Heidelberger Druckmaschinen Ag

Tobias Müller

Andreas Rupprecht

Michael Füner

A device for imaging a flat object, for example a paper sheet in a printing machine, includes a light source, preferably an LED row, a lens and an image sensor. An observation angle between the object plane and lens axis is flat, that is to say less than 45&#xb0;. The light source illuminates the flat object in a first, near region with light of a first wavelength and illuminates the flat object in a second, far region with light of a second wavelength. The first wavelength is shorter than the second wavelength, preferably being blue and red spectral regions. The first region is disposed nearer the image sensor than the second region. The device permits the so-called chromatic aberration of the lens to be utilized to advantageously reduce the tilt angle of the image sensor required by the so-called Scheimpflug condition. A printing machine having the device is also provided.

Device for imaging a flat object and printing material processing machine having the device

An image is recorded of the edge of a moving object, in particular a sheet, in a machine processing printing material. The illumination is carried out with an illuminating device, and an image is recorded of at least one part of the edge with an image recording device. The use of the illuminating device and/or the image recording device is substantially synchronous with the movement of the object and substantially parallel to the direction of movement of the object. A preferred illuminating device has a row or array of light sources which in each case are switched on and off synchronously with the movement of the object. The constant shadow or shadow strip produced by the illumination moves with the object and ensures adequate contrast between the brightly illuminated object and the dark background, so that the object can be segmented reliably, at least in the region of the edge, and its position, orientation and movement can be determined.

Method and apparatus for recording an image of an edge of a moving object

A method for controlling an operating process of a printing machine uses parameters of 3-D scenes taken with only one camera. A learning phase is performed in which the object in a non-moving state and its surroundings are illuminated from different directions by different fixed-location light sources, one after another. For each illumination scene, image signals reproducing the object and its surroundings are obtained with the image recording device. The image signals are processed and an unambiguous association between object edges and object shadows in relation to a light source in each case are determined and stored. In an operating phase, the moving object and its surroundings are illuminated simultaneously by a plurality of light sources, and, from the data stored in the learning phase and the image signals obtained continuously in the operating phase, the position of the object in space is determined.

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Hirschberg, Germany

Tobias Müller