1. Field of the Invention
The present invention relates to a liquid crystal projector designed to broaden a viewing angle of a liquid crystal panel and thereby improve the display evenness and contrast.
2. Description of the Related Art
There is known a liquid crystal projector which optically modulates light output from a light source by for example a transmission type liquid crystal panel to form an optical image and projects this optical image on a screen or the like.
For example, a three-panel type liquid crystal projector which modulates light by liquid crystal panels corresponding to the R, G, and B color light and combines the optical images of these colors formed by this optical modulation to form a color image can output a good quality color image.
Summarizing the disadvantages to be solved by the invention, in such a liquid crystal projector, where trying to improve the contrast, since the image is viewed projected on a screen arranged in a predetermined direction, it has been considered unnecessary to improve the viewing angle of the liquid crystal panels. Accordingly, in each liquid crystal panel, the contrast has been improved by reducing the transmittance of the light at the time of blocking light at the center position of incidence.
Note that for example notebook type personal computers etc. assume viewing of the same image by a number of users from positions of certain angles, so are designed considering viewing angle dependency.
Further, when constructing a liquid crystal projector, it is required that the distribution of the display luminance at the screen be constant when signals of an identical level are input to the entire panel. This uniformity of luminance on the screen is referred to as a high display uniformity and is regarded as one of the important factors for achieving high grade images.
One of the causes of display unevenness is considered to be, for example, unevenness in the luminance of a light emitting part of a light source. Such an unevenness of luminance is projected as it is on the screen, so a high display uniformity cannot be obtained.
Therefore, to correct this unevenness of luminance, the practice has been to arrange a required optical element between the light source and the liquid crystal panel so as to uniformly illuminate the incident surface of the liquid crystal panel. Accordingly, the viewing angle dependency of the liquid crystal panel per se had not been considered.
Further, for example, when using marginal light emitted at a relatively large angle with respect to the optical axis in order to make the light output from the light source contribute more to the image, the light blocking performance in the liquid crystal panel deteriorates and so-called the black display portions are displayed somewhat brightly, i.e., a so-called black color whitening phenomenon occurs. Due to this, in an image having a high luminance, there is remarkable black level whitening even if the contrast is the same and an image without good blackness will be formed.
Further, when trying to utilize the marginal rays, the deterioration of the contrast becomes greater in particular at the blue liquid crystal panel having a strong light intensity. When adjusting the white balance in such a state, it suffers from the disadvantage that the contrast of three R, G, and B colors is determined based on the blue liquid crystal panel having the worst contrast among the three liquid crystal panels.
For this reason, a liquid crystal projector effectively utilizing the light from a light source to improve the luminance for a wide viewing angle and thereby enabling formation of an image excellent in contrast in that state has been demanded.
An object of the present invention is therefore to provide a liquid crystal projector giving an image having a high luminance and excellent contrast.
According to a first aspect of the invention, there is provided a liquid crystal projector provided with a light source, an illumination optical system for converging the light emitted from the light source to a required optical path, a liquid crystal panel for optically modulating the light converged by the illumination optical system, and a projection lens for magnifying and projecting the light modulated by the liquid crystal panel, the liquid crystal projector further provided with a first polarization plate which is arranged at an incident side of the liquid crystal panel and transmits a first polarized light converged by the illumination optical system therethrough, a second polarization plate which is arranged at an exit side of the liquid crystal panel, transmits a second polarized light modulated by the liquid crystal panel therethrough, and outputs the same to the projection lens, and a phase difference means having one of a phase delay axis or a phase forward axis which is orthogonal to a polarization axis of the first or second polarization plate and arranged inclined by a predetermined angle about an axis of rotation comprised of an axis parallel to the polarization axis of the first or second polarization plate in the plane in which the phase correcting means is formed.
According to a second aspect of the invention, there is provided a liquid crystal projector provided with a light source, an illumination optical system for converging the light emitted from the light source to a required optical path, a liquid crystal panel for optically modulating the light converged by the illumination optical system, and a projection lens for magnifying and projecting the light modulated by the liquid crystal panel, the liquid crystal projector further provided with a first polarization plate which is arranged at an incident side of the liquid crystal panel and transmits a first polarized light converged by the illumination optical system therethrough, a second polarization plate which is arranged at an exit side of the liquid crystal panel, transmits a second polarized light modulated by the liquid crystal panel therethrough, and outputs the same to the projection lens, and an optical compensating means which has a phase delay axis in a required axial direction which is arranged at a required angle with respect to the polarization axis of the first or second polarization plate.
The present invention therefore provides, between the liquid crystal panel and a polarization plate, a phase difference means having one of a phase delay axis or a phase forward axis which is orthogonal to a polarization axis of the first or second polarization plate and arranged inclined by a predetermined angle about an axis of rotation comprised of an axis parallel to the polarization axis of the first or second polarization plate in the plane in which the first or second polarization plate is formed or provides, between the liquid crystal panel and a polarization plate, an optical compensating means which has a phase delay axis or phase forward axis in a required axial direction and arranged at a required angle with respect to the polarization axis of the first or second polarization plate.
Due to this, it is possible to obtain a beam of light in the polarization direction corresponding to a pretilt angle at an interface of an orientation film of the liquid crystal panel and possible to improve the light blocking property of the liquid crystal panel and thereby improve the contrast.