KR970010476B1 - Rear viewer projector type screen - Google Patents

Abstract

A screen of a back side projection type is disclosed. The screen of the back side projection type has a lens array of a horizontal direction on the front side(5) of the screen and controls an angle of a vertical direction. Also, the screen of the back side projection type has the lens array of the horizontal direction between two inclined sides(7) on the back side(6) of the screen and controls an angle of a horizontal direction. The screen of the back side projection type may increase the gain more than 20% and control the contrast by controlling a light absorption area.

Description

Rear projection screen

1 is a rear projection TV apparatus of a large screen.

2A, 2B and 3C are cross-sectional and perspective views showing details of the screen.

3 is a ray propagation in the horizontal direction.

4 is a control principle of the vertical visual angle.

5 is a change in vertical angle with respect to the radius of the sphere at the same resolution.

6 is a view of the change of the viewing angle and the light transmittance by the slope of the total reflection surface.

* Explanation of symbols for main parts of the drawings

1: screen 2: projection lens

CPT, 5: Screen Front 6: Screen Rear

7: inclined surface (total reflection surface) 8: coating

9: black paint.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projection type TV device, and more particularly, to a rear projection type screen suitable for improving brightness and contrast ratio.

In general, a projection apparatus is applied in many fields, including a large screen TV. A large screen projection TV is a device for projecting an image of a CPT onto a screen separated by a certain distance through a projection lens.

Such a device is such that the observer located in front of the light emitted through the screen formed of a transparent material to see the image through the screen.

In a typical three-color projection TV device, one CPT (3) is on the axis and the other two CPT (3) are off-axis, with each CPT producing its own color. And is projected onto the screen 1 through each projection lens 2 (see FIG. 1).

Also, in the projection TV device, the optical function of the screen 1 distributes the image light over a predetermined range vertically or horizontally so that viewers at different heights and positions with respect to the screen can see the same projected image. In addition, it should have a higher contrast ratio for external light, have a larger viewing angle, and have a high gain within the viewing angle.

Screens for achieving this function include a single sheet screen and a multi sheet screen. Multiscreen screens use at least two or more screens, so they have at least four sides, which is costly to produce the screen and has a lot of reflections that degrade performance, resulting in low contrast and low conductivity. However, the one-piece screen imposes many restrictions on the design, but the manufacturing cost is low, and the reflection surface is small, so the loss and transmission characteristics due to the reflection are increased. In practice, however, a Fresnel lens is placed on the front surface in order to focus the light of the image so that it is arranged in a circular or spiral lens shape. In addition, in order to inject the light, it is achieved by forming a layer of the lens on the plurality of lenses perpendicular to the horizontal direction, and in the vertical direction to disperse the light by having a dispersion layer or a dispersant. Therefore, moiré interference occurs between the array of Fresnel lenses on the circular lens and the array of lenses on the rear of the plurality of vertical lenses, and the absorption of light by the dispersant and reflection in the reverse direction exist to deteriorate the screen performance.

The present invention has been made to solve the above problems, an object of the present invention is to provide a rear projection screen suitable for improving the brightness and contrast ratio.

The screen of the present invention for achieving the above object is to adjust the viewing angle in the vertical direction by placing the lens array on the horizontal spherical lens on the front of the screen, the spherical surface between the two inclined surfaces and the two inclined surfaces of the back of the screen The lens is arranged on the lens to adjust the viewing angle in the horizontal direction.

With reference to the drawings will be described the configuration and effect of the present invention.

First, referring to FIGS. 2A, 2B and 2C, the present invention does not use a circular pronel lens and does not use a dispersant used in an existing screen, and the screen front surface 5 (projection surface) Place the lens array on the spherical lens in the horizontal direction to adjust the viewing angle in the vertical direction, and place the lens array on the spherical lens between the two inclined surfaces and the two inclined surfaces on the rear of the screen (6). The viewing angle can be adjusted.

In the rear surface 6, the two inclined surfaces 7 are totally reflected so that the totally reflected light is refracted through the sphere to go out, and the light rays reaching directly to the sphere are refracted by the sphere and go out to the outside (FIG. 3) Reference). The total reflection surface is coated with a coating film 8 having a small refractive index on the outside of the surface, and is coated with a black paint 9 on the outside of the coating film 8 to increase the contrast ratio.

The spherical lenticular lens arrangement on the front surface (projection surface) 5 has a light scattering function in the vertical direction with the focusing of light by lenticular lenosis (see FIG. 4).

As described above, the structure in which the front and rear lens-shaped lens arrays are orthogonal to each other has the following advantages.

First, since there is no moiré interference caused by straight lines orthogonal to each other, it is possible to eliminate the deterioration of image quality due to the moiré pattern caused by the existing circular Fresnel lens and the lenticular lens, and then the vertical visual angle by the disperser Conventional methods that need to be adjusted produce a non-uniformity of the vertical visual angle due to the uniformity of the mixing degree of the dispersant, and it is very difficult to adjust the vertical visual angle, but according to the present invention, the lens-like lens array of the projection surface This can be adjusted by changing the spherical surface of (see Figure 5). For example, it can be seen that as the radius of the sphere increases with respect to the same pitch, the vertical viewing angle decreases. Next, the light transmittance of the material is 70% or less in the case of the existing screen containing the dispersant, but in the case of the present invention, since the dispersant is not used, the light transmittance is determined according to the Fresnel formula.

Since the total amount of light is transmitted except for reflection, the light transmittance may be increased by 20% or more than in the case of the screen by the dispersant, thereby increasing the gain of the screen and making a bright screen easier.

Where θ ₁ is the angle of incidence, θ _r is the angle of refraction, and r _ref is the reflectance.

First, the viewing angle can be changed according to the spherical surface of the lens. The spherical radius is r, and the length of the string is considered, and the pitch of the lens array is 2r · sinθ. Is the half of the angle that forms the chord with respect to the length of the pitch seen from the center of the circle (see FIGS. 2A and 4). In the case of a horizontal lenticular lens, it is involved in the vertical viewing angle. In general, in the case of a pure spherical lens array having a circular cross section, it is known to decrease sharply in the case of 30 ° or more, but in the vertical case, a viewing angle of around 10 ° is known. Since the drawings are sufficient, the distribution of light for each viewing angle is also an ideal shape.

To consider the horizontal viewing angle, the lens array in the vertical direction on the visible side should be adjusted. In this case, the resolution of the lens array related to the horizontal resolution is the sum of the length of the string on the sphere and the projection length of the projection surface of the two inclined surfaces. The horizontal visual angle is the inclination and the length of the two inclined surfaces (7). By adjusting the spherical surface between the two inclined surfaces 7, the horizontal visibility angle can be changed. In this case, the viewing angle increases as the inclination α of the two inclined surfaces 7 is changed to increase (see FIGS. 3 and 6).

In this case, the light rays totally reflected from the two inclined surfaces 7 must be incident on the spherical surface to maximize the efficiency.

In addition, the inclination of the inclined surface is total reflection occurs only 0 ° to 18 ° with respect to the optical axis, and becomes close to 0 ° becomes impossible in manufacturing.

Accordingly, the viewing angle in the horizontal direction is adjusted to the sum of the advancing direction of the light by total reflection of the inclined plane and the advancing direction of the direct spherical incident light.

In addition, the screen of the present invention improves the contrast ratio by absorbing the external light by the coating film 8 and the black paint 9 on the surface of the total reflection surface 7, the degree of improvement is the area ratio of the area of the external light absorbing layer and the non-absorbing layer Since it is equivalent to, the contrast ratio can be adjusted.

In fact, the transmittance according to the viewing angle is shown as 5 and 6 degrees. This is not a gain according to the viewing angle, but the transmittance is proportional to the gain, so that the gain can be adjusted by adjusting it. In addition, the gain can be increased by at least 20% or more than in the case of a conventional dispersant, and the contrast ratio can be adjusted by adjusting the light absorption area.

Claims (2)

In a rear projection screen, a lens array on a horizontal spherical lens is placed on the front of the screen to adjust the viewing angle in the vertical direction, and a lens on a lens having a spherical surface between the two inclined surfaces on the back of the screen and the two inclined surfaces. A rear projection screen, characterized in that an arrangement is made to adjust the horizontal viewing angle. The rear projection screen according to claim 1, wherein a coating film for total reflection is coated on the outside of the two inclined surfaces, and a black paint is coated on the outside of the coating film to improve contrast ratio.

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