Variable geometry mirror having high-precision, high geometry controllability

A variable geometry cylinder mirror comprising:

• a frame member;
• a flexible thin film in which two end portions opposing each other are supported by said frame member;
• a reflection surface which is provided on said flexible thin film and reflects light;
• a first electrode provided integrally with said flexible thin film;
• a second electrode substantially fixed to said frame member so as to oppose said first electrode on an opposite side of said reflection surface;
• and
• a third electrode substantially fixed to said frame member so as to oppose said first electrode on the same side as said reflection surface,
• wherein an optical opening to introduce light into said reflection surface is provided on the side of said reflection surface,
• at least any one of said second and third electrodes is divided in the direction connecting said two end portions, and
• the configuration of said reflection surface is controlled to a desired configuration by applying a desired voltage selectively to between said first electrode and said divided second or third electrode.