Portrait holograms are recorded with a holographic camera of the
type GP-2J (brand Geola) with master-oscillator and second
harmonic generation. The resulting wavelength of 526.5 nm has a
small penetration depth into skin to minimize light diffusion.
Careful mode selection leads to a coherence length of
approximately 6 m. The laser output is split into three beams:
Two of them serve for homogeneous illumination of the
object. They are expanded by concave lenses and diffusor plates
at the output ports of the laser. The third beam serves as
reference beam. The hologram plate (30 cm 
40 cm, VRP-M
emulsion by Slavich) is developed with SM-6 and bleached with
PBU-Amidol to obtain phase holograms. A frequency doubled cw
Nd:YAG laser (COHERENT Verdi V-2) is used to reconstruct the
holographic real image. To obtain the 2D projections of the real
image, a diffusor (diffusor thickness 40 µm, diameter 380 mm) is
moved on a computer controlled linear positioning stage (PI
M-531.DD, max. resolution 10 µm) through the image volume. The
diffusor images are digitized by a KODAK Megaplus ES 4.0 digital
camera with 2048 x 2048 pixels.