Handbook of Biomedical Optics

488 Handbook of Biomedical Optics

phase plate is referred to as a quarter wavelength plate. Since light

waves are ltered by the phase plate in the back focal plane—the

Fourier plane of the objective lens—phase contrast imaging is

also known as a spatial ltering approach (Goodman 1996).

Destructive or constructive interference between the dif-

fracted and undiracted waves occurs at the image plane

depending on the net phase dierence between the waves. is

net phase dierence depends on the amount the diracted

light has been advanced or retarded by the object’s phase and

the eect of the phase plate. Destructive inter ...