- Place the etalon unit, E, on
the slide unit. Check that the gap between the two internal reflecting surfaces is about
1/2mm all the way round. If this is not the case, then make small adjustments to the 'x'
and 'y' adjuster knobs on the etalon unit.
- Switch on the laser diode and
look through the etalon. Three sets of small images will be seen, each of which will
probably consist of multiple dots of decreasing intensity. The central image will be the
brightest.
- Adjust the knobs so that only
three discrete images are seen.
- Place the ground glass
screen, GG, in front of the etalon. You should observe approximately circular interference
fringes. Make small adjustments to the knobs to change the position and shape of the
fringes
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