LIGHT SOURCE APPARATUS AND ENDOSCOPE APPARATUS WITH THE LIGHT SOURCE APPARATUS

A light source apparatus includes an optical fiber that guides light source light emitted from a light source, and a light detection section that detects a quantity of the light source light guided by the optical fiber. The light detection section includes a light detector that outputs a signal indicating a quantity of incoming light, a light extraction section that is provided at a part of the optical fiber and extracts a part of light source light guided by the optical fiber as detected light, and a detected light optimization section that changes the detected light extracted from the optical fiber by the light extraction section into light having a light characteristic appropriate for detection of a quantity of light by the light detector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light source apparatus.

2. Description of the Related Art

Specifically, the light source apparatus has the following structure. A step-index type optical fiber including a core and a cladding has an exposed portion of the core where a portion of the cladding is removed. The exposed portion of the core is provided with an irregular surface to scatter light. A photodiode is arranged in the proximity of the exposed portion of the core to detect scattered light leaking out from the exposed portion.

BRIEF SUMMARY OF THE INVENTION

A light source apparatus according to the present invention comprises at least one light source, at least one optical fiber that guides light source light emitted from the light source, and a light detection section that detects a quantity of the light source light guided by the optical fiber. The light detection section comprises a light detector that outputs a signal indicating a quantity of incoming light, a light extraction section that is provided at a part of the optical fiber and extracts a part of light source light guided by the optical fiber as detected light, and a detected light optimization section that changes the detected light extracted from the optical fiber by the light extraction section into light having a light characteristic appropriate for detection of a quantity of light by the light detector.

Advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

DETAILED DESCRIPTION OF THE INVENTION

As shown inFIG. 1, the light source apparatus of the present embodiment comprises a light source12, an optical fiber18that guides light source light emitted from the light source12, and a light detection section20that detects a quantity of the light source light guided by the optical fiber18.

The light source12includes a light emitting element14that emits light, and a lens16that couples light source light emitted from the light emitting element14to the optical fiber18.

The light source apparatus also includes a controller28that controls the light emitting element14based on a detection signal output from the light detection section20. In order to control the light emitting element14, the controller28includes an electric circuit that operates the detection signal, and the electric circuit includes a processor (including hardware) that calculates the detection signal.

The light emitting element14may comprise, for example, a semiconductor laser. A semiconductor laser is a solid light source apparatus that includes a semiconductor through which electricity is sent to emit laser light, and a variety of semiconductor lasers having various wavelengths, from ultraviolet light to infrared light, have become commercially practical. A semiconductor laser has advantages, such as small size and lower power consumption, and in recent years, semiconductor lasers with a high luminance and semiconductor lasers that oscillate at a novel wavelength have been widely developed. Generally, laser light is emitted at a line spectrum of a narrow wavelength. The width of a spectrum line is normally less than a few nm for a semiconductor laser. Semiconductor lasers include an edge light-emitting type semiconductor laser (a stripe laser) that emits light from the cleavage plane of a wafer, a plane light-emitting type semiconductor laser that emits light from the surface of a wafer (a vertical-oscillator type vertical cavity surface emitting laser), and the like. Furthermore, a hybrid semiconductor laser has been commercially practical, which is represented by a second harmonic type semiconductor laser (SHG semiconductor laser) that makes an oscillation wavelength of the semiconductor laser half by combining a nonlinear crystal with the emission section of the semiconductor laser.

For the light emitting element14, a device that emits non-interferential light, represented by an LED, may be used.

In the present embodiment, the optical fiber18is used to guide light source light from the light source12. Various optical fibers in practical use can be used as the optical fiber18. In the present embodiment, a multi-mode laser is used as the light emitting element14; thus, a multi-mode type optical fiber is used to effectively take into and guide light from the multi-mode laser. The multi-mode type optical fiber18may comprise, for example, a step index (SI) fiber having a core18aand a cladding18bas shown inFIG. 2, which generally has a core diameter from several tens of micrometers to200micrometers. The refractive index of the core18aof the optical fiber18is set higher than the refractive index of the cladding18b. A core diameter of the optical fiber18is preferably thick from the viewpoint of improving the incoming light rate of light source light emitted from the light emitting element14, on the other hand it is preferably small for flexibility and diameter reduction. For this reason, it can be selected based on the light emitting element14to be used, an optical structure of the part connecting the light emitting element14with the optical fiber18, the thickness of an apparatus into which the optical fiber18is incorporated, such as the insertion section of an endoscope, input/output conditions of an optical coupler that is described later, and the like. In the present embodiment, an optical fiber having a core diameter of 50 μm and a cladding diameter of 125 μm is used as the optical fiber18that is mounted in the insertion section of the endoscope, and guides light source light to a light emitting section. The optical fiber18is not limited to those mentioned herein; it maybe a single-mode fiber. The optical fiber18may be a grated index (GI) fiber.

A block diagram of the light detection section20is shown inFIG. 2. As shown inFIG. 2, the light detection section20comprises a light detector26that outputs a signal indicating a quantity of incoming light, a light extraction section22that is provided at a part of the optical fiber18and extracts a part of light source light guided by the optical fiber18as detected light, and a detected light optimization section24that changes the detected light extracted from the optical fiber18by the light extraction section22into light having an optical characteristic appropriate for the detection of a quantity of light by the light detector26.

To detect a quantity of light by the light detector26, the light extraction section22provided at the optical fiber18separates a part of light source light guided by the optical fiber18as detected light and passes it to the detected light optimization section24so that an appropriate quantity of detected light enters the light detector26. The detected light optimization section24causes the detected light received from the light extraction section22to enter the light detector26. At this time, the optical characteristic of the detected light is changed so as to facilitate the detection by the light detector26, in other words, so as to effectively detect light. The detected light that has exit from the detected light optimization section24enters the light detector26and is converted into an electrical signal, etc. to become a detection signal.

A specific structure of the light detection section20is shown inFIG. 3. As shown inFIG. 3, the optical fiber18is provided with a jacket (coating)18caround the cladding18b. The jacket18cserves to enhance the strength of the optical fiber18. An opening is formed at a part of the jacket18cto partially expose the cladding18b. A light extraction region30as the light extraction section22is formed at the exposed portion of the cladding18b. The light extraction region30comprises a region where the thickness of the cladding18bis locally reduced. A diffusion member32is provided at the concave part formed by forming the light extraction region30.

A photodiode (PD)36serving as the light detector26is disposed above and in the radial direction of the optical fiber18with respect to the diffusion member32. The PD36is disposed and supported so as to face the diffusion member32.

The light extraction region30spreads over a predetermined angle range at a cross section perpendicular to the axis of the optical fiber18. The thickness of the cladding18bin the light extraction region30is adjusted so as to allow a minimum quantity of detected light required for detection of a quantity of light performed by the PD36to leak out. For this reason, the thickness of the cladding18bin the light extraction region30is preferably thinner than a thickness of a region where light (evanescent light) leaks out from the core18aof the optical fiber18to the cladding18b.

It is known that when light propagates through media of different refractive indices, if an energy reflectance in total reflection is calculated, reflected light energy is equal to incoming light energy, and an evanescent wave slightly leaks on the opposite side of the boundary plane. Since the enter depth of the evanescent wave component is approximated on the order of π/2π (λ is a wavelength in the refractive index of the propagation region), the region where the evanescent wave leaks out from the core18ato the cladding18bis λ/2π from the outer periphery of the core18a. Thus, the thickness of the cladding in the light extraction region30is preferably thinner than λ/2π.

The light extraction region30spreads along the axis of the optical fiber18for a range of a predetermined length. For example, the length of the light extraction region30along the axis of the optical fiber18is preferably as long as or longer than the incident aperture of the PD36. If the opening is set at such a dimension, various modes of the light guided by the optical fiber18are emitted from the light extraction region30; accordingly, less influence by the modes, compared to the case where only specific modes of light are emitted, allows improved stability in the detection of a quantity of light.

The diffusion member32is constituted from a number of diffusing elements consisting of transparent and high-refractive particles, such as alumina particles and SiO2particles, for example, bound together by a resin. In other words, the diffusion member32is constituted by a member in which a number of diffusion elements are diffused in a resin. The diffusion member32may be provided so as to fill the concave part formed as a result of forming the light extraction region30. The surface of the diffusion member32may be bowed in a sphere shape. The resin binding a number of diffusing elements preferably has a refractive index halfway between the refractive index of the cladding18band the refractive index of air. Thus, the interface reflection between the cladding18band the diffusion member32is reduced, and the light extracted from the core18aof the optical fiber18through the light extraction region30is guided to the PD36with less loss.

A reflector34is disposed around the space from the light extraction region30to the PD36. The reflector34has a cylindrical shape and its inner surface is a mirror. The reflector34is not limited thereto; it may be a structure having a curved mirror that collects more light to the PD36.

The diffusion member32and the reflector34constitute a detected light optimization section that changes detected light extracted from the optical fiber18by the light extraction region30into light having an optical characteristic appropriate for detection of a quantity of light performed by the PD36.

Light source light emitted from the light emitting element14in the light source12enters the core18aof the optical fiber18through the lens16. The light source light that has entered the core18apropagates through repeated total reflection on the interface between the core18aand the cladding18b. A part of the light source light propagated in the core18apasses through the light extraction region30and leaks out of the optical fiber18as detected light. The detected light that has passed through the light extraction region30and has leaked out enters the diffusion member32and diffused by the diffusion elements in the diffusion member32, and the diffused light travels in different directions and a part of the light is emitted from the diffusion member32. A part of the detected light emitted from the diffusion member32directly enters the PD36, and another part of the detected light enters the PD36after being reflected by the mirror of the reflector34.

In this structure, the detected light emitted outside of the optical fiber18is light that has leaked out through the light extraction region30through the core18a, and has been diffused by the diffusion member32. Thus, fluctuation in detection sensitivity and loss of detection stability due to the influence of a mode in the optical fiber18and/or the influence of the relative position relationship between the optical fiber18and the PD36can be prevented. Furthermore, since the detected light emitted from the diffusion member32is favorably directed to the PD36by the mirror of the reflector34, the detection of a quantity of light is effectively performed. In other words, the detected light emitted from the optical fiber18is changed by the diffusion member32and the reflector34into light having an optical characteristic appropriate for the light detection by the PD36.

As described above, stable detection of a quantity of light can be performed while suppressing the loss of light guided by the optical fiber18.

A reflection film may be provided at the edge face of the cladding18bthat defines the light extraction region30, in other words, the portion where light from the core18ais not transmitted, including the inner periphery wall of the concave portion formed as a result of forming the light extraction region30. Thus, the light leaking out of the light extraction region30is prevented from entering the cladding18bof the optical fiber18to be lost.

An irregular shape with a dielectric multilayer film or a nano structure is formed on the surface of the diffusion member32facing the PD36, i.e., an emission plane of the detected light, to reduce a reflection loss on the emission plane.

The structure of the light source apparatus according to the present embodiment is shown inFIG. 4. In the drawings, the members referred to by the same reference numbers as the members in Embodiment 1 are the same members.

The light source apparatus according to the present embodiment comprises two light sources12, two optical fibers18that respectively guide light source light emitted from the two light sources12, an optical coupler38that combines light guided by the two optical fibers18, two optical fibers40that guide light combined by the optical coupler38, two illumination units42respectively optically-coupled to the two optical fibers40, and a light detection section50that detects a quantity of the light source light guided by one of the optical fibers40.

The two light sources12, the two optical fibers18, and the illumination units42are substantially the same, respectively. The two optical fibers40are substantially the same, except that a light detection section50is provided at one of them. The basic structure of each of the optical fibers40may be the same as that of the optical fiber18.

The light source apparatus also includes a controller28that controls two light emitting elements14in the two light sources12based on a detection signal output from the light detection section50.

The optical coupler38according to the present embodiment is a two-input two-output optical coupler having two input ends and two output ends. Such an optical coupler has a function of dividing light input from one of the two input ends at a predetermined division ratio and outputting the divided light from the two output ends. The division ratio of the optical coupler38in the present embodiment is 50:50, and the optical coupler38has a function of dividing the light source light input from one of the two input ends into an equal light quantity ratio and outputting the divided light from the two output ends.

The optical fibers18coupled to the light sources12are coupled to the input ends of the optical coupler38, and the optical fibers40coupled to the illumination units42are coupled to the output ends of the optical coupler38.

Each illumination unit42includes a holding member44having a through hole in a shape of a circular truncated cone, and a phosphor46and a diffusion member48are arranged inside the through hole of the holding member44. The optical fiber40is optically coupled at the opening on the small diameter side of the through hole in a shape of a circular truncated cone of the holding member44. The optical fiber40is inserted into a ferrule (not shown) fixed to the holding member44and is held.

The phosphor46is a wavelength conversion member that absorbs primary light that is light source light emitted from the light source12, and converts the primary light to have a longer peak wavelength, a broader spectrum shape, and a larger radiation angle. The phosphor46is made by mixing a powdery fluorescent material with a resin, glass, etc. having a property that transmits primary light and hardening the mixture. In the present embodiment, the fluorescent material of the phosphor46is composed of Ce-doped YAG (yttrium-aluminum-garnet) mixed with a transparent silicon resin. The thickness and concentration of the phosphor is adjusted so as to make the optical characteristic of the secondary light to be appropriately emitted as illumination light to illuminate an observation target.

The diffusion member48has a function of expanding a radiation angle of primary light, which is light source light emitted from the light source12, without converting a peak wavelength and a spectrum shape of primary light. The diffusion member48is made by mixing, within a member that transmits primary light, a diffusion material having a refractive index different from that of the primary light-transmitting member, and curing the mixture. For example, the diffusion member48is constituted by mixing glass fillers having the refractive index of 1.5 in a resin having the refractive index of 1.4. The thickness and concentration of the diffusion member48is adjusted so that the radiation angle of the secondary light is appropriate as illumination light to illuminate an observation target.

The light detection section50for detecting a quantity of the light source light guided by the optical fiber40is provided at one of the optical fibers40respectively connected to the two output ends of the optical coupler38. The basic structure of the light detection section50is similar to that of the light detection section20of Embodiment 1.

A specific structure of the light detection section50is shown inFIG. 5. As shown inFIG. 5, a jacket (coating)40cis provided around the cladding40bof the optical fiber40to intensify the strength of the optical fiber40. An opening is formed at a part of the jacket40c, and the cladding40bis partially exposed. A light extraction region54is formed at the exposed portion of the cladding40b. The details of the light extraction region54may be similar to those of the light extraction region30of Embodiment 1.

A photodiode (PD)60serving as the light detector26is disposed facing the light extraction region54. A diffusion member56is provided in the space between the light extraction region54of the optical fiber40and the PD60. The diffusion member56is disposed so as to be in direct contact with a SiO2film formed on the surface of a photoreceptor of the PD60. The details of the diffusion member56may be similar to those of the diffusion member32of Embodiment 1.

Furthermore, the exposed portion of the diffusion member56is covered by a reflector58in which the inner surface is a mirror. Accordingly, the diffusion member56is surrounded by the optical fiber40, the PD60, and the reflector58.

The lighting pattern example of the light source12in the light source apparatus of the present embodiment is shown inFIG. 6. InFIG. 6, one of the two light sources12is referenced as light source1, and the other as light source2. As shown inFIG. 6, only the light source1is lighted during the period1, both of the light sources1and2are lighted during the period2, and only the light source2is lighted during the period3. In other words, the light sources1and2are lighted in accordance with the lighting patterns including a period during which both of the light sources are lighted, that is, the period2, and periods during which one of the light sources are lighted, that is, the periods1and3. The left side ofFIG. 6shows an example in which both of the light sources1and2are lighted at the same output. It is not necessary to light the light sources1and2at the same output; they may be lighted at different outputs. The right side ofFIG. 6shows an example in which the light sources1and2are lighted at different outputs.

A quantity of output light from the light source1can be detected by detecting a quantity of incoming light into the PD60during the period1; a quantity of output light from the light source2can be detected by detecting the quantity of incoming light into the PD60during the period3; and a total quantity of output light from the light sources1and2can be detected by detecting a quantity of incoming light into the PD60during the period2.

In the present embodiment, since the light detection section50is provided at the optical fiber40connected to the output end of the optical coupler38, the mode of the light source light passing the light detection section50is made uniform by the optical coupler38. For this reason, the detection of a quantity of light at the light detection section50is less susceptible to a mode change at the light source12.

In the present embodiment, a two-input two-output type coupler is described as an example of the optical coupler38, but the embodiment is not limited thereto; other types, for example, a two-input one-output type coupler may be adopted.

The light detection50is, of course, provided at one optical fiber connected to one output end.

As shown inFIG. 7, preferably, the light detection section50, together with the adjacent optical fiber40, may also be fixed to a fixation member62, which does not easily deform. Fixing the light detection section50and the adjacent optical fiber40to the same fixation member62prevents deformation of the light extraction region54. As a result, the relationship between the light source light guided by the optical fiber40and the light detected by the PD60as a light detector, i.e., the detection sensitivity, is maintained constant, so that the detection can be more stably performed.

Regardless of the present embodiment, the light source apparatus of each of the embodiments may be mounted in the endoscope apparatus.FIG. 8schematically shows an endoscope apparatus to which the light source apparatus of the present embodiment as a representative is mounted. As shown inFIG. 8, the endoscope apparatus100includes an insertion section104having a distal end portion102to be inserted into an observation space, and an operation section106that holds the insertion section104, the operation section106being provided with various elements for operation. A universal cord108is connected to the operation section106, and to the light source section120through the connection section110provided at the edge portion of the universal cord108.

The light source12of the light source apparatus is provided within the light source section120, and the illumination unit42is provided at the distal end portion102of the insertion section104of the endoscope apparatus100. For example, the optical fiber/s18, the optical coupler38, and the optical fiber/s40are extended inside the endoscope apparatus100, and the light detection section50is fixed to a non-deformable portion of the endoscope apparatus100, for example. In other words, the fixation member that fixes the light detection section50may be anon-deformable portion, such as a case, etc., in the endoscope apparatus100. Such a non-deformable portion may be located inside of any of the operation section106, the insertion section104, and the distal end portion102.

The light detection section50may be disposed inside the light source section120with the optical coupler38and fixed to a member in the light source section120. In other words, the fixation member that fixes the light detection section50is a member, such as a case, etc. in the light source section120.

Modification 1 of Embodiment 2

Another structure example of the light detection section50is shown inFIG. 9. In this structure example, a diffusion member64is provided at a concave portion formed as a result of forming the light extraction region54, and a reflector66is disposed in the direction in which detected light leaks out strongly from the light extraction region54through the light extraction region54. The reflector66reflects detected light leaking out from the light extraction region54toward the PD60. The diffusion member64diffuses detected light leaking out through the diffusion member64to the extent that an error in detection of a quantity of light due to an error in the arrangement of the PD60can be suppressed. The space68between the diffusion member64and the PD60may be filled with the air or with a transparent resin.

Modification 2 of Embodiment 2

In the present structure example, the light source12emits light with a relatively short wavelength. For example, the light source12emits purple light at a wavelength near400nm, or blue light at the wavelength near450nm. The diffusion member56is replaced with a wavelength conversion member. The wavelength conversion member is constituted by, for example, what particles or powder of a phosphor, which are a number of wavelength conversion elements, are bound by a resin. In other words, the wavelength conversion member constituted by a member in which a number of wavelength conversion elements are diffused in a resin. In the wavelength conversion member, a number of diffusion elements may be diffused, in addition to a number of wavelength conversion elements.

The phosphor absorbs light source light of a relatively short wavelength and isotropically emits fluorescent light having a longer wavelength than the light source light. In other words, the phosphor converts light source light of a short wavelength into wavelength-converted light with a long wavelength.

In the PD60, the sensitivity in the wavelength of the wavelength-converted light is higher than the sensitivity in the wavelength of the light source light, as shown inFIG. 11. Preferably, the sensitivity of the PD60to the wavelength-converted light is more than twice as high as the sensitivity to the light source light.

A part of light source light (400 nm to 450 nm) guided by the optical fiber40is extracted as detected light by the light extraction region54and enters the wavelength converting member. A part of the detected light is wavelength-converted into red fluorescent light (600 nm to 650 nm). A part of the wavelength-converted fluorescent light enters the PD60and is detected.

Thus, in the present modification, the detected light extracted by the light extraction region54is converted into red fluorescent wavelength-converted light and detected. Since the PD60has a higher sensitivity in the wavelength range of the wavelength-converted light than the wavelength range of the light source light, the detected light can be detected with a high sensitivity in comparison to the case where the detected light is directly detected. Accordingly, the detection of a quantity of light is less susceptible to noise, etc., so that the detection can be more stably performed.

The structure of the light source apparatus according to the present embodiment is shown inFIG. 12. In the drawings, the members referred to by the same reference numbers as the members in Embodiments 1 and 2 are the same members.

The light source apparatus of the present embodiment is similar to the light source apparatus of embodiment 2, but it is different from the light source apparatus of the embodiment2in that a light detection section70that detects a quantity of the light source light guided by the two optical fibers40is provided in place of the light detection section50that detects a quantity of the light source light guided by one of the optical fibers40.

A specific structure of the light detection section70is shown inFIG. 13. As shown inFIG. 13, the light extraction region54is provided at each of the two optical fibers40, and a diffusion member72is provided at the concave portion formed as a result of the forming of the light extraction region54. Light emitting planes of the two diffusion members72are arranged parallel to a light-receptive plane of the PD60. Another diffusion member74is provided in the space between the two diffusion members72and the PD60. A reflector76in which the inner surface is a mirror is provided around the diffusion member74. The details of the diffusion members72and74may be similar to those of the diffusion member32of Embodiment 1.

The detected light extracted from each of the optical fibers40by the light extraction region54and passed through the diffusion member72enters in common to the PD60through the diffusion member74and the reflector76.

In the present embodiment, since the light extraction regions54are provided at both of the two optical fibers40, the sensitivity of the detection of a quantity of light by the PD60is improved. The detection of a quantity of light is not influenced by a change of the division ratio of the optical coupler38over time.

Modification of Embodiment 3

The two light sources12emit light source light of different wavelengths, respectively. The diffusion members72of the two optical fibers40are respectively replaced with wavelength conversion members having different wavelength conversion characteristics respectively corresponding to light source light of different wavelengths emitted from the two light sources12. The wavelength conversion members of the two optical fibers40effectively convert the wavelength of the light source light emitted from the two light sources12, respectively. Preferably, the wavelength conversion member of one of the optical fibers40effectively converts the wavelength of the light source light emitted from one of the light sources12, but does not convert the wavelength of the light source light emitted from the other light source12, and vice versa. The PD60preferably has a low detection sensitivity for the light source light emitted from the two light sources12, but has a high detection sensitivity for wavelength-converted light generated by the wavelength conversion member of the two optical fibers40. In other words, the light emitting element14of the light source12, the material of the wavelength conversion member, and the PD60are selected to favorably satisfy these requirements.

Such a configuration allows a quantity of the light source light emitted from the two light sources12to be separated and detected, using a single light detection section70.

The embodiments of the present invention have been described with reference to the drawings as in the foregoing; however, the present invention is not limited to those embodiments, and various modifications and changes maybe made to some extent that does not deviate from the scope of the embodiments. The modifications and changes mentioned herein include an implementation achieved by combining the above-described embodiments.