oring
1g them
Lity
ce to
ulated
ıminan-
d. by
if
if thc
istic
gi
where í is the slope of the linear region, i is the time of ex
position and C is the film sensitivity.
The luninance has three main sources which nave to be taken
in consideretion; nanely aj reflected sunlight, b) reflected
skylight and c) scattered sunlight by particles benssth the
ocean surface (15). Under the assumption of a calm sea, b) and
c) are roughly equal uhen visued vertically but a) is larger
than the other sources at any surface roughness condition. That
makes that the use of reflected sunlight for imaging waves may
overemphasize a particular slope, introducing a error in the
evaluation of the imagery. Hence that reflected sunlight should
be avoided.
B) Optical Analysis
The two dimensional power spectrum is obtained by optical
processing of information on surface waves, using the hologra-
phic method, The optical processor consists of two parts: an
optical transform computer and a photochemical equidensity con-
touring by which the power of the spectrum of the Fraunhofer
patterns on the film are determined.
In the revieued literature abundant references uere found
on optical Fourier transformates, 5vz cnly tuo sugossted vaguely
a method for improving the Fraunhofer images (12),(15). The
main problem that arised uhen following tne indications of
other authors (10), (11), (12), (14), (15), (16), (17), (19), (20) was
the strong limitation imposed by the size of the Fraunhofer
image. SUGIMCRI .(12)-suggested the reduction of scale of the
photograph, sc that the transformed image is ameliorated for
the analysis. Eventhough this is a rather simple method for
improving the information content of the photograpn, it might
become twofold disadventageous: i) the very high freauencies may
be overlooked, for the reduction causss a loss of definition,
and ii) the reduction of the photograph may mask some aspects
due to slight developing and/o- copying defects which are not
always obsarveble or avoidable. Thus that the usual configurat-
ion of the optical processor(figure 2) has been disregarded,
modifying it to an optimal and more simple design in uhich the
experimenter may control the scale of the Fourier transform.
This configuration is shown in figure 3. The modified optical
transform computer consists of a coherent light source (He-Ne
laser, A =6328 A), a microscope's objective (10/0.25) which
expands the laser beam, and a focusing lens (Vivitar 300mm,1:5.6).
The transparency to be analyzed is set on plane P, after the
lens L, and the diffraction pattern is registered by a convention
al ref ox camera (Asahi Pentax) without ob jective, located on
plane P, where the transformated image of P appears. ‘The peak
amplitude of the wave at L5 is A and at P, 1s impinging d'.A/d
in the geometrical-optics approximation (1s). If the beam dia-
meter at L, is D, than a circular region of diameter d.D/d' is
illuminated in the transparency plane. Using a paraxial eppro-
ximation to the spherical wave that illuminates P4 , the field