Thesis Defense Presentation

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Progress on Target Tracking Engagement
Demonstration
Presented by Lane Carlson1 M. Tillack1, T.
Lorentz1, J. Spalding1 N. Alexander2, G. Flint2,
D. Goodin2, R. Petzoldt2 (1UCSD, 2General
Atomics) HAPL Project Review General Atomics,
San Diego, CA August 8-9, 2006
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Review of Target Engagement Requirements

• Final Key Requirement
• 20 µm engagement accuracy in (x,y,z) at 20 m
  (10-6)

• Goals of this integrated demonstration
• Purpose To individually demonstrate successful
  table-top experiments of key elements,
  then integrate together.
• Final goal Provide a hit-on-the-fly target
  engagement demo meeting accuracy
  requirements.

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We are demonstrating an integrated target
engagement demo on the bench-top

• Poisson spot, fringe counting, crossing sensors,
  verification
• Provide in-flight steering instructions
  diagnostic, backup.
• Glint coincidence sensor
• Aligns beamlets provides final steering
  instructions

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Time sequence of tracking engagement demo -
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Time sequence - END
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Significant progress on individual systems in
support of hit-on-the-fly demo

• Three-fold speed improvement in Poisson spot
  centroiding algorithm.
• Using the fringe counters new telecom laser,
  characterized transverse robustness of the
  system.
• Set up real-time, on-the-fly target axial
  position prediction system using crossing
  sensors, accurate to 45 µm (1?).
• A verification system has been developed to
  confirm accurate target engagement for the
  hit-on-the-fly demo.
• We have used a glint return signal to steer a
  simulated driver beam with a fast steering mirror.

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A range of tracking/engagement scenarios call for
different requirements
Example 2 (less-stringent final mirror reqs, 200
µm post-Glint steering) in-flight mirror
corrections by Poisson, fringe counter
Example 1 (more-stringent final mirror reqs) no
in-chamber gas, glint provides final mirror
steering
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1 Transverse Target Tracking Using Poisson Spot
Centroid
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New hardware centroiding algorithm have yielded
a 3-fold speed increase

• Goal is to know centroid position to 5 µm every
  5 ms
• We have improved update rate from 25 ms to 10
  ms.
• New 1000 fps camera centroiding algorithm
  employ contrast thresholding techniques while
  maintaining lt 5 µm (1?) precision.

4mm sphere on translation stage
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New algorithm captures image computes centroid
with lt 5 µm repeatability (1? stationary target)
6) X,Y centroid computed with lt 5 µm error (1?)
1 ms
gt Target position update rate 10 ms
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Reduced region of interest (ROI) technique
further increases update rate

• Improved from 25 ms to 10 ms simply by using new
  thresholding technique
• A smaller ROI reduces number of pixels to
  process, substantially increasing speed.
• partial implementation of a dynamic ROI has
  reduced update time to 7 ms.

• Centroid is currently computed in software for
  ease of revision.
• Continually improving the centroiding algorithm
  integrating into the tracking system.

4mm sphere on translation stage
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2 Axial Target Tracking Using Interferometic
Fringe Counting
J. Spalding poster
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Fringe counting is still being pursued but may be
superceded by less-complex crossing sensors
Similar intensities

• Using new, stable laser, characterized transverse
  target sensitivity (100 µm.)
• A Michelson interferometer has proved to be more
  sensitive than initially anticipated.
• Without a glint system, we need distance to 10-6
  precision from zero crossing sensor.
• a Michelson interferometer is a good choice for
  this.

JDSU 1.54 µm telecom laser

• With glint system providing final steering
  correction, required axial tracking precision is
  reduced to 10-4.
• gt Two simple crossing sensors can do the job.

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3 Crossing Sensors Axial Position Prediction
T. Lorentz poster
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Crossing sensors real-time operating system
compute predicted target location on-the-fly

• Previous repeatability of 40 µm (1?) after
  post-processing.
• C1 provides zero-crossing, C1-C2 determine
  velocity, C3 verifies accurate timing
  prediction.
• New real-time operating system reports on-the-fly
  placement repeatability of 45 µm (1?) at C3.
• gt Sufficiently precise to trigger glint laser

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4 Target Engagement Verification for
Hit-on-the-fly Demo
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We devised a system to verify accurate target
engagement for our hit-on-the-fly demo

• Provides confirmation of accurate FSM steering
  target engagement.
• Pulses simulated driver beam and takes snapshot
  of target engagement.

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Camera position sensitive detector (PSD) verify
accurate target engagement to 1 µm
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5 Glint System Coincidence Sensor
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The glint system provides final position update
closes the beam steering loop
1) Fast steering mirror keeps alignment beam
centered in the coincidence sensor. 2) Glint
return provides error between alignment beam
actual target position 1-2 ms before chamber
center. 3) Error signal provides final
correction to FSM.
Optics In Motion fast steering mirror
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We have used a glint return signal on a PSD to
redirect a simulated driver beam with a fast
steering mirror

• For this demo, we use one CW laser for both glint
  alignment/driver beams.
• Chopper wheel alternates glint beam
  alignment/driver beam on the PSD.
• Translated target provides a moving glint return.
• Fast steering mirror redirects driver beam to
  coincide with glint return.

Retroreflector
Tracking accuracy 18 µm with 8 ms response time
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Summary of progress plans - continue
integrating subsystems into a combined demo
1 Transverse Tracking System Using Poisson
Spot Progress Improved update rate to 10
ms Plans Implement reduced region of interest
for even faster update rate 2 Axial Tracking
System Using Fringe Counting Progress
Characterized transverse sensitivity using new
telecom laser Plans Continue pursuit to
increase standoff robustness 3 Crossing
Sensors Triggering Prediction Progress
On-the-fly target location prediction
repeatability 45 µm (1?) Plans Trigger glint,
simulated driver beam verification camera 4
Target Engagement Verification Progress
Successfully demonstrated verification system
Plans Implement fast steering mirror take a
snapshot to verify engagement of an
in-flight target 5 Glint System Coincidence
Sensor Progress Successful demo with 18 µm
(1?) alignment 8 ms response Plans Implement
pulsed glint laser FSM to engage in-flight
target
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We hope you can stay for a tour of our lab
Glint system
Verification system
Integration table
In-flight target steering
Target injection