Patent ID: 6104537
Filing Date: 2000-08-15
Classification: G02B

Abstract:
An image-forming optical system comprising:a first lens unit disposed on an object side of said image-forming optical system which is closer to an object, said first lens unit being formed from a decentered optical system; anda second lens unit disposed on an image side of said first lens unit, said second lens unit having at least one lens,wherein said decentered optical system has at least one rotationally asymmetric surface having no axis of rotational symmetry intercepting nor non-intercepting said at least one rotationally asymmetric surface to correct rotationally asymmetric aberrations caused by decentration,wherein, a light ray emanating from a center of an object point and passing through a center of a pupil to reach a center of an image is defined as an axial principal ray, and a Y-axis is taken in a plane of decentration of each decentered surface, and an X-axis is taken in a direction perpendicularly intersecting the Y-axis, and further an axis constituting an orthogonal coordinate system in combination with the X- and Y-axes is defined as a Z-axis, and further said axial principal ray and a light ray which is parallel to said axial principal ray and a light ray which is parallel to said axial principal ray at a slight distance d in an X-axis direction are made to enter said image-forming optical system from an entrance side thereof, and a tangent of an angle formed between the two rays is projected on an XZ-plane at an exit side of said optical system is divided by the distance d to determine a value Px, and further said axial principal ray and a light ray which is parallel to said axial principal ray at the slight distance d in a Y-axis direction are made to enter said image-forming optical system from the entrance side thereof, and a tangent of an angle formed between the two rays as projected on a YZ-plane at the exit side of said optical system is divided by the distance d to determine a value Py, the following condition is satisfied:0.1<Px/Py<10 (1-1).