THERMOGRAPHY
&
HOLOGRAPHY
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Non Destructive Testing and Evaluation
B.Tech 4TH SEMESTER
METALLURGICAL AND MATERIAL
ENGINEERING
NIT SRINAGAR
THERMOGRAPHY
Thermography is a technique of obtaining image of
heat distribution over the surface.
 Special television
camera with infrared sensitive
detector and a lens which transmits radiation . Such
camera operates at normal video rates.
 Temperature variation in the object are then
displayed as the shades of the grey or can be
converted into the pseudo colour image .
 Bodies which have the temperature above 0 kelvin
radiates infrared waves.

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PRINCIPLES OF THERMOGRAPHY :
 Bodies give out infrared radiations .
 The infrared energy is dependent on absolute
surface temperature .
 The infrared energy is dependent on surface
emissivity.
 Semiconductor's are used to measure the infrared
energy .
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Basic thermal science’s:
 Heat
 Temperature
Basic heat transfer:
 Conduction
 Convection
 Radiation
Stefan's Boltzmann law:
It states that total energy radiated per unit
surface area of a black body in unit time is directly
proportional to fourth power of black bodies absolute
temperature T.
WBB=ρx𝑇 4
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Types of infrared camera:
 Single sensor.
 Focal plane array.
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Thermographic approach:
 Active
 Passive
Detectors:
 Uncooled microbolometric detector.
 Cooled detectors.
Uses:
 Detects different disease and disorders .
 Detects tumors and cancer cells.
 In electronic industry.
 Aerospace applications ,electrical inspections ,mechanical inspections
Advantages of thermography:

Non-contact method with low thermal stress.

Effective prevention of test scrap.

Simple analysis of large and uneven surface.

Meaningful analysis of the defects.
Disadvantages :

Need skilled and trained person.

Interpretation of thermal images also challenged.

Cost of equipment's is also high.

Image contrast is high so that ability to distinguish the detail is
poor,

We cannot inspect transparent material.
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HOLOGRAPHY

Holography : it is method of producing a visual threedimensional (3-D) image of the object by means of light
wave patterns recorded on a photographic plate.

Its an advanced form of photography that allows an
image to be recorded in three dimensions.

Holography from the Greek (whole+write) is the science of
producing holograms.

A photograph of an interference pattern which, when
suitably illuminated by laser light, produces a three
dimensional image.
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Working of Holography:
 Laser light….usually helium-neon =(HeNe) laser is
used.
 Beam splitter ….device that use mirrors and prisms to
split laser into two beams.
1.object beam
2.reference beam.
 Mirrors …direct the beams of light to correct locations
 Holographic film….to record image very high
resolution.
 Can be seen through naked eye.
Hologram properties:
 If you look at these holograms from different
angles,you see objects from different perspectives .
 It shows divisible property i.e if you cut one in
half,each half contains whole views if the entire
holographic image
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How to create a hologram:
 To create hologram, a laser beam (coherent light) is
split in two beams
 Reference beam: That stays undisturbed
 Object beam: strikes the objects and then bounces
onto the plate.
 Working of holography is divided into two phases
1.Recording
2.Reconstruction
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Applications of holography:
 Optical computers
 Bio-medical applications
 Compact disk
 Grocery store
 Holographic interferometery
 Holographic scanners
 Holostores
Reconstruction:
when a hologram is later illuminated
with coherent light of the same frequency
that created it,a three dimensional image
of the image of the subject appears.
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Photography vs Holography:
PHOTOGRAPHY
 2-D recording process
 Ordinary light can be used
 Lens system
 Image has poor resolution
HOLOGRAPHY
 3-D recording process
 Only laser light can be used
 Lens less system
 Very high resolution
Advantages:
 Cost effective
 High storage capacity
 Increased feasibility of objects(depth)
 Enables the achievement of multiple image on a
single plate and give 3-D images
 Ability to combine with other technologies
Disadvantages:
 Provide static images
 Do nit produce images of complex movement
 Require complicated precise machinery to
produce and view an image
 Reference illumination beams are collinear
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conclusions:
 Holographic technology has endless applications as
far as the human mind can imagine
 Holographic technologies are not just about art or
business communication, they are about
safety,security,education,planning and the strength of
our civilization here and beyond
 Holographic technology will become a very integral
part of human scoieties and civilizations in future
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THANK YOU