Biophotonics_Concepts_to_Applications

quartz envelope that contains a xenon gas under high pressure. The maximum
optical power emission from a Xe lamp comes from an area approximately 0.3 mm
by 0.5 mm in the arc region. Typically these lamps have an integrated parabolic
reflector, which collects the light that has been emitted into a large solid angle and
either images it onto a pinhole opening (with typical f numbers between 1.0 and 2.0)
or onto an objective lens to produce a collimated output.
Pulsed xenon lamps orflash lampsproduce microsecond to millisecondflashes
of high intensity light containing a broadband spectrum. This light can be generated
over a continuous spectrum from about 160 nm in the ultraviolet to 2000 nm in the
infrared. Typical outputs are 15 W with arc beam diameters of 3 or 8 mm.

4.3 Light-Emitting Diodes

Owing to attractive features such as low power consumption, good reliability, long
lifetimes, and availability of different emission colors in a broad range of wave-
lengths, light-emitting diodes are used worldwide for many categories of lighting
[ 7 – 10 ]. The applications include spotlights, vehicle taillights, road lights, indicator

200 300 400 500 600 700 800 900

Wa v e l e ngth (nm)

Relative emission intensity

0.5

1.0

0

312

546

579

365

405

436

297

254

Visible spectrum

Fig. 4.4 Typical emission
spectrum from a mercury arc
lamp

200 300 400 500 600 700 800 900

Wa v e l e ngth (nm)

0

1000

Visible spectrum

Relative emission intensity

0.5

1.0

475

827 885

919

980

Fig. 4.5 Typical emission
spectrum from a xenon arc
lamp

98 4 Fundamentals of Light Sources