JP7674858B2 - Lighting fixtures - Google Patents

Description

The present invention relates to lighting fixtures to be mounted on moving objects, and in particular to lighting fixtures suitable for use as landing lights and running lights for aircraft.

Aircraft are equipped with landing lights and running lights as lighting fixtures. For example, as shown in the schematic configuration in FIG. 1, the left and right main wings MW of aircraft AP are equipped with landing lights 1 at the leading edge near the fuselage, and are configured to emit light forward of the aircraft AP. As shown in FIG. 2, the landing lights 1 illuminate the forward area FA of the runway when the aircraft AP lands. Although not shown, running lights may also be equipped together with the landing lights 1, and the running lights illuminate the taxiway in front of the aircraft as it taxis.

In recent years, lighting fixtures that use semiconductor light-emitting elements as light sources have been proposed for illuminating such aircraft. For example, Patent Document 1 proposes a lighting fixture that uses an LED (light-emitting diode) as a light source, in which the light emitted by the LED is reflected by a reflector and irradiated as illumination light with the required light distribution characteristics.

JP 2014-89868 A

In the lamp of Patent Document 1, the reflector is formed in a plate shape and curved to obtain the required light reflection characteristics, so the dimension of the lamp in the front-to-rear direction is large, and as a result, the thickness dimension of the lamp is large, which can be an obstacle when installing it on an aircraft. In addition, because the reflector is supported at one end, it is difficult to increase its mechanical strength, and the reflector is easily deformed by changes in the external environment in which the aircraft is placed, particularly temperature changes. Even a slight deformation of the reflector can change the light reflection characteristics of the LED, which can change the light distribution of the illuminating light.

To solve these problems, lighting fixtures using lenses with optical steps have been considered. For example, there is a lighting fixture that uses a lens with so-called cylindrical steps, in which the cylindrical surfaces are arranged in a lattice pattern, to disperse light and illuminate a desired area. However, as will be described later, illumination using cylindrical steps has the problem that unevenness occurs in the light distribution, particularly brightness, in the illuminated area, making it difficult to achieve illumination with uniform brightness.

The object of the present invention is to provide a lighting fixture that allows illumination with uniform brightness in a lighting fixture that illuminates a desired area using optical steps provided in a lens.

The present invention includes a light source and a lens that transmits light emitted from the light source and emits it as illumination light, and the lens includes a light diverging step that diverges the light. The light diverging step has a plurality of unit steps arranged in a lattice pattern, and each unit step is formed of a non-arc concave cylindrical surface made up of a curve circumscribing a plurality of arcs whose radii gradually increase while shifting their center positions , and the radius of curvature of the central part of the non-arc concave cylindrical surface in the arrangement direction is smaller than the radius of curvature of both sides .

In the present invention, it is further preferable that the light divergence step comprises a plurality of unit steps having different light divergence angles, and that the unit steps are arranged so that the divergence angle of the unit step in the central region in the lens arrangement direction is larger than the divergence angles of the unit steps in both side regions.

In addition, in the present invention, it is preferable that the lens has light deflection steps in both side regions in a direction intersecting with the arrangement direction of the unit steps, which deflect light passing through the respective side regions toward the central region. Alternatively, when the light source is composed of a plurality of light-emitting elements arranged in both the direction of arrangement of the unit steps and in a direction intersecting with this arrangement direction, it is preferable that the light-emitting surfaces of the light-emitting elements arranged in the both side regions in the direction intersecting with the arrangement direction of the unit steps are inclined toward the central region.

Furthermore, the present invention preferably has the following form.
(1) A lamp includes a lamp case and an outer lens provided at an opening of the lamp case, a light source is housed within the lamp case, and a light diverging step is provided on the outer lens.
(2) An inner lens is disposed between the light source and the outer lens, and the inner lens is provided with a focusing step for focusing the light emitted from the light-emitting element.
(3) The light diverging step has a configuration in which a plurality of unit steps are arranged in the horizontal direction, and each unit step diverges light in the horizontal direction.

According to the present invention, the light divergence step provided in the lens allows the desired area to be illuminated, and the desired area can be illuminated with uniform brightness. Furthermore, according to the present invention, it is possible to provide a thin illumination with a stable light distribution.

FIG. 1 is a schematic diagram of a portion of an aircraft equipped with landing lights, with a partially cutaway external view. 1A is a schematic plan view showing the illumination state, and FIG. 1B is a light distribution diagram along line BB. FIG. 2 is a schematic, partially exploded perspective view of a landing light; Horizontal cross section of the landing light. FIG. 5 is an enlarged schematic diagram of a portion of FIG. 4 . FIG. 6 is a schematic diagram similar to FIG. 5 of a landing light of a reference example. 11A to 11C are schematic diagrams illustrating a design example of a non-arcuate concave cylindrical surface of a unit step. FIG. 6 is a horizontal cross-sectional view of a main part of a landing light according to a second embodiment. 11A and 11B are diagrams of a landing light of embodiment 3, in which (a) is a front view of an outer lens, and (b) is a vertical cross-sectional view of a main part of the landing light. FIG. 11 is a vertical cross-sectional view of a main part of a landing light according to a fourth embodiment.

Next, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a cutaway external view of a portion of an aircraft AP equipped with a landing light 1, a recess that opens forward is formed in the leading edge of the main wing MW of the aircraft AP, and a lamp housing chamber 100 is provided. The landing light 1 is housed within this lamp housing chamber 100, and is configured to emit illumination light through the opening. A translucent front cover 101 is attached to the opening edge 102 of this opening, and this front cover 101 seals the interior of the lamp housing chamber 100 and protects the landing light 1 from the external environment.

Figure 3 is an exploded perspective view of the landing light, and Figure 4 is a horizontal cross-sectional view of the landing light 1. This landing light is equipped with a circular dish-shaped lamp case 2 with an opening at the front, in which a light source substrate 3 and an inner lens 4 are installed, and an outer lens 5 is attached to a flange portion 21 at the front opening of the lamp case 1. As shown in Figure 1, this landing light 1 is fixed and supported in the lamp housing chamber 100 with the outer lens 5 facing forward, that is, with the outer lens 5 facing the front cover 101, and when lit, illumination light is emitted through the outer lens 5 and further through the front cover 101 toward the front of the aircraft AP.

The light source board 3 is formed in a circular plate shape and is supported along the inner bottom 20 of the lamp case 2 by a screw (small screw) 22. A plurality of light emitting elements, LEDs (light emitting diodes) 31 that emit white light, are mounted on the front surface of the light source board 3 (hereinafter, the side facing the outer lens 5 is referred to as the front) as a light source. In addition, although not shown, the light source board 3 is formed with the required wiring for supplying power to these LEDs 31. The multiple LEDs 31 are mounted in a required array over almost the entire area of the light source board 3 with their respective light emitting surfaces facing forward. In other words, they are mounted in multiple arrays in both the horizontal and vertical directions. Note that, in order to simplify the explanation, a smaller number of LEDs 31 than the actual number is shown in Figures 3 and 4.

The inner lens 4 is supported by screws 23 on the light source substrate 3 while maintaining a required distance from the front surface of the light source substrate 3. The inner lens 4 is made of a light-transmitting material, such as a transparent resin, and optical steps 41 are integrally formed on the rear surface of the inner lens 4 at positions facing the LEDs 31. In other words, the optical steps 41 are formed at positions where the light emitted from the light-emitting surface of each LED 31 is incident.

3 and 4 each show an enlarged view of one optical step 41, which is configured as a light-collecting step 41 that collects light emitted from the light-emitting surface of the LED 31 and functions as a condenser lens. The light-collecting step 41 protrudes rearward from the rear surface of the inner lens 4, and the outer peripheral surface 410 is formed in a shape similar to a truncated cone with a spindle surface that bulges outward to some extent. The upper bottom surface of the light-collecting step 41 faces the light-emitting surface of the LED 31 as a light-entering surface. An inverted cone-shaped recess is formed on the upper bottom surface, and the inner bottom surface of the recess is configured as the first entrance surface 411, and the inner peripheral surface 412 of the recess is configured as the second entrance surface. The first entrance surface 411 is formed as a spherical surface, and the second entrance surface 412 is formed as an inverted cone surface.

The outer lens 5 is made of a colorless translucent plate that allows light to pass through, and is fixed and supported in a state where it is fitted inside the flange portion 21 provided on the periphery of the lamp case 2. The outer lens 5 is also made of a translucent material, for example, a transparent resin. The outer lens 5 is formed in a roughly flat plate shape, and its front surface is formed flat as the light emission surface, but its rear surface is formed with an optical step for obtaining a predetermined light distribution, i.e., a light divergence step 51 for diverging light. The outer lens 5 may also be curved in a convex shape facing forward.

Before explaining this light dispersion step 51, we will explain the lighting distribution, particularly the brightness distribution (illuminance distribution) when lighting with this landing light 1. As shown in FIG. 2(a), the lighting light of the landing light 1 is irradiated in an oblique direction to the runway surface. Therefore, if the required area to be irradiated is, for example, an area close to a circle, the luminous flux shape of the light emitted from the landing light 1 (here, "luminous flux" means light with a required cross-sectional area), i.e., the cross-sectional shape of line B-B in the figure, is set to a lighting distribution P0 that is a horizontally flattened ellipse or oval shape, as shown in FIG. 2(b).

Therefore, in this embodiment 1, the light distribution is obtained by the light divergence step 51 of the outer lens 5. FIG. 5 is a schematic diagram of an enlarged portion of FIG. 4, in which the light emitted from the light-emitting surface of the LED 31 is transmitted through the inner lens 4, and is emitted from the front surface of the inner lens 4 as a substantially parallel light beam by the light collection step 41. That is, in the light collection step 41, the light emitted from the central region of the light-emitting surface of the LED 31 is incident on the first incident surface 411, refracted there, and emitted from the front surface of the inner lens 4. In addition, the light emitted from the peripheral region of the light-emitting surface of the LED 31 is incident on the second incident surface 412, refracted here, and then internally reflected at the outer peripheral surface 410 and emitted from the front surface of the inner lens 4.

As a result, the light emitted with the required spread from the light-emitting surface of the LED 31 is converged by passing through the focusing step 41, and is emitted from the front surface of the inner lens 4 as a light beam that is nearly parallel or has a slight spread. This light is then incident on the rear surface of the outer lens 5, and as it passes through the outer lens 5, it is diverged horizontally by the light divergence step 51 of the outer lens 5 and is emitted.

In order to disperse the light emitted from the outer lens 5 in the horizontal direction, the light diffusion step 51 is formed as a lattice-like step in which vertically extending strip-like unit steps 52 are arranged in multiple rows in the horizontal direction. Each unit step 52 has a horizontal cross section formed into a concave curved surface in order to disperse the light in the horizontal direction.

As shown in the schematic diagram of FIG. 6, the light divergence step 51A, which is the unit step 52A into which light is incident, has an incident surface 520 that is a concave cylindrical surface with a horizontal cross section of an arc (hereinafter referred to as an arc concave cylindrical surface). The light incident on this unit step 52A is refracted at the incident surface 520 and diverged in the horizontal direction. At this time, since the incident surface 520 of the unit step 52A is an arc concave cylindrical surface, the spread of the divergence of the light incident on the center part of the incident surface 520 (the center part in the horizontal direction, the same below) is smaller than the spread of the divergence of the light incident on both sides away from the center (the both sides sandwiching the center part in the horizontal direction, the same below).

Therefore, the light distribution of the landing light by the light diverging step 51A in which the unit steps 52A, whose entrance surface 520 is an arc-shaped concave cylindrical surface, are arranged in a lattice pattern, results in an illumination light distribution P1 with high illuminance in the central area and decreasing brightness toward both sides, as shown in Figure 6, making it difficult to illuminate the road surface with a uniform brightness.

On the other hand, the unit step 52 constituting the light divergence step 51 of the first embodiment shown in FIG. 5 has a horizontal cross-sectional shape of its entrance surface 521 formed as a non-arc cylindrical surface, that is, a concave cylindrical surface in which the radius of curvature gradually increases from the horizontal center toward both sides (hereinafter referred to as a non-arc concave cylindrical surface). For example, as shown in FIG. 7, a number of circles with gradually increasing radii while shifting the center positions are drawn, here an arc C1 of radius r1, an arc C2 of radius r2, and an arc C3 of radius r3, and a concave cylindrical surface formed of curves circumscribing these arcs is formed.

In the outer lens 5 having the light diverging steps 51 in which the unit steps 52 are arranged in a lattice pattern, as shown in FIG. 5, when the light emitted by the LED 31 passes through the inner lens 4 and is incident on the entrance surface 521 of the unit step 52, the incident light is diverged by refraction at the entrance surface 521 and is emitted from the front surface of the outer lens 5. At this time, since the entrance surface 521 of the unit step 52 is a non-arcuate concave cylindrical surface and the radius of curvature of the center is smaller than that of both sides, the light incident on this center is refracted at a larger angle than that of both sides and is diverged at a larger angle in the horizontal direction. In other words, the light diverged at the center of the entrance surface 521 is irradiated in a state where it spreads horizontally to the left and right with respect to the intended illumination area.

On the other hand, since the radius of curvature of both sides of the entrance surface 521 of the unit step 52 is larger than that of the center, the light incident on these sides is refracted at a smaller angle than that of the center, and the horizontal divergence angle is small. This divergence angle is designed to correspond to the illumination area, so that the light is irradiated in a state that spreads horizontally to the left and right toward the desired illumination area. This prevents the brightness of the central area of the desired illumination area from being partially high, and an illumination light distribution P with approximately uniform brightness in the horizontal direction is obtained.

Since this type of control of the illumination distribution is performed in each of the multiple unit steps 52 that make up the light divergence step 51, the illumination distributions of these multiple unit steps 52A are combined, and the illumination area illuminated by the landing light 1 is prevented from being partially brighter in the central area, resulting in an illumination distribution P with approximately uniform brightness in the horizontal direction.

In this embodiment 1, the desired lighting distribution is obtained by the light diverging step 51 formed on the plate-shaped outer lens 5, so the thickness dimension of the lamp in the front-to-rear direction is smaller than in a configuration with a curved reflector as in Patent Document 1, resulting in a thin landing light with a small dimension in the front-to-rear direction. In addition, since the outer lens 5 is supported by the lamp case 2 at its periphery, it is not deformed by changes in the external environment such as temperature changes, compared to a configuration using a cantilevered reflector as in Patent Document 1, and a stable lighting distribution is obtained.

In the first embodiment, as shown in FIG. 7, the entrance surface 521 of the unit step 52, i.e., the non-arc concave cylindrical surface, is designed based on the three arcs C1 to C3 with different radii of curvature, but the radii of curvature r1 to r3 of these arcs C1 to C3 may be designed to be different values, or the relative positions of the arcs C1 to C3 may be appropriately changed. The number of arcs may also be changed. By designing a non-arc shape in this way, the divergence of light on the entrance surface 521 of the unit step 52A can be adjusted to obtain the desired light distribution.

(Embodiment 2)
8 is a horizontal cross-sectional view of the main part of the landing light of the second embodiment, and parts equivalent to those of the first embodiment are given the same reference numerals. The second embodiment is the same as the first embodiment in that the light diverging step 51 of the outer lens 5 is composed of a plurality of unit steps each having a non-arcuate concave cylindrical surface, but in the second embodiment, the light diverging step 51 is composed of unit steps 52a, 52b, and 52c having different shapes of the entrance surface, and these unit steps 52a, 52b, and 52c are composed of non-arcuate concave cylindrical surfaces having different divergence angles of light diverged from the respective entrance surfaces.

In the second embodiment, the unit steps 52a, 52b, and 52c are composed of three types of entrance surfaces 521a, 521b, and 521c with relatively small, medium, and large divergence angles. In addition, unit steps 52a of the entrance surface 521a with a relatively large divergence angle are arranged in the horizontal central region of the outer lens 5, unit steps 52b of the entrance surface 521b with a smaller divergence angle than the central region are arranged in the intermediate regions on both sides, and unit steps 52c of the entrance surface 521c with an even smaller divergence angle are arranged in the regions on both sides of the outer lens 5.

When designing the incidence surfaces 521a-521c with different divergence angles, a non-arc concave cylindrical surface with different light divergence angles can be obtained by appropriately adjusting the radii, number, and relative positions of multiple circles as shown in FIG. 7. Note that FIG. 8 shows an example in which two unit steps 52a, 52b each with incidence surfaces with the same divergence angle are arranged, but the number of these is not limited.

In the outer lens 5 of embodiment 2, which has a light diverging step 51 in which unit steps 52a, 52b, and 52c of the incident surface with different divergence angles are arranged in the horizontal direction, the divergence angle of the unit step 52a in the central region is made larger than the unit steps 52b and 52c in the intermediate region and both side regions, so that the divergence angle of light incident on and transmitted through the central region of the outer lens 5 is larger when it is emitted than the light incident from the intermediate region of the outer lens 5 to both side regions.

As a result, in embodiment 2, the light diverged from the unit steps 52a in the central region of the outer lens 5 is irradiated in a state that spreads horizontally to the left and right toward the desired illumination region, preventing the brightness of the central region from being locally high. The same applies to the divergence of light from the unit steps 52b in the intermediate region, preventing the brightness of the intermediate region from being locally high. This results in an illumination light distribution with approximately uniform brightness in the horizontal direction.

In the second embodiment, each unit step 52a, 52b, 52c is composed of a non-arcuate concave cylindrical surface, but it may be configured to include unit steps of arcuate concave cylindrical surfaces with different radii of curvature. In this case, too, unit steps of arcuate concave cylindrical surfaces with smaller radii of curvature are arranged in the central region, and unit steps of arcuate concave cylindrical surfaces with relatively larger radii of curvature are arranged in the regions on both sides.

Even with the second embodiment, the thickness dimension in the front-to-rear direction of the lamp is smaller than that of a lamp using a reflector, resulting in a thin landing light. In addition, a stable lighting distribution that is resistant to changes in the external environment such as temperature changes is obtained. Furthermore, by appropriately designing the number of each of the multiple unit steps 52 with different divergence angles that make up the light divergence step 51, the light divergence state of the outer lens 5 as a whole can be adjusted to obtain the desired lighting distribution.

(Embodiment 3)
As shown in FIG. 1, the landing light 1 is installed in a lamp housing 100 provided in the main wing MW, and is configured to irradiate illumination light through the opening. Therefore, a part of the light emitted from the outer lens 5 of the landing light 1 may be blocked by the opening edge 102. In the landing light 1 of the first and second embodiments, the light divergence step 51 provided in the outer lens 5 suppresses the light divergence in both horizontal directions, so the light is rarely blocked by the opening edge 102. However, in the vertical direction of the outer lens 5, the light divergence is not particularly controlled, so that a part of the light emitted from the outer lens 5 may be blocked by the opening edge 102 in both vertical regions of the outer lens 5, i.e., the upper region and the lower region. Such blocked light is light that does not contribute to illumination, and the utilization efficiency of the light emitted by the LED is reduced.

Figure 9(a) is a schematic front view of the outer lens of the landing light 1 of embodiment 3. In embodiment 3, light deflection steps 53, 54 that deflect light toward the central region are formed in the upper and lower regions of the outer lens 5, respectively. When viewed from the front of the outer lens 5, these light deflection steps 53, 54 are regions that divide the upper and lower regions of the circular outer lens 5 by horizontal dividing lines. Figure 9(b) is a vertical cross-sectional view of the main part, in which the upper region of the outer lens 5 is formed as a lower light deflection step 53 in which the lens thickness gradually increases downward, and the lower region is formed as an upper light deflection step 54 in which the lens thickness gradually increases upward.

By providing these light deflection steps 53, 54, the light incident on the upper region of the outer lens 5 is refracted at the lower light deflection step 53 so that the emission direction is directed downward. Also, the light incident on the lower region of the outer lens 5 is refracted at the upper light deflection step 54 so that the emission direction is directed upward. This makes it difficult for the light emitted from the upper and lower regions of the outer lens to be blocked by the opening edge 102, and even if it is blocked, the amount of light blocked is small. Therefore, the efficiency of using the LED light can be improved.

Although not shown in the figures, the light deflection steps 53, 54 may be formed in the upper and lower regions of the rear surface of the outer lens 5. Even in this case, in the upper region, they are formed as lower light deflection steps in which the lens thickness gradually increases downward, and in the lower region, they are formed as upper light deflection steps in which the lens thickness gradually increases upward.

(Embodiment 4)
10 is a schematic vertical cross-sectional view of the landing light 1 of embodiment 4. The embodiment 4 can be considered a modification of the embodiment 3, and similarly to the embodiment 3, the purpose is to suppress a part of the light emitted from the outer lens 5 of the landing light 1 from being blocked by the opening edge 102 when the landing light is installed in the lamp housing chamber 100.

In this embodiment 4, the front surfaces of the upper region 32 and the lower region 33 of the light source substrate 3, i.e., the mounting surfaces on which the LEDs 31 are mounted, are each inclined toward the central region. In the upper region 32, the mounting surface is inclined downward at a required angle, and in the lower region 33, the mounting surface is inclined upward at a required angle. Therefore, the light emitting surface of the LEDs 31 mounted in the upper region 32 of the light source substrate 3 is inclined downward by the required angle. In addition, the light emitting surface of the LEDs 31 mounted in the lower region 33 of the light source substrate 3 is inclined upward by the required angle.

As a result, light incident on the inner lens 4 from the LEDs 31 in the upper region 32 of the substrate is directed downward, and light emitted from the inner lens 4 is deflected downward. Also, light incident on the inner lens 4 from the LEDs 31 in the lower region 33 of the substrate is directed upward, and light emitted from the inner lens 4 is deflected upward. As a result, light emitted from the inner lens 4 and then from the outer lens 5 is less likely to be blocked by the opening edge 102, and even if it is blocked, the amount of light blocked is small. Therefore, the effect of shading on the efficiency of LED light utilization can be ignored, and utilization efficiency can be increased.

In this fourth embodiment, the light-emitting surfaces of the LEDs 31 in the upper substrate region 32 and the lower substrate region 33 are inclined, and accordingly, the upper lens region 42 and the lower lens region 43 of the inner lens 4 arranged opposite these LEDs 31 are similarly inclined. Therefore, the light-collecting steps 41 in the upper lens region 42 and the lower lens region 43 are also inclined so as to face the light-emitting surfaces of the LEDs 31.

The present invention is not limited to the configuration of the embodiment described above, and light emitting elements other than LEDs can be used as the light source. Furthermore, the number of LEDs, i.e., the number of light emitting elements as the light source, and the number of focusing steps of the inner lens arranged opposite the light source are not limited. Furthermore, the shape of the focusing steps is not limited to the shapes described in the embodiment, and may be configured with steps that have light focusing properties, such as convex spherical steps.

In the embodiment, the outer lens is formed with light diverging steps and light deflecting steps, but a second inner lens separate from the inner lens described above may be provided and these steps may be formed on this second inner lens. That is, the second inner lens may be provided in front of the inner lens shown in the embodiment, and this second inner lens may be configured to diverge light horizontally or deflect light toward the center. In this case, the outer lens is configured simply as a translucent cover that transmits light.

In addition, the outer lens in the present invention does not necessarily have to be positioned at the outermost part of the lamp. For example, a translucent cover or a clear lens may be disposed on the outside of the outer lens to protect the outer lens or to enhance the design effect.

In the embodiment, the focusing step is disposed on the inner lens, but the focusing step and the light source may be configured as an integrated light source module, and when such a light source module is provided, the inner lens may be omitted. Alternatively, the outer lens may be configured as a clear lens, and a light diffusion step or a light deflection step may be formed on the inner lens.

The lighting fixture of the present invention is not limited to the landing lights of aircraft shown in the embodiment, but can be used as running lights of aircraft or lighting fixtures for other aircraft. It can also be used as a lighting fixture for lighting moving objects such as automobiles and trains. In addition, depending on the light distribution required for the lighting fixture, the light divergence step provided on the lens can be configured as a lighting fixture that diverges light in the vertical direction.

1. Landing lights (lighting fixtures)
2 Lamp case 3 Light source board 4 Inner lens 5 Outer lens 31 LED (light emitting element: light source)
32 Substrate lower region 33 Substrate upper region 41 Optical step (light collecting step)
42 Lens upper region 43 Lens lower region 51 Light diverging step 52, 52a, 52b, 52c Unit step 521, 521a, 521b, 521c Incident surface (non-arcuate concave cylindrical surface)
53 Lower light deflection step 54 Upper light deflection step 100 Lamp housing chamber 101 Front cover 102 Opening edge

Claims (9)

An illumination fixture comprising a light source and a lens that transmits light emitted from the light source and emits it as illumination light, the lens having a light divergence step that diverges light, the light divergence step being a plurality of unit steps arranged in a lattice pattern, each unit step being composed of a non-arc concave cylindrical surface composed of a curve circumscribing a plurality of arcs whose radii gradually increase as their center positions shift, the non-arc concave cylindrical surface having a smaller radius of curvature at a central portion in the arrangement direction than at both side portions, the plurality of unit steps being composed of a plurality of unit steps having different light divergence angles, and arranged so that the divergence angle of the unit step in the central region in the arrangement direction of the lens is greater than the divergence angle of the unit step in both side regions . 2. The illumination lamp according to claim 1 , wherein the lens includes light deflection steps in both side regions in a direction intersecting with an arrangement direction of the unit steps, the light deflection steps deflecting light passing through the both side regions toward a central region. The lighting fixture according to claim 1 or 2, wherein the light source is composed of a plurality of light-emitting elements arranged in the direction in which the unit steps are arranged and in a direction intersecting this arrangement direction. 4. The illumination lamp according to claim 3 , wherein the light emitting elements disposed in the two side regions in a direction intersecting the direction in which the unit steps are arranged have light emitting surfaces inclined toward the central region. 5. The illumination lamp according to claim 4 , comprising a lamp case and an outer lens provided at an opening of the lamp case, the light source being housed within the lamp case, and the light divergence step being provided on the outer lens. 6. The illumination lamp according to claim 5 , wherein an inner lens is disposed between the light source and the outer lens, and the inner lens is provided with a focusing step for focusing the light emitted from the light-emitting element. 7. The illumination lamp according to claim 1, wherein the light diverging step is configured by arranging a plurality of unit steps in a horizontal direction, and each unit step diverges light in the horizontal direction. 8. The illumination lamp according to claim 7 , which is mounted in a lamp housing chamber provided in the fuselage of an aircraft and emits light through an opening of the lamp housing chamber. 9. The lighting fixture according to claim 8 , configured as a landing light or a running light of an aircraft.

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