Patent ID: 6349006
Filing Date: 2002-02-19
Classification: G02B,H04N

Abstract:
A prism disposed between an external variable mirror element and an external projection lens having a projection optical axis parallel to a normal of said variable mirror element, said prism comprising:a first inner surface comprising a first end spaced a first distance apart from said variable mirror element and a second end, said first inner surface being inclined from said first end to said second end in a direction away from said variable mirror element, said first inner surface being configured to totally reflect a bundle of externally entered rays and to propagate said bundle of externally entered rays thus reflected toward said variable mirror element; and a second inner surface comprising first and second ends spaced second and third distances apart from said variable mirror element, respectively, said second inner surface being configured (i) to transmit said bundle of externally entered rays totally reflected from said first inner surface to propagate said bundle of externally entered rays to said variable mirror element, (ii) to transmit first and second bundles of rays in a first reflection state among bundles of rays reflected from said variable mirror element, and (iii) to totally reflect a bundle of rays in a second reflection state among said bundles of rays reflected from said variable mirror element, said second reflection state being different from said first reflection state, said first end of said first inner surface being located at a predetermined location adjacent to said second inner surface, which location is disposed between said first and second ends of said second inner surface, said third distance being greater than both of said first distance and said second distance, said first distance being greater than said second distance; and wherein, when said first bundle of rays in said first reflection state transmitted through said second inner surface enters said first inner surface, said first inner surface transmits said first bundle of rays in said first reflection state to propagate said first bundle of rays in said first reflection state toward said projection lens.