Source Type

Mean wavelength [nm]

Bandwidth [nm]

Coherence length

Hg arc (high pressure)

546.1

10.0

< 0.3 mm

Hg arc (low pressure)

546.1

1.0

< 0.3 mm

Ag laser

544.5

~.009

< 3 cm

He-Cd laser

441.6

~ 7 x 10-4

< 27.5 cm

He-Ne laser

632.8

10-5 to 10-6

~ 104 cm