A short-arc xenon lamp has a region in which the arc and the radiant flux become unstable since an acoustic resonance ocures at the specific frequencies of the lamp when current modulation is employed. Therefore, when this kind of lamp is used as a modulated light source by modulating it directly, it is recommended that it should be used below the frequencies at which the lamp becomes unstable.... “usable frequency band.”
In addition, the fundamental features of the short-arc xenon lamp as a modulated light source, such as signal transfer characteristics and light modulation characteristics, have not been clarified.
This paper discusses the relationship between the fundamental features of the lamp (form of lamp bulb, electrode spacing, gas pressure and input wattage) and the modulated operation characteristics (instability of radiant flux, usable frequency band, signal transfer characteristics and light modulation cut-off frequency).
The following formula was drawn from the result of this work: the lowest acoustical resonant frequency of the current modulated short-arc xenon lamp is given by
f
ar=0.88×10
4/
D(1+0.76(
W/
Or)
0.38)
0.5HZ
Where
D is the inside diameter in cm, W is the lamp input wattage in nonmodulated operation in watt,
Or=
As/δ, where As is the surface area of the bulb in cm
2, and δ is thickness of the bulb wall in mm.
Moreover, in the usable frequency band, the short-arc xenon lamp can be regarded as a signal transfer system of the first order time lag.
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