An apparatus operable to record a spatially low-frequency heterodyne
hologram including spatially heterodyne fringes for Fourier analysis
includes: a laser; a beamsplitter optically coupled to the laser; an
object optically coupled to the beamsplitter; a focusing lens optically
coupled to both the beamsplitter and the object; a digital recorder
optically coupled to the focusing lens; and a computer that performs a
Fourier transform, applies a digital filter, and performs an inverse
Fourier transform. A reference beam and an object beam are focused by the
focusing lens at a focal plane of the digital recorder to form a
spatially low-frequency heterodyne hologram including spatially
heterodyne fringes for Fourier analysis which is recorded by the digital
recorder, and the computer transforms the recorded spatially
low-frequency heterodyne hologram including spatially heterodyne fringes
and shifts axes in Fourier space to sit on top of a heterodyne carrier
frequency defined by an angle between the reference beam and the object
beam and cuts off signals around an original origin before performing the
inverse Fourier transform.