| 摘要 |
PURPOSE:To use a vacuum fluorescent tube and to obtain an optical writing head capable of having high luminous intensity, by setting density of thermion beams passing through a second grid larger than that of thermion beams passing through a first grid. CONSTITUTION:Density of thermion beams passing through a second grid 14 is set larger than that of thermion beams passing through a first grid 13. Name ly, two grids 13 and 14 are prepared, and thermion beams collected at aperture parts of the first grid 13 are focused at aperture parts of the second grid 14, so that density of thermions reaching an anode 12 is enlarged. It is effective to set widths of apertures of both grids, for example, so that a width of each slit-shaped aperture of the first grid 13 becomes larger than 1.2 times width of each slit-shaped aperture of the second grid 14. When thermions pass through the grids 13 and 14, density of thermions is thus enlarged so that sufficient luminous intensity can be obtained, and also high-speed recording and high quality picture recording are enabled. Since the grids 13 and 14 are disposed on two stages, sizes and luminous intensity of luminous dots can be easily controlled.
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