WO2016135373A1

WO2016135373A1 - System and method for monitoring and improving healthy living environment

Info

Publication number: WO2016135373A1
Application number: PCT/FI2016/000003
Authority: WO
Inventors: Antti Aunio
Original assignee: Antti Aunio
Priority date: 2015-02-23
Filing date: 2016-02-22
Publication date: 2016-09-01

Abstract

A system for monitoring flickering of light having adverse health effect. The system comprises a control unit (204) configured to receive a light measurement output from a light detector (202). The control unit (204) is further configured to determine flickering of detected light, and to determine whether a level of the flickering of the detected light exceeds a threshold.

Description

System and method for monitoring and improving healthy living environment

1.1 Inventors

Antti Aunio, Oulu (Fl)

Address: Jarvantie 5, 90410 Oulu, Finland

1.2 Technical field

The present invention relates to a system and a method for monitoring and improving healthy living environment.

1.3 Background of the invention

Almost all people in the world are affected by artificial light. Many people spend most of their time under artificial lighting. Many light sources may produce flickering light, for example fluorescent tubes and lamps, LEDs, and tungsten and halogen lamps.

Flicker may be caused by a broken lamp or a broken power supply circuit or control unit, for example. In many cases flickering begins when a lamp or other related electronics ages.

Depending on the frequency of the flickering light, a human being can either see the flicker or not. Some people can see higher frequencies than others. Most people can notice flickering below 50 Hz frequency. Some people cannot see 50 Hz flickering light. Also, some people can even see 100 Hz flickering light and find it unpleasant. Flickering fusion frequency describes the highest flickering frequency which one can observe.

Perceptible flickering light is usually inconvenient for most people and its severity depends on the frequency and intensity of the flicker. Still, even when a person is exposed to frequencies higher than the flicker fusion frequency, the flicker can be measured with electroencephalography (EEG) measurements of his or her brain. The brain and nervous system are affected when a certain level of flickering light is present.

For most people, flickering light decreases their reading performance. Flickering light may cause fatigue and decreased cognitive performance. Some studies have indicated that using fluorescent light with magnetic ballast, which combination typically flickers, reduced people's cognitive performance. Flickering light also raises the stress level of people and some animals, like birds, etc. Flickering light causes migraine seizures for approximately 38% of migraine patients. Some people suffering from epilepsy get epileptic seizures from flickering light.

Flickering light is unpleasant for most people, but it depends on the flicker frequency. If the flicker frequency is high enough, people cannot detect it. Therefore, one attempt to avoid the harms of flicker consists of increasing the flicker frequency as high as possible. For example, to eliminate the harms of (low-frequency) flicker, fluorescent lamps contain a high-frequency electrical ballast circuit that uses a ten-kHz or higher frequency to drive the lamps.

One of our important findings— contrary to common belief— is that frequencies higher than the fusion flicker frequency cannot only be seen in EEG measurements, but they may also cause symptoms similar to those caused by lower-frequency (perceptual) flicker.

Another important finding is that impacts to heath, like nausea or migraine seizures, may not appear until several hours after exposure to flickering light.

As a consequence of these findings we have noticed that because, firstly, one cannot necessarily see when there is harmful flickering light present if the flickering occurs at frequencies higher than one's flicker fusion frequency, and secondly, the health consequences may occur after hours of exposure, so this ends up being a significant problem for persons who are sensitive to flickering light. As far as we know, this problem has not been understood in the way we have found.

Because this problem has not been understood in this way, there have been no commercial devices on the market which could help especially to solve this problem.

We have also found that seasonal affected disorder (SAD) symptoms are not only the result of a lack of a daily dose of bright light, but many times the reason for SAD is the bad quality of artificial lights, which flicker, and people are exposed to this during the dark season. A person who is sensitive to flickering light may get symptoms similar to those in SAD. This has not been understood in this way and there has not been proper help for such persons.

An example of the currently offered treatment for people suffering from SAD is to use bright light lamps, the goal being to get a daily dose of light when there is not enough natural sunlight available. However, all people do not benefit from such bright light lamp treatment. Our understanding is that the reason is unperceived flicker from lamps used in bright light fixtures. It is not understood that the reason for SAD-like symptoms in some people is that they get symptoms exclusively or partly because of flickering artificial lights.

There are no commercially available devices that tell if a person is being exposed to harmful flickering of light. At the present, a person suffering from flickering light needs to visually see the flicker to know whether there are flickering lamps in the room. This is extremely difficult because only flicker that is intense enough and happening at lower frequencies can be seen by the human eye. In addition, if a person knows there is flickering light in the room, he typically cannot do much other than avoid being in that room.

US 20100037373 Al describes a method and an apparatus for detecting and controlling perceptible flicker. The method determines whether a light source flickers and whether said flicker exceeds a corresponding flicker fusion threshold value. However, the patent teaches how to detect and hide perceptible flicker, but does not teach about imperceptible flicker.

There are no commercially available devices which measure and analyze whether a space or a room has illumination or a lamp arrangement that can cause flicker when an observer is in said space or room and moves his head or eyes.

There are no commercially available devices that tell if a person is being exposed to harmful flickering of light. Especially in workplaces and school classrooms where people need to spend a lot of time during the day, there may be a lack of good-quality lighting that is flicker-free, has good spectral content, and produces sufficiently bright illumination for reading tasks, for example. There are no devices that can be installed in a room containing flickering illumination to function in a way that can help people who suffer from the harmful effects of flickering light.

Recently the problem of flicker has been solved by raising the driving frequency of a fluorescent lamp so high that it cannot be observed by a human. High-frequency electronic ballast is quite commonly used in a fluorescent lamp power source. Also, in many cases a DC voltage and current power supply is used to make a stable power source for lamps, where such a power supply can be used, like with LEDs, 12 V halogens, etc. In some cases a high-frequency PWM (Pulse Width Modulation) signal is used for a lamp power source.

These solutions do not take into account the fact that when electronics ages, these lamps could start to flicker. Also, these solutions mean that all power sources and lamps need to be replaced with new ones.

Many times in practice if a lamp starts flickering, time may elapse before the flickering lamp is replaced and so the flickering light is suffered even weeks.

Most of the currently used lamps cannot prevent flicker caused by the 50 Hz or 60 Hz AC input voltage or the corresponding 100 Hz and 120 Hz frequencies present at the light output. Even fluorescent lamps with electrical ballast have this problem. Many people do not perceive that a light is flickering at that high a frequency, but flicker nonetheless decreases cognitive performance.

There is a need for an inexpensive, easy to use, common solution for monitoring lamp flicker and eliminating it as soon as it occurs.

At the present, room illumination is adjusted by means of separate adjusting devices. Some applications employ a mobile application and some type of synchronization with said mobile application. To date there is no wireless application by which it is easy to identify, synchronize, and control a lamp in a room by means of, for example, a mobile device. For example, if lamps are added to a room or if an existing lamp is broken or replaced, there is no easy way by which a lighting fixture or an individual lamp or lighting fixture containing an integrated wireless communication link can be easily controlled via a user interface on a mobile phone, tablet PC, or laptop computer. The present invention seeks to overcome at least some of the above mentioned difficulties.

1.4 Summary

In accordance with one embodiment of the invention is a system for monitoring flickering of light having adverse health effect, the system comprising a control unit configured to receive a light measurement output from a light detector, to determine flickering of detected light, and to determine whether a level of the flickering of the detected light exceeds a threshold.

In accordance with another embodiment of the invention is a method for monitoring flickering of light having a physiological effect, the method comprising determining, by a device, a threshold for flickering of light; obtaining light measurement output from a light detector; and determining whether a level of the flickering of the detected light exceeds said threshold.

In accordance with another embodiment of the invention is a portable electronic device, comprising a wireless communication interface; and an electronics unit, wherein the portable electronic device is configured to determine a threshold for flickering of light, obtain light measurement output from a light detector, and determine whether a level of the flickering of the detected light exceeds said threshold.

In accordance with another embodiment of the invention is a portable device, comprising a wireless communication interface; and a user interface, wherein the portable device is configured to detect a user input, and, as a response to the user input, wirelessly transmit a control signal to a portable electronic device causing the portable electronic device to perform a flickering light measurement.

1.5 Brief description of the drawings

Aspects of these teachings are made more evident in the following detailed description when read in conjunction with the attached drawing figures, wherein:

FIG. 1 is a diagram illustrating flickering light in relation to continuous stable light intensity.

FIG. 2 is a flow chart of an embodiment of the invention.

FIG. 3 is a diagram illustrating flickering light intensity under continuous stable light.

FIG. 4 is a diagram illustrating a situation where flickering light intensity is dominating.

FIG. 5 illustrates a handheld measurement device.

FIG. 6 illustrates a handheld measurement device.

FIG. 7 is a flicker measurement camera.

FIG. 8 is a flow chart of an embodiment of the invention.

FIG. 9 is a diagram illustrating flickering light intensity compared with a stable DC light source. FIG. 10A is a diagram illustrating periodic flickering light intensity compared with a stable DC light source.

FIG. 10B is a diagram illustrating flickering light which is compensated by increasing the DC portion of light.

FIG. 11 is a diagram illustrating one arrangement of the invention to compensate flickering light in a room.

FIG. 12 is a diagram illustrating one arrangement of the invention to compensate flickering light in a room.

FIG. 13 is a flow chart of the invented device where flicker is measured from the light produced by a lamp.

FIG. 14 is a flow chart of the invention where a flickering signal is measured from power lines driving a lamp.

FIG. 15 is a fluorescent bulb connection with flicker detection. Said flicker detection is connected to an electrical ballast circuit.

FIG. 16 shows flicker detection connected to a switch circuit.

FIG. 17 shows flicker detection connected to a fluorescent bulb.

FIG. 18 shows side view of the flicker detection connected to a fluorescent bulb.

FIG. 19 shows flicker detection where a control interface is connected to a ballast circuit.

FIG. 20 is a fluorescent bulb driver connected to magnetic ballast, where flicker detection is integrated into a starter switch.

FIG. 21 shows flicker detection and a starter circuit controlling a main AC supply switch circuit.

FIG. 22 shows a mobile measurement device with a stick

1.6 Detailed description

1.6.1 Objectives and advantages

An objective of the invention is to provide systems and methods for monitoring and improving healthy living environment. A particular objective of the invention is to provide methods and devices by which to avoid and/or eliminate negative health effects from flickering lights.

Some advantages of the invention are:

- A person can receive information and a warning if lights are flickering and if the flickering is harmful even when he cannot perceive if lights are flickering or not.

- Less migraine and epileptic seizures. - A person who gets SAD-type symptoms from flickering light can require and start using better lights.

- One can check that a lamp is working properly and not have harmful flickering light.

- A better lamp can be produced which contains self -diagnosis.

- Young people are more sensitive to flickering lights; when flickering light is eliminated their nervous system won't become exhausted. This will have major specif ic consequences in learning new things at schools, etc.

- Animals will feel better when they do not have to suffer from harmful flicker.

- A possibility to eliminate the harmful health effects of flickering light even when a flickering lamp cannot be removed or shut down, as in a case of flickering ambient light,

- A possibility to integrate a flickering compensating device into a wearable device,

- Automatic or semiautomatic operation.

- The solution is inexpensive.

- Easy to use

- Increased understanding of light environment and its effect to ones well-being.

An embodiment of the invention provides a wearable or handheld device that gives a warning when there is overly strong flicker present. Said device will give an early warning to migraine and epileptic patients before they have been in a situation where there is flickering light too long. The device can help people see when there is an environment where there is flickering light which may affect their well-being. Said device helps people avoid a lighting environment that is not good for them.

1.6.2 Generalized embodiments

An embodiment of the invention provides a method which can be used to recognize an environment where there is a risk of getting flickering light when people are moving, like in a sport hall, etc. The device can measure the uniformity of room lighting and the effect generated when a person rotates his eyes or head, or when he is in movement, such as running, etc. If the room has large variations in uniformity, for example when there is an array of lamps on the ceiling, the high contrast of differences can cause a flicker effect when a person is moving or rotating his head or eyes. So, even when steady flicker-free lighting is used, such as led lights with a stable DC supply, one can be exposed to harmful flicker. Also, high-frequency electric ballast in florescent bulbs does not help eliminate flicker when flicker is caused by moment in a room with several light sources. The method can be used for lighting simulation models, when simulating the lighting of a room or environment. One parameter is an observer's movement in the room.

1.6.2.1 Flickering compensating illumination

Some embodiments of the invention provide a light source which is capable of compensating the flickering of ambient light. An embodiment of the invention provides a mobile phone application which measures light quality at a certain point and controls a high-quality illumination source so that harmful flicker is eliminated by increasing DC light intensity.

An embodiment of the invention provides a lighting fixture which has an integrated light detector that measures light reflected from an object, for example a table surface or pages of a book, and adjusts said light fixture's DC light intensity to a level where harmful flicker is eliminated and a level of illumination necessary for reading, for example, is achieved.

1.6.2.2 Flickering prevention device

Some embodiments of the invention provide device which prevents harm to people when a lamp starts flickering for any reason. The device may have the following functionalities:

- the lamp can be shut down immediately when flickering occurs

- the lamp shuts down if it flickers above the fusion frequency

- the lamp indicates when it need to be replaced because of flickering

- the lamp monitors lamp flicker to ensure that it remains below a guaranteed level

1.6.2.3 Device and method for illumination control

Some embodiments of the invention provide a light control system which can be used to control lighting fixtures or lamp(s) independently or separately in a room or space.

Some embodiments of the invention provide a mobile phone application which makes mobile phone control interface synchronization easy for the user. The application may have the following functionalities:

- The possibility to provide easy control interface synchronization by means of a mobile phone application for a lighting fixture(s).

- The possibility to control ambient lighting in a room where the user is.

- Automatic or semiautomatic operation.

- The possibility to provide an easy control interface synchronization procedure which can be used with any other wireless device control to gain control of a mobile device, laptop, or tablet personal computer.

1.6.2.4 Mobile frequency measurement device and method

An embodiment of the invention uses a mobile phone for detection and measuring of flickering light. In particular, the system may be able to detect and measure flickering which has adverse health effects. The solution according to the invention turns almost any mobile device with a camera into such a measurement device. Such mobile devices are for example mobile phones, tablets, some digital cameras etc. When measuring flicker for specific targets, such as lamps, it is sometimes advantageous to perform measurement close to the target. Closer distance may improve the accuracy of the measurement because when measuring the target from closer distance, the light from other light sources causes less disturbance to the measurement. The light intensity may also be higher when measuring from closer distances to the target. However, typically the lamps are on ceiling, which is difficult to reach by a mobile device. An embodiment of the invention provides means for measuring the target from closer distance as described later in more detail.

1.6.2.5 Measuring flicker in order to avoid it

Some embodiments of the invention provide a device which measures light and recognizes harmful flicker. This information is used to control lamps and devices which prevents people and animals from being exposed to harmful flicker.

Usually, in research on observable flicker, the effect of the duty cycle is studied and held as an important factor determining how well flicker can be perceived, which then correlates with how much flicker affects people. However, we have noticed that the duty cycle and AC intensity are not as important factors as the ratio of flickering AC light intensity to DC light intensity regarding effects to human health.

Figure 1 shows measured light intensity as a function of time. Said light intensity varies over time, so there is some flicker in the light. Total light intensity can be divided into a DC portion 104 which is constant over time and an AC portion 102 which contains the varying portion of the light signal. The AC/DC ratio is the peak-to-peak AC intensity divided by the constant DC intensity.

We have found that if the AC/DC ratio is large, for example greater than 30%, flicker more probably causes adverse effects to humans and animals than when the AC/DC ratio is small, for example less than 5%. The threshold value of the ratio depends on the flicker frequency, absolute light intensity, the light's spectral content, and also the patient's sensitivity.

Some embodiments of the invention provide methods of flicker measurements (AC/DC vs. frequency) for the purpose of avoiding exposure, optionally comparing those measurements with measurement of personal (AC/DC vs. frequency) sensitivity.

Some embodiments of the invention provide flicker measurement device and method, which may, for example warn if harmful flicker is detected and/or log exposure to flicker and store that data into a database.

Some embodiments of the invention provide flicker prevention device, which may shut down a lamp which is detected to be a source of flicker

1.6.2.6 Adding DC to minimize health affects

Some embodiments of the invention provide method for decreasing or eliminating the harmful effects of flickering lights by adding good quality DC light. This helps when a person needs to be in an environment where he may be exposed to harmful light flicker. Adding DC light may decrease the AC/DC ratio to a level which can be better tolerated.

An embodiment of the invention provides method for flickering compensation by measuring flicker (AC/DC vs. frequency) and adding DC by means of an additional light in order to make the AC/DC ratio smaller at certain frequencies. This flickering compensation method can be integrated for example in lamps, spot lamps, cabin lights, car interior lights, or wearable devices such as eyeglasses or helmets.

1.6.3 Flicker measurement device and method

Figure 2 shows a block diagram of an embodiment of the invention. Figure 2 shows light source 210, light detector 202, signal processing 204, user interface 206, and necessary power management 208. Light detector 202 indicates irradiance and flicker frequency. Light detector 202 can be a camera, a line or matrix diode array, a single light diode, or a combination of these. User interface 206 can be in the same device, but it can also be separate, like a mobile phones, a PC, etc., and a communication interface can be wired or wireless, like Bluetooth. The device includes the necessary electronics for light detection and for restricting a detected flicker frequency by suitable filtering.

Figure 1 shows a photodetector signal when periodic flicker 102 is weak with respect to average DC light 104 intensity. The AC/DC ratio is clearly less than one. Flicker can still be measured and it may be harmful to some degree. In particular, the adverse effect of the flicker is larger when the observer can see the object or the light source which is flickering, even when the flickering is only a small portion of the total illumination in the room. In that case, an advantageous embodiment of the invention is arranged so that said photodetector can be aimed in a certain direction to detect broken lamps, for example. The same can be achieved by using a camera sensor that can recognize flickering objects and show them, for example, on an LCD (Liquid Crystal Display).

Figure 3 shows a photodetector signal where flicker 302 is more intense than in Figure 1. The AC/DC ratio is close to one. The harmfulness of the flicker increases when the DC portion 304 of the illumination decreases with respect to the AC portion. In some spaces, all flickering lamps are in the same phase, and there is no DC portion even available.

Figure 4 shows a photodetector signal where a flickering signal 402 is dominating. DC light 404 is at some level, but in the worst case there is only a very low portion of DC light or none at all.

In the aforementioned figures, flickering light was shown to have a sinusoidal waveform. In practice, the flicker waveform can be a square wave or any form which includes a periodic component. The period (306, 406) of a flickering signal may also change and said signal may be a burst-type signal. This may occur when a person is moving in a room where there is a set of lighting figures; the speed of movement produces different flicker frequencies for the observer.

The spectral response of the measurement device can be in the visible range, 400-700 nm, or it can be broader, for example from 200 nm to 16000 nm. The device can include a microcontroller which controls the measurement electronics and may further process the results for the user in a desired format. For example, an audio signal or a visual user interface can express harmful flicker to the user.

The microcontroller can include an analog-to-digital converter to convert a light detector's analog signal to a digital signal. The microcontroller can be programmed so that stable DC light, flicker intensity, and frequency can be calculated. In the simplest case one light detector is needed. In some case the wavelength of the flickering light needs to be measured. For example, a camera cell can be used to roughly measure the spectrum of the light.

The microcontroller can process an image from a camera sensor and express the flickering portions of the image, for example, by using different colors, tables, or dots. When said camera sensor is used for continuous measurements and a live-measurement image is shown to a user, the microcontroller can remove the flickering portions of a video stream and express them, for example, by said means. For example, different colors can represent the harmfulness of the detected flicker.

The device includes electronics which are used to measure light intensity and the frequency characteristics of the detected light signal, especially flickering light in comparison with DC light. A very- high-frequency flickering light signal is also like DC to the human nervous systems and it can be handled like DC light. For example, a 45 kHz signal used in high frequency electrical ballast for fluorescent lamps is like DC to the human nervous systems.

The device is used to tell the portion of adverse flicker in total illumination. The device can show when a person is in surroundings where there are flickering lights which the eye cannot see. The device tells if illumination contains flicker that burdens the nervous system.

The device can measure the flicker frequency and flicker intensity at a certain frequency with respect to average ("DC") intensity.

In some cases the device measures flicker frequencies from for example below 1 Hz up to 130 Hz. In some cases the device measures flicker frequencies from below 1 Hz up to 1000 Hz, for example. Even higher frequencies, can be measured if the lamp or illuminated object is moving so that flicker becomes visible or harmful. Typically, the device measures frequencies that are higher than a person's flicker fusion frequency, too.

The device can take a user's movement into account as well as the effect of the movement on flicker. The device can analyze uniformity variations in a room and give a warning when lighting conditions are such that movement or head/eye rotation can cause a harmful flicker effect.

The device can measure other illumination properties at the same time, such as spectrum, illumination uniformity, etc. , The device can be configured to detect flicker at only certain wavelengths of light. For example, the device can measure flickering of only from blue light between 430 nm and 500 nm, or for example of light between 380 nm and 565 nm. The intensity and frequency of flicker can be compared with the DC level or averaged light intensity between, for example, 380 nm and 780 nm.

The device can also be used to measure a spectrum that is not visible to humans, like the infrared spectrum. In some cases long-wave infrared flicker can be harmful for some persons. Sources of this kind of flicker include, for example, electric heating devices, underfloor or ceiling heating resistors, or incandescent light bulbs. In such cases the device can be configured so that the infrared spectrum can be measured and flicker can be detected. The measured spectrum can be, for example, 700 nm to 16000 nm, or even longer wavelengths can be taken into account.

Flickering light causes the stress levels of the nervous system to rise if the person is exposed to flicker to a large extent during the day. The device can collect the user's exposure to flickering light during the day, and can, for example, give warning signals so that the user can avoid excess exposure to flicker.

The device can be implemented in a portable or wearable form. For example, the measurement device can be mounted onto, or integrated with, a watch or eyeglasses. Small implementations of the device can be integrated into a ring, a necklace, a hairpin, a button, etc.

The device can be used if it is suspected that flickering of ambient light may be the cause of fatigue or even migraine attacks. The flicker frequency of said light can be low enough to be perceptible or higher than that. Both perceptible and imperceptible flicker can cause an extra burden to the nervous system, weaken performance in doing tasks requiring accurate vision, cause fatigue, irritation, and/or nausea, reduce the amount of serotonin, just to mention a few.

Flicker can occur at several frequencies simultaneously, too, for example at 50 Hz and 100 Hz simultaneously.

An embodiment of the invention is a handheld device, shown in Figure 5 and in Figure 6, and comprising a detector 514 and a sight or a viewfinder for aiming the detector at an object 510 (here a lamp) whose flicker is to be measured, and a means, for example an LCD (506, 604), to express a measurement result to a user. The field-of-view of said detector can be arranged to be small enough, for example by using lenses and apertures. When the device is pointed at a diffuse screen, such as a paper, the device measures the characteristics of illumination the sum of ambient light and all other light sources which are illuminating said screen. When the device is pointed at a fluorescent lamp, for example, the device tells the characteristics of the illumination from said lamp. The device can have an integrated laser pointer 516 as a sight device, too.

The device can be an accessory to a cellular phone, such that the device itself does not contain a user interface, for example an LCD. The device contains a detector and possibly a means to aim a detecting beam, but data processing and a user interface are implemented by a phone or tablet application. A control interface can wired or wireless.

Said accessory device can use the camera of a cellular phone to store an image of the area under measurement together with measurement results. A laser pointer can show the measurement point, the result of the measurement point is shown on a display and a figure can be taken so that said laser point and result can be stored on said figure.

In an embodiment of the invention, an ALS meter, which can be found in many cellular phones, is used to measure flicker. An ALS meter typically measures ambient light according to the spectral sensitivity of the human eye. An application can be running on a cellular phone, which guides the phone to process data and present the results to the user.

Figure 7 shows an embodiment of the invention, where a cellular phone with a camera and a phone application is used to capture a still image or video of a target whose flicker characteristics need to be known. Flicker occurring within a certain frequency range can be detected from said captured image or video. Typically, a cellular phone has a CMOS sensor which reads images row by row. Especially flickering occurring at 100 Hz and 120 Hz frequencies can be seen if the flicker is intense at those frequencies. Image or video analysis can be done in a cellular phone and the results expressed to the user by using said phone's user interface. The results can be easily shared or stored to a cloud by using an internet connection. An advantage when capturing an image or video is that a multitude of points and objects are measured at the same time.

Figure 7 depicts the use of a mobile phone or camera for measuring light flickering in a certain room. 704 is a camera or mobile phone device. 710 is a display which can be a regular LCD but can also have a touch-sensitive interface. 702 is a light source in the room. On said display there can be seen a flickering light source 706 with a certain color darkness which indicates the flicker level. 708 is a color scale. Said color scale tells how large a portion of the light is flickering. The darkest color can indicate 100% flickering compared with the DC part of the light. Some part of the room can be shown with a lower flicker level if there is another light source(s) with a higher DC portion of light. Said color scale is only one possible means to indicate flicker in the image, and naturally other kinds of indications can be used too, such as dots, lines, numbers, etc.

The device can measure and indicate flicker not only directly from a light source, but also from reflected light. Some surfaces can reflect light from several light sources, and so the flicker characteristics of such surfaces can be very different in comparison with light sources alone. The flicker characteristics of various surfaces, especially the AC/DC ratio, can depend significantly, for example, on the scattering and reflecting properties of the surface.

An embodiment of the invention comprises a camera, image processing electronics, and user interface devices. Said camera can be configured to detect flicker frequencies over a wider frequency range and without such restrictions which are typical of cellular phone cameras. A sensor and electronics can be chosen such that very high frequencies can be measured, too. The spectral measurement range can be very wide or selective, or even tunable by adding a spectrograph to the device.

The device may measure spectral power distribution. The device may give a warning if blue light intensity is too high compared with the optimal spectral power distribution of the human eye. The device may be used as an aid for adjusting the spectral power at certain wavelengths of illumination. For example, elderly people may need more light intensity than a younger person for reading a book, etc. Also, blue light can be adjusted to a higher level because of the weakened blue light optical properties of an elder person's eyes. In the evening the device can give a warning if there is too much blue light in lighting, which will cause melatonin suppression and thereby may affect sleeping.

A wide-field lens may be attached to a device with a camera sensor, enabling measurement of a full hemisphere or even a larger field-of-view at a time. This way it is possible to analyze sources of flicker in an entire room by means of just one or two shots.

Even a constant DC light source can cause harmful flicker if the light is modulated by some means such as a moving object. For example, sunlight can be reflected from waves on the surface of water.

Said modulation can be caused by a person's own movement, head or eye movement, in particular. For example, when a person is travelling by a car or some other vehicle, sunlight may be modulated by trees on the roadside, which modulation causes harmful flicker for said person. Especially in the springtime, sunlight reflected from snow can cause adverse flicker for a person who is walking outside.

In vehicles, the device may be integrated in or mounted on a car window, car windshield, dashboard, motorcycle helmet, etc.

The device may control transmission through eyeglasses, through a helmet visor, through windows of cars, vehicles, or buildings, so that adverse flicker can be filtered or suppressed. Flicker whose frequency is higher than the flicker fusion frequency may also be filtered.

The device may control illumination so that the DC portion of light is increased in order to suppress the flickering portion of light and so to reduce harmful health consequences. In particularly, this method can be used in spot illumination, for example at work sites where work requiring high accuracy or reading is done.

LEDs (or other lights) can be integrated into or attached to the sides of eyeglasses so that flickering light entering the eyes can be suppressed by adding DC light directly or indirectly to the eyes.

The device may control interior light in order to suppress flicker coming from the outside through windows or openings. For example, the device can guide a car interior to be illuminated strongly if the light of the sun creates flickering shadows from trees. The device may log illumination data so that it can be analyzed later, too. Said logged data can contain, for example, one or more of the following data: light intensity and spectrum, flicker frequencies, flicker intensity, DC intensity, flicker waveforms, and time and location information.

The device may measure or in some other way obtain (for example through the internet) and store season and weather information such as temperature, wind velocity, and cloudiness, too. The season and weather conditions may worsen the effects of lighting to well-being.

The device may measure and log some physiological parameters from the user, such as pulse, EEG, and body temperature, for example.

The device may measure and store acceleration data, too. Acceleration data can be used to detect if the user is moving and if the movement causes flicker.

The device may measure speed and movement, like rotating, and take these parameters into account when calculating flicker. An accelerometer can also be used for power management. If the device is not moving, the device can go into a standby mode.

Measured and logged data may be combined with a patient's health information, such as migraine or epilepsy seizures, and the general condition and at each time point. This provides new opportunities for doctors to diagnose and treat patients.

Patients should be able to anticipate and avoid problems. Time and location information can be used to identify places and situations in which the user is exposed to flickering light. Acceleration information can be used to analyze whether illumination would be suitable, for example, for playing football so that said illumination would not cause flicker due to a person's movement.

Measured and logged information may be stored in databases. Said data can be shared through the internet with other interested parties, and the shared data can be available through a cloud service. Shared data from many users brings synergy effects to an individual user.

Collected data may be used to produce material which tells light characteristics as a function of time and location. A device knowing location data can be in connection with a cloud service which tells, for example, whether some public environments, shops, or terrain areas have adverse flicker.

Advertising may be used with device measurement. For example, when measuring some room lighting the device interface can be used to advertise some specific lighting fixtures or to give an internet link to a company's internet page. Said interface can ask some question related to the use of the space where the measurement is done. Is the room or space for reading, studying, school/sports, etc.? Device SW might ask the user to perform an extra measurement task, like moving in the space, how to hold the measurement device, etc. The device can be used for on-line service or advertising. For example, in a case of mobile camera use, advertising, sales, or technical personnel can give advice on how to improve lighting. Lighting can be simulated on-line in figures and shared with the user. Since some migraine patients also suffer from low-frequency sound signals, the flicker detector can be integrated with audio metering so that adverse audio signals can be detected. For example, 50 Hz buzzing from transformers can be detected.

In an embodiment of the invention the flickering of light is converted to an audio signal which can be heard by the user. For example 50 Hz flicker may be converted to 50 Hz audio signal, and 100 Hz flicker may be converted to 100 Hz audio signal. In some embodiments of the invention, the flickering is converted to audio signal by using a constant, which for example is a value between 1 and 10. The audio frequency corresponding to a certain flickering frequency is obtained by multiplicating the flickering frequency by the constant. The amplitude of the corresponding audio frequency can tell the harmfulness of the corresponding flickering frequency. For example the lower frequencies are more amplified than higher frequencies. In one embodiment of the invention, the system uses audio microphone connection to deliver the audio signal to the user.

In an embodiment of the invention, the system is integrated in hearing aid device or in earplug.

As described above, the flickering of lights cause adverse health effects to people and animals. The harmfulness may depend on the flickering frequency, the wavelength spectrum of the flickering light, and the AD/DC -ratio. Measured flickering is compared to a predefined threshold value, which may depend on these parameters for example. If flickering exceeds the threshold value, the flickering is harmful. There may be several different thresholds defined. For example one threshold value may tell if flickering may cause epileptic seizures in persons with such a tendency, and another threshold may tell if flickering is decreasing cognitive performance. People with different health conditions, and individuals generally, differ in respect to how they tolerate flickering light. Threshold may be defined individually, or be group specific, for example. The threshold may be defined as maximum AC/DC-ratio as a function of flicker frequency and wavelength of the light.

1.6.4 Flickering compensation

Figure 8 shows an embodiment of the invention where control unit 804 receives a light measurement output from light detector 802. Control unit 804 determines whether there is flicker and whether the level of flickering light is too high. Control unit 804 controls flicker-free light source 806 to increase light intensity 808 to a level where flickering light 810 is reduced to a suitable level. Control unit 804 can also be used to control light intensity to make it optimal for reading, for example.

Light detector 802 can be, for example, a light-detecting diode or a camera sensor, or it can be a spectrometer or a combination of different light detectors and filters.

Figure 9 shows the intensity of flickering light 902 and DC light 904 measured as a function of time. Flickering light can be seen as intensity peaks above the DC light level. Flickering light can be periodic, such as sinusoidal, partly periodic, or non-periodic, and its amplitude can vary. In Figure 9 the horizontal axis is time and the vertical axis is light intensity. Figures 10A and 10B show the light intensity of sinusoidal flickering light 1002 with stable DC light 1004 as a function of time. DC light can be characterized by its amplitude. Flicker can be characterized by its amplitude 1008 and wavelength 1006.

In Figure 10A the amplitude 1008 of flickering light 1002 is large in comparison with the amplitude of DC light 1004. This is an example of flicker that causes adverse health effects.

Figure 10B shows curves 1002 and 1004 with the same intensity as shown in figure 10A but on a different scale. Now DC light is added to the same space in which a detector is detecting. The intensity of said added DC light is substantially larger than the amplitude of AC light 1008. Curves 1010 and 1012 show the measured DC and AC intensities of total light after addition of said DC light. As can be seen, the portion of AC light intensity is substantially reduced with respect to total light intensity. The AC/DC ratio is substantially decreased by adding said DC light. The resulting illumination 1010, 1012 is an example of flickering light whose adverse effects to humans or animals are reduced or eliminated.

In addition to reducing the AD/DC ratio to eliminate flicker, adding DC light is many times more beneficial because of increased illumination, for example, in working areas.

Figure 11 shows an embodiment of the invention where light measurement device 1106 is on table 1112 and measures flicker caused by room lighting 1102 and controls the intensity 1110 of flicker-free spotlight 1100 so that flickering light 1104 is eliminated from the surface of table 1112. Said measurement device can be a mobile phone or a separate device or a combination of both. Said measurement device can include a user interface for monitoring and setting the level of light intensity.

A good light intensity level for reading is different for different people. A user can save an optimal intensity level value in a memory of said measurement device so that said stored value can then be used to set the right intensity level for said user in different locations.

Figure 12 shows an embodiment of the invention where a measuring and control unit is integrated into lamp 1200. A light detector in said control unit measures reflected light 1204 and 1202 from a table surface and controls flicker-free light 1210 from said lamp so that the flicker effect can be minimized at said table surface. Light 1204 is light reflected from room lighting 1202, light 1202 is light reflected from flicker-free light source 1200.

The device and method based on the invention are used to measure the flickering of ambient light and to eliminate adverse flicker by adding flicker-free light. Said flicker detector can be on a table, such as in Figure 11, where there is a paper which a user is reading, etc. Said detector can be also placed so that it measures light reflected from an object under lighting, such as in Figure 12.

For example, when a user is reading a book, said user can adjust illumination by placing said measurement device on a page of the book. Said device measures illumination and flicker and adjusts illumination from one or more lamps. Said measurement may be done by using a cellular phone with a suitable software application, which phone then communicates with said lamps. Said detector may also be a separate small device, such as a bookmark clip, which could be placed on the book so that it constantly monitors illumination.

The invention may be implemented so that a user uses a mobile phone camera or light detectors to detect lighting conditions in a certain space or on certain objects. The measured information can be used to actively change said lighting conditions in said space or object.

A communication interface between the separate measurement device and light fixture(s) may be wireless or may use wires, for example, when control and light/illumination units are integrated.

The light detector can be used to optimize lighting conditioning automatically or semi automatically for a certain user to achieve the best lighting conditions for doing a task such as reading a book.

The device may be part of a PC laptop's software so that said device can use the PC's camera to measure light quality, to give advice or a warning, and possibly to also control the light fixture(s).

The device may also be a separate device which is connected to a PC or any other device by using, for example, a USB interface as a power source and a control interface. Said separate device can be a measurement unit. It can also include a light source so that the USB port is used only as a power source.

The system may be integrated into a light fixture so that it measures the flickering of a lighted object, such as a table surface. The measurement result can be used to control flicker-free lamp light intensity so that flickering light on the table surface is eliminated.

Light spectrum measurement can also be included in the device and method. A lamp may have an adjustment related to its spectral content, which can be set by using the device when needed. The device can give a warning if blue light intensity is at too high a level compared with the rest of the spectrum. The blue light portion of the spectrum of a lighting fixture can be turned to a minimum or off during the night so that it does not cause melatonin suppression.

Flicker measurement can be limited to a certain portion of the light spectrum, or the device can measure flicker at different wavelengths of light separately. For example, flicker at only blue and/or green light wavelengths may be measured. Compensating DC light can be, for example, blue light or some other wavelength where flicker occurs.

The device may control illumination so that the DC portion of light is increased in order to suppress the flickering portion of light and so to reduce harmful health consequences. In particular, this method can be used in spot illumination, for example at work sites. In addition to removing the adverse effects of flicker, increasing DC light improves working conditions for reading or for work requiring accuracy. LEDs (or other light sources) may be integrated into or attached to the sides of eyeglasses so that flickering light entering the eyes can be suppressed by adding DC light directly or non-directly to the eyes. A light detector with a control unit can be integrated into said eyeglasses with compensation LEDs.

The device may be integrated into a wearable headlamp so that the headlamp's light intensity can be increased to eliminate flickering light. Flickering light measurement and headlight control can both be integrated into said headlamp. In some cases light measurement can be done in a separate device like a mobile phone. Said headlamp's DC light intensity can be increased manually or automatically. Said headlamp can include a communication interface for a measurement device.

The device may be wearable, like a wrist-worn device or a ring. The device may be integrated into a watch or a piece of jewelry. Thus the nearest spotlight can be turned directly at the device. If a user wants to read a book, the device can guide the spotlight to illuminate the book. Light adjustment, including flickering compensation and brightness adjustment, can be done automatically.

The device may control interior lights in order to eliminate flicker coming from the outside through windows or openings. For example, the device may guide a car interior to be illuminated strongly by DC light if the light of the sun creates flickering shadows from trees.

The device may be used to indicate flickering light which is harmful for a human being or for animals in a certain space or room and to reduce or eliminate harmful effects by adding DC light.

The device can include a microcontroller, which controls the measurement electronics and may further process results in a desired format for a user. For example, an audio signal or a visual user interface can express harmful flicker for the user.

Said microcontroller can include an analog-to-digital converter to convert a light detector analog signal to a digital signal. Said microcontroller can be programmed so that stable DC light, flicker intensity, and frequency can be calculated. In the simplest case one light detector is needed. In some cases the spectral wavelength of the flickering light needs to be measured. For example, a camera color sensor can be used to roughly measure the spectrum of the light.

The device may include electronics, which are used to measure the light intensity and frequency characteristics of the detected light signal, especially a flickering light in comparison with a DC light. A very-high-frequency flickering light signal is also similar to DC light for the human nervous system and it can be handled like DC light. An example is a 45-kHz signal used in high-frequency electrical ballast for fluorescent lamps.

The device may be integrated as part of another light quality measurement system or device. Such device could measure, for example, spectral flatness or uniformity of illumination in a space or room where there may be flickering lighting units. In an embodiment of the invention, flickering light is compensated by measuring the flickering light waveform, and then at each moment in time, adding such amount of light that total illumination is more constant. This is called variable compensation. However, embodiments of the invention where only DC light is added are robust, as they are insensitive to possible errors in variable compensation. An advantage of variable compensation is that flicker can be eliminated by adding only an amount of light that corresponds to AC intensity. This is beneficial if it is not possible to increase overall illumination high enough for the DC compensation method.

In an embodiment of the invention the device controls other lamps in a space or room in order to reduce the intensity of flickering lights so that it is easier to compensate flicker in desired areas or objects by adding DC light.

1.6.5 Flickering prevention

Figure 13 depicts a flow chart of the invention, which comprises lamp 1300, flicker detection block 1302 which detects light 1308 coming from lamp 1300, lamp control block 1304, lamp interface 1306 to a control interface and/or a main supply. Block 1304 may also comprise lamp control functionality. Lamp control interface 1312 may comprise a power supply for said lamp and/or control signals. In the same case there may be temperature monitoring of said lamp, etc. In Figure 13 light source 1300 may be a fluorescent lamp, LED, or any other lamp technology. The device of the invention is connected to or integrated in said lamp. Flicker detection includes a light detector which is placed so that it mainly detects light coming from lamp 1300. Said flicker detection includes electronics which detects a flickering light signal. If a flickering signal is detected and it is at too high a level, lamp control 1304 switches the lamp off. It may be possible that the lamp status can be read through a lamp control interface and/or that a lamp control block gives a flicker fail status through control interface 1314.

Figure 14 depicts a flow chart of a method where lamp power source signal 1404 (voltage or current) is monitored in 1406 and if too high a flicker frequency is present, control block 1404 can switch lamp 1400 off and can give a failure code to a control interface. A flicker failure may also be shown by an indicator LED.

Flicker detection may be used for active feedback to an electrical lamp driver circuit which changes lamp power supply parameters so that a flickering signal amplitude is eliminated or reduced to an acceptable level.

Said flicker prevention device may be integrated into the basic functionality of a new lighting fixture. If there is a microcontroller or logic integrated into said light fixture, it can automatically give a failure code which tells the reason for a failure in said lighting fixture, for example, too high a flicker level. There may also be an indicator LED which indicates the failure of said lighting fixture.

Figures 15 - 21 describe different fluorescent lamp flicker detection block diagrams. Figure 15 depicts a block diagram of a flicker prevention circuit that employs electrical ballast circuit 1512. Figure 15 shows flicker detection block 1504, interface 1514 between electrical ballast circuit 1512 and flicker detection 1504, fluorescent lamp 1502, electrode 1516, lamp interface 1506 to electrical ballast, line supply interface 1510, and in some cases control interface 1508. Flicker detection block 1504 is placed so that light from fluorescent lamp 1502 can be measured by a light detector inside said flicker detection block. Said electrical ballast circuit can drive a fluorescent lamp at a low frequency (for example, 50-120 Hz) or a high frequency (for example, 10-100 kHz).

Figure 16 depicts a block diagram of a configuration where flicker detection 1602 with flicker prevention control block 1604 is not integrated with electrical ballast circuit 1600. Flicker prevention control block 1604 may provide a power supply for flicker detection 1602, and when flicker detection circuit 1602 indicates that there is too high a flicker level in light coming from lamp 1502, flicker prevention control block 1604 will switch off line supply 1608 to said electrical ballast and said lamp is thus switched off. A control block interface may comprise line supply 1606 and control line 1614 for more precise control of flicker prevention control block 1604 and electrical ballast 1600. Said control block interface can be used to read the status of the lamp, change parameters like light intensity, and change the parameters of flicker prevention block 1604. In the same case a user can decrease flicker prevention block 1604 switch-off values when flicker is not so critical. Said control block interface may be realized by using a wire or wireless interface.

Figure 17 shows a configuration where flicker detection block 1704 is placed as close as possible to a fluorescent lamp. Flicker detection 1704 can be placed around fluorescent tube 1502. Said flicker detection may be ring-like. Figure 18 depicts a side view of the invention. Mechanically the holding part of flicker detection block 1704 may be ring 1806 or an open ring. It may also be placed near the connection by using any other mechanical structure. Said mechanical structure is realized so that only light from the lamp can enter flicker photodetection circuit 1804. Said flicker detection circuit may comprise one or more photo diodes, but it may also comprise other electronic component(s) like power management, a microcontroller, and an integrated circuit. Interface 1904 may be a light detection diode interface or a control interface with a power supply.

Figure 19 depicts a configuration where flicker detection is connected directly to electrical ballast 1902.

Figure 20 and Figure 21 depict said flicker detection invention used with magnetic ballast 2002 and fluorescent lamps 1502.

In Figure 20 said flicker detection and prevention control are integrated with starter switch 2008. Block 2008 is placed so that light from lamp 1502 can be detected by a light detector integrated in said starter switch. All electronics components needed for flicker detection can be integrated in said starter switch. Some part can be left outside the switch. When the lamp is switched on a line supply is connected on lines 2004 and 2010. The starter switch connects lines 2006 and 2012, which cause electrodes 1504 to warm up. After warm-up said starter switch switches off the connection between lines 2006 and 2012. After warm-up fluorescent lamp 1502 lights if the lamp is not broken. After the lamp is on and warmed up, flicker detection starts monitoring to ensure that flicker stays at a reasonable level. Because there is some flicker anyway when magnetic ballast is used, said flicker detection can be used to switch the lamp off when the flicker level gets too high. In Figure 20 switching off can be done so that when the flicker detector indicates that the flicker level is too high, the starter switch can be used to connect lines 2006 and 2012 together in a very short time, causing the lamp light to shut down. The starter can try to start the lamp again after the line supply has been switched off and on again.

If it is not possible to place the starter switch near the lamp, a photodetector can be taken out and placed so that it can detect the light coming from the lamp. Said photodetector can be placed as described in earlier figures, Figure 13, Figure 15, and Figure 16.

Figure 21 depicts a case where there is a switch for line supply 2004. The flicker detection and prevention circuits are integrated together in starter switch 2102, and when detected flicker is at too high a level, the control circuit will switch off line supply connection 2004 to line 2108. Power is supplied to the starter switch and flicker detection circuit through 2104 from interface 2106 and from line 2006. The starter switch can try to start the lamp again after the line supply has been switched off and on again.

Flicker detection can be a stand-alone device which may include a light detector, a power management circuit, signal filtering after the light detector, a microcontroller, or an integrated ASIC (Application Specific Integrated Circuit) which detects flicker and provides output information on the flicker level by means of an analog or digital signal. For example, by using PWM (Pulse Width Modulation) for an output signal, there is need for only one interface and it can be used to tell the flicker level of the light source. For example, a 50/50 PWM signal tells that there is 0% flickering of the light and a 25/75 PWM signal that there is 50% flickering of the light. The output can be a single digital interface. An unacceptable flicker level can be preset in SW or by means of electronics. For example, if the flicker level rises above 15%, the output signal will rise up.

Typically the 230 VAC, 50 Hz main supply leaks through the lamp. It can be seen as a 100 Hz light flickering signal. In the US the main supply is 120 VAC, 60 Hz, and it can be seen as 120-Hz flickering. In some cases it is enough to monitor these frequencies (100 Hz and 120 Hz) where the main supply is used for lighting fixture power supplies. In some cases of malfunction, lower frequencies can occur, like when a fluorescent lamp tries to start up.

One aspect of the invention is to mark on the lamp the main supply flicker (100 Hz and 120 Hz) percentage compared to the lamp's DC light. If 10 percent (%) of the main supply flickering signal is allowed to pass through, the lamp flicker self-test guarantees that this is not exceeded. For example, a LED lamp supplier marks the flickering of the lamp as under 5%, and if that value is exceeded the lamp will shut down. Another way is to use a mark which tells how much of the light is flickering light.

This invention may be used for any lamp including but not limiting to fluorescent, LED, incandescent, halogen, and gas-discharge lamps. There may be different levels of flicker allowed depending on the lighting condition requirements. So, in some cases a higher flicker amplitude compared with DC lighting may be allowed. In rooms or spaces where no harmful flickering light is allowed, the lamp will shut down when the flicker amplitude increases to too high a level.

The ratio between the AC and DC intensities of flickering light may vary according to the total light output of the lamp. Lamps with a higher lumen output may have a smaller guaranteed AC/DC ratio than lamps with a smaller lumen output.

One way to use the invention is to integrate flicker prevention functionality in a lamp. For example, when using a LED lamp with an E27 base lamp connection, flicker detection, prevention, and required electronics can be integrated with said LED lamp electronics. Flicker detection can be realized by using photodetection or by monitoring the supply current or voltage signal line going to the LED(s).

There may be a control interface which can be used to write and read lamp control parameters and status. Such parameters may include intensity, dimming, and light spectral quality, like increased blue light intensity during the daytime and decreased in the evening. One parameter can be used for the allowed flicker level. Said control interface may also be used to check the current flicker level of the lamp. Said control interface may also be used to allow a higher flicker amplitude, thus extending the lamp's use time.

The lamp may contain an indicator light, like a LED, which shows that the lamp has been shut down because of a high flicker level. This permits maintenance personnel to see why a lamp is not on.

1.6.6 Illumination control

Some embodiments of the invention include means for controlling illumination. Device synchronization may start with the user starting application software (SW) on a mobile phone. The (lighting) control application opens a wireless communication interface to search for wireless controllable lighting units nearby. If there are any controllable lighting fixtures, lamps, etc. the application SW gets information from them. The application SW opens the phone's camera viewfinder. It can use the camera on the front or back side of the phone. The same kind of application can be on a laptop or a tablet PC. Synchronization starts when the application finds a lighting fixture that is pulsing; it initiates synchronization with said lighting fixture. There can be specific pulse sequence with different lamps of lighting fixtures. Pulsing LED(s) can also be used to synchronize the viewfinder to recognize the correct lamp. When the application is synchronized with a certain lamp which is in the viewfinder it can start to control it by means of the user interface. Pulsing used for synchronization can be unnoticeable for people.

After the lamp has been synchronized by the application, the application can automatically or semi automatically save the place and other setup information. If the lamp is connected to a network it may be controlled through the internet. The user might provide other information about the lamp to the application SW. For example, living room main lamp, children's room light fixture, etc., or the controllable device (here a lamp) will provide information about the room or place. Place information can be saved in the controllable device's memory so it can provide it automatically. After the controllable device is synchronized with the application SW it can be used right away when the application is open. The application can show which controllable unit(s) are nearby and which can be controlled via the internet or any other communication path.

Lighting may also have a separate wire control by switching of a power supply, etc.

Location information can be also obtained by wirelessly measuring net power levels when the user moves to a different room. The application can obtain information from the network informing that the wireless RF power level is changing and the strongest RF power link is to devices in a certain room. The application can deduce that a certain control unit is in that room and first offer that room's lighting control possibilities to the user interface. Also moving in a certain room changes power levels in that room and this can be used for place/location indication.

Location information can be mapped with controllable device information. Said location information can be a certain room, place, GPS data, etc. The application can use the location information to trigger the application to search for devices which have been synchronized. The location information can be used for power saving.

The user can select in the mobile application viewfinder the lamp with which the application has wireless control interface synchronization.

The viewfinder can show/mark in the display for user which lamp(s) can be controlled. The application can obtain the parameters that can be controlled in a certain lamp. The user might also see if the lamp is not working properly. A lamp self-test can indicate whether the lamps is too hot, a flicker test failed, etc.

Control may be taken over a group of lamps. Lamps or lighting fixtures can be synchronized in groups in different rooms. When synchronization has been completed with one lamp in a room, the application may take control over other lamps in that room.

The mobile application can be used to measure the room's lighting quality parameters like illumination intensity, flicker level, spectral content, etc. The same kind of application can be used on a laptop, tablet PC, or separate control unit with a viewfinder (photodetector, camera, display, user interface, and so on.)

The application can be used to control illumination in different situations. For example, the user might want to read a book. The user places the mobile phone with the application open on a surface where there needs to be a sufficient level of illumination for reading. The user selects a reading mode in the application. If there is a good enough level of illumination for reading, there is no need for extra light. The application can inform user that illumination is OK. If not, the application will control a lamp that is nearby, which can be shown on the viewfinder. The application indicates if there is no controllable lighting device(s) nearby. The application might guide the user to turn the mobile phone so that the viewfinder can find a lamp which can be controlled.

The application can measure lighting parameters by using the device's photodetector(s) or camera. The application can measure a room's light intensity, ambient light's flicker level, spectral content, etc. If there is a flickering light source, which can be controlled, the user might switch it OFF or the device will automatically turn it OFF or adjust it to a lower intensity level. If the device cannot eliminate flickering light from the room, the user interface will indicate this to the user. If there is flickering light in room and it cannot be controlled by the application and there are also controllable flicker-free lamps in the room, the application can raise the DC light intensity of the flicker-free light source or sources to a level where flickering light is eliminated to a level that is not harmful and light intensity will be at a sufficient level for reading, for example. The device can also indicate if it cannot control light intensity to a suitable level. The user interface can indicate if the lighting is sufficient for office use, for reading, etc.

The application can take into account the user's personal lighting requirements. For example, elderly people need a higher level of light intensity for reading than a younger person. The requirements for the spectral content of light may also be different for different users. Elderly people may need a higher level of blue light intensity for reading tasks, etc. If there are light sources under the control of the application, it is also possible to tune the spectral contents of blue light to increase in such a case. Spectral content can also be changes during daily needs; it can be different during the night and at midday.

The application may take into account a migraine or epilepsy patient's lighting. For example, if the user uses the control interface to indicate that a migraine seizure is ongoing, the lighting control can change the spectral content and intensity of lighting in the room or space to a level that the patient can stand.

If it is known that lamps which are flickering are being used for room lighting, the application can give a warning to the user if he or she is sensitive to flicker. The application can use location information for this purpose. In some cases a wireless lamp can give a warning independently.

The intensity level of ambient light might change during the day. For example, during a sunny day there may be no need for extra illumination. The application can take that into account and change the intensity of illumination according measured results.

The mobile application can also be started to control other wireless devices. Control synchronization starts the same way as in the lighting control case. The user starts the application if the application finds via a wireless communication interface that there is device nearby which can be synchronized; it then starts the synchronization procedure. The application asks the user to find the device by controlling the device's viewfinder. Final synchronization is done after the device has completed the light pulsing procedure. The application asks if the user wants to take control of the device shown/pointed to in the viewfinder display. If the user selects said device shown/marked on the display, the user can obtain information from the device under control regarding which kind of control is allowed and possible to implement.

The application might use also the control synchronization procedure so that the user only sees in the viewfinder what kinds of wireless controllable devices are nearby and the user can immediately select on the viewfinder display the device he or she wants to control. Such a case could be when the user wants to control a washing machine, for example. If there is only one washing machine in the room the user can select the device right away. In some cases there may not be many wireless controllable devices nearby. Then the application can start blinking the controllable device's lights /LED(s) and the user can select on the control interface which device he/she wants to control. One case when the user can make a controllable device selection also right away is when the controllable device has a clear name and the user can see that over the wireless link.

The control interface can also be protected by a password. The user needs to know the password to gain control over the lighting control interface or any other device which uses same kind of procedure for synchronization.

1.6.7 Measuring close to target

In an embodiment of the invention a mobile device such as mobile phone or tablet for example, are converted to a flickering measurement device by a mobile application, which uses the camera sensor of the mobile device for measuring the flicker.

Figure 22 shows an embodiment of the invention, where the mobile device 2204 is attached to a stick 2201 with a control button 2202, which button 2202 sends a control signal to the mobile device 2204 to trigger the measurement from a target, which is a lamp 2203 in the figure. The connection may be wireless or non-wireless. The connection can use for example Bluetooth, WI-FI, USB, audio or any other suitable interface.

When user pushes the button, the mobile device triggers the measurement and/or some other operation such as storing the results. Various commands may be sent to the mobile device by pressing a single button by different length of time. For example a short (for example less than one second) pressing may trigger a new measurement, whereas a long (for example longer than one second) may trigger a storing of the last measurement. The stick may also have several buttons, so that each button, or their combinations, sends different commands to the mobile device. The stick may have a touch panel for controlling the mobile device. The touch panel may allow more versatile user interface than buttons. The stick may have a touch screen for controlling the mobile device and showing information to the user.

The stick may be a standard commercially available selfie stick, or it can be any device which contains the needed abovementioned functionality. The stick may be a telescope selfie stick.

Advantages of the use of the stick are for example: - lamps located on ceilings or floors can be measured close to the lamps easier, safer, and more accurate

- the stick extends the arm length of the user, so that measuring flicker from lamps and other illuminated objects is more convenient

Flicker measurement accuracy is improved when measurement can be made closer to the lamp, where illumination from other sources is proportionally weaker than illumination from the lamp under measurement.

Other construction may be that light sensor is a separated unit which can be set on top of the stick. Mobile phone can be used for user interface for measurement and for storing the data. Part of the signal processing can be done in the separated sensor unit and the mobile phone can be used for signal processing. Control interface can be wire or wireless as described earlier.

In addition to the abovementioned flicker measurement, the command sent from the stick may control the mobile device to perform any measurement available for the mobile device through its own sensors, or sensors connected to it. Such measurements can measure for example lamp radiance and/or spectral radiance.

Although described in the context of particular embodiments, it will be apparent to those skilled in the art that a number of modifications and various changes to these teachings may occur. Thus, while the invention has been particularly shown and described with respect to one or more embodiments thereof, it will be understood by those skilled in the art that certain modifications or changes may be made therein without departing from the scope of the invention as set forth above.

Claims

1. A system for monitoring flickering of light having adverse health effect, the system comprising:

a control unit (204) configured to receive a light measurement output from a light measurement unit (202, 514, 802, 1302, 1406), to determine flickering of measured light, and to determine whether a level of the flickering of the measured light exceeds a threshold.

2. The system of claim 1 , wherein the light measurement unit and the control unit are comprised in a same physical entity.

3. The system of any preceding claim, wherein the control unit is comprised in a portable electronic device (2204) having a wireless communication capability.

4. The system of any preceding claim 1 to 2, wherein the control unit is comprised in a lighting system.

5. The system of any preceding claim, wherein the measured light comprises a direct component, DC (104, 304, 404, 904, 1004, 1010), and an alternating component, AC (102, 302, 402, 902, 1002, 1012), and wherein the control unit is configured to detect the flickering of the measured light from the AC (102, 302, 402, 902, 1002, 1012).

6. The system of claim 5, wherein the determining whether the level of the flickering of the measured light exceeds the threshold comprises determining a ratio between the AC (102, 302, 402, 902, 1002, 1012) and the DC (104, 304, 404, 904, 1004, 1010).

7. The system of claim 6, wherein said ratio is a peak-to-peak AC (102, 302, 402, 902, 1002, 1012) intensity divided by the constant DC (104, 304, 404, 904, 1004, 1010) intensity and wherein the control unit determines whether said ratio exceeds said threshold.

8. The system of claim 5, wherein the determining whether the level of the flickering of the measured light exceeds the threshold comprises determining a ratio between AC (102, 302, 402, 902, 1002, 1012) on certain frequency and the DC (104, 304, 404, 904, 1004, 1010).

9. The system of claim 8, wherein the AC/DC ratio is determined on a plurality of AC (102, 302, 402, 902, 1002, 1012) frequencies.

10. The system of any preceding claim, wherein the control unit is further configured to determine the flickering of the measured light in flickering frequencies that are higher than a flickering fusion frequency.

11. The system of claim 10, wherein the control unit is configured to determine the flickering of the measured light on at least said frequencies that are higher than said flickering fusion frequency.

12. The system of any preceding claim, wherein the control unit is further configured to determine the flickering of the measured light on at least one frequency in a flickering frequency range from 1 Hz to 300 Hz.

13. The system of any preceding claim, wherein the control unit is further configured to determine the flickering of the measured light on a plurality of flickering frequencies.

14. The system of claim 13, wherein the control unit is further configured to determine the flickering of the measured light on the plurality of flickering frequencies simultaneously.

15. The system of any preceding claim, wherein the control unit is further configured to cause an output of a warning if the flickering of the measured light exceeds the threshold.

16. The system of any preceding claim, wherein the control unit is further configured to cause an output of a warning if a cumulative flickering dose exceeds a threshold for a predetermined period.

17. The system of claim 15, wherein the control unit is configured to output a first warning if the flickering frequency of the measured light is lower than the fusion frequency, and to output a second warning if the flickering frequency of the measured light is equal or higher than the fusion frequency.

18. The system of any preceding claim, further comprising: a database for storing measurement data, wherein the data comprises at least one of light intensity and spectrum data, flicker frequency data, flicker intensity data, DC (104, 304, 404, 904, 1004, 1010) intensity data, flicker waveforms data, time and location information data.

19. The system of any preceding claim, wherein the light measurement unit is capable of detecting light having a flickering frequency higher than the flickering fusion frequency.

20. The system of any preceding claim, wherein the control unit is further configured to control at least one light source in order to reduce the flickering of the measured light.

21. The system of claim 20, wherein the control unit is configured to control the at least one light source in response to determining that the flickering of the measured light exceeds the threshold.

22. The system of any preceding claim 20 to 21 , wherein the controlling the light source by the control unit comprises increasing DC (104, 304, 404, 904, 1004, 1010) of light from at least one light source.

23. The system of any preceding claim 20 to 22, wherein the controlling the light source by the control unit comprises decreasing AC (102, 302, 402, 902, 1002, 1012) of light from at least one light source.

24. The system of any preceding claim 20 to 23, wherein the controlling the light source by the control unit comprises switching off at least one light source.

25. The system of any preceding claim 20 to 24, wherein the one or more light sources are comprised in eyeglasses, in a head lamp, or in a helmet visor.

26. The system of any preceding claim 20 to 25, wherein the one or more light sources are attachable to a body tissue of a user, preferably close to eyes of the user, such that light is emitted substantially towards the body tissue of the user.

27. The system of any preceding claim, wherein the control unit is further configured to dim the at least one light source by controlling the at least one light source and/or at least one other entity.

28. The system of any preceding claim, wherein the control unit is further configured to receive a control signal from another apparatus and to initiate the light measurement as a response to the received control signal.

29. The system of any preceding claim, wherein the control unit is further configured to identify the at least one light source by causing the at least one light source to flash a communication message.

30. The system of any preceding claim, wherein the light measurement further comprises measuring wavelength of the measured light.

31. The system of any preceding claim, wherein the control unit is configured to determine the flickering of the measured light on at least one wavelength between about 350 nanometer, nm, and about 1100 nm.

32. The system of claim 31 , wherein the control unit is configured to determine the flickering of the measured light having a wavelength characteristics to blue light.

33. The system of any preceding claim, wherein the control unit is configured to determine the flickering of the measured light on at least one wavelength between about 6000 nm and about 6000 nm.

34. The system of any preceding claim, wherein the threshold for the level of the flickering of the measured light is user specific.

35. The system of any preceding claim, wherein the threshold for the level of the flickering of the measured light is dependent on at least one of intensity of the measured light, wavelength of the measured light.

36. The system of any preceding claim, wherein the threshold for the level of the flickering of the measured light increases when the wavelength of the measured light increases.

37. The system of any preceding claim 2 to 36, further comprising: a viewfinder for aiming the flicker measurement to a certain target.

38. The system of any preceding claim 2 to 37, wherein the control unit is further configured to measure motion of the physical entity, and wherein the determining the flickering of the measured light is at least partly based on said motion measurement.

39. A method for monitoring flickering of light having a physiological effect, the method comprising:

determining, by a device, a threshold for flickering of light; obtaining light measurement output from a light detector; and determining whether a level of the flickering of the measured light exceeds said threshold.

40. A computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into a portable electronic device, execute the method according to claim 39.

41. A portable electronic device, comprising:

a wireless communication interface; and

an electronics unit, wherein the portable electronic device is configured to: determine a threshold for flickering of light, obtain light measurement output from a light detector, and determine whether a level of the flickering of the measured light exceeds said threshold.

42. A portable device, comprising:

a wireless communication interface; and

a user interface, wherein the portable device is configured to: detect a user input, and, as a response to the user input, wirelessly transmit a control signal to a portable electronic device causing the portable electronic device to perform a flickering light measurement.