Patent ID: 6671099
Filing Date: 2003-12-30
Classification: G02B

Abstract:
An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising, in order from an object side thereof:a front unit including at least a first prism; an aperture stop; and a rear unit including a second prism; wherein said first prism and said second prism are each formed from a medium having a refractive index (n) larger than 1.3 (n>1.3), and wherein no intermediate image is formed; said first prism having three optical functional surfaces transmitting or reflecting a light beam; wherein when said three optical functional surfaces are defined as a first-first surface, a first-second surface, and a first-third surface, respectively, said first-first surface allows a light-beam from an object side thereof to enter said first prism through it, said first-second surface reflects the light beam entering through said first-first surface within said first prism, and said first-third surface allows the light beam reflected from said first-second surface to exit said first prism through it; said second prism having four optical functional surfaces transmitting or reflecting a light beam; wherein when said four optical functional surfaces are defined as a second-first surface, a second-second surface, a second-third surface, and a second-fourth surface, respectively, said second-first surface allows a light beam from an object side thereof to enter said second prism through it, said second-second surface reflects the light beam entering through said second-first surface within said second prism, said second-third surface reflects the light beam reflected from said second-second surface within said second prism, and said second-fourth surface allows the light beam reflected from said second-third surface to exit said second prism through it, and wherein said second-first surface and said second-second surface are disposed to face each other across said medium, and said second-third surface and said second-fourth surface are disposed to face each other across said medium, and further an optical path connecting said second-first surface and said second-second surface intersects an optical path connecting said second-third surface and said second-fourth surface; wherein said first-second surface of said first prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration; and wherein said second-second surface and said second-third surface of said second prism have a curved surface configuration that gives a power to a light beam, said curved surface configuration being a rotationally asymmetric surface configuration that corrects aberrations due to decentration.