Optical web monitoring apparatus

An optical web monitoring apparatus comprising:

• an illumination arrangement including a light source, and a transmitter-side strip-like concave mirror illuminated by said light source, for generating a strip of illumination on a surface of a moving elongated web spaced from the transmitter-side concave mirror, the strip of illumination extending transverse to the longitudinal direction of the web, a light receiving arrangment including an optical system, a photo-receiver arrangment formed by a line of diodes, and an electronic processing circuit, said light receiving arrangement projecting light emerging from the strip of illumination via said optical system onto said photoreceiver arrangement which delivers electrical signals corresponding to the received light to said electronic processing circuit, said transmitter-side concave mirror forming an image of an entry pupil of a total beam path from said light source at a location within the beam path extending from the light source to the photoreceiver arrangement, at a substantial distance behind the strip of illumination, in an objective located in front of the line of diodes, the objective imaging the strip of illumination onto the line of diodes in such a way that the strip-like image of the strip of illumination extends in the longitudinal direction of the line of diodes.