JPS6370838A - Transparent screen - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a transmissive screen equipped with a deflection means for emitting image light projected from the back in a forward direction with an angle, brightness, and directivity depending on the purpose. It is.

Background of the Invention In recent years, efforts have been made to make sets particularly compact for video projectors. Mainly to reduce the depth, deflection means has been developed to enter the image light obliquely from the back of the screen and deflect it forward before exiting the screen. Be prepared. So-called prism screens have come into use.

An example of a conventional prism screen will be described below with reference to the drawings.

FIG. 7 is a block diagram of the oblique incidence video projector, and FIG. 6 is a ray development diagram thereof.

FIG. 6 shows the principle of deflection using a prism screen. In the figure, 1 is a prism section of the screen 6, 8 is a lens, 9 is a CRT, 10 is a reflection mirror, and 11 is a projector body. An incident light beam 3 that is reflected by a reflection mirror 10 and enters a screen 6 is incident at an angle θ, is totally reflected by a prism surface 1, and is deflected forward into a light beam 4 to be emitted. In this case, the angle of the prism surface 1 is determined for each location so that the incident light can be deflected in the desired direction. However, when the incident angle is small, such as ray 3' in Fig. 5, the ray 7 does not pass through the total reflection surface of the prism and becomes a stray light within the screen.
occurs.

As shown in Figure 6, the incident angle at the center of the screen 6 is θ
Then, the angle of incidence at the top and bottom of one screen is α, respectively.
, β becomes 1 α × θ〈β.

In the video projector 11 having the configuration shown in FIG. 7, the angle of incidence is smaller α at the upper part of the screen.

The direction is disadvantageous for total reflection by the prism surface 1.

Ideally, as shown in FIG. 6, the incident light should be completely emitted in the forward direction over the entire screen, that is, the efficiency should be 100%.

Problems to be Solved by the Invention However, in reality, there is a demand to shorten the projection distance as much as possible in order to make the set size of the video projector compact, and the efficiency for the upper part of one screen is 8.
I have no choice but to use it between 0 and 90%. Also, in order to increase efficiency over the entire screen as much as possible, it is sufficient to reduce the cutting edge angle ω of the prism surface, but due to the screen manufacturing method, there is a limit to the cutting edge angle, which is about 46 degrees at most. . Also, if you reduce the cutting edge angle.

The cutting edge is more likely to chip, increasing the risk of damaging the prism surface. Therefore, the efficiency in the upper part of the screen has to be lower than 100%. In this case, all of the light emitted from one person is not emitted in the forward direction, but some of it becomes stray light, and while repeating multiple reflections within the screen, it appears on the screen at a certain position, although the brightness is low, and a virtual image appears compared to the original normal light. occurs, forming a double image.

In other words, the conventional prism screen 6 has a problem in that, in the case of the configuration shown in FIG. 7, which is closer to the projection distance, overlapping images occur from near the center of the screen to the top of the screen, resulting in deterioration of image quality.

Therefore, the present invention aims to provide a transmission screen that absorbs or diffuses incident light that cannot be polarized in the normal direction, thereby eliminating double images.

Means for Solving the Problems In order to solve the above problems, the transmission screen of the present invention coats a part of the prism surface with a black absorbent in order to absorb the incident light that cannot be deflected in the normal direction. It has a structure in which the surface is roughened by scratching or scratching a part of it to spread it out.

Effect of the Invention With the above-described configuration, the present invention can prevent double images from occurring due to stray light that cannot be deflected in the normal direction, and can improve the image quality of one screen. In addition, it is possible to protect against screen surface reflection caused by external light, so-called external light reflection, and the contrast can be improved.

EXAMPLE A transmissive screen for a video projector, which is an example of the present invention, will be described below.

FIG. 1 is a sectional view showing the detailed structure of the screen, and FIG. 2 is a front view thereof. Figure 1.

In Fig. 2, if the incident angle of the incident light 3 that cannot be deflected in the normal direction at the center of the screen 6 is 60 degrees, it will be about 1 inch above the screen 6; A black absorbent 2 is applied to the prism surface 1 in the glazed portion to eliminate double images. However, the projection distance is approximately 110 off, and the screen diagonal is 40 inches.

Further, the arrangement is made such that the area to which the black absorbent 2 is applied to the 11 prism surfaces 1 increases as one moves toward the top of the screen, depending on the degree of efficiency deterioration. Here, 4 is the emitted light.

Further, FIG. 3 shows the case of a screen having one screen, and FIG. 4 shows the case of a screen having two screens.

The surface on the opposite side of the prism surface 1 may have any shape, such as a lunticular, matte, or Fresnel surface. Here, 6 is a lenticular, matte or Fresnel screen.

In addition to applying a black absorbent, the prism surface may be roughened to scatter unnecessary human light.

Effects of the Invention As described above, the present invention has a prism screen that has the function of deflecting obliquely incident image light in the forward direction, by scattering or absorbing the incident light that cannot be used as totally reflected light by the prism surface. This can prevent stray light from becoming a double image within the screen and being emitted forward.

Additionally, unnecessary light from the outside can be absorbed, and the areas coated in black are effective in terms of reflecting outside light, improving contrast. In other words, the image quality of the prism screen can be improved.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a transmission screen according to an embodiment of the present invention, Fig. 2 is a front view thereof, Fig. 3 is a side view of a single screen including a prism screen, and Fig. 4 is a prism screen. A side view of a two-piece screen including;
FIG. 6 is a ray deflection diagram showing the deflection principle of a prism screen, FIG. 6 is a ray development diagram of a video projector, and FIG. 7 is an overall configuration diagram thereof. 1... Prism cross section, 2... Black absorber, 3... Incident light, 4... Outgoing light, 6
...Prism screen body. Name of agent: Patent attorney Toshio Nakao and 1 other person/
-1-Prism Wr surface part Z--black El and translation 1 3-incident light 311ffI Fig. 4 Fig. 5 Fig. 7

Claims (1)

[Claims] A transmissive screen that has a structure in which a large number of triangular prism elements are closely arranged in a horizontally extending manner as a deflection means to deflect image light incident obliquely on the back side toward the front, and the total internal reflection is utilized. Therefore, for incident light that cannot be used as total reflected light, an absorbent is applied to the prism surface to absorb the incident light, or the prism surface is roughened to scatter it and used as total reflected light. A transmissive screen characterized by a structure that prevents light from emitting in front of the screen.