| 摘要 |
1330709 Spatial filtering XEROX CORP 21 Dec 1970 [2 Jan 1970] 60556/70 Heading G2J In an optical read-out system in which a phase object 10 is illuminated by coherent polarised light, the phase object having surface deformations composed of a periodic carrier wave and an amplitude modulating signal containing input information, a spatial filter 40 is located in the back focal plane of lens 35, the filter comprising an opaque mask 41 having two clear apartures 42 centrable about a given diffracted order of the carrier wave frequency, one of the apertures having associated therewith a means 43 for rotating the plane of polarization of light passing that aperture 90 degrees with respect to light passing the other aperture. The means 43 may be a half-wave plate, or a doubly-refractive material, or an optically active material. In a further embodiment the other aperture also has associated therewith a polarization rotator, but so positioned that the two beams are athogonally polarized relative to each other. The rotators may be adjacent the apertures. |
