This document introduces the field of electro-optical instrumentation and optical sensors. It discusses how optoelectronic sensing techniques are used in various sectors like aerospace, automotive, and biomedical. Some key measurement techniques discussed include telemetry, triangulation, interferometry, and velocimetry. The document provides examples of how these techniques are applied, such as using laser telemetry to measure the distance from Earth to the moon and using interferometry for high-precision measurements. Optical sensors are described as transducers that convert distance or other physical quantities into voltage or digital information.

1. G. Giuliani - OEINSTR - Intro 1
ELECTRO-OPTICAL
INSTRUMENTATION
Guido Giuliani
Università di Pavia
e-mail: guido.giuliani@unipv.it
Recommended textbook:
S. Donati, “'Electro-Optical
Instrumentation”, Prentice Hall, 2004

2. G. Giuliani - OEINSTR - Intro 2
Introduction
 Opto-electronic sensing techniques are curently applied to many sectors:
 Aerospace
 Automotive
 Mechanics
 Bio-medical
 Precision Industries
 Industrial manufacturing
 …
 Measurement Techniques
 Telemetry
 Triangulation
 Interferometry
 Velocimetry
 Giroscopy
 Fiber optic based…

3. G. Giuliani - OEINSTR - Intro 3
Optical sensor
 One single device
 Photodiode
 …
 A “small” optoelectronic instrument
 CONTENT:
 Optoelectronic devices (SC lasers, photodetectors, …)
 Electronic devices and circuit
 Optics (lenses, filters, beamsplitters, mirrors, …)
 Mechanics / Opto-mechanics
 I/O
 User’s point of view:
 It is a transducer
 Distance  Voltage (or digital information)
 ? Laser safety ?

4. G. Giuliani - OEINSTR - Intro 4
Optical Sensors / Instruments
 ADVANTAGES
 Non-contact operation
 Remote measurements (fiber optic sensors)
 Optical transducers do not suffer from electronic noise & interferences
 Price ?
 Integration ?
 High precision / accuracy / resolution
 Spatial resolution
 DISADVANTAGES
 Price ?
 Integration ?
 Not multi-purpose

5. G. Giuliani - OEINSTR - Intro 5
Telemetry vs. Triangulation
 TELEMETRY: measurement of the “time of flight” (TOF) of a light pulse
 TRIANGULATION: measurement of the position of a laser spot onto a focal plane
L = 2c

6. G. Giuliani - OEINSTR - Intro 6
TELEMETRY
 LURE (LUnar Ranging Experiment)
 carried out in 1970 when the astronauts of Apollo 11 brought on the moon an array
of corner-cubes (100 x 1” dia.) . Five telescopes on earth aimed the array with their
Qswitched ruby laser, launching a 0.5-J, 10-ns pulse. Three telescopes got the return,
a ≈10-photon pulse. The time-of-flight measurement translated into a distance
measured with an accuracy ≈30cm of the 384000 km baseline.

7. G. Giuliani - OEINSTR - Intro 7
TELEMETRY
 MOLA (Mars-Orbiter -Altimeter)
 In 1999, the MOLA of the Pathfinder mission has completed a 2-year survey of the
topography with 5-m height resolution on 100x100-m individual areas covering Mars

8. G. Giuliani - OEINSTR - Intro 8
TELEMETRY / LIDAR (Laser IDentification And
Ranging)
 Car anti-collision radar

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TELEMETRY / LIDAR (Laser IDentification And
Ranging)
 Self-driving car
Google car

10. G. Giuliani - OEINSTR - Intro 10
TRIANGULATION
Valve motion measurement for engine R&D

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TRIANGULATION
Valve motion measurement for engine R&D

12. G. Giuliani - OEINSTR - Intro 12
INTERFEROMETRY
 Interferometric techniques exploit the high temporal and spatial coherence of laser
light, to perform high-accuracy and high-resolution measurements
LASER
experiment
PHOTO-
DETECTOR
REFERENCE
ARM
MEASUREMENT
ARM
frequency
shifter
(optional)
E0
Em
Er
Iph
 
m r
/2 
/2
 
I
ph
I
r
 Light travels along two paths:
 Reference path (Er)
 Measurement path (E0  Em)
 The two beams produce an interference on
the photodetector: the output signal is a
periodic function of the difference between
the two pathlengths
 Iph =  Em+Er 2
=  Em exp im +Er exp ir 2
Iph = Em
2+Er
2+2EmEr Re{exp i(m-rIm +r+2(√ImIrcos(m-r
 It is possible to measure the relative phase difference that arises along the measuring
arm

13. G. Giuliani - OEINSTR - Intro 13
Interferometric Configurations
FD
LASER
Fixed mirror
50/50 BS
Moveable
mirror
FD 1
LASER
FD 2
measurand
LASER
FD
measurand
Michelson
Mach-Zehnder
Sagnac

14. G. Giuliani - OEINSTR - Intro 14
APPLICATIONS
VIBRA
TION
Analyzers
LASER
INTER
FER
O
METR
Y
scientific
uses
technical
uses
s1km
s
1OOm
s1m
s<1cm
INTERFEROM
ETERS for
MECHANICAL
METROLO
GY
DOPPLER
VELOCIMETERS
forANEMOMETR
Y
ESPI(SPECKLEPA
TTERN)
RLG andFOG
GYROSCOPES
avionics
industrial
uses
SPACETELEMETR
Yof
GEODETICSA
TELLITES
EARTHTIDES
SENSING
LARGESTRUCT
VIBROMETR
Y
METROLOGYof
LENGTH (andderived
quantities)
BIOLOGICAL
MOTILITY
SENSING
ACOUSTICEMISSION
and SA
WSENSING
GEODETIC
GRA
VIMETRY
GRA
VITA
TIONAL
ANTENNAS
OPTICALFIBER
SENSORS
OPTICS ELECTRO
NICS
W
AVEandFIELDS
TECHNOLOGY
MEASUR.SCIENCE