Luminaire and method of manufacturing luminaire

A luminaire including a wavelength converter and a method of manufacturing the luminaire are provided. The wavelength converter radiates, based on a laser light beam, a light beam having a wavelength different from the laser light beam. The method of measuring the luminaire includes measuring wavelengths of laser light beams oscillated by a plurality of laser elements to identify main wavelengths of the plurality of laser elements, storing association information between main wavelength information items indicating the main wavelengths identified and element information items identifying the plurality of laser elements corresponding to the main wavelengths identified, selecting a combination of laser elements having a composite wavelength falling within a predetermined range, from the plurality of laser elements, based on the association information, and arranging optical paths to irradiate a same area of the wavelength converter with the laser light beams of the combination of laser elements selected.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of Japanese Patent Application Number 2016-168578 filed on Aug. 30, 2016, the entire content of which is hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a method of manufacturing a luminaire having laser light as a source of light and to the luminaire.

2. Description of the Related Art

There are conventionally known luminaires which illuminate by causing phosphor dispersed in a wavelength converter to emit light using laser light as excitation light, to thereby convert the laser light into visible light of a desired color such as white light. In order to enhance light emission brightness in such a luminaire, a single wavelength converter is overlappingly irradiated with laser light beams outputted from a plurality of laser diodes (for example, see Japanese Unexamined Patent Application Publication No. 2014-11034 (Patent Literature 1)).

SUMMARY

In the case of a luminaire which causes a wavelength converter to emit light with laser light as excitation light, there are instances where, even when the same type of luminaires are used, luminous color is different due to individual difference. With regard to such individual difference in luminous color of the luminaires, since the wavelength width of laser light radiated from laser diodes is narrow compared to LEDs, etc., a slight variation in the main wavelength of laser light due to the individual difference between the laser diodes included by the respective luminaires has a strong impact on the luminous color of the luminaires. Therefore, suppressing variation of luminous color (color temperature) and manufacturing a stable luminaire is problematic.

The present disclosure provides a method of manufacturing a luminaire having laser light as a light source and in which variation of luminous color between products is minimal, and the luminaire.

A method of manufacturing a luminaire according to an aspect of the present disclosure is a method of manufacturing a luminaire including a wavelength converter that radiates, based on a laser light beam oscillated by a laser element, a light beam having a wavelength different from a wavelength of the laser light beam, the method including: measuring wavelengths of a plurality of laser light beams oscillated by a plurality of laser elements to identify main wavelengths of the plurality of laser elements; storing first association information indicating association between main wavelength information and element information, the main wavelength information indicating the main wavelengths identified, the element information identifying the plurality of laser elements corresponding to the main wavelengths identified; selecting, from the plurality of laser elements and based on the first association information, a combination of laser elements having a composite wavelength falling within a predetermined first range; and arranging optical paths to irradiate a same area of the wavelength converter with laser light beams of the combination of laser elements selected.

According to the present disclosure, it is possible to manufacture a luminaire which has laser light as a light source and has reduced individual difference-caused luminous color variation, and to provide such a luminaire.

DETAILED DESCRIPTION

Hereinafter, a method of manufacturing a luminaire and the luminaire according to an exemplary embodiment of the present disclosure will be described with reference to the drawings. It should be noted that each of the subsequently-described exemplary embodiment and the variations thereof shows a specific example. Therefore, numerical values, shapes, materials, structural components, the arrangement and connection of the structural components, etc. shown in the following exemplary embodiment and variations thereof are mere examples, and are not intended to limit the scope of the present disclosure. Furthermore, among the structural components in the following exemplary embodiment and variations thereof, components not recited in any one of the independent claims which indicate the broadest concepts of the present invention are described as arbitrary structural components.

Furthermore, the respective figures are schematic diagrams and are not necessarily precise illustrations. Furthermore, in the respective figures, identical structural components are assigned the same reference sign and overlapping description thereof may be omitted.

FIG. 1is a diagram illustrating an outline of a luminaire according to an embodiment.

Luminaire100illustrated in the figure is an apparatus in which the same area of wavelength converter104is irradiated with laser light beams L oscillated by a plurality of laser elements to radiate a visible light V including light of a wavelength different from laser light beams L, and is for example an apparatus for illuminating a predetermined area indoors or outdoors. Luminaire100includes laser elements (first laser element111and second laser element112), light guides (first light guide121and second light guide122), base103, and wavelength converter104.

In this embodiment, luminaire100is a transmission type fixture in which one surface of wavelength converter104is irradiated with laser light beams L and white light is radiated from the surface on the opposite side. Specifically, the white light is radiated by way of the mixing of part of laser light beams L that have diffused and the light radiated from wavelength converter104which has a wavelength different from laser light beams L.

The laser elements including first laser element111and second laser element112are laser elements including what are called laser diodes which use recombination and light generation of semiconductors. In this embodiment, first laser element111and second laser element112are laser elements manufactured to have the same main wavelength, and the main wavelength of laser light beams L oscillated by the laser elements is selected from a range from 400 nm to 490 nm (bluish purple to blue), inclusive, which is used for excitation light for obtaining white light. It should be noted that, in consideration of the combination with wavelength converter104, ease of laser element manufacturing, etc., the wavelength of laser light beams L oscillated by the laser elements may be selected from a range from 440 nm to 470 nm, inclusive.

The light guides which include first light guide121and second light guide122are components which form optical paths so that the same area of wavelength converter104is irradiated with laser light beams L of the laser elements. In this embodiment, the light guides are what are called optical fibers which include a flexible core and cladding, and are components which, by making the refractive index of the core higher than the cladding, are able to retain laser light beams L inside the core by way of total reflection and thus guide laser light beams L efficiently. The core and the cladding are made of a material that is highly transmissive of laser light, such as silica glass, resin, etc.

It should be noted that the light guides may include a mirror, a lens, a prism, etc.

Base103is a component that holds wavelength converter104and holds the light guides so that the same area of wavelength converter104can be irradiated with the plurality of laser light beams L. In this embodiment, base103includes reflective surface131which reflects, toward a predetermined direction, the light radiated from wavelength converter104.

FIG. 2is a cross-sectional view of a wavelength converter.

Wavelength converter104is a component which wavelength-converts laser light beams L with which it is irradiated as excitation light, into visible light V having a different wavelength from laser light beams L, and includes wavelength converting material141, sealant142, and holding board143.

Wavelength converting material141is a substance that radiates fluorescence with laser light beams L as excitation light. In this embodiment, wavelength converter104includes particles of a yellow phosphor which radiates yellow fluorescence due to blue laser light beams L. Specifically, the yellow phosphor can be exemplified by an yttrium aluminum garnet (YAG)-based phosphor.

It should be noted that wavelength converter104may include a plurality of wavelength converting materials141. For example, wavelength converter104may include particles of a lutetium aluminum garnet (LAG)-based phosphor which is activated by cerium and emits green light, and particles of a SCASN-based phosphor represented by a (Sr, Ca) AlSiN3:Eu which emits red light.

In this embodiment, part of laser light beams L which are blue is wavelength-converted into yellow light by wavelength converting material141included in wavelength converter104. Then, the blue light that is not absorbed by wavelength converting material141and the yellow light resulting from the wavelength-conversion by the yellow phosphor are diffused and mixed inside wavelength converter104. With this, white light is emitted from wavelength converter104.

Sealant142is a component capable of holding wavelength converting material141in a dispersed state and transmitting laser light beams L and the fluorescence radiated from wavelength converting material141. The material of sealant142is not particularly limited and can be exemplified by for example an organic material such as a methyl-based silicone resin, an epoxy resin, a urea resin, or an inorganic material such as glass or ceramic, etc. In particular, when heat-resistance is required, an inorganic material is selected.

Holding board143is a structural component that can transmit laser light beams L and hold wavelength converter104. The material of holding board143is not particularly limited and can be exemplified by aluminum oxide crystal or glass, etc.

It should be noted that, in this embodiment, a dichroic coat which transmits laser light beams L and reflects fluorescence radiated from wavelength converting material141is formed on one surface of holding board143in order to improve white light extraction efficiency, and base142containing wavelength converting material141is applied or printed, etc. above the dichroic coat to thereby form wavelength converter104.

Next, the method of manufacturing luminaire100will be described,

FIG. 3is a diagram illustrating the flow of a luminaire manufacturing process.

The wavelength of each of the laser light beams oscillated by the plurality of laser elements is measured (wavelength measuring: S101). These laser elements are manufactured so as to oscillate laser light beams having the same main wavelength. Specifically, for example, the laser elements are designed and manufactured to have a main wavelength of 455 nm. However, due to individual difference, the main wavelengths of the laser lights oscillated by the respective laser elements vary within a range of approximately ±20 nm, inclusive.

FIG. 4andFIG. 5are graphs illustrating measurement results for laser light oscillated by different laser elements.

Next, the main wavelength is identified for each laser element based on the measurement result (main wavelength identifying: S102). Specifically, for example, the main wavelength is 450.9 nm in the case where the measurement result is the graph illustrated inFIG. 4, and the main wavelength is 458.2 nm in the case where the measurement result is the graph illustrated inFIG. 5.

The main wavelengths identified for the laser elements in the above manner are set as main wavelength information, and, as illustrated inFIG. 6, element information identifying the laser elements that are measured and the main wavelength information are stored in association with each other (an example of storing first association information) (associating: S103). The method of storing the associated element information and main wavelength information is not particularly limited and can be exemplified by a method which uses, for example, manufacturing management software, and stores the associated information as digital information in a memory.

Next, a combination of laser elements whose composite wavelength falls within a predetermined first range are selected based on the main wavelength information and element information which are stored in association with each other (i.e., selected based on the first association information) (combination selecting: S104).

Here, a composite wavelength is a value determined based on the respective main wavelengths of the selected laser elements, and is for example the average value of the main wavelengths when the output light intensities of the selected laser elements are the same. Alternatively, when the respective output light intensities of the selected laser elements are different, the center of gravity of the main wavelengths that are weighted according to the output light intensities may be used.

Furthermore, the first range may be a 3 nm range included in a range from 400 nm to 490 nm, inclusive. This is because, accordingly, most people see illumination in the same color under actual-use conditions of luminaires100. In addition, the first range may be limited to a 2 nm range included in a range from 400 nm to 490 nm, inclusive. Accordingly, even when a plurality of luminaires100are compared in an experiment, the plurality of luminaires100are recognized as having approximately the same chromaticity.

In this embodiment, the first range is 455±1.5 nm, inclusive. In this case, for example, by selecting the laser elements of element information002and element information038, the composite wavelength becomes (450.9 nm+458.2 nm)/2=454.55 nm and thus falls within the first range.

It should be noted that, when three or more laser elements are to be selected, the composite wavelength may be the average value of the main wavelengths of all the selected laser elements, or may be the average value of the maximum value and minimum value of such main wavelengths.

Furthermore, the laser elements to be selected may be selected from the laser elements whose main wavelengths fall within a range of ±10 nm, inclusive, from the median of the first range. This is because, when a laser element whose main wavelength falls outside the range of ±10 nm, inclusive, from the median is used, it s difficult to obtain luminaire100having the desired color temperature even when the composite wavelength falls within the first range.

Next, luminaire100is assembled with optical paths being arranged using the light guides such that the same area of wavelength converter104is irradiated with the laser light beams oscillated by the selected laser elements.

In this embodiment, first laser element111and second laser element112are two laser elements that are selected and, as illustrated inFIG. 1, are connected to first light guide121and second light guide121which are optical fibers that are of the same type and length.

According to the above, it is possible to suppress individual difference-caused variation of luminous color of luminaire100which includes a plurality of laser elements, and thus it is possible to manufacture luminaire100which is stable.

Working Example

Next, the result of observing variation in luminaires100using a plurality of combinations of laser elements is illustrated.

For the laser elements, the following combinations were selected. The light output of the respective laser elements are all approximately the same.

Luminaires100of the same type and having a target color temperature of 3,500 K were manufactured using laser element combinations A, B, C, and D, respectively, and the color temperature of each luminaire100was measured.

FIG. 7is an xy chromaticity diagram illustrating luminaire color temperature measurement results.

In the figure, each value 448 nm, 451 nm, 455 nm, 458 nm, and 462 nm beside plots indicates the composite wavelength of two laser elements, and the corresponding plot represents the chromaticity result for luminaire100when the two laser elements are used. Furthermore, the inside of the bold-line parallelogram near the center in the figure indicates the target chromaticity range of luminaires100. In this manner, laser element combinations B and C whose composite wavelengths fall within the range of 455±1.5 nm, inclusive, are within the target chromaticity range and have an acceptable chromaticity difference, that is, they are perceived by human eyes as having the same luminous color. In contrast, laser element combinations A and D have an unacceptable chromaticity difference, that is, they are perceived by human eyes as having luminous colors different from the luminous color of B and C.

As described above, by using laser element combinations in which the composite wavelength falls within the 3 nm range, it is possible to manufacture stable luminaires100which have no chromaticity variation and are capable of being perceived by human eyes as having the same luminous color.

In contrast, when laser elements are randomly combined, their composite wavelengths vary, for example, in a range from 448 nm to 462 nm, inclusive, and thus significantly go beyond the parallelogram inFIG. 7, and white chromaticity becomes significantly varied.

It should be noted that the present disclosure is not limited to the foregoing embodiment. For example, another embodiment realized by arbitrarily combining structural components or excluding some structural elements described in this written description may be included as an embodiment of the present disclosure. Furthermore, variations obtained by various modifications to the foregoing embodiment that can be conceived by a person having ordinary skill in the art, that are within the scope of the essence of the present disclosure, that is, the intended teachings of the recitations of the claims, are also included in the present disclosure.

For example, luminaire100may be manufactured by: measuring conversion characteristics of a plurality of wavelength converters104using a reference laser element; storing, in association with each other, (i) characteristic information each indicating one of the conversion characteristics measured and (ii) converter information each indicating one of the plurality of wavelength converters104measured (an example of storing second association information); and determining, based on the associated characteristic information and converter information (i.e., second association information), a combination including the combination of laser elements and one of the wavelength converters (target wavelength converter), such that the chromaticity of the light beam radiated by the one wavelength converter (target wavelength converter) based on the laser light beams of the combination of laser elements falls within a predetermined second range.

Specifically, for example, as illustrated inFIG. 8, the main wavelengths of laser elements are measured (S101to S104), and a plurality of combinations of laser elements whose composite wavelengths fall within the 3 nm range (preferably within the 2 nm range) are classified into two groups: a long wavelength side and a short wavelength side (S205). Meanwhile, the conversion characteristics of a plurality of wavelength converters104are measured (S206), and the plurality of wavelength converters104are classified into the two groups: wavelength converters104having a low y chromaticity and wavelength converters4having a high y chromaticity (S207). Then, a combination of laser elements belonging to the long wavelength side group and one wavelength converter104belonging to the group with a high y chromaticity, or a combination of laser elements belonging to the short wavelength side group and one wavelength converter104belonging to the group with a low y chromaticity are combined (S208). Lastly, luminaire100is manufactured based on such combination (S209). Accordingly, it becomes possible to further reduce individual difference-caused variation of luminous color of luminaire100.

Furthermore, the conversion characteristics of wavelength converters104may be measured based on the laser light beams which are guided by a plurality of light guides and with which the same area of wavelength converter104is irradiated. In other words, the conversion characteristics may be measured including the characteristics of the light guides.

Accordingly, individual difference-caused variation in chromaticity of luminaire100can further be suppressed.

Furthermore, aside from a transmission type luminaire100in which one surface of wavelength converter104is irradiated with laser light beams and white light is radiated from the opposite surface, luminaire100may be a reflective type luminaire100in which white light is radiated from the same surface of wavelength converter104which is irradiated with laser light beams, as illustrated inFIG. 9.

Furthermore, although it is described in the working example that the composite wavelength falls within the range of 455±1.5 nm, inclusive, the same advantageous effect can be obtained even with an arbitrary range such as 445±1.5 nm, 465±1.5 nm, etc.

Furthermore, the oscillation wavelength bands of the laser element having the longest main wavelength and the laser element having the shortest main wavelength, among the plurality of laser elements provided in one luminaire100, need not overlap. Individually, the oscillation wavelength bands have, for example, a wavelength width of 1/10 of the peak. Accordingly, the laser element combination can be flexibly selected, and laser elements can be efficiently applied to luminaire100.

Furthermore, the first range may be limited to a range that is further on the long wavelength side than the peak wavelength of the excitation spectrum of wavelength converter104or the excitation spectrum of at least one wavelength converting material141included in wavelength converter104.

Furthermore, a light-transmissive cover may be disposed in front of wavelength converter104. The cover may be a component which has glass, resin, etc., as a material, and serves to prevent foreign objects such as dust from settling on wavelength converter104. In addition, the cover may have an optical function such as light diffusion, light collecting, etc.