Light-emitting unit and luminaire

According to one embodiment, a light-emitting unit includes a light-emitting section, a diffusion cover, and a reflector. The light-emitting section includes an LED element. The diffusion cover diffuses light emitted from the light-emitting section. The reflector controls the light diffused by the diffusion cover.

INCORPORATION BY REFERENCE

The present invention claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2012-241118 filed on Oct. 31, 2012. The content of the application is incorporated herein by reference in their entirety.

FIELD

Embodiments described herein relate generally to light-emitting unit used as, for example, a floodlight and a luminaire including the light-emitting unit.

BACKGROUND

There has been a high-power luminaire used as a floodlight, a spotlight, or the like for lighting a signboard or the like or illuminating a building. As such a luminaire, in recent years, there has been known a luminaire including an LED (a light-emitting diode), which functions as a solid-state light-emitting element, as a luminous element for the purpose of an extension of life, energy saving, a reduction in weight, a reduction in size, or the like.

DETAILED DESCRIPTION

In general, according to one embodiment, a light-emitting unit includes a light-emitting section, a first optical system, and a second optical system. The light-emitting section includes a solid-state light-emitting element. The first optical system diffuses light emitted from the light-emitting section. The second optical system controls a luminous intensity distribution of the light diffused by the first optical system.

A configuration of a first embodiment is explained below with reference toFIG. 1toFIGS. 5(a) and5(b). InFIGS. 1 and 2, reference numeral11denotes a floodlight functioning as a luminaire. The floodlight11irradiates light on an irradiation target such as various signboards or a building. In the following explanation, it is assumed that the front back direction is set with reference to an optical axis direction (an irradiating direction).

The floodlight11includes a housing21functioning as a luminaire main body, a light-emitting unit22arranged in the housing21, an attachment arm23functioning as an attachment member that attaches the housing21to a not-shown attachment section of a structure or the like, a power supply section24that supplies electric power to a light-emitting section31, and a cover section25attached to the housing21.

The housing21is a thermal radiator formed in, for example, a bottomed hexagonal cylindrical shape by a light-weight member excellent in heat radiation properties such as aluminum or die-cast aluminum. On the back side of a bottom surface section of the housing21, a large number of radiation fins21afunctioning as thermal radiation sections are protrudingly provided. Further, the front end of the housing21is formed as an emission opening21bfrom which light is emitted. The emission opening21bis covered by the cover section25. In a circumferential edge portion at the front end of the housing21, a not-shown plurality of attachment seats for attaching and fixing the cover section25are protrudingly provided. In the attachment seats, screw holes for screwing and fixing not-shown screws or the like, which are fixing bodies, for fixing the cover section25are respectively opened.

The radiation fins21aare continuously formed in a longitudinal shape on the back of the entire bottom surface section of the housing21along, for example, the up down direction, i.e., a direction crossing (orthogonal to) the optical axis direction. The radiation fins21aare spaced apart from one another in the width direction at a predetermined interval (e.g., an interval of about 6 to 10 mm).

The light-emitting unit22includes the light-emitting section31, a diffusion cover32functioning as a first optical system detachably attached to the housing21to cover the light-emitting section31, and a reflector33functioning as a second optical system attached to the housing21to cover the light-emitting section31and the diffusion cover32.

In the light-emitting section31, for example, an LED element31afunctioning as a solid-state light-emitting element (a semiconductor light-emitting element) is used as a light source. In this embodiment, a COB (Chip On Board) system for mounting a plurality of LED elements31aon a circular substrate31bis adopted. Specifically, in the light-emitting section31, the plurality of LED elements31amounted on the substrate31bare electrically connected in series by wire bonding. The plurality of LED elements31aare integrally covered and sealed by a phosphor layer made of transparent resin such as silicone resin mixed with a phosphor. In this embodiment, the light-emitting section31is configured to emit white light by covering the LED element31a, which emits, for example, blue light, with a phosphor layer mixed with a yellow phosphor.

The diffusion cover32is a diffusion member that diffuses light from the light-emitting section31, i.e., distributes the light at a wide angle. The diffusion cover32is detachably arranged on the inside of the reflector33to cover the light-emitting section31. Therefore, the diffusion cover32is formed smaller than the reflector33. The diffusion cover32is formed in, for example, a bottomed cylindrical shape by a member made of synthetic resin or the like having translucency and diffusibility. The diffusion cover32is shaped to be gradually reduced in diameter from the rear side, which is the light-emitting section31side, to the front side. In other words, the diffusion cover32is formed in a substantially trapezoidal shape viewed from aside with respect to the optical axis direction. The diffusion cover32is arranged such that the center axis thereof coincides with the center of the light-emitting section31. A luminous intensity distribution of the diffusion cover32is controlled according to the height, i.e., the front back direction (axis direction) dimension, the diameter dimension, and the thickness of the diffusion cover32. The diffusion cover32is set to thickness of, for example, 1.0 mm. The diffusion cover32has a luminous intensity distribution not having maximum luminous intensity in the optical axis direction (the 0° direction), in other words, having maximum luminous intensity in directions (in this embodiment, for example, ±50° directions) different from the optical axis direction and having a ½ beam angle set to a ½ beam angle larger than 120°, in this embodiment, set to a ½ beam angle of, for example, about 220° (FIG. 3).

The reflector33is formed in a cylindrical shape opened at both the front and rear ends and is formed in a paraboloid shape expanded in diameter from the rear side to the front side. The inner surface, i.e., a reflection surface of the reflector33is formed in a mirror surface shape. Further, the reflector33is fixed to the housing21by, for example, screwing to have an optical axis along a direction substantially orthogonal to the surface direction of the bottom surface section thereof. The reflector33is configured to condense (control) the light diffused (distributed at a wide angle) by the diffusion cover32such that the ½ beam angle is smaller than 120°, in this embodiment, for example, about 30° and irradiate the light from the emission opening21b(via the cover section25) (FIG. 4(a)). The center of a front end32aof the diffusion cover32is located in the vicinity of the focal point of the reflector33.

The attachment arm23is a member for attaching and fixing the floodlight11to a predetermined attachment position at a predetermined angle. The attachment arm23is integrally formed by a member having rigidity made of metal or the like. The attachment arm23is formed in a U shape including a pair of arms23apivotably connected to both the sides of the housing21and a coupling section23bthat couples the arms23aand is attached pivotably with respect to the attachment position. The housing21is axially supported to be pivotable in the up down direction with respect to the attachment arm23. The attachment arm23is attached pivotably in the left right direction with respect to the attachment position. Consequently, the floodlight11is pivotable in the up down direction and the left right direction.

The power supply section24is configured in a unit shape with a not-shown plurality of power supplies arranged in a matrix shape in a case body24ahaving, for example, a square shape. The power supply section24is configured to supply predetermined direct-current electric power to the light-emitting section31.

The cover section25includes a cover25afunctioning as a cover section main body formed in, for example, a hexagonal plate shape by a member made of glass or the like having translucency and a frame body25bhaving a hexagonal frame shape that holds the outer edge of the cover25a. The cover25ais attached to cover the front end of the housing21. The frame body25bis fit in the front end of the housing21to cover the outer edge of the cover25ain a picture frame shape. The frame body25bincludes attachment piece sections25dthat project in a flange shape from the centers of side sections25cto the sides. In the attachment piece sections25d, through-holes25ealigned with screw holes of the attachment seats of the housing21are opened. Screws or the like are inserted into the screw holes through the through-holes25e.

The floodlight11is fixed by attaching the attachment arm23to the attachment position with bolts or the like and adjusting pivoting angles in the up down direction and the left right direction according to a positional relation between the irradiation target and the attachment position.

In this state, when the light-emitting section31supplied with electric power from the power supply section24emits light, distributed light from the light-emitting section31is diffused (distributed at a wide angle) by the diffusion cover32, then reflected on the inner surface of the reflector33and subjected to condensing control, and transmitted through and emitted from the cover25ato light the irradiation target.

As explained above, according to the first embodiment, the light from the light-emitting section31is diffused (distributed at a wide angle) by the diffusion cover32to control the luminous intensity distribution of the diffused light with the reflector33(condense and irradiate the light distributed at a wide angle with the reflector33) while reducing glare by preventing intense light from scattering in a direction parallel to an irradiation direction. Consequently, it is possible to easily light only the inside of a desired range. In other words, if emitted light is diffused by a diffuser, it is not easy to surely control luminous intensity distribution through design. Therefore, in this embodiment, the light once diffused (distributed at a wide angle) by the diffusion cover32to reduce glare is controlled (condensed) by the reflector33. Consequently, it is possible to easily control an irradiation range of the light with reduced glare.

Further, the diffusion cover32has the luminous intensity distribution not having maximum luminous intensity in the optical axis direction and having the ½ beam angle larger than 120°. The reflector33condenses the light such that the ½ beam angle is smaller than 120°. Consequently, it is possible to more surely irradiate only the inside of the desired range while more surely reducing glare.

Specifically, a ray is narrowed in the luminous intensity distribution of the light emitted from the floodlight11according to this embodiment (FIG. 4(a)) compared with a luminous intensity distribution in a comparative example (FIG. 4(b)) in which a diffuser is arranged, for example, between both the front and rear ends of (halfway up in) the reflector33. Therefore, it is seen that it is easy to light the inside of the desired range.

In a brightness distribution of a comparative example in which a light-emitting unit has a total luminous flux and a luminous intensity distribution substantially equal to those in this embodiment and does not include the diffusion cover32(FIG. 5(b)), an absolute value of brightness is large and a uniformity ratio of brightness is not achieved. On the other hand, in a brightness distribution in this embodiment (FIG. 5(a)), a uniformity ratio of brightness is relatively high and an absolute value of brightness is low. Therefore, it is seen that glare is reduced.

A second embodiment is explained with reference toFIGS. 6 to 8. Components and action same as those in the first embodiment are denoted by the same reference numerals and signs and explanation of the components and the action is omitted.

In the floodlight11according to the second embodiment, at least two kinds of light-emitting sections having light emission wavelengths different from each other, i.e., two kinds of (first and second) light-emitting sections41and42are set as the light-emitting section31.

The light-emitting section41emits white light. In the light-emitting section41, for example, a plurality of LED elements41athat emit blue light are mounted on a circular substrate41band electrically connected in series by wire bonding. The plurality of LED elements41aare integrally covered and sealed by a phosphor layer made of transparent resin such as silicone resin mixed with a yellow phosphor.

The light-emitting section42emits red light. The light-emitting section42is used to improve a color rendering property of emitted light from the floodlight11. Specifically, the light-emitting section42has a light emission spectrum distribution showing maximum intensity in a wavelength region of 600 to 650 nm. In the light-emitting section42, for example, a plurality of LED elements42athat emit red light are mounted on a circular substrate42band electrically connected in series by wire bonding.

The light-emitting sections41and42are, for example, alternately arranged to be spaced apart from each other in the circumferential direction on the same circumference. Overall, a plurality of light-emitting sections41and a plurality of light-emitting sections42, for example, four light-emitting sections41and four light-emitting sections42are provided.

The diffusion cover32and the reflector33are attached to the light-emitting section31. Specifically, the diffusion cover32is attached to the housing21to cover the entire light-emitting sections41and42. The reflector33is attached to the housing21to include the diffusion cover32.

The reflector33is configured to condense (control) light diffused (distributed at a wide angle) by the diffusion cover32such that a ½ beam angle is smaller than 120°, in this embodiment, for example, about 20° and irradiate the light from the emission opening21b(via the cover section25) (FIG. 7(a)).

In the floodlight11attached and fixed to the attachment position at a predetermined pivoting angle by the attachment arm23, when the light-emitting sections41and42set as the light-emitting section31and supplied with electric power from the power supply section24emit lights, distributed lights from the light-emitting sections41and42are diffused (distributed at a wide angle) by the diffusion cover32and mixed (mixed in colors), then reflected on the inner surface of the reflector33and subjected to condensing control, and transmitted through and emitted from the cover25ato light an irradiation target.

As explained above, according to the second embodiment, the light from the light-emitting section31is diffused (distributed at a wide angle) by the diffusion cover32to control the luminous intensity distribution of the diffused light with the reflector33(condense and irradiate the light distributed at a wide angle with the reflector33) while reducing glare by preventing intense light from scattering in a direction parallel to an irradiation direction. Consequently, it is possible to easily light only the inside of a desired range.

If the two kinds of light-emitting sections41and42having the light emission wavelengths different from each other are set as the light-emitting section31, it is likely that color unevenness occurs on an irradiated surface. In particular, if a reflector is used to make a beam angle relatively narrow in a high-power luminaire, it is not easy to reduce the color unevenness using the reflector. However, in this embodiment, the emitted lights from the light-emitting sections41and42are mixed when being diffused (distributed at a wide angle) by the diffusion cover32and subjected to luminous intensity distribution control (condensed) by the reflector33. Therefore, it is possible to make it less likely that color unevenness occurs on the irradiated surface while lighting only the inside of the desired range.

In particular, in the light-emitting section41in which the LED elements41athat emit blue light and a phosphor layer including a yellow phosphor are combined, white light emitted from the light-emitting section41has a low color rendering property. However, red light emitted from the light-emitting section42can be mixed with the white light without causing color unevenness. Therefore, it is possible to improve the color rendering property while reducing glare.

Specifically, for example, in a comparative example in which a light-emitting unit does not include the diffusion cover32, a luminous intensity distribution (FIG. 7(b)) is equal to a luminous intensity distribution (FIG. 7(a)) of the light emitted from the floodlight11according to this embodiment. However, color unevenness conspicuously occurs on the irradiated surface (FIG. 8(b)). On the other hand, in the light irradiated from the floodlight11according to this embodiment, color mixture can be sufficiently realized on the irradiated surface. It is seen that the light is irradiated without color unevenness (FIG. 8(a)).

In the second embodiment, if the light-emitting sections41and42are configured to have light emission wavelengths different from each other, in other words, have light emission colors different from each other, the light-emitting sections41and42are not limited to a combination of white and red.

Three or more light-emitting sections having light emission wavelengths different from one another may be used.

Further, in the embodiments, the light-emitting unit22can be applied to not only the floodlight11but also any luminaire.

If the diffusion cover32is set to have a luminous intensity distribution not having maximum luminous intensity in the optical axis direction and having the ½ beam angle larger than 120°, the diffusion cover32is not limited to the luminous intensity distributions in the embodiments.

Similarly, if the reflector33can condense and irradiate light such that the ½ beam angle is smaller than 120°, the reflector33is not limited to the luminous intensity distributions in the embodiments.