Vorrichtung zur photographischen Belichtung, vorzugsweise fuer Vergroesserungsgeraete

1,110,912. Control systems for discharge lamps. GESELLSCHAFT FœR MULTIBLITZGERATE DR. ING. D.A. MANNESMANN m.b.H. 12 July, 1965 [16 July, 1964], No. 29410/65. Heading H2H. [Also in Division G2] The light source in a photographic reproduction apparatus such as an enlarger comprises a tubular discharge lamp 7, coiled into a helix so as to reduce its size. It is supported by a hollow lamp socket 12 in a housing 15, through which cooling air can be blown on to the electrode seals 8 and through the helix itself. The lamp is operated under stroboscopic conditions, that is, to give a rapid sequence of short flashes within the normal exposure time. This is effected by the circuit of Fig. 4. The lamp is connected to two low capacity capacitors 17, 18, respectively of 0-1 pF and 1 pF. These are charged with 3200 volts via a fullwave rectifier 21 from a mains transformer 22, 221. The lamp ignition electrode 9 is connected via an ignition transformer 24 to a capacitor 25 which is charged with 500 volts from a transformer 28 and rectifier 27, which is also supplied to the anode of a thyratron 26. The first grid 261 of the thyratron acts as a control grid, and the second grid 2611 as a blocking grid. When switch 30 is closed, pulses applied to the ignition electrode 9 cause a pre-ionization of the discharge gap without a discharge actually striking, since contact 23 remains open. A time-delay relay 32 then comes into operation to close contact 23, and so initiate the striking of the discharge in lamp 7. As long as switch 30 remains closed, the discharge takes place with double the mains frequency, producing very short intensive flashes of light. The lamp 7 is disposed within a reflector 5, the light passing through a frosted glass sheet 6 and a condenser lens 4, and down on to a worktable 2.