Patent ID: 8820236

Claim:
A device for supplying radiant energy onto a printing substrate traveling in path through a printing press in a transport direction, the printing press including a printing unit and at least one printing nip in the printing unit, the printing substrate including inked portion, the device comprising: at least one radiant energy source emitting light on the printing substrate traveling in the path through the printing press in the transport direction downstream from the at least one printing nip in the printing unit, the light being emitted over a width of the inked portion of the printing substrate in a direction transverse to the transport direction so that a difference between a lowest value and a highest value in an intensity of the light is less than 15% in the direction transverse to the transport direction; and an optical system ensuring that the light emitted by the at least one energy source is substantially homogenous; wherein within a depth of focus of about 1 to 3 mm of the optical system, a power density does not vary more than 15%; wherein the light impinges on the printing substrate at a position in the path through the printing press and the position is selected such that at the position, the printing substrate moves in a substantially flutter-free manner with respect to a propagation direction of the light so the printing substrate is maintained at a focal distance of the at least one radiant energy source.