JPS62210440A - Lens sheet for transmission type projection screen - Google Patents

Abstract

PURPOSE:To diffuse incident light over a wide range and to eliminate the color irregularity by composing a projection-surface lenticular lens of a projection-side main lens lenticular lens, a total reflecting surface, and a totally reflected light projection surface. CONSTITUTION:Light beams 11-12 among light beams 11-14 incident on a lens sheet 1 are refracted by a lens L2 to reach M7, reflected totally by the M7, and then emitted within a range Y. The light beams 12-13 are incident on and refracted by a lens L1, refracted by a lens L4, and emitted within a range X; and the light beams 13-14 are refracted by a lens L5, reflected totally; by M8, and emitted within a range Z. The range of the light beams 12-13 is the same as usual and an observation area ranges by + or -30 deg., i.e. 60 deg., in total about a normal 3 perpendicular to a lenticular lens sheet. The ranges Y and Z of projection light are set outside the range X at + or -(30-50) deg. to, for example, the normal to separate in-charge ranges preferably.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is useful for configuring a projection screen of a type in which an image is projected from the back side and observed from the front side, that is, a so-called transmission type, with a small color shift. The present invention relates to a suitable lens sheet.

[Conventional technology]

Transmissive projection screens of various shapes have been invented for use in television projectors and the like. For example, if you use a double-sided lenticular lens sheet with black stripes, in which groups of lenticular lenses are provided on both sides of the sheet and correspond to each other in the same direction, and a light absorbing layer of black color or the like is provided on the part of the exit surface where no light is emitted. It is possible to construct a transmissive projection screen that has little vertical light loss, high image contrast, and little color shift (displacement in color balance due to different viewing angles).

[Problem that the invention seeks to solve]

However, even if you use the above-mentioned double-sided lenticular lens sheet with black stripes, the observable range is approximately 30° left and right around the optical axis, for a total of 60°.
It has the disadvantage that it remains within a narrow range.

[Means for solving problems]

According to the research of the present inventor, most of the light incident on the lens sheet is absorbed by the double-sided lenticular lens.
The remaining part of the incident light is totally reflected using a total reflection surface provided on a part of the exit surface of the lens sheet, and the remaining part of the incident light is emitted outside the range where most of the light is emitted. It has become clear that by combining the two, it is possible to widen the range from which the emitted light is emitted, and it is possible to increase the observable range to 60' or more.

The lenticular lens sheet for a transmission type projection screen of the present invention is a lenticular lens sheet for a transmission type projection screen.

"It is a double-sided lenticular lens in which groups of lenticular lenses are provided on both sides in the same direction and correspond to each other. It consists of a main lenticular lens and one auxiliary lenticular lens on the incident side, which is placed on each side of the lens and receives the remaining part of the incident light.

The lenticular lenses on the exit surface include an exit-side main lenticular lens that emits light that enters the entrance-side main lenticular lens, and one on each side of each exit-side main lenticular lens, so that light enters the entrance-side secondary lenticular lens. A total reflection light output surface that is arranged between a total reflection surface that totally reflects light and total reflection surfaces on both sides of each output-side main lenticular lens and emits the total reflection light from the total reflection surface to the output surface side. It is characterized by the following.

Hereinafter, the lens sheet of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a diagram showing an example of use of the lens sheet for a transmission type projection screen of the present invention, 1 is the lens sheet for a transmission type projection screen of the present invention, and 2 is a view for narrowing down incident light to an appropriate angular range. It is a Fresnel convex lens sheet of 1.
2 both show cross sections. In this way, although it is common to combine it with the Fresnel convex lens sheet 2, the Fresnel convex lens sheet 2 can be omitted. R on the left in Figure 1,
G and B show a television projector as an example; if it is a color television, red (flesh) and green (G
It consists of three projection CRTs for projecting information of each color (L, blue β). The line drawn from each CI'LT toward the center of the lens indicates the incident light,
If the light incident perpendicularly from green is used as a reference, and assuming that red, green, and blue are equally spaced vertically in the figure, the incident angles of the red and blue incident light will be compared to the reference by an angle represented by ε. It's off. This angle deviation of the incident light causes a deviation in the distribution of the emitted light. ε is, for example, about 10°.

FIG. 2 is an enlarged view of the cross-sectional shape of the lens sheet 1. The portion indicated by the solid line is one unit, and the lens sheet 1 is made by repeating this unit in the vertical direction in the figure.

In the lens sheet 1, the surface on the left side is the entrance surface S1, and the surface on the right side is the exit surface S2. Incidence surface S1
is made up of two types of lenses: an entrance-side main lenticular lens L that occupies most of the entrance surface, and entrance-side secondary lenticular lenses L2 and Ls that occupy the remaining part of the entrance surface. Lenses L2 and Ls are arranged one each in contact with both sides of lens L1.

The exit surface S2 is made up of three types of parts. That is,
At the center is an exit-side lenticular lens L4, and on both sides of the main lenticular lens L4 are total reflection light exit surfaces L.
5 and L6 are arranged in contact with each other, and furthermore, a total reflection surface M and a dove are arranged in contact with the outside of Ls and L6.

FIG. 3 shows the effects of each part of the lens sheet 1, especially the lenses L2, Ls, the total reflection surfaces M7, MB, and the exit surface L5.
, L6. The shape of the lens sheet 1 itself is exactly the same as that shown in FIG.

In FIG. 3, light rays 11. which are incident on the lens sheet 1.
12, 13, and 14 all show the case where they are parallel to the optical axis 3 of the lens, the rays between 11 and 12 are incident on the lens L2, the rays between 12 and 13 are incident on the lens L1, and the rays between 13 and 12 are incident on the lens L1.
The light rays between .about.14 are incident on lens L5.

First, the rays between 11 and 12 are focused by lens L2 and reach M7. M is a total reflection surface that totally reflects the light beam refracted by the lens L2, and after being totally reflected by M7, the light beam is emitted from Ls to the range Y. Next, 12-1
The light ray between 3 and 3 enters the lens L1, is refracted, is refracted by the lens L4, and exits to the range of X. The rays between 13 and 14 are refracted by lens L, and totally reflected by MB,
Emit light from L6 to the Z range.

Here, the point that the rays between 12 and 130 are emitted with a spread in the range of The observable area is ±30° with respect to the normal 3, which is 600 in total. Therefore, the ranges Y and Z of the emitted light are set outside the range of 'X, for example ± with respect to the normal line.
It is preferable to set it at 30' or more and at most ±50° so that the receiver shares the range, but it is also possible to set it at at least ±25° and at most 50° so that it overlaps with range X.

Here, referring to the shape and size of each part of the lens sheet 1, the pitch, the thickness P, and the thickness t of the lens vary depending on the overall size of the lens sheet 1 or the distance from the observer. Assuming the above television screen, P = 0.3 to 1.5, t = 0.3 to 1.5
(all units are in units).

The main lens L1 on the entrance surface side is a lenticular lens whose cross-sectional shape is a circle, an ellipse, or a part of a parabola,
The sub lenses L2, L are also similar to the lens L1. Width of lens L2 (measured in the direction of pitch P, same below)
and the sum of the width of lens Ls: The width of lens L1 is 1:9 to 4:
6, therefore, 90 to 60 inches of the incident light is transferred to the lens L1.
The remaining 10 to 40% is received by the lens L2 and the lens Ls and is made to enter.

Ru. Since the light refracted by the lens L1 is focused near the lens L4, the width of the lens L4 may be smaller than the width of the lens L1.

The total reflection surface M7 is the lens L2 on the incident surface side.

The light refracted by the lenses L2 and L is reflected and directed toward the lens sheet. As shown in FIG. 3, if the incident light is incident in the direction perpendicular to the lens sheet 1, the widths of the total reflection surfaces M1 and MB may be the same as the widths of the lenses L2 and Ls, but the incident light is Even if the position of M7 is constant, it will be incident at different angles depending on the part of the lens sheet 1, so it is better to keep the width of M7 wide, and it is better to make it 1.2 to 2 times the width of lenses L2 and L3. .

Now, the characteristics of the lens sheet of the present invention will be compared with a conventional type lens sheet having a total reflection surface, in which the light entrance surface is flat, a lenticular lens is formed on the light exit surface, and a part of the lens sheet is a total reflection surface. I will explain. Of the light that enters the lens sheet of the present invention, light that is not totally reflected, that is, the lens L
.

Regarding the incoming light, lenticular lenses are formed on the light entrance surface (lens L1) and the light exit surface (lens L4), so by appropriately designing the shapes of the lenses L1 and L4, it is possible to It is possible to achieve better color shift than a lens sheet in which only lenses are formed. Further, at this time, the horizontal viewing angle can be expanded to about 30'.

Next, we will discuss the light related to the total reflection surface, that is, the light that enters the lenses L2, L in the present invention. If there is no L5 and this part is flat, the light that enters the lens sheet perpendicularly will enter the total reflection surface M, , -M8, but at a certain angle (for example, about 10 degrees in the case of a TV projector). However, some of the light that enters the surface will be incident on areas other than the total reflection surface, which will worsen the color shift. On the other hand, when lenses L2 and L3 are formed as in the present invention, lens L
2. By concentrating the light at L3, the total reflection surface M7,
The amount of light that does not enter M8 can be significantly reduced.

Therefore, in this respect as well, the lens sheet of the present invention can provide better color shift. lens L2,
As for the shape of L, an appropriate shape that condenses light may be selected, such as a circle, part of an ellipse, or something else.

Furthermore, as mentioned above, it is better to form a lens on the light entrance surface as well, rather than on the light exit surface only, because it is possible to improve color shift by appropriately designing the shape of the lens surface. I can do it. Similarly, for light that exits after total reflection, only the total reflection light exit surface is a curved surface, and rather than the light entrance surface and total reflection surface being flat, the light entrance surface, total reflection surface, and total reflection light exit surface are all curved. If there is a curved surface, the color shift can be improved by appropriately designing the curved surface.

As described above, the lens sheet of the present invention has (1)
For light that is not totally reflected, a lens shape is formed on the light exit surface. (2) Regarding the light that is totally reflected, a lens is formed on the light entrance surface to reduce the light that does not enter the total reflection surface. (3) Further, by making the total reflection surface and the total reflection emission surface curved, color shift is improved. In other words, since it can correct the difference in the light output angle due to the light incidence angle, it has the advantage of better color shift than a conventional lens sheet with a total reflection surface, and is also easier to observe than a double-sided lenticular lens sheet with black stripes. This has the advantage that not only is the range expanded, but also that the balance of projected light of each color is maintained even in the expanded range.

Although the lens sheet of the present invention has the above-described configuration,
Since no light is emitted from the total reflection surface provided on the exit surface side, even if a light shielding layer 15 is provided to cover this portion as shown in FIG. 4, the characteristics of the lens will not be impaired. This is preferable because unnecessary light is incident or reflected from the exit surface side, or stray light exiting from the total reflection surface due to some reason can be blocked. As the material for forming the light-shielding layer 15, a composition having light-shielding and light-absorbing properties, such as a composition prepared by adding a pigment such as black and preferably a matting agent to a known paint or ink, may be used.

Furthermore, it is preferable to provide a light reflecting layer 16 made of a metal vapor deposited layer or the like on the total reflection surface as shown in FIG. 5 before providing the light shielding layer 15, since this increases the reflection efficiency of the total reflection surface.

Alternatively, if the angle of incidence between the ray incident on a total reflection surface and the normal to the total reflection surface is larger than the critical angle, total reflection will occur, so the critical angle should be larger than the maximum value of the incidence angle. , a light-absorbing material with a sufficiently small refractive index may be applied. As the light-absorbing substance, fluororesin, silicone resin, etc. are used, although it depends on the resin used as the base material.

The lens sheet of the present invention may be provided with light diffusing properties to diffuse emitted light in the vertical direction (up and down direction as seen from the observer). As a method of imparting light diffusivity,
For example, there is a method of adding a light diffusing material inside the lens sheet, in which fine particles that have the property of scattering light are kneaded into the material constituting the lens sheet. Extender pigments such as fine powder alumina,
Examples include glass powder, resin powder, etc., and the particle size is 0.5~
It has a diameter of about 30 μm, and is added at a rate of 0.5 to 5% by weight based on the material constituting the lens sheet. Note that in order to scatter the light, the refractive index of light of the fine particles and the material constituting the lens sheet need to be different.

Another method for imparting light diffusing properties to the lens sheet is to use the exit surface as a light diffusing surface. For example, when forming a lens sheet, a plastic film formed by adding a light diffusing material may be attached using a method such as heat fusion, or the exit surface of the lens sheet may be roughened by sandblasting. Illustrated.

The material constituting the lens sheet of the present invention may be any material as long as it is transparent and can be molded into a sheet shape, including acrylic resins such as polymethyl methacrylate, polyester resins, cellulose resins, and polyvinyl chloride resins. ,
Thermoplastic resins such as polystyrene resins and polycarbonate resins, or glass are preferred. Among these, when a thermoplastic resin is used, it can be manufactured easily and efficiently by a known molding method. There is a method in which a sheet of thermoplastic resin is heated and pressurized using an inverted mold (plate-like or roll-like) of a predetermined shape, and a method in which a sheet of thermoplastic resin is heated and pressurized immediately after production of the thermoplastic resin sheet, while the sheet is still cooled. A method of forming the lens sheet on an unprocessed lens sheet, casting using a mold, or other molding methods are suitable when the lens sheet is made of thermoplastic resin. Depending on the mold, the size of the lens sheet, etc., the thermoplastic resin sheet may be cut one by one and then processed, or a continuous sheet such as a rolled sheet may be continuously processed.

The lens sheet of the present invention has the function of a transmission projection screen when used alone, but if a Fresnel convex lens is placed on the incident surface side, projection light can be uniformly irradiated to every corner of the screen, making it more effective. be.

[Action/effect of the invention]

In the lens sheet of the present invention, most of the incident light is
It functions like a conventional double-sided lenticular lens, and is diffused by the main lenticular lenses on the entrance and exit sides. Of the incident light, the light that enters the secondary lenticular lenses on both sides of the main lenticular lens is reflected by the total reflection surface. Since the light is diffused to a range outside the diffusion range of the main lenticular lens, there is an advantage that the incident light can be diffused over a wider range than the conventional double-sided lenticular lens.

Further, in a preferred embodiment of the lens sheet of the present invention,
The light that enters from the incident side secondary lenticular lens, passes through the total reflection surface, and exits from the total reflection light output surface, the input surface, total reflection surface, and output surface are all made of curved surfaces, and the light enters at different angles of incidence. Since it has the function of concentrating and diffusing light in a more or less fixed position, even when CRTs for each color of a color television are arranged side by side, the distribution of the emitted light of each color can be adjusted. This has the advantage that there is no shift in color, and therefore no color unevenness occurs when viewed from any angle.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of the use of the lens sheet of the present invention, Figure 2
3 is a diagram showing the action of the lens sheet of FIG. 2, and FIGS. 4 and 5 are diagrams showing other embodiments of the lens sheet of the invention. It is. 1... Lens sheet 2... Fresnel convex lens sheet S1...
...... Entrance surface S2 ...... Output surface Ll ...... Main lenticular lenses L2, L5 on the entrance side... - Entrance side secondary lenticular lens L4 ...... Output side main lenticular lenses L5, L6...
・・Total reflection light exit surfaces M7, M8・・・・・・・Total reflection surfaces Fig. 1 ■ Lens sheet for transmission plate projection screen No. 21! l 3111 Figure 4 Figure 5

Claims (7)

[Claims] (1) A double-sided lenticular lens in which groups of lenticular lenses are provided on both sides in the same direction and correspond to each other, and the lenticular lens on the entrance surface includes an entrance-side main lenticular lens that receives most of the incident light, and It consists of an input side auxiliary lenticular lens, which is placed on each side of the input side main lenticular lens and receives the remaining part of the incident light.The output side lenticular lens enters the input side main lenticular lens. A main lenticular lens on the output side that emits the emitted light, a total reflection surface that is placed on each side of each main lenticular lens on the output side and totally reflects the light that enters the secondary lenticular lens on the input side, and each output side main lenticular lens. A transmission type characterized by comprising a total reflection light output surface disposed on both sides of the side main lenticular lens between the total reflection surface and the total reflection light output surface for outputting the total reflection light from the total reflection surface to the output surface side. Lens sheet for projection screens. (2) The lens sheet according to claim 1, wherein the total reflection surface is a curved surface that is convex toward the outside of the lens sheet. (3) The lens sheet according to claim 1 or 2, wherein the total reflection light exit surface is a curved surface that is concave toward the outside of the lens sheet. (4) The lens sheet according to any one of claims 1 to 3, wherein a reflective layer that reflects light within the lens sheet is provided on the surface of the total reflection surface. (5) The lens sheet according to claim 4, further comprising a light absorption layer provided on the reflection layer. (6) The lens sheet according to any one of claims 1 to 5, wherein a light diffusing material is added therein. (7) The lens sheet according to any one of claims 1 to 5, wherein the exit surface is a light diffusing surface.