Endoscope light source device

Abstract

The present invention provides an endoscope light source device that can stably obtain illumination light with a target emission spectrum with simple control, even when using a fluorescent semiconductor light source. [Solution] The green semiconductor light source 36 is provided integrally with a substrate 36a on which an excitation light LED 46 that emits blue excitation light LBe having a wavelength band that overlaps with at least a portion of the wavelength band of blue light LB is mounted, and a phosphor 47 that is excited by the blue excitation light LBe and emits green fluorescence LGf having a green wavelength band, and emits green fluorescence LGf emitted from the phosphor 47 and blue excitation light LBe. The third dichroic mirror 81 integrates the optical path through which the light integrated by the second dichroic mirror 80 passes and the optical path through which the green fluorescence passes, but does not integrate the optical path of the blue excitation light.

Description

Technical Field

[0001] The present invention relates to an endoscope light source device.

Background Art

[0002] In the medical field, endoscopic diagnosis using an endoscope system has become widespread. An 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 an image signal output from the endoscope. The endoscope has an insertion portion that is inserted into a living body, and at the tip of the insertion portion, an illumination window for irradiating illumination light to an observation site (subject) and an observation window for photographing the observation site are arranged. The endoscope incorporates a light guide composed 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 from the imaging element. By displaying the display image on a monitor, observation of the living body is performed.

[0003] Conventionally, a xenon lamp or a halogen lamp that emits white light has been used as a light source for the light source device. Recently, instead of these, a semiconductor light source having a light emitting element such as a laser diode (LD) or a light emitting diode (LED) has been proposed (see Patent Documents 1 and 2).

[0004] Patent Document 1 describes a light source device that uses a three-color semiconductor light source of blue, green, and red, each composed of three LEDs that emit light of each color of blue (B), green (G), and red (R), and synthesizes the three-color light emitted from the three LEDs to generate white light.

[0005] Xenon and halogen lamps have a constant 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 light intensity of each color, and the ratio of light intensity of each color can be freely changed. Therefore, it is possible to easily generate multiple types of illumination light with diverse emission spectra.

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

[0040] of Patent Document 2 describes a fluorescent green semiconductor light source composed of a blue excitation light LED that emits excitation light in the purple to blue wavelength range and a green phosphor that emits green fluorescence in the green wavelength range when this blue excitation light is used.

[0007] Currently, LEDs that emit light in the purple to blue wavelength range tend to have higher luminous efficiency and lower prices compared to LEDs that emit green light. Therefore, as a green semiconductor light source for a light source device, a fluorescent green semiconductor light source, such as the one described in Patent Document 2, is sometimes used instead of a semiconductor light source that has LEDs that emit green light. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2007-068699 [Patent Document 2] Japanese Patent Publication No. 2009-297290 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, if, for example, the fluorescent green semiconductor light source described in Patent Document 2 is used as the green semiconductor light source for the light source device in Patent Document 1, a problem arises in that it is not possible to stably obtain illumination light with the target emission spectrum. This is because, in a fluorescent green semiconductor light source, most of the blue excitation light is absorbed by the phosphor, but some is not absorbed by the phosphor and passes through the phosphor, irradiating the observation site along with the fluorescence. Therefore, 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 will affect the amount of blue light.

[0010] In endoscopic diagnosis, depending on the purpose of observation, the light intensity of blue, green, and red light may be set to a specific ratio to generate illumination light with a target emission spectrum. On the other hand, exposure control is performed to increase the light intensity of the illumination light when the overall light intensity of the displayed image is insufficient (underexposure), and to decrease the light intensity of the illumination light when the light intensity is too high (overexposure).

[0011] In exposure control when generating illumination light with a target emission spectrum by defining the ratio of light intensity for each color, if the exposure control is performed based on an image signal derived from the amount of light received by the image sensor, the exposure control must be performed according to the amount of illumination light, excluding the amount of excitation light received by the image sensor, and the overall light intensity must be increased or decreased without changing the emission spectrum of the illumination light. However, when using a fluorescent semiconductor light source, when the output of the fluorescent semiconductor light source is increased to change the amount of fluorescence, the amount of light that overlaps in wavelength band with the excitation light is affected by the excitation light as described above, so the emission spectrum of the illumination light changes. For this reason, when using a fluorescent semiconductor light source, it is not possible to stably obtain illumination light with a target emission spectrum. As a solution to this problem, it is conceivable to increase or decrease the amount of light that overlaps in wavelength band with the excitation light, taking into account the change in excitation light due to the change in fluorescence light intensity, but this is difficult to adopt because the control becomes complex.

[0012] Patent documents 1 and 2 do not describe the problem of not being able to stably obtain illumination light with the target emission spectrum when using a fluorescent semiconductor light source, and naturally, they do not describe any solution to this problem.

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

[0014] The present invention relates to an endoscope light source device for supplying illumination light to the light guide of an endoscope, comprising: a purple LED light source that emits purple light; a blue LED light source that emits blue light; a substrate on which an excitation light-emitting element that emits blue excitation light having a wavelength band in which at least a portion of the wavelength band of the blue light overlaps is mounted; and a phosphor that is excited by the blue excitation light and emits green fluorescence having a green wavelength band, integrally provided thereon, the green fluorescence emitted from the phosphor, a fluorescent LED light source that emits blue excitation light, a first dichroic mirror that integrates the optical path through which the purple light emitted from the purple LED light source passes and the optical path through which the blue light emitted from the blue LED light source passes, and a second dichroic mirror that integrates the optical path through which the light integrated by the first dichroic mirror passes and the optical path through which the green fluorescence emitted from the fluorescent LED light source passes, and does not integrate the optical path of the blue excitation light.

[0015] The present invention relates to an endoscope light source device for supplying illumination light to the light guide of an endoscope, comprising: a purple LED light source that emits purple light; a blue LED light source that emits blue light; an excitation light-emitting element that emits blue excitation light having a wavelength band in which at least a portion of the wavelength band of the blue light overlaps, packaged in a surface mount type; a phosphor that emits green fluorescence having a green wavelength band when excited by the blue excitation light; a fluorescent LED light source that emits blue excitation light; a first dichroic mirror that integrates the optical path through which the purple light emitted by the purple LED light source passes and the optical path through which the blue light emitted by the blue LED light source passes; and a second dichroic mirror that integrates the optical path through which the light integrated by the first dichroic mirror passes and the optical path through which the green fluorescence emitted from the fluorescent LED light source passes, but does not integrate the optical path of the blue excitation light.

[0016] The excitation photoluminescent element is preferably packaged on the substrate in a surface-mount type. The fluorescent LED light source is preferably provided integrally with a substrate on which the excitation photoluminescent element is mounted and a phosphor that emits green fluorescence having a green wavelength band when excited by blue excitation light.

[0017] The fluorescent LED light source is preferably a white LED light source. The endoscope light source device comprises a light source control unit that controls the power supply to each of the purple LED, blue LED, and white LED, and it is preferable that the light source control unit turns on all purple LED, blue LED, and white LED light sources when the vascular enhancement observation mode, which emphasizes blood vessels on the mucosal surface of biological tissue, is set, and turns off the purple LED and turns on the blue LED and white LED light sources when the normal observation mode, which irradiates with white light, is set.

[0018] In normal observation mode, it is preferable to generate a normal observation image based on image signals B, G, and R separated into their respective colors, and in vascular enhancement observation mode, it is preferable to generate a vascular enhancement observation image based on image signals B, G, and R separated into their respective colors.

[0019] In the blood vessel enhancement observation mode, the light source control unit preferably reduces the ratio of the light quantity of blue light in the illumination light compared to the normal observation mode. The excitation light emitting element is preferably a light emitting diode. The second dichroic mirror preferably does not integrate at least 50% or more of the optical path of the blue excitation light.

[0020] It is preferable to provide a white light quantity measurement sensor for measuring a part of the light quantity of the white light emitted by the white LED light source, and the light source control unit adjusts the supply power to the excitation light emitting element based on the measurement result of the white light quantity measurement sensor.

[0021] It is further preferable to provide a purple light quantity measurement sensor for measuring a part of the light quantity of the purple light emitted by the purple LED light source, and the light source control unit adjusts the supply power to the purple LED light source based on the measurement result of the purple light quantity measurement sensor.

[0022] It is further preferable to provide a blue light quantity measurement sensor for measuring a part of the light quantity of the blue light emitted by the blue LED light source, and the light source control unit adjusts the supply power to the blue LED light source based on the measurement result of the blue light quantity measurement sensor.

[0023] The endoscope light source device includes a light source control unit that controls the supply power to each of the purple LED light source, the blue LED light source, and the fluorescent LED light source. When the blood vessel enhancement observation mode for enhancing the blood vessels on the mucosal surface layer of the biological tissue is set, the light source control unit performs at least one of the controls of lighting all of the purple LED light source, the blue LED light source, and the fluorescent LED light source, or the control of lighting the purple LED light source and the fluorescent LED light source. When the normal observation mode for irradiating white light is set, it is preferable to perform the control of turning off the purple LED light source and lighting the blue LED light source and the fluorescent LED light source.

[0024] It is further preferable to include a condenser lens that condenses the light integrated by the second dichroic mirror at the incident end of the light guide. The blue excitation light preferably does not include the wavelength band of ultraviolet light.

Advantages of the Invention

[0025] According to the present invention, even when a fluorescent semiconductor light source is used, illumination light having a target emission spectrum can be stably obtained with simple control.

Brief Description of Drawings

[0026] [Figure 1] It is an external view of the endoscope system of the present invention. [Figure 2] It is a front view of the tip of the endoscope. [Figure 3] It is a block diagram showing the electrical configuration of the endoscope system. [Figure 4] It is a diagram showing a blue semiconductor light source. [Figure 5] It is a diagram showing a green semiconductor light source. [Figure 6] It is a graph showing the emission spectrum of blue light emitted by a blue semiconductor light source. [Figure 7] It is a graph showing the emission spectrum of red light emitted by a red semiconductor light source. [Figure 8] It is a graph showing the emission spectrum of purple light emitted by a purple semiconductor light source. [Figure 9] It is a graph showing the emission spectra of blue excitation light and green fluorescence emitted by a green semiconductor light source. [Figure 10] It is a graph showing the absorption spectrum of hemoglobin. [Figure 11] It is a graph showing the scattering coefficient of biological tissue. [Figure 12] It is a graph showing the emission spectrum of white light composed of blue light, green fluorescence, and red light. [Figure 13] It is a graph showing the spectral characteristics of the micro color filter of the imaging device. [Figure 14] It is an explanatory diagram showing the irradiation timing of illumination light and the operation timing of the imaging device in the normal observation mode. [Figure 15] It is an explanatory diagram showing the irradiation timing of illumination light and the operation timing of the imaging device in the blood vessel enhancement observation mode. [Figure 16] This is an explanatory diagram showing the image processing procedure in normal observation mode. [Figure 17] This is an explanatory diagram showing the image processing procedure in the blood vessel enhancement observation mode. [Figure 18] This diagram shows the arrangement of each semiconductor light source and the detailed configuration of the optical path integration unit. [Figure 19] This graph shows the transmission characteristics of the dichroic filter of the first dichroic mirror. [Figure 20] This graph shows the transmission characteristics of the dichroic filter of the second dichroic mirror. [Figure 21] This graph shows the transmission characteristics of the dichroic filter of the third dichroic mirror. [Figure 22] This figure shows an optical path integration section equipped with a first dichroic mirror on which a dichroic filter having the function of an excitation light cut filter of the second embodiment is formed. [Figure 23] This graph shows the transmission characteristics of the dichroic filter of the first dichroic mirror. [Figure 24] This figure shows an optical path integration unit equipped with an excitation light cut filter according to the third embodiment. [Figure 25] This graph shows the transmission characteristics of the excitation light cut-off filter. [Figure 26] This diagram shows an optical path integration unit equipped with a light intensity measuring sensor according to the fourth embodiment. [Figure 27] This graph shows the transmission characteristics of a filter placed in front of a green light intensity measuring sensor. [Figure 28] This graph shows the transmission characteristics of a filter placed in front of a red light intensity measuring sensor. [Figure 29] This is a diagram illustrating the configuration for controlling light intensity using a light intensity measurement sensor. [Figure 30] This diagram shows an optical path integration unit equipped with an excitation light cut filter and a light intensity measurement sensor. [Figure 31] This figure shows a light source unit equipped with a white semiconductor light source according to the fifth embodiment. [Figure 32]This figure shows another example of a green semiconductor light source according to the sixth embodiment. [Figure 33] This figure shows another example of a white semiconductor light source according to the sixth embodiment. [Modes for carrying out the invention]

[0027] [First Embodiment] In Figure 1, the endoscope system 10 includes an endoscope 11 for imaging an observation site within the body, a processor device 12 for generating a display image of the observation site based on the image signal obtained from imaging, a light source device 13 for supplying illumination light to the endoscope 11 to irradiate the observation site, and a monitor 14 for displaying the display image. An operation input unit 15, such as a keyboard or mouse, is connected to the processor device 12.

[0028] The endoscope system 10 is equipped with a normal observation mode for observing the observation site and a vascular enhancement observation mode for highlighting and observing blood vessels present within the mucosa of the observation site. The vascular enhancement observation mode is a mode for acquiring vascular patterns as vascular information and performing diagnoses such as differentiating between benign and malignant tumors. In vascular enhancement observation mode, illumination light containing a large amount of light components in a specific wavelength band with high absorbance to hemoglobin in the blood is irradiated onto the observation site. In normal observation mode, a normal observation image suitable for observing the overall characteristics of the observation site is generated as the display image, and in vascular enhancement observation mode, a vascular enhancement observation image suitable for observing the pattern of blood vessels is generated as the display image.

[0029] The endoscope 11 comprises an insertion section 16 that is inserted into the digestive tract of a living organism, an operating section 17 provided at the base end of the insertion section 16, and a universal cord 18 that connects the endoscope 11 to the processor unit 12 and the light source unit 13.

[0030] The insertion section 16 consists of a tip section 19, a curved section 20, and a flexible tube section 21, which are arranged in sequence from the tip. As shown in Figure 2, the tip surface of the tip section 19 is provided with an illumination window 22 for illuminating the observation site, an observation window 23 for capturing an image of the observation site, an air / water supply nozzle 24 for supplying air / water to clean the observation window 23, and a forceps outlet 25 for extending treatment instruments such as forceps and electrosurgical units to perform various procedures. Behind the observation window 23 are built-in image sensors 56 and an objective optical system 60 for imaging (see Figure 3 for both).

[0031] The curved section 20 consists of multiple connected curved pieces and bends in the up, down, left, and right directions by operating the angle knob 26 on the operating section 17. As the curved section 20 bends, the orientation of the tip section 19 is directed in the desired direction. The flexible tube section 21 is flexible so that it can be inserted into winding tubes such as the esophagus and intestines. The insertion section 16 is through which a drive signal that drives the image sensor 56 and a communication cable that transmits the image signal output by the image sensor 56 are passed, as well as a light guide 55 (see Figure 3) that guides illumination light supplied from the light source device 13 to the illumination window 22.

[0032] The control unit 17 includes an angle knob 26, a forceps channel 27 for inserting treatment instruments, an air / water supply button 28 for operating when supplying air or water from the air / water supply nozzle 24, and a shutter release button (not shown) for taking still images.

[0033] A communication cable and a light guide 55 extending from the insertion section 16 are inserted into the universal cord 18, and a connector 29 is attached to one end on the processor unit 12 and light source unit 13 side. The connector 29 is a composite type 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 unit 12 and the light source unit 13, respectively. One end of the communication cable is connected to the communication connector 29a, and the incident end 55a (see Figure 3) of the light guide 55 is connected to the light source connector 29b.

[0034] In Figure 3, the light source device 13 includes a light source unit 40 composed of four semiconductor light sources 35, 36, 37, and 38 of blue, green, red, and purple colors, an optical path integration unit 41 that integrates the optical paths of the respective colored light from each of the semiconductor light sources 35 to 38, and a light source control unit 42 that controls the driving of each of the semiconductor light sources 35 to 38.

[0035] The blue, red, and violet semiconductor light sources 35, 37, and 38 each have a blue LED 43 that emits light in the blue wavelength band, a red LED 45 that emits light in the red wavelength band, and a violet LED 46 that emits light in the violet wavelength band, respectively, as light-emitting elements. In contrast, 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 the violet to blue wavelength band, and a green phosphor 47 that is excited by the blue excitation light and emits green fluorescence in the green wavelength band.

[0036] Each LED 43-46 is, as is well known, a junction of a P-type semiconductor and an N-type semiconductor. When a voltage is applied, electrons and holes recombine near the PN junction, crossing the band gap, causing a current to flow, and energy equivalent to the band gap is emitted as light during the recombination. In each LED 43-46, increasing the power supply 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 increases in proportion to the increase in the amount of blue excitation light from the excitation light LED 44.

[0037] As shown in Figure 4, the blue semiconductor light source 35 consists of a substrate 35a on which the blue LED 43 is mounted, a mold 35b formed on the substrate 35a with a cavity for housing 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 light-diffusing material is dispersed in the resin 35c. The blue LED 43 is electrically connected to the substrate 35a by wiring 35d. This mounting configuration of the blue semiconductor light source 35 is generally called a surface mount type. Note that, except for the green semiconductor light source 36, each semiconductor light source 35, 37, and 38 has basically the same configuration, so the blue semiconductor light source 35 will be used as an example for explanation, and the explanations of the red and violet semiconductor light sources 37 and 38 will be omitted.

[0038] As shown in Figure 5, the green semiconductor light source 36, like the other semiconductor light sources 35, 37, and 38, has a substrate 36a and a mold 36b, and the excitation light LED 44 is packaged in a surface-mount type. The difference from 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 substance containing a fluorescent material and a diffusing agent dispersed in the sealing resin that encapsulates the excitation light LED 44. Reference numeral 36d indicates the wiring connecting the substrate 36a and the excitation light LED 44.

[0039] As shown in Figure 6, the blue LED 43 has wavelength components in the blue wavelength band, for example, around 440nm to 470nm, and emits blue light LB with a central wavelength of 455±10nm. Also, as shown in Figure 7, the red LED 45 has wavelength components in the red wavelength band, for example, around 615nm to 635nm, and emits red light LR with a central wavelength of 620±10nm. Furthermore, as shown in Figure 8, the purple LED 46 has wavelength components in the purple wavelength band, for example, around 395nm to 415nm, and emits purple light LV with a central wavelength of 405±10nm.

[0040] In Figure 9, the green semiconductor light source 36 emits mixed light (LBe+LGf) consisting of blue excitation light LBe emitted by the excitation light LED 44 and green fluorescence LGf emitted by the green phosphor 47 excited by this blue excitation light LBe. The blue excitation light LBe has wavelength components in the 420nm to 440nm wavelength range, for example, from violet to blue, with a central wavelength of 430±10nm. The green fluorescence LGf has wavelength components in the 500nm to 600nm wavelength range, for example, from green, with a central wavelength of 520±10nm. The wavelength range of the blue excitation light LBe partially overlaps with the wavelength range of blue light LB emitted by the blue semiconductor light source 35 and the wavelength range of violet light LV emitted by the violet semiconductor light source 38 (see also Figure 19, etc.).

[0041] 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 is transmitted through it. Therefore, the emission spectrum of the light emitted by the green semiconductor light source 36 contains two color components, as shown in the figure: a portion of the blue excitation light LBe that has been transmitted through the green phosphor 47 and the green fluorescence LGf.

[0042] The purple semiconductor light source 38 is a light source for vascular-enhanced observation (semiconductor light source for acquiring vascular information). In Figure 10, which shows the absorption spectrum of blood hemoglobin, the extinction coefficient μa of blood hemoglobin is wavelength-dependent, rising sharply in the wavelength band below 450 nm and peaking around 405 nm. Although the value is lower compared to the wavelength band below 450 nm, there is also a peak in the wavelength band of 530 nm to 560 nm. When light with a large extinction coefficient μa is shone on the observation site, absorption is large in blood vessels, resulting in an image with a difference in contrast between blood vessels and other parts of the body.

[0043] Furthermore, as shown in Figure 11, the light scattering characteristics of biological tissues also exhibit wavelength dependence, with the scattering coefficient μS increasing as the wavelength decreases. Scattering affects the depth of light penetration into biological tissues. That is, the greater the scattering, the more light is reflected near the surface of the mucous membrane, and the less light reaches the middle and deeper layers. Therefore, shorter wavelengths result in lower penetration depth, while longer wavelengths result in higher penetration depth. Considering these absorption characteristics of hemoglobin and the light scattering characteristics of biological tissues, the wavelength of light used for highlighting blood vessels is selected.

[0044] The violet light LV emitted by the violet LED 46, with a central wavelength of 405±10nm, has a relatively short wavelength and low penetration depth, resulting in significant absorption by superficial blood vessels. For this reason, violet light LV is used for highlighting superficial blood vessels. By using violet light LV, it is possible to obtain a blood vessel-enhanced observation image in which superficial blood vessels are depicted with high contrast. In addition, for highlighting mid- and deep-layer blood vessels, the green wavelength band of white light LW (see Figure 12) is used. In the absorption spectrum shown in Figure 10, the absorption coefficient changes more gradually in the green wavelength band of 530nm to 560nm compared to the blue wavelength band below 450nm, so the light for highlighting mid- and deep-layer blood vessels does not need to be as narrow-band as violet light LV. Therefore, as will be described later, for highlighting mid- and deep-layer blood vessels, the green image signal separated from the white light by the G-color microcolor filter of the image sensor 56 is used.

[0045] In Figure 3, drivers 50, 51, 52, and 53 are connected to each of the LEDs 43-46, respectively. The light source control unit 42 controls the on / off state and light intensity of each of the LEDs 43-46 via these drivers 50-53. The light intensity is controlled by changing the power supplied to each of the LEDs 43-46 based on the exposure control signal received from the processor unit 12.

[0046] Each driver 50-53, under the control of the light source control unit 42, continuously supplies a drive current to each LED 43-46 to light it up. Then, in accordance with the exposure control signal received from the processor unit 12, the driver changes the power supplied to each LED 43-46 by changing the value of the drive current supplied, thereby controlling the light intensity of the blue light LB, green fluorescent LGf, red light LR, and violet light LV, respectively. The light intensity of the green fluorescent LGf is controlled by controlling the light intensity of the blue excitation light LBe of the excitation light LED 44. Therefore, to increase the light intensity of the green fluorescent LGf, the drive current value supplied from the driver 51 to the excitation light LED 44 is increased to increase the light intensity of the blue excitation light LBe. Alternatively, instead of supplying the drive current continuously, it may be supplied in pulses, and PAM (Pulse Amplitude Modulation) control, which changes the amplitude of the drive current pulse, or PWM (Pulse Width Modulation) control, which changes the duty cycle of the drive current pulse, may be used.

[0047] The optical path integration unit 41 integrates the optical paths of the light of each color emitted by each semiconductor light source 35-38 into a single optical path. The light output section of the optical path integration unit 41 is located near the receptacle connector 54 to which the light source connector 29b is connected. The optical path integration unit 41 outputs the light incident from each semiconductor light source 35-38 to the incident end 55a of the light guide 55 of the endoscope 11. Although not shown in the figure, protective glass is provided on both the light source connector 29b and the receptacle connector 54.

[0048] Figure 12 shows the emission spectrum of the mixed light from the blue light LB, green fluorescent LGf, and red light LR from the blue, green, and red semiconductor light sources 35-37 integrated in the optical path integration unit 41. This mixed light is used as white light LW. As described later, the blue excitation light LBe is cut off by the third dichroic mirror 81 (see Figure 18), so 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 Figure 12 is just one example, and the emission spectrum of the target white light LW may be changed in various ways depending on the desired color of the displayed image. Specifically, the ratio of the light intensity of blue light LB, green fluorescent LGf, and red light LR (the ratio of the drive current values ​​of each LED 43-45) is changed to generate white light LW with the target emission spectrum.

[0049] The light source control unit 42 controls the exposure of the illumination light while maintaining the 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 supplied 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 remains constant.

[0050] Furthermore, the light source control unit 42 changes the emission spectrum of the illumination light between the normal observation mode and the vascular enhancement observation mode. In the vascular enhancement observation mode, in addition to white light LW, violet light LV for enhancing superficial blood vessels is irradiated, so the emission spectrum of the illumination light is white light LW with violet light LV added. In the emission spectrum of this mixed light of white light LW and violet light LV, the light source control unit 42 reduces the proportion of blue light LB compared to the normal observation mode so that violet light LV becomes dominant compared to blue light LB.

[0051] In Figure 3, the endoscope 11 includes a light guide 55, an image sensor 56, an analog processing circuit 57 (AFE: Analog Front End), and an image control unit 58. The light guide 55 is a fiber bundle formed by bundling multiple optical fibers. When the light source connector 29b is connected to the light source device 13, the incident end 55a of the light guide 55 located at the light source connector 29b faces the exit end of the optical path integration unit 41. The exit end of the light guide 55 located at the tip 19 is branched into two before the illumination windows 22 so that light is guided to the two illumination windows 22.

[0052] An illumination lens 59 is positioned behind the illumination window 22. Illumination light supplied from the light source device 13 is guided to the illumination lens 59 by the light guide 55 and illuminated from the illumination window 22 towards the observation area. The illumination lens 59 is a concave lens, which widens the divergence angle of the light emitted from the light guide 55. This allows illumination light to be directed over a wide area of ​​the observation area.

[0053] Behind the observation window 23, the objective optical system 60 and the image sensor 56 are arranged. The image of the observation area enters the objective optical system 60 through the observation window 23 and is formed on the imaging surface 56a of the image sensor 56 by the objective optical system 60.

[0054] The image sensor 56 consists of a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and multiple photoelectric conversion elements, such as photodiodes, which constitute pixels, are arranged in a matrix on its imaging surface 56a. The image sensor 56 converts the light received on the imaging surface 56a into photoelectric energy and accumulates a signal charge at each pixel corresponding to the amount of light received. The signal charge is converted into a voltage signal by an amplifier and read out. The voltage signal is output as an image signal from the image sensor 56 to the AFE 57.

[0055] The Analog Front End (AFE) 57 consists of a Correlated Double Sampling (CDS), an Auto Gain Circuit (AGC), and an Analog / Digital Converter (A / D) (all not shown in the diagram). The CDS applies correlated double sampling to the analog image signal from the image sensor 56 to remove noise caused by the reset of the signal charge. The AGC amplifies the image signal from which the noise has been removed by the CDS. The A / D converts the image signal amplified by the AGC into a digital image signal with a grayscale value corresponding to a predetermined number of bits and inputs it to the processor device 12.

[0056] The imaging control unit 58 is connected to the controller 65 in the processor unit 12 and inputs a drive signal to the image sensor 56 in synchronization with a reference clock signal input from the controller 65. Based on the drive signal from the imaging control unit 58, the image sensor 56 outputs an image signal to the AFE 57 at a predetermined frame rate.

[0057] The image sensor 56 is a color image sensor, and each pixel on the imaging surface 56a is assigned a microcolor filter of three colors, B, G, and R, having spectral characteristics as shown in Figure 13. The arrangement of the microcolor filters is, for example, a Bayer array.

[0058] B pixels assigned a B filter are sensitive to light in the wavelength range of approximately 380 nm to 560 nm, G pixels assigned a G filter are sensitive to light in the wavelength range of approximately 450 nm to 630 nm, and R pixels assigned an R filter are sensitive to light in the wavelength range of approximately 580 nm to 800 nm. The blue light LB, green fluorescence LGf, and red light LR that make up the white light LW are received by the B pixels as reflected light corresponding to the blue light LB, the G pixels as reflected light corresponding to the green fluorescence LGf, and the R pixels as reflected light corresponding to the red light LR. The reflected light corresponding to the violet light LV for vascular enhancement observation is received by the B pixels. Although the blue excitation light LBe is cut off by the third dichroic mirror 81 and does not irradiate the observation site, if the blue excitation light LBe were irradiated, the B pixels would be sensitive to the reflected light corresponding to the blue excitation light LBe.

[0059] As shown in Figures 14 and 15, the image sensor 56 performs an accumulation operation to accumulate signal charge in pixels and a readout operation to read out the accumulated signal charge within the acquisition period of one frame. In Figure 14, in the normal observation mode, each semiconductor light source 35 to 37, excluding the purple semiconductor light source 38, is lit in time with the accumulation operation of the image sensor 56, and white light LW (LB+LGf+LR), which is a mixture of blue light LB, green fluorescent LGf, and red light LR, is irradiated onto the observation area 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 into colors using a microcolor 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 LGf, and the R pixel receives the reflected light corresponding to the red light LR. In time with the readout timing, the image sensor 56 sequentially outputs image signals B, G, and R for one frame, which contain the pixel values ​​of B, G, and R pixels, according to the frame rate. These imaging operations are repeated while the normal observation mode is set.

[0060] In Figure 15, in the blood vessel enhancement observation mode, the purple semiconductor light source 38 is lit in conjunction with the accumulation operation of the image sensor 56, in addition to the semiconductor light sources 35-37. When the semiconductor light sources 35-38 are lit, the purple light LV is added along with the white light LW, which is the same as in the normal observation mode, and these mixed lights (LW+LV) are irradiated onto the observation site as illumination light.

[0061] Similar to the normal observation mode, the illumination light, which is white light LW with added violet light LV, is spectrally separated by the microcolor filter of the image sensor 56. The B pixels receive reflected light corresponding to the blue light LB as well as reflected light corresponding to the violet light LV. The G pixels and R pixels receive reflected light corresponding to the green fluorescence LGf and red light LR, respectively, just as in the normal observation mode. In the vascular 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 vascular enhancement observation mode is set.

[0062] In Figure 3, the processor unit 12 includes a controller 65, a DSP (Digital Signal Processor) 66, an image processing unit 67, a frame memory 68, and a display control circuit 69. The controller 65 has a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores control programs and setting data necessary for control, and a RAM (Random Access Memory) that loads programs and functions as working memory. The CPU controls each part of the processor unit 12 by executing control programs.

[0063] The DSP66 acquires the image signal output by the image sensor 56. The DSP66 separates the image signal, which contains signals corresponding to each of the B, G, and R pixels, into B, G, and R image signals, and performs pixel interpolation on each color image signal. In addition, the DSP66 performs signal processing such as gamma correction and white balance correction on each of the B, G, and R image signals.

[0064] Furthermore, the DSP66 calculates the exposure value based on the image signals B, G, and R, and outputs an exposure control signal to the controller65 that controls the illumination light intensity to increase if the overall light intensity of the image is insufficient (underexposure), and to decrease the illumination light intensity if the light intensity is too high (overexposure). The controller65 transmits the exposure control signal to the light source control unit42 of the light source device13.

[0065] The frame memory 68 stores image data output by the DSP 66 and processed image data processed by the image processing unit 67. The display control circuit 69 reads the processed image data 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.

[0066] As shown in Figure 16, in normal observation mode, the image processing unit 67 generates a normal observation image based on the image signals B, G, and R, which are color-separated into B, G, and R respectively by the DSP 66. This normal observation image is output to the monitor 14. The image processing unit 67 updates the normal observation image each time the image signals B, G, and R in the frame memory 68 are updated.

[0067] As shown in Figure 17, in the vascular enhancement observation mode, the image processing unit 67 generates a vascular enhancement observation image based on image signals B, G, and R. In the vascular enhancement observation mode, image signal B includes not only the reflected light component corresponding to the blue light LB that constitutes the white light LW, but also the reflected light component corresponding to the violet light LV, so that superficial blood vessels are depicted with high contrast. In lesions such as cancer, the density of superficial blood vessels tends to be higher compared to normal tissue, and the vascular pattern has distinctive features, so in vascular enhancement observation aimed at differentiating between benign and malignant tumors, it is preferable that superficial blood vessels are clearly depicted.

[0068] To further emphasize superficial blood vessels, for example, the region of superficial blood vessels in the image may be extracted based on image signal B, and contour enhancement processing may be applied to the extracted region of superficial blood vessels. Then, the contour-enhanced image signal B is combined with a full-color image generated from image signals B, G, and R. Similar processing may be applied to deep and mid-layer blood vessels in addition to superficial blood vessels. When emphasizing deep and mid-layer blood vessels, the region of deep and mid-layer blood vessels is extracted from image signal G, which contains a lot of information about deep and mid-layer blood vessels, contour enhancement processing is applied to the extracted region of deep and mid-layer blood vessels, and the enhanced image signal G is combined with a full-color image generated from image signals B, G, and R.

[0069] Since vascular-enhanced observation images are generated based on image signals B, G, and R, just like normal observation images, it is possible to display the observed area in full color. However, the image signal B in vascular-enhanced observation mode has a higher blue density compared to the image signal B in normal observation mode. Therefore, when generating vascular-enhanced observation images, color correction such as suppressing the blue density may be performed to achieve a similar color tone to normal observation images. The image processing unit 67 generates a vascular-enhanced observation image each time the image signals B, G, and R in the frame memory 68 are updated.

[0070] Furthermore, as a method for generating vascular-enhanced observation images, a method may be adopted in which the observation area is displayed in pseudo-color, such as a method in which the vascular-enhanced observation image is generated using only two colors, image signals B and G, without using image signal R, and image signal B is assigned to the B and G channels of monitor 14, and image signal G is assigned to the R channel of monitor 14.

[0071] In Figure 18, the optical path integration unit 41 is composed of collimator lenses 75, 76, 77, and 78 that collimate the light of each color emitted by each semiconductor light source 35 to 38, a first dichroic mirror 79, a second dichroic mirror 80, and a third dichroic mirror 81 (corresponding to the "optical element for optical path integration" of the present invention), and a focusing lens 82 that focuses the light emitted from the optical path integration unit 41 onto the incident end 55a of the light guide 55. Each of the dichroic mirrors 79 to 81 is an optical element in which a dichroic filter having predetermined transmission characteristics is formed on a transparent glass plate.

[0072] The green semiconductor light source 36 is positioned so that 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 positioned so that their optical axes are perpendicular to each other. A first dichroic mirror 79 is provided at the position where the optical axes of the green semiconductor light source 36 and the red semiconductor light source 37 intersect. Similarly, the blue semiconductor light source 35 and the violet semiconductor light source 38 are also positioned so that their optical axes are perpendicular to each other, and a second dichroic mirror 80 is provided at the position where their optical axes intersect. Furthermore, due to the action of the first and second dichroic mirrors 79 and 80, a third dichroic mirror 81 is provided at the position where all the optical paths of the blue light LB, the mixed light of blue excitation light LBe and green fluorescence LGf, the red light LR, and the violet light LV finally intersect. The first dichroic mirror 79 is positioned at a 45° angle to the optical axes of the green semiconductor light source 36 and the red semiconductor light source 37, the second dichroic mirror 80 is positioned at a 45° angle to the optical axes of the blue semiconductor light source 35 and the violet semiconductor light source 38, and the third dichroic mirror 81 is positioned at a 45° angle to the optical axes of the blue semiconductor light source 35 and the green semiconductor light source 36.

[0073] As shown in Figure 19, the dichroic filter of the first dichroic mirror 79 has the characteristic of reflecting light in the wavelength band of approximately 610 nm or more and transmitting light in the wavelength band below that. The first dichroic mirror 79 transmits the mixed light of blue excitation light LBe and green fluorescence LGf incident from the green semiconductor light source 36 downstream via the collimator lens 76, and reflects the red light LR incident from the red semiconductor light source 37 via the collimator lens 77. This integrates the optical paths of the mixed light of blue excitation light LBe and green fluorescence LGf and the red light LR.

[0074] As shown in Figure 20, the dichroic filter of the second dichroic mirror 80 has the characteristic of reflecting light in the wavelength band less than approximately 430 nm and transmitting light in the wavelength band greater than that. The second dichroic mirror 80 transmits blue light LB incident from the blue semiconductor light source 35 downstream via the collimator lens 75 and reflects violet light LV incident from the violet semiconductor light source 38 via the collimator lens 78. This integrates the optical paths of the blue light LB and the violet light LV.

[0075] The dichroic filter of the third dichroic mirror 81 has transmission characteristics that exclude at least the blue excitation light LBe from the emission spectrum of the mixed light of blue excitation light LBe and green fluorescence LGf emitted by the green semiconductor light source 36, as shown in Figure 9. In other words, the dichroic filter of the third dichroic mirror 81 functions as an excitation light cut-off filter that cuts out the blue excitation light LBe.

[0076] Specifically, as shown in Figure 21, the dichroic filter of the third dichroic mirror 81 has the characteristic of reflecting light in the wavelength band less than approximately 490 nm and transmitting light in the wavelength band greater than that. Therefore, the third dichroic mirror 81 reflects the blue excitation light LBe and transmits the green fluorescence LGf from the mixed light of blue excitation light LBe and green fluorescence LGf that has been transmitted through the first dichroic mirror 79. The third dichroic mirror 81 also transmits the red light LR that has been reflected by the first dichroic mirror 79. Furthermore, the third dichroic mirror 81 reflects the blue light LB that has been transmitted through the second dichroic mirror 80 and the violet light LV that has been reflected by the second dichroic mirror 80. This third dichroic mirror 81 integrates all the optical paths of blue light LB, green fluorescence LGf, red light LR, and violet light LV. Furthermore, the blue excitation light LBe does not enter the incident end 55a of the light guide 55, thus preventing the blue excitation light LBe from irradiating the observation site.

[0077] The operation of the above configuration will be explained below. When performing an endoscopic diagnosis, the endoscope 11 is connected to the processor unit 12 and the light source unit 13, and the power to the processor unit 12 and the light source unit 13 is turned on to start the endoscope system 10.

[0078] The insertion section 16 of the endoscope 11 is inserted into the patient's digestive tract to begin observation of the digestive tract. In normal observation mode, each semiconductor light source 35-37 is lit, except for the purple semiconductor light source 38. The light source control unit 42 sets the drive current value supplied to each LED 43-45 to the value for normal observation mode and starts lighting each semiconductor light source 35-37. Then, it controls the light intensity while maintaining the target emission spectrum.

[0079] The blue and red semiconductor light sources 35 and 37 emit blue light LB and red light LR, respectively, from the blue and red LEDs 43 and 45. The green semiconductor light source 36 emits 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 of light is incident on the collimator lenses 75 to 77 of the optical path integration unit 41, respectively.

[0080] The red light LR is reflected by the first dichroic mirror 79 and transmitted through the third dichroic mirror 81. The mixed light of blue excitation light LBe and green fluorescence LGf is transmitted 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 is transmitted through the third dichroic mirror 81. The optical paths of the red light LR and the mixed light of blue excitation light LBe and green fluorescence LGf are integrated by the first dichroic mirror 79. In addition, the blue excitation light LBe is cut off by the third dichroic mirror 81. Since the dichroic filter of the third dichroic mirror 81 functions as an excitation light cut-off filter, the configuration of the optical system of the optical path integration unit 41 can be simplified.

[0081] 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 integrate the optical paths of the blue light LB, green fluorescence LGf, and red light LR. These blue light LB, green fluorescence LGf, and red light LR are incident on the focusing lens 82. This generates white light LW, which is composed of the blue light LB, green fluorescence LGf, and red light LR. The focusing lens 82 focuses the white light LW onto the incident end 55a of the light guide 55 of the endoscope 11, and supplies the white light LW to the endoscope 11.

[0082] In the endoscope 11, white light LW is guided through the light guide 55 to the illumination window 22 and irradiated onto the observation site from the illumination window 22. The reflected light of the white light LW reflected from the observation site enters the image sensor 56 from the observation window 23. The image sensor 56 outputs image signals B, G, and R to the DSP 66 of the processor device 12. The DSP 66 separates the image signals B, G, and R by color and inputs them to the image processing unit 67. The imaging operation by the image sensor 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, and R. The normal observation image is output to the monitor 14 through the display control circuit 69. The normal observation image is updated according to the frame rate of the image sensor 56.

[0083] Furthermore, the DSP66 calculates the 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. Based on the received exposure control signal, the light source control unit 42 determines the drive current value for each semiconductor light source 35-37 so that the ratio of light intensity for each color light remains constant (so that the target emission spectrum does not change). Then, it drives each semiconductor light source 35-37 with the determined drive current value. This makes it possible to keep the light intensity of the blue light LB, green fluorescence LGf, and red light LR that constitute the white light LW from each semiconductor light source 35-37 constant in a ratio suitable for normal observation mode.

[0084] When changing the light intensity of the green fluorescent LGf during exposure control, the light intensity of the blue excitation light LBe from the excitation light LED 44 is changed. As shown in Figure 19, 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 illumination light, the light intensity of the blue light LB will also change in accordance with the change in the light intensity of the blue excitation light LBe, and the emission spectrum of the illumination light will change. However, since the blue excitation light LBe is cut off by the third dichroic mirror 81, the blue excitation light LBe does not affect the light intensity of the blue light LB, and the light intensity of the blue light LB can be controlled independently of the green fluorescent LGf. Therefore, even when exposure control is performed, illumination light with an emission spectrum suitable for normal observation mode can always be supplied to the endoscope 11, and the color of the normal observation image does not change.

[0085] If a suspected lesion is found in the normal observation mode, the system switches from the normal observation mode to the vascular-enhanced observation mode. In the vascular-enhanced observation mode, in addition to the semiconductor light sources 35-37, a purple semiconductor light source 38 is illuminated. The light of each color from each semiconductor light source 35-37 is converted into white light LW by the action of the optical path integration unit 41 described above and supplied to the endoscope 11.

[0086] The violet semiconductor light source 38 emits violet light LV from the violet LED 46. The violet light LV is incident on the collimator lens 78. The violet light LV is reflected by the second and third dichroic mirrors 80 and 81. The second and third dichroic mirrors 80 and 81 integrate the violet light LV into the same optical path as the white light LW. These violet light LV and white light LW are incident on the focusing lens 82. The focusing lens 82 focuses the violet light LV and white light LW onto the incident end 55a of the light guide 55 of the endoscope 11, supplying the violet light LV and white light LW to the endoscope 11. In this way, the violet light LV and white light LW are simultaneously irradiated onto the observation site. Even in this case, as in the normal observation mode, the blue excitation light LBe is cut off by the third dichroic mirror 81, so that illumination light with an emission spectrum suitable for the vascular enhancement observation mode can always be supplied to the endoscope 11.

[0087] The image sensor 56 receives reflected light from the observation area of ​​white light LW and violet light LV, 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-enhanced observation image based on the B, G, and R image signals. The vascular-enhanced observation image is output to the monitor 14. The vascular-enhanced observation image is updated according to the frame rate of the image sensor 56.

[0088] Because illumination light with an emission spectrum suitable for vascular-enhanced imaging mode is constantly emitted, the reliability of vascular-enhanced imaging images is increased. Since vascular-enhanced imaging images are used to differentiate between benign and malignant tumors, increased reliability of these images leads to more reliable results in differentiating between benign and malignant tumors.

[0089] Since the blue excitation light LBe, which affects the light intensity of blue light LB and violet light LV, is cut off by the third dichroic mirror 81, it is possible to stably obtain illumination light with the target emission spectrum without having to perform complex control such as increasing or decreasing the light intensity of blue light LB or violet light LV in response to the change in blue excitation light LBe due to the change in the light intensity of green fluorescence LGf.

[0090] [Second Embodiment] In the first embodiment described above, the dichroic filter of the third dichroic mirror 81, which integrates the optical paths of the mixed light of 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, functions as an excitation light cut filter. However, the function of the excitation light cut filter may also be assigned to the dichroic filter of a dichroic mirror other than the third dichroic mirror 81.

[0091] For example, as shown in the optical path integration unit 90 in Figure 22, the function of the excitation light cut filter may be performed by the dichroic filter of the first dichroic mirror 91 (corresponding to the first dichroic mirror 79 in the first embodiment above; corresponding to the "optical element for optical path integration" of the present invention), which integrates the optical paths of the mixed light of blue excitation light LBe and green fluorescence LGf emitted from the green semiconductor light source 36 and the red light LR emitted from the red semiconductor light source 37. Note that the optical path integration unit 90 in Figure 22 is the same as the optical path integration unit 41 in the first embodiment above, except that the first dichroic mirror 79 in the first embodiment above is replaced with the first dichroic mirror 91.

[0092] In this case, the dichroic filter of the first dichroic mirror 91 is given the characteristic of reflecting light in the wavelength band of approximately 610 nm or more and light in the wavelength band of less than approximately 490 nm, and transmitting light in other wavelength bands, as shown in Figure 23. In other words, it has a bandpass characteristic that combines the transmission characteristics of the first dichroic mirror 79 and the third dichroic mirror 81 of the first embodiment. However, if such a bandpass characteristic is given, the manufacturing cost will be higher than a short-pass characteristic that reflects light on the longer wavelength side and transmits light on the shorter wavelength side, or the opposite long-pass characteristic. Therefore, as in the first embodiment, it is more cost-effective to have the dichroic filter of the third dichroic mirror 81, which has a long-pass characteristic, perform the function of an excitation light cut filter.

[0093] [Third Embodiment] In the embodiments described above, an example was given in which the dichroic mirror also serves as the excitation light cut filter. However, as shown in the optical path integration unit 95 of the third embodiment in Figure 24, the excitation light cut filter may be provided separately from the dichroic mirror. In the optical path integration unit 95, the excitation light cut filter 96 is positioned between the green semiconductor light source 36 and the first dichroic mirror 79. The excitation light cut filter 96 has the characteristic of reflecting light in the purple and blue wavelength bands less than approximately 450 nm, and transmitting light in the other green and red wavelength bands, as shown in Figure 25, for example. Although not shown, the excitation light cut filter 96 may also 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 should be placed in 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 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 in the optical path upstream of that position.

[0094] [Fourth Embodiment] In the first embodiment described above, the light intensity of each color light is controlled by changing the drive current value supplied to each LED 43-46 based on the exposure control signal from the processor device 12. However, due to the effects of heat generation and degradation over time, the output light intensity of the semiconductor light source may fluctuate in relation to the drive current value. Therefore, a light intensity measuring sensor may be provided to measure the light intensity of each color light, and the light intensity of each color light may be monitored based on the light intensity measuring signal output by the light intensity measuring sensor to determine whether or not it has reached the target value.

[0095] In Figure 26, the optical path integration unit 100 includes, in addition to the configuration of the optical path integration unit 41 shown in Figure 18 of the first embodiment, blue, green, red, and purple light intensity measuring sensors 101, 102, 103, and 104 for measuring the amount of light of each color emitted by each semiconductor light source 35 to 38, and glass plates 105, 106, 107, and 108 provided directly in front of each semiconductor light source 35 to 38, which reflect a portion of the light of each color emitted by each semiconductor light source 35 to 38 and guide it to each light intensity measuring sensor 101 to 104.

[0096] Each glass plate 105-108 is positioned at an angle, for example, 35°, to the optical axis of each semiconductor light source 35-38. Each glass plate 105-108 transmits the light of each color emitted by each semiconductor light source 35-38. When light of each color is incident on each glass plate 105-108, Fresnel reflection occurs. Each glass plate 105-108 is a light guide member that utilizes this Fresnel reflection to guide a portion (approximately 4%-8%) of the light of each color emitted by each semiconductor light source 35-38 to each light intensity measuring sensor 101-104. Note that other light guide members, such as optical fibers, may be used instead of glass plates.

[0097] Filters 109 and 110 are provided in front of the green light intensity sensor 102 and the red light intensity sensor 103, respectively. Filter 109 is intended to restrict the light incident on the green light intensity sensor 102 to only light in the wavelength band of green fluorescence LGf, which ultimately constitutes part of the white light LW supplied to the endoscope 11. As shown in Figure 27, it has the characteristic of reflecting light in the red wavelength band of approximately 610 nm or more, and light in the purple and blue wavelength bands of less than approximately 490 nm, while transmitting light in the other green wavelength bands. In other words, filter 109 has bandpass characteristics that combine the transmission characteristics of the first dichroic mirror 79 and the third dichroic mirror 81 of the first embodiment, similar to the first dichroic mirror 91 of the second embodiment. Filter 109 ensures that only green fluorescence LGf, which is ultimately emitted as part of the white light LW, is incident on the green light intensity sensor 102, with the blue excitation light LBe cut off. This allows for the measurement of the pure light intensity of green fluorescence LGf.

[0098] Furthermore, the filter 110 is designed to restrict the light incident on the red light intensity measuring sensor 103 to only light in the wavelength range of red light LR, which ultimately constitutes part of the white light LW supplied to the endoscope 11. As shown in Figure 28, it has the characteristic of reflecting light in the green and blue wavelength ranges below approximately 610 nm and transmitting light in the red wavelength range above that. In other words, the filter 110 has transmission characteristics that are the inverse of the transmission characteristics shown in Figure 19 of the first dichroic mirror 79 of the first embodiment. With the filter 110, only red light LR, which is ultimately emitted as part of the white light LW, is incident on the red light intensity measuring sensor 103. This makes it possible to measure the pure light intensity of red light LR.

[0099] In Figure 29, each light intensity sensor 101-104 receives light of each color guided by Fresnel reflection from glass plates 105-108, outputs a light intensity measurement signal corresponding to the light intensity of each color received, and outputs this to the light source control unit 42. The light source control unit 42 compares the light intensity measurement signal with the target light intensity, and based on this comparison result, fine-tunes the drive current value supplied to each semiconductor light source 35-38, which is set in the exposure control, so that the light intensity reaches the target value. In this way, the light intensity of each color is constantly monitored by the light intensity sensors 101-104, and the drive current value supplied is fine-tuned based on the light intensity measurement result, so that the light intensity can always be controlled to conform to the target value. As a result, illumination light with the target emission spectrum can be obtained more stably.

[0100] Furthermore, as shown in the optical path integration unit 115 in Figure 30, an excitation light cut filter 116 having the same transmission characteristics as filter 109 may be provided at the position 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 Figure 24 of the third embodiment). In this case, filter 109 becomes unnecessary. However, since the excitation light cut filter 116 is larger in size than filter 109, from the viewpoint of cost and space saving, it is preferable to provide filter 109 rather than providing the excitation light cut filter 116.

[0101] In the fourth embodiment described above, light intensity sensors are placed for all semiconductor light sources to monitor the light intensity. However, it is also possible to monitor the light intensity of at least the blue, green, and red semiconductor light sources that emit light constituting white light LW, and the fluorescent semiconductor light source, while not placing light intensity sensors for other semiconductor light sources. Furthermore, among the blue, green, and red semiconductor light sources, only the light intensity of semiconductor light sources (fluorescent semiconductor light sources) that exhibit particularly large fluctuations in output light intensity with respect to the drive current value may be selectively monitored.

[0102] The fluorescent semiconductor light source is not limited to the green semiconductor light source 36 of each embodiment described above. Instead of, or in addition to, the red semiconductor light source may be composed of a blue excitation light-emitting element that emits blue excitation light in the purple to blue wavelength band, and a red phosphor that emits red fluorescence in the red wavelength band when excited by the blue excitation light. In this case as well, as in each embodiment described above, the excitation light cut filter should be provided at a position that integrates the optical paths of the mixed light of blue excitation light and red fluorescence emitted by the red semiconductor light source and the blue light emitted by the blue semiconductor light source, or on the optical path upstream of that position. For example, as in the first embodiment described above, the dichroic filter of the third dichroic mirror 81 may be made to perform the function of 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.

[0103] When the red semiconductor light source is composed of a fluorescent semiconductor light source, the excitation photoluminescent element is not limited to a blue excitation photoluminescent element that emits blue excitation light in the purple to blue wavelength range, but may also be a green excitation photoluminescent element that emits green excitation light in the green wavelength range. In this case, an excitation light cut filter having transmission characteristics that cut out green excitation light and transmit red fluorescence is placed between the red semiconductor light source and the first dichroic mirror 79 in the optical path integration unit 41 in Figure 18, for example.

[0104] [Fifth Embodiment] Furthermore, as shown in the light source unit 120 in Figure 31, a white semiconductor light source 121 may be used as a fluorescent semiconductor light source. The light source unit 120 is the same as the light source unit 40 of the first embodiment, but with the green semiconductor light source 36 and red semiconductor light source 37 removed and replaced with a white semiconductor light source 121. The optical path integration unit 122 is the same as the optical path integration unit 41 of the first embodiment, but with the collimator lens 77 and the first dichroic mirror 79 related to the green semiconductor light source 36 and red semiconductor light source 37 removed.

[0105] The white semiconductor light source 121 is composed of a blue excitation light-emitting element that emits blue excitation light LBe in the 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 the green and red wavelength bands, respectively. In this case, the white light LW is composed of blue light LB emitted by the blue semiconductor light source 35 and mixed light of green fluorescence LGf and red fluorescence LRf emitted by the white semiconductor light source 121. In this embodiment as well, 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. Therefore, similar to the embodiments with three color semiconductor light sources 35 to 37 described above, the embodiment with the blue semiconductor light source 35 and the white semiconductor light source 121 also suffers from the problem that the excitation light emitted by the fluorescent semiconductor light source affects the amount of light whose wavelength band overlaps with the excitation light, causing a change in the emission spectrum of the illumination light.

[0106] A dichroic mirror 123 is positioned at the point where the light emitted from each semiconductor light source 35, 38, and 121 finally intersects. The dichroic mirror 123 corresponds to the third dichroic mirror 81 in the first embodiment described above. The dichroic filter of the dichroic mirror 123 has the characteristic of reflecting violet light LV, blue excitation light LBe, and blue light LB, and transmitting green fluorescence LGf and red fluorescence LRf, and functions as an excitation light cut filter that cuts out blue excitation light LBe. This dichroic mirror 123 integrates all optical paths of each color of light and prevents the transmission of blue excitation light LBe.

[0107] In this embodiment as well, similar to the third embodiment described above, an excitation light cut filter may be provided separately from the dichroic mirror 123. Furthermore, as in the fourth embodiment, for example, a light intensity sensor may be provided on the white semiconductor light source 121 to monitor the light intensity.

[0108] Furthermore, the LED mounting configuration in the first embodiment described above is just one example, and other configurations may be adopted. For example, microlenses for adjusting the divergence angle may be provided on the light-emitting surface of the sealing resin 35c or the green phosphor 47 in Figures 4 and 5, or the LED may be housed in a bullet-shaped case with microlenses formed on it, rather than being a surface-mount type. In addition, although the green semiconductor light source 36 was described as having both the excitation light LED 44 and the green phosphor 47 integrally provided on the substrate 36a, the green phosphor 47 and the substrate 36a may be provided separately. In this case, a light-guiding member such as a lens or optical fiber is added between the excitation light LED 44 and the green phosphor 47 to guide the excitation light from the excitation light LED 44 to the green phosphor 47 via the light-guiding member.

[0109] [Sixth Embodiment] Furthermore, although the example described uses an LED as the light-emitting element, a laser diode (LD) may be used instead of the LED. For example, as shown in Figure 32, a green semiconductor light source 130, which consists of an excitation light LD 131 that emits blue excitation light and a green phosphor 132 placed 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 described above.

[0110] 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 the rotating plate 133 is rotated by a rotating mechanism 134 such as a motor, blue excitation light from the excitation light LD 131 is irradiated onto an eccentric position on the rotating plate 133. By rotating the rotating plate 133, the irradiation position of the excitation light is not concentrated on one point on the green phosphor 132. If the irradiation position of the excitation light is concentrated on one point, that point will become hot, which will accelerate the degradation of the green phosphor 132, but this can be prevented. Reference numeral 135 denotes a focusing lens that focuses the blue excitation light emitted by the excitation light LD 131 onto the rotating plate 133.

[0111] Furthermore, an excitation light cut filter may be integrally formed on the output side surface of the rotating plate 133. In addition, an organic EL (Electro-Luminescence) element may be used as the light-emitting element, in addition to LEDs and LDs. Not limited to fluorescent semiconductor light sources, LDs and organic EL elements may also be used as light-emitting elements in other semiconductor light sources (blue semiconductor light source 35, violet semiconductor light source 38, etc.).

[0112] The white semiconductor light source 140 shown in Figure 33 is a white version of the green semiconductor light source 130 in Figure 32. Similar to the green semiconductor light source 130, the white semiconductor light source 140 consists of an excitation light LD 141 that emits blue excitation light and green and red phosphors 142 positioned in front of the excitation light LD 141. This white semiconductor light source 140 may also be used as the white semiconductor light source 121 in the fifth embodiment. Note that other components, such as the rotating plate, are the same as those in the green semiconductor light source 130 in Figure 32, and therefore, the same reference numerals as in Figure 32 are used, and their description is omitted.

[0113] In the embodiments described above, an excitation light cut filter that cuts 100% of the excitation light was exemplified, but the present invention is not limited thereto. The excitation light cut filter only needs to be able to reduce the amount of excitation light to some extent, and for example, a filter having transmission characteristics that cut 50% of the excitation light is also included in the present invention. However, a cut closer to 100% is preferable as it yields a better effect.

[0114] The configuration of the optical path integration unit in each of the above embodiments is just one example, and various modifications are possible. For example, a dichroic mirror is used as the optical element with a dichroic filter formed on it, but instead a dichroic prism with a dichroic filter formed on it may be used. Alternatively, instead of optical elements with dichroic filters, such as a dichroic mirror or a dichroic prism, the optical path may be integrated using a branched light guide, for example, which has multiple incident ends facing each semiconductor light source and one exit end facing the incident end of the light guide of the endoscope. The branched light guide is a fiber bundle of bundled optical fibers, in which the optical fiber is divided into multiple predetermined numbers at one end, and the incident ends are branched into multiple. In this case, each semiconductor light source is arranged corresponding to each of the branched incident ends. An excitation light cut filter is placed between the fluorescent semiconductor light source and the incident end of the branched light guide.

[0115] In the embodiments described above, a violet semiconductor light source 38 emitting violet light LV was exemplified as a semiconductor light source for acquiring vascular information of biological tissue. However, other semiconductor light sources for acquiring vascular 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 hemoglobin in the blood as vascular information. Of course, if vascular information observation is not performed, only blue, green, and red semiconductor light sources may be provided without a semiconductor light source for acquiring vascular information.

[0116] Furthermore, in the first embodiment described above, only white light is used in the normal observation mode, and white light LW and violet light LV are simultaneously irradiated onto the observation site in the vascular enhancement observation mode. In both modes, white light is used, but a mode without white light may be provided. For example, a green semiconductor light source 36 and a violet semiconductor light source 38, or a green semiconductor light source 36 and a blue semiconductor light source 35 may be lit, and a vascular enhancement observation image may be acquired based on green fluorescence LGf.

[0117] In the embodiments described above, the image sensor 56 is a color image sensor that separates white light into colors using B, G, and R microcolor filters, and a simultaneous endoscope system and light source device used therein have been described as examples in which the color image sensor simultaneously acquires B, G, and R image signals. However, the present invention may also be applied to a plane-sequential endoscope system and 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 plane sequence.

[0118] Needless to say, each of the above embodiments can be implemented individually or in combination.

[0119] In the embodiments described above, the light source device and the processor device were described as being configured as separate units, but the two devices may be configured as an integrated unit. Furthermore, the present invention can also be applied to endoscopic systems and light source devices used therein, such as fiberscopes that guide the reflected light from the observation area of ​​the illumination light with an image guide, and ultrasonic endoscopes in which an image sensor and an ultrasonic transducer are built into the tip. [Explanation of Symbols]

[0120] 10 Endoscopy Systems 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 LEDs 46 Purple LED 47, 132 Green phosphor 55 Light Guide 56 Image sensor 79-81 1st-3rd Dichroic Mirrors 91. First Dichroic Mirror 96, 116 Excitation light cut filter 101-104 Light intensity measurement 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. In an endoscope light source device that supplies illumination light to the light guide of an endoscope, A purple LED light source that emits purple light, A blue LED light source that emits blue light, A substrate on which an excitation light-emitting element that emits blue excitation light having a wavelength band overlapping with at least a portion of the wavelength band of the blue light is mounted, and a phosphor that is excited by the blue excitation light and emits green fluorescence having a green wavelength band are integrally provided, the green fluorescence emitted from the phosphor and the fluorescent LED light source that emits the blue excitation light, A first dichroic mirror that integrates the optical path through which the purple light emitted by the purple LED light source passes and the optical path through which the blue light emitted by the blue LED light source passes, A second dichroic mirror integrates the optical path through which the light integrated by the first dichroic mirror passes, and the optical path through which the green fluorescence emitted from the fluorescent LED light source passes, but does not integrate the optical path of the blue excitation light. An endoscope light source device equipped with the following features.

2. In an endoscope light source device that supplies illumination light to the light guide of an endoscope, A purple LED light source that emits purple light, A blue LED light source that emits blue light, An excitation light-emitting element that emits blue excitation light having a wavelength band that overlaps with at least a portion of the wavelength band of the blue light is packaged in a surface-mount type, a phosphor that emits green fluorescence having a green wavelength band when excited by the blue excitation light is enclosed, the green fluorescence emitted from the phosphor and the fluorescent LED light source that emits the blue excitation light, A first dichroic mirror that integrates the optical path through which the purple light emitted by the purple LED light source passes and the optical path through which the blue light emitted by the blue LED light source passes, A second dichroic mirror integrates the optical path through which the light integrated by the first dichroic mirror passes, and the optical path through which the green fluorescence emitted from the fluorescent LED light source passes, but does not integrate the optical path of the blue excitation light. An endoscope light source device equipped with the following features.

3. The endoscope light source device according to claim 1, wherein the excitation photoluminescent element is packaged on the substrate in a surface-mount type.

4. The endoscope light source device according to claim 2, wherein the fluorescent LED light source comprises a substrate on which the excitation photoluminescent element is mounted and a phosphor that emits green fluorescence having a green wavelength band when excited by the blue excitation light.

5. The endoscope light source device according to any one of claims 1 to 4, wherein the fluorescent LED light source is a white LED light source.

6. The endoscope light source device comprises a light source control unit that controls the power supplied to each of the purple LED, the blue LED, and the white LED light sources, When the light source control unit is set to a vascular enhancement observation mode that emphasizes blood vessels on the mucosal surface of biological tissue, it lights up all of the purple LED, blue LED, and white LED light sources. The endoscope light source device according to claim 5, wherein when the normal observation mode for irradiating with white light is set, the purple LED is turned off and the blue LED and the white LED light source are turned on.

7. In the aforementioned normal observation mode, a normal observation image is generated based on the color-separated image signals B, G, and R, respectively. In the aforementioned blood vessel enhancement observation mode, the endoscope light source device according to claim 6 generates a blood vessel enhancement observation image based on color-separated image signals B, G, and R.

8. The light source control unit reduces the proportion of the amount of blue light in the illumination light compared to the normal observation mode in the blood vessel enhancement observation mode, according to claim 6, for the endoscope light source device.

9. The endoscope light source device according to any one of claims 1 to 4, wherein the excitation photoluminescent element is a light-emitting diode.

10. The endoscopic light source device according to any one of claims 1 to 4, wherein the second dichroic mirror does not integrate at least 50% or more of the optical path of the blue excitation light.

11. The endoscope light source device according to claim 6, further comprising a white light intensity measuring sensor that measures the amount of a portion of the white light emitted by the white LED light source, wherein the light source control unit adjusts the power supplied to the excitation light-emitting element based on the measurement result of the white light intensity measuring sensor.

12. The endoscope light source device according to claim 11, further comprising a purple light intensity measuring sensor that measures the amount of a portion of the purple light emitted by the purple LED light source, wherein the light source control unit adjusts the power supplied to the purple LED light source based on the measurement result of the purple light intensity measuring sensor.

13. The endoscope light source device according to claim 11, further comprising a blue light intensity measuring sensor that measures the amount of a portion of the blue light emitted by the blue LED light source, wherein the light source control unit adjusts the power supplied to the blue LED light source based on the measurement result of the blue light intensity measuring sensor.

14. The aforementioned endoscope light source device is The system includes a light source control unit that controls the power supplied to each of the purple LED light source, the blue LED light source, and the fluorescent LED light source, When the vascular enhancement observation mode, which emphasizes blood vessels on the mucosal surface of biological tissue, is set, the light source control unit performs at least one of the following: control to light up all of the purple LED light source, the blue LED light source, and the fluorescent LED light source, or control to light up the purple LED light source and the fluorescent LED light source. The endoscope light source device according to any one of claims 1 to 4, wherein when a normal observation mode for irradiating with white light is set, the purple LED light source is turned off and the blue LED light source and the fluorescent LED light source are turned on.

15. The endoscope light source device according to any one of claims 1 to 4, further comprising a focusing lens for focusing the light integrated by the second dichroic mirror onto the incident end of the light guide.

16. The light source device for endoscopes according to claim 1, wherein the blue excitation light does not include the wavelength band of ultraviolet light.

Images