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International Journal of Research In Science & Engineering
Volume: 1 Issue: 3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
Infrared Thermography and IR Camera
Pooja Battalwar , Janhvi Gokhale , Utkarsha Bansod
Student, electronics and telecomm. Dept.,Jawaharlal darda engg.and technology,[email protected]
ABSTRACT
This paper describes thermography and its principle on which it is based. Thermographic camera is used to
detect infrared radiation and it works in wavelength of 14,000nm.This context gives a brief description of
scanning mechanism of thermographic camera. It also includes advantages and disadvantages and possible
application of infrared thermography. Our eyes act as detectors that are designed to detect visible light . There
are other forms o f light (or radiation) that we cannot see. The human eye can onl y see a very small part of the
electromagnetic spectrum . At one end of t he spectrum we cannot see ultraviolet light, while at the other end our
eyes cannot see infrared. A thermo graphic camera or infrared camera is a device that forms an image
using infrared radiation, similar to a common camera that forms an image using visible light. It can detect
infrared radiation emitted by an object having high temperature. Instead of the 450 –750 nanometer range of the
visible light camera, infrared cameras operate in wavelengths as long as 14,000 nm (14 µm).
Keywords: Introduction, History, Principle used in thermography, Basics of camera, signal processing in IR
camera etc.
----------------------------------------------------------------------------------------------------------------------------1. INTRODUCTION
Hu man eye can see visible light or s mall part of electro magnetic spectrum. Hu man eye cannot see ultraviolet light
and infrared light. Infrared energy is just one part of the electromagnetic spectrum that encompasses radiation from
x-rays, gamma rays, ultra vio let, and a thin region of visible light, radio waves infrared, and microwaves. T o
remotely determine the temperature of an object, infrared radiation is used[1]. Thermogaphic camera detects
infrared rad iation in the range of electro magnetic spectrum roughly 0.9-14 micro meter and produce the picture of
that radiation that we can see.
Thermal energy is part of electro magnetic spectrum and makes upper part of infrared of light spectrum. The primary
source of infrared rad iation is heat or thermal rad iation. Any object that has a temperature above absolute zero ( 0
Kelv in) emits radiation in the infrared region. Every objects that are very cold, such as ice cubes, emit infrared
radiation. A lthough our eyes cannot see it, the nerves in our skin can feel it as heat. The warmer the object, the more
infrared radiation it emits.
Fig 1: Infrared spectrum
IJRISE| www.ijrise.org|[email protected] [9-14]
Volume: 1 Issue: 3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
1.1History
In 2009, Thermography used by Govern ment and airport personnel to detect suspected swine flu cases. The concept
of infrared rad iation was developed by astronomer W illiam Herschel in the early 19 th century. He discovered a type
of invisib le rad iation in the spectrum beyond red light . Kálmán Tihanyi, the Hungarian physicist did invent for antiaircraft defense the infrared-sensitive (night vision) electronic television camera first in 1929 [2].
2. THERMOGRAPHY
Infrared thermography technique which is non-contact, non destructive test method uses an infrared imaging to
detect, display and record thermal patterns and temperature across the surface of an object. Thermography can be
applied to any situation where thermal profile and temperature will provide mean ing data about a system or object. It
is equip ment wh ich senses infrared radiat ion by converting it into temperature and d isplays image of temperature
distribution.
2.1Principle Used In Thermography
Since in frared rad iation is emitted by all objects based on their temperatures, according to the black body radiation
law, thermography makes it possible to “see” one’s environment with or without visible illu mination. The amount of
radiation emitted by an object increases with temperature; therefore thermography allows one to see variat ions in
temperature. If the temperature an object gets hot enough, above 525°C the energy fro m that object will rad iate
energy in the visible spectrum. This is when we see an object like the burner on an electric stove “glowing” red. In
fact many times an object will emit or reflect energy in the same frequency of our eyes we will see it. All objects
emit a certain amount of b lack body radiat ion as a function of their temperatures. The higher an object’s temperature
is the more in frared radiation as black-body radiation it emits. A special camera can detect this radiation in a way
similar to an ordinary camera does visible light. It works even in total darkness because amb ient light level does not
matter. A thermal imaging camera is capable of processing algorithms to interpret that data and build an image.
Although the image shows the viewer an appro ximation of the temperature at which the object is operating, the
camera is actually using mu ltip le sources of data based on the areas surrounding the object to determine that value
rather than detecting the actual temperature.
Images fro m infrared cameras tend to have a single color channel because the cameras generally use a sens or that
does not distinguish different wavelengths of infrared rad iation. Co lor cameras require a more co mplex construction
to differentiate wavelength and color has less meaning outside of the normal visible spectrum because the differing
wavelengths do not map uniformly into the system of color vision used by humans. Sometimes these
monochromat ic images are displayed in pseudo-color, where changes in color are used rather than changes in
intensity to display changes in the signal. Th is is useful because although humans have much greater dynamic range
in intensity detection than color overall, the ability to see fine intensity differences in bright areas is fairly limited.
This technique is called density slicing .
3. BASICS OF INFRARED THERMAL IMAGING CAMERA
3.1The Fundamentals
Light detects by thermal imag ing camera and energy contain in a light wave depend on its wavelength. Energy
found in light is reciprocal to is wavelength. Colors are nothing but visible light. In colo rs, most energy is having
violet color and least energy having red color. In frared lights are the lights that are below red or darker than red that
cannot be seen by naked eye.
Volume: 1 Issue: 3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
3.2Types of Infrared Lights
There are three groups of infrared lights. They are as follows:Sr.No
I.
Types of infrared light
near infrared
Wavelength
0.7to 1.3 microns
II.
mid infrared
1.3 to 3 microns
III.
thermal infrared.
3 to 30 microns
Today, near infrared and mid infrared can be utilized in co mmon electronic devices such as electronics switches,
remote controls .
4. SIGNAL PROCESSING IN IR CAMERA
The principals' elements of thermal imager are[3] :
1. Image can form by the optical system using radiation in infrared wavelength range.
2. Thermal detector convert radiation into electrical signal which are falling on them.
3. So me system require scanning mechanism or some system not. Most of the time large detector array can be used
to completely cover the field of view of the imager.
4. Conversion of electrical signal into a video signal is done by an electronic processor and then visual image fro m
the video signal generated by display unit.
Fig 2: Block diagram of signal process in infrared camera
The above figure shows that processing of infrared signal from optical system to display.
4.1 Optical System
The design of optical system for visib le wavelength is same in thermal imager only difference is that different
materials are used. This is fact that 3-5m band or 8-14m band optical materials are different [4].
4.2Thermal Detectors
In camera, thermal detector is most important part. It is required to determine potential level of heat or thermal and
spatial resolution. Infrared thermal detectors are of two types [5].
1. Rising in the temperature due to IR radiation heating the detector element and after that triggering some
other physical mechanism that is taken as a measure of the radiat ion falling on the element. Th is detector
called as thermal detector.
2. To produce charge carriers which are generated across the detector element, it is necessary for photons,
which are the incident radiation, to interact at atomic or mo lecular level with the material of the detector. In
this mechanis m , electron always absorbing a photon and therefore quantum energy is moving fro m one
level to another. This detector called as a photon or quantum detector.
.
Volume: 1 Issue: 3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
Fig 3: cooled IR detectors
4.3 Scanning Mechanism
The image formed on detector element by the lens system which is move in well -controlled fashion. There are three
classes of scanner system as represented by one-dimensional (1D) oscillating mirror scanner arrangements. In the
first arrangement, space between optical system and the detector take place by scanner. In the next arrangement,
space between the external object and the image forming optical system take p lace by scanner and in the third
arrangement scanner is place between focal front end and image-forming back end of optical System.
For scanning IR image, one type of scanning mechanism is shown in figure below. In figure, there are two mirrors
with its respective motors and at the bottom of image there is IR lands with detector. There is one way to scan FOV
(field of view) by IR camera with single IR detector that is left mirror scans the vertical axis a nd right mirro r scans
the horizontal axis. Therefore, for scan all FOV (field of view) motor with mirror is used[6].
Fig 4: Scanning Mechanism
4.4 Displays
External display like co mputer screen or a small d isplay that forms part of the camera is required to view the image
generated by a thermal imager.LCD having flat screen, s mall and direct v iew display and it is a part of camera. It is
also used in eyepiece displays. Display may be monochro matic or colo r. To show temperature difference as color
difference, image can be color coded in latter case.
5. ADVANTAGES
5.1 Large Area
Large area is required for Thermography equipment to be assessed. Thermography use thermo-imaging equip ment
that allows seeing through smo ke, so it is used in firefighters. Thus, thermography provides safety innovation.
Thermography is a non-contact method[2]. It keeps user out of danger. Temperature can be eas ily measured for an
Volume: 1 Issue: 3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
object which is dangerous to get close to. Results are very useful to interpret because they obtain in image format
and images are used to extract information also.
5.2 Real Time
Thermography enables user to capture fast moving targets and also capture of fast changing thermal patterns of
objects. Thermal patterns can be visualized for analysis. Real time recording is done by a current thermography
technology. In various circu mstances, thermo -imaging is more useful[2]. In lu xury cars, automakers are including
live thermo imag ing technology. By using thermo imaging equip ment in vehicles, they help d rivers on the road and
also in parking.
5.3 Detecting Defects
For pipes and shafts that are built into homes, skyscrapers and building, in frared detection is used. To detect leaks in
pipes, thermographic cameras can be used in many construction companies for their h igh end project to ensure they
are repaired prior to fin ishing the project .Thermog raphy gives measurements in areas which is inaccessible or
hazardous for other methods.
6. DISADVANTAGES
6.1 Inaccurate Measurements
Infrared imaging can lead to misreading info rmation taken by the camera when temperature having very close range
and due to this objects can become indistinguishable. Thermal imaging technique can be applied to surface
temperatures.
6.2 Price
Thermo-imaging equip ment has a high price range. Cameras have a little bit accuracy. Due to their h igh cost, the
equipment is used by public services, large co mpanies or educational institutions only. Images are somewhat hard to
interpret even with experience.
7. APPLICATION
Thermography is widely used industry for predictive maintains quality assurance and forensic investigation of
electrical, mechanical and structural systems. There are many uses of thermal imaging photography. Some of wh ich
are
 Firefighting operations
 Military
 Law enforcement and anti-terrorism
 Automotive applications
 Roof inspection
 Medical imaging
 Night vision
 Medical field
 police target detection & acquisition
Volume: 1 Issue: 3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
9. CONCLUSION
Thermography enables us to see and measure heat. Th is method used thermal image for d isplay,detect and record
thermal patterns and temperatures across the surface of an object. In this paper, we studied the princip le of
thermography and how thermal image is processed in camera v ia optical system, thermal detectors, scanning
mechanis m and d isplay. The future focus on infrared thermography would be on more sensitive and fast IR cameras
together with powerfu l computers that make us possible to manage even more co mplex and efficient algorith ms and
larger data matrices. We conclude the topic by discussing wide area of application in Thermography along with their
advantages and disadvantages.
REFERENCES
[1] http://www.hungarianhistory.com/lib/sipka.doc
[2] www.wikipedia.co m
[3] T. L W illiams. An Introduction to Thermal Imaging, Thermal Imaging Cameras,.CRC Press, FL, 1st edition,
2009.
[4] P. Klocek. Handbook of infrared optical materials. Marcel Dekker, New York,1991.
[5] M. Henini and M Razeghi. Infrared: Detection technologies. Elsevier AdvancedTechnology, UK, 2002.
[6] J. Caniou. Passive Infrared Detection: Theory and applications. Kluwer AcademicPublisher, 1999.

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