| 摘要 |
PROBLEM TO BE SOLVED: To reduce consumption of an expensive piezoelectric material and also reduce a production cost by using a part of an optical element main body or a part of a holding member as the piezoelectric material. SOLUTION: A concave mirror 10 comprises a main body 12 consisting of the piezoelectric material and conductive films 14, 16 on a surface and a back face of the main body 12. The conductive films 14, 16 are electrodes for polarization and for driving, however the conductive film 14 on the front surface is used in common as reflective film. If DC voltage is applied in the same direction as polarizing direction for the polarized concave mirror 10, whole body of the concave mirror 10 is enlarged in a direction of thickness (a direction expressed by an arrow T) and as the result thickness of whole body is increased. However, in this case, as main body 12 is joined to a hard round frame 15 in a peripheral part of a mirror, shrinkage of a mirror diameter D is hardly occurred due to prevention of shrinkage in a diameter direction. Stress generated in this way is relaxed by shrinkage of curvature length L1, L2 of the mirror surface. Therefore, varying voltage applied to between the conductive films 14, 16 enables deforming a reflection surface 11 of the concave mirror 10.
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