Fluorescent object recognition system having self-modulated light source
First Claim
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1. A circuit for producing self-modulation of the light intensity of a mercury vapor lamp comprising:
- a transformer having primary and secondary windings;
a source of low frequency alternating voltage connected to said primary winding; and
a self-resonant circuit comprising the series connection of a copacitor and a mercury vapor lamp connected to said secondary winding, said resonant circuit having a resonant frequency higher than and a non-integral multiple of the frequency of said voltage source, wherein the light intensity of said lamp is caused to oscillate at the resonant frequency of said resonant circuit.
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Abstract
An object recognition system for detecting visible light of a predetermined wavelength emitted by a fluorescent material illuminated with modulated ultraviolet light produced by a self-modulated high pressure mercury vapor lamp. The lamp forms part of a resonant LC circuit which produces oscillations in the lamp intensity at a frequency higher than line frequency. The resulting visible light is detected, demodulated, and compared with a predetermined threshold to sense when the fluorescent material is present. Self-modulation of the UV lamp source eliminates external triggering, excitation or switching of the lamp power supply.
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Citations
17 Claims
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1. A circuit for producing self-modulation of the light intensity of a mercury vapor lamp comprising:
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a transformer having primary and secondary windings; a source of low frequency alternating voltage connected to said primary winding; and a self-resonant circuit comprising the series connection of a copacitor and a mercury vapor lamp connected to said secondary winding, said resonant circuit having a resonant frequency higher than and a non-integral multiple of the frequency of said voltage source, wherein the light intensity of said lamp is caused to oscillate at the resonant frequency of said resonant circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A circuit for producing self-modulation of the light intensity of a lamp of the type having a negative resistance characteristic comprising:
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a source of low frequency voltage, and self-resonant circuit means including a lamp having a negative voltage characteristic connected to said voltage source for causing the light intensity of the lamp to oscillate at a frequency which is higher than and a non-integral multiple of the frequency of said alternating voltage source. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification