This document discusses various applications of lasers for optical alignment and tooling. It explains that lasers provide higher brightness than conventional light sources, making them visible from long distances. Both helium-neon and semiconductor diode lasers have been used for tooling applications such as determining displacement and establishing angles. Laser tooling requires only one operator and provides more consistent measurements between operators compared to conventional optical tooling.

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412 PHYS
Lasers and their Applications
Department of Physics
Faculty of Science
Jazan University
KSA
laser applications
Lecture-10
Optical Alignment ----”Optical tooling”
Low-power lasers provide considerably higher radiance for tooling applications than conventional
light sources. They are easily visible in ambient lighting conditions even at distances of hundreds
of feet from the laser. Lasers have been specifically designed for tooling applications, and these
are sometimes called "tooling lasers."
Laser tooling involves the use of the unidirectional beam for such tasks as determining
displacement of objects from a line, determining angular alignment, establishing planes,
performing leveling, and establishing right angles. Both helium-neon and semiconductor diode
lasers have been used for this applications
Many practical alignment systems employ a laser and a centering detector that
automatically determines the location of the center of the beam.
Laser tooling requires only one person to set up and operate the equipment. The
measurement is made by reading linear displacement directly from a meter. The
readings compare well for different operators. This is in contrast to conventional
optical tooling, wherein a single operator may be able to obtain reproducible
readings, but different operators may arrive at different results.

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Angle Tracking
A laser source illuminates a target. Light reflected by the target is imaged on the
detector. Angular information about the target is derived from the known position
sensitivity of the detector as indicated in figure below.
The angle α between the incoming rays and the optical axis common to the objective
and the detector is given as
where y is the lateral displacement of the
image from the centerline of the detector
and f is the focal length of the lens. For
small values of a, less than 5o this may be
approximated by
Confocal setup for surface
metrology. The pinhole is replaced
by a micro-lens array to cover a
large field of view.
Laser Scanning Applications
Laser triangulation setup

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Dr. M Fadhali - Laser applications
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6/14/2015 Dr. M Fadhali - Laser applications
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6/14/2015 Dr. M Fadhali - Laser applications
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Laser Metrology - Interferometry
Basic Interferometry and Optical Testing
1. Two-Beam Interference
2. Fizeau Interferometer
3. Twyman-Green Interferometer
4. Laser-Based Fizeau Interferometer
5. Mach-Zehnder Interferometer
Holography
An ordinary photograph represents a two-dimensional recording of a threedimensional
scene. The emulsion on the photographic plate is sensitive only to the
intensity variations, and hence while a photograph is recorded, the phase distribution
which prevailed at the plane of the photograph is lost. Since only the intensity
pattern has been recorded, the three-dimensional character (e.g., parallax) of the
object scene is lost.
It was in the year 1948 that Dennis Gabor conceived of an entirely new
idea and proposed a method of recording not only the amplitude but also
the phase of the wave
The principle behind the method is the following: During the recording
process, one superimposes on the wave (emanating from the object) another
coherent wave called the reference wave
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The two waves interfere in the plane of the recording medium and produce
interference fringes.
This is known as the recording process. The interference fringes are characteristic
of the object and the recording medium records the intensity distribution in the
interference pattern.
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This interference pattern has recorded in it not only the
amplitude distribution but also the plane of the object wave.
Reconstruction
Process
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Holography
eye
reconstructed
image
reconstruction
beam
diffracted
reference beam
hologram
LASER
Hologram (photographic
plate)
reference beam
beam
expander
BS objec
t
illuminating
beam
photographic
plate
object
illuminating
beam
eye
2D representation of
image (no depth)
photograph
Photography - record electric field intensity of light scattered by object
Holography - record electric field intensity and phase
RECORDING READING / RECONSTRUCTING
Holographic One-Way Window
• Large hologram of a window display
masks the interior

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• Indoor environments have controllable optical environments
• Holography may provide a way to disguise or mislead intruders
Door With Edge
Illuminated Hologram

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Infrared Holography
• Infrared holography is appealing because viewing devices are much
less sophisticated than the human eye
• Color fidelity is much less important
• no such holograms exist nor do the materials to make them
Example
holography

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Laser Ring Gyroscopes
Lasers can be used to measure angular rotation with great accuracy and precision.
Commercially available laser based gyroscopes are currently used in both aircraft
and shipping with single or triple axis devices used for orientation and stabilization.
Laser gyroscopes have number of advantages over more conventional gyros such as :
· there are no moving parts
· simple design , generally less than 20 component parts
· very rugged , vibration g and g2 insensitive
· wide dynamic range (>109)
· output is inherently digital and TTL compatible
· fast update rate , less than 50ms to measure a rotation of 0.5o/hour
· long and reliable lifetime (>30,000 hours)
· low total cost of ownership , “fit and forget”, no maintenance

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It applies quite generally to any path with an
enclosed area A and perimeter S.
(This is often referred to as the Sagnac effect:
Sagnac successfully demonstrated a rotating
ring interferometer in 1913).
The basic equation used for angular rotation
rate measurement.
S
A
Sc
A
f

 



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Applications:
• Navigation
• Geophysics
• Relativity
• Symmetry testing
• Quantum Field Theory
Example: Frequency shift in a ring laser gyro
Let us calculate the frequency shift corresponding to a rotation rate of 0.1° h-1 in a
triangle with 0.1 m side length assuming l = 632.8 nm.
The area of the triangle is (√3 x 10-2)/4 m2
S
A
Sc
A
f

 



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Sol.

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Laser-Induced Fusion
It is well known that the enormous energy released from the sun and the stars is
due to thermonuclear fusion reactions, and scientists have been working for over 40
years to devise methods to generate fusion energy in a controlled manner. Once this
is achieved, one will have an almost inexhaustible supply of relatively pollutionf-ree
energy.
A thermonuclear reactor based on laser-induced fusion offers great
promise for the future. With the tremendous effort being expended on fabrication
of extremely high-power lasers, the goal appears to be not too far away, and once
it is practically achieved, it would lead to the most important application of the
laser.
Consider a nuclear reaction in which the two deuterons react to form a tritium
nucleus and a proton:

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The basic principle of pulsed laser range finding is shown in Figure 1. A short laser
pulse is sent out from a source directed to the target. Coincident with the emission of
this pulse a clock is started and, when the pulse is reflected from the target and returned
to a detector, the clock is stopped. The time for the round trip journey may be used to
calculate the distance to the target given that the speed of light is a known constant :
Military Applications
Given that the ranging pulse travels at the speed of
light, high speed timing will be required and the
shorter the range, or the smaller the error tolerance,
the more accurate the timing circuitry will need to
be. As an example take a target 100km distant. The
time of flight of the pulse will be approximately,
Timing Measurements

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