Light source for exciting fluorescence by laser
By simplifying the optical path and using thermal conductivity wavelength conversion sheets, the existing laser excitation fluorescent light source structure is solved, efficient laser conversion and the stability of large energy density laser beams are achieved, and the overall efficiency of the light source is improved and stability.
Patent Information
- Application Number
- CN202310686304.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-12
- Publication Date
- 2024-12-13
AI Technical Summary
The existing reflective laser excitation fluorescent light source has a complex structure, resulting in large optical path losses and low efficiency. The fluorescent materials are prone to failure under high energy density laser irradiation, and optical design needs to be improved to improve overall efficiency.
A laser excitation fluorescent light source is designed, including laser diodes, lenses, diffusion sheets, reflective sheets, wavelength conversion sheets, etc. The laser diodes and wavelength conversion sheets are along the same axis, and by simplifying the optical path and using a thermally conductive metal substrate, the wavelength conversion sheets are used. Reduce light energy loss and improve heat dissipation.
It has achieved compact structure, accurate optical path, high conversion efficiency and convenient assembly, the overall efficiency of the light source is improved by 23.5%, and can withstand the irradiation of a large energy density laser beam, and the luminous flux and illuminance have been significantly improved.
Smart Images
Figure CN119123365A_ABST
Abstract
Description
Technical Field
[0001] The invention is a light source for laser-excited fluorescence, which is used in the fields of lighting and display. Background Art
[0002] The light source technology based on laser excitation fluorescence, that is, relying on the monochromatic light generated by the laser diode to excite the fluorescent material to produce white light, is gaining more and more widespread applications. According to the different optical paths of the laser irradiating the fluorescent material to produce white light, the light source structure based on laser excitation fluorescence can be divided into two types: transmission type and reflection type. Although the transmission light source has a simple structure, the fixing method of the fluorescent material leads to poor heat dissipation conditions of the fluorescent material, which affects the conversion efficiency of laser to white light; especially when a high-power laser is used as the excitation light source, the fluorescent material may fail directly due to poor thermal conductivity under the irradiation of a high-energy-density laser. On the other hand, since the fluorescent material of the reflective light source can be directly attached to the metal heat sink, when it is irradiated by the laser, the heat generated can be better guided out, so that it has a higher blue-to-white light conversion efficiency than the transmission type. However, the optical path of the reflective light source generally used at present is usually more complicated, and the laser needs to be reflected multiple times before irradiating the fluorescent material, which not only leads to the complexity of the structure of the light source and the increase of manufacturing cost, but also causes energy loss due to the multiple reflections of the laser, affecting the overall efficiency of the light source. Therefore, it is necessary to improve the optical design to further improve the overall efficiency of the light source. Summary of the invention
[0003] The invention is a light source for laser-excited fluorescence, characterized in that it includes a laser diode, a first lens, a diffuser, a reflector, a second lens, a wavelength conversion plate, a laser diode fixing base, a reflector base, a wavelength conversion plate fixing base, a glass window, and a protective cover. The laser diode emits monochromatic laser light under the action of an external current, which is irradiated onto the wavelength conversion plate after passing through the first lens, the diffuser, and the second lens, generating white light on its surface and outputting from the glass window through the reflector.
[0004] Furthermore, the normal directions of the laser diode, the first lens, the diffusion plate, the second lens, and the wavelength conversion plate are on the same axis.
[0005] Furthermore, the laser wavelength emitted by the above laser diode is between 430nm-470nm.
[0006] Furthermore, the first lens is located behind the laser diode and before the diffusion sheet.
[0007] Furthermore, the diffusion sheet is located behind the first lens and before the reflection sheet, the diffusion angle of the diffusion sheet to the laser is between 0.5°-10°, and the thickness of the diffusion sheet is 0.3mm-2mm.
[0008] Furthermore, the reflective sheet is disposed behind the diffusion sheet and before the second lens, and has a reflectivity greater than 95% for white light (with a wavelength of 400nm-750nm).
[0009] Furthermore, the second lens is located behind the reflective sheet and before the wavelength conversion sheet.
[0010] Furthermore, the wavelength conversion sheet includes a metal substrate with good thermal conductivity, a reflective film, and a fluorescent material in sequence, which converts laser light with a wavelength between 430nm and 470nm into white light with a wavelength between 460nm and 700nm.
[0011] The present invention has the following beneficial effects:
[0012] (1) Compact structure: the distance between each component unit is small, the space required for the structure is small, and the overall volume of the light source is small; (2) Precise optical path: the light source and optical components are on the same axis, which makes it easy to achieve precise alignment; (3) High conversion efficiency: the laser energy loss before reaching the wavelength conversion plate is small, ensuring the overall efficiency of the light source; (4) Easy assembly: the number of overall component units of the light source is small, and the components are easy to position and assemble. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 Schematic diagram of the optical path system of the existing laser-excited fluorescence light source.
[0014] Figure 2 Schematic diagram of the optical path system of the laser-excited fluorescence light source designed for the present invention.
[0015] Figure 3 Schematic diagram of the structure of the light source for exciting fluorescence with a single laser diode.
[0016] Figure 4 Schematic diagram of the wavelength conversion plate structure.
[0017] Figure 5 This is a luminescence spectrum diagram of the light source for laser-excited fluorescence of the present invention.
[0018] Figure 6 Luminescence spectrum of existing laser-excited fluorescence light sources
[0019] Figure 7 Schematic diagram of the light source structure for exciting fluorescence with a laser module array. DETAILED DESCRIPTION
[0020] At present, the common light sources of reflective laser and laser fluorescence are as follows: Figure 1The optical path shown is that after the laser is generated by the laser diode (101), it passes through the first lens (102), is reflected for the first time at the first reflector (103), passes through the diffuser (104), is reflected for the second time at the second reflector (105), and then passes through the second lens (106) to reach the wavelength conversion plate (107) to generate white light.
[0021] Assuming that the output intensity of the laser diode (101) is I0, after passing through the various optical devices in the figure, when reaching the wavelength conversion plate (107), its intensity will be reduced to I1: I1=I0ητ1τ2ρ1ρ2………………………………(1)
[0022] Among them, τ1 and τ2 are the transmittance of the first and second lenses to the laser respectively, ρ1 and ρ2 are the reflectance of the first and second reflective plates to the laser respectively, and η is the efficiency of the laser passing through the diffuser.
[0023] Since the first and second reflectors are designed according to the incident angle of the laser beam at a certain angle (such as 45°), but in actual situations, the laser beam has a certain size and cannot be incident on the reflector at the same angle, the actual energy loss after reflection is relatively large, and the reflectivity of the laser is usually less than 90%. To simplify the calculation, assuming ρ1=ρ2=90%, then formula (1) can be rewritten as: I1=0.81I0ητ1τ2……………………(2)
[0024] It can be seen from equation (2) that after passing through the two reflectors, the laser light has lost 19% before entering the wavelength conversion plate (107) and becoming white light. Figure 1 In the optical path design, the laser beam needs to be reflected twice, which makes the optical path complicated and the difficulty of centering each optical device increases, which makes the processing and installation of the components of the entire optical system more difficult.
[0025] Figure 2 The optical path of the laser light source used in the present invention to excite fluorescence. Figure 2 As shown, according to the optical path adopted by the present invention, the light-emitting surface of the laser diode (201) is parallel to the white light surface of the wavelength conversion plate (206), and is on the same axis. The laser beam does not need to be reflected multiple times before reaching the wavelength conversion plate (206). The laser beam directly irradiates the surface of the wavelength conversion plate (206) through the small hole in the middle of the reflective plate (204), generates white light, and then is output through the emitting plate (204). Figure 2 In the optical path, a laser beam with an intensity of I0 enters a wavelength conversion plate (206) with an intensity of I2 after passing through a first lens (202), a second lens (205) and a diffusion plate (203): I2=I0ητ1τ2……………………(3)
[0026] Under the premise of using the same first and second lenses and diffuser, by comparing equations (3) and (2), it can be seen that the light intensity is improved:
[0027] Formula (4) shows that Figure 2 The intensity ratio of the laser beam before entering the wavelength conversion plate (206) is Figure 1 The optical path is increased by 23.5%. In addition, the optical path itself is greatly simplified, making it easier to install optical components.
[0028] Figure 3 Based on Figure 2 The structure diagram of the light source of laser excitation fluorescence with the optical path design is shown. The laser diode fixing base (301), the wavelength conversion plate base (303) and the reflector plate base (302) are fixed together to ensure their parallelism, and are positioned by the protective cover (304). The reflector plate (308) is placed on the reflector plate base (302). The central part of the reflector plate (308) is opened and is in the emission light path of the laser diode (305). The laser beam emitted by the laser diode (305) passes through the first lens (306), the diffuser (307), the center of the reflector plate (308), and the second lens (309) to reach the surface of the wavelength conversion plate (310). The incident angle of the laser beam on the wavelength conversion plate (310) is 0°, and the incident angle of the white light emitted by the wavelength conversion plate (310) on the reflection plate (308) is 45°, that is, the angle between the reflection plate (308) and the horizontal plane is 45°. After being reflected by the reflection plate (308), the white light is emitted through the glass window (311).
[0029] Figure 3 The structure of the medium wavelength conversion plate is as follows: Figure 4 As shown, it includes a metal substrate (401), a reflective film (402), a fluorescent material layer (403) and an optical anti-reflection film (404). The incident laser passes through the anti-reflection film (404) and enters the fluorescent material layer (402) to interact with it. Part or all of the incident laser is absorbed by the fluorescent material layer and the light of different wavelengths is converted into a part of the anti-reflection film (404) directly output from its outer surface, and part passes through the reflective layer (402) and then reflects out of the anti-reflection film (404). Generally, the fluorescent material layer is made of a mixture of fluorescent powder and low melting point organic matter, such as silica gel or epoxy resin, and has an obvious disadvantage of being difficult to withstand high energy density laser irradiation. The present invention uses a fluorescent material layer that does not contain any organic matter, which is directly sintered and combined with the metal substrate below at high temperature, so it can withstand relatively large energy density laser beam irradiation.
[0030] Further, press Figure 1 and Figure 3 The light sources were constructed with the structures of and tested, and the results are listed in Table 1. As shown in Table 1, when the driving power is 8.6W (operating voltage is 4.3V, current is 2A), Figure 1 The luminous flux of the constructed light source is 337lm, and the illumination at 11m is 6500lx. Figure 3 The luminous flux of the constructed light source is 470lm, and the illumination at 11m is 9000lx. This shows that according to Figure 3 The efficiency of the constructed light source is Figure 1 The constructed light source is 38.5% taller. Table 1. Press Figure 1 and Figure 3 Optical performance of constructed light sources
[0031] The luminous spectrum of the light source designed by the present invention and the existing light source is tested, and the results are as follows: Figure 5 , Figure 6 As shown in the figure, the spectrum reflects the corresponding relationship between the luminous intensity of the light source in different wavelength bands. Figure 5 It can be seen that most of the blue light emitted from the laser diode is converted into yellow light, but a small part of the blue light is not converted by the fluorescent layer in the wavelength conversion sheet and is directly reflected. This small part of the blue light and the yellow light are mixed together to form white light. By comparing the areas occupied by the white light parts in the two figures, it can be obtained that the white light part of the light source designed by the present invention accounts for a higher proportion.
[0032] Further, according to Figure 2 We can also use multiple laser diodes to form a laser module array as the light source to excite the wavelength conversion plate to obtain a light source with higher output power. Figure 7 The present invention is a schematic diagram of the structure of a light source for exciting fluorescence by a laser module array, wherein a single laser diode is replaced by a laser module array (701) composed of multiple laser diodes, so that the laser light intensity I0 is increased while keeping η, τ1, and τ2 unchanged, thereby increasing the white light intensity I and increasing the light-emitting area.
[0033] like Figure 7As shown, the laser module array (701) is fixed on the laser fixed base (707), the guide rail (708) is connected to the laser base (707), a first lens base (709) is arranged on the guide rail (708) for fixing the first lens (702), a reflector and wavelength conversion plate fixed base (710) is connected on the other side of the guide rail (708), a diffusion plate (703), a reflector (704), a second lens (705), and a wavelength conversion plate (706) are arranged thereon, and at the same time, the central normals of the laser module array (701), the first lens (702), the diffusion plate (703), the second lens (705), and the wavelength conversion plate (706) are ensured to coincide with each other and to be consistent with the opening direction of the reflector (704), so as to ensure the alignment of the optical path. Its working principle is the same as that of the light source for exciting fluorescence by a single laser diode. Because the guide rail (708) is arranged, the first lens (702) can be adjusted in the normal direction as needed.
[0034] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments. Without departing from the principles, the embodiments of the present invention may be deformed or modified in any way.
Claims
1. A light source for laser-excited fluorescence, characterized in that: It includes a laser diode, a first lens, a diffusion sheet, a reflection sheet, a second lens, a wavelength conversion sheet, a laser diode fixing base, a reflection sheet base, a wavelength conversion sheet fixing base, a glass window, and a protective cover.
2. A laser-excited fluorescence light source according to claim 1, characterized in that: The normal directions of the laser diode, the first lens, the diffusion sheet, the second lens and the wavelength conversion sheet are on the same axis.
3. The laser-excited fluorescence light source according to claim 1, characterized in that: The laser diode may be a single laser diode or a laser module array composed of multiple laser diodes.
4. The laser-excited fluorescence light source according to claim 1, characterized in that: The laser diode emits a laser with a wavelength between 430nm and 470nm.
5. The laser-excited fluorescence light source according to claim 1, characterized in that: The first lens is located behind the laser diode and before the diffusion plate.
6. The laser-excited fluorescence light source according to claim 1, characterized in that: The diffusion sheet is located behind the first lens and in front of the reflection sheet.
7. The laser-excited fluorescence light source according to claim 1, characterized in that: The diffusion angle of the diffuser to the laser is between 0.5° and 10°.
8. The laser-excited fluorescence light source according to claim 1, characterized in that: The thickness of the diffusion sheet is between 0.3 mm and 2.0 mm.
9. The laser-excited fluorescence light source according to claim 1, characterized in that: The reflective sheet is behind the diffusion sheet and before the second lens.
10. The laser-excited fluorescence light source according to claim 1, characterized in that: The reflectivity of the reflective sheet to white light (wavelength of 400nm-750nm) is greater than 95%.
11. The laser-excited fluorescence light source according to claim 1, characterized in that: The second lens is located behind the reflective sheet and before the wavelength conversion sheet.
12. The laser-excited fluorescence light source according to claim 1, characterized in that: The first and second lenses are both convex lenses.
13. The laser-excited fluorescence light source according to claim 1, characterized in that: The wavelength conversion sheet comprises a metal substrate with good thermal conductivity, a reflective film and a fluorescent material in sequence.
14. The laser-excited fluorescence light source according to claim 1, characterized in that: The wavelength conversion sheet converts laser light with a wavelength between 430nm and 470nm into fluorescence light with a wavelength between 400nm and 700nm.
15. The laser-excited fluorescence light source according to claim 1, characterized in that: The fluorescent material contained in the wavelength conversion sheet is one or more combinations of the following materials: YAG-Ce-based fluorescent material, LuAG-Ce-based fluorescent material, or oxynitride fluorescent material.