SYSTEMS AND METHODS OF DYNAMIC ILLUMINATION AND TEMPORALLY COORDINATED SPECTRAL CONTROL AND BIOLOGICAL DIMMING

Abstract

Lighting systems and methods for providing biologically optimized illumination throughout the day are disclosed. Systems and methods of providing LED light engines and associated illumination spectrums that are both visually appealing, rich in melanopic flux and that reduce blue light hazard exposure are disclosed. Embodiments of the invention relating to specific spectra of illumination containing high or low amounts of melanopic light, spectrally and spatially tunable LED lighting systems, programmed and automated controllers for temporally controlling bio-effective illumination, and dimming circuitry for tuning the spectral output of lighting devices are also disclosed.

Claims

1.-20. (canceled)

21. A method of facilitating circadian rhythm regulation, the method comprising: providing a light engine, wherein the light engine comprises i) a first LED module that emits white light, ii) a second LED module that emits light having a first peak emission intensity between 470 nm and 490 nm and a second peak emission intensity centered on 660 nm, and iii) a third LED module that emits a narrow band illumination in a wavelength band between 410 nm and 430 nm, wherein the light from the second LED module and the third LED module are emitted in an upward direction; adjusting a current flow to the second LED module such that an intensity of the light emitted between 470 nm to 490 nm is increased toward a daily maximum level during a first portion of a photoperiod, thereby providing illumination rich in melanopic light during a second portion of the photoperiod; adjusting the current flow to the second LED module such that the intensity of the light emitted between 470 nm to 490 nm is decreased during a third portion of the photoperiod, thereby providing illumination depleted in melanopic light during a fourth portion of the photoperiod; and adjusting a current flow to the third LED module such that the narrow band illumination is generated for a time period not exceeding 60 minutes during the first portion or the third portion; wherein: the first portion of the photoperiod is a ramping up period; the second portion of the photoperiod is after the first portion and corresponds to a circadian daytime in which the intensity of the light emitted between 470 nm to 490 nm is at or near the daily maximum level; the third portion of the photoperiod is a ramping down period after the second portion; and the fourth portion of the photoperiod corresponds to a circadian nighttime.

22. The method of claim 21 wherein: the light engine further comprises a fourth LED module operable to produce illumination enriched with red light emitted in a downward direction; and the first portion of the photoperiod further comprises: a first sub-period of generating the narrow band illumination from the third LED module, followed by a second sub-period of generating the illumination enriched with the red light from the fourth LED module, followed by a third sub-period during which the increasing of the intensity of light emitted between 470 nm to 490 nm occurs.

23. The method of claim 22 wherein the intensity of the narrow band illumination from the third LED module generated in the first sub-period and the intensity of the illumination from the fourth LED module generated in the second sub-period are decreased during the third sub-period comprising the increasing of the intensity of light emitted between 470 nm to 490 nm.

24. The method of claim 22 wherein the red light emitted from the fourth LED module creates indirect lighting to impact an upper hemisphere of a human's retina.

25. The method of claim 21 wherein the light from the second LED module and the third LED module create indirect lighting to impact a lower hemisphere of a human's retina.

26. The method of claim 21 wherein the adjusting the current flow to the third LED module comprises increasing the intensity of the narrow band illumination in the wavelength band between 410 nm and 430 nm from a first level to a second higher level and then from the second higher level back to the first level.

27. The method of claim 21 further comprising providing an afternoon lull support by temporarily generating the narrow band illumination from the third LED module during the second portion corresponding to the circadian daytime.

28. The method of claim 21 wherein the illumination depleted in melanopic light during the fourth portion of the photoperiod is directed spatially in a downward direction.

29. A method of facilitating circadian rhythm regulation, the method comprising: generating a twilight spectrum comprising a twilight peak emission intensity in a wavelength band between 410 nm and 430 nm, the twilight spectrum being generated for less than 60 minutes during a first sub-period of a first portion of a photoperiod to create an acute alerting effect; generating a melanopic spectrum during a second sub-period of the first portion of the photoperiod, wherein: the second sub-period begins after a start of the first sub-period; the melanopic spectrum comprises white light, melanopic light having a first peak emission intensity between 470 nm and 490 nm, and a second peak emission intensity centered on 660 nm; and the intensity of the melanopic light of 470 nm and 490 nm is increased during the second sub-period; maintaining the melanopic light of the melanopic spectrum at a daily maximum level during a second portion of the photoperiod corresponding to a circadian daytime, wherein the second portion is after the first portion; and decreasing the intensity of the melanopic light of the melanopic spectrum during a third portion of the photoperiod, the third portion being after the second portion and before a fourth portion of the photoperiod, the fourth portion corresponding to a circadian nighttime; wherein: i) a first LED module produces the white light, ii) a second LED module produces the melanopic light having the first peak emission intensity between 470 nm and 490 nm and the second peak emission intensity centered on 660 nm, and iii) a third LED module produces light having the wavelength band between 410 nm and 430 nm; and wherein the melanopic light from the second LED module and the light having the wavelength band between 410 nm and 430 nm from the third LED module are emitted in an upward direction.

30. The method of claim 29 wherein: a fourth LED module is operable to produce illumination enriched with red light emitted in a downward direction; and the first portion further comprises generating the illumination enriched with the red light from the fourth LED module after the start of the first sub-period and before the start of the second sub-period.

31. The method of claim 30 wherein the red light emitted from the fourth LED module creates indirect lighting to impact an upper hemisphere of a human's retina.

32. The method of claim 29 wherein the melanopic light from the second LED module and the light having the wavelength band between 410 nm and 430 nm from the third LED module create indirect lighting to impact a lower hemisphere of a human's retina.

33. The method of claim 29 wherein the generating of the twilight spectrum comprises increasing the intensity of light in the wavelength band between 410 nm and 430 nm from a first level to a second higher level and then from the second higher level back to the first level.

34. The method of claim 29 further comprising providing an afternoon lull support by temporarily generating the twilight spectrum from the third LED module during the second portion corresponding to the circadian daytime.

35. The method of claim 29 further comprising supplying a minimum current flow to the second LED module during the fourth portion corresponding to the circadian nighttime, thereby providing a nighttime spectrum depleted of the melanopic light of 470 nm to 490 nm; wherein the nighttime spectrum is directed spatially in a downward direction.

36. The method of claim 29 further comprising generating warm white light during a nighttime transition that transitions from the third portion to the fourth portion; wherein the warm white light is directed spatially in a downward direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIGS. 1a-b show, respectively, example spectral power distributions (SPDs) from conventional white light LEDs and the action spectrum of melanopsin and spectral region of blue light hazard overlaid and compared with the spectral power distributions (SPDs) of conventional white light LEDs.

[0027] FIG. 2 shows an example schematic illustration of the correlation of circadian rhythms, sleep pressure, sleep and wakefulness.

[0028] FIGS. 3a-b show spectral power densities (SPDs) of SkyBlue LED packages according to some embodiments.

[0029] FIG. 4 shows an SPD of a BIOS light engine that includes both a white light LED package and a SkyBlue LED package according to some embodiments.

[0030] FIG. 5 shows examples of SPDs corresponding to the Bio-dimming of an LED light engine according to some embodiments.

[0031] FIG. 6 shows a nighttime spectrum according to some embodiments.

[0032] FIG. 7 shows a spectral power density plot of the illumination of an LED light package that produces a twilight spectrum according to some embodiments.

[0033] FIG. 8 illustrates dynamic lighting and illumination methods that provide spectrally changing lighting throughout a photoperiod to facilitate circadian rhythm regulation according to some embodiments of the invention.

DETAILED DESCRIPTION

[0034] Embodiments of the invention include methods, systems and luminaires that dynamically generate high efficacy white light that comprises enhanced spectral components that vary at different times of the day to facilitate circadian regulation or entrainment. Embodiments of the invention include dynamic illumination methods and systems for providing relatively high melanopic flux during the day and relatively low melanopic flux at night. Other embodiments of the invention include lighting systems which provide for illumination systems that comprise enriched or depleted melanopic light from above such that exposure of melanopic light to photoreceptors in the lower hemisphere of the retina may be amplified or attenuated based on time of day in order to facilitate circadian rhythm regulation.

[0035] In some embodiments, a daytime spectrum is generated that has an enhanced circadian spectrum, i.e., melanopic light around 490 nm (or 480 nm-500 nm). In some embodiments illumination includes enhanced spectral components that are relevant to the skin optical window and sub dermal cellular stimulation (e.g., deep-red around 660 nm and/or infrared). Illumination spectrums produced by embodiments of the invention can increase biological stimulus at times where biological sensitivities are greatest. In some embodiments, illumination provided during nighttime will have relatively lower amounts of 480 nm light (i.e., melanopic light), than for example the illumination provided during the daytime. In some embodiments, illumination is produced by, inter alia, pulsing light of particular wavelength regions.

[0036] Embodiments of the invention include systems and luminaires that can alter the illumination spectrum at different times of the day, for example dynamic systems that can dynamically change the illumination spectrum over the course of a day. In some embodiments relatively higher amounts of deep-red or infrared light (or light in that optical region) are provided during specific times of day to facilitate biological responses including circadian regulation or changes to alertness.

[0037] In some embodiments, blue light in the 420 nm region is employed in a lighting system to provide illumination that results in an acute alerting affect. In some embodiments, this illumination is depleted in melanopic light (e.g., light in 490 nm or 460-500 nm) and thereby produces an alerting effect while providing no or reduced impact on the circadian rhythm. The lighting system according to these embodiments produces white light illumination with both high CRI and aesthetic appeal.

[0038] Other embodiments of the invention include methods, luminaires and systems for providing biologically relevant light (e.g., melanopic light) from indirect illuminating sources. Embodiments include using white light and/or monochromatic sources, and examples include cove lighting and indirect ceiling and floor lighting. Some embodiments include illumination systems that provide light, that may effect a biological stimulus (e.g., melanopic light), from below such that the light impacts the upper hemisphere of the retina where the opsin photoreceptors are less sensitive thereby reducing the potential biological stimulus. Embodiments include lighting, e.g., indirect light, from above which is depleted of melanopic light but of high CRI thus providing aesthetic white light but without or with reduced biologically stimulating light.

[0039] The effect on the circadian cycle as well as on sleep pressure and alerting response of light exposure is one that is highly influenced by daytime biological stimulus including light stimulus. For example, a construction worker who spends most of his days outdoors will experience a smaller impact from light at night compared to someone who spends more of the day in a computer lab with low light levels. This response is dynamic over the course of a day. First morning light helps stimulate cortisol awakening response. Likewise, adaptation for the circadian system is heavily influenced by the light exposure most recently preceding night time or darkness. For example, a high biological light exposure in the late afternoon is also beneficial to circadian regulation and rhythm.

[0040] FIG. 2 shows a schematic illustration of a correlation between circadian rhythms and sleep pressure and its relation to the waking-sleep cycle. It is believed that light, both in its intensity and spectral content, plays an important role in circadian rhythm regulation, sleep and wake habits, and alertness levels. A 24 hour period is shown with corresponding circadian drive 220 and sleep pressure 230. The circadian drive 220 represents and shows, inter alia, the state of arousal or awakeness throughout the day and the sleep pressure 230 represents the complementary sleep pressure or tendency opposing awakeness throughout the same period. The time period start and end times of 9 a.m. and 9 p.m. is just a common example and for illustrative purposes, and the actual timing and intensities of circadian drives and sleep pressures are variable among individuals and may peak and trough at different times throughout the day. It is believed that the sleep pressure 230 is generally driven, in large part, by the timing of the day, that is in coordination with the circadian rhythm of the individual. The circadian drive 220 is believed to be heavily influenced and driven by the timing and exposure to light. Furthermore, the circadian drives 220 response to light is also dependent on the intensity and spectral content of the light.

[0041] As further illustrated in the example shown in FIG. 2, the circadian drive 220 increases during the early part of the day and diminishes as the day progresses. Concomitantly, the sleep pressure 230 also increases and decreases throughout the 24 hour cycles. In a healthy optimum environment, the circadian drive 220 and sleep pressure 230 are relatively synchronized. For instance, the opening of the sleep gate 225 occurs near the same time as the maximum sleep pressure 235 occurs. However, because the circadian drive 220 is influenced by the timing of specific exposure to light, the circadian drive 220 can be shifted due to exposure to light causing the circadian drive 220 and sleep pressure 230 of an individual to lose synch causing a disruption in sleep patterns and loss of optimal sleep hygiene. Exposure to light, especially specific kinds and intensities of light, and specific timing of such exposure relative to an individual's circadian rhythm can dramatically influence that individual's circadian rhythm, sleep hygiene and ultimately general health. Embodiments of the invention include systems and methods for providing specific types and intensities of light at specific times of day or light cycle to facilitate and optimize circadian rhythm regulation, improve sleep hygiene and general health. Embodiments include methods of and systems for phase shifting of circadian rhythms.

[0042] FIGS. 3a-b show spectral power densities (SPDs) of SkyBlue LED modules according to some embodiments. The SkyBlue spectrums may be produced by color mixing multiple LED packages or in a preferred embodiment are the result of the illumination from a single LED package, e.g., a pump LED with an associated phosphor that together, when driven to illumination, produce the SkyBlue spectrum(s). The SkyBlue spectrums contain a first peak 330 of power illumination at around 490 nm (e.g., between 470-500 nm) and a second peak 340 centered around 650-670 nm according to these embodiments. The SkyBlue spectrum is preferably used in conjunction with other light packages to provide high efficacy white light with adequate melanopic or biologically effective light. In some embodiments, and as illustrated in FIG. 3b, the peak 330 of power illumination is a relatively narrow band of illumination; in some embodiments, the peak exhibits a FWHM of less than 30 nm. In some embodiments, as shown in FIG. 3a, the second peak 340 is relatively narrow peak with a FWHM of less than or equal to 30 nm; in other embodiments, as shown in FIG. 3b, the second peak 340, centered near 660 nm corresponds to a broader band of illumination. It is to be understood that the relative intensities and spectral widths of the SkyBlue spectrum as shown in FIGS. 3a-b are examples only and a variety of other spectral outputs corresponding to dual peaks, one centered in the melanopic region of the spectrum (e.g., between 480-500 nm) and the other centered near or around 660 nm are contemplated embodiments of the invention.

[0043] FIG. 4 shows an SPD of a BIOS light engine that includes both a white light LED package and the SkyBlue LED package according to some embodiments. A conventional white LED, e.g., 4000 k is combined with a SkyBlue package and both are electrically driven to illumination to produce the resultant spectrum as shown in FIG. 4. The illumination spectrum is both high efficacy, aesthetically pleasing and is rich in melanopic light. In some embodiments the white light LED and SkyBlue LED packages are electrically driven to yield a single static spectrum as shown. In other embodiments, the intensity of illumination from the SkyBlue package may be adjusted, e.g., via a dimming circuit, to reduce the amount of melanopic light in the resulting light engine spectrum. It is to be understood that the invention is not limited to a specific CCT of white light, and embodiments of the invention include the use of white light LED packages of a variety of color temperatures including but not limited to 2700 K, 3000 K, 3500K, etc. In some embodiments, the SkyBlue spectrum that is mixed with the white light spectrum to produce the spectrum shown in FIG. 4 is the spectrum shown in FIG. 3b.

[0044] FIG. 5 shows an example of bio-dimming according to some embodiments. FIG. 5 shows SPDs corresponding to an LED light engine containing a SkyBlue LED package and a white light LED package wherein the illumination from the SkyBlue package may be selectively varied using dimming circuitry (not shown). The dimming circuitry provides for variation (e.g., reduction) in the electrical current to the SkyBlue package thereby reducing illumination from the SkyBlue package according to some embodiments. Spectrum 510 of the light engine corresponds to the illumination output of the light engine when the SkyBlue LED package is fully energized and spectrum 520 corresponds to the illumination output of the light engine when the current to the SkyBlue LED package has been reduced (e.g., by 50%). According to these embodiments, the light engine comprises both a high efficacy white light package (e.g., 3500 K or 4000Kalthough the invention is not limited to any specific white CCT) and a SkyBlue package (for producing a SkyBlue spectrum, for example as shown in FIGS. 3a-b). As shown in 510, when the SkyBlue package is fully energized (100%), the output spectrum contains an emission peak 512 centered near 490 nm (i.e., rich in melanopic light) whereas when the light engine is bio-dimmed, that is the current to the SkyBlue LED package is reduced, e.g., by 50%, the emission in the melanopic region is greatly reduced and the output spectrum does not exhibit a peak in the melanopic region (e.g., 470-500 nm). Embodiments of the invention include dimmable light engines as described above that illuminate with varying amounts of melanopic light according to the dimming level. It is to be understood that the spectra shown in FIG. 5 are mere example embodiments and are not meant to be limiting. As will be evident to those skilled in the art, a variety of dimming levels and protocols allow for the fine tuning of the amount of melanopic light produced by the light engine (e.g., 90% of maximum, 10% of maximum, 0% maximum, etc.) such that the amount of melanopic light can be varied in intensity throughout the day or other photoperiod (e.g., circadian day). Embodiments of the invention include light engines with onboard dimming circuitry such that power delivered to the SkyBlue LED package may be selectively reduced and the SkyBlue package effectively dimmed thereby reducing the amount of melanopic light produced by the light engine.

[0045] In some embodiments a conventional 0-10 V dimmer switch is used to adjust the electrical current to the SkyBlue package thereby controlling the amount of the SkyBlue spectral component in the overall illumination of the light engine. By using the conventional dimming circuitry, the amount of SkyBlue spectrum is adjusted thereby increasing or decreasing the melanopic component of the resulting illumination. 510 is an SPD of the light engine where the SkyBlue component is not dimmed at all; SPD 510 is rich in melanopic light and appropriate for, inter alia, daytime lighting. 520 is an SPD showing an example of Bio-dimming wherein the intensity of the illumination from SkyBlue package has been reduced by 50% (e.g., current from the dimmer is set at 5 V) and the SkyBlue spectral component has been reduced in intensity. As shown in SPD 520, the amount of melanopic light has been greatly reduced. The SkyBlue component spectrum can be reduced to zero with an appropriate dimmer setting thereby eliminating all the melanopic light. Such a dimming level may be appropriate prior to bedtime.

[0046] Other embodiments include a bio-dimmable light engine that is linked to a clock and which automatically dims or adjusts the amount of SkyBlue component and thus melanopic light throughout the day to coordinate and facilitate circadian rhythm regulation. In some embodiments, biological dimming is accomplished using a 0-10 V wall dimmer switch. When the switch is set on maximum, i.e., 10 V, the SkyBlue component is at full intensity and decreasing the dimmer setting towards 0 V reduces the radiance from the SkyBlue component (i.e., decreases the melanopic light). In some embodiments, the color temperature is altered during dimming.

[0047] In other embodiments, the color temperature is maintained relatively constant while dimming. Embodiment variations include a light engine containing an additional LED package that emits in the 410-450 nm spectral region and which can be selectively driven to illumination via the dimmer switch or circuitry. Light in this spectral region has an acute alerting effect while not significantly impacting circadian drive and so can be used to wake up or increase arousal level while not disrupting circadian rhythms.

[0048] FIG. 6 shows a nighttime spectrum according to some embodiments. The nighttime spectrum has very little melanopic light as shown by the trough 610 in spectral intensity between 450 and 500 nm. In some embodiments, the nighttime spectrum results from a complete dimming of the SkyBlue spectral component in a light engine comprising both a white light LED and a SkyBlue LED. In other embodiments, the nighttime spectrum is contained within a single LED package and may be used as a single channel nighttime light.

[0049] FIG. 7 shows a spectral power density plot of the illumination of an LED light package that produces a twilight spectrum according to some embodiments. The twilight spectrum includes a peak 710 at or around 420 nm. The twilight spectrum also includes a peak 720 in the 465 nm region, and another peak 730 centered near the 660 nm region (640-680 nm). Peak 720 corresponds to light that maximally suppresses melatonin. In some embodiments, the twilight spectrum is generated by a light engine comprising multiple LED dies or chip of different colors. In these embodiments, the LEDs are essentially color mixed in order to produce the twilight spectrum. In other embodiments, the twilight spectrum is produced by a single LED package. The single LED package is fabricated using a choice selection of blue pump LEDs in conjunction with specific phosphor combinations. The twilight spectrum has a blue hue that may have a significant biological impact in terms of helping the body circadian system delineate between daytime and nighttime.

[0050] Embodiments of the invention include LED lighting systems that provide automated spectral control of illumination throughout day (or other photoperiod) to facilitate circadian rhythm regulation, optimize sleep hygiene, and help mitigate social jet lag. Embodiments of the invention include lighting systems that produce dynamic spectrums which have a heightened amount of 420 nm and a reduced or minimal amount of 490 nm during the beginning and the end of the daytime photoperiod. Embodiments include dynamic lighting that illuminates with red light prior to significant illumination with the melanopic light (e.g., 490 nm) in order to potentially amplify the human neurological response of melanopsin. In some of these embodiments, light with an enriched red component is provided just prior to light with the enriched melanopic light. In some other embodiments, red enriched light is provided after the illumination with a 420 nm rich twilight spectrum and prior to illumination with the 490 nm rich daytime spectrum. It is believed that such exposure to light enriched with red light prior to exposure to melanopic rich light will enhance human circadian signaling factors. In some embodiments the enriched red light is produced using a monochromatic LED. In other embodiments, the red light is created from a phosphor or quantum dot down conversion. Embodiments of the invention include dynamic lighting systems which begin the day with a heightened amount of 420 nm, followed by a heightened amount of red stimulation, followed by a heightened amount of 490 nm, followed by a heightened amount of red light followed by a heightened amount of 420 nm light, followed by a biological low stimulating nighttime light. Other embodiments of the invention do not include the red portion of this dynamic spectrum process.

[0051] Embodiments of the invention include a multi-channel light engine comprising select LED packages that is selectively electrically driven and operable to illuminate with varying spectral outputs throughout the course of the day or other photoperiod. In some embodiments, the LED light engine comprises a white light LED package (e.g., 3500 K, 4000K, or 5000K), a SkyBlue LED package (an LED package that illuminates the SkyBlue spectrum as shown in FIGS. 3a-b) and a Twilight LED package (an LED package that illuminates the SkyBlue spectrum as shown in FIG. 7). Embodiments include a control system for adjusting the output spectrum of the light engine. The control system may be manual, for example a wall dimmer switch or wireless smart phone control. In other embodiments, the control system is automated and controlled by an onboard or remote processor and may be pre-programmed to run without user input, for example in coordination with a local clock or other preprogrammed instructions. In wireless embodiments, the light engine includes or is coupled to a receiver antenna for receiving external commands or program instructions. In some of these embodiments, the amount of illumination coming from each of the LED packages may be independently varied with time to alter the overall output spectrum of the LED light engine throughout the day or other photoperiod. For example, during the daytime, the SkyBlue spectrum may be ramped up to supply enhanced melanopic light whereas in the evening, the intensity of the SkyBlue spectrum may be reduced or eliminated. In another example, the Twilight spectrum may be ramped up for a short time at the beginning and/or end of the day in order to simulate dawn or dusk. Some embodiments include only a white light LED package and a SkyBlue package. Other embodiments include an additional red light LED package. Some embodiments include a nighttime LED package that illuminates with a spectrum as shown in FIG. 6.

[0052] The lighting system according to some embodiments comprises one or more luminaires or light sources that illuminate the environment of one or more individuals throughout the photoperiod, and which are dynamically adjusted throughout the photoperiod to provide varying and appropriate spectral outputs. This dynamic spectrally controlled illumination throughout the photoperiod may be used to facilitate regulation of circadian rhythms, maintain alertness, enhance sleep hygiene and generally improve personal health. It may also be used to align the circadian rhythms of a population of individuals who are exposed to the same patterns of illumination. In some embodiments, the luminaires or lighting fixtures of the system may be distributed across different rooms or buildings and the lights may be synchronized to a common clock in order to provide the appropriate spectral/temporal output.

[0053] FIG. 8 illustrates an example of how embodiments of the invention provide spectrally dynamic lighting throughout a photoperiod. In the example illustrated, the photoperiod corresponds to a day (e.g., one circadian cycle). A typical circadian period is typically around 24 hours, but can vary slightly amongst individuals. The time evolution of the photoperiod day is represented along the horizontal axis and the time units are delimited as hours before or after an individual wakes from sleep. For example, W represents the time of waking, and W+1 and W+8 represent the times 1 hour and 8 hours after waking respectively. Similarly W-5 represents the time 5 hours prior to waking. S represents the time of sleep onset, and the times S-2 and S-5 represent the times 2 hours and 5 hours before the onset of sleeping respectively. Also shown in FIG. 8, along the vertical axis, is the circadian drive 850 (as in FIG. 2). The level of circadian drive varies throughout the day photoperiod and is schematically represented by the length of the vertical arrows. Specific types and quantity of light exposure during various points of the photoperiod can dramatically affect the circadian cycle. The proper type of light at the proper time may facilitate a smooth circadian rhythm, healthy sleep hygiene and other beneficial biological effects. Conversely, the wrong type of artificial light at the wrong time can disrupt the circadian cycle and interfere with sleep patterns and general health.

[0054] Examples of dynamic spectral output of light engines and luminaires according embodiments of the invention are shown in FIG. 8. In this example, the Twilight spectrum (B) is ramped up during the period near waking, e.g., W+/1 hour to coincide with and support the Cortisol Awakening Response 860. Likewise, the twilight spectrum (B) is again ramped up at the end of the day, for example at 3-5 hours prior to the expected onset of sleep, in order to coincide with and support the Wake Maintenance Zone 865. The increased exposure to the 420 nm light may provide an acute alerting effect. The Twilight spectrum (B) is maintained only for a brief time, e.g., 30-45 minutes to correspond to the twilight period of the day according to these embodiments. The twilight spectrum may also be ramped up briefly during midday to support and provide alerting light during the afternoon lull 870 that typically occurs during the day and is associated with reduced wakefulness.

[0055] According to some embodiments and as shown in FIG. 8, during the main part of the day, that is right after waking up and up to within 2-3 hours of initiating sleep, illumination with the BIOS spectrum (A) is provided (e.g., the spectrum as shown in FIGS. 3a-b). The BIOS spectrum is produced according to some embodiments from the combination of a white light LED (e.g., 2700 K, 3500 K, 4000 K, etc.) and a SkyBlue LED package that is rich in melanopic as discussed elsewhere herein. As the photoperiod approaches the sleep portion of cycle 875, the SkyBlue spectral component is dimmed such that the melanopic light is reduced or eliminated in advance of and to prepare for sleep. FIG. 8 shows the ramping down 880 of the SkyBlue spectral component between times S-3 and S-2 such that there is no melanopic light 2 hours prior to sleep time. Similarly and according to some embodiments, the SkyBlue spectrum is ramped up 885 beginning at the time of waking W to maximum intensity at W+1 and maintained there until the ramp down 880 at S-3. The illumination throughout the day with the SkyBlue enhanced spectrum facilitates circadian entrainment.

[0056] After the SkyBlue spectrum has been ramped down (or coinciding with its ramp down) a ramping up of one or more nighttime spectrums may be employed to maintain light level or provide aesthetic warm light for evening time. This nighttime transition 890 can be achieved using an optional warm white light package (C), e.g., 2700 K white light. Alternatively or additionally, illumination from a nighttime LED package may be used during the pre-sleep period or as a nightlight during the sleep period. An example embodiment of a nighttime spectrum E is shown in FIG. 8. An optional enriched red spectrum D may also be used for bi-stability support at various points in the photoperiod as discussed above. In the example shown, red enriched light D is provided just prior to the ramping up of the SkyBlue component or the Twilight component or both. In some embodiments, the BIOS spectrum A and the twilight spectrum B that emits 420 nm light may be directed spatially in an upward direction as indicated by the upward arrow on the left-hand side of FIG. 8, while the warm light spectrum C, the enriched red spectrum D and the nighttime spectrum E are directed spatially in a downward direction as indicated by the downward arrow on the left-hand side of FIG. 8. In some embodiments, an LED module that emits melanopic light (e.g., illumination with a maximum peak intensity between 475 nm to 495 nm or between 470 nm and 490 nm) and/or an LED module that emits illumination in a wavelength band between 410 nm and 430 nm (e.g., a peak intensity at about 420 nm in the wavelength band between 400 nm and 450 nm) are emitted in an upward direction. In some embodiments, LED modules that emit warm light (e.g., CCT of 2700 K), red light and/or a nighttime spectrum are emitted in a downward direction.

[0057] Although multiple spectral outputs corresponding to multiple LED packages are shown in the example of FIG. 8, embodiments of the inventions are not limited to the specific combinations or spectrums shown. Embodiments of the invention may include a subset of these outputs or additional outputs. Also, although the intensity of the various spectra are not illustrated in FIG. 8, it is to be understood that the intensity of the individual spectra is a parameter of the system and the intensities of one of more of the illumination outputs such as the SkyBlue or Twilight spectrums may be adjusted to achieve the desired total spectral illumination (see, for instance, Bio-dimming as discussed above).

[0058] While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. It should be understood that the diagrams herein illustrates some of the system components and connections between them and does not reflect specific structural relationships between components, and is not intended to illustrate every element of the overall system, but to provide illustration of the embodiment of the invention to those skilled in the art. Moreover, the illustration of a specific number of elements, such as LED drivers power supplies or LED fixtures is in no way limiting and the inventive concepts shown may be applied to a single LED driver or as many as desired as will be evident to one skilled in the art.

[0059] In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include many variants and embodiments. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.