JP2013122566A - Optical element and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element capable of uniformly illuminating an illumination object surface even when obliquely illuminating a flat illumination object surface using a light beam from a surface-emitting light source, and to provide a lighting device using the same.SOLUTION: In a first cross section shown in Figure 4, a power change at an exit surface LSd is gentle in a screen SC side with respect to a local maximum point LP to cause a weak light condensing action when passing through the area, so that a part of the light beam heads towards a farthest point FP side of the screen SC. On the other hand, on the other side of the screen SC with respect to the local maximum point LP, a power change at the exit surface LSd is steep to cause light condensing action when passing through the area, so that most light beams head towards the farthest point FP side of the screen SC.

Description

  The present invention relates to an optical element suitable for an illumination device using a surface-emitting light source, and an illumination device using the optical element.

  For example, commercial signs and information signs (signboards, etc.) standing on the roadside are often provided with a lighting device for illuminating the display at night. Here, in order to make it easier for a driver of a vehicle traveling on a road at a relatively high speed to visually recognize the display of a signboard or the like, it is desirable to illuminate as uniformly as possible while suppressing the luminance difference of the irradiated surface. On the other hand, from the viewpoint of energy saving and the like, it is considered to use an LED light source that consumes less current. However, since the LED light source has an illuminance characteristic different from that of an incandescent bulb or the like, illumination is performed from above or below a signboard. When doing it, some kind of ingenuity is required.

  More specifically, since the irradiated surface cannot be uniformly illuminated only by direct light from an LED light source or the like, an optical element having an effect of adjusting the irradiated light is required, but particularly toward an irradiated surface such as a signboard. When illuminating from above and below, it is necessary to increase the amount of irradiated light far from the light source and decrease the amount of irradiated light near the light source for uniform illumination. Furthermore, in a light source that emits light with a Lambertian-type light distribution such as an LED, in order to improve the light utilization efficiency, the light beam emitted to the opposite side of the irradiated surface as viewed from the light source It is important how to effectively collect the light on the irradiated surface.

  Patent Document 1 discloses an optical element that is provided below an irradiated surface and emits light rays from an LED chip obliquely toward the irradiated surface. However, the optical element of Patent Document 1 has a problem that the illuminance at the farthest part of the irradiated surface is reduced. For this reason, a device has been devised to increase the illuminance by curling the farthest part of the irradiated surface and bringing it closer to the optical element. However, curling a signboard or the like in this way is not preferable because it increases the cost, and there is also a problem that the display of the curled portion is difficult to visually recognize.

Japanese Patent No. 4285981

  The present invention has been made in view of such problems, and even when a flat irradiated surface is irradiated obliquely using a light beam from a surface-emitting light source, the irradiated surface is illuminated more uniformly. An object of the present invention is to provide an optical element that can be used and an illumination device using the optical element.

The optical element according to claim 1 is an optical element for illuminating a surface to be irradiated with uniform illuminance by transmitting light emitted from a surface-emitting light source,
The optical element comprises a single lens;
The incident side surface of the lens has a recess,
The exit side surface of the lens has a convex shape, and the irradiated surface side is loose when viewed from the maximum point, and the anti-irradiated surface side has a surface where the power changes more rapidly than that.

First, the illuminance on the irradiated surface decreases in proportion to the square of the distance from the light source. And it is proportional to the cosine of the angle which injects into the irradiated surface of a light ray. In other words, it is possible to think of the peripheral light quantity ratio, and connect any point on the irradiated surface to the light source in a cross section perpendicular to the irradiated surface including the perpendicular line from the light source to the irradiated surface and the optical axis. The illuminance on the irradiated surface decreases in proportion to the cosine cube of the angle ω formed by the ellipse and the perpendicular. That means
I (ω) = 1 / cos ³ (ω)
The illuminated surface may be illuminated with a luminance distribution that satisfies the above. This can be applied not only to the cross section but also to the entire irradiated surface.
For example, when illuminating the illuminated surface from below, such as a signboard, the distance between the nearest and farthest parts is large, so if the optical element is composed of a single lens, the surface emitting light source and the illuminated surface An optical surface that optimizes the emitted light luminance for each angle is required depending on the angle formed by the arbitrary point above and the perpendicular line from the light source center to the irradiated surface. Therefore, in the present invention, the exit side surface of the lens is configured with a surface that is loose on the irradiated surface side and viewed from the local maximum point and has a sudden power change (surface gradient) on the anti-irradiated surface side. Of the light rays emitted from the irradiation surface side, some light rays near the optical axis are emitted in the direction of the maximum point when viewed from the center of the light source, and are gradually irradiated as they move away from the vicinity of the optical axis. Gives a weak light condensing effect that illuminates the entire surface, and a light condensing effect that emits in the direction of the maximum point when viewed from the center of the light source can be given to the majority of the light emitted from the opposite surface. As a result, a part of the light irradiated to a region near the irradiated surface can be directed to a region far from the irradiated surface, so that the illuminance on the irradiated surface can be increased even if the irradiated surface is flat. It can be made uniform. Therefore, it is suitable for lighting such as a signboard.

Here, “uniform illuminance” means the lowest illuminance on the surface to be irradiated when the surface to be irradiated is viewed in a cross section including the optical axis and perpendicular to the surface to be irradiated, and the average illuminance of the surface to be irradiated. When ave, it means a state satisfying min / ave ≧ 0.3. However, it is more desirable to satisfy min / ave ≧ 0.5.
Alternatively, it is more preferable that min / ave ≧ 0.3 is satisfied where min is the lowest illuminance on the entire irradiated surface and ave is the average illuminance on the irradiated surface. It is even more desirable to satisfy min / ave ≧ 0.5.

“Surface emitting light source” refers to a light source having a light emitting surface of 0.25 mm ² or more, such as an LED or an organic EL. In the case of a single surface-emitting light source, the “optical axis” means an axis (line) that passes through the center of the light-emitting surface of the surface-emitting light source and is perpendicular to the light-emitting surface of the light source. In this case, as shown in FIG. 32, it means a perpendicular line passing through the center O of the circumscribed circle OC (radius R) of the surface emitting light source. “Maximum point” means that the z-axis is taken in the direction of the optical axis when the light-emitting surface of the surface-emitting light source is a plane of z = 0 and the center of the light-emitting surface is the origin of coordinates, and is the largest on the exit side of the lens The place where the value of z is taken is called the maximum point. “The side where the power changes suddenly when viewed from the maximum point” is the absolute angle between the z axis and the normal of the surface at the same distance (height) from the maximum point along the tangent line of the maximum point The one with the larger value shall be said. The opposite side is the loose power change side. Alternatively, the one having a larger sag amount difference from the maximum point at a point (height) away from the maximum point.

  An optical element according to a second aspect is characterized in that, in the invention according to the first aspect, the lens has a non-rotationally symmetric shape with respect to an optical axis of the surface-emitting light source.

  When the lens has a non-rotationally symmetric shape with respect to the optical axis of the surface light source, the irradiated surface side is loose when viewed from the maximum point and the anti-irradiated surface side has a sudden power change. Therefore, the illuminance on the irradiated surface can be made close to uniform.

  The optical element according to claim 3 is characterized in that, in the invention according to claim 1 or 2, an optical axis of the surface-emitting light source is inclined with respect to the irradiated surface.

  By installing the surface emitting light source with the optical axis tilted with respect to the irradiated surface, the maximum point with the highest light condensing effect can be directed to the far side of the irradiated surface, thereby enabling illumination with uniform illuminance. It becomes possible.

  An optical element according to a fourth aspect is the invention according to any one of the first to third aspects, wherein an optical axis of the surface-emitting light source is a Z-axis, and is an axis orthogonal to the Z-axis and parallel to the irradiated surface. Is the Y-axis, and the X-axis is the axis orthogonal to both the Z-axis and the Y-axis, the exit side surface of the lens is aligned with the Z-axis in the first section cut by the XZ plane passing through the maximum point. It is characterized by having an asymmetric shape.

  When the exit side surface of the lens has an asymmetric shape with respect to the Z-axis in the first cross section, the portion of the irradiated surface that is farthest from the surface emitting light source is most strongly illuminated, thereby Uniform illuminance can be realized by reducing illuminance variation.

  The optical element according to claim 5 is the invention according to claim 4, wherein the maximum point on the exit side surface of the lens is on the side opposite to the irradiated surface with respect to the optical axis of the surface-emitting light source in the first cross section. It is characterized by.

  When the maximum point on the exit side surface of the lens is on the side opposite to the irradiated surface with respect to the optical axis of the surface emitting light source in the first cross section, the area farthest from the surface emitting light source on the irradiated surface is most strongly illuminated. Thus, the illuminance variation on the irradiated surface can be reduced, and uniform illuminance can be realized.

The optical element according to claim 6 is the invention according to claim 4 or 5, wherein the maximum point on the exit side surface of the lens is relative to the optical axis in the first cross section when viewed from the center of the surface emitting light source. It exists in the position of angle (alpha) (degree) on the anti-irradiation surface side, and satisfy | fills the following formula | equation.
0 <α ≦ 20 (1)

  By satisfying the expression (1), the place farthest from the surface-emitting light source on the illuminated surface can be illuminated most strongly, and the illuminance variation on the illuminated surface can be reduced to achieve uniform illumination.

  The optical element according to claim 7 is the invention according to any one of claims 4 to 6, wherein the maximum point on the exit side surface of the lens is the center of the surface-emitting light source and the irradiated surface in the first section. It exists in the vicinity of a line segment connecting to the farthest point.

When the local maximum point on the exit side surface of the lens is present in the vicinity of a line segment connecting the center of the surface-emitting light source and the farthest point of the illuminated surface in the first cross section, a location farthest from the light source on the illuminated surface Can be illuminated most strongly, and the illuminance variation on the irradiated surface can be reduced to achieve uniform illuminance. The “near line segment” means an angle β (°) formed by a line segment connecting the surface emitting light source center and the farthest point of the irradiated surface and a line segment connecting the surface emitting light source center and the maximum point. Satisfies the following formula.
| β | ≦ 10 (2)
Moreover, it is preferable that the line segment connecting the surface emitting light source center and the maximum point is closer to the irradiated surface than the line connecting the surface emitting light source center and the farthest point of the irradiated surface. That is, in the first cross section, the angle between the line segment connecting the surface emitting light source center and the maximum point and the irradiated surface> the line segment connecting the surface emitting light source center and the farthest point of the irradiated surface. And the angle formed by the irradiated surface.

  The optical element according to claim 8 is the invention according to any one of claims 4 to 7, wherein the distance between the surface emitting light source center and the exit surface of the lens is the surface emitting light source in the first cross section. It is maximum near a line segment connecting the center and the farthest point of the irradiated surface.

  Thereby, the place farthest from the light source on the irradiated surface can be illuminated most strongly, and the illuminance variation on the irradiated surface can be reduced to achieve uniform illuminance. It is preferable that the distance is substantially maximum on a line segment connecting the surface emitting light source center and the farthest point of the irradiated surface in the first cross section.

  An optical element according to a ninth aspect is the invention according to any one of the first to eighth aspects, wherein an optical axis of the surface-emitting light source is a Z-axis, an axis perpendicular to the Z-axis and parallel to the irradiated surface. Is the Y axis, the exit side surface of the lens has a shape symmetric with respect to the Z axis in a second cross section cut by a plane passing through the maximum point and parallel to the YZ plane. .

  As a result, the exit side surface of the lens can have an anamorphic shape that is different in shape between the first cross section and the second cross section. It can be made uniform, and is particularly convenient when a plurality of illumination devices are arranged to illuminate a single irradiated surface.

  An optical element according to a tenth aspect is characterized in that, in the invention according to any one of the first to ninth aspects, the exit side surface of the lens is smoothly connected.

  Thereby, it is possible to further reduce the illuminance variation on the irradiated surface and realize a uniform illuminance.

  An optical element according to an eleventh aspect is characterized in that, in the invention according to any one of the first to tenth aspects, an incident side surface of the lens has an anamorphic surface shape.

  By making the incident side surface of the lens have an anamorphic shape in which the shape is different between the first cross section and the second cross section, for example, a uniform illuminance distribution can be obtained on the irradiated surface. .

  An optical element according to a twelfth aspect is the invention according to any one of the first to eleventh aspects, wherein an optical axis of the surface-emitting light source is a Z-axis, an axis perpendicular to the Z-axis and parallel to the irradiated surface. Is the Y axis, and the X axis is the axis orthogonal to both the Z axis and the Y axis, the incident side surface of the lens has an asymmetric shape in the first cross section cut by the XZ plane passing through the maximum point. It is characterized by having.

  The incident side surface of the lens has an asymmetric shape in the first cross section, so that the place farthest from the light source on the irradiated surface can be illuminated most strongly, and variation in illuminance on the irradiated surface is reduced. To achieve uniform illuminance. It may be asymmetric with respect to the Z axis or not with respect to the Z axis. The radius of curvature on the irradiated surface side of the incident side surface of the lens is preferably equal to or less than the radius of curvature on the anti-irradiated surface side. In particular, the radius of curvature is preferably a negative value on the irradiated surface side, and the radius of curvature is preferably 0 to a positive value on the anti-irradiated surface side. The irradiated surface side and the anti-irradiated surface side need not have Z = 0 as a boundary.

  An optical element according to a thirteenth aspect is the invention according to any one of the first to twelfth aspects, wherein an optical axis of the surface-emitting light source is a Z-axis, an axis perpendicular to the Z-axis and parallel to the irradiated surface. Is the Y axis, the incident side surface of the lens has a shape symmetric with respect to the Z axis in a second cross section cut by a plane passing through the maximum point and parallel to the YZ plane. .

  Thereby, since the illuminance on both sides of the irradiated surface can be made uniform across the optical axis, the entire irradiated surface can be illuminated uniformly. In particular, it is convenient when a plurality of illumination devices are arranged to illuminate a single irradiated surface.

  An optical element according to a fourteenth aspect is characterized in that, in the invention according to any one of the first to thirteenth aspects, an incident side surface of the lens is defined by two or more surface definition formulas.

  By configuring the incident side surface of the lens with discontinuous surfaces having different definition formulas mainly on the irradiated surface side and the anti-irradiated surface side, it is possible to uniformly illuminate a wider range. Note that the irradiated surface side and the non-irradiated surface side do not need to have Z = 0 as a boundary.

  An optical element according to a fifteenth aspect is characterized in that, in the invention according to any one of the first to fourteenth aspects, a total reflection surface based on a paraboloid is provided in a peripheral portion of the lens.

  By providing a total reflection surface based on a paraboloid on the periphery of the lens, it becomes possible to effectively irradiate the irradiated surface with light rays emitted from the surface emitting light source.

  An optical element according to a sixteenth aspect is characterized in that, in the invention according to any one of the first to fifteenth aspects, a flange portion is provided in a peripheral portion of the lens.

  By providing the flange portion in this way, the moldability of the lens is improved, and installation is facilitated by using the flange portion.

  An optical element according to a seventeenth aspect is the invention according to any one of the first to sixteenth aspects, wherein the lens is molded from a resin.

  When the lens is made of resin, mass production is possible by injection molding, and a highly accurate product can be provided at low cost.

  An illuminating device according to claim 18 includes the optical element according to any one of claims 1 to 17 and a surface-emitting light source.

  The illuminating device according to claim 19 is the invention according to claim 18, wherein another optical element is provided in addition to the optical element according to any one of claims 1 to 17. .

  As the surface emitting light source, a planar light emitting element such as an LED (Light Emitting Diode) or an organic EL is preferable. In particular, the surface on the optical element side is preferably flat, and more preferably a surface mount type.

  When using an LED light source, various types can be used, but a white LED is preferably used.

  As the white LED, a combination of a blue LED chip and a phosphor such as a YAG phosphor that emits yellow light by blue light emitted from the blue LED chip is preferably used, but a blue LED chip, a green LED chip, and a red LED are used. It may be a white LED that forms white light in combination with a chip. As white LED, what was described, for example in Unexamined-Japanese-Patent No. 2008-231218 can be used, However, It is not restricted to this.

  Specifically, the white LED light source in the present invention includes an LED chip and a phosphor layer formed on the LED chip so as to cover the LED chip. The LED chip emits light having a first predetermined wavelength. In the present embodiment, the LED chip emits blue light. However, the wavelength of the LED chip of the present invention and the wavelength of the emitted light from the phosphor are not limited, and the wavelength of the emitted light from the LED chip and the wavelength of the emitted light from the phosphor are in a complementary color relationship and the synthesized light is white. Any combination that provides light can be used.

  In addition, as such an LED chip, a well-known blue LED chip can be used. As the blue LED chip, any existing one including InxGa1-xN can be used. The emission peak wavelength of the blue LED chip is preferably 440 to 480 nm. In addition, as a form of the LED chip, the LED chip is mounted on the substrate and directly radiated upward or sideward, or the blue LED chip is mounted on a transparent substrate such as a sapphire substrate, and bumps are formed on the surface thereof. Any form of LED chip, such as a so-called flip chip connection type, in which it is formed and turned over and connected to an electrode on a substrate, can be applied.

  The phosphor layer has a phosphor that converts light having a first predetermined wavelength emitted from the LED chip into a second predetermined wavelength. In an embodiment described later, blue light emitted from the LED chip is converted into yellow light.

  The phosphor used for such a phosphor layer uses an oxide or a compound that easily becomes an oxide at a high temperature as a raw material of Y, Gd, Ce, Sm, Al, La and Ga, and converts them into a stoichiometric amount. The raw material is obtained by thoroughly mixing in a theoretical ratio. Alternatively, a coprecipitated oxide obtained by calcining a solution obtained by coprecipitation of oxalic acid with a solution obtained by dissolving a rare earth element of Y, Gd, Ce, and Sm in an acid at a stoichiometric ratio, and aluminum oxide and gallium oxide. Mix to obtain a mixed raw material. An appropriate amount of fluoride such as ammonium fluoride is mixed with this as a flux and pressed to obtain a molded body. The compact can be packed in a crucible and fired in air at a temperature range of 1350 to 1450 ° C. for 2 to 5 hours to obtain a sintered body having the phosphor emission characteristics.

  Moreover, although it is preferable that a single LED light source is provided for a lens, a plurality of LED chips may be associated with a single lens. In such a case, each of the plurality of LED chips may be arranged symmetrically with respect to the optical axis of the lens, or may be arranged asymmetrically. Here, as shown in FIG. 32, when a plurality of LED light sources are used, the diameter R of the smallest circle OC circumscribing the LED light sources is regarded as the diameter of the LED light sources and is contained within the inner diameter of the lens. It is desirable.

  The LED light source is preferably a high-power LED light source. Here, the high-power LED light source can be constituted by an LED having an output of 0.5 watts or more.

  The lens is disposed on the light emitting side of the surface light source, the incident side surface has a concave portion, and the exit side surface of the lens has a convex shape, which is preferably formed from a resin, but formed from other materials. May be.

  According to the present invention, an optical element capable of illuminating the irradiated surface more uniformly even when the flat irradiated surface is obliquely irradiated with the light from the surface-emitting light source and the same are used. A lighting device can be provided.

It is the figure which looked at the lens LS of the illuminating device concerning this Embodiment, and the screen SC which is a to-be-irradiated surface from the front of the screen SC. It is the figure which cut | disconnected the structure of FIG. 1 at the II-II surface containing optical axis OA, and looked at the arrow direction. FIG. 2 is an enlarged view obtained by cutting along the YZ section in the configuration of FIG. 1. FIG. 4 is an enlarged view showing an arrow IV part of the configuration of FIG. 2. It is YZ sectional drawing of the illuminating device concerning this Embodiment. It is XZ sectional drawing of the illuminating device concerning this Embodiment. In this Embodiment, it is a graph which takes the height (distance) from an optical axis regarding a 1st cross section on a horizontal axis, and takes the height of the output surface when the light source center is made into an origin on the vertical axis. In the present embodiment, the horizontal axis indicates the angle from the light source center when the optical axis is 0 ° with respect to the first cross section, and the vertical axis indicates the height of the emission surface when the light source center is the origin. It is a graph. In the present embodiment, the angle from the light source center when the optical axis is 0 ° with respect to the first cross section is taken on the horizontal axis, and the distance from the light source center to the exit side surface when the light source center is taken as the origin on the vertical axis. It is a graph shown. In the present embodiment, the horizontal axis represents the height (distance) from the maximum point with respect to the first cross section, and the vertical axis represents the angle γ (FIG. 6) formed by the normal of the exit surface and the optical axis. It is. FIG. 3 is a perspective view of the lens according to Example 1 viewed in a direction orthogonal to the XZ cross section. 3 is a perspective view of a lens according to Example 1 viewed in a direction orthogonal to a YZ section. FIG. 1 is an XZ sectional view of a lens according to Example 1. FIG. 1 is a YZ sectional view of a lens according to Example 1. FIG. It is a figure (linear scale) which shows the illumination intensity on a screen at the time of illuminating from the right direction with the illuminating device using the lens of Example 1. FIG. It is a figure (log scale) which shows the illumination intensity on a screen at the time of illuminating from the right direction with the illuminating device using the lens of Example 1. FIG. 1 is a cross-sectional view of illuminance distribution of Example 1. FIG. It is the perspective view seen in the direction orthogonal to the XZ cross section of the lens concerning a comparative example. It is the perspective view seen in the direction orthogonal to the YZ cross section of the lens concerning a comparative example. It is a figure (linear scale) which shows the illumination intensity on a screen at the time of illuminating from the right direction with the illuminating device using the lens of a comparative example. It is a figure (log scale) which shows the illumination intensity on a screen at the time of illuminating from the right direction with the illuminating device using the lens of a comparative example. It is illumination intensity distribution sectional drawing of a comparative example. FIG. 6 is a perspective view of a lens according to Example 2 viewed in a direction orthogonal to an XZ section. FIG. 6 is a perspective view of a lens according to Example 2 viewed in a direction orthogonal to a YZ section. 3 is an XZ cross section of a lens according to Example 2. FIG. 6 is a cross-sectional view of the lens according to Example 2 slightly tilted with respect to the YZ cross section. FIG. 6 is a cross-sectional view of illuminance distribution of Example 2. FIG. 6 is a perspective view of a lens according to Example 3 viewed in a direction orthogonal to an XZ section. FIG. 6 is a perspective view of a lens according to Example 3 viewed in a direction orthogonal to a YZ section. FIG. 6 is an illuminance distribution sectional view of Example 3. It is sectional drawing concerning an example of another lens. It is a figure for demonstrating a surface emitting light source.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view of a lens LS as an optical element of the illumination device according to the present embodiment and a screen SC that is a planar rectangular irradiation surface as viewed from the front of the screen SC, and FIG. FIG. 2 is a diagram in which the configuration of FIG. 1 is cut along the II-II plane including the optical axis OA and viewed in the direction of the arrow, but a holder and the like for attaching the illumination device are omitted. In this specification, the optical axis OA of the LED light source (surface emitting light source) of the lighting device is the Z axis, the axis orthogonal to the Z axis and parallel to the screen SC is the Y axis, and both the Z axis and the Y axis are used. The axis orthogonal to is the X axis. As is clear from FIG. 2, the illumination device is installed such that the optical axis OA is inclined with respect to the surface of the screen SC.

  FIG. 3 is an enlarged view obtained by cutting along the YZ section in the configuration of FIG. FIG. 4 is an enlarged view showing an arrow IV portion of the configuration of FIG. FIG. 5 is a YZ sectional view of the lighting device according to the present embodiment, and FIG. 6 is an XZ sectional view of the lighting device according to the present embodiment.

  5 and 6, the lighting device includes a single lens LS made of resin and an LED light source LED having a light emitting surface on the upper surface. A concave portion LSa is provided on the light source side incident surface side of the lens LS. More specifically, the lens LS has a main incident surface LSb that is the upper surface of the recess LSa, and a side incident surface LSC that surrounds the main incident surface LSb and surrounds the light emitting surface of the LED light source LED. The exit surface LSd of the lens LS is a smooth curved surface and has a convex shape that is non-rotational symmetric with respect to the optical axis OA. Further, a parallel plate-shaped flange portion LSe orthogonal to the optical axis OA is formed around the lens LS. A convex or annular leg portion LSf is formed on the lower peripheral surface of the flange portion LSe, and comes into contact with the substrate ST on which the LED light source LED is provided, whereby the LED light source LED and the lens LS. And positioning.

  In the cross section shown in FIG. 5 (referred to as the second cross section or the YZ cross section), the concave portion LSa and the exit surface LSd of the lens LS are symmetrical with respect to the optical axis OA, and are separated from the optical axis OA. It has a shape with a height that decreases accordingly.

  On the other hand, in the cross section shown in FIG. 6 (referred to as a first cross section or an XZ cross section), the main incident surface LSb of the concave portion LSa of the lens LS has a non-symmetrical shape with the optical axis OA interposed therebetween. More specifically, on the screen SC side (left side in FIG. 6) from the optical axis OA, the height of the main incident surface LSb decreases as the distance from the optical axis OA increases, and the screen SC side (FIG. 6 on the right), the height is constant regardless of the distance of the optical axis OA. That is, the main incident surface LSb has an anamorphic surface shape. The concave portion LSa of the lens is defined by two or more surface definition formulas.

  Furthermore, as shown in FIG. 6, the exit surface LSd of the lens LS has a non-symmetrical shape with the optical axis OA interposed therebetween. Further, the maximum point LP is in the first cross section and is on the side opposite to the irradiated surface from the optical axis OA.

  The maximum point LP will be described. FIG. 7 shows the height (distance) from the optical axis with respect to the first cross section on the horizontal axis in the present embodiment, and the height of the exit surface when the vertical axis is the light source center (in this specification). , “Sag amount” is a graph obtained by taking a value obtained by subtracting the height of an arbitrary position from the height of the maximum point on the exit surface, and FIG. 8 shows the first section in the present embodiment. 9 is a graph in which the horizontal axis represents the angle from the light source center when the optical axis is 0 °, and the vertical axis represents the height of the exit surface when the light source center is the origin. In the embodiment, the horizontal axis represents the angle from the light source center when the optical axis is 0 ° with respect to the first section, and the vertical axis represents the distance from the light source center to the emission side surface when the light source center is the origin. In these graphs, the screen side is shown as positive. 7-9, since the position where the graph becomes the highest is the maximum point LP, in the present embodiment, the position is about 1.7 mm from the optical axis OA to the opposite screen side, and the angle from the light source center is about 9 mm. It can be seen that there is a maximum point LP at the position of °.

  Further, in FIG. 6, the exit surface LSd is a surface on which the screen SC side is loose and the anti-screen SC side changes more rapidly than the local maximum point LP.

  The power change will be described. FIG. 10 shows the height (distance) from the maximum point with respect to the first cross section on the horizontal axis in the present embodiment, and the vertical axis shows the angle γ (FIG. 6) between the normal of the exit surface and the optical axis. This is a graph showing the screen side as positive. As shown in FIG. 10, γ = 0 at the maximum point, and as the distance from the point increases, the angle γ increases on both the screen SC side and the anti-screen SC side, but the increase amount is larger on the anti-screen SC side. . That is, the exit surface LSd can be said to be a surface where the screen SC side is loose and the anti-screen SC side undergoes a sudden power change.

Further, the maximum point LP on the exit surface LSd of the lens LS exists at a position of an angle α (°) on the side opposite to the screen SC with respect to the optical axis OA when viewed from the light source center OC in the first cross section shown in FIG. The following formula is satisfied.
0 <α ≦ 20 (1)

  Further, in the first cross section shown in FIG. 4, a straight line SL passing through the light source center OC and the maximum point LP and a line segment DL connecting the light source center OC and the farthest point FP (see FIG. 2) of the screen SC. The angle β is preferably within ± 10 °. That is, the local maximum point LP is preferably present in the vicinity of the line segment DL connecting the light source center OC and the farthest point FP of the screen SC. The distance between the light source center OC and the exit surface LSd of the lens LS is preferably maximized in the vicinity of a line segment DL connecting the light source center OC and the farthest point FP of the screen SC in the first cross section shown in FIG.

  Next, the operation of the present embodiment will be described. The light beam emitted from the light emitting surface of the LED light source LED enters the lens LS from the main incident surface LSb and the side surface incident surface LSC. Here, in the second cross section shown in FIG. 3, since the lens LS has a symmetrical shape, the light beam emitted from the emission surface LSd is also equally distributed to both sides across the optical axis OA, and illuminates the screen SC. (See FIG. 1).

  On the other hand, in the first cross section shown in FIG. 4, since the power change of the exit surface LSd on the screen SC side is gentler than the local maximum point LP, a weak light condensing action occurs when passing through this region. Some light beams are directed toward the farthest point FP side of the screen SC. On the other hand, since the power change of the exit surface LSd is abrupt on the side opposite to the screen SC from the maximum point LP, a condensing action occurs when passing through this region, and this causes the farthest point of the screen SC Most of the light rays are directed toward the FP side. In other words, when a light source that passes through either the screen SC side or the anti-screen SC side across the local maximum point LP is directed to the farthest point FP side, an LED light source having a Lambertian irradiation characteristic is used. However, the illuminance in the vicinity of the farthest point FP where the illuminance is most likely to decrease can be increased.

  Hereinafter, lenses according to examples of the present embodiment will be described. The shape of the aspherical surface in the following examples is such that the vertex of the surface is the origin, the Z-axis is taken in the optical axis direction, the height in the X-axis direction with respect to the optical axis is x, and the height in the Y-axis direction is y. It shall be expressed by the following formula 1 substituting the numerical values shown in the table. In the embodiment, the flange portion is omitted.

However,
αi, βi: i-th order aspheric coefficient (i = 3,4,5,6,... 20)
R (Lens data table, X direction radius is Rx, Y direction radius is Ry): Radius of curvature k (Lens data table, X direction radius is kx, Y direction radius is ky): Conic coefficient A power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02).

Example 1
Table 1 shows lens data of Example 1. FIG. 11 is a perspective view of the lens according to Example 1 as seen in a direction perpendicular to the XZ cross section, and FIG. 12 is a perspective view of the lens according to Example 1 as seen in a direction perpendicular to the YZ cross section. Each lens surface is represented by a wire. 13 is an XZ sectional view of the lens according to Example 1, and FIG. 14 is a YZ sectional view of the lens according to Example 1, which corresponds to FIGS. FIGS. 15 and 16 are diagrams showing the illuminance on the screen in monochrome shades when illuminated from the right direction by the illumination device using the lens of Example 1 (the white one has higher illuminance), and FIG. A linear scale is shown, and FIG. 16 is a log scale. The illuminance felt through human vision is closer to the log scale. FIG. 17 is an illuminance cross-sectional view of Example 1, showing an illuminance distribution when the center of the screen C in the XZ cross section is zero, and min / ave = 0.56.

  In Example 1, the height from the light source on the optical axis of the incident surface is 3.5 mm, the diameter of the incident surface is φ8 mm, and the height from the light source on the optical axis of the output surface is 10 mm. The exit surface diameter is 21 mm. The angle formed by the optical axis and the screen in the first cross section is 34.72 °. Also, α = 11.25 ° and β = 7.08 °.

  18 is a perspective view seen in a direction perpendicular to the XZ section of the lens according to the comparative example, and FIG. 19 is a perspective view seen in a direction perpendicular to the YZ section of the lens according to the comparative example. The surface is represented by a wire. 20 and 21 are diagrams showing the illuminance on the screen when illuminated from the right direction by the illumination device using the lens of the comparative example, FIG. 20 shows a linear scale, and FIG. 21 shows a log scale. ing. FIG. 22 is an illuminance cross-sectional view of a comparative example, showing an illuminance distribution when the center of the screen C in the XZ cross section is zero, and min / ave = 0.07.

  In the comparative example, the exit surface of the lens has a shape symmetrical with respect to the optical axis regardless of whether the XZ cross section or the YZ cross section. Further, the incident surface of the lens has a uniform height in the XZ section, and has a so-called saddle shape in which the height decreases in the YZ section as the distance from the optical axis increases.

  On the other hand, in Example 1, the exit surface of the lens has a shape that is symmetrical with respect to the optical axis in the YZ section, but in the XZ section, it has a non-symmetrical shape with the optical axis in between. From the point of view, the screen side (left side in FIG. 11) is loose and the anti-screen surface side is a surface where the power changes more suddenly. In addition, the incident surface of the lens has a uniform height in the XZ section, the highest in the vicinity of the optical axis in the YZ section, and the height decreases with increasing distance from the lens, and then the height of the incident surface is increased. The shape increases. This is an example, and there may be no point beyond the inflection point. Other specifications are common to the comparative example and the first embodiment.

  15, 16, and 17 and FIGS. 20, 21, and 22, it is clear that in the case of the comparative example, only the right center of the screen (near the lighting device) is bright and has uneven illuminance. . On the other hand, in Example 1, it turns out that the illumination intensity of the whole screen is uniform.

(Example 2)
Table 2 shows lens data of Example 2. FIG. 23 is a perspective view seen in a direction perpendicular to the XZ section of the lens according to Example 2, and FIG. 24 is a perspective view seen in a direction perpendicular to the YZ section of the lens according to Example 2. The surface of the lens is represented by a wire. FIG. 25 is an XZ cross section of the lens according to Example 2, and FIG. 26 is a cross sectional view slightly tilted to the YZ cross section of the lens according to Example 2, corresponding to FIGS. 23 and 24, respectively. doing. FIG. 27 is an illuminance cross-sectional view of Example 2, showing an illuminance distribution when the center of the screen C in the XZ cross section is zero, and min / ave = 0.47.

  In Example 2, the height from the light source on the optical axis of the incident surface is 5 mm, the diameter of the incident surface is φ10 mm, and the height from the light source on the optical axis of the output surface is 10 mm. The surface diameter is 21 mm. The angle formed between the optical axis and the screen in the first cross section is 35.72 °. Further, α = 13.10 ° and β = 5.58 °.

  In Example 2, the height of the incident surface of the lens is uniform in the XZ section and the YZ section only on the side opposite to the screen (left side in FIG. 23) from the optical axis OA. On the other hand, on the screen side from the optical axis OA, the height is uniform in the XZ section, whereas in the YZ section, the vicinity of the optical axis is the highest, and after moving away from the height, the inflection point decreases. The shape is such that the height increases across the wall. The exit surface is the same as in the first embodiment.

(Example 3)
Table 3 shows lens data of Example 3. 28 is a perspective view seen in a direction orthogonal to the XZ section of the lens according to Example 3, and FIG. 29 is a perspective view seen in a direction perpendicular to the YZ section of the lens according to Example 3. The surface of the lens is represented by a wire. FIG. 30 is an illuminance cross-sectional view of Example 1, showing an illuminance distribution when the center of the screen C in the XZ cross section is zero, and min / ave = 0.67.

  In Example 3, the height from the light source on the optical axis of the incident surface is 3.5 mm, the diameter of the incident surface is φ10 mm, and the height from the light source on the optical axis of the output surface is 9.5 mm. The exit surface diameter is φ18 mm. The angle formed by the optical axis and the screen in the first cross section is 30 °. Α = 8.21 ° and β = 5.40 °.

  In Example 3, the surface shape of Example 1 is used as a basis, and a total reflection surface based on a paraboloid is provided around the recesses that form the incident surface. A light beam emitted from an LED light source (not shown) is incident on the concave portion of the lens, and then a part of the light is reflected by the total reflection surface and emitted from the emission surface. When importance is attached to the uniformity of the illuminance on the screen, it is preferable not to provide a total reflection surface as in the first and second embodiments. However, when it is desired to ensure the absolute value of the illuminance on the screen, the third embodiment is effective. It is.

  The lighting device is not limited to the combination of the lens and the surface emitting light source according to the above-described embodiment, and in addition to the combination, a combination of another lens and the surface emitting light source may be provided. good. As such a lens, a lens LS ′ shown in FIG. 31 can be preferably used. More specifically, the lens LS ′ includes a concave portion LSa as a light source side incident surface, an output surface LSd, and a parabolic total reflection surface LSg provided between the concave portion LSa and the output surface LSd. Have. For example, the illumination device comprising the combination of the lens LS and the surface emitting light source according to the above-described embodiment is arranged in a line below the screen to illuminate the screen, and the illumination device includes lenses LS ′ at both ends of the arrangement. It is preferable that the four corners of the screen, which tends to be dark, are spot-illuminated to make the illuminance of the entire screen more uniform.

DL Line segment FP Farthest point LED LED light source LP Maximum point LS Lens LSa Recessed portion LSb Main entrance surface LSc Side entrance surface LSd Outgoing surface LSe Flange portion LSf Leg portion OA Optical axis OC Light source center SC Screen SL Linear ST Substrate

Claims (19)

An optical element for illuminating a surface to be irradiated with uniform illuminance by transmitting light emitted from a surface-emitting light source,
The optical element comprises a single lens;
The incident side surface of the lens has a recess,
An optical element having a convex shape on the exit side surface of the lens, and a surface on which the irradiated surface side is loose as viewed from the maximum point, and the anti-irradiated surface side has a power change that is steeper than that.   The optical element according to claim 1, wherein the lens has a non-rotationally symmetric shape with respect to an optical axis of the surface-emitting light source.   The optical element according to claim 1, wherein an optical axis of the surface-emitting light source is inclined with respect to the irradiated surface.   When the optical axis of the surface-emitting light source is the Z axis, the axis orthogonal to the Z axis and parallel to the irradiated surface is the Y axis, and the axis orthogonal to both the Z axis and the Y axis is the X axis, 4. The optical device according to claim 1, wherein an exit side surface of the lens has an asymmetric shape with respect to the Z axis in a first cross section cut along an XZ plane passing through the maximum point. element.   5. The optical element according to claim 4, wherein the maximum point on the emission side surface of the lens is located on the side opposite to the irradiated surface with respect to the optical axis of the surface-emitting light source in the first cross section. The maximum point on the exit side surface of the lens exists in the first cross section at an angle α (°) on the side opposite to the irradiated surface with respect to the optical axis as viewed from the center of the surface emitting light source. The optical element according to claim 4, wherein the optical element is satisfied.
0 <α ≦ 20 (1)   7. The local maximum point on the exit side surface of the lens is present in the vicinity of a line segment connecting the center of the surface-emitting light source and the farthest point of the irradiated surface in the first cross section. The optical element in any one.   The distance between the surface emitting light source center and the exit surface of the lens is maximized in the vicinity of a line segment connecting the surface emitting light source center and the farthest point of the irradiated surface in the first cross section. The optical element according to any one of claims 4 to 7.   When the optical axis of the surface-emitting light source is the Z-axis and the axis perpendicular to the Z-axis and parallel to the irradiated surface is the Y-axis, the exit side surface of the lens passes through the maximum point and is parallel to the YZ plane. 9. The optical element according to claim 1, wherein the optical element has a shape symmetric with respect to the Z axis in the second cross section cut along a smooth surface.   The optical element according to claim 1, wherein the exit side surface of the lens is connected smoothly.   The optical element according to claim 1, wherein an incident side surface of the lens has an anamorphic surface shape.   When the optical axis of the surface-emitting light source is the Z axis, the axis orthogonal to the Z axis and parallel to the irradiated surface is the Y axis, and the axis orthogonal to both the Z axis and the Y axis is the X axis, The optical element according to claim 1, wherein an incident side surface of the lens has an asymmetric shape in a first cross section cut along an XZ plane passing through the maximum point.   The incident side surface of the lens passes through the maximum point and is parallel to the YZ plane when the optical axis of the surface-emitting light source is the Z-axis and the axis orthogonal to the Z-axis and parallel to the irradiated surface is the Y-axis. The optical element according to claim 1, wherein the optical element has a shape symmetrical with respect to the Z axis in the second cross section cut along a smooth surface.   The optical element according to claim 1, wherein the incident side surface of the lens is defined by two or more surface definition formulas.   The optical element according to any one of claims 1 to 14, wherein a total reflection surface based on a paraboloid is provided in a peripheral portion of the lens.   The optical element according to claim 1, wherein a flange portion is provided in a peripheral portion of the lens.   The optical element according to claim 1, wherein the lens is molded from a resin.   An illumination device comprising the optical element according to claim 1 and a surface-emitting light source.   The lighting device according to claim 18, wherein another optical element is provided in addition to the optical element according to claim 1.