Optical projection systems

Claim 1

THE COMBINATION OF AN ELECTRIC INCANDESCENT LAMP COMPRISING A SEALED EVELOPE AT LEAST IN PART OF LIGHT TRANSMITTING MATERIAL, FIRST AND SECOND FILAMENTS IN SAID ENVELOPE, SAID SECOND FILAMENT HAVING A LOWER POWER RATING AND A LOWER VOLTAGE RATING THAN SAID FIRST FILAMENT, TERMINALS ON THE EXTERIOR OF THE ENVELOPE, AND LEAD-IN CONDUCTORS BETWEEN THE FILAMENT AND RESPECTIVE EXTERNAL TERMINALS, FIRST ELECTRICAL CONNECTIONS WITH A SOURCE OF ELECTRICAL ENERGY OF THE SAME VOLTAGE AS THE RATING OF SAID FIRST FILAMENT CONNECTED TO THE EXTERNAL TERMINALS OF SAID FIRST FILAMENT, FURTHER ELECTRICAL CONNECTIONS BETWEEN SAID SOURCE AND THE TERMINALS OF SAID SECOND FILAMENT, SAID FURTHER CONNECTIONS INCLUDING VOLTAGE REDUCING MEANS FOR REDUCING THE VOLTAGE APPLIED TO SAID SECOND FILAMENT TO A VALUE AT WHICH THE COLOR TEMPERATURE OF LIGHT EMITTED BY THE FILAMENT IS SUBSTANTIALLY THE SAME AS THAT OF LIGHT EMITTED BY THE FIRST FILAMENT AND SWITCHING MEANS FOR RENDERING SAID VOLTAGE REDUCING MEANS INOPERATIVE.