Pulsed light source discriminator system
First Claim
1. In a discrimination system for receiving pulsed light from a light source excited by an input signal from a pulse generator and having a light sensitive receiver which produces an electrical output signal in response to received light energy,means for periodically varying the frequency of the input signal from the pulse generator,means for receiving the input signal for producing a first gating signal having a predetermined time phase relative to the input signal,means for receiving the electrical output signal for producing a second gating signal having a predetermined time phase relative to the electrical output signal,means for receiving said first and second gating signals and producing a gated signal while said first and second gating signals are in time coincidence,and an output circuit for receiving said gated signals and producing a system output related to the discriminated pulsed light.
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Abstract
A system sensitive to light pulses which are substantially synchronous with a selected pulsed light source containing frequency components within the pulse which are above a predetermined frequency. A signal for exciting the selected pulsed light source is frequency modulated and connected to an AND gate as well as to the pulsed light source device. The pulsed light is received and conditioned producing a received signal which is also connected to the AND gate. Gate output occurs only during the period of time the received signal is in time coincidence with the frequency modulated pulsed light source excitation signal. Additional light pulses transmitted in the immediate area of the receiver by additional light pulse transmitting devices having frequency components within the light pulse above the predetermined frequency may be sensed by the receiver, but will not produce output at the AND gate unless in time coincidence with the frequency modulated signal. An occasional pulse or several pulses from the additional light source may, by chance, fall partially in time coincidence with the frequency modulated signal thereby producing one or several AND gate outputs in sequence. A step-charging filter receives the AND gate outputs requiring a predetermined number of sequential AND gate outputs to reach a predetermined filter output signal level. Thus the frequency modulated signal and the received signal must be in time coincidence for the predetermined number of sequential received pulses before the charging filter produces an output which initiates the system output. In this fashion a plurality of proximate pulsed light sensitive systems may operate with each system having a unique instantaneous transmitted light pulse frequency modulated phase by which associated receivers may discriminate between light pulse sources.
38 Citations
10 Claims
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1. In a discrimination system for receiving pulsed light from a light source excited by an input signal from a pulse generator and having a light sensitive receiver which produces an electrical output signal in response to received light energy,
means for periodically varying the frequency of the input signal from the pulse generator, means for receiving the input signal for producing a first gating signal having a predetermined time phase relative to the input signal, means for receiving the electrical output signal for producing a second gating signal having a predetermined time phase relative to the electrical output signal, means for receiving said first and second gating signals and producing a gated signal while said first and second gating signals are in time coincidence, and an output circuit for receiving said gated signals and producing a system output related to the discriminated pulsed light.
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7. A discriminator system for receiving pulsed light comprising
a pulse generator for producing output pulses, an oscillator connected to said pulse generator for frequency modulation of said output pulses over a predetermined frequency range, a light source producing light pulses excited by said output pulses, a light sensitive receiver for receiving said light pulses and producing an electrical output related thereto, means for receiving said electrical output and producing a first gating signal in predetermined time phase therewith, means for receiving said pulses and producing a second gating signal in predetermined time phase therewith, and means for receiving said first and second gating signals for producing a gated signal when said first and second gating signals are in time phase, whereby the system is insensitive to spurious light energy signals at frequencies other than the instantaneous frequency of said light source.
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9. A method for discriminating between transmitted pulses from one light source and other transmitted light pulses received by a light sensitive receiver all at a median frequency, comprising the steps of
modulating the frequency of light pulses from the one light source over a predetermined frequency band surrounding the median frequency, gating the desired received frequency pulses with the modulated frequency, and producing a system output from the gated frequency pulses, whereby light pulses received having a modulation frequency or phase distinct from those of the modulated frequency are rejected.
Specification