LIGHT BOX FOR PROVIDING A BACKGROUND ILLUMINATION HAVING BRIGHTNESS VALUES LOCALLY ADJUSTED TO THE DENSITY OF A TRANSPARENCY TO BE VIEWED BY MEANS OF THE LIGHT BOX

摘要

A device for directly viewing an image on a film transparency, in which the illuminating light source is controlled on the basis of discrete information elements written into and stored in a two-dimensional memory during a preliminary image brightness scanning operation. At option, the light beam produced by the light source either has its intensity or its scanning velocity controlled, in order to accordingly vary the brightness level of elementary film surface regions. Velocity modulation is to be preferred as the beam brightness level can then be maintained at an optimally constant value, while the dynamic contrast range of the image viewed by the observer is substantially determined by the beam velocity modulation range.