Patent Application
20080049280
The above and/or other exemplary aspects of the present invention will become apparent and more readily appreciated from the following detailed description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The exemplary embodiments are described below so as to explain the present invention by referring to the figures. The like elements will be described for a first exemplary embodiment and may not be further described for other embodiments.
Hereinafter, a display according to a first embodiment of the present invention will be described with reference to
The liquid crystal panel 100 comprises a first substrate (not shown), a second substrate (not shown) facing the first substrate, and a liquid crystal layer interposed between the first and second substrates. On the first substrate are formed pixels 110 (shown in
As shown in
As an optical member that diffracts and condenses incident light according to its wavelength, the hologram device 210 has a diffraction effect and a lens effect. Typically, the hologram device 210 comprises diffraction grids formed on a base member. The hologram device 210 diffracts light by adjusting an incident angle of light incident into the diffraction grids, or the like. In this manner, the hologram device 210 separates and condenses incident white light to form a continuous optical spectral distribution on its focus plane. Accordingly, when the liquid crystal panel 100 is properly arranged near the focus plane, the red, green and blue light components can be incident into the pixels 110 of the liquid crystal panel 100. That is, the white light incident into the hologram device 210 is separated to have a continuous optical spectrum and the red, green and blue components are emitted through the pixels 110 of the liquid crystal panel 100. Accordingly, it is possible to display a color image without requiring a color filter layer.
The light direction changing part 300 is arranged between the hologram part 200 and the laser light source part 400 and directs the light, which is emitted from the laser light source part 400, to the hologram part 200 so that an incident angle of the light becomes uniform with respect to a plane of the hologram part 200. That is, without the light direction changing part 300, there is a high possibility that the light emitted from a region behind the liquid crystal panel 100 would not uniformly be incident into the hologram part 200. If the intensity of incident light is not uniform, the brightness of an image displayed on the liquid crystal panel 100 may become irregular. Accordingly, the light direction changing part 300 plays a role of directing the light, which is emitted from the laser light source part 400, to the hologram part 200 in order to maximize an optical efficiency. In this embodiment, the light direction changing part 300 adjusts the incident light so that the light travels substantially perpendicularly to the plane of the hologram part 200.
The light direction changing part 300 having such a function may be formed by one of various optical members, for example, a Fresnel lens having prisms having different slopes and formed on a base member.
In this embodiment, as shown in
The plurality of laser light sources 411, 413 and 415 comprises a red light laser 411 emitting red light having a wavelength band of about 620 to 690 nm, a green light laser 413 emitting green light having a wavelength band of about 500 to 570 nm, and a blue light laser 415 emitting blue light having a wavelength band of about 430 to 490 nm. In addition, in this embodiment, a full width half maximum of the light emitted from the laser light sources 411, 413 and 415 is less than about 5 nm. White light is produced by a combination of the red light laser 411, the green light laser 413 and the blue light laser 415 having such a narrow full width half maximum. By passing the white light through the hologram device 210, it is possible to obtain discontinuous red, green and blue light components. That is, it is possible to obtain discontinuous different colors without arranging red, green and blue components among light having all continuous wavelength bands on the pixel 110. Accordingly, using the laser light sources 411 and 413 and 415 of different colors having different wavelengths and a narrow full width half maximum allows easier color separation in the hologram device 210. In this embodiment, to meet the above conditions, it is preferable, but not necessary, that the laser light sources 411, 413 and 415 may comprise a nonlinear light modulator using a laser diode or a solid state laser. Optical pumping using a laser diode or a solid state laser shows an optical output better than optical pumping using a lamp.
In addition, since the laser light sources 411, 413 and 415 typically output polarized light, optical loss may be reduced when the polarized light passes through polarizing plates attached to both sides of the liquid crystal panel 100. It is known that polarization state of white light emitted from the laser light sources 411, 413 and 415 may be varied while passing through the polarizing plates and the liquid crystal layer and some of the light that does not pass through the polarizing plates and the liquid crystal layer may be lost. The optical loss due to such polarization variation may be reduced by using laser sources emitting polarized white light.
In order to avoid an optical loss due to a color filter layer, there has been a related art method using a sequential driving method that red, green and blue lights are sequentially provided to the liquid crystal panel 100 without a color filer layer. In this case, however, since light of different colors has different emission timings, the red, green and blue lights may not be properly mixed. Like this, the related art sequential driving method has a drawback in that overall white color representation is difficult due to separation of colors and color reproducibility is poor. As in this embodiment, when lasers are used as light sources, the above-mentioned problem may be prevented since light of different colors can be simultaneously provided to the liquid crystal panel 100 without using a color filter.
The color of the light emitted from the laser light sources 411, 413 and 415 is not limited to red, green and blue, but may comprise cyan, magenta and yellow which can be produced by adjusting a laser wavelength.
The light mixing part 420 mixes the light emitted from the laser light sources 411, 413 and 415 to white light. The light emitted from the laser light sources 411, 413 and 415 is not separately provided to the liquid crystal panel 100, but is mixed in the light mixing part 420 to white light and then is projected through the projection lens 430. The light mixing part 420 may comprise a light guide tube with a plurality of reflecting plates or mirrors arranged therein. These reflecting plates or mirrors guide light emitted in different directions to a direction in which the projection lens 430 is located. In order to reduce an optical loss caused by light absorption in an inner wall of the light mixing part 420, a reflecting mirror may be arranged on the inner wall of the light mixing part 420.
The projection lens 430 spreads light incident from the light mixing part 420 and projects the spread light onto the liquid crystal panel 100. As shown in
The configuration of the light projection part is not limited to those light projection parts shown in the first and second embodiments. For example, the light projection part may be configured by only an aspheric mirror or a plurality of lenses, or may be designed in various ways in consideration of the size of the display device and a distance between the light projection part and the liquid crystal panel 100.
The diffusion plate 530 comprises a base plate and a coating layer including beads formed on the base plate. The diffusion plate 530 makes the luminescence of light uniform by diffusing light incident thereon through the hologram part 200.
The prism film 520 has a top surface on which triangular prisms are arranged in a regular pattern. The prism film 520 condenses light, which is diffused by the diffusion plate 530, in a direction perpendicular to a plane of the liquid crystal panel 100. Two sheets of prism films 520 are typically used to condense light, each of which has micro prisms formed thereon at a predetermined angle. Most of light passed through the prism film 520 travels vertically to provide a uniform luminescence distribution on the liquid crystal panel 100. A reflection polarizing film may be used along with the prism film 520, or only the reflection polarizing film may be used without the prism film 520.
The protective film 510, which is located on the prism film 520, protects the prism film 520, which is susceptible to scratches.
The plurality of films 510, 520 and 530 may be selectively provided or may be omitted in some cases. The kind of film may be selected in consideration of a user' need and a characteristic of a light source, and further, any known films may be used for light compensation.
As described above, according to the present invention, an optical efficiency is increased by using a hologram device 210 instead of a color filter, and a high light output can be obtained by using the laser light sources 411, 413 and 415 including a laser diode or the like for supplying white light. In addition, since light emitted from the laser light sources 411, 413 and 415 is separated into red, green and blue by the hologram device 210, an optical loss, which may be caused by transmission through other media, can be reduced.
As apparent from the above description, the present invention may provide a display device with increased optical efficiency and good color reproducibility, and a backlight unit for use in the display device.
Although a few exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0080687 | Aug 2006 | KR | national |
