KR100283448B1 - Projection type image display device - Google Patents

Abstract

Disclosed is a projection image display device comprising a light source for emitting light, a condenser lens, a first prism, a second prism, a third prism, a fourth prism, a reflective light modulator, a projection lens, and a screen. Four prisms are connected to each other, and hybrid prisms are formed by attaching dichroic filters, mirrors, and reflective light modulators to respective faces of the prism thus obtained. By integrating the rest of the components of the optical system except for the light source, the optical system can be compactly configured to reduce the cost. In addition, by using a reflective light modulator using both polarization components, the light efficiency can be greatly increased.

Description

Projection type image display device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device. More particularly, the present invention relates to a projection display device in which an optical system can be compactly used to reduce cost and improve light efficiency by using a reflection type light regulator.

In general, a spatial light modulator, which is an apparatus for projecting optical energy onto a screen, may be applied to various fields such as optical communication, image processing, and information display apparatus. Typically, such devices are classified into a direct-view image display device and a projection-type image display device according to a method of displaying optical energy on a screen.

An example of a direct-view image display device is a CRT (Cathode Ray Tube). The CRT device is called a CRT, which has excellent image quality but increases in weight and volume as the screen is enlarged, leading to an increase in manufacturing cost. There is. Projection type image displays include liquid crystal displays (LCDs), deformable mirror devices (DMDs), and actuated mirror arrays (AMAs). Such projection image display devices can be further divided into two groups according to their optical characteristics. That is, devices such as LCDs can be classified as Transmissive spatial light modulators, while DMD and AMA can be classified as Reflective spatial light modulators.

An LCD device is a display device using a liquid crystal that can electrically control the transmittance of light. The display device using the LCD (or liquid crystal projector) has a very simple optical structure, which makes it possible to reduce light weight and shorten the size of a CRT projector. Can be. In addition, it is widely used as a display device for high-definition television (HDTV) and video conferencing because large screens and high image quality can be obtained.

A liquid crystal panel used in a liquid crystal projector is commonly known as a matrix liquid crystal panel, in which pixels are arranged in a matrix in two directions perpendicular to each other, and are driven individually by a driving voltage to provide optical Change characteristics. The drive voltage can be applied to the individual pixels by a simple matrix system, and non-linear two-terminal elements such as metal-insulating metal (MIM) or three-terminal switching elements such as TFT (thin film transistor) are placed for each pixel. It can be applied to each pixel alternately by the active matrix system.

In such an active matrix system, the pixels should be arranged at a minimum pitch, thereby reducing the ratio of openings occupied by the pixels to the total area (aperture ratio). The transmittance of the liquid crystal plate is determined by the efficiency of the polarizer and the aperture ratio of each pixel. Therefore, in order to increase the aperture ratio, a method of disposing a microlens array on the light incident surface or the light incident surface and the exit surface of the display element corresponding to each pixel is mainly used. This microlens array includes multiple lens elements arranged at the same pitch as the pitch between the pixels, wherein light is focused on each pixel through lens elements disposed on the light incident surface.

1 is a schematic diagram showing the configuration of a projection display device using a conventional liquid crystal plate.

Referring to FIG. 1, a conventional projection display device 10 includes a projection lens 24 for projecting colored light (L), and red light (R), green light (G), and blue light (B). Each of the liquid crystal plates 20a, 20b, and 20c. The liquid crystal plates 20a, 20b, and 20c change their transmittances according to the applied image signal to transmit or block the red, green, and blue lights. The transmitted light is projected by the projection lens 24 into a ray L comprising three color rays.

In addition, the conventional projection display device 10 includes a metal halide lamp 12, a microlens array 14, a dichroic mirror 16a, 16b, and a mirror for emitting light rays. 17a, 17b, 17c, condenser lenses 18a, 18b, and dichroic prism 22 are further provided.

The microlens array 14 is composed of multiple lens elements arranged at the same pitch as the pitch between the pixels of the liquid crystal plates 20a, 20b, and 20c, and each pixel through lens elements disposed on a light incident surface. To focus the light on.

The dichroic mirrors 16a and 16b serve to separate the white light emitted from the halogen metal lamp 12 into three primary colors of light, that is, red light, green light and blue light. The dichroic mirrors 16a and 16b are reflectors made of many thin layers of materials having different refractive indices. The dichroic mirrors 16a and 16b reflect light of a certain color and transmit light of all other colors.

The dichroic prism 22 has a dichroic mirror reflecting only red light and transmitting other light and a dichroic mirror reflecting only blue light and transmitting other light in the form of 'X'. Thus, by reflecting the red light and blue light incident on the three mutually perpendicular surfaces of the prism and transmitting the green light as it is, three color light rays are synthesized and incident to the projection lens 24.

The operation principle of the conventional projection display device 10 will be briefly described as follows.

After white light is emitted from the halogen metal lamp 12, the emitted white light is focused by the microlens array 14 and irradiated to the dichroic mirror 16a. Among the white light, the green light G and the blue light B pass through the dichroic mirror 16a, while the red light R is reflected. The red light R is reflected by the mirror 17a and then passes through the R-liquid crystal plate 20a as the transmittance of the R-liquid crystal plate 20a changes. The red light R then enters the dichroic prism 22 and is reflected by a dichroic mirror that reflects only the red light in the dichroic prism 22. The reflected red light R enters the projection lens 24.

On the other hand, the green light G and the blue light B transmitted by the dichroic mirror 16a reflect the green light G by the dichroic mirror 16b and the blue light B is transmitted. The green light G passes through the G-liquid crystal plate 20b as the transmittance of the G-liquid crystal plate 20b changes. The green light G passing through the G-liquid crystal plate 20b enters the dichroic prism 22, passes through the dichroic prism 22, and enters the projection lens 24.

The blue light B transmitted through the dichroic mirror 16b passes through the condenser lens 18a and is then reflected by the mirror 17b to enter the condenser lens 18b. The blue light B passing through the condenser lens 18b is reflected by the mirror 17c and then passes through the B-liquid crystal plate 20c as the transmittance of the B-liquid crystal plate 20c changes. The blue light B passing through the B-liquid crystal plate 20c enters the dichroic prism 22 and is then reflected by a dichroic mirror reflecting only the blue light in the dichroic prism 22. The reflected blue light B enters the projection lens 24.

In this way, dichroic prism 22 synthesizes three rays (red, green, and blue rays), and projection lens 24 screens the synthesized rays L (not shown). Project on the image.

2A and 2B are schematic views for explaining the structure and operating principle of the liquid crystal plate 20 shown in FIG.

Referring to FIGS. 2A and 2B, the liquid crystal plate 20 includes a polarizer and an analyzer spaced at regular intervals, and a liquid crystal injected into a gap between the polarizer and the analyzer. Twisted Nematic (TN) liquid crystal is mainly used as the liquid crystal, and each transmission axis of the polarizer and the analyzer is perpendicular to each other.

Looking at the operating principle of the liquid crystal plate 20, when no voltage is applied, as shown in Figure 2A, incident light transmitted through the polarizer is detected by linearly polarized light (phase difference is mπ) rotated 90 ° by the TN liquid crystal Penetrates the group. On the other hand, when a voltage is applied to the liquid crystal plate 20, as shown in FIG. 2B, due to the dielectric anisotropy of the TN liquid crystal, the light incident through the polarizer may not be linearly polarized because the TN liquid crystal is standing upright. Since the transmission axis of the analyzer is perpendicular to the transmission axis of the polarizer, the incident light transmitted through the polarizer is completely blocked by the analyzer and cannot be transmitted.

In general, incident light is light that is not polarized but is polarized while passing through a polarizer. Polarized light consists largely of P-polarized light and S-polarized light, where P-polarized light is a component of a wave polarized in the plane of incidence perpendicular to the interface and defined by the wave vector of the incident wave, and S-polarized light is incident The component of the wave polarized perpendicular to the plane. When no voltage is applied to the liquid crystal plate 20, when the polarization direction of the polarizer is in the P-polarization direction, as shown in FIG. 2A, the S-polarized light is absorbed from the polarizer while the P-polarized light is transmitted through the polarizer. The transmitted P-polarized light is rotated 90 ° by the TN liquid crystal and is converted into S-polarized light, and then passes through the analyzer.

As described above, in the conventional projection display device, only one polarization component, that is, S-polarized light or P-polarized light, is transmitted by the polarizer of the liquid crystal plate and projected onto the screen by the projection lens. In general, the light utilization efficiency of the projection display device using the liquid crystal plate is mainly affected by the light collimation optics and the liquid crystal plate. In the conventional projection display device as described above, since one polarization component, that is, S-polarized light or P-polarized light is always lost by the polarizer of the transmissive liquid crystal plate, the light efficiency is significantly reduced.

Accordingly, it is an object of the present invention to provide a projection display device which can reduce the cost by compactly configuring the optical system and improve the light efficiency by using a reflective light regulator.

1 is a schematic diagram showing the configuration of a conventional projection display device.

2A and 2B are schematic views for explaining the structure and operating principle of a liquid crystal panel used in the projection display device shown in FIG. 1.

3 is a schematic view showing the configuration of a projection display device according to the present invention.

<Explanation of symbols for main parts of drawing>

100: projection display device 102: lamp

104: condenser lens 106: first prism

110: second prism 114: third prism

118: fourth prism 122, 124, 126: reflective optical modulator

128: projection lens 130: screen

The present invention to achieve the above object, the light source for emitting a light ray; A first prism including a first surface on which the light is incident and a portion of the first surface including a second surface coated with a dichroic filter, a first surface in contact with a third surface of the first prism, and a mirror coated agent A second prism comprising two sides, a third prism comprising a first side coated at least partially by a dichroic filter, and a first surface and a dichroic filter in contact with a second side of the third prism A fourth prism comprising a second side and a third side coated with; A reflective light modulator attached to the third surface of the second prism and the second and third surfaces of the fourth prism, respectively; And a projection lens for projecting the light beam reflected by the reflective light modulator onto the screen.

As described above, the present invention connects four prisms to each other and attaches a dichroic filter, a mirror and a reflective light modulator to each of the faces of the prism thus obtained, respectively. Therefore, the optical system can be compactly constructed by integrating the rest of the components of the optical system except for the light source, thereby reducing the cost. In addition, the transmissive light modulator uses only one polarized light of S-polarized light and P-polarized light, so the light efficiency is lower than 50%. However, in the present invention, the light efficiency is improved by using a reflective light modulator using both polarization components. Can be increased significantly.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

Fig. 3 is a schematic diagram showing the configuration of a projection image display device using the reflective light modulator according to the present invention.

Referring to FIG. 3, the projection image display apparatus 100 according to the present invention includes a light source 102 for emitting light rays, a condenser lens 104, a first prism 106, a second prism 110, and a third Prisms 114, fourth prisms 118, reflective light modulators 122, 124, 126, projection lens 128, and screen 130.

The light source 102 preferably emits long wavelength infrared (LWIR) to ultraviolet (UV) light in the spectrum as a halogen metal lamp of 170W to 250W.

The first prism 106 may include a first surface 107 to which light rays are incident, a second surface thereof partially coated with a dichroic filter, and a first surface 107 and a second surface. And a third side 109 in contact. The surface 108a coated with the dichroic filter among the second surfaces of the first prism 106 is a surface in contact with the first surface 107 of the first prism.

The second prism 110 has a first surface in contact with the third surface 109 of the first prism 106, a second surface 111 coated with a mirror, and a first reflective light modulator 122. And a third side to which is attached.

The third prism 114 includes a first surface whose part surface 115a is coated with a dichroic filter. Preferably, the second surface of the first prism 106 and the first surface of the third prism 114 are positioned at predetermined intervals. This alters the light path of the light rays passing through the distillation filter coated side 108a of the second side of the first prism 106 such that the light passes through the remaining uncoated side 108b of the second side. This is to avoid interference with light rays.

The fourth prism 118 is a first surface in contact with the second surface 116 of the third prism, a second surface 119 coated with a dichroic filter, and a third coated with a dichroic filter. Face 120. A second reflective light modulator 124 and a third reflective light modulator 126 are attached to the second surface 119 and the third surface 120 of the fourth prism, respectively.

Thus, in the present invention, four prisms are connected to each other, and dichroic filters, mirrors, and reflective light modulators are attached to respective surfaces of the prism thus obtained. That is, the components constituting the optical system, except for the light source, are integrated with the prism, and such a prism is defined as a hybrid prism.

The first reflection type light modulator 122, the second reflection type light modulator 124, and the third reflection type light modulator 126 are preferably reflective liquid crystal plates, and reflectances thereof in accordance with an image signal to be applied. This changes to reflect or block the red, green and blue rays.

The projection lens 128 screens red, green, and blue light rays reflected by the first reflective light modulator 122, the second reflective light modulator 124, and the third reflective light modulator 126, respectively. It serves to project on 130.

Hereinafter, the operation principle of the projection image display apparatus 100 according to the present invention will be described in more detail with reference to FIG. 3.

After white light is emitted from the halogen metal lamp 102, the white light is incident on the first surface 107 of the first prism 106 constituting the hybrid prism by the condenser lens 104. Light rays passing through the first surface 107 of the first prism 106 are irradiated to the second surface of the first prism 106 whose part surface 108a is coated with a dichroic filter. The surface 108a coated with the dichroic filter of the second surface transmits red and green light and reflects only blue light. The reflected blue light is irradiated onto the first surface of the second prism 110 in contact with the third surface 109 of the first prism 106 and then attached to the third surface of the second prism 110. Reflected by the first reflective light modulator 122. The blue light reflected by the first reflective light modulator 122 is reflected by the second surface 111 of the second prism 110 coated with a mirror, and then goes straight downward to the second prism 110. Passes continuously through the first side of and the second side of the first prism 106 of the side 108b which is not coated with a dichroic filter. The blue light enters the projection lens 128 through the first surface 115a and the third 117 of the third prism 114 positioned at predetermined intervals on the second surface of the first prism 106.

Among the second surfaces of the first prism 106, the red and green light transmitted through the surface 108a coated with the dichroic filter pass through the first surface 115a of the third prism 114 and the third prism ( The first face of the fourth prism 118 in contact with the second face 116 of 114 is irradiated. The red and green light passing through the first surface of the fourth prism 118 is transmitted by the second surface 119 of the fourth prism 118 coated with a dichroic filter, and the red light is reflected.

The red light transmitted through the second surface 119 of the fourth prism 118 is reflected by the second reflective light modulator 124 and then irradiated onto the third surface 120 of the fourth prism 118. . Since the third surface 120 of the fourth prism 118 is coated with a dichroic filter that reflects red light and transmits green light, the red light is applied to the third surface 120 of the fourth prism 118. Is reflected and irradiated to the surface 115b of the first surface of the third prism 114 coated with the dichroic filter. Since the face 115b is coated with a dichroic filter that transmits blue light and reflects red and green light, the red light is coated with a dichroic filter of the first surface of the third prism 114. And then enters the projection lens 128 via the third surface 117 of the third prism 114.

The green light reflected by the second surface 119 of the fourth prism 118 is reflected by the third surface 120 of the fourth prism 118 coated with a dichroic filter that reflects red light and transmits the green light. It is transmitted and irradiated to the third reflective light modulator 126. The green light reflected by the third reflective light modulator 126 is irradiated to a surface 115b coated with a dichroic filter among the first surfaces of the third prism 114. Since the face 115b is coated with a dichroic filter that transmits blue light and reflects red and green light, the green light is reflected by the face 115b and then the third face 117 of the third prism 114. Enters the projection lens (128).

In this way, the red, green and blue light rays passing through the projection lens 128 are imaged on the screen.

As described above, according to the projection type image display apparatus according to the present invention, four prisms are connected to each other and a dichroic filter, a mirror, and a reflective light modulator are attached to respective surfaces of the prism thus obtained. Therefore, the optical system can be compactly constructed by integrating the rest of the components of the optical system except for the light source, thereby reducing the cost. In addition, the transmissive light modulator uses only one polarized light of S-polarized light and P-polarized light, so the light efficiency is lower than 50%. However, in the present invention, the light efficiency is improved by using a reflective light modulator using both polarization components. Can be increased significantly.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (3)

A light source 102 for emitting light rays; A first prism 106 comprising a first surface 107 and a portion of the surface 108a of which the light is incident, a second surface coated with a dichroic filter, and a third surface 109 of the first prism A second prism 110 comprising a first surface in contact with the second surface and a second surface 111 coated with a mirror, the second surface of the first prism being positioned adjacent to a portion thereof, and a portion of the surface 115a is a dichroic A third prism 114 comprising a first side coated with a filter, a first side in contact with the second side 116 of the third prism and a second side 119 coated with a dichroic filter; A fourth prism 118 including a third face 120; A reflective light modulator (122, 124, 126) attached to the third and second and third surfaces of the second prism, respectively; And a projection lens (128) for projecting the light reflected by the reflective light modulator onto the screen (130). The projection image display device according to claim 1, further comprising a condenser lens (140) for focusing light rays emitted from said light source onto said hybrid prism. The projection image display device according to claim 1, wherein the reflective light modulator (122, 124, 126) is a reflective liquid crystal plate.

Images