Samuel Lin

US Patent:

45311978, Jul 23, 1985

Filed:

Apr 27, 1983

Appl. No.:

6/488924

Inventors:

Samuel S. Lin - Alexandria VA

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

G06G 719
G02F 111

US Classification:

364827

Abstract:

An optical Fourier transformer comprising an acousto-optical cell such as a Bragg cell upon which is impressed a chirp signal, a laser which is modulated by the signal to be analyzed, optical means for dividing the laser beam into two beams which strike one side of the acousto-optical cell with opposite orientations. The chirped acousto-optical cell diffracts the beams incident thereupon. The two diffracted beams are then recombined with their original orientations reestablished so that they interfere upon striking a time-integrating photo-detector array. The distribution of integrated intensities is related to the Fourier transform of the signal to be analyzed. Polarization discrimination can be used to split and recombine beams and to reduce extraneous beams. Background noise and direct current terms can be eliminated by comparing runs with 180. degree. of phase shift added between runs.

US Patent:

45311960, Jul 23, 1985

Filed:

Apr 27, 1983

Appl. No.:

6/488930

Inventors:

Samuel S. Lin - Alexandria VA

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

G06G 719
G02F 111

US Classification:

364827

Abstract:

An optical Fourier transformer comprising a laser which is modulated by the signal to be analyzed, a beam splitter for dividing the beam into two beams which are directed by optical means to opposite sides of a Bragg cell with the corresponding rays in the two beams striking opposite ends of the Bragg cell. A chirp signal impressed upon the Bragg cell causes each of the beams incident thereon to produce a diffracted beam. The diffracted beams are recombined by optical means with the corresponding rays becoming coincident and the recombined beams are directed to a time-integrating photo-detector array. The distribution of intensities on the array is related to the Fourier transform.