output by the DSP 66 and image data that has been processed by the image processing unit 67. The display control circuit 69 reads out the image data that has been processed from the frame memory 68, converts it into a video signal such as a composite signal or a component signal, and outputs it to the monitor 14.

[0060] 16, in the normal observation mode, the image processing unit 67 generates a normal observation image based on the image signals B, G, and R that have been color-separated into B, G, and R by the DSP 66. This normal observation image is output to the monitor 14. The image processing unit 67 updates the normal observation image every time the image signals B, G, and R in the frame memory 68 are updated.

[0061] 17, in the vessel enhancement observation mode, the image processor 67 generates a vessel enhancement observation image based on the image signals B, G, and R. The image signal B in the vessel enhancement observation mode contains a reflected light component corresponding to the violet light LV in addition to a reflected light component corresponding to the blue light LB constituting the white light LW, so that the superficial blood vessels are depicted with high contrast. Since lesions such as cancer have characteristic vascular patterns, such as a tendency for superficial blood vessels to be more dense than normal tissue, it is preferable that the superficial blood vessels be depicted clearly in vessel enhancement observation aimed at distinguishing benign or malignant tumors.

[0062] In order to further emphasize the superficial blood vessels, for example, the area of ​​the superficial blood vessels in the image may be extracted based on the image signal B, and the extracted area of ​​the superficial blood vessels may be subjected to contour enhancement processing or the like. Then, the image signal B subjected to the contour enhancement processing is synthesized with a full-color image generated based on the image signals B, G, and R. The same processing may be performed on the mid-deep blood vessels in addition to the superficial blood vessels. When emphasizing the mid-deep blood vessels, the area of ​​the mid-deep blood vessels is extracted from the image signal G, which contains a lot of information on the mid-deep blood vessels, contour enhancement processing is performed on the extracted area of ​​the mid-deep blood vessels, and the enhanced image signal G is synthesized with the full-color image generated from the image signals B, G, and R.

[0063] Like the normal observation image, the vascular enhancement observation image is generated based on the image signals B, G, and R, so that the observation site can be displayed in full color. However, the image signal B in the vascular enhancement observation mode has a higher blue density than the image signal B in the normal observation mode. Therefore, when generating a vascular enhancement observation image, color correction such as suppressing the blue density may be performed so that the color is similar to that of the normal observation image. The image processing unit 67 generates a vascular enhancement observation image every time the image signals B, G, and R in the frame memory 68 are updated.

[0064] As a method for generating a vascular enhancement image, a method may be adopted in which the vascular enhancement image is generated using only two colors, image signals B and G, without using the image signal R, and the image signal B is assigned to the B and G channels of the monitor 14, and the image signal G is assigned to the R channel of the monitor 14, thereby displaying the observed area in pseudo-color.

[0065] 18, the optical path combining unit 41 is composed of collimator lenses 75, 76, 77, and 78 that collimate the respective color lights emitted by the respective semiconductor light sources 35 to 38, a first dichroic mirror 79, a second dichroic mirror 80, and a third dichroic mirror 81 (corresponding to the "optical path combining optical member" of the present invention), and a condenser lens 82 that condenses the light emitted from the optical path combining unit 41 onto the incident end 55a of the light guide 55. Each of the dichroic mirrors 79 to 81 is an optical member in which a dichroic filter having a predetermined transmission characteristic is formed on a transparent glass plate.

[0066] The green semiconductor light source 36 is disposed at a position where its optical axis coincides with the optical axis of the light guide 55. The green semiconductor light source 36 and the red semiconductor light source 37 are disposed so that their optical axes are perpendicular to each other. A first dichroic mirror 79 is provided at a position where the optical axes of the green semiconductor light source 36 and the red semiconductor light source 37 are perpendicular to each other. Similarly, the blue semiconductor light source 35 and the violet semiconductor light source 38 are disposed so that their optical axes are perpendicular to each other, and a second dichroic mirror 80 is provided at a position where these optical axes are perpendicular to each other. In addition, a third dichroic mirror 81 is provided at a position where all the optical paths of the blue light LB, the mixed light of the blue excitation light LBe and the green fluorescence LGf, the red light LR, and the violet light LV finally intersect due to the action of the first and second dichroic mirrors 79 and 80. The first dichroic mirror 79 is arranged at an angle of 45° to the optical axes of the green semiconductor light source 36 and the red semiconductor light source 37, the second dichroic mirror 80 is arranged at an angle of 45° to the optical axes of the blue semiconductor light source 35 and the purple semiconductor light source 38, and the third dichroic mirror 81 is arranged at an angle of 45° to the optical axes of the blue semiconductor light source 35 and the green semiconductor light source 36.

[0067] 19, the dichroic filter of the first dichroic mirror 79 has the property of reflecting light in a wavelength band of approximately 610 nm or more and transmitting light in a wavelength band below that. The first dichroic mirror 79 transmits the mixed light of the blue excitation light LBe and the green fluorescence LGf incident from the green semiconductor light source 36 via the collimator lens 76 to the downstream side, and reflects the red light LR incident from the red semiconductor light source 37 via the collimator lens 77. This combines the optical paths of the mixed light of the blue excitation light LBe and the green fluorescence LGf and the red light LR.

[0068] 20, the dichroic filter of the second dichroic mirror 80 has the property of reflecting light in a wavelength band less than about 430 nm and transmitting light in a wavelength band greater than that. The second dichroic mirror 80 transmits blue light LB incident from blue semiconductor light source 35 via collimator lens 75 to the downstream side, and reflects purple light LV incident from purple semiconductor light source 38 via collimator lens 78. This combines the optical paths of the blue light LB and purple light LV.

[0069] The dichroic filter of the third dichroic mirror 81 has a transmission characteristic that removes at least the blue excitation light LBe from the emission spectrum of the mixed light of the blue excitation light LBe and the green fluorescence LGf shown in Fig. 9 emitted by the green semiconductor light source 36. In other words, the dichroic filter of the third dichroic mirror 81 functions as an excitation light cut filter that cuts off the blue excitation light LBe.

[0070] Specifically, as shown in FIG. 21, the dichroic filter of the third dichroic mirror 81 has a characteristic of reflecting light in a wavelength band less than about 490 nm and transmitting light in a wavelength band greater than that. Therefore, the third dichroic mirror 81 reflects the blue excitation light LBe and transmits the green fluorescence LGf out of the mixed light of the blue excitation light LBe and the green fluorescence LGf transmitted through the first dichroic mirror 79. The third dichroic mirror 81 also transmits the red light LR reflected by the first dichroic mirror 79. Furthermore, the third dichroic mirror 81 reflects the blue light LB transmitted through the second dichroic mirror 80 and the violet light LV reflected by the second dichroic mirror 80. The third dichroic mirror 81 integrates all the optical paths of the blue light LB, the green fluorescence LGf, the red light LR, and the violet light LV. Moreover, the blue excitation light LBe does not enter the incident end 55a of the light guide 55, and irradiation of the observation site with the blue excitation light LBe is prevented.

[0071] The operation of the above configuration will be described below. When performing endoscopic diagnosis, the endoscope 11 is connected to the processor device 12 and the light source device 13, and the power of the processor device 12 and the light source device 13 is turned on to start up the endoscope system 10.

[0072] The insertion section 16 of the endoscope 11 is inserted into the digestive tract of the subject, and observation of the inside of the digestive tract begins. In the normal observation mode, the semiconductor light sources 35-37, except for the purple semiconductor light source 38, are turned on. The light source control section 42 sets the drive current value to be given to each of the LEDs 43-45 to a value for the normal observation mode, and starts turning on each of the semiconductor light sources 35-37. Then, light intensity control is performed while maintaining a target emission spectrum.

[0073] The blue and red semiconductor light sources 35 and 37 respectively emit blue light LB and red light LR from the blue and red LEDs 43 and 45. The green semiconductor light source 36 emits a mixed light of blue excitation light LBe from the excitation light LED 44 and green fluorescence LGf from the green phosphor 47 excited by the blue excitation light LBe. Each color light is incident on the collimator lenses 75 to 77 of the optical path integrating unit 41.

[0074] The red light LR is reflected by the first dichroic mirror 79 and passes through the third dichroic mirror 81. The mixed light of the blue excitation light LBe and the green fluorescence LGf passes through the first dichroic mirror 79. Of this mixed light, the blue excitation light LBe is reflected by the third dichroic mirror 81 and the green fluorescence LGf passes through the third dichroic mirror 81. The optical paths of the red light LR, the mixed light of the blue excitation light LBe and the green fluorescence LGf are integrated by the first dichroic mirror 79. The blue excitation light LBe is cut by the third dichroic mirror 81. Since the dichroic filter of the third dichroic mirror 81 functions as an excitation light cut filter, the configuration of the optical system of the optical path integration unit 41 can be simplified.

[0075] The blue light LB passes through the second dichroic mirror 80 and is reflected by the third dichroic mirror 81. The second and third dichroic mirrors 80 and 81 combine the optical paths of the blue light LB, green fluorescence LGf, and red light LR. The blue light LB, green fluorescence LGf, and red light LR are incident on a condenser lens 82. As a result, white light LW composed of the blue light LB, green fluorescence LGf, and red light LR is generated. The condenser lens 82 condenses the white light LW on the incident end 55a of the light guide 55 of the endoscope 11, and supplies the white light LW to the endoscope 11.

[0076] In the endoscope 11, the white light LW is guided to the illumination window 22 through the light guide 55, and is irradiated from the illumination window 22 to the observation site. The white light LW reflected from the observation site is incident on the imaging element 56 through the observation window 23. The imaging element 56 outputs image signals B, G, R to the DSP 66 of the processor device 12. The DSP 66 separates the image signals B, G, R into an image processing unit 67. The imaging operation by the imaging element 56 is repeated at a predetermined frame rate. The image processing unit 67 generates a normal observation image based on the input image signals B, G, R. The normal observation image is output to the monitor 14 through a display control circuit 69. The normal observation image is updated according to the frame rate of the imaging element 56.

[0077] Furthermore, the DSP 66 calculates an exposure value based on the image signals B, G, and R, and transmits an exposure control signal corresponding to the calculated exposure value to the light source control unit 42 of the light source device 13. The light source control unit 42 determines the drive current values ​​of the semiconductor light sources 35-37 so that the ratio of the light amounts of the respective color lights is constant (so that the target emission spectrum does not change) based on the received exposure control signal. Then, the semiconductor light sources 35-37 are driven with the determined drive current values. This makes it possible to keep the light amounts of the blue light LB, green fluorescent light LGf, and red light LR constituting the white light LW from the semiconductor light sources 35-37 constant at a ratio suitable for the normal observation mode.

[0078] When the amount of light of the green fluorescence LGf is changed in the exposure control, the amount of light of the blue excitation light LBe of the excitation light LED 44 is changed. As shown in FIG. 19 and the like, the wavelength band of the blue excitation light LBe partially overlaps with the wavelength band of the blue light LB. Therefore, if the blue excitation light LBe is emitted as the illumination light, the amount of light of the blue light LB also changes with the change in the amount of light of the blue excitation light LBe, and the emission spectrum of the illumination light changes. However, since the blue excitation light LBe is cut by the third dichroic mirror 81, the blue excitation light LBe does not affect the amount of light of the blue light LB, and the amount of light of the blue light LB can be controlled independently of the green fluorescence LGf. Therefore, even if the exposure control is performed, the illumination light with an emission spectrum suitable for the normal observation mode can always be supplied to the endoscope 11, and the color of the normal observation image does not change.

[0079] If an observation site suspected of being a lesion is found in the normal observation mode, the observation mode is switched from the normal observation mode to the blood vessel enhancement observation mode. In the blood vessel enhancement observation mode, in addition to the semiconductor light sources 35-37, the purple semiconductor light source 38 is turned on. The colored lights from the semiconductor light sources 35-37 are converted into white light LW by the action of the optical path integration unit 41 described above, and are supplied to the endoscope 11.

[0080] The purple semiconductor light source 38 emits purple light LV from the purple LED 46. The purple light LV enters the collimator lens 78. The purple light LV is reflected by the second and third dichroic mirrors 80 and 81. The purple light LV is integrated into the same optical path as the white light LW by the second and third dichroic mirrors 80 and 81. The purple light LV and the white light LW enter the condenser lens 82. The condenser lens 82 condenses the purple light LV and the white light LW on the entrance end 55a of the light guide 55 of the endoscope 11, and supplies the purple light LV and the white light LW to the endoscope 11. In this way, the purple light LV and the white light LW are simultaneously irradiated onto the observation site. In this case, the blue excitation light LBe is cut by the third dichroic mirror 81 in the same manner as in the normal observation mode, so that illumination light with an emission spectrum suitable for the vessel enhancement observation mode can always be supplied to the endoscope 11.

[0081] The imaging element 56 receives the white light LW and the violet light LV reflected from the observation region, and outputs B, G, and R image signals to the DSP 66. The DSP 66 separates the B, G, and R image signals and inputs them to the image processing unit 67. The image processing unit 67 generates a vascular enhancement image based on the B, G, and R image signals. The vascular enhancement image is output to the monitor 14. The vascular enhancement image is updated according to the frame rate of the imaging element 56.

[0082] Since illumination light with an emission spectrum suitable for the vascular enhancement mode is always irradiated, the reliability of the vascular enhancement image is improved. Since the vascular enhancement image is used for distinguishing benign or malignant tumors, the reliability of the vascular enhancement image is improved, so that the results of the tumor discrimination can also be made more reliable.

[0083] Since the blue excitation light LBe, which affects the amount of blue light LB and violet light LV, is cut by the third dichroic mirror 81, it is possible to stably obtain illumination light having the target emission spectrum without performing complex control such as increasing or decreasing the amount of blue light LB and violet light LV by taking into account the change in the blue excitation light LBe that accompanies the change in the amount of green fluorescence LGf.

[0084] [Second embodiment] In the above first embodiment, the dichroic filter of the third dichroic mirror 81, which integrates the optical paths of the mixed light of the blue excitation light LBe and the green fluorescence LGf emitted by the green semiconductor light source 36 and the blue light LB emitted by the blue semiconductor light source 35, functions as an excitation light cut filter, but the dichroic filter of a dichroic mirror other than the third dichroic mirror 81 may be made to function as an excitation light cut filter.

[0085] For example, as in the optical path integrating section 90 shown in Fig. 22, the function of the excitation light cut filter may be assigned to a dichroic filter of a first dichroic mirror 91 (corresponding to the first dichroic mirror 79 in the first embodiment described above; corresponding to the "optical member for optical path integration" of the present invention) that integrates the optical paths of the mixed light of the blue excitation light LBe and the green fluorescence LGf emitted by the green semiconductor light source 36 and the red light LR emitted by the red semiconductor light source 37. The optical path integrating section 91 in Fig. 22 is the same as the optical path integrating section 41 in the first embodiment described above, except that the first dichroic mirror 91 replaces the first dichroic mirror 79 in the first embodiment described above.

[0086] In this case, the dichroic filter of the first dichroic mirror 91 is given a characteristic of reflecting light in a wavelength band of about 610 nm or more and light in a wavelength band of less than about 490 nm, and transmitting light in other wavelength bands, as shown in Fig. 23. In other words, a bandpass characteristic is obtained by combining the transmission characteristics of the first dichroic mirror 79 and the third dichroic mirror 81 of the first embodiment. However, when such a bandpass characteristic is given, the manufacturing cost is higher than that of a shortpass characteristic that reflects light on the long wavelength side and transmits light on the short wavelength side, or a longpass characteristic that does the reverse. Therefore, it is more cost-effective to make the dichroic filter of the third dichroic mirror 81, which has a longpass characteristic, function as an excitation light cut filter, as in the first embodiment.

[0087] [Third embodiment] In each of the above embodiments, an example in which the dichroic mirror also serves as an excitation light cut filter has been described, but an excitation light cut filter may be provided separately from the dichroic mirror, as in the light path integration unit 95 of the third embodiment shown in FIG. 24. In the light path integration unit 95, an excitation light cut filter 96 is disposed between the green semiconductor light source 36 and the first dichroic mirror 79. As shown in FIG. 25, for example, the excitation light cut filter 96 has a characteristic of reflecting light in the violet and blue wavelength bands less than about 450 nm and transmitting light in the other green and red wavelength bands. Although not shown, the excitation light cut filter 96 may be provided between the first dichroic mirror 79 and the third dichroic mirror 81. In short, it is sufficient to prevent the blue excitation light LBe from entering the incident end 55a of the light guide 55, and the excitation light cut filter may be provided on the optical path between the excitation light LED 44 and the light guide 55, more specifically, at a position where the optical paths of the mixed light of the blue excitation light LBe and green fluorescence LGf emitted by the green semiconductor light source 36 and the blue light LB emitted by the blue semiconductor light source 35 are integrated, or on the optical path upstream of that position.

[0088] [Fourth embodiment] In the first embodiment, the light intensity of each color light is controlled by changing the drive current value given to each LED 43-46 based on the exposure control signal from the processor device 12, but the semiconductor light source may fluctuate in the output light intensity relative to the drive current value due to the effects of heat generation and aging of the LEDs and phosphors. Therefore, a light intensity measuring sensor may be provided to measure the light intensity of each color light, and based on the light intensity measuring signal output by the light intensity measuring sensor, it may be monitored whether the light intensity of each color light has reached a target value.

[0089] 26, the light path combining unit 100 includes, in addition to the configuration of the light path combining unit 41 shown in FIG. 18 of the first embodiment, blue, green, red and purple light amount measuring sensors 101, 102, 103 and 104 for measuring the amount of light of each color emitted by each semiconductor light source 35-38, and glass plates 105, 106, 107 and 108 that are provided immediately before each semiconductor light source 35-38 and reflect a portion of each color light emitted by each semiconductor light source 35-38 and guide the light to each light amount measuring sensor 101-104.

[0090] Each of the glass plates 105-108 is disposed at an angle of, for example, 35° with respect to the optical axis of each of the semiconductor light sources 35-38. Each of the glass plates 105-108 transmits the corresponding color light emitted by each of the semiconductor light sources 35-38. When each color light is incident on each of the glass plates 105-108, Fresnel reflection occurs. Each of the glass plates 105-108 is a light-guiding member that utilizes this Fresnel reflection to guide a portion (approximately 4% to 8%) of each color light emitted by each of the semiconductor light sources 35-38 to each of the light quantity measuring sensors 101-104. Note that other light-guiding members such as optical fibers may be used instead of the glass plates.

[0091] Filters 109 and 110 are provided in front of the green light amount measuring sensor 102 and the red light amount measuring sensor 103, respectively. The filter 109 is for limiting the light incident on the green light amount measuring sensor 102 to only light in the wavelength band of the green fluorescence LGf constituting a part of the white light LW finally supplied to the endoscope 11, and has a characteristic of reflecting light in the red wavelength band of about 610 nm or more and light in the purple and blue wavelength bands of less than about 490 nm, and transmitting light in the other green wavelength bands, as shown in FIG. 27. That is, the filter 109 has a bandpass characteristic combining the transmission characteristics of the first dichroic mirror 79 and the third dichroic mirror 81 of the first embodiment, as with the first dichroic mirror 91 of the second embodiment. The filter 109 allows only the green fluorescence LGf, which is finally emitted as a part of the white light LW and from which the blue excitation light LBe has been cut, to be incident on the green light amount measuring sensor 102. The pure light amount of the green fluorescence LGf can be measured.

[0092] The filter 110 is for limiting the light incident on the red light quantity measuring sensor 103 to only light in the wavelength band of the red light LR constituting a part of the white light LW finally supplied to the endoscope 11, and has a characteristic of reflecting light in the green and blue wavelength bands less than about 610 nm and transmitting light in the red wavelength band above that, as shown in Fig. 28. That is, the filter 110 has a transmission characteristic that is the inverse of the transmission characteristic of the first dichroic mirror 79 of the first embodiment shown in Fig. 19. The filter 110 allows only the red light LR that is finally emitted as a part of the white light LW to be incident on the red light quantity measuring sensor 103. The pure light quantity of the red light LR can be measured.

[0093] In FIG. 29, the light quantity measuring sensors 101-104 receive the respective color lights guided by the Fresnel reflection of the glass plates 105-108, output a light quantity measuring signal according to the light quantity of each received color light, and output this to the light source control unit 42. The light source control unit 42 compares the light quantity measuring signal with a target light quantity, and based on the comparison result, finely adjusts the drive current value to be given to each semiconductor light source 35-38 set by exposure control so that the light quantity becomes the target value. In this way, the light quantity of each color light is constantly monitored by the light quantity measuring sensors 101-104, and the drive current value to be given is finely adjusted based on the measurement result of the light quantity, so that the light quantity can be controlled to always follow the target value. Therefore, illumination light with a target emission spectrum can be obtained more stably.

[0094] 30, an excitation light cut filter 116 having the same transmission characteristics as the filter 109 may be provided between the green semiconductor light source 36 and the first dichroic mirror 79 (the same position as the excitation light cut filter 96 shown in FIG. 24 of the third embodiment). This eliminates the need for the filter 109. However, since the size of the excitation light cut filter 116 is larger than that of the filter 109, from the standpoints of cost and space saving, it is preferable to provide the filter 109 rather than the excitation light cut filter 116.

[0095] In the above fourth embodiment, light quantity measuring sensors are provided for all semiconductor light sources to monitor their light quantities, but it is also possible to monitor the light quantities of at least the blue, green, and red semiconductor light sources that emit light constituting the white light LW and the fluorescent semiconductor light sources, and not provide light quantity measuring sensors for the other semiconductor light sources. Also, among the blue, green, and red semiconductor light sources, it is also possible to selectively monitor only the light quantities of semiconductor light sources (fluorescent semiconductor light sources) that have particularly large fluctuations in the output light quantity relative to the drive current value.

[0096] The fluorescent semiconductor light source is not limited to the green semiconductor light source 36 in each of the above embodiments. Instead of or in addition to the green semiconductor light source, the red semiconductor light source may be configured with a blue excitation light emitting element that emits blue excitation light in a wavelength band from violet to blue, and a red phosphor that is excited by the blue excitation light and emits red fluorescence in a red wavelength band. In this case, as in each of the above embodiments, the excitation light cut filter may be provided at a position where the optical paths of the mixed light of the blue excitation light and red fluorescence emitted by the red semiconductor light source and the blue light emitted by the blue semiconductor light source are integrated, or on the optical path upstream of that position. For example, as in the first embodiment, the dichroic filter of the third dichroic mirror 81 may function as an excitation light cut filter, or an excitation light cut filter may be provided between the first dichroic mirror 79 and the third dichroic mirror 81, or an excitation light cut filter may be provided between the red semiconductor light source and the first dichroic mirror 79.

[0097] When the red semiconductor light source is configured with a fluorescent semiconductor light source, the excitation light emitting element is not limited to a blue excitation light emitting element that emits blue excitation light in a wavelength band from violet to blue, but may be a green excitation light emitting element that emits green excitation light in a green wavelength band. In this case, an excitation light cut filter having a transmission characteristic of cutting off the green excitation light and transmitting the red fluorescence is disposed between the red semiconductor light source and the first dichroic mirror 79 in the optical path integration unit 41 in FIG. 18, for example.

[0098] [Fifth embodiment] 31, a white semiconductor light source 121 may be used as the fluorescent semiconductor light source. The light source unit 120 is obtained by removing the green semiconductor light source 36 and the red semiconductor light source 37 from the light source unit 40 of the above-mentioned first embodiment and providing a white semiconductor light source 121 instead. The optical path integrating unit 122 is obtained by removing the collimator lens 77 and the first dichroic mirror 79 associated with the green semiconductor light source 36 and the red semiconductor light source 37 from the optical path integrating unit 41 of the above-mentioned first embodiment.

[0099] The white semiconductor light source 121 is composed of a blue excitation light emitting element that emits blue excitation light LBe in a blue wavelength band, and green and red phosphors that are excited by the blue excitation light LBe and emit green fluorescence LGf and red fluorescence LRf in green and red wavelength bands. In this case, the white light LW is composed of the blue light LB emitted by the blue semiconductor light source 35 and a mixed light of the green fluorescence LGf and red fluorescence LRf emitted by the white semiconductor light source 121. In this embodiment, the wavelength band of the blue excitation light LBe emitted by the white semiconductor light source 121 overlaps with the wavelength band of the blue light LB emitted by the blue semiconductor light source 35. For this reason, as in the case of the above-mentioned embodiments having the three-color semiconductor light sources 35 to 37, the embodiment having the blue semiconductor light source 35 and the white semiconductor light source 121 of this embodiment also has a problem that the amount of light whose wavelength band overlaps with the excitation light is affected by the excitation light emitted by the fluorescent semiconductor light source, and the emission spectrum of the illumination light changes.

[0100] A dichroic mirror 123 is disposed at a position where the light emitted from each semiconductor light source 35, 38, 121 finally intersects. The dichroic mirror 123 corresponds to the third dichroic mirror 81 of the first embodiment. The dichroic filter of the dichroic mirror 123 has the property of reflecting the violet light LV, the blue excitation light LBe, and the blue light LB, and transmitting the green fluorescence LGf and the red fluorescence LRf, and functions as an excitation light cut filter that cuts the blue excitation light LBe. The dichroic mirror 123 integrates all the optical paths of the respective color lights, and prevents the transmission of the blue excitation light LBe.

[0101] In this embodiment, similarly to the third embodiment, an excitation light cut filter may be provided separately from the dichroic mirror 123. Also, as in the fourth embodiment, for example, a light quantity measuring sensor may be provided in the white semiconductor light source 121 to monitor the light quantity.

[0102] The mounting form of the LED in the first embodiment is one example, and other forms may be adopted. For example, a microlens for adjusting the divergence angle may be provided on the light exit surface of the sealing resin 35c or the green phosphor 47 in FIG. 4 and FIG. 5, or the LED may be accommodated in a bullet-shaped case on which a microlens is formed instead of a surface mount type. In addition, the green semiconductor light source 36 is described as an example in which the green phosphor 47 is integrally provided on the substrate 36a in addition to the excitation light LED 44, but the green phosphor 47 and the substrate 36a may be provided separately. In this case, a light guide member such as a lens or an optical fiber is added between the excitation light LED 44 and the green phosphor 47, and the excitation light of the excitation light LED 44 is guided to the green phosphor 47 through the light guide member.

[0103] [Sixth embodiment] Furthermore, although an example in which an LED is used as the light emitting element has been described, a laser diode (LD) may be used instead of the LED. For example, as shown in Fig. 32, a green semiconductor light source 130 including an excitation light emitting element, an excitation light LD 131 that emits blue excitation light, and a green phosphor 132 disposed in front of the excitation light LD 131, may be used instead of the green semiconductor light source 36 of the first to fourth embodiments.

[0104] In this case, the green phosphor 132 is formed on the surface of a disc-shaped transparent rotating plate 133 by a method such as coating. Then, while rotating the rotating plate 133 by a rotating mechanism 134 such as a motor, blue excitation light from the excitation light LD 131 is irradiated onto an eccentric position of the rotating plate 133. By rotating the rotating plate 133, the irradiation position of the excitation light is not concentrated on one point of the green phosphor 132. If the irradiation position of the excitation light is concentrated on one point, the point becomes hot, which accelerates the deterioration of the green phosphor 132, but this can be prevented. Reference numeral 135 denotes a condensing lens that condenses the blue excitation light emitted by the excitation light LD 131 onto the rotating plate 133.

[0105] An excitation light cut filter may be integrally formed on the emission side surface of the rotating plate 133. As the light emitting element, an organic EL (Electro-Luminescence) element may be used in addition to an LED or an LD. The light emitting element is not limited to a fluorescent semiconductor light source, and an LD or an organic EL element may be used as the light emitting element of other semiconductor light sources (such as the blue semiconductor light source 35 and the violet semiconductor light source 38).

[0106] The white semiconductor light source 140 shown in Fig. 33 is a white version of the green semiconductor light source 130 in Fig. 32. Like the green semiconductor light source 130, the white semiconductor light source 140 is composed of an excitation light LD 141 that emits blue excitation light, and green and red phosphors 142 arranged in front of the excitation light LD 141. This white semiconductor light source 140 may be used as the white semiconductor light source 121 of the fifth embodiment. Note that other configurations such as the rotating plate are the same as those of the green semiconductor light source 130 in Fig. 32, so the same reference numerals as those in Fig. 32 are used and description thereof will be omitted.

[0107] In each of the above embodiments, an excitation light cut filter that cuts 100% of the excitation light has been exemplified, but the present invention is not limited to this. The excitation light cut filter may be any filter that can reduce the amount of excitation light even slightly, and for example, a filter having a transmission characteristic that cuts 50% of the excitation light is also included in the present invention. However, the closer to 100%, the more effective the filter is, and therefore the more preferable it is.

[0108] The configuration of the light path integration unit in each of the above embodiments is one example, and various modifications are possible. For example, a dichroic mirror is used as an optical member on which a dichroic filter is formed, but a dichroic prism in which a dichroic filter is formed on a prism may be used instead. Also, instead of an optical member on which a dichroic filter is formed, such as a dichroic mirror or a dichroic prism, for example, a branched light guide having a plurality of input ends facing each semiconductor light source and one output end facing the input end of the light guide of the endoscope may be used to integrate the light paths. The branched light guide is a fiber bundle in which optical fibers are bundled, and the optical fibers are divided into a plurality of optical fibers at one end, and the input end is branched into a plurality of optical fibers. In this case, each semiconductor light source is arranged corresponding to each of the branched input ends. Then, an excitation light cut filter is arranged between the fluorescent semiconductor light source and the input end of the branched light guide.

[0109] In each of the above embodiments, the violet semiconductor light source 38 emitting violet light LV is exemplified as the semiconductor light source for acquiring blood vessel information for acquiring blood vessel information of living tissue, but other semiconductor light sources for acquiring blood vessel information may be provided separately from or in addition to the violet semiconductor light source 38. For example, a semiconductor light source emitting narrowband blue light with a central wavelength of 473±10 nm may be provided to acquire the oxygen saturation of blood hemoglobin as blood vessel information. Of course, when blood vessel information observation is not performed, only blue, green, and red semiconductor light sources may be provided without providing a semiconductor light source for acquiring blood vessel information.

[0110] In the first embodiment, the observation site is irradiated with only white light in the normal observation mode and with white light LW and violet light LV simultaneously in the vessel enhancement observation mode, and white light is used in both modes, but a mode that does not use white light may be provided. For example, the green semiconductor light source 36 and the violet semiconductor light source 38, or the green semiconductor light source 36 and the blue semiconductor light source 35 may be turned on to obtain a vessel enhancement observation image based on green fluorescence LGf.

[0111] In each of the above embodiments, a simultaneous type endoscope system and a light source device used therein have been described as examples in which the image sensor 56 has a color image sensor that separates white light using B, G, and R micro color filters, and the color image sensor simultaneously acquires B, G, and R image signals. However, the present invention may also be applied to a field sequential type endoscope system and a light source device used therein that has a monochrome image sensor and sequentially irradiates blue, green, and red light to acquire B, G, and R image signals in field sequential order.

[0112] Needless to say, the above-described embodiments can be implemented either alone or in combination.

[0113] In the above embodiments, the light source device and the processor device are configured as separate devices, but the two devices may be configured as one. The present invention can also be applied to a fiberscope that guides the reflected light of the illumination light from the observation site with an image guide, an ultrasonic endoscope with an imaging element and an ultrasonic transducer built into the tip, and an endoscope system and a light source device used therein. [Explanation of symbols]

[0114] 10 Endoscope System 11 Endoscopy 13 Light source device 35 Blue semiconductor light source 36, 130 Green semiconductor light source 37 Red semiconductor light source 38 Purple semiconductor light source 40, 120 Light source section 41, 90, 95, 100, 115, 122 Optical path integration section 42 Light source control unit 43 Blue LED 44 Excitation light LED 45 Red LED 46 Purple LED 47, 132 Green phosphor 55 Light Guide 56 Image sensor 79~81 1st~3rd dichroic mirrors 91 1st dichroic mirror 96, 116 Excitation light cut filter 101~104 Light quantity measuring sensor 105~108 Glass plate 109 Filters 121, 140 White semiconductor light source 123 Dichroic Mirror 131, 141 Excitation light LD 133, 143 Rotating plate 142 Green and Red Phosphors

Claims

1. An endoscope system including an endoscope and an endoscope light source device that supplies illumination light to a light guide of the endoscope, A purple LED light source that emits purple light; A blue LED light source that emits blue light; a green LED light source including an excitation light LED that emits blue excitation light having a wavelength band that at least partially overlaps with the wavelength band of the blue light, a substrate on which the excitation light LED is mounted, a sealing resin, and a green phosphor that is excited by the blue excitation light and emits green fluorescence in a green wavelength band, the green phosphor being diffused in the sealing resin; A red LED light source that emits red light; a first dichroic mirror that combines an optical path through which the purple light emitted from the purple LED light source passes and an optical path through which the blue light emitted from the blue LED light source passes; a second dichroic mirror that combines an optical path of the light combined by the first dichroic mirror and an optical path of the green fluorescent light emitted from the green LED light source, and does not combine an optical path of the blue excitation light; a condenser lens that condenses the light combined by the second dichroic mirror onto an input end of a light guide; a purple light amount measuring sensor provided between the purple LED light source and the first dichroic mirror and configured to receive a portion of the purple light emitted by the purple LED light source; a blue light amount measuring sensor provided between the blue LED light source and the first dichroic mirror and configured to receive a portion of the blue light emitted by the blue LED light source; a green light amount measuring sensor provided between the green LED light source and the second dichroic mirror and configured to receive a portion of the green fluorescence emitted by the green LED light source; a red light amount measuring sensor provided between the red LED light source and the second dichroic mirror and configured to receive a portion of the red light emitted by the red LED light source; an image sensor mounted in an insertion portion of the endoscope, receiving reflected light from an observation site irradiated with the illumination light and outputting an image signal; A light source control unit, The light source control unit is In a case where a driving current pulse to be applied to the purple LED light source, the blue LED light source, the excitation light LED, or the red LED light source is determined based on an exposure control signal corresponding to an exposure value calculated from the image signal, an endoscope system that, when set to a normal observation mode in which white light is irradiated, adjusts the drive current pulse to be provided to the blue LED light source based on the amount of light received by the blue light quantity measuring sensor, adjusts the drive current pulse to be provided to the excitation light LED based on the amount of light received by the green light quantity measuring sensor, and adjusts the drive current pulse to be provided to the red LED light source based on the amount of light received by the red light quantity measuring sensor.

2. The endoscope system according to claim 1 , wherein the central wavelength of the blue excitation light is between the central wavelength of the violet light and the central wavelength of the blue light.

3. 3. The endoscope system according to claim 1, wherein when a vascular enhancement observation mode in which the purple LED light source and the green LED light source are turned on is set, the light source control unit adjusts the drive current pulse to be provided to the purple LED light source based on the amount of light received by the purple light quantity measuring sensor, and adjusts the drive current pulse to be provided to the excitation light LED based on the amount of light received by the green light quantity measuring sensor.

4. The endoscope system according to claim 3 , wherein the proportion of the amount of blue light is reduced in the vessel enhancement imaging mode compared to the normal imaging mode.

5. the imaging element is a monochrome imaging element, 5. The endoscope system according to claim 1, wherein the light source control unit sequentially turns on the blue LED light source, the excitation light LED, or the red LED light source on a frame-by-frame basis to sequentially irradiate the blue light, the green fluorescent light, or the red light.

6. a collimator lens for purple light provided between the purple LED light source and the first dichroic mirror; a blue light collimator lens provided between the blue LED light source and the first dichroic mirror; a collimator lens for green fluorescence provided between the green LED light source and the first dichroic mirror; 6. The endoscope system according to claim 1, further comprising a collimator lens for red light provided between the red LED light source and the first dichroic mirror.

7. 7. The endoscope system according to claim 1, further comprising a third dichroic mirror that combines an optical path through which the green fluorescent light passes and an optical path through which the red light passes.

8. An endoscope system according to any one of claims 1 to 7, wherein the image signal B of the image signals is assigned to the B channel and G channel of a monitor, and the image signal G is assigned to the R channel of the monitor, thereby displaying the observed area in pseudo-color on the monitor.

9. The endoscope system according to claim 5 , wherein the imaging element sequentially outputs an image signal B, an image signal G, or an image signal R.

Images