Presentation on theme: "“Success is not the key to happiness. Happiness is the key to success."— Presentation transcript:
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-HallidayENEL 581
5 Outline Illumination Standards (CIE, IESNA) Colorimetry – CCT, CRI Psychology of colorPhysiology – Young eyes, old eyesLumen Efficacy and EfficiencyLighting Sources Comparison
6 Illuminance Standards CIE – Commission Internationale de l’ÉclariageIESNA – Illumination Engineering Society of North AmericaType of ActivityIlluminance (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 afterimagesA 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) / 0.27md/2 = 0.27m tan 32.5°d = cmArea meeting the NA Illumination Standards for reading (300 Lux).“ Ideal characteristic fora reading / task lamp – by developed world standards ”McTavishWLED Task Lampd = 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 spaceEach point in xy corresponds to many points in the original space.
20 Correlated Color Temperature (CCT) Cooler lightCCT 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 energyPlanckian Locus(Black body radiator)
22 Psychology of ColorEnvironmental 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 SourceCCT °KCandle / Kerosene lamp~ 1800100 W Incandescent2675Compact Fluorescent4200WLEDs5000Daylight (noon)5400Table 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 ExcellentCRI ≥ 85 Very Good60 ≥ CRI ≥ 80 Some Color DistortionCRI 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 DistortionPoor rendering indexes put strain on the eyes because of having to correct the color of objects.
25 Color Rendering Index (CRI) Light SourceCRICandle / Kerosene lamp80100 W Incandescent100 ??Warm white Fluorescent55Cool white Fluorescent65Daylight Fluorescent73WLEDs85Table 2: CRI Comparison between some light sources
26 Color Rendering Index Analysis General Color Rendering IndexRa (CRI)Integrates the reflectivity data for 8 specified samplesSpecial color rendering indices, refer to six additional test samplesRa 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 lamp0.1 – 1Incandescent5 - 18Compact FluorescentTube FluorescentWLEDsENEL 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 capabilityreduction 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 distributionAvoid glare or direct view of light sources or reflectionsUse high color rendering index light sources
32 References Lighting Principles: Mechanical and Electrical Equipment for buildingsStein, Benjamin. New York Wiley c2000, 9th EditionChapter 18Introduction to Solid State LightingArturas ZukauskasWiley Interscience, 2002Chapter 2 – Vision, Photometry and ColorymetryLighting The Way, a key to independenceMariana Gross FigueiroLighting Research CenterEnd ENEL Lec. 4 (19Sept2007) ; End ENEL 581 Lec. 4 (20Sept2007)End ENEL Lec. 3 (15Sept2008) ; End ENEL 581 Lec. 3 (16Sept2008)