ULTRAVIOLET IRRADIATION DEVICE

RELATED APPLICATION

Priority is claimed to Japanese Patent Application No. 2016-188380, filed on Sep. 27, 2016, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION
1. Field of the Invention

The present invention relates to ultraviolet irradiation devices.

2. Description of the Related Art

Ultraviolet light is widely used in the field of ultraviolet resin hardening, and for disinfection or sterilization in medical and food processing fronts. For example, an ultraviolet light source for resin hardening is exemplified by one in which an ultraviolet light emitting diode (LED) is used. One such device is configured such that a plurality of ultraviolet LEDs having different wavelength characteristics is combined to address a plurality of types of resin having different hardening wavelengths.

Ultraviolet LEDs actually used have individual differences in wavelength characteristics and output intensity, and the target of ultraviolet irradiation have sensitivity characteristics that depend on the wavelength. For this reason, the desired effect may not be obtained or the electric power may be wastefully consumed due to excessive irradiation, unless the wavelength characteristics of the light source and the target of irradiation are properly considered.

SUMMARY OF THE INVENTION

In this background, an illustrative purpose of the present invention is to provide an ultraviolet irradiation device capable of irradiating a target of irradiation with ultraviolet light efficiently.

An ultraviolet irradiation device according to an embodiment of the present invention includes: a light source unit that includes at least one ultraviolet LED; a driver that supplies a drive current to the ultraviolet LED; and a controller that controls an operation of the driver. The controller calculates a drive current value of the ultraviolet LED based on information indicating spectral intensity characteristics of the ultraviolet LED and information indicating spectral action characteristics of a target of irradiation irradiated by light from the light source unit, and the driver supplies a drive current of a value calculated by the controller to the ultraviolet LED.

According to the embodiment, it is possible to estimate an action given by light emission to the target of irradiation, based on the spectral intensity characteristics of the ultraviolet LED and the spectral action characteristics of the target of irradiation and to drive the ultraviolet LED so that the action is optimized. This prevents an insufficient or excessive irradiation level and makes it possible to obtain a desired effect by irradiating the target of irradiation with ultraviolet light efficiently.

The controller may calculate the drive current value of the ultraviolet LED so that an estimated action obtained by integrating a product of the spectral intensity characteristics of the ultraviolet LED and the spectral action characteristics of the target of irradiation over a wavelength meets a predetermined condition.

The controller may calculate the drive current value of the ultraviolet LED based on information indicating correlation between the light emission intensity of the ultraviolet LED and the drive current value of the ultraviolet LED.

The device may further include a measurement unit that measures a light emission intensity of the ultraviolet LED. The measurement unit may calculate the drive current value of the ultraviolet LED based on correlation between a result of measurement by the measurement unit and the drive current value of the ultraviolet LED.

The device may further include an input unit that receives designation of a target value of an action that should be given to the target of irradiation. The controller may calculate the drive current value of the ultraviolet LED to achieve the target value.

The controller may calculate a value indicating a duration of driving the ultraviolet LED to achieve the target value, and the driver may supply the drive current to the ultraviolet LED over the duration of driving of the value calculated by the controller.

The input unit may receive designation of a duration of light irradiation on the target of irradiation, and the controller may calculate the drive current value of the ultraviolet LED so as to meet both the target value of the action and the duration of light irradiation.

The light source unit may include a plurality of ultraviolet LEDs having different spectral intensity characteristics. The controller may calculate a plurality of drive current values corresponding to the plurality of ultraviolet LEDs, respectively, based on information indicating spectral intensity characteristics of the plurality of ultraviolet LEDs, and the driver supplies each of drive currents of a plurality of values calculated by the controller to a corresponding ultraviolet LED.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which:

FIG. 1 schematically shows functions and a configuration of an ultraviolet irradiation device according to an embodiment;

FIG. 2 is a graph schematically showing spectral intensity characteristics of the plurality of LEDs;

FIG. 3 is a graph schematically showing the spectral action characteristics of the target of irradiation;

FIG. 4 is a graph schematically showing examples of calculating the coefficients indicating the light emission intensity of the LEDs; and

FIG. 5 is a graph schematically showing the correlation between the light emission intensity of the LED and the drive current value I.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by reference to the preferred embodiments. This does not intend to limit the scope of the present invention, but to exemplify the invention.

A detailed description will be given of embodiments of the present invention with reference to the drawings. Like numerals are used in the description to denote like elements and a duplicate description is omitted as appropriate.

FIG. 1 schematically shows functions and a configuration of an ultraviolet irradiation device 10 according to an embodiment. The ultraviolet irradiation device 10 includes a light source unit 20, a driver 30, a measurement unit 40, a display control interface 50, and a controller 60. The ultraviolet irradiation device 10 is used for sterilization and resin hardening by ultraviolet irradiation. For example, the ultraviolet irradiation device 10 may be used by being built in a fluid sterilization device for irradiating a fluid such as water with ultraviolet light to sterilize the fluid continuously.

The light source unit 20 includes a plurality of LEDs 21, 22, 23, and 24. At least one of the plurality of LEDs 21, 22, 23, and 24 is configured to output deep ultraviolet light having a central wavelength or a peak wavelength included in a range of about 250 nm˜350 nm. Such an ultraviolet LED is exemplified by an aluminum gallium nitride (AlGaN) based LED. At least one of the plurality of LEDs 21-24 may be configured to output ultraviolet light or blue light having a central wavelength or a peak wavelength included in a range of about 350 nm˜450 nm. Such an ultraviolet or blue LED is exemplified by a gallium nitride (GaN) based LED. The light source unit 20 may include an LED for emitting visible light or infrared light having a wavelength longer than 450 nm. In this embodiment, the case of including four LEDs is illustrated, but the embodiment is non-limiting as to the number of LEDs included in the light source unit 20. The light source unit 20 may include a plurality of LEDs having substantially identical wavelength characteristics.

FIG. 2 is a graph schematically showing spectral intensity characteristics of the plurality of LEDs 21˜24. The plurality of LEDs 21˜24 has mutually different wavelength characteristics. The first LED 21 has the first intensity distribution P₁(λ) in which the central wavelength or the peak wavelength is the first wavelength λ₁. The first LED 22 has the second intensity distribution P₂(λ) in which the central wavelength or the peak wavelength is the second wavelength λ₂. The third LED 23 has the third intensity distribution P₃(λ) in which the central wavelength or the peak wavelength is the third wavelength λ₃. The fourth LED 24 has the fourth intensity distribution P₄(λ) in which the central wavelength or the peak wavelength is the fourth wavelength λ₄.

In one embodiment, the wavelength characteristics of the plurality of ultraviolet LEDs 21˜24 are configured to have central wavelengths or peak wavelengths such that λ₁<λ₂<λ₃<λ₄. Further, the wavelength characteristics are selected such that the intensity distributions of LEDs having adjacent central wavelengths or peak wavelengths overlap each other. In this case, the ultraviolet irradiation device 10 is configured to output ultraviolet light having a continuous spectrum in a wavelength range at least from the first wavelength λ₁to the fourth wavelength λ₄. In one variation, the wavelength characteristics may be selected such that the intensity distributions of LEDs having adjacent central wavelengths or peak wavelengths do not overlap. In this case, the device is configured not to output ultraviolet light in a certain limited wavelength range.

It is preferred that the plurality of wavelength characteristics of LEDs 21˜24 is selected in accordance with the usage of the ultraviolet irradiation device 10. In the case the ultraviolet irradiation device 10 is used for the purpose of sterilization, for example, it is preferred to include an LED capable of outputting ultraviolet light in a wavelength range of about 260˜270 nm, which is known to have high sterilization capability. In the case the ultraviolet irradiation device 10 is used for resin hardening, it is preferred to include an LED capable of outputting ultraviolet light in a wavelength range of about 300˜350 nm or a wavelength range of about 350 nm˜400 nm, depending on the resin hardening wavelength.

Referring back to FIG. 1, the driver 30 is configured to supply a drive current to the plurality of LEDs 21˜24 included in the light source unit 20. For example, the driver 30 includes a constant-current circuit for supplying a constant current to the plurality of LEDs 21˜24. The driver 30 is configured to supply drive currents of different values to the plurality of LEDs 21-24, respectively, in accordance with an instruction from the controller 60. The driver 30 is capable of controlling the light emission intensity of the plurality of LEDs 21˜24 independently.

The measurement unit 40 measures the output intensity of the light source unit 20 and transmits a result of measurement to the controller 60. The measurement unit 40 includes, for example, a power meter capable of measuring the light intensity. By providing the measurement unit 40, it is possible to monitor the output of the light source unit 20 and perform feedback control to maintain the output intensity of the light source unit 20 constant.

The measurement unit 40 may be configured to measure the spectral intensity characteristics of the light source unit 20 and may, for example, include a spectrometer. The measurement unit 40 may generate information related to the spectral intensity characteristics as shown in FIG. 2 by measuring the spectral characteristics of the output light of the LEDs 21˜24. The measurement unit 40 may be configured to measure the wavelength sensitivity of the target of irradiation. For example, the measurement unit 40 may be configured to measure the wavelength dependency of the absorption of light by the target of irradiation.

The display control interface 50 is an input unit for receiving a user operation from a user. For example, the display control interface 50 is comprised of a touch-sensitive panel device. The display control interface 50 displays a screen in which to enter or select an operating condition of the ultraviolet irradiation device 10 and allows the user to enter an operating condition of the ultraviolet irradiation device 10. The display control interface 50 may be comprised of a display unit and an input unit that are separate from each other.

For example, the display control interface 50 makes it possible to enter and configure parameters related to the target of irradiation or parameters related to the irradiation condition. Parameters related to the target of irradiation are exemplified by the type, quantity, density, etc. of the target of irradiation. The interface may receive an input of information related to the wavelength sensitivity (spectral action characteristics described later, etc.; see FIG. 3) of the target of irradiation, as a parameter related to the target of irradiation. The interface may receive an input of information related to the processing duration, the total amount of irradiation energy (total dose), the target value of action given to the target of irradiation, as parameters related to the irradiation condition.

The display control interface 50 may allow the user to select one of a plurality of irradiation modes that are made available. For example, a low power consumption mode, a short duration mode, an automatic mode, etc. may be made available. In the low power consumption mode, the drive current value is determined so that, for example, the power consumption required for the target action is minimized. In the short duration mode, the drive current value is determined so that, for example, the irradiation duration to obtain the target action is minimized. In the automatic mode, the drive current value is determined so that, for example, both the power consumption and the irradiation duration are optimized.

The display control interface 50 may allow the user to select one of a plurality of targets of irradiation available. In the case the device is used for sterilization, for example, a combination of a fluid subject to sterilization and a bacterial strain sought to be sterilized may be designated. In the case the device is used for resin hardening, the resin material subject to irradiation may be designated.

The controller 60 calculates drive current values of the plurality of LEDs 21˜24 based on the spectral intensity characteristics of the plurality of LEDs 21˜24 and the spectral action characteristics of the target of irradiation. The controller 60 maintains the information on the spectral intensity characteristics and the information on the spectral action characteristics. The controller 60 identifies the spectral action characteristics that should be referred to, based on an input in the display control interface 50. The controller 60 estimates the action given to the target of irradiation exposed to light, based on the spectral intensity characteristics of the plurality of LEDs 21˜24 and the spectral action characteristics of the target of irradiation. The controller 60 determines the light emission intensity of the LEDs 21˜24 so that the estimated action meets a predetermined condition and determines drive current values necessary to obtain the determined light emission intensity.

The action given to the target of irradiation exposed to light is a numerical degree of the desired effect expected to be obtained by ultraviolet irradiation. An action E is given by the following expression (1), using the spectral intensity distribution P(λ) of the light source unit 20, the spectral action characteristics α(λ) of the target of irradiation, and the duration t of ultraviolet irradiation. In other words, the action E is obtained by integrating, over the wavelength, the spectral intensity distribution P(λ) of the light source unit 20 as a whole and the spectral action characteristics α(λ) of the target of irradiation. The wavelengths λ_A, λ_Bdefining the range of integration correspond to the lower limit value and the upper limit value of the wavelength range in which the light source is capable of outputting light.

E=t∫
_λ
_A
^λ
^Bα(λ)P(λ)dλ (1)

The spectral action characteristics α(λ) of the target of irradiation is the wavelength dependency or the wavelength sensitivity with respect to the degree of the effect obtained by ultraviolet irradiation. For example, the spectral action characteristics in the case of sterilization represents the correlation between the wavelength λ of ultraviolet light and the rate of sterilization, and the spectral action characteristics in the case of resin hardening represents correction between the wavelength λ of ultraviolet light and the level of resin hardening by exposure to ultraviolet light.

FIG. 3 is a graph schematically showing the spectral action characteristics of the target of irradiation. The graph illustrates the spectral action characteristics α₁(λ) in sterilization and the spectral characteristics α₂(λ) in resin hardening. The spectral action characteristics α₁(λ) in sterilization has a curved form in which, for example, the level of sterilization is at maximum near λ=260 nm. The spectral action characteristics α₂(λ) in sterilization has a curved form in which, for example, the level of resin hardening is at maximum near λ=330 nm. The graph shown is for an illustrative purpose only, and it will be understood that the graph form varies depending on the type of the target of irradiation or the action sought to be obtained by ultraviolet irradiation.

The controller 60 determines the light emission intensity of the LEDs 21˜24 so that the action E obtained is maximized, based on the spectral intensity characteristics P₁(λ)˜P₄(λ) of the LEDs 21˜24 and the spectral action characteristics α(λ) of the target of irradiation. More specifically, the coefficients k_i(i:1˜4) indicating the relative values of light emission intensity of the respective LEDs are determined so that the estimated action ER per unit time calculated by using the following expression (2) is maximized. For example, the value of the coefficient k_iindicating the light emission of each LED is determined by a solving known optimization problem under the condition that the sum of the coefficients k_iis constant (e.g., k₁+k₂+k₃+k₄=1).

$\begin{matrix} E_{R} = \sum_{i = 1}^{n} \int_{λ_{A}}^{λ_{B}} α (λ) k_{i} P_{i} (λ) d λ & (2) \end{matrix}$

FIG. 4 is a graph schematically showing examples of calculating the coefficients k₁˜k₄indicating the light emission intensity of the respective LEDs. In the illustrated example, the coefficient k_iof the light intensity of each LED is calculated based on predetermined spectral action characteristics α₁(λ). In the illustrated example, the coefficients k_iare determined such that the coefficient k₁of the first LED 21 corresponding to the first wavelength λ₁having a high value in the spectral action characteristics α₁(λ) is large, and the coefficient k₄of the fourth LED 24 corresponding to the fourth wavelength λ₄having a low value in the spectral action characteristics α₁(λ) is small. In other words, the coefficients k_iare determined such that the higher the contribution of the LED to the spectral action characteristics α, the higher the light mission intensity. Thus, by ensuring that the light emission intensity is large at the wavelength λ characterized by large spectral action characteristics α and that the light emission intensity is small at the wavelength λ characterized by small spectral action characteristics α, the action E given to the target of irradiation is increased and the power consumption in the light source as a whole is decreased.

The controller 60 calculates the drive current values I1, I2, I3, and I4 of the LEDs 21˜24 to obtain the light intensity in accordance with the coefficients k_idetermined. The controller 60 maintains information indicating the correlation between the light intensity P and the drive current value I of the LED and determines the drive current value of each LED based on the correlation information. FIG. 5 is a graph schematically showing the correlation between the light emission intensity P and the drive current value I of the LED. By referring to the correlation as illustrated, it is possible to determine the drive current value I corresponding to the given light emission intensity P. In one variation, the drive current Ii (i: 1˜4) may be calculated in a simplified manner by multiplying the coefficient k_iindicating the light emission intensity k_iby a predetermined constant. Alternatively, the drive current value Ii may be calculated based on a result of measurement by the measurement unit 40.

The controller 60 may subject the drive current values I1˜I4 of the LEDs 21˜24 to feedback control so as to maintain the light emission intensity in accordance with the coefficient k_idetermined. For example, the drive current determined from the correlation between the light intensity emission and the drive current value shown in FIG. 5 may be defined as an initial value, and the light emission intensity of the LEDs 21˜24 driven by the initial value is measured by the measurement unit 40. Subsequently, the drive current value is determined in such a manner as to maintain the light emission intensity thus measured.

The controller 60 may calculate the values of the coefficients k_iindicating the light emission intensity of the respective LEDs so that the estimated action ER per unit time reaches a predetermined target value ET. The target value ET related to the action per unit time may be configured through an input via the display control interface 50, or the controller 60 may calculate the target value ET based on another parameter input via the display control interface 50. For example, the target value Et may be calculated based on parameters entered by the user such as the type of target of irradiation, the quantity or density of the target of irradiation, and the duration of irradiation. In the case that the target of irradiation is a fluid, the target value ET may be calculated based on information related to the flow rate.

When a plurality of solutions for combinations of coefficients k_iare obtained, the controller 60 may calculate the combination that minimizes the sum of the coefficients k_ias the solution. Alternatively, the controller 60 may calculate the solution of the coefficients k_iso that the sum of the drive current values I1˜I4 of the LEDs 21˜24 is minimized. In this process, the controller 60 may use the information indicating the correlation between the light emission intensity and the drive current values of the LEDs 21˜24 as shown in FIG. 5. The controller 60 may further maintain information indicating the maximum current value capable of driving the LEDs 21˜24 and calculate the solution for the coefficients k_iby using the maximum current value as a constraint condition. For example, the controller 60 may calculate the solution for the coefficients k_iso that the maximum current value is induced at least in one of the plurality of LEDs 21˜24.

The controller 60 may determine the light emission intensity of the LEDs based on a target value related to the duration of processing. for example, the controller 60 may calculate an action ER per nit time necessary to obtain a target value ET of the action within a predetermined duration of irradiation and may determine the light emission intensity of the LEDs so that the calculated action ER is obtained. In this case, the controller 60 may calculate a coefficient k_idifferent from the coefficient k_iof the light intensity calculated to minimize the power consumption. For example, the controller 60 may control the LEDs to be driven such that the target action ET is obtained in the shortest period of time at a certain cost of loss in irradiation efficiency.

The controller 60 may determine the duration t of ultraviolet irradiation based on a target value of the total amount of irradiation energy (total dose). For example, the controller 60 may calculate a target value EU of the total action necessary for processing by referring to the information such as the type, quantity, density of the target of irradiation and determine the duration of irradiation according to the expression t=EU/ER, using the estimated action ER per unit time. The controller 60 may estimate the dose irradiating the target of irradiation based on the light emission intensity measured by the measurement unit 40 and determine the time required for the total dose to reach the target value as the duration of irradiation.

A description will be given of the operation of the ultraviolet irradiation device 10 configured as described above. The ultraviolet irradiation device 10 first acquires the information related to the spectral intensity characteristics of the light source unit 20 and the information related to the spectral action characteristics of the target of irradiation. These items of information may be acquired from the measurement unit 40, stored in advance in the controller 60, entered via the display control interface 50, or acquired from an external device such as a database connected via a network.

The ultraviolet irradiation device 10 then receives configuration of parameters related to the target of irradiation and to the irradiation condition. The controller 60 determines the coefficients k_iindicating the relative values of light emission intensity of the LEDs 21˜24 based on the parameters configured and calculates the drive current values Ii of the LEDs 21˜24 to realize the coefficients k_i. The controller 60 may also calculate the duration of irradiation. The driver 30 supplies the calculated drive current values Ii to the associated LEDs 21˜24 to drive the LEDs 21˜24 in a light emission intensity ratio in accordance with the coefficients k_i. The controller 60 may stop driving the LEDs 21˜24 after an elapse of a predetermined duration of irradiation, and the display control interface 50 displays a message indicating that the irradiation process is completed.

According to the embodiment, the LED can be driven so that the action given to the target of irradiation is optimized by determining the drive current values of the LEDs 21˜24 based on the spectral intensity characteristics of the LEDs 21˜24 and the spectral action characteristics of the target of irradiation. The ultraviolet LED used in the light source unit 20 has a central wavelength or a peak wavelength as design values and a spread width (e.g., a full width at half maximum) of the wavelength distribution, but the wavelength characteristics vary between the individual LEDs that are actually used. If the light emission intensity or the duration of irradiation is determined without regard to the wavelength characteristics of individual ultraviolet LEDs, therefore, the irradiation level may become insufficient or excessive, which may result in failure to realize efficient ultraviolet irradiation. According to the embodiment, on the other hand, control based on the spectral intensity characteristics of individual LEDs and the spectral action characteristics of the target of irradiation is performed so that it is possible to drive the LEDs in a condition optimized for the irradiation process. This improves the efficiency of ultraviolet irradiation.

Described above is an explanation based on an exemplary embodiment. The embodiment is intended to be illustrative only and it will be understood by those skilled in the art that various design changes are possible and various modifications are possible and that such modifications are also within the scope of the present invention.

In the embodiments described above, the light source unit 20 is described as including a plurality of LEDs. In one variation, the light source unit 20 may include only one LED. It is also possible, in this case, to make the irradiation process efficient by determining the drive current values based on both the wavelength characteristics of the one ultraviolet LED and the wavelength characteristics of the target of irradiation.

It should be understood that the invention is not limited to the above-described embodiment but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.

	Number	Date	Country
Parent	PCT/JP2017/033911	Sep 2017	US
Child	16364855		US

ULTRAVIOLET IRRADIATION DEVICE

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