JPH05341254A - Projection type liquid crystal display device and optical element used therefor - Google Patents

Abstract

PURPOSE:To solve a problem that a thin line with fluctuating color appears in the center part of a screen, and the picture quality is deteriorated due to a fact that an interval between the respective interference fringes of two dichroic mirrors arranged on the same plane, in a liquid crystal projector for synthesizing light of red, green and blue by using cross dichroic mirrors, and projecting an image on the screen through a projection lens. CONSTITUTION:By arranging two dichroic mirrors 15, 16 in an L shape, and arranging a rectangular prism 30, the respective interference fringes formed in two sides of the prism, and the respective corresponding interference fringes of two dichroic mirrors can be arranged on the same plane at a negligible interval.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device and an optical element used therefor. The projection type liquid crystal display device (hereinafter also referred to as a liquid crystal projector) includes a white light source, a condensing optical system that condenses light from the light source, and light condensed by the condensing optical system. And a liquid crystal display panel for inputting, modulating, and outputting each primary color light corresponding to each of the separated and output three primary color lights. And a second optical element for combining and outputting the modulated light from each liquid crystal display panel, and a projection lens for projecting the combined light from the second optical element onto a screen. However, the present invention particularly relates to the second optical element (an optical element that combines the modulated light from each liquid crystal display panel and outputs the combined light toward the projection lens).

[0002]

2. Description of the Related Art A liquid crystal projector illuminates three liquid crystal panels with three primary color lights of red (R), green (G), and blue (B) produced by separating a white light source. .. On the other hand, when each liquid crystal panel is driven based on the video signals to be displayed in red, green, and blue, the illumination light transmitted through each liquid crystal panel or reflected from each liquid crystal panel can be modulated.

The three primary color lights respectively modulated by the three liquid crystal panels are combined by using an optical element (corresponding to the second optical element) such as a cross dichroic prism or a cross dichroic mirror, and then one projection is performed. Projects on a screen through a lens and reproduces a magnified color image. Since such a liquid crystal projector uses a liquid crystal panel which is smaller and lighter than a cathode ray tube (CRT), it has an advantage that a large screen color image of about 100 type can be reproduced by a small and light device. Development is actively done.

As a conventional example of a liquid crystal projector, Japanese Patent Application Laid-Open No. 62-62-62 has been proposed in which the three primary color lights from three liquid crystal panels are combined using a cross dichroic prism.
The method described in Japanese Patent No. 125791 and a method using a cross dichroic mirror are disclosed in JP-A-63-63.
Each of those described in JP-A-217788 can be mentioned.

FIG. 8 shows a typical configuration example of a liquid crystal projector using a cross dichroic mirror. Figure 8
In FIG. 1, 1 is a lamp, 2 is a reflecting mirror, 3 is a condenser lens (also referred to as a condenser lens), 4, 5 and 6 are dichroic mirrors respectively, and 7 is an optical element (optical that separates the lamp light into three primary color lights and outputs it. Element), 8, 9, 10, 1
Reference numeral 1 is a reflection mirror, 12, 13, 14 is a liquid crystal panel, 15, 16, 17 is a dichroic mirror, 18 is an optical element (an optical element that combines and outputs the three primary color lights from each liquid crystal panel), and 19 is Projection lens,
20 is a screen. Note that FIG. 10 is a characteristic diagram showing an example of the spectral transmittance characteristic of the dichroic mirror, and should be referred to for reference.

Next, the operation will be described with reference to FIG. White light emitted from a lamp (white light source) 1 such as a metal halide lamp is condensed using a reflecting mirror 2 and a condenser lens 3. The condensed white lamp light is separated by the optical element 7 into three primary color lights of red (R), green (G), and blue (B).

That is, the optical element 7 has three dichroic mirrors 4, 5 and 6 arranged in an X shape as shown in the figure. At this time, two short dichroic mirrors 5 and 6 sandwich one long dichroic mirror 4 at the center thereof to form an X-shape.

When one long dichroic mirror 4 receives white light from the lens 3, red light R therein is emitted.
Is used to reflect green light and transmit green light G and blue light B. Further, the two short dichroic mirrors 5 and 6 have characteristics of reflecting the blue light B and transmitting the green light G and the red light R. Therefore, the red light component of the white light from the lens 3 is reflected by the dichroic mirror 4.

The optical path of the red light R is changed by the reflection mirrors 9 and 11, and illuminates the liquid crystal panel 14 displaying a red image. Similarly, the blue component of the white light from the lens 3 is reflected by the dichroic mirrors 5 and 6, and then its optical path is changed by the mirrors 8 and 10 to illuminate the liquid crystal panel 12 displaying a blue image. Then, the green light G is not reflected by the dichroic mirrors 4, 5 and 6 and passes through as it is, and illuminates the liquid crystal panel 13 displaying a green image.

On the other hand, the liquid crystal panels 12, 13 and 14 are driven by the three primary color image signals of B, G and R to be displayed (the means thereof are not shown). The respective lights transmitted through the liquid crystal panels 12, 13 and 14 are incident on the optical elements 18 for combining the three primary color lights from the respective directions, and are combined into one light flux in the optical elements 18. The projection lens 19 projects the combined light combined by the optical element 18 onto the screen 20, and reproduces an enlarged color image on the screen 20.

[0011]

As described above, the conventional liquid crystal projector has the red, green, and
A cross dichroic prism or a cross dichroic mirror is used to combine the blue primary colors.

In the example described with reference to FIG. 8, a cross dichroic mirror is used, but it goes without saying that the cross dichroic prism can be used in place of the cross dichroic mirror. ..

In this case, since the cross dichroic prism is an optical element in which four triangular prisms are bonded together, it is necessary to process and polish the prism glass material, and to form an interference film. It is necessary to precisely bond and assemble the prism. Therefore, the cross dichroic prism becomes very expensive, and as a result, the liquid crystal projector is expensive.

The method using the cross dichroic mirror shown in FIG. 8 is, as described above, a method in which three dichroic mirrors are used to form an X-shape and thereby the incident three primary color lights are combined. Is. FIG. 9 shows an enlarged view of the optical element 18 for combining the three primary color lights in FIG.

In FIG. 9, 12, 13, 14 are liquid crystal panels, 15, 16, 17 are dichroic mirrors, 21 is a transparent substrate, and 22 is a characteristic that reflects blue light and transmits red and green light. The interference film 23 is an interference film having a characteristic of reflecting red light and transmitting other color light.

In FIG. 9, two short dichroic mirrors-16 and 17 are arranged orthogonal to one long dichroic mirror-15. The dichroic mirror 15 has an interference film 22 that reflects blue light and transmits red and green light, and a transparent substrate 21 such as a glass plate.
Then, the film is formed.

On the other hand, dichroic mirrors-16, 17
Is a transparent substrate 21 on which an interference film 23 having a characteristic of reflecting red light and transmitting light of another color is formed. The blue light transmitted through the blue liquid crystal panel 12 is reflected by the dichroic mirror-15, and the red light transmitted through the red liquid crystal panel 14 is reflected by the dichroic mirrors-16, 17. Further, the light transmitted through the green liquid crystal panel 13 is not reflected by the dichroic mirrors 15, 16 and 17 but is transmitted as it is, so that the three primary color lights can be combined into one light flux.

However, looking at the configuration of FIG. 9 in detail, the dichroic mirror-16 and the dichroic mirror-17 are shown.
Are separated by the dichroic mirror 15 in the form of being divided, so that the dichroic mirrors (16, 17) that reflect red light are at the central part when considering 16, 17 as a unit. Dichroic Mira-15
Has penetrated.

Therefore, the interference film 23 of the dichroic mirror (16, 17) is formed by the thickness of the transparent substrate 21 of the dichroic mirror (about 1.1 to 1.3 mm).
Will cause chipping. Therefore, the red light r2 emitted from the central portion of the red liquid crystal panel 14 is not reflected by the interference film 23 due to the lack of the interference film 23, and is reflected inside the transparent substrate 21 of the dichroic mirror 17 to be dichroic. It goes out from the end of the mirror 17.

As described above, the r2 light emitted from the central portion of the red liquid crystal panel 14 should be projected on the screen 20 but should not be projected on the screen 20. As a result, in the center of the screen,
The red color will be insufficient (other green and blue light will not cause such a thing), and in the end, the central part of the screen where the three primary color lights of R, G and B are combined is not white and the color tone is There was a problem that it appeared as different thin lines and the quality of the reproduced image deteriorated.

An object of the present invention is to solve the problems of the prior art and to improve the deterioration of the quality of a reproduced image caused by the above-mentioned circumstances, and a cross dichroic mirror and a projection type liquid crystal using the same. It is to provide a display device.

[0022]

To achieve the above object, in the present invention, a white light source, a condensing optical system for condensing light from the light source, and a light condensed by the condensing optical system are provided. A first optical element that is input and separates into three primary color lights and outputs; and a liquid crystal display panel that corresponds to each of the separated and output three primary color lights and that inputs and modulates and outputs each primary color light A second that combines and outputs the modulated lights from the liquid crystal display panels
In the projection type liquid crystal display device, the second optical element is configured as follows, in which the second optical element and the projection lens for projecting the combined light from the second optical element onto the screen.

A transparent substrate and a thin film formed on the substrate,
A cross dichroic mirror is composed of two dichroic mirrors each of which is made up of two parts, and two oblique sides orthogonal to each other, and an optical component having a thin film on each of the oblique sides. The thin film of the first dichroic mirror in the dichroic mirror and the thin film on the first hypotenuse of the two hypotenuses of the optical component are on the same plane with an interval substantially equal to the thickness of the thin film. The thin film of the second dichroic mirror in the two dichroic mirrors and the thin film on the second hypotenuse of the two hypotenuses of the optical component are arranged at a distance substantially equal to the thickness of the thin film. The cross dichroic mirror is configured so as to be arranged on the same plane with a space therebetween, and is used as the second optical element.

[0024]

In the prior art, the dichroic mirror (16, 17) that reflects red light has the dichroic mirror 15 penetrating in the central portion of the dichroic mirror (16, 17) when considering them as one unit. The interference film 23 of the dichroic mirror (16, 17) corresponds to the thickness of the transparent substrate 21 of -15 (about 1.1 to 1.3 mm).
However, according to the present invention, the thickness of the thin film on the substrate (about the wavelength of light is about 1.1 to 1.3 mm) according to the present invention. The size of the reproduced image is greatly reduced.

[0025]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a conceptual diagram showing the overall configuration of a liquid crystal projector as an embodiment of the present invention. In FIG.
The same parts as those in are given the same reference numerals. Figure 1
The embodiment shown in FIG. 8 differs from the conventional configuration shown in FIG. 8 in the optical element 18 for combining the three primary color lights. In the optical element 18, 30 is a right angle prism,
40 is a transparent medium.

Since the outline of the operation of the liquid crystal projector shown in FIG. 1 is the same as that of the conventional one described with reference to FIG. 8, it is not necessary to repeat the description. The problematic part related to the present invention is the optical element 18 for combining the three primary color lights in FIG. 1, so an enlarged view thereof is shown in FIG.

In FIG. 2, reference numerals 12, 13 and 14 are liquid crystal panels, 15 and 16 are dichroic mirrors, 30 is a right angle prism, 21 is a transparent substrate, and 22 and 2 are respectively.
3, 24 and 25 are interference films, 40 is a transparent medium,
Reference numeral 41 is a housing, and 42 is an O-ring.

Referring to FIG. The optical element 18 is composed of two dichroic mirrors 15, 16 arranged in an L shape at an angle of 90 degrees, and one right-angle prism 30. The dichroic mirror 15 is a dichroic that reflects blue light and transmits red and green light on a transparent substrate 21 (for example, a transparent glass plate having a plate thickness of 1.1 to 1.3 mm). The interference film 22 is formed.

The dichroic mirror 16 is a transparent substrate 2
1, an interference film 23 that reflects red light and transmits blue and green light is formed. Further, interference films 24 and 25 having substantially the same characteristics as the interference films 22 and 23 formed on the dichroic mirrors 15 and 16 are formed on the two sides of the right angle prism 30 that sandwich the right angle.

The interference film is a thin film of a substance having a low refractive index (eg, silicon dioxide, refractive index: n = 1.46) and a substance having a high refractive index (eg, titanium dioxide, n = 2.3). This is an interference film having a multi-layered film structure in which the above thin films are alternately formed by a method such as vapor deposition, and which exhibits a dichroic characteristic of reflecting or transmitting light in a desired wavelength range.

The interference films 24 and 25 on the two sides sandwiching the right angle of the right angle prism 30 are respectively dichroic mirror-1.
The interference films 22 and 23 of 5 and 16 are arranged on substantially the same plane. The interference film 22 of the dichroic mirror 15 and the interference film 24 of the prism 30 are positioned so as to be separated by a very small distance (for example, about 0.1 to 0.3 mm) as compared with the plate thickness of the transparent substrate 21. The dichroic mirror 15 and the prism 30 are relatively positioned.

Similarly, the interference film 23 of the dichroic mirror 16 and the interference film 25 of the prism 30 are formed by the transparent substrate 2
The dichroic mirror 16 and the prism 30 are relatively positioned so as to be positioned with a very small distance (for example, about 0.1 to 0.3 mm) compared to the plate thickness of 1.

As is clear from the above, the tip portions of the two sides of the right-angle prism 30 that sandwich the right angle, and the tip portions of the dichroic mirrors-15 and 16 facing the two sides,
An enlarged view is shown in FIG. In FIG. 3, the interference film 23 and the interference film 25 have a very small interval (for example, about 0.1 to 0.3 mm) as compared with the plate thickness of the transparent substrate 21, that is, about the thickness of the interference film 24. It will be appreciated that there is a small spacing M, as well as between the interference film 22 and the interference film 24.

The interval M is a very small interval,
Since it is less than 1/10 of the thickness of the transparent substrate,
It is an interval that can be regarded as almost zero. Returning to FIG. 2, an optically transparent medium 40 is filled between the liquid crystal panels 12, 13, 14 and the dichroic mirrors 15, 16. The purpose is to reduce unnecessary reflection of light as much as possible. For example, when light is emitted from glass into the air, it is known that about 4% of the reflected light is generated due to the difference in the refractive index between the two. This is to reduce the harmful effect in the invention.

For the above reason, the refractive index of the medium 40 is preferably close to that of the front glass of the liquid crystal panel or the transparent substrate of the dichroic mirror (n≈1.5), for example, 50% by weight or more. Ethylene glycol aqueous solution (n≈
1.45), an aqueous solution mixed with glycerin, ethylene glycol, glycerin, etc. (n≈1.42), an ultraviolet curable resin (n≈1.47), and a silicone gel (n≈1.4).
2; Dow Corning's Sylpot 368, Shin-Etsu Chemical Co., Ltd.'s KE105, etc.) were suitable as the medium 40.

In FIG. 2, the O (o-) ring 4
1, the housing 42 is used for enclosing the medium 40 inside the optical element 18, and the liquid medium 40 may be prevented from leaking to the outside by another method. Optical medium 40
By filling the liquid crystal panel, the difference in optical path length of light emitted from the central portion and the peripheral portion of each liquid crystal panel can be made almost zero, and uniform focus performance can be obtained over the entire surface of the liquid crystal panel. And
Since the back focal length of the projection lens can be shortened equivalently in inverse proportion to the optical refractive index of the medium, there is an advantage that the projection lens can be easily designed and manufactured.

In FIG. 2, the blue lights b1 and b2 at the central portion of the panel, which are controlled by the liquid crystal panel 12 displaying a blue image, are incident on the optical element 18, and the blue lights of the dichroic mirror 15 and the prism 30 are converted. It is reflected by the reflecting interference films 22 and 24.

Similarly, the lights r1 and r2 at the center of the red liquid crystal panel 14 are reflected by the dichroic mirror 16 and the interference films 23 and 25 of the prism 30 which reflect the red light. Then, the lights g1 and g2 of the central part of the liquid crystal panel 13 for green color pass through without being reflected by the dichroic mirrors-15 and 16 and the interference films 24 and 25 of the prism 30.

Therefore, the three liquid crystal panels 12, 1
The lights emitted from the central portions of 3, 14 are combined in the optical element 18, and combined lights (r1 + g1 + b1) and (r2
+ G2 + b2) and enters the projection lens. Similarly, light r3, g3, b3 emitted from the peripheral portion of each liquid crystal panel
Are also combined in the optical element 18 to form a combined light (r3 + g
3 + b3) and enters the projection lens.

The light combined by the optical element 18 is projected on the screen 20 by the projector 19 as shown in FIG. 1, and an enlarged color image can be obtained. In the projection light combined by the optical element 18 of the present invention, the interference films of the dichroic mirrors 15, 16 and the prism 30 are substantially continuous (the distance M therebetween can be regarded as substantially zero) in the central portion of the screen. , Each liquid crystal panel 12, 1
Almost all three primary colors of light from 3, 14 can be combined, and unlike the conventional cross dichroic mirror, there is no generation of thin streaks with a color change at the center of the screen.

Since the medium 40 is enclosed, the reflected light generated at the interface of the liquid crystal panel can be reduced and the contrast ratio of the displayed image can be improved. In FIG. 1, since the optical element 7 used for separating the lamp light (white light) into the three primary color lights is used for the illumination system of the liquid crystal panels 12, 13, 14, the dichroic mirrors 5 and 6 are the dichroic mirrors 4. As a result of the experiment, the adverse effect of forming the X-shape in the form divided by was not found.

FIG. 4 shows an optical element 18 for combining three primary color lights.
It is a block diagram which shows the 2nd Example of this. The embodiment shown in the figure is the same as that shown in FIGS. 2 and 3 in that two dichroic mirrors 15, 16 are arranged in an L shape, but two right-angle prisms are provided at the contact points. The configuration is different from that shown in FIGS. 2 and 3 in that a configuration in which 31 and 32 are arranged (instead of one right-angle prism) is adopted.

In FIG. 4, on the slope of the prism 31,
An interference film 24 having substantially the same characteristics as the interference film 22 of the dichroic mirror-15 is formed. An interference film 25 having substantially the same characteristics as the interference film 23 of the dichroic mirror-16 is formed on the slope of the prism 32.

Two such rectangular prisms 31, 32
When using, each of the right angle prisms 31 and 32 is
Since only one kind of interference film is formed, compared with the first embodiment shown in FIG. 2 and FIG. 3 in which two kinds of interference films are formed on one prism, the yield in prism manufacturing Can be improved.

FIG. 5 shows an optical element 18 for combining light of the three primary colors.
It is a block diagram which shows the 3rd Example of this. The embodiment shown in FIG. 5 is the same as that shown in FIGS. 2 and 3 in that the two dichroic mirrors 15, 16 are arranged in an L shape, but the contact point is an L-shaped transparent portion. This is different from that shown in FIGS. 2 and 3 in that the substrate 33 has a structure in which the interference films 24 and 25 are formed on both hypotenuses (instead of one right-angle prism).

The glass 43 is made of the L-shaped transparent substrate 33.
This is used to fill the L-shaped space with the optical medium 40. Compared with the case where one right-angle prism is used, this embodiment does not require a prism material for the space forming the L shape, and has an advantage that the cost can be reduced accordingly.

FIG. 6 shows an optical element 18 for combining light of the three primary colors.
It is a block diagram which shows the 4th Example of. In the embodiment shown in the figure, four dichroic mirrors-15, 16, 15 ',
16 'is arranged as shown, and the dichroic mirror 15
And 15 'of the interference films are arranged on substantially the same plane with a spacing sufficiently smaller than the thickness of the transparent substrate 21, and the interference films of the dichroic mirrors 16 and 16' are arranged on the substantially same plane of the transparent substrate. 21 are arranged at intervals sufficiently smaller than the plate thickness of 21.

FIG. 7 shows an optical element 18 for combining light of the three primary colors.
It is a block diagram which shows the 5th Example of this. In the embodiment shown in the figure, four dichroic mirrors-15, 16, 15 ', 16' are used as in the fourth embodiment (FIG. 6). In this embodiment, by filling the optical transparent medium 40 between the projection lens 19 and the optical element 18, the reflected light generated at the interface between the optical element 18 and the projection lens 19 can be reduced, and The contrast ratio can be improved as compared with the fourth embodiment.

Although the above-mentioned embodiments have explained the liquid crystal projector using the liquid crystal panel, the optical element of the present invention synthesizes images of at least two or more projection type cathode ray tubes and uses a projection lens to screen. Obviously, it can also be used in a projection type cathode ray display device for reproducing a color image on the display.

[0050]

According to the projection type liquid crystal display device using the optical element for synthesizing light of the three primary colors according to the present invention, conventionally, a streak having a color change is generated in the central portion of the image projected on the screen, and the image quality is improved. However, there is an advantage that a high-quality image can be reproduced (without using an expensive optical element such as a cross dichroic prism) without generating such a streak.

Since the optical element used in the present invention is less expensive than the expensive cross dichroic prism because the dichroic mirror is used, the projection type liquid crystal display device itself can be manufactured at low cost. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a liquid crystal projector as one embodiment of the present invention.

FIG. 2 is an enlarged view showing a configuration of an optical element as a main part of FIG.

FIG. 3 is an enlarged view of a central portion of FIG.

FIG. 4 is a configuration diagram showing another embodiment of the optical element of the present invention.

FIG. 5 is a configuration diagram showing another embodiment of the optical element of the present invention.

FIG. 6 is a constitutional view showing still another embodiment of the optical element of the present invention.

FIG. 7 is a constitutional view showing still another embodiment of the optical element of the present invention.

FIG. 8 is a configuration diagram showing a conventional example of a liquid crystal projector.

FIG. 9 is a configuration diagram showing a conventional optical element.

FIG. 10 is a characteristic diagram showing an example of a spectral transmittance characteristic of a dichroic mirror.

[Explanation of symbols]

1 ... Lamp, 2 ... Reflecting mirror, 3 ... Condensing lens (condenser lens), 4, 5, 6 ... Dichroic mirror, 7 ... Optical element, 8, 9, 10, 11 ... Reflecting mirror, 12, 1
3, 14 ... Liquid crystal panel, 15, 16, 17 ... Dichroic mirror, 18 ... Optical element, 19 ... Projection lens, 20
... screen, 22, 23, 24, 25 ... interference film, 30
... right angle prism, 40 ... transparent medium, 41 ... O-ring, 4
2 ... Housing, 43 ... Glass

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Oishi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture

Claims (12)

[Claims] 1. A white light source, a condensing optical system for condensing light from the light source, and light for converging light condensed by the condensing optical system, which is separated into three primary color lights and is output. Optical elements of
Corresponding to each of the separated and output three primary color lights, each liquid crystal display panel that inputs each primary color light and modulates and outputs it, and second liquid crystal display panel that combines and outputs the modulated light from each liquid crystal display panel In a projection type liquid crystal display device comprising an optical element and a projection lens for projecting the combined light from the second optical element onto a screen, the second optical element comprises a transparent substrate and a transparent substrate on the substrate. , A dichroic mirror consisting of a thin film having a multi-layered structure formed by alternately stacking a substance having a high refractive index and a substance having a low refractive index, and two oblique sides that are orthogonal to each other, and on each oblique side, A third optical element having a multi-layered thin film formed by alternately stacking a substance having a high refractive index and a substance having a low refractive index, and the modulated light from each of the liquid crystal display panels. Cross to synthesize A dichroic mirror, in which case a thin film constituting the first dichroic mirror of the two dichroic mirrors and a thin film on the first hypotenuse of the two hypotenuses of the third optical element Are arranged on the same plane at an interval substantially equal to the thickness of the thin film, and a thin film that constitutes the second dichroic mirror of the two dichroic mirrors, and two of the third optical element. A projection type liquid crystal display device, characterized in that the thin film on the second oblique side of the oblique side is arranged on the same plane at an interval substantially equal to the thickness of the thin film. 2. The projection type liquid crystal display device according to claim 1, wherein the third optical element has two oblique sides orthogonal to each other, and a substance having a high refractive index and a low refractive index are provided on each oblique side. A projection type liquid crystal display device, comprising a single prism in which a thin film as an interference film having different optical characteristics and having a multilayer structure constituted by alternately stacking substances is formed. 3. The projection type liquid crystal display device according to claim 1, wherein the third optical element has a multi-layered interference structure in which a substance having a high refractive index and a substance having a low refractive index are alternately laminated. A projection type liquid crystal display device comprising a thin film as a film and two prisms formed on the hypotenuse thereof. 4. The projection type liquid crystal display device according to claim 1, wherein the third optical element is an L-shaped transparent substrate.
An interference film having a multilayer structure formed by alternately laminating a substance having a high refractive index and a substance having a low refractive index on the two oblique sides of the L shape of the substrate, as an interference film having different optical characteristics from each other. A projection type liquid crystal display device comprising two thin films. 5. A white light source, a condensing optical system for condensing light from the light source, and light for converging light condensed by the condensing optical system, which is separated into three primary color lights and is output. Optical elements of
Corresponding to each of the separated and output three primary color lights, each liquid crystal display panel that inputs each primary color light and modulates and outputs it, and second liquid crystal display panel that combines and outputs the modulated light from each liquid crystal display panel In a projection type liquid crystal display device comprising an optical element and a projection lens for projecting the combined light from the second optical element onto a screen, the second optical element comprises a transparent substrate and a transparent substrate on the substrate. A cross dichroic mirror composed of four dichroic mirrors comprising a thin film having a multi-layer structure formed by alternately stacking a substance having a high refractive index and a substance having a low refractive index, wherein: Among the four dichroic mirrors, the thin film that constitutes the first dichroic mirror and the thin film that constitutes the second dichroic mirror are spaced apart by a distance approximately equal to the thickness of the thin film, and have the same thickness. The first combination arranged above, the thin film forming the third dichroic mirror among the four dichroic mirrors, and the thin film forming the fourth dichroic mirror are approximately equal to the thickness of the thin films. A projection type liquid crystal display device, characterized in that a second combination arranged on the same plane with a space therebetween is crossed. 6. The projection type liquid crystal display device according to claim 1, 2, 3, 4 or 5, wherein an optical refractive index is provided in an optical path from the liquid crystal panel to the lens via the second optical element. Is 1.3 or more and 2.0 or less, preferably 1.4 or more and 1.6 or less, by filling the transparent optical medium,
A projection type liquid crystal display device characterized by reducing generation of unnecessary reflected light. 7. Two dichroic mirrors each comprising: a transparent substrate; and a thin film having a multilayer structure formed by alternately stacking a substance having a high refractive index and a substance having a low refractive index on the substrate, An optical component having a thin film having a multilayer structure constituted by alternately laminating a substance having a high refractive index and a substance having a low refractive index on each of the oblique sides having two oblique sides,
And a thin film forming a first dichroic mirror of the two dichroic mirrors, and a thin film on a first hypotenuse of the two hypotenuses of the optical component. A first combination constituted by arranging them on the same plane at an interval substantially equal to the thickness of the optical disc, a thin film constituting the second dichroic mirror of the two dichroic mirrors, and the optical component. A second combination formed by arranging the thin film on the second oblique side of the two oblique sides on the same plane at an interval substantially equal to the thickness of the thin film, and a cross formed by crossing An optical element characterized by being a dichroic mirror. 8. The optical element according to claim 7, wherein the optical component has two oblique sides orthogonal to each other, and a material having a high refractive index and a material having a low refractive index are alternately laminated on each oblique side. An optical element characterized by comprising a single prism in which a thin film as an interference film having a different optical characteristic of the multilayer structure constituted by the above is formed. 9. The optical element according to claim 7, wherein the optical component is a thin film as an interference film having a multi-layer structure, which is formed by alternately stacking a substance having a high refractive index and a substance having a low refractive index, An optical element comprising two prisms formed on the hypotenuse. 10. The optical element according to claim 7, wherein
The optical component has a multi-layered structure in which a transparent substrate having an L-shape and two oblique sides forming the L-shape of the substrate are alternately laminated with a substance having a high refractive index and a substance having a low refractive index. , And two thin films as interference films having different optical characteristics from each other. 11. A dichroic mirror comprising four substrates: a transparent substrate; and a thin film having a multi-layer structure formed by alternately stacking a substance having a high refractive index and a substance having a low refractive index on the substrate. In the cross dichroic mirror, the thin film forming the first dichroic mirror among the four dichroic mirrors and the thin film forming the second dichroic mirror have a thickness substantially equal to that of the thin film. A first combination arranged on the same plane at equal intervals, a thin film forming a third dichroic mirror among the four dichroic mirrors, and a thin film forming a fourth dichroic mirror, A cross dichroic formed by crossing a second combination arranged on the same plane at an interval substantially equal to the thickness of the thin film. Optical element which is a color. 12. The optical element according to claim 7, 8, 9, 10 or 11, wherein light input from a liquid crystal panel located outside reaches the external projection lens through the optical element. , An optical refractive index of 1.3 to 2.0, preferably 1.4 to 1.
An optical element characterized by reducing generation of unnecessary reflected light by filling a transparent optical medium of 6 or less.