Lighting equipment and projector

Abstract

Lighting device comprising a light source (1), an optical unit (20) designed to adjust the direction of the light from the light source (1), and a reflector (7), characterized in that the lighting device further comprises a light tube (5) and an exciter (6), the light tube (5) receives light (L1) with a first wavelength from the optical unit (20) and directs the light (L1) with the first wavelength onto the exciter (6), the exciter (6) converts the light (L1) with the first wavelength into light (L2) with a second wavelength and reflects the light (L2) with the second wavelength onto the reflector (7), wherein a circumferential wall of the light tube (5) is designed to reflect the light (L1) with the first wavelength and to transmit the light (L2) with the second wavelength.

Description

[0001] The present invention relates to a lighting device and a projector. Background of the technology

[0002] Due to the characteristics of good monochromaticity, strong directivity, and high luminance of laser light sources (e.g., laser diodes (LD)), LD lighting devices are becoming increasingly important and are used in various fields (e.g., medical devices, automotive headlights, night vision surveillance, stage lighting, etc.). Compared with light-emitting diode (LED) lighting devices, LD lighting devices have a larger illumination range and a longer service life.

[0003] In the prior art, such an LD illumination device generally comprises a laser diode array configured to generate laser beams; collimating lenses, each corresponding to the laser diodes of the laser diode array and configured to collimate laser beams emitted from corresponding laser diodes; compression optics configured to reduce intervals between parallel laser beams emitted from respective collimating lenses; and a focusing lens configured to converge light emitted from the compression optics. Ideally, the collimating lenses can collimate the laser beams into parallel light, whereupon the parallel light is focused to a desired location after compression and convergence, as shown in Fig. 1. However, as in the practical case of Fig. 2, light emitted from the collimating lenses is not parallel due to tolerances in practical manufacturing and miscentering and tilting during assembly of the collimating lenses, whereby a light spot emitted from the focusing lens will have the following problems; for example, the light spot is broadened and deviates from a desired location (as indicated by an arrow in Fig. 2), and the luminous efficacy of the LD lighting device is reduced. WO 2005 / 107420 A2 describes a light source for emitting light. US 2011 / 0 148 280 A1 discloses a vehicle headlight and a lighting device. Summary of the invention

[0004] In order to solve the above-mentioned problems, an object of the present invention is to provide a lighting device which can solve the problem of low luminous efficiency of the above lighting device and obtain light rays having a desirable wavelength.

[0005] The lighting device according to the present invention comprises a light source, an optical unit designed to adjust the direction of the light from the light source, and a reflector, characterized in that the lighting device further comprises a light tube and an exciter, the light tube receives light with a first wavelength from the optical unit and projects the light with the first wavelength onto the exciter, the exciter converts the light with the first wavelength into light with a second wavelength and reflects the light with the second wavelength onto the reflector, wherein a circumferential wall of the light tube is designed to reflect the light with the first wavelength and to transmit the light with the second wavelength.

[0006] The concept of the present invention is to improve the lighting device by additionally providing a light tube whose circumferential wall is designed to reflect light at the first wavelength and transmit light at the second wavelength. The present invention proposes a light tube whose circumferential wall is designed to reflect light at the first wavelength and transmit light at the second wavelength, instead of a conventional light tube that reflects light at all wavelengths.In conventional light tubes in the related art, for example, when used in reflectors, after the blue laser is directed onto the exciter and converted into yellow light rays, the yellow light rays are reflected and scattered by the exciter. The reflected and scattered yellow light impinges on the inside of the light tube and is also reflected by the light tube. The yellow light ultimately exits the reflector at one end of the reflector that receives the blue laser, rendering the entire illumination device inoperable. The present invention proposes a light tube whose circumferential wall exhibits dichroism, so that, for example, the yellow light rays are directly transmitted through the circumferential wall without affecting the operation of the illumination device.

[0007] In addition, the light tube can solve the problems of lighting devices in which the useful light efficiency is reduced because the focus light spot is widened or deviated from a desired position due to tolerances in practical manufacturing and miscentering and tilting during installation of the collimating lenses, thereby increasing an allowable tolerance of the collimating lens of the lighting device and providing light with a desired wavelength according to requirements.

[0008] According to a preferred solution of the present invention, the light tube tapers. If the light tube tapers to a certain conical extent, the end of the light tube with the larger dimension is preferably used to receive light from the optical unit, thereby increasing the receiving area for receiving converged light beams. Thus, the focus light spot can enter the light tube even in a situation where the focus light spot deviates by a certain distance from the focus position or the focus light spot is widened, thus improving the permissible deviation of the collimating lenses of the illumination device.

[0009] According to a preferred solution of the present invention, an inner side of the circumferential wall of the light tube is coated with a dichroic coating, or the circumferential wall of the light tube is a dichroic mirror. Furthermore, the dichroic coating comprises, for example, a hydrophilic polymer film made of a dichroic pigment, for example, PVA film, locally formed PVA film, and locally saponified ethylene-vinyl acetate copolymer film. The dichroic mirror can be any of the known suitable dichroic mirrors.

[0010] According to a preferred solution of the present invention, the reflector is an elliptical reflector. The elliptical reflector can reflect light from a first focus thereof to a second focus thereof, so that converged light beams can be obtained at the second focus of the elliptical reflector. By obtaining the converted light beams at the focus of the elliptical reflector, the illumination light beams can have a small divergence angle, so that the luminous efficacy of the lighting device can be improved.

[0011] According to a preferred solution of the present invention, the reflector is a reflector with an opening, wherein the opening is configured such that the light tube is at least partially inserted into the reflector through the opening. By using the reflector with the opening, the light tube and the reflector can be assembled by at least partially inserting the light tube into the reflector, so that the volume of the lighting device is reduced. The advantage of the embodiment of the present invention is particularly evident in that the reflector has an output end of the light tube that is configured to reflect the light with the first wavelength and to transmit the light with the second wavelength.

[0012] According to a preferred solution of the present invention, the light tube comprises a first end and a second end, wherein the second end has a smaller size than that of the first end and the light tube is at least partially inserted into the elliptical reflector by means of the second end. The light with the first wavelength is emitted from the light tube in a collected manner by at least partially inserting the second end of the light tube into the elliptical reflector.

[0013] According to a preferred solution of the present invention, the optical axis of the light tube passes through the focus of the reflector. With such a configuration, the luminous efficacy of the illumination device can be improved, since if the optical axis of the light tube deviates from the focus, part of the light cannot be projected onto the exciter, resulting in reduced luminous efficacy.

[0014] According to a preferred solution of the present invention, the exciter is provided in the first focus position of the elliptical reflector so that light reflected from the exciter onto the elliptical reflector can be focused onto the second focus position of the elliptical reflector to thereby form collecting beams.

[0015] According to a preferred solution of the present invention, a distance between the exciter and the second end of the light tube is preferably 0.5 mm-1.0 mm, so that more uniform and more light can be incident on the exciter, preventing the exciter from being quenched by the laser light beams and improving the luminous efficiency of the illumination device. For example, if the light tube is preferably 20 mm, light entering the light tube is reflected and superimposed multiple times within the light tube so that light emitted from the light tube can have a uniform luminance distribution, further preventing the exciter from being quenched, thus extending the lifetime of the exciter and further improving the luminous efficiency of the illumination device.

[0016] According to a preferred solution of the present invention, the optical unit comprises collimation lenses, a compression lens, and a focus lens sequentially provided along a light path. The optical unit configured in this manner can adjust light beams emitted from the light source to have a relatively small light spot, thereby improving the light efficiency of the lighting device.

[0017] According to a preferred solution of the present invention, the elliptical reflector is a hollow elliptical reflector. If the elliptical reflector is a hollow elliptical reflector, the light tube is at least partially inserted into the hollow elliptical reflector through an opening of the hollow elliptical reflector, so that the lighting device is compact and miniaturized.

[0018] According to a preferred solution of the present invention, a reflective layer is applied to an end face of the second end of the light tube. The reflective layer applied to the end face can reflect the portion of the light rays incident on the end face, thus preventing the total internal reflection phenomenon of this portion of the light rays incident on the end face within the circumferential wall of the light tube, and the portion of the light rays can be reused. In particular, the portion of the light rays incident on the end face includes light having the first wavelength and light having the second wavelength. In a situation where the light having the first wavelength is reflected, the conversion efficiency of the exciter can be improved; and in a situation where light having the second wavelength is reflected, the light collection efficiency of the reflector can be improved.Therefore, the luminous efficiency of the lighting device can be further improved overall. Additionally, the reflective layer can be a standard reflective film of visible light wavelength.

[0019] According to a preferred solution of the present invention, the elliptical reflector comprises a first part and a second part, wherein the first part and the second part are assembled together to define a cavity for inserting the light tube. The assembly of the two parts to define the cavity for inserting the light tube can also miniaturize the lighting device. Furthermore, a further advantage of such a configuration is ease of processing and manufacturing.

[0020] According to a preferred solution of the present invention, the inner and outer surfaces of the first part and the second part are configured to reflect the light having the second wavelength and transmit the light having the first wavelength. With such a configuration, the total internal reflection phenomenon within the circumferential wall of the light tube can be avoided while realizing the above effects, so there is no need to coat the end surface of the second end of the light tube with a reflective layer.

[0021] According to a preferred solution of the present invention, the light tube has a length of 20 mm to realize uniform light distribution, while light is reflected and superimposed multiple times within the light tube. Furthermore, the dimension of the light tube depends on various factors. For example, a half-width R at the light tube entrance is determined by the device tolerance, and generally accepted values ​​should allow an assembly error of 0.1 mm for the collimating lenses; a half-width r at an output of the light tube is determined by considering the exciter efficiency, quenching, and aperture size at the second focus of the elliptical reflector. The aperture size of the second focus of the elliptical reflector is determined according to practical requirements. The length of the light tube depends on the dimension of the elliptical reflector, while the latter is decided according to device requirements.

[0022] According to a preferred solution of the present invention, the light tube comprises a quadrangular truncated cone, and the light tube comprises four wall sections that are assembled together, and the wall sections together form the circumferential wall of the light tube. With such a configuration, the light spot emitted from the illumination device can have a quadrilateral shape and can thus be used in a system requiring quadrilateral light beams, for example, for illuminating a digital micromirror device (DMD) array in a DLP projector.

[0023] According to a preferred solution of the present invention, the light tube is a circular truncated cone, and the light tube comprises two semi-cylindrical wall sections joined together, and the wall sections together form the circumferential wall of the light tube. With such a configuration, the light spot emitted from the lighting device can have a circular shape, and the lighting device can thus be used in an environment requiring circular light beams.

[0024] According to a preferred solution of the present invention, the exciter comprises a plurality of regions, each of which has different excitation properties, i.e., from which light of the first wavelength is excited to generate excited light of different colors, including, for example, red light, blue light, green light, and yellow light. Thus, the wavelength of the light beams emitted from the illumination device can be varied.

[0025] According to a preferred solution of the present invention, the exciter is a phosphor. The phosphor can be a red phosphor made of YBi3:Eu material, a green phosphor made of a ZnSiO4:Mn material, a blue phosphor made of a barium magnesium aluminate material doped with Eu2+ ions, and a yellow phosphor made of YAG.

[0026] Furthermore, the second object of the present invention is to provide a projector comprising the above illumination device, and light emitted from the illumination device can directly enter another light tube of the projector and then be projected onto a micromirror array. Since light reflected by the reflector can be focused onto the second focal point, the light efficiency can be improved.

[0027] Furthermore, the term "exciter" as used herein refers to a substance that, when illuminated by incident light of a specific wavelength (ultraviolet or visible light), absorbs the light energy to enter an excited state, and then transitions to the ground state or a less excited state while emitting light of a different wavelength than the incident light. The representative substance of the exciter is the emitting material that uses a rare earth compound as the base substance and rare earth elements as excitation agents, including, but not limited to, phosphors.

[0028] According to the lighting device of the present invention, the problem of low luminous efficiency of the above lighting device can be solved and light beams having a desired wavelength can be obtained. Short description of the drawings

[0029] The accompanying drawings form a part of this specification and are included to provide a further understanding of the present invention. Such accompanying drawings illustrate embodiments of the present invention and, together with the description, serve to describe the principles of the present invention. In the accompanying drawings, like components are designated by like reference numerals. Fig. 1 and Fig. 2 show lighting devices of the prior art, wherein light paths in an ideal situation and light paths in an actual situation are shown; Fig. 3 shows a schematic diagram of a first embodiment of a lighting device according to the present invention; Fig. Figure 4 shows a schematic diagram of light paths in a light tube and in a Fig. 3 reflector shown; Fig. 5 shows a schematic diagram of a second embodiment of a lighting device according to the present invention; Fig. Figure 6 shows a total internal reflection (TIR) ​​effect generated within a circumferential wall of the light tube; Fig. Figure 7 shows a schematic diagram of a third embodiment of a lighting device according to the present invention for eliminating the Fig. 6 shown total reflection effect; Fig. 8 shows a schematic diagram of a fourth embodiment of a lighting device according to the present invention; Fig. 9 is a schematic diagram showing a method of manufacturing the light tube of the lighting device of the first to fourth embodiments of the present invention; Fig. 10 shows a schematic diagram of a light deviation caused by the wall thickness of the light tube and Fig. Figure 11 shows a diagram of the relationship between light deviation and angle of incidence. Detailed description of the embodiments

[0030] Fig. 3 shows a schematic diagram of a first embodiment of an illumination device 10 according to the present invention. The illumination device 10 according to the present invention comprises a light source 1, a plurality of collimation lenses 2, a compression optics 3, a focus lens 4, a tapered light tube 5, a phosphor 6, and an elliptical reflector 7 with an opening 70. The light source 1 is a laser diode array containing a plurality of laser diodes and emitting, for example, blue laser light; the plurality of collimation lenses 2 each correspond to the plurality of laser diodes of the light source 1 and are configured to collimate blue laser light from the corresponding laser diode into parallel light; the compression optics 3 are configured to reduce intervals between parallel blue laser beams emitted from respective collimation lenses 2.the focus lens 4 is configured to converge the blue laser beams emitted from the compression optics 3; the tapered light tube 5 is configured to receive the blue laser beams from the focus lens 4; the phosphor 6 is configured to convert the blue laser beams emitted from the tapered light tube 5 into yellow light beams and reflect the yellow light beams; and the phosphor 6 is provided in the first focus position (for example, F1) of the elliptical reflector 7, and the elliptical reflector 7 is configured to reflect the yellow light beams reflected by the phosphor 6 to a second focus position (for example, F2).

[0031] In addition, the tapered light tube 5 is partially inserted into the elliptical reflector 7, and an optical light axis in the tapered light tube 5 passes through the first focus position (F1) of the elliptical reflector 7 where the phosphor 6 is located, and may be perpendicular to the phosphor 6 located at the focus F1 or form a certain angle with it.

[0032] In order for the lighting device to function well, a circumferential wall of the tapered light tube 5 is configured to reflect blue light rays and transmit the yellow light rays, as shown in Fig. 4, where solid lines L1 represent the light paths of the blue light rays in the tapered light tube 5 and the dashed lines L2 represent the light paths of the yellow light rays.

[0033] As in Fig. 3, due to the tolerance in practical manufacturing and the miscentering and tilting during assembly of the collimating lens 2, the blue laser light emitted from the collimating lens 2 is not parallel light, whereby a light spot emitted from the focusing lens 4 will be deviated and broadened (as shown in Fig. 2). By providing the tapered light tube 5 and using one end thereof with a larger size to receive light from the focus lens 4, a receiving area of ​​the converged laser beams is increased, so that the deviated light spot and widened light spot can also be received, and thus the luminous efficiency of the lighting device is improved.

[0034] As in Fig. 4 shown, shows Fig. 4 also shows the schematic diagram of light paths in the tapered light tube 5 and the elliptical reflector 7, wherein the blue laser beams (solid lines L1) entering the tapered light tube 5 are reflected and superimposed several times in the tapered light tube 5 and then exit the tapered light tube 5 onto the phosphor 6. The blue laser beams incident on the phosphor 6 are converted into yellow light beams (dashed lines L2) by the phosphor 6, and the yellow light beams are scattered and reflected by the phosphor 6 onto the elliptical reflector 7, whereupon the elliptical reflector 7 reflects the yellow light beams L2 to the second focus position F2 of the elliptical reflector 7, whereupon they exit from the focus F2.

[0035] Since the blue laser beams L1 are reflected and superimposed multiple times in the tapered light tube 5, the laser beams projected from the tapered light tube 5 onto the phosphor 6 are uniformly distributed, and thus, extinction of the phosphor 6 by laser beams can be prevented. Specifically, when the tapered light tube has a length of 20 mm, a maximum luminance on a focal plane is 99 W / mm2 when the laser beams enter the light tube and 10.6 W / mm2 when the laser beams exit the light tube.

[0036] In addition, Fig. 3. Since the tapered light tube 5 is inserted into the elliptical reflector 7, the illumination device 10 can be compact and miniaturized. Specifically, when the tapered light tube 5 has a length of approximately 20 mm and is not inserted into the elliptical reflector 7, a total length of the illumination device including another optical system for imaging on the phosphor 6 is longer than 100 mm, and when the tapered light tube 5 is inserted into the elliptical reflector 7, the illumination device 10 can be more compact.

[0037] Fig. Figure 5 shows a schematic diagram of a second embodiment of a lighting device according to the present invention. The second embodiment of the lighting device 100 of the present invention differs from the first embodiment of the lighting device 10 according to the present invention in that, in the second embodiment, the tapered light tube 5 is fully inserted into the elliptical reflector 7, so that the lighting device 100 can be further compact and miniaturized.

[0038] Fig. Figure 6 shows a total internal reflection (TIR) ​​effect generated within the circumferential wall of the light tube. As in Fig. 6, when a part of the yellow light (as indicated by the dotted line) reflected and scattered by the phosphor 6 hits the inside of the circumferential wall of the light tube 5, since the circumferential wall of the light tube 5 has a property of transmitting yellow light, this part of the light passes through the circumferential wall of the light tube 5 to hit the reflector 7. However, another part of the yellow light (as shown by the chain line) reflected by the phosphor 6 hits a surface of a lower end of the light tube 5 and is transmitted therethrough to enter the circumferential wall of the light tube 5, and moreover, this part of the yellow light is totally reflected within the circumferential wall and trapped in the circumferential wall, that is, so-called total internal reflection effect phenomenon, whereby the luminous efficiency will be reduced.

[0039] In order to avoid the above-mentioned problem, the present invention proposes to apply a reflective layer to the inner surface of the lower end of the light tube 5, so that the yellow light rays striking the end surface are reflected back to the phosphor 6 instead of entering the circumferential wall of the light tube 5, and the yellow light rays reflected back to the phosphor 6 are again reflected by the phosphor 6 to arrive at the ellipse reflector 7, as shown in Fig. 7. In addition, a small portion of the blue laser light (not shown) is reflected by the phosphor 6 onto the end face to produce the total reflection effect, in which case, due to the provision of the reflective layer, this small portion of the blue laser light reflected onto the end face of the light tube is also reflected back to the phosphor 6, so that the conversion efficiency of the phosphor 6 is improved and the luminous efficacy of the lighting device is correspondingly improved.

[0040] Fig. 7 is a schematic diagram of a third embodiment of a lighting device according to the present invention for eliminating the total internal reflection effect, as shown in Fig. 6. The third embodiment of the lighting device of the present invention differs from the second embodiment of the lighting device 100 of the present invention in that the end surface of the lower end of the light tube 5 is coated with a reflective layer 55. The reflective layer 55 may be a normal reflective film of visible light wavelength. With such a configuration, the occurrence of the TIR effect can be avoided, and thus this part of the light can be reused, and the luminous efficiency of the lighting device can be improved.

[0041] Fig. 8 is a schematic diagram of a fourth embodiment of a lighting device 200 according to the present invention.

[0042] As in Fig. As shown in Figure 8, the fourth embodiment of the lighting device 200 of the present invention differs from the second embodiment of the lighting device 100 of the present invention in that, in the fourth embodiment, the elliptical reflector 7 comprises a first glass block 7.1 and a second glass block 7.2, and the first glass block 7.1 and the second glass block 7.2 are assembled together by, for example, probing, glue, or mechanical mounting to define a cavity for inserting the light tube 5. In addition, the inner surfaces and outer surfaces of the first glass block 7.1 and the second glass block 7.2 are coated with a coating that reflects yellow light rays and transmits blue light rays. In the present embodiment, as shown in Fig. As shown in Figure 8, the blue laser beams are transmitted through the elliptical reflector 7, which is made of glass blocks, to enter the tapered light tube 5 and exit after being reflected several times within the tapered light tube 5. The blue laser beams exiting the tapered light tube 5 are projected onto the phosphor 6, the blue laser beams projected onto the phosphor 6 are converted into yellow light beams by the phosphor 6, the yellow light beams are reflected by the phosphor 6 onto the elliptical reflector 7, and then the yellow light beams are reflected by the elliptical reflector 7 onto the second focus position F2 of the elliptical reflector 7 and exit from the focus F2. Thus, the same effect as that of the second embodiment of the illumination device according to the present invention can be realized. In addition, the TIR phenomenon (as shown in Fig. 6) can be avoided in the fourth embodiment of the lighting device according to the present invention, since the elliptical reflector 7 is made of glass blocks, which can reflect the part of the yellow light rays and the blue light rays reflected and scattered by the phosphor 6 onto the phosphor 6 again, and thus this part of the blue light rays and yellow light rays can be reused, which also achieves the effect of improving the luminous efficiency of the lighting device.

[0043] Furthermore, also in the above-mentioned first to fourth embodiments, a better light collection efficiency at the second focus F2 of the elliptical reflector 7 can be obtained by modifying and optimizing a curved surface of the elliptical reflector 7, thus further improving the efficiency of the lighting device.

[0044] Those skilled in the art should note that although blue laser beams and yellow light beams were taken as examples in the first to fourth embodiments, that is, a blue laser diode array is used as the light source 1 and yellow phosphor is used as the phosphor 6, the above invention is not limited to the above.The blue laser light beams and the yellow light beams may also be light of other colors. For example, a red laser diode array and a green laser diode array may be used as the light source 1, so that red laser beams and green laser beams are used instead of the blue laser beams. Blue phosphor, red phosphor, or green phosphor may be used as the phosphor 6, so that blue light, red light, or green light can be emitted instead of the yellow light. This can be changed according to practical requirements, and the configuration of the light tube can be changed accordingly. Similarly, although the elliptical reflector was mentioned as an example in the description, the present invention should not be limited to this, and reflectors with other configurations, for example, aspherical reflectors and parabolic reflectors, may be used.

[0045] For example, in a situation where a parabolic reflector is used, the light emitted by the reflector is parallel light, and in this case the lighting device can be used for stage lighting, as a searchlight, etc.

[0046] Fig. 9 is a schematic diagram of a method for manufacturing the light tube of the lighting device of the first to fourth embodiments of the present invention. As in Fig. 9, a schematic diagram of a method for manufacturing the light tube is given by taking a quadrangular truncated cone-shaped light tube as an example. First, a quadrangular truncated cone-shaped solid rod 50 having a dimension substantially the same as that of the light tube cavity is prepared, and then four pieces of dichroic mirrors 51 are adhered to four side walls of the quadrilateral tapered solid rod using an adhesive such as glue. Then, the quadrangular truncated cone-shaped solid rod 50 is removed, thereby manufacturing a quadrangular truncated cone-shaped light tube 5.

[0047] It should be obvious to those skilled in the art that the method for manufacturing the light tube of the present invention is not limited to the above example, and other manufacturing methods are also conceivable, as long as the circumferential wall of the light tube of the present invention can have the function of reflecting excited light, such as blue laser beams, and transmitting excited light, such as yellow light beams. The light tube of the present invention can be manufactured, for example, by the manufacturing method as shown in Fig. 9, after coating four glass plates with a dichroic coating by means of a known coating process. Alternatively, in the present invention, a light pipe in the shape of a circular truncated cone can be formed by applying a dichroic coating to two semi-cylindrical glass plates by means of a known coating process and by means of a method similar to the manufacturing method as shown in Fig. 9 shown.

[0048] Additionally, as with the light tube, since the circumferential wall of the light tube can reflect excited light, such as blue laser beams, and transmit excited light, such as yellow light beams, the light tube will not affect the function of the reflector. However, the wall thickness of the light tube will affect the luminous efficacy of the illumination device 10. Fig. Figure 10 shows a schematic diagram of the light deviation caused by the wall thickness of the light tube. As in Fig. As shown in Figure 10, when the light rays reflected by the phosphor strike an inner wall of the light tube, they will deviate to a certain degree due to the influence of refraction when they exit from an outer wall of the light tube. As shown in Fig. 11, the larger the angle of incidence, the larger the deviation, and a relationship between the deviation Δ, the wall thickness d of the light tube and the angles θ1 and θ2 is Δ = d × (1 - tg(θ2) / tg(θ1)), according to which it can be found that a maximum deviation Δ is equal to the wall thickness d of the light tube. Such a light deviation will make the phosphor appear larger, as shown, for example, by the dashed lines to the left of the phosphor in Fig.10, which creates a larger equivalent light spot at focus F2, resulting in a reduced light scattering efficiency of the elliptical reflector.

[0049] Additionally, in the above embodiments of the present invention, the phosphor may be configured in a wheel shape and include multiple regions, each of which, upon excitation, generates light of a different wavelength, for example, blue light, red light, green light, and yellow light. Specifically, the multiple regions are blue phosphor, red phosphor, and green phosphor, respectively, so that the illumination device can emit blue light, red light, and green light. The illumination device with such a configuration can be used in a DLP projector.

[0050] The above are merely preferred embodiments of the present invention, but do not limit the present invention. Various modifications and alterations may be apparent to those skilled in the art. Any changes, equivalent substitutions, and improvements within the spirit and principle of the present invention are intended to be covered within the scope of the present invention.

Claims

[1] Lighting device comprising a light source (1), an optical unit (20) designed to adjust the direction of the light from the light source (1), and a reflector (7), characterized by that the lighting device further comprises a light tube (5) and an exciter (6), the light tube (5) receives light (L1) with a first wavelength from the optical unit (20) and directs the light (L1) with the first wavelength onto the exciter (6), the exciter (6) converts the light (L1) with the first wavelength into light (L2) with a second wavelength and reflects the light (L2) with the second wavelength onto the reflector (7), wherein a circumferential wall of the light tube (5) is designed to reflect the light (L1) with the first wavelength and to transmit the light (L2) with the second wavelength. [2] Lighting device according to claim 1, characterized by that the light tube (5) tapers. [3] Lighting device according to claim 2, characterized by that an inner side of the circumferential wall of the light tube (5) is coated with a dichroic coating. [4] Lighting device according to claim 2, characterized by that the surrounding wall of the light tube (5) is a dichroic mirror. [5] Lighting device according to one of claims 1-4, characterized by that the reflector (7) is an elliptical reflector. [6] Lighting device according to one of claims 1-4, characterized by that the reflector (7) is a reflector with an opening (70), and the opening (70) is configured in such a way that the light tube (5) is at least partially inserted into the reflector (7) through the opening (70). [7] Lighting device according to claim 6, characterized bythat the light tube (5) comprises a first end and a second end, the second end being smaller than that of the first end, and the light tube (5) is at least partially inserted into the elliptical reflector (7) by means of the second end. [8] Lighting device according to one of claims 1-4, characterized by that an optical axis of the light tube (5) runs through a focus of the reflector (7). [9] Lighting device according to claim 7, characterized by that the light tube (5) receives the light (L1) with the first wavelength from the optical unit (20) at the first end and directs the light (L1) with the first wavelength onto the exciter (6) at the second end. [10] Lighting device according to claim 5, characterized by that the exciter (6) is provided at the first focus (F1) of the elliptical reflector (7). [11] Lighting device according to claim 6, characterized bythat a distance between the exciter (6) and the second end of the light tube (5) is 0.5 mm-1.0 mm. [12] Lighting device according to claim 6, characterized by that the optical unit (20) comprises collimation lenses (2), a compression optic (3) and a focus lens (4) which are provided sequentially along a light path. [13] Lighting device according to claim 5, characterized by that the elliptical reflector (7) is a hollow elliptical reflector. [14] Lighting device according to claim 13, characterized by that a reflective layer (55) is applied to an end face of the second end of the light tube (5). [15] Lighting device according to claim 5, characterized by that the elliptical reflector (7) comprises a first part (7.1) and a second part (7.2), wherein the first part (7.1) and the second part (7.2) are assembled together to define a cavity for the introduction of the light tube (5). [16] Lighting device according to claim 15, characterized by that inner surfaces and outer surfaces of the first part (7.1) and the second part (7.2) are configured to reflect the light (L2) having the second wavelength and to transmit the light (L1) having the first wavelength. [17] Lighting device according to claim 2, characterized by that the light tube (5) is a quadrangular truncated cone, and the light tube (5) comprises four assembled wall sections, and the wall sections together form the circumferential wall of the light tube (5). [18] Lighting device according to claim 2, characterized by that the light tube (5) is a circular truncated cone, and the light tube (5) comprises two assembled semi-cylindrical wall sections, and the wall sections together form the circumferential wall of the light tube (5). [19] Lighting device according to claim 5, characterized bythat the exciter (6) comprises several areas with different excitation properties. [20] Lighting device according to claim 19, characterized by that the exciter (6) is a phosphor. [21] Projector, characterized by that it comprises the lighting device according to one of claims 1-20.

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