JPS593425A - Reflection type projection screen with high luminance - Google Patents

Abstract

PURPOSE:To obtain a clear video of high contrast even under outdoor daylight by superposing a light diffusing material and a circular Fresnel lens whose focal distance is positive on the reflective surface of a reflecting mirror. CONSTITUTION:A light diffusing material 1 is similar to frosted glass and is obtd. by subjecting one side (the left side) of a thin plate or a sheet of a transparent synthetic resin such as acrylic resin or vinyl chloride resin, glass or the like to light diffusion treatment. A reflecting mirror 2 is preferably obtd. by plating a smooth metallic plate with Cr or by vacuum depositing Al on the plate. A Fresnel lens 3 is a plate or a sheet of a transparent synthetic resin or glass having many circular grooves each having a wedgeshaped cross section. The diffusing plate 1 and the Fresnel lens 3 having the same shape and size are superposed on the reflective surface of the reflecting mirror 2 having a prescribed shape and size preferably in a close contact state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 4-degree reflective projection screen (hereinafter simply referred to as a reflective screen), and particularly relates to a reflective screen that can make a projected image much brighter than conventional ones. Regarding.

For advertising purposes, images are enlarged and projected onto a large reflective screen using a slide projector, etc. is easy,
Moreover, since color slide film is used, it is possible to produce manuscripts with vivid colors at low cost.Although this method has the advantage of being inexpensive, it has not become a mainstream advertising display method because of its excellent display effect.

The reason for this is that conventional reflective screens have low light reflection efficiency, so in order to attract attention, a large screen is used and the magnification is high. In particular, the places where reflective screens used for such purposes are installed are often relatively bright places, such as station concourses, and in addition to the projection from the slide projector, there are many places where reflective screens are installed. When the surrounding external light is also illuminated, the so-called S/N ratio becomes smaller, and even a color image that looks vivid in a dark place becomes whitish, even if it is a highly magnified image. C also loses some of its power.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a reflective screen that can provide bright images.

In order to achieve the above objects, the present invention uses a diffusing material, which is a transparent thin plate or sheet subjected to light diffusion treatment, and a circular Fresnel lens having a positive focal length, on the reflecting surface of a reflecting mirror. It is characterized by the fact that it is made to match.

Embodiment 1 of the present invention is shown below in drawing Y sub! Let me explain.

In the first area, code 1 is a diffusion material that has been subjected to light diffusion treatment.
Reference numeral 2 represents a reflecting mirror, and reference numeral 3 represents a circular Fresnel lens (hereinafter simply referred to as a Fresnel lens) having a positive focal length.

The above-mentioned diffusion material l is, for example, a thin plate or sheet of transparent synthetic resin such as acrylic resin or vinyl chloride resin, or transparent material such as glass. The glass has been treated to diffuse light, giving it the appearance of frosted glass.

The above-mentioned light diffusion treatment is performed by forming fine irregularities over the entire surface of a transparent thin plate or sheet. Such light diffusion treatment can be carried out by, for example, forming the material with a roll with minute irregularities in the case where the material 'W of the diffusion material 1 is a synthetic resin, or by surface treatment with a chemical containing fluorine + FI for polymerization of glass. This can be easily done by
Synthetic resin thin plates, synthetic resin sheets, frosted glass plates, etc. that have been subjected to light diffusion treatment are currently commercially available.

- The reflecting mirror 2 may be, for example, a flat metal plate made of a smooth metal plate plated with chrome, similar to a rotary plate, or a surface mirror made of a glass plate or a gold oval plate with aluminum (At) vacuum-deposited. A reflecting mirror with a high reflectance is suitable, and the substrate of the reflecting mirror may be made of a synthetic resin such as a metal plate or a glass plate.

Note that the term "reflector" here does not necessarily mean a highly rigid plate-like reflector; for example, a flexible sheet-like object such as aluminum foil with a brightly treated surface can provide sufficient reflection. Can be used as a mirror.

(On the other hand, the Fresnel lens 3 is made of a large number of annular lenses each having a rectangular surface shaped like a model, on the surface of a transparent synthetic resin or glass plate or sheet, as shown in FIGS. 1 and 2. It is formed concentrically with grooves, and has the function of being used as an eye lens.As is well known, a Fresnel lens can be made into a convex lens or a concave lens depending on the transversely curved shape of the annular groove during processing, and its focal point Although the distance also changes, the Fresnel lens 3 in the present invention has a positive focal length and functions as a convex lens.As mentioned above, the focal distance is determined by the reflection screen according to the present invention. Appropriate settings shall be made depending on the installation location and the spatial axis of the reflective screen viewer.

A reflective screen according to an embodiment of the invention has the required shape (rectangular in the illustrated embodiment) and size of the reflection w, 20
On the reflecting surface, a diffusing material 1 of the same shape and size and a Fresnel lens 3 are superposed, preferably in a dense N'' pattern 5. At this point, the center of the Fresnel lens 3 is aligned with that of the reflecting mirror 2. It is desirable to let it happen.

In addition, in order to make these diffusing material 1, reflecting mirror 2, and Fresnel lens 3 overlap each other, for example, it is necessary to make the co-reflecting mirror 2 and Fresnel lens 3 considerably thick and have a rigidity equal to 1.
If 11a is set, 'P' is better to sandwich the diffuser IV between the reflector 2 and Fresnel lens 3 and fix the periphery with Kurirag, etc., or to incorporate it into a wax-like frame (not shown in 1), and f. , all three are thin, flexible sheets, and the reflection 'Jc! The back side of 2 (the back plate that does not show the stiff Enu 1 on IL+, the surface 111 of Fresnel lens 3)
11 It is good to arrange a transparent plate with a large rigidity, and fix the three parts by sandwiching them between the R plate and the transparent plate. It is desirable that the transparent plate 15 on the surface of the Fresnel lens 3 is subjected to anti-reflection treatment, such as nano-glare treatment.

The reflective screen according to an embodiment of the present invention configured as described in 5 above is used by projecting an image onto the diffusing material I through the Fresnel lens 3 using a slide projector or the like.

The function of the reflective screen according to the present invention will be explained as follows in comparison with that of a conventional reflective screen. However, in order to simplify the drawings, we will proceed with the discussion without considering the existence of the Fresnel lens 3 until the middle of the explanation.

A conventional reflective screen is a sheet or plate-shaped body made of a material that reflects and scatters light, and as shown in Figure 3, it reflects and scatters a group of light rays R that forms an image of a dark point P, displaying +m1). 111, the scattered light DR is obtained. As is well known, in order for an image point to be visually recognized as an image point, the light from the image point must be more diffuse than the actual object point. The reflective screen has the function of converting the actual image projected by a slide projector or the like, which is generally invisible, into a visible image.

However, since the conventional reflective screen must be made of a material that causes light scattering, the reflectance of light is small (for example, from 9 to 10 degrees), and the exit aerial angle of the scattered light DR (31st movement) is large. In other words, the image on the screen becomes completely 1 (K), just as I did myself.

The reflective screen according to the present invention also has the ability to reflect light and at the same time amplify light. However, in Fukaki's) *projection screen''C, the reflecting mirror 2 reflects the light, and the diffusing material 1 subjected to the light diffusion treatment separates the phases and performs the light diffusion independently.

That is, as shown in FIG.
The light beam r having a very small diameter is diffused within a certain aerial angle on the surface of the diffusing material 1, enters the diffusing material 1, is reflected by the reflecting surface of the reflecting mirror 20, is diffused again on the surface of the diffusing material 10, The pseudo scattered light dr is emitted between the walls of the slide projector according to one rule. This pseudo-scattered light dr enters the viewer's naked eye on the reflective screen, and the image point P is visually recognized.

Note that an image is formed on the image point P by a conical light beam whose base is the exit pupil of a projection lens such as a slide projector and whose apex is the apex of the image point P (see Figure 3). In order to clearly illustrate the drawing, optical path tracing is performed for the minute diameter light flux r, which is a part of the light flux formed at the image point P'+-.

In addition, the terms of scattering and diffusion of light are used.The former is used when the light has a strong combination and the radiation air angle is close to 2π, while the latter is a general case where the radiation air angle is small and leads to scattering. Each is used differently for diffusion.

The optical system shown in Fig. 4 (well, the optical system shown in Fig. 5, f) has two diffusing materials 1.1 whose smooth surfaces are placed back to back, and a reflecting mirror 20 between which transmits light whose absolute value is equal to the reflectance. Therefore, the image projected on the reflective screen according to the present invention is equivalent to that of the light diffusing material 10 as if it were projected onto the light diffusing material 10 as a transparent screen. This is the same as viewing the image through the four transmission filters and the light diffusion surface of another diffusion material placed in front of you by a distance twice the thickness of the diffusion material. The transmittance is high, and the degree of light diffusion by the light diffusion surface can be reduced!
As a result, the image on the reflective screen becomes very bright.

-1- That is, rather than referring to Figs. 6 and 7, the diffuse reflected light # from the darkness P on the reflective screen can be promoted as a vector, its direction of reflection is shown by the arrow BJT, and any reflection The length of the line segment with the luminous flux W3 degrees in the direction is incorrect, and the state of reflection on a conventional reflective screen is
As shown in the figure, the curved surface touching the tip of the vector group arrow is almost a hemispherical surface. On the other hand, in the reflective screen according to the present invention, the IW ratio of diffusion is smaller than that of the conventional one, and the reflected light rays are mainly 1l.
The curved surface touching the tip of the arrow of the vector group representing the reflected light sl is drawn in the direction of the rigid line in Example 1 because it is concentrated near the normal line to the image point P in Fig. 7. As shown in the surface of the +1 column, when viewed from the reflective screen square, the reflective screen according to the present invention is much brighter than the conventional one.

However, when the reflective screen according to the present invention does not have the Fresnel lens 3, the light diffusing layer of the diffusing material 1 is particularly small, or the projection lens or wide-angle lens of a slide projector or the like, or the reflective screen and its viewer are If the distance is relatively short and the angle at which the player's naked eye sees the entire reflective screen is large, there is a risk that a part of the reflective screen will become very dark or cannot be seen at all. FIG. 8 shows the extreme case, in which reference numeral 5 indicates the Fresnel lens 3'&ji
The reference numeral 6 indicates a slide projector having a wide-angle lens and a reflective screen which has been removed.

As shown in FIG. 8, the main axis light #! of the slide projector 6 is shown. (5 lights along the main axis of the projection lens @) RC reflected light Ml
If this is expressed as a group of vectors as in FIGS. 6 and 7, the IMJ becomes an elongated water drop shape whose central axis is the main reflection 411Rrc that coincides with the principal axis light dRc and is perpendicular to the screen. However, the stone y of reflective screen 4 @
The light that reaches the department @! Since the main reflection axis #rr of RR is directed outward, most of the illustrated Il:511'17 is reflected from the slide projector in the direction shown in FIG. h is the light that reaches the left end of the reflective screen (the same applies to 11LK).

Therefore, for a person at a position AK very close to the reflective screen 5, the brightness of the image at the center is proportional to the length of the line segment Ac, but the image at both the left and right ends becomes almost invisible. Also, for a person at position B near the left end of the reflective screen, does the image at the left end of the line segment BeQ in some images have a brightness proportional to the length of the line segment Bt? You can hardly see the image and construction of the right 1 azure section. This is also the same in the vertical direction of the reflective screen.

Therefore, in the reflective screen according to the present invention, due to the presence of the Fresnel lens 3, as shown in No. 9 IXI.
The incident shot R to the reflective screen is the Fresnel lens 3.
The main reflection axis r is refracted twice by 1111 as shown. On the other hand, as described above and shown in FIG. 8, the main reflection axis r' in the absence of the Fresnel lens 3 is turned to the outside 11 by the dotted line.

Therefore, as shown in the first O-, the main reflection axis re at the center, right end, and left end of the reflective screen,
Both rr and rL will face inward 411111K, and for those in the position AK corresponding to FIG. 8 above, the center of the reflective screen, right! The images at the old <b and left end portions have approximately equal brightness proportional to the lengths of Ac, Ar, and At for hl+N, respectively, and the brightness of the images at the left end is approximately equal to that of the previous image. is B
The same applies to the image that can be connected from the position of . Also,
The same applies to the vertical direction of the reflective screen.

The main reflection Kiyoshikatsu r is within 11111 K for ll-)J because the Fresnel lens 3 is a convex lens'f! : Because it is k), Part 1. By adjusting the point VS G, it is possible to adjust the position of the intersection of the main reflections shown in the diagram; It is possible to adjust the spatial range of the screen viewer 11a, who can see the entire screen brightly, into the mouth.

Incidentally, since the eye body of the Fresnel lens is thin, it goes without saying that it does not impart any quality to the image on the reflective screen.

Furthermore, as is clear from FIG. 9, the light beam passes through the Fresnel lens 3 twice. When ICr is added to the transmission type optical system of the 51st unit 1 and the 4th unit, it is found that outside the diffusion material 1.1 of the 51st v1 unit, there is a false rib T-through filter 4 (α1 symmetrical). This is the same as arranging 3.3 pieces of two Fresnel lenses (as shown in the figure). Therefore, the Fresnel lens is The focal length of lens 3 is half that of the single lens.

In projection for advertising purposes, the distance between the reflective screen and the slide projector is large (and relatively large).
! Second, since the image is captured from a distance, the focal length of the Fresnel lens 3 is halved by the reflecting mirror 2, and in reality there is a light minute 'T' even if the degree of refraction of the Fresnel lens is extremely small.

FIG. 11 shows a modified embodiment of the present invention, and this actual example is as follows:
Light diffusion treatment is applied to the diffusion material 1 on both the front and back sides. In this case, since the light diffusion surface is doubled, the degree of light diffusion is increased, and the visible range of the reflective screen can be expanded.

As is clear from the above description, the present invention can use a reflecting mirror with a vine reflectance, and since there is no cause of loss of light when the original is transmitted through a diffuser plate, the degree of light diffusion can be improved. Coupled with the fact that it can be made smaller, it can be much brighter than conventional projection illuminations on reflective screens.

The present inventors used a surface mirror made of steamed aluminum as a reflecting mirror, a light diffusion treatment was applied to the surface of an acrylic plate with a thickness of 2 mm as a diffusing material, and a Fresnel lens polymerized on the surface. A reflective screen was constructed using a conventional reflective screen, and a projection experiment was conducted by placing the reflective screen parallel to the conventional reflective screen in the same plane. As a result, even when a conventional reflective screen would hardly be able to see the projected image in a bright room with daytime outside light, the reflective screen of the present invention allows you to see a vivid, contrasting, and bright image. did it.

In the dark room, the image on the conventional reflective screen was clear and had contrast, but the image fJI2 on the reflective screen of the present invention, which was placed alongside this, was several times brighter. It should be noted that the brightness of the image on the reflective screen according to the present invention is different between a bright room, an If room, and T.
: No difference was perceptibly recognized. However, the spatial range of the viewer 1111 who can clearly hear the projected image is relatively narrow compared to the conventional reflective screen.

In addition, since the Fresnel lens is combined with a diffusing material,
Even if the original degree of diffusion of the diffusing material is small, or even when projecting with a wide-angle lens, it is important to make the brightness of the image uniform across all projection directions. Ru.

Furthermore, the reflective function of the reflective screen is shared by the reflective plate and several light diffusers independently, so by adjusting the degree of diffusion of the diffusing material, the purpose of use and reflective screen design can be adjusted. AM! It has occasional effects such as being able to make knots.

In the embodiment shown in FIG. 1, the diffusing material is sandwiched between the Efresnel lens and the reflecting mirror, but the diffusing material may be exposed on the surface side 1. However, in this case, as is clear from FIG. 5, the optical distance between the pair of light diffusion directions is increased, so that the sharpness of the image is slightly reduced.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged cross-sectional view of a reflective screen 17 according to an embodiment of the present invention, FIG. 2 is a full view thereof, and FIG. FIG. 4 is a partially enlarged cross-section of a reflective screen according to an embodiment of the present invention, which is not explained here. In order to simplify the drawing, the Fresnel lens is omitted. Figure 4 is an enlarged cross-sectional view of the optical system equivalent to Figure 4. Figure 6 (2) shows the brightness and degree of diffusion of the reflected light in a conventional reflective screen. Figure 8 is a diagram showing an example of the brightness and degree of diffusion of reflected light rays in a reflective screen according to the present invention. A diagram for explaining the occurrence of unevenness, FIG. 9 is a partially enlarged sectional view showing the state of bending υf of the main anti-elbow axis in a reflective screen according to an embodiment of the present invention, and FIG. 10 is a diagram for explaining the occurrence of unevenness. Diagram for explaining the function of eliminating unevenness in image brightness on the anti-reflection screen according to the invention &c. There are 1 items. 1... Diffusion material, 2... Reflector, 3... Fresnel lens. Fig. 3 Fig. 4 Fig. 5 Fig. 7 Fig. 9 Fig. 11

Claims (1)

[Claims] 1. The reflective surface of the reflecting mirror is characterized by polymerization of a diffusing material made of a transparent thin plate or sheet subjected to light diffusion treatment and a circular Fresnel lens having a positive focal length. High brightness reflective projection screen. 2. A high-intensity reflective projection screen as claimed in claim 1, which has a diffusing material subjected to a light diffusion treatment to form fine irregularities on the surface. 36. A high-intensity reflective type embellishment screen according to claim 1 or 2, which has a diffusion material subjected to a light diffusion treatment on the 36th side. 4. A high-intensity reflective projection screen as described in claim 1 or (Gogumi 2), which has a diffusing material subjected to light diffusion treatment on both sides.