Abstract: A color combining optical system includes a first polarization splitting surface for light in a first wavelength range, and a second polarization splitting surface for light in a second and third wavelength range. The first polarization splitting surface guides illumination light in the first wavelength range to a first liquid crystal display (LCD) element and guides image light reflected from the first LCD element to a direction different from the illumination light. The second polarization splitting surface separates illumination light in the second and third wavelength range from each other, guides them to a second and third LCD element, respectively, and combines image light reflected from the second LCD element with image light reflected from the LCD element to guide combined light to the first polarization splitting surface which combines the image light reflected from the first LCD element with the combined light.

Abstract: An optical system for image projection is disclosed which is capable of improving contrast while suppressing reduction of light amount. The optical system includes a converging optical system, and a polarization beam splitting surface transmitting an incoming light flux having a first polarization direction from the converging optical system, to introduce it to the image-forming element and causing light having a second polarization direction, of an outgoing light flux from the image-forming element, to proceed to a projection optical system. In a first cross-section parallel to a normal to the polarization beam splitting surface, the converging optical system has a configuration causing an incident angle on the splitting surface of a light ray passing through a barycenter of intensity distribution of the outgoing light flux to be larger than an incident angle thereon of a light ray passing through a barycenter of intensity distribution of the incoming light flux.

Abstract: An optical system for image projection is disclosed which is easy to be manufactured and designed and capable of projecting a bright image with high contrast. The optical system includes an illumination optical system introducing a luminous flux emitted from a light source to an image-forming element through an optical surface having a light-splitting function, and a projection optical system projecting the luminous flux from the image-forming element through the optical surface onto a projection surface. The illumination optical system includes a conversion system which respectively converts the widths of the luminous flux in first and second cross-sections into widths different from those before entering thereinto. Conversion rates in the first and second cross-sections are different from each other.

Abstract: An illumination optical system configured to guide a light flux from a light source unit onto an illuminated surface includes a compression system configured to compress the light flux at a different compression ratio in a first cross section and a second cross section which are orthogonal to each other, and a polarized light splitting unit including a polarization split surface. The second cross section includes a line normal to the polarization split surface. Where a compression ratio for compressing a light flux in the first cross section is ?, a compression ratio in the second cross section is ?, and an F number smaller of F numbers calculated according to a maximum angle of a light flux incident on an illuminated surface in the first and the second cross sections is Fno, the following conditions are satisfied: ?0.18*(Fno)+1.245*(Fno)?1.260<?/?<1 1.4?Fno?3.6.

Abstract: A wavelength-selective polarization conversion element is disclosed which has a polarization conversion function that has been obtained by a polarization conversion element and a wavelength-selective phase plate in the past. The element includes a polarization beam splitting film and a phase plate. The film splits light and has a characteristic in which the transmittance for light with a first polarization direction and the transmittance for light with a second polarization direction are changed between a value higher than 50% and a value lower than 50% depending on wavelength region. The phase plate changes the polarization direction of light transmitted or reflected by the film between the first and second polarization directions. The element converts light in two of the first to third wavelength regions into polarized light with one polarization direction and converts light in the other wavelength region into polarized light with another polarization direction.

Abstract: A wavelength-selective polarization conversion element is disclosed, which is capable of reducing the number of optical elements in an optical system and simplifying the configuration thereof. The polarization conversion element comprises a beam splitting film which splits light by transmission and reflection and has a characteristic in which at least its transmittance for light with a first polarization direction changes between a transmittance higher than 50% and a transmittance lower than 50% depending on wavelength regions, and a phase plate which converts the polarization direction of light from the beam splitting film between the first polarization direction and a second polarization direction. The polarization conversion element converts light of two of first, second and third wavelength regions into light with one of the first and second polarization directions and converts light of the remaining wavelength region into light with the other polarization direction.

Abstract: An illumination optical system configured to guide a light flux from a light source unit onto an illuminated surface includes a compression system configured to compress the light flux at a different compression ratio in a first cross section and a second cross section which are orthogonal to each other, and a polarized light splitting unit including a polarization split surface. The second cross section includes a line normal to the polarization split surface. Where a compression ratio for compressing a light flux in the first cross section is ?, a compression ratio in the second cross section is ?, and an F number smaller of F numbers calculated according to a maximum angle of a light flux incident on an illuminated surface in the first and the second cross sections is Fno, the following conditions are satisfied: ?0.18*(Fno)+1.245*(Fno)?1.260<?/?<1 1.4?Fno?3.6.

Abstract: The wavelength-selective polarization conversion element includes a plurality of polarization splitting surfaces each of which separates entering light into two polarized light components having polarization directions different from each other, a plurality of phase plates that causes a polarization direction of one polarized light component in the two polarized light components from the polarization splitting surfaces to coincide with a polarization direction of the other polarized light component. The element further includes a plurality of dichroic surfaces that is disposed closer to a light entrance side than the plurality of polarization splitting surfaces or between the plurality of polarization splitting surfaces and the plurality of phase plates, each dichroic surface separating entering light into two wavelength region components different from each other.

Abstract: A color combining optical system includes a first polarization splitting surface for light in a first wavelength range, and a second polarization splitting surface for light in a second and third wavelength range. The first polarization splitting surface guides illumination light in the first wavelength range to a first liquid crystal display (LCD) element and guides image light reflected from the first LCD element to a direction different from the illumination light. The second polarization splitting surface separates illumination light in the second and third wavelength range from each other, guides them to a second and third LCD element, respectively, and combines image light reflected from the second LCD element with image light reflected from the LCD element to guide combined light to the first polarization splitting surface which combines the image light reflected from the first LCD element with the combined light.

Abstract: An image display apparatus includes a polarization conversion element which converts second color light of unpolarized light emitted from a light source into a first linear polarized light, and a light path separation element which separates the second color light emitted from the first and third color light; and performs image display by illuminating a first, a second and a third liquid crystal display elements with the first, second and third color light that pass through the light path separation element, wherein the light path separation element leads a first linear polarized light component of the second color light to the second liquid crystal display element, and wherein the light path separation element leads a second linear polarized light component whose direction of polarization is orthogonal to the first linear polarized light component of the second color light, in a direction different from any of the liquid crystal display elements.

Abstract: An optical system for image projection is disclosed which is capable of improving contrast while suppressing reduction of light amount. The optical system includes a converging optical system, and a polarization beam splitting surface transmitting an incoming light flux having a first polarization direction from the converging optical system, to introduce it to the image-forming element and causing light having a second polarization direction, of an outgoing light flux from the image-forming element, to proceed to a projection optical system. In a first cross-section parallel to a normal to the polarization beam splitting surface, the converging optical system has a configuration causing an incident angle on the splitting surface of a light ray passing through a barycenter of intensity distribution of the outgoing light flux to be larger than an incident angle thereon of a light ray passing through a barycenter of intensity distribution of the incoming light flux.

Abstract: An optical system for image projection is disclosed which is easy to be manufactured and designed and capable of projecting a bright image with high contrast. The optical system includes an illumination optical system introducing a luminous flux emitted from a light source to an image-forming element through an optical surface having a light-splitting function, and a projection optical system projecting the luminous flux from the image-forming element through the optical surface onto a projection surface. The illumination optical system includes a conversion system which respectively converts the widths of the luminous flux in first and second cross-sections into widths different from those before entering thereinto. Conversion rates in the first and second cross-sections are different from each other.

Abstract: A wavelength-selective polarization conversion element is disclosed which has a polarization conversion function that has been obtained by a polarization conversion element and a wavelength-selective phase plate in the past. The element includes a polarization beam splitting film and a phase plate. The film splits light and has a characteristic in which the transmittance for light with a first polarization direction and the transmittance for light with a second polarization direction are changed between a value higher than 50% and a value lower than 50% depending on wavelength region. The phase plate changes the polarization direction of light transmitted or reflected by the film between the first and second polarization directions. The element converts light in two of the first to third wavelength regions into polarized light with one polarization direction and converts light in the other wavelength region into polarized light with another polarization direction.

Abstract: A wavelength-selective polarization conversion element is disclosed, which is capable of reducing the number of optical elements in an optical system and simplifying the configuration thereof. The polarization conversion element comprises a beam splitting film which splits light by transmission and reflection and has a characteristic in which at least its transmittance for light with a first polarization direction changes between a transmittance higher than 50% and a transmittance lower than 50% depending on wavelength regions, and a phase plate which converts the polarization direction of light from the beam splitting film between the first polarization direction and a second polarization direction. The polarization conversion element converts light of two of first, second and third wavelength regions into light with one of the first and second polarization directions and converts light of the remaining wavelength region into light with the other polarization direction.