Design method of optical medium multilayer film device for improving color rendering index of LED lamp

Abstract

The invention belongs to the technical field of optics, and particularly relates to a design method of an optical medium multilayer film device for improving the color rendering index of an LED (light-emitting diode) lamp, which comprises the following steps of: performing normalization processing according to an emission spectrum curve of fluorescent powder, optimizing and inverting an optical medium regular film system by combining film system design software, and simulating the emission spectrum curve of the fluorescent powder; therefore, the color gap of the emission spectrum of the fluorescent powder is compensated through the film system, and the color rendering index of the LED lamp is also improved.

Description

Technical Field

[0001] The invention belongs to the field of optical technology, and in particular relates to a design method for an optical medium multilayer thin film device for improving the color rendering index of an LED lamp. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The currently widely used white light LED (Light-emitting diode) has the advantages of high luminous efficiency, energy saving, environmental protection, and long life. With the progress and development of related technical fields, its production cost and price are constantly decreasing, while its performance is constantly improving and improving. Therefore, white light LED is gradually replacing traditional lighting sources and becoming the mainstream light source for human lighting.

[0004] There are four main technical solutions for white light LEDs in the prior art: (1) Blue light chip + yellow light phosphor mode: The blue light emitted by the blue light chip is used to excite the yellow commercial phosphor to obtain yellow light, which is then mixed with the remaining blue light to obtain yellow-blue combined white light. This method is characterized by low cost and high light efficiency, and is currently the mainstream solution for white light LEDs. However, it has problems such as poor spectral continuity, high color temperature, poor color rendering index, high content of blue light components, and lack of red light components. (2) Blue light chip + red and green light phosphor mode: This solution supplements the lack of red light in solution (1) to improve the color rendering index. Its color temperature and color rendering index can be adjusted by adjusting the ratio of phosphors, so it has a large control range, which greatly improves the spectral indicators of white light LEDs. However, due to the use of blue light chips for excitation, there is still a blue peak problem in the spectrum, and the problem of blue light damage is inevitable. (3) RGB three-primary color LED chip mixing mode: This scheme uses red, green and blue chips to emit red light, green light and blue light respectively. The brightness and color ratio of the three LEDs can be flexibly controlled through the circuit to mix them to obtain white light. The advantage is that it has high luminous efficiency and color rendering index, but the disadvantage is that the structure is complex and the cost is high. In addition, since the light decay characteristics, temperature stability and circuit response characteristics of the three LED chips are different, the stability and durability of the light emission will be affected. The white light prepared in this way has excellent color rendering performance and high luminous efficiency, but this method requires the design of a special control circuit, and the performance of each chip is different, which will affect the life and stability of the device. (4) Near-ultraviolet / ultraviolet chip + three-primary color (blue, green, red) phosphor mode: Near-ultraviolet or ultraviolet LED chips excite blue, green and red three-primary color phosphors to emit blue light, green light and red light respectively. These three colors of light are mixed to obtain white light LED. By adjusting the ratio of the three primary color phosphors, high-quality white light with different color rendering indexes and color temperatures can be obtained. The white light LED spectrum obtained by this solution has good continuity, rich colors, a wide color range, low blue light damage, low cost, and high luminous efficiency.

[0005] In summary, the light emission of white light LED is a mixture of two or three colors of light using the principle of complementary light colors, so the problem of color deficiency is inevitable. Compared with the healthy and comfortable sunlight that humans have adapted to for a long time, there are still many defects such as poor spectral continuity, uneven light color and energy distribution. In order to obtain a lighting source closer to sunlight and meet human needs for healthy lighting, full-spectrum white light LED lighting has gradually become a research hotspot in the field of lighting. Full-spectrum white light LED requires a continuous spectrum in the wide range of visible light 380 to 760nm, smooth spectral transition, no obvious sharp peaks and valleys, and can truly restore the color of objects. The color rendering index is close to 100 (the color rendering index of the solar spectrum is 100), which is more in line with the growth law of humans and various organisms.

[0006] At present, full-spectrum white light LEDs mainly use near-ultraviolet / ultraviolet chips to excite three primary colors (blue, green, and red) phosphors, but there is still a color gap between the two colors of light in its spectrum, so it is difficult to achieve high color rendering index, high color reproduction and full-spectrum healthy lighting requirements. Therefore, in the design and manufacturing process of full-spectrum white light LEDs, effective measures need to be taken to avoid or reduce the impact of color gaps. The disclosed technologies include optimizing the ratio of phosphors, selecting more efficient fluorescent materials, and improving the spectral distribution of light sources, but the results are often not ideal. Summary of the invention

[0007] In order to solve the shortcomings of the prior art, the purpose of the present invention is to provide a design method for an optical dielectric multilayer thin film device that improves the color rendering index of LED lamps. By optimizing the design, an optical dielectric multilayer thin film device that improves the color rendering index is manufactured, so that LED lighting can be made into a truly healthy lighting method that is close to natural light.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a design method for an optical medium multilayer thin film device for improving the color rendering index of an LED lamp, wherein the LED lamp is made of near-ultraviolet / ultraviolet chips that excite three-primary color phosphors, and comprises the following steps:

[0010] Obtaining an actual emission spectrum curve of the phosphor, wherein the abscissa of the actual emission spectrum curve is wavelength and the ordinate is relative intensity;

[0011] Normalizing the ordinate of the actual emission spectrum curve of the phosphor;

[0012] The normalized ordinate is used as the discrete target of spectral transmittance, and the initial film system is obtained by optimizing it using the film system design software;

[0013] The initial film system is further optimized into an optimized film system according to the characteristics of the phosphor combined with film system design software, and an optical medium multilayer thin film device is manufactured according to the optimized film system.

[0014] As a preferred technical solution of the present invention, the method further includes using the film system design software to invert and simulate the emission spectrum curve of the phosphor and moving the peak wavelength of the simulated emission spectrum curve of the phosphor according to the characteristics of the phosphor.

[0015] As a preferred technical solution of the present invention, the formula for moving the amplitude of the peak wavelength of the simulated phosphor emission spectrum curve is λ E =2λ T -λ 0±Δλ, where λ E To optimize the peak wavelength of the film system, λ T is the target peak wavelength of the phosphor to be moved, λ 0 is the peak wavelength of the emission spectrum relative intensity normalization, and △λ is the peak wavelength empirical error fine-tuning value.

[0016] By adopting the above technical solution, the beneficial effects of the present invention are as follows: the peak wavelength and transmittance of the simulated phosphor emission spectrum curve change accordingly under the regulation of the optimized optical medium multilayer thin film device, that is, the peak wavelength of the phosphor emission spectrum can be moved by a specific wavelength using the method of the present invention. Thus, the color gap of the phosphor emission spectrum is compensated by optimizing the film system. Although the peak transmittance of the spectrum is reduced by setting the optical medium multilayer thin film device, the change in the shape of the spectrum is not large, and the characteristics of the original spectrum can be retained to a large extent. In addition, due to the dispersion characteristics of the film material, the refractive index of the film material decreases with the increase of the peak wavelength. After the center peak wavelength is shifted, the thickness of each layer of the film system will increase accordingly. It can be seen that the present invention has potential application value in solving the color gap problem in full-spectrum LED lighting. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 This is the original spectrum diagram of the phosphor measured in the embodiment of the present invention;

[0019] Figure 2 is the normalized processing result of the emission spectrum of the phosphor in the embodiment of the present invention;

[0020] Figure 3 The inversion simulation of the emission spectrum of the phosphor using the film system design software in the embodiment of the present invention;

[0021] Figure 4 It is the spectrum simulation result after the phosphor coating system is adjusted in the embodiment of the present invention. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] The term "color rendering index" in the present invention refers to a measure of the degree to which the color presented by an object under the light source to be measured matches the color presented by the object under the reference light source. CIE stipulates that a standard illuminant D is used as a reference light source, and a black body is used as a reference light source when the color temperature of the light source to be measured is lower than 5000K, and the color rendering index of the reference light source is stipulated to be 100. The color rendering index of a light source can be stipulated into three ranges. A light source with a color rendering index greater than 75 is a high-quality color rendering light source. The closer to 100, the better the color rendering; a light source with a color rendering index between 50 and 75 has average color rendering; a light source with a color rendering index less than 50 has poor color rendering. When the color rendering index of a light source is low, an object will change color or be distorted under this light source. The lower the color rendering index, the more serious the color change or distortion. At present, the color rendering index of the light source used in the printing industry is generally not less than 90, and color photography, color film and television and other color-related industries also require the use of a light source with a high color rendering index greater than 85.

[0025] The term "phosphor" in the present invention specifically refers to LED phosphor, which can absorb light of a specific wavelength and convert it into light of another wavelength. As an important component of LED lamps, it produces a light conversion process through specific substances.

[0026] The term "spectral curve" in the present invention refers to the relative intensity distribution curve of a light source. The light emitted by a light source is composed of many different wavelengths of light. Due to differences in the composition of the luminescent material of the light source and the principle of luminescence, the radiation intensity of each wavelength is also different. The spectral radiation intensity of the light source is divided according to the distribution of the peak wavelength, which we call spectral intensity distribution. A certain spectral intensity distribution shows a certain light color. The relative intensity value of the light wave at the peak wavelength of 400nm is set to 0, and the radiation power values ​​of other wavelengths of light are compared with it to obtain the corresponding values. The curve drawn with the peak wavelength of the spectrum as the horizontal coordinate and the relative intensity values ​​corresponding to each wavelength of light as the vertical coordinate is called a spectral curve.

[0027] The term "normalization processing" in the present invention refers to proportionally adjusting the relative intensity in the spectral curve so that the peak value is set to 1, so as to compare the degree and effect of the adjustment.

[0028] The term "film system design software" in the present invention is not limited in the present invention, for example: TFC, OptiLayer, EssentialMacleod, etc.

[0029] The term "initial film system" and "optimized film system" in the present invention refers to optical coating, that is, coating several layers of specific thin films on the surface of optical elements to change the propagation properties of light and enhance specific optical properties. The composition and structure of the thin films largely determine the reflection, transmission and absorption characteristics of the optical elements. "Initial film system" refers to the initial film system structure designed by film system design software. The initial film system is mostly a regular film system, that is, the film thickness of the same material is the same. The film system design software is used to calculate and optimize according to the actual needs of the phosphor. Finally, the film thickness of each layer changes, and the optimized film system is obtained.

[0030] The "optical medium multilayer thin film device" of the present invention refers to a coated optical device finally manufactured according to the optimized film system, which generally includes a lens material G as a substrate, and a multilayer thin film coated on the substrate, the thin film generally includes: H4 (titanium lanthanum oxide), Al 2 O 3 、TiO 2 、Ti 3 O 5 、 2 O 5 、NbO 2 As well as high refractive index materials represented by ZnS, and SiO 2 MgF 2 The low refractive index materials represented by etc. The matching scheme of each coating is generally selected according to the different characteristics of the phosphor.

[0031] A typical embodiment of the present invention provides a design method for an optical medium multilayer thin film device for improving the color rendering index of an LED lamp, wherein the LED lamp is made of near-ultraviolet / ultraviolet chips that excite three primary color phosphors, and 1. comprises the following steps:

[0032] Obtaining an actual emission spectrum curve of the phosphor, wherein the abscissa of the actual emission spectrum curve is wavelength and the ordinate is relative intensity;

[0033] Normalizing the ordinate of the actual emission spectrum curve of the phosphor;

[0034] The normalized ordinate is used as the discrete target of spectral transmittance. The initial film system can be a high-reflection film system composed of two materials with high and low refractive indices repeatedly stacked. According to experience, the number of layers is set to 20.

[0035] According to the characteristics of the phosphor and the film system design software, optimization is performed. The number of film layers can be set to be automatically added by the film system software, or can be increased or decreased manually. The optimized film system with fewer layers is preferably selected, and the initial film system is further optimized to an optimized film system. Based on the optimized film system, an optical medium multilayer thin film device is manufactured through optical vacuum coating technology.

[0036] In some embodiments, the method further comprises using the film system design software to invert a simulated phosphor emission spectrum curve and shifting a peak wavelength of the simulated phosphor emission spectrum curve according to the characteristics of the phosphor.

[0037] Furthermore, the formula for shifting the amplitude of the peak wavelength of the simulated phosphor emission spectrum curve is λ E =2λ T -λ 0 ±Δλ, where λ E To optimize the peak wavelength of the film system, λ T is the target peak wavelength of the phosphor to be moved, λ 0 is the peak wavelength of the emission spectrum relative intensity normalization, and △λ is the peak wavelength dispersion error fine-tuning value.

[0038] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0039] Example

[0040] The Sr prepared by high temperature solid phase method is selected. x Ba 1-x MgSi 4 O 10 :yEu 2+ The effectiveness of the method of the present invention is verified by using a LED white light lamp made of a series of phosphors. Although the peak wavelength of the emission spectrum of the phosphor can be adjusted between 464 and 483 nm to achieve a high color rendering index, each adjustment requires the re-preparation of the phosphor. The preparation cycle of the high-temperature solid phase method is long, the cost is high, and the energy consumption is high. For the convenience of research, the phosphor formula with a peak wavelength of 468 nm was selected as the research object. The spectrum of its original test data is shown in Figure 2. Figure 1 As shown, it can be seen that the peak wavelength of the emission spectrum of this phosphor is 468nm.

[0041] The next step is to normalize it, and the processing results are as follows Figure 2 shown.

[0042] The normalized relative intensity is used as the discrete target of spectral transmittance, and the optical thin film design software TFC is used for optimization. The initial film system is G|(HL)^S|A, where G is the substrate material, K9 glass with good spectral consistency in the visible light range is used, A represents air, H is a high refractive index material H4, and L is a low refractive index material MgF 2 , S represents the number of repetitions of high and low refractive index film layers, and the initial value is 10 (i.e. 20 layers). The final optimized film optical thickness results are as follows using the film system design software for further optimization:

[0043] G|3.11L0.49H0.04L2.29H1.03L1.20H0.42L0.88H1.53L0.68H1.08L0.17H1.76L1.47H1. 45L2.19H1.47L1.20H0.13L2.19H0.81L2.36H1.28L2.37H0.94L1.98H0.26L1.82H1.48|A

[0044] In order to verify the effect of optimizing the spectral regulation of the film system, the film system design software is further used to simulate the inversion of the phosphor emission spectrum. The simulation inversion results are as follows: Figure 3 As shown, it can be seen that the curve fits very well within the range of 400-650nm measured phosphor emission spectrum curve. Since there is no test data on both sides of the 400-650nm band, only the spectrum of the film system design curve is displayed, and two sharp peaks appear at 390nm and 685nm. After simulation, it is shown that the influence on the spectrum regulation is not significant. If there is any influence, it can be further optimized and adjusted through the film system design software.

[0045] Based on the interference theory of optical thin films, the thickness of each layer of the optical medium multilayer film is adjusted by moving the central peak wavelength using the film design software, which can achieve the adjustment of the transmittance of light at each peak wavelength. The peak wavelength of the film spectrum curve obtained by the above inversion simulation is moved, and the calculation formula for the required peak wavelength movement amplitude is: λ E =2λ T -λ 0 ±Δλ, where λ E To optimize the peak wavelength of the film system, λ T is the target peak wavelength of the phosphor to be moved, λ 0 is the peak wavelength of the normalized relative intensity of the emission spectrum, △λ is the peak wavelength empirical error fine-tuning value (a positive value, with a sign of - when moving toward the long-wave direction and a sign of + when moving toward the short-wave direction). After calculation, the shift amplitude is:

[0046] 2×481nm-468nm±△λ=494nm±△λ. If △λ is not considered, it is found that the actual peak wavelength of the movement is greater than 481nm, which means that when moving in the long-wave direction, there will be an error in the long-wave direction. Therefore, a certain amplitude value must be subtracted. When △λ is 4nm, the target peak wavelength to be moved returns to 481nm. Similarly, when moving in the band direction, the target peak wavelength to be moved is smaller, so a certain amplitude value must be added. The main reason for the generation of △λ is the dispersion of the film material, that is, the refractive index of the film material will decrease as the wavelength increases.

[0047] Therefore, the peak wavelength of the film spectrum is moved to 490nm. The results are as follows Figure 4 As shown. It can be seen that the simulated luminous intensity has changed accordingly under the adjustment of the thickness of each layer by the optical medium multilayer film, and the peak wavelength has also moved from 468nm to 481nm, that is, this method can be used to move the peak wavelength of the emission spectrum to a specific peak wavelength, indicating that it is possible to compensate for the color gap by optimizing the film system to shift the emission spectrum. The peak transmittance after adjustment has decreased, but the change in the spectral shape is not large, and the characteristics of the original spectrum can be retained to a large extent. In addition, due to the dispersion characteristics of the film material, the refractive index of the film material will decrease with the increase of the peak wavelength, and the thickness of each layer of the film system will increase accordingly after the central peak wavelength is shifted.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A design method for an optical medium multilayer thin film device for improving the color rendering index of an LED lamp, wherein the LED lamp is made of near-ultraviolet / ultraviolet chips that excite three primary colors of phosphors. It is characterized in that The steps include: Obtaining an actual emission spectrum curve of the phosphor, wherein the abscissa of the actual emission spectrum curve is wavelength and the ordinate is relative intensity; Normalizing the ordinate of the actual emission spectrum curve of the phosphor; The normalized ordinate is used as the discrete target of spectral transmittance, and the initial film system is obtained by optimizing it using the film system design software; The initial film system is further optimized into an optimized film system according to the characteristics of the phosphor combined with film system design software, and an optical medium multilayer thin film device is manufactured according to the optimized film system.

2. The design method according to claim 1, It is characterized in that The method also includes using the film system design software to invert and simulate the emission spectrum curve of the phosphor and moving the peak wavelength of the simulated emission spectrum curve of the phosphor according to the characteristics of the phosphor.

3. The design method according to claim 2, It is characterized in that The formula for shifting the peak wavelength of the simulated phosphor emission spectrum curve is λ E =2λ T -λ 0 ±Δλ, where λ E To optimize the peak wavelength of the film system, λ T is the target peak wavelength of the phosphor to be moved, λ 0 is the peak wavelength of the emission spectrum relative intensity normalization, and △λ is the peak wavelength empirical error fine-tuning value.

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