Optical: systems and elements – Single channel simultaneously to or from plural channels
Reexamination Certificate
1999-10-08
2001-04-24
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
C359S016000, C359S622000, C362S268000, C353S048000, C353S094000
Reexamination Certificate
active
06222674
ABSTRACT:
RELATED APPLICATION
This Application is based on applications Nos. 10-287718 and 11-121452 filed in Japan, the contents of which are hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to an image display apparatus, and more particularly, to a projective image display apparatus that modulates light with an image display panel such as a liquid crystal panel and projects the modulated light with a projecting optical system.
DESCRIPTION OF THE PRIOR ART
Among image display apparatuses is a projective image display apparatus that modulates light from a light source with a liquid crystal panel according to an image signal and projects the modulated light onto a screen to thereby display an image. The projective image display apparatus is used for presenting an image to a multiplicity of people at a time, and in recent years, has been used as a data projector and a television having a comparatively large screen.
Typically, in such a projective image display apparatus, a lamp is used as the light source, and a quadratic-surface reflector is disposed behind the lamp so that as much of the light emitted by the lamp as possible is used for image projection. FIGS.
13
(
a
) and
13
(
b
) show the intensity distribution of the light supplied to a liquid crystal panel and the range of the luminous flux used by the liquid crystal panel. In FIG.
13
(
b
), LB represents the luminous flux, and LC represents the liquid crystal panel. The light intensity decreases from the center of the luminous flux, and the intensity is low in the vicinity of the center because of the shadow cast by the lamp itself. For this reason, the light intensity distribution, having a mountain shape with a concave portion at the top as shown in FIG.
13
(
a
), is nonuniform.
When light of such an intensity distribution is used for projection, the brightness of the displayed image is nonuniform. To prevent the peripheral part of the displayed image from being dark, it is necessary to use only the central part as shown in FIG.
13
(
b
) and the light of the peripheral part is wasted. Even when only the central part is used, the intensity distribution within the range is still nonuniform, so that the brightness of the displayed image is nonuniform.
A way to harmonize the intensity distribution of the light directed to the liquid crystal panel is to dispose an integrator, comprising a first lens array, a second lens array and a superimposing lens, between the light source and the liquid crystal panel. By temporarily imaging light from a light source reflected at the reflector with the cells of the first lens array on the corresponding cells of the second lens array, a secondary light source of a surface form in which light source images are two-dimensionally arranged is formed on the second lens array. By directing light from each part of the secondary light source to the entire liquid crystal panel with the superimposing lens, light intensity distribution is harmonized and thus uniform. Consequently, images without any brightness nonuniformness can be displayed, and the low-intensity light of the peripheral part is also effectively used, so that brighter images can be displayed.
A liquid crystal panel modulates polarized light of a predetermined oscillation direction. The polarized component of an oscillation direction vertical to the predetermined oscillation direction is absorbed by a polarizing plate incorporated in the liquid crystal panel or disposed separately from the liquid crystal panel. Consequently, half of the light of a disordered oscillation direction is abandoned without being used for projection.
To improve light use efficiency by solving this problem, Japanese Laid-open Patent Applications Nos. 8-304739 and 9-146064 propose to perform polarization conversion by use of a polarization beam splitter (PBS) array or a PBS prism for separating two linearly polarized light beams whose oscillation directions are vertical to each other. By allowing one of the linearly polarized light beams separated by the PBS to pass through a half wave plate, the oscillation direction thereof can be made to coincide with that of the other linearly polarized light beam, so that the light from the light source having a disordered oscillation direction can all be used for image projection.
Japanese Laid-open Patent Application No. 6-242397 discloses a projective image display apparatus in which two light sources are provided, and the light beams from the light sources are synthesized and directed to the liquid crystal panel to thereby increase the brightness of the displayed images. In the apparatus of this prior art, the light beams from the light sources are converged at condensation positions close to each other, the converged two light beams are reflected at a mirror in the same direction as divergent luminous fluxes whose optical axes are parallel to each other, and the divergent luminous fluxes are converted into parallel luminous fluxes by a collimator lens and directed to the liquid crystal panel. The light beams from the two light sources are synthesized by being converted into divergent luminous fluxes whose optical axes are close to each other.
The harmonization of the intensity distribution of the light from the light source, the conversion of the light from the light source into linearly polarized light of one direction by polarization conversion, and the provision of two light sources are all effective in improving the brightness of displayed images. By combining these three, a projective image display apparatus will be realized that displays bright images and is capable of using the light from the light source without waste. However, such a projective image display apparatus has not been proposed.
Since three techniques are based on different principles, it is not easy to appropriately combine them all. For example, the integrator for harmonizing the light intensity distribution and the PBS for performing polarization conversion must not adversely affect each other, and how these elements should be disposed cannot be found in the known art. In the art of Japanese Laid-open Patent Application No. 6-242397 using two light sources, the closer to each other the condensation positions of the two light beams from the two light sources are, the greater the quantity of unreflected light at the mirror, so that it is necessary to give special consideration to the setting of the condensation positions when the provision of the two light sources is combined with the integrator for harmonizing the light intensity distribution for uniformity or with the PBS for performing polarization conversion.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved projective image display apparatus.
Another object of the present invention is to provide a projective image display apparatus capable of displaying images of high brightness by use of two light sources.
Yet another object of the present invention is to provide a projective image display apparatus using the light beams from the light sources without waste.
The above-mentioned objects are achieved by a projective image display apparatus having the following structure:
a projective image display apparatus that modulates light with a display panel and projects modulated light with a projecting lens to display an image is provided with:
a first light source;
a second light source;
a first condensing optical system converging a light beam from the first light source at a first condensation position;
a second condensing optical system converging a light beam from the second light source at a second condensation position close to the first condensation position;
a reflecting optical system having a reflecting surface reflecting at least one of the light beams from the first and the second light sources at the corresponding condensation position, and deflecting the light beams from the first and the second light sources so that optical axes thereof are parallel or close to parallel;
a collimator lens converting into parallel l
Mack Ricky
Minolta Co. , Ltd.
Sidley & Austin
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