KR100744503B1 - Optical System Of Liquid Crystal Projector - Google Patents

Abstract

The present invention relates to an optical system of a liquid crystal projector capable of minimizing the size of the optical system and the number of optical components by implementing a color image through two liquid crystal panels using a color selector and a color wheel.

The liquid crystal projector optical system of the present invention converts a first liquid crystal panel for displaying a first color image, a second liquid crystal panel for sequentially displaying second and third color images, and white light from a light source into one linearly polarized light. And a color selector for selectively polarizing the linearly polarized light from the illuminator according to the wavelength, and allowing the first and second liquid crystal panels to enter the first and second liquid crystal panels according to the linearly polarized light. And dichroic prism for synthesizing and outputting color light, and color separation means for separating colors sequentially between the dichroic prism and the second liquid crystal panel.

According to the configuration of the present invention, the optical system of the liquid crystal projector implements a color image through the two liquid crystal panels using a color selector and a color wheel, and thus the size of the optical system than the optical system of the liquid crystal projector using the conventional three liquid crystal panels. Minimizing the number of parts has the advantage of reducing the overall length of the optical system. Accordingly, the optical system of the liquid crystal projector can be thinned and manufacturing cost can be reduced.

Description

Optical System Of Liquid Crystal Projector             

1 is a plan view showing an optical system configuration of a conventional liquid crystal projector.

2 is a plan view showing an optical system configuration of a liquid crystal projector according to an embodiment of the present invention.

3 is a view showing in detail the color wheel shown in FIG.

4A and 4B are waveform diagrams showing a synchronization time scanned for each color light.

<Brief description of symbols for the main parts of the drawings>

4, 31: light source 6, 8, 32A, 32B: fly's eye lens (FEL)

10, 34: polarization separation (PBS) array 12, 16, 36: condensing lens

14, 28: total reflection mirror 18, 20: dichroic mirror

26R, 26G, 26B, 52RB, 52G: liquid crystal panel

27, 29: relay lens 30, 40: dichroic prism

32, 54: projection lens 38: color select

42: flat light separation surface 50: color wheel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector, and more particularly, to an optical system of a liquid crystal projector capable of minimizing the size and the number of optical parts by implementing a color image through two liquid crystal panels using a color selector and a color wheel. .

Recently, a projector that has a limited screen size and replaces a cathode ray tube display having a large size and has a thin screen and can realize a large screen has been in the spotlight. The projector employs a cathode ray tube or an LCD (Liquid Crystal Display) as a display constituting a small screen image, but a liquid crystal projector using an LCD has emerged in response to the trend of thinning. In the liquid crystal projector, a transmissive or reflective LCD is usually used.

Such liquid crystal projectors have been developed based on small size, light weight and high brightness, and LCD panels have been developed on the basis of high opening ratio and high resolution. Accordingly, in order to meet the flow of liquid crystal projectors of high resolution, miniaturization and low price, recently, there has been a trend to use a reflective LCD panel.

A liquid crystal projector implements an image on an LCD panel by using light from a light source, and forms an image on the screen by using an projection optical system to view an image formed on the screen. When the projector is constructed by directly projecting the image of the LCD panel on the rear screen, the projection distance must be secured between the screen and the projection optical system, and thus a lot of space is required behind the screen, which makes the thickness of the projector thick and difficult to thin. To solve this problem, the total thickness of the projector is reduced by inserting a total reflection mirror between the screen and the projection optical system to fold the optical path. However, the thickness of the projector can be further reduced by reducing the placement angle of the total reflection mirror, but there are limitations on the reduction of the placement angle of the projection optical system and the reflector so that the image is projected on the rear screen without distortion. There was a limit in reducing the thickness of the system due to the inherent length of the optical system composed of a lens system.

Referring to Fig. 1, an optical system for a conventional liquid crystal projector is shown.

The liquid crystal projector of FIG. 1 includes first and second fly eye lenses (hereinafter referred to as "FEL") 6, 8 arranged between the light source 4 and the total reflection mirror 14, and a polarization separation array ( Polarizing Beam Sprite Array (hereinafter referred to as " PBS array ") 10, a first condensing lens 12, a total reflection mirror 14 and a first dichroic mirror 18 disposed between the first 2 condensing lens 16 is provided. The white light emitted from the lamp of the light source 4 is reflected by the ellipsoid to travel toward the first FEL 6. The first FEL 6 divides the incident light into cells so as to focus on each lens cell of the second FEL 8. The second FEL 6 converts the incident light into parallel light with respect to a specific portion and transmits it to the PBS array 10. The PBS array 10 separates incident light into linearly polarized light having one optical axis, that is, P-polarized light and S-polarized light, and a half-wave plate (not shown) partially attached to the rear surface of the PBS array 10 is transmitted. P-polarized light is converted into S-polarized light. As a result, all of the incident light is converted into S-polarized light by the PBS array 10 so that almost all the light emitted from the light source 4 is incident on the liquid crystal panels 26R, 26G, and 26B.

The first condenser lens 12 focuses the incident light from the PBS array 10 to the total reflection mirror 14, and the total reflection mirror 14 totally reflects the incident light from the first condensing lens 12 so that the second condensing lens ( 16). The second condenser lens 16 focuses the incident light from the total reflection mirror 14 onto the first dichroic mirror 18. The first dichroic mirror 18 transmits light of the blue region of the incident light and reflects light of the green region and the red region having a wavelength longer than that of the blue light.

The optical system of the liquid crystal projector illustrated in FIG. 1 includes a second dichroic mirror 20, a first polarizing film 22R, arranged between the first dichroic mirror 18 and the red liquid crystal panel 26R. A second polarizing film 22G arranged between the first polarizing beam sprite prism (hereinafter referred to as “PBSP”) 24R and the second dichroic mirror 20 and the green liquid crystal panel 26G. And a first relay lens 27, a second total reflection mirror 28, and a second relay lens arranged between the second PBSP 24G, the first dichroic mirror 18, and the blue liquid crystal panel 26B. 29), the third polarizing film 22B, the third PBSP 24B, the dichroic prism 30 disposed between the first to third PBSPs 24R, 24G, and 24B, and the dichroic prism ( A projection lens 32 is further provided to face the light exit surface of 30. The second dichroic mirror 20 reflects the light in the green region of the light reflected from the first dichroic mirror 18 and propagates toward the second polarizing film 22G, and the light in the red region is The light is transmitted through the first polarizing film 22R. The second total reflection mirror 28 reflects the light of the blue region that is transmitted through the first dichroic mirror 18 and propagates toward the third polarizing film 22B. In this case, the first and second relay lenses 27 and 29 relay the imaging points of the blue region light as the field lenses and reimage the blue liquid crystal panel 26B. Each of the first to third polarizing films 22R, 22G, and 22B transmits only the S-polarized light parallel to its optical axis among the incident light, so that each of the first to third PBSPs 24R, 24G, and 24B is advanced. Each of the first to third PBSPs 24R, 24G, and 24B reflects red, green, and blue S-polarized light transmitted through the first to third polarizing films 22R, 22G, and 22B to reflect red, green, and blue liquid crystals. It proceeds to each of the panels 26R, 26G, 26B. In addition, each of the first to third PBSPs 24R, 24G, and 24B obtains image information from each of the red, green, and blue liquid crystal panels 26R, 26G, and 26B to transmit red, green, and blue light converted into P-polarized light. Advance toward dichroic prism 30. Each of the red, green, and blue liquid crystal panels 26R, 26G, and 26B is a reflective liquid crystal panel and converts the S-polarized light reflected from the first to third PBSPs 24R, 24G, and 24B into P-polarized light according to an image signal. By doing so, an image is realized.

The dichroic prism 30 obtains image information from the red, green, and blue liquid crystal panels 26R, 26G, and 26B, respectively, and combines red, green, and blue light incident to the projection lens 32 through the emission surface. Exited to the side. First and second polarization conversions for converting P polarized light from the first and second PBSPs 24R and 24B to S-polarized light between the first and third PBSPs 24R and 24B and the dichroic prism 30. Each film (not shown) is disposed. Accordingly, the dichroic prism 30 reflects the red light and the blue light of the S-polarized component incident through the first and second polarization conversion films toward the projection lens 32 and also via the second PBSP 24G. The green light of the incident P polarization component is transmitted toward the projection lens 32 to synthesize red, green, and blue images. The projection lens 32 enlarges and projects the image incident from the dichroic prism 30 on the screen.

The conventional liquid crystal projector having such a configuration requires a plurality of dichroic mirrors to separate the white light from the light source into red, green, and blue by adopting three liquid crystal panels. In addition, the conventional liquid crystal projector requires a plurality of polarization separation prisms to change the path of incoming and outgoing light based on the reflective liquid crystal panel as the reflective liquid crystal panel is used. In the optical system of a conventional liquid crystal projector using three reflective liquid crystal panels, the size of the optical system increases as the number of optical components required increases, thereby reducing the thickness of the system proportional to the overall length of the optical system. There was a difficult issue.

Accordingly, in recent years, an optical system having a two-layer structure in which the color separation unit is disposed on the upper layer of the color combining unit and the projection lens system has been proposed to reduce the overall length of the optical system. However, this two-layer optical system also has a limit in reducing the size of the optical system by employing a large number of optical components as in the conventional optical system.

Accordingly, it is an object of the present invention to provide an optical system of a liquid crystal projector capable of reducing the number of optical components and reducing the size and length of an optical system.

In order to achieve the above object, the liquid crystal projector optical system of the present invention comprises a first liquid crystal panel for displaying a first color image, a second liquid crystal panel for sequentially displaying second and third color images, and a light source from the light source. A light source for converting white light into one linearly polarized light, a color selector for selectively polarizing the linearly polarized light from the illumination unit according to the wavelength, and incident the first and second liquid crystal panels according to the linearly polarized light, And a dichroic prism for synthesizing and outputting color light by obtaining color image information from the second liquid crystal panel, and color separation means disposed between the dichroic prism and the second liquid crystal panel to separate colors sequentially in time. .

Other objects and features of the present invention in addition to the above objects will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 2 to 4B.

2 is a plan view illustrating an optical system of a liquid crystal projector according to an exemplary embodiment of the present invention. Referring to FIG. 2, the optical system of the liquid crystal projector includes first and second fly eye lenses (hereinafter referred to as "FEL") 32A and 32B, and a polarizing beam sprite array (hereinafter referred to as "PBS"). And an illumination unit for uniformly and efficiently radiating white light from the light source 30 to the first to second liquid crystal panels 52G and 52RB, and a dichro for light separation and synthesis. The exoprism 40, the color select 38 and the condenser 36 arranged on the optical path between the illumination unit and the dichroic prism 40, the dichroic prism 40 and the second liquid crystal A color wheel 50 disposed between the panels 52RB and a projection lens 54 arranged on the emission side of the light synthesized by the dichroic prism 40 are provided. The white light emitted from the light source 30 travels toward the first FEL 32A. The first FEL 32A divides the incident light into cells so as to focus on each lens cell of the second FEL 32B. The second FEL 32B converts incident light into parallel light with respect to a specific portion.

The PBS array 34 is integrated with the second FEL 32B to separate incident light into P-polarized light and S-polarized light having any one optical axis, and is partially attached to the rear surface of the PBS array 34 (not shown). (Not shown) converts the transmitted P-polarized light into S-polarized light and focuses the light through the condenser lens 36. The illumination unit improves light efficiency by allowing incident light to be converted into linearly polarized light in one direction, that is, S-polarized light, so that the incident light is uniformly incident on the first and second liquid crystal panels 52G and 52RB. The color select 38 selectively polarizes the S-polarized light incident from the PBS array 34 according to the wavelength region. For example, the color select 38 rotates the green light 90 degrees so that P-polarized light is converted into S-polarized light, and red light and blue light are transmitted while maintaining P-polarized light as it is.

The dichroic prism 40 reflects the S-polarized light incident from the color selector 38 to the first liquid crystal panel 52G by using the polarization separation surface 42, and the P-polarized light incident from the color selector 38 is reflected. In addition to being transmitted through the second liquid crystal panel 52RB, the green information of P polarized light emitted from the first liquid crystal panel 52G is transmitted toward the projection lens 54, and the S polarized light emitted from the second liquid crystal panel 52RB. Red and blue image information is reflected toward the projection lens 54.

The color wheel 50 sequentially transmits red and blue color light while rotating by a driving force of a motor (not shown). To this end, the color wheel 50 includes a red filter 46 for transmitting red light and a blue filter 48 for transmitting blue light as shown in FIG. 3. When the second liquid crystal panel 52RB displays a red image, the color wheel 50 is driven by a motor (not shown) so that the red filter 46 is positioned on the optical path. The second liquid crystal panel 52RB converts the P-polarized light transmitted through the red filter 46 into S-polarized light by the red image information inputted therein. Then, when the second liquid crystal panel 52RB displays the input blue image information, the color wheel 50 is driven by a motor (not shown) so that the blue filter 48 is positioned on the optical path. The second liquid crystal panel 52RB converts the P-polarized light transmitted through the blue filter 48 into S-polarized light by the blue image information to be input. The first liquid crystal panel 52G converts the S-polarized light reflected from the dichroic prism 40 into incident P-polarized light and emits the light.

The driving time for displaying an image of one frame in the first liquid crystal panel 52 and the second liquid crystal panel 52RB is as shown in FIGS. 4A and 4B. 4A and 4B, the first liquid crystal panel is driven during one frame driving time to display a green image, while the second liquid crystal panel is driven 1/2 frame to sequentially display red and blue images.

Accordingly, the dichroic prism 40 reflects the red S polarization and the blue S polarization incident on the flat separation plane 42 toward the projection lens 54 and the green P polarization incident on the flat separation plane 42. By transmitting toward the projection lens 54, the corresponding color image according to the image signal is realized. In this case, each of the first and second liquid crystal panels 52G and 52RB converts the linearly polarized light in one direction incident to the linearly polarized light in the other direction according to the image information to be emitted. The projection lens system 54 enlarges and projects the composite image incident on the screen from the flat separation plane 42 of the dichroic prism 40.

As described above, the optical system of the liquid crystal projector according to the present invention implements a color image through two liquid crystal panels using a color selector and a color wheel so that the optical system of the liquid crystal projector using the three liquid crystal panels of the prior art By minimizing the size and number of parts, there is an advantage that the overall length of the optical system can be reduced. Accordingly, the optical system of the liquid crystal projector can be thinned and manufacturing cost can be reduced.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (4)

A first liquid crystal panel for displaying a first color image, A second liquid crystal panel for sequentially displaying second and third color images; An illumination unit for converting white light from the light source into one linearly polarized light, A color selector for selectively polarizing the linearly polarized light from the illumination unit according to a wavelength; A dichroic prism for allowing the first and second liquid crystal panels to enter the first and second liquid crystal panels according to linear polarization of the incident light from the color selector, and to obtain color image information from the first and second liquid crystal panels to synthesize color light and to emit the color light; And a color separation means disposed between the dichroic prism and the second liquid crystal panel to separate colors sequentially in time. The method of claim 1, The color separation means includes a first color filter for transmitting first color light and a second color filter for transmitting second color light, and the first and second colors are synchronized with the color image driving timing of the second liquid crystal panel. An optical system of a liquid crystal project, characterized in that the filter is driven to be positioned on the optical path. The method of claim 2, The color separation means is an optical system of a liquid crystal project, characterized in that the color wheel. The method of claim 1, The first liquid crystal panel converts light into P-polarized light according to the image information from the dichroic prism and emits the light. The second liquid crystal panel converts light into S-polarized light according to the image information from the dichroic prism and outputs the light. The optical system of the liquid crystal projector characterized by the above-mentioned.

Images