1st class light sources2
TRANSCRIPT
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PHOTOMETRY LIGHT AND RADIATION SOURCES
The sun is the most important and most familiar source
of light and radiation. The total radiant power of the sunis said9 to be 3.9x 1023 Kw.
While most of this energy is radiated into space, the
irradiance at the earth’s outer atmosphere is between
132 and 140 mWcm-2 .
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This irradiance is attenuated by the atmosphere by a
factor of 0.7 to 0.8 on a clear day. As a round figure, 100
mWcm-2 has been proposed as the magnitude of “one
solar constant” and termed One sun.
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THE EFFICACY OF LIGHT AND RADIATION
There are two ways of defining the efficacy of
a light source.
If a monochromatic source is considered it
would be compared with a source of
wavelenght 555 nm of 673 lm/W.
If, on the other hand, a white light source
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It would be compared with an equal-energy
hypothetical source concentrated within the
visible spectrum with maximum efficacy of
about 187 lm/watt
The maximum luminous efficacy of white light
depends on the wavelength interval
considered visible.
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LUMINOUS EFFICIENCY
The luminous efficiency of this source must be
187/673 = 27.8% máx.
In this case the amounts 187 and 673 lm/W
means both are radiated
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The efficacy of the fluorescent lamps or sources
does not include the energy disipated in the
electronics.
It depends of the color
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One light source with a luminous efficacy of
115 lm/W
Compared with a maximum value for sources of
continuous spectre of 187 lm/W
It will be 115/187 = 61.5 % efficiency.
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The Illuminance of natural sources
The daylight is composed by the sun light plus
the skylight, both increase as the sun rise in the
sky.
The maximum Illuminance due to skylight is16,000 lx
The maximum Illuminance due to sunlight is
102,000 lx.
The maximum Illuminance due to both are
118,000 lx
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BLACK BODY RADIATION
The blackbody radiation is a hipotetical
source of radiant energy which is used as a
standard in order to compare other sources.
The blackbody is a radiator who radiation depends only of the temperature, it radiates
more energy to some temperature that
anybody at the same temperature.
It absorbes all the incidente optical radiation
without radiates any.
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COLOR TEMPERATURE
The color temperature of a source of light isthe temperature (kelvins) of a blacbody that
would radiate light of the same chromaticity.
e s r u on empera ure o a g source
is the temperature of a blackbody thet would
radiate light of the same spectral energy
distribution
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The term color temperature is often used
when the context implies the distributiontemperature, a light source non thermal can
have a temperature different of his color
.
Examples: A fluorescent source and a thermal
source masked with a filter, can be matched
the color temperature but the fisical
temperature are different
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The white mantle of a gas or gasoline lamp
was probably the first incandescent lamp, butthey are rarely used now because the electric
lamp is more efficient, easier to control, safier,
and provides more light for less money
easily switched. It is remarkably constant and
repeatable in performance if not operated at
too high a temperature.
The fused point is about 3650 K and it can be
operated at high temperature in vacuum and
in an inert gas.
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The white mantle of a gas or gasoline lamp
was probably the first incandescent lamp, butthey are rarely used now because the electric
lamp is more efficient, easier to control, safier,
and provides more light for less money
easily switched. It is remarkably constant and
repeatable in performance if not operated at
too high a temperature.
The fused point is about 3650 K and it can be
operated at high temperature in vacuum and
in an inert gas.
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This process produces energy as heat and
light , the latter being 5% of the total energy
consumed . Usually have a double coiled
in an atmosphere without oxygen : Ar , N.
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1.Incandescent inert atmosphere (common)are distinguished because they emit a
pleasant, warm light.
2.No need for auxiliary equipment on andrestart , this being instantaneous.
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1.On the market a variety of shapes, sizes ,wattages and colors; with and without
built-in reflector.
2.Intensity is proportional to the area of thefilament.
.temperature as power is dissipated in thecold bulb
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Its operating position is universal and are
provided with screw caps or bayonet
Fallas, by thinning the filament or vibration is so
placed support wires . The base is contact and
support.
The light emission gradually decreases in the
course of its life , since the filament is partially
evaporated , thereby reducing its sectionincreases resistance and also produces a
blackening of the bulb
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3) A halogen lamp, also known as a tungsten
halogen, quartz-halogen or quartz iodine lamp,
is an incandescent lamp that has a small amount
of ahalogen such as iodine or bromine added.
The combination of the halogen gas and
the tungsten filament produces a halogen
cycle chemical reaction which redeposits
evaporated tungsten back onto the filament,
increasing its life and maintaining the clarity of the
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Gas discharge lamps are a family of
artificial light sources (or lamps). These
lamps produce light by
sending electricity through a ionized gas.Most of these lamps use a noble gas, or a
combination of noble gases, but they often
contain other materials, such
as mercury, sodium or metalhalides.
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The gases in these lamps are ionized in
operation. This means that there arefree electrons.
When a electric current is sent through the
gas, e ec rons co e w a oms o e
gas and the metals. This will mean that
some reach a higher energy state. When
they fall back into the lower energy state,
they will emit the energy in the form
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Ultraviolet (UV) light is an electromagneticradiation with awavelength from 400 nm to
100 nm, shorter than that of visiblelight but longer than X-rays.
Though usually invisible, under some
conditions children and young adults cansee ultraviolet down to wavelengths ofabout 310 nm, and people with
aphakia (missing lens) can also see someUV wavelengths.
Near-UV is visible to some insects
and birds.
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An LED lamp is a light-emitting diode (LED)
product that is assembled intoa lamp (or light bulb) for use in lighting
fixtures.
amps ave a espan an e ec r ca
efficiency that is several times better
than incandescent lamps, and significantly
better than most fluorescent lamps, with
some chips able to emit more than 100
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LEDs emit light in a very narrow band of
wavelengths, emitting light of a colorcharacteristic of the energy bandgap of
the semiconductor material used to make the
.
either mixing light from red, green, and blue
LEDs, or using a phosphor to convert some of
the light to other colors.
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One method (RGB or trichromatic white LEDs)
uses multiple LED chips, each emitting adifferent wavelength, in close proximity to
generate white light. This allows the intensity of
color.
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The second method uses LEDs in conjunction
with a phosphor. The CRI (color renderingindex) value can range from less than 70 to
over 90, and color temperatures in the range of
7000 K are available
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A laser is a device that emits light through a
process of optical amplification based onthe stimulated emission of electromagnetic
radiation
A laser differs from other sources of light in that it
emits light coherently . Spatial coherence allows
a laser to be focused to a tight spot, enabling
applications such as laser
cutting and lithography.
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Spatial coherence also allows a laser beam to
stay narrow over great distances (collimation),enabling applications such as laser pointers.
Lasers can also have high temporal coherence,
narrow spectrum, i.e., they can emit a single
color of light.
Temporal coherence can be used to
produce pulses of light as short as a
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A laser diode, or LD, is an electrically
pumped semiconductor laser in which the activelaser medium is formed by a p-n junction of
asemiconductor diode similar to that found in
- .
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The laser diode is the most common type of laser
produced with a wide range of uses thatinclude fiber optic communications, barcode
readers, laser pointers, CD/DVD/Blu-ray
, ,
scanning and increasingly directional lighting
sources.
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Gaussian beam is a beam of
monochromatic electromagnetic
radiation whose transverse magnetic
and electric field amplitude profiles are given
by the
Gaussian function this also im lies a
Gaussian intensity (irradiance) profile.
This fundamental (or TEM00 )
, transverse gaussian mode describes the
intended output of most (but not all) lasers
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The mathematical expression for the electric field
amplitude is a solution to the paraxial Helmholtz
equation. Assuming polarization in the x direction and
propagation in the +z direction, the electric field
in phasor (complex) notation is given by:
where
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f(x) = ae(x-b)2
E (r,z) =E0 {W0/W(z)} exp [-r 2/W2(z)][exp (-
i(kz+k[r 2/2R(z)] -(z))
.
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Beam width or waist, Ancho del haz o tamaño del
punto
El haz Gausiano de ancho w (z ) esta dado como función de la
distancia axial z . La cintura o ancho mínimo del haz es w :
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Gaussian beam width w (z ) as a function of the axial
distance z . w 0: beam waist; b: depth of focus; z R:Rayleigh range; Θ: total angular spread
For a Gaussian beam propagating in free space, the
spot size w (z ) will be at a minimum value w 0 at one
place along the beam axis, known as the beam waist .
For a beam of wavelength λ at a distance z along the
beam from the beam waist, the variation of the spot size
is given by
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where the origin of the z-axis is defined, without
loss of generality, to coincide with the beam
waist, and where
is called the Rayleigh range.
Rayleigh range and confocal parameter a s ance rom e wa s equa o e ay e g
range z R, the width w of the beam is
The distance between these two points is calledthe confocal parameter or depth of focus of the
beam: