Patent ID: 8817382

Claim:
A optical projection system which, when an image is enlarged and projected on a surface to be projected, makes an aspect ratio of an image of a light modulation device different from an aspect ratio of the image projected on the surface to be projected, the optical projection system comprising: a diaphragm which restricts a passage of light flux; and a light modulation device side lens group which is arranged between the light modulation device and the diaphragm, configured to have different powers in a longitudinal direction and a lateral direction of the light modulation device, and configured to include an adjustment optical device group capable of advancing and retracting on an optical path, wherein the adjustment optical device group integrally advances and retracts on the optical path, and changes a focus in a side of the surface to be projected in a lateral section and a focus in a side of the surface to be projected in a longitudinal section of a subject side lens group; and wherein, when it is assumed that a distance between the focus in a side of the surface to be projected and an end surface in the side of the surface to be projected is set to “FFPx” in the lateral section of the light modulation device side lens group in a state in which the adjustment optical device group is arranged on the optical path, a distance between the focus in the side of the surface to be projected and the end surface in the side of the surface to be projected is set to “FFPy” in the longitudinal section of the light modulation device side lens group in the state in which the adjustment optical device group is arranged on the optical path, and a distance between the focus in the side of the surface to be projected and the end surface in the side of the surface to be projected is set to “FFPL” in the light modulation device side lens group in a state in which the adjustment optical device group is withdrawn from the optical path, FFPx, FFPy, and FFPL satisfy the following expressions: FFPx<FFPL<FFPy if FFPx<FFPy, and FFPy<FFPL<FFPx if FFPy<FFPx.