Reflective Conoscope

5) Miscellaneous images obtained with the reflective conoscope

Below we present some conoscopic images obtained with the apparatus:

a) b) c)

Photo of the Malta cross in a quartz sample.
a) in monochromatic (green - 555 nm) light for a sample of thickness equal to 3.9 mm;
b) in white light for the same sample thickness;
c) in monochromatic light (green – 555 nm) for a sample thickness of 190 microns.

The arms of the cross are curved (Airy spiral) in figures a) and b) because of the optical rotatory power of the quartz. The birefringence of the samples is 0.009 (low birefringence).

In figure c) the crystal is too thin to observe the bending of the cross arms

Quartz sample of thickness equal to 3.9 mm, but by using also a retarding plate so as to rectify the cross arms. Images taken at different spectral regions.