| 摘要 |
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°. 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.
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