JPH04104681U - Projection type LCD display - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the display brightness of a projection type liquid crystal display. [Structure] Light from a light source 1 is separated by a polarizing beam splitter 4 into a polarized component parallel to the plane of the paper and a polarized component perpendicular to the plane of the paper. The polarization direction of the polarized light component perpendicular to the plane of the paper is rotated by 90° by the phase plate 8. Therefore, the polarization direction of the light incident on the liquid crystal panels 16 to 18 is all parallel to the plane of the paper. Since the direction of the polarization axis of the rear polarizing plate of each liquid crystal panel is parallel to the plane of the paper, there is almost no loss of light due to the rear polarizing plate.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a projection type liquid crystal display, and particularly to its optical system.

0002

[Conventional technology]

Conventionally, devices in this type of field have been used, for example, "O pulse E No. 125 1". There is one described in "April 990 issue P79-P84". FIG. 2 is a configuration diagram of a conventional projection type liquid crystal display described in the above-mentioned document. be.

0003 In the figure, 21 is a white light source such as a metal halide lamp, and 22 is a visible light source. Cold mirror that reflects and transmits infrared light, 23 transmits visible light and transmits ultraviolet and red light. UV-IR cut filter that reflects external rays, 24 reflects only red of visible light. R reflecting mirrors 25 and 26 are B reflecting mirrors that reflect only blue among visible light; 27 is a G reflection mirror that reflects only green light among visible light, 28 and 29 are total reflection mirrors. 36 is a projection lens; 30, 31, 32 are the projection lenses 36; Condenser lenses 33, 34, and 35 are for red, blue, and condenser lenses, respectively. These are green liquid crystal panels R-LCD, B-LCD, and G-LCD.

0004 FIG. 3 is an explanatory diagram of the operation of the liquid crystal panels 33 to 35. As shown in the figure, a front polarizing plate 37 is arranged in front of the liquid crystal panel, and A rear polarizing plate 18 is placed on the surface so that the polarizing axis of the front polarizing plate 37 is orthogonal to the polarizing axis of the front polarizing plate 37. It is located. Next, the operation of the liquid crystal panel will be explained.

[0005] First, when no voltage is applied to the liquid crystal shown in (a), the liquid crystal molecules In the vicinity of the rear polarizing plate 38 and the front polarizing plate 37, the polarization axes and liquid crystal molecules are parallel to each other. The direction is from the rear polarizing plate 38 side to the front polarizing plate 37 side. The axes of the liquid crystal molecules 39 are twisted by 90° along the curve. In this state, the back When light enters from the polarizing plate 38 side, the back polarizing plate 38 first changes the polarization of the back polarizing plate 38. Only the polarized light component parallel to the axis enters the liquid crystal panel, and due to the twist of the axis of the liquid crystal molecules 39. The polarization direction of the incident light is also twisted, and the polarization direction is rotated by 90 degrees compared to when it was incident. The state will be as follows. The front polarizing plate 37 has a polarization axis perpendicular to that of the back polarizing plate 38. Therefore, light is transmitted.

[0006] On the other hand, when voltage is applied to the liquid crystal shown in (b), the liquid crystal molecules The axis of 39 is perpendicular to the front polarizing plate 37 and the back polarizing plate 38. In this state, the back When light enters from the polarizing plate 38 side, first the polarization of the rear polarizing plate 38 is changed as in the above case. Only polarized light components parallel to the optical axis enter the liquid crystal panel. After that, the polarization direction changes. Therefore, it is blocked by the front polarizing plate 37.

[0007] Next, the overall operation of a conventional projection type liquid crystal display will be explained based on Figure 2. do. The light emitted from the light source 21 is reflected by the cold mirror 22 and passes through the UV-IR cutoff. It passes through the filter 23 and enters the R reflection mirror 24, where only the red component is reflected and the blue component is reflected. The color/green component is transmitted.

[0008] The red component light reflected by the R reflection mirror 24 is reflected by the total reflection mirror 28, The light is focused by the condenser lens 30 and enters the red liquid crystal panel 33. 33, passes through the B reflecting mirror 26 and the G reflecting mirror 27, and then passes through the projection lens 3. Projected at 6. Also, among the blue and green components transmitted through the R reflection mirror 24, the blue component is absorbed by the B reflection mirror 24. The light is reflected by the blue color, condensed by the condenser lens 31, and incident on the blue liquid crystal panel 34. It passes through the blue liquid crystal panel 34, is reflected by the B reflection mirror 26, and is reflected by the G reflection mirror 26. 27 and is projected by a projection lens 36.

[0009] Of the blue and green components transmitted through the R reflection mirror 24, the green component is reflected by the B reflection. The light passes through the mirror 25, is condensed by the condenser lens 32, and is displayed on the green liquid crystal panel 35. The light enters the green liquid crystal panel 35, is reflected by the total reflection mirror 29, and is reflected by the G reflection mirror 29. It is also reflected by the projection mirror 27 and projected by the projection lens 36. As described above, the images generated by the red, blue, and green liquid crystal panels are combined and projected. be done.

0010

[Problem that the idea aims to solve]

However, in the conventional projection type liquid crystal display mentioned above, the light emitted from the light source consists of light with various polarization directions, while the light that passes through the liquid crystal panel is the same. Since the light is only in the direction of polarization, the loss of light at the back polarizer is at least 50 %, and the light usage efficiency is poor. As a result, the projected display image becomes dark and bright. The problem is that in order to do so, a light source with higher power consumption must be prepared. was there.

[0011] This invention solves the above-mentioned conventional problems, has good light usage efficiency, and has a bright display screen. The aim is to provide a projection-type liquid crystal display that is easy to use and consumes little power. Ru.

0012

[Means to solve the problem]

In order to solve the above problems, the present invention provides a light source and a liquid crystal panel having a back polarizing plate. In a projection type liquid crystal display equipped with a channel, the light from the light source is polarized orthogonally to each other. A polarizing beam splitter that separates the beam into two components in the direction, and a polarizing beam splitter that separates the beam into two components. A phase plate that rotates at least one polarization direction by 90 degrees is provided, and the light from the light source is to convert it into a polarized light component in the same direction as the polarization axis of the back polarizing plate of the liquid crystal panel. It is characterized by:

[0013]

[Effect]

According to the present invention, since the projection type liquid crystal display is configured as described above, the light source A polarizing beam splitter splits the light emitted from the The polarization direction of the component light is rotated by 90° using a phase plate, and then combined with the other component light. By adjusting the polarization axis of the back polarizing plate of the LCD panel, the light incident on the LCD panel is This improves the efficiency of light use by converting only the polarized light component of the direction.

[0014]

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a projection type liquid crystal display according to an embodiment of the present invention. In the figure, 1 is a white light source such as a metal halide lamp, and 2 is visible light. Cold mirror that reflects visible light and transmits infrared light, 3 transmits visible light and transmits ultraviolet and infrared light. 4 is a P-polarized light component (polarized light component parallel to the paper surface). , the S-polarized light component (the polarized light component perpendicular to the plane of the paper) is transmitted (shown as a dot on the optical axis). 5, 6, and 7 are polarizing beam splitters that reflect light Total reflection mirror 8 is a phase plate that rotates the polarization direction of incident light by 90 degrees. For example, it is made up of liquid crystal. 9 is an R reflective mirror that reflects only red visible light. , 10 and 11 are B reflecting mirrors that reflect only blue of visible light, and 12 is a visible light reflector. 19 is a projection lens, 13, 14, 15 are the above-mentioned G reflection mirrors that reflect only green color. Condenser lenses 16, 17, and 18 are used to condense light onto the projection lens 19, respectively. These are red, blue, and green liquid crystal panels, R-LCD, B-LCD, and G-LCD. The operations of the liquid crystal panels 16, 17, and 18 are the same as those explained in the conventional example. , the back polarizer is arranged so that its polarization axis is parallel to the plane of the paper, and the front polarizer is The plate is arranged so that its polarization axis is perpendicular to the plane of the paper.

[0015] Next, we will explain the overall operation of the projection type liquid crystal display in the embodiment of the present invention. I will clarify. The light emitted from the light source 1 has various polarization directions and is reflected by the cold mirror 2. The light passes through the UV-IR cut filter 3 and enters the polarizing beam splitter 4. Enter Of the emitted light, the polarized light component parallel to the paper surface (P polarized light component) is sent to the polarizing beam splitter. 4 and the polarized light component perpendicular to the plane of the paper (S-polarized component) is reflected.

[0016] The reflected S-polarized light component is reflected by the total reflection mirror 5, and for example, the entire panel is The light is incident on the phase plate 8 which is made up of a liquid crystal panel having a structure as shown in FIG. phase The polarization direction of the incident S-polarized light component is rotated by 90 degrees by plate 8, making it the same as the P-polarized light component. The light becomes polarized. Therefore, the light that has passed through the polarizing beam splitter 4 and the light that has been reflected have the same polarization direction. The light enters the R reflection mirror 9, and only the red component is reflected. The blue and green components are transmitted.

[0017] The red component light reflected by the R reflection mirror 9 is reflected by the total reflection mirror 6 and then The light is focused by the sensor lens and enters the red liquid crystal panel 16. The incident light is a red LCD panel. Since the direction of the polarization axis and the direction of polarization are the same as that of the back polarizing filter in filter 16, There is almost no loss of light in a plane polarizing filter. Light transmitted through the red liquid crystal panel 16 is transmitted through the B reflection mirror 11 and the G reflection mirror 12 and is projected by the projection lens 19. Ru.

[0018] Also, among the blue and green components transmitted through the R reflection mirror 9, the blue component is the B reflection mirror. The light is reflected by the color 10, focused by the condenser lens 14, and enters the blue liquid crystal panel 17. shoot At this time, as with the red LCD panel, there is almost no light loss in the back polarizing filter. There's no way. The light transmitted through the blue liquid crystal panel 17 is reflected by the B reflection mirror 11, The light passes through the G reflection mirror 12 and is projected by the projection lens 19.

[0019] Of the blue and green components transmitted through the R reflection mirror 9, the green component is reflected by the B reflection. The light passes through the mirror 10, is focused by the condenser lens 15, and enters the green liquid crystal panel 18. shoot At this time, like the red LCD panel and blue LCD panel, use a rear polarizing filter. Almost no light loss occurs. The light transmitted through the green liquid crystal panel 18 undergoes total internal reflection. reflected by the mirror 26, then projected by the G reflection mirror 12, and then projected by the projection lens 19. be projected.

[0020] As described above, the images generated by the red, blue, and green liquid crystal panels are combined and projected. be done. In the above embodiment, the polarization direction of the S-polarized component is rotated by a 90° phase plate. However, the polarization direction of the P-polarized light component may be rotated. In addition, the above example This is a projection type liquid crystal display that displays color images, but the present invention can display monochrome images. It is clear that the invention can be applied to projection type liquid crystal displays. In addition, this invention Various modifications are possible based on the purpose, and these are excluded from the scope of the present invention. isn't it.

[0021]

[Effect of the idea]

As explained in detail above, according to the present invention, the light emitted from the light source is converted into a polarized beam. A splitter separates the light into P-polarized light and S-polarized light, and one polarized light is passed through a phase plate. The polarization direction is rotated by 90° through the LCD panel to make the polarization component the same as the other polarization component. Since the structure is configured such that the light is incident on the beam, the following effects can be achieved. (1) There is almost no loss of light at the rear polarizing plate when it enters the liquid crystal panel. , display brightness is improved. (2) The same display brightness as before can be obtained with less power consumption.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a projection type liquid crystal display according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional projection type liquid crystal display.

FIG. 3 is an explanatory diagram of the operation of the liquid crystal panel.

[Explanation of symbols]

1 White light source 2 cold mirror 3 UV-IR cut filter 4 Polarizing beam splitter 5-7 Total reflection mirror 8 Phase plate 9 R reflective mirror 10, 11 B reflective mirror 12 G reflection mirror 13-15 Condenser lens 16-18 LCD panel 19 Projection lens

──────────────────────────────────────────────── ─── Continuation of front page (72) Creator Hiroshi Toyama Oki Electric, 1-7-12 Toranomon, Minato-ku, Tokyo Inside Kogyo Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A projection type liquid crystal display comprising a light source and a liquid crystal panel having a rear polarizing plate, comprising: (a) a polarizing beam splitter that separates light from the light source into two components with mutually orthogonal polarization directions; b) A phase plate that rotates the polarization direction of at least one of the two polarization components by 90° is provided, and the light from the light source is polarized in the same direction as the polarization axis of the back polarizing plate of the liquid crystal panel. A projection-type liquid crystal display that converts into