Optical Processing, 7

Optical processing is a technique which” is fascinating. The operator “sees” (1) what has been done, the procedures do not require calculations or passages or computer processing. Optical processing is very fast and low cost ; it allows notably : in the domain of ANALYSIS to look for, on seismic sections, pinchouts and counter dips, to make a TWO-DIMENSIONAL SPECTRUM of the seismic section of a line or noise spread (1), to make a ONE-DIMENSIONAL SPECTRUM of a seismic section, showing the frequency evolution along the line. From this a POWER SPECTRUM, the square of the AMPLITUDE SPECTRUM. This spectrum is obtained from sphero-cylindrical optics (2), to make autocorrelograms, working in sphero-cylindrical optics and by placing the power spectrum, mentioned above, in the object plane (3). These autocorrelograms allow, in one part, the ANALYSIS OF MULTIPLES and in the other the determination of the length and fundamental frequency of the SIGNAL. See SEISMIC NOISE, 8 . Sphero-cylindrical optics consist of attaching a convergent, cylindrical lens to the spherical lens in the figure on page 1. In effect, as seen in SPECTRUM 3, that the spectrum of an autoconvolution is equal to the power spectrum ; that is why : https://www.w3.org/1998/Math/MathML" display="inline"> A G 2 ( f ) ⟷ G ( t ) ⟷ G ( t )