Erwin Sick Gmbh Optik-elektronik

Dieter Ross

Klaus Ostertag

Erwin Sick

Siegfried Mankel

Viktor Baumgartner

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.

Fault detection apparatus for material webs

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.

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. In the former case the diffraction grating should have a fixed grating constant in the latter case the grating constant should change along the length of the diffraction grating to compensate for the different angles of incidence which arise as a result of the sector-like movement of a scanning light beam. The diffraction grating 11 is conveniently in the form of a hologram and can conveniently be incorporated in a light conducting rod 14.

Light collecting arrangement in combination with a light scanning

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. The system can also operate in transmission in which case the normally transmitted ray is deflected away from the light conducting rod. In this way the scattered beams which contain the useful information are detected without being swamped by the remainder of the light. A number of different angular range filters are disclosed including holograms 34, grids of thin plates 41, an array of stepped prisms 39 and an array of photoelectric detectors 43. Possible scanning devices include a fluorescent tube and beam scanning apparatus using a scanning beam 37 which is either continuously displaced parallel to itself (FIG. 1) or swept angularly through a sector-like range (FIG. 2).

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. Light reflected from the surface of the web or transmitted through holes in the web falls on light gathering devices in the form of either two rows of strip-like Fresnel lenses 5, 6 or two rows of light conducting rods 5', 6'. One light gathering device is associated with each of the inclined mirrors 9, 10. Light gathered by each of the light gathering devices is directed to an associated photoelectric detector 7 which is connected to an electronic processing circuit 8 for evaluating the signals from all the photoelectric detectors.

Monitoring apparatus

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. The signal at the photoelectric converter 19 is a maximum when the surface of the measurement object 35 is located in the desired plane 15. The position of the desired plane can be adjusted by optical means such as moving the front lens 14 and the extent of the movement required to maximize the signal at the photoelectric converter 19 is indicative of the change in the distance A. Various useful modifications are disclosed including the use of a comparison beam 36.

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Planegg, Germany

Dieter Ross