Abstract:
An open-path/free-space optical communication system using reflected light has modulated optical or laser sources and provides communication between the modulated source and a detector in an obstructed line-of-sight relationship. The system detects backscattered light impinging on a target illuminated by the source of light. Barrier objects positioned in a line-of-sight path between the source and detector are circumvented and a first device that provides the modulation signal for the source controls a remote second device.

Description:
RELATED APPLICATIONS  
       [0001]    The present application is a U.S. National Stage application claiming the benefit of prior filed International Application, Serial Number PCT/US02/02866, filed Jan. 30, 2002, which International Application claims a priority date of Jan. 30, 2001 based on prior filed U.S. Provisional Application Ser. No. 60/265,022. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to systems and methods for relaying information between two or more points by using laser or optically generated conductive transport means through the atmosphere to convey the information.  
           [0004]    2. Description of the Prior Art  
           [0005]    Open-Path, or Free-Space Optics is a line-of-sight technology that enables optical transmission of data, voice and video communications through the , providing optical connectivity without the need for expensive fiber-optic cable. Propagating optical signals through the air requires light signals generated by the use of either light emitting diodes (LEDs) or lasers.  
           [0006]    Free-Space optical systems can operate over a distance of several kilometers, provided the transmitting laser and the receiver are in a direct line-of-sight relationship. When a clear line of sight between the source and destination does not exist, optical communication between the devices has not been feasible because physical objects positioned in the line-of-sight path easily block direct line-of-sight communication. Thus, a cubical wall may separate two computers in a room from one another, for example, and prevent optical communication therebetween.  
           [0007]    However, at the time of the present invention, it was not obvious to those of ordinary skill in the art how this fundamental problem could be overcome.  
         SUMMARY OF INVENTION  
         [0008]    The long-standing but heretofore unfulfilled need for a communication device that enables data transfer between a data communication device transmitter and a data communication device receiver where a barrier means prevents line-of-sight communication therebetween is now met by a communication device for transmitting signals to a receiver that includes an optical light source adapted to generate light, a detector adapted to detect light, and an optical diffuse reflecting target in line-of-sight relation to the optical light source and in line-of-sight relation to the detector. A modulating device is connected in modulating relation to the optical light source and the detector is adapted to demodulate light reflected or backscattered by the target.  
           [0009]    The light source is selected from the group consisting of a laser light source and a light-emitting diode.  
           [0010]    In one embodiment, an enclosure having at least one wall member, or at least one ceiling member, or at least one floor member houses the optical light source, the detector, and the barrier. The at least one wall member, ceiling member, or floor member serves as the target.  
           [0011]    In another embodiment, the communication device includes a first data communication device adapted to transmit data and a laser source modulated by the first data communication device. A transmitter telescope is adapted to aim modulated light from the laser source to the light-reflecting target. A second data communication device is adapted to receive data and a transducer in the form of an optical detector is adapted to generate electrical signals corresponding to detected optical signals is connected in driving relation to the second data communication device. A receiving telescope is adapted to collect modulated light reflected from the light-reflecting target and to deliver the modulated light to the optical detector. Moreover, an optical bandpass filter is electrically connected between the receiving telescope and the optical detector. A barrier means preventing line-of-sight communications between the first and second data communication devices is adapted to be positioned between the first and second data communication devices. The transmitter telescope causes modulated light to reflect from the light-reflecting target and the receiver telescope causes reflected light to focus on the optical detector. Accordingly, the second data communication device receives electrical signals from the first data communication device.  
           [0012]    The light-reflecting target may be a ceiling, wall, or floor of a structure adapted to house the first and second data communication devices. The light-reflecting target may also be a natural structure such as a tree, or a man-made structure such as a building, external to a structure adapted to house the first and second data communication devices.  
           [0013]    In another embodiment, the device again includes a first data communication device adapted to transmit data and a laser source modulated by the first data communication device. A first optical lens means having a # to 2# steradians field of view is positioned in light dispersing relation to the laser source. A second data communication device is adapted to receive data and an optical detector adapted to generate electrical signals corresponding to detected optical signals is connected in driving relation to the second data communication device. A second optical lens means having a # to 2# steradians field of view is positioned in light focusing relation to the optical detector. A barrier means preventing line-of-sight communication between the first and second data communication devices is adapted to be positioned in an enclosure between the first and second data communication devices.  
           [0014]    Accordingly, the first optical lens means causes modulated light to reflect or backscatter in a diffuse manner from the ceiling, walls, or floor of the enclosure and the second optical lens means causes reflected light to focus on the optical detector. The second data communication device therefore receives electrical signals from the first data communication device.  
           [0015]    The first optical lens means may take the form of a hemispherical short focus lens or it may be provided in the form of transmitter optics.  
           [0016]    An electrical signal conditioning means is electrically connected between the first data communication device and the laser source.  
           [0017]    The second optical lens means may take the form of a hemispherical short focus lens.  
           [0018]    An electrical signal conditioning means may also be electrically connected between the optical detector and the second data communication device.  
           [0019]    An optical bandpass filter may be electrically connected between the second optical lens means and the optical detector.  
           [0020]    Another embodiment includes a LIDAR communication system. More particularly, a laser is adapted to generate a LIDAR beam and a transmitting device is provided for modulating the laser. A transmit telescope is adapted to aim the LIDAR beam at a remote target and a receiver telescope is adapted to collect the LIDAR beam after the LIDAR beam has reflected or backscattered from the remote target. An optical detector means adapted to generate electrical signals upon receiving reflected light from the remote target is in light-receiving communication with the receiver telescope. A data-receiving device is adapted to receive electrical signals from the optical detector. In this way, the data-receiving device receives data from the data-transmitting device even when the data-receiving device is positioned in a location distant from the data-transmitting device even when at least one obstacle prevents line-of-sight communication between the data-transmitting device and the data receiving device.  
           [0021]    An electrical signal conditioner adapted to condition signals from the data-transmitting device is preferably disposed in electrical communication between the data transmitting device and the laser. An electrical signal conditioner adapted to condition signals from the optical detector is also disposed in electrical communication between the optical detector and the data-receiving device.  
           [0022]    It is an object of the invention to provide an open-path optical or laser beam communication system that conveys information between two or more points within a building structure even when one or more physical objects are positioned in a line-of-sight path between said points.  
           [0023]    It is a further object of the invention to provide an open-path laser beam communication system that can convey information between two or more buildings even when one or more physical objects are positioned in a line-of-sight path between said buildings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0024]    [0024]FIG. 1 is an overall schematic of the laser communication system of the present invention;  
         [0025]    [0025]FIG. 2 is a schematic showing the laser communication system inside a closed building;  
         [0026]    [0026]FIG. 3 is a schematic of a second embodiment of the invention showing the communication system communicating between buildings; and  
         [0027]    [0027]FIG. 4 is a schematic of an expanded version of the FIG. 3 system.  
     
    
     DETAILED DESCRIPTION  
       [0028]    Referring now to FIG. 1, it will there be seen that an illustrative embodiment of the novel laser communication system is denoted as a whole by the reference numeral  10 .  
         [0029]    System  10  includes laser generator or other light source  12  connected in communication modulation relation to sending device  14 , i.e. sending device  14  modulates laser generator  12 . Transmitter telescope  13  is adapted to aim a laser or other optical beam from laser generator  12  toward a target area  16  which in this embodiment may take the form of an area of a ceiling  18  or similar structure such as a wall, floor, or other suitable light-reflecting surface. The light is scattered from target area  16  and excites sensor  20  attuned to the wavelength or wavelengths emitted by laser generator  12 . Sensor  20  is connected in driving relation to receiving device  22 . Accordingly, system  10  enables communication of a control function whereby sending device  14  may control receiving device  22 .  
         [0030]    Although not illustrated, upon disclosure of the FIG. 1 embodiment, it becomes apparent that receiving device  22  could be similarly connected in driving relation to a second laser generator and sending device  14  could similarly fitted with a second sensor so that device  22  could just as easily control device  14 .  
         [0031]    Sensor  20  is attuned to sense scattered light from a remote target area such as target area  16  by means of a highly sensitive device such as a receiver telescope means  24 . Accordingly, a straight line-of-sight light path relationship between laser generator  12  and sensor  20  is not required. This enables operation of a remote device such as receiving device  22  when a straight-line relationship between source  12  and detector  20  is unavailable due to a physical barrier such as obstruction  26  in the straight-line light path.  
         [0032]    Moreover, since the wavelength of a laser source is being detected, there is no need to bounce a wave away from target  16  to regenerate it at an intermediate station. Since the detector or sensor  20  can be a highly sensitive receptor device, there is no need for any amplification of the beam for the device to operate either at the source or at the intermediate target area. This enables use of a fairly lowlaser source, the sensitivity being a function of sensor  20  and not necessarily laser generator  12  or the presence of an unillustrated amplification device in target area  16  or anywhere else along the extent of the path of travel of the modulated beam.  
         [0033]    In a practical application of this invention, any number of laser generators, sending and receiving devices, sensors, telescopes, and the like may be employed using different target areas or the same target area if the signals are encoded or different wavelengths and optically filtered detectors are used.  
         [0034]    Laser generator  12  may be adapted to emit one of a plurality of wavelengths so that a specific signal will control a selective function at receiving device  22 . Moreover, sensor  20  may be encoded to a certain wavelength to perform selective functions at various different locations. In this way, a variety of functions may be controlled at a single site because the sensors are enabled to select a certain wavelength to correspond to a specific response.  
         [0035]    Optical bandpass filter  28  may also be used to pass preselected s and reject interfering light impinging on detector  20 .  
         [0036]    In the embodiment of FIG. 2, denoted  30  as a whole, a hemispherical or short focal length lens  32  scatters light to a plurality of points within a room. Lens  32  may be supplanted by transmitter optics. Data communication device transmitter  34  modulates infrared laser source  35  in much the same way as device  14  modulates laser  12  in the first embodiment. An LED or other suitable light source may also be used. Laser source  35  includes power supply  33 . Various electrical components, including signal conditioners  31 , provide an interface between transmitter  34  and laser source  35 .  
         [0037]    Light from lens  32  impinges upon surface or surfaces  36  and the reflected light is collected by hemispherical or short focal length lens  38 . The focused light impinges upon optical bandpass filter  39  which filters out the various wavelengths of light illuminating the room and allows light within the passed bandwidth to impinge upon optical detector  40 . Electrical signal conditioner  41  conditions the electrical signal generated by optical detector  40  and said signal is then received by data communication device receiver  42 . Communication is thereby established between transmitter  34  and receiver  42  that is not subject to interference by physical barriers or obstacles such as obstacle  43  which may be in the room. Transmitter  34  and receiver  42  may be computers, each of which includes an RS-232 or Internet port for data.  
         [0038]    This application is useful for any size room, including large spaces such as found in warehouse situations.  
         [0039]    Because the light sensed by detector  40  is scattered as a result of impinging on target surface  36 , the intensity of the beam emitted by laser source  35  is dictated by the sensitivity of the detector or sensor  40  and not on any requirements of an intermediate or relay system.  
         [0040]    In practice, this system can be used to control functions of televisions, computers, telecommunication devices, Internet devices, printers, and the like. In a specific embodiment of this system, with the use of a # or 2# steradian solid angle lens and detector, any problems caused by obstacle  43  may be overcome with ease. In addition to control functions, both analog and/or digital information may be conveyed in the light beam. This is accomplished by amplitude modulation of the power supply to the light source, such as an electromodulator or a high electromechanical chopper to encrypt the information.  
         [0041]    In the embodiment of FIG. 3, laser communication system  50  is modified to communicate between buildings  52  and  54 . In this embodiment, an external target, here shown as tree  51 , is used between source  54 , modulated by transmitting device  55 , and detector apparatus  56  that delivers the data to receiving device  57 . Transmitter and receiver telescopes  53  and  59  are used in the same manner as in the embodiment of FIG. 1. Other types of targets may be used, including, but not limited to, clouds, buildings, direct atmospheric aerosols, etc. As in the first two embodiments, the same type of information may be transmitted, and the same sources used, but greater distances are covered. Multiple transmitters may be employed in this system, and optical as well as laser sources may supply the light beam, and there may also be a plurality of receiving devices using different target areas or the same target area if the signals are encoded or different laser wavelengths and optically filtered detectors are used. Detection system  56  detects the scattered light emanating from target  51 , irrespective of any intervening object in the direct optical pathway, which prevents pointcommunication between source  54  and detector  56 .  
         [0042]    [0042]FIG. 4 depicts an expanded version of this system, denoted  60  as a whole, with an amplitude modulated continuous-wave GaAIAs 1.5 μm diode laser  62  as the source with encrypted electronic signals being carried by virtue of electronic modulation devices in the system. More specifically, electrical signal conditioners  66  condition signals from data transmitting device  64  and said conditioned signals modulate laser  62 . The LIDAR beam generated by laser  62  is directed by transmit telescope  68  through the atmosphere to a distant target  70 . The reflected beam is collected by receiver telescope  72  and delivered to optical detector  74 . The electrical signals generated by optical detector  74  are conditioned by electrical signal detector  76  and delivered to data receiving device  78 .  
         [0043]    It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained. Since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.  
         [0044]    It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.  
         [0045]    Now that the invention has been described,