High speed photography light source

Details High speed photography light source High speed photography light source

1999-09-24

2001-05-08

Vu, David (Department: 2821)

Electric lamp and discharge devices: systems

Discharge device load

Plural cathode and/or anode discharge device load

C315S112000, C315S111210, C313S491000, C313S493000, C313S634000

Reexamination Certificate

active

06229272

ABSTRACT:

BACKGROUND OF THE INVENTION
For high-speed photography, electronic imaging and other purposes, it is often necessary to provide intense broadband illumination. For providing a single burst of intense illumination lasers have been employed but are expensive and do not provide broadband illumination. An argon candle is also known for providing a one-time intense light burst that destroys the lamp. Such argon candles are also potentially destructive of their surroundings and are prone to malfunction. For repetitive light bursts, strobe lamps are known and can be made extremely cheaply however inexpensive lamps are not usually useful for high repetition rate applications. In addition, existing strobe lamps cannot handle very high power and therefore cannot provide levels of illumination necessary for many purposes. Surface discharge lamps are also known but have not achieved the necessary performance for many purposes.
BRIEF SUMMARY OF THE INVENTION
A flash illumination system is provided which is especially useful for high-speed photography. In one embodiment, the invention provides a surface discharge lamp which produces an intense broadband burst of light having an intended spectrum. Another embodiment of the invention provides a surface discharge lamp which produces multiple pulses of intense broadband illumination at very high pulse repetition rates. The lamp in either embodiment is fabricated in a relatively inexpensive manner and can be compactly constructed and of modular construction to suit various applications. The lamp is composed of a gas envelope in which is provided a dielectric substrate and electrodes at respective ends of a surface of the substrate. The substrate in some embodiments is a portion of the enclosure. A backplane is disposed outside the enclosure and confronting the opposite surface of the substrate between the electrodes. The backplane provides capacitive coupling to the plasma and constrains the plasma to a thin region near the dielectric substrate surface. The backplane is also operative to reduce the breakdown voltage necessary to initiate the plasma. In addition the external backplane serves as a heat sink for dissipation of heat generated during lamp operation.
The lamp is energized by a pulse-forming network (PFN) powered by a high voltage supply, and a plasma is created across the dielectric surface separating the electrodes. For single pulse operation, where the lamp produces a single high intensity burst of light, the backplane is connected to the ground electrode as a current return, and the lamp is triggered by an electrical pulse applied to the electrodes from the PFN. For repetitive pulse operation where the lamp produces a train of light pulses at high repetition rates, the backplane is not connected to the ground electrode but rather is connected to a trigger source. To initiate plasma discharge, the lamp is triggered by an electrical pulse applied to the backplane and plasma discharge is maintained by the pulses applied to the electrodes.
The lamp is of simple rugged construction and is relatively inexpensive. The geometry of the lamp can be readily configured to suit particular illumination requirements, and two or more lamps can be interconnected to provide a desired illumination pattern.
The PFN may be separated from the one or more lamps by a low inductance high capacitance interconnecting cable which is part of the PFN and which serves as a peaking capacitor to enhance the triggering voltage of the lamp(s). The separation of the lamp(s) from the PFN is especially useful in high speed photography of explosions and other events which are likely to destroy the lamp(s).
The plasma is predominantly composed of ions of the gas in the envelope, but includes a small contribution from the substrate material which can be employed to enhance the radiative output in selected spectral bands. Radiation is usually intended in the visible spectrum for exposure of photographic film. However, radiation can also be in the infrared (IR) and ultraviolet (UV) bands. For visible wavelengths and for infrared, the gas environment is typically xenon, argon or krypton For UV the gas can typically be xenon or argon. For some purposes, the lamp can be operated with or without an envelope in an air environment, and can also be used at sub-atmospheric pressure.


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Plasma discharge replacement for argon candles, Prepared by: Robert G. Root and Paul Falkos, p. 1-11 No Date.
Repetitively pulsed plasma illumination source improvements, Prepared by: Robert G. Root and Paul Falkos, p. 1-12 No Date.
Intense Visible Pulsed Light Source For Test Instrumentation, Prepared by: Robert G. Root and Paul Falkos, p. 1-108 No Date.

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