Method of reducing the temperature difference between upper and lower portions of a lamp bulb, optical unit, projection type display apparatus and projection television apparatus

摘要

A method and apparatus is disclosed which minimizes the temperature difference between upper and lower portions of a lamp bulb in an optical unit. A UV-IR cut filter is disposed in a downwardly inclined relationship such that an upper portion thereof is nearer to a discharge lamp than a lower portion thereof so that infrared rays and ultraviolet rays included in light emitted from a lamp bulb and reflected in a forward direction from an upper portion of a reflecting face are reflected toward a lower portion of the reflecting face. As the reflected light from the UV-IR cut filter is illuminated on the lower portion of the reflecting face, the temperature difference between upper and lower portions of the lamp bulb is reduced.