KR100342829B1 - Optical System Of Liquid Crystal Projector - Google Patents

Abstract

The present invention relates to an optical system of a liquid crystal projector capable of setting the same paths of red, green, and blue light incident on three reflective liquid crystal panels.

The liquid crystal projector optical system of the present invention includes a light source for generating a light beam, a first total reflection mirror for converting a light path from the light source, and a first dike for selectively transmitting and reflecting incident light from the first half mirror according to a wavelength. A first optical unit comprising a lower wing mirror, second and third total reflection mirrors that totally reflect the reflected light from the first dichroic mirror to be incident on the first liquid crystal panel, and transmitted light from the first dichroic mirror A second optical mirror comprising a fourth total reflection mirror for total reflection and a second dichroic mirror for selectively transmitting and reflecting the total reflection light from the fourth total reflection mirror according to the wavelength so as to be incident on the second and third liquid crystal panels, respectively; And the optical paths of the first optical part and the second optical part are set to be the same.

Accordingly, the red, green, and blue light paths incident on the three reflective liquid crystal panels are the same, thereby improving light efficiency and uniformity of light distribution.

Description

Optical System Of Liquid Crystal Projector

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full color liquid crystal projector, and more particularly, to an optical system of a liquid crystal projector capable of setting the same optical path incident on three liquid crystal displays.

Recently, as the demand for large screens and high-definition images increases as a display device, the spread of projectors that enlarge and project a small image using a projection lens is rapidly spreading. A typical projector is a liquid crystal projector which enlarges and projects a small screen image displayed on a liquid crystal display (LCD) onto a large screen. Liquid crystal projectors have been improved to overcome a lot of problems that can not see a clear screen in a bright environment. To this end, a lamp used as a light source has been improved to have a small light emission size, and a polarization conversion system for converting light generated from the light source into one linearly polarized light is introduced, and the liquid crystal panel has a high aperture ratio, thereby improving light efficiency. In addition, the microlenses in pixel units are attached to the inside of the liquid crystal panel to improve the effective aperture ratio through which the optical path passes rather than the geometric aperture ratio of the liquid crystal panel pixels, thereby improving light efficiency.

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 FELs) 6 and 8 arranged between the light source 2 and the total reflection mirror 14, and a polarizing beam split array (FIG. 1). Polarizing Beam Sprite Array (hereinafter referred to as a 'PBS array') 10, a first condensing lens 12, a total reflection mirror 14 and a first dichroic mirror 18 disposed between the first (Dichroric Mirror) 18 2 condensing lens 16 is provided. The light in the visible light region emitted from the lamp of the light source 2 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. Since the incident light is radiated to the entire liquid crystal panels 26R, 26G, and 26B by the first and second FELs 6 and 8, the uniformity of the light distribution irradiated to the liquid crystal panels 26R, 26G and 26B is ensured. You can do it. The PBS array 10 separates incident light into linearly polarized light having one optical axis, that is, P wave and S wave, and a half wave plate (not shown) partially attached to the rear surface of the PBS array 10 transmits the transmitted P. We will convert the wave to an S wave. Accordingly, the incident light is converted into linearly polarized light in one direction by the PBS array 10, that is, S-waves, so that almost all the light emitted from the lamp 2 is incident on the liquid crystal panels 26R, 26G, and 26B to be described later. Will be higher. The first condenser lens 12 focuses the incident light from the PBS array 10 onto the total reflection mirror 14, and the total reflection mirror 14 totally reflects the incident light from the first condensing lens 12 to produce a 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 blue light of the incident light and reflects light having a wavelength other than blue light. In this case, the light reflected from the first dichroic mirror 18 includes green light and red 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 first polarizing beam sprite prism (hereinafter referred to as a PBSP) 24R, a second polarizing film 22G arranged between the second dichroic mirror 20 and the green liquid crystal panel 26G, and The second total reflection mirror 28, the third polarizing film 22B, and the third PBSP 24B arranged between the second PBSP 24G, the first dichroic mirror 18, and the blue liquid crystal panel 26B. And a dichroic prism 30 disposed between the first to third PBSPs 24R, 24G, and 24B, and a projection lens provided on the light exit surface of the dichroic prism 30 so as to face the light exit surface. (32) is further provided. The second dichroic mirror 20 reflects the green light from the light reflected by the first dichroic mirror 18 and propagates toward the second polarizing film 22G, and transmits the red light to the first polarizing film. Proceed to (22R). The second total reflection mirror 28 reflects the blue light transmitted through the first dichroic mirror 18 and propagates toward the third polarizing film 22B. Each of the first to third polarizing films 22R, 22G, and 22B transmits only linearly polarized light (S wave) parallel to its optical axis among the incident lights, thereby allowing each of the first to third PBSPs 24R, 24G, and 24B to proceed. . Each of the first to third PBSPs 24R, 24G, and 24B reflects the linearly polarized light (S wave) transmitted through the first to third polarizing films 22R, 22G, and 22B to reflect red, green, and blue liquid crystal panels ( 26R, 26G, 26B). In addition, each of the first to third PBSPs 24R, 24G, and 24B transmits linearly polarized light (P wave) incident from each of the red, green, and blue liquid crystal panels 26R, 26G, and 26B, thereby allowing the dichroic prism 30 to pass through. To the side. Each of the red, green, and blue liquid crystal panels 26R, 26G, and 26B is a reflective liquid crystal panel, which transmits and reflects light incident from the first to third PBSPs 24R, 24G, and 24B, thereby reflecting an image according to an image signal. Will be implemented. In this case, the S waves incident on each of the red, green, and blue liquid crystal panels 26R, 26G, and 26B are converted into P waves by the liquid crystal panel and emitted. The dichroic prism 30 obtains image information from the red, green, and blue liquid crystal panels 26R, 26G, and 26B, respectively, and combines incident red, green, and blue light to the projection lens 32 through the exit surface. Got out. The projection lens 32 enlarges and projects the image incident from the dichroic prism 30 on the screen.

In the conventional liquid crystal projector having such a configuration, looking at the path of light incident from the light source 2 to the red, green, and blue liquid crystal panels 26R, 26G, and 26B, the red liquid crystal panel 26R and the green liquid crystal panel 26G are examined. The incident optical path length PATH1 is the same while the incident optical path length PATH2 is made relatively long. As the optical path length PATH2 incident to the blue liquid crystal panel 26B becomes relatively long, the light efficiency of blue light is lower than that of red light and green light, and thus the brightness uniformity of red, green, and blue light is inferior. In order to prevent this, as shown in FIG. 1, the first and second relay lenses 27 and 29 are additionally provided on the optical path PATH2 of the blue light. The first and second relay lenses 27 and 29 relay the imaging points of the blue light as the field lenses to the blue liquid crystal panel 26B to prevent deterioration of the light efficiency of the blue light and the brightness uniformity of the tricolor light. However, even if the optical efficiency and uniformity are compensated for using the first and second relay lenses 27 and 29, since the light is lost while being relayed, uniform brightness cannot be secured. In addition, since expensive first and second relay lenses 27 and 29 must be additionally provided, manufacturing costs are increased.

Accordingly, an object of the present invention is to provide an optical system of a liquid crystal projector capable of improving the light efficiency and uniformity by making the optical path lengths of red, green, and blue light the same.

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

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

<Explanation of symbols for the main parts of the drawings>

4: light source 6, 8: fly-eye lens

10: polarization separation array 12, 16: condensing lens

14, 42, 44, 46: total reflection mirror 18, 40, 48: dichroic mirror

22R, 22G, 22B, 50R, 50G, 50B: Polarizing Film

24R, 24G, 24B, 52R, 52G, 52B: Polarization Separation Prism

26R, 26G, 26B, 54R, 54G, 54B: liquid crystal panel 27, 29: relay lens

30, 56: dichroic prism 32, 72: projection lens

In order to achieve the above object, the liquid crystal projector optical system according to the present invention is a light source for generating a light beam, a first total reflection mirror for converting the optical path from the light source, and the incident light from the first total mirror according to the wavelength selective A first optical unit including a first dichroic mirror for transmitting and reflecting light, a second and third total reflection mirror for totally reflecting the reflected light from the first dichroic mirror to be incident on the first liquid crystal panel, and a first A fourth total reflection mirror for total reflection of the transmitted light from the dichroic mirror, and a second dike for selectively transmitting and reflecting the total reflection light from the fourth total reflection mirror according to the wavelength so as to be incident on the second and third liquid crystal panels, respectively And a second optical unit formed of a low-mirror mirror, wherein the optical paths of the first optical unit and the second optical unit are set to be the same.

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.

2 illustrates an optical system of a liquid crystal projector according to an exemplary embodiment of the present invention. The optical system of the liquid crystal projector shown in FIG. 2 includes first and second FELs 6 and 8, a PBS array 10, and a first condenser lens 12 arranged between the light source 2 and the total reflection mirror 14. And a second condenser lens 16 disposed between the total reflection mirror 14 and the first dichroic mirror 40. The light in the visible light region emitted from the lamp of the light source 2 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 wave and S wave, and a half wave plate (not shown) partially attached to the rear surface of the PBS array 10 transmits the transmitted P. We will convert the wave to an S wave. As a result, all of the incident light is converted into linearly polarized light in one direction, that is, S-wave by the PBS array 10, so that almost all the light emitted from the lamp 2 is incident on the liquid crystal panels 54R, 54G, and 54B to be described later. 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 ( Proceed to 16). The second condenser lens 16 focuses the incident light from the total reflection mirror 14 onto the first dichroic mirror 40. The first dichroic mirror 40 reflects the red light of the incident light and transmits the green light and the blue light having a wavelength shorter than the red light. In other words, the conventional first dichroic mirror 18 shown in FIG. 1 transmits blue light and reflects green and red light having a longer wavelength than the blue light, while the first dichroic mirror shown in FIG. 40 reflects red light and transmits light having a wavelength shorter than that of red light.

The optical system of the liquid crystal projector shown in FIG. 2 includes second and third total reflection mirrors 44 and first polarization arranged on an optical path between the first dichroic mirror 40 and the red liquid crystal panel 54R. A film 50R, a first PBSP 50R; A third total reflection mirror 46, a second dichroic mirror 48, a second polarizing film 50G, arranged on an optical path between the first dichroic mirror 40 and the green liquid crystal panel 54G, A second PBSP 52G; A third polarizing film 50B and a third PBSP 52B arranged on an optical path between the second dichroic mirror 48 and the blue liquid crystal panel 54B; It further includes a dichroic prism 50 disposed between the first to third PBSPs 54R, 54G, and 54B, and a projection lens 52 disposed to face the light exit surface of the dichroic prism 50. do. The second and third total reflection mirrors 42 and 44 are totally reflected by the red light reflected by the first dichroic mirror 40 to be incident on the first polarizing film 50R. In this case, in order to prevent the optical path of the red light reflected from the first dichroic mirror 40 and incident on the second total reflection mirror 42 from interfering with the third total reflection mirror 44, the first dichroic mirror ( 40) and the placement angle of the second total reflection mirror 42 should be properly adjusted. In other words, the conventional first dichroic mirror 18 shown in FIG. 1 is disposed to be inclined such that the angle of incidence of the light is 45 ° to the normal of the first dichroic mirror 18, while shown in FIG. The first dichroic mirror 40 is disposed to be inclined such that the incident angle of light becomes about 25 ° to 40 ° with a normal line of the first dichroic mirror 40. The fourth total reflection mirror 46 totally reflects the light incident through the first dichroic mirror 40 to be incident on the second dichroic mirror 48. The second dichroic mirror 48 reflects the green light from the light reflected from the fourth total reflection mirror 46 to be incident on the second polarizing film 50G, and transmits the blue light to transmit the third polarizing film 50B. To be incident). Each of the first to third polarizing films 50R, 50G, and 50B transmits only linearly polarized light that is parallel to its optical axis among the incident light, thereby allowing the first to third PBSPs 52R, 52G, and 52B to proceed. Each of the first to third PBSPs 52R, 52G, and 52B reflects linearly polarized light transmitted through the first to third polarizing films 50R, 50G, and 50B to reflect red, green, and blue liquid crystal panels 54R, 54G, 54B). In addition, each of the first to third PBSPs 52R, 52G, and 52B transmits linearly polarized light incident from each of the red, green, and blue liquid crystal panels 54R, 54G, and 54B, and proceeds to the dichroic prism 56. . Each of the red, green, and blue liquid crystal panels 54R, 54G, and 54B is a reflective liquid crystal panel, which transmits and reflects light reflected from the first to third PBSPs 52R, 52G, and 52B to reflect an image according to an image signal. Will be implemented. The dichroic prism 56 obtains image information from the red, green, and blue liquid crystal panels 54R, 54G, and 54B, respectively, and combines incident red, green, and blue light to the projection lens 58 through the exit surface. Exited to the side. The projection lens 58 enlarges and projects the image incident from the dichroic prism 56 onto the screen.

Alternatively, the first dichroic mirror 40 may have characteristics of reflecting blue light among incident light and transmitting red light and green light having a wavelength shorter than blue light. In this case, the positions of the red liquid crystal panel 26R and the blue liquid crystal panel 26B are exchanged.

As described above, in the liquid crystal projector according to the present invention, unlike the conventional liquid crystal projector, red, green and red incident on the red, green, and blue liquid crystal panels 54R, 54G, and 54B are respectively incident from the light source 2 by using two total reflection mirrors. The path length of the blue light can be set to be the same. Accordingly, the optical efficiency of the blue light can be further improved as well as the brightness uniformity of the tricolor light can be improved more than in the case of using an expensive relay lens as in the related art.

As described above, in the optical system of the liquid crystal projector according to the present invention, by further employing two total reflection mirrors, path lengths of red, green, and blue light can be set to be the same. Accordingly, the optical system of the liquid crystal projector according to the present invention can reduce manufacturing cost and compensate for the blue light having a relatively long path by using an expensive relay lens. The light efficiency and brightness uniformity can be improved.

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)

In the optical system of the liquid crystal projector for synthesizing and projecting the image displayed on the first to third liquid crystal panel, A light source for generating a light beam, A first total reflection mirror for converting the optical path from the light source, A first dichroic mirror for selectively transmitting and reflecting incident light from the first front mirror according to a wavelength; A first optical part including second and third total reflection mirrors which totally reflect the reflected light from the first dichroic mirror to be incident on the first liquid crystal panel; A fourth total reflection mirror for total reflection of the transmitted light from the first dichroic mirror, and total reflection light from the fourth total reflection mirror is selectively transmitted and reflected according to a wavelength to enter the second and third liquid crystal panels, respectively And a second optical portion composed of a second dichroic mirror, The optical system of the liquid crystal projector, wherein the optical path lengths of the first and second optical parts are set to be the same. The method of claim 1, The reflected light from the first dichroic mirror is any one of red light and blue light, The reflected light from the second dichroic mirror is green light. The method of claim 1, The first dichroic mirror is An optical system of a liquid crystal projector, characterized by being inclined such that the incident angle of light is 25 ° to 40 ° based on a normal to its horizontal plane. The method of claim 3, wherein And the second total reflection mirror is inclined at the same angle as the first dichroic mirror.