PURPOSE: To keep always a surface shape for deformation accurately by providing an elastic body, which has a gradient of modulus of elasticity in the direction of the optical axis internally, and a deforming member provided with an aperture part which projects or sinks the elastic body to deform the surface of the elastic body.
CONSTITUTION: An elastic body 1 has a gradient of modulus of elasticity in the direction of an optical axis 5 and has a maximum modulus of elasticity in an aperture part 4 and has the modulus of elasticity reduced gradually and continuously toward a bottom plate 2. The elastic body 1 having this characteristic is used in a variable focus optical element. An aperture plate 3 is moved in the direction of the optical axis 5 and the elastic body 1 is projected or sunk from the aperture part 4 of the aperture plate 3 to change the surface shape of the elastic body, thereby obtaining a desired focal length. When the elastic body 1 should be projected, the aperture plate 3 is moved toward the bottom plate 2 along the optical axis 5 to pressure the elastic body 1; and when the elastic body 1 should be sunk, the aperture plate 3 is moved upward along the optical axis 5 to apply a negative pressure to the elastic body 1.
NOSE TETSUSHI
BABA TAKESHI
NAKAJIMA TOSHIYUKI
OKUDA MASAHIRO
