Light deflection apparatus

An image blur prevention apparatus, comprising:

• a first member;
• a second member, said second member being inclined with respect to said first member and for deflecting a light beam;
• a coupling member for coupling said second member with said first member with a changeable inclination angle, said coupling member having a rigidity satisfying a relationship
• .DELTA.X/R>0.05,
• wherein when said second member receives a force for changing the inclination angle with respect to said first member in a state where said first member is held and when said second member is adapted to move along a direction which is at least different from the direction of the force, .DELTA.X is a displacement amount with which said second member is moved with respect to said first member due to the operation of gravity, and R is the distance between an operation position of the force and a rotation center about which the inclination angle of said second member is changed with respect to said first member by receiving the force in a state where said second member does not move with respect to said first member due to gravity;
• and
• driving means for applying the force for moving said second member at a slant with respect to said first member so as to prevent blurring of an image formed by a light beam passing through said second member.