1. “Success is not the key to happiness. Happiness is the key to success.
If you love what you are doing, you will be successful.”
Albert Schweitzer – 1965

2. This class is more important than simply the material we cover
This class is more important than simply the material we cover! If you don’t recognise the need to make a positive difference to our world, then we have failed you!

3. Summary of Lec. 2 Class answers re: 3rd & 4th optical sensor in mammalian eyes from Lec.2? Discuss in T2 Class answers to Batwing Question from Lec. 2? Demo Lux meter

4. Fundamentals of Light Part 2
Dr. Dave Irvine-Halliday
ENEL 581

5. Outline Illumination Standards (CIE, IESNA) Colorimetry – CCT, CRI
Psychology of color
Physiology – Young eyes, old eyes
Lumen Efficacy and Efficiency
Lighting Sources Comparison

6. Illuminance Standards
CIE – Commission Internationale de l’Éclariage
IESNA – Illumination Engineering Society of North America
Type of Activity
Illuminance (Lux)
Orientation and simple visual tasks (Public spaces)
Common visual tasks (Commercial, Industrial and Residential)
Special visual tasks (very small or very low-contrast critical elements)
Sun (at sea level)  105 – 104 Lux Moon (at sea level)  0.1 Lux

7. The human eye is capable of seeing somewhat more than a 2 trillion-fold range: The presence of white objects is somewhat discernible under starlight, at 5×10−5 lux, while at the bright end, it is possible to read large text at 10+8 lux, or about 1,000 times that of direct sunlight, although this can be very uncomfortable and cause long-lasting afterimages
A candle (6 lumen emitting into a hemisphere) can be seen at a distance of 10 miles (16 kms) in a clear atmosphere

8. Can 1 Watt WLED Lamps meet the Illumination Standards for reading?
27 cm above reading surface with 65° reflector

9. Illumination levels offered by 1 Watt WLED Lamps
Tan 32.5° = (d/2) / 0.27m
d/2 = 0.27m tan 32.5°
d = cm
Area meeting the NA Illumination Standards for reading (300 Lux).
“ Ideal characteristic for
a reading / task lamp – by developed world standards ”
McTavish
WLED Task Lamp
d = cm

10. What happens if we use more than one WLED in a lamp?

11. “Same beam angle as single WLED, but higher illumination levels…”

12. Standards for the Developing World?
“Measurement of Illuminance Levels in Class”

13. IESNA CIE Winter 2005 class (acceptable level)
“Same beam angle as single WLED, but higher illumination levels…”

14. Colorimetry Science of Measuring Colors
As it was inconvenient to have negative values in the matching functions CIE proposed a linear transformation of matching functions resulting in CIE x, y and z matching functions

15. CIE 1931 Color Matching Functions
Where the weights, X, Y and Z define a color in the CIE XYZ space and C() = Color

16. CIE 1931 Chromaticity Diagram
As the z component bears no additional information, it is often omitted.
xy space is just a projection of the 3D XYZ space
Each point in xy corresponds to many points in the original space.

17. CIE 1931 Chromaticity Diagram
5 mm WLED
X = 0.41
Y = 0.39
End ENEL Lecture 10 (2Oct2006)

18. Mixing of Colors
“The Blue Experience”

19. CIE 1976 Chromaticity Diagram
5 mm WLED
X = 0.41
Y = 0.39

20. Correlated Color Temperature (CCT)
Cooler light
CCT is defined as the absolute temperature (expressed in degrees Kelvin) of a theoretical black body whose chromaticity most nearly resembles that of its light source.
CCT rating is an indication of how "warm" or "cool" the light source is.
Ambient color and CCT of light have a psychological effect over the users.
Warmer light

21. Correlated Color Temperature (CCT)
A - tungsten
(2856° K)
B - direct sunlight
(4870° K)
C - overcast sunlight
(6770° K)
D - daylight
(6504° K)
E - Equal energy
Planckian Locus
(Black body radiator)

22. Psychology of Color
Environmental Color affects mood and feeling and is a common experience. From studies (Wohlfarth, Faber, Akashi, 1986) it has also been proved that light has also physiological effects on humans.
Red and Red hues of CCT, creates a sensation of heat. Tend to increase body tension, and stimulates the autonomic nervous system.
Blue and blue hues of CCT, creates a sensation of cool, Release tension and have lesser physiological effects.

23. Correlated Color Temperature (CCT)
Light Source
CCT °K
Candle / Kerosene lamp
~ 1800
100 W Incandescent
2675
Compact Fluorescent
4200
WLEDs
5000
Daylight (noon)
5400
Table 1: CCT comparison for some light sources

24. Color Rendering Index (CRI)
Daylight, by definition has a color rendering index of 100.
The higher the color rendering index from a lamp the better it is.
CRI ≥ 90 Excellent
CRI ≥ 85 Very Good
60 ≥ CRI ≥ 80 Some Color Distortion
CRI is defined as the capacity of artificial light sources to render the colors of the illuminated objects as compared to daylight at the same color temperature.
CRI ≤ 60 Serious Color Distortion
Poor rendering indexes put strain on the eyes because of having to correct the color of objects.

25. Color Rendering Index (CRI)
Light Source
CRI
Candle / Kerosene lamp 80
100 W Incandescent
100 ??
Warm white Fluorescent 55
Cool white Fluorescent 65
Daylight Fluorescent 73
WLEDs 85
Table 2: CRI Comparison between some light sources

26. Color Rendering Index Analysis
General Color Rendering Index
Ra (CRI)
Integrates the reflectivity data for 8 specified samples
Special color rendering indices, refer to six additional test samples
Ra varies to up to 100, it might be negative.

27. Luminous Efficacy and Efficiency
Luminous Efficacy (K): The ability of the radiated energy to produce a visual sensation, which is measured in lumens per watt of emitted light (Characterizes the radiation spectra rather than the source).
K = luminous flux (Φv) / Radiant Power (Φe)
Radiant Efficiency (ηe): Dimensionless designates the ability of the light source to convert the consumed power into radiant flux Φe (Can go from zero to unity).
ηe = Φe / Power (P)
Luminous Efficiency: Measured in lumens per watt, it is the ability of the light source to convert consumed electrical power into visible luminous flux Φv (Characterizes the source)
ηv = Φv / Power (P)

28. Luminous Efficiency Comparison
Light Source
(lm/W)
Candle / Kerosene lamp
0.1 – 1
Incandescent
5 - 18
Compact Fluorescent
Tube Fluorescent
WLEDs
ENEL End Lecture 11 (4Oct2006)
Table 1: ηv comparison for some light sources

29. Luminous Efficiency Trends Comparison
End ENEL 581 Lec. 3 (15Sept2009) ; End ENEL 669 Lec. 3 (16Sept2009)
(1) 5mm WLED introduced by Nichia Corporation of Japan in 1996,
(2) Luxeon Star – the first high-flux WLED in the market developed by Lumileds, USA
(3) Luxeon K2 – the brightest device up to date (also developed by Lumileds).

30. Physiology of Vision Aging of the human eye “a natural process” :
involves loss of accommodation of focussing capability
reduction of pupil size, thus reducing the amount of light entering the eye (older people require extra lighting).
Thickening of the optical lens (absorbing more light and scattering it). Images with less contrast and sharpness.
20 Year old eyes can receive 6 times more light than a 80 years old ones in bright conditions and 16 times more light in dark conditions.
Good lighting can make the difference between seeing and not seeing for older adults.

31. Physiology of Vision Recommendations:
Increase illumination levels over reading and working spaces (increase of luminous flux of light sources)
Diffuse light, keep a uniform light distribution
Avoid glare or direct view of light sources or reflections
Use high color rendering index light sources

32. References Lighting Principles:
Mechanical and Electrical Equipment for buildings
Stein, Benjamin. New York Wiley c2000, 9th Edition
Chapter 18
Introduction to Solid State Lighting
Arturas Zukauskas
Wiley Interscience, 2002
Chapter 2 – Vision, Photometry and Colorymetry
Lighting The Way, a key to independence
Mariana Gross Figueiro
Lighting Research Center
End ENEL Lec. 4 (19Sept2007) ; End ENEL 581 Lec. 4 (20Sept2007)
End ENEL Lec. 3 (15Sept2008) ; End ENEL 581 Lec. 3 (16Sept2008)