De-centered optical system and optical apparatus equipped therewith

An image projection apparatus having a de-centered optical system for use as a projection 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;
• an image display device disposed on the image surface;
• and
• a third optical element having a positive optical power, the pupil being positioned between the second optical element and the third optical element;
• wherein light emanating from the image display device is transmitted through the first optical element, the second optical element, and then the third optical element, and reaches a screen on which a real image of the image displayed on the image display device is formed;
• and
• wherein the image display device displays images different in size depending on the color thereof in order to cancel at least a chromatic aberration of magnification of the second optical element.