In-line phase retarder C-CM-PR4 (& C-CM-PR2)

By combining four mirror blocks into a pair or periscopes it is possible to produce an in-line unit where the
beam in and beam out are collinear. Put a ¼-wave phase retarder into the first mirror block and normal zerophase
mirrors in the other three and you have an in-line circular polariser unit. The C-CM-PR4 has to be
orientated correctly with respect to the linearly polarised beam entering the device; 45° to the S and P planes
– see Fig 1 below. Usually the plane of polarisation will be vertical or horizontal so that the unit itself will be
tilted over at 45°.

Fig. 1) Orientation of plane of polarisation with respect to S & P planes
It is also possible to order a C-CM-PR2 unit which is half the –PR4, consisting of two mirror block in a
periscope arrangement. If the user is not worried by the offset between the input and output beams, then the
C-CM-PR2 is a less expensive alternative.