| 摘要 |
PURPOSE:To provide a polarization light source for a projection type liquid crystal display device capable of improving the picture quality of the projected image, making the device small in size, light in weight and prolonging its life. CONSTITUTION:The acting surface of a polarization beam splitter 13 makes nearly an angle 45 deg. to the optical axis 19 of almost parallel incident beam, a 1/2 wavelength plate 14 makes 45 deg. to the acting surface of a polarization beam splitter 13 in the optical path of the reflected beam of the polarization beam splitter 13, a light beam reflection element 15 makes a prescribed angle smaller than 90 deg. to the acting surface of a polarization beam splitter 13, the 1/2 wavelength plate 14 is made in parallel with the optical axis 19 and the polarization beam splitter 13 and the light beam reflection element 15 are arranged in surface symmetry with the 1/2 wavelength plate 14. When a nearly parallel light beam is made incident from the light source, one of a polarization light beam is transmitted through the polarization beam splitter 13, travels straight, the other polarization light beam is reflected, transmitted through the 1/2 wavelength plate 14 and the polarization beam splitter 13, its optical path is changed by the light beam reflection element 15, the beam is transmitted and superimposed on the light beam travelling straight on a liquid crystal light valve 17. |
