Abstract:
An optical sensing system for optically detecting high density sensor inputs. The sensing system includes a sensor having a reflective portion for reflecting light in a desired direction corresponding to a condition of the sensor. The system also includes an optical fiber for receiving light from an illumination source and directing a light signal at the sensor. The light signal is reflected from the sensor according to the sensor&#39;s position and optically coupled through the optical fiber to a detector that detects an intensity of the reflected light signal transmitted through the optical fiber in response to the position of the sensor. In one form, the sensor is a switch having a reflective coating that reflects light in a desired direction corresponding to the position of the switch. In another form, the detector is a CCD for receiving many reflected light signals, each signal coupled to a respective pixel of the CCD.

Description:
SPECIFIC DATA RELATED TO THE INVENTION  
       [0001]    This application claims the benefit of U.S. provisional application, Application No. 60/396,403 filed Jul. 15, 2002, incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention is directed to an optical detector for sensing high density sensor outputs and, more particularly, to an optical means for sensing switch positions in high density switching applications.  
         BACKGROUND OF THE INVENTION  
         [0003]    Current technology for aircraft cockpit controls, flight simulator control systems, and manufacturing control systems utilize extensive numbers of switches to actuate various systems or features that may be present or used in each of the above systems and also use numerous sensors to detect various conditions. Each of these devices outputs a signal along a current conductor, typically a pair of copper conductors that transmit the status of a switch or other sensor to a computer or other type of device adapted to receive the multiple inputs from the various switches or sensors. In the aircraft environment, the number of switches and sensors in a cockpit is extensive and the cabling for such device conditions typically comprises wire bundles that may be multiple inches in diameter. Each of these devices is typically monitored by an electrical system that determines the condition of the device and causes actuation of some system to control some feature in the aircraft. In a simulator environment, switches and operator controls may not be connected to operative equipment, but may instead be monitored, such as electrically, to determine the current condition of the switch or control, and the condition may be provided to an input/output (I/O) system for generating a simulated response corresponding to the switch or control input. However, such a system may require a large number of conductors connecting each switch or control to electronic circuits for interpreting the switch or control condition and providing an appropriate signal to control the simulator. Other problems with conventional switching technology include the weight of the conductors for wiring the switches, relatively high power requirements, EMI susceptibility, complicated electronics for monitoring the switches, corrosion susceptibility, relatively high heat production, electronic crosstalk between conductors, and difficult maintainability.  
           [0004]    Accordingly, there is a need for a system that will reduce the volume of conductors and provide for a fast, reliable method of reading switch and sensor status.  
         SUMMARY OF THE INVENTION  
         [0005]    An optical sensing system is described herein as including a sensor having a reflective portion for reflecting light in a desired direction corresponding to a condition of the sensor. The system also includes an optical fiber having a illumination end for directing a light signal at the sensor and an illumination source, optically coupled to a coupling end of the optical fiber, for producing the light signal. The system further includes a detector, optically coupled to the coupling end of the optical fiber, for detecting an intensity of a reflected light signal transmitted from the coupling end of the optical fiber in response to a condition of the sensor. The system may also include a second optical fiber having a sensing end for receiving a reflected light signal from the sensor and an output end for transmitting the reflected light signal.  
           [0006]    In addition, a method of optically determining a condition of a sensor is described herein as including directing a light signal at a selectively reflective sensor; and detecting an intensity of the light signal reflected from the sensor in response to the condition of the sensor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The features of the invention believed to be novel are specifically set forth in the appended claims. The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which:  
         [0008]    [0008]FIG. 1 illustrates a switch position sensor system using a fiber optic, a reflective switch, and a detector.  
         [0009]    [0009]FIG. 2 illustrates a switch position sensor system using a single transmit and feed fiber optic array.  
         [0010]    [0010]FIG. 3 illustrates a switch position sensor system in which input light is transmitted at an angle to a single fiber optic array and reflected light from the fiber optic array is projected at different angle to a detector.  
         [0011]    [0011]FIG. 4 illustrates a switch position sensor system including a feed optic fiber array and a sensing optic fiber array.  
         [0012]    [0012]FIG. 5A illustrates a switch position sensor system incorporating an semiconductor light source.  
         [0013]    [0013]FIG. 5B is an exploded view of the switch position sensor system of FIG. 5A. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    The present invention is directed to a system that utilizes optical fibers as conductors and light as the medium for determining status of switches and sensors. In one form, as depicted in FIG. 1, the system utilizes an optical fiber  10  to direct an optical signal  12  produced by a light source  26  to an individual switch  14  for sensing the optical signal  12  received at a sensing end  18  of the fiber  10 . In an aspect of the invention, the switch  14  includes a means for changing the reflectivity, such as a retro-reflective coating  16  on the back of the switch  14  to reflect the optical signal  12  away from or into the sensing end  18  of the fiber  10 , depending on the position of the switch  14 . At a coupling end  20  of the fiber  10 , a charge coupled device (CCD)  22  or other type of light intensity sensing device scans the ends of a plurality of such fibers  10  and determines the status of the associated switch  14  or sensor by the amount of light that is reflected back through the fiber  10  and impinges the sensing device, or CCD  22 . The status of the switches can than be further processed to provide appropriate control actions. For example, as shown in FIG. 1, when the switch  14  is positioned in an “OFF” position, the retro-reflective coating  16  on the back of the switch  14  reflects the optical signal  12  back through the optical fiber  10  to the CCD  22  for detection. Accordingly, the intensity of the reflected light  24  detected at a specific location, such as a pixel or group of adjacent pixels of the CCD  22 , is correlated to a specific fiber and the received intensity processed to determine that the switch  14  is off. When the switch  14  is in an “ON” position, the optical signal  12  is reflected away from the sensing end  18  of the fiber  10  so that little or no reflected light  24  is conducted to the CCD  22 . Accordingly, a relatively reduced or no light intensity for the sensed switch  14  is detected by the CCD  22 , indicating, for example, that the switch  14  is in a different position compared to a condition when a relatively higher intensity of reflected light  24  is detected, such as when the switch is in the “ON” position. While a switch  14  is depicted in FIG. 1, any control device as known in the art may be adapted for use with the invention, for example, by configuring the device so that the device reflects or deflects light corresponding to a condition of the device.  
         [0015]    In an aspect of the invention, multiple fibers  10 , for example, arranged in a two dimensional array at coupling ends of the fibers, are used to sense multiple respective switches  14 . Each fiber  10  is coupled at its coupling end  20  to an area of the CCD  22 . In a further aspect of the invention, the individual fibers  14  can be glued or mechanically held in place in, for example, a bundled, two-dimensional array so that the CCD  22  will be able to read the position of thousands of input devices, such as switches  14 , simultaneously. Once the CCD  22  reads the switch  14  positions in a scan, the information obtained by the scan can be sent to a computer system (not shown) for decoding. Decoding the output of the CCD  14  may require averaging the pixels that contain information for particular input device and then storing the resulting information in an array for use by a higher-level control program. It is believed that a single CCD  14  having a 640 by 480 pixel array may control in excess of 300,000 input devices. However, the number of actual devices may be reduced by the amount of redundancy that may be required by any particular system, or if more than one pixel is used to detect the light intensity coming from a respective fiber.  
         [0016]    The advantages of the optical fiber and CCD arrangement over existing electrically wired input-output systems is that the optical system has less weight, requires lower power, is EMI proof, has simplified electronics, is corrosion resistant, can be made waterproof, can have simple redundancy, produces less heat and requires less cooling, may be less expensive, eliminates electronic crosstalk between conductors, is easier to construct, has increased reliability, has decreased repair time, and can be arranged in higher density configurations.  
         [0017]    [0017]FIG. 2 illustrates a switch position sensor system  30  layout using a single transmit and feed fiber optic array  32  in which a light source  34  directs light through a beam splitter  36 , or one-way mirror, onto fiber ends  38  in the fiber optic array  32 . The light source  34  may further include a reflector  52  and a heat shield  54 . The fibers  40  in the fiber optic array  32  are optically coupled to the various switches and sensor devices (not shown) so that the light directed onto the fiber ends is absorbed or reflected according to the position of the sensed switch or control. Light reflected by the switches is coupled back into the fibers  40  and directed into the system housing  42 , where the reflected light from each fiber  40  is directed back to the beam splitter  36  and reflected, for example, at 90 degrees onto an optical sensor  44 . The optical sensor may include a CCD  46  and associated optical elements  48 , such as focusing lenses. The CCD  46  can then scan all of the fiber optic signals being returned and provide electrical signals via an interface connection  50  to a computer system (not shown) for detecting the status of each of the switching devices and sensors.  
         [0018]    The light source  34  may be any of the well known light producing devices for use with optical fibers including incandescent, fluorescent, or high intensity discharge lighting elements. In addition, the light source may be a semiconductor light source, such as a light emitting diode (LED), or laser semiconductor, such as a side emitting or surface emitting laser semiconductor. Further, the beam splitter  36  used with the light source  34  may be constructed of glass or plastic, or other forms of focusing light may be used to direct light into the fiber optic array. Depending on the type of light source  34  that is used to direct light into the fiber optic array  32 , the light may be filtered to remove excessive heat, or the fibers  40  may be incorporated with some form of heat sink to absorb heat. Typically, the heat input to the fibers  40  is minimized by moving the focal point of the light to a point in front of the fibers ends  38  so that the light is not focused at the fiber ends  38 .  
         [0019]    While the embodiments described herein suggests that a broadband light may be used for the invention, it will be apparent that a narrow frequency beam such as a laser beam may be an alternate type of light that could be used for this invention. Further, with a broadband light, an optical multiplexer could also be incorporated to separate the light into various wave lengths that are applied to different sets of optical fibers in order to isolate different fiber bundles. Further, while a CCD has been shown as a form of a detector, other forms of detectors may also be utilized within the scope of the invention. Still further, the particular array of the optical fibers within the optical fiber holder may take various configurations and shapes depending upon the particular application and the manner in which it is desired to organize and arrange the optical fibers so as to be able to detect the particular switch or sensor being monitored.  
         [0020]    [0020]FIG. 3 illustrates a switch position sensor system  60  in which input light is transmitted at an angle to a single fiber optic array  62  and reflected light from the fiber optic array is projected at different angle to a detector  64 . This embodiment uses common fibers for transmitted and reflected light. A light source  66 , aligned at an angle, such as 15 degrees, with respect to a longitudinal axis of the detector  64 , directs light into fiber ends  68  of the fiber optic array  62 . The light source  66  may further include a reflector  70  and a heat shield  72 . The fibers  74  in the fiber optic array  62  are then optically coupled to the various switches and sensor devices (not shown) so that the light directed onto the fiber ends  68  is absorbed or reflected according to the position of the sensed switch or control. Light reflected by the switches is coupled back into the fibers  74  and directed through the system housing  76 , where the reflected light from each fiber  74  is directed into the detector  64 , angularly positioned with respect to a light aiming axis of the light source  66 . The detector  64  may include a CCD  78  and associated optical elements  80 , such as focusing lenses. The CCD  78  can then scan all of the fiber optic signals being reflected and provide electrical signals via an interface connection  82  to a computer system (not shown) for detecting the status of each of the switching devices and sensors.  
         [0021]    [0021]FIG. 4 illustrates a switch position sensor system  90  including a feed optic fiber array  92  and a sensing optic fiber array  94 . A light source  96 , directs light into fiber ends  98  of the feed fiber optic array  92 . The light source  66  may further include a reflector  102  and a heat shield  104 . The feed fibers  100  in the feed fiber optic array  92  are then optically coupled to the various switches and sensor devices (not shown) so that the light directed into the fiber ends  68  is reflected according to the position of the sensed switch or control. In addition, sensing fibers  106  are also optically coupled to the various switches and sensor devices. Light directed at the switches from the respective feed fibers  100  and reflected by the switches is coupled back into the associated sensing fibers  106  and directed through the system housing  108  and into the detector  110 . The detector  110  may include a CCD  112  and associated optical elements  114 , such as focusing lenses. The CCD  112  can then scan all of the fiber optic signals being returned and provide electrical signals via an interface connection  116  to a computer system (not shown) for detecting the status of each of the switching devices and sensors.  
         [0022]    [0022]FIG. 5A illustrates a switch position sensor system  120  incorporating a semiconductor light source, such as an LED array  122 . The LED array  122  directs light  126  through an optical coupling block  124 , such as an acrylic cube, onto fiber ends  132  in the fiber optic array  130 . The fibers  128  in the fiber optic array  130  are then optically coupled to the various switches and sensor devices (not shown) so that the light  126  directed onto the fiber ends  132  is absorbed or reflected according to the position of the sensed switch or control. Light reflected by the switches is coupled back into the fibers  128  and directed through the optical coupling block  124 , the LED Array  122  (which may include an aperture for passing the reflected light  134 ), and optional lens  136  to a CCD  138 . The CCD  136  can then scan all of the fiber optic signals being returned and provide electrical signals via an interface connection  140  to a computer system (not shown) for detecting the status of each of the switching devices and sensors.  
         [0023]    [0023]FIG. 5B is an exploded view of the switch position sensor system  120  of FIG. 5A. In an aspect of the invention, the LED array  122  may include a plurality of LED&#39;s  142  positioned circumferentially around a central aperture  144 . The aperture allows reflected light  134  from the fiber ends  132  to pass unimpeded from the optical coupling block  124  through the LED array  122  onto the CCD  138 . Accordingly, the LED array  122  can direct light  126  through an optical coupling block  124  onto fiber ends  132 , while allowing reflected light  134  to impinge on the CCD  134 .  
         [0024]    In an aspect of the invention, the individual LEDs  142  in the array may have a 15 degree viewing angle off-axis from a central axis as is known in the art. In addition, the LEDs  142  may be positioned in the LED array  122  such that the central axis of the LED is inclined (for example, by 15 degrees from a normal to the plain of the array) to point towards a center of the aperture  144 , to concentrate the light  126  onto the fiber ends  132 . The optical coupler  124 , such as a clear acrylic block, also serves to eliminate reflections inherent when shining light directly on the fiber ends  132 . Accordingly, any reflection due to a change in refractive index of the light emitted from the LEDs  142  will occur at the face of the LEDs  142  abutting the optical coupler  124  rather than the fiber ends  132 , so the reflected light  134  emitted from the fiber ends  132  represents only the reflected light  134  from the switches, and does not include a component of light reflected from the fiber ends  132  themselves. For example, the fiber ends  132  may be adhered to a face of the optical coupler  124  with an optical room temperature vulcanizing (RTV) compound that has index of refraction matching the fiber&#39;s  128  index of refraction so that reflection is minimized between the fiber ends  132  and the optical coupler  124 .  
         [0025]    In one form of the invention, 0.020 inch (0.051 cm) diameter fibers  128  can be used, allowing approximately 5000 fibers  128  to be arranged in a two-dimensional array at the fiber ends, such as a square having a 1.4 inch (3.56 cm) side, and held in place by a collar  148 . LEDs  142 , mounted in a ring configuration around a central aperture and having a dispersion angle of 15 degrees, can then illuminate all the fiber ends  132  in the fiber array  130  through the optical coupler  124 . A lens assembly  136  can be provided to align the reflected light  134  emitted from the fiber ends  132  through the aperture with respective individual pixels on the CCD  138 . Consequently, different fiber array  130  configurations would require different lens assemblies to ensure the focal area of the reflected light  134  on the CCD  138  is aligned with the desired individual pixels on the CCD  138 . In an aspect of the invention, if more fibers  128  are desired than can be accommodated with an existing lens assembly  146 , the thickness of the optical coupler  124  can be increased, thereby increasing the focal length of the lens assembly  146  and allowing all the reflected light  134  emitted by the fiber ends  132  to be projected on the CCD  138 .  
         [0026]    While only certain preferred features of the invention have been shown by way of illustration, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the present claims are intended to cover all such modifications and changes, which fall within the true spirit of the invention.