- Position the mirror unit, M1, to the left
of centre on the slide using the knob.
- Switch on the laser diode and raise the
search pin, SP, to its full height.
- Place the prism, P, on the turntable, TT,
and rotate mirror, M2, so that two images of the search pin are seen through the ground
glass screen, GG. Rotate the prism turntable in both directions by small amounts to set
the prism at minimum deviation - this can be carried out fairly accurately using the
turntable locking and adjuster knobs.
- Carefully adjust the 'x' and 'y' knobs at
the rear of mirror unit M1 so that the images of the search pin are co-incident. You may
see interference fringes immediately, but more likely, you will have to continue making
small adjustments until interference fringes are seen. The contrast and fringe spacing
will vary according to the homogeneity of the prism glass and the flatness of its
surfaces.
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