JP2985220B2 - Projection display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device which enlarges and projects an image formed on a liquid crystal light valve onto a screen, and to a high brightness.

[Prior Art] FIG. 6 is an explanatory diagram of an optical system of a conventional projection display device.

In the figure, (1) is a light source, (120) is a lamp, (13)
0) is a reflecting mirror, (2) is an illumination light beam emitted from the light source (1), (3) is a liquid crystal light valve, (8) and (9) are polarizing plates disposed before and after the liquid crystal light valve, and (4) ) Is a projection lens, (5) is a screen, and (10) is a condenser lens.

 Next, the operation will be described.

The light source (1) comprises a lamp (120) and a reflecting mirror (130), and irradiates a liquid crystal light valve (3) with an illumination light beam (2). As the lamp (120), for example, a discharge lamp such as a metal halide lamp or a xenon lamp, or a halogen lamp is used. The reflecting surface of the reflecting mirror (130)
It is a paraboloid that is rotationally symmetric with respect to a center line (20) indicated by a dashed line in the figure, and the emission center (121) of the lamp (120) is arranged at the focal position of the paraboloid as is known. , A parallel illumination light beam (2) having a circular cross-sectional shape is obtained. An image is displayed on the surface of the liquid crystal light valve (3) as described later, and the transmittance in the surface changes according to the density and color of the image. The light beam transmitted through the liquid crystal light valve (3) is further transmitted through the projection lens (4) to become a projection light (110), and is enlarged and formed on a screen (5) for viewing. The condenser lens (10) is provided to allow the illumination light beam to enter the projection lens with high efficiency and obtain a high-brightness projection image.

Next, the configuration and operation of the liquid crystal light valve (3) will be described with reference to FIG.

The liquid crystal (6) is sandwiched between two glass substrates (7), and polarizing plates (8) and (9) are arranged on both sides. When no voltage is applied, V = 0 (FIG. 7A), the linearly polarized light (2a) transmitted through the incident-side polarizing plate (8) is polarized by the optical rotation of the liquid crystal when transmitted through the liquid crystal (6). The direction rotates 90 °,
The light passes through the exit-side polarizing plate (9) disposed so that the polarization axis of the entrance-side polarizing plate (8) is orthogonal to that of the polarizing plate. On the other hand, the threshold voltage Vt
When a voltage V equal to or more than h is applied (FIG. 7 (b)), the optical rotation of the liquid crystal decreases, and the amount of light transmitted through the exit-side polarizing plate (9) decreases with an increase in the voltage. A two-dimensional image display element can be formed by utilizing such a transmittance control function and further forming the electrodes in a two-dimensional array.
The above liquid crystal has a TN (Twisted Nemati
c) The example in which the liquid crystal is used in the normally white mode has been described. The types of liquid crystal phase, the magnitude of the optical rotation angle, and the like are well known, and other modified examples are known. However, since they are not directly related to the subject of the present invention, the description is omitted.

FIG. 8 shows an optical system of a device using three liquid crystal light valves as a second conventional device. In the figure, reference numeral (1) denotes a light source, specifically, a lamp (120) for generating white light such as a metal halide lamp, a xenon lamp, or a halogen lamp, and a rotationally symmetric parabolic reflector (1).
30). (2) is an illumination light beam emitted from the light source (1), and is a parallel light beam having a circular cross-sectional shape as in the first conventional example. (14R) and (14B) are dichroic mirrors for color separation, (15B) and (15G) are dichroic mirrors for color synthesis, (11) and (12) are mirrors, (3R) and (3
G), (3B) are liquid crystal light valves, (8R), (8G), (8
B) is an incident side polarizing plate, (9R), (9G) and (9B) are outgoing side polarizing plates, and (10R), (10G) and (10B) are condenser lenses.

 Next, the operation of the second conventional apparatus will be described.

The illumination light beam (2) exits the white light source lamp (120) placed at the focal position of the parabolic reflector, is reflected by the reflector (130), and emerges as a parallel light beam from the light source (1). .

The dichroic mirror (14R) reflects red light and
Transmits green light. In addition, dichroic mirror (14B)
Reflects blue light and transmits green light. Accordingly, the liquid crystal light valves (3G), (3B), and (3R) are irradiated with green, blue, and red illumination light beams, respectively. LCD light valve (3
In G), (3B), and (3R), an image corresponding to green, blue, and red light is formed by an external circuit (not shown), and the irradiation light is transmitted and modulated in the light valve surface. The light emitted from the liquid crystal light valves (3G), (3B) and (3R) is a dichroic mirror (15B) that reflects blue light, a dichroic mirror (15G) that reflects green light, and a reflecting mirror (12)
As a result, the light enters the projection lens (4) as a combined light beam (100), and is formed on the screen (5) as the projected light beam (110), and the enlarged color image is provided for viewing. The condenser lenses (10R), (10G) and (10B)
Each of them is used to make red, green, and blue light incident on the projection lens (4) with high efficiency. The configuration and operation of each of the liquid crystal light valves (3R), (3G), and (3B) are the same as those described above with reference to FIG.

[Problem to be Solved by the Invention] Since the conventional projection display device is configured as described above, as shown in FIG.
The luminous flux which is not reflected by the light and diverges forward hardly enters the liquid crystal light valve (3), which increases the loss of the luminous flux and prevents high brightness.

The present invention has been made in order to solve the above-described problems, and prevents a loss of an illumination light beam caused by diverging forward without being reflected by a parabolic mirror. An object of the present invention is to provide a projection display device capable of realizing image display.

[Means for Solving the Problems] A projection display device according to the present invention includes a light valve for forming an image in a rectangular area, a projection lens for enlarging and projecting an image formed on the light valve, and illuminating the light valve. An optical system comprising light source means for emitting a light beam, the light source means being a lamp, a parabolic mirror disposed at the focal point of the lamp, facing the parabolic mirror sharing an optical axis, and A spherical mirror joined to the parabolic mirror so as to satisfy the following equation with the focal point and the center of curvature of the parabolic mirror as common points, and emitting the light beam from a rectangular aperture provided in the spherical mirror. Features.

r = X1 + f X2 = 2f Y2 = Y1, where r is the radius of curvature of the spherical mirror, X1 is the depth from the vertex of the parabolic mirror, X2 is the depth from the vertex of the spherical mirror, and Y1 is the opening of the parabolic mirror. The radius, Y2, is the radius of the opening of the spherical mirror, and f is the focal length of the parabolic mirror.

In addition, an inert gas is hermetically sealed in the inside where the parabolic mirror and the spherical mirror are joined.

[Operation] As described above, the optical axis is shared, the parabolic mirror and the spherical mirror are arranged so as to face each other such that the focal point and the center of curvature of the spherical mirror are shared, and the parabolic mirror and the spherical mirror satisfy the above equation. By connecting to the aperture, a part of the luminous flux that has been diverged forward without being reflected by the conventional parabolic mirror is emitted as a parallel luminous flux from the aperture while realizing a compact configuration, and it becomes an effective illumination luminous flux. There is.

Further, since the light beam emitted from the light source can be formed in a rectangular shape substantially similar to the shape of the light valve, the shape of the light beam reaching the display surface and the shape of the display surface can be substantially matched, and the light beam loss due to the shaking can be almost eliminated.

Furthermore, by injecting an inert gas into the interior where the parabolic mirror and the spherical mirror are joined, oxidation of the lamp electrodes and lead wires can be prevented.

Example The present invention will be described with reference to the drawings.

 FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

In the figure, (120) is a lamp, (130) is a parabolic mirror,
(140) is a spherical mirror, and (141) is a rectangular opening provided in the spherical mirror, which is similar to the image display area of the liquid crystal light valve (3) when viewed in the z direction (the emission direction of the illumination light (2)) in the figure. It has a simple rectangular shape. The inner surface of the parabolic mirror (130) and the inner surface other than the rectangular opening (141) of the spherical mirror (140) are mirror-finished so as to act as a reflecting mirror, and are coated with a reflecting film as necessary. I have.

The light source (1) consists of the lamp (120) and the parabolic mirror (13
0), a spherical mirror (140), and a rectangular aperture (141). The other components are the same as those in the sixth conventional example.
It is the same as the figure.

 Next, the operation of the embodiment will be described.

The parabolic mirror (130) and the spherical mirror (140) share the optical axis,
They are arranged facing each other such that the focal point of the paraboloid and the center of curvature of the spherical surface become a common point. The lamp (120) is arranged so that the light emission center (121) is located at this common point position. The light beam emitted from the lamp (120) is directly reflected by the parabolic mirror (130) and emitted from the rectangular aperture (141) as a light beam parallel to the center line (20) shown by a dashed line, or emitted. Object mirror (1
30) and the spherical mirror (140) are reflected between the rectangular aperture (14
1) The light is emitted as a light beam parallel to the optical axis (20). This situation will be described with reference to FIG. 2, which illustrates the inside of the light source (1) in detail. In the figure, the parabolic mirror (13
0) and the inner surface of the spherical mirror (140) are portions that function as a reflecting mirror, and the portion (141) shown by a broken line is a rectangular opening. In the figure, three representative rays (a), (b),
The behavior of (c) is shown. Ray (a) is a lamp (12
0) is a light ray that is reflected by the parabolic mirror (130) and exits through the end of the rectangular aperture (141). Lamp (12
The light emission center (121) of (0) is the optical axis (20) indicated by the dashed line.
The ray (a) is parallel to the optical axis (20) since it is located at the common point of the focal point of the parabolic mirror (130) and the center of curvature of the spherical mirror (140), which faces in a plane perpendicular to Illumination ray (2)
Becomes The light beam reflected by the parabolic mirror (130) at a point closer to the optical axis (20) than the light beam (a) is emitted as a parallel illumination light beam from the rectangular aperture (141), similarly to the light beam (a). The light ray (c) is incident on the spherical mirror (140) at a position higher than the rectangular aperture, and after reflection, the common point (12
1)), enters the parabolic mirror (130), and exits from the rectangular aperture (141) as a ray parallel to the optical axis (20) after reflection.

As is clear from the above description, the light beam directly entering the rectangular aperture (141) from the lamp (120) and the light beam (light beam (b) incident on the parabolic mirror (130) at a position higher than the light beam (a) Light rays other than)) are all emitted from the rectangular aperture (141) as an illumination light beam (2) having a rectangular cross section and being parallel to the optical axis (20). The illumination light beam (2) is a condenser lens (1
0), and is incident on the liquid crystal light valve (3) disposed immediately thereafter. The illumination light beam (2) is illuminated as a rectangular light beam having a size substantially equal to the size of the rectangular display area in the liquid crystal light valve (3), the size of the rectangular opening (141), the condenser lens (10), and the liquid crystal light. The arrangement relationship of the valve (3) is set. In an optical system in which the condenser lens (10) is omitted, the illumination light beam (2) enters the liquid crystal light valve (3) as a parallel light beam.
In this case, the cross-sectional shape of the parallel illumination light beam (2) is set to substantially the same size as the rectangular display area of the liquid crystal light valve. In FIG. 1, the point that the transmitted light of the liquid crystal light valve (3) passes through the projection lens (4), becomes the projected light (110), and is enlarged and projected on the screen (5) is the same as the conventional apparatus.

 Next, a method for producing the light source (1) will be described.

First, the rectangular opening (141) is preferably a hole provided in the spherical mirror (140), because unnecessary reflection from the opening can be prevented. As is well known, the parabolic mirror (130) and the spherical mirror (140) are made by molding or cutting a metal such as Al, or by molding a glass material. In the case of glass, it is appropriate to apply a reflective coating to the inner surface. In order to prevent unnecessary infrared rays and ultraviolet rays from being irradiated to the liquid crystal light valve (3) side, only the visible light (for example, a wavelength of 400 to 700 nm) is selectively reflected by the parabolic mirror (130). After coating, a part of the spherical mirror (140) other than the rectangular aperture (141) is broadband reflected (for example, with a reflectance of 9 in the wavelength range of 200 to 1000 nm).
0% or more).

Second, the rectangular opening (141) does not necessarily have to be physically opened as a transmission area (window area) partially provided in a spherical mirror (140) made of a transparent glass material. In this case, the rectangular opening (141) may be a mere transparent glass window without applying a reflective coating, or may be provided with a non-reflective coating for visible light (wavelength 400 to 700 nm) as necessary. The inner surface of the spherical mirror (140) other than the rectangular aperture (141) is suitably provided with a broadband reflective coating (for example, a reflectance of 90% or more in a wavelength range of 200 to 1000 nm). The coating of the rectangular opening (141) may be provided with a function of reflecting ultraviolet rays (wavelength of 400 nm or less) and infrared rays (wavelength of 700 nm or more) to prevent the liquid crystal light valve (3) from being irradiated with unnecessary spectrum.

Third, the parabolic mirror (130) and the spherical mirror (140) are opposed to each other, and the outer peripheral portion (indicated by symbol A) as shown in FIG.
May be joined by a known method such as welding. Not this case, the second rectangular opening (141) and transparent glass as in the configuration, the inside of the opposite parabolic mirror and the spherical mirror hermetically sealed in a known manner, inside the N _2, Ar, etc. By enclosing the active gas, it is possible to prevent the oxidation of the electrodes (not shown) of the lamp (120) and the lead wires connecting the electrodes and the driving circuit, which is effective for extending the life. FIG. 3 illustrates a method for determining the shape of a paraboloid and a spherical surface (inner surface) for hermetic sealing. In FIG. 3, the following expressions are established.

_{X 1 + X 2 = f +} r ···· Y 1 = Y 2 ···· Y 1 2 = 4fX 1 ···· r 2 = (X 1 -f) 2 + Y 1 2 ···· However, X ₁ Is the depth from the vertex of the parabolic mirror, X ₂ is the depth from the vertex of the spherical mirror, Y ₁ is the radius of the opening of the parabolic mirror, Y ₂ is the radius of the opening of the spherical mirror, and f is the parabolic mirror. And r is the radius of curvature of the spherical mirror.

Assuming that the parameters (f, X ₁ , Y ₁ ) of the parabolic mirror are given, an equation can be obtained by eliminating Y ₁ and X ₂ from the equation.

r ² = (X ₁ + f) ² ... Here, since r is a positive value, the solution of the equation is r = X ₁ + f. When the equation is used in the equation, X ₂ = 2f... By using the spherical mirror (140) having the parameters of the radius r of the equation, X _{2 of} the equation, and Y _{2 of} the equation, a parabolic mirror and a spherical mirror joined at the outer peripheral portion and opposed to each other are obtained as described above.

[Numerical example] When a parabolic mirror having f = 12.5 mm, Y ₁ = 46.5 mm, and X ₁ = 43.245 mm is used, from the equation, the spherical mirror is r = 55.745 m.
m, Y ₂ = 46.5 mm and X ₂ = 25.0 mm.

A plan view of the spherical mirror is shown on the right side of FIG.
The rectangular opening (141) has dimensions of a long side H and a short side V in a plan view. H: V is almost equal to the ratio of the long side to the short side of the effective display area of the liquid crystal light valve (3).

Another Embodiment Next, a second embodiment of the present invention will be described with reference to FIG.

In this embodiment, a parabolic mirror (130) and a spherical mirror (140) similar to those in FIG. 1 showing the first embodiment are used in the optical system shown in FIG. Light source (1) consisting of a lamp (120) with a center (121) arranged and a rectangular aperture (141)
This is an example in which is applied. As in the first embodiment, an illumination light beam (2) having a rectangular cross section exits from the rectangular opening (141) and enters the optical system after the dichroic mirror (14R). In addition, liquid crystal light valves (3R), (3G), (3B)
The size of the rectangular opening (141), the condenser lenses (10R), (10G), (10B), and the liquid crystal light valve (3
R), (3G), and (3B) are set. In this embodiment, as in the first embodiment, a part of the light beam diverging forward from the lamp (120) and being lost is effectively used as a parallel illumination light beam, and the advantage of realizing high brightness is the same. . Except for the light source (1), the description has been given in the second conventional example, and a description thereof will be omitted.

In each of the embodiments of the present invention, a transmissive liquid crystal light valve is used, but an apparatus using a reflective liquid crystal light valve is also known. FIG. 5 shows a light source (1) of the present invention.
A third embodiment in which is applied to an optical system using a reflection type liquid crystal light valve (3) is shown. As in the first and second embodiments, a parabolic mirror (130), a spherical mirror (140) having a rectangular opening (141), and a lamp (120) having a light emission center (121) at a common point are provided. The illumination light beam (2) having a rectangular cross section emitted from the light source (1) is reflected by the polarizing beam splitter (200) and becomes S-polarized illumination light traveling toward the liquid crystal light valve (3). When no voltage is applied to the pixels, the luminous flux incident on the reflective light valve is reflected by a reflecting mirror provided on the lower glass substrate (7) and has a polarization plane of 90 ° when exiting from the liquid crystal. Although the light rotates, when the voltage V equal to or higher than the threshold value is applied to the pixel, the above-mentioned optical rotation effect is reduced.
On the other hand, the reflected light from the liquid crystal light valve passes through the polarizing beam splitter (200) and then becomes a light flux (100) heading for the projection lens (4). The polarizing beam splitter (200) has a characteristic of transmitting P-polarized light and reflecting S-polarized light perpendicular to the plane of polarization, so that the transmittance in the cross section of the light beam according to the strength of the voltage applied to the pixels of the liquid crystal light valve. Is modulated into image information. Light flux (110) emitted from the projection lens (4)
Is enlarged and projected on the screen (5) as in the conventional example.

In the embodiment using the reflection type light valve described above,
As in the case of the transmissive type, the image display surface of the liquid crystal light valve (3) is rectangular, and high brightness can be achieved by the effect of the light source (1) as in the first and second embodiments. In the above embodiments, the method using the optical rotation of the liquid crystal has been described as the liquid crystal light valve. In addition, a method of electrically controlling the birefringence of the liquid crystal, such as ECB (electrically cont
A rolled birefringence type or the like is also known, and it goes without saying that the present invention can be applied to a projection display device using a liquid crystal light valve having an optical display mechanism other than optical rotation. Also, the number of light valves is not limited to three, but may be three.
More than one sheet or one or two sheets can be applied without any problem.

As is clear from the above, the main features of the present invention are listed as follows.

(1) The rectangular opening is provided in a part of the spherical mirror, and has a rectangular shape as viewed from the optical axis direction.

(2) The rectangular opening is a transparent portion provided in a part of the spherical mirror, and has a rectangular shape when viewed from the optical axis direction.

(3) The parabolic mirror and the spherical mirror are each rotationally symmetric with respect to the optical axis, have the same outer diameter, and are adhered to each other so as to form a closed structure.

[Effects of the Invention] As described in detail above, according to the projection display device of the present invention, the optical axis is shared, and the focal point of the parabolic mirror and the center of curvature of the spherical mirror are opposed to each other so as to be a common point. By arranging and joining the parabolic mirror and the spherical mirror so as to satisfy the following formula, while realizing a compact configuration, the luminous flux of the light beam that has diverged forward without being reflected by the parabolic mirror in the past is realized. There is an effect that a part of the light is emitted from the opening as a parallel light beam to make it an effective illumination light beam.

r = X1 + f X2 = 2f Y2 = Y1, where r is the radius of curvature of the spherical mirror, X1 is the depth from the vertex of the parabolic mirror, X2 is the depth from the vertex of the spherical mirror, and Y1 is the radius of the opening of the parabolic mirror. , Y2 is the radius of the opening of the spherical mirror, and f is the focal length of the parabolic mirror.

Further, by filling an inert gas into the inside where the parabolic mirror and the spherical mirror are joined, oxidation of the lamp electrodes and lead wires can be prevented, and the life can be extended. As a result, it is possible to realize a projection type display device for a high-brightness projection image.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a first embodiment of the present invention, FIG. 2 is a detailed explanatory view of a light source used in the present invention, and FIG. 3 is an opposing light source of a projection display device of the present invention. FIG. 4 is a view for explaining a design method of a parabolic mirror and a spherical mirror, and a shape of a rectangular opening.
FIG. 5 is an explanatory diagram of a second embodiment of the present invention, FIG. 5 is an explanatory diagram of a third embodiment of the present invention, FIG. 6 is a first configuration diagram of a conventional projection display device, and FIG. FIG. 8 is an explanatory view of the operation principle of a liquid crystal light valve, FIG. 8 is a second structural view of a conventional projection display apparatus, and FIG. 9 is an explanatory view of a luminous flux loss which is a problem of the conventional apparatus. In the figure, (3), (3R), (3G), and (3B) are liquid crystal light valves, (4) is a projection lens, (1) is light source means,
(120) is a lamp, (130) is a parabolic mirror, (140) is a spherical mirror, (141) is a rectangular aperture, and (121) is a light emission center. In the drawings, the same reference numerals indicate the same or corresponding parts.

Continuing on the front page (72) Inventor Eiichi Tsude 1 Baba Zujo, Nagaokakyo-shi, Kyoto Prefecture Mitsubishi Electric Corp. Electronic Product Development Laboratory (72) Inventor Hiroshi Kida 1 Baba Zujo, Nagaokakyo-shi, Kyoto Mitsubishi Electric (56) References Japanese Utility Model Sho-64-10724 (JP, U) Japanese Utility Model Hei 1-123881 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) ) G03B 21/00 G03B 21/14

Claims (2)

(57) [Claims] An optical system comprising a light valve for forming an image in a rectangular area, a projection lens for enlarging and projecting an image formed on the light valve, and light source means for emitting a light beam for illuminating the light valve. In the projection display device, the light source means includes a lamp, a parabolic mirror that places a light-emitting portion of the lamp at a focal point, an optical axis shared by the parabolic mirror, and the parabolic mirror. A projection type comprising a spherical mirror joined to the parabolic mirror so as to satisfy the following expression with a focal point and a center of curvature as a common point, and emitting the light beam from a rectangular aperture provided in the spherical mirror. Display device. r = X1 + f X2 = 2f Y2 = Y1 r is the radius of curvature of the spherical mirror, X1 is the depth from the vertex of the parabolic mirror, X2 is the depth from the vertex of the spherical mirror, Y1 is the radius of the opening of the parabolic mirror, Y2 Is the radius of the aperture of the spherical mirror,
f is the focal length of the parabolic mirror 2. The projection display device according to claim 1, wherein an inert gas is hermetically sealed in the inside where said parabolic mirror and said spherical mirror are joined.