TECHNICAL FIELD

The present invention relates generally to lighting systems, and in various embodiments to systems for providing mixed light for illumination and disinfection purposes.

BACKGROUND

It is known that certain wavelength ranges of light, particularly ultraviolet (UV) light, are germicidal—i.e., capable of killing or inactivating pathogens such as bacteria and viruses, rendering them incapable of causing disease. Illumination devices emitting germicidal light are frequently used to decontaminate medical tools and environmental surfaces. UV radiation is dangerous to humans, and some wavelength bands are more dangerous than others. As a result, broadband germicidal UV applications are typically deployed in oven-like devices that receive items to be decontaminated and are closed when the radiation is activated, thereby shielding personnel from harm. Although automated UV-based room-decontamination systems have been developed, these generally are not used when people are present. See, e.g., Livingston et al., “Efficacy of an ultraviolet-A lighting system for continuous decontamination of health care-associated pathogens on surfaces,”Am. J. Infection Control,48:337-339 (2020). Unfortunately, recontamination can occur quickly following device operation once people return and resume their activities.

The most effective germicidal wavelength band, UV-C (100-280 nm), is also the most dangerous to humans. The UV-A band (315-400 nm), on the other hand, can be safe for use in limited doses when people are present, and is known to have antimicrobial activity. Accordingly, it is possible to safely integrate UV-A lighting with general illumination, but the lighting sources used for these different wavelength ranges are different. Their outputs must be combined in a manner that preserves the quality of ambient light for affected personnel while ensuring safety.

SUMMARY

An increasing number of light fixtures utilize LEDs as light sources due to their lower energy consumption, smaller size, improved robustness, and longer operational lifetime relative to conventional filament-based light sources. Conventional LEDs emit light at a particular wavelength, ranging from, for example, red to UV light. However, for purposes of general illumination, the monochromatic emitted light by LEDs must be converted to broad-spectrum white light.

Embodiments of the present invention combine UV-A and white light with an adjustable CCT value so that any adverse effects from the the UV-A radiation are mitigated—that is, tunable adjustments to the output of the non-UV LEDs, or to all of the LEDs, result in an overall mixed output conforming to a target CCT value. In one embodiment, the LED illumination device employs an LED array having multiple LEDs that can be controlled individually or in a group to generate white light having a tunable CCT value within a range. Optionally, each of the LEDs may be disposed within a “cup-shaped” (e.g., parabolic) reflector for reducing “crosstalk” interactions between the light emitted from an LED and the photo-luminescent material(s) disposed above a neighboring LED. In addition, the reflector may be made of a high-reflectivity material so as to redirect upward light from the respective LED, thereby achieving at least partial collimation of the beam.

In various embodiments, the LEDs and/or photo-luminescent material(s) are encapsulated within a waveguide material made of, e.g., silicone. Light emitted from the LEDs, including unconverted light and light converted by the photo-luminescent material(s), can be mixed in a mixing region inside the waveguide and then directed to an output region for outputting white light for illumination. The illumination device may also include control circuitry for varying a parameter (e.g., the amplitude and/or duty cycle of the applied current or voltage) associated with each LED (or, in some embodiments, each group of the LEDs), thereby adjusting the CCT value of the mixed light to a target value.

Accordingly, in one aspect, the invention relates to a lighting device producing white light having a target CCT value and UV-A radiation. In various embodiments, the device comprises a plurality of red LEDs emitting red light having a wavelength between approximately 600 nm and approximately 670 nm, a plurality of blue LEDs emitting blue light having a wavelength between approximately 440 nm and approximately 485 nm, and a plurality of UV-A LEDs emitting UV radiation having a wavelength between approximately 315 nm and approximately 420; at least one photo-luminescent material for shifting a CCT value of at least one of (a) the red LEDs, (b) the blue LEDs or (c) the UV-A LEDs; and a waveguide material having (i) a mixing region for mixing the shifted and any unshifted light so as to generate white light having the target CCT value and (ii) an output region for outputting the white light. The red LEDs may have an emission peak at 630 nm, the blue LEDs have an emission peak at 450 nm, and the UV-A LEDs have an emission peak at 395 nm.

In some embodiments, the device also includes control circuitry for adjusting a parameter associated with at least one of the red LEDs, the blue LEDs or the UV-A LEDs so as to change the target CCT value of the generated white light. For example, the parameter may comprise at least one of an amplitude or a duty cycle of a current or a voltage associated with the red LEDs, the blue LEDs and/or the UV-A LEDs.

The control circuitry may be configured to adjust the parameter of each red LED, blue LED and UV-A LED to maintain the target CCT value while changing the intensity of the UV-A light. In some embodiments, the LEDs comprises a first group of the red LEDs and the UV-A LEDs electrically coupled to one another, a second group of the blue LEDs and the UV-A LEDs electrically coupled to one another, and a third group of the UV-A LEDs electrically coupled to one another; the control circuitry may be configured to adjust each of the groups individually. The UV-A LEDs in the third group may emit light at a wavelength having a lower interaction with the photo-luminescent material than the wavelengths emitted by the UV-A LEDs in the first group or the UV-A LEDs in the second group. Alternatively or in addition, the UV-A LEDs in the first group may emit light at a wavelength having a higher interaction with the photo-luminescent material than the UV-A LEDs in the second group. The photo-luminescent material may comprise at least one of a phosphor, a quantum dot material or a fluorescent dye.

In some embodiments, the lighting device further comprises a plurality of cup-shaped reflectors for at least partial collimation of light emitted from the LEDs, wherein each reflector has a top aperture and a bottom aperture and the bottom aperture has one of the LEDs disposed therein. At least one of the reflectors may be a parabolic reflector, and the respective LED disposed therein may be located at or near the focus of the parabolic reflector. The reflectors may comprise or consist essentially of silicone.

The lighting device may include an encapsulant material filled in a cavity space above one of the plurality of LEDs and surrounded by the respective reflector. In some embodiments, the lighting device further comprises a circuit board for mounting the LEDs thereon, and if desired, the lighting device may include a heat-dissipation structure thermally coupled to the circuit board for dissipating heat generated by the plurality of LEDs. In some embodiments, the lighting device further comprises at least one reflector located in the mixing region of the waveguide for promoting mixing of light. The waveguide material may comprise or consist essentially of silicone. The waveguide material may encapsulate at least one LED.

In another aspect, the invention relates to a lighting system comprising, in various embodiments, the lighting system includes a plurality of devices for producing white light having a target CCT value and UV-A radiation. Each of the devices may comprise a plurality of LEDs emitting visible light and a plurality of UV-A LEDs emitting UV radiation having a wavelength between approximately 315 nm and approximately 420; at least one photo-luminescent material for shifting a CCT value of at least some of the LEDs; a waveguide material having (i) a mixing region for mixing the shifted and any unshifted light and (ii) an output region for outputting the light; and a controller configured to operate the plurality of devices in (a) a normal mode, powering the LEDs, so as to generate white light having the target CCT value while emitting UV-A light or (b) in a boost mode, powering fewer than all of the LEDs emitting visible light and powering at least a majority of the UV-A LEDs at high intensity. In the normal mode, the UV-A light may have an intensity that is safe for human exposure and in the boost boost mode the intensity may exceed the intensity that is safe for human exposure. In the the boost mode, LEDs emitting red light may be operated to indicate a risk of harmful radiation. The plurality of LEDs emitting visible light may comprise (i) a plurality of red LEDs emitting red light having a wavelength between approximately 600 nm and approximately 670 nm and (ii) a plurality of blue LEDs emitting blue light having a wavelength between approximately 440 nm and approximately 485 nm.

The term “color” is used herein to denote the monochromatic or peak wavelength (or wavelengths) of light emitted by one or more LEDs. In addition, the term “uniform,” as used herein, refers to a light intensity distribution whose lower and upper intensity limits are within a factor of four, preferably within a factor of two of each other. As used herein, the terms “approximately,” “roughly,” and “substantially” mean±10%, and in some embodiments, ±5%. Reference throughout this specification to “one example,” “an example,” “one embodiment,” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example of the present technology. Thus, the occurrences of the phrases “in one example,” “in an example,” “one embodiment,” or “an embodiment” in various places throughout this specification are not necessarily all referring to the same example. Furthermore, the particular features, structures, routines, steps, or characteristics may be combined in any suitable manner in one or more examples of the technology. The headings provided herein are for convenience only and are not intended to limit or interpret the scope or meaning of the claimed technology.

