KR20080055051A - Back light unit for display panel - Google Patents

Abstract

A back light unit for a flat panel display device is provided to enable an optical scan system to reflect a laser beam from a laser light source to an X axis and a Y axis and diffuse the laser beam to the entire area of a light guide plate, thereby solving the non-uniformity of lighting and adjusting the brightness of the lighting selectively. A back light unit for a flat panel display device comprises a laser light source(100), a light guide plate, and an optical scan system(200). The laser light source generates laser beam. The light guide plate has a reflective pattern in the inside to diffuse light generated in the laser light source. The laser light source is positioned in the side of the light guide plate. The optical scan system diffuses the laser beam incident to the side of the light guide plate between the laser light source and the light guide plate. The optical scan system comprises a first mirror(210) and a second mirror(220). The first mirror is rotated to scan the light generated from the laser light source to a first axis on a plane. The second mirror is rotated to scan the laser beam reflected from the first mirror to a second axis on a plane.

Description

Back light unit for flat panel display elements {BACK LIGHT UNIT FOR DISPLAY PANEL}

1 is a schematic view showing a conventional backlight unit for a flat panel display device;

2 shows a schematic view of a backlight unit according to the invention,

3 is a view illustrating a principle of operation of an optical system having a scan mirror capable of diffusing laser light, which is a feature of the present invention, to the entire region of the light guide plate or illuminating the selective region;

4 is a perspective view showing a schematic configuration diagram of an optical system having a scan mirror as a component of a backlight unit according to the present invention;

5 is a front view showing a schematic configuration diagram of an optical system having a scan mirror as a component of a backlight unit according to the present invention;

6 is a view showing a scanning state of a laser beam by a second mirror of an optical system having a scan mirror as a component of a backlight unit according to the present invention.

The present invention relates to a display panel backlight unit, and more particularly, to a display panel backlight unit having high system configuration efficiency, excellent color reproducibility and uniform illumination.

Typically, a liquid crystal display (hereinafter referred to as "LCD") is a plurality of liquid crystal cells arranged in a matrix form and a plurality of control switches for switching the video signal to be supplied to each of these liquid crystal cells The amount of light transmitted from the back light unit (BLU) is adjusted by the configured liquid crystal panel to display a desired image on the screen.

Referring to Fig. 1, a configuration of a backlight unit for an LCD of the prior art is shown. The backlight unit for LCD illustrated in FIG. 1 converts a light source 1 for generating light, a lamp housing 3 installed in a form surrounding the light source 1, and light incident from the light source 1 into a planar light source. The light guide plate 5, a reflector 7 positioned below the light guide plate 5 to reflect the light traveling toward the lower surface and the side surface of the light guide plate 5 toward the upper surface, and diffuse the light through the light guide plate 5. Light passing through the first diffusion sheet 9, the first and second prism sheets 11 and 13 for adjusting the traveling direction of the light passing through the first diffusion sheet 9, and the second prism sheet 13 And a second diffusion sheet 15 for diffusing.

A cold cathode fluorescent lamp is mainly used as the light source 1, and the light generated by the light source 1 is incident on the light guide plate 5 through an incident surface existing on the side of the light guide plate 5. The lamp housing 3 has a reflecting surface on its inner surface to reflect light from the light source 1 toward the incident surface of the light guide plate 5.

The light guide plate 5 has an inclined rear surface and an exit surface that is horizontal and is manufactured such that the entrance surface and the exit surface are at right angles. The rear side of the light guide plate 5 is provided so that the reflecting plate 7 faces. The reflector 7 serves to reduce light loss by reflecting light incident to itself through the back of the light guide plate 5 toward the light guide plate 5.

In the above-described LCD backlight unit, when light enters the light guide plate 5 from the light source 1, it is reflected at a predetermined inclination angle from the rear surface which is an inclined surface and proceeds uniformly toward the exit surface. At this time, the light propagated to the lower surface and the side surface of the light guide plate 5 is reflected by the reflector 7 and proceeds toward the exit surface. The light emitted through the exit surface of the light guide plate 5 is uniformly diffused to the entire area by the first diffusion sheet 9.

On the other hand, when the light incident on the liquid crystal panel 17 is vertical, the light efficiency is increased. To this end, it is preferable to stack two first and second prism sheets 11 and 13 so that the traveling angle of the light emitted from the light guide plate 5 is perpendicular to the liquid crystal panel 17. The first and second prism sheets 11 and 13 are formed in the form of a plurality of triangular bars having hills and valleys. In addition, the first and second prism sheets 11 and 13 are arranged such that the prism arrangement directions are perpendicular to each other. The first and second prism sheets 11 and 13 change a propagation path of light so that light incident from the light guide plate 5 is incident perpendicularly to the upper liquid crystal panel 17. The second diffusion sheet 15 secondaryly diffuses the light via the first and second prism sheets 11 and 13.

The liquid crystal panel 17 implements an image by selectively transmitting or blocking light diffused from the second diffusion sheet 15. More specifically, the image is displayed by driving the liquid crystal by the voltage difference between the common electrode (not shown) formed on the upper substrate (not shown) of the liquid crystal panel 17 and the pixel electrode of the lower substrate (not shown). .

As described above, the LCD backlight unit according to the prior art includes a light source for generating light, a light guide plate for converting the generated light into a planar light source, a reflector for reflecting light traveling toward the lower surface and the side of the light guide plate toward the upper surface, A first diffusion sheet for diffusing light through the light guide plate, first and second prism sheets for adjusting the traveling direction of light, and a second diffusion sheet for diffusing light through the second prism sheet, The generated light is uniformly incident on the liquid crystal panel. In addition, the backlight unit uniformly injects light onto the front surface of the liquid crystal panel, and the liquid crystal panel implements an image by selectively transmitting or blocking light.

However, as a conventional backlight unit, as shown in FIG. 1 (b), when the light source is an LED or a lamp, there is a problem that the volume of the system becomes large or the color reproducibility is inferior, as in FIG. 1 (c). Laser is excellent in terms of system configuration efficiency and color reproducibility, but has a disadvantage in that it is difficult to form uniform illumination due to a narrow emission angle.

The technical problem to be solved by the present invention to solve the above problems is to configure the scanning optical system to solve the non-uniformity of the illumination light that may occur due to the linearity or coherence of the laser light source to enable uniform illumination, and the optical system In addition to controlling the illumination area selectively, it is possible to easily miniaturize the system by using micro-optical elements.

A first feature according to the present invention for solving the above problems is a laser light source for generating laser light; And a light guide plate having a reflection pattern formed therein to diffuse or scatter light generated by the laser light source, wherein the laser light source is positioned at a side of the light guide plate, and is disposed on a side of the light guide plate between the laser light source and the light guide plate. Scan optical system for diffusing the incident laser light is further provided.

The scanning optical system may include a first mirror rotated to scan light generated from the light source on a first axis on a plane, and a scan beam rotated to scan a laser beam reflected from the first mirror on a second axis on a plane. It is preferable to include two mirrors, and as the structure becomes smaller as the thickness of the light guide plate moves away from the light source, it is also preferable that the lower surface of the light guide plate is inclined.

In addition, the laser light source may preferably be to generate a laser beam of red (R), green (G) and blue (B) wavelength, and to reflect the light incident from the light source to the lower surface of the light guide plate upwards The reflective layer may be formed, and the driving unit for rotating the first mirror or the second mirror and the driving unit may further include a control unit for controlling the rotation of the first mirror or the second mirror. In addition, the first mirror and the second mirror is preferably made of a DMD.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

2 is a schematic view of a backlight unit according to the present invention; As shown in FIG. 2, the backlight unit according to the present invention includes a laser light source 100 for generating a laser light, and a scanning optical system for diffusing the laser light incident on the light guide plate to the entire region of the light guide plate. 200), a light guide plate 300 for converting the laser light diffused through the scanning optical system 200 into a planar light source, and an upper surface of the light that is located below the light guide plate 300 and propagates toward the bottom and side surfaces of the light guide plate 300. A reflecting plate 307 that reflects toward the first surface, a first diffusion sheet 310 that diffuses light through the light guide plate 300, and first and second adjustment directions of the light passing through the first diffusion sheet 310. The prism sheets 320 and 330 and a second diffusion sheet 340 for diffusing light via the second prism sheet 330 are provided.

The light guide plate 300 has an inclined rear surface and an exit surface that is horizontal, and is manufactured such that the entrance surface and the exit surface are at right angles. The rear side of the light guide plate 300 is provided so that the reflecting plate 307 faces. The reflector 307 serves to reduce light loss by reflecting light incident to itself through the rear surface of the light guide plate 300 toward the light guide plate 300.

When light from the laser light source 100 is incident on the light guide plate 300, the light is reflected at a predetermined inclination angle from the rear surface, which is an inclined surface, to uniformly move toward the exit surface. At this time, the light traveling to the lower surface and the side surface of the light guide plate 300 is reflected by the reflecting plate 307 and proceeds toward the exit surface. The light emitted through the exit surface of the light guide plate 300 is uniformly diffused to the entire area by the first diffusion sheet 310.

On the other hand, when the light incident on the liquid crystal panel 400 is perpendicular to the light efficiency is increased. To this end, it is preferable to stack two first and second prism sheets 320 and 330 such that the traveling angle of the light emitted from the light guide plate 300 is perpendicular to the liquid crystal panel 400. The first and second prism sheets 320 and 330 are formed in the form of a plurality of triangular bars having a hill and a valley. In addition, the first and second prism sheets 320 and 330 are arranged such that the prism arrangement directions are perpendicular to each other. The first and second prism sheets 320 and 330 change a traveling path of light such that light incident from the light guide plate 300 is incident perpendicularly to the upper liquid crystal panel 400. The second diffusion sheet 350 secondaryly diffuses light via the first and second prism sheets 320 and 330.

The liquid crystal panel 400 implements an image by selectively transmitting or blocking light diffused from the second diffusion sheet 350. More specifically, an image is displayed by driving a liquid crystal by a voltage difference between a common electrode (not shown) formed in an upper substrate (not shown) of the liquid crystal panel 400 and a pixel electrode of a lower substrate (not shown). .

Here, the light source is made of a laser light source, which is a light source of the backlight unit, the laser light source has a beam angle of 8 ° ~ 24 ° to the source, unlike conventional lamps or LEDs that come in the form of a wing (lambertian) The warhead is much smaller, so the system configuration efficiency is high and easy. In addition, the color coordinates are excellent, and the color reproduction range can be realized about 20% higher than the system using the LED lamp.

FIG. 3 is a view illustrating an operating principle of a scanning optical system having a scan mirror capable of diffusing laser light, which is a feature of the present invention, to the entire region of the light guide plate or illuminating the selective region. As illustrated in FIG. 3, in the scan optical system 200, the laser light source 100 may reflect light along the X and Y axes through a mirror to diffuse the light to the entire area of the panel LGP 300. This not only solves the illumination nonuniformity caused by the linear coherency of the laser light, but can also selectively adjust the brightness by adjusting the mirror.

4 is a perspective view showing a schematic configuration diagram of an optical system having a scan mirror as a component of a backlight unit according to the present invention, and FIG. 5 is a front view thereof. 4 and 5, a laser light source 100 that transmits a laser beam in a first direction perpendicular to the X-Y plane is positioned below the light guide plate or above the reflective film in the X-Y plane direction.

A first mirror between the laser light source 100 and the reflective film above to form a scanning line on the reflecting surface on the optical axis of rotation of the second mirror 220 by scanning the laser beam from the laser light source 100 in the X direction A second mirror 220 for scanning the laser beam from the first mirror 210 that scans 210 and the X direction is located.

The laser beam scanning apparatus of the present invention as described above is located in a state in which the laser light source 100 is upright in the first direction above the reflective film, but this is not limited and is most appropriate in consideration of the arrangement of the optical mirror and the shape of the reflective film. Of course, it can be arranged.

The first mirror 210 reflects the laser beam from the laser light source 100 in a horizontal direction or a horizontal direction slightly inclined in the horizontal direction, but is rotated within a predetermined angle range by the first mirror rotation axis to thereby cause a second mirror. Scan along the reflection line of the second mirror 220, that is, the scanning line located on the center of rotation of the.

The second mirror 220 reflects the laser beam on the scan line formed along the axis of rotation to the vertical bottom to form an illumination area, that is, a scan area on the reflective film. The lens device positioned between the second mirror 220 and the reflective film has a so-called F-theta which adjusts an optical distance such that the ray point beam reflected by the second mirror 220 is accurately focused on all parts of the scanning area. THETA) lens.

5 and 6, the scanning center axis of the laser beam reflected from the first mirror 210 shows a state inclined at a predetermined angle with respect to the Y'-Y 'line parallel to the XY plane, but this is a design condition. In accordance with the present invention, the first mirror 210 and the second mirror 220 may be maintained in parallel with the Y'-Y 'line by adjusting an appropriate arrangement angle.

As such, by configuring the laser scanning optical system shown in FIG. 4 or FIG. 5 to solve the non-uniformity of illumination light generated due to the linear coherency of the laser light source of the backlight unit according to the present invention, the entire area of the panel evenly. It is possible to illuminate, and the driving unit for driving the scan mirror and the control unit for controlling the driving unit are connected with the display panel control unit for detecting and controlling the luminance and color expression of the panel so that the color unevenness can be adjusted and corrected. This allows for selective adjustments to increase the lighting or brightness of specific parts.

In addition, it is preferable that a laser light source consists of a laser diode chip, and the mirror which is an optical element uses the micro optical element like DMD. This has the effect of precise control and reducing the volume of the entire system.

DMD (Digital Micromirror Device) is a digital micromirror device, and is a core optical device used in various fields such as small display devices. In particular, the DLP (Digital Optical Technology) method employs DMD in a display device that is the heart of the system. This is a chip in which a very small number of mirrors are placed on the surface, and one mirror corresponds to one pixel, which is a projection method completely different from the conventional CRT, liquid crystal, and plasma methods.

A tiny mirror of 14 to 16 mm (Micromirror / 500mm size) per pixel adjusts the angle of reflection according to the signal and realizes the image. The distance between the mirror and the mirror is very close to 1mm, so it is suitable for processing large-capacity and high-definition video such as high-definition (HD) digital televisions. It is stable because of excellent uniformity of color and brightness in the center and periphery of the screen.

The DMD chip is a reflective device and, furthermore, the reflection efficiency is high, so there is little energy left in the device itself. For this reason, even if a fixed button such as a still image, text information, drawings, etc. is continuously displayed for a long time, sticking phenomenon that occurs in other display methods does not occur. Moreover, there is no color bleeding or distortion of the image due to the influence of the magnetic field, and the original image and video are faithfully reproduced accurately.

Projection TV using DLP (Digital Lighting Processing) method uses a digital device that determines the blocking and opening of light through a circuit board and reflects the light reflected on the surface of many fine DMD devices. Depending on the angle of reflection to adjust the image.

Therefore, there is no noise or image quality deterioration when converting a digital signal to analog, and since the device does not correct different characteristics, the original picture can be perfectly reproduced.

In addition, because it uses the mirror reflection principle rather than the liquid crystal display (LCD) method, it is recognized as a complete silicon device that realizes high brightness and high-definition image with high light utilization efficiency. great.

Compared to Liquid Crystal Display (LCD) and Plasma Display Pannel (PDP) methods, the device's response speed is faster, so that it can be reproduced more smoothly and steadily in moving images. Simple, unaffected by iii), easy to adjust and suitable for both front and rear projection applications

By using such a micro-optical device, if the scanning optical system of the backlight unit for a flat panel display device according to the present invention is configured, precise control and miniaturization of the system volume can be achieved more easily.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from these descriptions.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all the things that are equivalent to or equivalent to the claims as well as the following claims will belong to the scope of the present invention. .

When providing the backlight unit according to the present invention, in order to use the laser light source with good color reproducibility and system configuration efficiency, scan to solve the unevenness of the illumination light that may occur due to the linearity or coherence of the laser light source The optical system can be configured to enable uniform illumination, and the optical system can be controlled to selectively adjust the illumination area, and the system can be easily miniaturized by using micro optical elements.

Claims (7)

A laser light source for generating laser light; It includes a light guide plate formed with a reflection pattern therein to diffuse or scatter the light generated from the laser light source, The laser light source is positioned on the side of the light guide plate, the backlight unit for a flat panel display device further comprises a scanning optical system for diffusing the laser light incident on the side of the light guide plate between the laser light source and the light guide plate. The method of claim 1, The scanning optical system may include a first mirror which is rotated to scan light generated from the light source on a first axis on a plane. And a second mirror rotated to scan the laser beam reflected by the first mirror on a second axis on a plane. The method according to claim 1 or 2, The thickness of the light guide plate becomes smaller as the distance from the light source, the backlight unit, characterized in that the lower surface of the light guide plate is inclined. The method according to claim 1 or 2, And the laser light source generates laser beams of red (R), green (G), and blue (B) wavelengths. The method according to claim 1 or 2, And a reflective layer formed on a lower surface of the light guide plate to reflect light incident from the light source upwardly. The method of claim 2, And a driving unit for rotationally driving the first mirror or the second mirror, and a control unit for controlling rotation of the first mirror or the second mirror. The method of claim 2, And the first mirror and the second mirror are made of DMD.

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