Relative quantum sensitivity

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L I G H T E X P O S U R E A S S E S S M E N T O F D A N I S H I N D O O R , O U T D O O R A N D N I G H T- S H I F T W O R K E R S

E X P E R I E N C E S F R O M A F I E L D S T U D Y

B Y: J A K O B M A R K VA R T, S E N I O R R E S E A R C H E R AT S B I

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• The Lux@r project

• The context of this talk

• Light and light exposure

• What When and Where

• Light as a “one-dimensional unit” – things that matters:

1. Spectral sensitivity 2. Spatial sensitivity

Light exposure assessment

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Lux@r

3 SBi – 19.12.2016

Funded by: Danish Working Environment Authority

(Arbejdsmiljøforskningsfonden) Project title:

“Health Consequences of the Light Environment at Work, Indoor and during Night”

(Lux@r) Partners involved:

• Occupational and Environmental Medicine, Aarhus University, Denmark

• National Research Centre for the Working Environment, Copenhagen, Denmark

• VELUX A/S, Hoersholm, Denmark

• Department of Occupational Medicine, Danish Ramazinni Centre, Aarhus University Hospital, Denmark

• Department of Occupational Medicine, Bispebjerg Hospital, Copenhagen, Denmark

• Department of Energy Performance, Indoor Environment and Sustainability of Buildings, Danish Building Research Institute, Aalborg University, Copenhagen, Denmark

Source: http://www.luxar.dk/?page_id=42

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R a d i a t i o n

• D a y l i g h t

• E l e c t r i c l i g h t

• H e a t / I R ?

• U V ?

• D a r k n e s s ?

Light - What do we (want to) measure?

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Global solar radiation (energy)

5 SBi – 19.12.2016

Source: http://upload.wikimedia.org/wikipedia/commons/4/4c/Solar_Spectrum.png 300 and 3000 nm (~99 %)

3-5% 42-43% 52-55%

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Total global solar radiation (energy)

The sum of:

• direct,

• diffuse, and

• reflected solar radiation

The daylight spectrum and intensity is continuously changing….

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Daylight

7 SBi – 19.12.2016

Overcast, diffuse light

Sunny, directed light

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Electric light

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Relative spectral composition – electric lighting

9 SBi – 19.12.2016

Spectrum of Fluorescent light Spectrum of

Incandescent light bulb (IllA)

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• The sum of:

• direct,

• diffuse, and

• reflected electric light

T h e s p e c t r u m a n d i n t e n s i t y o f l i g h t e x p o s u r e i s c o n t i n u o u s l y c h a n g i n g … . b e c a u s e p e o p l e m o v e !

Illumination (electric light and daylight)

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Measuring systems

11

Measuring errors can happen many places in the measuring system!

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Measuring systems

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Spectral sensitivity

(Input transducers/detectors, differences)

13

Courtesy: www.licor.com Courtesy: www.hagner.se

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Spectral sensitivity

(Input transducers/detectors, differences)

Discrepancies between V(λ) and the spectral response of a photometric instrument are characterized by the f1’ statistic.

The measuring system used in Lux@r:

f1’ statistic = 83% (white light)

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Spectral sensitivity, Human

15

Max: 464 507 555

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

380 420 460 500 540 580 620 660 700

Relative quantum sensitivity

Wavelength (nm)

Melatonin suppression Scotopic factor V′λ Photopic factor Vλ Photopic vision

V(λ) is based on the relative amount of power at each wavelength required to produce a criterion brightness response in a 2° foveal field of view

← Mesopic factor V_mes(λ)

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Spatial sensitivity

(direct and diffuse radiation)

One directional light:

Multi directional light:

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Spatial sensitivity, direct light

1 7 SBi – 19.12.2016

Courtesy: Price et al. 2012, Light. Res. Technol. 44, 17-26

Figure of Actiwatch spectrum spatial sensitivity

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Spatial sensitivity, diffuse light

≠

RGB sensor

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I m p o r t a n c e :

K n o w y o u r s e n s o r / m e a s u r i n g s y s t e m c o n c e r n i n g : 1 . s p e c t r a l a n d

2 . s p a t i a l

s e n s i t i v i t y W h y :

B e c a u s e l i g h t e x p o s u r e c h a n g e s w i t h t i m e , p l a c e a n d p o s i t i o n !

Sensor response, Spatial and spectral sensitivity

1 9 SBi – 19.12.2016

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Human light exposure measurements

We want to find relations between….

Health (circadian rhythms, sleep quality, depression, cancer….etc.)

……AND …light…

Preferable a one-dimensional unit of light exposure

!

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Side-by-side calibration

(to compensate for the inter-equipment variability)

21

(d = 15 x diameter of light source!)

Inverse Square Law: E

_v

= I

_v

/d

²

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Calibration

In the lab – Standard light source ”D65” Outdoor – Side-by-side ”D65”

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Directed vs. multi-directional ”D65”

(single) vs. (side-by-side)

2 3 SBi – 19.12.2016

White light C_val =

White light / Lux_Ref-Meas

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• >60% variation between devices

• Use a diffused overcast sky for side-by-side calibration

Conclusion Outdoor – Side-by-side ”D65”

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N o t p u b l i s h e d … y e t … .

Light exposure measurement – Some few results

2 5 SBi – 19.12.2016

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• L i g h t i s a m u l t i - d i m e n s i o n a l u n i t !

• B e a w a r e o f :

• I n t e r - e q u i p m e n t v a r i a t i o n s a n d

• i n t e r - h u m a n v a r i a t i o n s

• T h e v a r i a t i o n i n t h e l i g h t e x p o s u r e i s h u g e ! A N D … .

• D e p e n d s o n :

• S e a s o n

• W e a t h e r

• L o c a t i o n ( i n - o r o u t d o o r )

• I n d i v i d u a l h a b i t s

( l i k e e . g . w o r k a n d c o m m u t i n g h a b i t s )

• … . . ?

Conclusion:

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Thanks and contact info:

2 7 SBi – 19.12.2016

Jakob Markvart Cand.Hort., Ph.d., Senior Researcher

Department of Energy Performance, Indoor Environment and Sustainability of Buildings;

Danish Building Research Institute (SBi) Phone: (+45) 2497 6033,

Email: jam@sbi.aau.dk

Aalborg University Copenhagen | A.C. Meyers Vænge 15 | DK-2450 Copenhagen SV