Random phase plate for holography and process for manufacturing same

DETAILED DESCRIPTION What is claimed is: 1.
A process for producing a random phase holographic plate coated with polyvinyl butyral resin in which the thickness H of the resin varies in a continuous and random manner over the said plate relative to light of a wavelength .
lambda.
such that exp -4.
pi.
.
sup.
2 (n-n.
sub.
o).
sup.
2 .
sigma.
h.
sup.
2 /.
lambda.
.
sup.
2 .
ltoreq.
0.
10 where h.
sub.
m is a mean value of H, h=H-h.
sub.
m ; .
sigma.
h is a standard deviation of h; n is a refractive index of the solidified coating material for light of the wavelength .
lambda.
; n.
sub.
o is a refractive index of air for light of the wavelength .
lambda.
; and exp indicates exponentiation, comprising the steps of: (a) applying a 17.
5% by weight solution of polyvinyl butyral resin in benzene to the upper surface of a transparent substrate, and (b) solidifying the solution by rotating the substrate about a perpendicular rotary axis at a rate of from 200 to 1500 rpm to evaporate the solvent.
2.
The process according to claim 1 in which the substrate is a glass plate.
3.
A random phase holographic plate, comprising a transparent substrate and a transparent polyvinyl butyral coating on the substrate in which the thickness H of the coating varies in a continuous and random manner over the random phase plate relative to light of a wavelength .
lambda.
such that exp -4.
pi.
.
sup.
2 (n-n.
sub.
o).
sup.
2 .
sigma.
.
sub.
h.
sup.
2 /.
lambda.
.
sup.
2 .
ltoreq.
0.
10 where h.
sub.
m is a mean value of H, h=H-h.
sub.
m ; .
sigma.
.
sub.
h is a standard deviation of h; n is a refractive index of the coating material for light of the wavelength .
lambda.
; n.
sub.
o is a refractive index of air for light for the wavelength .
lambda.
; and exp indicates exponentiation.
4.
The plate according to claim 3, in which the transparent substrate comprises a glass plate.




Description:
The present invention relates to a random phase plate for Fourier transform holography and a process for manufacturing the plate.
It is known in the art of holography to place a random phase plate in contact with a subject illuminated by coherent light from a laser for holographic reproduction