Abstract: A detection device is disclosed for determining particle size from particle effected light scattering in a sensing region illuminated by a laser beam and receiving the particles in a medium, such as air. Background light from molecular scattering is reduced to a level that enables light scattered by particles having a size of at least as low as about 0.1 micron to be sensed in a high background of molecular scattering such as, for example, where molecular scattering can exceed the 0.1 micron particle's scattering by one hundred times.

Abstract: An apparatus and method for remotely sensing the angular displacement of a test surface 22. Two coherent collimated light beams 10,12 having different optical frequencies are directed toward optically reflective target areas 18,20. The beams are reflected and converge to form a fringe pattern in an interference zone 24. A sampling means 34 having at least one sampling aperture is positioned within the interference zone 24. The sampling aperture lies in a plane substantially perpendicular to a plane formed by the converging beams and it has a width smaller than the effective spatial period of the fringe field, .lambda..sub.es, where .lambda..sub.es =.lambda..sub.s /cos.phi., .lambda..sub.s being the spatial period of the finge field and .phi. being the angular deviation of the plane of the sampling aperture from a plane which is perpendicular to the fringe planes of the fringe field. A light detector 42 is positioned to receive the modulated optical radiation which is sampled from the interference zone.

Abstract: A magnifying optical system is described which is usable at a determined posture of the head of a user, when at least one of the user's eyes is directed onto an object's field to be magnified, which system comprises an objective, an ocular comprising an eye lens and at least one field lens, and a deflecting system interposed between the objective and the ocular, the optical system being located, at the determined head posture, outside the straight path of rays for free sight between the user's eye and the object's field looked at by the eye; the optical axis of the objective is directed toward the center of the object's field, the optical axis of the eye lens of the ocular is directed toward the center of the user's eye ball, both said optical axes forming an obtuse angle with one another, which optical axis of the objective and the central ray of free sight intersect one another under a flat acute angle at the center of the object's field (whereby the object's field can alternatingly been seen by the user ei