Scratch suppressing illumination system for photographic printer

DETAILED DESCRIPTION The problem described above is solved according to the present invention by providing an illumination system for a photographic printer, having a printing lens and a film gate, that includes a light source for producing a beam of light directed toward the film gate.
A reflector, disposed between the light source and the film gate, intercepts peripheral portions of the beam and redirects the peripheral portions toward the film gate.
The beam emerging from the reflector has a characteristic angular spread of between about .
+-.
35.
degree.
and .
+-.
65.
degree.
.
In addition, means are provided for conditioning the light emerging from the reflector such that: (1) the image produced by the printing lens is substantially uniform , (2) the angular spread of the light is not substantially increased, and (3) the total amount of light exiting the integrating bar is not significantly attenuated, thereby providing a relatively highly efficient scratch suppressing illumination system.
In one embodiment of the invention, the light conditioning means is a condenser lens disposed between the reflecting means and the film gate and adapted to form multiple images of the light source at the aperture of the printing lens such that the first order images of the light source are about half in and half out of the aperture.
In the preferred embodiment of the invention, the light conditioning means is a fibre optic plate disposed at the exit end of the reflecting means and adapted to light pipe and diffract axial rays within a diffraction pattern of controlled angular spread and to light pipe and diffract off-axis rays into annular cones also of controlled angular spread.
The angular spread of the diffraction pattern is governed by the fibre diameter and the total transmittance of the plate is greater than for diffusers of the prior art.
According to another feature of the present invention, the light source is constructed so that its off-axis luminance is 5-10% greater than its axial luminance, and the light conditioning means preserves this nonuniformity, thereby further improving the scratch suppressing qualities of the illumination system