Abstract:
A modular fiber optic sensor that uses a light source to transmits light through at least one optical fiber to a sensor support. The sensor support is releasably attached to the optical fiber(s) allowing the use of both a single and multiple fibers. Diaphragms are exchangably attached to the sensor support allowing numerous diaphragm configurations to be attached to the sensor support. The different diaphragm configurations allow the sensor to detect a wide range of physical phenomena. A detection system is coupled to the optical fiber(s) that determines the change in light intensity which is reflected from the diaphragm&#39;s reflector.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to fiber optic based sensors. Fiber optic sensors have been designed to detect a wide number of phenomena and are free from the problems of radiating electromagnetic fields (EMF) and are not susceptible to noise cause by electromagnetic interference (EMI). Further, fiber optic sensors can be used in a number of environments including high temperature and toxic environments with little or no degradation in performance. 
   Fiber optic based sensors are designed to detect one, possibly two, physical phenomena and the prior art sensors cannot be substantially modified or changed once constructed. This creates a problem in the manufacturability of a wide range of fiber optic sensors in that each type of sensor is made from substantially different components using substantially different fabrication and/or construction methods resulting in higher costs as compared to sensors based on electrical detection methods. 
   Prior art fiber optic sensors are limited to the practice of a specific optical detection method and a specific transduction mechanism that cannot be changed once the sensor is fabricated or constructed. This means that the end user has to use the detection method the fiber optic was designed for. The majority of the detection methods used simply are not required because the sensitivity is not required for the particular uses of the fiber optic sensors. For example, if a sensor is interrogated using interfermetric detection with light polarization detection equipment, the cost is very high. However, an interferometric technique may not be required and a less expensive interrogation technique, such as multifiber intensity detection, may be sufficient. The sensor described in this document allows the user to pick and select the detection system that is sufficient for said users needs. 
   It is therefore desirable to provide a modular fiber optic sensor that can be easily modified to detect a wide range of phenomena while also allowing the user to choose the detection method used to interrogate the sensor. 
   SUMMARY OF THE INVENTION 
   One feature of the present invention is the sensor support that allows diaphragms of different types and configurations to be exchangably connected to the sensor support. As used herein, “exchangably” shall be used in conjunction with a diaphragm that is modular in character, that can easily and manually be removed from the optical sensor, and that is easily and manually replaced with another diaphragm attached to the optical sensor. 
   The ability to use different diaphragms of different configurations results in a great advantage in manufacturing optical sensors because all sensor components are the same except for the diaphragms. Another advantage of being able to remove and replace the diaphragms allows the user to purchase the individual parts and configure the sensor to detect the physical phenomena that the user would like to detect. Yet another advantage of being able to exchange diaphragms is the longevity of the device is greatly increased. 
   Another feature of the invention is one or more optical fibers can be used to interrogate the sensor. Importantly, the optical fiber or fibers can be releasably attached to the sensor support. This releasably feature has the advantage of allowing the user to empirically determine what detection mechanism results in the most cost efficient utilization of the present invention. Additionally, this aspect of the invention also allows a wide range of diaphragms designs and configurations to be used with the sensor enabling the sensor to detect a variety of preselected phenomena. The preselected phenomena can be, but are not limited to, pressure, temperature, flow, sound, force, and chemical detection. 
   It is the novel and unique interaction of these simple elements which creates the apparatus and methods, within the ambit of the present invention. Pursuant to Title 35 of the United States Code, descriptions of preferred embodiments follow. However, it is to be understood that the best mode descriptions do not limit the scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent from the following detailed description which should be read in conjunction with the drawings, in which: 
       FIG. 1  is a photo of a modular sensor configured as a microphone with a multifiber intensity detection system; 
       FIG. 2  is a cross-sectional view of an embodiment of the modular sensor; 
       FIGS. 3A and 3B  are cross-sectional views of another embodiment of the modular sensor; 
       FIG. 4  is a frontal view of the embodiment shown in  FIG. 3 ; 
       FIGS. 5A and 5B  show an embodiment of the sensor utilizing a circular diaphragm and a simple set screw to releasably attach the fiber to the sensor; 
       FIGS. 6A and 6B  disclose an embodiment of the sensor utilizing a square diaphragm and a spring loaded mechanism to releasably attach the fiber to the sensor; 
       FIG. 7  teaches an embodiment of the sensor utilizing a triangular diaphragm and an assembly to releasably attach the fiber to the sensor where the assembly can also adjust the fiber in the x, y, and z directions; 
       FIG. 8  depicts a diaphragm that is membrane like with a reflective structure centered on the membrane; 
       FIG. 9  portrays a diaphragm that is a ring with a bimetallic strip centered in the ring with a reflective structure on the bimetallic strip; 
       FIG. 10  shows a diaphragm with four arms connected at the center of the diaphragm where a magnetic material is adhered to one side of the diaphragm and a reflective structure is adhered to the other side of the diaphragm; 
       FIG. 11  teaches a diaphragm composed of a metallic plate; 
       FIGS. 12A and 12B  disclose a diaphragm composed of a optically transparent material and coated with a material whose optical properties change with a change in a physical phenomena; 
       FIGS. 13A and 13B  teach a diaphragm including a central two beam structure where on a first side of the two beam structure a paddle is attached and a reflective structure is attached to a second side; 
       FIGS. 14A and 14B  show a fiber probe configuration containing a plurality of optical fibers wherein the central fiber is a illuminating fiber and the other fibers are light receiving fibers; 
       FIGS. 15A and 15B  portray a fiber probe configuration containing a single fiber that can be used with interferometric detection systems or velocimetry detection systems; 
       FIGS. 16  A and  16 B show a fiber probe configuration containing a single fiber wherein one end of the fiber probe has an angle between 0° and 8° to minimize back reflections; 
       FIG. 17  represents a velocimetric optical interrogation technique that can be used to interrogate a signal from the sensor; 
       FIG. 18  represents an interferometric optical interrogation technique based on a Michelson interferometer that can be used to interrogate a signal from the sensor; and 
       FIG. 19  represents an optical lever interrogation technique that can be used to interrogate a signal from the sensor. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Although the disclosure hereof is detailed to enable those skilled in the art to practice the invention, the embodiments published herein merely exemplify the present invention. 
   Referring now to the drawings by the reference numerals that are used to identify specific components on the invention. The invention is a modular sensor, and as can be appreciated, many preferred embodiments of the invention are disclosed. 
   Referring now to  FIG. 1 , a photo of a first prototype of the invention is shown on a optical table. The photo is taken from the back of the sensor showing the fiber probe protruding from the back portion of the fiber. 
   Referring now to  FIG. 2 , a cross-sectional view of one embodiment of the sensor where the diaphragm  1  is retained in the sensor support  6  by a first retaining ring  8  and a second retaining ring sealed with o-rings  7 . The second retaining ring  39  has a setscrew  5  that holds the fiber probe  4  containing the optical fiber  3 . The second retaining ring  39  is milled out so that the second retaining ring forms a space  10  between the fiber probe and the diaphragm  1 . The sensor is screwed into a wall  9 . 
   The sensor support  6 , and retaining rings  39  and  8  can be constructed of metallic, polymeric, ceramic, or hybrid materials. The diaphragm  1  can be fabricated from metal, polymeric, ceramic or hybrid materials as well. Diaphragms are composed of preselected compositions to detect specific phenomena. By way of illustration, diaphragms of the present modular sensor can be composed of metals, such as but not limited to aluminum, steel, and brass, polymers, such as but not limited to polyimide, polyethylene, Teflon, Nitrocellulose, acrylate, and polycarbonate, or dielectric materials, such as but not limited to glass, diamond, BK7, Quartz. Depending on the preselected composition of the diaphragms, changes in temperature, flow, magnetic fields, gas density or pressure can be measured. Diaphragms can also be coated with a polymeric coating sensitive to pressure and/or temperature providing for the transparency of the diaphragm to be altered with the changes in pressure and/or temperature. Examples of such coatings are temperature-sensitive liquid crystal material, thermochromic paints, temperature-Sensitive Ink, and lysolipid temperature sensitive liposomes. 
     FIG. 3  is a cross-sectional side view of one embodiment of the modular sensor where the diaphragm  1  is attached to a sensor support  6  by a cap screw  13  through a hole  14  in the diaphragm  1  and a hole in the sensor support  11  and tightened with a nut  12 . The sensor support has a slot  4  to receive a fiber probe and a setscrew  5  to hold the fiber probe (not shown in this view) in a releasable fashion. The sensor support  6  has a milled out area to form a space  10  between the fiber probe (not shown in this view) and the diaphragm  1 . 
   The sensor support  6  and diaphragm  1  can be milled, injection molded, molded, stamped, or formed by adhering layers of material together. Additionally, the sensor support  6  and diaphragm  1  can be composed of polymeric, metallic materials or hybrids.  FIG. 4  is a frontal view of the embodiment presented in  FIG. 3  where the diaphragm  1  includes a hole  14  to receive a cap screw and a hole  13  to receive the fiber probe. 
   Referring now to  FIGS. 5A  a frontal view and  5 B a cross-sectional side view of one embodiment of the modular sensor that is similar to the embodiment presented in  FIG. 3  where the sensor support  6  is extended to rest securely on a flat surface. 
     FIGS. 6A and 6B  are a frontal view and a cross-sectional side view of an embodiment of the modular sensor. Diaphragm  1  is square and a fiber sensor is held into place with a depressible spring mechanism  18 . The diaphragm  1  is magnetically held into place on the sensor support  6 . Magnets  16  are placed within the sensor support  6  and a magnetic material  17  is placed within the diaphragm  1 . 
     FIG. 7  is a cross-sectional side view of one embodiment of the modular sensor where the diaphragm  1  has a threaded portion  23  which screws onto threads  22  on the sensor support  6 . The fiber probe  2  is placed into the fiber holder  4  and held into place with a set screw  5  where the fiber holder is connected to a plate  24  that is tensionably connected to a second plate  40  where screws  19  can move the fiber probe  2  in pitch and yaw. A threaded component  21  can move the fiber probe  4  towards and away from the diaphragm  1 . 
   Referring now to  FIG. 8 , the diaphragm  1  is adhered to a thin plastic layer  25  with a mirror  26  attached to the center of the plastic layer  25 . Plastic layer  25  can be composed of, but not limited to, but not limited to polyimide, polyethylene, Teflon, nitrocellulose, acrylate, and polycarbonate. 
   Referring now to  FIG. 9 , the diaphragm  1  has a bimetallic strip  27  incorporated with a mirror  26  attached to the center of the bimetallic strip. Bimetallic strip  27  can be composed of iron and aluminum, iron and copper, and brass and invar. 
   Referring now to  FIG. 10 , the diaphragm  1  includes four intersecting arms  41  connected to one another at the center of the diaphragm and mirror  26  is also attached to the center of the diaphragm. Intersecting arms  41  can be composed of, but not limited to, metals, such as aluminum, steel, and brass, polymers, such as polyimide, polyethylene, Teflon, nitrocellulose, acrylate, and polycarbonate, or dielectric materials, such as glass, diamond, BK7, Quartz. 
   Referring now to  FIG. 11 , the diaphragm  1  is a contiguous piece of material with a mirror  26  adhered to the center of the diaphragm  1 , where the materials can include, but are not limited to, metals, such as aluminum, steel, and brass, polymers, such as polyimide, polyethylene, Teflon, nitrocellulose, acrylate, and polycarbonate, or dielectric materials, such as glass, diamond, BK7, Quartz. 
   Referring now to  FIGS. 12A and 12B , the diaphragm  1  is a contiguous piece of optically transparent material with a coating  29  whose optical properties change in response to a change in a physical phenomena. Within the scope of the present invention, optically transparent materials can include polymers, such as polyimide, polyethylene, Teflon, nitrocellulose, acrylate, and polycarbonate, or dielectric materials, such as glass, diamond, BK7, Quartz. Coatings  29  applied to the optically transparent materials can include pressure sensitive paints, ProCling pressure sensitive film, and thermochromic paints. 
   Referring now to  FIGS. 13A and 13B , the diaphragm  1  has a central portion  30  that has a paddle  31  oriented 90° to the surface of the diaphragm  1 . The central portion  30  is rotably movable when a force is applied to the paddle  31 . The diaphragm  1  has a mirror  26  adhered to the central member  30  on the side opposite the paddle  31 . 
   Referring now to  FIGS. 14A and 14B , a first possible fiber probe head configuration is shown for use with the modular sensor wherein the probe head  34  has a plurality of optical fibers  32  and an optical fiber  33 . The central fiber  33  is an illuminating fiber and the plurality of surrounding fibers  32  are receiving fibers. The optical fibers  33  and  32  are held into the probe head  34  with an epoxy matrix  35 . The fibers  36  are allowed to extend from one end of the fiber probe  34  and are polished flush on the other end  42 . 
   Referring now to  FIGS. 15A and 15B , another possible fiber probe head configuration is shown for use with the modular sensor where the probe head  34  has a single optical fiber  37  centrally located in the probe head  34 . The single fiber  37  is held in place within the probe head  34  with a epoxy matrix  35 . The single optical fiber  37  protrudes from one side of the probe head  34  and is polished flush on the opposite side  42  of the probe head  34 . 
   Referring now to  FIGS. 16A and 16B , a still another possible fiber probe head configuration is shown for use with the modular sensor where the probe head  34  has a single optical fiber  37  centrally located and held into place with an epoxy matrix  35 . The single optical fiber  37  protrudes from one end of the probe head  34  and is polished flush with the other end  38  of the probe head  34 . As shown, head  34  is slanted at an angle between 1° and 10°. 
   The probe head  34  can be formed by injection molding a polymeric or hybrid material around the fiber and then cleaving and polishing the fibers on one end of the probe head  34 . In the alternative the probe head  34  can be fabricated by centrally placing the optical fibers in a sleeve and epoxying the fibers into place. After the epoxy cures the fibers on one end of the probe head  34  can be cleaved and polished. The sleeve can be composed of a metal, polymer, or hybrid material. 
     FIG. 17  represents a possible optical interrogation technique based on velocimetry that can be used to interrogate a signal from the modular optical sensor  49 . In accordance with the present invention, the velocimetric technique utilizes a two by one fiber optic coupler  45  that receives light from a light source  44  where the light reflected from the sensor is detected by optical detector  43 . The optical coupler  45  can be comprised of single or multimode optical fibers. 
     FIG. 18  depicts a possible optical interrogation technique utilizing a michelson interferometer to interrogate a signal from the modular optical sensor  49 . The light from the light source  44  is directed a beam splitter  46  where 50% of the light is directed to a reference mirror  47  and 50% of the light is directed to the modular optical sensor  49  through an optical fiber  48 . The light reflected from the modular optical sensor  49  is directed back to the beam splitter  46  via an optical fiber  48  and recombined with the light from the reference mirror  47  and detected on a optical detector  43 . 
     FIG. 19  discloses another optical interrogation technique utilizing optical leverage to interrogate a signal from the modular optical sensor  49 . Light is directed from a light source  44  to the modular optical sensor  49  through at least one illuminating fiber  33 . The light reflected from the sensor is directed through at least one light receiving optical fiber  32  to the optical detector  43 . 
   Having disclosed the invention as required by Title 35 of the United States Code, Applicant respectfully requests that Letters Patent be granted for his invention in accordance with the scope of the claims appended hereto.