CN111022942B

CN111022942B - Laser lighting device

Info

Publication number: CN111022942B
Application number: CN201910724483.2A
Authority: CN
Inventors: 徐梦梦; 张贤鹏; 李屹
Original assignee: YLX Inc
Current assignee: YLX Inc
Priority date: 2018-10-09
Filing date: 2019-08-07
Publication date: 2023-07-21
Anticipated expiration: 2039-08-07
Also published as: CN111022942A; WO2020073732A1

Abstract

The present invention provides a laser lighting device comprising: a laser light source for emitting excitation light; the wavelength conversion device comprises a solid light guide, wherein the solid light guide comprises a first end face and a second end face which are oppositely arranged, and a first surface and a second surface which are oppositely arranged; the included angle between the first surface and the second end face is an obtuse angle. Through the angle design, the incidence angle of the excitation light diffusely reflected by the second end face on the first surface is increased, the total reflection area is enlarged, the excitation light directly emitted from the position, close to the second end face, of the first surface is greatly reduced, and the problem of uneven edge illuminance/color of the emitted light is reduced or eliminated.

Description

Laser lighting device

Technical Field

The invention relates to the technical field of illumination, in particular to a laser illumination device.

Background

The LED light source has the advantages of energy conservation, environmental protection, long service life, small volume, light weight, firm structure, low working voltage and the like, is honored as a fourth-generation light source behind an incandescent lamp, a fluorescent lamp and a high-strength gas lamp, but the existing LED has the problems of lower brightness, rapid efficiency and the like.

The laser fluorescent light source, namely the laser diode is used as an excitation light source to excite the fluorescent material to be used as a light source, has the advantages of high electro-optic conversion efficiency, high brightness, no efficiency dip phenomenon, small volume and the like, and receives more and more attention. The current commonly used laser fluorescent light source scheme adopts blue laser as an excitation light source to excite a wavelength conversion material to obtain emergent light with specific wavelength. Because the laser spot area is small, the excitation light power density is too high, and the local overheating of the fluorescent conversion material is easy to cause, so that the problems of lower luminous efficiency and the like are caused. In order to solve the problem, the conventional solution is to rotate or vibrate the wavelength conversion material, so that the excitation light power density is reduced and the heat is dispersed, but the technical solution is to add a driving component, so that the problems of reliability and the like exist.

In order to solve the problem that the heat of the laser fluorescent light source is too concentrated, the inventor sets the wavelength conversion material in the cavity, and irradiates the wavelength conversion material by uniformly diffusing the excitation light into a light spot with a larger area, thereby realizing the emission of high-brightness illumination light. However, in practical experiments, it was found that the luminance and color of the outgoing light near the edge position and the outgoing light near the center position of the outgoing surface have large differences, resulting in uneven distribution of the entire color and illuminance of the outgoing light.

Disclosure of Invention

Aiming at the defect of nonuniform color and illuminance distribution of the emergent light of the laser fluorescent light source in the prior art, the invention provides a laser lighting device with uniform color and uniform illuminance of the emergent light, which comprises: the laser light source is used for emitting excitation light; the wavelength conversion device comprises a wavelength conversion material, a solid light guide, a first surface and a second surface, wherein the solid light guide comprises a first end face and a second end face which are oppositely arranged, the first end face and the second end face are connected through the first surface, the first end face is a light incident face, the first surface is a light emergent face, the second end face is provided with a diffuse reflection structure, the excitation light enters the inside of the wavelength conversion device through the first end face, and the excitation light exits from the inside of the wavelength conversion device through the first surface; an included angle between the first surface and the second end face is an obtuse angle.

Compared with the prior art, the invention has the following beneficial effects: the laser excitation light incident from the first end face of the solid light guide of the wavelength conversion device mostly reaches the second end face provided with the diffuse reflection structure, the laser is reflected and scattered into light emergent towards all directions under the action of the diffuse reflection structure, and the angle between the first surface serving as the light emergent face and the second end face is set to be an obtuse angle, so that the incident angle of the excitation light from the second end face on the first surface is increased relative to the whole of the original scheme (namely, the scheme that the second end face is perpendicular to the first surface), the total reflection occurrence area is enlarged, the excitation light emergent directly from the position of the first surface close to the second end face is greatly reduced, and the problem of uneven edge illuminance/color of the emergent light is reduced or eliminated.

According to the technical scheme, the obtuse optical design is combined with the diffuse reflection structure, so that the technical problem is solved, and the obtuse optical design and the diffuse reflection structure are indispensable. If the diffuse reflection structure is not adopted, but a specular reflection structure is adopted, then the excitation light is directly reflected to the second surface, no excitation light directly reaches the first surface from the second end face, and the excitation light with the angular distribution unchanged by the diffuse reflection structure is concentrated in a small area of the second surface, so that optical damage is caused; if the optical design without an obtuse angle increases the light incidence angle from the second end surface to the first surface, more excitation light is directly emitted at the edge of the first surface near the second end surface, resulting in uneven color and illuminance at this location compared to the total emitted light.

In one embodiment, the angle between the first surface and the second end surface is between 104 DEG and 116.6 deg.

In one embodiment, the first surface is a polished surface. The technical scheme is beneficial to the total reflection of the light from the second end face when the light exits from the first surface.

In one embodiment, the wavelength conversion device includes a wavelength conversion layer comprising a wavelength conversion material, the wavelength conversion layer disposed at the second surface of the solid light guide.

In one embodiment, the solid light guide contains a wavelength converting material inside.

In one embodiment, the solid light guide is a fluorescent single crystal.

In one embodiment, the wavelength conversion device further comprises a second reflective structure disposed at the second surface.

In one embodiment, the wavelength conversion device comprises a wavelength conversion layer comprising a wavelength conversion material, the wavelength conversion layer being disposed at a first surface of the solid light guide, the wavelength conversion device further comprising a second reflective structure disposed at the second surface.

In one embodiment, the first end face is parallel to the second end face.

In one embodiment, the wavelength conversion device comprises a scattering structure disposed at the first surface.

In one embodiment, the wavelength conversion device further comprises a second wavelength conversion layer disposed on the first surface, the second wavelength conversion layer having a refractive index that is less than the refractive index of the solid light guide.

In one embodiment, the optical filter further comprises a filter film disposed on the first end surface, and the filter film transmits the excitation light with the incident angle not greater than a preset angle and reflects the excitation light with the laser light and the incident angle greater than the preset angle.

Drawings

Fig. 1 is a schematic structural diagram of a laser lighting device according to a first embodiment of the present invention;

fig. 2 is a schematic structural diagram of a laser lighting device according to a second embodiment of the present invention;

fig. 3 is a schematic structural diagram of a laser lighting device according to a third embodiment of the present invention;

fig. 4 is a schematic structural diagram of a laser lighting device according to a fourth embodiment of the present invention;

fig. 5 is a schematic structural diagram of a laser lighting device according to a fifth embodiment of the present invention;

fig. 6 shows the simulation result of illuminance distribution of the exit surface of the laser lighting device when the included angle between the first surface and the second end surface is different.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and the embodiments.

Fig. 1 is a schematic structural diagram of a laser lighting device according to a first embodiment of the invention. The laser lighting device 10 comprises a laser light source 110 and a wavelength conversion device 120.

Wherein the laser light source 110 is used for emitting excitation light. The wavelength conversion device 120 includes a wavelength conversion material for absorbing excitation light and emitting a lasing light.

Specifically, the wavelength conversion device 120 in the present invention includes a solid light guide 121 and a wavelength conversion layer 122. Wherein the solid light guide 121 comprises a first end face 121a and a second end face 121b arranged opposite to each other, and a first surface 121c and a second surface 121d arranged opposite to each other, the first end face 121a and the second end face 121b being connected by the first surface 121 c.

The first end face 121a is a light incident face of the solid light guide, and excitation light is incident from the first end face 121a to the solid light guide 121, enters the inside of the wavelength conversion device 120, and most of the light passes through the solid light guide 121 and reaches the second end face 121b. The second end surface 121b is provided with a diffuse reflection structure 123, and after the excitation light is diffusely reflected by the diffuse reflection structure 123, part of the light directly exits toward the first surface 121c, and the other part of the light exits toward the wavelength conversion layer 12 provided on the second surface 121 d. After the light incident on the wavelength conversion layer 122 is absorbed, the wavelength conversion layer 122 emits a laser beam, and the laser beam is emitted through the first surface 121c to form a part of the emitted light. That is, the first surface 121c is a light exit surface of the solid light guide 121, and the laser light exits from the inside of the wavelength conversion device 120 through the first surface 121 c.

In the present invention, the angle between the first surface 121c and the second end surface 121b is an obtuse angle, and the incident angle increases when the light diffusely reflected by the diffuse reflection structure 123 is directly incident on the first surface 121c, thereby increasing the area where total reflection occurs at the first surface 121c and reducing the light transmittance of the edge area of the first surface 121c near the second end surface 121b, thereby avoiding the unevenness of the illuminance and color of the edge.

In this embodiment, the first surface 121c of the solid light guide 121 is a polished surface with a surface roughness of less than 400nm, preferably less than 100nm, to avoid total reflection failure due to surface irregularities.

In the first embodiment, the wavelength conversion layer 122 contains a wavelength conversion material, while the solid light guide 121 does not contain a wavelength conversion material, and only performs light conduction, preferably sapphire in the present invention, and has both light transmittance and thermal conductivity. For the wavelength conversion device 120, the wavelength conversion layer 122 is an actual passive light source, and the light emitted by the wavelength conversion layer is transmitted through the solid light guide 121 and exits from the first surface 121 c.

In the present invention, the laser light source may be a semiconductor laser light source, for example, a laser diode, or may be a single laser diode light source or an array of light sources of a plurality of laser diodes. When the laser light source is a combination of a plurality of laser light emitting elements, the laser light source may be a light source of the same wavelength range or a combination of a plurality of light sources of different wavelengths.

In the invention, the wavelength conversion layer can be a structure of a layer of phosphor powder bonded by an organic binder such as silica gel or epoxy resin, a structure of a layer of phosphor powder bonded by glass powder after softening/melting, a structure of a layer of ceramic material and phosphor powder after co-sintering, or a fluorescent single crystal.

In this embodiment, the laser light source is a blue laser light source, the wavelength conversion material of the wavelength conversion layer 122 is yellow phosphor, that is, the wavelength conversion layer 122 is a yellow phosphor layer, and the wavelength conversion layer 122 emits yellow light after absorbing blue excitation light. The yellow light can be combined with the blue light to form white light for emission. It will be appreciated that the present invention is not limited to the spectrum of the light source or the wavelength conversion material, and light sources and wavelength conversion materials with other spectral ranges may be used, or multiple wavelength conversion materials may be disposed in one wavelength conversion layer at the same time. The wavelength conversion device may emit mixed light of excitation light and lasing light in some technical schemes, or may emit lasing light only in other technical schemes, which is not limited herein.

The diffuse reflection structure 123 in the present embodiment is a diffuse reflection layer formed of white scattering particles and an adhesive, and is disposed outside the second end face 121b. In other embodiments, the diffuse reflection structure may be achieved by roughening the surface of the second end surface and then coating a reflective film layer (such as a metal reflective film), and other types of known diffuse reflection layers may be used, which will not be described herein. The diffuse reflection structures of the present invention preferably have a reflectance of more than 90% for visible light.

In order to prevent unabsorbed excitation light from exiting the light incident surface in the opposite direction, the present embodiment additionally provides a filter film 124 at the first end surface 121a, where the filter film 124 transmits excitation light having an incident angle of not more than 5 ° and reflects excitation light that is subjected to laser light and has an incident angle of more than 5 °. Because the collimation of the laser light source is good, the divergence angle of the light beam is small, and the light utilization rate of the wavelength conversion device can be improved under the condition that the transmissivity of the excitation light is not obviously influenced by the type of the filter membrane. It is understood that the preset angle of the filter film is not limited in the present invention, and the preset angle may be other angles than 5 ° and may be designed according to the size of the solid light guide 121.

In a modification of the present embodiment, the filter film 124 may be replaced by a simple wavelength filter, which transmits the excitation light and reflects the laser light.

It will be appreciated that the filter membrane is not an essential feature of the laser lighting device of the present invention and that the membrane may not be provided to save costs.

A heat sink 125 is additionally provided on the side of the wavelength conversion device 120 of the present invention that is close to the second surface 121d of the solid light guide 121. Specifically, a heat sink 125 is disposed on a side of the wavelength conversion layer 122 remote from the solid light guide 121 for thermally conducting and cooling the wavelength conversion layer 122. It is understood that the heat sink 125 is not a necessary structure of the laser lighting device of the present invention.

Further, in order to study the influence of the angle between the first surface 121c and the second end surface 121b on the emitted light of the wavelength conversion device 120, the inventors performed an optical mode experiment. Specifically, taking blue light as a laser light source, taking yellow light as an outgoing and receiving laser light of a wavelength conversion layer, taking a solid sapphire light guide as an example, taking a size of 7×7×8 (8 is a length along the direction of incident light), setting angles between the first surface 121c and the second end surface 121b to be (a) 90 °, (b) 104 °, (c) 110.6 ° and (d) 116.6 °, and measuring illuminance distribution of the light outgoing surface 121c to obtain a result as shown in fig. 6 (the drawing in the specification is a gray pattern, cannot show color properties of light, and is described in text). The simulation results of (a), (b), (c) and (d) are shown in sequence from left to right.

It can be seen that when the first surface 121c is disposed perpendicular to the second end surface 121b, the illuminance distribution on the light exit surface is very uneven, and particularly, blue light is more and the illuminance is large near the second end surface 121b. When the included angle is increased to 104 degrees, the area with excessive blue light is reduced and the illumination is reduced; when the included angle is further increased to 110.6 degrees, the illuminance distribution of the whole light emergent surface is uniform; further increasing the included angle to 116.6 ° further, the blue light component increases and the illuminance increases at the position of the light exit surface far from the second end surface 121b, because the increase of the angle conducts the excitation light to the position of the first surface 121c near the first end surface 121a more, and the angle is changed by the first end surface 121a to be beneficial to exiting from the first surface 121 c.

Therefore, the included angle between the first surface 121c and the second end surface 121b in this embodiment should be set between 104 ° and 116.6 ° to ensure the illuminance and color uniformity of the exit surface. The inventor finds that, in various embodiments, the included angle between the first surface and the second end surface is not too large, and the ideal and acceptable result can be obtained by 104-116.6 degrees through changing the simulation parameters of the solid light guide and performing multiple experiments.

Fig. 2 is a schematic structural diagram of a laser lighting device according to a second embodiment of the invention. The laser illumination device 20 includes a laser light source 210 and a wavelength conversion device 220. The difference from the first embodiment is that the solid light guide 221 of the wavelength conversion device 220 in this embodiment contains a wavelength conversion material inside.

Specifically, the solid light guide 221 in the present embodiment is a fluorescent single crystal, and has both light-transmitting light guide and light conversion functions. When the laser light source is a blue light source, the fluorescent monocrystal can be a Ce-YAG monocrystal, and the light transmission performance is good.

The first end surface 221a, the second end surface 221b, the first surface 221c, and the second surface 221d of the solid light guide 211 in the present embodiment can be described with reference to the first embodiment. The diffuse reflection structure 223, from which the excitation light incident from the first end surface 221a reaches the second end surface 221b, is scattered and reflected, and the first surface 221c is a polished surface, and the excitation light from the diffuse reflection structure 223 is mostly totally reflected at the first surface 221c due to the obtuse structural design.

The wavelength conversion layer in the first embodiment is not included in the present embodiment, and the solid light guide and the wavelength conversion layer in the first embodiment are combined into one.

Further, the second surface 221d of the solid light guide 221 in the present embodiment is a light reflecting surface (preferably a diffuse reflecting surface) to prevent light incident on the second surface 221d from directly exiting the wavelength conversion device.

In a variant of this embodiment, a second reflective structure may be provided on the second surface, which may be a separate reflective structure, such as a diffuse reflective layer with white scattering particles bonded in layers.

Another difference between the present embodiment and the first embodiment is that the filter film 224 disposed on the first end surface 221a is a film coated with a film coated region 224a, which transmits the excitation light and reflects the laser light, and the region outside the film coated region 224a of the filter film 224 is a reflective region, which reflects the excitation light and the laser light.

In a variant of this embodiment, the filter film may be replaced by a reflective sheet with holes, and the excitation light is incident from the holes of the reflective sheet.

The wavelength conversion device 220 in this embodiment also includes a heat sink 225, and the surface of the heat sink 225 that contacts the solid light guide 221 may also be configured as a reflective surface.

The description of the other devices in the second embodiment may refer to the description of the first embodiment, and will not be repeated here.

Fig. 3 is a schematic structural diagram of a laser lighting device according to a third embodiment of the invention. The laser illumination device 30 includes a laser light source 310 and a wavelength conversion device 320. The difference from the embodiment shown in fig. 1 is that the wavelength conversion layer 322 in this embodiment is arranged at the first surface 321c of the solid light guide 321, and that the wavelength conversion device 320 further comprises a second reflective structure 326 arranged at the second surface 321 d.

The wavelength conversion layer 322 in this embodiment is disposed on the light exit surface, and after the excitation light incident on the solid light guide 321 from the first end surface 321a is reflected by the diffuse reflection structure of the second end surface 321b, part of the excitation light reaches the second reflection structure 326 of the second surface 321d, and the second reflection structure 326 is preferably a diffuse reflection layer, and after the excitation light is scattered and reflected by the diffuse reflection layer, the spot area is greatly increased relative to the incident spot area of the first end surface 321a, so as to form uniform excitation light, and then the uniform excitation light exits from the first surface 321c, and exits after the light conversion effect of the wavelength conversion layer 322.

The structure of the solid light guide 321 in the third embodiment is described with reference to the first embodiment, and will not be described here.

Fig. 4 is a schematic structural diagram of a laser lighting device according to a fourth embodiment of the invention. The laser illumination device 40 includes a laser light source 410 and a wavelength conversion device 420.

The difference of the present embodiment from the first embodiment is that the wavelength conversion device 420 of the present embodiment further includes a second wavelength conversion layer 427 disposed on the first surface 421c of the solid light guide 421, wherein the refractive index of the second wavelength conversion layer 427 is smaller than that of the solid light guide.

In this embodiment, the wavelength conversion layer 422 is a yellow phosphor layer, and the second wavelength conversion layer 427 is a red phosphor layer, so that the proportion of red light in the outgoing light can be improved. It is understood that in other embodiments of the present invention, other combinations of the wavelength conversion layer and the second wavelength conversion layer may be used to achieve the effect of adjusting the color temperature and color rendering index of the emitted light.

For other descriptions of the first end surface 421a, the second end surface 421b, the first surface 421c, the second surface 421d, the wavelength conversion layer 422, the heat sink 425, the filter membrane 424, the diffuse reflection structure 423, etc., please refer to the corresponding devices in the first, second and third embodiments, and the descriptions thereof are omitted herein.

In a variant of embodiment four, the combination of the solid light guide 421 and the wavelength converting layer 422 of embodiment four is replaced by a fluorescent crystal as in embodiment two.

In a variant of the fourth embodiment of the invention, the second wavelength-converting layer arranged on the first surface may also be replaced by a scattering element (such as a film containing scattering particles or a film with prisms or other rugged microstructures, the scattering particles or microstructures in the whole scattering element may be of one or more types, the spatial distribution of the scattering particles or microstructures may be uniform or non-uniform), which is preferably in optical contact with the first surface of the solid light guide. The technical scheme improves the uniformity of emergent light and the light extraction efficiency.

Fig. 5 is a schematic structural diagram of a laser lighting device according to a fifth embodiment of the invention. The laser illumination device 50 includes a laser light source 510 and a wavelength conversion device 520.

The difference from the above embodiments is that the first end face 521a and the second end face 521b of the solid light guide 521 of the present embodiment are parallel.

For other descriptions of the first end face 521a, the second end face 521b, the first surface 521c, the second surface 521d, the wavelength conversion layer 522, the heat sink 525, the diffuse reflection structure 523, etc., reference is made to the descriptions of the corresponding devices in the above embodiments, and the descriptions are not repeated here.

In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.

The foregoing description is only of embodiments of the present invention, and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes using the descriptions and the drawings of the present invention or directly or indirectly applied to other related technical fields are included in the scope of the present invention.

Claims

1. A laser lighting device, comprising:

the laser light source is used for emitting excitation light;

the wavelength conversion device comprises a wavelength conversion material, a solid light guide, a first surface and a second surface, wherein the solid light guide comprises a first end face and a second end face which are oppositely arranged, the first end face and the second end face are connected through the first surface, the first end face is a light incident face, the first surface is a light emergent face, the second end face is provided with a diffuse reflection structure, the excitation light enters the inside of the wavelength conversion device through the first end face, and the excitation light exits from the inside of the wavelength conversion device through the first surface;

an included angle between the first surface and the second end face is an obtuse angle.

2. The laser light device of claim 1, wherein an included angle between the first surface and the second end surface is between 104 ° and 116.6 °.

3. The laser light device of claim 1, wherein the first surface is a polished surface.

4. A laser lighting device as claimed in any one of claims 1 to 3, wherein the wavelength conversion device comprises a wavelength conversion layer comprising a wavelength conversion material, the wavelength conversion layer being disposed at the second surface of the solid light guide.

5. A laser light illumination device as claimed in any one of claims 1 to 3, wherein the solid light guide internally comprises a wavelength converting material.

6. The laser light illumination device of claim 5, wherein the solid light guide is a fluorescent single crystal.

7. The laser light illumination device of claim 5, wherein the wavelength conversion device further comprises a second reflective structure disposed on the second surface.

8. A laser light illumination device as claimed in any one of claims 1 to 3, wherein the wavelength conversion device comprises a wavelength conversion layer comprising a wavelength conversion material, the wavelength conversion layer being disposed at a first surface of the solid light guide, the wavelength conversion device further comprising a second reflective structure disposed at the second surface.

9. A laser light source as claimed in any one of claims 1 to 3, wherein the first end face is parallel to the second end face.

10. A laser light source as claimed in any one of claims 1 to 3, wherein the wavelength conversion device comprises a scattering structure disposed on the first surface.

11. A laser light illumination device as claimed in any one of claims 1 to 3, wherein the wavelength conversion device further comprises a second wavelength conversion layer disposed on the first surface, the second wavelength conversion layer having a refractive index less than the refractive index of the solid light guide.

12. A laser lighting device as set forth in any one of claims 1 to 3, further comprising a filter film disposed on said first end face, said filter film transmitting excitation light having an incident angle not greater than a predetermined angle and reflecting excitation light having a laser light and an incident angle greater than the predetermined angle.