JPH08248417A - Liquid crystal video projector - Google Patents

Abstract

PURPOSE: To effectively utilizing the light quantity of the light beams from two light sources as the illumination light of liquid crystal display panels by disposing polarization direction aligning elements in the fore stage of a PBS for synthesizing the light beams from the two light sources and in the fore stage of the respective liquid crystal display panels on which the three color light beams formed by separating the light from the PBC. CONSTITUTION: The polarization direction aligning elements 7A, 7B, 7C are arranged between the respective light source sections 1A, 1B and the PBS 4 and in the fore stages of the respective liquid crystal display panels 8A, 8B, 8C. The light beam 3C outputted from the polarization direction aligning element 2A is polarized to an S polarized light beam and the light beam 3D outputted from the polarization direction aligning element 2B is polarized to a P polarized light beam. Both polarized light beams are effectively synthesized by the PBS 4. The three primary color light beams 3F, 3H, 3I separated by the dichroic mirrors 5A, 5B are unified to the P polarized light beams by the polarization direction aligning elements 7A, 7B, 7C before these beams are made incident on the liquid crystal display panels 8A, 8B, 8C.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention uses a liquid crystal display panel to perform brightness modulation on each of the three color-separated primary colors, and then combines these three primary colors to project a color image on a screen. More specifically, the present invention relates to a liquid crystal video projector that uses a polarization direction alignment element that converts unpolarized light from a light source into linearly polarized light in a predetermined direction while maintaining the amount of light.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal video in which color-separated three primary color lights are modulated by a predetermined video signal using a liquid crystal display panel, these modulated lights are combined by a dichroic prism, and then enlarged and projected on a predetermined screen. Projectors are widely known.

By the way, the liquid crystal cell, which is the main body of the liquid crystal display panel, is required to have a single direction of polarization of illumination light because of its nature. Therefore, a polarizing plate is usually provided on the front and rear surfaces of the liquid crystal cell. However, it is configured such that only a predetermined unidirectional polarization component is made incident on the liquid crystal cell.

However, in this case, the light component in the non-selection direction is cut in the polarizing plate provided in front of the liquid crystal cell, and only half of the total light amount of the light source light can be used as illumination light.

As a technique for solving such a problem, the technique described in JP-A-6-202041 is known.

That is, in this technique, a polarization direction alignment member including a polarization beam splitter, a total reflection prism and a λ / 2 optical phase plate is provided between the light source and the liquid crystal display panel. This polarization direction alignment member transmits the P polarization component of the light beam from the light source and reflects the S polarization component at a right angle by the polarization beam splitter, and reflects the reflected S polarization component at a further right angle by the total reflection prism. Then, it is aligned in parallel with the P-polarized light component transmitted through the polarization beam splitter, and further, this S
The polarization direction of the polarization component is rotated by 90 ° so as to be converted into the P polarization component. As a result, the light amount of the light beam emitted from the light source is effectively used as the illumination light of the liquid crystal display panel.

However, in recent years, the demand for higher screen brightness by liquid crystal video projectors has been increasing.

Therefore, two light sources are used as the light source of the projector, and the light beams from the respective light sources are each made into a single-direction polarization component by the polarization direction aligning member as described above, and these two-system polarization beams are combined to form a liquid crystal. By using the illumination light of the display panel, a method of doubling the amount of the illumination light can be considered.

[0009]

However, as described above, two light sources are used, a polarization direction alignment member is used for each light source, and then PBS is used to synthesize the light beams of these two systems to form a liquid crystal. Even if the amount of illumination light on the display panel is doubled, P
Since the BS combines P-polarized light and S-polarized light, the combined light beam includes both P-polarized light and S-polarized light components. As described above, since the liquid crystal cell is configured so that only the polarized light component in a predetermined single direction is incident, the light beam emitted from the light source eventually has only half of the light amount in the liquid crystal cell. Cannot be incident on.

That is, the front surface of the liquid crystal display panel is directly irradiated with light beams from two light sources, but only the light amount equivalent to the light amount of the light beam from one light source is effectively used.

This makes it meaningless to use two light sources.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal video projector that can effectively use the light amounts of light beams from two light sources as illumination light for a liquid crystal display panel. It is a thing.

[0013]

A liquid crystal video projector of the present invention separates light from a light source into three primary color lights by a color separation dichroic mirror and irradiates a liquid crystal display panel corresponding to each primary color light. In each of these liquid crystal display panels, the respective primary color lights are brightness-modulated by a video signal corresponding to the primary color lights, these modulated primary color lights are combined by a dichroic mirror for color combination, and the combined 3
In a liquid crystal video projector for enlarging and projecting two primary color lights on a predetermined screen, the light source includes first and second light sources.
A first polarization direction aligning element for aligning and outputting the light from the first light source to P-polarized light, and a second for aligning and outputting the light from the second light source to S-polarized light. Polarization direction aligning element, a polarization beam splitter for combining the P polarization and S polarization from these two polarization direction aligning elements, and the light combined by this polarization beam splitter is separated by the color separation dichroic mirror. It comprises a third, a fourth and a fifth polarization direction aligning element which outputs the three primary color lights in the preceding stage of each of the liquid crystal display panels by aligning the polarized light according to the liquid crystal display panel. It is a thing.

The dichroic mirror includes a dichroic prism.

Further, the above-mentioned predetermined "alignment with polarized light" is performed.
Means that, out of two orthogonal polarization components, one input polarization component is converted into the other polarization component and output, and the other input polarization component is output as it is.

[0016]

According to the above construction, by using two polarization direction aligning elements, one of the two light sources is aligned with the P polarization component and the other is aligned with the S polarization component.
Since the two polarization components are composed by PBS,
At the time of output, the total light quantity of the light beams from the two light sources can be effectively held.

The light from the two light sources combined with PBS has a P-polarized component and an S-polarized component, and after being separated by the dichroic mirror into the three primary colors of R, G, and B, each of the above two components is separated. Although it has a polarization component, the polarization direction aligning element arranged in the front stage of each liquid crystal display panel can align the polarized light corresponding to the liquid crystal display panel before the three primary color lights are incident on the liquid crystal display panel. Therefore, the light beam applied to the liquid crystal display panel enters the liquid crystal cell without reducing the light amount. After this,
The three primary color lights carrying image information, which have passed through each liquid crystal display panel, are combined by a dichroic mirror and enlarged and projected on a screen via a projection lens.

As a result, the two light beams output from the two light sources are
Since the total light amount of the light beam of the system is maximally utilized as the illumination light, it becomes possible to efficiently project a bright image on the screen.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing a liquid crystal video projector according to an embodiment of the present invention. As shown in the figure, this liquid crystal video projector is composed of a parabolic reflector which is a reflecting means and a halogen lamp or a metal halide lamp which is arranged near the focal point of the reflector.
Light source units 1A and 1B each including one light source, and a polarization direction alignment element 2A that converts a light beam 3A, which is natural light emitted from the light sources directly or through a reflecting mirror, into S-polarized light 3C while maintaining its light amount, Similarly, a polarization direction alignment element 2B for converting the light beam 3B, which is natural light, into P-polarized light 3D while maintaining its light quantity, and S from the polarization direction alignment element 2A.
The polarized light 3C is reflected by about 100% and the P-polarized light 3D from the polarization direction alignment element 2B is transmitted by about 100%.
And a PBS 4 that synthesizes two polarized lights 3C and 3D.

Further, the light beam 3 synthesized by the PBS 4
Dichroic mirror 5A that reflects and separates blue light 3F of E and transmits light beam 3G including the remaining color light
And a dichroic mirror 5B that reflects and separates the red light 3H and transmits the green light 3I of the light beam 3G from the dichroic mirror 5A, and the dichroic mirror 5
An aluminum coating total reflection mirror 6 that changes the beam direction of the blue light 3F separated by A by 90 °, and three primary colors R, G, B separated by these two dichroic mirrors 5A, 5B and total reflection mirror 6. Light 3F, 3
Align H and 3I to P polarization (or S polarization),
Three polarization direction alignment elements 7A, 7B and 7C corresponding to the respective primary color lights 3F, 3H and 3I and the respective primary color lights 3F, 3H and 3I of R, G and B are modulated according to a predetermined image signal, It has three monochrome liquid crystal display panels 8A, 8B, 8C as image forming means.

Further, these liquid crystal display panels 8A, 8
A prism 9 having a cross section of an isosceles right triangle and two prisms 10 and 11 having a parallelogram cross section, which combine the three primary color lights 3F, 3H, and 3I output from B and 8C, and these prisms 9, It is composed of a projection lens 12 for enlarging and projecting on a screen 13 a light beam 3J in which the three primary color lights are combined by 10 and 11.

On the front and back surfaces of the liquid crystal display panels 8A, 8B, and 8C, the direction of the easy axis of polarization transmission with respect to the polarization direction of incident P-polarized light (or S-polarized light).
Since the polarizing plate tilted by 45 ° is arranged, the polarization direction of the incident light is rotated by 45 ° about the optical axis and then incident on the liquid crystal display panels 8A, 8B, 8C. In order to rotate the polarization direction by 45 ° about the optical axis, 1/2 optical phase plates 14A, 14 as optical rotatory elements are provided at the front and rear stages of each liquid crystal display panel 8A, 8B, 8C.
B, 14C, 15A, 15B, 15C are provided.

Further, the joint surface 9A between the prism 9 and the prism 10 and the joint surface 10A between the prism 10 and the prism 11 are dichroic coated dichroic surfaces, and the joint surface 9A transmits the blue light 3F. The red light 3H is reflected to combine the two, and the joint surface 10A transmits the combined light and reflects the green light 3I to combine the R, G, and B primary color lights. The end surface 11A of the prism 11 is coated with a reflection coat, and the green light 3
The beam direction of the I light beam is changed by 90 °.

By the way, in the present invention, the polarization direction alignment element is arranged in the rear stage of each light source and in the front stage of each liquid crystal display panel, and this polarization direction alignment element is one of the points of the present invention. The polarization direction alignment elements 2A, 2B, 7A, 7B and 7C in the above embodiment will be described in detail below with reference to FIGS. 2 and 3.

FIG. 2 shows the polarization direction alignment elements 2A and 2A.
The unit elements 110A constituting B, 7A, 7B, and 7C are shown. That is, the unit element 110A has a polarizing beam splitter 111, a first total reflection prism 112, and a second total reflection prism 11 whose surfaces adjacent to each other are adhered.
It consists of three. The polarization beam splitter 111 and the second total reflection prism 113 are cubic blocks of the same size, and the first total reflection prism 112 is a triangular prism block of a size obtained by cutting the cube block in half. Light beam 10
3 A is incident on the polarization beam splitter 111 and is separated into two polarization components orthogonal to each other at this polarization beam splitter 111. That is, the first polarization component 114 A
Passes through the working surface (deposited film surface) 111 A and emerges from the front surface 111 B of this polarization beam splitter 111, while the second polarization component 114 B is reflected laterally at the working surface 111 A and Is reflected upward by the reflection surface 112 A of the second total reflection prism 112, is further reflected forward by the reflection surface 113 A of the second total reflection prism 113, and is emitted from the front surface 113 B of the second total reflection prism 113. It The two reflection surfaces 112 A and 113 A are arranged so that the beam of the second polarization component 114 B is incident at an incident angle of 45 °, and the second polarization component 114 B is formed by these reflection surfaces 112 A and 113 A. A, 113 A is reflected at a right angle. Therefore, the second polarization component 114 B emitted from the front surface 113 B of the second total reflection prism 113 is the working surface 111 of the polarization beam splitter 111.
The plane of polarization is rotated by 90 ° with respect to the second polarization component 114 B when reflected from A, and eventually the second light emitted from the front surface 113 B of the second total reflection prism 113 2.
The polarization component 114 B of the
The first polarization component 114A emitted from 1B and its beam traveling direction and polarization direction are parallel to each other.

As a result, substantially the total amount of light of the unpolarized light beam 103A is converted into polarized light having a polarization plane in a predetermined direction.

Further, as shown in FIG. 3, a unit element 110A composed of a polarization beam splitter 111, a first total reflection prism 112 and a second total reflection prism 113, and an optical member for the unit element 110A. A unit element 110B composed of a polarization beam splitter 121, a first total reflection prism 122 and a second total reflection prism 123 whose arrangement is bilaterally symmetric.
By combining and in the front-back direction, two light beams 103 A and 103 B to four polarization components 114 A, 114 B,
124 A, 124 B can be generated.

That is, the unit element 110A causes the light beam 103A incident on the polarization beam splitter 111 to move to the first
Of the first polarization component 114 A and the second polarization component 114 B of which the beam traveling direction and the polarization direction are parallel to the first polarization component 114 A of the first polarization component 114 A, and the polarization beam splitter 121 B is converted by the unit element 110 B. Light beam 103 incident on
B is converted into a first polarized light component 124 A and a second polarized light component 124 B whose beam traveling direction and polarization direction are parallel to the first polarized light component 124 A.

If the beam traveling directions of the two unpolarized light beams 103 A and 103 B are parallel to each other, the polarization components 114 A and 110 A emitted from these two unit elements 110 A and 110 B are emitted.
114B, 124A, and 124B have the beam traveling direction and the polarization direction parallel to each other.

2 and 3, the unit element 110 is shown.
A and 110 B incident light beams 103 A and 103 B and polarization components emitted from these unit elements 110 A and 110 B
Although the beams of 114 A, 114 B, 124 A, and 124 B are shown as straight lines, in reality, each light beam 103 A, 103 B is incident on the entire area of the rear surface of the corresponding polarization beam splitter 111, 121. However, since the light is emitted from the entire area of the front surfaces of the polarization beam splitters 111 and 121 and the second total reflection prisms 113 and 123, a square surface equivalent to four times the area of the front surfaces of the polarization beam splitters 111 and 121 is eventually obtained. The polarized light components aligned in the same polarization direction are emitted from all the regions.

The light beam 103 A input to the unit element 110 A is the first total reflection prism 122 of the unit element 110 B.
Of the polarization component 124 which is transmitted through the unit element 110B and emitted from the unit element 110B.
A transmits through the first total reflection prism 112 of the unit element 110A, but these first total reflection prism 112
, 122 are substantially transparent in the front-rear direction, and the amount of light does not substantially decrease even after passing through the first total reflection prisms 112, 122.

Next, the operation of the apparatus of the above embodiment will be described. The light beam 3A output from the light source unit 1A is converted into S-polarized light by the polarization direction aligning element 2A and output, while the S-polarized light component is output as it is as S-polarized light, so that it is all aligned with S-polarized light. The converted light beam 3C is input to the PBS 4. Similarly, the light source unit 1B
The light beam 3B output from the light source is converted into a P-polarized light beam 3D which is input to the PBS 4 in a direction orthogonal to the light beam 3C.

The S-polarized light beam 3C is reflected at a right angle by the PBS 4, and the P-polarized light beam 3D is P.
Since the light beams 3C and 3D are transmitted through the BS 4, they are combined by the PBS 4 and output.

Therefore, the light beam 3E output from the PBS 4 has both P-polarized component and S-polarized component, and the blue light 3F, red light 3H and green separated by the two dichroic mirrors 5A and 5B. The light 3I also has a P polarization component and an S polarization component, respectively.

Next, the respective color lights 3F, 3H, 3I are input to the corresponding polarization direction alignment elements 7A, 7B, 7C, and the S polarization component (or P polarization component) is converted into P polarization (or S polarization). And output, while the P-polarized component (or S-polarized component) is directly P-polarized (or S-polarized component).
Output as polarized light, and eventually P polarized light (or S polarized light)
Are available.

Thus, the polarization direction alignment element 7A,
7B and 7C align each color light into a single polarization component, which corresponds to the fact that only a single polarization component is used as the illumination light of the liquid crystal display panels 8A, 8B and 8C. Thus, the liquid crystal display panels 8A, 8B, 8
In the preceding stage of C, the light beams 3A, 3B output from the two light source units 1A, 1B are obtained by aligning the incident light with one of the P-polarized component and the S-polarized component without reducing the light amount. The liquid crystal display panels 8A, 8B, 8
It can be effectively used as the illumination light of C.

Thereafter, the polarization direction alignment elements 7A, 7
The colored lights 3F, 3H, and 3I that are P-polarized (or S-polarized) by B and 7C are ½ optical phase plates 14A and 14
The polarization directions are rotated by 45 ° about the optical axis by B and 14C, and are aligned with the directions of the easy axes of polarization transmission of the front side polarizing plates of the liquid crystal display panels 8A, 8B and 8C, and the respective color lights 3F, 3H and 3I. Is designed to efficiently enter the liquid crystal cell.

Generally, the liquid crystal display panels 8A, 8B,
The direction of the easy axis of polarization transmission of the front polarizing plate of 8C (corresponding to the arrangement direction of the liquid crystal cells) is inclined by 45 ° with respect to the vertical direction of the panels 8A, 8B and 8C about the optical axis. As described above, the liquid crystal display panel 8A,
1/2 optical phase plate 14A, 14B, 14C in front of 8B, 8C
However, when the direction of the axis of easy transmission of polarized light has an inclination other than 45 ° with respect to the vertical direction, a predetermined optical axis according to this inclination is used instead of the 1/2 optical phase plate. It is desirable to use an optical phase plate that can shift the phase by the length.

Further, the liquid crystal display panels 8A, 8B, 8
Each color light 3F, 3 carrying image information output from C
The polarized lights of H and 3I are the liquid crystal display panels 8A, 8B and 8C.
The polarization direction is further rotated by 45 ° by the 1/2 optical phase plates 15A, 15B, and 15C arranged in the subsequent stage to be S-polarized (or P-polarized), and the light enters the prisms 9, 10, and 11.

Then, the blue light 3F incident on the prism 9 is
And the red light 3H incident on the prism 10 are combined by being reflected by the former and transmitted by the former at the joint surface 9A which is a dichroic surface, and the combined light is incident on the prism 11 and is an end surface 11A which is a reflecting surface. The green light 3I reflected by (1) is transmitted by the former at the joint surface 10A, which is a dichroic surface, and the latter is reflected, and is emitted to the outside of the prism 11 as a light beam 3J combining the three primary color lights.

In this embodiment, the prisms 9 and 1
Each of the primary color lights 3F, 3H, 3I incident on 0, 11 is S-polarized (or P-polarized), and is a unidirectional component of polarized light.
When the two color lights 3F, 3H, 3I are combined in A and 9B, the rising and falling shapes of the transmission / reflection characteristics for the respective color lights 3F, 3H, 3I of the dichroic surface become sharp, and eventually the three color lights 3F, 3H. , 3I can be accurately synthesized.

Thereafter, the light beam 3J, which is the combined light of the three primary colors carrying the above-mentioned image information, is enlarged and projected on the screen 13 by the projection lens 12, and the desired image is displayed on this screen.
13 will be projected. As a result, the screen brightness can be sufficiently increased by effectively utilizing the total amount of light beams 3A and 3B emitted from the two light source units 1A and 1B.

The liquid crystal video projector of the present invention is not limited to the above-mentioned embodiment, and various modifications can be made. For example, the polarization direction aligning element may be any element that can match a single polarization component without reducing the amount of natural light from the light source, and the 1/2 optical phase plate as described in the prior art is used. It may be a polarization direction alignment member.

Further, two dichroic prisms (dichroic mirrors) having dichroic mirror surfaces and one total reflection mirror are used in place of the above-mentioned three prisms of the composite system, and air is interposed between these three members. It may be configured to do so. However, it should be noted that in the case of such a configuration, the presence of air causes an influence due to a difference in refractive index between air and glass, disturbance of air, and the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a liquid crystal video projector according to an embodiment of the present invention.

FIG. 2 is a view for explaining in detail a part of a polarization direction alignment element of the embodiment apparatus shown in FIG.

FIG. 3 is a diagram for explaining in detail a polarization direction alignment element of the embodiment apparatus shown in FIG.

[Explanation of symbols]

 1A, 1B Light source part 2A, 2B, 7A, 7B, 7C Polarization direction alignment element 3A, 3B Light beam 3F Blue light 3H Red light 3I Green light 4 PBS 5A, 5B Dichroic mirror 8A, 8B, 8C Liquid crystal display panel 9,10 , 11 Prism 9A, 10A Bonding surface (dichroic mirror surface) 12 Projection lens 13 Screen

Claims (1)

[Claims] 1. The light from a light source is separated into three primary color lights by a color separation dichroic mirror, and the liquid crystal display panels corresponding to the respective primary color lights are irradiated with the respective primary color lights. Luminance modulation is performed by a video signal corresponding to the primary color light, and each of the modulated primary color lights is combined by a dichroic mirror for color combination, and the combined 3
In a liquid crystal video projector for enlarging and projecting two primary color lights on a predetermined screen, the light source comprises two light sources, a first light source and a second light source, and outputs the light from the first light source by aligning it with P-polarized light. Polarization direction aligning element, a second polarization direction aligning element that aligns and outputs light from the second light source to S polarization, and a polarization that combines P polarization and S polarization from these two polarization direction aligning elements. A beam splitter, and the light combined by the polarization beam splitter is separated by the dichroic mirror for color separation 3
A liquid crystal video comprising a third, a fourth and a fifth polarization direction aligning element which outputs primary color light in front of each of the liquid crystal display panels by aligning the polarized light according to the liquid crystal display panel. projector.