Variable magnification optical system with light shielding mechanism

A variable magnification optical system for projecting an image onto a projection surface, comprising:

• a lens for forming an image of an original document on the projection surface, said lens having an optical axis;
• a lens moving member supporting said lens;
• a mirror group arranged between said lens and the projection surface, for directing light from said lens to the projection surface;
• a lens driving mechanism that drives the lens moving member in a direction of the optical axis of said lens to vary the magnification of the projected image;
• a housing having a bottom base plate, a front side at one end in the direction of said optical axis, and a rear side in the direction of said optical axis, said housing being open at a top side, and said housing accommodating said lens, said lens moving member, said mirror group, and said lens driving mechanism;
• a light shielding cover shielding a top side of said base plate and extending from said rear side of said housing toward said front side of said housing, a space for allowing image-forming light into said housing being formed between said light shielding cover and said front side of said housing;
• a flexible light shielding member attached to an upper portion of said lens moving member, said flexible light shielding member extending in the direction of said rear side of said housing, and said flexible light shielding member sized to block said space between said light shielding cover and said front side of said housing;
• and
• a guide member formed at said rear side of said housing for urging said flexible light shielding member in a downward direction when said lens moving member is moved to said rear side of said housing.