Abstract An illumination installation, in particular for lighting a transparent table or supporting step-by-step microfilm camera apparatus, such installation providing for the even illumination of a condenser of an image projecting apparatus. A plurality of lamps are distributed over the surface to be illuminated, the lamps being divided into at least two groups. In certain embodiments the current supply circuit for feeding the lamps is divided into two parallel circuits, each of which contains a resistor, there being an amplifier which scans the voltage drop at the resistors and operates an optical and/or acoustical signal transmitter upon an unbalance of the voltage drops through the respective resistors. In another embodiment, the feeding of current to the lamps is divided into at least two parallel circuits, the passage of circuit through which is compared by a compensatory current transformer which controls a relay controlling an optical and/or acoustic signal transmitter and/or a switch controlling a further apparatus controlling circuit.
In a uniform illumination system: a source of energizing voltage; at least two first paths each comprising a plurality of serially connected lamps; a second path comprising a pair of serially connected resistors; first means for coupling the first paths and the second path across the source; a glow lamp; and second means for coupling the glow lamp between the junction of the resistors and the midpoint of each of the first paths, each such midpoint dividing the resistance of the associated first path in half.
Claim 2
Dependent Claim
86 words
In a uniform illumination system: a source of energizing voltage; at least two first paths each comprising a plurality of serially connected lamps; a second path comprising a pair of serially connected resistors; first means for coupling the first paths and the second path across the source; a glow lamp; and second means for coupling the glow lamp between the junction of the resistors and the midpoint of each of the first paths, each such midpoint dividing the resistance of the associated first path in half.
Claim 3
Dependent Claim
28 words
A system as defined in claim 1, in which the second means comprises a plurality of similarly poled diodes individually associated with the midpoint of each first path.
Claim 4
Dependent Claim
107 words
A system as defined in claim 2, in which the apparatus has three first paths; in which the first coupling means comprises, in cOmbination, means for directly connecting two of the first paths across the source, and first normally unoperated switching means operable to connect the remaining first path across the source; and in which the second coupling means further comprises, in combination, means for directly connecting said two first paths to the glow lamp through their associated dioded, and second normally unoperated switching means operable in synchronism with the first switching means for connecting said remaining first path to the glow lamp through its associated diode.