Post on 14-Feb-2016
description
OPEN-ATMOSPHERE PHASE-SHIFT CAVITY RINGDOWN INSTRUMENT
NOAA’S ARK
Michael TanksalvalaDmitriy Polyakov
Adam Ornstein Troy Owens
John Trytko
OVERVIEW 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
OBJECTIVES Low Level
Detect optical ringdown on breadboardAutomatic cavity length adjustmentSave data to memory
Mid-LevelDetect optical phase shiftAutomatic cavity alignmentTime stamped data saved to SD card
High LevelBuild self-contained unitRecreate faster-than-light neutrinosAutomatic beam profile correction
Dmitriy John Michael Adam Troy
MILESTONES Milestone 1
Show ringdown signal on oscilloscopeDemonstrate microcontroller-based beam-steering
and cavity length adjustmentSave sample string to SD card
Milestone 2Demonstrate phase shift detectorAutomated photo-diode signal maximizationCollect and save formatted data to SD card
Dmitriy John Michael Adam Troy
CAPSTONE EXPOSITION Demonstration 1
Show output of phase shift detector on oscilloscopePlace dry ice near cavity and show phase shift (voltage)
increaseRemove SD card and plot contained data in MATLAB
Demonstration 2Connect camera to monitor and photodiode to oscilloscopeManually misalign mirrors and watch automatic readjustment
Demonstration 3 (if possible)Insert SD card, turn on system, initiate data acquisitionPlace self-contained unit near dry iceTurn off system, take out SD card, plot data in MATLAB
Dmitriy John Michael Adam Troy
LASER SAFETY
Class 3b (continuous wave, 50 mW)Visible wavelengths (633 or 680 nm)High power/area (~200 mW/cm2)
PrecautionsNever look into laserDo not open testing area designated by curtainLaser safety signs will be posted
Dmitriy John Michael Adam Troy
FUNCTIONAL DECOMPOSITION
LEVEL 1 DESIGN
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.
Data StorageAnd User I/O
AutomaticAlignment
Atmosphere
User Input
SD Card
SD Card (Data) Clock Display
Optical Generation and Signal Detection
Dmitriy John Michael Adam Troy
LEVEL 2 DESIGN
ALGNRGB
OS
SD
Dmitriy John Michael Adam Troy
LEVEL 2 DESIGN (OPTICS)
Dmitriy John Michael Adam Troy
OPTICAL SYSTEM
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
OPTICAL MODULES 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
OPTICAL MODULES 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
OPTICAL MODULES (CONT) 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
LEVEL 2 DESIGN (ALIGNMENT)
ALGNRGB
Dmitriy John Michael Adam Troy
ACTIVE FEEDBACK/ALIGNMENT
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
ALIGNMENT MODULES CMOS Camera
Outputs NTSC Signal on single signal lineOutput must be separated into red, green, and blue
components 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
RGB
ALIGNMENT MODULES (CONT)
Microcontroller28 x Piccolo C200040-80 MHzReads pixel values from signal extractorThresholded average pinpoints beam locationPID Controller aims beam at desired locationSimpler algorithms maximize signal strength by
optimizing desired beam location.Manual interface to alter desired position and call
basic functionsJohn Dmitriy Michael Adam Troy
ALGN
ALIGNMENT SOFTWAREInitialization
John Dmitriy Michael Adam Troy
Photodiode (PD) Voltage >
(prev_volts * .9)?
Optimize Beam Position
Beam Missing PD?
Optimize Cavity Length
Beam Sweep
Optimize Beam Position
prev_volts = PD Voltage
Correct Beam Mode
NO
YES
YES
NO
ALIGNMENT SOFTWARE MODULES
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
ALIGNMENT SOFTWARE MODULES
Optimize Cavity LengthIncrease 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
LEVEL 2 DESIGN (OS)
ALGN
OS
SD
Dmitriy John Michael Adam Troy
OPERATING SYSTEM
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
DATA FLOW
ValidPhase Time
File Formatted SD Card
BufferSD Card LCD
AlignmentADC External Clock
collectData=START =!
STOP
START /STOP
Dmitriy John Michael Adam Troy
OPERATING SYSTEMInitialization
collectData == START ?
SD Buffer Empty?
Write to SD Card
NO YES
YES
NO
John Dmitriy Michael Adam Troy
New Data?
Write to SD Buffer
NO
SD Buffer Full?
Close File If Open
NO
YES
YES
Push Time to LCD
Scheduler
SD CARD
Contains files with gathered data Standardized portable memory FAT32 file system
John Dmitriy Michael Adam Troy
Image obtained from: http://alumni.cs.ucr.edu/~amitra/sdcard/Additional/sdcard_appnote_foust.pdf/
EXTERNAL CLOCK
AntennaReceives Atomic Clock Signal
ReceiverDecodes Antenna Signal
Microcontroller DecoderOutputs time in RS232
John Dmitriy Michael Adam Troy
Image obtained from: http://alumni.cs.ucr.edu/~amitra/sdcard/Additional/sdcard_appnote_foust.pdf/
USER I/O
InputsPower SwitchStart / Stop Button
OutputsLCD display – Time
○ Blinking – Not collecting dataGreen LED – WorkingRed LED – Error
John Dmitriy Michael Adam Troy
POWER SYSTEM
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
POTENTIAL ISSUES / CONTINGENCY PLANS 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
DIVISION OF LABORTask 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
SCHEDULE
John Dmitriy Michael Adam Troy
PARTS LIST
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
FUNDING AND GRANTS NOAA
Providing optical parts (mirrors, mounts, laser controller, optical breadboard, laser)
Will keep the prototype upon completion Additional Funding
Received $1,000 from UROPAny necessary additional money will be
gathered from generous donations from team members.
John Dmitriy Michael Adam Troy
QUESTIONS?
John Dmitriy Michael Adam Troy