1. Functional light and what about health?
With functional light is meant the light needed to have the work done in a proper way. The norm is used to describe the minimum average lux value, the evenness of the light, the CRI value and sometimes the color temperature and maximum glare value. So, in the years that light is specified, the functional requirements are understood and specified.
This is different to the extent of how healthy light can be. In this presentation we will look at two norms that deal with health aspects related to light.
Norms and measurements

2. Healthy light DIN SPEC 67600:2013-04 DIN SPEC 5031-100:2015-08
Biologically effective illumination, design guidelines
DIN SPEC :
Measurement using the eye, of the melanopic effect of light on humans: variables, formula symbols and actionspectrum
Two norms are mentioned here. One is the that gives recommendations. This is based on a 2009 version of the DIN V 5031, and talks about biological light and gives design guidelines for using biologically effective light in different work situations such as classrooms, office work, work in shofts and nursery homes.
In the mean time since the has been published, and update of the 5031 was made. When speaking about healthy light we mean to say light that has an influence on various processes of the human body. We do not refer to the process of vision. This is then why we do not use the term biological anymore (that would include the vision process) but instead, we will use the term melanopical. This is the color pigment found in ganglion cells inside the human eye and it is believed that these cells do have an impact on many processes (non visual) of the human body.
The 5031 in 2015 did get updated over 2009, with respect to the action spectrum of the melanopic light.

3. Biologically effective light can be healthy
The following positive effects
Stabilization of human circadian system
Synchr. sleep-wake with 24 hour day-night
Re-inforcement of amplitude of biol. clock
Activation and improvement of concentration
Facilitation and fostering of regeneration
Improvement moods
Strengthening immune system
Note: to be applied to right time of the day!
There are a number of positive results to be obtained when melanopically effective light is used in the right amount and right time of the day.

4. Human circadian system
Biological rhythm of about 1 day length, variations in
body temperature
hormone descretion
rhythm of heart
activity and rest
Light can affect it and reset the timing of it
In short some info about what is the human circadian system. However that is not the red line of this presentation and one should better look on Wiki or other sources to get more detailed info.

5. DIN SPEC 67600:2013-04 Observations but not further considered here
Light enters human not only via eyes (skin, hair roots)
Production of Vit-D done by UV-B
Focus in norm on
Non-visual effects of light transmitted through the eyes
Design guidelines for living spaces (extended stay)
Statement: bio. effective light is not related to energy efficiency of visual light  keep separate
Statement: better to use melanopic effects since normal vision is not considered (in biologic effects normal vision is included).
When looking at the 67600, it does acknowledge that light is perceived not only by the eyes. However when light is used then the most effect it can have on the human body is believed to come via the eyes. And in particular the ganglion cells. This is why the mentioned norm only looks at the eye sensitivity to melanopical effective light (in this norm biological is used but that word is deprecated).

6. Melanopic effectiveness
Minimum 250 lux as vertical illuminance on the eye
At Tc = 8000 K (at eye) of a fluorescent TL
Beware of reflections and filtering!
Several hours of exposure a day
Preferably in the morning
Solid angle of light source is important
< 0.1 sr no effect (20 deg view angle)
> 0.1 sr and < 0.5 sr effect increases
> 0.5 sr good effect (46 deg view angle)
Coming from above or upper part of visual field
The mentioned norm gives some clear statements as to what light is believed to be melanopically effective. Later, with help of the 5031, we are able to compute a melanopical effectivity parameter for this specific light. We can also compute such an effectivity parameter for any other light, and therewith we can compare different lights on theit merit of being melanopically effective.
This page lists a number of items to beware of when dealing with light to be melanopically effective. The time of the day when applied, and the size of the light emitting area are not included in the calculations of how effective light can be, so be informed that the calculations that follow are just a basic comparison between lights of different spectra. Before any light becomes effective make sure that most of these items mentioned here are fulfilled.

7. Office space 200lx_vert@3000K
Dependent on visual task (EN ) (also lx_horiz)
The norm gives design guidelines of how to apply melanopically effective light during the day, for instance in office space. Important here is the application of melanopically effective light during the morning hours, to reset the human biological clock. Here the CCT of 8000K is used to indicate melanopically effective light, as light with high CCT is containing more blue and that is what is believed to be effective.
This light with high CCT is also used after the lunch to get people out of their lunch-dip and active for work again.
A period of time between 6-8PM is mentioned where only warm white light is used in order not to disturb the human biological processes.

8. Classroom i
Dependent on visual task (EN ). See example for school day.
An other practical work example mentioned in the are classrooms. And also important here is not to disturb the human circadian system late in the evening. More info on how to apply light effectively during the day is given in the next slide.

9. Class- room ii 650lx_horiz@12000K (synchr biol. clock)
(normal lesson)
(test/concentration work)
(calming after test)
(activate after lunch)
Here a typical set of activities during the day, in a classroom. Also present is the high amount of very blue-isch (12000K) light during the early morning to synchronize the human biological clock with the regular day-night rhythm.
Furthermore there is a difference between normal teaching (4000K) and tests/exams (6000K), the latter requiring more attention. Also, the getting out of an eventual after dinner dip is done by using melanopically effective light of K in this example.
It is not that a natural day there are a lot of these color temperature changes, however these artificially introduced change sin color temperature can be used to get people in an active mode or get them in a more rest mode during appropriate times of the day in a classroom.

10. DIN SPEC :
a_mel_v = melanopic factor for visual radiation
A: Determine melanopic effect of light with spectrum X_λ
B: Determine visual effect of light with spectrum X_λ
Divide A/B to get a_mel_v
s_mel(λ)
The DIN 5031 is specifically focusing on the computation of how melanopically effective light can be. For that, it defines an action spectrum called s_mel, which is basically an indication of what part of a light spectrum does count much to be melanopically effective. So looking at the graph of s_mel, one sees that that spectrum part around 480 nm is specifically effective melanopically, much more than light with a wavelength of 580 nm.
The parameter calculated here, to indicate effectivity for melanopic processes, is the a_mel_v, meaning melanopic factor for visual radiation.
We get into an example on the next page.

11. Example a_mel_v Example of how to compute the a_mel_v.
In black we have the spectrum of the light of the Fluorescent TL of 8000K. We weigh this light against the sensitivity curve of the melanopic action spectum, meaning multiplying the red curve with the black curve and adding all resulting values.
We weight this light also against the Photopic sensitivity curve in blue by multiplying the black with the blue curve and adding the resulting values.
The a_mel_v is the division of these two values.
In the norm was mentioned that, due to little overlap between the a_mel_v and Photopic visibility spectrum, the melanopic effect is not relating to the effiiency. We here see that the curves overlap at 520 nm. And also that 22 % of the melanopic value comes from the spectrum part from and above 520 nm. And that 11 % of the photopic value comes from the spectral part below 520 nm. This is significant, given that this 8000K light source is a reference for the norm to be used to generate melanopically effective light! Therefore, the statement that melanopic effective light is to be evaluated separately from photopic effective light is not really true.

12. Example a_mel_v Example of how to compute the a_mel_v.
In black we have the spectrum of the light of the LED with 3075K CCT. We weigh this light against the sensitivity curve of the melanopic action spectum, meaning multiplying the red curve with the black curve and adding all resulting values.
We weight this light also against the Photopic sensitivity curve in blue by multiplying the black with the blue curve and adding the resulting values.
The a_mel_v is the division of these two values.
In the norm was mentioned that, due to little overlap between the a_mel_v and Photopic visibility spectrum, the melanopic effect is not relating to the effiiency. We here see that the curves overlap at 520 nm. And also that 37 % of the melanopic value comes from the spectrum part from and above 520 nm. And that 5 % of the photopic value comes from the spectral part below 520 nm. This is significant, however there is no real melanopic effect to be expected from this light with this low CCT so this light is only usable as visually effective light and not as melanopic effective light. The overlap here is not interesting since a_mel is not effective.

13. a_mel_v in practice Reference values:
From 67600: 250 lux_vert for 8000K fluorescent TL
a_mel_v = 0.867
From 67600: 200 lux_vert for 3000K light
a_mel_v = 0.387
Given any lamp, once spectrum is determined we calculate the a_mel_v
Compare to a_mel_v of 8000K Tl for which a recommendation exists, determine relation
Then change 250lx_vert into lux for any lamp using relation
So how to use these calculated results is to first look at the reference values mentioned in the Here these are: 250 lux (vertically) of 8000K fluorescent TL. This light has an a_mel_v of We can compute the a_mel_v of the spectrum of the light of any other lamp and then compare these two a_mel_v’s. The more effective the other lamp’s spectrum is, the lower the 250 lux can be in order for it to be effective melanopically.

14. a_mel_v in practice ii
So in practice, I have measured the light coming from my cell phone when it was put to completely white. I recorded its spectrum and calculated the a_mel_v of it. It appeared to be 17 % higher than that of 8000K fluorescent TL, meaning that less is needed for lux_vert in order for it to be melanopically effective.
If the eulumdat file (a photometrical file) of the cell phone’s light would be available, then it can be used to determine the vertical lux values at the eye of a person when using for instance Dialux.
a_mel_v_NOTEii/a_mel_v_8000KTL= 1.015/0.867=1.17 So needed 250/1.17= 214 lux_vert  simulate Dialux!

15. Pupil and transmission effects
Correction factor based on Age: k_mel(A)
k_mel(A)=k_mel,trans(A)*k_mel,pupil(A)
Trans = transmission through eye medium
Pupil = pupil size
a_mel_v(A)=a_mel_v(32)*k_mel(A)
k_trans values for 8000K TL: (25yr), (32yr), (50yr), (75yr), (90yr)
Adapt a_mel_v for transmission effects and pupil effects. These effects can be calculated when age is known. They reduce the effectiveness of the a_mel_v by a factor.
So in order to compare the resulting a_mel_v values for people with an age other than 32 years, I also give the k_trans values for the 8000K fluorescent TL used as a reference in

16. Spectral transmission effect
This graph shows the effect on transmission through the eye, with increasing age. Less blue light is transmitted.

17. Pupil effect
This graph shows the correction factor due to pupil size. It becomes clear that with increasing age the pupil size decreases. The effect is less with higher adaptation luminances. For normal viewing indoors, the Luminance is taken to be 200 cd/mˆ2.

18. All lamps of Indusled Agency were tested by OliNo
Flicker content
Color spectrum with CRI and CQS
Blue Light Hazard
Ask For lamp measurement info
This presentation is given on LED-EXPO in The Netherlands on Jan 28th During this LED-EXPO we as OliNo are present on a stand, doing measurements on lamps brought by visitors of our stand. Also giving more explanations or answers on questions that may arise.