JP2014132918A - Light source device and endoscope system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light use efficiency.SOLUTION: A light source device 13 that supplies illumination light to a light guide 43 of an endoscope 10 includes a light-emitting device 66, a fluorescent body 36, and a light guide rod 40. The light-emitting device 66 has a laser diode LD1 that emits excitation light for the fluorescent body 36. The light guide rod 40 includes an incident end surface 70, an emission end surface 71, and a side surface 72 that connects the incident end surface 70 and the emission end surface 71, and guides the light incident from the incident end surface 70 to the emission end surface 71 while totally reflecting it, the side surface 72 being a shape tapered with respect to the optical axis so that the area of the emission end surface 71 is larger than that of the incident end surface 70. The incident end surface 70 is optically connected to a light emitting surface 69 of the fluorescent body 36. In the range from the incident end surface 70 to midway toward the emission end surface 71, a reflection film 73 is formed on the whole periphery of the side surface 72.

Description

  The present invention relates to a light source device for supplying illumination light to an endoscope, and an endoscope system using the same.

  In the medical field, endoscopic diagnosis using an endoscopic system is widespread. The endoscope system includes an endoscope, a light source device for supplying illumination light to the endoscope, and a processor device that processes an image signal output from the endoscope. The endoscope has an insertion part that is inserted into a living body, and an illumination window that irradiates the observation part with illumination light and an observation window for photographing the observation part are arranged at the tip of the insertion part. The endoscope has a built-in light guide made of a fiber bundle in which optical fibers are bundled. The light guide guides the illumination light supplied from the light source device to the illumination window. An imaging element such as a CCD is disposed in the back of the observation window. The inside of the living body can be observed by imaging an observation site irradiated with illumination light with an imaging device, generating an observation image with a processor device based on an image signal obtained thereby, and displaying the observation image on a monitor.

  Conventionally, xenon lamps and halogen lamps that emit white light have been used as light sources in light source devices, but recently, instead of these, light-emitting elements composed of semiconductors such as laser diodes (LDs) and LEDs, A light source that generates white light by combining with a phosphor that emits fluorescence when excited by light emitted from a light emitting element has also been proposed (see Patent Document 1).

  In FIG. 11 of Patent Document 1, an LED that emits blue light including ultraviolet light and a phosphor that emits yellow fluorescence when excited by blue light are combined, and white light is generated by mixing blue light and yellow fluorescence. A light source module including a light source to be generated and a light guide rod that guides light from the light source in an optical axis direction is disclosed. The light emitting surface of the phosphor from which the mixed light of the blue light and the fluorescence is emitted is abutted against the incident end surface of the light guide rod. In addition, a reflecting member is provided around the phosphor to reflect the light toward the periphery of the phosphor toward the incident end face of the light guide rod.

  A part of the light of the light emitting element is used for exciting the phosphor, and the remaining light is transmitted through the phosphor and emitted from the light emitting surface of the phosphor together with the fluorescence. In general, a phosphor is a powdery fluorescent material hardened with a binder, and has a diffusing action of diffusing incident light by the fluorescent material or the binder. The light divergence angle of the light emitting element is relatively small at the time of incidence on the phosphor, but is widened when emitted from the light emitting surface of the phosphor due to the diffusion action of the phosphor. Since the fluorescence is also emitted from the entire light emitting surface, the divergence angle is relatively large.

  The light guide rod is provided in order to reduce the divergence angle of the light whose divergence angle is widened by the diffusing action of the phosphor and efficiently enter the light guide of the endoscope. The light guide rod has an incident end face and an exit end face, a side face that connects the entrance end face and the exit end face, and guides light incident from the entrance end face to the exit end face while totally reflecting the light, and the exit end face is more than the entrance end face. The side surface has a tapered shape inclined with respect to the optical axis so that the surface area becomes larger. In this way, in the thick light guide rod having the exit end face area larger than the entrance end face area, the divergence angle of the incident light becomes small in the process of repeating total reflection on the side face.

JP 2009-266390 A

  In a configuration such as the light source module shown in FIG. 11 of Patent Document 1 in which a phosphor is disposed between the light emitting element and the light guide rod, the light emitted from the phosphor is incident on the light guide rod without any excess, and How to guide the light incident on the light guide rod without loss is the key to improving the light utilization efficiency.

  In patent document 1, in order to improve light utilization efficiency, the reflection member which reflects the light which goes to the peripheral direction of fluorescent substance toward the incident end surface of a light guide rod is provided. However, in a light source module in which a phosphor and a light guide rod are combined, simply providing such a reflecting member is insufficient as a measure for improving light utilization efficiency.

  For example, in Patent Document 1, the light emitting surface of the phosphor and the incident end surface of the light guide rod are abutted. However, in order to efficiently make the light emitted from the phosphor incident on the light guide rod, the light emitting surface and the light emitting surface can be compared with the wavelength of the propagating light by simply abutting the light emitting surface of the phosphor and the light incident end surface of the light guide rod. Since the gap between the incident end faces is too large and the light loss due to reflection at the incident end face of the light guide rod is large, it is insufficient as a measure for improving the light utilization efficiency. Therefore, even if a reflecting member is provided as in Patent Document 1 and light directed toward the periphery of the phosphor is reflected toward the incident end surface of the light guide rod, the light emitting surface of the phosphor and the incident end surface of the light guide rod are It is not possible to expect a significant improvement in light utilization efficiency simply by making contact.

  In addition, since the light emitted from the light emitting surface of the phosphor has a large divergence angle, the high angle component having a large divergence angle out of the light incident from the phosphor to the light guide rod has an incident angle on the side surface of the light guide rod. It becomes smaller than the critical angle, and it is transmitted from the side surface without being totally reflected on the side surface, resulting in light loss. For this reason, even if the light reflected by the reflecting member is fortunately incident on the light guide rod, if the divergence angle of the light is large, it is transmitted from the side surface and eventually results in light loss.

  The present invention has been made in view of the above problems, and in a configuration in which a phosphor is disposed between a light emitting element and a light guide rod, a light source device capable of improving light utilization efficiency, and an internal view using the light source device An object is to provide a mirror system.

  In order to achieve the above object, a light source device for supplying illumination light to a light guide of an endoscope of the present invention includes a light emitting element made of a semiconductor, a phosphor, and a light guide rod. The phosphor has a light emitting surface that emits mixed light of light emitted from the light emitting element and fluorescence excited by the light. The light guide rod has an incident end face and an exit end face, a side face that connects the entrance end face and the exit end face, and guides the light incident from the entrance end face to the exit end face while totally reflecting the light, and the exit end face is more than the entrance end face. The side surface has a tapered shape inclined with respect to the optical axis so that the surface area becomes larger. The light emitting surface and the incident end surface are optically joined. A reflection film is formed on the entire circumference of the side surface in the range from the incident end surface to the exit end surface.

  “Optical bonding” means that the bonding surfaces (in this case, the light emitting surface and the incident end surface) of two optical members are bonded to each other with an optically transparent adhesive or the like. “Optical bonding” is a phenomenon in which the bonding surfaces of two optical members are mirror-polished to form a flat surface, and the bonding surfaces are brought into contact with each other by intermolecular force. It also includes a phenomenon in which the bonding surfaces are closely bonded at an interval shorter than the wavelength of the light guided between the two optical members.

  The reflective film is formed by any one of dielectric multilayer coating, metal film coating, or metal film adhesion. More preferably, the reflective film is formed by coating a dielectric multilayer film.

When the critical angle at the side surface of the light incident on the light guide rod is θc, the inclination angle with respect to the optical axis of the side surface is α, and the area of the incident end surface is Sa, the formation length of the reflective film from the incident end surface is The area Sb of the cross section of the light guide rod parallel to the incident end face at the end on the exit end face side is a length that satisfies the following conditional expression 1.
Conditional expression 1: Sb ≧ Sa / cos ² (θc−α)

More preferably, the formation length of the reflecting film from the incident end face is such that the area Sb of the cross section of the light guide rod parallel to the incident end face at the end of the reflecting film on the exit end face side satisfies the following Equation 1. Length.
Equation 1: Sb = Sa / cos ² (θc−α)

  The light guide rod has a square cross section perpendicular to the optical axis.

When the critical angle at the side surface of the light incident on the light guide rod is θc, the inclination angle with respect to the optical axis of the side surface is α, and the length of the side of the incident end surface is da, the reflecting film satisfies the following conditional expression 2. Has a formation length L from
Conditional expression 2: L ≧ da · [{1 / cos (θc−α)} − 1] / (2 tan α)

More preferably, the reflective film has a formation length L that satisfies Equation 2 below.
Equation 2: L = da · [{1 / cos (θc−α} −1] / (2 tan α)

  The light emitting element emits excitation light having a center wavelength of 445 nm. The phosphor is excited by the excitation light and emits fluorescence in a wavelength region extending from the green region to the red region. White light is generated as mixed light by the excitation light and fluorescence.

  The light emitting element has either a laser diode or an LED.

  Further, the present invention provides an endoscope system including an endoscope in which a light guide that guides illumination light is incorporated and a light source device that supplies illumination light to the light guide, wherein the light source device is formed of a semiconductor. A light emitting device, a phosphor, and a light guide rod. The phosphor has a light emitting surface that emits mixed light of light emitted from the light emitting element and fluorescence excited by the light. The light guide rod has an incident end face and an exit end face, a side face that connects the entrance end face and the exit end face, and guides light incident from the entrance end face to the exit end face while totally reflecting the light, and the exit end face is more than the entrance end face. The side surface has a tapered shape inclined with respect to the optical axis so that the surface area becomes larger. The light emitting surface and the incident end surface are optically joined. A reflection film is formed on the entire circumference of the side surface in the range from the incident end surface to the exit end surface.

  According to the present invention, the light emitting surface of the phosphor and the incident end surface of the light guide rod are optically joined, and the reflective film is provided on the entire circumference of the side surface of the light guide rod in a range from the incident end surface to the middle of the exit end surface. Since it is provided, the light emitted from the phosphor can be incident on the light guide rod without any excess, and the light incident on the light guide rod can be guided without loss. Therefore, in the configuration in which the phosphor is disposed between the light emitting element and the light guide rod, the light utilization efficiency can be improved.

It is an external view of the endoscope system of the present invention. It is a front view of the front-end | tip part of an endoscope. It is a block diagram which shows the electric constitution of an endoscope system. It is a graph which shows the spectrum of illumination light. It is a graph which shows the absorption spectrum of hemoglobin. It is a graph which shows the scattering coefficient of a biological tissue. It is a graph which shows the spectral characteristic of the color microfilter of an image pick-up element. It is explanatory drawing which shows the irradiation timing and imaging timing of illumination light in each of (A) normal light observation mode, (B) blood vessel emphasis observation mode, and (C) oxygen saturation observation mode. It is explanatory drawing which shows the image processing procedure in each of (A) normal light observation mode, (B) blood vessel emphasis observation mode, and (C) oxygen saturation observation mode. It is a perspective view of a light source module. It is a principal part perspective view of a light source device. It is explanatory drawing which shows a mode that light propagates the inside of a light guide rod. It is a comparison table | surface of the reflectance by the kind of reflection film, and manufacturing cost. It is explanatory drawing which shows a mode that light propagates in the light guide rod, (A) shows the case where a reflective film is not provided, and (B) shows the case where a reflective film is provided. It is explanatory drawing which shows the various parameters for guide | inducing the conditional expression of the formation length L of a reflecting film. It is a table | surface which shows the specific example of inclination-angle (alpha) with respect to the optical axis of the side surface of a light guide rod, the formation length L of a reflecting film, and the full length of a light guide rod.

  In FIG. 1, an endoscope system 10 includes an endoscope 11 that images an observation site in a living body, a processor device 12 that generates an observation image of the observation site based on an image signal obtained by imaging, and an observation site. Is provided with a light source device 13 for supplying illumination light to the endoscope 11 and a monitor 14 for displaying an observation image. An operation input unit 15 such as a keyboard or a mouse is connected to the processor device 12.

  The endoscope system 10 uses white light as illumination light, a normal light observation mode for observing an observation site under white light, and a blood vessel existing in the observation site using special light as illumination light. A blood vessel enhancement observation mode and an oxygen saturation observation mode are provided. The blood vessel enhancement observation mode and the oxygen saturation observation mode are special light observation modes for grasping the characteristics of the blood vessel pattern, the oxygen saturation, and the like, and making a diagnosis such as tumor quality discrimination. In the blood vessel enhancement observation mode and the oxygen saturation observation mode, narrowband light in a wavelength region having a high absorbance for blood hemoglobin is used as the special light. In the blood vessel enhancement observation mode, a blood vessel enhancement image in which blood vessels are enhanced is displayed. In the oxygen saturation observation mode, an oxygen saturation image indicating the oxygen saturation of blood hemoglobin is displayed.

  The endoscope 11 includes an insertion portion 16 inserted into a digestive tract of a living body, an operation portion 17 provided at a proximal end portion of the insertion portion 16, and between the operation portion 17, the processor device 12, and the light source device 13. And a universal cord 18 to be connected.

  The insertion portion 16 includes a distal end portion 19, a bending portion 20, and a flexible tube portion 21 that are continuously provided from the distal end. As shown in FIG. 2, an illumination window 22 for irradiating the observation site with illumination light, an observation window 23 for capturing an image of the observation site, and an air supply for cleaning the observation window 23 are provided on the distal end surface of the distal end portion 19. An air supply / water supply nozzle 24 for supplying water and a forceps outlet 25 for performing various treatments by projecting a treatment tool such as forceps and an electric knife are provided. In the back of the observation window 23, an image sensor 44 and an objective optical system 51 for image formation (both see FIG. 3) are incorporated.

  The bending portion 20 includes a plurality of connected bending pieces, and is bent in the vertical and horizontal directions by operating the angle knob 26 of the operation portion 17. By bending the bending portion 20, the direction of the distal end portion 19 is directed in a desired direction. The flexible tube portion 21 is flexible so that it can be inserted into a tortuous duct such as the esophagus or the intestine. The insertion unit 16 includes a communication cable that communicates a drive signal for driving the image sensor 44 and an image signal output from the image sensor 44, and a light guide 43 that guides illumination light supplied from the light source device 13 to the illumination window 22. (See FIG. 3) is inserted.

  In addition to the amble knob 26, the operation unit 17 includes a forceps port 27 for inserting a treatment instrument, an air / water supply button 28 that is operated when air / water is supplied from the air / water supply nozzle 24, and a still image. A release button (not shown) for photographing is provided.

  A communication cable and a light guide 43 extending from the insertion portion 16 are inserted into the universal cord 18, and a connector 29 is attached to one end of the processor device 12 and the light source device 13. The connector 29 is a composite type connector composed of a communication connector 29a and a light source connector 29b. The communication connector 29a and the light source connector 29b are detachably connected to the processor device 12 and the light source device 13, respectively. One end of a communication cable is disposed on the communication connector 29a, and an incident end of the light guide 43 is disposed on the light source connector 29b.

  In FIG. 3, the light source device 13 includes three types of light source modules 31, 32, and 33 having different emission wavelengths, and a light source control unit 34 that drives and controls them. The light source control unit 34 controls the drive timing and synchronization timing of each unit of the light source device 13.

  The light source modules 31 to 33 have laser diodes LD1, LD2, and LD3 that respectively emit narrowband light in a specific wavelength range. As shown in FIG. 4, in the blue (B) region, the laser diode LD1 emits narrowband light N1 whose wavelength region is limited to 440 ± 10 nm and whose center wavelength is 445 nm, for example. In the blue region, the laser diode LD2 emits narrowband light N2 whose wavelength region is limited to 410 ± 10 nm and whose center wavelength is 405 nm, for example. In the blue region, the laser diode LD3 emits narrowband light N3 whose wavelength region is limited to 470 ± 10 nm and whose center wavelength is 473 nm, for example. As the laser diodes LD1 to LD3, InGaN-based, InGaNAs-based, or GaNAs-based ones can be used. The laser diodes LD1 to LD3 are preferably broad area laser diodes having a wide stripe width (waveguide width) capable of increasing output.

  The light source modules 32 and 33 are connected to a coupler 39c through two optical fibers 39a and 39b. The light source module 31 and the coupler 39c are connected to the coupler 39f through two optical fibers 39d and 39e. These four optical fibers 39a, 39b, 39d, 39e and the two couplers 39c, 39f integrate the optical paths of the light source modules 31-33 into one optical path. The incident ends of the optical fibers 39d, 39a, and 39b face the light source modules 31, 32, and 33, respectively. Since there is only one incident end of the light guide 43 of the endoscope 11, the optical fibers 39a, 39b, 39d, 39e and the couplers 39c, 39f are provided in the previous stage of supplying the light from the light source modules 31 to 33 to the endoscope 11. As a result, the light paths of the light sources 31 to 33 are integrated.

One optical fiber 39g is connected to the coupler 39f, and the phosphor 36 is connected to the output end of the optical fiber 39g. As shown in FIG. 4, the phosphor 36 is excited by the 445 nm blue narrow-band light N1 emitted from the laser diode LD1, and emits the fluorescence FL in the wavelength region extending from the green (G) region to the red (R) region. Emits light. The phosphor 36 absorbs part of the narrowband light N1 to emit fluorescence FL, and transmits the remaining narrowband light N1 that has not been absorbed. The narrowband light N1 that passes through the phosphor 36 is diffused by the phosphor 36. White light is generated by the mixed light of the transmitted narrow-band light N1 and the excited fluorescence FL. As the phosphor 36, for example, a YAG-based or BAM (BgMgAl ₁₀ O ₁₇ ) -based phosphor is used.

  The light source module 32 is a light source for blood vessel enhancement observation. In FIG. 5 showing the absorption spectrum of blood hemoglobin, the absorption coefficient μa of blood hemoglobin has a wavelength dependence, increases rapidly in the region where the wavelength is 450 nm or less, and has a peak in the vicinity of 405 nm. Yes. Moreover, although it is a low value compared with the wavelength of 450 nm or less, it also has a peak at wavelengths of 530 nm to 560 nm. When the observation site is irradiated with light having a wavelength having a large extinction coefficient μa, the blood vessel has a large absorption, so that an image having a large contrast between the blood vessel and the other portion is obtained.

  Further, as shown in FIG. 6, the light scattering characteristics of the living tissue also have wavelength dependence, and the scattering coefficient μS increases as the wavelength becomes shorter. Scattering affects the depth of light penetration into living tissue. That is, the greater the scattering, the more light that is reflected near the mucosal surface layer of the biological tissue and the less light that reaches the mid-depth layer. Therefore, the shorter the wavelength, the lower the depth of penetration, and the longer the wavelength, the higher the depth of penetration. In view of such light absorption characteristics of hemoglobin and light scattering characteristics of living tissue, the wavelength of light for blood vessel enhancement is selected.

  Since the 405 nm narrow-band light N2 emitted from the light source module 32 has a low depth of penetration, the absorption by the surface blood vessels is large. For this reason, the narrow-band light N2 is used as light for surface blood vessel enhancement. By using the narrowband light N2, the superficial blood vessel can be depicted with high contrast in the observation image. Further, the green component of white light emitted from the light source module 31 is used as the light for emphasizing the middle-layer blood vessel. In the absorption spectrum shown in FIG. 5, the light absorption coefficient gradually changes in the green region of 530 nm to 560 nm as compared with the blue region of 450 nm or less. It is not required to be. Therefore, as will be described later, a green component that is color-separated from white light by the G-color microcolor filter of the image sensor 44 is used for medium-depth blood vessel enhancement.

  The light source module 33 is a light source for oxygen saturation observation. In FIG. 5, the solid line absorption spectrum Hb shows the absorption spectrum of reduced hemoglobin not bonded to oxygen, and the one-dot chain line absorption spectrum HbO2 shows the absorption spectrum of oxidized hemoglobin bonded to oxygen. Thus, reduced hemoglobin and oxyhemoglobin have different light absorption characteristics, and a difference occurs in the light absorption coefficient μa except for the isosbestic point (intersection of each spectrum Hb and HbO 2) showing the same light absorption coefficient μa. If there is a difference in the extinction coefficient μa, even if the light having the same light intensity and the same wavelength is irradiated, the reflectance changes if the oxygen saturation changes. In the oxygen saturation observation mode, narrowband light N3 having a wavelength of 473 nm emitted from the light source module 33 is used as a wavelength having a difference in the absorption coefficient μa, and the oxygen saturation is measured.

  In FIG. 3, the light source control unit 34 controls the turning on / off of the laser diodes LD <b> 1 to LD <b> 3 and the amount of light via a driver 37 connected to the laser diodes LD <b> 1 to LD <b> 3. Specifically, the light source control unit 34 turns on the laser diodes LD <b> 1 to LD <b> 3 by giving a drive pulse of current from the driver 37. Then, by performing PWM (Pulse Width Modulation) control for controlling the duty ratio of the drive pulse, the drive current value is changed to control the light emission amount of each of the narrowband lights N1 to N3. The control of the drive current value may be PAM (Pulse Amplitude Modulation) control that changes the amplitude of the drive pulse.

  A light guide rod 40 and a reduction optical system 41 are provided on the downstream side of the optical path of the phosphor 36. The reduction optical system 41 is disposed in the vicinity of the receptacle connector 42 to which the light source connector 29b is connected. The light emitted from the light guide rod 40 is supplied to the incident end of the light guide 43 disposed in the light source connector 29b via the reduction optical system 41. Although not shown, each of the light source connector 29b and the receptacle connector 42 is provided with protective glass.

  The endoscope 11 includes a light guide 43, an imaging element 44, an analog processing circuit 45 (AFE: Analog Front End), and an imaging control unit 46. The light guide 43 is a fiber bundle obtained by bundling a plurality of optical fibers. When the light source connector 29 b is connected to the light source device 13, the incident end of the light guide 43 disposed on the light source connector 29 b faces the reduction optical system 41 of the light source device 13. The exit end of the light guide 43 located at the distal end portion 19 is branched into two at the front stage of the illumination window 22 so that light is guided to the two illumination windows 22.

  An irradiation lens 48 is disposed behind the illumination window 22. The light supplied from the light source device 13 is guided to the irradiation lens 48 by the light guide 43 and irradiated from the illumination window 22 toward the observation site. The irradiation lens 48 is a concave lens, and widens the divergence angle of the light emitted from the light guide 43. Thereby, illumination light can be irradiated to the wide range of an observation site | part.

  In the back of the observation window 23, an objective optical system 51 and an image sensor 44 are arranged. The image of the observation site enters the objective optical system 51 through the observation window 23 and is formed on the imaging surface 44 a of the imaging element 44 by the objective optical system 51.

  The imaging element 44 is composed of a CCD image sensor, a CMOS image sensor, or the like, and has an imaging surface 44a in which a plurality of photoelectric conversion elements constituting pixels such as photodiodes are arranged in a matrix. The image sensor 44 photoelectrically converts the light received by the imaging surface 44a and accumulates signal charges corresponding to the amount of received light in each pixel. The signal charge is converted into a voltage signal by an amplifier and read out. The voltage signal is output from the image sensor 44 to the AFE 45 as an image signal.

  The image pickup device 44 is a color image pickup device, and micro-color filters of three colors B, G, and R having spectral characteristics as shown in FIG. 7 are assigned to each pixel on the image pickup surface 44a. The white light emitted from the light source module 31 is split into three colors of B, G, and R by the micro color filter. The arrangement of the micro color filter is, for example, a Bayer arrangement.

  As shown in FIG. 8, the image sensor 44 performs an accumulation operation for accumulating signal charges in the pixels and a read operation for reading the accumulated signal charges within an acquisition period of one frame. As shown in FIG. 8A, in the normal light observation mode, the laser diode LD1 is turned on in synchronization with the accumulation operation timing of the image pickup device 44, and is composed of mixed light of narrowband light N1 and fluorescence FL as illumination light. White light (N1 + FL) is irradiated onto the observation site, and the reflected light is incident on the image sensor 44. The image sensor 44 separates white light with a micro color filter. The B pixel receives reflected light corresponding to the narrow-band light N1, the G pixel receives reflected light corresponding to the G component in the fluorescence FL, and the R pixel receives reflected light corresponding to the R component in the fluorescence FL. Receive light. The image sensor 44 sequentially outputs the image signals B, G, and R for one frame in which the pixel values of the B, G, and R pixels are mixed according to the frame rate in accordance with the readout timing. Such an imaging operation is repeated while the normal light observation mode is set.

  In the blood vessel enhancement observation mode, as shown in FIG. 8B, in addition to the light source module 31, the light source module 32 is turned on in accordance with the accumulation operation timing of the image sensor 44. When the light source modules 31 and 32 are turned on, the narrowband light N2 is added together with the white light similar to the normal light observation mode, and the mixed light (N1 + FL + N2) is irradiated onto the observation site as illumination light.

  As in the normal light observation mode, the illumination light in which the narrow band light N2 is added to the white light is split by the B, G, and R micro color filters of the image sensor 44. The B pixel of the image sensor 44 receives the narrowband light N2 in addition to the narrowband light N1. The G pixel receives the G component of the fluorescence FL. The R pixel receives the R component of the fluorescence FL. Even in the blood vessel enhancement observation mode, the image sensor 44 sequentially outputs the image signals B, G, and R according to the frame rate in accordance with the readout timing. Such an imaging operation is repeated while the blood vessel enhancement observation mode is set.

  In the oxygen saturation observation mode, as shown in FIG. 8C, first, the light source module 31 is turned on in accordance with the timing of the accumulation operation of the image sensor 44. When the light source module 31 is turned on, the observation site is irradiated with white light as in the normal light observation mode. In the next frame, the light source module 31 is turned off, the light source module 33 is turned on, and the narrow-band light N3 is irradiated to the observation site. Even in the oxygen saturation observation mode, the image sensor 44 sequentially outputs the image signals B, G, and R according to the frame rate in accordance with the readout timing.

  However, in the oxygen saturation observation mode, unlike the normal light observation mode and the blood vessel enhancement observation mode, the white light and the narrowband light N3 are alternately irradiated. Therefore, the image signals B and G corresponding to the white light in the first frame are used. , R are output, and in the next frame, the image signals B, G, R corresponding to the narrowband light N3 are output, and the information carried by the image signals B, G, R corresponding to each illumination light Also changes every other frame. Such an imaging operation is repeated while the oxygen saturation observation mode is set.

  In FIG. 3, the AFE 45 includes a correlated double sampling circuit (CDS), an automatic gain control circuit (AGC), and an analog / digital converter (A / D) (all not shown). The CDS performs a correlated double sampling process on the analog image signal from the image sensor 44, and removes noise caused by resetting the signal charge. AGC amplifies an image signal from which noise has been removed by CDS. The A / D converts the image signal amplified by AGC into a digital image signal having a gradation value corresponding to a predetermined number of bits and inputs the digital image signal to the processor device 12.

  The imaging control unit 46 is connected to the controller 56 in the processor device 12 and inputs a drive signal to the imaging device 44 in synchronization with a reference clock signal input from the controller 56. The imaging element 44 outputs an image signal to the AFE 45 at a predetermined frame rate based on the drive signal from the imaging control unit 46.

  In addition to the controller 56, the processor device 12 includes a DSP (Digital Signal Processor) 57, an image processing unit 58, a frame memory 59, and a display control circuit 60. The controller 56 includes a CPU, a ROM that stores a control program and setting data necessary for control, a RAM that loads the program and functions as a working memory, and the like. To control.

  The DSP 57 acquires an image signal output from the image sensor 44. The DSP 57 separates an image signal in which signals corresponding to B, G, and R pixels are mixed into B, G, and R image signals, and performs pixel interpolation processing on the image signals of the respective colors. In addition, the DSP 57 performs signal processing such as gamma correction and white balance correction on each of the B, G, and R image signals.

  The frame memory 59 stores image data output by the DSP 57 and processed data processed by the image processing unit 58. The display control circuit 60 reads the image processed image data from the frame memory 59, converts it into a video signal such as a composite signal or a component signal, and outputs it to the monitor 14.

  As shown in FIG. 9A, in the normal light observation mode, the image processing unit 58 uses the normal light based on the image signals B, G, and R color-separated into B, G, and R colors by the DSP 57. A display image for observation is generated. This display image is output to the monitor 14 as an observation image. The image processing unit 58 updates the display image every time the image signals B, G, and R in the frame memory 59 are updated.

  As shown in FIG. 9B, in the blood vessel enhancement observation mode, the image processing unit 58 generates a display image for blood vessel enhancement observation based on the image signals B, G, and R. The image signal B in the blood vessel enhancement observation mode includes information on the narrow band light N2 in addition to the B component of white light (including a part of the narrow band light N1 and the fluorescence FL). It is drawn with high contrast. In lesions such as cancer, compared to normal tissues, there is a feature in the pattern of blood vessels such as the density of superficial blood vessels tend to be high, so in blood vessel enhancement observation for the purpose of tumor quality discrimination, It is preferable that the superficial blood vessel is clearly depicted.

  When emphasizing the superficial blood vessels, for example, a superficial blood vessel region is extracted based on the image signal B, and contour enhancement processing or the like is performed on the extracted region. Then, the image signal B that has undergone the contour enhancement processing is combined with a full-color image generated from the image signals B, G, and R. By doing so, the superficial blood vessels are more emphasized. The same processing may be performed on the middle- and deep-layer blood vessels in addition to the surface blood vessels. When emphasizing the middle-and-deep blood vessel, the region of the middle-and-deep blood vessel is extracted from the image signal G that includes a lot of information about the middle-and-deep blood vessel, and contour enhancement processing is performed on the extracted region. The completed image signal G is combined with a full-color image generated from the image signals B, G, and R.

  The display image for blood vessel enhancement observation is generated based on the three color image signals B, G, and R, as in the case of normal light observation, so that the observation site can be displayed in full color. The image signal B in the observation mode has a higher blue density than the image signal B in the normal light observation mode. For this reason, when a display image for blood vessel enhancement observation is generated, color correction may be performed so that the same color as that of the display image for normal light observation is obtained. The image processing unit 58 generates a display image for blood vessel enhancement observation every time the image signals B, G, and R in the frame memory 59 are updated.

  As a method for generating a display image for blood vessel enhancement observation, the image signal R is generated using only two colors of the image signals B and G without using the image signal R, and the image signal B is generated by the B channel and the G channel of the monitor 14. In addition, a method of displaying the observation region in a pseudo color, such as a method of assigning a signal corresponding to the image signal G to the R channel of the monitor 14, may be employed.

  As shown in FIG. 9C, in the oxygen saturation observation mode, the image processing unit 58 is acquired under the image signals G1 and R1 acquired under white light and the narrowband light N3. Based on the obtained image signal B2, oxygen saturation calculation processing is performed. The pixel value of the image signal B2 includes blood volume information in addition to oxygen saturation. In order to obtain the oxygen saturation more accurately, it is necessary to separate blood volume information from the pixel value of the image signal B2. The image processing unit 58 performs an inter-image calculation with the image signal B using the image signal R showing a high correlation with the blood volume, and separates oxygen saturation and blood volume information.

  Specifically, the image processing unit 58 collates the pixel values at the same position of the image signals B2, G1, and R1, and determines the signal ratio B2 / G1 between the pixel value of the image signal B2 and the pixel value of the image signal G1. The signal ratio R1 / G1 between the pixel value of the image signal R1 and the pixel value of the image signal G1 is obtained. The image signal G1 is used as a reference signal representing the brightness level of the observation region in order to normalize the pixel values of the image signal B2 and the image signal R1. Then, based on a table in which the correlations between the signal ratios B2 / G1 and R1 / G1, the oxygen saturation and the blood volume are stored in advance, the oxygen saturation from which the blood volume information is separated is calculated. Then, the full color image generated based on the image signals B1, G1, and R1 is subjected to color conversion in accordance with the calculated oxygen saturation value to generate a display image for oxygen saturation observation.

  In FIG. 10, the light source module 31 includes a light emitting element 66 and a condenser lens 68. In the light emitting element 66, a laser diode LD1 as a semiconductor chip is attached to one surface of a disk-shaped stem 66a serving as a support, and the laser diode LD1 is covered with a resin-made cylindrical transparent cap 66b. A lead wire 66c extends from the back surface of the stem 66a. As indicated by the broken line, the light emitting element 66 and the condenser lens 68 are accommodated in a case 67, and the case 67 is provided with a connecting portion 67a to which the incident end of the optical fiber 39d is connected. That is, the light source module 31 is a so-called receptacle type semiconductor light source.

  The laser diode LD1 is a semiconductor chip in which a P layer made of a P-type semiconductor and an N layer made of an N-type semiconductor are joined with an active layer interposed therebetween, and emits laser light from the active layer by laser oscillation. Laser light is highly divergent, but is divergent light whose beam shape spreads from the light emitting point in a substantially conical shape. The condensing lens 68 is disposed opposite to the incident end of the optical fiber 39d, and the laser light emitted from the laser diode LD1 is condensed by the condensing lens 68 on the incident end of the optical fiber 39d.

  Similarly to the light source module 31, the light source modules 32 and 33 also collect the light emitting elements having the laser diodes LD2 and LD3 and the laser light emitted from the laser diodes LD2 and LD3 at the incident ends of the optical fibers 39a and 39b. And an optical lens. Since the configuration of the stem and the like of the light emitting element is the same as that of the light emitting element 66 of the light source module 31, the illustration is omitted. In addition, it is good also as a structure which accommodated the condensing lens in the transparent cap of a light emitting element.

  In FIG. 11, the phosphor 36 is filled in a cylindrical protective case 62 having a light shielding property. An insertion hole into which the emission end of the optical fiber 39g is inserted is formed at the center of the phosphor 36. The optical fiber 39g is inserted into the insertion hole with a connection ferrule (not shown) attached to the exit end. The phosphor 36 is obtained by dispersing and solidifying a powdery fluorescent material in a binder made of a resin material, and has a cylindrical shape following the protective case 62. Since the fluorescent material is dispersed, the emission point of the excited fluorescence FL is the entire emission surface 69 of the phosphor 36. Further, since the narrow-band lights N1 to N3 that pass through the phosphor 36 are also diffused in the phosphor 36 by the light diffusing action of the binder, the entire light-emitting surface 69 of the narrow-band lights N1 to N3 becomes a light emitting point.

  A light guide rod 40 for changing the divergence angle of incident light is joined to the phosphor 36. The phosphor 36 and the light guide rod 40 are joined so that the centers of the light emitting surface 69 of the phosphor 36 and the incident end surface 70 of the light guide rod 40 coincide, and the light emitting surface 69 and the incident end surface 70 are optically joined. ing. Specifically, the distance between the light emitting surface 69 and the incident end surface 70 when the light emitting surface 69 and the incident end surface 70 are brought into contact is determined by the wavelength of light guided from the light emitting surface 69 to the incident end surface 70. In order to obtain a short interval, the surface is made extremely flat by mirror polishing, and then both are joined. In the case of this example, as shown in FIG. 4, since the shortest wavelength of the fluorescence FL and the narrowband light N1 to N3 is about 350 nm, the distance between the light emitting surface 69 and the incident end surface 70 is, for example, 350 nm or less. ing. The case where the light emitting surface 69 and the incident end surface 70 are bonded using an optically transparent adhesive is also included in the optical bonding. In addition, after the light emitting surface 69 and the incident end surface 70 are optically bonded, the periphery of the light emitting surface 69 and the incident end surface 70 may be reinforced with an adhesive.

  The light guide rod 40 has the incident end face 70, an exit end face 71 that emits light incident on the entrance end face 70, and four side surfaces 72 that connect the entrance end face 70 and the exit end face 71. The light guide rod 40 is made of solid transparent glass or the like, has a square cross-sectional shape orthogonal to the optical axis C of the light guide 43, and the side surface 72 has a larger area of the emission end surface 71 than the incident end surface 70. Has a tapered shape inclined with respect to the optical axis C. As shown in FIG. 12, the light guide rod 40 reflects light incident from the incident end face 70 in the direction of the light guide 43 while reducing the divergence angle while totally reflecting the light on the four side faces 72 serving as the interfaces with the air. Propagate and exit from the exit end face 71. More specifically, the light incident from the incident end face 70 at the divergence angle β1 is totally reflected twice at the side surface 72 at the incident angles γ1 and γ2, and the output end face 71 at the divergence angle β2 (β2 <β1) smaller than β1. Exits from.

  The divergence angle decreases as the number of reflections on the side surface 72 increases, and the number of reflections of incident light on the side surface 72 increases as the length (full length) of the light guide rod 40 in the optical axis C direction increases. Furthermore, the larger the inclination angle α (see FIG. 15) of the side surface 72 with respect to the optical axis C, the larger the reduction amount of the divergence angle by one reflection.

  The total length and the inclination angle α of the light guide rod 40 are such that the divergence angle of light incident on the light guide 43 through the reduction optical system 41 is the NA (numerical aperture) of the optical fiber that becomes the strand of the light guide 43 that is a fiber bundle. Aperture). As is well known, an optical fiber is composed of a core having a high refractive index and a clad having a low refractive index disposed around the core, and light incident from the incident end of the optical fiber is at the boundary between the core and the clad. It propagates in the direction of the optical axis C while being totally reflected. In order to propagate the light, it is necessary to make the light incident on the incident end of the optical fiber at an incident angle that satisfies the total reflection condition.

  NA is an index representing how much light can be collected by the optical fiber, and is defined by the sine of the maximum light receiving angle θmax (NA = sin θmax). The larger the maximum light receiving angle θmax, the larger the NA value. If the incident angle of the light beam incident on the optical fiber is equal to or smaller than the maximum light receiving angle θmax, total reflection occurs at the boundary between the core and the clad within the optical fiber, so that the incident light propagates in the optical axis C direction of the light guide 43. Light is guided. When the incident angle exceeds the maximum light receiving angle θmax, the incident light is transmitted without being totally reflected, so that the light guide 43 is not guided. Incident light that is not guided becomes a light transmission loss. In order to reduce this light transmission loss, the light guide rod 40 and the reduction optical system 41 restrict the beam divergence angle of the light source module 31 to be equal to or less than the maximum light reception angle θmax. The reduction optical system 41 condenses the light emitted from the light guide rod 40 on the light guide 43.

  As shown by hatching, a reflection film 73 is formed on the entire circumference of the side surface 72 in the range from the incident end face 70 to the middle of the exit end face 71. The reflection film 73 is formed by coating the side surface 72 with a dielectric multilayer film by vapor deposition. If the reflective film 73 is a dielectric multilayer film, a reflectivity of 99% or more can be achieved. Instead of coating the dielectric multilayer film, the reflective film 73 may be formed by coating a metal film such as aluminum by vapor deposition or bonding a metal film. Although metal films and metal films are somewhat inferior in reflectance compared to dielectric multilayer films, manufacturing costs can be reduced.

  FIG. 13 shows a comparison table of reflectance and manufacturing cost according to the type of the reflective film 73. “A” indicates the most excellent one, and “C” indicates the inferior one. A dielectric multilayer film is superior to others in terms of reflectivity, but the manufacturing cost is the highest. The metal film is average in both reflectance and manufacturing cost. A metal film is the cheapest to manufacture, but is inferior in terms of reflectivity. For the purpose of improving the light utilization efficiency, the reflective film 73 is most preferably a dielectric multilayer film.

  As shown in FIG. 14A, when the reflection film 73 is not provided, the incident angle γ11 that is smaller than the critical angle θc at the side surface 72 of the light incident on the light guide rod 40 out of the light incident on the incident end surface 70. The light incident at (γ11 <θc) is transmitted through the side surface 72 and radiated into the air, and becomes so-called leakage light. As shown in FIG. 14B, the reflection film 73 reflects light incident at an incident angle γ11 smaller than the critical angle θc, which normally becomes leaky light and reduces the light utilization efficiency, thereby guiding the light. It is provided for propagating through the rod 40. On the other hand, light having an incident angle γ12 (γ12 ≧ θc) equal to or greater than the critical angle θc is propagated through the light guide rod 40 by repeating total reflection on the side surface 72 regardless of the presence or absence of the reflection film 73.

  In FIG. 14B, the light incident from the incident end face 70 at the incident angle γ11 smaller than the critical angle θc is repeatedly reflected by the reflective film 73, and the area of the exit end face 71 becomes larger than the incident end face 70. Thus, by the action of widening the divergence angle of the side surface 72 inclined with respect to the optical axis C, the incident angle to the side surface 72 gradually increases (γ11 <γ21 <γ31 <γ41), and is greater than the critical angle θc (γ41 ≧ θc). And the light guide rod 40 propagates toward the light guide 43 without the help of the reflective film 73. For this reason, the reflective film 73 does not need to be formed over the entire light guide rod 40, and is a reflection in which the incident angle to the side surface 72 of the light incident from the incident end face 70 with an incident angle smaller than the critical angle θc is equal to or greater than the critical angle θc. It suffices if it is formed in a range from the incident end face 70 toward the exit end face 71 as long as the number of times can be obtained.

With reference to FIG. 15, the conditions of the formation length L from the incident end surface 70 of the reflective film 73 are considered. First, it is known that etendue, which is the product of the light emitting area and divergence angle of a light source, is preserved. Assuming that the area of the light emitting surface 69 of the phosphor 36 and the area of the incident end face 70 of the light guide rod 40 are substantially the same, the etendue at the incident end face 70 of the light guide rod 40 and the end of the reflecting film 73 on the exit end face 71 side. The relationship with the etendue of the cross section 74 of the light guide rod 40 parallel to the incident end face 70 is as follows. That is, when the area of the incident end face 70 is Sa, the area of the cross section 74 is Sb, the divergence angle of light incident from the light emitting surface 69 on the incident end face 70 is Ωa, and the divergence angle of light on the cross section 74 is Ωb, The following equation (1a) holds.
Sa · sin ² (Ωa / 2) = Sb · sin ² (Ωb / 2) (1a)
Here, the divergence angle of the light emitted from the light emitting surface 69 is π (unit: rad), and the light emitting surface 69 and the incident end face 70 are optically joined. Is incident on. Therefore, Ωa = π. Therefore, the expression (1a) is rewritten to the following expression (1b).
Sa = Sb · sin ² (Ωb / 2) (1b)

When the refractive index of the light guide rod 40 is n, the critical angle θc can be expressed by the following equation (2) from Snell's law.
θc = sin ⁻¹ (1 / n) (2)

When the inclination angle of the side surface 72 with respect to the optical axis is α, the incident angle γ of the light having the divergence angle Ωb to the side surface 72 is expressed by the following equation (3).
γ = π / 2− (Ωb / 2−α) (3)
If the light having the incident angle γ is totally reflected by the side surface 72 and propagates in the direction of the light guide 43, it can serve as the reflection film 73. That is, the incident angle γ may be equal to or greater than the critical angle θc, and can be expressed by the following formula (4a).
γ ≧ θc (4a)
Substituting the right side of equation (3) into γ of equation (4a) and solving for Ωb / 2, equation (4a) becomes the following equation (4b).
Ωb / 2 ≦ π / 2 + α−θc (4b)
Since sin (Ωb / 2) = (Sa / Sb) ^1/2 from the equation (1b), the equation (4b) becomes the following equation (4c) after all.
From equation (4b), sin (Ωb / 2) ≦ sin (π / 2 + α−θc)
(Sa / Sb) ^1/2 ≦ cos (θc−α) (4c)
Solving this for Sb, equation (4c) can be expressed by the following equation (4d).
Sb ≧ Sa / cos ² (θc−α) (4d)

On the other hand, assuming that the lengths of the sides of the incident end face 70 and the cross section 74 are da and db, db is the formation length L of the reflection film 73 and the inclination angle α of the side surface 72 with respect to the optical axis as shown in the following equation (5a). It can be expressed as
db = da + 2L · tan α (5a)
When equation (5a) is solved for L, the following equation (5b) is obtained.
L = (db−da) / (2 tan α) (5b)

Further, since Sa = da ² and Sb = db ² , the expression (4d) becomes the following expression (4e).
db ≧ da / cos (θc−α) (4e)
When this equation (4e) is modified, the following equation (4f) is obtained.
(Db-da) / (2 tan α) ≧ da · [{1 / cos (θc−α)} − 1] / (2 tan α) (4f)

The left side of equation (4f) is nothing but the right side of equation (5b). Therefore, the conditional expression for the formation length L of the reflective film 73 can be expressed by the following expression (6).
L ≧ da · [{1 / cos (θc−α)} − 1] / (2 tan α) (6)
The reflective film 73 is formed with a length L equal to or more than the right side of the formula (6), more preferably equal to the right side of the formula (6).

If the formation length L of the reflection film 73 is shorter than the right side of the equation (6), the incident angle of the light incident from the incident end face 70 on the side surface 72 at an incident angle smaller than the critical angle θc does not exceed the critical angle θc. Since the reflection film 73 is eliminated, light leaks like the light having the incident angle γ11 in FIG. On the other hand, when the formation length L of the reflection film 73 is equal to or larger than the right side of the formula (6), the incident angle to the side surface 72 of the light incident from the incident end face 70 with an incident angle smaller than the critical angle θc is equal to or larger than the critical angle θc. In spite of this, even in subsequent reflections, the light is reflected by the reflective film 73 that is inferior in reflectance to the side surface 72, so that spectral loss occurs. In the case of the reflective film 73 having a relatively low reflectance, the light loss is particularly large. In addition, an extra reflective film 73 that does not contribute to the purpose of making the incident angle of the light incident from the incident end face 70 at the incident angle smaller than the critical angle θc to the side surface 72 equal to or larger than the critical angle θc, and on the contrary, causes light loss. It takes useless cost to form. Therefore, as shown in the following formula (7), the reflective film 73 is more preferably formed with a length L equal to the right side of the formula (6).
L = da · [{1 / cos (θc−α)} − 1] / (2 tan α) (7)
When the above concept is similarly applied to the equation (4d), the following equation (8) is obtained.
Sb = Sa / cos ² (θc−α) (8)

  The formation length L of the reflection film 73 when the refractive index of the light guide rod 40 is n = 1.46, da = 1 mm, and the divergence angle of the light emitted from the emission end face 71 is 10 ° in half width at half maximum. FIG. 16 is a table showing the results obtained by calculating from the equation (7) and the total length of the light guide rod 40. From the table, the greater the inclination angle α of the side surface 72 with respect to the optical axis C, the shorter the total length of the light guide rod 40, and the shorter the formation length L of the reflective film 73. The formation length L of the reflective film 73 with respect to the total length of the light guide rod 40 is about 3% to about 4%, and is about 1/30 to about 1/25 of the total length of the light guide rod 40. It can be seen that it is sufficient to form the reflective film 73.

  Hereinafter, the operation of the above configuration will be described. When performing an endoscopic diagnosis, the endoscope 11 is connected to the processor device 12 and the light source device 13, the processor device 12 and the light source device 13 are turned on, and the endoscope system 10 is activated.

  The insertion part 16 of the endoscope 11 is inserted into the subject's digestive tract, and observation in the digestive tract is started. In the normal light observation mode, the light source module 31 is turned on, and the observation site is irradiated with white light in which the narrowband light N1 emitted from the laser diode LD1 and the fluorescence FL emitted from the phosphor 36 are mixed.

  The observation site is imaged by the imaging element 44 during the white light irradiation, and the DSP 57 generates B, G, and R image signals. The image processing unit 58 generates a display image for normal light observation based on the B, G, and R image signals. The display control circuit 60 converts the display image for normal light observation into a video signal and displays it on the monitor 14.

  When blood vessel enhancement observation is performed, a mode switching operation is performed by the operation input unit 15, and the processor device 12 is set to the blood vessel enhancement observation mode.

  In the blood vessel enhancement observation mode, the light source module 32 is turned on in addition to the light source module 31, and the white light and the narrowband light N2 are simultaneously irradiated onto the observation site. While the white light and the narrow-band light N2 are irradiated, the observation site is imaged by the imaging device 44, and B, G, and R image signals are generated by the DSP 57. In the blood vessel enhancement observation mode, the image processing unit 58 generates a display image for blood vessel enhancement observation based on the B, G, and R image signals. The display control circuit 60 converts a display image for blood vessel enhancement observation into a video signal and displays it on the monitor 14. Since the spot irradiated with the beam at the observation site is substantially the same for the white light and the narrow-band light N2, a display image without color unevenness is obtained. In the blood vessel enhancement observation mode, since the image signal B includes the narrowband light N2 in addition to the B component of white light, the superficial blood vessels are depicted with high contrast in the observation image.

  When performing oxygen saturation observation, mode switching operation is performed from the operation input part 15, and the operation mode of the processor apparatus 12 is set to oxygen saturation observation mode.

  In the oxygen saturation observation mode, the light source module 31 and the light source module 33 are alternately turned on every frame, and white light and narrowband light N3 are alternately irradiated on the observation site. The image sensor 44 sequentially outputs image signals corresponding to the white light and the narrowband light N3 to the DSP 57. The DSP 57 generates an image signal of each color of B1, G1, and R1 based on the image signal acquired under the white light, and generates an image signal of B2 based on the image signal acquired under the narrowband light N3. Is generated. The image processing unit 58 calculates the oxygen saturation by performing an inter-image calculation of the image signals B2, G1, and R1. Then, the full color image generated based on the image signals B1, G1, and R1 is subjected to color conversion in accordance with the calculated oxygen saturation value to generate a display image for oxygen saturation observation.

  If the light emitting surface 69 of the phosphor 36 and the incident end surface 70 of the light guide rod 40 are not optically joined, the air layer between the light emitting surface 69 and the incident end surface 70 compares the light emitted from the light emitting surface 69. The high angle component having a large divergence angle is not incident on the incident end face 70 and results in light loss. However, in this example, the light emitting surface 69 and the incident end face 70 are optically joined. Including the light, the light emitted from the light emitting surface 69 is incident on the incident end face 70 without any surplus. Further, light having an incident angle smaller than the critical angle θc, which is normally leaked light, is reflected by the reflective film 73, so that the incident angle to the side surface 72 becomes light having a critical angle θc or more, and the light in the light guide rod 40 is lighted. Propagated toward the guide 43. Compared to the case where the light emitting surface 69 and the incident end surface 70 are not optically joined and the side surface 72 is not provided with the reflective film 73, the light utilization efficiency is increased by about 20%. Therefore, a sufficient amount of light for observation can be obtained with a relatively low driving power.

  By setting the formation length L of the reflective film 73 to be equal to or longer than the right side of the formula (6), light having an incident angle smaller than the critical angle θc that is normally leaked light can be confined and propagated in the light guide rod 40. . Furthermore, if the formation length L of the reflection film 73 is made equal to the right side of the equation (6), the light loss caused by the reflection by the reflection film 73 can be minimized.

In the said embodiment, although the cross-sectional shape orthogonal to an optical axis has illustrated the light guide rod 40 with a square, the shape of a light guide rod is not limited to this. A light guide rod having a circular and substantially conical cross section may be used. In the case of a substantially conical light guide rod, the expression (6) is changed to the following expression (9) using the radius ra of the incident end face.
L ≧ ra · [{1 / cos (θc−α)} − 1] / tan α (9)
Similarly, Expression (7) is changed to the following Expression (10).
L = ra · [{1 / cos (θc−α)} − 1] / tan α (10)
In addition, a light guide rod having a rectangular or polygonal cross-sectional shape orthogonal to the optical axis may be used. Even when the cross-sectional shape orthogonal to the optical axis is not square, the same effect as the above embodiment can be obtained.

  The emission wavelength ranges of the narrowband light N1 to N3 and the fluorescence FL are not limited to the above examples, and can be changed as appropriate. For example, treatment light having a center wavelength of 635 nm for killing the tumor may be used as the narrowband light N3. Alternatively, a phosphor that emits fluorescence FL in the infrared wavelength region may be used.

  In the above embodiment, a configuration in which a light source for blood vessel enhancement observation and oxygen saturation observation is added to the configuration in which the phosphor 36 is disposed between the light emitting element 66 and the light guide rod 40 is exemplified. There is no need for a light source for observation or oxygen saturation observation. Moreover, although the thing which has a laser diode is illustrated as a light emitting element, you may use the light emitting element which has LED, EL, etc. other than a laser diode. Even when a light-emitting element having an LED, an EL, or the like is used, the same effect as in the above embodiment can be obtained.

  In the above-described embodiment, an example of a simultaneous method in which white light is color-separated by a micro color filter and a plurality of color images are simultaneously acquired using a color image sensor provided with B, G, and R micro color filters is described. However, the present invention may be applied to a frame sequential method in which images of respective colors are sequentially acquired using a monochrome imaging element not provided with a color filter.

  In the above embodiment, the example in which the light source device and the processor device are configured separately is described, but the two devices may be configured integrally. The present invention also provides an ultrasonic endoscope in which an image pickup element and an ultrasonic transducer are built in the tip, an industrial endoscope for inspecting cracks in piping, a rod-shaped rigid endoscope with a hard insertion portion, and the like. The present invention can also be applied to a light source device that supplies illumination light to an endoscope of the form and an endoscope system using the same.

DESCRIPTION OF SYMBOLS 10 Endoscope system 11 Endoscope 12 Processor apparatus 13 Light source apparatus 31-33 Light source module 34 Light source control part 36 Phosphor 40 Light guide rod 43 Light guide 44 Imaging element 46 Imaging control part 56 Controller 58 Image processing part 66 Light emitting element 69 Light emitting surface 70 Incident end surface 71 Outgoing end surface 72 Side surface 73 Reflective film LD1-LD3 Laser diode

Claims (11)

In a light source device that supplies illumination light to a light guide of an endoscope,
A light emitting device composed of a semiconductor;
A phosphor having a light emitting surface that emits mixed light of the light emitted from the light emitting element and the fluorescence excited by the light;
An incident end face and an exit end face; and a side face that connects the incident end face and the exit end face and guides mixed light incident from the incident end face to the exit end face while totally reflecting the mixed light. A light guide rod having a tapered shape in which the side surface is inclined with respect to the optical axis so that the area of the emission end surface is increased;
The light emitting surface and the incident end surface are optically bonded,
In the range from the incident end face to the exit end face, a reflection film is formed on the entire circumference of the side face.   2. The light source device according to claim 1, wherein the reflection film is formed by any one of a dielectric multilayer film coating, a metal film coating, and a metal film adhesion.   The light source device according to claim 2, wherein the reflective film is formed by coating the dielectric multilayer film. The length of formation of the reflective film from the incident end surface when the critical angle of the side surface of the light incident on the light guide rod is θc, the inclination angle of the side surface with respect to the optical axis is α, and the area of the incident end surface is Sa. The length Sb of the cross section of the light guide rod parallel to the incident end face at the end of the reflecting film on the output end face side satisfies the following conditional expression 1. The light source device according to claim 1.
Conditional expression 1: Sb ≧ Sa / cos ² (θc−α) 5. The light source device according to claim 4, wherein the formation length is a length such that an area Sb of the cross section satisfies Equation 1 below.
Equation 1: Sb = Sa / cos ² (θc−α)   The light source device according to claim 1, wherein the light guide rod has a square cross section perpendicular to the optical axis. When the critical angle at the side surface of the light incident on the light guide rod is θc, the inclination angle with respect to the optical axis of the side surface is α, and the length of the side of the incident end surface is da, the reflective film has the following conditional expression: The light source device according to claim 6, wherein the light source device has a formation length L from the incident end surface that satisfies 2.
Conditional expression 2: L ≧ da · [{1 / cos (θc−α)} − 1] / (2 tan α) The light source device according to claim 7, wherein the reflective film has the formation length L that satisfies Equation 2 below.
Equation 2: L = da · [{1 / cos (θc−α)} − 1] / (2 tan α) The light emitting element emits excitation light having a central wavelength of 445 nm,
The phosphor is excited by the excitation light and emits fluorescence in a wavelength region extending from a green region to a red region,
The light source device according to claim 1, wherein white light is generated as mixed light by excitation light and fluorescence.   The light source device according to claim 1, wherein the light emitting element includes a laser diode or an LED. An endoscope with a built-in light guide for guiding illumination light;
In an endoscope system having a light source device that supplies illumination light to the light guide,
The light source device includes a light emitting element made of a semiconductor,
A phosphor having a light emitting surface that emits mixed light of the light emitted from the light emitting element and the fluorescence excited by the light;
An incident end face and an outgoing end face; and a side face that connects the incident end face and the outgoing end face and guides light incident from the incident end face to the outgoing end face while totally reflecting the incident end face; A light guide rod having a tapered shape in which the side surface is inclined with respect to the optical axis so as to increase the area of the end surface;
The light emitting surface and the incident end surface are optically bonded,
An endoscope system, wherein a reflective film is formed on the entire periphery of the side surface in a range from the incident end surface to the exit end surface.

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