Patent ID: 6457830
Filing Date: 2002-10-01
Classification: G02B,H04N

Abstract:
A reflection-type projector comprising:a light source that generates and emits light; an optical path changer that changes a traveling path of an incident beam; an image former that has an on-state and an off-state and that reflects a first portion of a plurality of incident rays, emitted from said light source and transmitted through said optical path changer, to form a plurality of necessary reflected rays when said image former is in the on-state and a plurality of unnecessary reflected rays when said image former is in the off-state, wherein the necessary and unnecessary reflected rays have first and second reflection paths, respectively, that differ from each other, said image former comprising a window forming a protective layer, wherein said window reflects a second portion of the plurality of incident rays to form a plurality of surface-reflected rays; and a projection lens unit that magnifies and projects the necessary reflected rays, wherein said optical path changer comprises a beam separation prism comprising: a first critical surface that is slanted so that the plurality of incident rays emitted from said light source pass through said first critical surface, and the necessary reflected rays and the surface-reflected rays are reflected by said first critical surface; an entrance-exit surface that faces said image former and one surface of said projection lens unit, wherein the necessary reflected rays, the unnecessary reflected rays, and the surface-reflected rays enter and the necessary rays exit through said entrance-exit surface; and a second critical surface that is slanted with respect to an optical axis of the necessary reflected rays reflected from said first critical surface, wherein said second critical surface transmits the unnecessary reflected rays and the surface-reflected rays reflected from said first critical surface, and wherein said second critical surface reflects the necessary reflected rays reflected from said first critical surface to said projection lens unit.