Abstract: A granular body, from which an article having a nonuniform refractive index may be formed, has grains of two substances which have different refractive indicies in a geometric distribution in the granular body corresponding to the geometric distribution of the substances required for the nonuniform refractive index of the article and a way of shape-stabilizing the granular body. A method of making the granular body comprises controllably feeding the grains into the geometric distribution in the granular body and shape-stabilizing it. Preferably the granular body is compressed into a porous compact which holds itself together and is treated with a gas to achieve desired optic properties in the article.

Abstract: Disclosed is a method for the axial building up, in a vertical arrangement, of a hollow cylindrical soot body having no internal support and consisting substantially of silicon dioxide by means of at least one flame hydrolysis build-up burner serving for the soot production. In this method the soot is deposited at the beginning of the build-up onto an auxiliary body, and during the build-up the build-up burner and the growing soot body are rotated relative to one another, and the burner is at the same time held at an unvarying distance from the growing end of the hollow cylinder and centrally above the predetermined cross section of the upwardly growing end of the cylinder wall. The penetration of soot into the interior of the cylinder is prevented by means of a directed gas stream.

Abstract: Faults in a material web are detected by scanning the web with a beam of light along a line transverse to its direction of movement and by detecting the angular ranges into which the incident light is scattered by these faults. For this purpose a light conducting rod is arranged parallel to the scanned line in a reception plane. The light conducting rod has a stepped prism arrangement along its side surface opposite to the light inlet and the inclination of the individual, unmirrored, prism surfaces is such that specularly reflected light passes through the prisms whereas scattered light falls on the prism surfaces at angles of total reflection and is reflected to a photodetector at an end face of the light conducting rod.

Abstract: Fault detection apparatus for material webs comprising a light transmitting device for generating a line of light on the material web and an elongate light receiving device which extends parallel to the line of light and is so arranged that it can receive light which enters a predetermined reception plane from the line of light, with the predetermined reception plane lying at a specified angle to the plane normal to the material web and containing the line of light, and with the line of light being formed by a bead of light which scans the web point by point, line by line. The light receiving device (43) comprises a plurality of light receivers (1 to 30) which can be selectively switched in, with at least one of the light receivers being switched out at each particular instant.

Abstract: A light collecting arrangement particularly for use with beam scanning apparatus for monitoring for faults in web material has a diffraction grating 11 and a light collecting surface usually in the form of photoelectric converter 19 arranged at right angles to the diffraction grating 11. The characteristics of the diffraction grating 11 are so selected that only light incident within a predetermined range is deflected to the light collecting surface. A number of different arrangements are disclosed. The light collecting arrangement can, for example, be used with a scanning light beam which is continuously displaced parallel to itself to effect point by point line by line scanning of the web material 17 or can take the form of a scanning light beam which executes a sector-like scanning movement.

Abstract: Faults in a material web 47 are detected by scanning the web with a beam of light 37 along a line transversely to its direction of movement F and by detecting the angular ranges into which the incident light is scattered by these faults. For this purpose an elongate light receiving device 33, which is preferably a light conducting rod, extends parallel to the line of scanning on the web with the axis of the light conducting rod and the line of scanning defining a reception plane. An elongate angular range filter 34 is arranged in this plane between the line of scanning and the light conducting rod and serves to deflect beams of light 35 close to the angle of specular reflection away from the light conducting rod. Light which is scattered in other angular ranges within the reception plane is however transmitted by the angular range filter 34 to the light conducting rod and is detected by a photoelectric detector positioned at the end face thereof.

Abstract: A light beam 2 from a laser light source 30 is split by a beam splitting arrangement 21, 22 into two slightly convergent light beams which are deflected by a deflecting mirror 31 onto the surface of a mirror wheel 23. The mirror wheel 23 that deflects these light beams via deflecting mirrors 24', 25' onto two strip-like concave mirrors 24, 25 which produce respective parallel scanning light beams which are continuously displaced parallel to themselves in the image spaces of the strip-like concave mirrors. These scanning light beams fall on respective rows of inclined dividing mirrors 9 and 10 which are arranged one behind the other in an alternating sequence. The inclined mirrors deflect the incident light beams through substantially 90.degree. to form a continuous light curtain which can be used to scan web material.

Abstract: Change of distance measuring apparatus features a light transmitter - receiver unit 23 which is used to sense the distance A to the surface of a measurement object 35 and more particularly to sense changes in the distance A occurring due to changes in thickness of the measurement object 35 as it moves against a guide surface in the direction of the arrow F. The optical system features a front objective 14 which focuses a parallel beam of light received from a laser light source via beam widening optics 13', 13", a modal aperture 12 for limiting the beam to the zero order diffraction image of the laser light source and a beam dividing mirror 33. Light returned from the surface of the measurement object whether specularly reflected or scattered is gathered by the front objective 14 and is passed to a photoelectric converter 19 via the dividing mirror 33, a further objective 16 and a second modal aperture stop 18.

Abstract: The reflective mirror system of a laser is shaped and arranged relative to the pump source and active material so that the light from the pump source passing by or through the active material is reflected back into the pump source. This is intended to increase the proportion of light absorbed by the active material.