| 摘要 |
PROBLEM TO BE SOLVED: To improve the retentiveness of a formed image. SOLUTION: No voltage is applied to piezoelectric elements during an initial condition. An air gap 28 is maintained in a longitudinally collapsed condition (A). Voltage is applied to the elements when an image is to be formed. The elements are made thin in a planar direction, the gap 28 is spread in a spherical shape in the planar direction and a rotary spherical body 22 freely rotates (B). At the same time, the body 22 is selectively rotated based on image data (B). Having formed an image, the application of the voltage to the elements is stopped and the elements are inflated to the original condition in the planar direction. Thus, the gap 28 is collapsed in the longitudinal direction. The body 22 is held by the walls of the gap 28 and is no longer freely rotated (C).
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