KR20010010329A - Optical Device Of Liquid Crystal Projector - Google Patents

Abstract

PURPOSE: An optical device of a liquid crystal projector is provided to use only excellent reflectors while reducing a path of blue light to reduce a brightness loss of blue light so that the brightness of a screen can be improved. And the device enables white balance to be easily regulated, as paths of red light, green light and blue light are equal. CONSTITUTION: A blue light reflection mirror(50) reflects blue light in light generated in a light source, and transmits yellow light. A red light transmission mirror(18) transmits red light in yellow light transmitting the blue light reflection mirror(50), and reflects green light. A blue-green reflection mirror reflects blue light from the blue light reflection mirror(50) to be progressed to a liquid crystal panel for blue(44), and reflects green light from the red light transmission mirror(18) to be progressed to the liquid crystal panel for green(30). First/second blue reflection mirrors(34,38) reflect blue light from the blue-green reflection mirror to be progressed to the liquid crystal panel for blue(44). A red light reflection mirror(20) reflects red light from the red light transmission mirror(18) to be progressed to a liquid crystal panel for red(24). Three light collecting lenses(22,28,40) collect light incident to the liquid crystal panels(24,30,44) in available areas of the liquid crystal panels(24,30,44).

Description

Optical device of liquid crystal projector

The present invention relates to an image display projector, and more particularly to an optical device of a liquid crystal projector that can improve the brightness of the projector.

Recently, with the development of the computer, the use of the projector instead of the Overhead Poojector (OHP) is increasing. A typical projector is a liquid crystal projector that projects an image of a small screen displayed on an LCD onto a large screen. One of the important performances of these projectors is brightness, and products that improve the brightness of projectors are being released. The biggest influence on the increase in brightness can be said to be a lamp. The amount of light output from the lamp can be said to be proportional to the brightness of the projector. Of course, most lamps currently in use have discharge electrodes in the form of discharges, and the intervals between these discharge electrodes increase the efficiency of the brightness, so it is not necessarily the only lamp with a large amount of light. However, because the lamps in current projectors use about the same, making a bright projector depends on how efficiently you use the light from the lamps. When the amount of front output light of a lamp having a reflector is 100, only about 20% of the light output from the final projector is used. For this reason, if the efficiency of the optical system is maximized, the brighter projector can be realized even with the same lamp. In an effort to increase the light efficiency of the projector, the lamp is improved to have a small light emission size, a polarization conversion system for converting light generated from the light source into one linearly polarized light, and the liquid crystal panel has a high aperture ratio.

Referring to Fig. 1, an optical system configuration of a conventional high efficiency liquid crystal projector is shown. The liquid crystal projector of FIG. 1 includes a 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 the first condenser lens 12, the second condenser lens 16, the red transmission mirror 18, and the red light arranged between the total reflection mirror 14 and the red liquid crystal panel 24. Reflective mirror 20 and red condenser lens 22, blue transmission mirror 26 and green condenser lens 28 arranged between red transmission mirror 18 and green liquid crystal panel 30, blue transmission mirror A first relay lens 32, a first blue reflecting mirror 34, a second relay lens 36, a second blue reflecting mirror 38, and blue arranged between the 26 and the blue liquid crystal panel 44 Light exit surface of the dichroic prism 46 and the dichroic prism 46 provided between the condenser lens 40 and the polarizing plate 42, the red, green, and blue liquid crystal panels 24, 30, 44. A projection lens 48 is provided to face to.

In FIG. 2, light in the visible light region emitted from the lamp 2 travels toward the first fly's eye lens 6 through the parabolic 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 back of the PBS array 10 has a P wave as an S wave. Will be converted. The incident light is converted into polarized light in one direction by the PBS array 10 and is incident on the first condensing lens 12. As a result, almost all the light emitted from the lamp 2 is incident on the first condensing lens 12 to increase the light efficiency and is emitted from each lens cell of the first and second fly-eye lenses 6 and 8. Since light is irradiated to the whole of the liquid crystal panels 24, 30 and 44, the uniformity of the light distribution irradiated to the liquid crystal panel can be ensured. The first condensing lens 12, the total reflection mirror 14, and the second condensing 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 10 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. Not using a separate polarizing plate to increase the cooling efficiency of the red and green liquid crystal panels 24 and 30 The polarizing plates corresponding to the red and green liquid crystal panels 24 and 30 may be a red condenser lens 22 and a green condensing lens. It is attached to the exit surface of the lens 28. On the other hand, in the case of blue, since the energy efficiency is the highest, more efficient cooling is required, thereby attaching the polarizing plate 42 to a separate transmission plate. In addition, the polarizers to be attached to the exit surfaces of the liquid crystal panels 24, 30 and 44 are also attached to the incidence surface of the dichroic prism 46 due to a cooling problem. 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 the 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 such a conventional liquid crystal projector, the distance from the illumination system to the liquid crystal panel for implementing red and green is the same. On the other hand, since the blue path is about twice as long, the amount of blue light is lost. In comparison with the transmittance of the filter / mirror and the like which transmit or reflect the color, the amount of light is largely transmitted. This is because absorption and total internal reflection of the medium itself occur during transmission, and absorption does not exist in reflection. In addition, in the case of blue light, in order to correct an extended path, light is emitted to the blue condensing lens by using two relay lenses, so that the amount of light is lost while passing through the relay lens.

As a result, in the conventional liquid crystal projector, blue light is insufficient due to the loss of light due to a relatively long path, so that the green or red light is relatively lowered to adjust the color temperature of the white light. This is called white balance adjustment, and if you try to match a specific color temperature (for example, 9000 degrees for most data projectors), you will need to reduce the intensity of the red and green light because the blue light is insufficient and the overall light efficiency will drop. There is a problem that the brightness is lowered.

Accordingly, it is an object of the present invention to provide an optical device of a liquid crystal projector that can increase the brightness of the projector by providing that the amount of red and green light can be increased by increasing the light amount of blue light.

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.

<Description of the code | symbol about the principal part of drawing>

2: lamp 4: parabolic

6: first fly's eye lens 8: second fly's eye lens

10: PBS array 12: the first condenser lens

14: total reflection mirror 16: the second condensing lens

18: red transmission mirror 20: red reflection mirror

22: red condenser lens 24: red liquid crystal panel

26: blue transmission mirror 28: green condensing 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

42 polarizer 44 blue liquid crystal panel

46: dichroic prism 48: projection lens

50: blue reflection mirror 52: third fly's eye lens

54 second PBS array 56 third condenser lens

58: cyan reflective mirror 60: fourth condenser lens

62: yellow reflecting mirror

In order to achieve the above object, the liquid crystal projector optical device according to the present invention is a blue reflection mirror that reflects blue light from the light generated from the light source and transmits the remaining yellow light, and transmits red light from the yellow light transmitted through the blue reflection mirror. The green light is provided with a red transmission mirror which reflects the light, and separated into three colors of red, green, and blue to be incident on each of the red, green, and blue liquid crystal panels.

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, a preferred embodiment of the present invention will be described in detail with reference to FIG.

2 illustrates an optical system configuration of a liquid crystal projector according to an exemplary embodiment of the present invention. The liquid crystal projector of FIG. 2 includes a first fly's eye lens 6, a blue reflector's mirror 50, a second fly's eye lens 8, and a first PBS array arranged between the lamp 2 and the yellow reflecting mirror 62. 10 and the first condenser lens 12, the second condenser lens 16, the red transmission mirror 18, the red reflection mirror (arranged between the yellow reflection mirror 62 and the red liquid crystal panel 24) 20) and a red condenser lens 22, a cyan reflector 58 and a green condenser lens 28 arranged between the red transmission mirror 18 and the green liquid crystal panel 30, and a blue reflecting mirror 50 And a third fly's eye lens 52, a second PBS array 54, a third condenser lens 56 arranged between the cyan reflecting mirror 58 and the cyan reflecting mirror 58 and the blue liquid crystal panel 44. The fourth condenser lens 60, the first and second blue reflecting mirrors 34 and 38, the blue condenser lens 40 and the polarizing plate 42, and the red, green and blue liquid crystal panel 24 arranged therebetween. Of the dichroic prism 46 and the dichroic prism 46 provided between the plurality of nozzles 30, 44. A projection lens 48 is provided to face the surface.

Most of the visible light region of the white light emitted from the lamp 2 in FIG. 2 is reflected by the parabolic mirror 4 toward the first fly's eye lens 6. The first fly's eye lens 6 splits the incident light into cells so that the light is collected at a specific distance. The blue reflecting mirror 50 reflects the blue light of the incident light focused by the first fly's eye lens 6 in the unit of cells toward the third fly's eye lens 52, and the light other than the blue light, that is, the yellow light is the second light. The light is transmitted to the fly's eye lens 8. The second fly's eye lens 8 penetrates the blue reflection mirror 50, converts yellow light focused on each lens cell into parallel light of a specific portion, and transmits the light toward the PBS array 10 to irradiate the effective area of the liquid crystal panel. The light distribution to be made uniform. The PBS array 10 separates incident light into P waves and S waves, and the half-wave plate 10A attached to the rear surface of the PBS array 10 converts P wave components that are not used in the liquid crystal panel into S waves. The light efficiency is improved by converting the incident light into S-waves used in the liquid crystal panel and emitting the light by the PBS array 10. The first condensing lens 12, the yellow reflecting mirror 62, and the second condensing lens 16 focus the incident light on the red transmission mirror 18. The red transmission mirror 18 transmits the red light of the incident yellow light through the red reflection mirror 20 and reflects the green light toward the cyan reflection mirror 58. 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 to the effective area of the red liquid crystal panel 24 and is coated with red to improve red purity. The cyan reflecting mirror 58 reflects the incident green light from the red transmission mirror 18 toward the green condenser lens 28. The green condenser lens 28 condenses the incident green light to the effective area of the green liquid crystal panel 30 and increases the purity of green by coating green transmission.

The third fly's eye lens 52 is reflected by the blue reflecting mirror 50 and converts the blue light focused on each lens cell into parallel light of a specific portion and transmits it to the second PBS array 54 so as to transmit the effective area of the liquid crystal panel. The light distribution irradiated onto is made uniform. The second PBS array 54 converts all incident light into S waves and emits them toward the third condensing lens 56. The third condenser lens 56 focuses the incident light toward the cyan reflecting mirror 58. The cyan reflection mirror 58 totally reflects the incident blue light toward the fourth condensing lens 60. The fourth condenser lens 60 collects blue light reflected and diffused by the cyan reflecting mirror 58. The first and second blue reflecting mirrors 34 and 38 change the path of the incident blue to the blue condensing lens 40. 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. Not using polarizers to increase the cooling efficiency of the red and green liquid crystal panels 24 and 30 The polarizing plates corresponding to the red and green liquid crystal panels 24 and 30 include the red condenser lens 22 and the green condenser lens 28. It is attached to the exit surface of). On the other hand, in the case of blue, since the energy efficiency is the highest, more efficient cooling is required, thereby attaching the polarizing plate 42 to a separate transmission plate. In addition, the polarizer to be attached to the exit surface of the liquid crystal panels 24, 30, 44 is also attached to the incident surface of the dichroic prism 46 due to a cooling problem. The red, green, and blue liquid crystal panels 24, 30, and 44 adjust and transmit light transmittances of red, green, and blue light incident through the respective incident surfaces 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.

As described above, in the liquid crystal projector of the present invention, the light paths of red, green, and blue are the same by separating blue from the inside of the illumination system. In other words, it is possible to reduce the loss of the blue light amount by reducing the blue light path than before. This is possible because only the reflective surface is used without using the relay lens system as in the related art. Specifically, only the couples having a difference in calculating the amount of light before being incident on the red, green, and blue liquid crystal panels 24, 30, and 44 from the lamp 2 are compared.

Conventional blue light efficiency = transmittance 95.5% of total reflection mirror x reflectance 99.1% of red transmission mirror x transmittance 94.4% of blue transmission mirror x transmittance 98.9% of relay lens = 88.4%

Blue light efficiency in the present invention = 98.6% reflectance of the blue reflecting mirror x 98.6% reflectance of the cyan reflecting mirror = 97.2%

Conventional and Invention Ratio of Blue Light in the Present Invention = 97.2 / 88.4 = 1.10

As such, it can be seen that the amount of blue light is improved by about 10%. When the blue fly coating is applied to the third fly's eye lens 52, the second PBS array 54, and the third and fourth condenser lenses 56 and 60 positioned in the path of blue light, It may be incident on the liquid crystal panel 44. In addition, in the path of the red light and the green light, if a dedicated coating corresponding to each color is applied, the light amount can be increased beyond the loss of the light amount generated while passing through the blue reflection mirror 50. As a result, as the amount of blue light, which is an important factor to increase the brightness of the projector, increases the amount of green and red light, the total composite brightness of the projected image increases by about 10%. .

As described above, according to the optical device of the liquid crystal projector according to the present invention, since only the reflective surface with good light efficiency is used while the path of the blue light is relatively reduced, the amount of light loss of the blue light can be reduced. Accordingly, a configuration capable of increasing the amount of red and green light causes the overall brightness of the screen to increase. In addition, according to the optical device of the liquid crystal projector according to the present invention, since the paths of the red light, the green light, and the blue light are all the same, the white balance can be easily adjusted.

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 device of the liquid crystal projector for separating the light generated from the light source into three colors of red, green, and blue and incident on each of the red, green, and blue liquid crystal panels, A blue reflecting mirror reflecting blue light from the light emitted from the light source and transmitting the remaining yellow light; And a red transmission mirror which transmits red light and reflects green light from yellow light passing through the blue reflection mirror. The method of claim 1, A blue green reflecting mirror for reflecting the blue light from the blue reflecting mirror toward the blue liquid crystal panel and reflecting the green light from the red transmitting mirror toward the green liquid crystal panel; First and second blue reflecting mirrors for reflecting blue light from the cyan reflecting mirror toward the blue liquid crystal panel; A red reflection mirror for reflecting red light from the red transmission mirror toward the red liquid crystal panel; And three condensing lenses for converging light incident on the three liquid crystal panels to the effective area of the liquid crystal panel. The method of claim 1, And an optical separation / polarization conversion element for converting the light generated from the light source into uniform light distribution and converting the light into one linearly polarized light. The method of claim 3, wherein The optical device of the liquid crystal projector, characterized in that the blue transparent coating on the optical elements located on the path of the blue light.