JP2013092717A - Fresnel lens and luminaire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fresnel lens which prevents a sudden illuminance change in the center portion and also prevents a ring-shaped pattern from occurring around the center portion.SOLUTION: A fresnel lens 1 has an arcuate portion R at either one or both of the top portion of a protrusion 12 or the deepest portion of a recess 13, a blast surface 11 (surface scattering part) as a scattering part for scattering incident light and/or a lens body 10 (volume scattering part) formed of a light scattering light guiding body.

Description

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

  In the case of illumination that requires intense illumination in a relatively narrow light irradiation range, such as downlights or spotlights, a Fresnel lens is used on the emission side of the light source in order to concentrate the light in the narrow light irradiation range. Those are known (for example, see Patent Document 1).

  A general conventional Fresnel lens obtained by flattening a Fresnel lens as disclosed in Patent Document 1 will be described with reference to FIGS. FIG. 12 illustrates a light source 100 that is, for example, an LED (Light Emitting Diode), a Fresnel lens 101 having a Fresnel lens surface formed on the side facing the light source 100, incident light 102 on the Fresnel lens 101, and the Fresnel lens 101. It is a figure which shows the loss light 104 used as the light which is refracted | refracted to the periphery and becomes the light which is not condensed among the emitted light from the center. FIG. 13 is a diagram illustrating a state in which the Fresnel lens 101 in FIG. 12 is viewed from the front side on which light is incident, and is a diagram illustrating the light source 100 with a two-dot chain line (virtual line). FIG. 14 is an enlarged view showing the Fresnel lens 101 in FIG. 12 and also shows the states of the incident light 102, the central light 103, and the loss light 104. In addition, the semicircle of the light source 100 shown in FIG. 12 shows the irradiation range of the light source 100 typically.

  As shown in FIG. 14, the Fresnel lens 101 has a saw-toothed Fresnel lens surface, and a gentle slope 105 that functions as a normal lens surface and a steep slope 106 that generates lost light are alternately and alternately arranged. The state of the gentle slope 105 and the steep slope 106 is also shown enlarged on the upper right of FIG. As a result, the convex portions 107 and the concave portions 108 are alternately formed. Incident light 102 from the light source 100 is refracted or reflected by the gentle slope 105 and the steep slope 106 of the Fresnel lens 101 and passes through the Fresnel lens. In FIGS. 12 and 14, the reflected light is not shown.

  FIG. 15 is a projection pattern of the center light 103 and the loss light 104 shown in FIGS. 12 and 14, and shows a pattern projected on the projection plane parallel to the Fresnel lens 101 and separated by a predetermined distance. The upper square range in FIG. 15 represents a range of 50 mm (millimeters) left and right and up and down with respect to light emitted vertically from the center of the light source 100, and the lower square range in FIG. 15 represents the center of the light source 100. A range of 250 mm is shown on the left, right, and top and bottom with the light emitted vertically from the center. In FIG. 15, the upper and lower scale displays are omitted. The upper diagram in FIG. 15 shows the projection pattern of the central light 103, and the lower diagram shows the projection pattern of the central light 103 and the loss light 104. In the upper diagram of FIG. 15, a region 110 is a portion with the highest illuminance. Next, the illuminance decreases sequentially from the regions 111 to 114. Further, in the lower diagram of FIG. 15, a region 115 is a projection portion of the central light 103 in the upper diagram of FIG. 15. In the lower diagram of FIG. 15, among the regions 116, 117, 118, 119, and 120, the regions 117 and 119 are portions with relatively high illuminance.

  The illuminance distribution of the central light 103 in the upper diagram of FIG. 15 is shown in the lower diagram of FIG. As shown in FIG. 16, it can be seen that the region 110 occupies most of the projected area of the central light 103. The illuminance distribution of the central light 103 and the lost light 104 in the lower diagram of FIG. 15 is shown in the lower diagram of FIG. The vertical axis in the lower part of FIG. 16 is Lux, which is a unit of illuminance. As shown in FIG. 17, since the illuminance of the regions 116, 118, and 120 is extremely low, particularly the illuminance of the regions 118 and 120 is low, while the illuminance of the regions 117 and 119 is high, the lost light 104 is It can be seen that a ring-shaped pattern is formed around the central light 103.

JP 2010-262187 A

  As described above, in the projection pattern of the central light 103, the area of the region 110 having the highest illuminance occupies most of the area, and the illuminance rapidly decreases in the narrow regions 111 to 113 around the area 110, and the region 114 is compared with the region 110. Then it becomes almost zero. Such a change in illuminance is abrupt and unnatural and uncomfortable for human eyes. Further, there is a problem that the ring-shaped pattern due to the lost light 104 generated around the central light 103, that is, the regions 117 and 119, appear as ring spots.

  The present invention has been performed under such a background, and there is no sudden change in illuminance in the portion corresponding to the central light, and no ring-shaped pattern is generated around the central portion where the illuminance is high. An object of the present invention is to provide a Fresnel lens that can be configured as described above.

  One aspect of the present invention is a viewpoint as a Fresnel lens. The Fresnel lens of the present invention is a Fresnel lens in which concave portions and convex portions are alternately and repeatedly arranged on one side of a lens body that transmits light, and either or both of the top of the convex portion or the deepest portion of the concave portion. In addition to the arc-shaped portion, the light-scattering portion has a scattering portion that scatters incident light.

  For example, the scattering portion of the Fresnel lens can have one or both of a surface scattering portion and a volume scattering portion. For example, the surface scattering portion has a surface that does not have the convex portion and the concave portion of the lens body, or a surface that has the convex portion and the concave portion of the lens body, or has a convex portion and a concave portion of the lens body. It is formed by blasting both the non-side surface and the surface of the lens body having the convex and concave portions. Further, for example, the volume scattering portion is formed such that the lens body is a light scattering light guide in which light scattering particles are contained in a transparent resin.

  Another aspect of the present invention is a viewpoint as a lighting device. The illuminating device of this invention has the Fresnel lens of this invention, and the light source arrange | positioned facing the single side | surface side of a Fresnel lens.

  For example, in the illuminating device of the present invention, it is preferable that the light source is provided on a side facing a Fresnel surface in which convex portions and concave portions are alternately arranged.

  According to the present invention, there is no abrupt illuminance change of the central light, and a ring-shaped pattern due to lost light can be prevented from occurring.

It is a figure which shows the Fresnel lens of embodiment of this invention with a light source, incident light, center light, and loss light. It is a figure which shows the state which looked at the Fresnel lens of FIG. 1 from the front in the light incident side, and is a figure which shows a light source with a virtual line (two-dot chain line). FIG. 2 is a partially enlarged view of the Fresnel lens of FIG. 1 and also shows an optical path of central light and loss light generated from a part of incident light. The figure which shows the projection pattern of the light which passed the Fresnel lens of FIG. 2, an upper stage shows the part corresponded to the conventional center light, its vicinity, and the lower stage shows the part corresponding to the conventional center light and loss light, and its periphery It is. It is a figure which shows the projection pattern shown in the upper stage of FIG. 4, and its illumination distribution. It is a figure which shows the projection pattern shown in the lower stage of FIG. 4, and its illumination distribution. FIG. 7 is a diagram showing a projection pattern of Comparative Example 1 in which the upper part shows a portion corresponding to conventional central light and its vicinity, and the lower part shows a portion corresponding to conventional central light and lost light and its surroundings. It is a figure which shows the projection pattern shown in the lower stage of FIG. 7, and its illumination distribution. FIG. 7 is a diagram showing a projection pattern of Comparative Example 2 in which the upper part shows a portion corresponding to conventional central light and its vicinity, and the lower part shows a portion corresponding to conventional central light and lost light and its surroundings. It is a figure which shows the projection pattern shown in the lower stage, and its illumination distribution. It is a figure which shows the light distribution of embodiment of this invention, the comparative example 1, the comparative example 2, and the Fresnel lens of a prior art example. It is a figure which shows the Fresnel lens of a prior art example with a light source, incident light, center light, and loss light. It is a figure which shows the state which looked at the Fresnel lens of FIG. 12 from the front in the light incident side, and is a figure which shows a light source with a virtual line (two-dot chain line). FIG. 13 is an enlarged view of a part of the Fresnel lens of FIG. 12 and an enlarged view of the optical path of central light and loss light generated from a part of incident light. It is a figure which shows the projection pattern of the light which permeate | transmitted the Fresnel lens of FIG. 12, an upper stage shows center light and its vicinity, and a lower stage shows center light, loss light, and its periphery. It is a figure which shows the projection pattern shown in the upper stage of FIG. 15, and its illumination intensity distribution. It is a figure which shows the projection pattern shown in the lower stage of FIG. 15, and its illumination intensity distribution.

  A Fresnel lens 1 according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the Fresnel lens 1 is disposed so that the light source 2 at a distance L away from the Fresnel lens surface. In this lighting device, the distance L is about 20 mm (millimeters). The light source 2 is an LED 7, and its irradiation range is schematically shown as a semicircle 8. In this illuminating device, incident light 3 which is a part of light emitted from the light source 2 is center light 4 refracted by the Fresnel lens 1, loss light 5 refracted by the Fresnel lens 1, and outgoing light 18, which will be described later. 19 is emitted from the Fresnel lens 1. As shown in FIG. 2, when the Fresnel lens 1 is viewed from the front side where light enters, a plurality of large and small concentric circles 6 are formed. The concentric circle 6 is formed with a concentric circle 6 a formed by a convex portion 12 and a concentric circle 6 b formed by a concave portion 13. As shown in FIGS. 1 and 2, the Fresnel lens 1 and the light source 2 are arranged such that the light source 2 is perpendicular to the Fresnel lens surface of the Fresnel lens 1 and at a distance L from the center of the Fresnel lens surface. It is arranged to come.

  As shown in FIGS. 1 and 3, the Fresnel lens 1 generates a lens body 10, a rough blast surface 11, a convex portion 12, a concave portion 13, a gentle slope 14 that functions as a normal lens surface, and loss light. A steep slope 15 is provided. The lens body 10 forming the Fresnel lens 1 is made of, for example, a transparent resin. On the side of the lens body 10 facing the light source 2, convex portions 12 and concave portions 13 are alternately and repeatedly arranged around the center of the Fresnel lens surface. Further, the gentle slope 14 and the steep slope 15 connected by the convex portion 12 and the concave portion 13 are also arranged so as to be alternately repeated. The surface of the lens body 10 opposite to the light source 2 is a blast surface 11 having a rough surface. Further, the top of the convex portion 12 and the deepest portion of the concave portion 13 each have an arc shape. Hereinafter, this is referred to as an arcuate portion R.

  As shown in FIG. 3, the Fresnel lens surface of the Fresnel lens 1 has a gentle slope 14 that gently falls from the uppermost portion (that is, the top) of the convex portion 12 and reaches the lowermost portion (that is, the deepest portion) of the concave portion 13. It is divided into a steep slope 15 that rapidly descends from the uppermost part (top) of the convex part 12 and reaches the lowermost part (deepest part) of the concave part 13. Further, the straight slope 16 has a straight straight gentle slope 16 excluding the arc-shaped portion R from the gentle slope 14, and the steep slope 15 has a straight straight steep slope 17 excluding the arc-shaped portion R. For example, when the incident light 3 enters the straight gentle slope 16, it is emitted as the center light 4, and when the incident light 3 enters the straight steep slope 17, it is emitted as the loss light 5. On the other hand, when the light enters the arcuate portion R of the convex portion 12 and the concave portion 13, the incident light 3 is diffused in a wider direction than in the past. Further, the central light 4, the loss light 5, and the light from the arcuate portion R emitted from the blast surface 11 are further scattered by the blast surface 11.

  That is, as shown in FIG. 3, the bundle 3a of light entering the straight gentle slope 16 of the incident light 3 is scattered by the blast surface 11 and emitted as the central light 4a. Further, the light bundle 3b entering the straight steep slope 17 is also scattered by the blast surface 11 and emitted as the lost light 5a. Furthermore, the bundle of light 3c incident on the arcuate portion R of the convex portion 12 is refracted over a wider angle range as compared to the conventional case, and similarly, the bundle of light 3d incident on the arcuate portion R of the concave portion 13 is compared with the conventional case. Refracts over a wider angular range. The light refracted over a wide angle range is scattered by the blast surface 11 of the Fresnel lens 1 and is further dispersed. The light bundle 3c is emitted as the outgoing light 18, and the light bundle 3d becomes the outgoing light 19. And exit. As described above, in the Fresnel lens 1, the light emitted from the Fresnel lens 1 is not separated into the center light 4 and the loss light 5 due to diffusion in the arcuate portion R and scattering by the blast surface 11.

As shown in FIG. 3, the shape of the arc-shaped portion R between the convex portion 12 and the concave portion 13 described above is such that the interval between the convex portion 12 and the convex portion 12 or the concave portion 13 and the concave portion 13 is P (mm: millimeter). When the radius of the arc-shaped portion R is r (mm), for example, 0.01 <r / P ≦ 0.3
It is. In the Fresnel lens 1 of this embodiment,
r / P = 0.17
It was. The r / P value was changed in various ways using a mirror surface without forming the blast surface 11. There is almost no light that enters between the central light 4 and the loss light 5 that is the light emitted from the straight steep slope 17, while if the value of r / P is greater than 0.3, the region with high illuminance spreads. I knew it would be over.

The surface roughness Ra (μm: micrometer) of the blast surface 11 is
0.3 ≦ Ra ≦ 40
It is. In the Fresnel lens 1 of this embodiment,
Ra = 25 (μm)
It was. The Ra value was changed variously in the same manner as in the conventional case where the arcuate portion R was not formed. However, when the Ra value was smaller than 0.3 μm, surface scattering was hardly confirmed, and the same arrangement as the conventional mirror surface was used. It was found that when the light state was reached and the value of Ra was larger than 40 μm, the illuminance of the central light 4 was lowered and the light distribution was too wide.

  FIG. 4 is a diagram showing a projection pattern of light that has passed through the Fresnel lens 1 of FIG. This projection pattern shows a case where light emitted from the LED 7 of the light source 2 enters the entire Fresnel lens surface and exits from the entire blast surface 11. 4 represents a range of 50 mm (millimeters) left and right and up and down with respect to the light source 2, and the lower square range of FIG. Represents the range. In FIG. 4, upper and lower scale displays are omitted. FIG. 4 shows a pattern in which light emitted from the Fresnel lens 1 is projected onto a projection plane that is parallel to the Fresnel lens 1 and separated by a predetermined distance. The upper diagram in FIG. 4 shows the projection pattern of the range corresponding to the conventional central light 103 and the vicinity thereof, and the lower diagram shows the projection pattern of the conventional central light 103, the conventional loss light 104, and the surroundings thereof. This is a projection pattern.

  In the upper diagram of FIG. 4, the region 20 is a portion with the highest illuminance. The narrow region 21 on the outer periphery of the region 20 has slightly lower illuminance than the region 22 on the outer periphery of the region 21. Next, the illuminance decreases sequentially with the regions 22 to 26. Further, in the lower diagram of FIG. 4, a region 30 is a portion of regions 20 to 25 in the upper diagram of FIG. 4. Further, in the lower diagram of FIG. 4, a region 31 is a projection pattern in a range corresponding to the conventional loss light 104.

  The illuminance distribution of the projection pattern in the upper diagram of FIG. 4 is shown in the lower diagram of FIG. The vertical axis in the lower part of FIG. 5 indicates Lux, which is a unit of illuminance. As shown in FIG. 5, it can be seen that although the region 21 is slightly depressed, the illuminance gradually decreases gradually from the region 20 to the region 26. This is also apparent from a comparison with the conventional example of FIG. 16 corresponds to the illuminance of the region 20 in FIG. 5, but the area of the region 20 is smaller than the area of the region 110. Thereby, the illuminance decrease change in the areas 21 to 26 around the area 20 is gentler than the illuminance decrease change in the areas 111 to 114 around the area 110.

  The illuminance distribution of the projection pattern in the lower diagram of FIG. 4 is shown in the lower diagram of FIG. The vertical axis in the lower part of FIG. 6 indicates Lux, which is a unit of illuminance. As shown in FIG. 6, a region 31 corresponding to the conventional loss light 104 exists on the outer periphery of the region 30, and the change in illuminance is gentle. The region 32 is hardly irradiated with emitted light. When the illuminance distribution of FIG. 6 is compared with the illuminance distribution of the conventional example of FIG. 17, the regions 117 and 119 where the illuminance generated in FIG. 17 is higher than the adjacent portions do not exist in the illuminance distribution of FIG. Accordingly, there is no ring-shaped pattern in the illuminance distribution of FIG.

(Comparative Example 1)
Next, as Comparative Example 1, the arc-shaped portion R in the convex portion 12 and the concave portion 13 of the Fresnel lens 1 shown in FIG. 3 is eliminated so that scattering by the arc-shaped portion R is eliminated, and scattering is caused only by the blast surface 11. A projection pattern of the lens 1A is shown in FIG. The upper square range in FIG. 7 represents a range of 50 mm each in the left and right and up and down directions with respect to the light source 2, and the lower square range in FIG. Represents. In FIG. 7, the upper and lower scale displays are omitted. In Comparative Example 1, a region corresponding to the conventional center light 103 is denoted as center light 4A, and a region corresponding to the conventional loss light 104 is denoted as loss light 5A.

  As shown in FIG. 7, the projection pattern of the central light 4 </ b> A is almost the same as the projection pattern shown in FIG. 5 and has regions 20 to 26. On the other hand, unlike the projection pattern according to the embodiment of the present invention shown in FIG. 6, the projection pattern of the loss light 5 </ b> A has a dark region 40 between the bright regions 30 and 41. The lower part of FIG. 8 shows the illuminance distribution of the projection pattern of the lossy light 5A shown in the lower part of FIG. As shown in FIG. 8, according to the comparative example 1, the projection pattern of the loss light 5 </ b> A exhibits a thin ring-shaped pattern although the area 41 is slightly because the illuminance of the area 40 is lower than the illuminance of the area 41. .

  Comparing Comparative Example 1 with the embodiment of the present invention, the arc-shaped portion R in the convex portion 12 and the concave portion 13 of the Fresnel lens 1 generates a ring-shaped pattern mainly in a region corresponding to the conventional loss light 104. The effect of preventing it is observed. On the other hand, the blast surface 11 has an effect of moderately reducing the illuminance reduction of the central light 4A. The comparative example 1 is better than the conventional one, and the comparative example 1 may be adopted depending on the application.

(Comparative Example 2)
Next, as Comparative Example 2, FIG. 9 shows a projection pattern of the Fresnel lens 1B having the convex portion 12 and the concave portion 13 of the Fresnel lens 1 shown in FIG. The upper square range in FIG. 9 represents a range of 50 mm each in the left and right and up and down directions with respect to the light source 2, and the lower square range in FIG. Represents. In FIG. 9, upper and lower scale displays are omitted. In Comparative Example 2, a region corresponding to the conventional center light 103 is denoted as center light 4B, and a region corresponding to the conventional loss light 104 is denoted as loss light 5B.

  As shown in FIG. 9, the projection pattern of the center light 4B is substantially the same as the center light 103 shown in FIG. 16 as a conventional example, has regions 50 to 54, and a rapid decrease in illuminance occurs. Moreover, the projection pattern of the loss light 5B has regions 60 to 63, and the ring-shaped pattern that becomes a ring pattern is thin. The lower part of FIG. 10 shows the illuminance distribution of the projection pattern of the lost light 5B shown in the lower part of FIG. As shown in FIG. 10, according to the comparative example 2, the projection pattern of the loss light 5B has a slightly darker portion than the surroundings in the region 61, but overall the illuminance is in the order of the regions 60 to 63. It is getting lower step by step. Thereby, a ring-shaped pattern hardly occurs in the range of the regions 60 to 62.

  Comparing Comparative Example 2 and the present embodiment, it is recognized that the blast surface 11 of the Fresnel lens 1 mainly has an effect of gently smoothing the illuminance change in the area corresponding to the conventional central light 103. That is, in Comparative Example 2, since there is no blast surface 11, a sharp decrease in illuminance occurs in the central portion. Since this comparative example 2 is also improved over the conventional example, this comparative example 2 may be adopted depending on the application.

(About light distribution)
The light distribution of the Fresnel lenses 1, 1A, 1B and the conventional Fresnel lens 101 will be described with reference to FIG. FIG. 11 is a diagram showing the light distribution of the Fresnel lenses 1, 1 </ b> A, 1 </ b> B and the conventional Fresnel lens 101. In FIG. 11, the horizontal axis indicates the angle viewed from the light source 2, and the vertical axis indicates the luminous intensity ratio. In FIG. 11, the solid line shows the light distribution of the Fresnel lens 1, the broken line shows the light distribution of the Fresnel lens 1A, the two-dot chain line shows the light distribution of the Fresnel lens 1B, and the one-dot chain line shows the conventional Fresnel lens 101. The light distribution is shown.

  As shown in FIG. 11, the angle at the half value (0.5) of the luminous intensity ratio of the Fresnel lenses 1, 1A, 1B is substantially the same as that of the Fresnel lens 101 of the conventional example, and sufficient light is obtained even near the center. Is done.

(effect)
As described above, the Fresnel lens 1 according to this embodiment has the top of the convex portion 12 and the deepest portion of the concave portion 13 having the arc-shaped portion R, and the blast surface 11 that scatters incident light on the surface. According to this, as shown in FIG. 5, the change in illuminance at the central portion is gentler than that of the conventional example shown in FIG. Further, as shown in FIG. 6, the change in illuminance in the region corresponding to the conventional lost light 104, that is, the region surrounding the central portion is also gentle, and for example, a ring-shaped pattern like the conventional example shown in FIG. 17 is exhibited. There is nothing. As a result, the conventional problem can be solved, and there is no sudden change in illuminance in the central portion, so that a ring-shaped pattern does not occur around the central portion where the illuminance is high.

  That is, in the conventional Fresnel lens 101, since the convex portion 107 and the concave portion 108, which are connected portions of the gentle slope 105 and the steep slope 106, are both acute angles, the incident light 102 is incident on the gentle slope 105 and the steep slope 106. Divided into things. In other words, in the conventional Fresnel lens 101, a portion with low illuminance such as the regions 116, 117, and 118 is generated between the central light 103 and the lost light 104, resulting in a ring-shaped pattern. In the Fresnel lens 1 of the present embodiment, since the top of the convex portion 12 and the deepest portion of the concave portion 13 have the arcuate portion R, the light passing through the top of the convex portion 12 and the deepest portion of the concave portion 13 has a wide angular range. Since the light is buried between the central light 103 and the loss light 104, no ring-shaped pattern is generated in the region corresponding to the loss light 104. Furthermore, since the Fresnel lens 1 of the present embodiment has the blast surface 11, the central portion emitted from the Fresnel lens 1 is scattered and exhibits a gentle change in illuminance.

  In the Fresnel lens 1, the convex portion 12 and the concave portion 13 are provided on the side of the lens body 10 that faces the light source 2. According to this, the convex portion 12 and the concave portion 13 are not exposed to the outside air, and it is possible to prevent a problem such as accumulation of dust in the concave portion 13.

  Further, in the Fresnel lens 1, since the top of the convex portion 12 and the deepest portion of the concave portion 13 have a round arc-shaped portion R instead of an acute angle, when the Fresnel lens 1 is molded with a mold, The deepest portion of the recess 13 can be easily removed from the mold. According to this, the yield rate in the process of manufacturing the Fresnel lens 1 can be improved. Moreover, it is advantageous for cost reduction and long life of the mold.

(Other embodiments)
Various modifications can be made to the embodiment of the present invention without departing from the gist thereof.

  For example, in the above-described embodiment, the arc-shaped portion R is provided on both the convex portion 12 and the concave portion 13, but the arc-shaped portion R may be provided on either the convex portion 12 or the concave portion 13.

  In the above-described embodiment, the blasted surface 11 is provided as the surface scattering portion. However, instead of the blasted surface 11, the surface may be finely roughened by sanding or the like. Alternatively, instead of the blast surface 11, a sheet that scatters light may be attached to the surface of the lens. Alternatively, the transparent resin body that forms the lens body 10 may be used without the surface scattering portion such as the blast surface 11 or after the surface scattering portion such as the blast surface 11 is provided. You may provide the volume scattering part formed with the scattering light guide (for example, refer Unexamined-Japanese-Patent No. 2011-49233).

  In addition, the blast surface 11 has been described as having the convex portion 12 and the concave portion 13 of the lens body 10, but in addition, the blast surface 11 on the side having the convex portion 12 and the concave portion 13 of the lens body 10 is also provided. You may have on the surface of the surface which does not have the convex part 12 and the recessed part 13 of the lens main body 10, and the side which has the convex part 12 and the recessed part 13 of the lens main body 10. In particular, if the blast surface 11 is provided on both the surface of the lens body 10 that does not have the convex portion 12 and the concave portion 13 and the surface of the lens body 10 that has the convex portion 12 and the concave portion 13, the surface Since the area of the scattering portion increases, surface scattered light can be increased. According to this, the effect | action which smoothes the illumination intensity change of the area | region equivalent to the conventional center light 103 of the blast surface 11 is further strengthened.

  In the above-described embodiment, the convex portion 12 and the concave portion 13 are provided on the side of the lens body 10 facing the light source 2, and the blast surface 11 is provided on the opposite side of the lens body 10 from the light source 2. The part 12 and the recessed part 13 may be provided on the exit surface side, and the blast surface 11 may be provided on the side facing the light source 2.

  In the above-described embodiment, the Fresnel lens 1 is configured with the surface of the lens body 10 as a plane. However, the lens body 10 may have an arc shape or the like, and the Fresnel lens surface may have a curved surface. In that case, only the Fresnel lens surface may be a curved surface and the opposite side may be a flat surface, or both the Fresnel lens surface and the opposite side may be curved. Further, the surface roughness Ra of the blast surface 11 is set to any one of the ranges of 0.3 ≦ Ra ≦ 40, and r / P, which is the relationship between the radius r of the arcuate portion R and the pitch P of the Fresnel lens surface, is set to 0. 17 or 0.01 <r / P ≦ 0.3. Also, r / P may be any of 0.01 <r / P ≦ 0.3, and Ra may be 25 μm.

DESCRIPTION OF SYMBOLS 1 ... Fresnel lens, 2 ... Light source, 10 ... Lens main body (volume scattering part), 11 ... Blast surface (surface scattering part), 12 ... Convex part, 13 ... Concave part, R ... Arc-shaped part

Claims (6)

In a Fresnel lens in which convex portions and concave portions are alternately and repeatedly arranged on one side of a lens body that transmits light,
It has an arcuate part at one or both of the top of the convex part or the deepest part of the concave part, and has a scattering part that scatters incident light,
This is a Fresnel lens. The Fresnel lens according to claim 1,
The scattering part has either one or both of a surface scattering part and a volume scattering part,
This is a Fresnel lens. The Fresnel lens according to claim 2,
The surface scattering portion is a surface of the lens main body that does not have the convex portion and the concave portion, or a surface of the lens main body that has the convex portion and the concave portion, or the convex portion of the lens main body. Formed by blasting both the surface of the lens body and the surface not having the concave portion and the surface of the lens body having the convex portion and the concave portion.
This is a Fresnel lens. The Fresnel lens according to claim 2 or 3,
The volume scattering portion is formed of a light scattering light guide in which the lens body contains light scattering particles in a transparent resin.
This is a Fresnel lens. The Fresnel lens according to any one of claims 1 to 4,
A light source disposed to face one side of the Fresnel lens;
Having
A lighting device characterized by that. The lighting device according to claim 5.
The light source is provided on the side facing the Fresnel surface where the convex portions and concave portions are alternately and repeatedly arranged,
A lighting device characterized by that.