using the daysimeter: what can we measure?...to 500 lux, and has retrofitted lighting in one...

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Using the Daysimeter:Using the Daysimeter:What can we measure?What can we measure?

John D. Bullough, Ph.D. John D. Bullough, Ph.D. March 7, 2007March 7, 2007


OutlineOutline

Conventional illuminance measurementsConventional illuminance measurementsSpectral power distribution Spectral power distribution ““analyzeranalyzer””Circadian stimulus/response measurementCircadian stimulus/response measurementTemporal analysesTemporal analyses


Conventional illuminance Conventional illuminance measurementsmeasurements

Example: Suppose the State Office on Example: Suppose the State Office on Aging is considering changing Aging is considering changing recommended (horizontal) light levels in recommended (horizontal) light levels in nursing facility residential areas from 300 nursing facility residential areas from 300 to 500 lux, and has retrofitted lighting in to 500 lux, and has retrofitted lighting in one facility with the increased illuminance.one facility with the increased illuminance.One could use the Daysimeter instrument One could use the Daysimeter instrument to validate whether before/after to validate whether before/after illuminances are indeed 300 lux/500 lux.illuminances are indeed 300 lux/500 lux.


Spectral response for illuminance Spectral response for illuminance measurementsmeasurements

The response of the The response of the DaysimeterDaysimeter’’ss photopic sensor is within that found in photopic sensor is within that found in commercially available illuminance meters.commercially available illuminance meters.


Spectral power distribution Spectral power distribution "analyzer""analyzer"

Since the Daysimeter has two independent Since the Daysimeter has two independent sensors with known spectral sensitivity, sensors with known spectral sensitivity, different light sources will have different different light sources will have different ratios between photopic and shortratios between photopic and short--wavelength illuminanceswavelength illuminancesReference light source (Reference light source (Ep/EbEp/Eb = 1.0) is = 1.0) is 3500 K fluorescent3500 K fluorescent


Eb/EpEb/Ep values: Indoor lightingvalues: Indoor lightingLamp type Typical Ep/Eb value Incandescent 0.7-0.8 Tungsten-halogen 1.0-1.1 2700 K compact fluorescent 0.6-0.7 3500 K fluorescent 0.9-1.0 4100 K fluorescent 1.1-1.2 6500 K fluorescent 1.9-2.0 Daylight (window) 1.8-2.5

Eb/EpEb/Ep values: Outdoor lightingvalues: Outdoor lightingLamp type Typical Ep/Eb valueLow pressure sodium 0.0-0.1High pressure sodium 0.3-0.5Mercury vapor 1.2-1.3Metal halide 1.2-1.3


Caveats when making field Caveats when making field measurementsmeasurements

A single light source rarely provides all A single light source rarely provides all illumination in a locationillumination in a location

0.80.8--1.01.0Incandescent + Incandescent + 10% daylight10% daylight

0.70.7--0.80.8IncandescentIncandescent

Resulting Resulting EEpp/E/Ebb valuevalueLight sourceLight source


Caveats when making field Caveats when making field measurementsmeasurements

Walls and other surfaces can affect the spectral Walls and other surfaces can affect the spectral distribution of illumination reaching the eyes, distribution of illumination reaching the eyes, but differences are small unless totally indirect but differences are small unless totally indirect lighting is used or very saturated colors are usedlighting is used or very saturated colors are used

0.580.582700 K CFL 2700 K CFL (light blue back wall)(light blue back wall)

0.530.532700 K CFL 2700 K CFL (yellow back wall)(yellow back wall)

0.560.562700 K CFL 2700 K CFL (flat white back wall)(flat white back wall)

Resulting Resulting EEpp/E/Ebb valuevalueLighting conditionLighting condition


Deducing locationsDeducing locations

Indoor light levels differ from exterior levelsIndoor light levels differ from exterior levelsAdditionally, time of day information will be Additionally, time of day information will be informative (light at midnight is unlikely to be informative (light at midnight is unlikely to be daylight)daylight)

(Figueiro et al., 2006)


Circadian stimulus/response Circadian stimulus/response characterizationcharacterization

Signals from two sensors can be combined Signals from two sensors can be combined to provide an estimate of circadian to provide an estimate of circadian stimulus (Rea et al., 2005)stimulus (Rea et al., 2005)›› Circadian stimulus is based on physiology as Circadian stimulus is based on physiology as

well as data from multiple studies of nocturnal well as data from multiple studies of nocturnal melatonin suppression by light (melatonin suppression by light (BrainardBrainard et et al., 2001; al., 2001; ThapanThapan et al., 2001; Rea et al., et al., 2001; Rea et al., 2001, 2002; Figueiro et al., 2004)2001, 2002; Figueiro et al., 2004)


Circadian Circadian stimulusstimulusmeasurementmeasurement

0 1 2 3 4 5 6 7-2

0

2

4

6

Time (days)

log 10

(lux

or C

S)

unit 24.txt Filtered

R2 =

0 1 2 3 4 5 6 7-2

0

2

4

6

0 1 2 3 4 5 6 7-2

0

2

4

6

Time (days)

log 10

(lux

or C

S)


R2 =

0 1 2 3 4 5 6 7-2

0

2

4

6

Time (days)

log 10

(lux

or C

S)


0 1 2 3 4 5 6 7-2

0

2

4

6

Time (days)

log 10

(lux

or C

S)


Day

shi

ftD

ay s

hift

Grant #NIHGrant #NIH--RO1RO1--OH008171OH008171

Nig

ht s

hift

Nig

ht s

hift


Stimulus versus responseStimulus versus response

One can calculate precisely a One can calculate precisely a stimulusstimulus›› Below threshold, all stimuli, Below threshold, all stimuli,

regardless of magnitude, result regardless of magnitude, result in zero responsein zero response

›› Above saturation, all stimuli, Above saturation, all stimuli, regardless of magnitude, result regardless of magnitude, result in maximum responsein maximum response

Thus, it is often important to Thus, it is often important to understand the resulting understand the resulting response in addition to the response in addition to the stimulusstimulus

(Figueiro et al., 2006)(Figueiro et al., 2006)


Circadian Circadian responseresponse measurementmeasurement

0 1 2 3 4 5 6 7-1

0

1

2

3

4

log 10

(CS)

Time (days)0 1 2 3 4 5 6 7

0

0.2

0.4

0.6

0.8

Rel

ativ

e R

espo

nse



Temporal analysesTemporal analyses

Unlike most conventional photometric Unlike most conventional photometric equipment, the Daysimeter date stamps equipment, the Daysimeter date stamps and records data continuouslyand records data continuouslyCan provide estimates of periodicity and of Can provide estimates of periodicity and of day/night light exposureday/night light exposureCan relate measurements to specific Can relate measurements to specific events (e.g., in diaries or sleep logs)events (e.g., in diaries or sleep logs)


Day shift light exposure and Day shift light exposure and activityactivity


0 1 2 3 4 5 6 7-2

0

2

4

6

Time (days)

log 10

(lux

or C

S)


0 1 2 3 4 5 6 70

0.1

0.2

0.3

0.4

Time (days)

Activ

ity (

rms

g)

R2 = 0.556

0 1 2 3 4 5 6 7-2

0

2

4

6

Time (days)

log 10

(lux

or C

S)


0 1 2 3 4 5 6 70

0.1

0.2

0.3

0.4

Time (days)

Activ

ity (

rms

g)

R2 = 0.556


Night shift light exposure and activityNight shift light exposure and activity

0 1 2 3 4 5 6 7-2

0

2

4

6

Time (days)

log 10

(lux

or C

S)


0 1 2 3 4 5 6 70

0.2

0.4

0.6

0.8

Time (days)

Activ

ity (

rms

g)



Periodicity analysisPeriodicity analysis

0 1 2 3 4 5 6 7 8 9 10 11 120

1

2

Frequency (Cycles Per Day)Ampl

itude

(lo

g 10CS

)

unit 24.txt Circadian Stimulus Filtered

0 1 2 3 4 5 6 7 8 9 10 11 120

0.05

0.1

Frequency (Cycles Per Day)

Ampl

itude

(rm

sg) Activity

0 1 2 3 4 5 6 7 8 9 10 11 120

1

2

0 1 2 3 4 5 6 7 8 9 10 11 120

1

2


itude

(lo

g 10CS

)


0 1 2 3 4 5 6 7 8 9 10 11 120

0.05

0.1


itude

(lo

g 10CS

)


0 1 2 3 4 5 6 7 8 9 10 11 120

0.05

0.1


Ampl

itude

(rm

sg) Activity


Ampl

itude

(rm

sg) Activity

0 1 2 3 4 5 6 7 8 9 10 11 120

1

2


itude

(lo

g 10CS

)


0 1 2 3 4 5 6 7 8 9 10 11 120

0.1

0.2


Ampl

itude

(rm

sg) Activity

0 1 2 3 4 5 6 7 8 9 10 11 120

1

2

0 1 2 3 4 5 6 7 8 9 10 11 120

1

2


itude

(lo

g 10CS

)


0 1 2 3 4 5 6 7 8 9 10 11 120

0.1

0.2


itude

(lo

g 10CS

)


0 1 2 3 4 5 6 7 8 9 10 11 120

0.1

0.2


Ampl

itude

(rm

sg) Activity


Ampl

itude

(rm

sg) Activity

Day

shi

ft

Day

shi

ft

Nig

ht s

hift

Nig

ht s

hift


Day/night light exposure Day/night light exposure and activity estimatesand activity estimates

Shift status

CS: Day

CS: Night

Activity: Day

Activity: Night

Day/Night CS ratio

Day/Night Activity Ratio

Day shift 172.1 2.55 0.0819 0.0273 67.49 3.00

Night shift 63.3 16.23 0.1305 0.1194 3.90 1.09

Day shift 184.4 6.74 0.1235 0.0661 27.36 1.87Grant #NIHGrant #NIH--RO1RO1--OH008171OH008171


Using diaries or sleep logsUsing diaries or sleep logs

(Figueiro et al., 2006)


Thank you.Thank you.

using the daysimeter: what can we measure?...to 500 lux, and has retrofitted lighting in one...

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