JP3170239B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display using a liquid crystal light valve.

[0002]

2. Description of the Related Art FIG. 10 is a configuration diagram showing an optical system of a conventional liquid crystal display device. Conventionally, the light emitted from the light source 1 directly enters the light separating means 29, and the light
The light is separated into three primary colors of green and blue, and light is modulated by liquid crystal light valves 12R, 12G, and 12B corresponding to the three primary colors.
There has been known a liquid crystal display device that is enlarged and projected on a front screen 17 by a projection lens 31 after being synthesized by the light synthesizing means 30. Liquid crystal light valves l2R, l2
G and 12B are respectively provided with polarizers 18 and 19 before and after that.
In the light, the P-polarized light component or the S-polarized light component is selectively transmitted by the incident side polarizing plate 18, and the unnecessary polarized light component is absorbed by the incident side polarizing plate 18. The selectively transmitted polarized light components are selectively transmitted again by the exit-side polarizing plate 19 after passing through the liquid crystal light valves 12R, 12G, and 12B, thereby enabling image display.

[0003]

However, in the prior art, the light emitted from the light source 1 is taken into the light separating means 29,
Unnecessary polarization components are absorbed by the incident-side polarization plates 18 of the liquid crystal light valves 12R, 12G, and 12B, and desired polarization components are selectively transmitted.
0% is automatically lost, and the desired brightness cannot be obtained even with the use of a high-luminance light source.
Further, the temperature of the incident side polarizing plate 18 significantly increases due to heat absorption. Since the incident side polarizing plate 18 that has absorbed the heat is provided immediately before the liquid crystal light valves 12R, 12G, and 12B as shown in FIG. 10, the liquid crystal light valves 12R, 12G are provided. , 12B is also remarkable, and in order to guarantee reliability under a wide range of environmental temperature conditions, a high-rotation type cooling fan 32 having a high cooling capacity is required.
Need to be provided in the immediate vicinity of the polarizing plates 18 and 19 and the liquid crystal light valves 12R, 12G and 12B as shown in FIG.
The high-speed cooling fan 32 generates noise corresponding to the number of revolutions. On the other hand, in order to satisfy the life and color characteristics of the light source 1, it is necessary to provide a cooling fan 33 in the immediate vicinity thereof, and the synergistic effect of this and the high-speed cooling fan 32 further increases the noise. It is not suitable as an AV-oriented liquid crystal display device.

[0004] The liquid crystal display device of the present invention solves the above-mentioned problems, and an object thereof is to realize a high-brightness image by making maximum use of a light beam emitted from a light source, and to realize a high reliability under a wide range of environmental temperature conditions. It is an object of the present invention to provide a low-cost liquid crystal display device which has high performance and low noise and which can be adapted to today's AV orientation.

[0005]

In order to solve the above-mentioned problems, a display device according to the present invention comprises a light source, a light valve for modulating light from the light source, and a projection for projecting the light modulated by the light valve. And a display device comprising:
A polarizing beam splitter for separating light from the light source into light of a P-polarized component and light of an S-polarized component; and a polarization direction of light of one of the polarized components separated by the polarized beam splitter. A polarization direction converting means for converting the light of the other polarization component separated by the polarization beam splitter, and a reflection means for reflecting the light of the other polarization component in a direction parallel to the light of the one polarization component, separated by the polarization beam splitter, The light converted into the polarization direction of the other polarization component by the polarization direction conversion means and the light separated by the polarization beam splitter and reflected by the reflection means are condensed, and the cross-sectional area of the light flux is reduced. Light condensing means for reducing the size, wherein the light condensed by the light condensing means is incident on the light valve, and the polarization direction converting means is Characterized in that it is disposed in contact with the light exit surface of the polarization beam splitter.

[0006]

[0007]

In the display device constructed as described above, the light emitted from the light source is separated into a P-polarized light component and an S-polarized light component by a polarizing beam splitter, and a desired polarized light component is redirected by a reflection means, Further, the undesired polarized light component is converted into a desired polarized light component by passing through the polarization direction converting means, and is incident on the light valve. Therefore, all light incident on the polarization beam splitter is incident on the light valve as desired light.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an optical system according to an embodiment of the present invention. In FIG. 1, light emitted from a light source 1 enters a polarizing beam splitter 2 and
The P (S) polarized light component is transmitted and the S (P) polarized light component is reflected on the reflecting surface of. The P (S) polarization component transmitted through the polarization beam splitter 2 is a λ / 4 plate 3 serving as a polarization rotation element.
Is transmitted, the linearly polarized light is converted into circularly polarized light, and the propagation direction of the circularly polarized outgoing light is reversed by being reflected by the front reflection means 4, and then transmitted through the λ / 4 plate 3 again. Then, the light is again linearly polarized, is converted into an S (P) polarization component orthogonal to the linearly polarized light before entering the λ / 4 plate 3, and returns to the polarization beam splitter 2. The S (P) polarization component returned to the polarization beam splitter 2 is turned by 90 ° at the reflection surface of the polarization beam splitter 2,
After the direction change is repeated by the reflection means 5, 6, and 7, the light becomes parallel to the optical axis of the light source 1 and enters the light separation means 8. On the other hand, the S (P) polarization component first reflected on the reflection surface of the polarization beam splitter 2 is the above-mentioned S (P)
Reflection of the polarization component and the mirror surface state with respect to the optical axis of the light source 1 is repeated by the reflection means 5, 6, and 7. The light is also parallel to the optical axis of the light source 1 and enters the light separating means 8. The S (P) polarized light component that has entered both is reflected by the blue reflecting dichroic mirror 9 to reflect noble color light (light of about 500 nm or less) and transmit other light (yellow light). The direction of the reflected blue light is changed by the reflection mirror 10 and enters the blue liquid crystal light valve 12B. The light transmitted through the blue reflecting dichroic mirror 9 enters the red transmitting dichroic mirror 11 and reflects green light (light between about 500 nm and about 600 nm), and red light (about 600 nm) as other light.
Above light). The reflected edge light enters the liquid crystal light valve 12G for edge color, and the transmitted red light enters the liquid crystal light valve 12R for red. Each incident color light is
After undergoing light modulation corresponding to each color by the liquid crystal light valves l2R, l2G, l2B, the light enters the light combining means l3,
The blue light is transmitted through the blue transmission dichroic mirror 14 and then reflected by the red transmission dichroic mirror 15, the green light is reflected by the blue transmission dichroic mirror 14 and the red transmission dichroic mirror I5, and the red light is reflected by the reflection mirror 1
After being reflected at 0, it passes through a red transmitting dichroic mirror 15. The light combined as described above enters the projection lens 16 and is enlarged and projected on the screen 17 in front.

Liquid crystal light valves l2R, l2G, l2B
Can display an image by receiving the selection of the polarization components in the polarizers 18 and 19 before and after the polarizer, however, since the polarizer 18 is used as an auxiliary polarizer of the polarization beam splitter 2, the polarization degree of the polarization beam splitter 2 is increased. Is not necessary when the value is close to 100%.

FIG. 2 shows the principle of the λ / 4 plate 3 described above. The angle θ formed between the linearly polarized light plane 22 of the incident light beam and the optical axis direction 21 of the crystal of the λ / 4 plate 3 is 45 °. FIG. 6 illustrates that in some cases, linearly polarized incident light can be converted to circularly polarized light (or vice versa).

FIG. 3 shows another embodiment in which the light from the light source 1 is monopolarized. The light emitted from the light source 1 transmits a P (S) polarization component on the reflection surface of the polarization beam splitter 2. The S (P) polarization component is reflected. Penetrated P
(S) The polarization component is a λ / 2 plate 2 which is a front polarization rotation element.
3, the plane of polarization is rotated by 90 °, and S
(P) The light enters the light separating means 8 as a polarized light component. On the other hand, the reflected S (P) polarized light component has its course changed once in a direction parallel to the optical axis of the light source 1 by the reflecting means 5 and again enters the light separating means 8. Therefore, also in this case, all the light incident on the polarizing beam splitter 2 is S
(P) It turns out that it becomes a polarization component. In this case, λ
FIG. 4 shows the principle of the 板 / 2 plate 23. When the angle θ formed between the linear polarization plane 22 of the incident light beam and the optical axis direction 21 of the crystal of the λ / 2 plate 23 is 45 °, the light is incident. Since the plane of polarization of linearly polarized light is rotated by 90 °, the P (S) polarization component is S
(P) It is converted into a polarized light component.

As described above, since the undesired polarized light component hardly enters the light dividing means 8, the liquid crystal light valves l2R, l2
The temperature rise of 2G, 12B is minimized, and even if environmental temperature conditions are taken into account, the liquid crystal light valves 12R, 12B
A cooling fan dedicated to G and 12B is not required, and cooling as a device is performed by a light source l and a liquid crystal light valve l as shown in FIG.
It is sufficient to use the cooling fan 20 for cooling the 2R, 12G, 12B and the polarizing plates 18, 19 simultaneously.

FIGS. 5 and 6 show a polarizing beam splitter 2.
This is an embodiment in which a glass plate 26 is used. As described above, the polarizing beam splitter 2 generally has a cube shape in which the slopes of a pair of right-angle prisms are bonded to each other as described above. In this case, a degree of polarization of about 98% can be achieved, so that the polarizing plate 18 is unnecessary. It will be expensive.
The polarization beam splitter shown in FIGS. 5 and 6 realizes low cost, and its principle will be described with reference to FIG. In FIG. 7, the refractive index of the glass plate 26 is n, and the incident angle of light is ζ.
When the glass plate 26 is provided in a relation of ζ = tan ⁻¹ n, the P-polarized light component 27
Is transmitted by 100% and about 15% of the S-polarized light component 28 is reflected. (In this case, ζ is the Brewster's angle.) Therefore, when a plurality of glass plates 26 are stacked in parallel to form a structure as shown in FIGS.
Is transmitted by 100%, and the S-polarized light component 28 is reflected by 100%. In the actual measurement, when the number of glass plates 26 is plotted on the horizontal axis and the degree of polarization is plotted on the vertical axis, the relationship shown in FIG.
When about 8 to 10 sheets are used, a degree of polarization of about 80% can be achieved. As described above, the degree of polarization of about 80% can be achieved by arranging eight to ten glass plates 26 in parallel so that the incident angle of the superposed light becomes the Brewster angle. The absorption of the S-polarized component by the polarizing plate 18 is less than 30%, and the temperature rise of the polarizing plate 18 can be minimized. Therefore, even if this polarizing plate 18 is provided immediately before the liquid crystal light valves 12R, 12G, 12B, the polarizing plate 18
Liquid crystal light valves l2R, l2G, l
The influence on the liquid crystal light valves 12R, 12G, and 2B is extremely small even when the environmental temperature conditions are taken into consideration.
A cooling fan dedicated to 12B is not required, and cooling as a device is performed by a light source 1 and a liquid crystal light valve 12 as shown in FIG.
It is sufficient to use the cooling fan 20 for cooling the R, 12G, 12B and the polarizing plates 18, 19 simultaneously. In FIGS. 5 and 6, the relationship among the light source, the polarization beam splitter, the polarization rotation element, the reflection means, and the light separation means is exactly the same as that described with reference to FIGS.

FIG. 9 shows an embodiment in which a convex lens 24 and a concave lens 25 are provided in combination in front of the light separating means 8 in FIG. 3. According to this configuration, the cross-sectional area of light incident on the light separating means 8 is reduced. Therefore, a combination of a larger light source and a smaller light separating means becomes possible, and the above-described configuration is more effective for brightness. This is exactly the same in the cases of FIGS. 1, 5 and 6.

[0015]

As described above, the display device of the present invention separates outgoing light from a light source into a P-polarized light component and an S-polarized light component by a polarizing beam splitter, and the components on both sides become parallel by a polarization direction converting means. Since the light beam is incident on the light valve in such a manner, high-luminance display can be realized by making maximum use of the light beam emitted from the light source.

Further, since the temperature rise of the light valve can be minimized by the above configuration, reliability under a wide range of environmental temperature conditions can be secured, and the light source and the light valve can be cooled by a common cooling fan. Therefore, it is possible to realize a display device that is low noise and can be adapted to today's AV orientation.

[0017]

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical system of a liquid crystal display device of the present invention.

FIG. 2 is a principle diagram of a λ / 4 plate used in the present invention.

FIG. 3 is a configuration diagram of another embodiment related to the polarizing means of the present invention.

FIG. 4 is a principle diagram of a λ / 2 plate used in the present invention.

FIG. 5 is a configuration diagram in the case of using a λ / 2 plate by another polarization beam splitter of the present invention.

FIG. 6 is a configuration diagram in the case of using a λ / 4 plate by another polarization beam splitter of the present invention.

FIG. 7 is a principle diagram of a polarization beam splitter of the present invention.

FIG. 8 is a diagram showing the relationship between the number of glass plates and the degree of polarization by the polarizing beam splitter of the present invention.

FIG. 9 is a configuration diagram of another embodiment related to the polarizing means of the present invention.

FIG. 10 is a configuration diagram of an optical system of a conventional liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 light source 2 polarizing beam splitter 3 λ / 4 plate (polarization rotating element) 4, 5, 6, 7 reflecting means 8 light separating means 12 liquid crystal light valve 13 light combining means 16 projection lens 17 screen 18 and 19 polarizing plate 20 cooling fan 2l The direction of the optical axis of the crystal, 22 The plane of linear polarization of incident light 23 λ / 2 plate (polarization rotating element) 24 Convex lens 25 Concave lens 26 Glass plate 27 P polarization component 28 S polarization component

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI G03B 33/12 G09F 9/00 360D G09F 9/00 360 H04N 5/74 K H04N 5/74 G02F 1/1335 530

Claims (1)

(57) [Claims] 1. A display device comprising: a light source; a light valve for modulating light from the light source; and a projection unit for projecting light modulated by the light valve, wherein the light from the light source is a P-polarized component. A polarizing beam splitter that separates the light into S-polarized light and light having one S-polarized light; and a polarization direction converting unit that converts the light of one polarized light separated by the polarizing beam splitter into the polarization direction of the light of the other polarized light. A reflection unit that reflects the light of the other polarization component separated by the polarization beam splitter in a direction parallel to the light of the one polarization component; and the other polarization separated by the polarization beam splitter and the polarization direction conversion unit. The light converted into the polarization direction of the component light and the light separated by the polarizing beam splitter and reflected by the reflecting means are collected. Light condensing means for reducing the cross-sectional area of the light beam, wherein light condensed by the light condensing means is incident on the light valve, and the polarization direction conversion means comprises light from the polarization beam splitter. A display device, which is arranged in contact with an emission surface.