Transcript Open-Atmosphere Phase

Michael Tanksalvala
Dmitriy Polyakov
Adam Ornstein
Troy Owens
John Trytko
The system measures the phase shift of light
to determine the concentration of particles in
the air (higher concentration yields greater
phase shift).
 This is used in conjunction with other
instruments to compute specific
concentrations of various aerosols.
 The project is being developed in
cooperation with the National Oceanic and
Atmospheric Administration (NOAA).

Dmitriy John Michael Adam Troy

Low Level
 Detect optical ringdown on breadboard
 Automatic cavity length adjustment
 Save data to memory

Mid-Level
 Detect optical phase shift
 Automatic cavity alignment
 Time stamped data saved to SD card

High Level
 Build self-contained unit
 Recreate faster-than-light neutrinos
 Automatic beam profile correction
Dmitriy John Michael Adam Troy

Milestone 1
 Show ringdown signal on oscilloscope
 Demonstrate microcontroller-based beam-steering
and cavity length adjustment
 Save sample string to SD card

Milestone 2
 Demonstrate phase shift detector
 Automated photo-diode signal maximization
 Collect and save formatted data to SD card
Dmitriy John Michael Adam Troy

Demonstration 1
 Show output of phase shift detector on oscilloscope
 Place dry ice near cavity and show phase shift (voltage)
increase
 Remove SD card and plot contained data in MATLAB

Demonstration 2
 Connect camera to monitor and photodiode to oscilloscope
 Manually misalign mirrors and watch automatic
readjustment

Demonstration 3 (if possible)
 Insert SD card, turn on system, initiate data acquisition
 Place self-contained unit near dry ice
 Turn off system, take out SD card, plot data in MATLAB
Dmitriy John Michael Adam Troy

Class 3b (continuous wave, 50 mW)
 Visible wavelengths (633 or 680 nm)
 High power/area (~200 mW/cm2)

Precautions
 Never look into laser
 Do not open testing area designated by curtain
 Laser safety signs will be posted
Dmitriy John Michael Adam Troy
Optical Generation
and Signal Detection
Atmosphere
User Input
SD Card
Data Storage
And User I/O
SD Card (Data)

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Automatic
Alignment
Clock Display
Measure and record phase shift over several hours.
Send the photodiode output to the phase shift detector
unit.
Output the camera data to alignment system.
Output phase shift data to the data storage system.
Alignment system directly controls mirrors.
Dmitriy John Michael Adam Troy
OS
R
G
B
ALGN
Dmitriy John Michael Adam Troy
SD
Dmitriy John Michael Adam Troy
Objective: Determine the concentration of
aerosol particles within the cavity.
 Optical system uses amplitude-modulated
laser signal within a cavity to determine the
phase shift the cavity introduces.
 Ringdown cavity simulates effective length of
several kilometers through the use of highly
reflective mirrors.

John Dmitriy Michael Adam Troy

Laser Controller
 Input: On if instrument is on.
 Output: Intensity modulated sine wave (~50 kHz) via laser
to cavity and initial phase shift signal to phase shift
detector.
 Testing: Modulating the laser at a low frequency (~1 Hz)
will be visible on a matte surface. Higher frequencies can
be verified with a photodiode and an oscilloscope.

Laser Cavity
 Resonates laser with two concave mirrors.
 Outputs ringdown signal to photodiode.
 Testing: Shine output into photodiode. Connect
photodiode to oscilloscope. Measure photodiode output
on scope, and look for a quick rise followed by an
exponential decay.
Dmitriy John Michael Adam Troy

Photodiode
 Input: Laser beam from ringdown cavity, 12 volt bias
voltage.
 Sensitive to both wavelengths we are considering (633,
680 nm)
 Output: current passed to phase shift detector.

Mirror mounts
 Front: 99.97% reflection, 0.01% transmission. Rear: .2% T
 Concave mirrors, 1 m focal length, 6.35 mm thick.
 Input: One 0-30 V signal per quadrant. To turn mirror to
the left, apply a positive voltage to the right two quadrants.
 Testing: Aim laser at mirror mount, with the reflection
hitting a far wall. Apply 0 V across one side of the piezo
and 30 V across the other. Watch for beam movement.
Dmitriy John Michael Adam Troy

Phase shift detector
 Integrates initial phase shift and final phase
shift.
 Input: Photodiode voltage, initial signal from
laser controller.
 Output: Voltage (representing phase shift) to
microcontroller.
Dmitriy John Michael Adam Troy
R
G
B
ALGN
Dmitriy John Michael Adam Troy
Objective: Maintain maximum signal power
 Keeps beam pointed at photodiode
 If signal is lost, methodically scans over area
to try to find it
 Concave mirrors provide small amount of
passive beam alignment
 Uses PID Controller to maintain beam
location

John Dmitriy Michael Adam Troy

CMOS Camera
 Outputs NTSC Signal on single signal line
 Output must be separated into red, green, and blue
components

R
G
B
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Signal Extractor
 Converts single-channel NTSC to three signals with
which the microcontroller and monitor can interface
 Implementation: a quadrature detector
Mirror Mount Voltage Amplifiers
 Input: Microcontroller voltage (0-5 V)
 Output: Mirror Mount voltage (0-30 V)
John Dmitriy Michael Adam Troy
ALGN

Microcontroller
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28 x Piccolo C2000
40-80 MHz
Reads pixel values from signal extractor
Thresholded average pinpoints beam location
PID Controller aims beam at desired location
Simpler algorithms maximize signal strength by
optimizing desired beam location.
 Manual interface to alter desired position and call
basic functions
John Dmitriy Michael Adam Troy
Initialization
Photodiode (PD) Voltage
>
(prev_volts * .9)?
Correct Beam Mode
Beam Missing PD?
Optimize Beam Position
Beam Sweep
Optimize Cavity Length
Optimize Beam Position
prev_volts = PD Voltage
John Dmitriy Michael Adam Troy

Correct Beam Mode
 Detect the positions of the most intense locations on the beam profile
 Use lookup table to correlate this to beam mode type and find solution
 Testing: Connect the camera output to a monitor. Manually induce
different beam modes by altering cavity length and alignment, run
function, and watch for the beam profile to turn Gaussian.

Optimize Beam Position
 Loop: Bump mirror 1 in last successful direction (end on failed_dir==4)
○ If photodiode voltage decreases, reverse the movement and increment
last successful direction and failed_dir. else, failed_dir = 0;
 Testing: Connect photodiode to multimeter. Point beam at photodiode
and run program. Watch for photodiode output increase.

Beam Sweep
 Move mirror 2 (coarse mirror) in grid pattern, searching for a photodiode
signal.
 Stop when signal is found.
 Testing: Connect photodiode output to multimeter. Turn beam away
from photodiode, run the function, and watch for the photodiode output
to increase.
John Dmitriy Michael Adam Troy

Optimize Cavity Length
 Increase voltage across all quadrants uniformly, searching
for a power maximum. If the function finds no oscillatory
behavior, the laser is misaligned. Call Beam Sweep.
 Testing: Manually adjust cavity alignment and length to get
good signal. Mess up alignment. Call function and watch
photodiode output increase.

Beam Missing PD?
 Goal: see if beam is pointed at photodiode.
 Essentially the same as Optimize Cavity Length, but alters
the cavity length minimally, to test for voltage fluctuations.
 If the voltage decreases in at least one direction, output
false.
John Dmitriy Michael Adam Troy
OS
ALGN
Dmitriy John Michael Adam Troy
SD
Objective: Store data to file in SD Card
 Reads Timestamp from atomic clock chip
 Measures phase shift as analog voltage
 Measures valid bit as analog voltage
 Stores these to comma-delimited text file

 <timestamp>,<phase>,<valid>
Dmitriy John Michael Adam Troy
ADC
Phase
Alignment
Valid
External Clock
Time
File
Formatted
SD Card
Buffer
Dmitriy John Michael Adam Troy
START
/STOP
collectData
=START
=!STOP
Initialization
Scheduler
Close File If Open
SD Buffer Empty?
Write to SD Card
collectData == START ?
SD Buffer Full?
New Data?
Write to SD Buffer
John Dmitriy Michael Adam Troy
Push Time to LCD
Contains files with gathered data
 Standardized portable memory
 FAT32 file system

Image obtained from: http://alumni.cs.ucr.edu/~amitra/sdcard/Additional/sdcard_appnote_foust.pdf/
John Dmitriy Michael Adam Troy

Antenna
 Receives Atomic Clock Signal

Receiver
 Decodes Antenna Signal

Microcontroller Decoder
 Outputs time in RS232
Image obtained from: http://alumni.cs.ucr.edu/~amitra/sdcard/Additional/sdcard_appnote_foust.pdf/
John Dmitriy Michael Adam Troy

Inputs
 Power Switch
 Start / Stop Button

Outputs
 LCD display – Time
○ Blinking – Not collecting data
 Green LED
 Red LED
– Working
– Error
John Dmitriy Michael Adam Troy
Laser Controller – 3 V, 50 mA
 Camera - DC 12 V, 50 mA
 Photodiode - 12 V, 50 mA
 Phase Shift Detector - 12 V, 50 mA
 Microcontroller (2x) - Core Supply: 3.3 Volts,
I/O Supply: 1.8 Volts
 Mirror Mount Voltage Amplifier – 30 V

John Dmitriy Michael Adam Troy

Phase shift detector doesn’t work
 Plan: Software alternative

Not able to integrate OS with optics
 Plan: demonstrate the systems separately at Expo

Beam size too large for camera to measure position
 Plan: Use quadrant detector

Beam power too low
 For photodiode: Right Bumper to pick up Spartan Laser
 For camera: Use quadrant detector

Complicated OS doesn’t work
 Plan: Use previously-developed simple OS

SD card Interface does not work
 Plan: save to onboard flash memory
John Dmitriy Michael Adam Troy
Task
Primary
Secondary
OS Design and Data Storage
Adam
Michael
Mechanical Structure/Alignment Dmitriy
John
Control Systems
Michael
Adam
Power System
Troy
Dmitriy
Board Layout/Construction
Troy, Michael
John
Optical Construction and
Detection
John, Troy,
Dmitriy
Design Documentation
All
Chief Financial Officer (CFO)
Michael
John Dmitriy Michael Adam Troy
John Dmitriy Michael Adam Troy
Equipment
Estimated Price
Acquired
Laser / Laser Controller
Borrowed from NOAA
Testing Version
Mirror Mounts/Mirrors
Borrowed from NOAA
No
Optical Breadboard
Borrowed from NOAA
Yes
5 x Photodiode
5 x $30
Testing Version
2 x Beam-Splitter
2 x $60
No
4 x MSP430
4 x $25
Testing Version
2 x CMOS Camera
2 x $35
Yes
3 x PCB
3 x $60
No
5 x Piezoelectric Buzzer
5 x $5
Yes
Conductive Glue
$20
No
Power Components
$50
No
2 x SD Sockets
2 x $5
No
SD Card
$10
No
Oscillator
$10
No
Final Project Poster
$50
No
Dry Ice
$50
No
Structure Materials
$100
No
Other (replacement parts, shipping, etc.)
$200
No
TOTAL
$1145
John Dmitriy Michael Adam Troy

NOAA
 Providing optical parts (mirrors, mounts,
laser controller, optical breadboard, laser)
 Will keep the prototype upon completion

Additional Funding
 Received $1,000 from UROP
 Any necessary additional money will be
gathered from generous donations from
team members.
John Dmitriy Michael Adam Troy
John Dmitriy Michael Adam Troy