Projection-type display apparatus having polarized beam splitters and an illuminating device

A color separating/light guiding optics comprises two independent dichroic mirrors, reflection mirrors and correcting lenses. A horizontal plane region occupied by these optical components is entirely involved in a horizontal plane region occupied by a light modulating/color compositing/image projecting optics. A red beam is guided along a detoured optical path extending across a dead space below a projection lens. Although the optical path length of the red beam becomes longer than those of the blue beam and the green beam, the detoured optical path provides a sufficient space for installing the correcting lenses. The substantial optical path lengths of three primary color beams can be equalized with each other by the provision of these correcting lenses.

If you were to search for Projection-type display apparatus having polarized beam splitters and an illuminating device using relaxed search criteria, these patents would come up:

What is claimed is:

1. A projection-type display apparatus comprising:

a light source for emitting white color light;

a color separating/light guiding optics for separating said white color light emitted from said light source into three primary color beams and for guiding the separated primary color beams to a light modulating/color compositing/image projectingoptics located at a deck different from that of said color separating/light guiding optics;

said light modulating/color compositing/image projecting optics comprises:

a cross-type dichroic prism with two reflection films crossing each other and having wavelength selectivity for selecting two of three primary colors;

a projection lens disposed at an outgoing surface of said cross-type dichroic prism;

polarized beam splitters having outgoing surfaces respectively facing to three incident surfaces of said cross-type dichroic prism and incident surfaces for receiving corresponding primary color beams incoming from said color separating/lightguiding optics, said polarized beam splitters having polarizing films directed in predetermined directions in such a manner that said incident surfaces of said polarized beam splitters face toward said color separating/light guiding optics; and

reflection-type spatial light modulating sections respectively facing to other surfaces opposing to said outgoing surfaces of said polarized beam splitters;

wherein said color separating/light guiding optics comprises two independent dichroic mirrors which are spatially separated and a plurality of reflection mirrors; and

a plane region occupied by said color separating/light guiding optics is entirely involved in a plane region occupied by said light modulating/color compositing/image projecting optics when seen in an up-and-down direction.

2. A projection-type display apparatus comprising a light modulating/color compositing/image projecting optics located at a predetermined deck and a color separating/light guiding optics located at another deck, wherein

said light modulating/color compositing/image projecting optics comprises:

a cross-type dichroic prism with two reflection films crossing each other and having wavelength selectivity for selecting two of three primary colors;

a projection lens disposed at an outgoing surface of said cross-type dichroic prism;

polarized beam splitters having outgoing surfaces respectively facing to three incident surfaces of said cross-type dichroic prism;

reflection-type spatial light modulating sections respectively facing to other surfaces opposing to said outgoing surfaces of said polarized beam splitters;

said color separating/light guiding optics separates white color light emitted from a light source into three primary color beams and guides the separated primary color beams to incident surfaces of corresponding polarized beam splitters providedin said light modulating/color compositing/image projecting optics;

said polarized beam splitters have polarizing films directed in predetermined directions in such a manner that said incident surfaces of said polarized beam splitters face toward said color separating/light guiding optics,

said color separating/light guiding optics comprises two independent dichroic mirrors and a plurality of reflection mirrors, and

a plane region occupied by said color separating/light guiding optics is entirely involved in a plane region occupied by said light modulating/color compositing/image projecting optics when seen in an up-and-down direction, wherein

said color separating/light guiding optics guides first and second primary color beams along first and second optical paths identical in length and extending from said light source to corresponding polarized beam splitters facing to neighboringincident surfaces of said cross-type dichroic prism of said light modulating/color compositing/image projecting optics,

said color separating/light guiding optics guides a third primary color beam along a third optical path serving as a detoured optical path longer than said first and second optical paths and extending from said light source to the correspondingpolarized beam splitter across a dead space below said projection lens of said light modulating/color compositing/image projecting optics, and

at least one correcting lens is provided in said detoured third optical path to substantially equalize the optical path length of said third primary color beam with those of said first and second primary color beams.

3. The projection-type display apparatus in accordance with claim 1, wherein an intermediate deck of a polarized light selecting optics is interposed between said two decks,

said polarized light selecting optics comprises three polarized beam splitters facing to corresponding incident surfaces of respective polarized beam splitters of said light modulating/color compositing/image projecting optics, and

each of said polarized beam splitters of said polarized light selecting optics allows one polarized component of the corresponding primary color beam to pass through and enter the corresponding polarized beam splitter of said lightmodulating/color compositing/image projecting optics and reflects the other polarized component in a direction different from said one polarized component.

4. The projection-type display apparatus in accordance with claim 2, wherein

said light source is a xenon lamp equipped with a convergence-type reflector and an illuminating means for unifying an illuminance distribution.

5. The projection-type display apparatus in accordance with claim 4, wherein said illuminating means comprises a collimator lens and a pair of fly-eye lenses, and said collimator lens has a spherical aberration not smaller than 0.01 f.

6. The projection-type display apparatus in accordance with claim 4, wherein said illuminating means comprises a light pipe having a rectangular hollow space defined by an aspect ratio of 3:4 and a diagonal aperture length of 5 to 10 mm, andsaid light pipe is located in the vicinity of a second focal point of said xenon lamp.

7. A projection-type display apparatus comprising:

a light source for emitting white color light,

a color separating/light guiding optics for guiding first and second primary color beams along first and second optical paths identical in length and extending from said light source to corresponding polarized beam splitters facing to neighboringincident surfaces of a cross-type dichroic prism of a light modulating/color compositing/image projecting optics,

wherein

said light modulating/color compositing/image projecting optics is positioned above said color separating/light guiding optics,

said color separating/light guiding optics guides a third primary color beam along a third optical path serving as a detoured optical path longer than said first and second optical paths and extending from said light source to a correspondingpolarized beam splitter across a dead space below a projection lens of said light modulating/color compositing/image projecting optics, said projection lens overhanging outward from said cross-type dichroic prism, and

at least one correcting lens is provided in said detoured third optical path to substantially equalize the optical path length of said third primary color beam with those of said first and second primary color beams.

8. The projection-type display apparatus in accordance with claim 7, wherein said color separating/light guiding optics comprises a first dichroic mirror and a second dichroic mirror which are separately provided,

said first dichroic mirror guides said first and second primary color beams along said first and second optical paths, and

said second dichroic mirror guides said third primary color beam along said third optical path.

9. The projection-type display apparatus in accordance with claim 7, wherein a plane region occupied by said color separating/light guiding optics is entirely involved in a plane region occupied by said light modulating/color compositing/imageprojecting optics when seen in an up-and-down direction.