| 摘要 |
The lamphouse is used for the production of prints on variable control paper and comprises a first tungsten filament lamp from which light passes through a color selective filter which passes light in one of two mutually exclusive wavebands. A second filament lamp and filter passes light in the other of the two mutually exclusive wavebands. A diffusing screen is placed to pass the filtered light out of the lamphouse and through a transparency which is to be printed. Between each lamp and an alternating voltage source is connected a bidirectional thyristor, whose phase angle of conduction is determined by a microprocessor according to data stored in a read-only memory and by single manual controls for the selecting alternative addresses in the memory according to the contrast of print to be made. The data stored in the memory is chosen to cause the bidirectional thyristors to adjust the currents through the two lamps so that the energies of the light in the two mutually exclusive wavebands vary in a complementary manner as the chosen contrast of print is varied.
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