JPH1083135A - Light diffuser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light diffusion characteristic which does not depend on an incident angle by laminating plural layers of thin film-like light diffusion layers forming volume type holograms varying in lattice vector from each other at every microregion within plane. SOLUTION: This light diffuser is constituted by laminating plural layers of the thin film-like light diffusion layers forming the volume type holograms 11a to 11e, 12a to 12c, 13a to 13d, 14a to 14c, 15a to 15e varying in the lattice vector from each other at every microregion within plane. The respective microholograms 11a to 11e, 12a to 12c, 13a to 13d, 14a to 14c, 15a to 15e are formed by periodically changing the refractive index of a transparent medium. The microholograms having the lattice vectors corresponding to all combinations of such incident directions and diffraction directions that the incident angle to the light diffuser 1 and the exit angle from the light diffuser 1 are both made smaller than predetermined angles are included in this light diffuser. Then, the incident light is emitted by diffusing in all directions within the range of the predetermined exit angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffuser for diffusing incident light and emitting the light.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional light diffuser. In FIG. 7, as a light diffuser for diffusing incident light 2 incident from a certain direction in a direction within a predetermined range, for example, a surface uneven shape that forms unevenness on one surface of a transparent plate-like medium is used. Light diffusers 6 are known. On the surface of the light diffusing body 6 with surface irregularities, minute regions 6a to 6g inclined in various directions are formed in an aggregated manner.

[0003] With such a configuration, the light diffuser 6 having an uneven surface is provided.
Incident light 2 (21a to 21d) is refracted by the uneven surfaces 6a to 6g and is deflected in different directions for each of the minute regions 6a to 6g of the surface, and the incident light 2 is determined in advance for the entire light diffuser 6. Can be diffused in various directions within the given range. FIG.
FIG. 3 shows diffused light 8 emitted from the uneven surface light diffuser 6 when the incident direction of the incident light 2 incident on the uneven surface light diffuser 6 is changed. That is, FIG. 8A shows incident light that is incident in a direction perpendicular to the other surface of the uneven surface type light diffuser 6 where there is no surface irregularity (hereinafter, this direction is referred to as an optical axis).
(21a-21d) are refracted by the uneven surfaces 6a-6g, and diffused light 81a-
81f is emitted. Similarly, FIG. 8B and FIG.
(C) shows incident light (22a to 22a) obliquely incident on the optical axis.
d) and (23a to 23d) are refracted by the uneven surfaces 6a to 6g, and diffused lights (82a to 82f) and (83a to 83f) having different emission angles are emitted.

[0004]

Since the light diffuser of the prior art deflects light using a refraction phenomenon, the refraction angle of the emitted light changes according to the incident angle of the incident light. I do. Accordingly, as shown in FIGS. 8A to 8C, when the incident direction to the light diffuser is different, the diffusion range of the diffused light emitted from the light diffuser changes accordingly. For this reason, there is a problem that the direction of the incident light from the light source to the light diffuser must be constant in applications requiring a constant diffusion direction, for example, when used in a backlight of a liquid crystal display.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to solve the above-mentioned problems, and to provide a diffusion characteristic in which the angular distribution of emitted diffused light does not depend on the incident direction of incident light. A light diffuser is provided.

[0006]

In order to achieve the above object, the present invention provides a thin film light diffusion layer for forming a volume hologram having a different lattice vector from each other for each minute area in a plane. Shall be laminated. With this configuration, it is possible to obtain a light diffusion characteristic that does not depend on the incident angle.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 are explanatory diagrams for explaining the structure and diffusion principle of a light diffuser as one embodiment of the present invention. FIG. 4 is an explanatory diagram for explaining the diffusion characteristics of the light diffuser. FIG. 5 is an explanatory view for explaining a method of manufacturing the light diffuser, FIG. 6 is an explanatory view for explaining the type of the light diffuser, and the same functional members corresponding to FIG. 7 and FIG. is there.

In FIG. 1, a light diffuser 1 includes volume holograms (11a to 11a) having different directions for each minute area in a plane.
e), (12a-11c), (13a-13d), (14a-14c), (15a-15e)
Are formed by laminating a plurality of thin-film light diffusion layers 11, 12, 13, 14, and 15 that form a thin film. Each micro hologram (11a ~ 11
e), (12a-11c), (13a-13d), (14a-14c), (15a-15e)
Are formed by periodically changing the refractive index of a transparent medium.

With this configuration, the volume hologram has the property of strongly diffracting light incident at a specific wavelength and direction, and the condition of the incident light is called the Bragg condition.
It is expressed by equation (1).

[0010]

Κd = κi + β (1) where κi and κd are the incident light vector and the diffracted light vector, respectively, and their directions are the incident light to the hologram and the diffracted light from the hologram, respectively. Equal to the direction of propagation,
Its magnitude is 2π / λ, where λ is the wavelength of the incident light.

Β is the lattice vector, the direction of which is equal to the normal to the hologram's isorefractive index surface, and its magnitude is 2π / p, where p is the length of one period of the refractive index change. Therefore, for each hologram, the combination of the incident direction and the diffraction direction satisfying the Bragg condition of the hologram is one.
Corresponds to one. Here, since the medium is transparent, the incident light incident on a certain micro hologram deviating from the Bragg condition is transmitted through the micro hologram with little diffraction. Many small volume holograms (11a-11e), (12a-11c), (13a-13d), (14a-14)
c), thin-film light diffusing layers 11, 12, 13, 14, comprising (15a to 15e)
Light 2 incident on the light diffuser 1 constituted by laminating a large number of 15
(In the illustrated example of FIG. 1, 21a to 21c) are each layer 1 of the light diffuser 1.
The light sequentially passes through 1,12,13,14,15 and is diffracted by the small holograms (14a, 11c, 15d) satisfying the Bragg condition. Diffracted light from a large number of micro holograms (14a, 11c, 15d) is emitted as a light obtained by diffusing the incident light 2 as a whole. The incident light 2 (22a to 22c in the example shown in FIG. 2) and the incident light 2 (23a to 23c in the example shown in FIG. 3) having different incident directions to the light diffuser 1 are separated into different micro holograms (13a, 15b, 11e), (1
1a, 13b, 15e).

The light diffuser 1 used here is a diffuser 1
A micro hologram having a lattice vector corresponding to any combination of the incident direction and the diffraction direction such that both the incident angle to and the exit angle from the diffuser 1 are smaller than a predetermined angle is included. Shall be. Accordingly, incident light having an incident angle smaller than the above-mentioned predetermined angle can be diffused and emitted in all directions within the range of the predetermined emission angle.

[0013]

Embodiment 1 FIGS. 1 to 3 show how the light diffuser 1 diffuses light having different incident angles. FIG. 1 shows a case where the incident light 2 is parallel to the optical axis. Since the incident light 21a does not satisfy the Bragg condition in the minute holograms 12a and 13a,
Transmit as it is. The transmitted incident light 21a is first diffracted by the minute hologram 14a while satisfying the Bragg condition, and becomes a diffused light 31a. Similarly, the incident lights 21b and 21c incident on other places are diffracted by the micro holograms 11c and 15d, respectively, satisfying the Bragg condition for the first time, and become diffused lights 31a and 31c, respectively.

FIG. 2 shows a case where the incident light 2 is incident at an angle to the optical axis. In this case as well, the incident light
22a, 22b, 22c are micro holograms 13a, 15b, 11e, respectively.
For the first time, the light is diffracted while satisfying the Bragg condition, and becomes diffused light 32a, 32b, 32c, respectively. Similarly, FIG. 3 shows a case where the incident light 2 is incident at another angle with respect to the optical axis. The incident lights 23a, 23b, 23c are
The diffusing action of such a light diffuser 1 which first satisfies the Bragg condition at a, 13b and 15e and becomes diffused light 33a, 33b and 33c, respectively, is macroscopically shown in FIG. . In FIG. 4A, when the incident light 21 is parallel to the optical axis, the incident light 21 is diffused light 41a to 41e around the optical axis.
Becomes Also, as shown in FIG. 4B, even when the incident light 22 has an angle with respect to the optical axis, the incident light 22 is diffused light 42a to 42e centered on the optical axis. Similarly, in the case of FIG. 4C, the incident light 23 becomes diffused lights 43a to 43e centered on the optical axis.

[0015]

Second Embodiment Next, referring to FIG. 5, the volume holograms (11a to 11e) for each layer constituting the light diffuser 1 shown in FIG.
A method of manufacturing a volume hologram corresponding to (12a to 11c), (13a to 13d), (14a to 14c), and (15a to 15e) will be described. In FIG. 5, a volume hologram (illustrated by interference fringes 7a to 71d) of each layer constituting the light diffuser 1 is a photosensitive hologram recording material 7 such as a photopolymer (hereinafter referred to as a photosensitive hologram recording for simplicity). The material can be manufactured by irradiating coherent diffused light 8a to 8h onto a photosensitive material and exposing the same. This exposure light (diffused light) 8a ~
As 8h, for example, as shown in FIG.
Coherent diffused lights 8a to 8h generated by passing 21d through the surface hologram 6 are used.

Two light beams (8a, 8b), (8c, 8d), (8e,
8f), (8g, 8h) form interference fringes 7a, 7b, 7
The spatial intensity distribution of light generated corresponding to c and 7d is recorded as a refractive index change in the photosensitive material as it is to form a hologram. Then, the combination of the incident light and the diffracted light that satisfies the Bragg condition of this hologram matches the combination of the two light beams that have exposed this hologram.

As described above, the description of FIGS. 1 to 5 has described the light diffuser 1 using a hologram that transmits, diffuses and emits the incident light 2 as a light diffusion layer. As shown in FIG. 6, the present invention can also be configured by using a hologram 9 that reflects and diffuses the incident light 2.

[0018]

As described above, according to the present invention, the light diffuser is formed by laminating a plurality of thin-film light diffuser layers for forming volume holograms having different lattice vectors from each other for each minute region in the plane. By doing so, if the angle of incidence on the light diffuser is within a predetermined range, it is possible to provide a diffusion characteristic in which the angle distribution of the diffused light emitted from the light diffuser does not depend on the incident direction of the incident light. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating the configuration and diffusion principle of a light diffuser as one embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating the configuration and diffusion principle of a light diffuser in which the angle of incident light is changed.

FIG. 3 is an explanatory diagram illustrating the configuration and diffusion principle of a light diffuser in which the angle of incident light is changed.

FIG. 4 is an explanatory diagram for explaining diffusion characteristics of a light diffuser.

FIG. 5 is an explanatory view illustrating a method for manufacturing a light diffuser.

FIG. 6 is an explanatory diagram illustrating types of light diffusers.

FIG. 7 is an explanatory diagram illustrating the configuration and diffusion principle of a light diffuser according to a conventional technique.

FIG. 8 is an explanatory diagram illustrating diffusion characteristics of a light diffuser according to a conventional technique.

[Explanation of symbols]

1 Light diffuser 11-15 Thin light diffuser 11a-11e, 12a-12c, 13a-13d, 14a-14c, 15a-15e
Hologram 1A, 1B End face 2, 21a-21c, 22a-22c, 23a-23c Incident light 3,31a-31c, 32a-32c, 33a-33c Outgoing light 41a-41e, 42a-42e, 43a-43e, 51a-51e , 8 diffused light 6 light diffuser with uneven surface 7 photosensitive material 7a ~ 7d interference fringe

Claims (1)

[Claims] 1. A light diffuser comprising a plurality of thin-film light diffusion layers for forming volume holograms having mutually different lattice vectors for each minute region in a plane.