| 摘要 |
An arc length changing apparatus for an exposing device, and a method in which the light quantity incident on the peripheral and central portion of a Braun tube panel is made constant by changing variably the arc length of the exposing device so that bending phenomenon of a fluorescent film stripe formed on the internal surface of the panel is improved. Apparatus of the invention is comprised of a mercury lamp, a lamp house, a shutter and etc. as usual, and a circular control disc 10 having an elliptical opening 11 at its center and sprocket teeth 12 around its periphery, a rack 15a formed at one side frame of the shutter 3, a pinion 16 for meshing with said rack, and a sprocket wheel 13 integrally formed with said pinion and coupled with said sprocket teeth by a chain 14. Method of the invention is carried out by synchronizing rotation of the circular control disc 10 with shutter moving speed, and controlling variably the arc length by the major axis or minor axis of said elliptical opening, making the light quantity at the peripheral and central portions of the panel 9 constant. According to the invention, bending phenomenon of fluorescent film on the Braun tube can be prevented and fluorescent film of clear stripe form can be formed.
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