Lighting apparatus

A lighting apparatus includes a plurality of LEDs arranged in a row; an elongated wiring board on which the LEDs are mounted; and an optical lens covering all the LEDs and controlling distribution of light emitted from each LED. The light emitted from each LED has an optical axis orthogonal to the wiring board. The optical lens is a converging lens and includes a first light incident surface on which the light emitted from the LED is incident, a medium that guides the light incident from the light incident surface, a light emitting surface, and a diffusion section that contains diffusing particles for causing the light incident from the LED to diffuse. The concentration of the diffusing particles in the diffusion section is high in the vicinity of the optical axis of the light emitted from the LED and gradually decreases as a distance from the optical axis increases.

FIELD OF THE INVENTION

The present invention relates to a lighting apparatus that illuminates a ceiling in a cabin of an aircraft.

BACKGROUND OF THE INVENTION

Examples of lighting apparatuses provided in a cabin of an aircraft include: lighting apparatuses provided at a floor surface of an aisle at prescribed intervals; lighting apparatuses that locally illuminate passenger seats for passengers reading books or the like; and lighting apparatuses that illuminate a ceiling above the aisle. Among these lighting apparatuses, the brightness in the cabin is mainly controlled by the lighting apparatuses that illuminate the ceiling above the aisle.

In recent years, for improvement of fuel efficiency of aircrafts, not only the body of an aircraft but also various apparatuses installed in the cabin of the aircraft are required to be reduced in weight. For this purpose, a lighting apparatus for use in the cabin of an aircraft, which uses LEDs as light sources, has been known (refer to Patent Document 1, for example). In particular, many lighting apparatuses for illuminating the ceiling above the aisle are provided along the overall length of the cabin, and therefore, the use of compact and lightweight LEDs as light sources of each lighting apparatus contributes to reduction in the total weight of the aircraft.

FIG. 9is a diagram showing an example of installation of lighting apparatuses of this type. InFIG. 9, lighting apparatuses101and102are used for illuminating a ceiling C above an aisle P in a cabin of an aircraft AP, and are provided above and along one side and the other side of the aisle P, respectively. The lighting apparatuses101and102are mounted to upper ends of overhead storage bins SRp and SRw above an aisle-side seat Sp and a window-side seat Sw, respectively, so as to be invisible from passengers sitting in the seats Sp and Sw. InFIG. 9, dashed arrows indicate optical axis directions of illuminating light emitted from the lighting apparatuses101and102.

CITATION LIST

Patent Document

BRIEF SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

However, when two rows of lighting apparatuses101and102are provided for one aisle P as shown inFIG. 9, the total weight of the lighting apparatuses is great, and the total weight of the aircraft AP is increased by that weight, resulting in poor fuel efficiency of the aircraft AP. However, if each lighting apparatus101is mounted to the upper end of only the window-side storage bin SRw as shown inFIG. 10, the optical path length is increased in a direction (direction of an optical axis L of the lighting apparatus) from the lighting apparatus101to the ceiling C in the vicinity of the aisle-side storage bin SRp, and therefore, the area in the vicinity of the aisle-side storage bin SRp becomes dark. On the other hand, if an optical member having high convergence property in the direction of the optical axis L is used in the lighting apparatus101, the ceiling C in the vicinity of the aisle-side storage bin SRp can be made bright. In this case, however, only this area is brightened as if illuminated with spotlight, and the entire ceiling C is not uniformly illuminated, which might deteriorate the appearance of the ceiling.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a lighting apparatus that can uniformly illuminate the interior of a cabin of an aircraft even if less number of the lighting apparatuses than are conventionally used are provided in the cabin, and can contribute to reduction in the total weight of the aircraft and improvement of the fuel efficiency.

Solution to the Problems

The present invention is a lighting apparatus including: a plurality of LEDs arranged in a row; a wiring board having an elongated shape, on which the LEDs are mounted; and an optical lens that covers all the LEDs, and controls distribution of light emitted from each of the LEDs. The light emitted from each LED has an optical axis orthogonal to the wiring board. The optical lens is a converging lens, and includes a light incident surface on which the light emitted from the LED is incident, a medium that guides the light incident from the light incident surface, a light emitting surface that emits the light guided through the medium, and a diffusion section that contains diffusing particles for causing the light incident from the LED to diffuse. The concentration of the diffusing particles in the diffusion section is high in the vicinity of the optical axis of the light emitted from the LED and gradually decreases with a distance from the optical axis increases.

In the above lighting apparatus, preferably, the optical lens is configured to have a Fresnel structure at the light emitting surface.

In the above lighting apparatus, preferably, the optical lens further includes a translucent coating member that coats the light emitting surface, and the translucent coating member has a refractive index higher than a refractive index of the medium.

In the above lighting apparatus, preferably, the optical lens is configured to have a Fresnel structure at the light incident surface.

In the above lighting apparatus, preferably, the medium contains the diffusing particles to provide the diffusion section.

In the above lighting apparatus, the translucent coating member contains the diffusing particles to provide the diffusion section.

Effects of the Invention

According to the present invention, the lens converges light emitted from each LED in the direction of the optical axis of the light, while causing the light to diffuse around the optical axis because the concentration of the diffusing particles is high in the vicinity of the optical axis. Thus, the luminous flux is not concentrated in the direction of the optical axis. Therefore, for example, if the lighting apparatus is provided above and along one side of an aisle in a cabin, light emitted from the lighting apparatus can uniformly illuminate not only an area in the vicinity of the side where the lighting apparatus is provided but also an area in the vicinity of the other side of the aisle. Accordingly, it is possible to effectively illuminate the interior of the cabin with less number of lighting apparatuses as compared to the case where the lighting apparatuses are provided above and along the both sides of the aisle. Furthermore, the reduction in the number of the lighting apparatuses contributes to reduction in the total weight of the aircraft, and improvement of fuel efficiency.

DETAILED DESCRIPTION OF THE INVENTION

A lighting apparatus according to an embodiment of the present invention will be described with reference toFIGS. 1 to 6. As shown inFIG. 1, lighting apparatuses1are used for illuminating a ceiling C inside a cabin of an aircraft AP. The lighting apparatuses1are mounted to upper ends of overhead storage bins SRp and SRw located above an aisle-side seat Sp and a window-side seat Sw, respectively, along each of two passenger aisles P extending in the traveling direction of the aircraft AP. InFIG. 1, dashed arrows indicate optical axis directions of illuminating light emitted from the lighting apparatuses1.

As shown inFIG. 2, each lighting apparatus1has an elongated shape, and includes a plurality of LED units2arranged linearly. InFIG. 2, for example, ten LED units2are arranged at intervals of 20.8 mm. Each LED unit2includes three or more LEDs3(e.g., a red LED3R, a green LED3G, and a blue LED3B) arranged in a row. The LEDs3are arranged at intervals of 0.5 mm such that the length of the LED unit2is 10.3 mm in the direction along which the LEDs3are arranged. Since the LED units2and the LEDs3are arranged as described above. efficient mixing of light is achieved between the LED units2as well as among the LEDs3in each LED unit2.

As shown inFIG. 3, the lighting apparatus1includes: a wiring board4on which the LED units2are mounted; a drive circuit5, mounted on the wiring board4, for driving the LED units2; and an optical member (optical lens; hereinafter referred to as “lens6”) for controlling distribution of light emitted from each LED unit2. In addition, the lighting apparatus1includes a frame7that holds the above-mentioned components. The drive circuit5includes drivers (not shown) for individually driving the red LED3R, the green LED3G, and the blue LED3B, respectively.

The lens6has an elongated shape that covers all the ten LEDs unit2, and includes a medium60made of translucent resin such as polycarbonate, as a base. The lens6has a first light incident surface61on which light emitted from each LED unit2is incident, second light incident surfaces62provided outside the first light incident surface61, and a light emitting surface63that emits light guided through the medium60. Further, the lens6has a pair of flange portions64extending outward from both ends thereof in the transverse direction. The pair of flange portions64is slidingly inserted in a pair of grooves71provided along the longitudinal direction of the frame7, and thus the lens6is detachably mounted to the frame7. Further, the light emitting surface63and the flange portions64, on the side opposite to the wiring board4, are coated with a translucent coating member65. The medium60contains diffusing particles8that cause the incident light from the LED unit2to diffuse, and serves as a diffusion section. Preferably, the diffusing particles8have a refractive index higher than that of the medium60, and a difference between the refractive indices is about 0.17±0.02. The diffusing particles8are made of cross-linked acryl, for example. Preferably, the diffusing particles8are nanoparticles, and the mean particle diameter thereof is 0.8 to 2 nm.

As shown inFIG. 4, the red LED3R includes a red LED chip31R that emits red light, a base32on which the red LED chip31R is mounted, and an encapsulant33that encapsulates the red LED chip31R. The red LED3R is mounted on the wiring board4via a mounting surface32bof the base32on the side opposite to an LED-chip-mounted surface32aof the base32. The base32has a wiring (not shown) having one end connected to the red LED chip31R and the other end led from the mounting surface32b. The wiring led from the mounting surface32bis connected to a wiring pattern (not shown) on the wiring board4. The base32is made of a material excellent in heat conductivity and heat resistance, such as aluminum or ceramics.

The blue LED3B is configured in the same manner as the red LED3R, except having a blue LED chip31B that emits blue light, instead of the red LED chip31R.

The green LED3G includes a blue LED chip31B, a base34on which the blue LED chip31B is mounted, and green phosphor35that is dispersed in the encapsulant33and performs wavelength conversion of blue light to green light. The base34has a recess34aat the center thereof, and the blue LED chip31B is disposed on the bottom surface of the recess34a. Like the base32of the red LED3R and the blue LED3B, the base34also has a wiring (not shown), and the wiring connects the blue LED chip31B to the wiring pattern (not shown) on the wiring board4.

Generally, a green LED chip that emits green light has lower energy-to-light conversion efficiency and lower emission luminance than a blue LED chip or the like. The green LED3G configured by the use of the blue LED chip31B and the green phosphor35as described above has improved energy-to-light conversion efficiency and improved emission luminance as compared to a green LED configured by the use of a green LED chip.

The red LED3R and the blue LED3B configured as described above each have a relatively narrow light distribution angle (e.g., 80°), like a general LED. In contrast, the green LED3G has a relatively wide light distribution angle (e.g., 120°) because the entirety of the encapsulant33including the green phosphor35acts like a light source that emits green light. The green LED3G having the wide light distribution angle is disposed in the center (at an inner position) in the row of the LEDs3in the LED unit2, and the red LED3R and the blue LED3B having the narrow light distribution angle are disposed at both ends of the row of the LEDs3.

According to the above configuration, since the green LED3G having the wide light distribution angle is disposed in the center, green light emitted from the green LED3G is effectively mixed with red light and blue light emitted from the red LED3R and the blue LED3B adjacent to the green LED3G. Therefore, color nonuniformity of illuminating light can be reduced. Further, since the drive circuit5individually drives the respective LEDs3, the color of illuminating light emitted from the lighting apparatus1can be arbitrary controlled. Accordingly, it is possible to perform various kinds of artificial lighting, such as producing an atmosphere of early morning by illuminating the ceiling in the cabin with pale light, and producing an atmosphere of twilight by illuminating the ceiling with orange light.

FIG. 5shows a side sectional view of the lens6of the present embodiment. The first light incident surface61of the lens6has a curved surface convex toward the LED unit2. In the cross section of the lens6shown inFIG. 5(the cross section orthogonal to the longitudinal direction of the wiring board (refer toFIG. 3)), the concentration of the diffusing particles8is high in the vicinity of the optical axis L of the light emitted from the LED unit2and gradually decreases as the distance from the optical axis L increases. The second light incident surfaces62are formed outside and adjacent to the first light incident surface61. The second light incident surfaces62are configured to have a Fresnel structure.

In the lens6thus configured, light r1 emitted from the LED unit2and incident on the first light incident surface61is refracted at the first light incident surface61ahaving the convexly curved surface, guided through the medium60, and again refracted at a portion of the light emitting surface63having a Fresnel structure. As a result, the light r1 incident on the first light incident surface61is refracted twice and converged in the direction of the optical axis L. Further, light r2 incident on the second light incident surface62is refracted and totally reflected at the second light incident surface62, and again refracted at the Fresnel structure of the light emitting surface63. As a result, the light r2 incident on the second light incident surface62is also converged in the direction of the optical axis L. Since the lens6is configured to have the Fresnel structure at the both surfaces, the overall thickness of the lens6is reduced, thereby realizing weight reduction of the lens6and size reduction of the lighting apparatus1.

Since the light r1 and the light r2 incident on the first light incident surface61and the second light incident surface62, respectively, are converged in the direction of the optical axis L, the luminous flux of the light emitted from the LED unit2is increased most in the direction of the optical axis L. In the lens6of the present embodiment, the concentration of the diffusing particles8contained in the medium60is high in the vicinity of the optical axis L of the light emitted from the LED unit2and gradually decreases as the distance from the optical axis increases. Therefore, the lens6causes the light from the LED unit2to diffuse around the optical axis L while converging the light in the direction of the optical axis L.

According to a general lens, if the light converging property of the lens is improved to increase the light transmittance thereof, nonuniformity is more likely to occur at a surface illuminated with light. On the other hand, if the light diffusing property is improved, such nonuniformity at the illuminated surface is less likely to occur, but the luminance at the illuminated surface is degraded. That is, there is a tradeoff between the transparency of the lens and the light diffusing property. In contrast, according to the lens6of the present embodiment, the light converging property of the lens6is improved by its own shape to improve the light transmittance of the lens6. In addition, the concentration of the diffusing particles8is increased in the vicinity of the optical axis L where the luminous flux is increased to achieve the light diffusing property. Therefore, it is possible to achieve both the transparency of the lens and the light diffusing property.

Therefore, according to the present embodiment, the lens6converges the light emitted from the LED unit2in the direction of the optical axis L while causing the light to diffuse around the optical axis L because the concentration of the diffusing particles8is high in the vicinity of the optical axis, whereby the luminous flux is not concentrated in the direction of the optical axis L. Accordingly, if the lighting apparatus1is provided above and along one side of the aisle P in the cabin (refer toFIG. 1), light emitted from the lighting apparatus1uniformly illuminates not only an area in the vicinity of the side where the lighting apparatus is provided but also an area in the vicinity of the other side of the aisle P. Accordingly, it is possible to effectively illuminate the interior of the cabin with less number of lighting apparatuses as compared to the case where the lighting apparatuses are provided above and along both sides of the aisle P (refer toFIG. 10). Furthermore, the reduction in the number of the lighting apparatuses contributes to reduction in the total weight of the aircraft AP, and improvement of the fuel efficiency.

Further, since the diffusing particles8are used in the lens6, incident light is guided in multiple directions in the lens6, and light guided to the flange portions64is increased. However, in the lens6of the present embodiment, the Fresnel structure is provided extending from the light emitting surface63to the ends of the flange portions64. Therefore, the light guided to the flange portions64can be converged to the optical axis L side, and light that has conventionally disappeared on the frame7side (refer toFIG. 3) can be taken out as effective light.

Further, the light emitting surface63is coated with the translucent coating member65. The translucent coating member65is made of a material having a refractive index n2higher than a refractive index n1of the medium60. On the light emitting surface63having the Fresnel structure, diagonal planes and vertical planes of a sawtooth pattern are provided at prescribed intervals in the direction orthogonal to the optical axis L, and a boundary between the light emitting surface63and the medium60contacting the light emitting surface63, i.e., an interface that causes a difference in refractive index, serves as a diffraction grating. Generally, a refractive index has wavelength dependence, and therefore, as shown inFIG. 6, a low refractive index material (refractive index: n1) has a greater variation width in refractive index per wavelength as compared to a high refractive index material (refractive index: n2). Therefore, for example, if a lens is made of the low refractive index material, light having a certain wavelength component is diffracted to cause interference fringes, which might cause nonuniformity of color at a surface illuminated with the light. Therefore, in the present embodiment, the light emitting surface63is coated with the translucent coating member65having the refractive index n2higher than the refractive index n1of the medium60to reduce the difference in refractive index at the interface of the light emitting surface63, which makes it difficult to cause diffraction at any wavelength, thereby reducing nonuniformity of color of the illuminating light.

Next, a lighting apparatus according to a modification of the present embodiment will be described with reference toFIG. 7. In the modification shown inFIG. 7, the translucent coating member65contains diffusing particles8to provide a diffusion section. This configuration facilitates production of the diffusion section. If a plurality of translucent coating members65having different concentrations of the diffusing particles8or gradients are produced and appropriately exchanged, it is possible to change the transparency of the lens6and the light diffusing property. Alternatively, the diffusion section may be a translucent coating member65having a surface on which diffusion dots are printed.

Next, a lighting apparatus according to another modification of the present embodiment will be described with reference toFIG. 8. In the modification shown inFIG. 8A, the lens6is formed to have a recess at a light incident surface61A. The recessed light incident surface61A has a bottom surface serving as a first light incident surface61aon which light emitted from the LED unit2in the forward direction is incident, and has side surfaces of a cylindrical shape serving as second light incident surfaces61bon which light emitted from the LED unit2at a wide angle is incident. The first light incident surface61ais a curved surface convex toward the LED unit2. Further, the lens6has total reflection surfaces62A that are provided opposed to the second light incident surfaces61b, and totally reflect the light incident from the second light incident surfaces61b. Like in the above embodiment, in the cross section of the lens6shown inFIG. 8A(the cross section orthogonal to the longitudinal direction of the wiring board (refer toFIG. 3)), the concentration of the diffusing particles8is high in the vicinity of the optical axis L of the light emitted from the LED unit2and gradually decreases as the distance from the optical axis increases. Since the lens6is a general-purpose hybrid lens having a light emitting surface on which a Fresnel structure or the like is formed, it is easy to design and produce the lens6. Also in this modification, the translucent coating member65may contain diffusing particles8to provide a diffusion section as shown inFIG. 8B.

The lighting apparatus according to the present invention is not limited to the above embodiment and the modifications thereof, and may be modified in various manners. For example, the lighting apparatus may include an LED that emits light of a color other than RGB. Specifically, the lighting apparatus may include a white LED that emits white light in addition to the RGB LEDs, and these LEDs may be individually subjected to dimming control. Since the lighting apparatus of the present invention is configured such that a difference in luminance according to a difference in optical path length hardly occurs between an area near the lighting apparatus and an area far from the lighting apparatus, the lighting apparatus is also applicable to an aircraft having a single aisle. However, in the case of a single aisle, symmetry of illumination is strongly demanded. Further, in terms of right and left weight balance of the aircraft, the lighting apparatus is preferably applied to an aircraft having two aisles.

DESCRIPTION OF REFERENCE CHARACTERS