Abstract: An apparatus for optical monitoring of the surface of rod-shaped smoking articles and/or filter rods for the tobacco industry comprises a conveying means transporting the rods perpendicularly to their longitudinal direction and a high-pressure lamp which serves as light source and which is connected via an optical fibre cable to a sensor block; the optical fibre cable is divided amongst at least two cross-section transformers with strip-shaped light exit regions whose light rays are directed via a further optical system from above and below respectively onto the line-shaped region of the surface of the rod. In addition the sensor block contains a row of photoelectric transducers which simultaneously the line-shaped surface region in the longitudinal direction of the rod and thereby pick up the light reflected at the surface of the rod.

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: Two optical receiving systems for electromagnetic radiation are provided with separate detectors. The systems are essentially coaxial with the outer system being fixed and the inner system being rotatable. The outer receiving system carries out a first detection of the angle of incidence of the electromagnetic radiation with the help of several detectors, as a panoramic optical system. Then, on the basis of the angle of incidence obtained in this manner, the inner optical system is coarsely positioned to the direction of incidence of the electromagnetic radiation. A fine follow up is then carried out with the help of the inner optical receiving system, the inner system being provided with a smaller receiving opening, and with the help of one or more further detectors in order to obtain the exact direction of incidence.