KR20010054283A - Optical System Of Liquid Crystal Projector Using Two Lamps - Google Patents

Abstract

PURPOSE: An optical system is provided to be capable of increasing the brightness and the optical efficiency using two lamps. CONSTITUTION: An optical system includes the first and second light sources(50,52). The first and second reflection mirrors(66,68) are positioned between the first and second light sources(50,52) and a prism(62). A collimating lens(64) is arranged between the prism(62) and the third total reflection mirror(14). A focusing lens(16), a red transparent mirror(18) and a red focus lens(22) are arranged between the first and second fly eye lens(6,8), the third total reflection mirror(14) and a red liquid crystal panel(24). A blue transparent mirror(26) and a green focusing lens(28) are arranged between the red transparent mirror(18) and the green liquid panel(30). The first relay lens(32), the first blue reflection mirror(34), the second relay lens(36), the second blue reflection mirror(38) are arranged between the red transparent mirror(26) and the blue liquid crystal panel(44). A dichroic prism(46) is installed between the red, green and blue liquid crystal panels(24,30,44). A projection lens(48) is installed facing an optical outgoing surface of the dichroic prism(46).

Description

Optical system of liquid crystal projector using two lamps

The present invention relates to a liquid crystal projector, and more particularly, to an optical device of a liquid crystal projector capable of improving the brightness of the projector by using two lamps.

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 configuration of a high efficiency liquid crystal projector disclosed in '97 SID Digest L1.1 pp. 993 to 996 is shown. The liquid crystal projector of FIG. 1 includes first and second fly eye lenses 6 and 8 arranged between a lamp 2 and a total reflection mirror 14, and a polarizing beam sprite array. 10) and a condenser lens 16, a red transmission mirror 18, a red reflection mirror 20 and a red condenser lens arranged between the total reflection mirror 14 and the red liquid crystal panel 24. 22, the blue transmission mirror 26 and the green condenser lens 28 arranged between the red transmission mirror 18 and the green liquid crystal panel 30, the blue transmission mirror 26 and the blue liquid crystal panel 44 ), The first relay lens 32, the first blue reflecting mirror 34, the second relay lens 36, the second blue reflecting mirror 38, the blue condensing lens 40, and red and green A dichroic prism 46 provided between the blue liquid crystal panels 24, 30 and 44, and a projection lens 48 provided to face the light exit surface of the dichroic prism 46. Light in the visible light region emitted from the lamp 2 travels toward the first fly's eye lens 6 via the ellipsoidal mirror 4. The first fly's eye lens 6 splits the incident light into cells so that each lens cell of the second fly's eye lens 8 is focused. The second fly's eye lens 6 converts the incident light into parallel light of a specific portion and transmits it to the PBS array 10. The PBS array 10 separates incident light into linearly polarized light (P wave or S wave) having any one optical axis, and the half wave plate 10A attached to the rear surface of the PBS array 10 has a P wave as an S wave. Will be converted. The incident light is converted into linearly polarized light (i.e., S-wave) in one direction by the PBS array 10, so that almost all the light emitted from the lamp 2 is incident on the total reflection mirror 14, thereby increasing the light efficiency and Since the light emitted from each of the lens cells of the first and second fly's eye lenses 6 and 8 is irradiated to the entire liquid crystal panel 24, 30 and 44, the uniformity of the light distribution irradiated to the liquid crystal panel can be ensured. Will be. The total reflection mirror 14 and the condenser lens 16 focus the incident light on the red transmission mirror 18. The red transmission mirror 18 transmits red light of the incident light to the red reflection mirror 20 and reflects light having a wavelength other than red light toward the blue transmission mirror 26. The red reflection mirror 20 totally reflects the incident red light toward the red condensing lens 22. The red condenser lens 22 condenses the incident red light onto the red liquid crystal panel 24 to create a better incidence condition on the effective area of the red liquid crystal panel 24, and is coated with a red transparent coating to increase red purity. Is given. The blue transmission mirror 26 reflects the green light of the incident light from the red transmission mirror 18 toward the green condensing lens 28, while transmitting the blue light toward the first relay lens 32. The green condenser lens 28 condenses the incident green light onto the green liquid crystal panel 30 to create a better incidence condition on the effective area of the green liquid crystal panel 30, and is coated with a green transparent coating to increase green purity. Is given. The blue light transmitted through the blue transmission mirror 26 passes through the first relay lens 32, the first blue reflection mirror 34, the second relay lens 36, and the second blue reflection mirror 38. 40). Here, since the path of the blue light is longer than the other red and green light, the first and second relay lenses 32 and 36 are used to correct the blue light. In other words, the first relay lens 32 serving as a field lens is inserted at a distance equal to the distance between the blue transmission mirror 26 and the green condenser lens 28 to prevent the blue light from spreading, and the first relay lens ( The second relay lens 36 is inserted to form an image at the same distance as 36). The blue condenser lens 40 focuses the incident blue light on the effective area of the blue liquid crystal panel 44 regardless of the color purity. The red, green, and blue liquid crystal panels 24, 30, and 44 transmit light by adjusting light transmittance according to the input image information. The dichroic prism 46 passes through the red, green, and blue liquid crystal panels 24, 30, and 44, respectively, to obtain image information, and then combines incident red, green, and blue light to project the projection lens 48 through the emission surface. Turned out towards). The projection lens 48 enlarges and projects the image incident from the dichroic prism 46 on the screen.

With this configuration, it is possible to see in bright environments by increasing the brightness, but still have a problem that the screen is less clear under bright light on a large screen of 100 "or more. To overcome this problem, high-power lamps are used. However, high power lamps are not only inefficient and have difficulty in cooling because their light size is not proportional to power increase due to the increase in the arc size of the lamp. The lamp has a short lifespan.

It is therefore an object of the present invention to provide an optical system of a liquid crystal projector which can increase the brightness by using two lamps.

Another object of the present invention is to provide an optical system of a liquid crystal projector capable of increasing light efficiency in using two lamps.

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

2 is a diagram illustrating a configuration of an optical system using two lamps installed in parallel.

3 is a view showing the configuration of an optical system using two lamps opposed to each other.

4 is a view illustrating dispersion characteristics of a light beam when the optical axis of the collimator lens illustrated in FIG. 3 and the reflecting surface of the prism form an angle of 45 degrees. FIG.

FIG. 5 is a view illustrating dispersion characteristics of a light beam when the optical axis of the collimator lens and the reflecting surface of the prism of FIG. 3 form an angle smaller than 45 degrees. FIG.

6 is a view for explaining effective light in a fly's eye lens and a PBS array;

7 is a layout view of a fly's eye lens and a PBS array for enhancing effective light in a PBS array.

8 is a view showing the configuration of an optical system of a liquid crystal projector using two lamps in an embodiment of the present invention.

FIG. 9 illustrates the optical system shown in FIG. 8 in a vertical in-line form. FIG.

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

2: lamp 4: ellipsoid

6, 54: 1st FEL 8, 56A: 2nd FEL

10: PBS array 14, 66, 68: total reflection mirror

16: condenser lens 18: red transmission mirror

20: red reflection mirror 22: red condenser lens

24: red liquid crystal panel 26: blue transmission mirror

28: green condenser lens 30: green liquid crystal panel

32: first relay lens 34: first blue reflecting mirror

36: second relay lens 38: second blue reflecting mirror

40: blue condenser lens 44: blue liquid crystal panel

46: dichroic prism 48: projection lens

50, 52: first and second light sources 56: second FEL and PBS array

58: condenser lens system 60: liquid crystal panel

62: prism 64: collimation lens

In order to achieve the above object, the liquid crystal projector optical system according to the present invention comprises a first and second light sources comprising a lamp for generating a light beam and an ellipsoid for advancing the light beam from the lamp in one direction, and the first and second light sources. Collimating the collimating lens for converting the light beam from the two light sources into the parallel light, at least one turning mirror portion for allowing the light beams from the first and second light sources to overlap the collimating lens, and the light beam from the collimating lens. And an illumination system for incident on the liquid crystal panel, wherein the lamp is positioned at the first focal point of the ellipsoidal mirror and the ellipsoidal mirror is arranged so that the second focal point coincides with the central axis of the liquid crystal panel.

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.

Prior to the description of the embodiments of the present invention, a background of the present invention will be described. In the present invention, in order to improve the brightness of the projector, instead of using a high-power lamp that is inefficient in light efficiency and uses a plurality of low-power lamps. In the case of using a plurality of lamps of low power, a method of basically allowing the light beams output from the two lamps to be optically side by side and a method of allowing the light beams from the two lamps to be combined so as to overlap.

First, as shown in FIG. 2, when the two light sources 50 and 52 are positioned in parallel so that the light beams output from the lamps are reflected by the ellipsoid and travel in parallel, the first fly's eye lens 54 has good parallelism. ) And the second fly's eye lens and the PBS array 56 can be polarized and converted to have the same light transmittance as that of one conventional lamp. However, the size of the optical component is increased, and the angle of light focused to the liquid crystal panel 60 via the condenser lens system 58 is increased by about two times, so that the transmittance of the liquid crystal panel 60 having the microlens array is reduced, resulting in low light efficiency. It has a disadvantage.

On the contrary, when the light beams from the two lamps are combined to overlap, the light output from the lamps of the two light sources 50 and 52 is focused by an ellipsoidal reflector as shown in FIG. The prism 62 having two reflecting surfaces is positioned. The two directions of light reflected by the prism 62 are spatially superimposed. The collimating lens 64 converts the light spread from the prism 62 into parallel light and enters the first fly's eye lens 54. In this case, since the size of the optical component is the same as when one lamp is used, the light incident angle incident on the liquid crystal panel 60 increases as shown in FIG. 2, so that the light transmittance of the liquid crystal panel 60 may be overcome. have. Therefore, in the present invention, as shown in FIG.

In addition, in synthesizing and using the light beams from two lamps superimposed, a method of further improving the light efficiency should be considered. In using two lamps, the light efficiency is the same as when using one lamp as much as the characteristics of the light beam incident on the first fly's eye lens, and PBS composed of half the array of lens cells of the fly's eye lens. It can be influenced by the method of efficiently illuminating the illumination spot from each array to each cell.

Here, the method of making the characteristics of the light beam incident on the first fly's eye lens 54 from the two lamps the same as when using at most one lamp depends on the optical system configuration from the two lamps to the fly's eye lens. . In other words, in order to increase the light efficiency, it is necessary to maximize the parallelism of light incident from the two lamps to the first fly's eye lens 54. In this case, basically, the light incident from the two lamps onto the first fly's eye lens 54 needs to overlap. To this end, the light output from each lamp is condensed in the form of a small spot using an elliptical reflector, and each of the collected light is superimposed in the same direction through a small optical element and synthesized. In this case, the light efficiency reflected by the small optical element emitted by the light must be converted into parallel light as much as possible. This is because the greater the parallelism of the light incident on the first fly's eye lens 54 as shown in FIG. 4, the greater the effective light and the greater the transmission efficiency of the polarized light.

In detail, in FIG. 4, the PBS array 56B and the λ / 2 plate 56C improve light efficiency by converting the incident light beam into one linearly polarized light, for example, S polarized light, in accordance with the polarization characteristics of the liquid crystal panel. For this purpose, each of the PBSs of the PBS array 56B separates the incident light beam into P-polarized light and S-polarized light, and the λ / 2 plate is attached only to the rear surface of the PBS located in the center of each cell of the second fly's eye lens 56A. 56C converts P-polarized light transmitted through PBS into S-polarized light so that all incident light is converted into S-polarized light. In this case, light incident in parallel to each cell of the first fly's eye lens 54 passes through each cell of the second fly's eye lens 56A to the center of each cell of the second fly's eye lens as shown in FIG. 4. By condensing with the located PBS, both the PBS and the λ / 2 plate 56C can be converted into effective light. On the other hand, light incident obliquely to the first fly's eye lens 54 is disposed at the periphery of each cell of the second fly's eye lens 56A via each cell of the second fly's eye lens 56A as shown in FIG. 4. By condensing with the PBS, it is emitted as P-polarized light, that is, ineffective light. Accordingly, in order to increase the light efficiency, the parallelism of the light incident on the first fly's eye lens 54 should be made as large as possible. The parallelism of this light can be determined by the angle made by the reflecting surface of the prism 62 for reflecting the light beam from the two lamps. Hereinafter, referring to FIGS. 5 and 6, the relationship between the angle formed by the reflecting surface of the prism 62 and the parallelism is as follows.

Referring to FIG. 5, the optical axes of the first and second light sources 50 and 52 and the optical axes of the collimating lens 64 are orthogonal to each other, and the reflective prism 62 of the right angle is positioned near orthogonal points of each other. When the angle formed by the normal line of the reflecting surface of the prism 62 and the optical axis of the reflecting mirror, that is, the angle θ formed between the optical axis of the collimating lens 64 and the reflecting surface of the reflecting prism 62, becomes 45 degrees, The bifocal f2 is present on a line parallel to the optical axis at the height of the point where the optical axis of each reflecting mirror and the reflecting surface of the prism 62 fit. Therefore, by having two source points on the non-axis of the collimating lens 64, the prism 62 outputs light having an angle by the collimating lens 64 as shown in FIG. In other words, when the angle θ formed between the optical axis of the collimating lens 64 and the reflecting surface of the reflecting prism 62 becomes 45 degrees, the parallelism of the light emitted from the collimating lens 64 falls. In order to reduce the phenomenon of the stockpiling source, the point that matches the reflective surface of the prism 62 should be located on the optical axis. To this end, when the prism 62 is moved backward, since the lamps of the light sources 50 and 52 have the light emission size, the point condensation is not formed at the second focal point f2 and thus the spot size is obtained. Since the light passing through the reflection surface is not reflected, the light incident to the effective optical path is reduced, resulting in low light efficiency. Therefore, as shown in FIG. 6, the angle θ formed between the optical axis of the collimating lens 64 and the reflecting surface of the reflecting prism 62 is set to be smaller than 45 degrees so that the optical second focal point f2 of the reflecting mirror is the collimating lens. It is necessary to be able to coincide with the optical axis of (64).

In addition, unlike the case of one lamp in the overlapping light of the two lamps, the lamp optical axis has a predetermined angle with respect to the optical system optical axis with respect to the direction in which the lamps are placed side by side. As a result, the characteristics of the beam in the direction in which the two lamps are placed and the characteristics of the beam in the direction perpendicular to the two lamps are somewhat different. In particular, the beam characteristics in the direction in which the lamps are placed become relatively large. To compensate for this, in the present invention, the direction of parallel installation of the lamps is perpendicular to the direction in which the PBS array is arranged. As shown in FIG. 4, the PBS array 56B having a stripe-shaped PBS having a half width of the fly's eye lens cell is arranged in consideration of polarization conversion transmission efficiency. The aspect ratio of the liquid crystal panel 60 is arranged in a larger direction. Commonly used displays have an aspect ratio of 3: 4 or 9:16. Here, in the case where the liquid crystal panel 60 has an aspect ratio of 3: 4, the width of each PBS in the PBS array 56B has a length ratio of 2 with respect to the vertical 3, and the length of 8 with respect to the vertical 9 at 9:16. Let it rain As a result, each PBS is set so that the length of the direction (ie, vertical) perpendicular to it is longer than the length of the PBS array direction (ie, horizontal). This means that the vertical direction of the PBS array direction can transmit much effective light with respect to the illumination spot on the PBS plane corresponding to each cell of the first fly's eye lens 54. Therefore, in the present invention, the arrangement direction of the lamps is arranged perpendicular to the arrangement direction of the PBS array, that is, the longitudinal direction of the effective area of the liquid crystal panel is arranged.

FIG. 8 illustrates an optical system of the liquid crystal projector according to an exemplary embodiment of the present invention, and FIG. 9 illustrates an optical system of the liquid crystal projector shown in FIG. 8 in an in-line form. The optical system of FIG. 8 includes first and second light sources 50 and 52, and first and second total reflection mirrors 66 and 68 disposed between the first and second light sources 50 and 52 and the prism 62, respectively. ), Collimating lenses 64, first and second fly-eye lenses 6 and 8 arranged between the prism 62 and the third total reflection mirror 14, and the PBS 10, 3 A condenser lens 16, a red transmission mirror 18, a red reflection mirror 20 and a red condenser lens 22 arranged between the total reflection mirror 14 and the red liquid crystal panel 24, and a red transmission mirror ( 18 and the first relay arranged between the blue transmission mirror 26 and the green condenser lens 28 and the blue transmission mirror 26 and the blue liquid crystal panel 44 arranged between the green liquid crystal panel 30. The lens 32, the first blue reflecting mirror 34, the second relay lens 36, the second blue reflecting mirror 38, the blue condensing lens 40, and the red, green and blue liquid crystal panel 24, The dichroic prism 46 provided between 30 and 44 and the light exit surface of the dichroic prism 46 are provided to face each other. The projection lens 48 is provided.

In FIG. 8, the first and second light sources 50 and 52 are arranged side by side in a small length direction among aspect ratios of the liquid crystal panel to increase light efficiency. The light emitted from each of the lamps of the first and second light sources 50 and 52 travels forward by the ellipsoid, and as shown in FIG. 9, the first and second total reflection mirrors respectively installed in front of the ellipsoid ( 66, 68 will be reflected toward the prism 62. In FIG. 8, when the first and second light sources 50 and 52 are disposed on the front and rear surfaces of the ground, the first and second total reflection mirrors 66 and 68 are not required. The prism 62 reflects the light beams from the first and second total reflection mirrors 66 and 68 and propagates toward the collimating lens 64. The collimating lens 64 causes the divergent light beam from the prism 62 to travel toward the first fly's eye lens 6 in parallel. The first fly's eye lens 6 divides incident light into cells so that the lens is focused on each lens cell of the second fly's eye lens 8. The second fly's eye lens 6 converts the incident light into parallel light of a specific portion and transmits the light toward the PBS array 10. The PBS array 10 is arranged in a large longitudinal direction of the aspect ratio of the liquid crystal panel to separate incident light into linearly polarized light (P wave and S wave) having any one optical axis, and the λ / 2 plate attached to the rear surface of the PBS array 10. 10A converts the P wave into an S wave. The third total reflection mirror 14 and the condenser lens 16 focus the incident light on the red transmission mirror 18. The red transmission mirror 18 transmits red light of the incident light to the red reflection mirror 20 and reflects light having a wavelength other than red light toward the blue transmission mirror 26. The red reflection mirror 20 totally reflects the incident red light toward the red condensing lens 22. The red condenser lens 22 condenses the incident red light onto the red liquid crystal panel 24 to create a better incidence condition on the effective area of the red liquid crystal panel 24, and is coated with a red transparent coating to increase red purity. Is given. The blue transmission mirror 26 reflects the green light of the incident light from the red transmission mirror 18 toward the green condensing lens 28, while transmitting the blue light toward the first relay lens 32. The green condenser lens 28 condenses the incident green light onto the green liquid crystal panel 30 to create a better incidence condition on the effective area of the green liquid crystal panel 30, and is coated with a green transparent coating to increase green purity. Is given. The blue light transmitted through the blue transmission mirror 26 passes through the first relay lens 32, the first blue reflection mirror 34, the second relay lens 36, and the second blue reflection mirror 38. 40). Here, since the path of the blue light is longer than the other red and green light, the first and second relay lenses 32 and 36 are used to correct the blue light. In other words, the first relay lens 32 serving as a field lens is inserted at a distance equal to the distance between the blue transmission mirror 26 and the green condenser lens 28 to prevent the blue light from spreading, and the first relay lens ( The second relay lens 36 is inserted to form an image at the same distance as 36). The blue condenser lens 40 focuses the incident blue light on the effective area of the blue liquid crystal panel 44 regardless of the color purity. The red, green, and blue liquid crystal panels 24, 30, and 44 transmit light by adjusting light transmittance according to the input image information. The dichroic prism 46 passes through the red, green, and blue liquid crystal panels 24, 30, and 44, respectively, to obtain image information, and then combines incident red, green, and blue light to project the projection lens 48 through the emission surface. Turned out towards). The projection lens 48 enlarges and projects the image incident from the dichroic prism 46 on the screen.

In this manner, the optical system of the liquid crystal projector of the present invention can increase the brightness of the projector by using two lamps. In addition, the optical system of the liquid crystal projector of the present invention, in using two lamps, maximizes the parallelism of the light beam incident on the first fly's eye lens, and arranges the two lamps in a small length direction of the aspect ratio of the liquid crystal panel. By arranging in the longitudinal direction of the liquid crystal panel aspect ratio, the light efficiency can be improved.

As described above, according to the optical system of the liquid crystal projector according to the present invention, it is possible to improve the brightness by using two lamps and to increase the life of the lamp than when using one high power lamp. In addition, according to the optical system of the liquid crystal projector according to the present invention, in using two lamps, the parallelism of the light beam incident on the first fly's eye lens is maximized, and the two lamps are arranged in a small length direction of the liquid crystal panel aspect ratio. By arranging PBS arrays in the longitudinal direction of the liquid crystal panel aspect ratio, it is possible to increase the light efficiency.

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 (7)

In the optical system of the liquid crystal projector for magnifying and projecting the image displayed on the liquid crystal panel, First and second light sources comprising a lamp for generating a light beam and an ellipsoidal mirror for advancing the light beam from the lamp in one direction A collimating lens for converting light beams from the first and second light sources into parallel light; At least one turning mirror unit configured to cause the light beams from the first and second light sources to overlap the collimating lens, An illumination system for injecting the light beam from the collimating lens into the liquid crystal panel, And placing the lamp at the first focal point of the ellipsoid and arranging the ellipsoid such that the second focal point coincides with the central axis of the liquid crystal panel. The method of claim 1, The turning mirror unit And an prism positioned at a second focal point of the ellipsoidal mirror. The method of claim 2, The turning mirror unit And a total reflection mirror for totally reflecting the light beam from the ellipsoid toward the prism. The method according to any one of claims 2 and 3, The angle formed between the reflecting surface and the reflecting surface of the prism is set to 90 degrees or less optical system of the liquid crystal projector. The method of claim 1, The light source is an optical system of a liquid crystal projector, characterized in that arranged side by side in the small longitudinal direction of the liquid crystal panel. The method of claim 1, The illumination system A micro lens for dispersing the light beam from the collimating lens to make the light distribution uniform; A polarization beam splitter array for converting the light beam from the microlens into linear polarization suitable for the polarization characteristic of the liquid crystal panel; And a condenser lens portion for condensing the light beam from the polarization beam splitter array to the liquid crystal panel. The method of claim 6, And the polarizing beam splitter array is arranged side by side in a large longitudinal direction of the liquid crystal panel.