| 摘要 |
PURPOSE:To always hold the temperature of a light source at the time of picture reading to constant and to stabilize the light quantity of the light source by preliminarily lighting the light source before picture reading, and controlling the light source to be held in the constant temperature. CONSTITUTION:When environmental temperature (c) is smaller than a low limit temperature (a), a central control part 6 operates light source lighting parts 5, lights a lamp 1 and raises the tube surface temperature. When the tube surface temperature of the lamp 1 exceeds a high limit temperature (b), the central control part 6 lights off the lamp 1 and lowers the tube surface temperature. When the tube surface temperature falls and comes below the low limit temperature (a), said part 6 lights the lamp 1 again, and raises the tube surface temperature. With repeating this, the tube surface temperature can always be held between the temperature (a) and the temperature (b), and the satisfactory light quantity of the lamp 1 can be obtained even in initial picture reading.
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