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Enhancements in 4D Interferometry: A New Experimental Setup by Runa Briguglio

This study presents an innovative configuration of a 4D interferometer that mitigates convection and vibration noise, allowing for the precise acquisition of influence functions (IF) and the determination of KL modes. Key advancements include dynamic interferometry with high sensitivity, rapid external triggering, and improved data acquisition processes. We detail the software modifications and enhancements that support real-time measurements, continuous image sampling, and reliable data transfer. This novel setup is expected to significantly enhance alignment and phase detection capabilities.

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Enhancements in 4D Interferometry: A New Experimental Setup by Runa Briguglio

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  1. IF and KL measurementswith 4D interferometer Runa Briguglio, OAA

  2. Rationale New experimental set-up (4D+BCU39), that permits the reduction of convection and vibration noise. Acquisition of Influence Functions Determination of KL modes and testing

  3. Table of contents • 4D interferometer • Dinamic interferometry • High sensitivity • High speed external trigger • Improvements and tests • RamDisk • Software modifications • Trigger interface • Measurements • Exp. Set-up and connections • Acquisition procedure • IF: Zonal & Modal • KL

  4. 4D interferometer • Simultaneous phase shifting • No moving parts • No delay between frames • Single CCD for 0°,90°,180°,270° phases • High sensitivity • High density of fringes is detectable • Great help for alignment and first flattening • External trigger

  5. Burst acquisition:few points • Continous images sampling, 0.14Hz<F<28.5Hz • Data flow: • .raw • .cal • .h5 • External triggering • Programmable delay between trigger edge and capturing

  6. 1 Improvementspimp my 4D… • SW: Acquisition steps splitted Capture  .raw 28 Hz Process  .cal 9 Hz Reduce  .h5 1.2 Hz Independent sessions: Sampling -- Processing Faster capturing

  7. 2 Improvements • Data transfer to HD unreliable • RamDisk installed • Storage: 1600 frames, 0% faults …Depending on Frequency and n° of frames… No faults found at f<15Hz Ok for IF acquisition, at max freq.

  8. 3 Improvements • Testing: • GUI  scripting conflict • GUI commands reset the trigger settings • Ext trigger > Fmax is processed • ! Rising edges are detected after 1/28Hz • Internal delay verified • Using a sinchronized PZT • Repeatability better than 0.5ms

  9. 4 Improvements • Trigger interface converter • From BCU39 to 4D Interface BCU39 4D No delay, 200 us pulses 0-5V TTL Optic Fiber, 40MHz bus (25 ns pulses) TTL & Opto-coupled (TTL used)

  10. Sampling sessions Shapes AOWS WFS AdSec PhaseCam Fastlink1 BCU39 Start of Frame Interface TX 4D Trigger Sampling

  11. Timeline Time BCU39 AdSec 4D 0 20 40 ms A! Start of frame 12ms Start of frame Slopes to AdSec Slopes to AdSec Received commands Commands applied Oversampling period (5 ms) B! A! Trigger Trigger 8 ms Image acquisition 8 ms Image acquisition

  12. ! • A!: the image is captured Before the mode application The transient is not seen! We command a trefoil and 4 zero-shapes as starting point reference

  13. Starting trefoil +mode -mode +mode

  14. TriggerCommand TriggerCommand

  15. 1 Sampling procedure 0. connect & set-up • Connect HW • Set the shell • Configure BCU & 4D • Create a set of shapes (IF, MirModes, KL) • Start 4D acquisition (no action on trigger) • Enable the shapes sending • Commands to AdSec • Pulses to 4D interface 30 min 2 sec 2sec noise measurements

  16. 2 Sampling procedure 50sec 40sec 5 min 0. Commands applied by AdSec • +zeroes+starting trefoil… • Oversampling • Modes commands template: [1,-1,1] • Images are captured • ‘Move’ from RamDisk to HD • Download of command history from SDRAM Images ‘production’ (process+reduction:.dat .h5) Data analisys w/template: [1,-1,1] Analisys of electrical data 30min 20min 1 min

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