CN114245518A - Spectrum fitting method - Google Patents

Spectrum fitting method Download PDF

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CN114245518A
CN114245518A CN202111414734.0A CN202111414734A CN114245518A CN 114245518 A CN114245518 A CN 114245518A CN 202111414734 A CN202111414734 A CN 202111414734A CN 114245518 A CN114245518 A CN 114245518A
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led
spectrum
leds
fitting
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CN114245518B (en
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贺晓阳
赵晨宇
郁玲
邹念育
高英明
杨轶
曹帆
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Dalian Polytechnic University
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V19/00—Fastening of light sources or lamp holders
    • F21V19/001—Fastening of light sources or lamp holders the light sources being semiconductors devices, e.g. LEDs
    • F21V19/003—Fastening of light source holders, e.g. of circuit boards or substrates holding light sources
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
    • F21V29/50—Cooling arrangements
    • F21V29/60—Cooling arrangements characterised by the use of a forced flow of gas, e.g. air
    • F21V29/67—Cooling arrangements characterised by the use of a forced flow of gas, e.g. air characterised by the arrangement of fans
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
    • F21V29/50—Cooling arrangements
    • F21V29/70—Cooling arrangements characterised by passive heat-dissipating elements, e.g. heat-sinks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
    • F21V29/85—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems characterised by the material
    • F21V29/89—Metals
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/20—Controlling the colour of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/345—Current stabilisation; Maintaining constant current
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • H05B47/175—Controlling the light source by remote control
    • H05B47/19—Controlling the light source by remote control via wireless transmission
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00—Light-generating elements of semiconductor light sources
    • F21Y2115/10—Light-emitting diodes [LED]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

The invention relates to a spectrum fitting method, which comprises the steps of firstly collecting a target spectrum and spectrum data of an optional LED under a specific current, and then dividing the target spectrum into a gentle section and a steep section according to the steep degree of the waveform change of the target spectrum. The optimal number of LEDs in each waveband of the target spectrum is found by measuring the spectrum data of the LEDs with different peak wavelengths and the target spectrum and using different numbers of LEDs in different wavebands. And determining the types and the number of the LEDs used in different wave bands according to the fitting result, and realizing accurate regulation and control of the output irradiance of each LED by utilizing a mode of outputting PWM by a microcontroller. The invention can find the optimal LED combination when the total number of the LEDs is certain, and finally outputs the target spectrum with high fitting degree.

Description

Spectrum fitting method
Technical Field
The invention belongs to the field of illumination control, and particularly relates to a spectrum fitting method.
Background
The spectrum adjustable light source is widely applied to the fields of radiometric calibration of optical remote sensors, sunlight simulation, biological illumination and the like, and the selection of the light source is crucial to the precision of the simulated spectrum. Compared with the defects of high cost, short service life, low quantum efficiency, high maintenance cost, uncontrollable emission spectrum and the like of the traditional spectrum, the LED serving as the component of the spectrum-adjustable light source has more advantages, the cost is lower, the service life is long, the quantum efficiency is high, the spectrum emission is relatively narrow, the output irradiance is approximately in direct proportion to the input current, and the fitting spectrum can be more accurately regulated and controlled.
The existing spectrum-adjustable light source system integrates a large number of LEDs, can meet the full coverage of visible light bands, infrared bands and ultraviolet bands, but the problems of serious system heating, high power consumption, inconvenient current control and the like caused by the large number of LEDs are also caused, and the spectrum-adjustable light source system is not suitable for specific conditions requiring system input current, power consumption and the like when the number of LEDs is required to be certain. According to the spectrum-adjustable light source and the adjusting method disclosed by the invention patent CN110954217A, all LEDs are integrated on one LED array lamp panel, the initial current of each LED is calculated through a multiple linear regression algorithm, and the output spectrum accuracy is further improved through a feedback mechanism of the initial current, but when the total number of the LEDs is required to be constant, the optimal LED combination cannot be found.
Disclosure of Invention
The invention aims to provide a spectrum fitting method to fit any spectrum.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a spectrum fitting method applies a spectrum adjustable light source system which comprises a system controller, a microcontroller, an adjustable constant current source, an LED driving module, an LED module, a temperature control module, a spectrometer and an integrating sphere.
The system controller is connected with the microcontroller, the microcontroller is connected with the LED driving module, the LED driving module is connected with the LED module, the LED module is connected with the integrating sphere, the integrating sphere is connected with the spectrometer, the adjustable constant current source supplies power to the LED driving module, and the temperature control module is installed on the LED module.
The spectrum fitting method comprises the following steps:
s1, collecting spectrum data of a target spectrum by using a spectrometer, and simultaneously collecting spectrum data of a plurality of LEDs with different peak wavelengths when the LEDs input respective corresponding rated currents, wherein the collected target spectrum data points and the LEDs under the corresponding input currents are required to be the same in number.
S2, dividing the target spectrum into a gentle wave band and a steep wave band according to the steep degree of the waveform change on different wave bands of the target spectrum; if the waveform slope exceeds 0.5, the steep section is obtained, otherwise, the gentle section is obtained.
S3, determining the total number N of used LEDs according to system design requirements, selecting N LEDs from the LEDs with different peak wavelengths collected in the step 1, enabling the peak wavelengths of the selected LEDs to be distributed at equal intervals in the whole wave band range of a target spectrum, determining the number of the LEDs used on the gentle section and the steep section at the moment, then continuously reducing the number of the LEDs used on the gentle wave band to 1, increasing the number of the LEDs used on the steep section to N-1, and obtaining a plurality of groups of different LED selection schemes.
And S4, calculating the fitting coefficient of each LED under different LED selection schemes through a multiple linear regression algorithm according to the collected target spectrum and the spectrum data of the N selected LEDs, thereby obtaining the fitting spectrum under the different LED selection schemes.
And S5, calculating and comparing the fitting degrees of the fitting spectra under different LED selection schemes, finding the scheme with the highest fitting degree, and determining the optimal LED selection combination.
S6, determining the actual required current value of each LED, which comprises the following steps:
suppose that the kth LED is at current IkM spectral data S are measuredk(λi) (i is 1, 2, 3, …, m), and the fitting coefficient of the kth LED is calculated to be e by a multiple linear regression algorithmkAnd determining the actual required current value e of the kth LED by combining the characteristic that the output radiant flux of the LED is approximately proportional to the input currentk*IkAnd the required current can be output by adjusting the PWM duty ratio.
In the above method for fitting a spectrum, preferably, the step S1 specifically includes:
m spectrum data are collected for the target spectrum to obtain m data points f (lambda)i) (i ═ 1, 2, 3, …, m), and the spectra of the individual LEDs at the input of their respective rated currents were measured to yield m data points S (λ @)i) ( i 1, 2, 3, …, m), and after n LED spectra are measured successively, LED spectrum data set S is obtainedj(λi)(i＝1，2，，3，…，m，j＝1，2，，3，…n)。
In the above method for fitting a spectrum, preferably, the step S4 specifically includes:
after the LED spectrum data and the target spectrum data are obtained, fitting the spectrum L (lambda) into L (lambda) ═ e by the spectrum superposition principle1·S1(λi)+e2·S2(λi)+…+en·Sn(λi)(i＝1，2，3，…，m)；
Recording vector S1＝(S1(λ1)，S1(λ2)，…，S1(λm))；
The matrix A ═ S1，S2，…，Sn)，b＝(f(λ1)，f(λ2)，…，f(λn))T，x＝(e1，e2，…，en) And thus, an equation set Ax is constructed, the solution x of the equation set is the fitting coefficient of each LED, and finally, a fitting spectrum can be obtained through calculation.
In the above method for fitting a spectrum, preferably, the step S5 specifically includes:
to illustrate the degree of similarity between the fitted spectrum and the target spectrum, a correlation coefficient R is used2The accuracy degree of the spectrum fitted by different monochromatic LED combinations is represented by the expression
Figure BDA0003374862470000031
Wherein y is spectral data, yaIs the mean value of y, yiA mathematical expectation of y; r2Less than or equal to 1, correlation coefficient R2The larger the fitting accuracy, if R2If 1, the fitted spectrum completely falls on the target spectrum; correlation coefficient R of fitting spectrum under different groups of LED selection schemes is calculated respectively2Then, the degrees of fit of the different groups are compared and the correlation coefficient R is found2And the corresponding LED selection scheme of the largest group is the optimal LED selection combination.
In the above spectrum fitting method, preferably, in step S3, the selected LEDs have peak wavelengths that are distributed at equal intervals in the whole wavelength band of the target spectrum, and the intervals are 20 nm.
In the spectrum fitting method, in a preferred mode, the system controller comprises a PC end upper computer and a mobile phone end, and the mobile phone end utilizes Bluetooth to remotely regulate and control the dimming system.
In the spectrum fitting method, in an optimal mode, the LED driving module is composed of a plurality of parallel LED drivers supporting PWM dimming with adjustable voltage reduction, and is powered by the adjustable constant current source; each LED driver supporting PWM dimming is correspondingly connected with one LED in the LED module, and the input current value of the corresponding LED is adjusted according to the PWM signal transmitted by the microcontroller.
According to the spectrum fitting method, in a preferred mode, the LED module is composed of a plurality of LEDs, the LEDs are welded on the square aluminum-based circuit board and are arranged in a regular hexagon shape, and the distances between the LEDs are the same.
In the above spectrum fitting method, preferably, the temperature control module is composed of two parts, namely an aluminum heat sink and an external fan; the aluminum radiator is connected with the square aluminum-based circuit board where the LEDs are located through heat-conducting silicone grease, and the aluminum radiator is actively cooled by the external fan.
The invention has the beneficial effects that: when a target spectrum is fitted, if the total number of LEDs required to be used is certain, an optimal LED selection scheme can be found and the actually required current value of each LED is determined through the spectrum fitting method, a microcontroller outputs a plurality of paths of different current control signals to an LED driving module, the LED driving module outputs the corresponding required current value of each LED, the output irradiance of different LEDs is different, and finally the spectrums are superposed to obtain a fitting spectrum with high fitting degree. The fitting degree of the fitting spectrum actually obtained is measured by using the spectrometer and the integrating sphere, and the temperature control module can ensure the long-time stable work of the system.
Drawings
FIG. 1 is a system diagram of a spectrally tunable light source system according to an embodiment of the present invention;
fig. 2 is a circuit diagram of an LED driving module of a spectrally tunable light source system according to an embodiment of the present invention;
FIG. 3 is a block diagram of a temperature control module of a spectrally tunable light source system according to an embodiment of the present invention;
fig. 4 is a schematic flowchart of a spectrum fitting method according to an embodiment of the present invention.
In the figure: 1. a system controller; 2. a microcontroller; 3. an adjustable constant current source; 4. an LED driving module; 5. an LED module; 6. a temperature control module; 7. an integrating sphere; 8. a spectrometer; 6a, an aluminum radiator; 6b, a fan.
Detailed Description
The specific embodiment is as follows:
for a detailed description of the technical features, practical objects and final effects of the present invention, embodiments of the present invention will be described below with reference to the accompanying drawings.
The invention relates to a spectrum fitting method, which applies a spectrum adjustable light source system. Referring to fig. 1, the spectrally adjustable light source system includes a system controller 1, a microcontroller 2, an adjustable constant current source 3, an LED driving module 4, an LED module 5, a temperature control module 6, an integrating sphere 7, and a spectrometer 8.
The system controller 1 is connected with the microcontroller 2, the microcontroller 2 is connected with the LED driving module 4, the LED driving module 4 is connected with the LED module 5, the LED module 5 is connected with the integrating sphere 7, the integrating sphere 7 is connected with the spectrometer 8, the adjustable constant current source 3 supplies power for the LED driving module 4, and the temperature control module 6 is installed on the LED module 5.
The microcontroller 2 is connected with the system controller 1 through a Serial Peripheral Interface (SPI), according to a spectrum fitting result, the system controller 1 sends a dimming signal to the microcontroller 2, the microcontroller 2 converts the received dimming signal into a PWM signal (such as PWM1, PWM2, and PWM3...... PWMn in fig. 1) with a different duty ratio through a digital-to-analog converter, and transmits the PWM signal to the LED driving module 4, and then the LED driving module 4 drives each LED on the LED module 5 to output a specific irradiance.
The system controller 1 comprises a mobile phone end and a PC end, wherein the mobile phone end realizes the regulation and control of the microcontroller by using Bluetooth, and the PC end realizes the regulation and control of the microcontroller 2 by using a Serial Peripheral Interface (SPI) to connect with the microcontroller 2; the mobile phone end communicates with the microcontroller 2 through Bluetooth to realize remote portable adjustment of the system light source.
Referring to fig. 2, the LED driving module 4 is composed of a plurality of parallel LED drivers (such as P1, P2, and P3...... P11 in fig. 2) with adjustable voltage reduction supporting PWM dimming, and is powered by an adjustable constant current source 3. Each of the LED drivers supporting PWM dimming is connected to one LED (e.g., LED1, LED2, LED3...... LED11 in fig. 2) in the LED module 5, and adjusts an input current value of the corresponding LED according to a PWM signal transmitted by the microcontroller 2. The module can be expanded, and more LEDs can be controlled in a mode of adding an LED driver when fitting a spectrum with a wide wavelength range and complex waveform change, so that the fitting precision is improved.
The LED module 5 is composed of a plurality of LEDs, all the LEDs are welded on the square aluminum-based circuit board and are arranged in the shape of a regular hexagon, and the distances between the LEDs are the same. The luminous intensity and the spectral characteristic of the LED are sensitive to temperature change, and in order to avoid errors caused by the temperature change, the system dissipates heat through the temperature control module.
The temperature control module 6 is composed of two parts. The aluminum radiator 6a is connected with the LED square aluminum-based circuit board through heat-conducting silicone grease, and then is actively cooled by an external fan 6 b;
referring to fig. 3, an aluminum heat sink 6a is connected to the LED quad-aluminum based circuit board.
Referring to fig. 4, a spectrum fitting method applied to the spectrum tunable light source system as described above includes the steps of:
s1, collecting spectrum data of a target spectrum by using a spectrometer, and simultaneously collecting spectrum data of a plurality of LEDs with different peak wavelengths when the LEDs input respective corresponding rated currents, wherein the collected target spectrum data points and the LEDs under the corresponding input currents are required to be the same in number;
s2, dividing the target spectrum into a gentle wave band and a steep wave band according to the steep degree of the waveform change on different wave bands of the target spectrum, wherein the steep wave band is generally considered to be a steep section when the waveform slope exceeds 0.5, otherwise the steep wave band is considered to be a gentle section;
s3, determining the total number N of used LEDs according to system design requirements, selecting N LEDs from the LEDs with different peak wavelengths collected in the step 1, enabling the peak wavelengths of the selected LEDs to be distributed at equal intervals in the whole wave band range of a target spectrum, determining the number of the LEDs used on the gentle section and the steep section at the moment, then continuously reducing the number of the LEDs used on the gentle wave band to 1, increasing the number of the LEDs used on the steep section to N-1, and obtaining a plurality of groups of different LED selection schemes.
In general, the selected LEDs have peak wavelengths that are equally spaced over the entire wavelength band of the target spectrum, with an interval of 20nm, and one LED is used at an interval of 20nm, for example, 15 LEDs are used at a wavelength band of 300nm, and the resulting fitted spectrum has relatively high accuracy and substantially meets the design requirements. The total number of LEDs used is determined by design requirements, such as the total power consumption of the system, and determines the maximum number of LEDs that can be used.
S4, calculating the fitting coefficient of each LED under different LED selection schemes through a multiple linear regression algorithm according to the collected target spectrum and the spectrum data of the N selected LEDs, and obtaining the fitting spectrum under the different LED selection schemes;
s5, calculating and comparing fitting degrees of fitting spectra under different LED selection schemes, finding the scheme with the highest fitting degree, and determining the optimal LED selection combination;
s6, determining the actual required current value of each LED, which comprises the following steps:
suppose that the kth LED is at current IkM spectral data S are measuredk(λi) (i is 1, 2, 3, …, m), and the fitting coefficient of the kth LED is calculated to be e by a multiple linear regression algorithmkAnd determining the actual required current value e of the kth LED by combining the characteristic that the output radiant flux of the LED is approximately proportional to the input currentk*IkAnd the required current can be output by adjusting the PWM duty ratio.
The step S1 is specifically as follows:
m spectrum data are collected for the target spectrum to obtain m data points f (lambda)i) (i ═ 1, 2, 3, …, m), and the spectra of the individual LEDs at the input of their respective rated currents were measured to yield m data points S (λ @)i) ( i 1, 2, 3, …, m), and after n LED spectra are measured successively, LED spectrum data set S is obtainedj(λi)(i＝1，2，，3，…，m，j＝1，2，，3，…n)。
The step S4 specifically includes:
after the LED spectrum data and the target spectrum data are obtained, fitting the spectrum L (lambda) into L (lambda) ═ e by the spectrum superposition principle1·S1(λi)+e2·S2(λi)+…+en·Sn(λi) ( i 1, 2, 3, …, m) and the vector S is written1＝(S1(λ1)，S1(λ2)，…，S1(λm) The matrix a ═ S1，S2，…，Sn)，b＝(f(λ1)，f(λ2)，…，f(λn))T，x＝(e1，e2，…，en) And thus, an equation set Ax is constructed, the solution x of the equation set is the fitting coefficient of each LED, and finally, a fitting spectrum can be obtained through calculation.
Step S5 specifically includes:
to illustrate the degree of similarity between the fitted spectrum and the target spectrum, a correlation coefficient R is used2The accuracy degree of the spectrum fitted by different monochromatic LED combinations is represented by the expression
Figure BDA0003374862470000061
Wherein y is spectral data, yaIs the mean value of y, yiIs a mathematical expectation of y. R2Less than or equal to 1, correlation coefficient R2The larger the fitting accuracy, if R2The fit spectrum falls exactly on the target spectrum, 1. Correlation coefficient R of fitting spectrum under different groups of LED selection schemes is calculated respectively2Then, the degrees of fit of the different groups are compared and the correlation coefficient R is found2And the corresponding LED selection scheme of the largest group is the optimal LED selection combination. And determining the actually required current value of each LED by combining the spectral data measured by each LED under the specific current and the corresponding fitting coefficient. The adjusting microcontroller outputs multiple paths of PWM signals with different duty ratios to the LED driving module, and the LED drivers which are connected in parallel and can adjust the voltage and support the PWM dimming can output specific current values to all LEDs on the LED module according to the input PWM signals so as to synthesize fitting spectra.
Referring to fig. 1 to 3, embodiment 1 of the present invention is:
a spectrum fitting method applies a spectrum adjustable light source system which comprises a system controller 1, a microcontroller 2, an adjustable constant current source 3, an LED driving module 4, an LED module 5, a temperature control module 6, an integrating sphere 7 and a spectrometer 8.
Referring to fig. 1, a system controller 1 is connected with a microcontroller 2, the microcontroller 2 is connected with an LED driving module 4, the LED driving module 4 is connected with an LED module 5, the LED module 5 is connected with an integrating sphere 7, the integrating sphere 7 is connected with a spectrometer 8, an adjustable constant current source 3 supplies power to the LED driving module 4, and a temperature control module 6 is installed on the LED module 5. The system controller is a PC end upper computer or a mobile phone control end, and the mobile phone control end can realize remote portable regulation and control of the light source spectrum by utilizing Bluetooth.
As shown in fig. 1, the microcontroller 2 is connected to the system controller 1(PC end upper computer or mobile phone end) through a Serial Peripheral Interface (SPI), according to the spectrum fitting result, the system controller 1 sends a dimming signal to the microcontroller 2, the microcontroller 2 converts the received dimming signal into a PWM signal with a different duty ratio through a digital-to-analog converter (DAC) and transmits the PWM signal to the LED driving module 4, and then each LED on the LED module 5 outputs a specific irradiance.
Referring to fig. 2, the LED driving module 4 is composed of a plurality of parallel LED drivers supporting PWM dimming with adjustable voltage reduction, an input voltage of 7V to 30V, an output current of 700mA, and a power of 3W, and is powered by the adjustable constant current source 3. Each LED driver supporting PWM dimming is correspondingly connected with one LED in the LED module 5, and the input current value of the corresponding LED is adjusted according to the PWM signal transmitted by the microcontroller 2.
In example 1, 11 LED drivers are used in total, and 11 LEDs having different peak wavelengths are controlled, respectively, and all the LED peak wavelengths range from 400nm to 700 nm.
As shown in fig. 3, the LED module 5 is composed of 11 LED lamp beads, all the LEDs are soldered on a 10 × 10cm square aluminum-based circuit board and arranged in a regular hexagon shape, and the distance between the LEDs is 2.2 cm. The luminous intensity and spectral characteristics of an LED are sensitive to temperature variations, which may shift the peak wavelength of the LED. In order to avoid errors caused by temperature variations, the system dissipates heat through the temperature control module 6.
As shown in fig. 3, an aluminum heat sink 6a is attached to the LED square aluminum-based circuit board. The temperature control module 6 consists of two parts. The aluminum radiator 6a is connected with the LED square aluminum-based circuit board through heat-conducting silicone grease, and then is actively cooled by the external fan 6 b.
Referring to fig. 4, embodiment 2 of the present invention is:
a spectrum fitting method is applied to the spectrum adjustable light source system and comprises the following steps:
s1, collecting spectrum data of a target spectrum by using a spectrometer, and simultaneously collecting spectrum data of a plurality of LEDs with different peak wavelengths when the LEDs input respective corresponding rated currents, wherein the collected target spectrum data points and the LEDs under the corresponding input currents are required to be the same in number.
The peak wavelengths of the series of LEDs used in this example were measured as shown in table 1, and their electrical parameters as shown in table 2.
TABLE 1 Peak wavelength of selectable series of LEDs
Figure BDA0003374862470000081
TABLE 2 Peak wavelength and Electrical parameters of alternative series of LEDs
Peak wavelength/nm 385 392 397 409 421 423 431 446
Rated voltage/V 3.2～3.8 3.2～3.4 3.2～3.8 3.2～3.4 3.2～3.4 3.2～3.4 3.2～3.4 1.8～2.2
Rated current/mA 500 500 500 700 700 700 700 700
Peak wavelength/nm 461 463 470 487 495 519 528 576
Rated voltage/V 3.2～3.4 3.2～3.4 3.2～3.4 3.2～3.4 3.2～3.4 3.2～3.6 3.2～3.6 3.0～3.4
Rated current/mA 700 700 700 700 700 700 700 700
Peak wavelength/nm 594 610 626 638 643 660 669 687
Rated voltage/V 3.0～3.4 2.2～2.4 2.2～2.4 2.2～2.6 1.8～2.2 2.2～2.6 1.8～2.2 2.3～3.6
Rated current/mA 700 500 500 700 700 700 700 700
S2, dividing the target spectrum into a gentle wave band and a steep wave band according to the steep degree of the waveform change on different wave bands of the target spectrum, wherein the steep wave band is generally considered to be a steep section when the waveform slope exceeds 0.5, otherwise the steep wave band is considered to be a gentle section; in the embodiment, the gentle wave band is 500-630 nm, and the steep wave band is 400-500 nm, 630-700 nm.
And S3, fitting the target spectrum by using 11 LEDs, and selecting 11 LED combinations with peak wavelengths in a 400 nm-700 nm wave band and distributed as far as possible at equal intervals from the LEDs with different peak wavelengths collected in the step 1. At this time, 6 LEDs are used in the gentle section and 5 LEDs are used in the steep section. And continuously reducing the number of the LEDs on the gentle wave band until 1, and increasing the number of the LEDs on the steep wave band until 10 to obtain six different LED selection schemes. When the peak wavelengths of the selected LEDs are distributed at equal intervals in the whole wave band range of the target spectrum, and the intervals are 20nm, the accuracy of the obtained fitting spectrum is relatively high, and the design requirements are basically met. The total number of LEDs used is determined by design requirements, such as the total power consumption of the system, and determines the maximum number of LEDs that can be used.
And S4, calculating the fitting coefficient of each LED under different LED selection schemes through a multiple linear regression algorithm according to the collected target spectrum and the spectrum data of the 11 LEDs with different peak wavelengths, thereby obtaining the fitting spectrum under the different LED selection schemes.
In this embodiment, the target spectral wavelength range is 400nm to 700nm, and fitting is performed by using 11 LEDs having different peak wavelengths. With 1nm as an interval, 300 spectrum data points are respectively collected for the target spectrum and all the LEDs, and are respectively ftarget(λi) ( i 1, 2, 3, …, 300) ( i 1, 2, 3, …, 300), 11 LEDs constitute a spectral data set Sj(λi) (i-1, 2, 3, …, 300, j-1, 2, 3, … 11) and fitting a spectrum L (λ) to L (λ) e by the principle of spectral superposition1·S1(λi)+e2·S2(λi)+…+en·Sn(λi) ( i 1, 2, 3, …, 300, n1, 2, 3, … 11), then e1To e11I.e. the fitting coefficients of 11 LEDs. And obtaining the corresponding LED fitting coefficients of different LED selection schemes according to the data acquisition and fitting coefficient calculation method.
And S5, calculating and comparing the fitting degrees of the fitting spectra under different LED selection schemes, finding the scheme with the highest fitting degree, and determining the optimal LED selection combination.
In this step, the correlation coefficient R is used2The accuracy degree of the spectrum fitted by different monochromatic LED combinations is represented by the expression
Figure BDA0003374862470000091
Wherein y is spectral data, yaIs the mean value of y, yiIs a mathematical expectation of y. R2Less than or equal to 1, correlation coefficient R2The larger the fitting accuracy, if R2The fit spectrum coincides with the target spectrum, 1.
Respectively calculating the fitting degree and the correlation coefficient R under different LED selection schemes in the step 42The highest is the best LED option.
The present embodiment exemplifies the calculation process of the correlation coefficient by using a combination of 8 LEDs in the steep segment and 3 LEDs in the gentle segment. Target spectrum ftargetChlorophyll b absorption spectrum of 400 to 700nm (0.057, 0.0574, 0.0578, 0.001) and ffittingFirst, f is calculated as a fitted spectrum (0.0172, 0.0201, 0.0232,.., 0.0015) obtained by combining the LEDs and corresponding fitting coefficients, each of which contains three hundred spectral data pointsfittingAnd ftargetThe sum of the squares of the residuals of (1) is Rss＝∑(ftarget-ffitting)20.0414, f is calculatedtargetMathematical expectation of (f)a0.0514, by correlation coefficient R2The expression of (c) is calculated to yield:
Figure BDA0003374862470000092
the relationship between the number of LEDs used in the steep section and the correlation coefficient of the fitted spectrum obtained by the above calculation is shown in Table 3.
TABLE 3 correlation coefficient of LED usage number on steep segment and its corresponding fitting spectrum
Number of LEDs used in steep section 5 6 7 8 9 10
Correlation coefficient 0.9038 0.9142 0.9274 0.9315 0.9266 0.8876
As can be seen from table 3, 8 LEDs are used in the steep segment, 3 LEDs are used in the gentle segment, and the highest correlation coefficient is 0.9315, so as to determine the optimal LED selection combination.
The peak wavelength of the LED used with the optimal LED selection combination and the corresponding fitting coefficient are shown in table 4.
11 LED peak wavelengths and corresponding fitting coefficients used in Table 4
Peak wavelength/nm Coefficient of fit Peak wavelength/nm Coefficient of fit
409 0.1408 576 1.0000
431 0.0168 610 1.0000
446 0.0057 643 0.0898
461 0.0517 660 0.0877
470 0.1331 669 0.0072
528 0.0741
S6, determining the actual required current value of each LED, which comprises the following steps:
and determining the actually required current value of each LED by combining the rated current value and the fitting coefficient when the spectral data are measured. Suppose that the kth LED is at current IkM spectral data S are measuredk(λi) (i ═ 1, 2, 3, …, m). Calculating by a multiple linear regression algorithm to obtain a fitting coefficient e of the kth LEDk. Combining the characteristic that the output radiant flux of the LED is approximately proportional to the input current, determining the actual required current value of the kth LED as ek*IkAnd the required current can be output by adjusting the PWM duty ratio. The current values corresponding to the 11 selected LEDs are shown in table 4. Taking an LED with a peak wavelength of 409nm as an example, the rated current I is shown in Table 1kAt 700mA, the fitting coefficient e is shown in Table 4k0.1408, the current value is 700mA × 0.1408 mA to 98.45 mA.
11 LED peak wavelengths and corresponding current values used in Table 4
Figure BDA0003374862470000101
Figure BDA0003374862470000111
The invention has the beneficial effects that: when the target spectrum is fitted, if the total number of LEDs required to be used is constant, the optimal LED selection scheme can be found and the actual required current value of each LED is determined through the spectrum fitting method, a plurality of paths of different current control signals are output to an LED driving module through a microcontroller, then the LED driving module outputs the required current value corresponding to each LED (namely, the input current value of each LED on the LED module is controlled in a mode that the microcontroller outputs a plurality of paths of PWM wave signals with different duty ratios), so that the output irradiance of different LEDs is different, and finally the spectrum is superposed to obtain the fitting spectrum with high fitting degree. The fitting degree of the fitting spectrum actually obtained by the spectrometer and the integrating sphere is measured, the temperature control module can ensure long-time stable work of the system, and the LED cannot cause spectrum deviation to finally cause errors due to temperature change.
In summary, the present invention provides a spectrum fitting method. The same number of spectrum data points are collected at corresponding wavelengths for a target spectrum and optional LEDs, and the spectrum data points are divided into a gentle wave band and a steep wave band according to the steep degree of the change of the target spectrum waveform. After the total number of the used LEDs is determined, the LED combinations with peak wavelengths distributed at intervals as much as possible in the target spectral band range are selected, and the number of the used LEDs on different bands is determined. The number of LEDs used in the gentle section is continuously reduced, the number of LEDs used in the steep section is increased, and a plurality of groups of LED selection schemes are obtained. And calculating the fitting coefficients of different LEDs under different LED selection schemes by utilizing a multiple linear regression algorithm, and calculating to obtain corresponding fitting spectra. And comparing the fitting accuracy of the fitting spectra of different groups, finding the combination with the highest fitting accuracy, wherein the corresponding LED selection scheme is the optimal combination. The system controller controls the microcontroller to output a plurality of paths of PWM signals with different duty ratios to the LED driving module, and the LED driving module consists of a plurality of LED drivers connected in parallel and is powered by an adjustable constant current source. Each LED driver is correspondingly connected with one LED in the LED module, and the actually required current value of each LED is determined by the fitting coefficient and the corresponding current value when the spectrum is measured. In order to prevent errors caused by temperature change and guarantee long-time work of the system, all LEDs are arranged in a regular hexagon shape and are welded on a square aluminum-based circuit board, meanwhile, heat-conducting silicone grease is used for installing the LEDs on an aluminum radiator, an external fan 6b is used for active cooling, and finally the obtained actual spectrum can be measured by a spectrometer and an integrating sphere. The output irradiance of the LED light source is controlled by adjusting the input current values of different LEDs, the output spectrum of the system can be adjusted according to the spectrum superposition principle, the number of LED drivers can be expanded when the target spectrum with more complex wavelength change and wider wavelength range is fitted, and more LEDs are used for fitting the target spectrum to improve the fitting precision.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.

Claims (9)

1. A spectrum fitting method is characterized in that a spectrum adjustable light source system is applied, and the spectrum adjustable light source system comprises a system controller, a microcontroller, an adjustable constant current source, an LED driving module, an LED module, a temperature control module, a spectrometer and an integrating sphere;
the system controller is connected with the microcontroller, the microcontroller is connected with the LED driving module, the LED driving module is connected with the LED module, the LED module is connected with the integrating sphere, the integrating sphere is connected with the spectrometer, the adjustable constant current source supplies power to the LED driving module, and the temperature control module is installed on the LED module;
the spectrum fitting method comprises the following steps:
s1, collecting spectrum data of a target spectrum by using a spectrometer, and simultaneously collecting spectrum data of a plurality of LEDs with different peak wavelengths when the LEDs input respective corresponding rated currents, wherein the collected target spectrum data points and the LEDs under the corresponding input currents are required to be the same in number;
s2, dividing the target spectrum into a gentle wave band and a steep wave band according to the steep degree of the waveform change on different wave bands of the target spectrum; if the waveform slope exceeds 0.5, the steep section is obtained, otherwise, the gentle section is obtained;
s3, determining the total number N of used LEDs according to system design requirements, selecting N LEDs from the LEDs with different peak wavelengths collected in the step 1, wherein the peak wavelengths of the selected LEDs are distributed at equal intervals in the whole waveband range of a target spectrum, determining the number of the LEDs used in the gentle section and the steep section at the moment, continuously reducing the number of the LEDs used in the gentle section to 1, increasing the number of the LEDs used in the steep section to N-1, and obtaining a plurality of groups of different LED selection schemes;
s4, calculating the fitting coefficient of each LED under different LED selection schemes through a multiple linear regression algorithm according to the collected target spectrum and the spectrum data of the N selected LEDs, and obtaining the fitting spectrum under the different LED selection schemes;
s5, calculating and comparing fitting degrees of fitting spectra under different LED selection schemes, finding the scheme with the highest fitting degree, and determining the optimal LED selection combination;
s6, determining the actual required current value of each LED, which comprises the following steps:
suppose that the kth LED is at current IkM spectral data S are measuredk(λi) (i is 1, 2, 3, …, m), and the fitting coefficient of the kth LED is calculated to be e by a multiple linear regression algorithmkDetermining the actual required current value of the kth LED as ek*IkAnd the required current can be output by adjusting the PWM duty ratio.
2. The spectrum fitting method according to claim 1, wherein the step S1 is as follows:
m spectrum data are collected for the target spectrum to obtain m data points f (lambda)i) (i ═ 1, 2, 3, …, m), and the spectra of the individual LEDs at the input of their respective rated currents were measured to yield m data points S (λ @)i) (i 1, 2, 3, …, m), and after n LED spectra are measured successively, LED spectrum data set S is obtainedj(λi)(i＝1，2，，3，…，m，j＝1，2，，3，…n)。
3. The spectrum fitting method according to claim 2, wherein the step S4 specifically comprises:
after the LED spectrum data and the target spectrum data are obtained, the fitting spectrum L (lambda) is upper (lambda) ═ e according to the spectrum superposition principle1·S1(λi)+e2·S2(λi)+…+en·Sn(λi)(i＝1，2，3，…，m)；
Recording vector S1＝(S1(λ1)，S1(λ2)，…，S1(λm))；
The matrix A ═ S1，S2，…，Sn)，b＝(f(λ1)，f(λ2)，…，f(λn))T，x＝(e1，e2，…，en) And thus, an equation set Ax is constructed, the solution x of the equation set is the fitting coefficient of each LED, and finally, a fitting spectrum can be obtained through calculation.
4. The spectrum fitting method according to claim 3, wherein the step S5 is specifically as follows:
to illustrate the degree of similarity between the fitted spectrum and the target spectrum, a correlation coefficient R is used2The accuracy degree of the spectrum fitted by different monochromatic LED combinations is represented by the expression
Figure FDA0003374862460000021
Wherein y is spectral data, yaIs the mean value of y, yiA mathematical expectation of y; r2Less than or equal to 1, correlation coefficient R2The larger the fitting accuracy, if R2If 1, the fitted spectrum completely falls on the target spectrum; correlation coefficient R of fitting spectrum under different groups of LED selection schemes is calculated respectively2Then, the degrees of fit of the different groups are compared and the correlation coefficient R is found2And the corresponding LED selection scheme of the largest group is the optimal LED selection combination.
5. The method according to claim 1, wherein in step S3, the selected LEDs have peak wavelengths that are equally spaced over the entire wavelength range of the target spectrum, and the spacing is 20 nm.
6. The spectrum fitting method according to any one of claims 1 to 5, wherein the system controller comprises a PC upper computer and a mobile phone terminal, and the mobile phone terminal remotely controls the dimming system by Bluetooth.
7. The spectrum fitting method according to any one of claims 1 to 5, wherein the LED driving module is composed of a plurality of LED drivers which are connected in parallel and can reduce voltage and support PWM dimming, and is powered by the adjustable constant current source; each LED driver supporting PWM dimming is correspondingly connected with one LED in the LED module, and the input current value of the corresponding LED is adjusted according to the PWM signal transmitted by the microcontroller.
8. The spectrum fitting method according to any one of claims 1 to 5, wherein the LED module is composed of a plurality of LEDs, the LEDs are welded on a square aluminum-based circuit board and are arranged in a regular hexagon shape, and the distances between the LEDs are the same.
9. The method according to any one of claims 1 to 5, wherein the temperature control module is composed of two parts, namely an aluminum heat sink and an external fan;
the aluminum radiator is connected with the square aluminum-based circuit board where the LEDs are located through heat-conducting silicone grease, and the aluminum radiator is actively cooled by the external fan.
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