JPH0341434A - Projection type display device - Google Patents

Abstract

PURPOSE:To reduce light loss caused at the time of synthesizing by permitting color light, which is reflected from a dichroic optical element one time or more, to be made incident on the element by p-polarization and permitting all color light, which is transmitted through the element, to be made incident on it by s-polarization. CONSTITUTION:Light from a light source 1 is separated into three colors of red R, green G, and blue B by passing the light through a color separation dichroic mirror 5 via a polarizing plate 4, and then they are synthesized by a dichroic prism 13 via respective TN type liquid crystal panels 7, 8, and 9 and respective polarizing plates 10, 11, and 12 to be projected. The light R and B both of which are reflected from the dichroic surface of the prism 13 one time or more is made incident on the dichroic surface by p-polarization (polarized light perpendicular to the surface of a paper); all the light G which is transmitted through the dichroic surface is made incident on it by s- polarization (polarized light horizontal to the surface of the paper).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection type display device for displaying video images, computer images, etc. The present invention relates to a projection type display device using a liquid crystal light valve, which has excellent contrast and can realize a compact size.

[Conventional technology]

Our company has commercialized a conventional projection display device using a liquid crystal light valve with the configuration shown in Figure 4.
Epson, video projector-VPJ-700).

[Problem to be solved by the invention]

However, in the conventional projection display device with the configuration shown in Figure 4, a large portion of the light energy is absorbed by the three polarizing plates on the incident side and converted into thermal energy, causing The brightness of the light source cannot be increased too much, and the brightness of the display screen becomes too high.
The problem was that it was dark. Also, clear the task. The cooling system required for this purpose was also large-scale, which became a bottleneck in reducing prices.

In order to solve these problems, a configuration as shown in Figure 5 in which the polarizing plate on the incident side is separated from the liquid crystal panel is effective.
This has already been proposed (Japanese Unexamined Patent Publication No. 125791/1983).

In this case, since only one polarizing plate is required, there is also the advantage that costs can be reduced. However,
In this case, the polarization planes of the three colored lights will all be parallel to the plane of the paper in Figure 5, and the light loss at the color synthesis means will be larger than in the case of 14 components as shown in Figure 4. There was a problem.

Therefore, an object of the present invention is to solve the above-mentioned problems.

[Issues, means for solving problems]

The projection type display device of the present invention includes a light source, a color separation means for separating light from the light source into three different colored lights, and three for modulating each of the three different colored lights separated by the color separating means.
a color synthesizing means comprising a dichroic optical element group for synthesizing the three colored lights modulated by the three light valves, and a single projection optical means for projecting the light synthesized by the color synthesizing means. The three light valves include three TN liquid crystal panels, three polarizing means on the output side corresponding to the three TN liquid crystal panels, and polarizing means on the input side common to the three TN liquid crystal panels. The three colored lights include a first type of colored light that is reflected at least once by a dichroic optical element included in the color synthesizing means, and a first type of colored light that is completely transmitted through the dichroic optical element included in the color synthesizing means. two types of colored light, the first type of colored light is p-polarized and incident on a dichroic optical element included in the color combining means, and the second type of colored light is included in the color combining means. It is characterized in that the directions of the transmission axes of the three polarizing means on the output side and the one polarizing means on the input side are adjusted so that the light enters the dichroic optical element as S-polarized light.

[Effect]

In a projection display device configured as described above, as shown in Figure 1, the polarizing plate on the incident side and the liquid crystal panel are spatially separated, and the problem of heat generated in the polarizing plate on the incident side is a problem. In addition, the polarizing plate on the incident side can be cut into three liquid crystal panels and it is low cost, and the polarization axis can be aligned once with the polarizing plate on the incident side that is common to the three liquid crystal panels. When the colored light from a book passes through the corresponding liquid crystal panel, the polarization axis may or may not rotate, and when the colored light is combined by the color synthesis means, the polarized light is such that light loss is minimized. It can be made to have an axis.

[Embodiment 1] FIG. 1 is a diagram showing the optical configuration of a projection type display device of the present invention. 1 is a light source. 2 is a reflector. 3 is heat filter 4
The incident side polarizing plate 1°5 is a dichroic mirror for color separation, and there are two of them. 6 is a mirror for bending the optical path.

7 is an R TN type liquid crystal panel 1 for modulating red color light, 8 is a G TN type liquid crystal panel 1 for modulating green color light, and 9 is a G type TN type liquid crystal panel 1 for modulating blue color light. B
This is a TN type liquid crystal panel 1 for use. Also 10, 11.12
are 8. 9. This is an output side polarizing plate 1 for R, G, and B used in correspondence with No. 10 TN type liquid crystal panel. A TN type liquid crystal panel functions as a light valve by combining a polarizing plate on the incident side and a polarizing plate on the output side. 13 is a dichroic prism for color synthesis. 14 is a projection lens.

Here, the directions of the transmission axes of the incident side and output side polarizing plates are set to the first direction.
Shown in the table.

Table 1 Directions of the transmission axes of the polarizing plates on the input side and the output side The transmission axes of the polarizing plates corresponding to red and blue color light are set almost parallel to the plane of the paper on the input side and almost perpendicular to the plane of the paper on the output side. An orthogonal nicol arrangement was used. In addition, the transmission axis of the polarizing plate corresponding to green color light was set almost parallel to the plane of the paper on the incident side, and f parallel to the plane of the paper on the output side, resulting in a parallel Nicol arrangement.

With this configuration, among the three colored lights modulated by each light valve, the red and blue lights that are reflected at least once by the dichroic surface included in the color synthesis dichroic prism are reflected onto the paper surface. It enters as perpendicularly polarized light (i.e., p-polarized light with respect to the dichroic surface) and completely passes through the dichroic surface for color synthesis.
The green color light is incident on the page as horizontally polarized light (that is, S-polarized light with respect to the dichroic surface).

Therefore, as shown in Table 2, the light loss could be minimized using the color synthesis dichroic prism.

Table 2 Reflectance and transmittance for p-polarized light and s-polarized light Although an example is shown in which a polarizing plate is used as the polarizing means on the incident side and the polarizing means on the output side, the polarizing beam is not limited to this. The present invention is effective even with a splitter or other means.

Furthermore, a rear projection display device using the above-described optical system as a projection optical unit has similar effects.

As described above, in the projection display device of this embodiment, the problem of heat generated by the polarizing means on the incident side is reduced compared to the conventional one, the number of polarizing means on the incident side is only one, and the light during color synthesis is reduced. Since loss can also be minimized, as a result, a projection type display device with a bright display screen can be provided at a lower price than before.

[Embodiment 2] FIG. 2 is a diagram showing a different optical configuration from Embodiment 1 of the projection type display device of the present invention. The optical configuration is almost the same as that of Example 1, but the polarization direction of the polarization means is different. (See Table 3) Table 3 Directions of the transmission axes of the polarizing plates on the input side and output side The transmission axes of the polarizing plates corresponding to red and blue color light are set almost perpendicular to the plane of the paper on the input side, and on the output side as well. The parallel Nicol arrangement was made almost perpendicular to . Further, the transmission axis of the polarizing plate corresponding to green color light was set to be substantially perpendicular to the plane of the paper on the incident side and substantially horizontal to the plane of the paper on the output side, so that a crossed Nicol arrangement was adopted.

1 By adopting such a 41Pi angle, substantially the same effect as the configuration of Example 1 was obtained.

[Example 3] Figure 3 shows Example 1 and Example 2 of the projection type display device of the present invention.
FIG. 3 is a diagram showing a different optical configuration.

By adopting this configuration, substantially the same effect as the configurations of Examples 1 and 2 was obtained.

Also, of the two dichroic mirrors used for color synthesis, red color light is reflected by one and transmitted by the other, so almost the same effect can be obtained with a parallel Nicol arrangement rather than an orthogonal Nicol arrangement. .

〔Effect of the invention〕

The projection type display device of the present invention includes a light source, a color separation means for separating light from the light source into three different colored lights, and three for modulating each of the three different colored lights separated by the color separating means.
a color synthesis means consisting of a group of dichroic optical elements for synthesizing the three colored lights modulated by the three light valves, and a single projection optical means for projecting the light beams stabilized by the color synthesis means. =12- The three light valves have three TN liquid crystal panels, three polarizing means on the output side corresponding to the three TN liquid crystal panels, and a polarization means common to the three TNW1 and crystal panels. a first type of colored light that is reflected at least once by a dichroic optical element included in the color synthesizing means; and a dichroic optical element included in the color synthesizing means. the first type of colored light is incident as p-polarized light on the dichroic optical element included in the color combining means, and the second type of colored light is completely transmitted through the color In order to adjust the directions of the transmission axes of the three polarizing means on the output side and the one polarizing means on the input side so that the S-polarized light enters the dichroic optical element included in the combining means, The problem of heat generated by polarizing means is reduced,
Only one polarizing means is required on the incident side, and light loss during color synthesis can be minimized. As a result, a projection display device with a bright display screen can be provided at a lower cost than before.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a projection type display device according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram of a projection type display device according to a second embodiment of the present invention. FIG. 3 is a configuration diagram of a projection type display device according to Embodiment 3 of the present invention. FIG. 4 is a configuration diagram of a conventional projection display device. FIG. 5 is another configuration diagram of a conventional projection type display device. 1...Light source 2...Reflector 3...Heat filter 4...Incidence side polarizing plate 1 5...Dichroic mirror for color separation 6...Mirror 7...TN type for R Liquid crystal panel 1 8...TN type liquid crystal panel 1 for G 9...TN type liquid crystal panel 1 for B 10...Emission side polarizing plate 1 for R 11...Emission side polarizing plate for G 1 l2... Output side polarizing plate 1 for B 13... Dichroic prism for color synthesis 14...
Projection lens 15...Incoming side polarizing plate 2 16...TN type liquid crystal panel 2 for R 17...TN type liquid crystal panel 2 for G 18...TN type liquid crystal panel 2 for B 19...・Output side polarizing plate 2 for R 20...Output side polarizing plate 2 for G 21...Output side polarizing plate 2 for B 22...Dichroic mirror for color synthesis 23...R
TN type liquid crystal panel 3 for 24... TN type liquid crystal panel 3 for G 25... TN type liquid crystal panel 3 for B 26... Output side polarizing plate 3 for R 27... TN type liquid crystal panel 3 for G Output side polarizing plate 3 28...Output side polarizing plate 3 for B 29...Screen 30...Light valve 4 for R 31...Light valve 4 for G 5- 32...Light valve for B 4 33...Metal halide lamp 34...Reflector 4 35...Collimator lens 36...Incoming side polarizing plate 5 37...Mirror 5 38...Dichroic prism for color separation 39...
TN type liquid crystal panel 5 for R 40... TN type liquid crystal panel 5 for G 41... TN type liquid crystal panel 5 for B 42... Output side polarizing plate 5 for R 43... Output side polarizing plate for G 5 44... B output side polarizing plate 5 or more

Claims (1)

[Scope of Claims] A light source, color separation means for separating light from the light source into three different colored lights, three light valves that respectively modulate the three different colored lights separated by the color separation means; It has a color synthesizing means made of a dichroic optical element group that synthesizes the three colored lights modulated by the three light valves, and a single projection optical means that projects the light synthesized by the color synthesizing means, The three light valves have three TN liquid crystal panels, three output side polarizing means corresponding to the three TN liquid crystal panels, and an input side polarizing means common to the three TN liquid crystal panels, The three colored lights include a first type of colored light that is reflected at least once by a dichroic optical element included in the color synthesizing means, and a second type of colored light that is transmitted through all the dichroic optical elements included in the color synthesizing means. the first type of colored light is p-polarized and incident on the dichroic optical element included in the color synthesizing means, and the second type of colored light is incident on the dichroic optical element included in the color synthesizing means. A projection type display device characterized in that the directions of the transmission axes of the three polarizing means on the exit side and the polarizing means on the one incident side are adjusted so that S-polarized light is incident.