ILLUMINATION DEVICE FOR LIQUID CRYSTAL DISPLAY UNIT

摘要

PROBLEM TO BE SOLVED: To provide a liquid crystal(LC) display unit illuminating device capable of executing accurate luminance adjustment corresponding to the transmissivity of LC. SOLUTION: A mold type transformer is used for a transformer 2 and a reference driving pulse is impressed to the gate of an FET connected to the primary winding 2a of the transformer 2 through a transistor logical circuit 5. A previously measured pulse frequency reducing ratio is set up in the circuit 5 correspondingly to the transmissivity of LC in a view finder and a driving pulse of the set pulse frequency is supplied to the gate of the FET 4, so that the view finder can be illuminated by a plane fluorescent tube 3 at accurate luminance corresponding to the transmission factor of the LC without causing the humming of the transformer 2.