Patent ID: 6705731
Filing Date: 2004-03-16
Classification: G02B,H04N

Abstract:
A projection type display apparatus for projecting an image onto a screen, said projection type display apparatus comprising:a plurality of light valves corresponding to a plurality of primary colors; a polarizing/separating element for polarizing and separating primary color lights for illuminating the light valves and primary color lights modulated by the light valves; and a color synthesizing element for color-synthesizing primary color lights which are necessary for projection to a screen in the primary color lights emitted from the polarizing/separating element, wherein the polarizing/separating element comprises, for each of the primary colors, a pre-polarizing beam splitter, a main polarizing beam splitter, and a post-polarizing beam splitter in this order on an optical path of the respective primary color light, said pre-polarizing beam splitter having a function for removing polarized component which is unnecessary for illumination of the respective light valve, said main polarizing beam splitter having a function for removing polarized component which is unnecessary for illumination of the respective light valve and polarized component which is unnecessary for projection to the screen in the primary color light modulated by the respective light valve, and said post-polarizing beam splitter having a function for removing polarized component which is unnecessary for projection to the screen in the primary color light modulated by the respective light valve wherein the pre-polarizing beam splitters and the post-polarizing beam splitters take out the polarized components necessary for the illumination and projection by means of transmission, and the pre-polarizing beam splitter and the post-polarizing beam splitter which are used for the same primary color light have the almost equivalent extinction ratio, and wherein, in each of the main polarizing beam splitters, an extinction ratio when a necessary polarized component is taken out by reflection is almost equivalent to an extinction ratio when a necessary polarized component is taken out by transmission.