Light source

ONE MILLION POINTS OF LIGHT

LIGHT EMITTING DIODES

PROS

LEDs are cheap, low power, and easy to mount. UV LEDs exist.

CONS

LEDs typically have very short profiles around their maximum, which makes them more difficult to use.

For example, a typical white LED (blue LED with phosphor fluorescence) has a fairly uneven power distribution 450-650 nm, with sharp LED peak around blue (450 nm) and wider phosporescence hump around 550 nm.

UV LEDs are difficult to get, especially deep UV.

GAS DISCHARGE LAMPS

PROS

Mercury and xenon arc lamps have a very high spectral range, including the UV. They can be found in a variety of places including soda machines (germicidal UV xenon lamps), LCD backlights ( wide-range xenon).

CONS

It seems that they are hard to wire in and power. In order to ignite the arc, a high voltage pulse must be used, although they can be somewhat low power (10W in microscopes). High-voltage pulses can often cause ambient noise in the system.

Although they can be scrounged, they are not necessarily cheap.

Many mercury and xenon lamps have recently been banned, making an illegal spec.