| 摘要 |
PURPOSE:To control an image formation state by using an optical element which varies the state of the wave front of incident luminous flux by moving a grain body in liquid. CONSTITUTION:When a specific voltage is impressed to the heating resistance body 6b of an optical element, etc., the vapor bubble 7 of the grain body is formed nearby the resistor 6b of a liquid layer 2 of ethyl glycol, etc., between a reflecting layer 3 and a transparent protection plate 1 and never disappears even when the voltage impressed to the resistance body 6b, etc., is lowered. In this state, the hold voltage to the resistance body 6b is cut off and a necessary voltage corresponding to the distance from the resistance body 6b, etc., is impressed to an adjacent resistance body 6c, etc., so that the air bubble 7 moves to the position of the resistance body 6c and is held similarly. Only a light beam which has high incidence height to a pupil as to an incidence light beam is shifted in phase owing to absorption and scattering by variation in the wave front state of the incident luminous flux by the grain body, so when the optical element is inserted into the optical system as a soft-focus filter, only a part with high incidence height of spherical aberration is affected to cause flare aberration, thereby controlling the image formation state such as drawing ability.
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