Circadian lighting for medium light levels

Abstract

The invention provides a light generating system (1000) comprising: (i) a light generating device (100) configured to generate device light (101) having a controllable radiant flux and a controllable spectral power distribution; and (ii) a control system (300) configured to control the radiant flux and the spectral power distribution of the device light (101); wherein: (A) a ratio B / Y of the device light (101) is defined as a ratio of a radiant flux of the device light (101) in a 450-500 nm wavelength range to a radiant flux of the device light (101) in a 550-600 nm wavelength range; (B) in a first operating mode of the light generating system (1000), the control system (300) is configured to change from a first device light setting to a second device light setting different from the first device light setting; (C) the first device light setting and the second device light setting are selected from: (a) a high radiant flux first setting (SI) in which the device light (101) is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a low radiant flux second setting (S2) in which the device light (101) is a second light having a second radiant flux I2 and a second B / Y ratio R2; and (D) I2 < II, and Rl < R2.

Description

TECHNICAL FIELD

[0001] The present invention relates to a light generating system and a method for controlling light such as from the light generating system. BACKGROUND

[0002] Light sources designed to take into account the circadian rhythm are known in the art. For example, US2015062892 describes a light source comprising: at least one first LED emission source characterized by a first emission; and at least one second LED emission source characterized by a second emission; wherein the first emission and the second emission are configured to provide a first combined emission and a second combined emission; the first combined emission is characterized by a first SPD and fractions Fvl and Fcl; the second combined emission is characterized by a second SPD and fractions Fv2 and Fc2; Fvl represents the power fraction of the first SPD in the wavelength range of 400 nm to 440 nm; Fcl represents the power fraction of the first SPD in the wavelength range of 440 nm to 500 nm; Fv2 represents the power fraction of the second SPD in the wavelength range of 400 nm to 440 nm; Fc2 represents the power fraction of the second SPD in the wavelength range of 440 nm to 500 nm; the color rendering index of the first SPD and the second SPD is higher than 80; Fvl is at least 0.05; Fc2 is at least 0.1; and Fcl is at least 0.02 smaller than Fc2.

[0003] WO2020 / 097597A discloses a device for converting an existing light source into a biophilic light source, the device comprising an energy conversion component removably attached to the existing light source, wherein the energy conversion component is configured to convert light from the existing light source into light in either a first state having a M / P ratio of XI, wherein XI is at least 0.70, a correlated color temperature of 4000-14000 K, and an average CRI of at least 70, and a second state having a M / P ratio of X2, wherein X2 is not greater than 0.40, a correlated color temperature of 2200-4000 K, and an average CRI of at least 70. SUMMARY

[0004] The key to our sleep / wake cycle is melatonin, a hormone that promotes sleep during the night. During the day, natural daylight with a high correlated color temperature (CCT; also denoted as “color temperature” herein) and intensity suppresses the production of melatonin in the body and thus energizes people, making them more alert and vigilant. At the beginning and end of the day, the spectrum moves towards lower CCT and intensity levels, causing melatonin secretion.

[0005] More than about 60% of adults sleep less than they think they need. In addition, close to three out of ten parents (29%) report having trouble falling asleep (insomnia) at least a few nights a week. The production of melatonin is directly influenced by light (natural and artificial). Bright night-time lighting can suppress the production of melatonin and delay sleep, making it more difficult to wake up in the morning. Especially in the last two hours before bedtime, it seems beneficial to use only dim and low blue content light. Many people use artificial lighting in the hours before sleep, for example for reading. But exposure to light in the evening can suppress melatonin production and prevent sleepiness. In addition, it can be desirable to have light with low radiant flux in (other) situations, while still needing to remain alert. However, current lamps do not seem to satisfactorily solve these problems.

[0006] It is therefore an aspect of the present invention to provide an alternative light generating system which preferably further at least partially obviates one or more of above-described drawbacks. It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0007] In a first aspect, the present invention provides a light generating system ("system") comprising: (i) a light generating device ("device") and a control system ("controller"). In particular, the light generating device is configured to generate device light having a controllable radiant flux and a controllable spectral power distribution. Further, in particular, the control system can be configured to control the radiant flux and the spectral power distribution of the device light. In embodiments, a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in a wavelength range of 450-500 nm to a radiant flux of the device light in a wavelength range of 550-600 nm. In embodiments, in a first operating mode of the light generating system, the control system can be configured to change from a first device light setting to a second device light setting different from the first device light setting. In particular embodiments, the first device light setting and the second device light setting can be selected from: (a) a high radiant flux first setting (SI), wherein the device light is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a low radiant flux second setting (S2), wherein the device light is a second light having a second radiant flux I2 and a second B / Y ratio R2. In particular embodiments, I2 < II. Further, in specific embodiments, Rl < R2. Thus, the present invention provides, inter alia, a light generating system comprising: (i) a light generating device configured to generate device light having a controllable radiant flux and a controllable spectral power distribution; and (ii) a control system configured to control the radiant flux and the spectral power distribution of the device light; wherein: (a) a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in a wavelength range of 450-500 nm to a radiant flux of the device light in a wavelength range of 550-600 nm; (b) in a first operating mode of the light generating system, the control system is configured to change from a first device light setting to a second device light setting different from the first device light setting; (c) the first device light setting and the second device light setting are selected from: (a) a high radiant flux first setting (SI), wherein the device light is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a low radiant flux second setting (S2), wherein the device light is a second light having a second radiant flux I2 and a second B / Y ratio R2; and (d) I2 < II, and Rl < R2.

[0008] With such a system, light can be provided at relatively low light intensities that does not suppress melatonin. Contrary to earlier concepts, it appears that at low intensity levels a relatively high blue content can promote sleep, while at high intensities a relatively high yellow level can (also) promote sleep. Thus, the present system can, inter alia, provide the possibility to provide light that can promote sleep at different dimming levels, and can e.g. be used to dim the intensity while maintaining a non-suppressive effect on melatonin by shifting the spectral power distribution.

[0009] As mentioned above, the light generating system can comprise a light generating device configured to generate device light having a controllable radiant flux and a controllable spectral power distribution. The light generating device can comprise one or more light sources which individually or together allow controlling the radiant flux and the spectral power distribution of the device light.

[0010] The term "radiant flux" especially refers to the emitted radiant energy per unit of time (by the light generating device). Instead of the term "radiant flux", the term "intensity" or "radian power" can also be applied. The term "radiant flux" can have as a unit of energy, in particular as a Watt. The term "spectral power distribution" especially refers to the power distribution of light (in particular in Watt) as a function of wavelength (in particular in nanometer), especially in embodiments on the human visible wavelength range (380-780 nm). In particular, the term "spectral power distribution" can refer to the radiant flux per unit of frequency or wavelength, typically expressed in Watt / nm. Instead of the term "spectral power distribution", the term "spectral flux" can also be applied. Hence, instead of the phrase "controllable spectral power distribution", the phrase "controllable spectral flux" can also be applied. The spectral flux can be expressed as power per unit of frequency or wavelength (Watt). In particular, the spectral flux is herein expressed as radiant flux per unit of wavelength (W / nm). Further, the spectral flux and the radiant flux herein are especially based on the spectral power of the device light in the 380-780 nm wavelength range. Hence, the blue-yellow ratio determined herein in the 450-500 nm and 550-600 nm range does not necessarily imply that there is no spectral power in the wavelength range of 380-450 nm and / or 500-550 nm and / or 600-780 nm (see also below) (or optionally even outside the visible wavelength range).

[0011] The term "light source" can in principle relate to any light source known in the art. It can be a conventional (tungsten) bulb, a low-pressure mercury lamp, a high-pressure mercury lamp, a fluorescent lamp, an LED (light-emitting diode), an OLED, a laser, etc. In a particular embodiment, the light source comprises a solid-state LED light source, such as an LED or a laser diode (or "diode laser"). The term "light source" can also relate to a plurality of light sources, such as 2-200 (solid-state) LED light sources. Hence, the term LED can also refer to a plurality of LEDs. Further, the term "light source" can in embodiments also refer to a so-called Chip-On-Board (COB) light source. The term "COB" especially refers to an LED chip in the form of a semiconductor chip which is neither encapsulated nor connected but mounted directly onto a substrate such as a PCB. Hence, a plurality of light-emitting semiconductor light sources can be configured on the same substrate. In embodiments, the COB is a multi-LED chip configured together as a single lighting module.

[0012] The light source has a light exit surface. With reference to a conventional light source, such as a light bulb or a fluorescent lamp, this can be the outer surface of a glass or quartz envelope. For an LED, this can be the LED die, for example, or the outer surface of the resin when resin is applied to the LED die. In principle, it can also be the termination of an optical fiber. The term "exit surface" is especially related to the part of the light source in which light actually leaves or escapes from the light source. The light source is configured to provide a light beam. This light beam (thus) escapes from the light exit surface of the light source.

[0013] The term "light source" can refer to a semiconductor light emitting device such as a light emitting diode (LED), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSEL), an edge emitting laser, etc. The term "light source" can also refer to an organic light emitting diode (OLED), such as a passive-matrix (PMOLED) or active-matrix (AMOLED). In a particular embodiment, the light source comprises a solid state light source, such as an LED or a laser diode. In one embodiment, the light source comprises an LED (light emitting diode). The term "light source" or "solid state light source" can also refer to a superluminescent diode (SLED).

[0014] The term LED can also refer to a plurality of LEDs. Further, the term "light source" can also refer to a so-called chip-on-board (COB) light source in embodiments. The term "COB" especially refers to an LED chip in the form of a semiconductor chip that is neither encapsulated nor connected but mounted directly onto a substrate such as a PCB. Hence, a plurality of semiconductor light sources can be configured on the same substrate. In embodiments, the COB is a multi-LED chip that is configured together as a single lighting module.

[0015] The term "light source" can also relate to a plurality of (essentially identical (or different)) light sources, e.g. 2-2000 solid state light sources. In embodiments, the light source can comprise one or more micro-optical elements (microlens array) downstream of a single solid state light source (such as an LED) or downstream of a plurality of solid state light sources (i.e. e.g. shared by a plurality of LEDs). In embodiments, the light source can comprise an LED with on-chip optics. In embodiments, the light source comprises a pixelated single LED (with or without optics) (providing on-chip beamsteering in embodiments).

[0016] In embodiments, the light source can be configured to provide primary radiation which is used as such, such as e.g. a blue light source like a blue LED, or a green light source such as a green LED, and a red light source such as a red LED. Such LEDs which can not comprise luminescent material ("phosphor") can be denoted as direct color LEDs.

[0017] However, in other embodiments the light source can be configured to provide primary radiation, and part of the primary radiation is converted into secondary radiation. The secondary radiation can be based on conversion by a luminescent material. Hence, the secondary radiation can also be denoted as luminescent material radiation. In embodiments, the luminescent material can be comprised by the light source, such as a LED with a luminescent material layer or a dome comprising a luminescent material. Such a LED can be denoted as phosphor-converted LED or PC LED (phosphor-converted LED). In other embodiments, the luminescent material can be configured at a distance ("remote") from the light source, such as a LED with a luminescent material layer not in physical contact with the die of the LED. Hence, in a particular embodiment the light source can be a light source that emits during operation at least light with a wavelength selected from the range of 380-470 nm. However, other wavelengths are also possible. Such light can be partly used by the luminescent material.

[0018] In embodiments, the light generating device can comprise a luminescent material. In embodiments, the light generating device can comprise a PC LED (phosphor-converted LED). In other embodiments, the light generating device can comprise a direct LED (i.e. without phosphor). In embodiments, the light generating device can comprise a laser device, like a laser diode. In embodiments, the light generating device can comprise a superluminescent diode. Hence, in a particular embodiment the light source can be selected from the group of laser diodes and superluminescent diodes. In other embodiments, the light source can comprise a LED.

[0019] The light source is in particular configured to generate light source light having an optical axis (O) (beam shape) and a spectral power distribution. In embodiments, the light source light can comprise one or more bands, which have a bandwidth known for lasers. The optical axis can coincide with the direction of light having the highest radiant intensity.

[0020] The term "light source" can (hence) refer to a light generating element, e.g. a solid state light source, or to a package of light generating elements, such as a solid state light source, and one or more of an element comprising a luminescent material and (other) optical means, e.g. a lens, a collimator. A light converter element ("converter element" or "converter") can comprise an element comprising a luminescent material. For example, a solid state lamp, such as a blue LED, is a light source. A combination of a solid state light source (as light generating element) and a light converter element (such as a blue LED and a light converter element) optically coupled to the solid state light source can also be a light source. Hence, a white LED is a light source.

[0021] The term "light source" herein can also refer to a light source comprising a solid state light source, such as a LED or laser diode or superluminescent diode. Hence, the term "light source" in embodiments can also refer to a light source that is (also) based on light conversion, such as a light source in combination with a luminescent converter material. Hence, the term "light source" can also refer to a combination of a LED and a luminescent material configured to convert at least part of the LED radiation, or a combination of a (diode) laser and a luminescent material configured to convert at least part of the (diode) laser radiation. In embodiments, the term "light source" can also refer to a combination of a light generating device, such as a LED, and a filter, which can alter the spectral power distribution of the light generated by the light generating device.

[0022] The phrase "different light sources" or "a plurality of different light sources" and similar phrases can in embodiments refer to a plurality of solid state light sources selected from at least two different bins. Likewise, the phrase "same light sources" or "a plurality of same light sources" and similar phrases can in embodiments refer to a plurality of solid state light sources selected from the same bin.

[0023] The light generated by the system can essentially consist of device light.

[0024] Further, the system can comprise a control system configured to control the radiant flux and the spectral power distribution of the device light.

[0025] The term "control" and similar terms especially refer to at least determining a behavior of an element or supervising a running of an element. Hence, "control" and similar terms herein can for example refer to imposing a behavior (determining a behavior or supervising a running of an element) etc. on an element, such as measuring, displaying, actuating, opening, displacing, changing a temperature, etc. In addition thereto, the term "control" and similar terms can additionally comprise monitoring. Hence, the term "control" and similar terms can comprise imposing a behavior on an element and imposing a behavior on an element and monitoring the element. The control of an element can be done with a control system, which can also be denoted as "controller". The control system and the element can thus be functionally coupled at least temporarily or permanently. The element can comprise the control system. In embodiments, the control system and the element can not be physically coupled. The control can be done by wired and / or wireless control. The term "control system" can also refer to a plurality of different control systems, which are especially functionally coupled, and wherein for example one control system can be a master control system and one or more other control systems can be slave control systems. The control system can comprise or can be functionally coupled to a user interface.

[0026] The control system can also be configured to receive and execute instructions from a remote control. In embodiments, the control system can be controlled via an App on a device, e.g. a portable device, such as a smart phone or I-phone, a tablet, etc. Hence, the device does not have to be coupled to the lighting system, but can be (temporarily) functionally coupled to the lighting system.

[0027] Hence, in embodiments, the control system can (also) be configured to be controlled by an App on a remote device. In such embodiments, the control system of the lighting system can be a slave control system or control in slave mode. For example, the lighting system can be identified with a code, in particular a unique code for the respective lighting system. The control system of the lighting system can be configured to be controlled by an external control system that has access to the lighting system based on knowledge of the (unique) code (input through a user interface with an optical sensor, e.g. a QR code reader). The lighting system can also comprise a device for communicating with other systems or devices, such as based on Bluetooth, WIFI, LiFi, ZigBee, BLE or WiMAX, or other wireless technologies.

[0028] A system, apparatus or device can perform an action in a "mode" or "operating mode" or "mode of operation" or "operational mode". The term "operational mode" can also be denoted as "control mode". Likewise, in a method, an action or phase or step can be performed in a "mode" or "operating mode" or "mode of operation" or "operational mode". This does not exclude that the system, apparatus or device can also be adapted to provide another control mode or a plurality of other control modes. Likewise, this can not exclude that one or more other modes can be performed before and / or after the performance of the mode.

[0029] In the operational mode, the control system can change from one device light setting to another device light setting different from the first device light setting (as from the first device light setting to the second device light setting in embodiments). Hence, in such operational mode, the spectral power distribution can change and / or the radiant flux can change. In particular embodiments, the radiant flux can change and / or the R-value can change.

[0030] However, in other operational modes, the device light setting can be fixed. Hence, in such operational mode, the radiant flux and the spectral power distribution remain substantially unchanged during such operational mode.

[0031] However, in embodiments, a control system can be available which is adapted to provide at least a control mode. Selection of such mode can especially be performed via a user interface if other modes are available, although other options, like performing a mode according to a sensor signal or a (time) scheme, are possible. In embodiments, the operational mode can also refer to a system, device or apparatus which is only capable of operating in a single operational mode (i.e. “on” without further tunability).

[0032] Hence, in embodiments, the control system can control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor) and a timer. The term “timer” can refer to a clock and / or a predetermined time scheme.

[0033] At least four operational modes are described below. In embodiments, the system can be configured to perform one or more of these operational modes. Or, in other words, the system can operate in one or more of these operational modes. In particular, the system can perform at least a first operational mode. When the system is capable of performing more than one operational mode, the operational mode can for example be performed consecutively, or can for example be performed in response to a sensor signal, or can for example be performed in dependence of a user instruction via a user interface. In embodiments, the system can be configured to only perform one of these operational modes.

[0034] In particular, the system can be configured to provide white device light in one or more operational modes (of the system). The term “white light” herein is known to the person skilled in the art. It especially relates to light having a correlated color temperature (CCT) between about 1800 K and 20000 K, for example between 2000 K and 20000 K, especially 2700-20000 K, such as in embodiments up to 14000 K; for general lighting, in particular a correlated color temperature (CCT) in the range of about 2700 K and 6500 K. Further, in embodiments, the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL. Visible light with a CCT lower than 1800 K is also possible, which can appear as red (doughnut shaped) instead of white, such as light with a CCT of about 800-1800 K.

[0035] The terms "visible", "visible light" or "visible emission" and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm. In the present context, UV especially refers to wavelengths selected from the range of 200-380 nm. The terms "light" and "radiation" are used interchangeably herein unless the term "light" is clearly specified to refer to visible light only from the context. Hence, the terms "light" and "radiation" can refer to UV radiation, visible light and IR radiation. In particular embodiments, especially for lighting applications, the terms "light" and "radiation" refer at least to visible light.

[0036] The device light can have a variable intensity ratio in a wavelength range which can comprise at least part of the blue wavelength range and in a wavelength range which can comprise at least part of the yellow wavelength range. Note that the intensity can also be variable in other wavelength ranges, such as in the green and / or red wavelength range.

[0037] The term "blue light" or "blue emission" herein especially relates to light having a wavelength in the range of about 450-500 nm (including some violet and cyan hues). Instead of the term "blue light", the term "light with a blue color" can also be applied. The term "yellow light" or "yellow emission" herein especially relates to light having a wavelength in the range of about 550-600 nm. Instead of the term "yellow light", the term "light with a yellow color" can also be applied. The term "orange light" or "orange emission" herein especially relates to light having a wavelength in the range of about 600-620 nm. The term "red light" or "red emission" especially relates to light having a wavelength in the range of about 620-780 nm. The term "pink light" or "pink emission" refers to light having a blue and a red component. The term "cyan" can refer to one or more wavelengths selected from the range of about 490-520 nm. The term "amber" can refer to one or more wavelengths selected from the range of about 585-605 nm, for example about 590-600 nm.

[0038] Hence, especially in the present context, the ratio B / Y of the device light is defined as the ratio of the radiant flux of the device light in the wavelength range of 450-500 nm of the device light and in the wavelength range of 550-600 nm of the device light. Hence, the total radiant flux in the range of 380-780 nm from the device light, the first radiant flux of the device light in the wavelength range of 450-500 nm, denoted by B, and the second radiant flux of the device light in the wavelength range of 550-600 nm, denoted by Y, are used to define the ratio B / Y. Hence, the first radiant flux or radiant flux of the device light in the wavelength range of 450-500 nm can be the radiant flux integrated over the range of 450-500 nm. Likewise, the second radiant flux or radiant flux of the device light in the wavelength range of 550-600 nm can thus be the radiant flux integrated over the range of 550-600 nm.

[0039] It appears that by controlling this ratio, the suppression of melatonin can be controlled. Basically, the following settings (S1-S4) can apply:

[0040]

[0041] The settings are indicated with indications S1, S2, S3 and S4. The relevant ratios are indicated with indications R1, R2, R3 and R4.

[0042] As indicated above, the phrase "radiant flux of the device light in the 450-500 nm wavelength range" and similar phrases can refer to the integrated intensity (in particular the radiant flux) of the spectral power distribution over the 450-500 nm wavelength range. Likewise, the phrase "radiant flux of the device light in the 550-600 nm wavelength range" and similar phrases can (thus) refer to the integrated intensity (in particular the radiant flux) of the spectral power distribution over the 550-600 nm wavelength range.

[0043] In an operational mode, one of the settings can remain constant. In such embodiments, a control system can not be necessary and the light generating device can have a fixed setting. In other operational modes, there can be at least a change from one of the four settings to another of the four settings. In other embodiments, there can be at least a change of one of the four settings. In the latter embodiments, a control system can be necessary as the radiant flux and / or the spectral power distribution can change over time.

[0044] In embodiments, in the first operational mode of the light generating system, the control system can be configured to change from the first device light setting to a second device light setting different from the first device light setting. For example, this can be from a high radiant flux first setting (SI) to a low radiant flux second setting (S2), but this can also be from a low radiant flux second setting (S2) to a high radiant flux first setting (SI). It can also be a change from a high radiant flux third setting (S3) to a low radiant flux fourth setting (S4) or from a low radiant flux fourth setting (S4) to a high radiant flux third setting (S3) (see also below). It can also be a change from a high radiant flux third setting (S3) to a low radiant flux second setting (S2) or from a low radiant flux second setting (S2) to a high radiant flux third setting (S3) (see also below). However, it can also be a change from a high radiant flux first setting (SI) to a low radiant flux fourth setting (S4) or from a low radiant flux fourth setting (S4) to a high radiant flux first setting (SI) (see also below). It can also be a change from a high radiant flux third setting (S3) to a high radiant flux first setting (SI) or from a high radiant flux first setting (SI) to a high radiant flux third setting (S3) (see also below). It can also be a change from a low radiant flux second setting (S2) to a low radiant flux fourth setting (S4) or from a low radiant flux fourth setting (S4) to a low radiant flux second setting (S2) (see also below).

[0045] For example, in embodiments, this can be a change from a high intensity setting (especially a high radiant flux third setting (S3)) where alertness or activity is desired (e.g. artificial light in a hospital) to a low intensity setting (especially a low radiant flux second setting (S2)) during the night where a reduction in intensity is desired and people can sleep. Between the high radiant flux setting with melatonin suppression and the low radiant flux setting without melatonin suppression, there can be a setting with (relatively) high intensity and without melatonin suppression (especially a high radiant flux first setting (SI)). However, after a night, the setting can change again from the low radiant flux second setting (S2) to the high radiant flux third setting (S3) via the high radiant flux first setting (SI).

[0046] Embodiments especially relating to the SI-S2 transition

[0047] Thus, in embodiments, the first device light setting and the second device light setting can be selected from: (a) a high radiant flux first setting (SI) in which the device light is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a low radiant flux second setting (S2) in which the device light is a second light having a second radiant flux I2 and a second B / Y ratio R2. In particular, I2< II, and Rl < R2.

[0048] Thus, there can be a change from a high-radiant-flux first setting (SI) (e.g. in the evening) to a low-radiant-flux second setting (S2) (e.g. at night) or from a low-radiant-flux second setting (S2) (e.g. at night) to a high-radiant-flux first setting (SI) (e.g. in the morning). The high B / Y ratio R1 at high intensity can be used to prevent melatonin suppression, while the low B / Y ratio R2 at low intensity can also be used to prevent melatonin suppression.

[0049] In embodiments, the light generating device can have a maximum radiant flux, which in embodiments can especially be such that at the maximum radiant flux a high light level will be provided. This can especially be applied in applications in which the light generating device can be designed, like office lighting, hospital (room) lighting, hotel lighting, corridor lighting, home lighting, etc. However, this can also be used for street lighting (road lighting), outdoor area lighting, etc. for example.

[0050] In particular embodiments, the high light level can be at least in a range of 10% or more of the maximum radiant flux, and the low light level can be at a maximum of 90% of the maximum radiant flux, wherein the latter light level is at least less than the former light level. For example, II > 0.6 * I max and I2 < 0.4 * I max Thus, in particular embodiments, the light generating device is capable of generating device light having a maximum radiant flux I max with II > 0.1 * I max and I2 < 0.9 * I max and with I2 / II < 0.9. For example, in embodiments, II > 0.1 * I max and I2 < 0.09 * I max In other embodiments, II > 0.9 * I max and I2 < 0.85 * I max such as I2 < 0.75 * I max In other embodiments, II > 0.6 * I max and I2 < 0.4 * I max In embodiments, I2 / II < 0.8, for example I2 / II < 0.7.

[0051] The phrase “the light generating device is capable of generating device light” or “the light generating device can be capable of generating device light” can mean that the light generating device in an operational mode will provide such device light.

[0052] In embodiments, the second light can have a relatively high correlated color temperature. The dimmed light that can produce a dimmed scene can typically have a relatively low correlated color temperature. However, in embodiments in which it is desired to suppress melatonin at low light levels, for example to promote sleep, it can seem desirable to have a relatively high CCT. For example, the second correlated color temperature can be at least 2200 K. However, at relatively high intensities, it can be desirable that the CCT is not too high, so as to not substantially suppress melatonin. Hence, the first correlated color temperature can in embodiments be at most about 3400 K. Thus, in specific embodiments, the first light has a first correlated color temperature T C1 wherein the second light has a second correlated color temperature T C2 wherein: T C1 < 3400 K, T C2 > 2200 K, and T C2 < T C1 Further, in specific embodiments, R2 is > 2. More particularly, R1 can be less than 0.41, even more particularly less than 0.3, yet even more particularly less than 0.25, and / or R2 can be at least 0.2, for example at least about 0.23, even more particularly at least about 0.25, as in embodiments at least about 0.4. In embodiments, 0.25 < R2 < 2.2. Alternatively or in addition, in embodiments 0.05 < R4 < 0.25.

[0053] In embodiments, the change from the high radiant flux first setting (SI) to the low radiant flux second setting (S2) or from the low radiant flux second setting (S2) to the high radiant flux first setting (SI) can be gradual. For example, this can be by linear gradual decrease or increase or by non-linear decrease or increase. Hence, in embodiments, the change (from the high radiant flux first setting (SI) to the low radiant flux second setting (S2) or from the low radiant flux second setting (S2) to the high radiant flux first setting (SI)) can be a gradual change over a change time selected in the range from 2-120 minutes, such as at least 5 minutes, such as 15-120 minutes, such as at most about 30 minutes. However, the change can in embodiments also be an instant change. Further, in specific embodiments, the control system can be configured to control the change from the first device light setting to the second device light setting in dependence on one or more of an input signal of a user interface, a sensor signal, and a timer.

[0054] Embodiments in particular relating to S3-S4 transition

[0055] As mentioned above, in the operational mode of the light generating system, the control system can be configured to change from the device light setting to another device light setting different from the previous device light setting, which in embodiments can especially be from the high radiant flux third setting (S3) to the low radiant flux fourth setting (S4) or from the low radiant flux fourth setting (S4) to the high radiant flux third setting (S3) (see also above). When a reduction of the radiant flux is desired (in both the high radiant flux third setting (S3) and the low radiant flux fourth setting (S4)) but also a melatonin suppression is desired, a change from the high radiant flux third setting (S3) with a relatively high blue-yellow ratio R3 to the low radiant flux fourth setting (S4) with a relatively low blue-yellow ratio R4 can be useful. In such embodiments, the high radiant flux third setting (S3) can provide a device light with a higher correlated color temperature, while the low radiant flux fourth setting (S4) can provide a device light with a lower correlated color temperature. This can also be denoted as "warm dimming".

[0056] For example, in embodiments this can be a change from a high intensity setting (especially the high radiant flux third setting (S3)) in which alertness or activity is desired (e.g. artificial light in a hospital, control room, etc.) to a low intensity setting during the night in which a reduction of the intensity is desired but still alertness or activity is desired (especially the low radiant flux fourth setting (S4)). However, after a night, the setting can again be changed from the low radiant flux fourth setting (S4) to the high radiant flux third setting (S3).

[0057] In the second operational mode of the light generating system, the control system is configured to change from the third device light setting to a fourth device light setting different from the third device light setting. The third device light setting and the fourth device light setting are selected from: (a) the high radiant flux third setting (S3), in which the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) the low radiant flux fourth setting (S4), in which the device light is a fourth light having a fourth radiant flux I3 and a fourth B / Y ratio R3, wherein I4

[0058] Further, in an aspect, the present invention provides a light generating system comprising: (i) a light generating device configured to generate device light having a controllable radiant flux and a controllable spectral power distribution; and (ii) a control system configured to control the radiant flux and the spectral power distribution of the device light; wherein: (a) a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in a wavelength range of 450-500 nm to a radiant flux of the device light in a wavelength range of 550-600 nm; (b) in a second operational mode of the light generating system, the control system is configured to change from a third device light setting to a fourth device light setting different from the third device light setting; (c) the third device light setting and the fourth device light setting are selected from: (a) a high radiant flux third setting (S3) in which the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low radiant flux fourth setting (S4) in which the device light is a fourth light having a fourth radiant flux I4 and a fourth B / Y ratio R4; and (d) I4 < I3 and R3 > R4.

[0059] Thus, there can be a change from the high radiant flux third setting (S3) (e.g. during the day or in the evening) to the low radiant flux fourth setting (S4) (e.g. in the evening or at night) or from the low radiant flux fourth setting (S4) (e.g. in the evening or at night) to the high radiant flux third setting (S3) (in the morning or during the day). The high B / Y ratio R3 at high intensity can be used for melatonin suppression, while the low B / Y ratio R4 at low intensity can also be used for melatonin suppression.

[0060] In embodiments, the light generating device can have a maximum radiant flux, which in embodiments can especially be such that at the maximum radiant flux a high light level will be provided. This especially applies to applications in which the light generating device can be designed, like office lighting, hospital (room) lighting, hotel lighting, corridor lighting, home lighting, control room lighting, etc.

[0061] In specific embodiments, the high light level can be at least in a range of 10% or more of the maximum radiant flux, and the low light level can be at the maximum 90% of the maximum radiant flux, wherein the latter light level is at least less than the former light level. For example, I3 > 0.6 * I max and I4 < 0.4 * I max Thus, in specific embodiments, the light generating device is capable of generating device light having a maximum radiant flux I max , wherein I3 > 0.1 * I max and I4 < 0.9 * I max , and wherein I4 / I3 < 0.9. For example, in embodiments, I3 > 0.1 * I max and I4 < 0.09 * I max In other embodiments, I3 > 0.9 * Imax and I4 < 0.85 * I max for example I4 < 0.75 * I max In other embodiments, I3 > 0.6 * I max and I4 < 0.4 * I max In embodiments, I4 / I3 < 0.8, for example I4 / I3 < 0.7.

[0062] In embodiments, the fourth light can have a relatively low correlated color temperature. However, in embodiments where suppression of melatonin is desired at low light levels, for example to promote sleep, it can seem desirable to have a relatively low CCT. For example, the fourth correlated color temperature can be at most 2450 K. However, at relatively high intensities, it can be desirable to have a relatively high CCT in order to substantially suppress melatonin. Thus, the third correlated color temperature can in embodiments be at least about 3000 K. Thus, in specific embodiments, the third light can have a third correlated color temperature T C3 where the fourth light has a fourth correlated color temperature T C4 where: T C3 > 3000 K and T C4 < 2450 K. Furthermore, in specific embodiments, R4 < 0.41, more particularly R4 < 0.3, even more particularly R4 is less than 0.25. More particularly, R3 can be at least 0.25. In particular, in embodiments 0.25 < R3 < 2.2 and / or R4 can be 0.05 < R4 < 0.25.

[0063] In embodiments, the change from the high-radiant-flux third setting (S3) to the low-radiant-flux fourth setting (S4) or from the low-radiant-flux fourth setting (S4) to the high-radiant-flux third setting (S3) can be gradual. For example, this can be by linear gradual decrease or increase or by non-linear decrease or increase. Thus, in embodiments, the change (from the high-radiant-flux third setting (S3) to the low-radiant-flux fourth setting (S4) or from the low-radiant-flux fourth setting (S4) to the high-radiant-flux third setting (S3)) can be a gradual change over a change time selected in the range from 2-120 minutes, such as at least 5 minutes, such as 15-120 minutes, such as at most about 30 minutes. However, the change can in embodiments also be an instant change, or a change within 2 minutes, such as within 30 seconds, such as within 1 second. Furthermore, in embodiments, the control system can be configured to control the change from the first device light setting to the second device light setting in dependence on one or more of an input signal of a user interface, a sensor signal, and a timer. Embodiments particularly relating to the S2-S3 transition

[0064] As mentioned above, in the operational mode of the light generating system, the control system can be configured to change from the device light setting to another device light setting different from the previous device light setting, which can in particular be a change from the high-radiant flux third setting (S3) to the low-radiant flux second setting (S2) or from the low-radiant flux second setting (S2) to the high-radiant flux third setting (S3) (see also above).

[0065] For example, in embodiments this can be a change from a high intensity setting (in particular the high-radiant flux third setting (S3)) where alertness or activity is desired to a low intensity setting during the night where a reduction in intensity is desired, but where alertness or activity can be less desired (in particular the low-radiant flux second setting (S2)). However, after a night, the setting can again be changed from the low-radiant flux second setting (S2) to the high-radiant flux third setting (S3).

[0066] Hence, in a particular embodiment in the third operational mode of the light generating system, the control system can be configured to change from the third device light setting to a second device light setting different from the third device light setting. Moreover, in a particular embodiment, the third device light setting and the first device light setting can be selected from: (a) a high-radiant flux setting (S3) in which the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low-radiant flux second setting (S2) in which the device light is a second light having a second radiant flux I2 and a second B / Y ratio R2 as defined herein. In embodiments, R3 > R2. In particular, in embodiments, I2 < I3. Moreover, in specific embodiments, 0.5 < R2 / R3 < 0.95. However, in other embodiments, R2 > R3. In particular, in embodiments, I3 < I2. Moreover, in specific embodiments, 0.5 < R3 / R2 < 0.95. When R2 is smaller than R3, this can be one embodiment of warm dimming. When R2 is larger than R3, this can be a kind of cold dimming, although suppression of melatonin is substantially avoided. This is for example useful in hospital applications.

[0067] In yet another aspect, the application provides a light generating system comprising: (i) a light generating device configured to generate device light having a controllable radiant flux and a controllable spectral power distribution, and (ii) a control system configured to control the radiant flux and the spectral power distribution of the device light; wherein: (a) a ratio B / Y of the device light is defined as a ratio of the radiant flux of the device light in the wavelength range of 450-500 nm to the radiant flux of the device light in the wavelength range of 550-600 nm; (b) in a third operational mode of the light generating system, the control system is configured to change from a third device light setting to a second device light setting different from the third device light setting; (c) the third device light setting and the first device light setting are selected from: (a) a high radiant flux setting (S3) in which the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3, and (b) a low radiant flux second setting (S2) in which the device light is a second light according to any one of the preceding claims having a second radiant flux I2 and a second B / Y ratio R2; and (d) I3 < I2 and 0.5 < R2 / R3 < 0.95.

[0068] Thus, there can be a change from the high radiant flux third setting (S3) (e.g. in the evening) to the low radiant flux second setting (S2) (e.g. at night) or from the low radiant flux second setting (S2) (e.g. at night) to the high radiant flux third setting (S3) (e.g. in the morning). The high B / Y ratio R3 at high intensity can be used for melatonin suppression, while the low B / Y ratio R2 at low intensity can also be used to prevent melatonin suppression.

[0069] In embodiments, the light generating device can have a maximum radiant flux, which in embodiments can in particular be such that at the maximum radiant flux a high light level will be provided. This is in particular applicable for applications in which the light generating device can be designed, like office lighting, hospital (room) lighting, hotel lighting, corridor lighting, home lighting, etc.

[0070] In particular embodiments, the high light level can be at least in a range of 10% or more of the maximum radiant flux, and the low light level can be at maximum 90% of the maximum radiant flux, wherein the latter light level is at least less than the former light level. Thus, in particular embodiments, the light generating device is capable of generating device light having a maximum radiant flux I max , wherein I3 > 0.1 * I max and I2 < 0.9 * I max , and wherein I2 / I3 < 0.9. For example, in embodiments I3 > 0.1 * I max and I2 < 0.09 * I max . In other embodiments, I3 > 0.9 * I max and I2 < 0.85 * I max , for example I2 < 0.75 * Imax In other embodiments, I3≥ 0.6*I max and I2≤ 0.4*I max In embodiments, I2 / I3≤ 0.8, for example I2 / I3≤ 0.7.

[0071] In embodiments, the second light can have a relatively high correlated color temperature. The dimmed light that can produce a dimmed scene of a darkened scene can typically have a relatively low correlated color temperature. However, in embodiments where it is desired to suppress melatonin at low light levels, for example to promote sleep, it can seem desirable to have a relatively high CCT. For example, the second correlated color temperature can be at least 2700K. However, at relatively high intensities, it can be desirable that the CCT is also relatively high, in order to substantially suppress melatonin. Thus, in embodiments, the third correlated color temperature can be at least about 4000K. Thus, in specific embodiments, the third light has a third correlated color temperature T C3 where the second light has a second correlated color temperature T C2 where: T C3 ≥ 1200K, T C2 ≥ 2200K, and T C2 < T C3 Further, in specific embodiments, R2≥ 0.2, for example in particular at least 0.23, even more in particular at least 0.25. Further, R3may be at least 0.2, for example at least 0.23, even more in particular at least 0.25. More in particular, R3may be 0.25≤ R3≤ 2.2 and / or R2may be 0.25≤ R2≤ 2.2.

[0072] In embodiments, the change from the high-radiant-flux third setting (S3) to the low-radiant-flux second setting (S2) or from the low-radiant-flux second setting (S2) to the high-radiant-flux third setting (S3) can be gradual. For example, this can be by linear gradual decrease or increase or by non-linear decrease or increase. Thus, in embodiments, the change (from the high-radiant-flux third setting (S3) to the low-radiant-flux second setting (S2) or from the low-radiant-flux second setting (S2) to the high-radiant-flux third setting (S3)) can be a gradual change over a change time selected from the range of 2-120 minutes, like at least 5 minutes, like 15-120 minutes, like at most about 30 minutes. However, the change can also be an instant change in embodiments. Further, in specific embodiments, the control system can be configured to control the change from the third device light setting to the second device light setting in dependence on one or more of an input signal of a user interface, a sensor signal, and a timer.

[0073] Embodiments in particular relating to S1-S4 transitions

[0074] In yet another aspect, the application provides a light generating system comprising: (i) a light generating device configured to generate device light having a controllable radiant flux and a controllable spectral power distribution; and (ii) a control system configured to control the radiant flux and the spectral power distribution of the device light; wherein: (A) a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in a wavelength range of 450-500 nm to a radiant flux of the device light in a wavelength range of 550-600 nm; (B) in a fourth operational mode of the light generating system, the control system is configured to change from a first device light setting to a fourth device light setting different from the first device light setting; (C) the first device light setting and the fourth device light setting are selected from: (a) a high radiant flux first setting (SI), wherein the device light is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a low radiant flux fourth setting (S4), wherein the device light is a fourth light having a fourth radiant flux I4 and a fourth B / Y ratio R4; and (D) I4 < II. Further, in specific embodiments, R4 / R1 is 0.5 < R4 / R1 < 0.95.

[0075] However, in other embodiments, R4 > Rl. For example, 0.5 < Rl / R4 < 0.95. This can for example be useful in case high flux sleep is desired to be suppressed but low flux alertness and / or good color rendering can (still) be desired.

[0076] Thus, in particular embodiments, R4 < 0.25 and / or Rl < 0.25. Further, in particular embodiments, R2 > 0.25 and / or R3 > 0.25.

[0077] In specific embodiments, the high light level can be at least in a range of 10% or more of the maximum radiant flux, and the low light level can be at the maximum 90% of the maximum radiant flux, wherein the latter light level is at least less than the former light level. Thus, in specific embodiments, the light generating device is capable of generating device light having a maximum radiant flux I max , wherein II > 0.1 * I max and I4 < 0.9 * I max , and wherein II / I4 < 0.9. For example, in embodiments, II > 0.1 * I max and I4 < 0.09 * I max . In other embodiments, II > 0.9 * I max and I4 < 0.85 * I max , for example I4 < 0.75 * I max . In other embodiments, II > 0.6 * I max and I4 < 0.4 * I max . In embodiments, I4 / II < 0.8, for example I4 / II < 0.7.

[0078] In embodiments, the change from the high-radiant-flux first setting (SI) to the low-radiant-flux fourth setting (S4) or from the low-radiant-flux fourth setting (S4) to the high-radiant-flux first setting (SI) can be gradual. For example, this can be by linear gradual decrease or increase or by non-linear decrease or increase. Thus, in embodiments, the change (from the high-radiant-flux first setting (SI) to the low-radiant-flux fourth setting (S4) or from the low-radiant-flux fourth setting (S4) to the high-radiant-flux first setting (SI)) can be a gradual change over a change time selected in the range from 2-120 minutes, such as at least 5 minutes, such as 15-120 minutes, such as at most about 30 minutes. However, the change can also be an immediate change in embodiments. Further, in specific embodiments, the control system can be configured to control the change from the first device light setting to the fourth device light setting depending on one or more of an input signal of a user interface, a sensor signal, and a timer.

[0079] For example, the low-intensity fourth setting can be used for indoor light situations where vision is required via a window to a low light level outdoor scene. In this case, the visual system should be dark adapted, but at the same time should suppress melatonin to maintain alertness.

[0080] Embodiments especially relating to the S1-S3 transition

[0081] In yet another aspect, the present invention provides a light generating system comprising: (i) a light generating device configured to generate device light having a controllable radiant flux and a controllable spectral power distribution; and (ii) a control system configured to control the radiant flux and the spectral power distribution of the device light; wherein: (A) a ratio B / Y of the device light is defined as a ratio of the radiant flux of the device light in the wavelength range of 450-500 nm to the radiant flux of the device light in the wavelength range of 550-600 nm; (B) in a fifth mode of operation of the light generating system, the control system is configured to change from a first device light setting to a third device light setting different from the first device light setting; (C) the first device light setting and the third device light setting are selected from: (a) a high-radiant-flux first setting (SI) in which the device light is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a high-radiant-flux third setting (S3) in which the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3. Further, in specific embodiments, R3 / R1 > 1, such as R3 / R1 > 1. In other specific embodiments, R3 / R1 = 1. Further, in specific I3 / I1 > 1, such as I3 / I1 > 1. In further specific embodiments, I3 / I1 = 1.

[0082] However, in other embodiments, I1 / I3 > 1. This can also be a kind of cold dimming, which is for example of interest for keeping a person alert at a relatively low luminous flux.

[0083] Thus, in particular in embodiments, 0.05 < R1 < 0.25 and / or 0.25 < R3 < 2.2. Further, in particular in embodiments, R3 > 0.25, for example R3 > 0.35, and / or R1 < 0.25, for example R1 < 0.2.

[0084] The operational mode in which the transition between the first high-radiant-flux setting and the third high-radiant-flux setting takes place can for example be used to suppress jetlag effects or to promote sports performance. Other applications can be lighting at high-risk locations, for example control rooms of nuclear reactors. However, this is also useful for sports applications.

[0085] In embodiments, the change from the high-radiant-flux first setting (SI) to the high-radiant-flux third setting (S3) or from the high-radiant-flux third setting (S3) to the high-radiant-flux first setting (SI) can be gradual. For example, this can be by linear gradual decrease or increase or by non-linear decrease or increase. Thus, in embodiments, the change (from the high-radiant-flux first setting (SI) to the high-radiant-flux third setting (S3) or from the high-radiant-flux third setting (S3) to the high-radiant-flux first setting (SI)) can be a gradual change over a change time selected in a range from 2-120 minutes, like at least 5 minutes, like 15-120 minutes, like at most about 30 minutes. However, the change can in embodiments also be an instant change. Further, in particular embodiments, the control system can be configured to control the change from the first device light setting to the third device light setting depending on one or more of an input signal of a user interface, a sensor signal and a timer.

[0086] Embodiments in particular relating to S2-S4 transition

[0087] In yet another aspect, the present application provides a light generating system comprising: (i) a light generating device configured to generate device light having a controllable radiant flux and a controllable spectral power distribution; and (ii) a control system configured to control the radiant flux and the spectral power distribution of the device light; wherein: (A) a ratio B / Y of the device light is defined as the ratio of the radiant flux of the device light in the 450-500 nm wavelength range to the radiant flux of the device light in the 550-600 nm wavelength range; (B) in a sixth mode of operation of the light generating system, the control system is configured to change from a second device light setting to a fourth device light setting different from said second device light setting; (C) the second device light setting and the fourth device light setting are selected from: (a) a low radiant flux second setting (S2) in which the device light is a second light having a second radiant flux I2 and a second B / Y ratio R2; and (b) a low radiant flux fourth setting (S4) in which the device light is a fourth light having a fourth radiant flux I4 and a fourth B / Y ratio R4. Further, in specific embodiments, R4 / R2 < 1, for example R4 / R2 < 1. Further, in specific embodiments, I4 / I2 < 1, for example I4 / I2 < 1. However, in other embodiments, I4 / I2 > 1, for example I4 / I2 > 1. In yet further specific embodiments, I4 / I2 = 1.

[0088] Thus, in particular in embodiments, 0.05 < R4 < 0.25 and / or 0.25 < R2 < 2.2. Further, in particular in embodiments, R2 > 0.25, for example R2 > 0.35, and / or R4 < 0.25, for example R4 < 0.2.

[0089] wherein the mode of operation in which the transition between the second low radiant flux setting and the low radiant fourth flux setting occurs can for example be used for e.g. outdoor lighting. For example, first at a relatively high (but lower than 30 lux Eeye) level I4, one can want to keep road users alert (in particular R < 0.25), and at night, the light can be dimmed to a lower level I2 (I2 < I4), and one can want not to suppress melatonin, which can for example be achieved by increasing R to R > 0.25. In particular, in embodiments, I4 / I2 > 1.

[0090] In embodiments, the change from the low-radiant flux second setting (S2) to the low-radiant flux fourth setting (S4) or from the low-radiant flux fourth setting (S4) to the low-radiant flux second setting (S2) can be gradual. For example, this can be by linear gradual decrease or increase or by non-linear decrease or increase. Thus, in embodiments, the change (from the low-radiant flux second setting (S2) to the low-radiant flux fourth setting (S4) or from the low-radiant flux fourth setting (S4) to the low-radiant flux second setting (S2)) can be a gradual change over a change time selected in a range from 2-120 minutes, such as at least 5 minutes, such as 15-120 minutes, such as at most about 30 minutes. However, the change can also be an immediate change in embodiments. Further, in specific embodiments, the control system can be configured to control the change from the second device light setting to the fourth device light setting in dependence on one or more of an input signal of a user interface, a sensor signal, and a timer.

[0091] Further aspects and embodiments

[0092] In embodiments, the change from one setting to another setting can be performed without an intermediate further setting. However, in other embodiments, the change from one setting to another setting can be performed via an intermediate further setting (of the settings described herein).

[0093] In yet another aspect, the present application also provides a method for controlling a controllable radiant flux and a controllable spectral power distribution of a device light, wherein: (A) a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in a wavelength range of 450-500 nm to a radiant flux of the device light in a wavelength range of 550-600 nm; (B) the method comprises (in a first operational mode) changing from a first device light setting to a second device light setting different from the first device light setting; (C) the first device light setting and the second device light setting are selected from: (a) a high-radiant flux first setting (S1), wherein the device light is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a low-radiant flux second setting (S2), wherein the device light is a second light having a second radiant flux I2 and a second B / Y ratio R2; and (D) I2 < II, and Rl < R2. In specific embodiments, R2 > 0.25 and wherein Rl < 0.25.

[0094] Further embodiments with respect to this (first) operational mode are also described above.

[0095] In one specific embodiment, the method can further comprise: (in the second operational mode) changing from the third device light setting to a fourth device light setting different from the third device light setting; wherein (i) the third and fourth device light settings are selected from: (a) a high-radiant-flux third setting (S3) in which the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low-radiant-flux fourth setting (S4) in which the device light is a fourth light having a fourth radiant flux I4 and a fourth B / Y ratio R4; and (ii) I4 < I3 and R3 > R4.

[0096] In yet another aspect, the present application provides a method for controlling a controllable radiant flux and a controllable spectral power distribution of a device light, wherein: (A) a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in a wavelength range of 450-500 nm to a radiant flux of the device light in a wavelength range of 550-600 nm; (B) the method further comprises: (in a second operational mode) changing from a third device light setting to a fourth device light setting different from the third device light setting; (C) the third and fourth device light settings are selected from: (a) a high-radiant-flux third setting (S3) in which the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low-radiant-flux fourth setting (S4) in which the device light is a fourth light having a fourth radiant flux I4 and a fourth B / Y ratio R4; and (D) I4 < I3 and R3 > R4.

[0097] Further embodiments regarding this (second) operational mode are also described above.

[0098] In one specific embodiment, the method can further comprise: (in the third operational mode) changing from the third device light setting to a second device light setting different from the third device light setting; wherein (i) the third and first device light settings are selected from: (a) a high-radiant-flux setting (S3) in which the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low-radiant-flux second setting (S2) in which the device light is a second light having a second radiant flux I2 and a second B / Y ratio R2 as defined herein. In particular, in embodiments, I2 < I3. Moreover, in specific embodiments, 0.5 < R2 / R3 < 0.95.

[0099] In yet another aspect, the present application provides a method for controlling a controllable radiant flux and a controllable spectral power distribution of a device light, wherein: (A) a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in a wavelength range of 450-500 nm to a radiant flux of the device light in a wavelength range of 550-600 nm; (B) the method further comprises (in a third operating mode) changing from a third device light setting to a second device light setting different from the third device light setting; (C) the third device light setting and the first device light setting are selected from: (a) a high radiant flux setting (S3), wherein the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low radiant flux second setting (S2), wherein the device light is a second light having a second radiant flux I2 and a second B / Y ratio R2 according to any of the preceding claims; and (D) I3 < I2, and 0.5 < R2 / R3 < 0.95.

[0100] Further embodiments regarding this (third) operating mode are also described above.

[0101] In general, the present application also provides a method for controlling a controllable radiant flux and a controllable spectral power distribution of a device light, wherein: (A) a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in a wavelength range of 450-500 nm to a radiant flux of the device light in a wavelength range of 550-600 nm; (B) the method comprises (in an operating mode) changing from a first device light setting to a second device light setting different from the first device light setting; (c) the first device light setting and the second device light setting are selected from: (a) a high radiant flux first setting (S1), (b) a low radiant flux second setting (S2), (C) a high radiant flux third setting (S3), (b) a low radiant flux fourth setting (S4), wherein the first device light setting and the second device light setting are different (and wherein the settings S1-S4 are defined herein).

[0102] Here below, some further embodiments are provided:

[0103] Light level Sleep / rest - no melatonin suppression Alertness / activity - melatonin suppression Low light level 0.25 < R2 < 2.2 0.05 < R4 < 0.25 High light level 0.05 < R1 < 0.25 0.25 < R3 < 2.2

[0104] Several types of lighting can be considered.

[0105] For example, a first type (or category) of lighting can refer to lighting in e.g. a parking garage, a dock, a harbor, etc. Here, the illuminance of the parking garage deck, the dock, the harbor can be in the order of 75-100 lux. The luminous intensity can be chosen from a range of about 675-222000 candelas, measured on the optical axis of the light source and perpendicular to the optical axis of the light source.

[0106] For example, the second type (or category) of lighting can refer to lighting in a home, warehouse, auditorium, outdoor sports, (petroleum) chemical plant, offshore platform, public park, lounge, corridor, changing room, living room, dining room, bedroom, bathroom, etc. Here, the illuminance can be of the order of 100-200 lux. At 1 m from the light generating device, the luminous intensity can be chosen from a range of about 400-80000 candela.

[0107] For example, the third type (or category) of lighting can refer to lighting in an office, assembly line, machine hall, school, training room, museum, cafeteria, ICU, hospital room, etc. Here, the illuminance can be about 200-750 lux. At 1 m from the light generating device, the luminous intensity can be chosen from a range of about 800-48000 candela.

[0108] For example, the fourth type (or category) of lighting can refer to lighting in fine work, food processing, supermarket, old people's residence, nursery, etc. Here, the illuminance can be of the order of 750-1000 lux. At 1 m from the light generating device, the luminous intensity can be chosen from a range of about 3000-64000 candela.

[0109] However, the fifth type (or category) of lighting can refer to road and street lighting, park lighting, square lighting, emergency lighting. The illuminance at the road or street can be of the order of 3-75 lux. At 1 m from the light generating device, the luminous intensity can be chosen from a range of about 12-30000 candela.

[0110] However, the amount of lighting received by the eye can be different, because the four categories of illuminance values indicated by the former can be horizontal illuminance, while the eye can essentially receive vertical illuminance, unless the observer lies in a position in which he / she looks upwards.

[0111] It appears that, for illuminances falling in the range of about 20-40 lux, such as in the range of 24-36 lux, like in the range of about 28-32 lux, such as falling in the range of about 30 lux, at the human eye, the change that occurs is that at lower illuminances, a higher R value (i.e. a higher blue / yellow ratio) does not (or less) suppress the melatonin level, while at higher illuminances, a lower R value (i.e. a lower blue / yellow ratio) does not (or less) suppress the melatonin level.

[0112] Thus, for Category 1 lighting, the low light level can be about 80% of the illuminance maximum, and the high light level can be about at least 40% of the illuminance maximum. Of course, the illuminance of the low light level is lower than the illuminance of the high light level. In particular embodiments, for Category 1 lighting, the low light level can be about at most 40% of the illuminance maximum, and the high light level can be about at least 80% of the illuminance maximum.

[0113] Thus, for Category 2 lighting, the low light level can be about at most 75% of the illuminance maximum, and the high light level can be about at least 30% of the illuminance maximum. Of course, the illuminance of the low light level is lower than the illuminance of the high light level. In particular embodiments, for Category 2 lighting, the low light level can be about at most 30% of the illuminance maximum, and the high light level can be about at least 75% of the illuminance maximum.

[0114] Thus, for Category 3 lighting, the low light level can be about at most 25% of the illuminance maximum, and the high light level can be about at least 10% of the illuminance maximum. Of course, the illuminance of the low light level is lower than the illuminance of the high light level. In particular embodiments, for Category 3 lighting, the low light level can be about at most 10% of the illuminance maximum, and the high light level can be about at least 25% of the illuminance maximum.

[0115] Thus, for Category 4 lighting, the low light level can be about at most 10% of the illuminance maximum, and the high light level can be about at least 7.5% of the illuminance maximum. Of course, the illuminance of the low light level is lower than the illuminance of the high light level. In particular embodiments, for Category 4 lighting, the low light level can be about at most 7.5% of the illuminance maximum, and the high light level can be about at least 10% of the illuminance maximum.

[0116] Thus, for Category 5 lighting, the low light level can be about at most 70% of the illuminance maximum, and the high light level can be about at least 60% of the illuminance maximum. Of course, the illuminance of the low light level is lower than the illuminance of the high light level. In particular embodiments, for Category 5 lighting, the low light level can be about 60% of the illuminance maximum, and the high light level can be about at least 70% of the illuminance maximum.

[0117] In one aspect, the present application provides a method in which one of the following is applied: (i) decreasing the radiant flux while increasing the correlated color temperature, and (ii) increasing the radiant flux while decreasing the correlated color temperature.

[0118] The present application also provides a light generating system configured to perform one of the following in an operational mode: (i) decreasing the radiant flux while increasing the correlated color temperature, and (ii) increasing the radiant flux while decreasing the correlated color temperature.

[0119] In particular, the luminous intensity can be determined at 1 meter from the light source.

[0120] In embodiments, the change from one device light setting to another device light setting can be a change from a B / Y ratio of at least 0.25 to a B / Y ratio of less than 0.25. In other embodiments, the change from one device light setting to another device light setting can be a change from a B / Y ratio of less than 0.25 to a B / Y ratio of at least 0.25. In embodiments, the change in the ratio can be at least 0.02, more particularly at least 0.05, for example at least 0.1, such as at least 0.15 in specific embodiments. In embodiments, one device light setting is a high radiant flux setting, while the other device light setting is a low radiant flux setting. In embodiments, one device light setting is a low radiant flux setting, while the other device light setting is a high radiant flux setting. In embodiments, one device light setting and the other device light setting can substantially have the same radiant flux setting.

[0121] In embodiments, the change from one device light setting to another device light setting can be a change from a B / Y ratio of at least 0.25 to another ratio of at least 0.25. In embodiments, the change in the ratio can be at least 0.02, more particularly at least 0.05, for example at least 0.1, such as at least 0.15 in specific embodiments. In embodiments, one device light setting is a high radiant flux setting, while the other device light setting is a low radiant flux setting. In embodiments, one device light setting is a low radiant flux setting, while the other device light setting is a high radiant flux setting. In embodiments, one device light setting and the other device light setting can substantially have the same radiant flux setting.

[0122] In embodiments, the change from one device light setting to another device light setting can be a change from a B / Y ratio of less than 0.25 to another ratio of less than 0.25. In embodiments, the change in the ratio can be at least 0.02, more particularly at least 0.05. In embodiments, one device light setting is a high radiant flux setting, while the other device light setting is a low radiant flux setting. In embodiments, one device light setting is a low radiant flux setting, while the other device light setting is a high radiant flux setting. In embodiments, one device light setting and the other device light setting can substantially have the same radiant flux setting.

[0123] Thus, the change from one device light setting to another device light setting different from the one device light setting can imply a difference in the R value of at least 0.02, more particularly at least 0.05. The R value can be changed by, for example, changing the spectral power distribution.

[0124] In embodiments, the change from one device light setting to another device light setting can be a change from a high radiant flux setting to a low radiant flux setting. In embodiments, the B / Y ratio can not change. In other embodiments, the B / Y ratio can increase. In other embodiments, the B / Y ratio can decrease.

[0125] In embodiments, the change from one device light setting to another device light setting can be a change from a low radiant flux setting to a high radiant flux setting. In embodiments, the B / Y ratio can not change. In other embodiments, the B / Y ratio can increase. In other embodiments, the B / Y ratio can decrease.

[0126] In embodiments, the light generating system can be configured such that, in normal use, a user can experience an illuminance of more than 30 lux in one device light setting and less than 30 lux in another device light setting. In particular, this can be the illuminance at the (human) eye. Hence, in particular embodiments, the change from one device light setting to another device light setting can comprise a change in illuminance at the human eye from below 30 lux to above 30 lux or from above 30 lux to below 30 lux.

[0127] A reason for the S3→S2 transition can be that at the higher radiant flux setting, alertness can be required (and melatonin levels can be suppressed); when dimming to the lower radiant flux setting, it is desirable that melatonin levels are not suppressed (beneficial for sleep). Instead of choosing a warmer light (lower R), the light can be relatively cooler, and R can remain above 0.25. Of course, the same applies for the S2→S3 transition, but then up-regulating from the lower radiant flux level to the higher radiant flux level.

[0128] Furthermore, in particular embodiments, the third device light setting and the first device light setting can be selected from: (a) a high radiant flux setting (S3), wherein the device light is a third light having a third radiant flux I3 and a third B / Y ratio R3. In specific embodiments, R2>R3. This can result in a transition between settings where dR / dI<0. For example, assuming a high I3, with a relatively low CCT (relatively low R value), e.g. CCT=3000K, this can provide visual comfort. Upon dimming to a lower radiant flux I2, in embodiments it is desirable that people can sleep, i.e. substantially no suppression of melatonin levels. Then, it can be desirable to have an R value larger than 0.25, e.g. by having a light with a CCT of at least 4500K.

[0129] In embodiments, the light generating system can comprise one or more first light sources configured to generate visible light having a correlated color temperature of at most 1800 K, and one or more second light sources configured to generate blue light. In particular, the radiant flux of the one or more second light sources is less than the radiant flux of the one or more first light sources, e.g. at least 2 times less, at maximum power. Such a light generating system can be used to control the change of S1-S2. In particular, the one or more first light sources comprise solid state light sources, like LEDs. In particular, the one or more second light sources comprise solid state light sources, like LEDs.

[0130] In embodiments, the light generating system can comprise one or more first light sources configured to generate visible light having a correlated color temperature of at most 2500 K, e.g. at most 2450 K, e.g. 2200 K, and one or more second light sources configured to generate blue light. For example, in embodiments, the one or more first light sources configured to generate visible light can have a correlated color temperature selected from the range of 1800-2500 K.

[0131] In embodiments, the light generating system can comprise one or more third light sources configured to generate visible light having a correlated color temperature of at least 2450 K, even more particularly at least about 3000 K, and one or more fourth light sources configured to generate red light. In particular, the radiant flux of the one or more fourth light sources is less than the radiant flux of the one or more third light sources, e.g. at least 2 times less, at maximum power. Such a light generating system can be used to control the change of S3-S4. In particular, the one or more third light sources comprise solid state light sources, like LEDs. In particular, the one or more fourth light sources comprise solid state light sources, like LEDs.

[0132] In one aspect, the application also provides a computer program product which, for example when loaded onto a computer (functionally coupled to a light generating system or light generating device) performs a method as defined herein. In yet another aspect, the application provides a record carrier (or data carrier) storing a computer program product as defined herein, e.g. a USB stick, a CD, a DVD, a memory card, etc. The computer program product thus implements or enables implementation of a method as described herein when run on or loaded into a computer (functionally coupled to a light generating system or light generating device). In yet another aspect, the application also provides a computer program product which, when run on a computer functionally coupled to or comprised by an apparatus, device or system, controls one or more controllable elements of such apparatus, device or system.

[0133] In yet another aspect, the present application also provides a computer program product, which, when running on a computer functionally coupled to or comprised by an apparatus, device or system as described herein, performs a method as described herein. In yet another aspect, the present application (thus) provides a software product, which, when running on a computer (functionally coupled to a light generating system or light generating device) is able to implement a method (one or more embodiments) as described herein.

[0134] In yet another aspect, the present application also provides a light generating system, in particular configured to provide light with a low radiant flux, e.g. for controlling a room, a cockpit, a driver space in a motor vehicle, a hospital room, a prison, etc., wherein it can be desirable to suppress sleep and / or promote activity despite the relatively low intensity.

[0135] Thus, in an aspect, the present application provides a light generating system comprising a light generating device configured to provide a device light beam, wherein: (a) the light generating system is configured to provide the device light with an intensity selected from the range of 12-220000 candelas on a surface normal to the optical axis at a first distance (dl) from the device, wherein dl is 1 m, wherein the device light; (b) a ratio B / Y of the device light is defined as the ratio of the radiant flux of the device light in the wavelength range of 450-500 nm to the radiant flux of the device light in the wavelength range of 550-600 nm, in a particular embodiment selected from the range of R4<0.25, in particular from the range of 0.05≤R4<0.25. Thus, in embodiments, a static lamp for night / low intensity light applications is provided herein, wherein melatonin should be suppressed. In particular, in embodiments, dl is selected from the range of 1-4 m, and / or the illuminance is e.g. selected from the range of 5-75 lux. In particular, in embodiments, the device light can have a correlated color temperature selected from the range of 800-2450 K, in particular maximum 1200 K. In embodiments, the device light beam has an optical axis (O). In particular embodiments, the light generating system can be configured to provide the device light with an intensity selected from the range of 12-220000 candelas.

[0136] In yet another aspect, in which melatonin suppression is undesirable, the present invention provides a light generating system comprising a light generating device configured to provide a device light beam, wherein: (a) the light beam of the device light has an optical axis (O); the light generating system is configured for providing the device light on a surface normal to the optical axis at a first distance (dl) from the device, wherein dl is selected from the range of 1 m; and (c) a ratio B / Y of the device light is defined as a ratio of a radiant flux of the device light in the wavelength range of 450-500 nm to a radiant flux of the device light in the wavelength range of 550-600 nm, the ratio being selected from the range of 0.25 < R2< 2.2.

[0137] In yet another aspect, the light generating system can comprise one or more first light sources configured to generate first (white) light having a first correlated color temperature CCT1. The one or more first light sources together can have a first maximum electric power W1. The one or more first light sources can be configured for generating first light having a first luminous flux F1. Further, the light generating system can comprise one or more second light sources configured to generate second (white) light having a second correlated color temperature CCT2. The one or more second light sources together can have a second maximum electric power W2. The one or more second light sources can be configured to generate second light having a second luminous flux F2. In embodiments, 2 < W1 / W2 < 100, in particular 4 < W1 / W2 < 100, such as in particular 8 < W1 / W2 < 50, more in particular 10 < W1 / W2 < 25. In embodiments, 1.5 < F1 / F2 < 20, more in particular 2.5 < F1 / F2 < 10, such as 3.5 < F1 / F2 < 5. In embodiments, CCT1 < 2450 K, such as about 2200 K. In embodiments, CCT2 > 5000 K, such as about 6500 K. In embodiments, 2000 K < CCT2 - CCT1 < 5000 K.

[0138] In embodiments, the first light has a first x color coordinate xi and the second light has a second x color coordinate x2, wherein xi is equal to or larger than a predetermined x value x p , and wherein x2 is equal to or smaller than a predetermined value, wherein the coordinates are according to CIE 1931, and wherein x2 < xi. In embodiments, xi - x2 > 0.03, such as xi - x2 > 0.05, like in particular embodiments xi - x2 > 0.1. p is selected from the range of about 0.35 - 0.4. For instance, x2 is smaller than 0.35 and xi is larger than 0.35. Or, for instance, x2 is smaller than 0.4 and xi is larger than 0.4. In embodiments, xi - x2 > 0.03, such as xi - x2 > 0.05, like in particular embodiments xi - x2 > 0.1.

[0139] Thus, in a particular embodiment, the light generating system can comprise one or more first light sources configured to generate first (white) light, wherein the first light has a first x color coordinate xi, and one or more second light sources configured to generate second (white) light, wherein the second light has a second x color coordinate x2, wherein xi > 0.35, wherein x2 < 0.4, wherein xi - x2 > 0.03, wherein the one or more first light sources together can have a first maximum electric power Wi, wherein the one or more second light sources together can have a second maximum electric power W2, and wherein 2 < Wi / W2 < 100, e.g. in particular 4 < Wi / W2 < 100. The system light can comprise one or more of the first light and the second light, and the spectral power distribution of the system light can be controllable (in particular by controlling the one or more first light sources and the one or more second light sources). Thus, the light generating device can comprise the one or more first light sources and the one or more second light sources.

[0140] In particular, the color coordinates are according to CIE 1931 (color space).

[0141] In an embodiment (of the method), the method can comprise performing the change of the irradiance I and the B / Y ratio R such that dR / dl < 0.

[0142] The light generating system can be part of or applied in e.g. an office lighting system, a home application system, a shop lighting system, a home lighting system, a spot lighting system, a spotlight lighting system, a theater lighting system, a fiber optic application system, a projection system, a self-lit display system, a pixelated display system, a segmented display system, a warning sign system, a medical lighting application system, an indication sign system, a decorative lighting system, a portable system, a car application, an (outdoor) road lighting system, a city lighting system, a greenhouse lighting system, horticulture lighting, digital projection or LCD backlighting. The light generating system (or luminaire) can be part of or can be applied in e.g. an optical communication system or a disinfection system.

[0143] The light escaping from the system can be denoted the system light. In particular, in an embodiment, the system light can essentially consist of the device light of the light generating device.

[0144] In a particular embodiment, the light generating system can comprise a parking garage lighting device, a harbor lighting device, a port lighting device, a road lighting device, a street lighting device, a park lighting device, a square lighting device, an emergency lighting device, a tunnel lighting device, a regional lighting device, an office lighting device, an industrial lighting device, a residential lighting device, a hospital lighting device, a ward lighting device, a retail lighting device, a warehouse lighting device, a stable lighting device, and an animal husbandry lighting device. However, other embodiments are possible as well.

[0145] In operation mode, the device light can comprise spectral power in one or more wavelength ranges selected from (i) 450-500 nm and (ii) 550-600 nm. In particular, in operation mode, the device light comprises spectral power in these wavelength ranges. The device light can further comprise spectral power in one or more wavelength ranges selected from (iii) 380-450 nm, (iv) 500-550 nm and (v) 600-780 nm, especially in at least one of (iv) 500-550 nm and (v) 600-780 nm. At least 90%, even more particularly at least 95% of the spectral power of the device light can be in the wavelength range of 380-780 nm. Further, in embodiments, at least 30% of the spectral power of the device light in the wavelength range of 380-780 nm is in one or more wavelength ranges selected from (i) 450-500 nm and (ii) 550-600 nm. Further, in embodiments, at least 30% of the spectral power of the device light in the wavelength range of 380-780 nm is in one or more wavelength ranges selected from (iii) 380-450 nm, (iv) 500-550 nm and (v) 600-780 nm.

[0146] In yet another aspect, the present application also provides a lamp or luminaire comprising a light generating system as defined herein. The luminaire can further comprise a housing, optical elements, louvers, etc. The lamp or luminaire can further comprise an envelope enclosing the light generating system. The lamp or luminaire can comprise a light window or an envelope opening in the envelope through which system light can escape from the envelope. In yet another aspect, the present application also provides a projection device comprising a light generating system as defined herein. In particular, the projection device or "projector" or "image projector" can be an optical device that projects an image (or a moving image) onto a surface such as a projection screen. The projection device can comprise one or more light generating systems as described herein. Thus, in one aspect, the present application also provides a light generating device selected from the group of a lamp, a luminaire, a projector device, a disinfection device and an optical wireless communication device, comprising a light generating system as defined herein. The light generating device can comprise an envelope or carrier configured to house or support one or more elements of the light generating system. For example, in embodiments, the light generating system can comprise an envelope or carrier configured to house or support one or more light generating devices. Thus, in yet another aspect, the present application also provides a light generating device selected from the group of a lamp, a luminaire, a projector device, a disinfection device and an optical wireless communication device, comprising a light generating system as defined herein, especially a light generating device selected from the group of a lamp and a luminaire. BRIEF DESCRIPTION OF DRAWINGS

[0147] Embodiments of the application will now be described by way of example only, and with reference to the accompanying schematic drawings, in which corresponding reference signs indicate corresponding parts, and in which:

[0148] Figures 1A-1C Aspects are schematically depicted;

[0149] Figure 2 Dimming regions and effects on melatonin are schematically depicted; and

[0150] Figure 3 Some (application) embodiments are schematically depicted. The schematic drawings are not necessarily to scale. DETAILED DESCRIPTION

[0151] Figures 1A-1C is a schematic drawing of an embodiment of the application. Figure 1A An embodiment of a light generating system 1000 is schematically shown, which comprises (i) a light generating device 100 configured to generate a device light 101 having a controllable radiant flux and a controllable spectral power distribution, and (ii) a control system 300 configured to control the radiant flux and the spectral power distribution of the device light 101. In particular, a ratio B / Y of the device light 101 is defined as a ratio of a radiant flux of the device light 101 in a wavelength range of 450-500 nm to a radiant flux of the device light (101) in a wavelength range of 550-600 nm. In embodiments, in a first operational mode of the light generating system 1000, the control system 300 is configured to change from a first device light setting to a second device light setting different from the first device light setting. Further, in embodiments, the first device light setting and the second device light setting are selected from: (a) a high radiant flux first setting S1, in which the device light 101 is a first light having a first radiant flux II and a first B / Y ratio R1; and (b) a low radiant flux second setting S2, in which the device light 101 is a second light having a second radiant flux I2 and a second B / Y ratio R2. In particular, in embodiments, I2< II. Further, in particular, in embodiments, R1< R2. II and I2 can be on an energy scale, e.g. in Watts.

[0152] In particular embodiments, the light generating device 100 is capable of generating a device light 101 having a maximum radiant flux I max , wherein II > 0.1 * I max and I2 < 0.9 * I max , and wherein I2 / II < 0.9.

[0153] Further, in particular embodiments, R2 is > 2.

[0154] In embodiments, the control system 300 is configured to control the change from the first device light setting to the second device light setting in dependence on one or more of an input signal of a user interface, a sensor signal, and a timer, wherein the change is a gradual change over time in embodiments changing from a range of 15-120 minutes.

[0155] In further embodiments, in the second operating mode of the light generating system 1000, the control system 300 is configured to change from the third device light setting to a fourth device light setting different from the third device light setting. In particular, in embodiments, the third device light setting and the fourth device light setting are selected from: (a) a high radiant flux third setting S3, wherein the device light 101 is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low radiant flux fourth setting S4, wherein the device light 101 is a fourth light having a fourth radiant flux I4 and a fourth B / Y ratio R4. In particular, in embodiments, I4 < I3. Further, in specific embodiments, R3 > R4.

[0156] In particular, in embodiments, the light generating device 100 is capable of generating the device light 101 having a maximum radiant flux I max In particular, in embodiments I3 > 0.1 * I max and I4 < 0.9 * I max Further, in specific embodiments I4 / I3 < 0.9. Further, in embodiments, the third light has a third correlated color temperature T C3 wherein the fourth light has a fourth correlated color temperature T C4 wherein in specific embodiments T C3 > 4000 K, T C4 < 3000 K.

[0157] Further, in specific embodiments, the control system 300 is configured to control the change from the third device light setting to the fourth device light setting in dependence on one or more of an input signal of a user interface, a sensor signal, and a timer, wherein the change is a gradual change over a change time selected from a range of 15-120 minutes.

[0158] Also in embodiments, in a third operational mode of the light generating system 1000, the control system 300 is configured to change from the third device light setting to a second device light setting different from the third device light setting. In particular, in embodiments, the third device light setting and the first device light setting are selected from: (a) a high radiant flux setting S3, in which the device light 101 is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low radiant flux second setting S2, in which the device light 101 is a second light having a second radiant flux I2 and a second B / Y ratio R2. Further, in embodiments, I2 < I3. In particular, in embodiments 0.5 < R2 / R3 < 0.95.

[0159] Further, in embodiments, the light generating device 100 is capable of generating the device light 101 having a maximum radiant flux I max , wherein I3 > 0.1 * I max and I2 < 0.9 * I max , and wherein I2 / I3 < 0.9.

[0160] Further, in embodiments, the control system 300 is configured to control the change from the third device light setting to the second device light setting in dependence on one or more of an input signal of a user interface, a sensor signal, and a timer, wherein the change is a gradual change over a change time selected in a range from 15-120 minutes.

[0161] Hence, the present invention also provides a method for controlling a controllable radiant flux and a controllable spectral power distribution of a device light 101, wherein: (a) a ratio B / Y of the device light 101 is defined as a ratio of a radiant flux of the device light 101 in a wavelength range of 450-500 nm to a radiant flux of the device light (101) in a wavelength range of 550-600 nm; (b) the method comprises (in a first operational mode) changing from a first device light setting to a second device light setting different from the first device light setting; (c) the first device light setting and the second device light setting are selected from: (i) a high radiant flux first setting S1, in which the device light 101 is a first light having a first radiant flux I1 and a first B / Y ratio R1; and (ii) a low radiant flux second setting S2, in which the device light 101 is a second light having a second radiant flux I2 and a second B / Y ratio R2. In particular, in embodiments, I2 < I1. Further, in embodiments, R1 < R2.

[0162] In particular embodiments, the control system 300 is configured to control the change from the third device light setting to the fourth device light setting in dependence on one or more of an input signal of a user interface, a sensor signal, and a timer, wherein the change is a gradual change over a change time selected in a range from 15-120 minutes.

[0163] The method comprises changing from the third device light setting to a fourth device light setting different from the third device light setting in the second operational mode. The third device light setting and the fourth device light setting are selected from: (a) a high radiant flux third setting S3, wherein the device light 101 is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low radiant flux fourth setting S4, wherein the device light 101 is a fourth light having a fourth radiant flux I4 and a fourth B / Y ratio R4, wherein I4 < I3 and wherein R3 > R4.

[0164] Further, in a particular embodiment, the method comprises (in the third operational mode) changing from the third device light setting to a second device light setting different from the third device light setting. In particular, in embodiments, the third device light setting and the first device light setting are selected from: (a) a high radiant flux setting S3, wherein the device light 101 is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low radiant flux second setting S2, wherein the device light 101 is a second light having a second radiant flux I2 and a second B / Y ratio R2 according to any of the preceding claims. In particular, in embodiments, I3 < I2. Further, in specific embodiments, 0.5 < R2 / R3 < 0.95.

[0165] Reference is made to Figure 1B , showing four possible states, wherein column NA represents a “non-activated state”, and column MS represents a “melatonin suppression” state (or activated state). Reference signs IL and IH represent a low radiant flux light level and a high radiant flux light level, respectively. Reference signs (1), (2), (3) and (4) represent a first operational mode, a second operational mode, a third operational mode and a fourth operational mode, respectively. Reference signs 5 and 6 represent other operational modes, wherein S2-S4 or S1-S3 transitions, respectively, can occur.

[0166] Reference is made to Figure 1C , schematically showing some possible changes in intensity between a low radiant flux state and a high radiant flux state. Note that other changes are possible as well, such as abrupt changes. On the y-axis is represented the B / Y ratio (or R value), and on the x-axis is represented the intensity between 0% and 100%.

[0167] Figure 2 is schematically depicted in Figure 1BA graph of a table. On the y-axis, the R value is shown, and exemplary possible correlated color temperatures are added. On the x-axis, the lux on the human eye is indicated, between about 0.05-5000 lux. Reference signs S and NS indicate melatonin suppression and no melatonin suppression, respectively. Reference sign a schematically describes street light dimming. Reference sign b represents home light dimming or patient room dimming, reference sign c represents another example of patient dimming. For example, in one case, one can not want to disturb a patient's sleep, but provide good visual inspection; in another case, one can want to promote sleep or wake up. Reference sign d represents an example of work-sleep transition. Reference sign RD represents regular dimming, reference sign WD represents warm dimming. Regular dimming especially means that the CCT remains substantially constant, while the flux is changed, while warm dimming especially means that the CCT decreases with decreasing flux.

[0168] Figure 3 Some embodiments of such a light generating system are schematically shown, for example a light generating device 1200 selected from the group of a lamp 1, a luminaire 2, a projector device 3, a disinfection device and an optical wireless communication device, comprising a light generating system 1000 as defined herein. Figure 3 One embodiment of a luminaire 2 comprising a light generating system 1000 as described above is schematically shown. Reference sign 301 represents a user interface, which can be functionally coupled with a control system 300 comprised by or functionally coupled with the light generating system 1000. Figure 3 One embodiment of a lamp 1 comprising a light generating system 1000 is also schematically shown. Reference sign 3 represents a projector device or projector system, which can be used for projecting images on a wall, for example, which can also comprise a light generating system 1000.

[0169] Reference Figure 1A and Figure 3The present invention can also provide a fixture system, such as a system having substantially no controllability of the spectral power distribution (and / or substantially no controllability of the intensity). In aspects, the present invention also provides a light generating system 1000 comprising a light generating device 100 configured to provide a light beam 115 of device light 101, wherein: (a) the light beam 115 of device light 101 has an optical axis O; (b) the light generating system 1000 is configured to provide the device light 101 having an intensity selected from the range of 12-220000 candelas on a surface 9 at a first distance dl from the device 100, wherein dl is 1 m, wherein the device light 101; (c) a ratio B / Y of the device light 101 is defined as a ratio of a radiant flux of the device light 101 in the wavelength range of 450-500 nm to a radiant flux of the device light (101) in the wavelength range of 550-600 nm is at least 2. In one example, a road lighting luminaire is used having 2000 lumens at 2300K, B / Y = 0.192.E. eye A value of B / Y < 0.25 can be chosen in the early and late peak hours (first and last hour of the lighting period) alertness event for road users, which can be achieved using 10 white LEDs (2200K) powered with a total of 9.75 W el , producing 6.23 W opt of device light. During the night quiet hours: less disturbance for residents and occasional road users, a value of B / Y > 0.25, and dimming to 25% of the nominal level. The same 10 white LEDs are powered with 2.25 W el , and one additional blue (450 nm) LED is powered with 1.0 W el , producing 500 lm (2.20 W opt ) together at 3800K, and a value of B / Y = 1.68 can be chosen. To achieve the required B / Y shift, a ratio of the "installed power" of the two LED colors in the range of e.g. 1% < P Blue / P White ≤ 45% can be needed.

[0170] In one example, in a living room, in the evening people can want to study, where visual performance and comfort can require 200 lux E h , while using a 5 W LED lamp of 100 lux E eye , 2350K white light produces 1100 lm, R = 0.227 (no suppression). However, later in the evening, in the early night and desiring relaxation (after studying, before going to sleep, no suppression is desired), the light can be dimmed to 20 lux E eye (20%), and 0.23 W is added.el of 2850K with a flux of 220 lm and R value = 0.49.

[0171] In the above example, many people find 2350K less comfortable (more fatiguing) for high spatial resolution visual tasks (e.g. reading, sewing) than the higher CCT. One option is to set the illuminance for visual demanding tasks just below the threshold (e.g. E eye = 20 lux, but choose a higher CCT and / or R value (e.g. 4200K, R = 1.65). Later in the evening, a warm and cozy atmosphere can be created by changing to a lower CCT (e.g. 2400K (R can be about 0.23)), but to prevent melatonin suppression, the light level can be increased slightly (as opposed to warm dimming), e.g. to 40 lux E eye . One can use 2400K (9.5 W el , 2000 lm, R = 0.246) LEDs, dim these to 48% and add 1.9 W el (1.33 W opt ) of 450 nm blue LEDs, resulting in a flux of 1000 lm, R = 1.65 (CCT = 4200K).

[0172] In one example, in outdoor sports / area / workplace lighting, during hours of high activity (or sports training / competition), one can choose 100 lux E hor , which can be equal to about 40 lux E eye (high visual performance, no melatonin suppression needed). One can provide light of 2400K, R = 0.23. This can be created using 100 LEDs, consuming 120 W el , giving 21000 lm. During hours of lower activity, dim the lighting to save energy and reduce melatonin suppression. By dimming the white LEDs to 18 W and adding 4 W el (2.8 W opt ) of 480 nm blue LEDs, one can dim the light to 8 lux E eye , 4000 lm flux, R value = 1.0 (about 3000K).

[0173] In one example, e.g. for lighting for animal keeping / housing (e.g. dairy barns, pigs, chickens, aquaculture, zoos...), one can want to extend the light period beyond daylight with a high enough E eye (e.g. > 100 lux) to suppress melatonin. One can apply a light source of 36000 lumens, CCT of 4500K, resulting in E eye= 100 lux. During the extended light period (a few hours (typically 2 to 6 hours) before night, immediately after sunset) the light source can be set to produce a lower light level, for example 20 lux at R = 0.2, to still have melatonin suppression. During the intended dark phase, a monitoring / observation light can be needed. Typical light levels are about 5 lux (E hor ). To prevent melatonin suppression, R can be > 0.25, in particular > 0.4 (for a "farmer" equal visual performance with "whiter" light (higher R, higher CCT, higher CRI), lower light levels are sufficient. (E.g. a farmer can perceive better at 3 lux 4000K CRI 70 than at 5 lux red light). In both cases, these conditions can be applied for the first part of the light period; thereafter, the CCT can be lowered to for example below 0.2.

[0174] In one example, for example for patient room lighting (hospital environment), a regular day light can be provided, with about 200 Lux (E eye ( the patient can be lying down) ; melatonin can be suppressed, B / Y about > 0.25. For example, 3500 lm can be applied from 15 LEDs, each consuming 2W, 3000K, B / Y = 0.412. Dimming to an observation night light, where no suppression is desired, 20 lux, 350 lm of light is provided. This can be achieved by dimming the white LEDs to 2.92W el and adding 0.5w el blue LEDs, resulting in B / Y = 1.46 (5200K).

[0175] In one example, an observation night light is provided, where no suppression is desired, R > 0.25, and E eye < 30 lux. Sometimes, a higher light level can be needed to provide a more detailed view, but without melatonin suppression; then E eye may become > 30 lux; thus, R can be reduced to < 0.25. The latter can be produced using a light source of 2350K 22W el LEDs, giving a flux of 5100 lm at R = 0.64. Dimming to 30% and adding 1W el (0.7Wopt) of blue 450nm LEDs light can result in a flux of 1530 lm with R = 0.73.

[0176] In one example, for example in an office workplace or indoor workplace, a luminaire of 4000 lm can be applied. A high light level E eye>30 lux (e.g. 100 lux). For alertness, melatonin suppression is desired. I.e. for example: CCT can be 4400 K, R = 1.07; 10 W opt may be applied el When dimming to E eye = 10 lux, but still melatonin suppression is desired, R can be chosen for example 0.238. Using 6 W el LEDs of 2400 K dimmed to 33% can achieve the lowest dimming level. By increasing to 100% and increasing 12 W el of 6500 K white LEDs to reach 4000 lm at 4400 K, R = 1.07.

[0177] In one example, during a change from E eye above 30 lux to E eye below 30 lux (or vice versa), while keeping the same level of melatonin suppression (meaning R also changes on the R = 0.25 border), R can be particularly close to 0.25 to prevent undesired effects in melatonin suppression, for example around 20 lux. Thus, for any dimming curve that travels “diagonally” (see Figure 2 ), the dimming curve can be a continuous function, crossing the area given by the borders 20 < E eye < 40 lux and / or 0.2 < R < 0.3. In other words, while ideally the same level of melatonin suppression can be maintained when dimming, R ideally is close to 0.25, for example between 0.2 and 0.3, when E eye is between 20 lux and 40 lux.

[0178] The term “a number of” means two or more.

[0179] The terms “substantially” or “generally” and similar terms herein will be understood by the skilled person. The terms “substantially” or “generally” can also include embodiments with “completely”, “entirely”, “all” and the like. Thus, in embodiments, the adjective “substantially” or “generally” can also be removed. Where applicable, the term “substantially” or the term “generally” can also relate to 90% or more, for example 95% or more, in particular 99% or more, even more in particular 99.5% or more, including 100%.

[0180] The term “comprising” also includes embodiments where the term “comprising” is interpreted as “consisting of”.

[0181] The term "and / or" refers to and to both or one of the items. For example, the phrase "item 1 and / or item 2" and similar phrases can refer to one or both of item 1 and item 2. The term "comprises" can in one embodiment mean "consists of", but in another embodiment can also mean "contains at least the defined species and optionally one or more other species".

[0182] Furthermore, the terms first, second, third, etc. can be used in this specification to distinguish like elements and are not necessarily used in a sequence or chronological sense. It will be understood that the terms so used in this description are interchangeable under appropriate circumstances and that the embodiments of the application described herein are capable of operating in other sequences than described or illustrated herein.

[0183] These devices, apparatus or systems can here be described during operation. As will be clear to a person skilled in the art, the application is not limited to methods of operation, or devices, apparatus or systems in operation.

[0184] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0185] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0186] The use of the verb "comprise" and its conjugations does not exclude the presence of elements other than those stated in the claims. In the entire description and claims, the word "comprising" and its conjugations should not be interpreted as being restricted to the meaning of "consisting of", but should be interpreted as meaning "including at least the mentioned elements".

[0187] The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0188] The application can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In yet another aspect, the application (thus) provides a software product, which when run on a computer, is capable of implementing a method (embodiment(s)) as described herein.

[0189] The present application also provides a control system, which can control a device, an apparatus or a system, or which can execute the method or process described herein. Furthermore, the present application also provides a computer program product, which, when running on a computer functionally coupled to or comprised by a device, an apparatus or a system, controls one or more controllable elements of such device, apparatus or system.

[0190] The present application also applies to a device, an apparatus or a system comprising one or more characterizing features described in the description and / or shown in the attached drawings. The present application further relates to a method or process comprising one or more characterizing features described in the description and / or shown in the attached drawings.

Claims

1. A light generating system (1000) comprising: (i) a light generating device (100) configured to generate a device light (101) having a controllable radiant flux and a controllable spectral power distribution, and (ii) a control system (300) configured to control the radiant flux and the spectral power distribution of the device light (101); wherein: - a ratio B / Y of the device light (101) is defined as a ratio of a radiant flux of the device light (101) in a wavelength range of 450 nm to 500 nm to a radiant flux of the device light (101) in a wavelength range of 550 nm to 600 nm; - in a first operating mode of the light generating system (1000), the control system (300) is configured to change from a first device light setting to a second device light setting different from the first device light setting; - the first device light setting and the second device light setting are selected from: (a) a high radiant flux first setting (SI), wherein the device light (101) is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a low radiant flux second setting (S2), wherein the device light (101) is a second light having a second radiant flux I2 and a second B / Y ratio R2; - I2 < II and Rl < R2; - in a second operating mode of the light generating system (1000), the control system (300) is further configured to change from a third device light setting to a fourth device light setting different from the third device light setting; - the third device light setting and the fourth device light setting are selected from: (a) a high radiant flux third setting (S3), wherein the device light (101) is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low radiant flux fourth setting (S4), wherein the device light (101) is a fourth light having a fourth radiant flux I4 and a fourth B / Y ratio R4; and - I4 < I3 and R3 > R4.

2. The light generating system (1000) according to claim 1, wherein the light generating device (100) is capable of generating device light (101) having a maximum radiant flux I max , wherein I1≥ 0.1 I max and I2≤ 0.9 I max , and wherein I2 / I1≤ 0.

9.

3. The light generating system (1000) according to any one of the preceding claims, wherein R2 > 0.25 and wherein Rl < 0.

25.

4. The light generating system (1000) according to claim 1 or 2, wherein the light generating device (100) is configured to provide, in the low radiant flux second setting (S2), a light beam (115) of the device light (101) having a maximum luminous intensity selected from a range of 12 to 220000 candela; and wherein the device light (101) in the first device light setting and the second device light setting is white light.

5. The light generating system (1000) according to claim 1 or 2, wherein R4 < 0.41 and wherein R3 > 0.

25.

6. The light generating system (1000) according to claim 1 or 2, wherein the light generating device (100) is capable of generating a device light (101) having a maximum radiant flux I max , wherein I3≥ 0.1 I max and I4≤ 0.9 I max , and wherein I4 / I3≤ 0.9; and wherein R3≥ 0.25 and wherein R4< 0.

25.

7. The light generating system (1000) according to claim 1 or 2, wherein the light generating device (100) is configured to provide, in the low radiant flux fourth setting (S4), a light beam (115) of the device light (101) having a maximum luminous intensity selected from a range of 12 to 220000 candela.

8. The light generating system (1000) according to claim 1 or 2, wherein: - in a third operational mode of the light generating system (1000), the control system (300) is configured to change from the third device light setting to the second device light setting, which is different from the third device light setting; - the third device light setting and the first device light setting are selected from: (a) the high radiant flux setting (S3), wherein the device light (101) is a third light having the third radiant flux I3 and a third B / Y ratio R3; and (b) the low radiant flux second setting (S2), wherein the device light (101) is a second light having the second radiant flux I2 and a second B / Y ratio R2; and - I2 < I3, and 0.5 < R3 / R2 < 0.

95.

9. The light generating system (1000) according to claim 8, wherein the light generating device (100) is capable of generating a device light (101) having a maximum radiant flux I max , wherein I3≥ 0.1 I max and I2≤ 0.9 I max , and wherein I2 / I3≤ 0.

9.

10. The light generating system (1000) according to any one of the preceding claims 8-9, wherein R2 > 0.

25.

11. The light generating system (1000) according to claim 1 or 2, comprising one or more first light sources configured to generate a first white light, wherein the first light has a first x color coordinate xi, and one or more second light sources configured to generate a second white light, wherein the second light has a second x color coordinate x2, wherein xi > 0.35, wherein the color coordinates are according to CIE 1931, wherein x2 < 0.4, wherein xi - x2 > 0.03, wherein the one or more first light sources together can have a first maximum electric power Wi, wherein the one or more second light sources together can have a second maximum electric power W2, and wherein 2 < Wi / W2 < 100.

12. The light generating system (1000) according to claim 1 or 2, wherein the light generating system (1000) comprises a parking garage lighting device, a harbor lighting device, a port lighting device, a road lighting device, a street lighting device, a park lighting device, a square lighting device, an emergency lighting device, a tunnel lighting device, a regional lighting device, an office lighting device, an industrial lighting device, a residential lighting device, a hospital lighting device, a ward lighting device, a retail lighting device, a warehouse lighting device, a stable lighting device, and an animal husbandry lighting device.

13. A method for controlling a controllable radiant flux and a controllable spectral power distribution of a device light (101), wherein: - a ratio B / Y of the device light (101) is defined as a ratio of a radiant flux of the device light (101) in a wavelength range of 450 nm to 500 nm to a radiant flux of the device light (101) in a wavelength range of 550 nm to 600 nm; - the method comprises changing from a first device light setting to a second device light setting, which is different from the first device light setting; - the first and second device light settings are selected from: (a) a high radiant flux first setting (SI), wherein the device light (101) is a first light having a first radiant flux II and a first B / Y ratio Rl; and (b) a low radiant flux second setting (S2), wherein the device light (101) is a second light having a second radiant flux I2 and a second B / Y ratio R2; - I2< II, and Rl < R2; - the method further comprises: - changing from a third device light setting to a fourth device light setting different from the third device light setting; the third and fourth device light settings are selected from: (a) a high radiant flux third setting (S3), wherein the device light (101) is a third light having a third radiant flux I3 and a third B / Y ratio R3; and (b) a low radiant flux fourth setting (S4), wherein the device light (101) is a fourth light having a fourth radiant flux I3 and a fourth B / Y ratio R3; and I4< I3, and R3 > R4.

14. The method according to claim 13, the method further comprising: - changing from the third device light setting to a second device light setting different from the third device light setting; the third and first device light settings are selected from: (a) a high radiant flux setting (S3), wherein the device light (101) is a third light having the third radiant flux I3 and the third B / Y ratio R3; and (b) the low radiant flux second setting (S2), wherein the device light (101) is a second light having the second radiant flux I2 and the second B / Y ratio R2; and I2< I3, and 0.5 < R2 / R3 < 0.

95.

15. A light generating device selected from the group of a lamp (1), a luminaire (2), a projector device (3), a disinfection device, and an optical wireless communication device, the light generating device (1200) comprising a light generating system (1000) according to claim 1 or 2.

Images