Strobe light and laser beam detection for laser receiver

Abstract

A laser receiver detects a thin beam of laser light and distinguishes between the beam of laser light and an omni-directional pulse of light from a strobe by the use of an additional photo-detector. The device takes into account the possibility that the additional photo-detector could be illuminated simultaneously with the main photo-detectors at the end of the main photo-detectors closest to the additional photo-detector.

1. A method for detecting a moving, relatively thin beam of laser light, and distinguishing between such a moving, relatively thin beam of laser light and an omni-directional pulse of light, comprising the steps of:
 positioning a plurality of photo-detectors in a generally vertical row, each of said photo-detector elements providing an electrical output when illuminated, 
 positioning an additional photo-detector at a point remote from said plurality of photo-detectors, 
 providing a portion of the electrical output of each photo-detector in the row as a first reference signal related to the spacing of the photo-detector from a first end of the row, and providing a portion of the electrical output of each photo-detector in the row as a second reference signal related to the spacing of the photo-detector from the second end of said row, 
 providing the electrical output of said additional photo-detector as a third reference signal, and 
 interpreting a third reference signal of sufficiently low amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by a thin beam of laser light, and interpreting a third reference signal of sufficiently high amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by an omni-directional pulse of light. 
 
     
     
       2. The method according to  claim 1  in which the step of positioning an additional photo-detector at a point remote from said plurality of photo-detectors comprises the step of positioning said additional photo-detector at a point closer to said first end of said row than to said second end of said row, and in which the step of interpreting further includes the step of interpreting a third reference signal of sufficiently high amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by an omni-directional pulse of light only if the first reference signal is less than a value set as substantially four times the third reference signal and also the first reference signal is less than a value set as substantially twice the second reference signal. 
     
     
       3. The method according to  claim 1 , further comprising the step of determining the position of said beam of laser light with respect to said row based on the levels of said first and second reference signals from said row of photo-detectors in the event that illumination of said photo-detectors by a moving, relatively thin beam of laser light is indicated. 
     
     
       4. The method according to  claim 3 , further comprising the step of displaying an indication of said position of said beam of laser light with respect to said row. 
     
     
       5. The method according to  claim 1 , in which the step of positioning a plurality of photo-detectors includes the step of positioning a plurality of PIN diodes. 
     
     
       6. The method according to  claim 1 , in which the step of providing a portion of the electrical output of each photo-detector in the row as a first reference signal related to the spacing of the photo-detector from a first end of the row, and providing a portion of the electrical output of each photo-detector in the row as a second reference signal related to the spacing of the photo-detector from the second end of said array row includes the step of separating said portions of said electrical outputs using a tapped transformer with each of said plurality of photo-detectors being connected to said transformer. 
     
     
       7. A method for detecting a moving, thin beam of laser light, and distinguishing between such a moving, thin beam of laser light and an omni-directional pulse of light, comprising the steps of:
 providing a plurality of photo-detectors which produce first and second reference signals indicative of the vertical position of the thin beam of laser light with respect to the upper and lower limits of detection of said plurality of photo-detectors, 
 positioning an additional photo-detector at a point remote from said plurality of photo-detectors, 
 providing a first reference signal related to the spacing of the thin beam of laser light from the upper limit of detection of said plurality of photo-detectors, and providing a second reference signal related to the spacing of the thin beam of laser light from the lower limit of detection of said plurality of photo-detectors, 
 providing the electrical output of said additional photo-detector as a third reference signal, and 
 interpreting a third reference signal of sufficiently low amplitude as indicating simultaneous illumination of said plurality of photo-detectors as illumination by a thin beam of laser light, and interpreting a third reference signal of sufficiently high amplitude as indicating simultaneous illumination of said plurality of photo-detectors as illumination by an omni-directional pulse of light. 
 
     
     
       8. The method according to  claim 7 , further comprising the step of determining the position of said beam of laser light with respect to said upper and lower limits of detection based on the levels of said first and second reference signals from said plurality of photo-detectors in the event that illumination of said plurality of photo-detectors by a moving, relatively thin beam of laser light is indicated. 
     
     
       9. The method according to  claim 8 , further comprising the step of displaying an indication of said position of said beam of laser light with respect to said upper and lower limits of detection. 
     
     
       10. The method according to  claim 7 , in which the step of providing a plurality of photo-detectors which produce first and second reference signals indicative of the vertical position of the thin beam of laser light with respect to the upper and lower limits of detection of said plurality of photo-detectors includes the steps of:
 positioning a plurality of photo-detectors in a generally vertical row extending between said upper and lower limits of detection, each of said photo-detector elements providing an electrical output when illuminated, and 
 providing a portion of the electrical output of each photo-detector in the row as said first reference signal related to the spacing of the photo-detector from a first end of the row, and providing a portion of the electrical output of each photo-detector in the row as said second reference signal related to the spacing of the photo-detector from the second end of said row. 
 
     
     
       11. The method according to  claim 7 , in which the step of providing a plurality of photo-detectors which produce first and second reference signals indicative of the vertical position of the thin beam of laser light with respect to the upper and lower limits of detection of said plurality of photo-detectors includes the steps of:
 providing first and second photo-detectors, which extend vertically between the upper and lower limits of detection, said first photo-detector being wider adjacent said upper limit of detection and narrower adjacent said lower limit of detection, and said second photo-detector being wider adjacent said lower limit of detection and narrower adjacent said upper limit of detection. 
 
     
     
       12. A device for detecting a moving, relatively thin beam of laser light, and distinguishing between illumination of photo-detectors by such a moving, relatively thin beam of laser light, and illumination of photo-detectors by an omni-directional pulse of light, comprising:
 a plurality of photo-detectors arranged in a generally vertical row, each of said photo-detector elements providing an electrical output when illuminated,   a weighting circuit associated with said plurality of photo-detectors, said weighting circuit providing a portion of the electrical output of each photo-detector as a first reference signal related to the spacing of the photo-detector from a first end of said row, and providing a portion of the electrical output of each photo-detector as a second reference signal related to the spacing of the photo-detector from a second end of said row,   an additional photo-detector, positioned at a point remote from said plurality of photo-detectors, for providing an electrical output as a third reference signal,   circuitry, responsive to the reference signals, for interpreting a third reference signal of sufficiently low amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by a thin beam of laser light, and interpreting a third reference signal of sufficiently high amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by an omni-directional pulse of light.   
     
     
       13. A device for detecting a moving, relatively thin beam of laser light, and distinguishing between illumination of photo-detectors by such a moving, relatively thin beam of laser light, and illumination of photo-detectors by an omni-directional pulse of light, according to  claim 12 , in which said additional photo-detector is positioned at a point closer to said first end of said row than to said second end of said row, and in which said circuitry interprets a third reference signal of sufficiently high amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by an omni-directional pulse of light only if the first reference signal is less than a value set at approximately four times the third reference signal and also the first reference signal is less than a value set at approximately twice the second reference signal. 
     
     
       14. A device for detecting a moving, relatively thin beam of laser light, and distinguishing between illumination of photo-detectors by such a moving, relatively thin beam of laser light, and illumination of photo-detectors by an omni-directional pulse of light, according to  claim 12 , in which said circuitry further determines the position of said beam of laser light with respect to said row based on the levels of said first and second reference signals from said row of photo-detectors in the event that illumination of said photo-detectors by a moving, relatively thin beam of laser light is indicated. 
     
     
       15. A device for detecting a moving, relatively thin beam of laser light, and distinguishing between illumination of photo-detectors by such a moving, relatively thin beam of laser light, and illumination of photo-detectors by an omni-directional pulse of light, according to  claim 12 , in which said photo-detector elements comprise PIN diodes. 
     
     
       16. A device for detecting a moving, relatively thin beam of laser light, and distinguishing between illumination of photo-detectors by such a moving, relatively thin beam of laser light, and illumination of photo-detectors by an omni-directional pulse of light, according to  claim 12 , in which said weighting circuit comprises a tapped transformer circuit with each of said plurality of photo-detectors being connected to said tapped transformer circuit. 
     
     
       17. A device for detecting a moving, relatively thin beam of laser light, and distinguishing between illumination of photo-detectors by such a moving, relatively thin beam of laser light, and illumination of photo-detectors by an omni-directional pulse of light, comprising:
 first and second photo-detectors which extend vertically between the upper and lower limits of detection, said first photo-detector being wider adjacent said upper limit of detection and narrower adjacent said lower limit of detection, and said second photo-detector being wider adjacent said lower limit of detection and narrower adjacent said upper limit of detection, said first and second photo-detectors providing first and second reference signals indicative of the vertical position of the thin beam of laser light with respect to the upper and lower limits of detection,   an additional photo-detector, positioned at a point remote from said first and second photo-detectors, for providing an electrical output as a third reference signal,   circuitry, responsive to the reference signals, for interpreting a third reference signal of sufficiently low amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by a thin beam of laser light, and interpreting a third reference signal of sufficiently high amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by an omni-directional pulse of light.   
     
     
       18. A device for detecting a moving, relatively thin beam of laser light, and distinguishing between illumination of photo-detectors by such a moving, relatively thin beam of laser light, and illumination of photo-detectors by an omni-directional pulse of light, according to  claim 17 , in which said additional photo-detector is positioned at a point closer to said upper limit of detection than to said lower limit of detection, and in which said circuitry interprets a third reference signal of sufficiently high amplitude as indicating simultaneous illumination by an omni-directional pulse of light only if the first reference signal is less than a value set at approximately four times the third reference signal and also the first reference signal is less than a value set at approximately twice the second reference signal. 
     
     
       19. A method for detecting a moving, relatively thin beam of laser light, and distinguishing between such a moving, relatively thin beam of laser light and an omni-directional pulse of light, comprising the steps of:
 providing a plurality of photo-detectors which, if illuminated by light, produce a plurality of reference signals;   positioning an additional photo-detector at a point remote from said plurality of photo-detectors, said additional photo-detector, if illuminated by light, producing an additional reference signal;   providing a processor, for processing said reference signals;   receiving said additional reference signal and determining if its comparative amplitude indicates a simultaneous illumination of said plurality of photo-detectors by a relatively thin beam of laser light; and   receiving said additional reference signal and determining if its comparative amplitude indicates a simultaneous illumination of said plurality of photo-detectors by an omni-directional pulse of light.   
     
     
       20. The method according to claim 19, further comprising the step of: after determining that a relatively thin beam of laser light had illuminated said plurality of photo-detectors, then determining a position substantially where said relatively thin beam of laser light struck said plurality of photo-detectors. 
     
     
       21. The method according to claim 20, further comprising the step of: displaying an indication of whether the relatively thin beam of laser light was above, below, or within a centered reference band. 
     
     
       22. A method for detecting a moving, relatively thin beam of laser light, and distinguishing between such a moving, relatively thin beam of laser light and an omni-directional pulse of light, comprising the steps of:
 providing a plurality of photo-detectors which, if illuminated by light, produce a plurality of reference signals;   positioning an additional photo-detector at a point remote from said plurality of photo-detectors, said additional photo-detector, if illuminated by light, producing an additional reference signal; and   interpreting an additional reference signal of sufficiently low amplitude as indicating simultaneous illumination of said plurality of photo-detectors as illumination by a relatively thin beam of laser light, and interpreting an additional reference signal of sufficiently high amplitude as indicating simultaneous illumination of said plurality of photo-detectors as illumination by an omni-directional pulse of light.   
     
     
       23. The method according to claim 22, further comprising the step of: after determining that a relatively thin beam of laser light had illuminated said plurality of photo-detectors, then determining a position substantially where said relatively thin beam of laser light struck said plurality of photo-detectors. 
     
     
       24. The method according to claim 23, further comprising the step of: displaying an indication of whether the relatively thin beam of laser light was above, below, or within a centered reference band. 
     
     
       25. A method for detecting a moving, relatively thin beam of laser light, and distinguishing between such a moving, relatively thin beam of laser light and an omni-directional pulse of light, comprising the steps of:
 providing a plurality of photo-detectors which, if illuminated by light, produce a plurality of reference signals;   positioning an additional photo-detector at a point remote from said plurality of photo-detectors, said additional photo-detector, if illuminated by light, producing an additional reference signal;   receiving said additional reference signal and determining by an output circuit if its comparative amplitude indicates a simultaneous illumination of said plurality of photo-detectors by a relatively thin beam of laser light; and   receiving said additional reference signal and determining by said output circuit if its comparative amplitude indicates a simultaneous illumination of said plurality of photo-detectors by an omni-directional pulse of light.   
     
     
       26. The method according to claim 25, further comprising the step of: after determining that a relatively thin beam of laser light had illuminated said plurality of photo-detectors, then determining a position substantially where said relatively thin beam of laser light struck said plurality of photo-detectors. 
     
     
       27. The method according to claim 26, further comprising the step of: displaying an indication of whether the relatively thin beam of laser light was above, below, or within a centered reference band.