Patent ID: 6646812
Filing Date: 2003-11-11
Classification: G02B

Abstract:
A de-centered optical system comprising:a first optical element and a second optical element each of which is disposed between a pupil and an image; the first optical element being a prism having at least three optical surfaces including first, second and third optical surfaces, and a portion surrounded by these three surfaces being made of a medium having a refractive index of more than 1; the first optical surface being positioned closest to the pupil among these three surfaces and having a function of refracting light and a function of reflecting light inside the optical element; the third optical surface being positioned closest to the image surface among these three surfaces and having a function of refracting light; the second optical surface being disposed on a de-centered position from an optical axis which is a center line of a light bundle, and shaped as a curved surface having a positive optical power when reflecting light inside the optical element; the second optical element being disposed on the pupil side of the first optical element, having a positive optical power, and at least a surface on the pupil side thereof being a convex surface; the second optical element producing a chromatic aberration of magnification; wherein the de-centered optical system is so configured that when light goes through the de-centered optical system from the second optical element side to the first optical element, it forms a larger image at a light wavelength region of red than that of green, and at a light wavelength region of green than that of blue; and the first optical element and the second optical element satisfy at least one of the following conditions (1) and (2): 0.12x<1â€ƒâ€ƒ(1) 0.12y<1â€ƒâ€ƒ(2) wherein, when assuming a light ray passing through the center of the exit pupil and the center of the image surface as an axial chief ray, a plane in which the axial chief ray travels as a Y-Z plane and a direction in which the optical system is de-centered as a Y-axis, Fy is a focal length of the optical system in the Y-direction, Fx is a focal length of the optical system in an X-direction perpendicular to the Y-Z plane, F2y is a focal length of the second optical element in the Y-direction, and F2x is a focal length of the second optical system in the X-direction.