Decentered image-forming optical system

An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising:

• a first prism and a second prism, each of said first prism and second prism being formed from a medium having a refractive index (n) larger than 1.3 (n>1.3), said second prism being placed at a position on an image side of said first prism, in an optical path exiting said first prism and intersecting a plane where said object image is formed,
• wherein an intermediate image is not formed,
• said first prism having three optical surfaces said three optical surfaces comprising:
• a first surface through which a light beam from an object enters said first prism;
• a second surface that reflects the light beam entering through said first surface in said first prism;
• said first surface further reflecting the light beam reflected by said second surface in said first prism;
• and
• a third surface through which the light beam reflected by said first surface exits from said first prism;
• wherein at least one of said first surface and said second surface has a curved surface having a power;
• said curved surface having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;
• said second prism having at least one reflecting surface, said reflecting surface having a rotationally asymmetric surface configuration having a power and correcting aberrations due to decentration.