JP3490886B2 - Projection type image 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 projection type image display device for enlarging and projecting light passing through an image display element from a light source such as a liquid crystal projection onto a screen by a projection lens.

[0002]

2. Description of the Related Art In recent years, a three-plate type liquid crystal projection using liquid crystal display elements corresponding to red, green and blue is called a method of performing color separation / combination with a dichroic mirror (hereinafter referred to as a mirror sequential method). , A method in which color separation is performed by a dichroic mirror and color combination is performed by a cross dichroic prism (hereinafter referred to as a cross dichroic prism method) has been put into practical use.

In the former mirror sequential system, as shown in FIG. 27, white light from a light source 101 having a parabolic mirror 102 is converted into red light by two dichroic mirrors 701 and 702.
After being separated into green and blue, they are made incident on the corresponding liquid crystal display elements 105R, 105G and 105B. And
Then, the light modulated by the liquid crystal display elements 105R, 105G, and 105B is converted into dichroic mirrors 703 and 7B.
The method is such that the light is emitted from the light source 101 to the liquid crystal display elements 105R and 1R.
Since the distances to 05G and 105B are the same, the white balance is not shifted, but at least a dichroic mirror is provided on the optical path from the liquid crystal display elements 105R, 105G, and 105B to the projection lens 112. Since a space for arranging the two lenses is required, the back focus of the projection lens 112 (distance from the projection lens to the liquid crystal display element) becomes long, and the projection lens 112 becomes large. .

Therefore, in the mirror sequential system, a lens is usually arranged on the light emitting side or the light incident side of the liquid crystal display element, and the light passing through the liquid crystal display element is condensed near the pupil position of the projection lens. The scheme is taken.

In this case, a dichroic mirror 703 inserted between the projection lens and the liquid crystal display element,
The condensed light is incident on 704. The dichroic mirrors 703 and 704 change the spectral characteristics of light transmitted and reflected by the dichroic mirror when the incident angle of light changes, and when the condensed light enters, red, green, and
When the convergent light is made incident, it is possible to make the film thickness so that the spectral characteristics with respect to the lights incident at different angles are substantially the same because the color purity of blue decreases and the color unevenness occurs. .

Further, in this mirror sequential system, dichroic mirrors 703 and 704 formed by forming a dielectric multilayer film on a parallel plate glass are obliquely inserted between the projection lens and the liquid crystal display element. Therefore, there is a problem that astigmatism occurs. This astigmatism occurs when light passes through the dichroic mirror.Therefore, in this method in which the number of times the light passes through the dichroic mirror differs depending on the red, green, and blue optical paths, the astigmatism depends on the red, green, and blue optical paths. The amount of aberration generated is different, and it is difficult to correct all of these aberrations with the projection lens.

In order to solve such a problem as described above, in JP-A-5-61129 and JP-A-7-325283, as shown in FIG. 28, a projection lens 112 and liquid crystal display elements 105R, 105G and 105B are used. There is also disclosed a method in which a glass prism 711 formed by bonding a plurality of glasses is inserted between and.

In such a system, the glass prism 71
By inserting 1, the back focus of the projection lens 112 can be shortened, and color combination is performed by the dielectric films formed on the bonding surfaces a and b of the glass prism 711, so that astigmatism is reduced. It prevents the occurrence.

In the latter cross dichroic prism system, for example, as disclosed in Japanese Patent Application Laid-Open No. 1-293385, color separation is performed by dichroic mirrors 721 and 722, and the respective lights are directed to the corresponding liquid crystal display element 1.
This is a method in which the color combination is performed by one cross dichroic prism 111 after the light is made incident on 05R, 105G, and 105B. For example, it is put into practical use by the configuration shown in FIG.

In such a cross dichroic prism system, the back focus of the projection lens 112 can be shortened and the projection lens 112 and the liquid crystal display elements 105R and 105R can be compared with the above-mentioned mirror sequential system.
Since it is not necessary to obliquely insert the dichroic mirror between the G and 105B, it is possible to prevent the generation of astigmatism.

Further, in the mirror sequential system, there is a problem that when the liquid crystal display elements have a fine pitch due to the deflection of the dichroic mirror or the like, the convergence of the three liquid crystal display elements is deviated. In the cross dichroic prism method, since the dielectric multilayer film is formed on the side surfaces of the four triangular prisms that form the cross dichroic prism 111, there is an advantage that deflection does not occur and the convergence adjustment can be performed accurately. ing.

At present, this method is used in most projections using a high temperature p-Si liquid crystal display panel having a small liquid crystal display element and a small pixel pitch.

The above-mentioned method is adopted in a projection using a transmissive liquid crystal display element, but in recent years, a projection using a reflective liquid crystal display element has been announced and put into practical use. There is. An example of the optical system is shown in FIG.

In this system, the dichroic mirror 73
1, 732 sequentially performs color separation, and each light is polarized beam splitter (hereinafter referred to as PBS) 303.
It is made incident on R, 303G, and 303B. PBS303
In R, 303G, and 303B, incident light is separated into P-polarized light and S-polarized light, and one light is reflected to the reflective liquid crystal display element 304R,
It is made incident on 304G and 304B. The light reflected by the reflective liquid crystal display elements 304R, 304G, 304B is incident on the PBSs 303R, 303G, 303B again, and the reflective liquid crystal display elements 304R, 304G, 304B.
Only the light whose polarization direction is modulated by is combined by the cross dichroic prism 111 and projected on the screen by the projection lens 112.

In a projection using a transmissive / reflective liquid crystal display element for performing color combination with these cross dichroic prisms, an arrangement as shown in FIGS. 4 and 14 described later (in the height direction of the triangular prisms forming the cross dichroic prism) is used. And the arrangement in which the short side direction of the display area of the liquid crystal display element is aligned) has been put to practical use.

[0016]

However, the above-mentioned projection type image display device has the following problems.

First, in the projection type image display device disclosed in Japanese Patent Laid-Open Nos. 5-611129 and 7-325283, a glass block is inserted in the optical path between the projection lens and the liquid crystal display element. Therefore, not only the weight of the system itself becomes very heavy, but also it becomes very expensive as compared with the dichroic mirror.

Further, even if the back focus is shortened by the glass block, compared with the method of performing color combination at once with the cross dichroic prism, when the liquid crystal display element of the same size is used, the optical path length of about twice is required. , Its effect will be small.

Further, Japanese Patent Laid-Open No. 7-325283 also discloses a projection type image display device in which a reflection type liquid crystal display element is applied to a mirror sequential system.
In this case, a PBS that separates natural light from the light source into linearly polarized light whose vibration directions are orthogonal is required between each liquid crystal display element and the projection lens, which not only makes the system heavier but also backs up the projection lens. The focus becomes even longer.

On the other hand, in the cross dichroic prism system, since the color composition is performed at once by the cross dichroic prism, the back focus can be made extremely short and astigmatism does not occur. However, in this method, the price of the cross dichroic prism increases in proportion to the prism volume,
If the size of the liquid crystal display device becomes large for the following reason, there is a problem in that it is disadvantageous in terms of price. In particular, in a projection using a reflection type liquid crystal display element that requires both a PBS and a cross dichroic prism, the price of the PBS also increases in proportion to the volume, similar to the cross dichroic prism. It is more disadvantageous in terms of price than the projection using a display element.

In general, in a liquid crystal display device, pixel electrodes arranged regularly in a matrix form a three-terminal device or a non-linear device.
An active matrix type in which a terminal element is provided and an optical characteristic of liquid crystal is changed by applying a drive voltage corresponding to an image signal to display an image or a character is used.

In the case of this active matrix type liquid crystal display device, switching elements such as MIM (metal-insulator-metal) elements and TFT (thin film transistor) elements and wiring electrodes for supplying a driving voltage to the pixel electrodes. And must be provided.

When strong light enters this switching element, the element resistance in the OFF state is lowered, and not only the electric charge charged when a voltage is applied is discharged, but also the area where the switching element and the wiring electrode are formed is discharged. The existing drive voltage is not applied to the existing liquid crystal portion, the original display operation is not performed, and light leaks even in the black state, and the contrast ratio is lowered.

Therefore, as shown in FIG.
A light shielding unit called a black matrix 802 is provided on the counter substrate that faces the TFT substrate provided with the switching element such as 801 and the pixel electrode with the liquid crystal layer interposed therebetween, and the light incident on the light incident region described above is provided. Need to shut off. Therefore, in the case of such a liquid crystal display element,
TFT 801 and gate bus line 80, each of which has a light shielding property
In addition to 3 and the source bus line 804, light is shielded by the black matrix 802, so that the area of the effective pixel opening in the pixel region, that is, the aperture ratio becomes small.

Furthermore, it is very difficult to form these switching elements and wiring electrodes in a size below a certain level due to restrictions on their electrical performance and manufacturing technology. Therefore, as the pitch of the pixel electrodes becomes smaller, the aperture ratio further decreases as the resolution and size of the liquid crystal display element become smaller.

Therefore, as the liquid crystal display device becomes finer, it is necessary to increase the panel size in order to secure the aperture ratio. The increase in the size of the liquid crystal display panel described above also applies to the reflective liquid crystal display element.

Further, in this method, when light is condensed and made incident on a projection lens as in the mirror sequential method, color unevenness, color purity, brightness deterioration, etc. within the screen may occur. Since the display characteristics are greatly deteriorated, the light passing through the liquid crystal display element is not blocked and is allowed to enter the projection lens. In order to make the diameter of the projection lens, the cross dichroic prism, and the PBS shown in FIG. (B)
As shown in (only the green optical path is shown in the figure), the size must be increased so that all the light having the divergence angle θ emitted from the end of the liquid crystal display element 105G can be taken in, resulting in a significant cost increase. I will end up.

At this time, the reason why the light cannot be condensed and made incident on the projection lens is that it is very difficult to make a gradient in the dielectric film of the cross dichroic prism. As shown in FIG. 33, this cross dichroic prism is formed by forming a dielectric multilayer film on one of the opposite side surfaces of four triangular prisms and accurately bonding the vertices of the four triangular prisms. Therefore, the film a, the film a ′, and the film b
And the film b'become films that are formed in different triangular prisms and reflect the same color. It is practically difficult to form a dielectric multilayer film by continuously grading the surfaces of these different triangular prisms, and it is discontinuous at the boundary between the film a and the film a ′ (or the film b and the film b ′). Therefore, there is a problem in that this boundary line is displayed on the screen and the display quality is impaired.

The present invention has been made to solve the above-described problems, and an object thereof is to realize a small size, light weight, low cost, good display quality, and bright projection type image display device. Especially.

[0030]

A projection type image display apparatus according to claim 1 of the present invention comprises a light source, color separation means for separating light from the light source into red, green and blue light fluxes, and Image display means corresponding to each of the red, green, and blue light beams separated by the color separation means, a cross dichroic prism for synthesizing light modulated according to the image signal by the image display means, and the cross dichroic prism In a projection type image display device provided with a projection means for projecting the light combined in step 3, the direction of the long side of the area where the image is displayed by the image display means, and the height of the triangular prism forming the cross dichroic prism. It is characterized in that it is configured so that the direction of the vertical direction is substantially the same, and by that,
To achieve the above objectives.

Further, the above-mentioned object is achieved by further comprising a polarization selective reflection means for reflecting or transmitting the light from the light source according to the polarization direction, and the image display means being a reflection type image display element.

Further, it is desirable that the signal input terminal to the image display means is formed in the short side direction of the display area of the image display means.

Further, the light incident on the cross dichroic prism is a convergent light having a condensing point on the projection lens side with respect to the light emitting surface of the cross dichroic prism, thereby achieving the above object.

The operation of the present invention will be described below.

According to the configuration of claim 1 of the present invention,
By making the direction of the long side of the effective area for image display of the image display means substantially coincide with the direction of the height of the triangular prism forming the cross dichroic prism, the back focus of the projection lens is shortened. Therefore, it is possible to reduce the size and cost.

Here, as shown in FIG. 20A, the distance b between the image display means 105 and the projection lens 112 (back focus of the projection lens) b is greatly influenced by the distance L of the cross dichroic prism 111. This distance L is determined by the size of the display area in the direction parallel to the L direction of the image display means 105.

Therefore, as shown in FIG. 20B, if the direction of the short side of the display area of the image display means 105 is made to coincide with the direction of L, L '<L, and the image display means 10
5 and the projection lens 112 can be shortened.

The cross dichroic prism 1 is made to match the short side direction of the image display means 105 and the L'direction of the cross dichroic prism 111.
The size in the height direction of the triangular prism constituting 11 is increased on the contrary. For example, when an image display element having an aspect ratio of 3: 4 is used, the cross dichroic prism 111 is used.
The ratio between the height of the triangular prism and L'is approximately 4:
3, the volume is about 25% smaller when the configuration of the present invention is applied.

Further, the cross dichroic prism 11
As described above, 1 increases the cost almost in proportion to the volume. Therefore, the cost of the cross dichroic prism 111 itself can be reduced by applying the configuration of the present invention. The cost reduction effect of the cross dichroic prism 111 has been described by using an image display element having an aspect ratio of 3: 4 as an example, but the same effect can be obtained when an image display element having an aspect ratio of 16: 9 is used. Considering this, the volume of the cross dichroic prism 111 can be reduced by about 44%, and the cost can be reduced accordingly. Therefore, it is more effective than the case where the image display device having the aspect ratio of 3: 4 is used. is there.

According to the configuration of claim 2 of the present invention,
Up to now, as shown in FIG. 21A, in the projection using the reflective image display element 304, the PBS 30 for separating and synthesizing the light from the light source according to the polarization direction thereof.
Since 3 is required, the back focus b of the projection lens 112 becomes longer as much as the PBS 303 than in the projection using the transmissive image display element. The length of the back focus b is determined by the lengths of L and N in the PBS 303 and the cross dichroic prism 111 shown in the figure.

When the present invention is applied to a projection using such a reflective image display device 304, L'and N'shown in FIG. 21 (b) are replaced by L '<L, N'<.
Since the size of the PBS 303 and the cross dichroic prism 111 in the direction influencing the back focus of the projection lens 112 can be reduced, the back focus of the projection lens 112 can be further shortened. The size and cost of the device can be reduced.

Further, in the projection using the reflection type image display element 304, the cost is increased due to the addition of the PBS 303, but the PBS 303, like the cross dichroic prism 111, has a cost almost proportional to its volume. Therefore, by applying the configuration of the present invention, it is possible to reduce the cost of both the PBS 303 and the cross dichroic prism 111 in the same manner as the cost reduction of the cross dichroic prism 111 described in claim 1 above. It is possible.

In the present invention, the three PBSs 303 are used.
The case where R, 303G, 303B and one cross dichroic prism 111 are combined has been described, but as shown in FIGS. 22 (a) (b) (c), for example, P
BS303 and dichroic mirror, PBS303 and Philips type prism 901, and one PB
S303 and one cross dichroic prism 111
Is also effective when using.

According to the configuration of claim 3 of the present invention,
When the signal input terminal to the image display element is formed in the long side direction of the display area of the image display element, generally, FIG.
As shown in the conceptual diagram of the image display element shown in FIG. 3, a cable for driving the image display element is installed in the long side direction.

This cable is a Flexible Pr
integrated Circuit cable (hereinafter, FPC
Call. ), It is a foldable printed circuit board, but if it is bent at an extreme angle, wire breakage etc. will occur, so
When the image display device is applied to the optical system according to claims 1 and 2, as shown in FIGS. 24 (a) and 24 (b), if the space necessary for bending the FPC is not secured, the light passing through the light is transmitted. The FPC on the road (inside the dotted line along the optical axis in the figure) falls on the optical path and blocks light.

However, in order to secure a space for this purpose, in the projection using the reflection type image display device, not only the back focus of the projection lens becomes long, but also the entire system becomes large, resulting in a large cost. I will upload it. Further, even in the projection using the transmissive image display element, the cost similarly increases as the system becomes larger.

Since the light incident on the image display element has a divergence angle with respect to the principal ray to some extent, PB
If the S303 and the cross dichroic prism 111 are designed so that all the light incident on the periphery of the image display element can pass therethrough as shown in FIG. 32 (b), the size must be increased as the distance from the image display element increases. I won't. Therefore, when the distance between these components becomes large, the PBS 303 and the cross dichroic prism 11
The number 1 itself will also become larger.

On the other hand, in the present invention, since the signal input terminal to the image display means is formed in the short side direction of the image display means, the FPC of the projection type image display apparatus shown in FIGS. 1 and 9 is used. Since it can be taken out in the direction perpendicular to the paper surface, there is no need to make a region for bending. Therefore, the optical components can be arranged without creating a useless space, and the optical system can be made compact. Further, in the projection using the reflection type image display element, the back focus of the projection lens can be shortened to the limit depending on the size of the optical component, so that the cost can be further reduced. Further, since the PBS 303 and the cross dichroic prism 111 themselves can be downsized, the cost can be further reduced.

According to the configuration of claim 4 of the present invention,
Usually, a cross dichroic prism 111 for color combination
Since the reflective surface has an incident angle dependency, when the convergent light is incident, the spectral characteristic on the reflective surface changes, and color unevenness and a decrease in color purity occur in the screen. The reason for this is
The film thickness of the dielectric film is designed so that only a specific wavelength band is reflected or transmitted when light is incident from a specific angle on the reflective surface coated with a multilayered dielectric film such as TiO ₂ or SiO _2. However, this is because the film thickness through which light passes substantially changes when the incident angle of light changes.

For example, as shown in FIG. 25, when light is incident from the direction A'to a dielectric multilayer film having spectral characteristics optimized for light incident from the direction A, the dielectric The light passing through the dielectric film in the directions A and A'has different distances (in the case of FIG. 25, A ').
The light incident from the direction A has a shorter distance to pass through the film than the light incident from the direction A), and the spectral characteristics also change. Although only one dielectric film is shown in FIG. 25 for the sake of explanation, in practice, a layer such as TiO ₂ or SiO ₂ is multilayer-coated.

In this way, the light emitted from the image display element 105 is condensed and the cross dichroic prism 111 is used.
When the light is incident on the image display element 105, the light collecting angle becomes larger in the light from the long side direction of the image display element 105 than in the light from the short side direction.

Here, the cross dichroic prism 1
11, for example, when the image display element 105 is arranged as shown in FIG. 4, the light emitted from the center of the image display element 105 is incident on the cross dichroic prism 111 at a designed angle. The spectral characteristic of the dichroic prism 111 does not change. However, the incident angle changes toward the end of the image display element 105 in the long side direction, and the spectral characteristic changes as described above.

On the other hand, as shown in FIG.
When converging light is made incident on the projection in which the image display element 105 is arranged in the direction as described in (1), the incident angle of light changes toward the end in the short side direction, but as shown in FIG. Since the side length is shorter than the arrangement of 105, the change in the incident angle of light with respect to the light reflecting surface of the cross dichroic prism 111 is small and the shift amount of the spectral characteristic is small.

On the other hand, in the case of arranging as shown in FIG. 2 described above, the length of the side becomes longer in the long side direction,
Although the incident angle of light on the light reflecting surface of the cross dichroic prism 111 is largely changed, light incident from this direction changes its incident direction on the light reflecting surface, but the incident angle hardly changes, and the spectral characteristic shifts. There is almost no.

Therefore, by disposing the image display element 105 in the structure as in the present invention, even if the convergent light is incident on the cross dichroic prism 111, the color purity of red, green, and blue is reduced and the color unevenness is caused. Occurrence of is minimized. In addition, by inputting convergent light, FIG.
As shown in FIG. 3, in order to make the light having a divergence angle with respect to the principal ray incident on the projection lens 112 without hitting, the size of the cross dichroic prism 111 or the size of the projection lens 112 must be increased. However, by applying the configuration of the present invention, the converged light can be incident on the cross dichroic prism 111 as shown in FIG. 26, so that the cross dichroic prism 111 and the projection lens 112 can be downsized. Not only is it possible to reduce the size of the cross dichroic prism 111, but
The back focus can be further shortened, which is extremely effective in reducing the size, weight and cost of the system.

As described above, the operation of the present invention has been described focusing on the projection using the transmissive image display element. For example, as shown in FIG. 17, the projection using the reflective image display element 304 is used. Even when the present invention is applied to, there is an effect that the cross dichroic prism 111 and the projection lens 112 described above can be downsized, and the back focus of the projection lens 112 can be shortened.

Also, with respect to the polarization separation characteristic of the PBS 303, by adopting the configuration according to the present invention, as with the cross dichroic prism 111, the incident angle of light on the PBS 303 changes toward the end in the short side direction, Does not change as much as the long side direction. In the case of the cross dichroic prism 111, the change of the incident angle mainly affected the color purity and the color unevenness, but in the case of the PBS 303,
It mainly affects the polarization separation characteristics and causes a decrease in the light utilization rate. Therefore, by applying the present invention, it is possible to reduce the decrease in the light utilization rate. Note that although the converging angle becomes large in the long side direction of the reflective image display element 304,
Similarly to the cross dichroic prism 111, the incident direction of the PBS 303 with respect to the light reflecting surface changes greatly, but the incident angle itself hardly changes, and the influence on the polarization separation characteristic is small. Further, the PBS 303 itself can be downsized, which leads to a large cost reduction.

[0058]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic view showing a projection type color image display device of the present invention. In the first embodiment, the light source 101 is 150 W and the arc length is 2 mm.
The metal halide lamp of was used. As the light source 101, a halogen lamp, a xenon lamp, or the like can be used instead. And on the back of the light source 101,
A parabolic mirror 102 for emitting the light from the light source 101 as substantially parallel light is arranged.

In front of such a light source 101, the light source 1
Of the white light from 01, the light in the red wavelength band is transmitted,
A dichroic mirror 103 that reflects light in the green and blue wavelength bands is arranged. This dichroic mirror 1
The red light that has passed through 03 is reflected by the reflection mirror 104, and the field lens 106R and the polarizing plate (not shown).
And then enters the liquid crystal display panel 105R.

On the other hand, the light in the green and blue wavelength bands reflected by the dichroic mirror 103 is incident on the dichroic mirror 107 which transmits light in the blue wavelength band and reflects light in the green wavelength band, and Light is field lens 106G
And the liquid crystal display panel 1 after passing through a polarizing plate (not shown).
It is incident on 05G. In addition, the dichroic mirror 107
The blue light that has passed through passes through a polarizing plate (not shown) via the relay lens 108 and the reflection mirrors 109 and 110, and then enters the liquid crystal display panel 105B.

As shown in FIG. 2, the liquid crystal display panel 105 includes a color combining cross dichroic prism 111.
The height direction of the triangular prisms forming the and the long side direction of the display area of the panel are aligned with each other.

Then, the liquid crystal display panels 105R, 105
The light, which has passed through G and 105B and has its polarization direction modulated, passes through the polarizing plates arranged on the exit side of the liquid crystal display panels 105R, 105G, and 105B, and then enters the cross dichroic prism 111.

In the first embodiment, as shown in FIG. 3, the cross dichroic prism 111 is made incident with light whose principal ray is substantially parallel to the optical axis. And
After that, this light is transmitted to the cross dichroic prism 111.
Are combined with each other and enter the projection lens 112.

In the first embodiment, the liquid crystal display panel 10 is used.
As No. 5, a 1.3-inch XGA panel (1024 × 768 dots) was used. The panel was designed so that the FPC 113 was attached in the short side direction of the liquid crystal display panel. Therefore, the FPC 113 can be taken out in the direction perpendicular to the paper surface in FIG.

In the vicinity of the light source 101, a fly-eye lens 114 in which lenses are two-dimensionally arranged is used for the purpose of making the illuminance distribution on the panel surface uniform.

When the optical system is constructed under the above conditions, a bright image with good contrast can be obtained.
In addition, the cross dichroic prism 111 is made smaller by about 25% as compared with the case where the short side direction of the liquid crystal display panel is arranged so as to coincide with the height direction of the triangular prism forming the cross dichroic prism 111 as shown in FIG. And the mounting direction of the FPC 113 can be
Since it is arranged in the short side direction of the liquid crystal display panel, it is possible to arrange the optical components without creating a wasteful space, and it is possible to shorten the back focus of the projection lens 112, thereby significantly reducing the system size. It has become possible to reduce costs and reduce costs.

In the first embodiment, the dichroic mirror 103 transmits red light and reflects green and blue light. However, any combination such as blue transmission and green and red reflection may be used. However, the configuration shown in FIG. 5 may be adopted. In such a case, in the configuration as shown in FIG. 1, the optical path length from the light source of one panel among the three panels becomes long, and light loss occurs between them, so that the light is not changed as it is. Since white balance shifts when combined, the method of transmitting light to the panel surface by the relay lens 108 is used, but it is not possible to completely eliminate light loss due to lens aberration and surface reflection. Further, the use of the relay lens 108 increases the cost accordingly.

On the other hand, in the structure shown in FIG. 5, as a method of separating the light from the light source into the three primary colors, the cross dichroic mirror or the cross dichroic prism 2 is used.
At 01, two colors of light with the same traveling direction (green, red or blue)
And light of one color (blue or red) that travels in substantially the opposite direction. And further dichroic mirror 20
2 reflects green.

By adopting the configuration as described above,
From the light source 1 to the liquid crystal display panels 105R, 105G, 105
It is possible to make the respective optical path lengths (converted values in air) up to B almost equal distances. By this,
In addition to eliminating the light loss that has occurred in the past and achieving an image with good white balance, it is also possible to reduce the cost because no relay lens is required.

As described above, the illumination system shown in FIG. 5 has its own effect independently of the installation direction of the liquid crystal display panel.

(Second Embodiment) FIG. 6 is a schematic diagram of a projection type color image display device according to a second embodiment of the present invention. In the second embodiment, the above-described first embodiment is used.
The same optical components as those described above will be described using the same numbers.

In the above-described first embodiment, light whose principal ray is substantially parallel is made incident on the cross dichroic prism 111, but in the second embodiment, convergent light is made incident as shown in FIG. The difference from the first embodiment is only in the point where it is made (only the green optical path is shown). FIG. 7 is a conceptual diagram of the light emitted from the liquid crystal display panel 105, and the traveling direction of the light in the cross dichroic prism 111 actually changes.

In the second embodiment, as shown in FIG.
With respect to the cross dichroic prism 111, the incident angle is ± 5.6 ° from the short side direction of the display area of the liquid crystal display panel 105, and the incident angle is ± 5.6 ° from the long side direction with the design incident angle as the center.
Convergent light was incident on which 7.5 ° light was incident. The angle of incidence of light from the long side direction is larger than that from light from the short side direction, but as described in the section of action, there is almost no effect on the spectral characteristics of light incident from the long side direction. Absent.

On the other hand, in the case of the conventional arrangement in which the long side direction and the short side direction of the liquid crystal display panel 105 are arranged in the opposite direction, the cross dichroic prism 111 is changed from the direction that greatly affects the spectral characteristics. , Liquid crystal display panel 10
The light in the range of ± 7.5 ° which is the convergent light from the long side direction of No. 5 is incident, and the shift of the spectral characteristic becomes large.

In FIG. 8, ± 5.6 ° centered on the design incident angle.
An example of the shift amount of the spectral characteristics when incident at 1 ° and when incident at ± 7.5 ° is shown. As is apparent from FIG. 8, when the present invention is applied, the shift of the spectral characteristic is suppressed significantly.

Further, by making the convergent light incident, the prism size can be reduced by 40% or more and the projection lens size can be reduced by 20% or more as compared with the first embodiment, and the back focus of the projection lens is also the first embodiment. Than 15%
Since it can be shortened to some extent, the system quality can be further reduced without significantly lowering the display quality as compared with the first embodiment.
It is possible to reduce costs.

(Third Embodiment) FIG. 9 is a schematic view of a projection type color image display device according to a third embodiment of the present invention. In the third embodiment, the above-described first embodiment is used.
The same optical components as those described above will be described using the same numbers.

In the third embodiment, as the light source 101,
A metal halide lamp with 150 W and an arc length of 2 mm was used. As the light source 101, a halogen lamp, a xenon lamp, or the like can be used in addition to the above. And
A parabolic mirror 102 for emitting light from the light source 101 as substantially parallel light is arranged on the back surface of the light source 101.

In front of the light source 101, of the white light from the light source 101, the dichroic mirror 301 that transmits the light in the red and green wavelength bands and reflects the light in the blue wavelength band.
Are arranged. The red and green light transmitted through the dichroic mirror 301 is incident on the dichroic mirror 302 that reflects the green light and transmits the red light. The red light transmitted through the dichroic mirror 302 enters the PBS 303R, and the S-polarized light enters the reflective liquid crystal display panel 304R. The green light reflected by the dichroic mirror 302 enters the PBS 303G, and the S-polarized light enters the reflective liquid crystal display panel 304G.

On the other hand, the light in the blue wavelength band reflected by the dichroic mirror 301 enters the PBS 303B via the reflection mirror 305 and the relay lens 108, and the S-polarized light enters the reflective liquid crystal display panel 304B. .

In the third embodiment, as the PBS 303, one made of cube-shaped glass having a reflection surface having a polarization separator made of a dielectric multilayer film is used. For example, a polarization selective reflection film manufactured by 3M (Optic
al Film D-BEF) and JP-A-57-1588.
No. 01 publication, a liquid immersion type P in which a polarizing element or a plate on which a film for polarization separation is deposited is immersed in a liquid.
BS or the like may be used. These elements are made of glass P
It has an advantage that the contrast ratio can be prevented from lowering due to birefringence generated in BS.

D-BEF and Japanese Patent Laid-Open No. 57-1588.
The polarizing element disclosed in Japanese Patent Publication No. 01 has an optical axis in its plane, reflects a linearly polarized light component of the incident light in the direction of the optical axis, and is orthogonal to the optical axis. It has a function of transmitting the light of the polarized component of.

The basic structure of these elements will be described with reference to FIG. These elements are layers in which layers having birefringence due to molecular orientation and isotropic layers are alternately laminated. The birefringent layer has an optical axis 40 in the laminated plane.
Have one. The refractive index of the isotropic layer is selected to be the same as the refractive index n0, ne of ordinary light or extraordinary light of the birefringent layer. Light incident on these elements is transmitted through the first layer 402, which is a birefringent layer, and the second layer 403, which is an isotropic layer.
Incident on. When the refractive index of the second layer 403 is selected to match the refractive index of the ordinary light of the first layer 402, the ordinary component 404 of the incident light is transmitted and the extraordinary component 405 is transmitted.
Some of them are reflected due to the difference in refractive index. Further, since the birefringent layers and the isotropic layers are alternately laminated, part of the extraordinary light is reflected in each layer, and as a result, the ordinary light component 4
04 is transmitted, and the extraordinary light component 405 is reflected. Therefore, the extraordinary light component is reflected by the same principle as that of the dielectric thin film.

The light incident on the reflection type liquid crystal display panel 304 is modulated in the polarization direction according to the image signal, and then the PB
S303R, 303G, 303B is incident again, only the light whose polarization direction is modulated, PBS303R, 303G, 3
After passing through 03B, it is combined by the cross dichroic prism 111 for color combination and is incident on the projection lens 112.

As shown in FIG. 11, the reflection type liquid crystal display panel 304 includes a color combining cross dichroic prism 1.
The height direction of the triangular prisms forming 11 is aligned with the long side direction of the display area of the reflective liquid crystal display panel 304.

In the third embodiment, the PBS 30
3. The cross dichroic prism 111 has the structure shown in FIG.
As shown in (only green light ray is shown), light whose principal ray is substantially parallel to the optical axis is made incident. In addition, the third embodiment
Then, as the reflective liquid crystal display panel 304, a 1.3 type X
A GA panel (1024 × 768 dots) was used. The liquid crystal mode is vertical alignment, and when no voltage is applied as shown in FIG. 13A, the liquid crystal molecules 502 are aligned vertically with respect to the glass substrate 501, and linearly polarized light is incident on the liquid crystal molecules 502. Is also reflected in the same polarization state. These lights are reflected by the PBS 303 and returned to the light source. On the other hand, when a voltage is applied as shown in FIG. 13B, the liquid crystal molecules 502 are aligned in the horizontal direction with respect to the glass substrate 501. When linearly polarized light is incident on this, the polarization direction is modulated by the anisotropy of the refractive index of the liquid crystal.

At this time, while the light travels back and forth through the liquid crystal layer, the cell thickness of the liquid crystal and Δn (the long axis of the liquid crystal molecule and the long axis of the liquid crystal molecule are set so that the phase difference of the light with respect to the long axis and the short axis of the liquid crystal becomes 1 / 2λ. When the (refractive index difference on the short axis) is adjusted, the light reflected by the reflective liquid crystal display panel 304 becomes linearly polarized light that is rotated by 90 ° with respect to the polarization direction of the incident light, and passes through the PBS 303. In addition to the above-described vertical alignment, any mode that uses polarization of light such as TN can be applied to the liquid crystal mode.

The FPC 11 of the reflection type liquid crystal display panel
The liquid crystal display panel was designed so that the mounting direction of 3 was the short side direction of the liquid crystal display panel. Therefore, FPC11
3 can be taken out in the direction perpendicular to the paper surface in FIG.

In the vicinity of the light source 101, a fly-eye lens 114 in which lenses are two-dimensionally arranged is used for the purpose of making the illuminance distribution on the panel surface uniform.

In the third embodiment, in addition to the above-mentioned optical components, in order to improve the contrast ratio and prevent ghosts,
Polarizing plate 3 before and after PBS 303R, 303G, 303B
06 and 307 were placed. The polarizing plate 307 on the incident side is P
Its transmission optical axis is to the paper surface so as to cut the polarized light,
It is set in parallel. This allows PBS303
Only the light of S polarization component is incident on R, 303G, and 303B, and even if the extinction ratio of the PBS 303 is poor, only S polarization is incident on the reflective liquid crystal display panel 304, so that the contrast ratio is improved.

If this polarizing plate 307 is not provided,
Both the S-polarized light component and the P-polarized light component are incident on the PBSs 303R, 303G, and 303B, most of the P-polarized light is transmitted, and the S-polarized light is reflected. However, due to the characteristics of the PBS 303, the partially reflective liquid crystal display panel 304 P-polarized light is reflected in the direction of. Of the P-polarized light that has entered the reflective liquid crystal display panel 304, most of the reflected light that has not been modulated in the polarization direction passes through the PBS 303 this time and is projected on the screen, so the contrast ratio decreases. Resulting in. The polarizing plate 112 on the output side is arranged with its axis orthogonal to the polarizing plate on the input side. Polarizing plate 30
6 also has a function of improving the contrast ratio based on the same principle.

These polarizing plates 306 and 307 are made of PBS.
Although they are arranged on both the light incident side and the light emitting side of 303R, 303G, and 303B, the effect can be obtained even if they are arranged on either the light incident side or the light emitting side. Further, it is desirable that no optical component be arranged between the incident side polarization plates 306 and 307 and the PBSs 303R, 303G and 303B. This is because the polarization of light is disturbed by these optical components, and the effect is reduced.

When the optical system is constructed under the conditions as described above, it is possible to obtain a bright image with good contrast, and to compare with the case where the reflection type liquid crystal display panel is arranged as shown in FIG. Each of the dichroic prism 111 and the PBS 303 can be reduced by about 25%, and the FPC 113 is mounted in the short side direction of the reflective liquid crystal display panel 304. Since it can be arranged and the back focus of the projection lens 112 can be shortened, the system can be significantly downsized and the cost can be reduced.

In the third embodiment, the red and green light is transmitted and the blue light is reflected by the dichroic mirror 301, but any combination such as transmitting blue and green and reflecting red can be used. It is possible to use the illumination optical system used in the first and second embodiments, and the configuration shown in FIG. 15 may be used.

In this case as well, the same effect as described in the first embodiment can be obtained. Furthermore, in order to reduce the size of the optical system, a configuration as shown in FIG. 16 may be used. This optical system includes a dichroic mirror 601 that reflects blue (or red) and green and transmits red (or blue) among white light from the light source 101, and a dichroic mirror 601 that transmits blue (or red) and transmits green light. Among them, PBS 602 having a function of reflecting one polarization direction and transmitting light of a polarization direction orthogonal to the polarization direction is used.

By using such an optical system, it is possible to reduce the size of the optical system to the same extent as the liquid crystal projection using the transmissive liquid crystal display panel described in the first and second embodiments.

Further, although the S-polarized light is made incident on the reflection type liquid crystal display panel in the third embodiment, the P-polarized light may be made incident. In this case, when a PBS that separates or synthesizes polarized light with the dielectric mirror used in the third embodiment is used, it is necessary to move the reflective liquid crystal display panel to the P-polarized light side that transmits the PBS. Also, a polarization selective reflection film (Optical Film D- manufactured by 3M)
BEF) or a flat-plate PBS as described in JP-A-57-158801, the reflection type liquid crystal display panel may be moved as described above.
The position of the reflective liquid crystal display panel is the same, and the flat panel PB
Even if the optical axis of S is rotated by 90 °, P-polarized light can be made incident.

(Fourth Embodiment) FIG. 17 is a schematic diagram of a projection type color image display device according to a fourth embodiment of the present invention. In the second embodiment, the same optical components as those in the first embodiment will be described using the same numbers.

In the third embodiment, the light whose principal ray is substantially parallel is made incident on the PBS 303 and the cross dichroic prism 111. However, in the fourth embodiment,
As shown in FIG. 18, it differs from the third embodiment only in that convergent light is incident. FIG. 18 is a conceptual diagram of light reflected from the reflective liquid crystal display panel 304,
Actually, the traveling direction of light in the PBS 303 and the cross dichroic prism 111 changes.

In the fourth embodiment, as shown in FIG. 18, with respect to the PBS 303 and the cross dichroic prism 111, the incident angle from the short side direction of the display area of the reflective liquid crystal display panel 304 is centered on the designed incident angle. ± 5.6
The convergent light, which is incident by ± 7.5 ° from the long-side direction, was incident. The incident angle of light from the long side direction is larger than that from light from the short side direction, but as described in the section of the action, the polarization separation characteristics and the spectral characteristics of the light incident from the long side direction. Has almost no effect on

On the other hand, the reflective liquid crystal display panel 30
In the conventional case in which the long side direction and the short side direction of 4 are arranged opposite to each other, the reflection type liquid crystal display is applied to the PBS 303 and the cross dichroic prism 111 from the direction that greatly affects the polarization separation characteristic and the spectral characteristic. Light in the range of ± 7.5 °, which is the convergent light from the long side direction of the panel 304, is incident, resulting in a decrease in light utilization efficiency and a large shift in spectral characteristics.

FIG. 19 shows the PBSs when incident at ± 5.6 ° with respect to the design incident angle and when incident at ± 7.5 °.
An example of the polarization separation characteristic change amount of 303 is shown. The separation efficiency on the vertical axis is the reflectance Rs for S-polarized light and the transmittance Tp for P-polarized light.
Shows the efficiency multiplied by, and the separation efficiency is 1 when all the incident S-polarized light is reflected and all the P-polarized light is transmitted.
It becomes 00%.

Further, the cross dichroic prism 11
The shift amount of the spectral characteristic of No. 1 is the same as that of FIG. 8 shown in the above-described second embodiment. As is apparent from this, when the configuration of the present invention is applied, the light utilization rate is increased, and at the same time, the shift of the spectral characteristic of the cross dichroic prism 111 is suppressed, and a bright image with a wide color reproduction range is realized. Is possible.

By making the convergent light incident, the size of the PBS 103 and the cross dichroic prism 111 and the size of the projection lens 112 can be reduced by about 15 to 20% as compared with the third embodiment, and the back focus of the projection lens can be further reduced. Since the length can be shortened, it is possible to further reduce the size and cost of the system without significantly lowering the display quality as compared with the third embodiment.

[0106]

As described above, the present invention has the following effects. That is, the direction of the long side of the effective area for displaying an image of the image display means and the direction of the triangular prism forming the cross dichroic prism in the height direction are substantially matched to each other, so that the projection lens back Not only can the focus be shortened, the size and cost can be reduced, but by applying the configuration of the present invention, the cross dichroic prism itself can also be made smaller, so that the cost can be further reduced. Has become.

Further, according to the present invention, in the projection using the reflection type image display device, the size of the PBS and the cross dichroic prism on the side affecting the back focus of the projection lens can be reduced, so that the projection lens The back focus can be shortened, the size and cost of the device can be reduced, and in the projection using the reflection type image display element,
Although the cost is increased due to the addition of S, the cost of the PBS also increases in proportion to the volume thereof in the same manner as the cross dichroic prism. Therefore, by applying the configuration of the present invention, the size can be reduced and the cross dichroic Similar to the cost reduction of the prism, it is possible to reduce the cost of both the PBS and the cross dichroic prism.

Further, the signal input terminal to the image display means is
By forming in the short side direction of the image display means, it is not necessary to form a region for bending the FPC for inputting a signal to the image display element, so that the optical components can be densely arranged. Therefore, not only the optical system can be made compact, but also the back focus of the projection lens can be shortened to the limit depending on the size of the optical system. Further, since the PBS and the cross dichroic prism can be downsized, the cost can be further reduced.

Further, according to the present invention, even if the convergent light is made incident on the cross dichroic prism, it is possible to minimize the deterioration of the color purity of each of red, green and blue. Moreover, not only the cross dichroic prism and the projection lens can be downsized by injecting convergent light, but also the downsizing of the cross dichroic prism
The back focus of the projection lens can be further shortened, and a very large effect can be achieved in reducing the size, weight and cost of the system.

Further, in the projection using the reflection type image display element, in addition to the effect that the cross dichroic prism and the projection lens are downsized and the back focus of the projection lens can be shortened, the reduction of the light utilization rate is reduced. Not only that, but also the PBS itself can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a projection-type image display device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an installation direction of a liquid crystal display panel.

FIG. 3 is an explanatory diagram of light passing through a cross dichroic prism.

FIG. 4 is an explanatory diagram of an installation direction of a conventional liquid crystal display panel.

FIG. 5 is an explanatory diagram when another illumination system according to the first embodiment is used.

FIG. 6 is a schematic diagram of a projection-type image display device according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram of light passing through a cross dichroic prism.

FIG. 8 is a diagram showing incident angle dependence of spectral characteristics of a cross dichroic prism.

FIG. 9 is a schematic diagram of a projection-type image display device according to a third embodiment of the present invention.

FIG. 10 is an explanatory view of the principle of a polarization selective reflection film.

FIG. 11 is an explanatory diagram of an installation direction of a liquid crystal display panel.

FIG. 12 is an explanatory diagram of light passing through a PBS and a cross dichroic prism.

FIG. 13 is an operation explanatory diagram of a reflective liquid crystal display panel.

FIG. 14 is an explanatory diagram of an installation direction of a conventional liquid crystal display panel.

FIG. 15 is an explanatory diagram when another illumination system according to the third embodiment is used.

FIG. 16 is an explanatory diagram when another illumination system according to the third embodiment is used.

FIG. 17 is a schematic diagram of a projection-type image display device according to a fourth embodiment of the present invention.

FIG. 18 is an explanatory diagram of light passing through a PBS and a cross dichroic prism.

FIG. 19 is a diagram showing the light incident angle dependence of PBS.

20 (a) and 20 (b) are explanatory views of the effect of the present invention.

21 (a) and 21 (b) are explanatory views of the effect of the present invention.

22 (a), (b) and (c) are other configuration diagrams to which the present invention can be applied.

FIG. 23 is an enlarged view of a reflective liquid crystal display panel.

24 (a) and 24 (b) are explanatory views of problems of projection using a conventional reflective liquid crystal display panel.

FIG. 25 is a diagram showing the incident angle dependence of a dielectric mirror.

FIG. 26 is an explanatory diagram of effects of the present invention.

FIG. 27 is an explanatory diagram of a conventional mirror sequential system.

FIG. 28 is an explanatory diagram of a conventional mirror sequential system.

FIG. 29 is an explanatory diagram of a conventional cross dichroic mirror system.

FIG. 30 is an explanatory diagram of projection using a conventional reflective liquid crystal display panel.

FIG. 31 is an enlarged view of a pixel portion of a transmissive liquid crystal display panel.

32 (a) and 32 (b) are optical path diagrams of a color synthesizing unit for projection using a cross dichroic prism.

FIG. 33 is an explanatory diagram of a cross dichroic prism.

[Explanation of symbols]

101 light source 102 parabolic mirror 103 dichroic mirror 104 reflection mirror 105R image display device (liquid crystal display panel) 105G image display device (liquid crystal display panel) 105B image display device (liquid crystal display panel) 106R field lens 106G field lens 106B field lens 107 Dichroic mirror 108 Relay lens 109 Reflection mirror 110 Reflection mirror 111 Cross dichroic prism 112 Projection lens 113 FPC 114 Fly-eye lens 201 Cross dichroic mirror or cross dichroic prism 202 Dichroic mirror 301 Dichroic mirror 302 Dichroic mirror 303R PBS 303R PBS 303B PBS 304R Reflection type Liquid crystal display panel 304G reflective liquid crystal Display panel 304B Reflective liquid crystal display panel 305 Reflecting mirror 306 Polarizing plate 307 Polarizing plate 401 Optical axis 402 Birefringent layer (first layer) 403 Birefringent layer (second layer) 404 Ordinary light component 405 Extraordinary light component 501 Glass substrate 502 Liquid crystal Molecule 601 Dichroic mirror 602 PBS 701 Dichroic mirror 702 Dichroic mirror 703 Dichroic mirror 704 Dichroic mirror 711 Glass prism 712 Glass prism 721 Dichroic mirror 722 Dichroic mirror 731 Dichroic mirror 732 Dichroic mirror 801 TFT source line 802 Black line Matrix 80 prism

Claims (4)

(57) [Claims] 1. A light source, a color separation means for separating the light from the light source into red, green, and blue light fluxes, and an image corresponding to each of the red, green, and blue light fluxes separated by the color separation means. In a projection type image display device comprising display means, a cross dichroic prism for combining the light modulated according to the image signal by the image display means, and a projection means for projecting the light combined by the cross dichroic prism Forming the cross dichroic prism with the direction of the long side of the image display area of the image display means 3
A projection-type image display device, characterized in that the direction of the prism in the height direction is substantially matched. 2. The polarized light selective reflection means for reflecting or transmitting the light from the light source according to the polarization direction, and the image display means is a reflection type image display element. The projection-type image display device described. 3. A signal input terminal to the image display means,
The projection type image display device according to claim 1 or 2, wherein the projection type image display device is formed in a short side direction of a display area of the image display means. 4. The light incident on the cross dichroic prism is convergent light having a condensing point on the projection lens side with respect to the light exit surface of the cross dichroic prism. The projection-type image display device described.