JPH08160388A - Projection type color liquid crystal display device - Google Patents

Abstract

PURPOSE: To accomplish a full color image of high quality without reducing light utilization efficiency and color purity by forming plural sheet-like luminous flux splitting means equipped with a selective reflection surface installed on its surface so that the front side and the rear side of the means may not be parallel to each other. CONSTITUTION: Light emitted from a white light source 1 is collimated by a reflection mirror 2 so as to become parallel rays, then, ultraviolet rays and infrared rays are removed by a filter 3, thereafter, the light is made incident on dichroic mirrors (luminous flux splitting means) 4 and 5 and a dichroic mirror (reflection mirror) 6 which are arranged in a shape like a fan. A microlens array 8 is prepared for converging plural luminous fluxes split by the dichroic mirrors 4 to 6 equipped with each selective reflection surface for reflecting the light of a specified wavelength area on the corresponding pixel area of a liquid crystal panel 7 by every wavelength area, and a projecting optical system 9 is prepared for projecting plural luminous fluxes modulated through the liquid crystal panel 7 on a screen 10. At this time, each selective reflection surfaces (front side) of the dichroic mirrors 4 to 6 are formed so as not to be parallel to the rear side of the glass substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type color liquid crystal display device applied to, for example, a liquid crystal television system or an information display system.

[0002]

2. Description of the Related Art Projection-type color image display systems using liquid crystal panels include a three-plate system using three liquid crystal panels according to three primary colors and a single-plate system using only one liquid crystal panel. The three-plate type is
It consists of an optical system that splits white light into the three primary colors of red, green, and blue, and three liquid crystal panels that form images according to each color. It is something to do. This method has advantages such as high light utilization efficiency and high color purity, but on the other hand, it is difficult to reduce the cost and the size because the number of optical system members including the liquid crystal panel increases.

On the other hand, since the single-panel type projection type color liquid crystal display device has one liquid crystal panel, the number of optical system members is smaller than that of the three-plate type, and the cost and size can be relatively easily realized. In this single plate type, further by the spectroscopic method,
There are a method of projecting a liquid crystal panel by providing a mosaic or striped three-primary color filter pattern, and a method of projecting the reflected light of a fan-shaped dichroic mirror to each pixel of the liquid crystal panel. The former has a very low light utilization efficiency because light is absorbed by the color filter, while the latter has a high light utilization efficiency and is a system having the advantages of the three-plate type and the single-plate type.

An apparatus adopting this system is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-60538. The device configuration will be described with reference to FIGS. 2 and 3 which are explanatory views of the present invention. First, as shown in FIG. 2, the light emitted from the white light source 1 is reflected by the reflecting mirror 2 to become parallel rays, the UV / IR filter 3 removes the ultraviolet rays / infrared rays, and the dichroic mirror 4 arranged in a fan shape.・
It is incident on 5.6.

The dichroic mirrors 4, 5 and 6 have different spectral reflection characteristics in different wavelength ranges, and are arranged so that the incident light rays I have different elevation angles. Therefore, the incident light ray I is a light ray reflected by the first dichroic mirror 4 (hereinafter, referred to as a first principal ray L _M1 ) and a light ray reflected by the second dichroic mirror 5 (hereinafter, a second principal ray L _M2). That is, the light beam reflected by the third dichroic mirror 6 (hereinafter referred to as the third chief ray L _M3 ) is split into light beams having different wavelength ranges and different emission angles. For example, dichroic mirror 4
If 5 and 6 are reflection mirrors that selectively reflect the red, green, and blue wavelength regions, respectively, the first to third chief rays L _M1
· L _{M2-L M3} are each a red, green and blue light, is incident on the microlens array 8.

As shown in FIG. 3, the microlens array 8 includes three signal electrodes 7d of red, green and blue of the liquid crystal panel 7.
Each one of 7e and 7f has one microlens 8a. Then, the first to third chief rays L _M1 , L _M2 , L _M3 are
Each signal electrode 7d, 7e,
It is converged to the pixels driven at 7f. Therefore,
If signals corresponding to the colors of the incident light rays are applied to these signal electrodes 7d, 7e, and 7f and projected onto the screen 10 by the projection optical system 9 shown in FIG. 2, the light utilization efficiency is high and a bright full-color image is obtained. Can be provided.

Conventionally, as shown in FIG. 14, the dichroic mirrors 4 ', 5', 6'as described above have a dielectric plate on the surface of a transparent flat glass substrate 4b ', 5b', 6b '. Body membrane 4
It is constructed by multi-layer coating of a '・ 5a' ・ 6a '. And these dichroic mirrors 4 ', 5', 6 '
Are, for example, 50 degrees and 45 degrees with respect to the illustrated x-axis.
They are arranged at an inclination of 40 degrees. At this time, the inclinations of the first to third chief rays L _M1 , L _M2, and L _M3 reflected on the respective surfaces with respect to the x-axis (hereinafter referred to as emission angles) are each −10.
It becomes 0 degrees and 10 degrees. As a result, the angles of incidence on the microlenses 8a are the first to third chief rays L _M1.
It is different for each of L _M2 and L _M3 , and as a result, each chief ray L _M1
The convergence positions of L _M2 and L _M3 correspond to each pixel of the liquid crystal panel 7.

[0008]

However, in the configuration of the conventional dichroic mirrors 4 ', 5', 6'as described above,
Color mixing occurs due to reflected light other than the first to third chief rays L _M1 , L _M2, and L _M3 , which causes a problem that the color purity decreases and a high-quality projected image cannot be obtained.

That is, as shown in FIG. 14, the reflected light from each dichroic mirror 4 ', 5', 6'is not only the desired first to third chief rays L _M1 , L _M2 , L _M3, but also the first Internal reflection light on the back surface of the glass substrate 4b 'of the first dichroic mirror 4' (hereinafter referred to as first reflection light L _S1 ), internal reflection light on the back surface of the glass substrate 5b 'of the second dichroic mirror 5' ( Hereinafter, the second reflected light L _S2 ) and multiple reflected light between the back surface of the first dichroic mirror 4 ′ and the front surface of the second dichroic mirror 5 ′ (hereinafter referred to as the third reflected light L _S3 ). Exists. Although there are reflected lights other than those shown in the figure, the internal reflected light on the back surface of the glass substrate 6b 'of the third dichroic mirror 6'and the third reflected light L
The further multiple reflected light of _S3 and the multiple reflected light generated between the second and third dichroic mirrors 5'and 6'are incident on the subsequent imaging system due to the small amount of light and the large emission angle. Since it does not occur, the degree of influence is small and can be ignored.

Of these, the first and second reflected lights L _S1 and L _S2 are unique to the dichroic mirror,
The same occurs in the above-mentioned three-plate type. The third reflected light L _S3 is peculiar to the single plate type in which the dichroic mirrors are arranged in a fan shape. Moreover, the third reflected light L _S3 has the same wavelength range as the second chief ray L _M2 and has the same exit angle as the third chief ray L _M3 .

That is, each dichroic mirror 4 '・ 5'
As described above, when the inclination of 6'is 50 degrees, 45 degrees, and 40 degrees with respect to the illustrated x-axis, respectively, the exit angles of the first to third chief rays L _M1 , L _M2, and L _M3 are Each with respect to x-axis
It is 10 degrees, 0 degrees, and 10 degrees, and at this time, the first and second reflected lights L _S1 and L _S2 are naturally the first and second chief rays L _M1 and L _M2.
Therefore, the output angles are −10 degrees and 0 degrees, respectively. In addition, the third chief ray L _M3 has an exit angle of 10 degrees, which also matches the third chief ray L _M3 .

The above-mentioned microlens array 8 makes the convergence position different depending on the incident angle of each light ray. In other words, the light rays having the same incident angle are applied to the same pixel. . That is, in the above example, the first
The principal ray L _M1 and the first reflected light L _S1 , the second principal ray L _M2 and the second reflected light L _S2 , and the third principal ray L _M3 and the third reflected light L _S3 respectively illuminate the same pixel. Become. Naturally, the color purity of the projected image is determined by the purity of the color light with which the pixel is irradiated. Therefore, the presence of the first to third reflected lights L _S1 , L _S2, and L _S3 causes the originally desired first to first 3 chief rays L _M1・ L _M2・ L
The color purity of the colored light of _M3 will decrease.

Further, the first to third reflected lights L _S1 · L _S2 · L
_{Since S3} is incident on a pixel that should not be originally incident, it is not appropriate in terms of light utilization efficiency in each color light.

The present invention has been made in view of the above-mentioned conventional problems, and it is a projection color capable of realizing a high-quality full-color image without lowering the light utilization efficiency and the color purity. An object is to provide a liquid crystal display device.

[0015]

In order to achieve the above object, a projection type color liquid crystal display device according to claim 1 of the present invention divides light from a white light source into a plurality of light fluxes having different wavelength ranges. Therefore, a plurality of plate-like luminous flux splitting means each having a selective reflection surface for reflecting light in a specific wavelength region are provided on the surface, and the split luminous fluxes are distributed to corresponding pixel regions of the liquid crystal panel for each wavelength region. In a projection type color liquid crystal display device comprising a microlens array for converging and a projection means for projecting a plurality of light fluxes modulated through the liquid crystal panel, at least one of the light flux splitting means has a front surface and a back surface which are mutually It is characterized by being formed non-parallel.

A projection type color liquid crystal display device according to a second aspect is the device according to the first aspect, wherein each of the light beam splitting means comprises two first and second dichroic mirrors having different spectral characteristics from each other, and a white light source. The first and second dichroic mirrors and the reflection mirror having a reflecting surface for reflecting the light transmitted through both dichroic mirrors on the optical path of the incident light from the It is characterized in that they are sequentially arranged with a predetermined inclination angle.

According to a third aspect of the present invention, in the projection type color liquid crystal display device according to the second aspect, the inclination angles of the front and back surfaces of the first and second dichroic mirrors and the front surface of the reflection mirror are different from each other. It has a feature.

According to a fourth aspect of the present invention, there is provided the projection type color liquid crystal display device according to the second aspect, wherein the first and second dichroic mirrors have different front and back surface inclination angles. The tilt angle between the back surface and the front surface of the reflection mirror is the same.

The projection type color liquid crystal display device according to a fifth aspect is the device according to the third or fourth aspect, in which the first dichroic mirror selectively reflects green color light and the second dichroic mirror emits blue color light. It is characterized in that it is set to selectively reflect.

A projection type color liquid crystal display device according to a sixth aspect is the device according to the second aspect, wherein the inclination angles of the front surface and the back surface of the first dichroic mirror are different from each other and the front surface and the back surface of the second dichroic mirror are different from each other. And the back surface of the first dichroic mirror and the front surface of the second dichroic mirror have the same tilt angle, and the back surface of the second dichroic mirror and the surface of the reflection mirror are tilted. The corners are the same as each other.

A projection type color liquid crystal display device according to a seventh aspect is the device according to the sixth aspect, wherein the first dichroic mirror selectively reflects blue color light and the second dichroic mirror selectively reflects green color light. The feature is that it is set to.

[0022]

In the projection type color liquid crystal display device according to claim 1, a plate-like light beam splitting means having a selective reflection surface for reflecting light in a specific wavelength range on the surface thereof, for example, a dichroic mirror as described in claim 2. The plate-shaped light velocity splitting means made of is formed such that the front surface and the back surface thereof are not parallel to each other. At this time, for example, referring to the first dichroic mirror 4 shown in FIG. 1, the first chief ray L _M1 reflected by the front surface S ₁ thereof and the internal main reflection by the rear surface S _1B of the mirror 4 are reflected. And the first reflected light L _S1 emitted through the front surface S ₁ have different emission directions. Therefore, it is possible to prevent unnecessary reflected light from being mixed in an image displayed with a desired chief ray, and thereby it is possible to display an image with higher color purity.

In the projection type color liquid crystal display device according to the third aspect, for example, as shown in FIG. 1, the front and rear surfaces S ₁ and S ₂ and the rear surface S of the _first and second dichroic mirrors 4 and 5, respectively.
The inclination angles of _1B · S _2B and the surface S ₃ of the third dichroic mirror 6 as a reflection mirror are different from each other.
That is, an angle (hereinafter, referred to as an elevation angle) formed with respect to a plane direction (x-axis direction in the drawing) orthogonal to the incident light ray I is the front surface S ₁ · S ₂ and the back surface S of the _first and second dichroic mirrors 4 and 5. _If α ₁ · α ₂ · α _1B · α _2B in _1B · S _2B and α _{3B in} the surface S ₃ of the third dichroic mirror 6, for example, α _1B >
It is set so that α ₁ > α ₂ > α ₃ > α _2B .

At this time, the first and second reflected lights L _S1 and L _S2 internally reflected by the respective rear surfaces S _1B and S _2B of the first and second dichroic mirrors 4 and 5 and emitted, and the second dichroic mirror 5 are emitted. On the optical path of the second chief ray L _M2 reflected by the front surface S ₂ of the first dichroic mirror 4 and the back surface S _1B of the first dichroic mirror 4 and the front surface S ₂ of the second dichroic mirror 5, and transmitted through the first dichroic mirror 4. Reflected light L _S3
The output directions of and are the dichroic mirrors 4, 5 and 6 respectively.
First to third chief rays L _M1 · L _M2 · L respectively reflected on the surface of
_Does not match any of the _M3s .

Therefore, for example, these first to third chief rays L _M1 , L _M2 , corresponding to the color lights of the red, green, and blue wavelength regions, respectively.
Since none of the first to third reflected lights L _S1 , L _S2, and L _S3 is mixed in L _M3 , it is possible to display a color image with high color purity.

A color liquid crystal display device according to a fourth aspect is
For example, as shown in FIG. 7, the inclination angles of the front surfaces S ₁ and S ₂ and the rear surfaces S _1B and S _2B of the first and second dichroic mirrors 4 and 5 are different from each other, and the rear surface S _2B of the second dichroic mirror 5 is different. And the surface S ₃ of the third dichroic mirror 6
The inclination angles of and are set to be the same. That is, the elevation angle is, for example, α _1B > α ₁ > α ₂ > α _2B = α
₃ and is set to be.

At this time, the emission directions of the first and third reflected lights L _S1 and L _S3 do not coincide with any of the first to third chief rays L _M1 , L _M2 and L _M3 , and the second reflected light Since the emission direction of the light L _S2 is α _2B = α ₃ , it coincides with the third chief ray L _M3 . However, the second reflected light L _S2 is the third chief ray L
_Since the light has the same wavelength range as _M3 , the color purity does not decrease and the intensity increases. As a result, the color purity is further increased and the light utilization efficiency is improved.

In the projection type color liquid crystal display device according to claim 5, in the device according to claim 3 or 4, for example, FIG.
Alternatively, the first dichroic mirror 4 in FIG. 7 is set to selectively reflect the green color light as the first principal ray L _M1 and the second dichroic mirror 5 selectively reflects the blue color light as the second principal ray L _M2. ing.

At this time, the spectral characteristic of the first chief ray L _M1 is
It becomes a light beam according to the spectral reflection characteristic of the first dichroic mirror 4, and the second chief ray L _M2 corresponds to (spectral transmittance of the first dichroic mirror 4) ² × (spectral reflectance of the second dichroic mirror 5) It becomes a characteristic. Further, the third chief ray L _M3 is (spectral transmittance of the first dichroic mirror 4) ² × (spectral transmittance of the second dichroic mirror 5)
² × (spectral reflectance of the third dichroic mirror).

Due to such spectral characteristics, each chief ray L _M1
~ L _M3 , the difference in the relative ratio between the intensity in the desired wavelength range and the intensity in the other wavelength ranges is the first chief ray L _M1 · second
The principal ray L _M2 and the third principal ray L _M3 increase in this order.

On the other hand, as a result of various studies by the inventors of the present invention on the tendency of color purity deterioration due to color mixing in each color light, the order of weakness in color mixing is red, blue and green. The mixture of green and red is more tolerant than other cases. Green, blue, and red are in the order of increasing color mixture and causing problems. I newly discovered that point.

Therefore, in accordance with the difference in the relative ratio in the spectral characteristics, the first dichroic mirror 4 is divided into green and the second dichroic mirror 5 is divided into blue in order of strength against color mixture. It is possible to display a color image with high color purity as a whole.

In the color liquid crystal display device according to the sixth aspect, as shown in FIG. 9, for example, the front surface S ₁ and back surface S _{1B of} the first dichroic mirror 4 and the front surface S ₂ and back surface S of the second dichroic mirror 5 are provided. The inclination angles of _2B are different from each other, and the back surface S _1B of the first dichroic mirror 4 and the front surface S ₂ of the second dichroic mirror 5 and the back surface S _2B of the second dichroic mirror 5 and the front surface S ₃ of the third dichroic mirror 6 are included. Are set to have the same inclination angle. That is, the elevation angle is, for example, α
It is set such that ₁ > α _1B = α ₂ > α _2B = α ₃ .

At this time, since α _2B = α ₃ , the second reflected light L in the same wavelength range as the third chief ray L _M3 is obtained as described above.
The emission direction of _S2 coincides with the third chief ray L _M3 . further,
The emission direction of the third reflected light L _{S3 in} the same wavelength range as the second principal ray L _M2 is α _1B = α ₂ , and therefore coincides with the second principal ray L _M2 . In this case, the emission direction of the second principal ray L _M2 first reflected light L _S1 having different wavelength ranges and also, but will correspond to the second principal ray L _M2, this arrangement, reduction in color purity It is possible to further improve the light utilization efficiency while suppressing as much as possible.

In the projection type color liquid crystal display device according to the seventh aspect, the blue color light is selectively reflected by the first dichroic mirror and the green color light is selectively reflected by the second dichroic mirror. That is, in the device according to claim 6,
The first reflected light L _S1 having a different wavelength range from the second chief ray L _M2 is mixed. Therefore, as described above, the green color light that is strong in color mixing is set to be the second chief ray L _M2, and the red color light that is weak in color mixing is set to the third chief ray L _M3 as described above.
By doing so, the deterioration of the overall color purity can be suppressed as much as possible,
In addition, the light utilization efficiency can be further improved.

[0036]

【Example】

[Embodiment 1] An embodiment of the present invention will be described with reference to FIGS.
The explanation is based on the following.

As shown in FIG. 2, the projection type color liquid crystal display device according to this embodiment is provided with a white light source 1 which is, for example, a metal halide lamp. The output is, for example, 150 W, arc length AL = 5 mm, arc diameter A = 2.2.
mm, and the arc is arranged so as to be perpendicular to the paper surface in the drawing. As the white light source 1, for example, a halogen lamp or a xenon lamp may be used instead of the above metal halide lamp.

A reflecting mirror 2 having a parabolic surface is arranged behind the white light source 1 with its focal position aligned with the center of the white light source 1. As a result, the light from the white light source 1 is reflected by the reflecting mirror 2 to become parallel rays, which are emitted downward in the figure.

A UV / IR filter 3 for blocking ultraviolet rays and infrared rays is arranged in the emitting direction. Then, the first and second dichroic mirrors 4 and 5 serving as light beam splitting means and the third dichroic mirror serving as a reflecting mirror are provided on the optical path of a light beam (hereinafter referred to as an incident light beam I) that has passed through the UV / IR filter 3. 6 and 6 respectively incline at an angle of about 45 degrees with respect to the above incident light ray I,
Further, they are arranged so as to overlap each other along the optical path of the incident light ray I. The tilt angles of the dichroic mirrors 4, 5, and 6 with respect to the incident light beam I will be described in detail later.

The above dichroic mirrors 4, 5 and 6
As described below, each is formed by applying a well-known multilayer thin film coating on the surface of a transparent glass substrate. In this embodiment, the first dichroic mirror 4 arranged on the white light source 1 side is formed so as to reflect green color light in the range of approximately 570 nm to 500 nm and transmit light in other wavelength ranges. . The second dichroic mirror 5 in the middle is formed so as to reflect blue color light having a wavelength shorter than about 500 nm. In addition, the third dichroic mirror 6 arranged farthest from the white light source 1.
Are formed to reflect red color light having a wavelength longer than about 600 nm. The reason why the first to third dichroic mirrors 3, 4 and 5 are configured so that the incident light ray I is reflected in the order of green, blue and red will be described later in detail. .

The above-mentioned first to third dichroic mirrors 4
・ 5 and 6 indicate the tilt angle with respect to the incident ray I as described above.
They are arranged so as to be different from each other within a predetermined angle range centered on 5 degrees. For example, the second dichroic mirror 5
When the reflected light beam at 1 is set so as to change its direction by 90 degrees in a direction substantially orthogonal to the incident light beam I, the reflected light beam at the first dichroic mirror 4 is The angle formed is about 100 degrees, and the reflected light beam from the third dichroic mirror 6 is set so that the angle formed with respect to the incident light beam I is about 80 degrees.

The liquid crystal panel 7 is arranged in the direction in which these reflected light rays are directed. In this liquid crystal panel 7,
A microlens array 8 is attached to the incident surface side. As shown in FIG. 3, the liquid crystal panel 7 is configured by enclosing a liquid crystal layer 7c between a pair of glass substrates 7a and 7b. Although not shown, stripe-shaped scanning electrodes for driving the liquid crystal layer 7c in a simple matrix are formed on the surface of the first glass substrate 7a on the light incident side.
Signal electrodes 7d, 7e, and 7f that are respectively orthogonal to the scanning electrodes are formed on the second glass substrate 7b on the light emitting side. Then, by inputting R, G, B signals to these signal electrodes 7d, 7e, 7f, respectively, the pixel regions in the liquid crystal layer 7 are driven independently.

The signal electrodes 7d, 7e, 7f and the scanning electrodes are both made of a transparent conductive film.
Further, in the figure, the polarizing plate, the alignment film and the like which are the constituent elements of the liquid crystal panel 7 are omitted for simplification.

The microlens array 8 attached to the surface of the first glass substrate 7a of the liquid crystal panel 7 has a pair of signal electrodes 7d, 7e, ... A lenticular lens having a width dimension corresponding to the entire 7f (microscopic lens 8 having a semi-cylindrical shape)
a) arranged in parallel) are arranged on a transparent substrate by an ion exchange method to form a lenticular lens substrate.

Microlens array 8 having such a configuration
Through the first to third dichroic mirrors 4 and 5
The light rays reflected at 6 are condensed on the liquid crystal panel 7.
At this time, the light reflected by the second dichroic mirror 5 (hereinafter referred to as the second chief ray L _M2 ) that enters the microlenses 8 a substantially in parallel to the optical axis direction is the light of the microlenses 8 a. The light is focused on the pixel area driven by the signal electrode 7e positioned on the axis. Further, the reflected light (hereinafter, referred to as the first principal ray L _M1 ) reflected by the first dichroic mirror 4 that is incident from the upper side in the figure with respect to the optical axis of the microlens 8a is below the signal electrode 7e. The light is focused on the pixel area driven by the signal electrode 7f adjacent to the side. Similarly, the light reflected by the third dichroic mirror 6 (hereinafter referred to as the third chief ray L _M3 ) that is incident from the lower side in the figure with respect to the optical axis of the microlens 8 a is the signal electrode 7 e. Signal electrode 7 adjacent to the upper side of the
It is focused on the pixel area driven by d.

As described above, the first to third chief rays L _M1 , L _M2, and L _M3 reflected by the first to third dichroic mirrors 4, 5, and 6 and incident on the liquid crystal panel 7 are the microlens array. Through each of the microlenses 8a forming the unit 8, light is divided into three adjacent pixel regions to collect the light.

In the light emission direction of the liquid crystal panel 7, as shown in FIG. 2, a projection optical system 9 as a projection means.
Field lens 9a and projection lens 9b constituting the
And a screen 10 are further provided. The light rays that pass through and exit the liquid crystal panel 7 are converged by the field lens 9a at the position where the projection lens 9b is provided, and are projected on the screen 10 by the projection lens 9b.

In the above structure, the light emitted from the white light source 1 is reflected by the reflecting mirror 2 and becomes a parallel light beam as described above. Further, visible light rays from which ultraviolet rays and infrared rays have been removed by the UV / IR filter 3 enter the dichroic mirrors 4, 5 and 6. By these dichroic mirrors 4, 5, and 6, white light is divided into three primary colors and reflected toward the liquid crystal panel 7. Then, the light flux of each color is incident on the microlens array 8 at different angles according to the angles at which the dichroic mirrors 4, 5, and 6 are arranged, as described above.

Through the microlens array 8, the light is focused on the pixel region corresponding to each color. At this time, the R, G, and B video signals corresponding to the focused colors are supplied to the signal electrodes 7d and 7e. By applying to 7f, the luminous flux of each color is intensity-modulated according to the above video signal. The modulated light flux passes through the field lens 9a and the projection lens 9b and then is projected on the screen 10 to display a color image on the screen 10.

By the way, in the structure using the dichroic mirrors 4, 5 and 6 as described above, the respective mirrors 4 and 5 and 6 are
In addition to the desired reflected light at 1, that is, the first to third chief rays L _M1 , L _M2 , L _M3 described above, unintended reflected light is generated. Therefore, conventionally, there has been a problem that an image having a sufficient color purity cannot be displayed. Therefore, a configuration further adopted in this embodiment to solve this problem will be described below.

FIG. 1 schematically shows an enlarged view of the shapes and arrangements of the dichroic mirrors 4, 5, and 6 in this embodiment. As shown, each dichroic mirror 4.5
6 shows that the dielectric layers 4a, 5a, 6a each having a spectral characteristic of reflecting a certain wavelength range are vapor-deposited on one surface (the upper surface in the figure) of the plate-like transparent glass substrate 4b, 5b, 6b. It is configured.

When the surfaces of the respective glass substrates 4b, 5b, 6b on which the dielectric layers 4a, 5a, 6a are vapor-deposited are the selective reflection surfaces S ₁ , S ₂ , S ₃ , the respective glass substrates 4b, 5b, 6b. The back surfaces S _1B , S _2B , S _3B of 5b, 6b are not necessarily parallel to the selective reflection surfaces S ₁ , S ₂ , S ₃ , respectively, but are formed with different inclination angles with respect to the respective incident light rays I. Therefore, regarding the setting of these tilt angles,
Each selective reflection surface S ₁ · S ₂ · S ₃ and back surface S _1B · S _2B ·
In S _3B , an angle formed with respect to the illustrated x-axis (hereinafter,
The elevation angle) is defined as α ₁ · α ₂ · α ₃ · α _1B ·
The following description will be made assuming that α _2B and α _3B .

In addition, each of the above dichroic mirrors 4
5 and 6, the first principal ray L _M1 and the first principal ray L _M1 which are the rays reflected by the selective reflection surface S ₁ of the first dichroic mirror 4 with respect to the incident ray I which is incident from above in substantially parallel to the y-axis. The ray reflected by the selective reflection surface S ₂ of the second dichroic mirror 5 is the second principal ray L _M2 , and the ray reflected by the selective reflection surface S ₃ of the third dichroic mirror 5 is the third principal ray L _M3. And

These first to third chief rays L _M1 , L _M2 , L _M3
Are light rays reflected by the dielectric layers 4a, 5a and 6a of the dichroic mirrors 4, 5 and 6, respectively, and are condensed by the microlens array 8 at desired pixels in the liquid crystal panel 7 as described above. It is a ray of light.

Then, as the light rays which affect the color purity in the color image display, the following three light rays are considered. That is, of the light transmitted through the selective reflection surface S ₁ of the first dichroic mirror 4, a light ray internally reflected by the back surface S _1B of this mirror 4 and emitted from the selective reflection surface S ₁ of this mirror 4 (hereinafter, referred to as the first that the reflected light L _S1) and internally reflected by the second dichroic backside S _2B of dichroic mirror 5, the rays of light outgoing selective reflection surface S ₂ · first dichroic mirror 4 of the mirror 5 are sequentially transmitted to (hereinafter, the second reflected light L _S2 ) On the optical path of the second chief ray L _M2 , the light is reflected by the back surface S _1B of the first dichroic mirror 4, and further reflected by the selective reflection surface S ₂ of the second dichroic mirror 5, and then the first dichroic mirror 4. rays transmitted to emit (hereinafter, a third of the reflected light L _S3) in practice, the light rays emitted by multiple reflection between the first through third dichroic mirrors 4, 5, 6 in addition to the above there They, the number of reflections and the dichroic mirror 4
-Increasing the number of transmissions of 5 and 6 significantly reduces the strength. Therefore, the influence on the color purity described later is extremely small and can be ignored.

The first to third chief rays L _M1 and L _M2
L _M3 and the first to third reflected lights L _S1 , L _S2 , L _S3 are the inclination I _IN of the incident light beam I from the y-axis in the figure, and the glass substrates 4b, 5b, 6b of the dichroic mirrors 4, 5, 6 Refractive index, elevation angle α ₁ · α ₂ · α ₃ · α _1B · α _2B ·
The inclination with respect to the x-axis (hereinafter referred to as the emission angle) changes depending on α _3B . The emission angles of the first to third chief rays L _M1 , L _M2 , L _M3 are the f value of the microlens 8a, the plate thickness of the glass substrate 7a in the liquid crystal panel 7, the size of the pixel,
It must match the incident angle of the incident light beam on the microlens array 8 necessary for condensing the light on the pixels, which is determined by the pitch or the like.

On the other hand, the first to third reflected lights L _S1 , L _S2 , L _S3
If the emission angles of these light fluxes coincide with the emission angles of the principal rays L _M1 , L _M2, and L _M3 , of course, the same optical path as the coincident principal ray is traced. It will not collect light. However, since a pixel has an area, not a point, in fact, there is an effective range in the incident angle of the microlens incident light flux for entering the pixel. This effective incident angle is determined by the microlens f value and the size of the pixel. Therefore, it suffices to make the light incident on the pixel within the effective incident angle, and to prevent the light from entering the pixel outside the effective incident angle.

From the above, the first to third chief rays L _M1 ·
The emission angles and spectral distributions of L _M2 and L _M3 and the first to third reflected lights L _S1 , L _S2 and L _S3 are important points. These are calculated theoretically. In FIG. 1, the inclination of the incident light ray I with respect to the y-axis is I _IN (the downward-rightward direction is positive, and hereinafter referred to as parallelism), and each dichroic mirror 4
・ 5 and 6 selective reflection surfaces S ₁・ S ₂・ S ₃ and back surface S _1B
・ The incident angle and refraction angle at S _2B and S _3B are θn as shown in the figure.
(N = 1 to 34).

Further, the first to third chief rays L _M1 · L _M2 ·
The emission angles of L _M3 and the first to third reflected lights L _S1 , L _S2, and L _S3 (upward to the right are positive) are DR _1K , DR _2K , DR _3K, and DGR _1K , respectively.
・ DGR _2K・ DTR _2K , the spectral intensity distribution is I ₁
(λ) ・ I ₂ (λ) ・ I ₃ (λ) ・ I ₄ (λ) ・ I ₅ (λ) ・ I ₆
(λ) [λ: wavelength]. Further, the spectral intensity distribution of the incident light ray I is set to I _IN (λ), and the dichroic mirrors 4 and 5 are used.
・ 6 for each spectral reflectance characteristic, DR ₁ (λ) ・ DR
₂ (λ) and DR ₃ (λ). It is assumed that the dielectric layers 4a, 5a, 6a of the dichroic mirrors 4, 5, 6 and the glass substrates 4b, 5b, 6b do not absorb light, and the refractive index thereof is _ng . Further, it is assumed that the wavelength dependence of the transmittance and the refractive index is so small that it can be ignored. Therefore, the reflectance on the glass surface is obtained by the following equation.

[0060]

[Equation 1]

From the above, the exit angle DR _{1K of} the first chief ray L _M1
The intensity I ₁ (λ) is DR _1K = 90 ° −α ₁ −θ ₁ θ ₁ = α ₁ −I _IN I ₁ (λ) = I _IN (λ) · DR ₁ (λ) Second chief ray L _M2 the exit angle DR _2K, the intensity I ₂ (λ) _{is, DR 2K = (90 ° -α} 1) -θ 13 θ 13 = sin -1 (n g sin θ 12) θ 12 = sin -1 (sin θ 10 / N _g ) + α _1B −α ₁ θ ₁₀ = sin ⁻¹ ( _ng sin θ ₃ ) + 2α ₂ −2α _1B θ ₃ = sin ⁻¹ (sin θ ₁ / n _g ) + α _1B −α ₁ I ₂ (λ ) = I _IN (λ) ・ [1-DR ₁ (λ)] ²・ [1-R
(Θ ₃ , θ ₄ )] × DR ₂ (λ) ・ [1-R (θ ₁₀ , θ ₁₁ )] θ ₄ = sin ⁻¹ ( _ng sin θ ₃ ) θ ₁₁ = sin ⁻¹ (sin θ ₁₀ / _Ng ) The exit angle DR _3K and intensity I ₃ (λ) of the third chief ray L _M3 are DR _3K = (90 ° −α ₁ ) −θ ₂₁ θ ₂₁ = sin ⁻¹ ( _ng sin θ ₂₀ ). θ ₂₀ = sin ^-1 (sin θ ₁₈ / _ng ) + α _1B −α ₁ θ ₁₈ = sin ⁻¹ ( _ng sin θ ₁₆ ) −α _1B + α ₂ θ ₁₆ = sin ⁻¹ (sin θ ₁₄ / _ng ) + Α _2B −α ₂ θ ₁₄ = sin ⁻¹ ( _ng sin θ ₇ ) −2α _2B + 2α ₃ θ ₇ = sin ⁻¹ (sin θ ₅ / n _g ) + α _2B −α ₂ θ ₅ = sin ⁻¹ ( _ng sin θ ₃ ) + α ₂ −α _1B I ₃ (λ) = I _IN (λ) ・ [1-DR ₁ (λ)] ²・ [1-R
(Θ ₃ , θ ₄ )] × [1-DR ₂ (λ)] ² · [1-R (θ ₃₁ ,
θ ₃₂ )] × DR ₃ (λ) · [1-R (θ ₁₄ , θ ₁₅ )] × [1
-R (θ ₁₈ , θ ₁₉ )] θ ₃₁ = sin ^-1 ( _ng sin θ ₃ ) + 2α ₂ -2α _1B θ ₃₂ = sin ^-1 (sin θ ₃₁ / n _g ) θ ₁₅ = sin ^-1 (sin θ ₁₄ / _ng ) θ ₁₉ = sin ⁻¹ (sin θ ₁₈ / _ng ) The emission angle DGR _{1K of} the first reflected light L _S1 and the intensity I ₄ (λ) are DGR _1K = (90 ° −α ₁ ). −θ ₂₃ θ ₂₃ = sin ⁻¹ ( _ng sin θ ₂₂ ) θ ₂₂ = sin ⁻¹ (sin θ ₁ / n _g ) + 2α _1B −2α ₁ I ₄ (λ) = I _IN (λ) · [1- DR ₁ (λ)] ² · R (θ ₃ ,
θ ₄ ) The emission angle DGR _2K and intensity I ₅ (λ) of the second reflected light L _S2 are DGR _2K = (90 ° −α ₁ ) −θ ₂₉ θ ₂₉ = sin ⁻¹ ( _ng sin θ ₂₈ ) θ ₂₈ = sin ^-1 (sin θ ₂₆ / _ng ) + α _1B −α ₁ θ ₂₆ = sin ⁻¹ ( _ng sin θ ₂₄ ) −α _1B + α ₂ θ ₂₄ = sin ⁻¹ (sin θ ₅ / _ng ) + 2α _2B -2α ₂ I ₅ (λ) = I _IN (λ) ・ [1-DR ₁ (λ)] ²・ [1-R
(Θ ₃ , θ ₄ )] × [1-DR ₂ (λ)] ² · R (θ ₇ , θ ₈ ) ×
[1-R (θ ₂₆ , θ ₂₇ )] θ ₈ = sin ⁻¹ ( _ng sin θ ₇ ) θ ₂₇ = sin ⁻¹ (sin θ ₂₆ / _ng ), the exit angle DTR _{2K of} the third reflected light L _S3 , Intensity I ₆ (λ) is DTR _2K = (90 ° −α ₁ ) −θ ₃₄ θ ₃₄ = sin ⁻¹ ( _ng sin θ ₃₃ ) θ ₃₃ = sin ⁻¹ (sin θ ₃₁ / _ng ) + α _1B- α ₁ θ ₃₁ = sin ^-1 ( _ng sin θ ₃ ) + 2α ₂ -2α _1B I ₆ (λ) = I _IN (λ) ・ [1-DR ₁ (λ)] ²・ [1-R
(Θ ₃ , θ ₄ )] × DR ₂ (λ) · R (θ ₁₀ , θ ₁₁ ) × [1-R
(Θ ₃₁ , θ ₃₂ )].

A simulation is carried out based on the above theoretical formulas, and elevation angles α ₁ , α ₂ , α ₃ , α _1B of the front and back surfaces of the dichroic mirrors 3, 4 and 5 capable of avoiding a decrease in color purity are obtained.
α _2B and α _3B were calculated. The simulation was performed under the following conditions to simplify the simulation.

Microlens 8 in liquid crystal panel 7
Effective incident angle to a is −10 ° (design center value) ± 2 °
(Effective angle), 0 ° ± 2 °, 10 ° ± 2 °. The spectral intensity distribution I _IN (λ) of the incident light beam I is shown in FIG.
FIG. 4 shows the spectral reflectance characteristics DR ₁ (λ), DR ₂ (λ), and DR ₃ (λ) of the dichroic mirrors 4, 5, and 6, respectively.
(B) -Figure (c) -Figure (d). That is, it is assumed that the visible light region is roughly divided into A, B, and C regions as shown in the drawing, and the characteristics in each area are flat and the cutoff characteristics are steep. Further, it is assumed that there is no change in the characteristics with respect to the incident angle. The parallelism I _IN of the incident light beam I is 0 °.

As a result of the above simulation, the elevation angles of the dichroic mirrors 3, 4 and 5 are set to, for example, α ₁ = 50 °, α _1B = 52 °, α ₂ = 43.19 °, α
By setting _2B = 38 ° and α ₃ = α _3B = 42.35 °, the first to third chief rays L are generated in each pixel area of the liquid crystal panel 7.
Only _M1・ L _M2・ L _M3 are incident and the first to third reflected light L _S1・
L _S2 and L _S3 will not be incident.

Under these setting conditions, the first to third chief rays L _M1
L _M2 · L _M3, exit angle _{DR 1K · DR 2K · DR 3K} · DGR 1K · DGR 2K · DTR 2K of the first to third reflected light _{L S1 · L S2 · L S3} , the spectral intensity distribution (area A · B・ Calculated for each C) I ₁ (λ)
・ I ₂ (λ) ・ I ₃ (λ) ・ I ₄ (λ) ・ I ₅ (λ) ・ I ₆ (λ)
Is as shown in Table 1 from the above theoretical formula.

[0066]

[Table 1]

Further, FIG. 5 is shown based on the results of Table 1, and as can be seen from the figure, the exit angles of the first to third chief rays L _M1 , L _M2 , L _M3 are each −10. °, 0
The angle becomes 10 °, which coincides with the design center value of the effective incident angle of the microlens required to enter each pixel (Δd ₁ · Δd ₂ · Δd ₃ shown is the range of the effective incident angle of the microlens. , Respectively corresponding to the range of incidence on each of the pixel regions described above in FIG.

On the other hand, the first to third reflected lights L _S1 , L _S2 , L _S3
The emission angles of -18.7 °, 18.2 °, 17.9 °
Therefore, it can be seen that none of them is within Δd ₁ · Δd ₂ · Δd ₃ . Note that the intensity characteristics for the areas A, B, and C shown in FIG.
It can be said that the smaller the respective intensities in the region, the higher the color purity of the color light having the wavelength region of the A region.

From the above, according to the configuration of this embodiment in which the elevation angles are set for the dichroic mirrors 3, 4, and 5 as described above, the three color lights incident on the pixel are ~ The third chief rays L _M1 , L _M2 , L _M3 only and not affected by the first to third reflected lights L _S1 , L _S2 , L _{S3 that} cause color mixing, and thus the color light with extremely high color purity Can be emitted to the liquid crystal panel 7.

Next, in the present embodiment, as described above, the incident light beam I is reflected by the first, second and third dichroic mirrors 3, 4 and 5 in the order of green, blue and red.・ Explain the reason why 4 and 5 are arranged.

In determining such an arrangement, white light is converted into red (R), green (G), and three dichroic mirrors.
An experiment was conducted to determine which combination of R, G and B lights mixed with each other in the case of spectrally splitting into blue (B) color light, which combination resulted in the largest decrease in color purity.

The conditions of the experiment at this time are as follows.

The R, G, B lights used are those actually commercialized as a three-panel liquid crystal projector,
When used as R, G, and B lights of a liquid crystal projector, it is a light beam having a purity that poses no practical problems. The magnitude of the decrease in color purity depends on the color difference Δu'v 'obtained by the following equation.
Judgment according to the size of. [Delta] u'v '= ^{_{[(u 1 -u 2) 2 +}} (v 1 -v 2) 2 ]
^1/2 u ₁ , ₂ = 4x ₁ , ₂ / (-2x ₁ , ₂ + 12y ₁ , _{2
+3) v 1, 2 = 9y} 1, 2 / (- 2x 1, 2 + 12y 1, 2
+3) x ₁ , y ₁ : Chromaticity before color mixing x ₂ , y ₂ : Chromaticity after color mixing When the color mixing means tries to mix G light with R light, for example, G light is transmitted flat over the entire visible range. An ND filter having an index is interposed, and the light transmitted through this filter is combined with the R light as mixed color light. The transmittance at this time is the color mixture. The measurement points are 40-inch (4: 3 screen) 9-point average chromaticity x, y projected by the projection lens.

As a result of performing the experiment under the above conditions, the change in the color difference Δu'v 'with respect to the color mixture ratio is as shown in FIG. In the figure, for example, “R ← G” is displayed when R light is mixed with G light, and “R ← G + B” is displayed.
This means a case where R light is mixed with G light and B light. Also,
The larger Δu′v ′, the larger the decrease in color purity. From the above, the following can be concluded.

R, B, and G are in the order of weakness in color mixing (the decrease in color purity increases even with a slight color mixing).

The mixing of the G light and the mixing of the R light with the B light is considerably wider than the other cases.

The order in which mixed color light causes the problem to increase is
G, B and R.

On the other hand, as can be seen from FIG.
From the relative intensities of the respective regions in the third chief ray L _M1 , L _M2, and L _M3 , the order of the rays having higher color purity is the third chief ray L _M3.
The second chief ray L _M2 and the first chief ray L _M1 are in this order. Therefore,
From the result that the order weak to color mixture is R, B, G, the third chief ray L _M3 is R light, the second chief ray L _M2 is B light, and the first chief ray L _M1 is G. It can be said that it is best to use light.

Based on such a conclusion, in the present embodiment,
As described above, the first dichroic mirror 4 located on the white light source 1 side selectively reflects green color light, and the second dichroic mirror 5 located in the middle selectively reflects blue color light. The third dichroic mirror 6 farthest from the unit 1 is configured to reflect the red color light. As a result, the projection type color liquid crystal display device of the present embodiment can display a color image with higher color purity on the screen 10.

[Embodiment 2] The following will describe another embodiment of the present invention in reference to FIGS. 7 and 8. For convenience of explanation, members having the same functions as the members shown in the first embodiment will be designated by the same reference numerals and detailed description thereof will be omitted. The same applies to other embodiments described later.

In this embodiment, as shown in FIG.
The dichroic mirrors 4, 5, 6 are arranged so that the emission angle of the second reflected light L _S2 is substantially the same as the emission angle of the third chief ray L _M3.
Selective reflection surface S ₁ · S ₂ · S ₃ and back surface S _1B ·
S _2B / S _3B elevation angles α ₁ / α ₂ / α ₃ / α _1B / α _2B / α
_3B is set.

That is, in the second reflected light L _S2 , the wavelength range of selective reflection at the first dichroic mirror 4 and the wavelength range of selective reflection at the second dichroic mirror 5 are sequentially removed from the visible light region. This is a light ray, which is a light ray that is transmitted through the second dichroic mirror 5 and then reflected by the third dichroic mirror 6, that is, light in the same wavelength range as the third chief ray L _M3 . Therefore, this second reflected light L _S2
Is added to the third chief ray L _M3 , the use efficiency of light is increased without causing a decrease in color purity.

As a result of the simulation based on the theoretical formula in the first embodiment having such a configuration, the elevation angles of the dichroic mirrors 4, 5 and 6 are, for example, α.
₁ = 50 °, α _1B = 52 °, α ₂ = 43.19 °, α _2B =
It is set to α ₃ = α _3B = 40.45 °.

At this time, the first to third chief rays L _M1 · L _M2 ·
The emission angles and the spectral intensity distributions of L _M3 , the first to third reflected lights L _S1 , L _S2, and L _S3 are as shown in Table 2 from the above theoretical formula.

[0085]

[Table 2]

Further, FIG. 8 is shown based on the result of Table 2, and as can be seen from the figure, the exit angles of the first to third chief rays L _M1 , L _M2 , L _M3 are respectively −10. °, 0
The angle becomes 10 °, which coincides with the design center value of the effective incident angle of the microlens.

On the other hand, the emission angles of the first reflected light L _S1 and the third reflected light L _S3 are -18.7 ° and 18.0 °, respectively.
It does not exist in Δd ₁ · Δd ₂ · Δd ₃ . Then, the emission angle of the second reflected light L _S2 becomes 10 °, and the third chief ray L _M3
Matches

As a result, also in this embodiment, the color light of the luminous flux entering each pixel of the liquid crystal panel 7 has high color purity and the light utilization efficiency is improved.

As shown in FIG. 8, among the light rays obtained by adding the second reflected light L _S2 to the first chief ray L _M1 , the second chief ray L _M2 , and the third chief ray L _M3 , The order of the rays of increasing color purity is the third principal ray L _M3 (+ second
The order is the reflected light L _S2 ), the second chief ray L _M2, and the first chief ray L _M1 . Therefore, the order that is weak to the above-mentioned color mixture is R ・ B ・
From the result of G, the third principal ray L _{M3 is changed} to R light, the second principal ray L _{M2 is changed} to B ray, and the first principal ray L _{M1 is changed} to G ray in the present embodiment. The first dichroic mirror 4 selectively reflects green color light, the second dichroic mirror 5 selectively reflects blue color light, and the third dichroic mirror 6 reflects red color light, whereby the color purity is further improved. It is possible to display high-quality color images.

[Third Embodiment] The following description will explain still another embodiment of the present invention with reference to FIGS. 9 and 10.

In the present embodiment, as in the case of Embodiment 2, on the assumption that the second reflected light L _S2 is added to the third chief ray L _M3 , as shown in FIG. In addition to L _S3 to the second chief ray L _M2 , that is, in the dichroic mirrors 4, 5, and 6 so that each exit angle of the third reflected light L _S3 substantially matches the exit angle of the second chief ray L _M2 . selective reflection surface S ₁ · S ₂ · S ₃ and the back S _1B · S _2B · S each elevation _{α 1 · α 2 · α 3} · α 1B · α 2B · α 3B and _3B are set.

As in the second embodiment, by adding the second reflected light L _S2 to the third chief ray L _M3 , the light utilization efficiency can be improved without lowering the color purity. The same applies to the addition of the third reflected light L _S3 to the second chief ray L _M2 . That is, since the third reflected light L _S3 is light branched from the second chief ray L _M2 , its wavelength range is the same.

The third reflected light L _S3 is reflected by the back surface S _1B of the first dichroic mirror 4 and the second dichroic mirror 5.
Since the reflection occurs between the selective reflection surface S _{2 of} the second dichroic mirror 5 and the second principal ray L _M2 reflected by the selective reflection surface S ₂ of the same second dichroic mirror 5, the above-mentioned rear surface S _{1B is used.} And the selective reflection surface S ₂ are parallel to each other.

At this time, the emission angle of the first reflected light L _S1 internally reflected by the back surface S _1B of the first dichroic mirror 4 is also the same as that of the second chief ray L _M2, and the first reflected light L _S1 is also the first reflected light L _S1 . 2 will be added to the chief ray L _M2 . Therefore, although a slight decrease in color purity occurs, compared to the comparative example described later,
Good color purity is maintained. Therefore, in this embodiment, the use efficiency of each color light is improved as much as possible by using the first to third reflected lights L _S1 , L _S2, and L _S3 while minimizing the decrease in color purity.

If an example of a concrete structure at this time is shown,
According to the simulation based on the theoretical formula in the first embodiment, the elevation angles of the dichroic mirrors 4, 5 and 6 are, for example, α ₁ = 50 °, α _1B = α ₂ = 47.33 °, α
_2B = α ₃ = α _3B = 44.38 °.

At this time, the first to third chief rays L _M1 · L _M2 ·
The emission angles and the spectral intensity distributions of L _M3 and the first to third reflected lights L _S1 , L _S2, and L _S3 are as shown in Table 3 from the above theoretical formula.

[0097]

[Table 3]

Further, FIG. 10 is shown based on the result of Table 3, and as can be seen from the figure, the exit angles of the first to third chief rays L _M1 , L _M2 , L _M3 are respectively −10. °, 0
The angle becomes 10 °, which coincides with the design center value of the effective incident angle of the microlens.

On the other hand, the exit angles of the first and third reflected lights L _S1 and L _S3 are 0 °, respectively, and coincide with the second chief ray L _M2 .
The emission angle of the second reflected light L _S2 is 10 °, which coincides with the third chief ray L _M3 .

According to the configuration of this embodiment, the three color lights incident on each pixel in the liquid crystal panel 7 are the first chief ray L _M1 , the second chief ray L _M2 + the first reflected light L _S1 + the third chief ray L _M2 . Reflected light L
_S3 becomes the third principal ray L _M3 + second reflected light L _S2 , the color purity of the color light of the first principal ray L _M1 is high, the light utilization efficiency of the second principal ray L _M2 is improved, and It is possible to improve the light utilization efficiency while increasing the color purity of the three chief rays L _M3 .

In this embodiment, as can be seen from FIG. 10, the ray having a large color mixture is the second principal ray L _M2 . Moreover, of the first to third reflected lights, the first intensity is the largest.
The reflected light L _S1 is added. Therefore, it can be said that it is optimal to use the second chief ray L _M2 as the G light, because the above-mentioned G light is strong in color mixing. On the other hand, the third chief ray L _M3 is preferably R light in the same way as in the first and second embodiments. At this time, it is the light flux of R that mixes with the second chief ray L _M2 of G light, and in particular, from the above result that G light is the strongest against the color mixture of R light, the second chief ray L of G light is The decrease in color purity of _M2 is minimized, which also results in the optimum configuration.
At this time, the first chief ray L _M1 becomes B light.

Therefore, in this embodiment, the first dichroic mirror 4 selectively reflects blue color light, the second dichroic mirror 5 selectively reflects green color light, and the third dichroic mirror 6 reflects red color light. It has a mirror configuration.

Comparative Example As shown in FIG. 14 above, the dielectric layer 4 was formed on each of the parallel glass substrates 4b ′, 5b ′, 6b ′.
The structure of three dichroic mirrors 4 ', 5', 6'formed by providing a ', 5a', 6a 'is taken as a comparative example, and simulation results based on the above theoretical formula in this structure are shown.

In this case, the first to third chief rays L _M1 · L _M2 ·
Α ₁ = 50 ° (= α _1B ), α ₂ = 45 in order that L _M3 has the emission angles of −10 °, 0 °, and 10 °, respectively.
This is when ° (= α _2B ), α ₃ = 40 ° (= α _3B ).
At this time, the first to third chief rays L _M1 · L _M2 · L _M3 , the first to third
The output angles and intensity distributions of the third reflected light L _S1 , L _S2 , L _S3 are
From the above theoretical formula, Table 4 is obtained.

[0105]

[Table 4]

Further, FIG. 11 is an illustration based on the results of Table 4, and as is apparent from FIG.
Since the reflected lights L _S1 , L _S2, and L _S3 respectively match the first to third chief rays L _M1 , L _M2, and L _M3 , each chief ray becomes a color light with considerably poor color purity and is emitted from the liquid crystal panel. To do.

Next, the selective reflection surfaces S ₁ , S ₂ , S ₃ and the back surfaces S _1B , S _2B , S of the first to third dichroic mirrors 4, 5, and 6 in each of the above-described first, second, and third embodiments. Further consideration will be given to the variation of the elevation angle of _3B and the variation of the parallelism in the incident ray I. First, the elevation angle α ₁ · α ₂ ·
When α ₃ · α _1B · α _2B · α _3B change by Δt degrees, for example, in the configuration of the third embodiment, the first to third chief rays L _M1 · L _M2 · L _M3 , the first to third Reflected light L _S1・ L _S2・
L _S3 changes as shown in FIG.

By the way, the angles for these light rays to enter the pixel area of the liquid crystal panel 7 are as described above.
Since there is an effective incident angle, some fluctuation is within the allowable range. For example, if the range of the effective incident angle is ± 2 ° as in the above-mentioned simulation, Δd
_{Since 1 to} Δd ₃ is in the effective incident angle range, if the variation Δt of each elevation angle is within ± 1 °, the incident angle is set. As a practical matter, in the glass substrate processing, the accuracy with respect to the inclination can be sufficiently 3 '(= 0.05 °), so naturally, there is no variation exceeding ± 1 °. As in the example, it is practically possible to realize a configuration in which the front and back surfaces of the plate-shaped glass substrates 4b and 5b forming the dichroic mirrors 4 and 5 are set in a predetermined non-parallel state to control reflected light. is there.

On the other hand, considering the incident light ray I, FIG.
In the single plate method shown in FIG. 3, the outgoing angle (tilt) of each light ray reflected from each dichroic mirror 4, 5, 6 is very important. In other words, dichroic mirror 4
The parallelism I _IN in the light ray I incident on 5 and 6 becomes important. That is, the first to third chief rays L _M1 · L _M2 · L
_{If the} incident light beam I fluctuates to the _{extent that} the exit angles of _M3 are the same, this single-plate method will not work in principle.

Therefore, FIG. 13 shows the results of the examination of the parallelism range of the incident light ray I where such a phenomenon begins to occur in the structure of Example 3 and the structure of the comparative example. When the parallelism range of the incident light ray I is 0 ° ± 5 °, the first chief ray L _M1 is −15 ° to −5 in the comparative example shown in FIG.
, The second chief ray L _M2 has an emission angle of −5 ° to 5 °, and the third chief ray L _M3 has an emission angle of 5 ° to 15 °.
_M1 and the second chief ray L _M2 have an exit angle of −5 ° and a second chief ray L.
_M2 and the third chief ray L _M3 coincide with each other at an exit angle of 5 °.

On the other hand, in the configuration of the third embodiment shown in FIG. 9A, the first chief ray L _M1 is −15 ° to −5 °,
The second chief ray L _M2 is −4.32 ° to 4.48 °, and the third chief ray L is
_M3 is 6.05 ° to 14.17 °, and there is no exit angle where the principal rays coincide with each other. This means that the variation of the parallelism of the incident ray I is stronger than that of the comparative example.

In each of the above embodiments, desired exit angles of the first to third chief rays L _M1 , L _M2 , L _M3 are −10 °, 0 °,
Although the case of 10 ° is given as an example, the elevation angle of each dichroic mirror may be set based on the above-described theoretical formula with the same idea even if the desired emission angle changes. Also,
It is also possible to use a total reflection mirror instead of the third dichroic mirror 6 in each of the above embodiments.
Further, in each of the above-described embodiments, the liquid crystal panel 7 having a simple matrix drive has been taken as an example, but the present invention can be applied to a device having another configuration adopting active matrix drive, for example.

[0113]

As described above, in the projection type color liquid crystal display device according to claim 1 of the present invention, in order to divide the light from the white light source into a plurality of light fluxes of different wavelength bands, a specific wavelength band is formed on the surface. A plurality of plate-like light beam splitting means each having a selective reflection surface for reflecting the above-mentioned light, for example, a light beam splitting means comprising a dichroic mirror as described in claim 2 is provided, and the plurality of split light beams are divided into respective wavelength ranges. In a projection type color liquid crystal display device comprising a microlens array for converging to a corresponding pixel area of a liquid crystal panel, and a projection means for projecting a plurality of light beams modulated through the liquid crystal panel, at least one of the light beam splittings. The front surface and the back surface of the means are configured to be non-parallel to each other.

As a result, the chief ray reflected on the front surface is prevented from being mixed with the reflected light which is internally reflected and emitted on the back surface, so that it is possible to display an image with higher color purity. Play.

The projection type color liquid crystal display device according to a third aspect is the device according to the second aspect, wherein the inclination angles of the front and back surfaces of the first and second dichroic mirrors and the front surface of the reflection mirror are different from each other. is there.

As a result, the first and second reflected lights that are internally reflected and emitted on the respective back surfaces of the first and second dichroic mirrors, and the back surface of the first dichroic mirror and the front surface of the second dichroic mirror are sequentially arranged. The third reflected light that is reflected and emitted does not mix with any of the first to third chief rays that are respectively reflected on the surface of each dichroic mirror and the surface of the reflection mirror, so that a color image display with high color purity is performed. There is an effect that can be.

A projection type color liquid crystal display device according to a fourth aspect is the device according to the second aspect, wherein the inclination angles of the front surface and the back surface of the first and second dichroic mirrors are different from each other and the second dichroic mirror has the same inclination angle. The inclination angles of the back surface and the surface of the reflection mirror are the same.

As a result, the emission directions of the first and third reflected lights do not coincide with any of the first to third chief rays, and
The emission direction of the second reflected light in the same wavelength range as the third chief ray coincides with the third chief ray. As a result, the color purity is further increased, and the light utilization efficiency can be improved.

A projection type color liquid crystal display device according to a fifth aspect is the device according to the third or fourth aspect, wherein the first dichroic mirror selectively reflects the green color light and the second dichroic mirror emits the blue color light. The configuration is such that selective reflection is performed sequentially.

As described above, the order of division of each color light is from the first to the first.
By setting it according to the spectral characteristic of the third chief ray,
There is an effect that the color purity of each color is minimized and color display with high color purity can be performed.

According to a sixth aspect of the present invention, there is provided the projection type color liquid crystal display device according to the second aspect, wherein the front surface and the back surface of the first dichroic mirror have different inclination angles, and the front surface and the back surface of the second dichroic mirror are different from each other. And the back surface of the first dichroic mirror and the front surface of the second dichroic mirror have the same tilt angle, and the back surface of the second dichroic mirror and the surface of the reflection mirror are tilted. The corners have the same configuration.

As a result, the emission direction of the second reflected light in the same wavelength range as the third principal ray coincides with the third principal ray, and
The third reflected light in the same wavelength range as the second chief ray and the first reflected light coincide with the second chief ray. As a result, there is an effect that it is possible to further improve the light use efficiency while suppressing the decrease in color purity as much as possible.

A projection type color liquid crystal display device according to a seventh aspect is the device according to the sixth aspect, wherein the first dichroic mirror selectively reflects blue color light and the second dichroic mirror selectively reflects green color light. The configuration is set to do so.

As a result, even if the structure of claim 6 is presupposed, the second chief ray mixed with the first reflected light L _S1 having a different wavelength range is made into green colored light, and the red colored light which is weak in color mixing is made into the first colored light. By using three chief rays, it is possible to suppress the deterioration of the overall color purity as much as possible and to further improve the light utilization efficiency.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a main configuration of a projection type color liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an overall configuration of the liquid crystal display device.

FIG. 3 is a schematic sectional view showing a liquid crystal panel and a microlens array in the liquid crystal display device.

FIG. 4 is a graph showing the spectral distribution of white light and the spectral reflection characteristics of each dichroic mirror set when calculating the emission angles of the reflected light at the first to third dichroic mirrors in the liquid crystal display device.

FIG. 5 is an explanatory diagram showing an example of a simulation result of reflected light from first to third dichroic mirrors in the liquid crystal display device.

FIG. 6 is a graph in which changes in color difference due to color mixture of R, G, and B color lights are actually measured.

FIG. 7 is a schematic cross-sectional view showing the main configuration of a projection type color liquid crystal display device according to another embodiment of the present invention.

8A to 8C are first to third parts of the liquid crystal display device shown in FIG.
It is explanatory drawing which shows an example of the simulation result of the reflected light in a dichroic mirror.

FIG. 9 is a schematic cross-sectional view showing a main configuration of a projection type color liquid crystal display device according to still another embodiment of the present invention.

10 is an explanatory diagram showing an example of a simulation result of reflected light from the first to third dichroic mirrors in the liquid crystal display device shown in FIG.

FIG. 11 is an explanatory diagram showing a simulation result of reflected light from the first to third dichroic mirrors in the conventional liquid crystal display device as a comparative example.

FIG. 12 is a graph showing a change in reflected light emission angle with respect to a change in elevation angle in a dichroic mirror.

FIG. 13 is an explanatory diagram showing a variation range of a reflected light emission angle at the dichroic mirror when the parallelism of incident light rays is 0 ° ± 5 °.

FIG. 14 is a schematic sectional view showing a configuration of a main part of a conventional projection type color liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 White light source 4 1st dichroic mirror (beam splitting means) 5 2nd dichroic mirror (beam splitting means) 6 3rd dichroic mirror (reflection mirror) 7 Liquid crystal panel 8 Micro lens array 9 Projection optical system (projection means) L _M1 1 principal ray L _M2 2nd principal ray L _M3 3rd principal ray L _S1 1st reflected light L _S2 2nd reflected light L _S3 3rd reflected light I Incident ray S ₁ · S ₂ · S ₃ Selective reflection surface (surface) Back of S _1B , S _2B , S _3B

Claims (7)

[Claims] 1. A plurality of plate-like light beam splitting means each provided with a selective reflection surface for reflecting light in a specific wavelength region on a surface thereof so as to divide the light from a white light source into a plurality of light beams in different wavelength regions. Projection type including a microlens array that converges a plurality of divided light beams into corresponding pixel regions of a liquid crystal panel for each wavelength range, and a projection unit that projects the plurality of light beams modulated through the liquid crystal panel In the color liquid crystal display device, the front surface and the back surface of at least one of the light beam splitting means are
A projection type color liquid crystal display device, characterized in that they are formed non-parallel to each other. 2. Each of the light beam splitting means comprises two first and second dichroic mirrors having different spectral characteristics,
In the optical path of the incident light from the white light source, these first and second
A feature that a dichroic mirror and a reflecting mirror having a reflecting surface for reflecting light transmitted through both dichroic mirrors are sequentially arranged with a predetermined inclination angle with respect to an incident light beam from a white light source. The projection type color liquid crystal display device according to claim 1. 3. The projection type color liquid crystal display device according to claim 2, wherein the front and back surfaces of the first and second dichroic mirrors and the front surface of the reflection mirror have different inclination angles. 4. The tilt angles of the front and back surfaces of the first and second dichroic mirrors are different from each other, and the tilt angles of the back surface of the second dichroic mirror and the front surface of the reflection mirror are the same. The projection type color liquid crystal display device according to claim 2. 5. The setting according to claim 3, wherein the first dichroic mirror selectively reflects green color light and the second dichroic mirror selectively reflects blue color light. Projection type color liquid crystal display device. 6. The front and back surfaces of the first dichroic mirror have different tilt angles, the front and back surfaces of the second dichroic mirror have different tilt angles, and the back surface and the second surface of the first dichroic mirror are different from each other. The projection color according to claim 2, wherein the dichroic mirror has the same inclination angle with respect to the front surface, and the back surface of the second dichroic mirror has the same inclination angle with respect to the front surface of the reflection mirror. Liquid crystal display device. 7. The projection type apparatus according to claim 6, wherein the first dichroic mirror selectively reflects blue color light and the second dichroic mirror selectively reflects green color light. Color liquid crystal display device.