WO2010035200A1

WO2010035200A1 - Apparatus and techniques for simulating natural light cycles

Info

Publication number: WO2010035200A1
Application number: PCT/IB2009/054114
Authority: WO
Inventors: Daniel Nathan Adams; Kent Savage; David James Burrows; Sean Scott Wheelhouse
Original assignee: Koninklijke Philips Electronics, N.V.
Priority date: 2008-09-26
Filing date: 2009-09-18
Publication date: 2010-04-01

Abstract

A light therapy technique includes gradually increasing or decreasing an intensity of light in a manner that approximates a change in light intensity during a natural light event, such as dawn or dusk. Graphs of the intensities of both the natural and simulated light events plotted over time may have an S, or sigmoidal, shape. The intensity curve of the simulated light event may be modified (e.g., a portion of the curve may be compressed or elongated relative to the corresponding portion of the curve of the natural light event) to provide a desired result, such as to allow a subject to sleep until an expected wake up time. Optionally, the color of light during the simulated light event may also mimic light coloring during the corresponding natural light event. Light therapy apparatus, such as clocks, that effect such methods are also disclosed.

Description

APPARATUS AND TECHNIQUES FOR SIMULATING NATURAL LIGHT

CYCLES

[0001] The present invention relates generally to light therapy devices and techniques, more specifically, to light therapy techniques in which the rising and/or setting of the sun is simulated and to light therapy devices that effect such techniques.

[0002] A variety of techniques have been used to awaken individuals at a desired time. Perhaps the most common technique is the use of an audible alarm clock, which often abruptly jars the individual from a state of restful sleep before the natural sleep cycle is complete. A common result of waking up in a manner that does not allow for the natural completion of a sleep cycle (i.e., gradual awakening) is known as "sleep latency." When an individual suffers from sleep latency, they continue to feel sleepy and frequently suffer from a reduced state of alertness.

[0003] So-called dawn simulators are intended to operate in a manner that allows an individual to wake up in a more natural, gradual manner. Dawn simulation typically involves a gradual increase in light intensity along a straight line 1 or a slightly bulging curve 2, such as those shown in FIG. 8. While the results of dawn simulation are often preferable to those of an abrupt, audible alarm, the types of dawn simulation that are depicted by FIG. 8 still do not approximate the manner in which light intensity increases during a natural sunrise.

[0004] These and other aspects of existing techniques and apparatus for awakening individuals may be improved upon.

[0005] In a natural sunrise, light intensity increases very gradually at first, then at a much faster rate, then more gradually again. When the light intensity of a natural sunrise is graphed, or plotted, over time, the result is an S-shaped, or sigmoidal, curve.

[0006] The present invention, in various embodiments, includes light therapy apparatus that simulate natural light events, such as the rising of the sun, or dawn, and/or the setting of the sun, or dusk. A specific embodiment of such an apparatus is a dawn simulator. A dawn simulator that incorporates teachings of the present invention may be configured to cause a light source to gradually increase in intensity, with the increase in intensity substantially following a generally sigmoidal curve over time. In a more specific embodiment, the generally sigmoidal curve includes an initial period at which the intensity of output light increases at a slow, first rate (e.g., along a best-fit line having a slope of about 0.5 or less, etc.), a central period at which the intensity of output light increases at a quicker, second rate (e.g., along a best-fit line having a slope of about 1 or more, etc.), and a terminal period at which the intensity of output light increases at a slow, third rate (e.g., along a best-fit line having a slope of about 0.5 or less).

[0007] A dawn simulation apparatus of the present invention may use a modified sigmoidal light intensity curve. In some embodiments, the modification may be a relative elongation of a central period of the sigmoidal light intensity curve. Such elongation may increase the percentage of the portion of the light intensity curve that is occupied by central period relative to the percentage of a standard sigmoidal light intensity curve. The elongation may merely comprise stretching the central period over a longer relative duration or the inclusion of a delay segment along the length of the central period. In embodiments that include a delay segment, the intensity of light either does not increase (i.e., the slope of a best-fit line through the delay segment is zero) or it increases at a much slower rate than the rate at which light intensity increases throughout the remainder of the central period of the modified sigmoidal curve (i.e., the slope of a best-fit line through the delay segment is less than the slope of a best- fit line through the remainder of the central period of the sigmoidal curve). In other embodiments where the sigmoidal light intensity curve is modified, the initial period of the curve may be elongated and/or the central period may be compressed.

[0008] The intensity of light during dusk simulation may also vary, over time, along a sigmoidal curve or a modified (relative to natural dusk) sigmoidal curve. Of course, when dusk is simulated, the intensity of light decreases gradually, slowly during an initial period of the curve, more quickly during a central period of the curve, and slowly again during a terminal period of the curve. One or more of these periods may be tailored (e.g., expanded or compressed) in a manner that may better lull a subject to sleep.

[0009] The present invention also includes light therapy apparatus that simulate the colors of a natural light event, such as the rising or setting of the sun. As an example, the initial period of a sigmoidal curve that represents a sunrise may include more blue light than other colors of light, while green or yellow light may predominate at some point during the central period, and there may be more orange or red light than other colors during the terminal period of the sigmoidal curve.

[0010] In addition, the present invention includes light therapy techniques in which light is gradually increased or decreased in a manner that mimics a natural light event, such as the rising or setting of the sun. A specific embodiment of such a technique, in which a subject is awakened by artificial light that simulates a sunrise, the intensity of the artificial light is gradually increased along a generally sigmoidal curve. In some even more specific embodiments, the sigmoidal curve may include a delay segment at a point before the intensity increases enough to cause the subject to awaken to a substantially conscious state.

[0011] Other aspects, as well as features and advantages, of the present invention will become apparent to those in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims.

[0012] In the drawings, which depict various aspects of the present invention:

[0013] FIG. 1 is a frontal perspective view of an embodiment of light therapy apparatus according to the present invention;

[0014] FIG. 2 is a rear view of the embodiment of light therapy apparatus shown in FIG. 1;

[0015] FIG. IA is a schematic representation of another embodiment of light therapy apparatus of the present invention;

[0016] FIG. 3 is a schematic representation of various features of an embodiment of light therapy apparatus of the present invention;

[0017] FIG. 4 is an embodiment of a sigmoidal light intensity curve that may be used to wake a subject up in accordance with teachings of the present invention;

[0018] FIGs. 5 and 6 are embodiments of modified sigmoidal light intensity curves that may be followed in simulating a sunrise to awaken a subject;

[0019] FIG. 7 is a graph that shows an example of the manner in which light may decrease at dusk, or during dusk simulation; and

[0020] FIG. 8 is a curve that illustrates the manner in which light intensity is increased over time by existing dawn simulation devices. [0021] An embodiment of a light therapy apparatus 10 is shown in FIGs. 1 and 2. In the depicted embodiment, light therapy apparatus 10 is a so-called "dawn/dusk simulator," which is configured to cause light to be output in a manner that mimics a sunrise and to output light in manner that mimics a sunset. Light therapy apparatus 10 includes a housing 12, a power input 20 and a power output 30, as well as a variety of other features, including internal features (e.g., a clock, an audible alarm, a radio/compact disk (CD)/.mp3 player, speakers, control elements for various features, power supply, etc.) that are contained within housing 12 and external features (e.g., input elements, output elements, etc.) that are accessible or visible from an exterior of housing 12.

[0022] Light therapy apparatus 10 is configured to be used with one or more light sources (e.g., an analog light source, such as incandescent light; a digital light source, such as a light-emitting diode (LED) device; etc.). In the illustrated embodiment, light source 40 is separate from light therapy apparatus 10. In other embodiments, a light source may be integrated into the same housing as light therapy apparatus 10.

[0023] Power input 20 is configured to supply power to light therapy apparatus 10, as well as to a light source 40 associated with light therapy apparatus 10. As illustrated, power input 20 includes a receptacle 22 configured to receive and couple to a plug 24 at one end of a power cord 26 that has another plug 28 at its opposite end for plugging into an alternating current (AC) power source, such as an AC power outlet in a wall.

[0024] Power output 30 is configured to provide power to light source 40. As depicted, power output includes a receptacle 32 that receives a plug 34 at one end of a power cord 36 that supplies power to the light source 40, with a plug 38 at the opposite end of power cord 36 configured to receive and couple to a plug at the end of a power cord of the light source 40. Alternatively, receptacle 32 of power output 30 may be configured to receive and couple to the plug of a power cord of the light source 40.

[0025] In alternative embodiments, such as that shown in FIG. IA, the power output features may be part of a power output device 30' that is separate from a light therapy apparatus 10'. In such embodiments, light therapy apparatus 10' may communicate remotely, in a manner known in the art (e.g., ZigBee (802.15) signals, Z-wave signals, 802.11 signals, Bluetooth signals, etc.), with a separately housed power output device 30'. The separate power output device may plug directly into an electrical outlet and provide power directly to light source 40.

[0026] Internally, as schematically illustrated by FIG. 3, light therapy apparatus 10 includes various electrical components 52, a control element 54, and control components 56 of types and in arrangements that are known or apparent to those of ordinary skill in the art. Electrical components 52 enable light therapy apparatus 10 to use power from an external source of power (e.g., an AC power source) or, optionally, from an internal power supply (e.g., a direct current (DC) power source, such as a battery). Among other functions, in embodiments where light therapy apparatus 10 is configured to operate on AC power, electrical components 52 receive at least a portion of the AC power that is input into light therapy apparatus 10 through power input 20 and converts the AC power to DC power. The DC power operates control element 54 and, optionally, various other digital features (e.g., display with touch-sensitive regions, a digital light source, etc.) of light therapy apparatus 10.

[0027] Control element 54 may include a control circuit board, as well as one or more processors, other control elements (e.g., resistors, capacitors, diodes, transistors, inductors, etc.), and a switch that are carried by or otherwise associated with the control circuit board.

[0028] Control components 56 are electrical devices that enable control element 54 to control the power that is supplied to light source 40. For the sake of simplicity, electrical components 56 are collectively referred to herein as a "dimmer" 56. Dimmer 56, which operates in accordance with programming of control element 54, controls the amount of power that is supplied to power output 30 and, thus, to the light source 40. In embodiments where light source 40 operates off of AC power, dimmer 56 may include a one or more thyristors, such as a so-called "TRIAC" or a pair of rectifiers (e.g., silicon-controlled rectifiers (SCRs)), a sine wave dimmer (which relies on an insulated gate bipolar transistor (IGBT)), a rheostat, an autotransformer, or any other type electrical component that may be used in or as a dimmer. In embodiments where the light source 40 may operate off of DC power, pulse width modulation (PWM) may be used to provide the desired changes in intensity.

[0029] As shown by FIG. IA, in embodiments where power output device 30' is separate from light therapy apparatus 10', power output device 30' may include a communication element 58', a control element 54', and dimmer 56. Communication element 58' may comprise an antenna or other suitable element that receives signals (e.g., ZigBee (802.15) signals, Z-wave signals, 802.11 signals, Bluetooth signals, etc.), from a corresponding communication element 58 (e.g., an antenna, etc.) of light therapy apparatus 10', with the communication element 58 of light therapy apparatus 10' operating under control of its control element 54 (FIG. 3). Control element 54' of power output device 30', which may comprise control circuitry of a known type, receives signals from communication element 58' of power output device 30' to operate dimmer 56. Dimmer 56 provides power to an electrical outlet 59 of known configuration, which may communicate power to a light source 40 (FIGs. 1 and 2) in a manner known in the art.

[0030] With returned reference to FIG. 1, examples of external features of light therapy apparatus 10 include an output element 60 and one or more input elements 70. Of course, each output element 60 and input element 70 communicates with control element 54 in any known, suitable manner.

[0031] In some embodiments, output element 60 merely displays information. In other embodiments, output element 60 comprises a user interface device, such as a touch-sensitive display. More specifically, the user interface device may be a touch-sensitive liquid crystal device (LCD) that includes one or more non-sensitive display regions 62 and one or more touch-sensitive control regions 64. Display regions 62 may be configured to show various information, such as the current time, the time at which a light therapy program (e.g., a dawn simulation, a dusk simulation, etc.) is configured to begin or to have a desired effect on a subject (e.g., wake the subject, terminate dusk simulation, etc.), the remaining duration of a particular function, information regarding activated functions (e.g., light therapy programming, light output, an audible alarm, a radio, etc.), or the like. Control regions 64 may enable a user to control the operation of light therapy apparatus 10, set the durations and start times of light therapy (e.g., sunrise, sunset, etc.) programs, tailor the programming of light therapy apparatus 10, alter an active light therapy program (e.g., manually increase or decrease light intensity, etc.), or for any other purpose.

[0032] Input elements 70, which may comprise push buttons of a type known in the art, may likewise control various functions and/or programming of light therapy apparatus 10. For example, light therapy apparatus 10 may include input elements that supply power to and/or control the brightness of a light source 40, control a radio, illuminate and/or control the brightness of output element 60, postpone the sounding of an audible alarm (i.e., a "snooze" function), set an audible alarm to sound after a specified duration of time (i.e., a "nap" function), enable a user to set times and/or tailor various light therapy programs of light therapy apparatus 10 (e.g., directly, by allowing the user to set times or tailor programming of light therapy apparatus through the touch sensitive control regions 64, etc.), or otherwise control the operation of light therapy apparatus 10.

[0033] Control element 54 of a light therapy apparatus 10 of the present invention may, in some embodiments, be programmed to cause dimmer 56 to effect dawn simulation, by way of gradually increasing the intensity of light output by a light source 40, in a manner that follows a sigmoidal curve 100, such as that shown in FIG. 4. Sigmoidal curve 100 approximates a natural sunrise and its natural phases.

[0034] In an initial period, or region, of sigmoidal curve 100, referred to herein as a "predawn phase" 110, the intensity 102 of output light slowly increases over time, at about a first rate. As a nonlimiting example, light intensity 102 may increase at a rate that may be approximated by the slope of a best-fit line 112 through predawn phase 110. When sigmoidal curve 100 represents a thirty minute dawn simulation, the slope of best fit line 112 may be about 0.5. During predawn phase 100, the intensity of light generated along sigmoidal curve 100 may increase from zero at the left side of sigmoidal curve 100 to about 15% of the maximum light intensity of sigmoidal curve 100 (i.e., the intensity at the right end of sigmoidal curve 100). [0035] In a central period, or "waking phase" 120, of sigmoidal curve 100, the intensity of output light increases from about 15% of the maximum intensity at the beginning of waking phase 120 to about 90% of the maximum intensity at the end of waking phase 120. The increase in light intensity during waking phase 120 is effected at about second rate, which is quicker than the above-mentioned first rate. Without limiting the scope of the present invention, the second rate may be approximated by a best- fit line 122 through waking phase 120. In embodiments where sigmoidal curve 100 represents a dawn simulation that lasts for thirty minutes, best-fit line 122 may have a slope of about one or more.

[0036] The intensity of light increases at about a third rate, from about 90% of the maximum intensity to about 100% of the maximum intensity, over the course of a terminal period, or "alertness phase" 130, of sigmoidal curve 100. The third rate is less than the second rate. In the depicted example, the third rate may be approximated by the slope of a best fit line 132 through alertness phase 130 of sigmoidal curve 100. In the depicted embodiment, where sigmoidal curve 100 represents a thirty minute dawn simulation, best- fit line 132 has a slope of about 0.5 or less.

[0037] In the sigmoidal curve 100 illustrated by FIG. 4, the durations of predawn phase 110, waking phase 120, and alertness phase 130 are approximately the same. A total duration of the embodiment of sigmoidal curve 100 shown in FIG. 4 is about 90 minutes, although sigmoidal curves with a wide variety of other durations (e.g., 30 minutes, 45 minutes, 60 minutes, 75 minutes, 105 minutes, 120 minutes, etc.) may also be used in accordance with teachings of the present invention.

[0038] Of course, in embodiments where the overall duration of a sigmoidal curve is modified from that shown in FIG. 4, the x-axis components of best-fit lines 112, 122, 132 may remain the same while the y-axis components, or lengths, of best-fit lines may decrease or increase. The slopes of best fit lines 112, 122, 132 and, thus, the rates at which light intensity increases in each period 110, 120, 130 of sigmoidal curve 100 may correspondingly increase or decrease.

[0039] The depicted sigmoidal curve mimics a sunrise at a somewhat medial longitude in the Northern Hemisphere (e.g., at the latitude of American Fork, Utah) at mid-summer. Light therapy apparatus that employ sigmoidal curves that imitate sunrises, as perceived either indoors or outside, at other locations and/or at other times of year are also within the scope of the present invention. In some embodiments, the sigmoidal curve may be tailored (e.g., by programming, etc.) to change throughout the year in the same manner as a natural sunrise. In other embodiments, a user may select a sigmoidal curve that represents a sunrise at a particular, desired location (e.g., at the user's home, which may be desirable as the user travels away from home; at another desired location, such as a resort or other location that a user finds relaxing; etc.).

[0040] In some embodiments, sigmoidal curve 100 and the resulting light output are substantially smooth, with no visible changes in intensity.

[0041] FIG. 5 illustrates an embodiment of a modified sigmoidal curve 100'. Modified sigmoidal curve 100' includes an predawn phase 110' and an alertness phase 130' that may be substantially the same (e.g., in shape, intensity, etc.) as their respective predawn phase 110 and alertness phase 130 of a standard sigmoidal curve 100, such as that shown in FIG. 4. However, a waking phase 120' of modified sigmoidal curve 100' differs from, and has a longer proportional duration than, waking phase 120 of sigmoidal curve 100 and than the waking phase of a natural sunrise.

[0042] Specifically, waking phase 120' of the depicted embodiment of sigmoidal curve 100' is interrupted by a discontinuity, which is referred to herein as a "delay segment" 124. In some embodiments, the intensity of light does not increase during the duration of delay segment 124; i.e., the slope of a best- fit line 126 through delay segment 124 is zero. In other embodiments, the rate at which a light intensity increases during delay segment 124 is significantly less than the rates at which light intensity increases throughout the duration of a remainder of waking phase 120' of sigmoidal curve 100'; i.e., the slope of best-fit line 126 is less than the slope of a best-fit line through the remainder of waking phase 120'.

[0043] The positioning and configuration of delay segment 124 may be configured in such a way that the time at which the simulated sunrise wakes a subject up will coincide with a time at which the subject would like to wake up. In some embodiments, one or more of the location of delay segment 124 along sigmoidal curve 100', the shape of delay segment 124, the orientation of delay segment 124, and the duration of delay segment 124 may be configured to eliminate or decrease the amount of time that elapses between the time when the light causes a subject to begin to wake up and the time at which the light has fully awakened the subject.

[0044] Referring now to FIG. 6, another embodiment of modified sigmoidal curve 100" that may be used in accordance with teachings of the present invention is depicted. The light intensity ranges of the predawn phase 110", the waking phase 120", and the alertness phase 130" may remain substantially the same as the intensity ranges of the corresponding phases of the sigmoidal curve 100 shown in FIG. 4 and the modified sigmoidal curve 100' of FIG. 5. The duration of predawn phase 120" of modified sigmoidal curve 100", in proportion to the total length of modified sigmoidal curve 100", is, however, extended relative to the percentages of the total durations of sigmoidal curve 100 and modified sigmoidal curve 100' that are occupied by their respective predawn phases 110 and 110'. Consequently, the duration of one or both of waking phase 120" and alertness phase 130"of modified sigmoidal curve 100" may also be compressed, or comprise a smaller percentage of the total duration of modified sigmoidal curve 100" than the percentages of the total durations of sigmoidal curve 100 and modified sigmoidal curve 100' that are comprised of their respective waking phases 120 and 120' and alertness phases 130 and 130'. In the depicted embodiment, both waking phase 120" and alertness phase 130" are compressed.

[0045] Other variations of sigmoidal curves, including sigmoidal curves that are configured to tailor the manner in which a subject wakes up, are also within the scope of the present invention.

[0046] In another aspect, the present invention includes light therapy techniques and apparatus in which the color of light is tailored and varied to mimic the color of light at a particular time of day (e.g., sunrise, sunset, etc.). Without limiting the scope of the present invention, there may be more blue light than any other color of light during the predawn phase, with the proportion of green or yellow light increasing over the course of the waking phase, and orange or red light becoming more predominant during the alertness phase. [0047] A light therapy apparatus 10 of the present invention may also include sensors that detect the intensity and, optionally, color, of light during a natural light event at a particular location. The light intensity and optional color information may then be processed to generate a curve or modified curve and optional color output that may be used by control element 54 to effect a simulated version of the light event.

[0048] Although the foregoing description is centered on a discussion of dawn simulation, light therapy techniques that include simulation of other natural light events, such as dusk, are also within the scope of the present invention, as are apparatus that effect such techniques. Natural changes in light (e.g., changes in light intensity, light color, etc.) during such events may be accurately simulated, or may be modified to provide a desired result. Some of these other natural light events, such as dusk, may also include light intensity changes that follow a generally sigmoidal curve. Accordingly, the simulated versions of such events may include use of a sigmoidal curve that has been modified to achieve a particular result. As a non-limiting example, dusk simulation may follow a modified sigmoidal curve that lulls a subject to sleep more quickly or more effectively than a natural dawn.

[0049] Without limiting the scope of the present invention, light therapy apparatus and light therapy techniques that employ teachings of the present invention may be used to improve the manner in which a subject wakes up or falls asleep. Examples of situations where such techniques and/or apparatus may be useful include, but are not limited to, situations the subject needs to wake up or fall asleep at times that do not coincide closely with natural light events, while the subject is traveling, or in other situations where the simulation of natural light events would be therapeutic or otherwise helpful to the subject.

[0050] Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the present invention, but merely as providing illustrations of some embodiments. Similarly, other embodiments of the invention may be devised which do not exceed the scope of the present invention. Features from different embodiments may be employed in combination. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions and modifications to the invention as disclosed herein which fall within the meaning and scope of the claims are to be embraced thereby.

Claims

CLAIMS:

1. A light therapy technique, comprising: exposing a subject to light that gradually increases in intensity along a modified sigmoidal curve in which light intensity increases over time in a manner that simulates a natural sunrise, including: a predawn phase; a waking phase; and an alertness phase, with the waking phase and at least of the predawn phase and the alertness phase comprising percentages of a duration of the modified sigmoidal curve that differ from corresponding percentages of a duration of the natural sunrise that are comprised by a natural waking phase and at least one of a natural predawn phase and a natural alertness phase of the natural sunrise.

2. The light therapy technique of claim 1, wherein percentages of the duration of the modified sigmoidal curve that are comprised of both the predawn phase and the alertness phase differ from the corresponding percentages of the duration of the natural sunrise that are comprised of the natural predawn phase and the natural alertness phase.

3. The light therapy technique of claim 1 , wherein the predawn phase of the modified sigmoidal curve comprises a larger percentage of the duration of the modified sigmoidal curve than the corresponding percentage of the duration of the natural sunrise that is comprised of the natural predawn phase.

4. The light therapy technique of claim 1 , wherein the waking phase of the modified sigmoidal curve comprises a smaller percentage of the duration of the modified sigmoidal curve than the corresponding percentage of the duration of the natural sunrise that is comprised of the natural waking phase.

5. The light therapy technique of claim 4, wherein: the predawn phase comprises about 50% to about 80% of a total duration of the modified sigmoidal curve; the waking phase comprises about 10% to about 25% of the total duration of the modified sigmoidal curve; and the alertness phase comprises about 10% to about 25% of the total duration of the modified sigmoidal curve.

6. The light therapy technique of claim 1 , wherein the waking phase of the modified sigmoidal curve comprises a larger percentage of the duration of the modified sigmoidal curve than the corresponding percentage of the duration of the natural sunrise that is comprised of the natural waking phase.

7. The light therapy technique of claim 6, wherein the waking phase of the modified sigmoidal curve includes a delay segment that is discontinuous with a curve of a remainder of the waking phase.

8. The light therapy technique of claim 7, wherein a location of the delay segment is configured to cause light to awaken the subject at a desired time.

9. The light therapy technique of claim 1, including: increasing an intensity of light increases from zero to about 15% of a maximum light intensity of the modified sigmoidal curve during the predawn phase; increasing the intensity of light from about 15% of the maximum light intensity to about 90% of the maximum light intensity during the waking phase; and increasing the intensity of light from about 90% to about 100% during the alertness phase.

10. The light therapy technique of claim 1 , further comprising: simulating a change in light colors that occurs during the natural sunrise.

11. A light therapy technique, comprising: exposing a subject to light with an intensity that gradually changes over time along a modified sigmoidal curve, including: an initial period; a central period; and a terminal period, with at least one of the initial period, the central period, and the terminal period comprising a percentage of a duration of the modified sigmoidal curve that differs from a corresponding percentage of a duration of a corresponding natural light event that is comprised by a corresponding natural initial period, a corresponding natural central period, or a corresponding natural terminal period of the natural light event.

12. The light therapy technique of claim 11 , wherein the natural light event comprises a dawn.

13. The light therapy technique of claim 11 , wherein the natural light event comprises a dusk.

14. The light therapy technique of claim 11 , wherein a curve of each of the initial period, the central period, and the terminal period is substantially continuous.

15. The light therapy technique of claim 11 , wherein a curve of at least one of the initial period, the central period, and the terminal period includes a delay segment comprises a discontinuity in the curve.

16. The light therapy technique of claim 11 , further comprising: simulating a change in light colors that occurs during the natural light event.

17. A light therapy device, comprising: a power supply for at least one light source; and a control element for controlling the power supply and illumination of the at least one light source, the control element programmed to control the power supply in a manner that will, over time, vary an amount of power output by the power supply so as to increase or decrease an intensity of light output by the at least one light source along a modified sigmoidal curve including: an initial period; a central period; and a terminal period, the modified sigmoidal curve corresponding to a natural light event including: a natural initial period; a natural central period; and a natural terminal period, at least one of the initial period, the central period, and the terminal period of the modified sigmoidal curve comprising a different proportion of the modified sigmoidal curve than a corresponding proportion of the natural light event comprised by the corresponding natural initial period, natural central period, or natural terminal period.

18. The light therapy device of claim 17, wherein the at least one light source comprises a separately housed light source.

19. The light therapy device of claim 17, wherein the control element is programmed to control the power supply so as to cause the at least one light source to simulate a dawn.

20. The light therapy device of claim 17, wherein the control element is programmed to control the power supply so as to generate a dawn with an extended central period.

21. The light therapy device of claim 20, wherein the extended central period includes a delay segment.

22. The light therapy device of claim 17, wherein the control element is programmed to control the power supply so as to cause the at least one light source to simulate a dusk.

23. The light therapy device of claim 17, whererin the control element is programmed to cause the at least one light source to vary the colors of output light in a manner that simulates colors of the natural light event.

24. The light therapy device of claim 17, further comprising: a clock in communication with the control element.

25. The light therapy device of claim 17, wherein the control element communicates remotely with the power supply.