Lighting equipment

Abstract

The method includes emitting a first light having a first color on a first tritan confusion color line defined by a tritan common point, and emitting a second light having a second color on a second tritan confusion color line defined by a tritan common point, the second light being emitted out of phase with the first light, such that the first tritan confusion color line, the tritan common point, and the second tritan confusion color line form an angle of less than 10 degrees.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is an international application claiming priority to U.S. Provisional Patent Application No. 63 / 278,680, filed November 12, 2021, the contents of which are incorporated herein by reference.

[0002]

[0002] This application incorporates by reference the entire disclosures of the following applications: U.S. Patent Application No. 16 / 708,563, filed December 10, 2019; U.S. Patent Application No. 16 / 545,853, filed August 20, 2019; U.S. Patent Application No. 16 / 545,750, filed August 20, 2019; U.S. Patent Application No. 15 / 943,210, filed April 2, 2018; International Application No. PCT / US2018 / 020395, filed March 1, 2018; U.S. Provisional Patent Application No. 62 / 546,475, filed August 16, 2017; U.S. Provisional Patent Application No. 62 / 508,286, filed May 18, 2017; U.S. Provisional Patent Application No. 17 / 100,536, filed November 20, 2020; U.S. Provisional Patent Application No. 63 / 024,806, filed May 14, 2020; and U.S. Provisional Patent Application No. 62 / 939,037, filed November 22, 2019. [Background technology]

[0003] background

[0003] For reasons such as jet lag or adapting to an unusual work shift, it may be useful to change a person's circadian rhythm or "sleep cycle." A person's circadian rhythm is primarily controlled by the suprachiasmatic nucleus (SCN), a small region in the hypothalamus of the brain. Conventional methods for changing a person's circadian rhythm have generally involved directly stimulating the photoreceptor protein melanopsin in intrinsically photosensitive retinal ganglion cells (ipRGCs), which account for about 1% of the retinal ganglion cells in the retina. It is believed that illuminating the retina with blue light (e.g., in a narrow range of wavelengths around about 480 nanometers) will excite melanopsin in the person's ipRGCs and stimulate the SCN via neural pathways, thereby altering the person's circadian rhythm (e.g., delaying the onset of fatigue). However, because ipRGCs have a relatively low photosensitivity, are relatively sparsely distributed in the retina, and have a slow photoactivation response, such methods are undesirable in that they illuminate the retina for a relatively long period of time at an intensity that is uncomfortable or even painful. Summary of the Invention [Means for solving the problem]

[0004] overview

[0004] One aspect of the present disclosure is a method that includes emitting a first light having a first color on a first tritan confusion color line defined by a tritan common point, and emitting a second light having a second color on a second tritan confusion color line defined by the tritan common point, where the second light is emitted out of phase with the first light, and where the first tritan confusion color line, the tritan common point, and the second tritan confusion color line form an angle of less than 10 degrees.

[0005]

[0005] Another aspect of the present disclosure is a control system configured to cause a lighting device to perform a function including emitting a first light having a first color on a first tritan confusion color line defined by a tritan common point and emitting a second light having a second color on a second tritan confusion color line defined by the tritan common point, where the second light is emitted out of phase with the first light, and where the first tritan confusion color line, the tritan common point, and the second tritan confusion color line form an angle of less than 10 degrees.

[0006]

[0006] Another aspect of the present disclosure is an illumination device that includes a light source assembly and a control system configured to cause the light source assembly to perform functions including emitting a first light having a first color on a first tritan confusion color line defined by a tritan common point and emitting a second light having a second color on a second tritan confusion color line defined by the tritan common point, wherein the second light is emitted out of phase with the first light, and the first tritan confusion color line, the tritan common point, and the second tritan confusion color line form an angle of less than 10 degrees.

[0007]

[0007] The terms "about" or "substantially" with respect to quantities or measurements described in this specification mean that the referenced characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including, for example, tolerances, measurement errors, limits of measurement precision, and other factors known to those of skill in the art, may occur to an extent that does not interfere with the effect that the characteristic is intended to provide.

[0008]

[0008] The above-described features, functions, and advantages may be realized independently in various examples or may be combined in yet other examples, further details of which will become apparent with reference to the following description and drawings.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Novel features believed characteristic of the illustrative examples are set forth in the appended claims. However, the illustrative examples, as well as their preferred uses, further objects and explanations, will best be understood by reference to the following detailed description of exemplary embodiments of the present disclosure taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram of a lighting device according to an example. [Diagram 2]

[0011] 4 illustrates intensity waveforms of a first light and a second light according to an example. [Diagram 3]

[0012] 1 illustrates colors of a first light and a second light in a color space according to an example. [Figure 4]

[0013] 1 illustrates colors of a first light and a second light in a color space according to an example. [Diagram 5]

[0014] 1 illustrates colors of a first light and a second light in a color space according to an example. [Figure 6]

[0015] FIG. 2 is a block diagram of a method according to an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Detailed Description

[0016] As discussed above, current methods of altering circadian rhythm via direct stimulation of melanopsin in intrinsically photosensitive retinal ganglion cells (ipRGCs) are often inconvenient, uncomfortable, and / or somewhat ineffective. Thus, disclosed herein are improved devices and methods for altering circadian rhythm.

[0012]

[0017] Circadian rhythms can be changed more conveniently and efficiently through stimulation of S, M, and L cones in the retina, which causes indirect stimulation of ipRGCs downstream of the cones along neural pathways.While conventional methods have optimized the photoactivity of melanopsin by illuminating ipRGCs with blue light (e.g., λ of about 480 nm), the methods disclosed herein generally illuminate the retina with wavelengths designed to stimulate S cones, which have maximum photosensitivity at about 419 nm, M cones, which have maximum photosensitivity at about 530 nm, and / or L cones, which have maximum photosensitivity at about 559 nm.

[0013]

[0018] More specifically, stimulating cones, which are densely packed in the retina and have higher light sensitivity than ipRGCs, can excite ipRGCs more efficiently than direct stimulation of ipRGCs via sunlight. This indirect excitation of ipRGCs can stimulate the suprachiasmatic nucleus (SCN). This method of indirectly exciting ipRGCs via excitation of cones can be performed when a person's circadian rhythm is prone to change.

[0014]

[0019] For example, the method performed by the lighting device can be performed when one or more people in a position to view the light emitted by the lighting device are approaching or have recently experienced the daily minimum of their respective circadian rhythms. For example, if the light emitted by the lighting device is viewed by a person who is approaching their sleepiest time of the day (e.g., within the past four hours), the light will tend to delay the onset of drowsiness. For many people, the sleepiest time of the day is between midnight and 2:30 a.m. (0:00-2:30). On the other hand, if the light emitted by the lighting device is viewed by a person who has recently experienced their sleepiest time of the day (e.g., within the past four hours), the light will tend to hasten the onset of drowsiness.

[0015]

[0020] ipRGCs, like all retinal ganglion cells, are driven by upstream cone photoreceptors. Thus, rapid increases or decreases in illuminance (delta) of light incident on the cones reliably drive ipRGC signaling. For example, ipRGC activity (and consequently downstream SCN activity) is maximized in response to rapid increases in light absorption by M-cones (e.g., green light) and L-cones (e.g., red light) and rapid decreases in light absorption by S-cones (e.g., violet light).

[0016]

[0021] More specifically, a lighting device can vibrate two colors of light fast enough to appear static (e.g., as one static color) to humans, but slow enough that the cone photoreceptors still respond and drive activity via ipRGCs to the circadian center. Thus, lighting devices useful for general home or workplace lighting can be used to regulate human circadian rhythms.

[0017]

[0022] The disclosed examples are described in more detail below with reference to the accompanying drawings, which show some, but not all, of the disclosed examples. Indeed, although several different examples are described, the invention should not be construed as being limited to the examples disclosed herein. Rather, these examples are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0018]

[0023] 1 illustrates a lighting device 100 that includes a light source assembly 102 and a control system 104. In some examples, the light source assembly 102 may include one or more light sources, such as a light emitting diode (LED), a laser, an organic light emitting diode (OLED), an incandescent bulb, or a halogen bulb, although other examples are possible.

[0019]

[0024] The control system 104 may be in the form of any combination of software and / or hardware configured to cause the light source assembly 102 and / or the lighting device 100 to perform any of the functions described herein. For example, the control system 104 may include one or more Boolean circuits, programmable logic controllers (PLCs), and / or special purpose circuits configured to provide power and / or control signals to the light source assembly 102 to perform any of the functions described herein. Additionally or alternatively, the control system 104 may include one or more processors and a computer readable medium having instructions stored thereon that, when executed by the processors, cause the light source assembly 102 and / or the lighting device 100 to perform any of the functions described herein. The control system 104 may additionally include a signal generator.

[0020]

[0025] In various examples, the lighting device 100 may be integrated into or in the form of a wearable device, goggles, headband, armwear, wristwear, or therapeutic wearable device configured to deliver light to a subject's retina. In some examples, the lighting device 100 is incorporated into a vehicle, such as an automobile, airplane, helicopter, boat, ship, or train. The lighting device 100 may also be incorporated into a dashboard, accent lighting unit, general cabin lighting unit, or headlight unit. In various embodiments, the lighting device 100 is incorporated into a display device, such as a mobile phone, tablet computer, monitor, or television. The lighting device 100 may also be incorporated into a lighting unit, such as a lamp, night light, chandelier, overhead light, or the like.

[0021]

[0026] In some embodiments, the lighting device 100 may be in the form of a white light source having a color rendering index greater than 70 compared to daylight, a black body, or other lighting reference standard. As used herein, the term "white light" may refer to any polychromatic light having a color rendering index greater than 70 as defined by the Commission Internationale de l'Eclairage (CIE) Ra scale. Such white light may include non-zero intensities across the entire visible spectrum from 400 to 700 nm. Thus, a "white light source" may include any light source configured to generate white light as described above. As used herein, the term "color rendering index" (CRI) may be generally defined with reference to the CIE Ra scale.

[0022]

[0027] 2 shows two types of light emitted from the lighting device 100. The lighting device 100 and related methods disclosed herein can be used to advance or delay a person's circadian cycle for a variety of purposes. Such methods can be used to treat subjects suffering from Seasonal Affective Disorder (SAD) or other mood disorders such as depression, bipolar disorder, dysthymia, etc. Sleep disorders and irregular sleep can also affect people suffering from cancer and / or heart disease, and these methods can be used appropriately to counteract such effects.

[0023]

[0028] The lighting device 100 emits a first light 10 and a second light 18. The lighting device 100 emits a second light 18 that is out of phase with the first light 10 (e.g., 180 degrees out of phase) as shown. In FIG. 2, the first light 10 and the second light 18 both have a sinusoidal waveform, but the first light 10 and the second light 18 may be in other forms, such as a square wave, a sine wave, a sawtooth wave, a triangular wave, or any oscillating wave. The light source assembly 102 may include one or more first light sources configured to emit the first light 10 and one or more second light sources configured to emit the second light 18, although other examples are possible.

[0024]

[0029] More specifically, FIG. 2 shows the oscillating intensity of each of the first light 10 and the second light 18, where the intensity of the first light 10 is out of phase (e.g., 180 degrees) with the intensity of the second light 18. That is, the horizontal axis represents time and the vertical axis represents the intensity of the light. In some examples, the periodic minimum intensity 11 of the first light 10 and the periodic minimum intensity 13 of the second light 18 are both zero, although examples with non-zero minimum intensities of the first light 10 and the second light 18 are also possible. In examples where the waveforms are non-sinusoidal, the duty cycles of the first light 10 and the second light 18 may or may not be equal.

[0025]

[0030] The intensity of the first light 10 generally oscillates at the same frequency as the second light 18. For example, the common oscillation frequency of the first light 10 and the second light 18 may be in the range of 1 Hz to 50 Hz. In various examples, the common oscillation frequency of the first light 10 and the second light 18 is greater than 8 Hz, greater than 10 Hz, or greater than 15 Hz. Also, the common oscillation frequency of the first light 10 and the second light 18 is in the range of 17 Hz to 21 Hz, more specifically approximately equal to or exactly equal to 19 Hz.

[0026]

[0031] These oscillation frequencies are useful because the critical fusion frequency of human S-cones is approximately 8 Hz to 10 Hz. Thus, displays of light oscillating at frequencies greater than 8 Hz to 10 Hz, each with a color on the common tritan confusion line, can be used to excite human S-cones without the user perceiving a change in color of the light emitted by the lighting device 100. An oscillation frequency of approximately 19 Hz may be useful because it is greater than the flicker fusion frequency of the S-cones, but low enough that the S-cones exhibit a reliable physiological response that is somewhat synchronous with the oscillating first light 10 and second light 18. These phenomena are described in more detail below.

[0027]

[0032] 3 shows the colors of the first light 10 and the second light 18 in the Commission Internationale de l'Eclairage (CIE) 1931XYZ color space. The CIE 1931XYZ color space is a visual representation of how human perception of color relates to a particular distribution of wavelengths in the electromagnetic visible spectrum. Other color spaces, such as the CIE 1931 RGB color space or the 1976 CIELUV color space, may also be used as a basis for defining the colors of the first light 10 and the second light 18.

[0028]

[0033] As shown, the lighting device 100 emits a first light 10 having a first color on a first tritan confusion line 14 defined by a tritan common point 16. In this example, the first color of the first light 10 is a non-spectral yellow. The first tritan confusion line 14 has a first end point at the tritan common point 16 and a second end point 17 that is a spectral yellow at a single wavelength of about 573 nm. The tritan common point 16 corresponds to a spectral purple at a single wavelength of about 380 nm. Another way to define the tritan common point 16 is to have an x ​​coordinate of about 0.17045 and a y coordinate of about 0 in CIE 1931 XYZ. The tritan common point may be defined slightly differently in other color spaces.

[0029]

[0034] The tritan confusion line 16 is the end point of an infinite number of tritan confusion lines. That is, all tritan confusion lines start at the tritan confusion line 16. Any particular tritan confusion line defines a spectrum of colors that differ only in the degree to which they excite the S cones in humans. That is, two colors that lie on the same tritan confusion line will cause the same excitation of the L and M cones, but different excitation of the S cones. This means, by the way, that a person with tritan deficiency has difficulty distinguishing between two colors that lie on the same tritan confusion line.

[0030]

[0035] The lighting device 100 also emits a second light 18 having a second color on a second tritan confusion line 20 defined by the tritan common point 16. In this example, the second color of the second light 18 is a non-spectral pink color. The second tritan confusion line 20 has a first endpoint at the tritan common point 16 and a second endpoint 19 that is a spectral yellowish-orange color at a single wavelength of about 582 nm.

[0031]

[0036] As mentioned above, the second light 18 is emitted out of phase with the first light 10. Furthermore, the first tritan confusion line 14, the tritan common point 16, and the second tritan confusion line 20 form an angle 24 that is less than 10 degrees. In FIG. 3, the angle 24 is not necessarily drawn to scale and may correspond to different tritan confusion lines and / or colors than those mentioned above as examples. The angle 24 shown in FIG. 3 and the 10 degree angle are merely examples. In various examples, the angle 24 may be less than 5 degrees, less than 2.5 degrees, or less than 1 degree, with smaller angles 24 resulting in less of a color change perceived by the user.

[0032]

[0037] Of note, FIG. 3 shows that two colors that are not quite aligned on the same tritan confusion line can still benefit the user. For example, the out-of-phase vibration of the first light 10 and the second light 18 will generally produce vibration excitation in the user's S cones, and the user will generally only perceive slight color changes through changes in the excitation of the L and M cones. For example, because the vibration frequency of 19 Hz is greater than the critical fusion frequency of the S cones, the user will generally not perceive the resulting differential excitation of the S cones. Instead, the user will generally perceive a time-averaged excitation of the S cones (e.g., corresponding to an average color representing the midpoint 21 between the first color of the first light 10 and the second color of the second light 18). However, because the critical fusion frequency of the L and M cones is greater than 19 Hz (e.g., about 40 Hz), the user will generally perceive, at least to some extent, the time-varying excitation of the L and M cones represented by the first light 10 and the second light 18. Excitation of S-cones generally induces a shift in the user's circadian rhythm, whether or not the excitation is perceived.

[0033]

[0038] To provide a user with an experience that does not include a vibrational change in perceived color, it is useful to emit the first light 10 and the second light 18 such that they are on the same tritan confusion line, resulting in a vibrational frequency greater than the critical fusion frequency of the S-cones, which are the only cones that can perceive the difference between two colors on the same tritan confusion line.

[0034]

[0039] FIG. 4 shows an example where a first color of a first light 10 and a second color of a second light 18 lie on the same tritan confusion line 14 .

[0035]

[0040] As shown, the lighting device 100 emits a first light 10 having a first color on the tritan confusion line 14 defined by the tritan common point 16. In this example, the first color of the first light 10 is a non-spectral yellow. The lighting device 100 also emits a second light 18 having a second color on the tritan confusion line 14. In this example, the second color of the second light 18 is a non-spectral greenish and / or yellowish white.

[0036]

[0041] Of note, FIG. 4 shows that two colors aligned on the same tritan confusion color line may bring more benefits to the user. For example, out-of-phase vibrations of the first light 10 and the second light 18 having colors on the common tritan confusion color line 14 generally provide vibration excitation exclusively to the user's S cones, with substantially zero change in excitation of the L and M cones. For example, since the vibration frequency of 19 Hz is greater than the critical fusion frequency of the S cones, the user generally does not perceive a different excitation occurring in the S cones. Instead, the user perceives a time-averaged excitation of the S cones (e.g., equivalent to the average color representing the midpoint 21 on the tritan confusion color line 14 between the first color of the first light 10 and the second color of the second light 18). The excitation of the S cones generally causes a shift in the user's circadian rhythm, regardless of whether the excitation is perceived. As mentioned above, all colors on the common tritan confusion color line excite the L and M cones at the same level. Therefore, even if the first light 10 and the second light 18 oscillate below the critical fusion frequency of the L and M cones, it is irrelevant as no change in the excitation of the L or M cones occurs. Thus, the user generally sees colors that do not change over time, but the oscillating light causes a shift in the circadian rhythm.

[0037]

[0042] As shown in Figure 4, the first color of the first light 10 and the second color of the second light 18 are on opposite sides of the blackbody locus 31. The blackbody locus 31 represents the color spectrum of an incandescent black body at various temperatures in Kelvin. General purpose "white" room lighting often emits colors that are close to or on the blackbody locus 31. As shown, the midpoint 21, which represents the average color of the first light 10 and the second light 18, lies on the blackbody locus 31.

[0038]

[0043] In various examples, it may be advantageous for the second color of the second light 18 to be at least 10%, at least 20%, at least 30%, at least 40%, or at least 50% closer to the tritanopia common point 16 than the first color of the first light 10. That is, a greater variation in S-cone excitation caused by the first light 10 compared to the second light 18 will generally result in a greater and / or earlier circadian shift.

[0039]

[0044] Figure 5 shows another example where the first color of the first light 10 and the second color of the second light 18 lie on the same tritanopia confusion line 14. However, in Figure 5, the average color represented by the midpoint 21 does not lie on the blackbody locus 31. Figure 5 may therefore represent a lighting device 100 configured for circadian shifting with a non-spectral pink mood lighting function rather than a dedicated "white" lighting.

[0040]

[0045] FIG 6 is a block diagram of a method 200. Method 200 is an example of a method that may be performed by a lighting device 100, such as that shown in FIGS. 1-5. As shown in FIG 6, method 200 includes one or more operations, functions, or actions, such as those shown in blocks 202, 204. Although the blocks are shown in sequential order, the blocks may be performed in parallel and / or in orders different than those described herein. Additionally, various blocks may be combined into fewer blocks, divided into additional blocks, and / or eliminated based on a desired implementation.

[0041]

[0046] In block 202, the method 200 includes emitting a first light 10 having a first color on a first tritan confusion line 14 defined by a tritan shared point 16. Block 202 is described above with reference to FIGS.

[0042]

[0047] In block 204, the method 200 includes emitting a second light 18 having a second color on a second tritan confusion line 20 defined by the tritan common point 16. The second light 18 is emitted out of phase with the first light 10. Additionally, the first tritan confusion line 14, the tritan common point 16, and the second tritan confusion line 20 form an angle 24 of less than 10 degrees. Block 204 is described above with reference to FIGS. 1-5.

[0043]

[0048] The description of the various advantageous arrangements has been presented for purposes of illustration and description and is not intended to be exhaustive or to be limited to the examples in the disclosed form. Many modifications and variations will become apparent to those skilled in the art. Moreover, different advantageous examples may describe different advantages over other advantageous examples. The selected example or examples have been selected and described to explain the principles and practical applications of these examples and to enable others skilled in the art to understand the present disclosure with various modifications to suit the particular use contemplated.

Claims

1. emitting a first light having a first color on a first tritan confusion line defined by a tritan shared point; emitting a second light having a second color on a second tritan confusion color line defined by the tritan common point, wherein the second light is emitted out of phase with the first light, and the first tritan confusion color line, the tritan common point, and the second tritan confusion color line form an angle of less than 10 degrees.

2. 2. The method of claim 1, wherein the first tritan confusion line, the tritan shared point, and the second tritan confusion line form an angle of less than 5 degrees.

3. 2. The method of claim 1, wherein the first tritan confusion line, the tritan shared point, and the second tritan confusion line form an angle of less than 2.5 degrees.

4. 2. The method of claim 1, wherein the first tritan confusion line, the tritan shared point, and the second tritan confusion line form an angle of less than 1 degree.

5. 2. The method of claim 1, wherein the first tritan confusion line and the second tritan confusion line are the same tritan confusion line.

6. The method of any one of claims 1 to 5, wherein the first color and the second color are on opposite sides of the blackbody locus.

7. The method of any one of claims 1 to 5, wherein an average color of the first color and the second color lies on the blackbody locus.

8. The method of any one of claims 1 to 5, wherein the average color of the first color and the second color does not lie on the blackbody locus.

9. The method of any one of claims 1 to 5, wherein the first color and the second color are both non-spectral colors.

10. The method of any one of claims 1 to 5, wherein the second color is at least 10% closer to the tritan sharing point than the first color.

11. The method of any one of claims 1 to 5, wherein the second color is at least 20% closer to the tritan sharing point than the first color.

12. The method of any one of claims 1 to 5, wherein the second color is at least 30% closer to the tritan sharing point than the first color.

13. The method of any one of claims 1 to 5, wherein the second color is at least 40% closer to the tritan sharing point than the first color.

14. The method of any one of claims 1 to 5, wherein the second color is at least 50% closer to the tritan sharing point than the first color.

15. The method of any one of claims 1 to 5, wherein emitting the second light comprises emitting the second light 180 degrees out of phase with the first light.

16. 6. The method of claim 1, wherein emitting the first light comprises emitting the first light such that a first intensity of the first light oscillates at a first frequency, and wherein emitting the second light comprises emitting the second light such that a second intensity of the second light oscillates at a second frequency equal to the first frequency.

17. 17. The method of claim 16, wherein the first frequency is in the range of 1 Hz to 50 Hz.

18. 17. The method of claim 16, wherein the first frequency is greater than 8 Hz.

19. 17. The method of claim 16, wherein the first frequency is greater than 10 Hz.

20. 17. The method of claim 16, wherein the first frequency is greater than 15 Hz.

21. 17. The method of claim 16, wherein the first frequency is in the range of 17 Hz to 21 Hz.

22. 17. The method of claim 16, wherein the first frequency is equal to 19 Hz.

23. The method according to any one of claims 1 to 5, wherein the first light is in the form of a square wave, a sine wave, a sawtooth wave, a triangular wave, or any other oscillating wave.

24. The method according to any one of claims 1 to 5, wherein the second light is in the form of a square wave, a sine wave, a sawtooth wave, a triangular wave, or any other oscillating wave.

25. The method of any one of claims 1 to 5, wherein the first light and the second light are in the form of waves with equal duty cycles.

26. The method of any one of claims 1 to 5, wherein the first light and the second light are in the form of waves with unequal duty cycles.

27. The method of any one of claims 1 to 5, wherein the first light periodically reaches a minimum value greater than zero.

28. The method according to any one of claims 1 to 5, wherein the first light periodically reaches a minimum value equal to zero.

29. The method of any one of claims 1 to 5, wherein the second light periodically reaches a minimum value greater than zero.

30. The method according to any one of claims 1 to 5, wherein the second light periodically reaches a minimum value equal to zero.

31. A control system configured to cause a lighting device to perform the method of any one of claims 1 to 5.

32. a light source assembly; and a control system configured to cause said light source assembly to perform the method of any one of claims 1 to 5.

Images