| 摘要 |
1507330 Photo-electric communications PRECITRONIC GES FUR FEINMECHANIK UND ELECTRONIC mbH 10 Nov 1975 [8 Nov 1974] 46403/75 Heading G1A A transponder receives an incident light beam, identifies the beam, modulates it and reflects it back along the incident path. The transponder may be attached to an object such as a military installation or vehicle, so that the object can be interrogated and identified from a distance. In Fig. 1 the incident beam 1 or 1' is reflected back on itself by a reflector 8, and passes through a modulator 7, a photo-detector 2 also receives the incident light and produces an electric signal in response. The signal is demodulated at 4 to see whether the incoming beam carries suitable identifying modulation. The result of the demodulations is displayed at 5, and the modulator 7 is activated by a microphone 10 or a stored code 11 so as to reply to the interrogation by modulating the reflected light. The modulator is preferably opaque in the absence of suitably identified incident light, to prevent reflector 8 being used to locate the transponder. A three dimensional array of transponders may be made, Fig. 2, with individual or common detectors 2 or 2', a spherical array may be approximated by adding further transponders at the top and bottom of Fig. 2. The reflectors and modulators may be coated with filters to restrict the wavelengths reflected. |
