Simultaneous spectral calibration of two phase plates

Based on a new model for the spectral calibration of phase plates in pairs, experimental results are presented for three mica plates between 430 and 6 84 nm. One of the plates is 36.4 mu m thick and the remaining two are ident ical, each being 28.6 pm thick. In the studied spectral range, the retardan ces varied from 123.5 degrees to 86.8 degrees for the first plate and from 96.9 degrees to 68 degrees for each of the two other plates. Different proc edures for performing the calibration of the plates and the special case of two identical plates are discussed. (C) 2000 Elsevier Science Ltd. All rig hts reserved.