JPH03181935A - Fresnel lens sheet bonding structure and bonding method - Google Patents

Abstract

PURPOSE:To allow the joining of Fresnel lens sheets in a surface direction with sufficient bending strength and to prevent the deterioration in image quality by joining the lens sheets in the non-effective parts on the side outer than the frustum of pyramid formed by the loci of the rays which are projected from a projector, are transmitted through the lens sheets and are emitted therefrom. CONSTITUTION:The lens sheets 1, 2 are joined by a joint part 3 at the respective longitudinal ends. The section of this joint part 3 has the triangular columnar shape of a wedge shape and the width on the light source side is slender toward the observation surface. Further, this joint part 3 is formed by diagonally cutting the joint end face of the ends of the lens sheets 1, 2 by machining and butting the lens sheets 1, 2 to each other, then superposing and adhering the end faces. The joint part 3 of the lens sheets 1, 2 is then invisible from the observation surface and the sufficient bending strength is obtd. even when the lens sheets 1, 2 are bent.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a Fresnel lens sheet used when a plurality of Fresnel lens sheets are arranged in a plane direction and their ends are joined to produce a polygonal Fresnel lens sheet. The present invention relates to a joint structure of lens sheets and a projector thereof.

[Conventional technology]

In recent years, there has been a demand for large-sized video display devices, and projection video systems that enlarge and project images onto a screen for observation are expected to be systems that can easily produce large-sized images of 100 inches or more. There is.

Among these projection image systems, a so-called transmissive projection system in which an image projected from the rear is observed through a transmissive screen can provide an image with high contrast and good visibility.

For transmission type screens, it is essential to use a lens sheet in which a large number of fine lens portions are formed with high precision. Furthermore, it is necessary to use a Fresnel lens sheet as a field lens to make the brightness of the entire screen uniform.

This transmissive screen is made of synthetic resin with good translucency such as acrylic resin and molded using a mold using a thermoforming method, casting method, etc. in order to form a large number of fine lens parts with high precision. has been done.

In this case, molding a large screen of 100 to 200 inches or more requires the use of molds and high precision, making it difficult to manufacture and expensive, making it impractical. There was a problem.

In order to solve this problem, a multi-image system has been proposed in which a plurality of projection systems are arranged to produce a large-sized image. In this system, uniformity of screen brightness is very important, so as a component of the transmissive screen,
Fresnel lens sheets have become essential. Therefore, in a multi-image system, a polygonal Fresnel lens sheet is required, which is made by arranging a plurality of Fresnel lens sheets in the plane direction and joining them to increase the size.

FIG. 11 is a perspective view showing a conventional Fresnel lens sheet bonding structure.

Conventionally, when producing a polygonal Fresnel lens sheet, a Fresnel lens sheet 12.
13 were arranged vertically or horizontally, and their ends were joined together by an adhesive layer 14. This adhesive layer 1
The thickness of No. 4 is usually about 1 to 5 mm.

Other bonding structures include creating a lattice-like frame using synthetic resin or the like and inserting the Fresnel lens sheet into the frame, or fixing the Fresnel lens sheet to a transparent substrate using metal screws, etc. Are known.

[Problem to be solved by the invention]

However, in the conventional bonding structure described above, when bonding is performed using the adhesive layer 14, Fresnel lens sheathing)12. '
The elastic modulus of the adhesive layer 14 is often smaller than the elastic modulus of the base material 13.

Therefore, when the Fresnel lens sheets 12 and 13 are deformed and curved perpendicularly to the lens surface, the adhesive layer 1
Since the bending stress is concentrated at 4, the lens sea) 12.13
There was a problem in that the adhesive layer 14 cracked.

In order to provide sufficient bending strength, it is possible to make the adhesive layer 14 thicker than 1 mm, or to use a bond that is strong against bending, such as polymer bonding.

This polymer adhesive uses the same material as the base material of the lens sheet, so there is no difference in elastic modulus, and stress will not concentrate on that part and cause it to break.

However, polymer adhesives suffer from volumetric shrinkage, so after filling the adhesive layer with the polymerization solution, it is necessary to add a solution to account for the shrinkage. This shrinkage solution flows into the adhesive layer and polymerizes, so if the adhesive layer does not have a certain width, the solution will not flow easily and will not adhere uniformly. Therefore, it is necessary to increase the width of the adhesive layer.

For this reason, when the thickness of the adhesive layer is 1 mm or more, or when the adhesive layer is made of thick polymer adhesive, the adhesive part with different optical properties from the lens part stands out on the screen, resulting in another problem: image quality is impaired. will occur.

When placing a Fresnel lens sheet in a lattice frame,
Since the lens sheet is held by the frame, the frame itself is required to have strength. Furthermore, even if the lens sheet expands or contracts due to environmental changes such as temperature and humidity, it is necessary to prevent the lens sheet from coming off the frame. Therefore, since the frame had a certain width, there was a problem in that the frame was black and stood out on the screen.

When attaching Fresnel lens sheets to a transparent substrate with screws or the like, gaps are provided between each lens sheet to absorb expansion and contraction of the lens sheets.

Even in this case, there is a problem in that the image quality deteriorates because the gap portion has different optical characteristics from other portions and stands out on the screen.

An object of the present invention is to solve the above-mentioned problems, and when manufacturing a polygonal Fresnel lens sheet, it is possible to join the sheet in the plane direction with sufficient bending strength, and the joint part is not noticeable and the image quality is deteriorated. It is an object of the present invention to provide a joint structure of Fresnel lens sheets and a projector that do not cause any damage.

[Means to solve the problem]

In order to solve the above problems, the joint structure of Fresnel lens sheets according to the present invention arranges a plurality of Fresnel lens sheets in the plane direction in correspondence with a plurality of projectors, and the thickness portion of the end portion of each Fresnel lens sheet In the joining structure of Fresnel lens sheets joined together at The structure is such that the optically ineffective portion outside the truncated pyramid formed by the trajectory of the emitted light rays is joined.

In this case, the optically ineffective portion is incident at a distance l determined by the following equation (1) inward in the surface direction from the foot of the perpendicular drawn from the end of the exit surface to the entrance surface. Since it is outside the trajectory of the light ray, it can be easily determined.

= Ttan β ・・・・・・(1) sin
α β=arcsin() ...(2) However, α; Incident angle β of light source light; Refraction angle n of light source light; Refractive index T of Fresnel lens sheet; Thickness of Fresnel lens sheet Each Fresnel lens sheet has a first bonded end surface, which is on the exit surface side and is perpendicular to the exit surface and is in contact with each Fresnel lens sheet, and a first bonded end surface that is closer to the entrance surface than the first bonded end surface. The optically non-effective portion may include a first joint end surface formed within the optically non-effective portion and parallel to the first end surface within the non-effective portion.

In this case, the optically ineffective portion is the ineffective portion (4), the entrance side surface of the optically ineffective portion, or
It is possible to adopt a configuration in which a light shielding portion with an ineffective portion is formed.

On the other hand, the method of joining Fresnel lens sheets according to the present invention involves arranging a plurality of Fresnel lens sheets in the plane direction and joining them at the thick end portions of each Fresnel lens sheet in correspondence with a plurality of projectors. In a lens sheet projector, the Fresnel lens sheets are arranged in a plane direction, and among the light rays that pass through the Fresnel lens sheets and exit, the trajectory of the light rays exits from the end of the exit side. When joining at the optically ineffective portion outside the truncated pyramid formed by the truncated pyramid, the first joining end surface where each Fresnel lens sheet is brought into contact with a plane on the exit surface side and perpendicular to the exit surface. and is formed in the optically ineffective portion on the entrance surface side of the first bonding end surface, and is formed in the ineffective portion parallel to the first end surface. and is configured to be joined parallel to or at an angle with the first joining end surface.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings and the like.

1 and 2 are diagrams showing a first embodiment of a Fresnel lens sheet joining structure according to the present invention, with FIG. 1 being a perspective view and FIG. 2 being a side view.

In this example, each lens sheet 12 made of acrylic resin on which a Fresnel lens pattern is formed has a size of 50 inches (aspect ratio 4:31 dimension 1016
A piece with a size of 7610 mm x 6 mm and a thickness of 6 mm is used.

The lens sheets 1.2 are joined at their respective longitudinal ends by joints 3.

This joint 3 has a triangular prism shape with a wedge-shaped cross section,
The width on the light source side is 2 mm and tapers toward the observation side.

The joint portion 3 is formed by machining the ends of the lens sheets 1 and 2 and cutting the joint end faces diagonally.
After the two are brought together, they are polymerized and bonded. In this example, since the lens sheet 1.2 is made of acrylic resin, acrylic silub (a monomer slightly polymerized) is used for polymerization adhesion.

Since the lens sheets 1.2 are joined by such a joining part 3, the joining part 3 of the lens sheets 1.2 is not visible from the viewing side, so that the image quality does not deteriorate.

In addition, since the joint part 3 is widened so that it becomes wider toward the light source, it has sufficient bending strength even when the lens sheets 1 and 2 are curved, and the joint part 3 can be easily bent as in the conventional case. It will not break apart.

Next, the reason why the joint portion 3 is shaped into the aforementioned wedge shape will be explained.

FIG. 3 is a diagram schematically showing the optical system of a projection type image display device using a Fresnel lens sheet, and FIG.
FIG. 3 is a diagram showing the trajectory of light rays at the end of the lens sheet of the optical system shown in the figure.

Note that the parts that perform the same functions as those in the above-mentioned embodiment include:
The description will be given with the same reference numerals.

In FIG. 3, ■ is a lens sheet on which a Fresnel lens pattern is formed on the observation side, 4 is a projector for projecting an image, and 5 is a condensing point on the observation side where light from the projector is focused.

Here, if the distance from the projector 4 to the lens sheets 1 to 3- is fl, the distance from the lens sheet 1 to the observation side focal point 5 is f2, and the focal length of the lens sheet 1 is f, then f, f+, There is a relationship between fz as shown in the following equation.

In this case, if r=r, f2 becomes infinite, and all the light emitted from the lens sheet 1 is perpendicular to the lens sheet 1.

By the way, the function of the lens sheet 1 is to make the brightness of the screen uniform as a field lens. For this reason, the value of f2 is preferably infinity or about 10 m, where the light is slightly focused. In special cases where the observation range is limited to a fairly narrow range, it is desirable to focus the light on that observation range, but if f2 is too short, reflections on the lens sheet will occur at the periphery of the lens sheet 1. In addition, the amount of light emitted from the peripheral area decreases. Therefore, 4
For a screen size of 0 to 100 inches, f2 is desirably set to be several meters at the shortest, and approximately 100 times the radius r of the lens sheet l.

On the other hand, the relationship between the radii r and f of the lens sheet 1 is determined by the angle of view of the magnifying lens of the projector 4. If the angle of view of the magnifying lens is too large, the surrounding scenery will deteriorate,
Further, since focusing performance also deteriorates, it is desirable that the angle is about 30°. Therefore, fl is approximately 1.7 times r.

From the following, the distance mr2 is 10 of the radius r from infinity.
The distance f1 is preferably about 0 times the radius r, and the distance f1 is preferably about 2 to 1.7 times the radius r.

Next, the projection light passing through the end of the lens sheet 1 mentioned above will be explained.

Light 4L42 projected from the projector 4 and incident on the end of the lens sheet 1 is refracted twice by the lens sheet 1 and exits as light 43.44. At this time, light 43.
44 is the edge of the lens sheet 1 (the outermost edge of the screen)
Even when the light 41.42 is emitted from the
It does not pass through the outermost end of the back surface of the lens sheet l, but passes through a portion a certain distance i+j inside from the outermost end.

This distance °C is determined by the angle that the light 43.44 emitted from the end of the lens sheet 1 makes with the lens sheet 1 when it enters the back surface of the lens sheet 1, that is, the incident angle α, and the thickness of the lens sheet 1. It can be determined by the refractive index n of the lens sheet 1.

In other words, light 41.42 incident on the lens sheet 1 with a refractive index n at an incident angle α has a refraction angle β, that is, Sln α β=arcsin () . . .
...(4), so if the thickness of the lens sheet 1 is T, the distance C is ff=Ttan β...
... is given by (5).

Here, the angle of incidence α is determined by the angle of view of the magnifying lens of the projector 4 and the aspect ratio of the lens sheet 1, but if the angle of view is about 30° and the aspect ratio is 4:3, the angle of incidence α is about 19°. become.

Therefore, if the refractive index n is 1.49, β-12,
If the angle is about 6° and the thickness T is 8 mm, the scarcity is 1.8
It will be about mm.

Since this statement is true at all the upper and lower ends of the lens sheet 1, there are wedge-shaped optically ineffective areas 3 at the upper and lower ends of the lens sheet 1, through which the projection light does not pass.
a, 3a exist. Similarly, lens sea 1-1
There is also an optically ineffective part at the left and right ends where no light passes, but the distance of this part from the extreme end on the back surface of the lens sheet 1 is because the aspect ratio of the screen is 4:3.
It is longer than the distance l at the upper and lower ends. Under the conditions described above, the distance is approximately 2.4 mm.

In this way, it can be seen that there are wedge-shaped optically ineffective portions at all of the upper, lower, left, and right ends of the lens sheet 1 through which the projection light does not pass.

7 Here, the optical system shown in FIG. 3 and the calculations described above are all based on the case where the light source of the projector 4 is located on the optical axis of the lens sheet 1. However, in the projection system described above, the lens It is desirable to arrange the light source on the optical axis of the sheet 1 in terms of image quality, and it is also easy to design and manufacture the light source, so it is usually arranged in this way. It is clear that the above holds approximately even when the light source is placed near the optical axis of the lens sheet 1, and in a normal projection system, the There is an optically ineffective portion 3a at the end through which light does not pass.

This optically ineffective portion 3a through which light does not pass does not affect the image at all even if it has different optical properties from other portions, so it can be said that there is no need for light to pass therethrough.

Therefore, as shown in FIGS. 1 and 2, when a plurality of lens sheets are arranged in the plane direction, by using the optically ineffective portion through which light does not pass as the joint 3, it is theoretically possible to In this case, the joint 3 is not visible at all from the observation side. Furthermore, since the light source side can be made thicker, sufficient bending strength can be provided.

FIG. 5 is a side sectional view showing a part of a second embodiment of the Fresnel lens sheet joining structure according to the present invention.

In the second embodiment, the joint portion of the lens sheet 1.2 is
The part near the exit surface is joined by a thin first joint 6 perpendicular to the entrance surface, and the part near the entrance surface is thick and connected from the exit side to the entrance side. They are joined by a second joint portion 7 which gradually becomes thicker.

The first joint 6 has a length of 2 mm and a thickness of 0.1 to 0.
The width is about 3mm. This first joint 6 uses a highly viscous adhesive. The material for the first bonding part 6 is one that easily adheres to the base materials of the lens sheets 1 and 2, and can be selected as appropriate depending on the material of the base materials. Examples include acrylic adhesives and epoxy adhesives.

The second bonding portion 7 is polymerized and bonded using a liquid with low viscosity, and has a width of 2 mm on the light source side.

In this embodiment, since the first joining portion 6 is designed to have a certain length, the lens sheets 1.2 are butted against each other at their ends, and the lens sheets 1.2 can be easily joined.

In addition, by forming the first bonding part 6, the low viscosity liquid used for polymerization bonding will not leak onto the exit surface of the lens sheet (12) in which the minute lens part is formed, so that the lens sheet can be more securely bonded. 1.2 can be joined.

FIG. 6 is a side sectional view partially showing a third embodiment of the Fresnel lens sheet joining structure according to the present invention.

The third embodiment connects the lens sheet 1.2 to the first joint 6
and are joined by a second joint part 8.

The lens sheets 1, 2 and the first joint portion 6 are the same as in the second embodiment.

The second bonding portion 8 is formed on the incident surface side of the lens sheets 1 and 2, and has a prismatic shape with a rectangular cross section.

This second joint 8 may also be formed by polymeric adhesion.

In this embodiment, since the second joint portion 8 is formed into a prismatic shape, the lens sheet 1.2 can be easily brought into contact with the lens sheet 1.2, and the work of joining is simplified.

FIG. 7 is a side sectional view showing a fourth embodiment of the Fresnel lens sheet joining structure according to the present invention.

In the fourth embodiment, the lens sheet 1 is similar to the second embodiment.
．． 2 are joined by a first joining part 6 and a second joining part 7, and the second joining part 7 is a light-absorbing light-shielding part 9 that prevents the projection light from passing through.

The reason for this is that when a projection system is configured using a polygonal Fresnel lens sheet made by joining a plurality of lens sheets 12 and a plurality of projectors 4A, 4B, .
As shown in FIG. 7, stray lights 45 and 46 from the projectors 4A and 4B may enter the joint 7. This stray light 45, 46 is absorbed by the light shielding part 9,
This prevents stray light 45° 46 from interfering with other images and causing deterioration in image quality.

This light-shielding portion 9 is obtained by mixing black dye or the like into the sillage used when forming the first joint portion 7.

8 to 10 are side sectional views partially showing a modification of the fourth embodiment of the Fresnel lens sheet joining structure according to the present invention.

The light shielding section 9 that absorbs stray light is not limited to the above-mentioned example, and can have various forms.

For example, as shown in FIG. 8, after joining at the first joint 6 and then joining at the second joint 10A, the second joint 1
A light shielding portion 9A may be provided outside 0A.

Further, as shown in FIG. 9, the second joint 10 is divided into a joint 10B on the exit surface side and a joint 10C on the entrance surface side,
A light shielding portion 9B may be formed in between.

Furthermore, as shown in FIG. 10, a light shielding part 11 may be provided on the surface of the second joint part 10D by pasting a black tape or coating it with black paint. .

Various modifications can be made without being limited to the embodiments described above.

The lens sheets 1 to 1 are not limited to circular Fresnel lens sheets, but may be linear Fresnel lens sheets or the like.

1st. The second joint portion is not limited to the shape described above, but may have another shape as long as it is within the optically ineffective portion. For example, if fine irregularities are formed on the end face of the joining part, more reliable joining can be achieved.

(Initiative effect) As explained in detail above, according to claim (1), since the joining is performed at an optically ineffective part, the joining part cannot be seen from the viewing side and the image quality does not deteriorate. do not have.

Further, since this optically ineffective portion gradually becomes wider toward the light source side, if the lens sheet is bonded at this portion, sufficient bending strength can be provided even when the lens sheet is curved.

According to claim (2), the aforementioned optically ineffective portion can be easily found, and the structure of the joint end surface of the lens sheet can be easily determined.

According to claim (3), the first. Since the second bonding end surface is provided, the lens sheets can be easily and reliably bonded to each other.

According to claim (4), since stray light from the projection display device is absorbed by the light shielding portion, deterioration of image quality due to stray light can be prevented.

On the other hand, according to the projector of claim (5), since the joining is first performed at the joining end face perpendicular to the emission surface, and then the joining is performed at the thick joining part, joining can be easily and reliably performed.

[Brief explanation of drawings]

FIGS. 1 and 2 show a Fresnel lens seal according to the present invention.
- is a diagram showing a first embodiment of the joining structure of the first embodiment.
The figure is a perspective view, and FIG. 2 is a side view. FIG. 3 is a diagram schematically showing the optical system of a projection type image display device using a Fresnel lens sheet, and FIG.
FIG. 3 is a diagram showing the trajectory of light rays at the end of the lens sheet of the optical system shown in the figure. FIG. 5 is a side sectional view showing a part of a second embodiment of the Fresnel lens sheet joining structure according to the present invention. FIG. 6 is a side sectional view showing a part of a third embodiment of the Fresnel lens sheet joining structure according to the present invention. FIG. 7 is a side sectional view showing a fourth embodiment of the Fresnel lens sheet joining structure according to the present invention. FIGS. 8 to 10 are side sectional views showing modifications of the fourth embodiment of the Fresnel lens sheet joining structure according to the present invention. FIG. 11 is a perspective view showing a conventional Fresnel lens sheet bonding structure. 12... Lens sheet 3... Joint portion 4... Projector 5...
・Observation side focal point 6...Joint part 7.8.10...
Joint part 9.11...light absorption part

Claims (5)

[Claims] (1) In a joining structure of Fresnel lens sheets in which a plurality of Fresnel lens sheets are arranged in a plane direction and joined at the thick end portions of each Fresnel lens sheet in correspondence with a plurality of projectors, each of the Fresnel lens sheets is an optically ineffective portion outside the truncated pyramid formed by the locus of the light ray that is emitted from the extreme end on the emission side, among the light rays that are projected from the projector, transmitted through the Fresnel lens sheet, and emitted. A Fresnel lens sheet bonding structure characterized by bonding with. (2) The optically ineffective portion is defined by the trajectory of a ray of light incident at a distance l determined by the following formula inward in the surface direction from the foot of a perpendicular drawn from the end of the exit surface to the entrance surface. The Fresnel lens sheet joining structure according to claim 1, wherein the Fresnel lens sheet is also located on the outside. Note l=Ttanβ β=arcsin(sinα/n) where α; Incident angle β of light source light; Refraction angle n of light source light; Refractive index T of Fresnel lens sheet; Thickness of Fresnel lens sheet (3) Each of the Fresnel lens sheets has a first bonded end surface that is in contact with each Fresnel lens sheet on the exit surface side and perpendicular to the exit surface, and an entrance surface that is closer to the first bonded end surface. a second end surface formed in the optically ineffective portion on the side and provided parallel to or inclined to the first end surface;
The Fresnel lens sheet joining structure according to claim 1 or 2, characterized in that it has a joining end surface of. (4) A claim characterized in that the optically ineffective portion has a light-absorbing light-shielding portion formed on the entrance side surface of the ineffective portion, or in all or part of the ineffective portion. A joining structure of Fresnel lens sheets according to items (1) to (3). (5) In a method for joining a Fresnel lens sheet, in which a plurality of Fresnel lens sheets are arranged in a plane direction in correspondence with a plurality of projectors, and each Fresnel lens sheet is joined at a thickness portion of an end portion of the Fresnel lens sheet, each of the Fresnel lens sheets is an optically ineffective portion outside the truncated pyramid formed by the locus of the light ray that is emitted from the extreme end on the emission side, among the light rays that are projected from the projector, transmitted through the Fresnel lens sheet, and emitted. When joining, an adhesive is applied between the first joining end surfaces that are in contact with each Fresnel lens sheet on the exit surface side and perpendicular to the exit surface, and then the first Bonding by applying an adhesive between second bonding end surfaces that are closer to the incident surface than the bonding end surfaces and are formed within the optically ineffective portion and are provided parallel to or inclined to the first end surface. A method for joining Fresnel lens sheets, characterized by comprising: