JP3072676B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device used in a liquid crystal television or the like.

[0002]

2. Description of the Related Art In a display device used in a liquid crystal television or the like, an image displayed in a display area 2 of a liquid crystal display panel 1 is enlarged and projected on a screen 4 by one convex lens 3 as shown in FIG. In some cases, the display screen is enlarged.

[0003]

By the way, in such a conventional display device, for example, an image of an image height P ₀ (25 mm) displayed on the display area 2 of the liquid crystal display panel 1 is doubled on the screen 4. In the case of enlarging and projecting to P ₁ (= 2P ₀ = 50 mm), if the angle of view θ of the convex lens 3 is 30 °,
The minimum focal length f of the convex lens 3 is f = P _{0 /} tan θ = 43.3 mm, and it is necessary to use the convex lens 3 having a minimum focal length f of 43.3 mm. If the magnification M is (−2), The distance S from the liquid crystal display panel 1 to the screen 4 is S = f {2-M- (1 / M)} = 194.85 mm, and the entire apparatus is considerably thicker than the size of the image projected on the screen 4. Problem. SUMMARY OF THE INVENTION It is an object of the present invention to provide a display device capable of shortening the distance from a display panel to a screen and reducing the overall thickness of the device.

[0004]

According to the first aspect of the present invention,
Bar-shaped lenses are arranged at intervals in a direction perpendicular to the optical axis between each display area of a display panel having a plurality of display areas and a screen. According to a second aspect of the present invention, the refractive index of each of the rod-shaped lenses gradually changes from the axial center toward the outer peripheral side. According to a third aspect of the present invention, the length of each of the rod-shaped lenses is set to 3/4 times the meandering period of light passing through the rod-shaped lenses.

[0005]

According to the present invention, each bar-shaped lens is arranged at an interval in a direction perpendicular to the optical axis, so that each image displayed in each display area of the display panel corresponds to each other. The projection is carried out without overlapping each other on the screen by the rod-shaped lens. in this case,
Since the image height of each image displayed in each display area of the display panel becomes smaller, each rod-shaped lens can shorten its focal length considerably, and therefore, the distance from the display panel to the screen can be considerably shortened. As a result, the overall device can be made thinner. In this case, assuming that the refractive index of the rod-shaped lens gradually changes from the axial center toward the outer peripheral side, it is possible to reduce the transmission loss as compared with the case of transmitting light by total internal reflection. If the length of the rod-shaped lens is set to 3/4 times the meandering cycle, an erect equal-magnification image can be formed.

[0006]

FIG. 1 shows a schematic configuration of a display device according to an embodiment of the present invention. This display device includes a liquid crystal display panel 11. The liquid crystal display panel 11 has a display region 12 at each of an upper portion, a central portion, and a lower portion in the vertical direction of the surface, and has a mask (non-display region) 13 between the respective portions. Similarly, a plurality of display areas and masks are alternately provided. A backlight (not shown) is arranged on the back side of the liquid crystal display panel 11. On the front surface side of the liquid crystal display panel 11, rod-shaped lenses 14 are arranged via hollow light guide members 15 corresponding to the respective display areas 12. Each rod-shaped lens 14 is arranged at intervals in a direction perpendicular to the optical axis. One translucent screen 16 is arranged at a predetermined interval on the light emission side of the rod-shaped lens 14.

The rod-shaped lens 14 is a kind of gradient index lens, and is called a rod lens, a selfoc lens, or the like. When a distance in the radial direction from the center axis is r, the refractive index n (r) is approximate. And the following equation. Here, G is a refractive index distribution constant. As a method of creating a n (r) = n (0 ) {1- (1/2) × Gr 2} Such rod-shaped lenses, how to create a glass by ion exchange method, created in the resin by diffusion polymerization method There are known methods. Further, in such a rod-shaped lens, regardless of the incident position and the incident angle of the light beam incident on the end face, all the light beams follow the sinusoidal optical path at the same meandering period Q (= 2π / √G). Has become. Therefore, if the length Z of the rod-shaped lens is selected to be 3/4 times the meandering period Q of the light beam passing through the lens,
An erect equal-magnification image can be formed. The rod-shaped lens 14 used in this embodiment has such a structure, and forms an erect equal-magnification image.

Here, as an example, a case where the image of the liquid crystal display panel 11 is enlarged and projected to a size of six times with this display device will be specifically described. First, as a precondition, the vertical length of the upper and lower display areas 12 is 5
mm, and the vertical length of the central display area 12 is 6.7 m.
m, and the vertical length of the mask 13 between them is 16.65.
mm. Also, the upper rod-shaped lens 14
Is located on the lower end of the upper display area 12, the optical axis of the central rod lens 14 is located on the center of the central display area 12, and the optical axis of the lower rod lens 14 is on the lower side. Is located on the upper end of the display area 12.

Next, a relational expression for determining the length Z of the rod-shaped lens 14 is shown below. Meandering period Q = 2π / √G (1) length Z = 3 / 4Q (2) focal length f = 1 / ｛n (0) √Gsin (√GZ)｝ (3) The following equation is obtained from these three equations. f = 1 / {− n (0)} G} (4) From the equation (4), the following equation is obtained. {G = 1 / ｛− n (0) f} (5) Here, the image height P ₀ is 5 mm (that is, the length of the upper and lower display areas 12 in the vertical direction), and the angle of view θ Is 30 °, the focal length f becomes f = P _{0 /} tan θ = 8.66 mm. Then, assuming that the focal length f is -8.66 mm and the refractive index n (0) on the optical axis is 1.5, from equation (5), ΔG
Is 0.077 (1 / mm). Next, the following equation is obtained from the equations (1) and (2). Z = 3π / {2 {G} (6) Since √G is 0.077 (1 / mm), the length Z of the rod-shaped lens 14 is 61.2 mm from the equation (6). Next, the rod-shaped lens 1 is moved from the image display surface of the liquid crystal display panel 11.
Distance L ₁ to the incident surface of the 4, when determining the distance L ₂ from the exit surface of the rod-shaped lens 14 to the screen _{16, L 1 = f {1-} (1 / -M)} = 10.1mm L 2 = 6L ₁ = 60.6 mm Therefore, the minimum distance L from the liquid crystal display panel 11 to the screen 17 is L = L ₁ + Z + L ₂ = 131.9 mm.

In this display device, when the backlight is turned on, light beams corresponding to the respective images in the respective display areas 12 of the liquid crystal display panel 11 are emitted, and these light beams are guided by the corresponding light guide members 15, respectively. Light is incident from the incident surface of the rod-shaped lens 14, travels through each rod-shaped lens 14 along a sinusoidal optical path, and light rays corresponding to each image are emitted from the exit surface of each rod-shaped lens 14. Is enlarged and projected to 6 times the size without overlapping. In this case, the lengths of the mask 13 in the vertical direction and the horizontal direction are set to prevent the images enlarged and projected on the screen 16 from overlapping each other.

As described above, in this display device, even if the image on the liquid crystal display panel 11 is enlarged and projected to six times the minimum distance L from the liquid crystal display panel 11 to the screen 16.
Is 131.9 mm, which is much shorter than that of the conventional one using one convex lens 3, and the entire device can be made thinner. In this case, the length of the rod-shaped lens 14 is such that an erect equal-magnification image can be formed. Therefore, the image displayed on the liquid crystal display panel 11 can be enlarged and projected as it is without being inverted. Therefore, the driving circuit of the liquid crystal display panel 11 is simplified.

[0012]

As described above, according to the present invention, the focal length of each rod-shaped lens for enlarging and projecting each image displayed on each display area of the display panel can be considerably shortened. Therefore, the distance from the display panel to the screen can be considerably reduced, and the overall device can be made thinner.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a display device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional display device.

[Explanation of symbols]

 Reference Signs List 11 liquid crystal display panel 12 display area 14 rod-shaped lens 16 screen

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/13 505 G02F 1/1335 G03B 21/00 H04N 5/74

Claims (3)

(57) [Claims] 1. A display device comprising a display panel having a plurality of display areas and a bar-shaped lens disposed between each display area and a screen at intervals in a direction perpendicular to an optical axis. . 2. The display device according to claim 1, wherein the refractive index of each of the rod-shaped lenses gradually changes from an axial center toward an outer peripheral side. 3. The display device according to claim 2, wherein the length of each rod-shaped lens is 3/4 times the meandering period of light passing through the rod-shaped lens.