Patent ID: 7553031

Claim:
A projection optical unit to be used in a projection image display apparatus, comprising: a first optical system including plural numbers of lenses therein, for projecting a display image on an image display element, enlargedly, and being a coaxial optical system, which is constructed with surfaces, an optical axis of each of which passes through at almost a center of said image display element and each having a symmetric configuration with respect to said optical axis; and a second optical system for projecting an enlarged image from said first optical system onto said screen, obliquely, being inclined thereto; wherein said second optical system includes an optical element having a free shaped surface, for compensating a trapezoidal distortion and/or an aberration, which is/are caused due to an oblique projection of said enlarged image; wherein said optical element includes a curved surface reflection mirror, and within said curved surface reflection mirror, a portion for reflecting the light of a lower image below a center on said image display element is curved to direct a concave into the reflection direction thereon, thereby having a positive power, and a portion for reflecting the light of an upper image above the center on said image display element is curved to direct a convex into the reflection direction thereon, thereby having a negative power.