JP3413226B2 - Polarization conversion device and projection display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization conversion device for converting randomly polarized light into linearly polarized light having a plane of polarization in one direction, and a projection type display device for enlarging and projecting an image of a liquid crystal light valve by a projection lens.

[0002]

2. Description of the Related Art A conventional polarization converter uses a polarizer or a birefringent crystal to selectively obtain only linearly polarized light having a specific polarization plane in order to obtain unidirectional polarized light from random polarized light. There are a method of taking out the light, a method of aligning the polarization direction by a right-angle prism used in the polarization conversion element of the actual open flat plate 1-88902, and a polarization conversion element using a beam splitter of JP-A-2-189504. Actual Kaihei 1-8890
The second polarization conversion element is one in which linearly polarized light is spatially separated using a beam splitter, and the separated mutually orthogonal polarization axes are aligned by twisting the polarization direction using a right-angle prism. The polarization conversion element of Kaihei 2-189504 performs polarization separation spatially using a beam splitter, and either polarization direction is ¼ λ plate or 1 / λ plate.
The 2λ plate makes the polarization directions uniform.

Further, in a conventional projection type liquid crystal display device, as shown in the projection type display device of Japanese Patent Laid-Open No. 61-102892, a liquid crystal light valve uses a TN liquid crystal having a polarization characteristic, and a polarization axis conversion element is used in advance. 2. Description of the Related Art There is a projection display device or the like in which polarized light having a polarized polarization axis is incident.

[0004]

However, in the case of the above-mentioned conventional polarization conversion element, another light synthesizing means is required in order to superimpose the light spatially polarized and separated by the beam splitter on one axis. Therefore, as a result, the distance from the lamp to the irradiation surface becomes long, and the brightness of the irradiation surface on which the polarization axes are aligned and irradiated is not increased. Further, when the light emission axes are irradiated by two axes, a light combining means is not required, but since the two irradiation axes have different optical path lengths, a difference in luminance of the irradiation surfaces occurs when half the irradiation surfaces are irradiated.

In the case of the conventional projection type liquid crystal display device, if the polarization axis of the light passing through the polarization beam splitter is the X axis, the reflected light is the Y axis and the axes are aligned through the liquid crystal to form a convex lens and a concave lens. It narrows down and leads to liquid crystal. Since the liquid crystal is responsible for each half of the area to be finally illuminated, a difference in brightness is generated in the center of the display portion in the left-right direction or in the up-down direction due to the difference in the irradiation distance from the lamp.

A polarization conversion device and a projection type display device using the same according to the present invention are for solving the above problems.
The purpose is that between the light source and the emission surface,
To provide a polarization conversion device having a high light-collecting efficiency by using a plurality of two-dimensional light sources with a first multi-lens lens and irradiating the irradiation surface with a second multi-lens lens so as to superimpose them. is there. Further, with respect to the light spatially separated into p- or s-polarized light from a plurality of two-dimensional light sources by the beam splitter, the second multi-lens lens irradiates two same lengths or different optical path lengths. It is an object of the present invention to provide a polarization conversion device in which desired polarization axes are combined on a single axis at the shortest by illuminating so that the optical axes are superposed on a surface, and color unevenness is small and illuminance distribution is uniform.

[0007]

In order to solve the above-mentioned problems, a polarization conversion device of the present invention collects light from a light source,
A first multi-lens lens forming a plurality of two-dimensional light sources, a polarization separation means for spatially separating random polarized light from the light sources into linear polarized light whose polarization planes are orthogonal to each other, and polarization separation. A reflection mirror for reflecting either one of the linearly polarized light polarized, a polarization rotation means for rotating the polarization plane of the polarization-separated linearly polarized light into a linearly polarized light having a polarization plane in one direction, and the polarized light. A second multi-lens lens provided on the light emitting side of the separating means and superimposing an image of the first multi-lens lens on the irradiation surface, and the polarization separating means includes the first multi-lens lens. It is characterized in that it is arranged between the second multi-lens type lens.

Further, the second multi-lens lens is arranged in the vicinity of the focal length of each lens of the first multi-lens.

Further, the projection type display device of the present invention includes a light source optical system, a light separating means for separating light from the light source optical system, a liquid crystal light valve for modulating light from the light separating means, and In a projection display device having a light combining means for combining the light modulated by the liquid crystal light valve and a projection lens for projecting the light from the light combining means, the light source optical system collects the light from the light source. A first multi-lens lens forming a plurality of two-dimensional light sources, a polarization separation means for spatially separating random polarized light from the light sources into linearly polarized light whose polarization planes are orthogonal to each other, and polarization separation A reflection mirror that reflects either one of the linearly polarized light, and a polarization rotation means for rotating the polarization plane of the polarization-separated linearly polarized light into a linearly polarized light having a polarization plane in one direction,
A second multi-lens lens which is provided on the light emitting side of the polarization splitting means and which superimposes the image of the first multi-lens lens on the irradiation surface;
And the polarization splitting means is arranged between the first multi-lens lens and the second multi-lens lens.

Further, the second multi-lens type lens is arranged in the vicinity of the focal length of each lens of the first multi-lens type lens.

[0011]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the polarization conversion device of the present invention, and the main constituent elements will be described below. Light flux emitted from a light source 1 such as a halogen lamp, a xenon lamp, or a metal halide lamp is reflected by a reflector 2
Is reflected to become substantially parallel unpolarized light 1 and enters the multi-lens lens 3. As shown in FIG. 4, the first multi-lens lens 3 is a combination of lenses cut into a plurality of rectangles, and the focal length a of each lens is the apparent one of the second multi-lens lens. An image is formed at the entrance pupil position.

The shape of the lens cut into the rectangle is
The first multi-lens type lens 3 has a shape similar to the shape of the irradiation surface, and is arranged so as to be inscribed or circumscribed within the rim diameter of the parabolic reflector when viewed from the emission surface side of the light source. Has been done.

The polarization beam splitter 4 provided perpendicularly to the optical axis of the first multi-lens lens 3 is a glass for separating polarized light at an incident angle of 45 degrees, or a glass such as ethylene glycol is refracted on the inner surface. It is formed by a beam splitter filled with a liquid equivalent to the index. The polarization beam splitter 4 has a light incident surface coated with an antireflection film, and has the least surface reflection. The dielectric film that separates the polarization characteristics is a high-refractive-index layer such as magnesium oxide, titanium oxide, or zirconium oxide on the reflective surface that forms an angle of 45 degrees with respect to the incident surface, and a low-refractive index such as magnesium fluoride or silicon oxide. It is a stack of alternating layers. This beam splitter splits two linearly polarized lights (p-polarized light and s-polarized light) whose polarization directions are orthogonal to each other with equal intensity to each other. The separated s-polarized light has a first T
The light is incident on the optical rotation plate of the N liquid crystal 5. First TN liquid crystal 5
Is a liquid crystal for rotating the s-polarized light emitted from the polarization beam splitter 4, which rotates at an angle of rotation of a little less than 45 degrees, transmits through the second multi-lens lens 6 and is mirror-symmetric by the total reflection mirror 7. It becomes the desired polarization axis in consideration. Similarly, the p-polarized light separated by the polarization beam splitter 4 is rotated by the second TN liquid crystal 8 at about 45 degrees. The angles of optical rotation of the first and second TN liquid crystals need to be in the optical rotation directions so that the polarization axes of the respective lights coincide with each other at the light combining points.

The materials of the first and second TN liquid crystals are, for example, liquid crystal NO. High temperature liquid crystal of ZLI-4103 (clearing point cr = 104 ° C,
Δn = 0.07) is used to fill a cell thickness of about 25 μm. The light emitted from the first and second TN liquid crystals is incident on the second multi-lens type lens. As shown in FIG. 4, this second multi-lens lens is composed of a lens that is cut into the same rectangular shape as the first multi-lens. Each lens of the second multi-lens type superimposes a rectangular image of each lens of the first multi-lens type lens on the irradiation surface having a similar shape.

The total reflection mirror 7 is a mirror for changing the optical path of each of the separated lights and adjusting them in the same direction.
Then, the polarization direction is inverted symmetrically. The two lights having different paths enter the respective second multi-lens lenses. The lens divided into each of the second multi-lens lenses is composed of a so-called tilt optical system in which the optical axes are shifted in parallel, and a plurality of light sources in the first multi-lens are used. By forming an image on the irradiation surface and synthesizing it, it is possible to convert the random polarized light from the light source into a specific linearly polarized light with high efficiency without causing most light loss. Further, by using the high temperature liquid crystal for the first and second TN liquid crystals, the clearing point does not undergo a phase transition up to 104 ° C, and since Δnd is 1.8, the optical rotatory dispersion of light is extremely small. The light spectrum of white light is not attenuated either.

(Embodiment 2) FIG. 2 is a configuration diagram of an optical system showing an embodiment of a projection type liquid crystal display device configured by using the polarization conversion device of Embodiment 1. The light source 10 is composed of a lamp such as a metal halide lamp or a xenon lamp, and makes highly parallel white light incident on the polarization conversion element 12. The polarization conversion element 12 converts the s-polarized light having a polarization characteristic perpendicular to the plane of incidence and the p-polarized light having a polarization characteristic horizontal to the plane of incidence into a desired straight line of the liquid crystal light valves 17R, 17G, and 17B. The light is emitted according to the axis of polarization. The linearly polarized light obtained by the polarization conversion element 12 enters the light separation means 13. The light separation means 13 is composed of dichroic mirrors 14 and 15 and a reflection mirror 16, and for example, by providing the dichroic mirror 14 with a reflection characteristic for red reflection and providing the dichroic mirror 15 with a wavelength characteristic for blue transmission. ,
The incident light is separated into three primary colors of red, blue and green. The respective color lights separated by the light separating means are incident on the liquid crystal light valves 17R, 17B and 17G corresponding to the respective colors, and the light modulation corresponding to the respective colors, that is, the image is formed by the change of the transmittance according to the signal voltage. And is incident on the photosynthesis means 18.

Liquid crystal light valves 17R, 17G, 17B
In general, a polarizing plate is arranged before and after the active matrix liquid crystal panel, but the polarizing plate on the light source side is unnecessary when the polarization degree of the polarization conversion element 12 is close to 100%. The photosynthesis means 18 is a dichroic mirror-1.
9 and 20 and a reflection mirror 16. For example, a dichroic mirror 19 is provided with a wavelength characteristic for transmitting red light, and a dichroic mirror 20 is provided with a wavelength characteristic for transmitting blue light. And the screen 22 by the projection lens 21.
Magnify and project.

FIG. 3 shows an embodiment in which the polarization conversion element of the projection type liquid crystal display device shown in Embodiment 2 of FIG. 2 is partially incorporated in a color separation optical system.

The light emitted from the light source 10 enters the beam splitter 4 through the first multi-lens type lens 3.
The s-polarized component of the incident light is transmitted through the second multi-lens type lens 6 due to the reflection characteristic of the polarization selection surface, and is radiated to the blue light valve 17B by the blue-reflecting dichroic mirror 20. On the other hand, the light transmitted through the beam splitter is rotated by the liquid crystal panel 8 and is applied to the green light valve 17G by the other second multi-lens lens 6 via the green reflection dichroic mirror 24. Since the light transmitted through the green dichroic mirror 24 is light of magenta color, the red light filter 17R is color-selected and irradiated by the red selection filter 26.

In this embodiment, regarding the light whose polarization has been converted, the s-polarized component does not go through the liquid crystal, but the light is directly transmitted through the second multi-lens lens 6 and the other p-polarized light is the liquid crystal panel. The light is rotated by 8 to match the polarization direction.

[0022]

As described above, according to the polarization conversion device of the present invention, the first multi-lens lens that collects light from the light source to form a plurality of two-dimensional light sources, Polarization separating means for spatially separating random polarized light from a light source into linearly polarized light whose planes of polarization are orthogonal to each other, a reflection mirror for reflecting either one of the linearly separated polarized light, and a linearly separated linearly polarized light Polarization rotating means for rotating the plane of polarization of polarized light to convert it into linearly polarized light having a plane of polarization in one direction,
A second multi-lens lens which is provided on the light emitting side of the polarization splitting means and which superimposes the image of the first multi-lens lens on the irradiation surface;
By disposing the polarization separating means between the first multi-lens lens and the second multi-lens lens, it is possible to guide light to the irradiation surface without changing the direction of the polarization direction. Therefore, highly efficient polarization conversion becomes possible. The polarized light separating means used for the polarized light separating means may be glass, but is composed of a beam splitter filled with a liquid having a refractive index substantially equal to that of the glass, so that the beam splitter is protected against heat emitted from the lamp. Does not deteriorate the dielectric film for polarization separation by absorbing heat by the convection of the liquid filled with, and is also thermally stable by attaching the first multi-lens to the beam splitter, In addition, it can be placed closest to the lamp, and polarized light can be separated efficiently and thermally. Also, by using this polarization conversion device in a projection display device, bright display is possible, and bright projection is achieved by adjusting the second multi-lens lens to the swallow angle determined from the F number value of the projection lens. A type display device can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment constituting a polarization conversion element of the present invention.

FIG. 2 is a configuration diagram of a projection display device using the polarization conversion element of the present invention.

FIG. 3 is a configuration diagram of a projection type display device in which the polarization conversion element of the present invention is partially incorporated in a color separation optical system.

FIG. 4 is a perspective view showing the configuration of a multi-lens lens of the present invention.

[Explanation of symbols]

1 ... Light source 2 ... Reflector 3 ... The first multi-lens 4 ... Polarizing beam splitter 5: First TN liquid crystal 6 ... Second multi-lens 7 ... Total reflection mirror 8 ... Second TN liquid crystal 10 ... Light source 12 ... Polarization conversion element 13 ... Optical separation means 14, 15, 19, 20 ... Dichroic mirror 17 ... Liquid crystal light valve 16 ... Reflective mirror 21 ... Projection lens 22 ... Screen 18 ... Photosynthesis means 23 ... Blue reflective dichroic mirror 24: Green reflection dichroic mirror 26: Red selection filter

Claims (4)

(57) [Claims] 1. A first multi-lens lens that collects light from a light source to form a plurality of two-dimensional light sources, and randomly polarized light from the light source into linearly polarized light whose polarization planes are orthogonal to each other. It has a polarization splitting means for spatially splitting, a reflection mirror that reflects either one of the polarization-split linearly polarized light, and a unidirectional polarization plane by rotating the polarization plane of the polarization-splitting linearly polarized light. A polarization rotation means for converting into linearly polarized light; a second multi-lens lens provided on the light emitting side of the polarization splitting means for superimposing an image of the first multi-lens lens on an irradiation surface;
The polarized light separating means includes the first multi-lens type lens and the second multi-lens type lens.
And a multi-lens type lens. 2. The polarization conversion device according to claim 1, wherein the second multi-lens lens is disposed near a focal length of each lens of the first multi-lens. 3. A light source optical system, a light splitting means for splitting the light from the light source optical system, a liquid crystal light valve for modulating the light from the light splitting means, and a light modulated by the liquid crystal light valve. In a projection type display device having a light combining means for combining and a projection lens for projecting the light from the light combining means, the light source optical system collects light from the light source, and a plurality of two-dimensional light sources. A first multi-lens lens for forming a polarized light, a polarization separation means for spatially separating random polarized light from a light source into linearly polarized light whose polarization planes are orthogonal to each other, and either one of the linearly polarized light separated Is provided on the light exit side of the polarization separation means, and a reflection mirror for reflecting the polarized light, polarization rotation means for rotating the polarization plane of the polarization-separated linear polarization to convert it into linear polarization having a polarization plane in one direction. The above A second multi-view lens superimposing the image of the first multi-lens lens to the irradiation surface,
The polarized light separating means includes the first multi-lens type lens and the second multi-lens type lens.
A projection display device, characterized in that the projection display device is arranged between the multi-lens lens. 4. The projection display device according to claim 3, wherein the second multi-lens lens is arranged near a focal length of each lens of the first multi-lens. .