Patent Publication Number: US-10760743-B2

Title: Lamp

Description:
TECHNICAL FIELD 
     The invention relates to the field of lighting, in particular to the field of decorative lighting. 
     BACKGROUND 
     The lamps belong to the traditional field, and there are many kinds of lamps. After the emergence of LEDs, kinds of LED-based lamps are also emerging. However, with the improvement of people&#39;s living standards, there is an increasing demand for lighting, especially decorative lighting, and this demand has not yet been fully met. 
     SUMMARY 
     The invention provides a lamp, which includes a light source. The light source includes a laser diode and a wavelength conversion plate. The laser light emitted by the laser diode is focused on the wavelength conversion plate and excites the wavelength conversion plate to emit converted light. The wavelength conversion plate includes a transparent thermally conductive substrate and a wavelength conversion coating attached to the surface of the substrate. The laser emitted by the laser diode passes through the transparent thermally conductive substrate and is focused on the wavelength conversion coating. The surface of the transparent thermally conductive substrate is coated with an optical film that transmits laser light and at least partially reflects converted light. The position of the light spot is called the excitation area, and the area outside the excitation area is called the non-excitation area. It also includes a diaphragm placed after and close to the wavelength conversion plate along the optical path. The diaphragm includes light transmitting region and light blocking region, which are closely adjacent to each other. The light transmitting region is aligned to the excitation area of the wavelength conversion plate, and at least one point on the edge of the light transmitting region has a distance from the center of the excitation area smaller than the characteristic distance, and the characteristic distance L equals to L=2dtgθ, where θ=arcsin(1/n), d and n are the thickness and refractive index of the transparent thermally conductive substrate respectively. The lamp also includes a light collimation element for receiving and collimating light emitted from the diaphragm. 
     The laser light emitting diode and the wavelength conversion plate could be used to realize a small light spot, so that a highly collimated light beam could be achieved after being collimated by a light collimation element. The diaphragm could at least partially block the diffused light ring around the light spot, in order to obtain a better decorative effect of the lamp. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       In order to more clearly illustrate technical solutions in embodiments of the present disclosure or in the related art, the accompanying drawings used in the embodiments and in the related art are briefly introduced as follows. Obviously, the drawings described as follows are merely part of the embodiments of the present disclosure, and other drawings could also be acquired by those skilled in the art without paying creative efforts. 
         FIG. 1  is a schematic structural diagram of a lamp according to a first embodiment of the present invention; 
         FIG. 2  is a schematic structural diagram of a lamp according to another embodiment of the present invention; 
         FIG. 3  is a schematic structural diagram of a lamp according to another embodiment of the present invention; 
         FIG. 4  is a schematic structural diagram of a lamp according to another embodiment of the present invention; 
         FIG. 5 a    shows a schematic structural diagram of a light source in a lamp according to another embodiment of the present invention; 
         FIG. 5 b    shows a schematic structural diagram of a light source in a lamp according to another embodiment of the present invention; 
         FIG. 6 a    shows an optical path for the diffusion of fluorescence in a transparent thermally conductive substrate in the embodiment shown in  FIG. 5   a;    
         FIG. 6 b    shows a front view of the fluorescent coating in the embodiment shown in  FIG. 5   a;    
         FIG. 7 a    shows a schematic structural diagram of a light source in a lamp according to another embodiment of the present invention; 
         FIG. 7 b    is a schematic structural diagram of a light source in a lamp according to another embodiment of the present invention; 
         FIG. 7 c    shows a front view of a fluorescent coating and a diaphragm in a lamp according to another embodiment of the present invention; 
         FIG. 8 a    shows a schematic structural diagram of a light source in a lamp according to another embodiment of the invention; 
         FIG. 8 b    shows a front view of a fluorescent coating in a lamp according to another embodiment of the present invention; 
         FIG. 9 a    is a schematic structural diagram of a lamp according to a first embodiment of the present invention; 
         FIG. 9 b    is a schematic structural diagram of a light source in the lamp of the embodiment of  FIG. 9   a;    
         FIG. 10 a    is a schematic structural diagram of another light source in the lamp of the embodiment of  FIG. 9   a;    
         FIG. 10 b    shows the evolution of the light beam on both sides of the fluorescent sheet in the embodiment of  FIG. 10   a;    
         FIG. 11  is a schematic structural diagram of a lamp according to another embodiment of the present invention; 
         FIG. 12  is a schematic structural diagram of a lamp according to another embodiment of the present invention; 
         FIG. 13  is a schematic structural diagram of a lamp according to another embodiment of the present invention; 
         FIG. 14  is a schematic structural diagram of a lamp according to another embodiment of the present invention; 
         FIG. 15  is a schematic structural diagram of a lamp according to another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention provides a lamp, the structure diagram of which is shown in  FIG. 1 . The lamp includes a light source  119  and a light collimation element  113 , wherein the light source  119  includes a laser diode  111  and a wavelength conversion plate  112 . The laser light  121  emitted by the laser diode  111  focuses on the wavelength conversion plate  112  and excites the wavelength conversion plate to emit converted light  122  and  123 . The light collimation element  113  is used for receiving light from the light source  119  and collimating it to form a collimated light  124  for emission. The full angle of the effective aperture of the light collimation element relative to the light emitting point is A, and A is not greater than 60 degrees. That is to say, the light collimation element  113  only collects the light (such as the light  122 ) emitted by the light source  119  within an angle of 30 degrees to the optical axis, but does not receive the light (such as the light  123 ) with emitting angle greater than 30 degrees to the optical axis. This part of light with emitting angle greater than 30 degrees is wasted. For a Lambertian light source (uniform light source), the energy of the light emitted within an angle of 30 degrees to the optical axis accounts for only 25% of the total energy. For the lamp of the present invention, the light collection efficiency of the light collimation element  113  is very low. In the art, low light collection efficiency means low output light energy and poor lighting effect, so such low collection efficiency is not a conventional design in the art. However, the present invention is designed in this way because the inventors found through experiments that the smaller the full angle of the effective diameter of the light collection element to the light emitting point, the more collimated the light beam passing through the light collection element, and at the same time the central light intensity is not reduced. In other words, the light lost by reducing the full angle of the light collimation element to the light emitting point, is the light with a larger emitting angle after passing through the light collimation element, so that the light intensity at the center has not decreased. This is obviously not the same conclusion with traditional optical theory, because the optical theory says that as long as the light source is placed at the focal point of the lens, the light could be collimated regardless of the angle, so reducing the collection angle will also reduce the central light intensity. 
     The inventors did not have a good theoretical explanation for the above experiments, but in practice it was found that collecting only the central light energy of the light source does not reduce the center light intensity, and the divergence angle of the collimated beam could be made smaller. 
     Classical optical theory tells us that the collimation degree of collimated light in a light collimation system is inversely proportional to the size of the light spot, that means the larger the light spot, the lower the degree of collimation. In the present invention, the laser light emitted by the laser diode is focused on the wavelength conversion plate. Since the laser light is coherent light emitted from a small light emitting chip, a very small light emitting spot could be formed on the wavelength conversion plate, so that a highly collimated light beam could be formed according to optical theory. At the same time, using the above mentioned experimental conclusion discovered by the inventors, controlling the full angle of the light collimation element to the light emitting point to a angle less than 60 degrees, could further improve the collimation degree of the collimated beam. In this way, a highly collimated outgoing beam could be obtained, which will not significantly spread at a distance a few meters or even tens of meters away. Such beams have many uses in decorative lighting. 
     Preferably, the full angle of the light collimation element to the light emitting point of the light source is less than 30 degrees, so that the collimation degree of the light beam could be further improved. 
     The embodiment shown in  FIG. 2  takes an example of an application in lighting device. In the lamp of this embodiment, an curved-surface mirror array  214  located after the light collimation element along the optical path is also included, which including a plurality of plane mirrors  214   a - 214   e , and the plurality of plane mirrors are arranged in an array along a curved surface. The collimated light beam  224  emitted from the light collimation element is incident on the curved mirror array  214 , each of the plane mirrors  214   a ,  214   b ,  214   c ,  214   d , and  214   e  receives a small portion of the light and reflects it to form multiple sub-beams, each sub-beam  225  is also a collimated light beam. Because multiple plane mirrors are arranged along an curved surface, the normal direction of each mirror slightly changes, so that the directions of multiple sub-beams reflected by them are also different. Because the collimated beam  224  is highly collimated, and the plane mirrors do not change the collimation of the light, so each sub-beam is also highly collimated. In this way, a plurality of highly collimated sub-beams will form a plurality of small light spots at a distance (for example, a few meters away from the lamp), thereby achieving the decorative lighting effect of “stars in the sky”. In this embodiment, the key to the decorative effect of the “stars in the sky” is that each light spot is small and bright enough, which requires the collimation degree of the beam  224  to be sufficiently high and the central light intensity to be sufficiently large. It is precisely for the above mentioned reasons that the collimated beam generated by the embodiment shown in  FIG. 1  of the present invention has the characteristics of high collimation and strong central intensity. 
     The previous embodiment has a problem that the light path from the light source to the light collimation element is very long, which is determined by the small full angle of the light collimation element to the light emitting point of the light source. The length of this light path is approximately equal to the effective aperture of the collimating element divided by the full angle (radian). The smaller the full angle, the longer this light path. This makes the entire system long and inconvenient in applications. This problem is solved in the embodiment shown in  FIG. 3 . Different from the embodiment shown in  FIG. 1 , this embodiment further includes two mirrors  316   a  and  316   b . The light  322  emitted from the light source is reflected respectively by the reflection mirrors  316   a  and  316   b , and then incident on the light collimation element  313 . In this way, the optical path could be effectively prevented from being too long in one direction. But after the reflections of the mirrors, the overall optical path appears approximately equal length in both directions. In this embodiment, two mirrors are used. In fact, one or three or more mirrors could be used to reduce the optical path length. 
     Another difference between this embodiment and the embodiment shown in  FIG. 1  is that it further includes diaphragms  315   a  and  315   b  located between the light source and the light collimation element  313  along the optical path. The diaphragm includes a light transmitting aperture  315   c . Part of the light energy passes through the aperture  315   c  of the diaphragm, and this part of the light completely covers the effective aperture of the light collimation element. The remaining light  323  emitted by the light source is blocked by the diaphragm. This could reduce the ineffective light  323  into stray light and affect the decorative effect of the output light. 
     In the above embodiments, the light collimation elements are all a lens, and a part of the light emitted by the light source is incident on the lens and collimated after being refracted. The lens may be spherical lens or aspheric lens, preferably an aspheric lens in order to achieve better collimation. Since the refractive index of a transparent material varies with the wavelength of light, the light emitted by the light source will undergo dispersion after being refracted by the lens. In another embodiment, the light collimation element could also reflect the incident light to form collimated light in a reflective manner, as shown in  FIG. 4 . 
     In the embodiment shown in  FIG. 4 , the light collimation element  413  is an curved reflector, and the light  422  emitted from the light source is incident and reflected by the light collimating light  424  to exit. Specifically, the cross section of the curved reflector on the plane of the paper surface in  FIG. 4  is a section of a parabola, and the parabola is focused on the light emitting point of the light source. The cross section of the curved reflector on the plane which is perpendicular to the plane of the paper in  FIG. 4  and parallel to the axis of incident light is a section of a circle, and the circle is centered on the light emitting point of the light source. It could also be understood that a segment of the parabola with the light emitting point as the focal point is rotated for some degree with the axis RX which passes through the light emitting point and is perpendicular to the light emitting light axis as the symmetry axis to obtain the curved reflector. 
     Unlike using a lens, the curved reflector does not have chromatic aberrations due to the refraction of light, so the color uniformity of the outgoing light is better. It could be understood that, in addition to the lens and the curved reflector, other light collimation elements could also be used in the present invention. 
     In the foregoing embodiments, the laser is focused on the wavelength conversion plate and excites the wavelength conversion plate to generate converted light, and the converted light is emitted isotropic in all directions, so about half of the light energy is emitted toward the light source, causing light loss. The embodiments from  FIG. 5  to  FIG. 10  are further optimized and explained with respect to the structure of the light source and the wavelength conversion plate. 
     In the embodiment shown in  FIG. 5 a   , the wavelength conversion plate includes a transparent thermally conductive substrate  512   a  and a wavelength conversion coating  512   b  attached to the surface of the substrate  512   a . The laser light  521  emitted by the laser diode  511  passes through the transparent thermally conductive substrate  512   a  and focuses on the wavelength conversion coating  512   b . The transparent thermally conductive substrate could be made of a transparent thermally conductive material such as sapphire, diamond, or silicon carbide, which could help the wavelength conversion coating dissipate heat. The surface of the transparent thermally conductive substrate is coated with an optical film that transmits laser light and at least partially reflects converted light. In this way, at least part of the converted light excited by the laser diode could be reflected by the optical film and emitted toward the light collimation element, thereby effectively improving the light emission of the light source. Preferably, the optical film is coated on the surface of the transparent thermally conductive substrate  512   a  facing the wavelength conversion coating, which means the optical film is located between the transparent thermally conductive substrate and the wavelength conversion coating. In this way, the light emitted by the wavelength conversion coating could be directly reflected by the optical film without passing through the transparent thermally conductive substrate, reducing the lateral spread of the light. 
     In the embodiment shown in  FIG. 5 b   , it is more preferable to further include a filter  517  positioned close to the wavelength conversion plate after the wavelength conversion plate along the optical path, for transmitting converted light having a light emission half-angle less than or equal to A/2 and at least partially reflecting the converted light with half-angle greater than A/2. As mentioned above, since the light collimation element could only receive converted light emitted by the light source at a half-angle of less than or equal to A/2, this part of the effective light will directly pass through the filter  517 , and the remaining invalid light will be reflected back to the wavelength conversion plate. This part of the light will be emitted again after being scattered and reflected by the wavelength conversion plate, and some of it will change direction due to the scattering effect and be emitted within the range of emission half-angle less than or equal to A/2, and the rest of the light will be reflected back to the converted light by the filter  517  again. In other words, the original ineffective light is partially reused as the effective light after being reflected by the filter  517  and scattered by the wavelength conversion plate, thereby increasing the energy of the light source that could be incident on the light collimation element, which also improves the system efficiency. 
     In the embodiment shown in  FIGS. 5 a  and 5 b   , there is a problem that light is lateral spread along in a transparent thermally conductive substrate, as shown in  FIG. 6 a   . The laser light  621  passes through the transparent thermally conductive substrate  612   a  and is focused on the wavelength conversion coating  612   b  and excites it to emit converted light. In  FIG. 6 a   , the converted light  631  and  632  are indicated by solid arrows, and the remaining laser light  633  not absorbed by the wavelength conversion coating is indicated by dotted arrows. Even if the optical film described in the embodiment of  FIG. 5 a    exists, the optical film could not completely block the converted light, so besides the directly out put converted light  631 , a part of the converted light  632  still enters the transparent thermally conductive substrate. This part converted light  632  with a larger incident angle will be totally reflected on the other opposite surface of the transparent thermally conductive substrate  612   a , and return to the surface where the wavelength conversion coating is located, and at least partially exit. In this way, a light energy distribution as shown in  FIG. 6 b    is formed on the surface of the wavelength conversion coating.  FIG. 6 b    is a front view of the wavelength conversion plate when viewed facing the output direction of light emission. The spot where the laser focuses and incident on the wavelength conversion coating corresponds to the central spot  641  where the brightness is largest and most of the light exits directly from. This area is called the excitation area in the present invention, which means the area where the laser directly excites the converted light. The area outside the excitation area is called the non-excitation area, which is the area that is not directly excited by the laser to emit light. In the non-excitation area, the lateral spread converted light  632  entering the transparent thermally conductive substrate shown in  FIG. 6 a    will form a diffused light ring  643  at the periphery on a distance away from the central light spot  641 . There is a dark ring  642  exists between the central light spot  641  and the diffused light ring  643  and there is a dark region  644  exists outside the diffused light ring  643 . It could be seen that the non-excitation area includes at least two regions, a region of dark ring  642  surrounding the excitation area  641  and adjacent to the excitation area, and a peripheral region not adjacent to the excitation area. The position of the boundary of these two areas—that is, the inner circle of the diffused light ring  643 —is easy to be calculated. According to geometric optics, this corresponds to the incident position of the converted light that could be totally reflected on the lower surface of the transparent thermally conductive substrate. Minimum incident angle of total reflected converted light θ determined by θ=arcsin(1/n), Where n is the refractive index of the transparent thermally conductive substrate. For example, for a transparent thermally conductive substrate made of sapphire, n=1.765, it could be calculated that θ=34.5 degree. Referring to  FIG. 6 a   , converted light with an incident angle of θ is reflected once in a transparent thermally conductive substrate with a propagation distance of L, and L=2dtgθ, where d is the thickness of the transparent thermally conductive substrate. For the convenience of description later, define L as the characteristic distance. The distance from the boundary of the dark ring  642  and the diffused light ring  643  to the center of the excitation area is the characteristic distance. The characteristic distance is related to the material and thickness of the transparent thermally conductive substrate. For example, for a transparent thermally conductive substrate made of sapphire with a thickness of 0.3 mm, the characteristic distance is equal to 0.41 mm. 
     It could be understood that the central spot (excitation area)  641  is the main player for lighting or decorative lighting, and the diffused light ring  643  as stray light will have a destructive effect on this lighting or decorative lighting, so the diffused light ring  643  should be reduced. To achieve this, at least two technical means could be used. They are illustrated in the following examples. 
     The lamp of the embodiment shown in  FIG. 7 a    further includes an diaphragm  717  placed after and close to the wavelength conversion plate along the optical path. The diaphragm  717  includes a light transmitting region  717   a  and a light blocking region, which are closely adjacent to each other. The light transmitting region  717   a  is aligned to the point on the wavelength conversion plate on which the laser light focused. In this embodiment, the laser  721  is transmitted through the transparent thermally conductive substrate  712   a  and focused on the wavelength conversion coating  712   b , while the diaphragm  717  is placed next to the wavelength conversion coating  712   b  and its light transmitting region  717   a  is aligned to the point on the wavelength conversion coating on which the laser light focused. At least one point on the edge of the light transmitting region has a distance from the center of the excitation area smaller than the characteristic distance L. In this way, the effective light emitted from the excitation area could at least partially pass through the light transmitting region  717   a  and finally achieve the purpose of decorative lighting. At the same time, the diffused light ring is at least partially outside the light transmitting region so that the stray light is reduced. Preferably, the diffused light ring is all outside the light transmitting region of the diaphragm. At this time, the distance from all points on the edge of the light transmitting region to the center of the excitation area of the wavelength conversion plate is less than the characteristic distance L, so that all the light emitted by the diffused light ring will be blocked, so that the diffused light ring does not affect decorative lighting effects. 
     In the embodiment shown in  FIG. 7 a   , the diaphragm  717  uses an opaque sheet to punch holes to achieve the light transmitting region  717   a . This is a manufacturing method of the diaphragm. The limitation of this method is that it is difficult to make the hole with a very small diameter. More preferably, as shown in  FIG. 7 b   , the diaphragm  717  is made of a transparent material, wherein the light blocking region  717   b  is formed by a light blocking coating film that absorbs or reflects incident light. There are many choices of transparent materials used to make the diaphragm, such as glass, quartz, and sapphire. The light blocking region is coated with a light blocking coating, and the part without the coating is the light transmitting region  717   a . There are many advantages. Firstly, it could be realized by using a semiconductor process. The size and shape of the light transmitting region are almost unlimited, and the cost is low. Secondly, the thickness of the light blocking coating is negligible, so it will not affect the transmission of light transmitted in the light transmitting region. The light blocking coating film could be coated with a metal reflective film or an absorption film, and could also be coated with a non-metallic film, which is a very mature process. Preferably, the side of the diaphragm coated with the light blocking coating film is close to the wavelength conversion coating  712   b , so that there is no light propagation distance between these two elements, so that the area where the diaphragm blocks light is more accurate. 
     Preferably, the diaphragm is coated with a filter film, which is used to transmit converted light having a emission half-angle equal to or smaller than A/2 and at least partially reflect converted light having a emission half-angle greater than A/2, so that the invalid converted light having emission half-angle greater than A/2 could be reused and more light is incident into the effective aperture of the light collimation element. Of course, in this embodiment, the light collimation element could also be designed to collect light from a larger angle from the light source, which obviously does not affect the beneficial effects of the diaphragm in this embodiment. 
     In the aforementioned embodiment shown in  FIG. 7 a    and  FIG. 7 b   , there is no limitation on the minimum size of the light transmitting region. Generally, in order to achieve the purpose of maximizing the light emitted from the excitation area on the wavelength conversion plate, the light transmitting region of the diaphragm should obviously be larger than and completely cover the excitation area of the wavelength conversion plate while the light transmitting region is aligning to the excitation area of the wavelength conversion plate, to ensure that all the light emitted from the excitation area could be emitted from the light transmitting region. However, in other occasions of decorative lighting, considering that the light emitted from the light transmitting region of the diaphragm will form an image on the decorative lighting field, the shape of the light transmitting region could be circular, pentagram, cross star, heart shape, triangle shape, square shape, regular hexagon shape, or elliptical shape, and may be smaller than the excitation area of the wavelength conversion plate to achieve a better decorative effect. For example, in the case shown in  FIG. 7 c   , the light transmitting region on the diaphragm  717  is a cross-shaped region  717   a , and the remaining region are light blocking region  717   b . The light transmitting region  717   a  is aligned to the excitation area  741  of the wavelength conversion coating. In this way, although a large part of the light emitted by the excitation area  741  is blocked by the light blocking region and could not be emitted, a bright cross-shaped star will be displayed in the final decorative lighting field, achieving a special decorative effect. In this embodiment, the light transmitting region  717   a  is not limited to the inside of the excitation area of the wavelength conversion coating, and the tops of the four corners of the cross star also extend beyond the excitation area  741  of the wavelength conversion coating to achieve darkening effect at corner tops. It could be seen from this example that both the light transmitting region and the excitation area of the wavelength conversion plate must be aligned to each other, but the size and specific positional relationship between the two are not fixed, and they must be designed and determined according to the actual decorative effect requirement. For example, the light transmitting region of the diaphragm could also be smaller than the excitation area of the wavelength conversion coating. At this time, it could be ensured that the light emitted from the light transmitting region is the brightest, and the edge of the output light spot would have a clear light-dark boundary. 
     In the embodiment shown in  FIG. 7 a    to  FIG. 7 c   , one type of method for reducing diffused light ring is described, and another type of method is described below with the embodiment shown in  FIGS. 8 a  and 8 b   .  FIG. 8 a    is a schematic structural view of a light source in this embodiment, and  FIG. 8 b    is a front view of a wavelength conversion coating facing the light emitting direction. In this embodiment, referring to  FIG. 8 b   , a non-excitation area of the wavelength conversion coating  812   b  is at least partially coated with a light-absorbing paint  812   c , and the portion coated with the light-absorbing paint includes at least one region, and the distance between the center of this region and the center of excitation area is equal to the characteristic distance L, then this area must at least partially cover the diffused light ring  643  so that the purpose of reducing the light emission of the diffused light ring is achieved. Preferably, the light-absorbing paint is an oil-based paint, which has the advantage that, for a hydrophilic wavelength conversion coating, the coating range of the oil-based paint is easy to control and does not spread to a large area in the wavelength conversion coating. 
     Obviously, in order to completely remove the influence of the diffused light ring, the portion of the wavelength conversion coating coated with the light-absorbing paint should completely cover the diffused light ring. In actual operation, the portion  812   c  coated with the light-absorbing paint should cover a region outside a circle region of the wavelength conversion coating, and the circle region has its center at the center of the excitation area and has radius of the characteristic distance L, that is, the area covering  843  region in  FIG. 8 b    and its periphery. 
     For the dark ring adjacent to the excitation area, this part could be coated or not with light-absorbing paint, because this area also hardly emits light. Considering that the light-absorbing paint spreads in the wavelength conversion coating during the coating process, the dark ring could be used as a buffer zone for coating the light-absorbing paint.  FIG. 8 b    is a front view of the wavelength conversion coating in this case. In this embodiment, the diffused light ring  843  around the dark ring  842  is completely covered by the light-absorbing paint, and the light-absorbing paint  812   c  will inevitably partially spread into the dark ring  842  (buffer zone). At the same time, due to the separation of the dark ring  842 , the spread light-absorbing paint does not spread into the central excitation area  841 . Therefore, the dark ring  842  will be divided into two parts, and one part far from the excitation area will be coated with light-absorbing paint, while the other part near the excitation area will not be coated with light-absorbing paint. 
     Preferably, in this embodiment, a filter (not shown in the figure) placed after and close to the wavelength conversion plate along the optical path, which is used to transmit converted light having a emission half-angle equal to or smaller than A/2 and at least partially reflect converted light having a emission half-angle greater than A/2, so that the invalid converted light having emission half-angle greater than A/2 could be reused and more light is incident into the effective aperture of the light collimation element. Of course, in this embodiment, the light collimation element could also be designed to collect light from a larger angle from the light source, which obviously does not affect the beneficial effects of the light-absorbing paint in this embodiment. 
     In the above embodiments, the wavelength conversion plate is composed of a transparent thermally conductive substrate and a wavelength conversion coating layer coated on the surface. As described in  FIG. 6 a    and the related description, in this case, there is a problem that part of the converted light lateral spread in the transparent thermally conductive substrate. Actually, there is another way to realize the wavelength conversion plate. The following embodiments illustrate this, and its structure diagram is shown in  FIG. 9   a.    
     In the lamp of this embodiment, the wavelength conversion plate may emit converted light in a reflection form. The laser diode  911  emits a laser light  921  which is focused and incident on the wavelength conversion plate  912  and excites it to emit converted light. Specifically, the structure of the light source is shown in  FIG. 9 b   . The wavelength conversion plate includes a reflective substrate  912   a  and a wavelength conversion coating  912   b  coated on the surface of the reflective substrate. The laser light  921  emitted from the laser diode  911  is incident on the wavelength conversion coating  912   b . Due to the reflection effect of the substrate, the wavelength conversion coating could only emit converted light back to the direction of the reflective substrate. It could be understood that if the laser light  921  is vertically incident on the wavelength conversion coating  912   b , the converted light is directed toward the laser diode, and a light output would be blocked by the laser diode. In this embodiment, the angle between the optical axis of the laser  921  and the normal plane of the wavelength conversion coating  912   b  is greater than A/2. At this time, a light beam  922  with a half angle greater than A/2 emits from the side face and could be collected and collimated by the light collimation device  913 . In this method, there is no transparent light-guiding layer, so there is no lateral spread of converted light, and light could be more concentrated. 
     Preferably, the angle between the laser optical axis and the normal plane of the wavelength conversion coating is 45 degrees. As shown in  FIG. 10 a   , the angle between the laser optical axis  1021  and the reflective substrate  1012   a  surface is 45 degrees. Referring to  FIG. 10 b   , excitation light spot with circular cross section becomes an approximately elliptical spot and excites a converted light spot  1041  of the same shape, and the light collimation element receives the light emitted by the converted light spot  1041  from the direction of 45 degrees. Therefore, when looking at the receiving direction of the light collimation element, an approximately elliptical converted light emission spot will be re-projected into a circular converted light beam  1022 , thereby finally forming a circular light spot. The circular light spot has a better device effect and is easier to be accepted by people. 
     In the foregoing embodiments, several implementation forms of the light source and the light collimation device are exemplified. In the embodiment shown in  FIG. 2 , how to use such a light emitting device (including the light source and the light collimation device) with an mirror array on a curved surface is described to achieve the decorative lighting effect of “stars in the sky”. In this embodiment, a plurality of plane mirrors are arranged along an irregular curved surface. In the embodiment shown in  FIG. 11 , the difference is that a plurality of planar mirrors  1114   a  and  1114   b  are distributed on a convex surface  1114   x , and the normal direction of each planar mirrors is the same as that of the convex surface at this position. Obviously, the normal directions of each plane mirrors are different so that the directions of the multiple sub-beams formed by these plane mirrors are different. 
     In the lamp of the embodiment shown in  FIG. 12 , the concave mirror array located after the light emitting device (including the light collimation element) along the light path includes a plurality of plane mirrors  1214   a  and  1214   b , etc., and the plurality of plane mirrors are arranged in an array along a concave surface  1214   x . The light emitted from the light emitting device is reflected by the mirror array on concave surface to form a plurality of collimated sub-beams  1225 . Geometric optics tells us that any concave mirror could reflect a collimated beam into a converged beam, and in this embodiment, the normal direction of each plane mirror  1214   a  and  1214   b  is the same as the normal direction of the concave surface at this position. Therefore, the normal directions of plane mirrors  1214   a  and  1214   b  continuously change and the plurality of collimated sub-beams reflected by the plurality of plane mirrors  1214   a  and  1214   b  are converged. In the lamp of this embodiment, a housing  1218  is further included, and a mirror array on concave surface is located in the housing  1218 . The surface of the housing  1218  includes a transmitting region  1218   a , and a plurality of sub-beams are converged and transmitted through the transmitting region  1218   a . Since the sub-beams are converged, the area where these sub-beams converge will obviously be smaller than the size of the concave mirror array, so the transmitting region on the housing could also be relatively small to allow all the sub-beams to pass through. In detail, the dimension of the transmitting region  1218   a  in one direction is smaller than the dimension of the concave mirror array in same direction. From the perspective of the product, a small transmitting region on the housing could give people the impression that all the sub-beams are emitted from one point, and it is not easy to see all the structures inside the housing  1218  from the transmitting region inward so that the appearance is good. 
     Preferably, the shape of the light-transmitting region  1218   a  on the surface of the housing is circumscribed with the envelope of the total light spot formed when multiple sub-beams pass through the transmitting region. It could also ensure that the area of the transmitting region is minimized. Preferably, the transmitting region on the surface of the housing is circular, pentagonal, drop-shaped, elliptical, square, rectangular, trapezoidal, heart-shaped, regular hexagon, or triangular to achieve a better appearance effect. In this embodiment, the concave surface  1214   x  is a spherical surface or an ellipsoidal surface. The concave surface  1214   x  may also have different curvatures in two mutually perpendicular dimensions to achieve different light point distributions after reflection. 
     Further, the lamp in this embodiment further includes a motor (not shown) for driving the curved-surface mirror array to rotate with respect to the normal direction AX of the center of the concave surface  1214   x . With the rotation of the concave surface and each of the plane mirrors  1214   a  and  1214   b , the sub-beams reflected by the concave mirror array will also rotate. Multiple rotating light spots are formed to achieve a good visual effect. Of course, the motor could also drive the curved-surface mirror array to perform other periodic motions to achieve other visual effects. 
     Obviously in this embodiment, the light emitting device does not necessarily adopt the structure of the light source and the light collimation element shown in  FIG. 1 . As long as the light emitting device could emit a collimated light beam, the beneficial effects of this embodiment could be achieved. 
     The embodiment shown in  FIG. 13  is a further improvement of the embodiment of  FIG. 12 . In the lamp of this embodiment, the concave mirror array after the light emitting device along the light path includes a plurality of plane mirrors. The plurality of plane mirrors are arranged in an array along a concave surface. After reflection, multiple sub-beams  1325   u ,  1325   v , and  1325   w  are formed, and the multiple sub-beams are irradiated on the target surface  1351  to form multiple sub-spots. 
     Obviously, the incident angle of the sub-beam  1325   u  incident on the target surface  1351  (the angle between the incident light and the normal of the target surface at the incident point) is greater than the incident angle of the sub-beam  1325   w  incident on the target surface  1351 . Assume that the number of plane mirrors per unit area in the concave mirror array (that is, the density of the plane mirrors) is uniform. Due to the influence of the projection angle, The distance between the light spots formed by the sub-beam  1325   u  and its adjacent sub-beam on the target surface is necessarily greater than the distance between the light spots formed by the sub-beam  1325   w  and its adjacent sub-beam on the target surface  1351 . In this way, the spot array formed on the target surface  1351  is non-uniform: the spot density of the region  1352   u  where the sub-beam  1325   u  is incident is smaller than the spot density of the region  1352   w  where the sub-beam  1325   w  is incident. 
     However, a uniform light spot density could achieve better visual effects. In order to achieve a more uniform light spot density, in this embodiment, it is considered that the area  1314   u  on the concave mirror array reflects incident light beam to form the sub-beam  1325   u , and the area  1314   w  reflects incident light beam to form a sub-beam  1325   w , and the number of plane mirrors per unit area of the  1314   u  area (density of the plane mirrors) is greater than the number of plane mirrors per unit area of the  1314   w  area, so that the difference in distance between adjacent light spots caused by the projection angle could be at least partially compensated. For the sub-beams  1325   v  and  1325   w , the incident angles on the target surface  1351  are similar, so the density of the plane mirrors on the corresponding regions  1314   v  and  1314   w  could be set to be similar. 
     In summary, the concave mirror array includes dense area and sparse area. The number of plane mirrors per unit area in the dense area is greater than the number of plane mirrors per unit area in the sparse area. The average incident angle of the sub-beam of dense area incident on the target surface is greater than the average incident angle of the sub-beams of the sparse area incident on the target surface. Rely on a higher density of plane mirrors of dense area to compensate for the effect of larger spot distance caused by larger incident angle of the reflected sub-beams on the target surface, spots distance on the target surface becomes uniform. In this embodiment, the area  1314   u  on the concave mirror array is a dense area, and the area  1314   w  is a sparse area. In this embodiment, the dense area is located on an end of the concave surface near the light emission direction, and the sparse area is located on an end of the concave surface away from the light emission direction. It could be understood that there may be multiple pairs of dense and sparse areas on the concave mirror array. 
     In this embodiment, a concave mirror array is used as an example. Obviously, the settings of the dense area and the sparse area could also be applied to the convex mirror array (see the embodiment shown in  FIG. 11 ) and other types of curved mirror arrays, and the mode of action and the rules are not related to the specific form of the curved surface. 
     Obviously, in this embodiment, the light emitting device does not necessarily adopt the structure of the light source and the light collimation element shown in  FIG. 1 , as long as the light emitting device could emit a collimated light beam, the beneficial effects of this embodiment could be achieved. 
     In addition to the curved mirror array described in the above embodiments, a lamp in the present invention may further include a reflection plate and a motor after the light emitting device (including the light source and the light collimation element) along the light path. The motor drives the reflection plate to rotate or periodically move. The schematic is shown in  FIG. 14 . The reflecting plate  1414  reflects the collimated light emitted by the light emitting device, and the motor drives the reflecting plate to rotate, so that a reflected light spot could be controlled to move in scanning mode to form the visual effect of the moving light spot. The motor could also drive the reflector to perform other periodic movements to form other light spot movement modes. 
     In the lamp of the embodiment shown in  FIG. 15 , a micro mirror array  1514  is included after the light emitting device that emits the collimated light beam along the light path. And the micro mirror array  1514  includes a plurality of micro mirrors  1514   a  and  1514   b  to reflect incident collimated light to form a plurality of sub-beams. The mirrors  1514   a  and  1514   b  in the mirror array could be independently controlled to flip, which corresponds to that the propagation directions of multiple sub-beams could be independently controlled. An array of light spots formed on the target surface (not shown) and each spot could be controlled and moved independently to form a unique visual effect. Further, the lamp in this embodiment further includes a motor  1519  for driving the mirror array to rotate or periodically move. In this way, the light spot array formed on the target surface could be rotated or moved periodically, and the independent control movement of each light spot could be performed simultaneously, forming a unique visual effect. Obviously, in this embodiment, the light emitting device does not necessarily adopt the structure of the light source and the light collimation element shown in  FIG. 1 , as long as the light emitting device could emit a collimated light beam, the beneficial effects of this embodiment could be achieved. 
     The above description is only for embodiments of the present invention, and thus does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description and drawings of the present invention, or directly or indirectly applied to other related technologies belongs to the fields of patent protection of the present invention.