Lighting device and lighting system

A lighting device is provided which includes: a wavelength converter that emits, from laser light, light having a wavelength different from a wavelength of the laser light; and a reflector surrounding the wavelength converter and including a surface of revolution that reflects the light emitted from the wavelength converter. The reflector includes, in the surface of revolution, a through-hole through which the laser light passes.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of Japanese Patent Application Number 2016-161650 filed on Aug. 22, 2016, the entire content of which is hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a lighting device and a lighting system which use laser light emitted from a light source.

2. Description of the Related Art

A lighting device is conventionally known which emits light by exciting, using laser light as excitation light, phosphors dispersed in a wavelength converter, so that the wavelength converter converts the laser light into visible light of a desired color. With such a lighting device, laser light output from a laser diode is guided to a region near the wavelength converter using an optical fiber, and the laser light emitted from an end portion of the optical fiber irradiates the wavelength converter. Thus, the end portion of the optical fiber is disposed at a position where the end portion of the optical fiber does not block the visible light emitted from the wavelength converter (see Japanese Unexamined Patent Application Publication No. 2008-108553, for example).

SUMMARY

However, with a lighting device that achieves desired light, distribution by having a reflector in a region surrounding the wavelength converter, an end portion of the optical fiber needs to be disposed outside the reflector, thereby increasing the distance between an end surface of the optical fiber that emits laser light and the wavelength converter. Conversely, laying the optical fiber over the reflector to a region near the wavelength converter causes the emitted visible light to have a blurred portion due to the optical fiber.

In view of the above circumstances, it is an object of the present disclosure to provide a lighting device and a lighting system which use laser light emitted from a light source and achieve substantially axially-symmetric light distribution.

It should be noted that the term “substantially axially-symmetric” in the Specification and the Claims is used to allow a certain amount of error and to include imperfect axial symmetry, as well as perfect axial symmetry.

A lighting device according to an aspect of the present disclosure is a lighting device including: a wavelength converter that emits, from laser light, light having a wavelength different from a wavelength of the laser light; and a reflector surrounding the wavelength converter and including a surface of revolution that reflects the light emitted from the wavelength converter, wherein the reflector includes, in the surface of revolution, at least one through-hole through which the laser light passes.

According to the present disclosure, it is possible to provide a lighting device which uses laser light emitted from a light source and emits visible light with substantially axially-symmetric light distribution.

DETAILED DESCRIPTION OF EMBODIMENT

Hereinafter, a lighting device according to an embodiment of the present disclosure will be described with reference to the drawings. It should be noted that the embodiment and variations thereof described below are to show specific examples of the present disclosure. Therefore, the numerical values, shapes, materials, structural elements, and the arrangement and connection of the structural elements, etc., shown in the following embodiment and variations are mere examples, and are therefore not intended to limit the present disclosure. As such, among the structural elements in the following embodiment and variations, elements not recited in any one of the independent claims indicating the broadest inventive concepts will be described as arbitrary structural elements.

It should also be noted that each drawing is a schematic illustration and not necessarily a precise illustration. Furthermore, in the drawings, like reference signs are given to like structural elements, and the description of such structural elements may not be repeated.

Embodiment

[Outline of Configuration of Lighting Device]

FIG. 1is a perspective view illustrating an exterior appearance of a lighting device according to an embodiment.

Lighting device100illustrated inFIG. 1emits, from laser light L (seeFIG. 3), visible light having a wavelength different from the wavelength of laser light L, and is, for example, a spotlight that illuminates an indoor or outdoor predetermined place. Lighting device100includes wavelength converter101and reflector102, and further includes base103and irradiator104.

FIG. 2is a cross sectional view illustrating a wavelength converter.

Wavelength converter101converts, using laser light L as excitation light, laser light L into visible light having a wavelength different from the wavelength of laser light L, and includes wavelength converting material111, base material112, and reflective plate113.

Wavelength converting material111is a substance that emits fluorescence using laser light L as excitation light. In the present embodiment, wavelength converting material111is a yellow phosphor that emits yellow fluorescence using blue laser light L. Specifically, an yttrium aluminum garnet (YAG) phosphor is an example of the yellow phosphor.

In the present embodiment, a portion of blue laser light L is wavelength-converted into yellow light by wavelength converting material111included in wavelength converter101. Blue light not absorbed by wavelength converting material111and the yellow light obtained through the wavelength conversion by the yellow phosphor are then diffused and mixed in wavelength converter101. As a result, wavelength converter101emits white light.

Base material112can hold wavelength converting material111dispersedly, and transmit laser light L and the fluorescence emitted from wavelength converting material111. Although not particularly limited, examples of the material of base material112include an organic material such as a methyl silicone resin, an epoxy resin, or a urea resin, and an inorganic material such as glass or ceramics. When heat resistance is required in particular, an inorganic material is selected.

Reflective plate113reflects laser light L and the fluorescence emitted from wavelength converter101. Although not particularly limited, examples of the material that forms reflective plate113include a plate-shaped component containing a metal material such as aluminum or an aluminum alloy, and a plate-shaped component having a metal layer formed on a surface of a glass substrate.

It should be noted that in the present embodiment, wavelength converter101is formed by, for example, applying or printing base material112containing a wavelength converting material onto a surface of reflective plate113. Although the shape etc., of wavelength converter101is not particularly limited, base material112and reflective plate113in the present embodiment have a disc shape, and are coaxially arranged with surface of revolution121of later-described reflector102about revolution axis120(seeFIG. 3).

Reflector102has surface of revolution121that surrounds wavelength converter101and that reflects light emitted from wavelength converter101. Reflector102includes, in a portion of surface of revolution121, through-holes122through which laser light L passes.

Here, surface of revolution121is a curved surface obtained by rotating, about revolution axis120, a curved or straight line disposed in space. In the present embodiment, revolution axis120coincides with the optical axis. When viewed along revolution axis120, surface of revolution121is axially symmetric; the shape of surface of revolution121does not change in the circumferential direction, and the distance from revolution axis120to surface of revolution121changes depending on the position on revolution axis120. It should be noted that because end portions of through-holes122are open in portions of surface of revolution121, surface of revolution121is, at least partially, not perfectly axially-symmetric. In the present embodiment, at least the open end of surface of revolution121and the nearby region are axially symmetric.

In the present embodiment, reflector102includes through-holes122at two positions, and two through-holes122are equally spaced in the circumferential direction, that is, two through-holes122are disposed at such positions where two through-holes122match each other when rotated 180 degrees about revolution axis120.

Further, surface of revolution121of reflector102is bowl-shaped, that is, the open area gradually increases with an increase in distance from wavelength converter101. Through-holes122have an elongated slit shape along revolution axis120of surface of revolution121. This makes it possible to reduce the occurrence of the walls of through-holes122blocking laser light L that obliquely travels toward wavelength converter101and to suppress the influence that through-holes122have on light distribution of lighting device100.

It should be noted that although the material that forms reflector102is not particularly limited, forming reflector102with a material having high heat conductivity such as metal allows heat generated by wavelength converter101to be dissipated also by reflector102.

Surface of revolution121may have minute asperities thereon by texturing, for example.

Base103includes: main body132holding wavelength converter101, reflector102, and irradiator104; and heat dissipating fins131that dissipate into the external space the heat generated by wavelength converter101. Heat dissipating fins131are integrally formed with main body132, at positions across main body132from wavelength converter101.

Although the material that forms base103is not particularly limited, a material having high heat conductivity such as metal may be used.

FIG. 3is a cross sectional view illustrating an irradiator and the nearby region.

As illustrated inFIG. 3, irradiator104holds an end portion of optical fiber202that guides laser light L, mirror141, and lens system144, and is removably attached to base103.

Irradiator104enables collective assembly of optical components such as mirror141and lens system144, which require highly precise positional adjustment.

FIG. 4is an exploded perspective view illustrating a state in which the irradiator is removed from the base.

As illustrated inFIG. 4, main body132of base103includes holding hole133for (i) inserting optical fiber202that guides laser light L to allow laser light L to pass through through-hole122and (ii) inserting and attaching irradiator104.

This enables accurate alignment of irradiator104with respect to wavelength converter101attached to base103. Furthermore, because optical fiber202can be laid without being disposed outside base103, it is possible to easily install lighting device100in a hole provided in a construction material such as a ceiling.

Irradiator104includes connector145which allows irradiator104and optical fiber202to be removably attached to each other. This allows optical fiber202inserted through holding hole133to be connected to irradiator104removed from base103, and allows irradiator104connected with optical fiber202to be attached to base103. Accordingly, it becomes easier to install lighting device100.

Mirror141reflects laser light L emitted from an end portion of optical fiber202attached to irradiator104, and irradiates wavelength converter101with reflected laser light L. This eliminates the need to bend optical fiber202in order to irradiate wavelength converter101with laser light L. Moreover, since there is no need to secure space for moderately bending optical fiber202, lighting device100can be made smaller in size.

Lens system144is for efficiently irradiating wavelength converter101with laser light L emitted from the end portion of optical fiber202, and includes first lens142and second lens143.

First lens142is what is known as a collimating lens that converts laser light L emitted radially from the end portion of optical fiber202into parallel light having a predetermined diameter.

Second lens143is for matching, with the shape of wavelength converter101, the shape of the region irradiated with laser light L obliquely entering the surface of wavelength converter101. In the present embodiment, because the shape of the surface of wavelength converter101is a substantially perfect circle, a cylindrical lens which can approximate the shape of the region irradiated with obliquely entering laser light L to a perfect circle is used as second lens143. This allows the entirety of wavelength converter101to emit visible light.

Next, lighting system200according to the embodiment will be described.

FIG. 5is a block diagram illustrating a lighting system.

As illustrated inFIG. 5, lighting system200is a spotlight installed on, for example, a ceiling of a building to emit visible light toward a floor, and includes: lighting device100described above; light source device201; and optical fiber202.

Light source device201generates laser light L, and supplies laser light L to lighting device100via optical fiber202. Light source device201includes one or more semiconductor laser elements that emit laser light L having a wavelength in the blue-violet to blue region (400 nm to 490 nm), for example.

In the present embodiment, light source device201is adjusted such that the power of laser light L emitted from one of two irradiators104included in lighting device100to wavelength converter101via corresponding through-hole122is equal to the power of laser light L emitted from the other one of two irradiators104to wavelength converter101via corresponding through-hole122. Specifically, for example, the respective powers of laser light L irradiating wavelength converter101can be made equal by (i) connecting optical fiber202to each one of semiconductor laser elements having the same output, (ii) tying these optical fibers202into a pair of bundles such that each bundle has the same number of optical fibers202, and (iii) connecting each bundle to a different one of irradiators104.

With this, laser light L from two irradiators104passes through through-holes122equally spaced in the circumferential direction, and geometrically equally (rotationally symmetrically) irradiates wavelength converter101. Further, the respective powers of laser light L are equal. Thus, wavelength converter101emits visible light that is axially symmetric about revolution axis120. In addition, as a result of the visible light being reflected by surface of revolution121disposed about the optical axis of the visible light, it is possible to achieve light distribution which is axially symmetric about the optical axis (revolution axis120).

As described above, lighting device100according to the present embodiment is lighting device100including: wavelength converter101that emits, from laser light L, light having a wavelength different from a wavelength of laser light L; and reflector101surrounding wavelength converter101and including surface of revolution121that reflects the light emitted from wavelength converter101, wherein reflector102includes, in surface of revolution121, at least one through-hole122through which laser light L passes.

According to this configuration, since substantially axially-symmetric surface of revolution121can reflect visible light emitted from wavelength converter101, it is possible to achieve light distribution that is substantially axially-symmetric about the optical axis.

Specifically, reflector102of lighting device100according to the present embodiment includes a plurality of through-holes122, and the plurality of through-holes122are equally spaced along surface of revolution121.

According to this configuration, the pattern for irradiating wavelength converter101with laser light L, which is excitation light, is substantially symmetric, and it is thus possible to emit visible light from wavelength converter101in a substantially symmetric manner. Furthermore, space for providing irradiator104to base103can be more easily secured.

Further, surface of revolution121of reflector102includes an open area that gradually increases with an increase in distance from wavelength converter101, and through-hole122is elongated along a revolution axis of surface of revolution121.

According to this configuration, the proportion of the area of the opening of through-hole122to the area of surface of revolution121can be kept low, which means that the area for reflecting the visible light emitted from wavelength converter101can be increased. In addition, the influence that the opening of through-hole122has on the light distribution can be reduced.

Further, respective powers of laser light L passing through the plurality of through-holes122are equal.

According to this configuration, the irradiation patterns of laser light L, as well as the powers of laser light L, can be equalized, and thus the visible light can be evenly emitted from wavelength converter101, thereby making it possible to easily achieve light distribution that is axially symmetric about the optical axis.

Further, lighting device100includes base103including (i) main body132holding wavelength converter101and (ii) heat dissipating fins131disposed across main body132from wavelength converter101, wherein main body132of base103includes holding hole133which allows optical fiber202guiding laser light L to be laid between heat dissipating fins133, and which allows an end portion of optical fiber202to be disposed on a side on which wavelength converter101is disposed.

According to this configuration, one or more optical fibers202can be disposed on the side where heat dissipating fins131are provided, and thus it makes it easier to handle the one or more optical fibers202when installing lighting device100.

Further, lighting device100further includes mirror141that reflects laser light L emitted from optical fiber202and irradiates wavelength converter101with laser light L.

According to this configuration, laser light L emitted from optical fiber202can be bent at an acute angle to irradiate wavelength converter101, thereby making it possible to reduce the size of lighting device100as a whole.

Furthermore, lighting device100further includes irradiator104that holds mirror141and an end portion of optical fiber202, and is removably attached to base103. Reflector102is also removably attached to base103.

According to this configuration, each component having a predetermined function can be constituted as a module, and each module can be used as a component common to lighting devices100of different types. In particular, treating irradiator104as a separate component enables adjustment of the path of laser light L, that is, adjustment of the position and angle of the optical components, in a separate process.

It should be noted that the present disclosure is not limited to the above embodiment. For example, different embodiments achieved by any combination of the structural elements described in this Specification and embodiments achieved by excluding some of the structural elements may be considered as the embodiments of the present disclosure. Furthermore, variations achieved through various modifications to the above embodiment that can be conceived by a person of ordinary skill in the art without departing from the essence of the present disclosure, that is, the meaning of the recitations in the claims, are included in the present disclosure.

For example, lighting device100may include three or more equally spaced through-holes122and irradiators104as illustrated inFIG. 6.

The openings of through-holes122need not have a slit-like shape and may have any shape such as an elliptical shape.

Wavelength converter101need not include reflective plate113and may be directly attached to base103.

As illustrated inFIG. 7, wavelength converter101may be irradiated with laser light L by bending optical fiber202, without the use of a mirror, for example. In this case, an end portion of optical fiber202may be inserted into through-hole122.

A light-transmissive cover may be disposed in front of wavelength converter101and reflector102. The cover may contain a material such as glass or resin, and may, for example, have a role of reducing adherence of a foreign substance such as dust to wavelength converter101. Further, the cover may have an optical function such as light diffusion or light concentration.