WO2019193658A1 - Lighting device - Google Patents

Lighting device Download PDF

Info

Publication number
WO2019193658A1
WO2019193658A1 PCT/JP2018/014321 JP2018014321W WO2019193658A1 WO 2019193658 A1 WO2019193658 A1 WO 2019193658A1 JP 2018014321 W JP2018014321 W JP 2018014321W WO 2019193658 A1 WO2019193658 A1 WO 2019193658A1
Authority
WO
WIPO (PCT)
Prior art keywords
excitation light
lighting device
conversion element
wavelength conversion
cross
Prior art date
Application number
PCT/JP2018/014321
Other languages
French (fr)
Inventor
Jing Li
Karl Peter WELNA
Valerie Berryman-Bousquet
Koji Takahashi
Original Assignee
Sharp Kabushiki Kaisha
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sharp Kabushiki Kaisha filed Critical Sharp Kabushiki Kaisha
Priority to PCT/JP2018/014321 priority Critical patent/WO2019193658A1/en
Publication of WO2019193658A1 publication Critical patent/WO2019193658A1/en

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0087—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for illuminating phosphorescent or fluorescent materials, e.g. using optical arrangements specifically adapted for guiding or shaping laser beams illuminating these materials
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
    • C09K11/7774—Aluminates
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V5/00—Refractors for light sources
    • F21V5/002—Refractors for light sources using microoptical elements for redirecting or diffusing light
    • F21V5/004—Refractors for light sources using microoptical elements for redirecting or diffusing light using microlenses
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V5/00—Refractors for light sources
    • F21V5/008—Combination of two or more successive refractors along an optical axis
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
    • F21V9/30—Elements containing photoluminescent material distinct from or spaced from the light source
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
    • H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
    • H05B33/145—Arrangements of the electroluminescent material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2101/00—Point-like light sources
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/50—Wavelength conversion elements
    • H01L33/507—Wavelength conversion elements the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0071—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for beam steering, e.g. using a mirror outside the cavity to change the beam direction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings
    • H01S5/02208—Mountings; Housings characterised by the shape of the housings
    • H01S5/02212—Can-type, e.g. TO-CAN housings with emission along or parallel to symmetry axis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
    • H01S5/323—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/32308—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm
    • H01S5/32341—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm blue laser based on GaN or GaP

Definitions

  • the present invention relates to a lighting device including (i) a light source configured to emit excitation light and (ii) a wavelength conversion element on which the excitation light emitted by the light source is incident.
  • a lighting device in accordance with an embodiment of the present invention includes: a light source configured to emit excitation light; and a wavelength conversion element tilted, with respect to an optical axis of the excitation light, around a first tilt axis perpendicular to the optical axis, a cross-sectional size of the excitation light traveling toward the wavelength conversion element being defined on a basis of a tilting angle of the wavelength conversion element with respect to the optical axis.
  • a lighting device in accordance with another embodiment of the present invention includes: a light source configured to emit excitation light; a microlens array including a plurality of microlenses through which the excitation light passes; and a wavelength conversion element on which the excitation light having passed through the microlens array is incident, the microlens array being tilted around a tilt axis perpendicular to an optical axis of the excitation light.
  • a lighting device in accordance with still another embodiment of the present invention includes: a light source configured to emit excitation light; a microlens array including a plurality of microlenses through which the excitation light passes; and a wavelength conversion element on which the excitation light having passed through the microlens array is incident, the plurality of microlenses being arranged so that the long axis of the microlens is parallel to a long axis of a cross section of the excitation light.
  • An aspect of the present invention makes it possible to provide a lighting device capable of causing a wavelength conversion element to emit light in a desired pattern without use of a mask.
  • FIG. 1 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 1.
  • (b) of Fig. 1 is a diagram illustrating a cross section of excitation light taken along section C1-C1 shown in (a) of Fig. 1.
  • (c) of Fig. 1 is a diagram illustrating a cross section of excitation light taken along section C2-C2 shown in (a) of Fig. 1.
  • (a) to (f) of Fig. 2 are each a diagram illustrating an example shape and dimensions of a cross section of excitation light arriving on the wavelength conversion element included in the lighting device.
  • Fig. 3 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 2.
  • (a) of Fig. 1 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 2.
  • FIG. 4 is a diagram illustrating (i) an example microlens array provided in the lighting device and (ii) a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light.
  • (b) of Fig. 4 is a diagram illustrating another example microlens array and a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light.
  • (c) of Fig. 4 is a diagram illustrating still another example microlens array and a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light.
  • FIG. 5 is a diagram illustrating an example microlens array as viewed along the optical axis of the excitation light.
  • (b) of Fig. 5 is a diagram illustrating still another example microlens array as viewed along the optical axis of the excitation light.
  • (a) of Fig. 6 is an image of an excitation spot generated in a case where use is made of an untilted wavelength conversion element and a microlens array.
  • (b) of Fig. 6 is an image of an excitation spot generated in a case where use is made of a tilted wavelength conversion element and a microlens array.
  • FIG. 6 is an image of an excitation spot generated in a case where use is made of a tilted wavelength conversion element and a microlens array .
  • FIG. 7 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 3.
  • Fig. 8 is an image of an excitation spot generated in a case where use is made of a tilted wavelength conversion element and a microlens array in accordance with Embodiment 3.
  • (a) of Fig. 9 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 4.
  • (b) of Fig. 9 is a diagram illustrating a cross section of excitation light taken along section C1-C1 shown in (a) of Fig. 9.
  • FIG. 9 is a diagram illustrating a cross section of excitation light taken along section C2-C2 shown in (a) of Fig. 9.
  • (a) of Fig. 10 is a diagram illustrating (i) an example microlens array provided in the lighting device in accordance with Embodiment 5 and (ii) a cross section of excitation light both emitted by the excitation light source as viewed along the optical axis of the excitation light.
  • (b) of Fig. 10 is a diagram illustrating another example microlens array and a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light.
  • (c) and (d) of Fig. 10 are each a diagram illustrating still another example microlens array and a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light.
  • FIG. 1 is a diagram schematically illustrating the configuration of a lighting device 2 in accordance with Embodiment 1.
  • (b) of Fig. 1 is a diagram illustrating a cross section of excitation light 8 taken along section C1-C1 shown in (a) of Fig. 1.
  • (c) of Fig. 1 is a diagram illustrating a cross section of excitation light 8 taken along section C2-C2 shown in (a) of Fig. 1.
  • the lighting device 2 includes an excitation light source 1 (light source) and a wavelength conversion element 5.
  • the excitation light source 1 is configured to emit excitation light 8 along the Z axis.
  • the wavelength conversion element 5 is tilted around the X axis (first tilt axis), which is perpendicular to the optical axis 6, by a tilting angle ⁇ 1 with respect to the optical axis 6 of the excitation light 8 emitted by the excitation light source 1.
  • the excitation light 8 includes, for example, laser light.
  • the present specification uses the term "wavelength conversion element" to refer to a member that is configured to, in response to light (for example, laser light) having a first wavelength, emit light having a second wavelength different from the first wavelength and that contains a material such as a fluorescent material.
  • the excitation light 8 is specifically light emitted from a semiconductor laser and having a blue-violet color within a wavelength range of 395 to 415 nm or a blue color within a wavelength range of 440 to 460 nm.
  • the wavelength conversion element contains, as appropriate, (i) a mixture of phosphors that emit light having three respective colors of red, blue, and green or (ii) a mixture of phosphors that emit light having two respective colors of blue and yellow or blue-green and orange. The colors of light emitted from the phosphors are mixed to produce white light.
  • the wavelength conversion element may contain a phosphor (for example, YAG:Ce) that can be excited by blue light to emit yellow light.
  • a phosphor for example, YAG:Ce
  • the blue color of the excitation light and the yellow color of light emitted from the phosphor are mixed with each other to produce white light.
  • FIG. 1 illustrates a cross section 17 of excitation light 8 that has exited from the excitation light source 1 and that travels toward the wavelength conversion element 5.
  • (c) of Fig. 1 illustrates a cross section 18 (excitation spot 9) of excitation light 8 taken along a surface of the wavelength conversion element 5 on which the excitation light 8 is projected.
  • the excitation light 8, immediately before reaching the wavelength conversion element 5, has a cross section 17 perpendicular to the optical axis 6 which cross section 17 has a dimension a1 and a dimension b1.
  • the excitation light 8 has a cross section 18 taken along a surface of the wavelength conversion element 5 on which the excitation light 8 is projected which cross section 18 has a dimension a2 and a dimension b2.
  • the dimensions a1 and a2 are each defined as the largest length along the X axis of the corresponding one of the cross sections 17 and 18.
  • the dimensions b1 and b2 are each defined as the largest length along the Y axis of the corresponding one of the cross sections 17 and 18.
  • FIG. 2 are each a diagram illustrating an example shape and dimensions of a cross section 17 of excitation light 8 emitted by an excitation light source 1 included in the lighting device 2.
  • the dimensions a1 and b1 of the excitation light 8 are adjusted in order to prevent the excitation spot from being stretched and allow the excitation spot 9 on the wavelength conversion element 5 to have a desired shape and a desired aspect ratio.
  • the cross section 17 of the excitation light 8 may be in the shape of a square as illustrated in (a) of Fig. 2 or a rectangle as illustrated in (b) of Fig. 2.
  • the cross section 17 of the excitation light 8 may further be in the shape of a hexagon, a triangle, an ellipse, or a pentagon as illustrated in (c) to (f) of Fig. 2.
  • Fig. 3 is a diagram schematically illustrating the configuration of a lighting device 2A in accordance with Embodiment 2.
  • (a) of Fig. 4 is a diagram illustrating (i) an example microlens array 3 provided in the lighting device 2A and (ii) a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8.
  • (b) of Fig. 4 is a diagram illustrating another example microlens array 3 and a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8.
  • FIG. 4 is a diagram illustrating still another example microlens array 3 and a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8.
  • Any constituent element of the present embodiment that has already been described for an embodiment above is assigned a similar reference sign, and the detailed description thereof is not repeated here.
  • Embodiment 2 includes a microlens array 3 and a condensing lens 4 between the excitation light source 1 and the wavelength conversion element 5.
  • the microlens array 3 includes a plurality of microlenses 12 each having a size based on the tilting angle ⁇ 1 of the wavelength conversion element 5.
  • the condensing lens 4 is configured to concentrate the excitation light 8, having passed through the microlenses 12, on the wavelength conversion element 5.
  • the excitation light 8 having been concentrated on the wavelength conversion element 5 excites the phosphor contained in the wavelength conversion element 5 to cause converted light 10 to be emitted from the wavelength conversion element 5.
  • the microlens array 3 allows an excitation spot 9 to be generated on a tilted wavelength conversion element 5 which excitation spot 9 has uniform intensity distribution and well-defined shape.
  • the microlens array 3 may be a diffuser plate.
  • the plurality of microlenses 12 have respective cross sections perpendicular to the optical axis 6 which cross sections may all be identical in shape to one another as illustrated in (a) and (b) of Fig. 4 or may be different from one another as illustrated in (c) of Fig. 4.
  • the plurality of microlenses 12 may be arranged in a periodical pattern as illustrated in (a) of Fig. 4 or may be arranged in a randomized pattern as illustrated in (b) and (c) of Fig. 4.
  • the shape of the excitation light 8 and thus the shape of the excitation spot 9 are determined by the respective shapes of the microlenses 12.
  • the excitation spot 9 on an untilted wavelength conversion element 5 will also be square.
  • the excitation spot 9 on a tilted wavelength conversion element 5 will become rectangular due to the stretching of the excitation spot.
  • Embodiment 2 is configured to adjust the respective aspect ratios of the microlenses 12 to prevent the excitation spot 9 from being stretched.
  • the microlenses 12 each have an aspect ratio Ym defined as the ratio between the largest length along the X axis and the largest length along the Y axis as in Embodiment 1 described earlier.
  • the microlenses 12 each have an aspect ratios Ym of (-1/cos ⁇ 1).
  • Embodiment 2 uses, as the microlens array 3, one of two different microlens arrays: a first microlens array 3 including microlenses 12 having respective square shapes identical to one another with a size of 400 ⁇ m ⁇ 400 ⁇ m (the aspect ratio being 1) as illustrated in (a) of Fig. 5; and a second microlens array 3 including microlenses 12 having respective rectangular shapes identical to one another with a size of 400 ⁇ m ⁇ 200 ⁇ m (the aspect ratio being 2) as illustrated in (b) of Fig. 5.
  • the microlenses 12 share the same radius of curvature of 8 mm for both the first microlens array 3 and the second microlens array 3.
  • FIG. 6 is an image of an excitation spot 9 generated in a case where use is made of an untilted wavelength conversion element 5 and the first microlens array 3.
  • (b) of Fig. 6 is an image of an excitation spot 9 generated in a case where use is made of a tilted wavelength conversion element 5 and the first microlens array 3.
  • (c) of Fig. 6 is an image of an excitation spot 9 generated in a case where use is made of a tilted wavelength conversion element 5 and the second microlens array 3.
  • the excitation spot 9 also has a square shape with a size of 400 ⁇ m ⁇ 400 ⁇ m (the aspect ratio being 1) as illustrated in (a) of Fig. 6.
  • the excitation spot 9 has a rectangular shape with a size of 400 ⁇ m ⁇ 800 ⁇ m (the aspect ratio being 1/2) due to the stretching of the excitation spot as illustrated in (b) of Fig. 6.
  • the excitation spot 9 maintains a square shape with a size of 400 ⁇ m ⁇ 400 ⁇ m (the aspect ratio being 1) with the stretching of the excitation spot corrected as illustrated in (c) of Fig. 6.
  • Fig. 7 is a diagram schematically illustrating the configuration of a lighting device 2B in accordance with Embodiment 3.
  • Fig. 8 is an image of an excitation spot 9 generated in a case where use is made of a tilted wavelength conversion element 5 and a microlens array 3 in accordance with Embodiment 3. Any constituent element of the present embodiment that has already been described for an embodiment above is assigned a similar reference sign, and the detailed description thereof is not repeated here.
  • Embodiment 3 uses a microlens array 3 tilted around a rotation axis 15 (second tilt axis), which is perpendicular to the optical axis 6 and the X axis.
  • This configuration allows the microlens array 3 to have a tilting angle adjusted with respect to the wavelength conversion element 5.
  • the above configuration also reduces interference between (i) a portion of the excitation light 8 which portion has passed one of the plurality of microlenses 12 and (ii) a portion of the excitation light 8 which portion has passed through another one of the plurality of microlenses 12 and allows laser light incident on the wavelength conversion element 5 to be uniform.
  • the adjustment of the tilting angle of the microlens array 3 allows the aspect ratio of the excitation spot 9 to be maintained, that is, allows the aspect ratio of the excitation spot 9 before the excitation light 8 passes through the microlens array 3 to be identical to the aspect ratio of the excitation spot 9 on the surface of a tilted wavelength conversion element 5.
  • the tilting angle ⁇ 1 between the surface normal 11 of the wavelength conversion element 5 and the optical axis 6 (Z axis) is assumed to be 120°.
  • Embodiment 3 uses a single microlens array as the microlens array 3.
  • the microlens array 3 includes microlenses 12 having respective square shapes identical to one another and each having a size of 400 ⁇ m ⁇ 400 ⁇ m (the aspect ratio being 1).
  • the microlenses 12 each have a radius of curvature of 8 mm.
  • the microlens array 3 is tilted around the rotation axis 15 together with its surface normal 16 by an angle of 120° with respect to the Z axis as illustrated in Fig. 7.
  • the excitation spot 9 has a square shape with a size of 1 mm ⁇ 1 mm as illustrated in Fig. 8 (the aspect ratio being 1).
  • the aspect ratio is the same as in a case where both the wavelength conversion element 5 and the microlens array 3 are untilted.
  • FIG. 9 is a diagram schematically illustrating the configuration of a lighting device 2C in accordance with Embodiment 4.
  • (b) of Fig. 9 is a diagram illustrating a cross section of excitation light 8 taken along section C1-C1 shown in (a) of Fig. 9.
  • (c) of Fig. 9 is a diagram illustrating a cross section of excitation light 8 taken along section C2-C2 shown in (a) of Fig. 9.
  • Embodiment 4 concerns the orientation of excitation light 8 with respect to the wavelength conversion element 5, and may or may not include a microlens array 3.
  • the excitation light 8 may be generated by one or more excitation light sources 1, and may pass through one or more optical elements before reaching the wavelength conversion element 5.
  • the excitation light 8 may become collimated, convergent, or divergent before reaching the wavelength conversion element 5.
  • the excitation light 8 is assumed to have, on a plane immediately before the wavelength conversion element 5, a cross section perpendicular to the optical axis 6 which cross section has a size of a1 ⁇ b1 as illustrated by section C1-C1 in (b) of Fig. 9.
  • the excitation light 8 is assumed to have a cross section taken along a surface of the wavelength conversion element 5 on which surface the excitation light 8 is projected which cross section has a size of a2 ⁇ b2 as illustrated by section C2-C2 in (c) of Fig. 9.
  • the excitation spot 9 will have a dimension b2 along the Y axis which dimension b2 is stretched by a factor of (-1/cos ⁇ 1).
  • the excitation light 8 needs to be oriented such that a1 ⁇ b1. This may be achieved by, for instance, (i) rotating the excitation light source 1 around the optical axis 6 and (ii) changing or rotating an optical element(s) between the excitation light source 1 and the wavelength conversion element 5.
  • the wavelength conversion element 5 is assumed to be tilted around the X axis such that the angle between the surface normal 11 and the optical axis 6 (Z axis) is equal to 120°.
  • the excitation light 8 is assumed to have a cross section 17 with a size of 400 ⁇ m ⁇ 200 ⁇ m.
  • the excitation spot 9 has a dimension a2 of 400 ⁇ m and a dimension b2 of 400 ⁇ m, and is symmetrical along the X axis and Y axis.
  • the excitation spot 9 has a dimension 2a of 200 ⁇ m and a dimension b2 of 800 ⁇ m, and is less symmetrical.
  • FIG. 10 is a diagram illustrating (i) an example microlens array 3 provided on the lighting device in accordance with Embodiment 5 and (ii) a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8.
  • (b) of Fig. 10 is a diagram illustrating another example microlens array 3 and a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8.
  • (c) and (d) of Fig. 10 are each a diagram illustrating still another example microlens array 3 and a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8.
  • Embodiment 5 concerns a lighting device including one or more microlens arrays 3 each including a plurality of microlenses 12 to generate on a wavelength conversion element 5 an excitation spot 9 having uniform intensity distribution and a desired, well-defined shape.
  • the wavelength conversion element 5 may be untilted or tilted.
  • the one or more microlens arrays 3 may each be untilted or tilted.
  • the plurality of microlenses 12 included in each microlens array 3 may have respective shapes identical to one another or different from one another.
  • the plurality of microlenses 12 may be arranged in a regular pattern or may be arranged in a randomized pattern.
  • the optical configuration of a typical lighting device is also illustrated in Fig. 3.
  • the cross section 13 of the excitation light 8 on a surface of each microlens array 3 does not have a rotational symmetrical shape.
  • the present specification uses (i) the term “short axis” to refer to the direction in which the cross section 13 of excitation light 8 has the smallest dimension and (ii) the term “long axis” to refer to the direction orthogonal to the short axis.
  • the present specification uses, also for the microlens array 3, (i) the term “short axis” to refer to the direction in which a microlens 12 has the smallest dimension and (ii) the term "long axis” to refer to the direction orthogonal to the short axis.
  • the short axis of the cross section 13 of the excitation light 8 is, in order to generate an excitation spot 9 having a more uniform light distribution, oriented such that the excitation light 8 overlaps with as many microlenses 12 on each microlens array 3 as possible.
  • the microlenses 12 are, in other words, arranged such that the long-axis direction of each microlens 12 is parallel to the long-axis direction of the cross section 13 of the excitation light 8.
  • the cross section 13 of the excitation light 8 has a long axis along the X axis
  • the microlenses 12 each have a long axis along the X axis as well
  • the cross section 13 of the excitation light 8 has a short-axis dimension 20 along the Y axis (that is, the short-axis direction of a microlens 12).
  • the cross section 13 of the excitation light 8 has a long axis along the Y axis
  • the microlenses 12 each have a long axis along the Y axis as well
  • the cross section 13 has a short-axis dimension 20 along the X axis (that is, the short-axis direction).
  • a lighting device 2, 2A, 2B, 2C in accordance with a first aspect of the present invention includes: a light source (excitation light source 1) configured to emit excitation light 8; and a wavelength conversion element 5 tilted, with respect to an optical axis 6 of the excitation light 8, around a first tilt axis (X axis) perpendicular to the optical axis 6, a cross-sectional size of the excitation light 8 traveling toward the wavelength conversion element 5 being defined on a basis of a tilting angle ⁇ 1 of the wavelength conversion element 5 with respect to the optical axis 6.
  • the excitation light traveling toward the wavelength conversion element has a cross-sectional size defined on the basis of the tilting angle ⁇ 1 of the wavelength conversion element 5 with respect to the optical axis. This allows the shape of the excitation spot of the excitation light projected on the wavelength conversion element to be corrected on the basis of the tilting angle ⁇ 1 of the wavelength conversion element.
  • the above configuration thereby causes the wavelength conversion element to emit light in a desired pattern.
  • ⁇ 1 is the tilting angle.
  • a lighting device 2, 2A, 2B, 2C in accordance with a third aspect of the present invention is configured as in the first aspect and preferably further includes: a cross-sectional size correcting member configured to correct the cross-sectional size on a basis of the tilting angle ⁇ 1.
  • a cross-sectional size correcting member configured to correct the cross-sectional size on a basis of the tilting angle ⁇ 1.
  • a lighting device 2A, 2B in accordance with a fourth aspect of the present invention is configured as in the third aspect and is preferably configured such that the cross-sectional size correcting member includes at least one microlens 12 having a dimension based on the tilting angle ⁇ 1; and the excitation light 8 travels through the at least one microlens 12 toward the wavelength conversion element 5.
  • the above configuration causes excitation light to pass through a microlens having a dimension based on the tilting angle of the wavelength conversion element for correction of the cross-sectional size of the excitation light.
  • a lighting device 2A, 2B in accordance with a fifth aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the at least one microlens 12 includes a plurality of microlenses 12; and the cross-sectional size correcting member includes (i) a microlens array 3 including the plurality of microlenses 12 and (ii) a condensing lens 4 configured to concentrate, on the wavelength conversion element 5, the excitation light 8 having passed through the plurality of microlenses 12.
  • a lighting device 2B in accordance with a seventh aspect of the present invention is configured as in the fifth aspect and is preferably configured such that the microlens array 3 is tilted around a second tilt axis (rotation axis 15) perpendicular to the optical axis 6 and the first tilt axis (X axis) so as to reduce interference between (i) a first portion of the excitation light 8 which first portion has passed through a first one of the plurality of microlenses 12 and (ii) a second portion of the excitation light 8 which second portion has passed through a second one of the plurality of microlenses 12.
  • the microlens array being tilted around the second tilt axis reduces interference between different portions of excitation light 8 on the wavelength conversion element.
  • a lighting device 2, 2A, 2B, 2C in accordance with an eighth aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the at least one microlens 12 includes a plurality of microlenses 12; and the plurality of microlenses 12 are arranged so that the long axis of the microlens 12 is parallel to a long axis of a cross section 13 of the excitation light 8.
  • the above configuration allows a cross section of excitation light to overlap with more microlenses along the short axis.
  • a lighting device 2B in accordance with a ninth aspect of the present invention is configured as in the seventh aspect and is preferably configured such that the plurality of microlenses 12 each have a shape of a rectangle having a first dimension along the first tilt axis (X axis) and a second dimension along the second tilt axis (Y axis), the second dimension being larger than the first dimension; and a ratio between the first dimension and the second dimension is based on the tilting angle ⁇ 1.
  • the above configuration can correct the stretching of an excitation spot on the wavelength conversion element.
  • a lighting device 2, 2A, 2B, 2C in accordance with a tenth aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the plurality of microlenses 12 are arranged in a regular pattern.
  • the above configuration allows the microlens array to have a simplified arrangement.
  • a lighting device 2, 2A, 2B, 2C in accordance with an eleventh aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the plurality of microlenses 12 are arranged in an irregular pattern.
  • the above configuration reduces interference between different portions of excitation light having passed through the microlenses and concentrated on the wavelength conversion element.
  • a lighting device 2, 2A, 2B, 2C in accordance with an twelfth aspect of the present invention is configured as in the first aspect and is preferably configured such that the light source (excitation light source 1) is a laser light source configured to emit laser light.
  • a lighting device 2B in accordance with a thirteenth aspect of the present invention includes: a light source configured to emit excitation light; a microlens array including a plurality of microlenses through which the excitation light passes; and a wavelength conversion element on which the excitation light having passed through the microlens array is incident, the microlens array being tilted around a tilt axis perpendicular to an optical axis of the excitation light.
  • the microlens array being tilted around the second tilt axis reduces interference between different portions of excitation light 8 on the wavelength conversion element.
  • a lighting device in accordance with a fourteenth aspect of the present invention includes: a light source configured to emit excitation light; a microlens array including a plurality of microlenses through which the excitation light passes; and a wavelength conversion element on which the excitation light having passed through the microlens array is incident, the plurality of microlenses being arranged so that the long axis of the microlens is parallel to a long axis of a cross section of the excitation light.
  • the above configuration allows a cross section of excitation light to overlap with more microlenses along the short axis.
  • the present invention is not limited to the embodiments, but can be altered by a skilled person in the art within the scope of the claims.
  • the present invention also encompasses, in its technical scope, any embodiment derived by combining technical means disclosed in differing embodiments. Further, it is possible to form a new technical feature by combining the technical means disclosed in the respective embodiments.
  • Excitation light source (light source, laser light source) 2 Lighting device 3 Microlens array 4 Condensing lens 5 Wavelength conversion element 6 Optical axis 8 Excitation light 9 Excitation spot 10 Light 11 Surface normal 12 Microlens 13 Cross section 15 Rotation axis 16 Surface normal 17 Cross section 18 Cross section 20 Short-axis dimension

Abstract

The lighting device (2) includes an excitation light source (1), a wavelength conversion element (5), and a microlens array (3). The excitation light source (1) is configured to emit excitation light (8). The wavelength conversion element (5) is tilted around a first tilt axis, which is perpendicular to the optical axis (6) of the excitation light (8), with respect to the optical axis (6). The microlens array (3) is configured to, on the basis of the tilting angle of the wavelength conversion element (5) with respect to the optical axis (6), correct a cross-sectional size of the excitation light (8) traveling toward the wavelength conversion element (5).

Description

LIGHTING DEVICE
The present invention relates to a lighting device including (i) a light source configured to emit excitation light and (ii) a wavelength conversion element on which the excitation light emitted by the light source is incident.
There has been known a lighting device configured to emit white light by exciting, with use of excitation light emitted by an excitation light source, a wavelength conversion element containing a phosphor and tilted with respect to the optical axis of the excitation light (see Patent Literature 1).
U.S. Patent Application Publication No. 2012/0224385 (Publication date: September 6, 2012) Japanese Patent Application Publication, Tokukai, No. 2011-181381 (Publication date: September 15, 2011) International Patent Application Publication No. 2017/154807 (Publication date: September 14, 2017)
With the technique disclosed in Patent Literature 1 above, in which a wavelength conversion element containing a phosphor is tilted with respect to the optical axis of excitation light, the excitation spot of excitation light projected on the wavelength conversion element is stretched in correspondence with the tilting angle of the wavelength conversion element. The above technique thus fails to make it possible to cause a wavelength conversion element to emit light in a desired pattern.
There has been known a technique of providing a wavelength conversion element with a mask for controlling the shape of excitation light (emission pattern) incident on the wavelength conversion element to prevent the excitation spot from being stretched (Patent Literatures 2 and 3).
It is an object of an embodiment of the present invention to provide a lighting device capable of causing a wavelength conversion element to emit light in a desired pattern without use of a mask.
In order to attain the above object, a lighting device in accordance with an embodiment of the present invention includes: a light source configured to emit excitation light; and a wavelength conversion element tilted, with respect to an optical axis of the excitation light, around a first tilt axis perpendicular to the optical axis, a cross-sectional size of the excitation light traveling toward the wavelength conversion element being defined on a basis of a tilting angle of the wavelength conversion element with respect to the optical axis.
In order to attain the above object, a lighting device in accordance with another embodiment of the present invention includes: a light source configured to emit excitation light; a microlens array including a plurality of microlenses through which the excitation light passes; and a wavelength conversion element on which the excitation light having passed through the microlens array is incident, the microlens array being tilted around a tilt axis perpendicular to an optical axis of the excitation light.
In order to attain the above object, a lighting device in accordance with still another embodiment of the present invention includes: a light source configured to emit excitation light; a microlens array including a plurality of microlenses through which the excitation light passes; and a wavelength conversion element on which the excitation light having passed through the microlens array is incident, the plurality of microlenses being arranged so that the long axis of the microlens is parallel to a long axis of a cross section of the excitation light.
An aspect of the present invention makes it possible to provide a lighting device capable of causing a wavelength conversion element to emit light in a desired pattern without use of a mask.
(a) of Fig. 1 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 1. (b) of Fig. 1 is a diagram illustrating a cross section of excitation light taken along section C1-C1 shown in (a) of Fig. 1. (c) of Fig. 1 is a diagram illustrating a cross section of excitation light taken along section C2-C2 shown in (a) of Fig. 1. (a) to (f) of Fig. 2 are each a diagram illustrating an example shape and dimensions of a cross section of excitation light arriving on the wavelength conversion element included in the lighting device. Fig. 3 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 2. (a) of Fig. 4 is a diagram illustrating (i) an example microlens array provided in the lighting device and (ii) a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light. (b) of Fig. 4 is a diagram illustrating another example microlens array and a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light. (c) of Fig. 4 is a diagram illustrating still another example microlens array and a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light. (a) of Fig. 5 is a diagram illustrating an example microlens array as viewed along the optical axis of the excitation light. (b) of Fig. 5 is a diagram illustrating still another example microlens array as viewed along the optical axis of the excitation light. (a) of Fig. 6 is an image of an excitation spot generated in a case where use is made of an untilted wavelength conversion element and a microlens array. (b) of Fig. 6 is an image of an excitation spot generated in a case where use is made of a tilted wavelength conversion element and a microlens array. (c) of Fig. 6 is an image of an excitation spot generated in a case where use is made of a tilted wavelength conversion element and a microlens array . Fig. 7 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 3. Fig. 8 is an image of an excitation spot generated in a case where use is made of a tilted wavelength conversion element and a microlens array in accordance with Embodiment 3. (a) of Fig. 9 is a diagram schematically illustrating the configuration of a lighting device in accordance with Embodiment 4. (b) of Fig. 9 is a diagram illustrating a cross section of excitation light taken along section C1-C1 shown in (a) of Fig. 9. (c) of Fig. 9 is a diagram illustrating a cross section of excitation light taken along section C2-C2 shown in (a) of Fig. 9. (a) of Fig. 10 is a diagram illustrating (i) an example microlens array provided in the lighting device in accordance with Embodiment 5 and (ii) a cross section of excitation light both emitted by the excitation light source as viewed along the optical axis of the excitation light. (b) of Fig. 10 is a diagram illustrating another example microlens array and a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light. (c) and (d) of Fig. 10 are each a diagram illustrating still another example microlens array and a cross section of excitation light emitted by the excitation light source both as viewed along the optical axis of the excitation light.
Embodiment 1
(a) of Fig. 1 is a diagram schematically illustrating the configuration of a lighting device 2 in accordance with Embodiment 1. (b) of Fig. 1 is a diagram illustrating a cross section of excitation light 8 taken along section C1-C1 shown in (a) of Fig. 1. (c) of Fig. 1 is a diagram illustrating a cross section of excitation light 8 taken along section C2-C2 shown in (a) of Fig. 1.
The lighting device 2 includes an excitation light source 1 (light source) and a wavelength conversion element 5. The excitation light source 1 is configured to emit excitation light 8 along the Z axis. The wavelength conversion element 5 is tilted around the X axis (first tilt axis), which is perpendicular to the optical axis 6, by a tilting angle θ1 with respect to the optical axis 6 of the excitation light 8 emitted by the excitation light source 1. The excitation light 8 includes, for example, laser light.
The present specification uses the term "wavelength conversion element" to refer to a member that is configured to, in response to light (for example, laser light) having a first wavelength, emit light having a second wavelength different from the first wavelength and that contains a material such as a fluorescent material.
The excitation light 8 is specifically light emitted from a semiconductor laser and having a blue-violet color within a wavelength range of 395 to 415 nm or a blue color within a wavelength range of 440 to 460 nm. In a case where the excitation light has a blue-violet color, the wavelength conversion element contains, as appropriate, (i) a mixture of phosphors that emit light having three respective colors of red, blue, and green or (ii) a mixture of phosphors that emit light having two respective colors of blue and yellow or blue-green and orange. The colors of light emitted from the phosphors are mixed to produce white light. In a case where the excitation light has a blue color, the wavelength conversion element may contain a phosphor (for example, YAG:Ce) that can be excited by blue light to emit yellow light. In this case, the blue color of the excitation light and the yellow color of light emitted from the phosphor are mixed with each other to produce white light.
(b) of Fig. 1 illustrates a cross section 17 of excitation light 8 that has exited from the excitation light source 1 and that travels toward the wavelength conversion element 5. (c) of Fig. 1 illustrates a cross section 18 (excitation spot 9) of excitation light 8 taken along a surface of the wavelength conversion element 5 on which the excitation light 8 is projected.
The description below assumes the following: The excitation light 8, immediately before reaching the wavelength conversion element 5, has a cross section 17 perpendicular to the optical axis 6 which cross section 17 has a dimension a1 and a dimension b1. The excitation light 8 has a cross section 18 taken along a surface of the wavelength conversion element 5 on which the excitation light 8 is projected which cross section 18 has a dimension a2 and a dimension b2. The dimensions a1 and a2 are each defined as the largest length along the X axis of the corresponding one of the cross sections 17 and 18. The dimensions b1 and b2 are each defined as the largest length along the Y axis of the corresponding one of the cross sections 17 and 18.
(a) to (f) of Fig. 2 are each a diagram illustrating an example shape and dimensions of a cross section 17 of excitation light 8 emitted by an excitation light source 1 included in the lighting device 2.
In a case where the wavelength conversion element 5 is tilted around the X axis together with its surface normal 11, the excitation spot 9 on the cross section 18 is stretched along the Y axis from b1 to b2 in correspondence with the tilting angle θ1 (90° < θ1 < 180°) of the wavelength conversion element 5, where b2 = (-1/cosθ1) × b1 and a1 = a2.
The dimensions a1 and b1 of the excitation light 8 are adjusted in order to prevent the excitation spot from being stretched and allow the excitation spot 9 on the wavelength conversion element 5 to have a desired shape and a desired aspect ratio.
In order to prevent the excitation spot from being stretched and maintain the excitation spot 9 on a tilted wavelength conversion element 5, the cross section of excitation light 8 needs to have an aspect ratio adjusted in accordance with the following Formula 1:
a1adj/b1adj = (-1/cosθ1)a1/b1 ... Formula 1
This formula applies no matter whether the excitation light 8 becomes collimated, convergent, or divergent before reaching the wavelength conversion element 5.
The cross section 17 of the excitation light 8 may be in the shape of a square as illustrated in (a) of Fig. 2 or a rectangle as illustrated in (b) of Fig. 2. The cross section 17 of the excitation light 8 may further be in the shape of a hexagon, a triangle, an ellipse, or a pentagon as illustrated in (c) to (f) of Fig. 2.
Embodiment 2
Fig. 3 is a diagram schematically illustrating the configuration of a lighting device 2A in accordance with Embodiment 2. (a) of Fig. 4 is a diagram illustrating (i) an example microlens array 3 provided in the lighting device 2A and (ii) a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8. (b) of Fig. 4 is a diagram illustrating another example microlens array 3 and a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8. (c) of Fig. 4 is a diagram illustrating still another example microlens array 3 and a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8. Any constituent element of the present embodiment that has already been described for an embodiment above is assigned a similar reference sign, and the detailed description thereof is not repeated here.
Embodiment 2 includes a microlens array 3 and a condensing lens 4 between the excitation light source 1 and the wavelength conversion element 5.
The microlens array 3 includes a plurality of microlenses 12 each having a size based on the tilting angle θ1 of the wavelength conversion element 5. The condensing lens 4 is configured to concentrate the excitation light 8, having passed through the microlenses 12, on the wavelength conversion element 5. The excitation light 8 having been concentrated on the wavelength conversion element 5 excites the phosphor contained in the wavelength conversion element 5 to cause converted light 10 to be emitted from the wavelength conversion element 5.
The microlens array 3 allows an excitation spot 9 to be generated on a tilted wavelength conversion element 5 which excitation spot 9 has uniform intensity distribution and well-defined shape. The microlens array 3 may be a diffuser plate.
The plurality of microlenses 12 have respective cross sections perpendicular to the optical axis 6 which cross sections may all be identical in shape to one another as illustrated in (a) and (b) of Fig. 4 or may be different from one another as illustrated in (c) of Fig. 4. The plurality of microlenses 12 may be arranged in a periodical pattern as illustrated in (a) of Fig. 4 or may be arranged in a randomized pattern as illustrated in (b) and (c) of Fig. 4.
In a case where the microlens array 3 is oriented perpendicular to the optical axis 6 as illustrated in Fig. 3, the shape of the excitation light 8 and thus the shape of the excitation spot 9 are determined by the respective shapes of the microlenses 12. In a case where, for instance, the plurality of microlenses 12 have respective square shapes identical to one another, the excitation spot 9 on an untilted wavelength conversion element 5 will also be square. In a case where the wavelength conversion element 5 is tilted around the X axis together with its surface normal 11 by a tilting angle θ1 with respect to the Z axis, the excitation spot 9 on a tilted wavelength conversion element 5 will become rectangular due to the stretching of the excitation spot.
Embodiment 2 is configured to adjust the respective aspect ratios of the microlenses 12 to prevent the excitation spot 9 from being stretched. The microlenses 12 each have an aspect ratio Ym defined as the ratio between the largest length along the X axis and the largest length along the Y axis as in Embodiment 1 described earlier.
In a case where the wavelength conversion element 5 is tilted around the X axis together with its surface normal 11 by a tilting angle θ1 with respect to the Z axis, in order to prevent beam stretching and maintain the excitation spot 9 on a tilted wavelength conversion element 5, the respective aspect ratios Ym of all the microlenses 12 need to be scaled by a factor of (-1/cosθ1). This allows the following Formula 1 mentioned for Embodiment 1 to be satisfied:
a1adj/b1adj = (-1/cosθ1)a1/b1 ... Formula 1
In order to form an excitation spot 9 in a square pattern on the wavelength conversion element 5, for example, the microlenses 12 each have an aspect ratios Ym of (-1/cosθ1).
The tilting angle θ1 between the surface normal 11 of the wavelength conversion element 5 and the optical axis 6 (Z axis) is assumed to be 120°. Embodiment 2 uses, as the microlens array 3, one of two different microlens arrays: a first microlens array 3 including microlenses 12 having respective square shapes identical to one another with a size of 400 μm × 400 μm (the aspect ratio being 1) as illustrated in (a) of Fig. 5; and a second microlens array 3 including microlenses 12 having respective rectangular shapes identical to one another with a size of 400 μm × 200 μm (the aspect ratio being 2) as illustrated in (b) of Fig. 5. The microlenses 12 share the same radius of curvature of 8 mm for both the first microlens array 3 and the second microlens array 3.
(a) of Fig. 6 is an image of an excitation spot 9 generated in a case where use is made of an untilted wavelength conversion element 5 and the first microlens array 3. (b) of Fig. 6 is an image of an excitation spot 9 generated in a case where use is made of a tilted wavelength conversion element 5 and the first microlens array 3. (c) of Fig. 6 is an image of an excitation spot 9 generated in a case where use is made of a tilted wavelength conversion element 5 and the second microlens array 3.
In a case where the first microlens array 3 is used together with an untilted wavelength conversion element 5, the excitation spot 9 also has a square shape with a size of 400 μm × 400 μm (the aspect ratio being 1) as illustrated in (a) of Fig. 6. In a case where the first microlens array 3 is used together with a wavelength conversion element 5 tilted by a tilting angle θ1 of 120°, the excitation spot 9 has a rectangular shape with a size of 400 μm × 800 μm (the aspect ratio being 1/2) due to the stretching of the excitation spot as illustrated in (b) of Fig. 6. In a case where the second microlens array 3 is used together with a wavelength conversion element 5 tilted by a tilting angle θ1 of 120°, the excitation spot 9 maintains a square shape with a size of 400 μm × 400 μm (the aspect ratio being 1) with the stretching of the excitation spot corrected as illustrated in (c) of Fig. 6.
Embodiment 3
Fig. 7 is a diagram schematically illustrating the configuration of a lighting device 2B in accordance with Embodiment 3. Fig. 8 is an image of an excitation spot 9 generated in a case where use is made of a tilted wavelength conversion element 5 and a microlens array 3 in accordance with Embodiment 3. Any constituent element of the present embodiment that has already been described for an embodiment above is assigned a similar reference sign, and the detailed description thereof is not repeated here.
Embodiment 3 uses a microlens array 3 tilted around a rotation axis 15 (second tilt axis), which is perpendicular to the optical axis 6 and the X axis. This configuration allows the microlens array 3 to have a tilting angle adjusted with respect to the wavelength conversion element 5. The above configuration also reduces interference between (i) a portion of the excitation light 8 which portion has passed one of the plurality of microlenses 12 and (ii) a portion of the excitation light 8 which portion has passed through another one of the plurality of microlenses 12 and allows laser light incident on the wavelength conversion element 5 to be uniform. Further, the adjustment of the tilting angle of the microlens array 3 allows the aspect ratio of the excitation spot 9 to be maintained, that is, allows the aspect ratio of the excitation spot 9 before the excitation light 8 passes through the microlens array 3 to be identical to the aspect ratio of the excitation spot 9 on the surface of a tilted wavelength conversion element 5.
In a case where the wavelength conversion element 5 is tilted around the X axis together with its surface normal 11 by a tilting angle θ1 with respect to the Z axis, in order to maintain the aspect ratio of the excitation spot 9, the microlens array 3 needs to be tilted around the rotation axis 15, and the surface normal 16 of the microlens array 3 needs to be tilted by the same tilting angle θ1 with respect to the Z axis. This allows the following Formula 1 mentioned for Embodiment 1 to be satisfied:
a1adj/b1adj = (-1/cosθ1)a1/b1 ... Formula 1
In an example, the tilting angle θ1 between the surface normal 11 of the wavelength conversion element 5 and the optical axis 6 (Z axis) is assumed to be 120°. Embodiment 3 uses a single microlens array as the microlens array 3. The microlens array 3 includes microlenses 12 having respective square shapes identical to one another and each having a size of 400 μm × 400 μm (the aspect ratio being 1). The microlenses 12 each have a radius of curvature of 8 mm. The microlens array 3 is tilted around the rotation axis 15 together with its surface normal 16 by an angle of 120° with respect to the Z axis as illustrated in Fig. 7. The excitation spot 9 has a square shape with a size of 1 mm × 1 mm as illustrated in Fig. 8 (the aspect ratio being 1). The aspect ratio is the same as in a case where both the wavelength conversion element 5 and the microlens array 3 are untilted.
Embodiment 4
(a) of Fig. 9 is a diagram schematically illustrating the configuration of a lighting device 2C in accordance with Embodiment 4. (b) of Fig. 9 is a diagram illustrating a cross section of excitation light 8 taken along section C1-C1 shown in (a) of Fig. 9. (c) of Fig. 9 is a diagram illustrating a cross section of excitation light 8 taken along section C2-C2 shown in (a) of Fig. 9. Any constituent element of the present embodiment that has already been described for an embodiment above is assigned a similar reference sign, and the detailed description thereof is not repeated here.
Embodiment 4 concerns the orientation of excitation light 8 with respect to the wavelength conversion element 5, and may or may not include a microlens array 3. The excitation light 8 may be generated by one or more excitation light sources 1, and may pass through one or more optical elements before reaching the wavelength conversion element 5. The excitation light 8 may become collimated, convergent, or divergent before reaching the wavelength conversion element 5.
The excitation light 8 is assumed to have, on a plane immediately before the wavelength conversion element 5, a cross section perpendicular to the optical axis 6 which cross section has a size of a1 × b1 as illustrated by section C1-C1 in (b) of Fig. 9. The excitation light 8 is assumed to have a cross section taken along a surface of the wavelength conversion element 5 on which surface the excitation light 8 is projected which cross section has a size of a2 × b2 as illustrated by section C2-C2 in (c) of Fig. 9.
In a case where the wavelength conversion element 5 is tilted around the X axis together with its surface normal 11 by a tilting angle θ1 (90° < θ1 < 180°) with respect to the Z axis, the excitation spot 9 will have a dimension b2 along the Y axis which dimension b2 is stretched by a factor of (-1/cosθ1). In order for the excitation spot 9 to be more symmetric along the X axis and Y axis, the excitation light 8 needs to be oriented such that a1 ≧ b1. This may be achieved by, for instance, (i) rotating the excitation light source 1 around the optical axis 6 and (ii) changing or rotating an optical element(s) between the excitation light source 1 and the wavelength conversion element 5.
As an example, the wavelength conversion element 5 is assumed to be tilted around the X axis such that the angle between the surface normal 11 and the optical axis 6 (Z axis) is equal to 120°. The excitation light 8 is assumed to have a cross section 17 with a size of 400 μm × 200 μm. In a case where the excitation light 8 is oriented such that a1 = 400 μm and b1 = 200 μm, the excitation spot 9 has a dimension a2 of 400 μm and a dimension b2 of 400 μm, and is symmetrical along the X axis and Y axis. As a comparison, in a case where the excitation light 8 is oriented such that a1 = 200 μm and b1 = 400 μm, the excitation spot 9 has a dimension 2a of 200 μm and a dimension b2 of 800 μm, and is less symmetrical.
Embodiment 5
(a) of Fig. 10 is a diagram illustrating (i) an example microlens array 3 provided on the lighting device in accordance with Embodiment 5 and (ii) a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8. (b) of Fig. 10 is a diagram illustrating another example microlens array 3 and a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8. (c) and (d) of Fig. 10 are each a diagram illustrating still another example microlens array 3 and a cross section 13 of excitation light 8 both as viewed along the optical axis 6 of the excitation light 8. Any constituent element of the present embodiment that has already been described for an embodiment above is assigned a similar reference sign, and the detailed description thereof is not repeated here.
Embodiment 5 concerns a lighting device including one or more microlens arrays 3 each including a plurality of microlenses 12 to generate on a wavelength conversion element 5 an excitation spot 9 having uniform intensity distribution and a desired, well-defined shape. The wavelength conversion element 5 may be untilted or tilted. The one or more microlens arrays 3 may each be untilted or tilted. The plurality of microlenses 12 included in each microlens array 3 may have respective shapes identical to one another or different from one another. The plurality of microlenses 12 may be arranged in a regular pattern or may be arranged in a randomized pattern. The optical configuration of a typical lighting device is also illustrated in Fig. 3. The cross section 13 of the excitation light 8 on a surface of each microlens array 3 does not have a rotational symmetrical shape. The present specification uses (i) the term "short axis" to refer to the direction in which the cross section 13 of excitation light 8 has the smallest dimension and (ii) the term "long axis" to refer to the direction orthogonal to the short axis. The present specification uses, also for the microlens array 3, (i) the term "short axis" to refer to the direction in which a microlens 12 has the smallest dimension and (ii) the term "long axis" to refer to the direction orthogonal to the short axis.
The short axis of the cross section 13 of the excitation light 8 is, in order to generate an excitation spot 9 having a more uniform light distribution, oriented such that the excitation light 8 overlaps with as many microlenses 12 on each microlens array 3 as possible.
The microlenses 12 are, in other words, arranged such that the long-axis direction of each microlens 12 is parallel to the long-axis direction of the cross section 13 of the excitation light 8. In the examples illustrated in (a) and (c) of Fig. 10, the cross section 13 of the excitation light 8 has a long axis along the X axis, the microlenses 12 each have a long axis along the X axis as well, and the cross section 13 of the excitation light 8 has a short-axis dimension 20 along the Y axis (that is, the short-axis direction of a microlens 12).
In the examples illustrated in (b) and (d) of Fig. 10, the cross section 13 of the excitation light 8 has a long axis along the Y axis, the microlenses 12 each have a long axis along the Y axis as well, and the cross section 13 has a short-axis dimension 20 along the X axis (that is, the short-axis direction).
Recap
A lighting device 2, 2A, 2B, 2C in accordance with a first aspect of the present invention includes: a light source (excitation light source 1) configured to emit excitation light 8; and a wavelength conversion element 5 tilted, with respect to an optical axis 6 of the excitation light 8, around a first tilt axis (X axis) perpendicular to the optical axis 6, a cross-sectional size of the excitation light 8 traveling toward the wavelength conversion element 5 being defined on a basis of a tilting angle θ1 of the wavelength conversion element 5 with respect to the optical axis 6.
With the above configuration, the excitation light traveling toward the wavelength conversion element has a cross-sectional size defined on the basis of the tilting angle θ1 of the wavelength conversion element 5 with respect to the optical axis. This allows the shape of the excitation spot of the excitation light projected on the wavelength conversion element to be corrected on the basis of the tilting angle θ1 of the wavelength conversion element. The above configuration thereby causes the wavelength conversion element to emit light in a desired pattern.
A lighting device 2, 2A, 2B, 2C in accordance with a second aspect of the present invention is configured as in the first aspect and is preferably configured such that the excitation light 8 has a cross section in a rectangular shape; and the cross-sectional size has a width a1 and a length b1 that satisfy Formula 1 below:
a1adj/b1adj = (-1/cosθ1)a1/b1 ... Formula 1
where θ1 is the tilting angle.
The above configuration allows the shape of the excitation spot of the excitation light projected on the wavelength conversion element to be corrected on the basis of the tilting angle θ1 of the wavelength conversion element.
A lighting device 2, 2A, 2B, 2C in accordance with a third aspect of the present invention is configured as in the first aspect and preferably further includes: a cross-sectional size correcting member configured to correct the cross-sectional size on a basis of the tilting angle θ1.
The above configuration allows the cross-sectional size of excitation light to be corrected with use of the cross-sectional size correcting member.
A lighting device 2A, 2B in accordance with a fourth aspect of the present invention is configured as in the third aspect and is preferably configured such that the cross-sectional size correcting member includes at least one microlens 12 having a dimension based on the tilting angle θ1; and the excitation light 8 travels through the at least one microlens 12 toward the wavelength conversion element 5.
The above configuration causes excitation light to pass through a microlens having a dimension based on the tilting angle of the wavelength conversion element for correction of the cross-sectional size of the excitation light.
A lighting device 2A, 2B in accordance with a fifth aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the at least one microlens 12 includes a plurality of microlenses 12; and the cross-sectional size correcting member includes (i) a microlens array 3 including the plurality of microlenses 12 and (ii) a condensing lens 4 configured to concentrate, on the wavelength conversion element 5, the excitation light 8 having passed through the plurality of microlenses 12.
The above configuration causes excitation light having passed through a microlens array including a plurality of microlenses to be concentrated on the wavelength conversion element.
A lighting device 2A, 2B in accordance with a sixth aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the at least one microlens 12 has a cross section in a rectangular shape; and the at least one microlens 12 has a cross-sectional size having a width a1 and a length b1 that satisfy Formula 1 below:
a1adj/b1adj = (-1/cosθ1)a1/b1 ... Formula 1
where θ1 is the tilting angle.
With the width a1 and the length b1 satisfying a1adj/b1adj=(-1/cosθ1)a1/b1 as above, the cross-sectional size of excitation light is corrected.
A lighting device 2B in accordance with a seventh aspect of the present invention is configured as in the fifth aspect and is preferably configured such that the microlens array 3 is tilted around a second tilt axis (rotation axis 15) perpendicular to the optical axis 6 and the first tilt axis (X axis) so as to reduce interference between (i) a first portion of the excitation light 8 which first portion has passed through a first one of the plurality of microlenses 12 and (ii) a second portion of the excitation light 8 which second portion has passed through a second one of the plurality of microlenses 12.
With the above configuration, the microlens array being tilted around the second tilt axis reduces interference between different portions of excitation light 8 on the wavelength conversion element.
A lighting device 2, 2A, 2B, 2C in accordance with an eighth aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the at least one microlens 12 includes a plurality of microlenses 12; and the plurality of microlenses 12 are arranged so that the long axis of the microlens 12 is parallel to a long axis of a cross section 13 of the excitation light 8.
The above configuration allows a cross section of excitation light to overlap with more microlenses along the short axis.
A lighting device 2B in accordance with a ninth aspect of the present invention is configured as in the seventh aspect and is preferably configured such that the plurality of microlenses 12 each have a shape of a rectangle having a first dimension along the first tilt axis (X axis) and a second dimension along the second tilt axis (Y axis), the second dimension being larger than the first dimension; and a ratio between the first dimension and the second dimension is based on the tilting angle θ1.
The above configuration can correct the stretching of an excitation spot on the wavelength conversion element.
A lighting device 2, 2A, 2B, 2C in accordance with a tenth aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the plurality of microlenses 12 are arranged in a regular pattern.
The above configuration allows the microlens array to have a simplified arrangement.
A lighting device 2, 2A, 2B, 2C in accordance with an eleventh aspect of the present invention is configured as in the fourth aspect and is preferably configured such that the plurality of microlenses 12 are arranged in an irregular pattern.
The above configuration reduces interference between different portions of excitation light having passed through the microlenses and concentrated on the wavelength conversion element.
A lighting device 2, 2A, 2B, 2C in accordance with an twelfth aspect of the present invention is configured as in the first aspect and is preferably configured such that the light source (excitation light source 1) is a laser light source configured to emit laser light.
A lighting device 2B in accordance with a thirteenth aspect of the present invention includes: a light source configured to emit excitation light; a microlens array including a plurality of microlenses through which the excitation light passes; and a wavelength conversion element on which the excitation light having passed through the microlens array is incident, the microlens array being tilted around a tilt axis perpendicular to an optical axis of the excitation light.
With the above configuration, the microlens array being tilted around the second tilt axis reduces interference between different portions of excitation light 8 on the wavelength conversion element.
A lighting device in accordance with a fourteenth aspect of the present invention includes: a light source configured to emit excitation light; a microlens array including a plurality of microlenses through which the excitation light passes; and a wavelength conversion element on which the excitation light having passed through the microlens array is incident, the plurality of microlenses being arranged so that the long axis of the microlens is parallel to a long axis of a cross section of the excitation light.
The above configuration allows a cross section of excitation light to overlap with more microlenses along the short axis.
The present invention is not limited to the embodiments, but can be altered by a skilled person in the art within the scope of the claims. The present invention also encompasses, in its technical scope, any embodiment derived by combining technical means disclosed in differing embodiments. Further, it is possible to form a new technical feature by combining the technical means disclosed in the respective embodiments.
1 Excitation light source (light source, laser light source)
2 Lighting device
3 Microlens array
4 Condensing lens
5 Wavelength conversion element
6 Optical axis
8 Excitation light
9 Excitation spot
10 Light
11 Surface normal
12 Microlens
13 Cross section
15 Rotation axis
16 Surface normal
17 Cross section
18 Cross section
20 Short-axis dimension

Claims (15)

  1. A lighting device, comprising:
    a light source configured to emit excitation light; and
    a wavelength conversion element tilted, with respect to an optical axis of the excitation light, around a first tilt axis perpendicular to the optical axis,
    a cross-sectional size of the excitation light traveling toward the wavelength conversion element being defined on a basis of a tilting angle of the wavelength conversion element with respect to the optical axis.
  2. The lighting device according to claim 1, wherein
    the excitation light has a cross section in a rectangular shape; and
    the cross-sectional size has a width a1 and a length b1 that satisfy Formula 1 below:
    a1adj/b1adj = (-1/cosθ1)a1/b1 ... Formula 1
    where θ1 is the tilting angle.
  3. The lighting device according to claim 1, further comprising:
    a cross-sectional size correcting member configured to correct the cross-sectional size on a basis of the tilting angle.
  4. The lighting device according to claim 3, wherein
    the cross-sectional size correcting member includes at least one microlens having a dimension based on the tilting angle; and
    the excitation light travels through the at least one microlens toward the wavelength conversion element.
  5. The lighting device according to claim 4, wherein
    the at least one microlens includes a plurality of microlenses; and
    the cross-sectional size correcting member includes (i) a microlens array including the plurality of microlenses and (ii) a condensing lens configured to concentrate, on the wavelength conversion element, the excitation light having passed through the plurality of microlenses.
  6. The lighting device according to claim 4, wherein
    the at least one microlens has a cross section in a rectangular shape; and
    the at least one microlens has a cross-sectional size having a width a1 and a length b1 that satisfy Formula 1 below:
    a1adj/b1adj = (-1/cosθ1)a1/b1 ... Formula 1
    where θ1 is the tilting angle.
  7. The lighting device according to claim 5, wherein
    the microlens array is tilted around a second tilt axis perpendicular to the optical axis and the first tilt axis so as to reduce interference between (i) a first portion of the excitation light which first portion has passed through a first one of the plurality of microlenses and (ii) a second portion of the excitation light which second portion has passed through a second one of the plurality of microlenses.
  8. The lighting device according to claim 4, wherein
    the at least one microlens includes a plurality of microlenses; and
    the plurality of microlenses are arranged so that the long axis of the microlens is parallel to a long axis of a cross section of the excitation light.
  9. The lighting device according to claim 7, wherein
    the plurality of microlenses each have a shape of a rectangle having a first dimension along the first tilt axis and a second dimension along the second tilt axis, the second dimension being larger than the first dimension; and
    a ratio between the first dimension and the second dimension is based on the tilting angle.
  10. The lighting device according to claim 4, wherein
    the plurality of microlenses are arranged in a regular pattern.
  11. The lighting device according to claim 4, wherein
    the plurality of microlenses are arranged in an irregular pattern.
  12. The lighting device according to claim 1, wherein
    the light source is a laser light source configured to emit laser light.
  13. A lighting device, comprising:
    a light source configured to emit excitation light;
    a microlens array including a plurality of microlenses through which the excitation light passes; and
    a wavelength conversion element on which the excitation light having passed through the microlens array is incident,
    the microlens array being tilted around a tilt axis perpendicular to an optical axis of the excitation light.
  14. A lighting device, comprising:
    a light source configured to emit excitation light;
    a microlens array including a plurality of microlenses through which the excitation light passes; and
    a wavelength conversion element on which the excitation light having passed through the microlens array is incident,
    the plurality of microlenses being arranged so that the long axis of the microlens is parallel to a long axis of a cross section of the excitation light.
  15. The lighting device according to claim 13 or 14, wherein
    the light source is a laser light source configured to emit laser light.
PCT/JP2018/014321 2018-04-03 2018-04-03 Lighting device WO2019193658A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/JP2018/014321 WO2019193658A1 (en) 2018-04-03 2018-04-03 Lighting device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2018/014321 WO2019193658A1 (en) 2018-04-03 2018-04-03 Lighting device

Publications (1)

Publication Number Publication Date
WO2019193658A1 true WO2019193658A1 (en) 2019-10-10

Family

ID=68100236

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2018/014321 WO2019193658A1 (en) 2018-04-03 2018-04-03 Lighting device

Country Status (1)

Country Link
WO (1) WO2019193658A1 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060291185A1 (en) * 2005-06-28 2006-12-28 Sato Atsushi Planar light source device and display using the same
US20140369064A1 (en) * 2013-06-18 2014-12-18 Sharp Kabushiki Kaisha Light-emitting device
US20160138766A1 (en) * 2014-11-18 2016-05-19 Stanley Electric Co., Ltd. Semiconductor light source apparatus
JP2016092268A (en) * 2014-11-06 2016-05-23 三菱電機株式会社 Light source device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060291185A1 (en) * 2005-06-28 2006-12-28 Sato Atsushi Planar light source device and display using the same
US20140369064A1 (en) * 2013-06-18 2014-12-18 Sharp Kabushiki Kaisha Light-emitting device
JP2016092268A (en) * 2014-11-06 2016-05-23 三菱電機株式会社 Light source device
US20160138766A1 (en) * 2014-11-18 2016-05-19 Stanley Electric Co., Ltd. Semiconductor light source apparatus

Similar Documents

Publication Publication Date Title
JP5966843B2 (en) Light source device and image display device
EP2940524B1 (en) Light-emitting device and related projection system
EP3051344B1 (en) Light source device and projector having the light source device
JP5805719B2 (en) Optical system
JP2016212962A (en) Luminaire
CN113168082A (en) Light source optical system, light source device and image projection device
DE102014221668B4 (en) lighting device
US10634979B2 (en) Lighting apparatus changing aspect ratio of screen and projection type image display apparatus provided with the lighting apparatus
US10866495B2 (en) Fly-eye lens and illumination optical device
WO2019193658A1 (en) Lighting device
JP6206551B2 (en) Light source device and image display device
JP6187612B2 (en) Light source device and projector provided with the light source device
CN217846875U (en) Projection light source and projection apparatus
US20230335971A1 (en) Light source device
JP2017053876A (en) Projection type image display device
CN109642997B (en) Light emitting device
US10677407B2 (en) Irradiation unit with pump radiation source and conversion element
WO2017043185A1 (en) Light source device
US11940719B2 (en) Light source device, projector and light intensity distribution uniformization method
CN114072729A (en) Light source device, projector, and light intensity distribution uniformizing method
US20230168571A1 (en) Light source apparatus and projector
JP7287668B2 (en) lighting equipment
US11300721B2 (en) Lighting apparatus having an oblong optic corresponding to multiple light sources
TWI660209B (en) Non-coaxial light mixing device
CN112856272A (en) Dodging element, light source system and lighting equipment

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 18913388

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 18913388

Country of ref document: EP

Kind code of ref document: A1