JP2001188300A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive projection-type image display device in which a decrease in light amount due to reflection at an interface between a prismatic optical element and air is small. SOLUTION: A light source 101, at least one polarization separation element 105, a color separation element 107, at least two reflection type liquid crystal display elements 109R and 109G, a color synthesis element 107, and a projection lens 113 are provided. At least two optical elements of the color separating element 107, the color synthesizing element 107, and the at least one polarization separating element are formed of prisms and are optically integrated.

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 using a reflection type liquid crystal display element, and more particularly to a projection type image display device applied to a large screen projection type TV system or information display system. About.

[0002]

2. Description of the Related Art A projection type image display device using a liquid crystal display device (hereinafter referred to as a "projection type liquid crystal display device") has a color reproduction range which is smaller than that of a projection type display device using a cathode ray tube (CRT). Is large, compact and lightweight, and is not affected by geomagnetism, so convergence adjustment is not required.
Has very good features such as. The liquid crystal display element used in this projection type liquid crystal display device includes a "transmission type" for displaying using light transmitted through the liquid crystal display element and a "reflection type" for displaying using light reflected by the liquid crystal display element.
There is. Among these, the reflection type projection type liquid crystal display device has an advantage that the effective area of the pixel is larger and the display luminance can be increased as compared with the transmission type liquid crystal display device, and therefore, the reflection type liquid crystal display device has been increasingly used recently.

[0003] The configuration and operation of a conventional reflective projection type liquid crystal image display device 700 will be described with reference to FIG.

[0004] The projection type liquid crystal display device 700 has, as basic components, a light source 101, a polarizing plate 103, a polarizing beam splitter (hereinafter abbreviated as “PBS”) 105, polarization control elements 104 and 111, Dichroic prism 107 and reflective liquid crystal display elements 109R, 109G
And 109B, and a projection lens 113.
The PBS 105 functions as a polarization separation element, and the combination of the polarization control element 104 and the PBS 105, and the dichroic prism 107 each function as a color separation element, and the dichroic prism 107 and the PBS 1
The combination of the polarization control element 05 and the polarization control element 111 functions as a color combining element. The projection-type liquid crystal display device 700 further has a glass cube 110 for adjusting the optical path length and a polarizing plate 112 for improving the contrast.

The light source 101 emits a non-polarized white light beam. This white light beam is converted into substantially parallel light by the parabolic mirror 102, and then enters the polarizing plate 103. The polarizing plate 103 is disposed so as to transmit only a light beam whose polarization direction is perpendicular to the paper surface, and the light beam transmitted through the polarizing plate 103 is
The light enters the polarization control element 104.

The polarization control element 104 has a characteristic of rotating the polarization direction of only the G light component among the three primary colors of light, red, green, and blue (hereinafter, R, G, and B) by 90 degrees. Have. Here, the polarization direction of the G light component transmitted through the polarizing plate 103 and having a polarization direction perpendicular to the paper surface is converted into a direction parallel to the paper surface. As the polarization control element 104, for example, a polarization control element disclosed in US Pat. No. 5,751,384 can be used. US Patent 5,7
The polarization control element disclosed in Japanese Patent No. 51,384 has a structure in which a plurality of wavelength plates are stacked by changing the arrangement angle of each optical axis (slow axis), and only light in a specific wavelength range is provided. Has the function of rotating the polarization direction of

The light beam transmitted through the polarization control element 104 enters a PBS 105 formed of a glass prism. The PBS 105 has a polarization separation surface 106
Reflects the polarization component (polarization direction perpendicular to the paper surface) and the P polarization component
(Polarization direction parallel to the paper) is transmitted. Accordingly, the R light component and the B light component of the light flux that has passed through the polarization control element 104 and entered the PBS 105 are separated by the polarization separation surface 10.
The G light component is reflected by 6 and enters the dichroic prism 107, and the G light component passes through the polarization splitting surface 106 and enters the glass cube 110.

[0008] The dichroic prism 107 reflects the B light component and transmits the R light component on its color separation surface (here, the B light reflection surface) 108B. Color separation surface 108B
The B light component reflected by the light enters the reflection type liquid crystal display element 109B, and the R light component transmitted through the color separation surface 108B enters the reflection type liquid crystal display element 109R.

The reflection type liquid crystal display elements 109B and 109
R is the image signal (B component and R
The B light component and the R light component are modulated and reflected according to the (component). Reflective liquid crystal display elements 109B and 109R
(The same applies to 109G described later) has a plurality of picture element regions arranged in a matrix, and changes the alignment state of the liquid crystal layer in each of the picture element regions according to an input image signal. The polarization direction of the light beam incident on the pixel region having the highest luminance (bright state) is rotated by 90 degrees, and the light beam incident on the pixel region having the lowest luminance (dark state) is not changed but the respective light beams are changed. reflect.

[0010] Reflective liquid crystal display elements 109B and 109
The B light component and the R light component reflected from the pixel region in the dark state of R pass through the dichroic prism 107 in the reverse direction to that described above, with the polarization directions unchanged and in the S polarization state. Are reflected by the polarization splitting surface 106 of the PBS 105, and finally travel to the light source 101.

On the other hand, the B light component and the R light component reflected from the bright picture element regions of the reflection type liquid crystal display elements 109B and 109R are incident on the dichroic prism 107 in the P polarization state and are synthesized. Dichroic prism 1
07, the B light component and the R light component are PB
The polarization control element 1 that has passed through the polarization separation surface 106 of S105
It is incident on 11.

The G light component transmitted through the polarization splitting surface 106 of the PBS 105 passes through the glass cube 110 provided to make the optical path lengths coincide with the R light component and the B light component described above, and the reflective liquid crystal display. The light enters the element 109G.

The reflection type liquid crystal display element 109G, like the reflection type liquid crystal display elements 109B and 109R, changes the polarization direction of a light beam incident on a pixel region having the highest luminance (bright state) by 90 degrees.
Each light beam is reflected without changing the polarization direction of the light beam incident on the picture element region having the lowest luminance (dark state). Since the G light component incident on the reflective liquid crystal display element 109G is in the P-polarized state, the G light component incident on the pixel region having the highest luminance (bright state) is changed to the S-polarized state by the reflective liquid crystal display element 109G. Converted and reflected, PBS10
5 is incident.

The G light component in the S-polarized state is reflected by the polarization splitting surface 106, is combined with the R light component and the B light component, and enters the polarization control element 111. The polarization control element 111 rotates only the polarization direction of the G light component by 90 degrees, converts the S polarization state to the P polarization state, and aligns the same polarization direction with the R light component and the B light component.

The R light component, the B light component and the G light component which have been color-combined as described above and whose polarization directions have been aligned are transmitted through a polarizing plate 112 provided for improving a contrast ratio, and then projected onto a projection lens. The image is projected on a screen (not shown) by 113. Thus, the projection type liquid crystal display device projects and displays an image corresponding to the image signal input to the reflection type liquid crystal display element.

Next, the configuration and operation of another conventional reflection type projection type liquid crystal image display device 800 will be described with reference to FIG. In the following drawings, components having substantially the same functions as those of the projection type liquid crystal display device shown in FIG. 7 are denoted by the same reference numerals, and the description thereof will be omitted. It should be noted that the PBSs 105a, 105b, 10
Reference numerals 5c and 105d denote respective polarization separation surfaces 1 similarly to the PBS 105 of the projection type liquid crystal display device of FIG.
S at 06a, 106b, 106c and 106d
Reflects polarized light (polarization direction perpendicular to the paper surface) and transmits P-polarized light (polarization direction parallel to the paper surface). In addition, the polarization control element 10
4 and 111 rotate the polarization direction by 90 degrees only for the G light component, and the polarization control elements 114 and 115 rotate the polarization direction by 90 degrees only for the B light component.

The light is emitted from a light source 101 and is parabolic mirror 102
The unpolarized white luminous flux converted into substantially parallel light by the polarizing plate 103
Incident on. The polarizing plate 103 in the projection type liquid crystal display device 800 is arranged so as to transmit only a light beam in a polarization direction (P polarization) parallel to the paper surface. Polarizing plate 10
The P-polarized light that has passed through No. 3 is incident on the PBS 105 a after only the G light component is converted into S-polarized light by the polarization control element 104.

S of the light beam incident on the PBS 105a
The G light component in the polarization state is converted into PB light by the polarization separation surface 106a.
The R light component and the B light component that are reflected toward S105b and are in the P polarization state pass through the polarization separation surface 106a and pass through the PBS1.
It is emitted toward 05c.

The G light component incident on the PBS 105b is reflected by the polarization splitting surface 106b, and is reflected by the reflection type liquid crystal display device 10.
It is incident on 9G. The G light component reflected in the bright pixel region of the reflective liquid crystal display element 109G has a polarization direction of 9
The light is rotated by 0 degrees to become P-polarized light, and the polarization splitting surface 106b of the PBS 105b and the polarization splitting surface 106d of the PBS 105d are rotated.
After being rotated by the polarization control element 111 and converted into S-polarized light, the light passes through the polarizing plate 112 and the projection lens 113 and is projected on a screen (not shown).

On the other hand, the polarization splitting surface 106 of the PBS 105a
After the R light component and the B light component (both in the P polarization state) transmitted through the polarization control element 114, the polarization direction of only the B light component is rotated by the polarization control element 114 to be in the S polarization state.
5c.

Of the R and B light components incident on the PBS 105c, the B light component (S-polarized light)
The R light component is reflected by 6c and travels to the reflection type liquid crystal display element 109B, passes through the polarization splitting surface 106c, and travels to the reflection type liquid crystal display element 109R.

The B light component reflected by the picture element region in the bright state of the reflection type liquid crystal display element 109B becomes a P-polarized light by rotating the polarization direction by 90 degrees, and the picture element in the light state of the reflection type liquid crystal display element 109R becomes P polarization. The R light component reflected by the region has its polarization direction rotated by 90 degrees to become S-polarized light. In the reflection type liquid crystal display elements 109R and 109B, the R light component and the B light component that have not been rotated in the polarization direction return to the light source 101 by respectively going back the above-described optical path, and the rotated R light component and the B light component have been rotated. Is emitted to the polarization control element 115 side.

Of the R light component and the B light component incident on the polarization control element 115, only the B light component is rotated by 90 degrees in the polarization direction, becomes the same S-polarized light as the R light component, and enters the PBS 105d. The B light component and the R light component in the S-polarized state that have entered the PBS 105d are reflected by the polarization splitting surface 106d, and are polarized by the polarization control element 111, the polarizing plate 112, and the projection lens 1.
13 and is projected on a screen (not shown).

As in the above-mentioned projection type liquid crystal display devices 700 and 800, in a conventional reflection type projection type liquid crystal display device, PBS is generally used to separate incident light and reflected light to the liquid crystal display element. It is used for The PBS is a prism-shaped optical element, and transmits or reflects light on a polarization separation surface according to the polarization direction of an incident light beam. In addition, by using the PBS in combination with a polarization control optical element that rotates the polarization direction of a light component in a specific wavelength range, it is possible to perform color separation and color synthesis together with polarization separation.

[0025]

As described above, FIG.
And the conventional projection type liquid crystal display devices 700 and 800 shown in FIG. 8 are provided with a plurality of prismatic optical elements such as a PBS and a dichroic prism, and the luminous flux emitted from the light source is After passing through the interface between air and air many times, it is projected on the screen.
The change in the refractive index at the interface between the prism-shaped optical element and air (hereinafter also referred to as the “air interface”) is large, and the amount of light decreases each time the light passes through the interface due to the reflection caused by the difference in the refractive index. As a result, the conventional projection type liquid crystal display device having the above-described configuration has a problem that the display luminance is reduced.

Conventionally, in order to suppress the phenomenon of the amount of light due to the reflection at the air interface, the surface of each prismatic optical element forming the interface with air on the optical path has an AR (An).
A method of applying a reflection (anti-reflection) coat has sometimes been adopted. However, the AR coating treatment is expensive, and it is necessary to perform the AR treatment by the number of air interfaces, which causes an increase in cost.

The present invention has been made to solve the above-mentioned problems, and provides an inexpensive projection-type image display device in which the amount of light is not reduced by reflection at the interface between a prismatic optical element and air. The purpose is to do.

[0028]

According to the present invention, there is provided an image display apparatus comprising: a light source for emitting a light beam; and at least one polarized light for separating the light beam emitted from the light source into at least two light beams having different polarization directions. A separation element, a color separation element that separates the light beam emitted from the light source into at least two color light beams having different colors, and at least two reflective liquid crystal displays that respectively modulate the at least two color light beams Element and the reflective liquid crystal display element,
An image display device comprising: a color synthesizing element that synthesizes the at least two color light beams that are modulated and reflected; and a projection lens that projects a light beam that is synthesized by the color synthesizing element, wherein the color separation element The at least two optical elements of the color combining element and the at least one polarization splitting element are formed of prisms and are optically integrated, thereby achieving the above object. .

[0029] The at least two optical elements formed from a prism may be a single optical component integrally formed, or the at least two optical elements formed from a prism may be an optical element. They may be adhered to each other in a state where proper alignment is achieved.

It is preferable that the color separation element be configured to function also as the color synthesis element.

The operation of the present invention will be described below.

At least two optical elements provided in the image display device of the present invention, including at least one of a color separation element and a color synthesis element and a polarization separation element, are formed of prisms, and It is integrated into. Therefore, in the optical system of the projection type image display device,
Since the number of air interfaces through which the light beam emitted from the light source passes is smaller than in the conventional configuration, a decrease in the amount of light due to reflection at the air interface is suppressed. As a result, the projection-type image display device of the present invention can display a bright projection image, and does not require expensive AR processing as in the related art, and can be manufactured at low cost.

"Optical element integrated optically"
It refers to an integrated optical element such that no interface (boundary) exists for light passing through the inside of the integrated optical element. The optically integrated, at least two prismatic optical elements can also be obtained by manufacturing the optical element to be integrated as a single part, and the optical element to be integrated can be made of the material comprising them. Can also be obtained by bonding together using an adhesive having a refractive index close to that of the above. If the optical elements to be bonded have different refractive indices, it is preferable to use an adhesive having a refractive index between those values. Of course, it is preferable to make the refractive indexes of the integrated optical element and the adhesive the same. In the specification of the present application, a structure in which a plurality of optical elements each having a specific function (polarization separation, color separation, or color synthesis) are integrated with an adhesive is referred to as an “integrated optical element structure”. A plurality of optical elements are distinguished from a “single optical component” manufactured as a single component. The single optical component is bonded only on the functional surface (polarization separating surface, color separating surface, or color combining surface), and has no interface for bonding other than the functional surface.

By using the optically integrated optical element, the number of optical components is reduced, so that the number of jigs and work for fixing and aligning the optical components can be reduced. The cost of the device can be reduced. Furthermore, manufacturing the integrated optical element as a single optical component reduces the number of surfaces to be polished in the optical component manufacturing process, and is therefore less expensive to manufacture than individual optical elements. can do. Of course, when an optical element manufactured as a single optical component is used, since there is no interface between the optical elements, there is an advantage that a decrease in the amount of light due to reflection can be completely eliminated.

Further, by making the color separation element an optical system that also functions as a color synthesis element, the number of parts can be reduced and the optical system can be made compact.

[0036]

Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, components having substantially the same functions as the components of the projection type liquid crystal display device shown in FIGS. 7 and 8 are denoted by the same reference numerals, and the description thereof will be omitted.

Embodiment 1 The configuration and operation of a projection type liquid crystal display device 100 according to Embodiment 1 of the present invention will be described with reference to FIG.

As shown in FIG. 1, the projection type liquid crystal display device 100 has a light source 101, a polarizing plate 103, a PBS 105, polarization control elements 104 and 111, a dichroic prism 107, It has a reflection type liquid crystal display element 109R, 109G and 109B, and a projection lens 113. The PBS 105 functions as a polarization separation element, and the polarization control element 104 and the PBS 105
And the dichroic prism 107
Each function as a color separation element, the dichroic prism 107, the PBS 105, and the polarization control element 11
The combination with 1 functions as a color combining element. The projection type liquid crystal display device 100 further includes a glass cube 110 for adjusting the optical path length and a polarizing plate 112 for improving the contrast.

In the projection type liquid crystal display device 100, the dichroic prism 107 and the glass cube 110 are PB
It is substantially the same as the projection type liquid crystal display device 700 shown in FIG. 7 except that it is bonded to S105 via the bonding layers 10a and 10b and is optically integrated. The optical element integrated by the adhesive layers 10a and 10b is referred to as an integrated optical element structure 100A.

As the white light source 101, a halogen lamp, a metal halide lamp, a xenon lamp, or the like can be used. Incidentally, ultraviolet rays and infrared rays radiated from the light source 101 are reflected by the reflection type liquid crystal display elements 109R, 109R.
If there is a possibility of adversely affecting the G and 109B and other optical elements, a filter for blocking ultraviolet rays or infrared rays may be provided at an appropriate position between the white light source 101 and the polarizing plate 103.

The parabolic mirror 102 has a rotationally symmetric shape, and a white light source 101 is disposed near the focal point.
Are emitted as substantially parallel light beams. On the reflecting surface of the parabolic mirror 102, a so-called cold mirror that reflects only visible light and transmits infrared light is used as necessary. In addition, as a configuration of the light source unit,
In addition to the above, a combination of a spherical mirror or a spheroidal mirror and a condenser lens may be used to obtain a parallel light beam. Further, by providing a polarization conversion optical system between the light source 101 and the polarizing plate 103 for converting all non-polarized light emitted from the light source 101 into linearly polarized light polarized in one direction, the light use efficiency is improved. You can also.
As such a polarization conversion optical system, for example, Japanese Unexamined Patent Publication No.
No. 304739 can be used.

The dichroic prism 107 and the glass cube 110 are bonded to the PBS 105 via bonding layers 10a and 10b, and are optically integrated. The integrated optical element structure 100A, in which the dichroic prism 107, the glass cube 110, and the PBS 105 are optically integrated, is bonded to at least one of a pair of opposing surfaces (simply referred to as "adhered surfaces") bonded to each other. After applying the agent, it is formed by bonding the adhesive surfaces and curing the adhesive. As the adhesive, an adhesive having high visible light transmittance after curing and little disturbance of polarization is preferable. In addition, since strong light passes through the bonding surface, it is preferable to use a material having high light resistance, little change over time, and high reliability. In addition, while the refractive index of air is 1,
The refractive index of a general adhesive is 1.4 or more and 1.6 or less, and the refractive index of a general optical element (prism) is 1.5 to 1.6.
Since it is about 1.8, the effect of suppressing the decrease in the amount of light due to interfacial reflection can be obtained by bonding the optical elements using an adhesive.

In order to more effectively suppress the decrease in the amount of light due to reflection at the bonding surface (air interface in the conventional configuration), the refractive index n1 of the material (typically glass) used for the PBS 105 and the dichroic Prism 107
For each of the refractive indices n2 and n3 of the glass cube 110, the refractive index na of the adhesive forming the adhesive layer 10a is preferably an intermediate value between n1 and n2, and forms the adhesive layer 10b. The refractive index nb of the adhesive is
Those having a refractive index of an intermediate value between n1 and n3 are preferred. Further, it is preferable to form an optical element using the same material or to use a material having a refractive index as close as possible so that n1 = n2 and n1 = n3. P
The refractive index difference (n1-n2 and n1-n3) of the material (glass material) forming the BS 105, the dichroic prism 107 and the glass cube 110 is preferably 0.3 or less.

As the polarization control elements 104 and 111 of the projection type liquid crystal display device 100 of the present embodiment, US Pat.
An element as disclosed in U.S. Pat. No. 751,384 is used. The polarization control element disclosed in this U.S. Patent has a function of stacking a plurality of wavelength plates by changing the angle of the optical axis thereof and selectively rotating the polarization direction of light in a specific wavelength range. In this embodiment, only the polarization direction of the G light component is rotated. As the polarization control elements 104 and 111, any elements having the same function can be used, and for example, the polarization control elements 104 and 111 can be configured using cholesteric liquid crystal or the like.

As the reflection type liquid crystal display elements 109R, 109G and 109B, vertically aligned liquid crystal mode display elements are used. As the liquid crystal mode, any other mode such as the TN mode can be used.

The polarizing plate 112 blocks a light component that should be originally removed (returned to the light source 101) by the PBS 105 from the light beam transmitted through the polarization control element 111, thereby improving the contrast ratio. Conversely, in order to remove the light component to be removed by the PBS 105 by using the polarizing plate 112, the polarization directions of the R light component, the G light component, and the B light component used for display are matched. Therefore, the polarization control element 111 is provided.

The reflection type liquid crystal display elements 109R, 10R
Although not shown, a quarter-wave plate or the like may be arranged between 9G and 109B and the color separation prism 107 or the glass cube 110 as necessary. The quarter-wave plate causes the luminous flux to deviate from the normal to the incidence surface of the PBS (45
The deviation of the polarization direction that occurs when the light beam enters (with deviation from °) is compensated when the light beam goes and returns, and the contrast ratio of the projected image is improved.

The projection type liquid crystal display device 100 of the present embodiment
Is dichroic prism 107, glass cube 1
Since the optical system 10 and the PBS 105 are optically integrated, the number of air interfaces through which the light beam emitted from the light source 101 passes is reduced as compared with the conventional configuration, so that a decrease in the amount of light due to reflection at the air interface is suppressed. . As a result, the projection-type liquid crystal display device 100 of the present embodiment can display a projection image that is brighter than the conventional projection-type liquid crystal display device 700, and requires expensive AR processing as in the related art. Therefore, it can be manufactured at low cost.

Further, in the manufacturing process of the projection type liquid crystal display device 100, the dichroic prism 107, the glass cube 110 and the P
Since the alignment adjustment and fixing of the BS 105 are completed, the number and work of jigs for alignment and fixing can be simplified. Also, dichroic prism 107,
Since the alignment between the glass cube 110 and the PBS 105 is substantially completed by the step of bonding them together, the alignment accuracy is high and the operation is simple.

In the above example, the dichroic prism 107, the glass cube 110 and the PBS 105
The dichroic prism 107 and the PB
Only S105 may be integrated, or only the glass cube 110 and the PBS 105 may be integrated. Further, the glass cube 110 can be omitted. At least, by optically integrating the PBS 105 and another optical element (a color separation element or a color synthesis element), an effect of improving the light use efficiency by reducing the air interface can be obtained.

In the projection type liquid crystal display device 100, the combination of the polarization control element 104 and the PBS 105 and the dichroic prism 107 each function as a color separation element.
7 and the combination of the PBS 105 and the polarization control element 111 function as a color synthesizing element, and some or all of the color separating element and the color synthesizing element are configured using a common optical element. And a compact optical system can be realized.

In this embodiment, the polarization control elements 104 and 111 for rotating the polarization direction of the G light component are used.
The color light component for rotating the polarization direction is not limited to this.
Polarized light and S-polarized light may be switched. Further, in the present embodiment, the white light is separated by the PBS 105 from the G color light and the B color light, but the R color light may be separated from the G color light and the B color light, and the B color light may be separated from the G color light and the R color light. It may be separated. In this case, the polarization control elements 104 and 111
The color light to be rotated and the color light reflected by the color separation (reflection surface) 108B are appropriately changed.

In the above example, the three primary colors of light (R · G
The projection type liquid crystal display device capable of full-color display using the light beam of B) has been exemplified. However, since color display is possible using at least two different color light beams, for example, a dichroic prism in the projection type liquid crystal display device 100 107
In addition, the reflection type liquid crystal display element 109R and the like can be omitted. This configuration change can be easily performed by those skilled in the art. This is the same for the other embodiments described below.

Next, the configuration and operation of another projection type liquid crystal display device 200 according to the first embodiment will be described with reference to FIG.

The projection type liquid crystal display device 200 shown in FIG.
Is a device in which the integrated optical element structure 100A of the projection type liquid crystal display device 100 shown in FIG. 1 is replaced with a single optical component (hereinafter, referred to as "integrated prism") 200A.

The integrated prism 200A has an L-shape in which a parallelogram prism 201, a triangular prism 202, and a trapezoidal prism 203 are bonded to each other. Parallelogram prism 201 and triangle prism 202
Is a color separation surface (B light reflection surface) 108B, and a boundary surface between the parallelogram prism 201 and the trapezoidal prism 203 is the polarization separation surface 106. It should be noted that the trapezoidal prism 203 can be changed to a triangular prism and the function corresponding to the glass cube 110 in FIG. 1 can be omitted.

The integrated prism 200A can be manufactured as follows.

First, the polarization separation surface 106 and the color separation surface 1
08B, a film having the respective functions is formed, and then the parallelogram prism 2
01 and a trapezoidal prism 203, and a parallelogram prism 201 and a triangular prism 202 are bonded to each other with an optical adhesive through a color separation surface 108B to obtain an L-shaped integrated prism 200A.

The integrated prism 2 manufactured as described above
00A is bonded only on functional surfaces (polarization separating surface 106 and color separating surface 108B) that are indispensable to be bonded, and has no interface for bonding other than this functional surface. This structure is called an “integrated prism”. Further, the projection type liquid crystal display device 10
0 is an optical element having a specific function, each of which is an individually formed prism (PBS 105, dichroic prism 107).
And a glass cube 110), the individual prisms (parallelogram prism 201, triangular prism 202, trapezoidal prism 203, and trapezoidal prism 203) constituting the integrated prism 200A in the projection type liquid crystal display device 200. ) Does not have a specific function (polarization separation or color separation), and becomes a single optical component having a specific function for the first time by bonding them on a functional surface.

The projection type liquid crystal display device 200 has the same effects as the above-mentioned projection type liquid crystal display device 100. Further, the integrated optical element structure 100A in the projection type liquid crystal display device 100 is a single optical component (integrated prism) 2
Since it is formed as 00A, the number of surfaces to be polished in the manufacturing process of the optical component is reduced, so that it can be manufactured at a lower cost than manufacturing individual optical elements. In addition, when the integrated prism 200A is used, since there is no interface between the optical elements, there is an advantage that the decrease in the amount of light due to reflection can be completely eliminated.

(Embodiment 2) The configuration and operation of a projection type liquid crystal display device 300 according to Embodiment 2 of the present invention will be described with reference to FIG.

The projection type liquid crystal display device 300 includes a PBS 10
5a and PBS 105d adhere to PBS 105b
It is substantially the same as the projection type liquid crystal display device 800 shown in FIG. 8 except that it is bonded through Oa and 30b and is optically integrated. The adhesive layer 30
The optical element integrated by a and 30b is referred to as an integrated optical element structure 300A.

Since the polarization control elements 114 and 115 exist between the PBS 105c and the PBS 105a and between the PBS 105c and the PBS 105d, respectively, the size of the PBS 105c is reduced by the thickness of the polarization control elements 114 and 115, or the reflection is reduced. LCD device 109B
And the positions of 109R are adjusted.

The projection type liquid crystal display device 300 of the present embodiment
Are PBS105a, PBS105b and PBS10
Since 5d is optically integrated, the number of air interfaces through which the light beam emitted from the light source 101 passes is smaller than in the conventional configuration, and a decrease in the amount of light due to reflection at the air interface is suppressed. As a result, the projection-type liquid crystal display device 300 of the present embodiment can display a projection image that is brighter than the conventional projection-type liquid crystal display device 800, and requires expensive AR processing as in the related art. Therefore, it can be manufactured at low cost. In order to more efficiently suppress the decrease in the amount of light due to reflection at the bonding interface, the first embodiment
As described above, the refractive index of the material of the integrated PBS and the refractive index of the adhesive may be appropriately set.

Further, the PBS 105c and the PBS 105
a, and the PBS 105c and the PBS 105d are bonded to each other with the polarization control elements 114 and 115 interposed therebetween, thereby suppressing a decrease in the amount of light due to reflection at the interface between the polarization control elements 114 and 115 and the PBS. be able to.

The projection type liquid crystal display device 1 of the first embodiment
As in the case of 00, the number of components can be reduced, so that alignment and fixing of the optical components can be easily performed. In addition,
In the above example, the PBS 105a, the PBS 105b, and the PBS 105d are integrated, but at least two PBs are used.
Needless to say, by optically integrating S, the effect of improving the light use efficiency by reducing the air interface can be obtained.

The configuration of the projection type liquid crystal display device 300 of the present embodiment is not limited to the above example. As described above in the first embodiment, the configuration of the light source section, the configuration of the polarization control element used, and the luminous flux used for display. The polarization direction, the combination of the color lights for color separation, and the like can be changed as appropriate.

Next, the configuration and operation of another projection type liquid crystal display device 400 according to the second embodiment will be described with reference to FIG.

The projection type liquid crystal display device 400 shown in FIG.
Is obtained by replacing the integrated optical element structure 300A of the projection type liquid crystal display device 300 shown in FIG. 3 with a single optical component (hereinafter, referred to as "integrated prism") 400A.

The integrated prism 400A includes two triangular prisms (large) 211 and two triangular prisms (small) 212.
Have an L-shaped shape attached to each other. The boundary surface between the triangular prism 211 and the triangular prism 212 is
The polarization separation surfaces 106a and 106d are provided, and the boundary surface between the two triangular prisms 210 is the polarization separation surface 106b. That is, similarly to the integrated prism 200A, the integrated prism 400A does not have an interface for bonding other than the functional surface (polarization separating surface). Integrated prism 4
00A can be manufactured by substantially the same method as the integrated prism 200A of the first embodiment.

The projection type liquid crystal display device 400 has the same effects as the above-mentioned projection type liquid crystal display device 300. Further, the integrated optical element structure 300A in the projection type liquid crystal display device 300 is a single optical component (integrated prism) 4
Since it is formed as 00A, the number of surfaces to be polished in the manufacturing process of the optical component is reduced, and it can be manufactured at a lower cost than manufacturing individual optical elements.
In addition, when the integrated prism 400A is used, since there is no interface between the optical elements, there is an advantage that the decrease in the amount of light due to reflection can be completely eliminated.

(Embodiment 3) The configuration and operation of a projection type liquid crystal display device 500 according to Embodiment 3 of the present invention will be described with reference to FIG. The projection type liquid crystal display device 500 differs from the projection type liquid crystal display device of the previous embodiment in that it does not have a polarization control element.

The projection type liquid crystal display device 500 of the present embodiment
Includes a white light source 101, a parabolic mirror 102 constituting a light source unit together with the white light source 101, a cross dichroic mirror 300M, two total reflection mirrors 301, a dichroic mirror 302G, and three PBSs 105.
Reflective liquid crystal display elements 109R, 109G and 109B
, Cross dichroic prism 303, polarizing plate 1
12 and a projection lens 113. Three PBs
In step S105, the cross dichroic prism 303
They are adhered via adhesive layers 50a, 50b and 50c, respectively, and are optically integrated. The optical element integrated by the adhesive layers 50a, 50b, and 50c is referred to as an integrated optical element structure 500A.

In the substantially parallel white light flux obtained from the white light source 101 and the parabolic mirror 102, the R light component is reflected on the reflection surface 300R of the cross dichroic mirror 300M in the right-hand direction on the paper surface, and the G light is reflected on the reflection surface 300BG. Component and B
The light component is reflected in the left direction on the paper. R light component and G
The light component and the B light component are the total reflection mirror 30 respectively.
1 is directed upward in the plane of the drawing. The G light component and the B light component are color-separated by a dichroic mirror 302G into a reflected G light component and a transmitted B light component.

The R, G, and B color light components are incident on the corresponding PBS 105, and the S-polarized light component is
06, the reflection type liquid crystal display elements 109R, 109
G and 109R. In this example, PBS 10
The P-polarized light component incident on No. 5 passes through the polarization splitting surface 106 and goes out of the optical system, and is not used for display.
As described with respect to the light source unit of the first embodiment, by using the polarization conversion optical system to convert all the light beams emitted from the light source 101 into S-polarized light, it is possible to prevent a reduction in light use efficiency. Can be. Further, in order to improve the contrast ratio of the projected image, a polarizing plate may be disposed before the light flux enters each PBS 105 (on the light source side on the optical path).

Of the light beams reflected by the reflection type liquid crystal display elements 109R, 109G, and 109B, each color light component reflected from the picture element region in the bright state is rotated by 90 degrees to become P-polarized light. The light passes through the polarization separation surface 106 and enters the cross dichroic prism 303.
The R light component and the B light component in the P-polarized state are respectively transmitted to the color reflecting surface 304R of the cross dichroic prism 303.
And 304B, and is projected on a screen (not shown) through the polarizing plate 112 and the projection lens 113.

The projection type liquid crystal display device 500 of the present embodiment
Is the cross dichroic prism 303 and each PBS1
Since the optical element 05 is optically integrated, the number of air interfaces through which the light beam emitted from the light source 101 passes is small, and a decrease in the amount of light due to reflection at the air interface is suppressed. As a result, the projection-type liquid crystal display device 500 of the present embodiment can display a brighter projected image than a projection-type liquid crystal display device having a configuration that is not optically integrated, and is expensive as in the related art. Since no special AR processing is required, it can be manufactured at low cost. Further, by integrating the optical element, the effects described in the first and second embodiments can be obtained. Of course, the projection-type liquid crystal display device 500 of the present embodiment can be appropriately modified similarly to the first and second embodiments.

Next, the configuration and operation of the projection type liquid crystal display device 600 of this embodiment will be described with reference to FIG.

The projection type liquid crystal display device 600 shown in FIG.
Is obtained by replacing the integrated optical element structure 500A of the projection type liquid crystal display device 500 shown in FIG. 5 with a single optical component (hereinafter, referred to as "integrated prism") 600A.

The integrated prism 600A has a T-shape in which three triangular prisms 306, three trapezoidal prisms 307, and a small triangular prism 308 are bonded to each other. The boundary surfaces between the three triangular prisms 306 and the three trapezoidal prisms 307 are respectively polarized light separation surfaces 1
06, and the boundary surface between the small triangular prism 308 and the two trapezoidal prisms 307 is a color reflection surface 304R.
And 304B. The integrated prism 600A can be manufactured by substantially the same method as the integrated prism 200A of the first embodiment.

The projection type liquid crystal display device 600 has the same effect as the projection type liquid crystal display device 500 described above. Further, the integrated optical element structure 500A in the projection type liquid crystal display device 500 is a single optical component (integrated prism) 6
Since it is formed as 00A, the number of surfaces to be polished in the manufacturing process of the optical component is reduced, and it can be manufactured at a lower cost than manufacturing individual optical elements.
Further, when the integrated prism 600A is used, since there is no interface between the optical elements, there is an advantage that the decrease in the amount of light due to reflection can be completely eliminated.

The material of the prism (or prism-shaped optical element) used in the first to third embodiments is typically glass, but other transparent materials can be used. Further, as the reflection type liquid crystal display device, known devices of various display modes can be used. Also, the present invention has been described by taking a projection type image display device using a reflective liquid crystal display element as an example. However, the present invention provides a projection type image display apparatus using a display element having substantially the same function as a reflective liquid crystal display element. It can be applied to an image display device of a type.

[0083]

According to the present invention, there is provided an inexpensive projection-type image display apparatus in which the amount of light is less reduced due to reflection at the interface between a prismatic optical element and air. In the image display device of the present invention, since the prism-shaped optical element is optically integrated, in the conventional image display device,
A reduction in the amount of light due to light reflection at the interface between the plurality of prismatic optical elements and air is suppressed, a bright projected image can be displayed, and low cost is achieved without the need for expensive AR processing as in the past. Can be manufactured. Further, by forming the prism-shaped optical element as a single optical component, the display luminance can be further increased and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a projection-type liquid crystal display device 100 according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a projection-type liquid crystal display device 200 according to a first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a projection type liquid crystal display device 300 according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a projection type liquid crystal display device 400 according to Embodiment 2 of the present invention.

FIG. 5 is a schematic configuration diagram of a projection type liquid crystal display device 500 according to a third embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a projection type liquid crystal display device 600 according to Embodiment 3 of the present invention.

FIG. 7 is a schematic configuration diagram of a conventional projection type liquid crystal display device 700.

FIG. 8 is a schematic configuration diagram of a conventional projection-type liquid crystal display device 800.

[Explanation of symbols]

100, 200, 300, 400, 500 Projection type liquid crystal display device 100A, 300A 500A Integrated optical element structure 200A, 400A, 600A Single optical component (integrated prism) 101 White light source 102 Parabolic mirror 103, 112 Polarized light Plate 104, 111 Polarization control element 105, 105a, 105b, 105c, 105d P
BS 106 Polarization separation surface 107 Dichroic prism 108B Color separation (B reflection) surface 109R, 109G, 109B Reflective liquid crystal display element 110 Glass cube 113 Projection lens 114, 115 Polarization control element 201 Parallelogram prism 202 Triangular prism 203 Trapezoid prism 204 Polarization separation surface 211 Triangular prism (large) 212 Triangular prism (small) 300M Cross dichroic mirror 300R, BG color reflection surface 301 Total reflection mirror 302G Dichroic mirror 303 Cross dichroic prism 304R Color (R) reflection surface 304B Color (B) reflection surface 306 Triangular prism (large) 307 Trapezoidal prism (small) 308 Triangular prism (small) 600, 700 Projection type liquid crystal display

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 EA14 EA15 EA16 HA18 HA20 HA23 HA24 HA28 MA06 MA16 2H091 FA08X FA10X FA21X FA26X FA41X FD15 LA13 LA16

Claims (4)

[Claims] A light source for emitting a light beam; at least one polarization separation element for separating the light beam emitted from the light source into at least two light beams having different polarization directions; and the light beam emitted from the light source A color separation element that separates the light into at least two color light fluxes having different colors, at least two reflective liquid crystal display elements that respectively modulate the at least two color light fluxes, and modulation by the reflective liquid crystal display element. An image display device comprising: a color combining element configured to combine the reflected at least two color light fluxes; and a projection lens configured to project the light flux combined by the color combining element. At least two optical elements of the color combining element and the at least one polarization splitting element are formed of prisms, and are optically An integrated image display device. 2. The image display device according to claim 1, wherein the at least two optical elements formed of a prism are a single optical component formed integrally. 3. The image display device according to claim 1, wherein the at least two optical elements formed of a prism are adhered to each other in an optically matched state. 4. An image display device wherein the color separation element also functions as the color synthesis element.