JP5403453B1 - Fresnel lens sheet and lighting device - Google Patents

Abstract

Rainbow irregularities that occur when using a Fresnel lens are made inconspicuous.
A lighting device 1 according to the present invention includes a Fresnel lens 11 having a Fresnel lens 11, a light diffusion layer 20 for diffusing light, and a surface 10b of the Fresnel lens sheet 10 on which the Fresnel lens 11 is formed. Comprises a light source 2 disposed to face the opposite surface 10c. The Fresnel lens 11 includes a plurality of lens surfaces 12 and a rise surface 13 that connects two adjacent lens surfaces 12. The light source 2 has a light emitting surface 5a, diffused light is emitted from each position on the light emitting surface 5a, and a projection area S1 obtained by projecting the light emitting surface 5a onto a projection surface parallel to the sheet surface 10a of the Fresnel lens sheet 10 is: It is smaller than the projected area S2 obtained by projecting the Fresnel lens 11 on the projection surface.
[Selection] Figure 1

Description

  The present invention relates to a Fresnel lens sheet including a Fresnel lens and an illumination device including the Fresnel lens sheet.

  The Fresnel lens formed on the Fresnel lens sheet has a plurality of lens surfaces arranged in the arrangement direction, and is a fixed lens for incident light that forms a divergent light beam or a parallel light beam by a combination of the plurality of lens surfaces. Has an effect. A rise surface is formed between two adjacent lens surfaces. The rise surface is usually a surface that is not expected to have a lens effect on light. The rise surface typically extends parallel to the normal direction of the sheet surface of the Fresnel lens sheet (see Patent Documents 1 and 2).

JP 2013-24959 A JP 2008-33245 A

By the way, in many illuminating devices, the white light irradiated from the light source which has the comparatively small area light emission surface is condensed with a Fresnel lens. At this time, if the light emitting surface of the light source is sufficiently small compared to the size of the Fresnel lens, a certain amount of light incident on the Fresnel lens follows the optical path of the divergent light beam, and as a result, the Fresnel lens The light is focused on a certain area by the lens action. However, strictly speaking, diffused light is emitted from each position on the light emitting surface of the light source, and when viewed as a whole, the light source emits white diffused light from the light emitting surface. That is, the light from the light source includes light whose optical path cannot be corrected by the Fresnel lens. As a result of confirmation by the present inventors, in such an illuminating device, rainbow-like color unevenness (hereinafter simply referred to as “rainbow unevenness”) in which color dispersion is performed around an area where white light is condensed occurs. confirmed. Such rainbow unevenness is a very important issue when used for indoor lighting applications, particularly for stage lighting devices. In addition, if the occurrence of rainbow unevenness can be suppressed, the utilization efficiency of the light source light can be improved, and energy saving and CO ₂ reduction can be realized.

  When the inventor further investigated the cause of the rainbow unevenness, the following findings were obtained. FIG. 4 shows how light incident on the Fresnel lens is refracted by the lens surface. The Fresnel lens 511 shown in FIG. 4 is expected to exhibit the same lens action as a plano-convex lens by combining a plurality of lens surfaces 512. Accordingly, light L51, L52, L53, and L54 incident from a direction that can have a lens action that is expected to be applied to the Fresnel lens 511 or a direction that is in the vicinity thereof are corrected in a predetermined direction. The traveling direction of these lights is bent toward the side approaching the optical axis X by refraction at the lens surface 511. On the other hand, for the light L55 and L56 incident from a direction deviated to some extent from the direction in which the lens action of the Fresnel lens 511 can be expected, the lens action on the lens surface 512 is not effectively exhibited, and the light May enter the rise surface 513 adjacent to the incident lens surface 512. As a result of the optical path tracking performed by the present inventors, light that refracts on the lens surface 512 and unintentionally enters the rise surface 513 forms rainbow unevenness.

  The present invention is based on the findings of the present inventors as described above, and an object thereof is to make rainbow unevenness generated when a Fresnel lens is used inconspicuous.

The Fresnel lens sheet according to the present invention is a Fresnel lens sheet comprising a Fresnel lens including a plurality of lens surfaces and a rise surface that connects two adjacent lens surfaces,
A rise surface extending from the reference position where the lens surface having the smallest angle with respect to the sheet surface of the Fresnel lens sheet is positioned to the side away from the reference surface along the arrangement direction of the lens surface is relative to the sheet surface. If the rise angle formed by the lens is an acute angle, the rise angle of at least one rise surface is at least one other riser closer to the reference position along the arrangement direction of the lens surfaces than the one rise surface. It is smaller than the rise angle of the rise surface.

  In the Fresnel lens sheet according to the present invention, the rise angle of any one rise surface is that of another rise surface disposed closer to the reference position along the arrangement direction of the lens surfaces than the one rise surface. It may be below the rise angle.

  In the Fresnel lens sheet according to the present invention, the rise angle of each rise surface may be not less than 30 degrees and not more than 90 degrees.

  The Fresnel lens sheet according to the present invention may further include a light diffusion layer that diffuses light.

  In the Fresnel lens sheet according to the present invention, the rise angles of all the rise surfaces may be acute angles.

An illumination device according to the present invention includes a Fresnel lens sheet having any one of the above characteristics,
A light source disposed facing the surface of the Fresnel lens sheet opposite to the surface on which the Fresnel lens is formed, and
The light source has a light emitting surface, and diffused light is emitted from each position on the light emitting surface.

  In the illumination device according to the present invention, a projected area obtained by projecting the light emitting surface on a projection plane parallel to the sheet surface of the Fresnel lens sheet may be smaller than a projected area obtained by projecting the Fresnel lens on the projected surface.

A second lighting device according to the present invention includes a Fresnel lens sheet including a plurality of lens surfaces, a rise surface that connects two adjacent lens surfaces, and a light diffusion layer that diffuses light. ,
A light source disposed facing the surface of the Fresnel lens sheet opposite to the surface on which the Fresnel lens is formed, and
The light source has a light emitting surface, diffused light is emitted from each position on the light emitting surface,
A projected area obtained by projecting the light emitting surface on a projection surface parallel to the sheet surface of the Fresnel lens sheet is smaller than a projected area obtained by projecting the Fresnel lens on the projected surface.

  In the second lighting device according to the present invention, the light diffusion layer may include a main portion and a diffusion component that diffuses the light dispersed in the main portion.

  According to the present invention, rainbow unevenness that occurs when using a Fresnel lens can be made inconspicuous.

FIG. 1 is a schematic view showing an illumination device including a Fresnel lens sheet according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the Fresnel lens sheet of the illumination device shown in FIG. FIG. 3 is a schematic cross-sectional view showing a region A shown in FIG. 1 in an enlarged manner. FIG. 4 is a schematic cross-sectional view showing how light incident on a conventional Fresnel lens is refracted by the lens surface.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale, the vertical / horizontal dimension ratio, and the like are appropriately changed and exaggerated from those of the actual product. 1 and 2 are diagrams for explaining an embodiment according to the present invention. Among these, FIG. 1 is a schematic view showing a lighting device provided with the Fresnel lens sheet in one embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing the Fresnel lens sheet of the lighting device shown in FIG. .

  In the present specification, the terms “sheet”, “film”, and “plate” are not distinguished from each other only based on the difference in names. Therefore, for example, the “plate” is a concept including a member that can also be called a sheet or a film.

  As shown in FIG. 1, the lighting device 1 is disposed so as to face a Fresnel lens sheet 10 including a Fresnel lens 11 and a surface 10 c opposite to the surface 10 b of the Fresnel lens sheet 10 on which the Fresnel lens 11 is formed. The light source 2 is provided. The light source 2 has a light emitting surface 5a and emits diffused light from each position on the light emitting surface 5a.

  As shown in FIG. 1, the light emitted from the light source 2 is collected near the focal region by the lens action of the Fresnel lens 11, and then spreads away from the focal point. Hereinafter, the Fresnel lens sheet 10 including the Fresnel lens 11 that exerts such an optical action will be described. In the following description, an example in which the Fresnel lens 11 of the Fresnel lens sheet 10 is a circular Fresnel lens will be described. However, the present invention is not limited to this example, and the Fresnel lens 11 is a linear Fresnel lens. Also good.

  As shown in FIG. 2, the Fresnel lens 11 of the Fresnel lens sheet 10 includes a plurality of lens surfaces 12 and a rise surface 13 that connects two adjacent lens surfaces 12.

  The illustrated Fresnel lens 11 is expected to exhibit the same lens action as a convex lens by combining a plurality of lens surfaces 12. Each lens surface 12 has an annular shape, and a plurality of lens surfaces 12 are arranged concentrically. That is, as shown in FIG. 2, in an arbitrary cross section that is orthogonal to the sheet surface 10a of the Fresnel lens sheet 10 and passes a reference position T described later, the plurality of lens surfaces 12 are arranged in order along the arrangement direction d1. Yes.

  In this specification, “sheet surface (film surface, plate surface)” is the same as the planar direction of the target sheet-like member when the target sheet-like member is viewed as a whole and globally. It refers to the surface to be used. In the present embodiment, the sheet surface 10a of the Fresnel lens sheet 10 and the surface 10c on the light source 2 side of the Fresnel lens sheet 10 are parallel to each other.

  As shown in FIG. 2, the angle formed by the lens surface 12 and the sheet surface 10 a of the Fresnel lens sheet 10 is a lens angle and is denoted by α. Here, “the angle between the lens surface 12 and the sheet surface 10 a of the Fresnel lens sheet 10” means that both end portions of the lens surface 12 are in a cross section perpendicular to the sheet surface 10 a of the Fresnel lens sheet 10 and along the arrangement direction P. An angle formed by the connecting straight line and the sheet surface 10a. Further, the position of the lens surface 12 where the size (absolute value) of the lens angle α is the smallest is set as the reference position T. In a Fresnel lens having a typical focal point, the reference position T is located on a straight line connecting a pair of focal points located on both sides of the Fresnel lens 11.

  In the Fresnel lens 11, the lens angle α tends to be larger on the lens surface 12 that is arranged further away from the reference position T along the arrangement direction d1. In the present embodiment, the lens angle α of any one lens surface 12 is the lens of another lens surface 12 arranged closer to the reference position T along the arrangement direction d1 than the one lens surface 12. More than the angle α. For this reason, the lens angle α of the lens surface 12 arranged farthest from the reference position T along the arrangement direction d1 is the largest.

  In addition, when the dimension of each lens surface 12 in the normal direction nd of the Fresnel lens sheet 10 is a height h, the lens surface 12 arranged further apart from the reference position T along the arrangement direction d1 is The height h tends to increase. In the present embodiment, the height h of any one lens surface 12 is higher than the other lens surfaces 12 arranged closer to the reference position T along the arrangement direction d1 than the one lens surface 12. More than h. Therefore, the height h of the lens surface 12a located at the reference position T is the smallest, and the height h of the lens surface 12 that is arranged farthest from the reference position T along the arrangement direction d1 is the largest. .

  Further, as shown in FIG. 2, a rise surface 13 is disposed between two adjacent lens surfaces 12. The rise surface 13 is usually a surface that is not expected to have a light lens action.

  Here, an angle formed by the rise surface 13 with the sheet surface 10a of the Fresnel lens sheet 10 is defined as a rise angle θ. Here, “the angle formed by the rise surface 13 and the sheet surface 10a of the Fresnel lens sheet 10” means that both end portions of the rise surface 13 are defined in a cross section perpendicular to the sheet surface 10a of the Fresnel lens sheet 10 and along the arrangement direction P. An angle formed by the connecting straight line and the sheet surface 10a. The rise surface 13 extending from the reference position T along the arrangement direction d1 of the lens surface 12 toward the side away from the reference position T has an acute angle, more specifically, 0, which is a rise angle θ formed with respect to the sheet surface 10a. Defined as an angle with an angle greater than 90 ° and less than 90 °. Furthermore, in other words, as shown in FIG. 2, the end 12b1 of the lens surface 12b on the side close to the reference position T and the end 12b1 on the side away from the reference position T is The rise angle θ of the rise surface 13 that connects the two lens surfaces 12b and 12c when it is closer to the reference position T than the end portion 12c1 on the side close to the reference position T is defined as an acute angle. Note that the rise angle θ may be referred to as a rise surface angle.

  In the present embodiment, the rise angle θ of at least one rise surface 13 is at least one other arranged closer to the reference position T along the arrangement direction d1 of the lens surface 12 than the one rise surface 13. The relationship that it is smaller than the rise angle θ of the rise surface 13 is satisfied.

  Furthermore, in the present embodiment, the rise angle θ of any one rise surface 13 is other rise surface 13 arranged closer to the reference position T along the arrangement direction d1 than the one rise surface 13. Is less than the rise angle θ. Furthermore, the rise angle θ of any one rise surface 13 is greater than the rise angle θ of another rise surface 13 disposed closer to the reference position T along the arrangement direction d1 than the one rise surface 13. It is getting smaller. Therefore, the rise angle θ of the rise surface 13 arranged closest to the reference position T is the largest, and the rise angle of the rise surface 13 arranged farthest from the reference position T along the arrangement direction d1. θ is the smallest.

  As an example, the rise angle θ of each rise surface 13 may be not less than 30 degrees and not more than 90 degrees.

  In such a Fresnel lens 11, the pitch P of the lens surface 12 is a geometrical relationship between the height h of the lens surface 12, the lens angle α of the lens surface 12, and the rise angle θ of the rise surface 13. Determined based on relationship.

  Further, the Fresnel lens sheet 10 of the present embodiment further includes a light diffusion layer 20 on the light source 2 side than the Fresnel lens 11. The surface of the light diffusion layer 20 on the light source 2 side defines the surface of the Fresnel lens sheet 10 on the light source 2 side. The light diffusion layer 20 has a light diffusion function for diffusing light incident on the Fresnel lens sheet 10 from the light source 2. For example, the light diffusion layer 20 may include a main part 21 and a diffusion component 22 that diffuses the light dispersed in the main part 21. The diffusion component 22 here is a component that can act on the light traveling in the light diffusion layer 20 by changing the path direction of the light by reflection or refraction. Such a light diffusing function (light scattering function) of the diffusing component 22 can be achieved, for example, by configuring the diffusing component 22 from a material having a refractive index different from that of the material forming the main portion 21 of the light diffusing layer 20, or It can be applied by constructing the diffusing component 22 from a material that can have a reflective effect on the light. Examples of the diffusion component 22 having a refractive index different from that of the material forming the main portion 21 include a metal compound, a porous substance containing a gas, and a simple bubble.

  Alternatively, as another example, the light diffusion layer 20 may include fine irregularities formed on the surface 10c on the light source 2 side of the Fresnel lens sheet 10 by embossing or the like.

  Next, the light source 2 that irradiates the Fresnel lens sheet 10 with diffused light will be described. The light source 2 of the present embodiment is configured as a so-called chip-on-board type LED light source. Specifically, as shown in FIG. 1, the light source 2 includes, for example, an aluminum substrate 3 disposed to face the Fresnel lens sheet 10, and a plurality of LED chips 4 arranged on the substrate 3. And a cover 5 that covers the plurality of LED chips 4.

  The cover 5 of the present embodiment forms the aforementioned light emitting surface 5a located between the Fresnel lens sheet 10 and the LED chip 4, and is connected to the periphery of the light emitting surface 5a to form a plurality of LED chips 4 in an annular shape. A surrounding side surface 5b is also formed. The light emitting surface 5a faces the Fresnel lens sheet 10, and in the present embodiment, the reference position T and the center of the light emitting surface 5a face each other. In the illustrated example, the light emitting surface 5 a has a circular shape corresponding to the shape of the Fresnel lens 11.

  The light emitting surface 5a has a light diffusing function for emitting light toward the Fresnel lens sheet 10 while diffusing light from the LED chip 4. This light diffusion function may be an isotropic diffusion function or an anisotropic diffusion function. In the present embodiment, an isotropic diffusion function of the light emitting surface 5a is realized by dispersing a diffusion component that diffuses light in the cover 5.

  With such a configuration, light from each LED chip 4 enters the light emitting surface 5a, and diffused light is emitted from each position on the light emitting surface 5a.

  Here, as shown in FIG. 1, the projection area S1 obtained by projecting the light emitting surface 5a on the projection plane parallel to the sheet surface 10a of the Fresnel lens sheet 10 is greater than the projection area S2 obtained by projecting the Fresnel lens 11 on the projection plane. Is also getting smaller. For this reason, in order to make light incident on each lens surface 12 of the Fresnel lens 11, diffused light is emitted from each position of the light emitting surface 5 a, and when viewed as a whole, divergent light is irradiated from the light source 2 toward the Fresnel lens 11. It has come to be. In the illustrated example, the projection surface is the surface 10c of the Fresnel lens sheet 10 on the light source 2 side.

  Next, the operation of the present embodiment configured as described above will be described with reference to FIG.

  As shown in FIG. 1, in the light source 2, light from each LED chip 4 enters the light emitting surface 5a, and diffused light L is emitted toward the Fresnel lens sheet 10 from each position on the light emitting surface 5a. Overall, the Fresnel lens sheet 10 having the large projected area S2 is irradiated with the divergent light from the light source 25 having the small projected area S1. The light L incident on the Fresnel lens sheet 10 approximately following the diverging light path is collected near the focal region by the lens action of the Fresnel lens 11, and then spreads away from the focal point to illuminate the illumination region R. . In addition, about the illumination area | region R, you may set the distance from a focus timely according to the range to illuminate.

  Here, with reference to FIG. 3, consider the light incident on each lens surface 12 of the Fresnel lens 11. FIG. 3 is an enlarged view showing the lens surface 12 of the Fresnel lens 11. As described above, the reference position T and the center of the light emitting surface 5a face each other, and diffused light is emitted from each position on the light emitting surface 5a. Therefore, the light traveling from one position on the light emitting surface 5a toward one lens surface 12 has a luminance peak in the direction connecting the lens surface 12 and the center of the light emitting surface 5a, and the direction in which the luminance peak is obtained. The luminance in this direction decreases as the angle is inclined. The light L1 in the peak direction that is generally incident from the direction connecting the lens surface 12 and the center of the light emitting surface 5a is refracted by the lens surface 12 and travels toward the vicinity of the light collection region. Therefore, most of the light incident on the lens surface 12 becomes light that travels in a desired direction due to the lens action of the Fresnel lens 11.

  On the other hand, since diffused light is emitted from each position on the light emitting surface 5a, each lens surface 12 has light L13 and L14 that are greatly inclined with respect to the direction in which the luminance peak of light incident on the lens surface 12 is obtained. Is also incident. Further, even if the light is incident on the Fresnel lens sheet 10 along the direction in which the luminance peak is obtained or in the vicinity thereof, the path direction is set by the light diffusion layer 20 disposed on the light source 2 side of the lens surface 12. A part of the incident light is incident on each lens surface 12 from a direction that is largely inclined with respect to the direction in which the luminance peak is obtained.

  As shown in FIG. 3, the light L13, L14 traveling in a direction greatly inclined with respect to the direction in which the luminance peak is obtained, in other words, in a direction in which the light is corrected toward the focal region by refraction at the lens surface 12. On the other hand, the light L13, L14 traveling in a direction greatly inclined does not have an effective lens action from the lens surface. Therefore, the lights L13 and L14 are refracted to the side away from the reference position T on the lens surface 12 and approach the rise surface 13 located on the side away from the reference surface T. As described above with reference to FIG. 4, such light causes rainbow unevenness and decreases light use efficiency.

  On the other hand, in the present embodiment, the rise angle θ of the rise surface 13 is lower than the rise angle θ of other rise surfaces 13 arranged closer to the reference position T along the arrangement direction d1 than the rise surface 13. It has become. That is, unlike a typical conventional Fresnel lens, all the rise surfaces 13 do not extend parallel to the normal direction nd. All the rise surfaces 13 are separated from the reference position T in parallel with the normal direction nd to the sheet surface 10a of the Fresnel lens sheet 10 or with respect to the normal direction nd to the sheet surface 10a of the Fresnel lens sheet 10. So as to extend. In other words, the rise angle θ is 90 ° or less. In addition, the rise angle θ of the rise surface 13 becomes smaller at a position away from the reference position T where the angle formed by the luminance peak of the incident light with respect to the normal direction nd is large. Therefore, if the lens action on the lens surface 12 is not sufficiently exhibited, the traveling direction after refraction on the lens surface 12 is inclined to the side away from the reference position T with respect to the normal direction nd. Even if it is L13 and L14, it can avoid effectively entering into the rise surface 13. FIG. As a result, the lights L13 and L14 can then travel to the illumination region R.

  That is, the light L13 and L14 incident on the Fresnel lens 11 from the direction greatly inclined with respect to the direction in which the lens action planned by the Fresnel lens 11 is exerted are incident on the rise surface 13 and further refracted by another lens surface 12. This makes it easier for light to be focused on the desired illumination region R than the conventional Fresnel lens 511 shown in FIG. 4 in which each rise surface 513 extends parallel to the normal direction nd. That is, the light use efficiency is improved as compared with the conventional Fresnel lens 511 shown in FIG. Thereby, the fall of the condensing efficiency of a lens can be improved and the rainbow nonuniformity formed around the illumination area | region R can be made inconspicuous.

  As described above, according to the present embodiment, the rise angle θ of at least one rise surface 13 is closer to the reference position T along the arrangement direction d1 of the lens surface 12 than the one rise surface 13. It is smaller than the rise angle θ of at least one other rise surface 13 arranged. For this reason, the light collection efficiency of the Fresnel lens can be improved, and the occurrence of rainbow unevenness can be suppressed.

  In addition, according to the present embodiment, the rise angle θ of any one rise surface 13 is set to be different from other rises arranged closer to the reference position T along the arrangement direction d1 than the one rise surface 13. It is below the rise angle θ of the surface 13. In this case, the light L13 and L14 that are greatly inclined with respect to the direction in which the lens action scheduled by the Fresnel lens 11 is exerted are more unlikely to enter the rise surface 13 and be further refracted by another lens surface 12. Therefore, it becomes easier for the light to be condensed on the desired illumination region R than the conventional Fresnel lens. That is, the light utilization efficiency is improved as compared with the conventional Fresnel lens. Thereby, the fall of the condensing efficiency of a lens can be improved and the rainbow nonuniformity formed around the illumination area | region R can be made further inconspicuous.

  Further, according to the present embodiment, the rise angle θ of each rise surface 13 is not less than 30 degrees and not more than 90 degrees. When the rise angle θ is 30 degrees or more, the Fresnel lens 11 can be realized without greatly changing the arrangement of the lens surfaces 12. For this reason, the rainbow nonuniformity formed around the illumination region R can be made inconspicuous while the condensing function of the lens surface 12 is maintained.

  Further, the Fresnel lens sheet 10 of the present embodiment further includes a light diffusion layer 20 that diffuses light. Since the light diffusion layer 20 can change the path direction of a part of the light emitted from the light emitting surface 5a, the light having various wavelengths can reach the illumination region R. For this reason, light having various wavelengths is mixed around the illumination region R, and rainbow unevenness can be made inconspicuous. In addition, a part of the light whose path direction is changed by the light diffusion layer 20 enters the lens surface 12 with a large inclination with respect to the direction in which the luminance peak is obtained. According to the present embodiment, the light L13 and L14 that are largely inclined with respect to the direction in which the luminance peak is obtained and enter the lens surface 12 are further refracted by another lens surface 12 after entering the rise surface 13. Therefore, even such light L13 and L14 can be directed to the desired illumination region R to some extent. As a result, even if the light diffusion layer 20 is further provided, the rainbow unevenness can be made inconspicuous without greatly reducing the light collection efficiency of the lens.

  Further, according to the present embodiment, the projection area S1 obtained by projecting the light emitting surface 5a onto the projection plane 10c orthogonal to the normal direction nd of the Fresnel lens sheet 10 is the projection area S2 obtained by projecting the Fresnel lens 11 onto the projection plane 10c. Smaller than. In this case, since divergent light is irradiated from the light emitting surface 5a toward the Fresnel lens 11, light L13 and L14 that are greatly inclined with respect to the direction in which the luminance peak is obtained are likely to enter each lens surface 12. . When a large amount of light L13, L14 that is greatly inclined with respect to the direction in which the luminance peak is obtained is incident on each lens surface 12, the condensing efficiency of the lens is reduced, and rainbow unevenness formed around the desired illumination region R is reduced. Easy to stand out. Therefore, the Fresnel lens sheet 10 and the illumination device 1 according to the present embodiment improve the decrease in the light collection efficiency of the lens in such a manner, and make the rainbow unevenness formed around the illumination region R inconspicuous. The function of, can be effectively exhibited.

  Moreover, the illuminating device 1 of this Embodiment is the Fresnel lens 11 containing the several lens surface 12, the rise surface 13 which connects the two adjacent lens surfaces 12, and the light-diffusion layer 20 which diffuses light. , And a light source 2 disposed to face a surface 10c opposite to the surface 10b on which the Fresnel lens 11 of the Fresnel lens sheet 10 is formed. 5a, the diffused light is emitted from each position on the light emitting surface 5a, and the projection area S1 obtained by projecting the light emitting surface 5a onto the projection surface parallel to the sheet surface 10a of the Fresnel lens sheet 10 is the Fresnel lens 11 on the projection surface. Is smaller than the projected area S2 projected. In this case, since divergent light is irradiated from the light emitting surface 5a toward the Fresnel lens 11, light L13 and L14 that are greatly inclined with respect to the direction in which the luminance peak is obtained are likely to enter each lens surface 12. . When a large amount of light L13, L14 that is greatly inclined with respect to the direction in which the luminance peak is obtained is incident on each lens surface 12, rainbow unevenness formed around the desired illumination region R is easily noticeable. In this respect, according to the illumination device 1 of the present embodiment, the light diffusion layer 20 can change the course direction of a part of the light emitted from the light emitting surface 5a. It is possible to reach light having a wavelength of. For this reason, light having various wavelengths is mixed around the illumination region R, and rainbow unevenness can be made inconspicuous.

DESCRIPTION OF SYMBOLS 1 Illuminating device 2 Light source 5a Light emission surface 10 Fresnel lens sheet 10a Sheet surface 11 Fresnel lens 12 Lens surface 13 Rise surface 20 Light diffusion layer d1 Arrangement direction θ Rise angle θ
α Lens angle S1 Projection area S2 Projection area T Reference position X Optical axis

Claims (7)

A Fresnel lens sheet comprising a Fresnel lens including a plurality of lens surfaces and a rise surface that connects two adjacent lens surfaces, the lens having the smallest angle with respect to the sheet surface of the Fresnel lens sheet When the rise surface extending from the reference position where the surface is located to the side away from the reference position along the lens surface arrangement direction is an acute angle with respect to the sheet surface, the rise angle of at least one rise surface Is a Fresnel lens sheet that is smaller than the rise angle of at least one other rise surface disposed closer to the reference position along the arrangement direction of the lens surfaces than the one rise surface ,
A light source disposed facing the surface of the Fresnel lens sheet opposite to the surface on which the Fresnel lens is formed, and
The light source has a light emitting surface, diffused light is emitted from each position on the light emitting surface,
Part of the light incident on the Fresnel lens sheet from the light emitting surface and transmitted through the lens surface of the Fresnel lens sheet approaches the rise surface located on the side away from the reference position of the incident lens surface. Lighting equipment that goes on . 2. The illumination according to claim 1, wherein a rise angle of the rise surface where a part of light incident on the Fresnel lens sheet from the light emitting surface and transmitted through the lens surface of the Fresnel lens sheet approaches is an acute angle. apparatus. Rise angle of any one of the rise surface is less rise angle other rise surface than the one rise surface disposed in proximity to the reference position along the arrangement direction of the lens surface, claim The lighting device according to 1 or 2 . The lighting device according to any one of claims 1 to 3 , wherein a rise angle of each rise surface is not less than 30 degrees and not more than 90 degrees. The illumination device according to claim 1 , further comprising a light diffusion layer that diffuses light. The illuminating device according to any one of claims 1 to 5 , wherein all the rise surfaces have acute angles. Projection area obtained by projecting the light emitting surface parallel projection plane on the sheet surface of the Fresnel lens sheet is smaller than the projection area obtained by projecting the Fresnel lens to the projection plane, any one of the preceding claims the illumination device according to.

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