Kareem Nammari
Edward Nicholson
Kari Skupa
Wes Stanway
Cui Sun
1
This is a surveillance device that will use a laser
to pick up vibrations on a surface and convert
it to sound.
Cole
2




Use a laser to measure the vibration on a
surface.
Save and playback signal.
Be able to post process the signal.
Identify the audio source.
Cole
3
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

Covert Surveillance
Distance Measurements
Vibration Monitoring
Cole
4
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
Allows for long range surveillance
Difficult to detect
Needs stable environment
Alignment
Cole
5
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Relatively Cheap
Reliable Data
Hard to Detect
Established Market
Cole
6

Working laser based sound detector
◦ 45º Bounce System



Basic filtering
Data output over Serial
Terminal Control
Cole
7
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
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
Working Laser Sound Detector Using
Interferometry
Multiple Analog Filters
DSP
Serial I/O
◦ Terminal Control
◦ Serial Communication to Matlab
Cole
8


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Wireless Communication to Computer
Data Storage
LCD Display
On Box Options
◦ Fourier
◦ Filter Selection
◦ Output on Display
Cole
9

Why use an interferometer?
◦ Sensitive to small signals
◦ Perpendicular setup

Complications
◦ Phase difference between beams
◦ Coherence Length
Kareem
10
Kareem
11


To get a good signal at the sensor ΔL needs
to impart a phase shift in the laser beam of φ
radians.
φ must be such that the intensity of the
combined wave falls in one of the linear
regions of Cos(t)+Cos(t+φ).
Kareem
12
Kareem
13
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

Small signal leads to low distortion
Large signals will produce a frequency that is
a multiple of the original.
Differential measurement reduces distortions
Kareem
14
Kareem
15
Kareem
16
Kareem
17
Kareem
18
Interferometer
Laser
Detector
Optics
Analog
Filters
A/D
Converter
SPI
Microprocessor
Selector /
Mux
Audio
Amplifier
Memory
Software
Audio
Source
I/O
Audio Out
RS232
Hardware
Post Processing
POWER
+5 V
±15 V
Terminal
Matlab
+3.3V
Wes
19

Filters
◦ Minimum filtering is an anti-aliasing filter right
before the A/DC.



Audio Amplifier
Detector
A/D converter
Wes
20

Coherence

ΔL

Bandwidth small enough for ΔL
c
L 
n  f
Wes
21
Requirements
Silicon Diode
HeNe Gas Laser
DFB
Coherence Length
1-10nm
30cm
0.07-100m
Wavelength
375-2680nm
632nm
808-2000nm
Power
5V 100mA
1250V 4mA
3.2V 100mA
Cost
$3-30
$10-200
$50-1000
Size
Small Packages
Large Tubes
Small Packages
Wes
22


Range from Class 2 to Class 3B
Class 2
◦ Safe because of Blink Reflex (0.25 sec viewing)
◦ 400-800nm
◦ Limited to 2mW

Class 3B
◦
◦
◦
◦
Hazardous if exposed directly to eye
Diffused reflections are not harmful
315-2000nm
Limited to 0.5mW
Wes
23

Photodiodes
◦ Respond quickly to photons.
◦ Provide a very small current.

Phototransistors
◦ Respond slowly to photons.
◦ Provide a moderate current.
Wes
24


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Wall Wart (~20 Vdc @ 1 A)
Laser Driver
± 15 V
+5V
+ 3.3 V
Wes
25

A/D Converter
◦ Low resolution
◦ Separate chips

Serial I/O
◦ Terminal control
◦ Matlab communication

Memory
◦ Minimum capture rate of 44,100 samples per
second
◦ Flash may be too slow.
Kari
26

MSP430 series
◦
◦
◦
◦
◦
◦
◦
16-bit CPU
8-16 MHz CPU speed
Up to 256 kB of flash memory and 16 kB of RAM
Up to 80 I/O pins
Built-in ADC/DAC components
Low cost
Low power consumption
Kari
27

Resolution
◦ 8 to 10 bits of resolution for audio

SPI interface
◦ Two Way Communication
◦ High Speed
◦ Low Power
MCP3002 -
ADS1115 -
Kari
28
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
Play back recorded audio.
Matlab
◦ DSP
◦ FFT

Terminal
◦ I/O interface
◦ Debugging
Kari
29
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
Serial Communication
DSP
◦ Filtering Specific Frequencies

FFT
◦ Voice Identification
Kari
30

Conceptual
◦ Simulate Optics
◦ Proof of Concept in Optics Lab


Hardware
Software
Kari
31

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Window vibration in comparison to the
wavelength of the laser
Alignment and spacing of lasers and beam
splitter
Noise Filtering
Coherence length of lasers
Integration between Hardware and Software
Kari
32


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Time
Budget
Physics
Knowledge Base
Sun
33
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

Standard Components
Precise Alignment
RoHS Compliance Capable
Sun
34
Kari
Sun
Cole
Wes
Kareem
Software
Analog
Hardware
Software
Layout
Optics
Digital
Hardware
Optics
Digital
Hardware
Full Schematic
Analog
Hardware
Sound Box
Power
Sound Box
Power
Detector
Optics
Populate
Board
Populate
Board
Populate
Board
Budget
Sun
35
Sun
36
Block
Estimated Cost
Laser
$200
Optics
$400
PCBs
$100
Digital
Components
$150
Analog
Components
$200
Power
$100
Demo Box
$75
Expo Materials
$75
Total
$1300
Sun
37

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UROP $1000.00
Attempt DEPS funding
Personal donation $100 each
Donation/loans of equipment
Sun
38
Sun
39
40