Lighting device

A lighting device includes a light emitting element; a first lens that receives light emitted from the light emitting element and emits first emission light; and a second lens that receives the first emission light and emits second emission light. The first lens has a first emission surface emitting the first emission light, the first emission surface having a convex shape protruding in a Z direction.

BACKGROUND

1. Technical Field

The present disclosure relates to a lighting device having a cutoff function.

2. Description of the Related Art

In the related art, there is a lighting device having a cutoff function. For example, in a floodlight or the like used for an outdoor ground, light emitted in a predetermined direction is cut so that the light does not leak to a peripheral portion of the ground.

In Japanese Patent Unexamined Publication No. 2018-206600, the light incident on an upper portion of a first lens is reflected downward by a second reflection surface formed on the first lens and light incident on an upper portion of the second lens is cut. The light reflected by the second reflection surface is superposed on the light not reflected by the second reflection surface and is incident on a lower portion of the second lens. Since the second lens has a convex light incident portion, the light incident on a side wall (side surface portion) of the second lens can be reduced. Therefore, in Japanese Patent Unexamined Publication No. 2018-206600, stray light and a decrease in optical efficiency are prevented.

SUMMARY

In order to achieve the object described above, a lighting device according to one aspect of the present disclosure includes a light emitting element; a first lens that receives light emitted from the light emitting element and emits first emission light; and a second lens that receives the first emission light and emits second emission light. The first lens has a first emission surface emitting the first emission light. The first emission surface has a convex shape protruding in a traveling direction of the light emitted from the light emitting element.

DETAILED DESCRIPTIONS

Although an emission surface of a first lens in Japanese Patent Unexamined Publication No. 2018-206600 is a flat surface, when the first lens is formed by molding, sink marks are likely to occur on the emission surface of the first lens. In particular, when the first lens is rapidly cooled in order to shorten a manufacturing time of the first lens, the emission surface of the first lens is likely to be concave.

In a case where a second lens is formed by die molding, processing R is given to the emission surface. Although it is possible to suppress processing R by creating the second lens separately for a side surface portion and an emission surface portion, it is necessary to create a plurality of molds, which significantly increases the cost.

In a case where the emission surface of the first lens has the concave shape and processing R is given to an upper portion of the emission surface of the second lens, the light incident on the emission surface of the first lens from the light emitting element is refracted upward on the emission surface of the first lens by a concave lens effect of the first lens, and is further refracted upward on the emission surface of the second lens by processing R formed on the emission surface of the second lens. Therefore, light is emitted upward from the emission surface of the second lens, and stray light is generated.

An object of the present disclosure is to provide a lighting device having a cutoff function, which can suppress the generation of stray light while suppressing the cost.

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the drawings. The description of the preferred exemplary embodiments below is merely an example in nature and is not intended to limit the present disclosure, an application thereof, or a use thereof.

FIG. 1illustrates a side view of a lighting device according to the present exemplary embodiment, andFIG. 2illustrates a plan view of a second lens and a diffusion plate according to the exemplary embodiment. As illustrated inFIG. 1, lighting device10includes light emitting element1, first lens2, second lens3, and diffusion plate4. In the following description, a Z-axis represents an optical axis of light emitting element1, and a traveling direction of light emitted from light emitting element1is a positive direction of the Z-axis. A Y-axis is an axis extending in a vertical direction, and an upward direction is a positive direction of the Y-axis. An X-axis represents a direction perpendicular to the Y-axis and the Z-axis. First lens2, second lens3, and diffusion plate4are respectively made of transparent resin. First lens2, second lens3, and diffusion plate4are made of, for example, polypropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride, ABS resin, acrylic, polyamide, polycarbonate, Teflon (registered trademark), or the like.

Light emitting element1is configured of an LED or the like and has an optical axis on the Z-axis.

First lens2receives light emitted from light emitting element1and emits the first emission light to second lens3. Specifically, first lens2includes first incident port21, first emission surface22, and first top surface portion23and first bottom surface portion26provided between first incident port21and first emission surface22. First top surface portion23and first bottom surface portion26are collectively referred to as a first side surface portion.

First incident port21is formed on a left side of first lens2in the drawing, and is formed in a concave shape so as to surround light emitting element1. First incident port21receives the light emitted from light emitting element1.

First top surface portion23includes first reflection surface24. First bottom surface portion26includes second reflection surface25.

First reflection surface24is formed so as to spread from an upper end portion of an opening of first incident port21obliquely upward to the right in the drawing and in an X direction. First reflection surface24reflects the light incident on first lens2from first incident port21toward first emission surface22or toward second reflection surface25.

Second reflection surface25is formed so as to spread from a lower end portion of first emission surface22obliquely downward to the left in the drawing and in the X direction. Second reflection surface25reflects the light incident on first lens2from first incident port21toward first emission surface22. Second reflection surface25also reflects the light reflected by first reflection surface24toward first emission surface22.

First emission surface22is formed on the right side of first lens2in the drawing. First emission surface22emits, to second lens3, the light emitted from light emitting element1, the light reflected by first reflection surface24, and the light reflected by second reflection surface25as the first emission light. First emission surface22is formed so that a curvature on the X-axis and a curvature on the Y-axis are different from each other.

In first lens2, the light emitted from light emitting element1toward the lower side of the drawing is reflected by second reflection surface25and emitted from first emission surface22toward the upper side of the drawing. Therefore, second reflection surface25cuts the light emitted from first emission surface22toward the lower side of the drawing.

The light emitted from light emitting element1toward the upper side of the drawing is reflected by first reflection surface24toward the lower side of the drawing, and is reflected by second reflection surface25toward the upper side of the drawing. Thus, the light is emitted from first emission surface22toward the upper side of the drawing. Therefore, the optical efficiency of lighting device10can be increased by first reflection surface24and second reflection surface25.

Second lens3receives the first emission light emitted from first lens2and emits the second emission light. Second lens3is an anamorphic lens having different curvatures on the Y-axis and the X-axis.

Specifically, second lens3includes second incident surface31, second emission surface32, and second top surface portion33and second bottom surface portion36provided between second incident surface31and second emission surface32. Second top surface portion33and second bottom surface portion36are collectively referred to as a second side surface portion.

Second incident surface31is formed on the left side of second lens3in the drawing, and is formed so as to be convex in the negative direction of the Z-axis. Second incident surface31receives the first emission light emitted from first emission surface22of first lens2.

Second emission surface32is formed on the right side of second lens3in the drawing, and is formed so as to be convex in the positive direction of the Z-axis. Second emission surface32emits the light incident on second lens3as the second emission light.

Lens processing portion34is provided on a lower side (lower portion of second emission surface32) of second lens3in the drawing. Lens processing portion34is a portion to which R is given on second emission surface32in a case where second lens3is created by integral molding. The light emitted from first emission surface22of first lens2becomes stray light when incident on lens processing portion34.

Diffusion plate4is a plate-shaped member formed so as to extend in the X-axis and the Y-axis. Diffusion plate4receives the second emission light emitted from second lens3and diffuses the second emission light in the X-axis direction. Specifically, surface41of diffusion plate4facing second lens3is waved. Therefore, when the second emission light is incident on diffusion plate4, it is diffused by surface41of diffusion plate4in the positive direction or the negative direction of the X-axis.

FIG. 3illustrates a side view of a lighting device of the related art. InFIG. 3, since first lens2ais created by molding, first emission surface22ahas a concave shape. Emission light R1ais emission light in a case where first emission surface22ais a flat surface, and emission light R2ais actual emission light.

Emission light R2aincident on first lens2afrom light emitting element1and reflected by first reflection surface24ahas an emission direction from first emission surface22a, which is downward from emission light Ma in the drawing by the concave lens effect of first emission surface22a. Since emission light R2ais incident on lens processing portion34aof second lens3a, emission light R2ais emitted further downward from the emission light R1ain the drawing. Therefore, emission light R2abecomes stray light.

Therefore, inFIG. 1, first lens2is created so that first emission surface22of first lens2has a convex shape. Specifically, first emission surface22has a convex shape protruding in the positive direction of the Z-axis.

As illustrated inFIG. 1, emission light R3incident on first lens2from light emitting element1and reflected by first reflection surface24of first lens2is emitted from first emission surface22. In this case, since first emission surface22is formed in the convex shape, it is refracted upward in the drawing from emission light R2aofFIG. 3. Therefore, emission light R3is incident on second emission surface32so as not to be incident on lens processing portion34of second lens3. That is, by forming first emission surface22in the convex shape, emission light R3does not become stray light. Therefore, in lighting device10having the cutoff function, it is possible to suppress the generation of stray light while suppressing the cost. In the present exemplary embodiment, lighting device10can cut the light which goes to the positive direction of the Y-axis.

A relationship between first lens2and second lens3will be described.

First lens2and second lens3are disposed so as to satisfy at least one of the following expressions (1) to (3).
0.7×F≤D≤1.3×F(1)
0.9×F≤D≤1.1×F(2)
0.95×F≤D≤1.05×F(3)

Here, D is a distance from main plane S of second lens3to apex p1of first emission surface22of first lens2, and F is a distance from main plane S of second lens3to focal point f of the second lens.

Main plane S of second lens3passes through midpoint p4between apex p2of second incident surface31and apex p3of second emission surface32of second lens3, and is an XY plane perpendicular to the Z-axis (direction in which the optical axis of light emitting element1is extended). Apex p1on first emission surface22is a point closest from second lens3on the Z-axis. Apex p2on second incident surface31is a point closest from first lens2on the Z-axis. Apex p3is a point on second emission surface32farthest from first lens2on the Z-axis. Focal point f is a point where the light incident on second lens3from first lens2side along the Z-axis is collected.

In order to provide lighting device10with a high degree of light distribution performance, it is preferable to satisfy the expression (1), more preferably the expression (2), and further preferably the expression (3).

First lens2is created so as to satisfy the following relationship.
0.003×L≤T(4)

Here, L is a length of first emission surface22on the Y-axis. T is a distance on the Z-axis from an end (point farthest from second lens3on the Z-axis) of first emission surface22to apex p1. Accordingly, it is possible to suppress distortion of first emission surface22when first lens2is created.

First lens2and second lens3are created and disposed so as to satisfy the following expressions (5) to (7).
T≤0.1×F(5)
T≤0.05×F(6)
T≤0.02×F(7)

Thereby, lighting device10can be provided with a high degree of light distribution performance. In order to provide lighting device10with a high degree of light distribution performance, it is preferable to satisfy the expression (5), more preferably the expression (6), and further preferably the expression (7).

OTHER EXEMPLARY EMBODIMENTS

The exemplary embodiments are described above as examples of the technique disclosed in the present application. However, the technique in the present disclosure is not limited to these, and is also applicable to exemplary embodiments in which changes, replacements, additions, omissions, and the like are appropriately made.

In the exemplary embodiment described above, first lens2is created through a cooling step of cooling first lens2after a molding step of molding with a mold or the like. First emission surface22of first lens2does not necessarily have to be formed in a convex shape during use, and may be created in a convex shape during manufacturing (particularly, during the molding step). In other words, when being used, first emission surface22doesn't need to be concave, and may be flat or convex. Thereby, it is possible to prevent first emission surface22of first lens2from being concave, and thus it is possible to prevent light from being incident on lens processing portion34of second lens3, and the effect described above can be obtained.

In the exemplary embodiment described above, diffusion plate4may not be provided.

The lighting device of the present disclosure can be applied to a lighting device having a cutoff function, such as a vehicle headlight and floodlight installed on the ground.