JPS62113131A - Transmission screen - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a rainbow pattern by providing a total reflection face, from which a part of the luminous flux incident on an incidence face is totally reflected on the counter face and is emitted to the observation side, in a part of a prism piece and providing a means, which prevents light from going straight, on the part of the incidence face on which the luminous flux which does not strike the total reflection face is made incident. CONSTITUTION:A light diffusing layer 6 consisting of a diffusing agent 4 and a low-refractive index material 5 is formed to cover a part B, which receives a luminous flux L' which is not incident on a total reflection face 2, to diffuse the incident light L', thereby suppressing adverse influences upon images. Though an incident light L is reflected on the total reflection face 2 because of the existence of the low-refractive index material 5, it is preferable that the diffusing agent is not brought into contact with the total reflection face 2 for the purpose of not hindering the function of total refection. With respect to this transmission screen, a Fresnel lens is formed, and the light diffusing layer 6 is formed by postworking. If a paint is pressed in with a roll or the like to form the light diffusing layer 6, it is convenient because the paint remains scarcely on top parts (parts A) of prisms.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission type screen with a Fresnel lens used as a rear projection screen or the like.

[Conventional technology]

Rear projection screens are used as screens for video projectors, microfilm readers, etc., and in order to provide a light-condensing effect, sheets of Fresnel lenses of circuit error are often used. Such Fresnel lenses, for example, It has transmission characteristics as shown in the figure.

That is, such a Fresnel lens is configured such that a large number of prisms 10 having a triangular cross section are arranged,
This prism 10 consists of a lens surface 11 and a non-lens surface 12. If the Fresnel lens surface of this Fresnel lens is used as the entrance surface X, the incident light will be emitted to the exit surface Y as shown in the figure.

At this time, the light incident on the lens surface 11 is refracted toward the exit surface Y side as effective light and exits, but the non-lens surface 12
The incident light L' does not contribute to the light focusing effect.

This tendency becomes more severe as the light source approaches the screen at a location farther away from the light source or even at the same location, and in such a case, the amount of sight incident on the non-lens surface 12 of the prism 10 increases. Furthermore, in such a case, since the angle of incidence of the light beam entering the prism 10 increases, the amount of transmitted light also decreases due to surface reflection, making it increasingly difficult to expect an effective amount of light.

This surface reflectance can be determined by Fresnel's equation, and the following equation 0 is used to illustrate this.

Note that here, i is the incident angle and γ is the refraction angle.

Next, if the material of the Fresnel lens is acrylic resin (refractive index n = 1.49), the following ■
holds, nZ −=n ・・・・・・・・・・・・・・・・・・
...■mlnγ where n is the refractive index.

The surface reflectance is calculated from the above 0.0 formula. For example, when the angle of incidence is 70°, the surface reflectance is 15%, and the angle of incidence is 80''.
In the case of 40 inches, this amount of loss occurs just due to surface reflection. Based on Koguyu's calculation, assuming that the distance from the light source is 1,000W and the fishing distance of the Fresnel lens is f''1. It can be seen that most of the light amount is lost.

Recently, there has been a movement to further increase the size of this type of screen, and there is also an opportunity to reduce the depth of the device, so the above-mentioned loss of light amount has come to be seen as a problem.

For this reason, the present author has already proposed a Fresnel lens equipped with a prism piece at the periphery so that a portion of the light rays incident on one lens surface is totally reflected on another lens surface and then emitted. (Patent application No. 57-227909)
issue). FIG. 5 shows the prism piece in this case, and the prism piece 20 is equipped with two lens surfaces 21 and 22.
A part of the light incident on one of the lens surfaces 21 is totally reflected on the other lens surface 22 and exits.

This has the advantage that the loss of light quantity (L/ rays) in the region where the angle of incidence on the Fresnel lens sheet is large is reduced compared to the Fresnel lens shown in FIG. Therefore, when the projection distance to the Fresnel lens sheet is short, that is, when the angle of incidence is large, it is possible to reduce the loss of light and eliminate the emission to the observation side compared to the conventional method.

[Problem that the invention seeks to solve]

However, in a prism piece with a total reflection surface 22 as shown in FIG. 5, the luminous flux L' enters the incident surface 21 and then exits to the observation side without hitting the total reflection surface 22, becoming a luminous flux L〃. This luminous flux L'' causes rainbow patterns, color separation, and pie shading on the screen, resulting in a problem in which the quality of the image on the screen is degraded.

[Means for solving problems]

It is an object of the present invention to solve the above-mentioned problems and provide a good transmission screen that does not cause rainbow patterns or the like.

The purpose of the above is to provide a transmissive screen with a Fresnel lens that uses a Fresnel lens surface as a light receiving surface, in which at least a portion of the prism piece constituting the light receiving surface is incident on the incident surface and a portion of the subsequent light beam is transmitted. It has a total reflection surface that is totally reflected at the facing side and exits to the observation side, and a portion of the entrance surface where the light beam that does not hit the total reflection surface is incident,
This is achieved by a patented transmission screen with lens, which is characterized by being provided with a means for preventing light from going straight.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows a first embodiment of the present transmission type screen, and is an enlarged view of a Fresnel lens piece. I died in the same picture,
Reference numeral 1 designates an entrance surface, and 2 designates a total reflection surface that reflects the light from the entrance surface 1 and emits it to the observation side. The incident surface IK has a part B that receives the light flux L' that does not hit the total reflection surface 2 and a part C that does not receive light.
Surface 3 (of course, only B may be used) is roughened to
Luminous flux L that causes rainbows due to light diffusion due to roughening of the surface
# is not generated.

The Fresnel lens sheet having the prism pieces of the first embodiment can be easily manufactured by making a mold with the above-mentioned portions roughened and performing thermal transfer.

FIG. 2 shows a second embodiment of the present transmission type screen, and is an enlarged view of a Fresnel lens piece. In the figure, 1 is an incident surface, 2 is a total reflection surface, 4 is a diffusing agent, and 5 is a low refractive index material. In this embodiment, a light diffusing layer 6 is formed by a diffusing agent 4 and a low refractive index substance 5, and a light beam L' that does not enter the total reflection surface 2 is
By forming the light diffusing layer 6 so as to cover the receiving portion B, the incident light L' is diffused and adverse effects on the image can be suppressed.

The incident light is reflected by the total reflection surface 2 due to the presence of the low refractive index substance 5, but the diffusing agent 4 is arranged so as not to interfere with the total reflection function.
It is preferable not to contact the total reflection surface 2. Further, the diffusing agent 4 has a light diffusing layer 6 in order to efficiently diffuse the incident light L'.
It is preferable to position it on the surface of. In order to position the diffusing agent 4 on the layer surface, the low refractive index material 5 is placed on the total reflection surface 2.
There are methods of applying the coating liquid containing the diffusing agent (there is no need to separately add the low refractive index substance 5) on top of the material and then applying it again, or using the difference in specific gravity between the diffusing agent 4 and the low refractive index substance 5. There are methods for positioning the diffusing agent 4 on the surface of the layer.

The method for manufacturing this transmission screen is to create a Fresnel lens and then create the light diffusion layer 6 in post-processing. It is convenient to form the light diffusing layer by pushing the paint into it using a 6-layer roll, since almost no paint will remain on the top part of the prism (corresponding to the above-mentioned part A).

FIG. 3 shows a third embodiment of the present transmission type screen, and is an enlarged view of a Fresnel lens piece. In the figure, 1 is an incident surface, 2 is a total reflection surface, 5 is a low refractive index material, and 7 is a light absorbing material. In this embodiment, a low refractive index material 5 is coated, and then a light absorbing material 7 is coated thereon. In this way, the light beam L' that does not enter the total reflection surface 2 is absorbed by the light absorbing material 7.
The incident light L' is absorbed by the incident light L', thereby eliminating the harmful effects of the incident light L'. Also, since the layer of low refractive index material 5 provided on the total reflection surface 2 is located between the light absorbing materials 7, the total reflection function is not inhibited.

The coating method of this embodiment is similar to that of the second embodiment, and can be easily manufactured by pushing the paint into a roll.

Further, the transmission screen of the present invention is the first one. The second and third embodiments are not limited to those shown in the third embodiment, and it is possible to take other embodiments of the heels according to the purpose of use.

For example, it can be applied to the rear projection screen of the following patent application No. 119340/1983, which has a prism with a total reflection surface on its periphery, and prism pieces with a refraction surface and prism pieces with a total reflection surface are alternately combined. Patent application 1974-17434
The present invention can be applied to the transmission type screen of No. 7, as well as the transmission type screen of Nen Patent Application No. 158328/1983, which is an improved version of the invention.

Next, patent application 14922/1986 in which the angle of incidence of a prism piece with a total reflection surface changes depending on the position on the screen.
It can also be applied to a transmission screen using a No. 4 Fresnel lens.

However, the surface roughening method of the first embodiment can also be applied to a screen in which prism pieces having a refractive surface and prism pieces having a total reflection surface are alternately combined. The coating method of the third embodiment can be used only in areas where total reflection prism pieces are continuous. This is because the coating liquid adheres to the refractive surface of the prism piece that has a refractive surface and prevents light from entering from the refractive surface.Next, we will explain the specific manufacturing method of the total reflection Fresnel lens for the transmission screen of the present invention. state

(Example 1) As described in the first example, FIGS.
The total reflection Fresnel lens of the first example was obtained by thermally transferring methyl methacrylate to a mold with a roughened surface.

(Example 2) A total reflection Fresnel lens with P (pitch) = 0.5, refractive index n = 1.39, and plate thickness of 3 mm was prepared, and hynylidene fluoride 2
0%, 60% methisobutyl ketone (MIBK), and 20% methyl ethyl ketone (MEK), 1/100 of alumina oxide At203 was added as a diffusing agent and mixed uniformly.The mixture was coated with a full roll coater, and the second implementation was carried out. Express total reflection Fresnel lens as an example.

(Example 3) P (% Sochi) = 0.5, refractive index n = 1.39,
A total reflection Fresnel lens with a thickness of 3 is prepared, consisting of 20% vinyl fluoride, 60% MIBK, and 20% MEK.
% paint with a roll coater, and after drying, apply [Musashi Paint Glaace 716:] Enamel Black with a roll coater. In this way, the total reflection Fresnel lens of the third embodiment in which the light absorption layer was formed at the bottom of the valley between the prisms was obtained. Second. A screen was created by combining the total reflection Fresnel lens of the third embodiment with a light-transmissive diffuser plate having a certain diffusion characteristic (screen beak din approximately 20 to 30, diffusion angle characteristic β = ±10°). A visual evaluation of a reflective Fresnel resin and a screen using the above-mentioned diffusion plate was performed. The results are summarized in Table 1.

〔Effect of the invention〕

As can be seen from Table 1, according to the transmission screen of the present invention, it was possible to obtain a good transmission screen with no occurrence of streaks or blurred images compared to the conventional transmission screen.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 respectively show the first part of the transmission screen of the present invention. Second. The third embodiment is shown, and each is an enlarged view of a Fresnel lens piece. FIG. 4 is a schematic diagram showing a conventional refractive Fresnel lens, and FIG. 5 is a schematic diagram showing a conventional total reflection Fresnel lens. 1: Incident surface, 2: Total reflection surface, 3: Rough surface, 4: Diffusing agent, 5
;Low refractive index material, 6: Light diffusing layer, 7; Light absorbing material Representative Patent Attorney Jo Taira Yamashita Figure 4 Figure 5

Claims (4)

[Claims] (1) A transmissive screen with a Fresnel lens that uses a Fresnel lens surface as a light-receiving surface, in which at least a part of the prism pieces that make up the light-receiving surface completely reflects a part of the light beam incident on the incident surface on the opposite surface. It has a total reflection surface such that the light beam is emitted toward the observation side, and a means for preventing light from going straight is provided on a portion of the entrance surface where the light beam that does not hit the total reflection surface is incident. Transparent screen with Fresnel lens. (2) A transmission with a Fresnel lens according to claim 1, wherein the means for preventing light from going straight is performed by roughening a portion of the incident surface and diffusing the incident light on that portion. type screen. (3) The Fresnel lens according to claim 1, wherein the means for preventing light from going straight is performed by diffusing the incident light in that part by a low refractive index material layer mixed with a diffusing agent. Comes with a transparent screen. (4) The means for preventing light from going straight is carried out by absorbing incident light in that portion by a light absorption layer formed on the low refractive index material layer. Transparent screen with Fresnel lens.