JPS61296342A - Reflex projecting screen - Google Patents

Abstract

PURPOSE:To eliminate the insufficiency of contrast in a dark part by providing the visual field lens of a convergence optical system on the front, a reflex lenticular lens on the back and a transparent optical medium with a high refraction factor between former two. CONSTITUTION:A lenticular lens surface 3 equipped with the refraction surface 1 of the visual field lens of the convergence optical system on the front and a reflex layer 2 on the back is provided, and the transparent optical medium 4 with a high refraction factor is filled in an intermediate space constructed with both lens surfaces. Thus the forward space on the reflex surface is filled with the transparent material with a high temperature refraction factor, and therefore the inclination of an incident beam develops a change in a direction of an angle twice said incline angle when the beam is made obliquely incident. The beam turns out to be a beam having the incident angle twice its initial one, again is made incident in the direction reverse to its initial one, and has a larger refraction angle than the incident angle due to the reaction of refraction when said beam enters air with a refraction factor of '1' from the optical material with a high refraction factor. Then the direction of said beam is further changed. Thus the projecting screen of an intensive light system can be obtained due to a high efficiency in terms of using a projected flux.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a reflective projection screen suitable for an image projection device, and particularly relates to a reflective projection screen that has high brightness over the entire area of the projection screen. be.

(Prior Art) In recent years, so-called reflective image projection devices such as projection television devices, projection type single-image display devices, and enlarged projectors have become widespread.

This type of device projects image light from a projection screen (= light projection device) and observes the image. Various devices have been developed because they can easily make the screen larger, but they have advantages and disadvantages. It is still insufficient.

I will explain this in two parts below.

A matte screen can be represented by a simple piece of white paper, white cloth, or a white plastic sheet. Equally in all directions (because it reflects two elements, it appears to be about the same brightness over a wide area, but the projection light flux is wasted even in areas where there are no audience members (: because it is dispersed, the absolute value of the amount of light received by each audience member is low) There is a disadvantage.

Z Bead screen white background (coated with two transparent glass beads (fine powder) that reflects the projection light in the direction of incidence, so it is bright but has a so-called backlefter-like property that covers an area suitable for viewing. There is.

3. Aluminum foil screen Made of specially treated and rolled thin sheets of aluminum, fitted into a slightly curved frame. It is difficult to manufacture a screen because effective projection requires special processing of the screen surface and proper curvature without distortion.

4. Metal lenticular screen The surface of transparent synthetic resin is coated with metal and has minute irregularities that act as small mirrors.

The continuous beam of light that comes out of the audience seats is reflected directly back into the audience seats, damaging the image.

5. Non-metallic lenticular screen The surface has irregularities like the metal lenticular screen, but there is no metal coating. The general properties are almost the same as metal lenticular screens.

However, since both metal and non-metallic lenticular screens can change the shape of the surface irregularities and the shape of the mirror during the manufacturing process, they have a wide variety compared to other screens.

(Problems to be Solved by the Invention) The conventional reflective screens described above are all the same in that they have a limited dynamic range of contrast.

Therefore, as mentioned earlier, even if you used a projector with high light power to make the light sufficiently bright, the contrast in the dark areas was insufficient, and the deep details in the dark areas were not visible.

(Means for solving the problems) The present invention was made to solve the problems of the conventional technology as described above. This is a reflective projection screen characterized by having a transparent optical medium with a high refractive index on the rear surface between the two.

(Function) Since the present invention has the above-described configuration, the converging optical lens on the front surface faces the projection lens, and the diverging luminous flux of the projection light using the exit pupil of the projection lens as the secondary light source is directed to the entire surface of the projection screen. In response, these beams are collimated into parallel beams, which are incident perpendicularly to the reflective directional lenticule surface on the back surface of the metal. Therefore, as in the past, these parallel light beams are subjected to the primary action of the lenticular directional reflecting surface, change direction by an angle twice the inclination angle of the reflecting surface, and enter the converging optical system surface again at that angle. The light is emitted into the air under the effect of refraction and convergence, and is irradiated onto the audience arrangement range corresponding to the design using the dispersion distribution of the conjugate image of the exit pupil of the projection lens.

(Example) The present invention will be explained below with reference to the drawings.

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, which has a refractive surface 1 of a field lens of a converging optical system on the front surface and a lenticular lens surface 3 provided with a reflective layer 2 on the rear surface. The constructed intermediate space is filled with a transparent optical medium 4 having a high refractive index.

In this case, the reflective layer surface and the lenticular lens surface can be considered to be the same surface both physically and optically. Consider an optical system that is a plano-convex lens with a convex front surface and a flat back surface, with a reflective mirror surface provided on the back surface. It goes without saying that the convergence surface may be a Fresnel lens surface, since it is sufficient to have a convergence effect.

Now, as mentioned earlier (2), the projection light flux uses the exit pupil of the projection lens as a secondary light source, and the entire surface of the projection screen is uniformly irradiated with the projection light flux.This diverging light flux is collimated by the converging lens surface and becomes a parallel light flux. The light then enters the reflection plane almost perpendicularly.Then, it is reflected, enters the converging lens surface again, and is converged again to the conjugate point of the projection lens exit pupil (: This convergence that connects the light source image is as shown in Figure 2. be.

In the case of the present invention, the convergent optical system functions as a collimator and an objective lens, but if you look at it from a different perspective, as shown in Figure 3, there is a lenticular structure inside the double-convex single lens, which acts as a light diffuser. You can see it there.

A general transmission projection screen requires the converging power of two surfaces because it has one field lens that takes on the action of the collimator and one lens and the action of the objective lens.

Therefore, since the angle of inclination at the outer periphery of the field of view is steep with respect to the incident light beam, the luminous flux density becomes low, resulting in a decrease in the amount of light at the periphery of the screen.

When the field lens is used twice back and forth as in the present invention, the convergence effect is only halved, the curvature is halved, and therefore the slope of the surface is also halved, so there is little influence on the amount of peripheral light and it is possible to prevent and reduce a decrease in the amount of light.

This is extremely advantageous optically. Furthermore, in this case, there is no difficulty in arbitrarily setting the projection distance and viewing distance by appropriately selecting the curvature of the spherical surface.

Under the above conditions, the spherical surface of the field lens passes the light beam again and again, and is subjected to its converging action.

Furthermore, since both the front and back surfaces are used, only one lens material is required, making it very economical.

Next, the reflective lenticular surface in the present invention will be considered.

The present invention has a structure in which a field lens surface is arranged on the front surface, a reflective lenticular surface is arranged on the rear surface, and the space between the two is filled with a transparent optical material having a high refractive index.

In this way, if the space in front of the two reflective surfaces is filled with a transparent material with a high refractive index and the light rays are incident obliquely, even if the inclination is slight, the angle of inclination or the direction of incidence of the light rays will be
If the reflective surface is tilted, the direction changes by an angle twice the tilt angle of the surface, and these rays further become rays with an incident angle twice the initial tilt angle and reach the incident surface. When the light re-enters in the opposite direction to the original direction and exits from the optical material with a high refractive index into the air with a refractive index of 1, the refraction angle becomes larger than the angle of incidence due to the effect of refraction, and the direction is further changed.

This is the immersion microscopy method used in microscopy.

In general liquid immersion or oil immersion methods such as those using a microscope, a convergent light beam from a wide angle is condensed into a light beam at a narrow angle, as shown in FIG. As shown in the figure, it is the opposite, and utilizes the effect of converting a light beam at a narrow angle into a divergent light beam at a wider angle.

In FIGS. 4 and 5, 10 represents air and 11 represents a high refractive index medium.

In this case, if we pay attention to the traveling direction of the light, in Fig. 4 we can see that the incident angle θ is
When the light beam enters the high refractive index medium, the refraction angle μ
It becomes 0 degrees when exiting the high refractive index medium.

Furthermore, by designing and arranging optical shapes on the reflective surface, the incident light beam can be diffused in a wide variety of ways.

That is, the reflective lenticular surface makes use of the above-mentioned advantages, and its degree of influence is much lower than that of the transmissive lenticular surface, which relies mainly on refraction.

The projection screen of the present invention not only utilizes reflection and refraction in combination to change the direction of light rays, but also utilizes a field lens to reciprocate.

That is, the reflective lenticular surface reflective projection screen of the present invention makes thorough use of these influences, which can be explained with reference to FIGS. 6 and 7.

Figure 6 (2) If we take an optical model with an apex angle α and assume that a ray of light is incident perpendicularly to one surface of the model, then when the light passes through, when sin α is equal to the angle α, θ1nα is If the angle is β, then β=N・α. However, N is the refractive index of the transparent optical material. If the angle between the direction of the refractive index of a general transparent body and the direction of the refracted ray is r, then γ=β−α=l('α -α=(published-1) αThe refractive index N of a general transparent body is about 1.5, so γ=(1,5-1)
-α=0.5α Then, as shown in FIG. 7, when the rear surface is used as a reflecting surface and the light is reflected, the reflection angle is twice the incident angle, that is, 2α, and the light re-enters the incident surface.

At this time, the angle of refraction δ into space after incidence is sin δ = N・(sin 2α) = 1°5
sin 2a) After approximately C2 reflection, the refraction angle δ at the interface with air is taken as 1,5X2α, ie 3α.

Therefore, when the direction change γ in 4 units of refraction is 0.5α, δ in reflection is 3α, and by comparison, δ/γ=6α10.5α=6 times.

Therefore, the overall effect of the reflection action at the lenticular metal reflection surface and the refraction action at the interface between the medium and the air is extremely large.

Next, Figures 8 and 9 show the state of reflective light.1 In this case, assuming that the reflective lenticular surface is a convex or concave curved surface, its radius of curvature is r, and the incident height from the optical axis is h. Then, the change in direction of the light ray due to the curved surface is ε=sin”−1k
It becomes y'r.

That is, the angle of reflection of the light beam by the reflecting surface is 2ε, and the angle of re-incidence is also the same.

Therefore, the refraction angle ζ after re-incidence is sin ζ = NI sin2g In this way, the amount of change in the direction of the light ray differs due to - times of reflection and once refraction from a high refractive index medium to air.

In contrast, if there is only a refractive effect, sinφ=(N
-1) sin ε, that is, the half-angle of ε. This is a big difference.

We will now compare the limit of the diffusion angle of the reflective lenticular surface with that of the transmissive lenticular lens surface.

In the reflective lenticular surface, after being reflected, the light beam re-enters the interface between the high refractive index medium surface and the air. However, since the angle of re-incidence can be freely adjusted up to the critical angle of the medium, the angle of refraction will be 90 degrees when the beam exits the air after re-incidence.

This angle of refraction is the angle of diffusion. Theoretically, there is a diffusion range of 90 degrees to the left and right of the front of the 4th act, so you have the freedom to decide as you like depending on the conditions of use.

On the other hand, on the transmission type lenticular lens surface, light is similarly emitted into the air from a high refractive index medium, but at this time, if the incident angle is a critical angle, the refraction angle is 90 degrees, that is, the tangential surface of the refraction surface, and the traveling direction of the light is is in the direction of the supplementary angle of the critical angle, and light will not be diffused beyond that direction. That is, if the refractive index N is 1,492, then 1
/ 1°492: In 8in4, φ is approximately 42 degrees and its supplementary angle is 48 degrees. This is about half that of a reflective lenticular surface. (See Figures 11 and 12) The above is the diffusion limit for both reflective and transmissive lenticular surfaces, but since the distribution of light intensity is weak from this limit to about 20 degrees, it is not considered to be an effective range. Not considered. Therefore, the effective value becomes even narrower than the limit range.

However, the differences between the two are obvious.

To give a simple example, in the case of a reflective lenticular surface with a radius of curvature of 0.5 m, the incident height from the optical axis is 0.18ff.
It reaches a critical angle at low temperatures. -The pitch is twice that, 0.36m
becomes. Generally, the practical pitch of the lenticular surface is about 0.2 to 0.75 ff, so the example just given can be said to be a practical example.

This means that it is easy to obtain a wide-angle lens with a total diffusion range of 140 degrees and a total diffusion range of 70 degrees on each side.

On the transmission lenticular surface, the total diffusion angle is 60 degrees, about 30 degrees on each side. This difference in the distribution range of the projection light flux is a large difference in practical use.

In the above various points (=), the reflective lenticular surface is superior to the refractive lenticular surface.

Next, consider the case where the above-described function of the field lens and function of the lenticular metal reflective surface are integrated and superimposed as follows.

That is, the projection light beam is a diverging light beam that uses the exit pupil of the projection lens as a secondary light source, and is distributed over the entire surface of the field lens. This diverging light flux becomes a group of parallel light fluxes by the field lens on the front surface of the projection base and is incident on the rear lunticular metal reflective surface. Here, the parallel beam group becomes a predetermined diverging beam group due to the action of lenticular metal reflection. These diverging beam groups change their inversion direction and re-enter the field lens ζ2, where they receive the converging action of the field lens, and the conjugate image group of the exit pupil, which is the light source, is designed corresponding to each diffuse beam group. Distributed images are formed in the distribution range of the audience according to the audience.

As a result, the audience located within the design range can view clear images with uniform brightness.Fourth, let us discuss the detailed structure of the lenticular metal reflection angle used in the present invention.

As already mentioned, the reflective surface responds sensitively to slight inclinations and changes in inclination. This indicates that there are strict requirements for machining accuracy during manufacturing on the negative side. This proves that it is effective in controlling the direction of the light beam.

Next, some specific examples of lenticular metal reflective surfaces are listed (see Figures 8, 9, and 10): (1) Convex or concave spherical surface (2) Convex or concave cylindrical surface (3) Convex or concave cylindrical surface A metal reflective surface of a lenticular made of a transparent material such as an acrylic resin molded on a concave aspherical surface or a back reflective surface can be coated with metal by general metal film forming means such as vapor deposition or sputtering.

(Effects of the Invention) Since the present invention is a reflective screen, it does not require extra projection space unlike a transmissive screen, and has a much wider contrast dynamic range than a conventional reflective screen.
It is possible to provide a projection screen that has a high-light projection screen with high utilization efficiency of projection luminous flux.

[Brief explanation of the drawing]

Fig. 1 is a side view showing an example of the reflective projection screen of the present invention, and Fig. 2 is a light refraction diagram of the convergent optical system (having a reflective mirror surface on the back surface of plano-convex lenses) in the projection screen of the present invention. , FIG. 3 is a light refraction diagram when there is a lenticular structure inside the biconvex single lens itself. Fig. 4 is an explanatory diagram of the immersion method in a microscope, Fig. 5 is an explanatory diagram of the immersion action of the present invention, Fig. 6 is a refraction diagram of light of a transparent optical wedge with an apex angle α, and Fig. 7 is an illustration of the apex A refraction diagram of light in a reflective optical wedge having an angle α, FIG. 8 is a refraction diagram of light when the reflective lenticular surface is a curved surface concave toward the light beam, and FIG. 9 is a diagram of refraction of light in the opposite case. Figure 10 shows the reflective lenticular surface as shown in Figure 8.
Figure 9 is an explanatory diagram of the catadioptric state of mixed light; Figure 11 is an explanatory diagram of a transmission type projection screen that is convex toward the light beam;
FIG. 2 is an explanatory diagram of a transmission type projection screen that is concave toward the light beam. Agent Patent Attorney Mamoru Takeuchi Figure 1 Figure 3 Figure 8 Figure 9 Procedural Amendment (July 24, 1985 Director General of the Patent Office Michibu Uga 1, Indication of Case 1985 Patent Application No. No. 138325 λ Name of the invention Reflective projection screen 3, Relationship to the amended case Patent applicant address 10-3 Jujo Nakahara-chome, Kita-ku, Tokyo Name
Yup Co., Ltd. Representative: Kaku Yodebe 4, Agent address: 101 Address: Nanbu Building 6, 15413 Uchikanda 2-chome, Chiyoda-ku, Tokyo Number of inventions to be slightly increased by amendment: 07, Subject of amendment: 1, Details In the second line from the bottom of page 7 of the book, the text ``high temperature refractive index'' has been corrected to ``high refractive index.'' 2. Specification letter page 10, line 1 “Refractive index of general transparent bodies”
Correct it to "incident ray". 3. On page 15, line 11 of the detailed letter, the word "system" is corrected to "power."

Claims (1)

[Claims] A reflective projection screen characterized by having a viewing lens with a convergent optical system on the front surface, a reflective lenticular lens on the rear surface, and a transparent optical medium with a high refractive index in the space between the two.