JPH0410592Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a rear projection screen, particularly a rear projection screen having a light diffusion section for reproducing a projected image and a lens surface for providing light directionality. The purpose of this is to make the image brightness distribution uniform.

The rear projection screen (hereinafter referred to as RPS) is
Image information is projected from a projector placed on the opposite side of the viewer to the RPS located between the viewer and the projector.
This is an optical element that reproduces image information on the RPS, and is used, for example, in an optical display device such as a movie projection device.

In recent years, RPS has begun to be used as an optical element in the display section of projection television equipment. The performance required for this RPS is higher than that for conventionally used RPS. Due to constraints on the utilization rate of projection cathode ray tubes in television projectors and the emission brightness of phosphors, generally three projection cathode ray tubes (blue, green, and red) with different optical axes are used in the same horizontal plane. Because color images are obtained by combining image information from each optical system on the RPS, the intensity of each color has a different light distribution, and color changes occur depending on the observation position. In order to reduce this, characteristics such as having a sufficiently wide directional characteristic, screen gain to obtain sufficient image information, and directional distribution characteristics that widen the viewer's suitable viewing range in the horizontal direction compared to the vertical direction are required. is required.

The present invention attempts to provide an RPS that satisfies each of the above characteristics by creating an RPS using a new construction method. The present invention will be described below with reference to the drawings. Note that in each drawing, the same components are given the same reference numerals.

The movie projection device in which RPS has conventionally been used;
In microfilm readers and the like, image information is projected by a single projector with sufficient brightness.
In addition, the observation position is within a narrow predetermined range, and the RPS size is no more than 20 inches (20 inches).
Fine particles such as silica (SiO2), which has a light-diffusing effect, are dispersed in acrylic resin or styrene resin, and a desired shape with a thickness of 1 to 1.5 mm is made by an appropriate molding method such as compression molding. RPS of size was used. Further, as shown in FIG. 1, a circular Fresnel lens 3 is provided on one surface of the screen base 1 on the projector 2 side as necessary in order to make the luminance distribution of the projected image uniform.

However, projection television equipment
Since the size of the RPS is 40 to 50 inches (40 to 50 inches) or more, and it is necessary to increase mechanical strength, its thickness must necessarily be 5 mm or more. In the method of reproducing projected image information by dispersing light-diffusing fine particles in the screen base constituent material, the resolution-contrast characteristics (hereinafter referred to as MTF characteristics) deteriorate as the RPS thickness increases, so this light-diffusion method is It cannot be used in projection television equipment. Therefore, it may be possible to reduce the deterioration of the MTF characteristics by providing a thin layer having a light diffusion effect on the surface of the screen base. One specific method is to uniformly apply a coating liquid in which light-diffusing particles are dispersed to the screen base surface, or to form a sheet of light-diffusing particles dispersed in resin in advance. Another method is to roughen a desired surface of the screen base to provide a light diffusion effect.

On the other hand, as mentioned above, in projection television equipment, an RPS with large screen gain, wide directional characteristics, and wider directivity in the horizontal direction than in the vertical direction is desired. If you try to make it larger, the directivity will become sharper and narrower, which is a contradictory property. In order to satisfy these two characteristics, as shown in FIG. 2, a circular Fresnel lens 3 is provided on one surface of the screen base 1 on the projector 2 side, and a lenticular Fresnel lens 4 is installed vertically on one surface of the screen base 1 on the viewer side. A conceivable configuration is that a layer 5 having a light diffusion effect (hereinafter referred to as a light diffusion layer) is arranged on the lenticular lens 4 surface. In addition, Fig. 3 and Fig. 4 are respectively A- in Fig. 2.
It is a sectional view along A, BB.

However, the four surfaces of the lenticular lens, which are not flat surfaces, are coated uniformly with a coating liquid in which the light-diffusing fine particles are dispersed, or the light-diffusing fine particles are dispersed in a resin and molded into a sheet. It is very difficult to form a light diffusing layer by pasting a material. On the other hand, even if the lenticular lens surface is roughened directly by sandblasting or by using a mold that has been roughened in advance, a light diffusion effect can be obtained. However, the inventor's experiments have revealed that by roughening the lenticular lens surface, the lens action is lost and a wide directivity characteristic cannot be obtained. That is, the lens surface must be a substantially mirror surface.

However, according to the present invention, by coating the lenticular lens surface roughened by the above-mentioned surface roughening method with a material having a refractive index different from that of the lens portion, the lens function of the original lenticular lens can be restored. It is possible to provide an RPS with a structure that has both a light diffusion effect and a wide directional characteristic without losing the characteristics.

FIG. 5 shows a state in which an incident light ray 7 is incident on a roughened lenticular lens surface 6, and the incident light ray 7 is only diffused by the roughened lenticular lens surface 6 and is not subjected to any lens action. There is. On the other hand, FIG. 6 shows an embodiment of the present invention, in which the lenticular lens portion is provided on the viewer's side of the screen base made of a substantially transparent material. The incident light ray 7 is diffused by the roughened lenticular lens surface 6 which is in contact with a coating layer 8 having a different refractive index from that of the lenticular lens portion, and is then diffused at a substantially mirror surface portion which is in contact with the air side of the coating layer 8 and is shaped like a lenticular lens. is given by the lens action and exits. In general, the degree of surface roughening is on the order of several tens of microns in the depth direction, taking the sandplast method as an example, so the thickness of the coating layer made of a material different from the refractive index of the lenticular lens is approximately the same. The present invention can be realized with a thickness close to this value, and even if a material with somewhat inferior light transmittance is used, it will not be a major problem, so materials can be selected from a wide range. Moreover, coating the entire RPS with a somewhat uneven thickness does not cause any visual problems. According to the inventor's experiments, the RPS was easily implemented by immersing the entire RPS in a solution of the material that would become the coating layer, or by a spray method, and a product with satisfactory properties was obtained.

As described above, according to the present invention, the lenticular lens surface on the RPS is roughened in advance, and the surface is coated with a material whose refractive index is different from that of the lenticular lens, thereby improving lens action and light. This results in something that has a diffusion effect at the same time. In particular, since it is possible to provide a circular Fresnel lens, a linear Fresnel lens, and a lenticular lens on each surface of a single RPS, and to provide a function that has a light diffusion effect on the lenticular lens surface side, it is possible to project images using a single RPS. A high-performance RPS with uniform brightness distribution of the surface image and a wide observation range with high resolution and little image degradation can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a conventional rear projection screen. FIG. 2 is a perspective view showing an embodiment of a rear projection screen provided with a conventional light diffusion layer, FIG.
-B sectional view. Figure 5 shows how the light rays incident on the roughened lenticular lens surface receive only the light diffusion effect. Figure 6 shows the roughened lenticular lens surface. FIG. 3 is a diagram showing how a light beam incident on a structure coated with different materials receives both a light diffusion effect and a lens effect. 1...Screen base, 2...Projector, 3...
Circular Fresnel lens, 4... Lenticular lens, 5... Light diffusion layer, 6... Lenticular lens surface, 7... Incident light beam, 8... Covering layer.

Claims (1)

[Scope of utility model registration request] A lenticular lens surface formed on the viewer side of a screen base made of a substantially transparent material is roughened to such an extent that lens action is lost, and this roughened lens surface is coated with a material having a different refractive index from that of the screen base. Then, a new lenticular lens surface is constructed by making the surface of this coating material in contact with the air a substantially mirror surface,
A rear surface characterized in that the interface between the roughened lens surface and the coating layer has a light diffusion function, and the newly configured lenticular lens surface also has a light directivity control function. projection screen.