Phase Contrast Microscopy - Biomedical Optical Phase Microscopy and Nanoscopy - page 6

S-wave is attenuated to
be a more similar amplitude to
the D-wave and is phase
shifted (advanced) by λ /4

C

D-wave—phase shifted
(retarded) by ∼λ /4

The sum of these is very
different from the S-wave so
contrast is produced

Figure 1.4
Phase shift between the diffracted wave and the phase shifted surround wave.

S-wave
D-wave
P, the sum of S D

A phase shift is produced by
the sample ( λ /4 from
diffraction and a smaller phase
shift due to optical path length
difference) but is of smaller
amplitude than the S-wave and
so the P-wave is similar in
phase and ampitude to the
S-wave

The D- and S-waves are
almost perfectly out of
phase and of very similar
amplitudes so destructively
interfere to produce a very
low intensity P-wave.

Figure 1.5
Phasor diagrams of the phase shifts in Figures 1.3 and 1.4 .