Patent ID: 6937401
Filing Date: 2005-08-30
Classification: G02B

Abstract:
1. A projection lens in a projection system receives a synthesized light formed by separating light from a light source into a plurality of color light beams, forming each of the separated color light beams as an image color light beam by a rectangular image formation element and synthesizing the image color beams and projects the received synthesized light in an enlarged scale on a screen, wherein said projection lens is formed as a projection lens of a retrofocus type wherein a first lens set having a negative refractive power and light path conversion means built therein, an iris, and a second lens set having a positive refractive power are disposed in order from the screen to the image formation element, said first lens set includes a first A lens set having a negative refractive power and including at least one aspheric lens, said light path conversion means, and a first B lens set having a positive refractive power, and said second lens set includes an aspheric lens, lenses in said first A lens set have an outer diameter with a portion thereof cut off outside an effective light ray in a direction of light path conversion, the direction of light path conversion by said light path conversion means is a direction of a shorter side of the rectangular image formation element, and where a focal length of the projection system is represented by FL, a back focus by FB, a front side focal position of said second lens set by FFP are satisfied.