Uniformly illuminating linear light source - has diaphragm or reflector shaped to compensate end effects of fluorescent tube

摘要

The system for uniformly illuminating a line of a document uses a fluorescent tube of a similar length to that of the line to be illuminated. A diaphragm (2) is placed in front of the tube to define the area which is to be illuminated. For the greater part of its length the diaphragm defines a narrow parallel sided window. Near the ends of the tube the diaphragm window widens out so as to allow more light through, compensating for the end effect of the tube. Alternatively, a reflector is used behind the tube. This is narrow and parallel sided for the greater part of its length, but extends around the tube near the tube ends. This again compensates for the lower amount of light near the ends of the tube.