Abstract:
To provide a fluorescent temperature sensor wherein light is propagated reliably with an easy adjustment. A fluorescent temperature sensor for producing a temperature signal from fluorescent light of an optically excited fluorescent material includes: a light emitting device for projecting light to the fluorescent material; a photoreceiving element for receiving fluorescent light emitted from the fluorescent material  1 ; a case for housing both the light emitting device and the photoreceiving element; and an optical fiber, between the case and the fluorescent material, for propagating the light of both the light emitting device and the fluorescent material. The case and the optical fiber are positioned so that the light from the light emitting device is received within the optical fiber, and so that the light from the fluorescent material is incident on the photoreceiving element from within the optical fiber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under U.S.C. §119 to Japanese Patent Application No. 2008-092081, filed Mar. 31, 2008. The contents of this application is incorporated herein by referenced in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a fluorescent temperature sensor for producing a temperature signal from a fluorescent light of a fluorescent material that has undergone optical excitation. 
     BACKGROUND OF ART 
     As this type of optical temperature sensor there is, for example, a known fluorescent temperature sensor wherein a light source, as a light emitting device and a photoreceiving element are spatially separated, as illustrated in U.S. Pat. No. 5,470,155 (“the &#39;155 patent”). In this fluorescent temperature sensor, light from a light source is caused to be incident on an optical fiber that faces a fluorescent material, through the half mirror or a dichroic mirror on the one hand, and the fluorescent light that is emitted from the fluorescent material is caused to illuminate the photoreceiving element through the half mirror or dichroic mirror. 
     SUMMARY OF THE INVENTION 
     However, in the conventional fluorescent temperature sensor of the &#39;155 patent, it is necessary to perform alignments twice: the adjustment (of the alignment of the light source relative to the optical fiber) for causing the light from the light source to be incident on the optical fiber, and the adjustment (of the alignment of the photoreceiving element relative to the optical fiber) in order to cause the light from the fluorescent material to be incident on the photoreceiving element. Additionally, because a half mirror or a dichroic mirror is used, it is also necessary to adjust the angle thereof. Because of this, the manufacturing process is complex, and not only does this decrease the productivity, but there is also a shortcoming in that this leads to increases in the product cost. 
     Given this, in contemplation of the situation set forth above, the object of the present invention is to provide a fluorescent temperature sensor wherein the light can be propagated reliably through simple adjustments. 
     The fluorescent temperature sensor of a first invention is a fluorescent temperature sensor for producing a temperature signal from fluorescent light of a fluorescent material that has been optically excited, comprising: a light emitting device for projecting light onto the fluorescent material; a photoreceiving element or receiving fluorescent light that is emitted from the fluorescent material; a case housing both the photoreceiving element and the light emitting device; and a light propagating medium for conducting, between the case and the fluorescent material, both the light that is emitted from the light emitting device and the fluorescent light that is emitted from the fluorescent material; wherein: the case and the light propagating medium are connected at a position wherein the light that is emitted by the light emitting device is received within the light propagating medium and the fluorescent light that is emitted from the fluorescent material is incident on the photoreceiving element from within the light propagating medium. 
     In the fluorescent temperature sensor of the first invention, the light propagating medium and the case are connected in a position wherein the light that is emitted from the light emitting device is incident into the light propagating medium and the fluorescent light that is emitted from the fluorescent material is incident on the photoreceiving element from within the light propagating medium. Because of this, there is no need for the alignment of the light emitting device and the light propagating medium, nor for the alignment of the photoreceiving element and the light propagating medium, making it possible to conduct the light reliably through the simple adjustment of disposing the photoreceiving element and the light emitting device appropriately within the case. 
     The fluorescent temperature sensor of a second invention is the fluorescent temperature sensor as set forth in the first invention, wherein the light propagating medium is an optical fiber; and the optical fiber is connected to the case so that the core of the optical fiber is positioned within the range of directional characteristics of the light emitting device, and the photoreceiving element is positioned within the range of the aperture angle of the optical fiber. 
     With the lessons temperature sensor as set forth in the second invention, when the light propagating medium is a simple optical fiber, it is possible to cause the light that is emitted by the light emitting device to be incident into the core by positioning the core of the optical fiber within the range of the directional characteristics of the light emitting device. On the other hand, it is possible to cause the fluorescent light that is emitted from the fluorescent material to be incident on to the photoreceiving element through positioning the photoreceiving element within the range of the aperture angle of the optical fiber. Given this, it is possible to reliably conduct the light, even when using a single fiber, through a simple adjustment of positioning the light emitting device and the photoreceiving element within the case as described above. 
     The fluorescent temperature sensor as set forth in the third invention is a fluorescent temperature sensor as set forth in the first invention, wherein the light propagating medium is a fiber optic bundle wherein a plurality of optical fiber element fibers are bundled together; and the fiber optic bundle is connected to the case by positioning the cores of at least a portion of the optical fiber element fibers of the fiber optic bundle within the range of the directional characteristics of the light emitting device, and the photoreceiving element is positioned within the range of the angle or aperture of at least a portion of the optical fiber element fibers of the fiber optic bundle. 
     In the fluorescent temperature sensor as set forth in the third invention, the light propagating medium being a fiber optic bundle, enables the light that is emitted from the light emitting device to be incident into the cores of the optical fiber element fibers through positioning the cores of a portion of those optical fiber element fibers comprising the fiber optic bundle within the scope of the directional characteristics of the light emitting device. On the other hand, it is possible to cause the fluorescent light that is emitted from the fluorescent materials to be incident onto the photoreceiving element by positioning the photoreceiving element within the scope of the aperture angle of a portion of the optical fiber element fibers that comprise the fiber optic bundle. This makes it possible to convey the light reliably, even when using a fiber optic bundle, through the simple adjustment of positioning the light emitting device and the photoreceiving element appropriately within the case as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall structural diagram of a fluorescent temperature sensor according to the present example of embodiment. 
         FIG. 2  is an explanatory diagram illustrating a specific structure of a fluorescent temperature sensor according to the present example of embodiment. 
         FIG. 3  is a diagram illustrating the positional relationship between the LED, the photodiode, and the optical fiber in  FIG. 2 . 
         FIG. 4  is a partial cross-sectional diagram shown from the direction of the section IV-IV in  FIG. 3 . 
         FIG. 5  is a partial cross-sectional diagram of a modified example of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A fluorescent temperature sensor according to one example of embodiment according to the present invention will be explained in reference to  FIG. 1  through  FIG. 5 . 
     The overall structure of the fluorescent temperature sensor according to the present example of embodiment will be explained in reference to  FIG. 1 . The fluorescent temperature sensor comprises: a fluorescent: material  1  that exhibits fluorescent characteristics that vary depending on the temperature; a light emitting device  2  for projecting light onto the fluorescent material  1 ; a driving circuit  3  for driving the light emitting device  2 ; a photoreceiving element  4  for receiving fluorescent light emitted from the fluorescent material  1 ; and a signal processing circuit  5  for generating and outputting a temperature signal in accordance with an output signal from the photoreceiving element  4 . A power supply  6  is connected to the signal processing circuit  5 , to supply, from the power supply  6 , the electric power that is required for the operation of the fluorescent temperature sensor. 
     Additionally, the fluorescent temperature sensor further comprises an optical fiber  7  as light propagating means connecting between the fluorescent material  1 , the light emitting device  2  and the photoreceiving element  4 , and a case  8  for housing the light emitting device  2  and the photoreceiving element  4 . 
     The light emitting device  2  is provided with an LED  21  of a specific wavelength. (See  FIG. 2 .) The driving circuit  3  applies a pulse current to the LED  21  to cause the period of emission of the LED  21  for a single measurement to be any time period between 2 ms and 500 ms. 
     The receiving element  4  is provided with a photodiode  41  (shown in  FIG. 2 ) for measuring the luminosity (brightness) of the incident light. The signal processing circuit  5  measures the attenuation characteristics of the fluorescent light of the fluorescent material  1 , measured by the photodiode  41 , and measures, in particular, the fluorescent relaxation time. Additionally, the signal processing circuit  5  calculates and outputs the temperature of the temperature measurement environment in which the fluorescent material  1  exists, from the relationship (included in a data table, map, or the like) between the fluorescent relaxation time and the fluorescent material  1 , which provided in advance. 
       FIG. 2  will be referenced next to explain a specific structure of the fluorescent temperature sensor. 
     The fluorescent material  1  is disposed facing a core portion  7   a  (shown in  FIG. 3 ) of an optical fiber  7  within a protective tube  11  provided so as to cover one end portion of the optical fiber  7 . 
     The case  8  is provided with a connector receiving portion  81  as connecting means for connecting the optical fiber  7  to one end side, and a hollow internal space  82  wherein fits a tube-shaped module unit  9  containing the LED  21  and the photodiode  41  on the other end side. 
     The connector receiving portion  81  is a receiving portion corresponding to a connector  71  that is connected on the other end side of the optical fiber  7 , where the connector receiving portion  81  and the connector  71  are objects that are already standardized based on JIS specifications, or the like, so detailed explanations thereof are omitted. 
     The connector receiving portion  81  comprises a tubular connecting portion  84  that protrudes to the outside of the case  8 , a female screw groove  85  formed on the inner periphery of the connecting portion  84 , and a plug portion  86  that communicates with the internal space  82  and into which the tip of the connector  71  is plugged. On the other hand, the connector  71  comprises a ferrule  72  into which the optical fiber  7  is inserted and integrated, a guide member  73  that fits around the ferrule  72  and which can slide in the axial direction to protect the ferrule  72 , a coil spring  74  that applies a force on the ferrule  72  towards the tip end portion, and a male screw groove  75  formed on the outer periphery of the guide member  73 . 
     The module unit  9  is disposed across a specific gap so that the LED  21  on the substrate  91 , the photodiode  41 , and the core portion  7   a  of the optical fiber  7  (shown in  FIG. 3  and  FIG. 4 ) will have the relationship described below. The bottom portion  92  is adjacent to the outside of the substrate  91 , and a plurality of terminal electrodes  93  is provided penetrating through the substrate  91  and the bottom portion  92 . Additionally, each of the terminal electrodes  93  is connected, directly or through a lead wire  94 , to the LED  21  or the photodiode  41 . 
     Additionally, the module unit  9  is provided with a casing  95  so as to cover over the substrate  91 , including the LED  21  and the photodiode  41 , from the bottom portion  92 , and a window portion  96  is formed wherein quartz glass fits into a portion of the ceiling of the casing  95 . 
     The positional relationship between the LED  21 , the photodiode  41 , and the optical fiber  7  will be explained next. 
     When the ferrule  72  of the connector  71  is plugged on to the plug portion  86  of the connector receiving portion  81 , the tip end of the ferrule  72  comes into contact with a window portion  96  of a module unit  9  that is plugged over the inner space  82 . Additionally, the male screw groove  75  and the female screw groove  85  are tightened by a tightening portion  84 , to secure the connector  71  and the connector receiving portion  81 . At this time, the tip end of the ferrule  72  is pushed by the force of the coil spring  74  into the window portion  96  of the module unit  9  to be held in this state. 
     In this way, in a state wherein the case  8  and the optical fiber  7  are connected, the light emitting portion  21   a  of the LED  21  and the photoreceiving portion  41   a  of the photodiode  41  are disposed facing the core portion  7   a  of the optical fiber  7 , as illustrated schematically in  FIG. 3 . Specifically, the core portion  7   a  of the optical fiber  7  is positioned within the range  21   b  of the directional characteristics of the LED  21 , and the photoreceiving portion  41   a  of the photodiode  41  is positioned within the range of the aperture angle θ that is determined by the core portion  7   a  of the optical fiber  7 . 
     As a result, the case  8  and the optical fiber  7  the light that is emitted from the light-emitting portion  21   a  of the LED  21  is received within the core portion  7   a  of the optical fiber  7 , and the light from the fluorescent material  1  is incident on the photoreceiving portion  41   a  of the photodiode  41  from within the core portion  7   a , as shown by the cross-sectional diagram in  FIG. 4  of the components when viewed in the direction of the section IV-IV in  FIG. 3 . 
     Here, when the intensity of the light from the fluorescent material  1  is sensed in the photoreceiving portion  41   a , a mixture of light that is emitted from the light-emitting portion  21   a  of the LED  21  and the light from the fluorescent material  1  is received, so there is the danger of not being able to sense the fluorescent light intensity correctly, and thus in practice preferably the structure is one wherein the light from the fluorescent material  1  is sensed immediately after the LED  21  has been turned off. 
     In this way, the fluorescent light temperature sensor of the present form of embodiment eliminates the need for the alignment between the LED  21 , as the light emitting device  2 , and the optical fiber  7 , which is the light propagating medium, and eliminates the need for the alignment between the photodiode  41 , as the photoreceiving element  4 , and the optical fiber  7 , and disposing the LED  21  and the photodiode  41  with a specific gap therebetween within the case  8  enables a simple structure to reliably perform photoprotection from the light emitting device  2  to the fluorescent material  1 , and photoreception from the fluorescent material  1  to the photoreceiving element  4 . 
     Note that although in the form of embodiment described above the light propagating medium is structured from a single optical fiber  7 , the present invention is not limited thereto, but rather, as illustrated in  FIG. 5 , may be a fiber-optic bundle comprising a plurality of optical fiber element fibers  7 . In this case, disposing the cores  70   a  of at least a portion of the optical fiber element fibers  70  of the fiber-optic bundle with in the range of the directional characteristics of the LED  21  enables the reliable illumination of the light from the LED  21  into the core portions [sic]  70   a  of the optical fiber element fibers  70 . Additionally, positioning the photoreceiving portion  41   a  of the photodiode  41  within the scope of the aperture angle of at least a portion of the optical fiber element fibers  70  of the fiber-optic bundle enables the reliable illumination of the light from the fluorescent material  1  onto the photoreceiving portion  41   a.    
     Additionally, while in the present form of embodiment a module unit  9  wherein the LED  21  and the photodiode  41  are disposed with a specific gap therebetween was fitted into an inner space  82  in the case  8 , the present invention is not limited thereto, but rather the LED  21  and the photodiode  41  may be disposed directly in the case  8 .