“tunable filter tecnique :” a phase ambiguity solution with pyramid phasing sensor (pyps)
TRANSCRIPT
Technological development for the ELTs
ONE OF THE KEY ACTIVITIES: PHASING AND ALIGNMENT OF THE PRIMARY MIRROR SEGMENTS
ARE CORRECTEDSIMULTANEOUSLY
tiptilt
piston errorsof segmented mirror
Pyramid Wavefront Sensor: 2005
closed loop
PYramid Phasing Sensor (PYPS)Based on the sensing of phase step On the segment edges
!! !! limitation of signal ambiguity introduced by the phase periodicity
ambiguity
mirror surface step
wavelenght usedfor the sensing
PYPS signal
3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS
two wavelenght closed loop
wavelenght sweep tecnique (WST)
segment sweep tecnique (SST)
main task for an optical phasingmain task for an optical phasing sensor: to keep phased the segments sensor: to keep phased the segments during the observation during the observation PYPS
tip tilt piston errors correctionsimoultaneously
this has been done operating PYPS in closed loopsource nm
3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS
two wavelenght closed loop
wavelenght sweep tecnique (WST)
segment sweep tecnique (SST)
main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS
tip tilt piston errors correctionsimoultaneously
this has been done operating PYPS in closed loopsource nm
open loop mode:open loop mode:sine function 22] not phase ambiguity
closed loop mode:closed loop mode: extended to ] around sinus zeroin this range the function of sin is preserved!
- ++2-2 0
3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS
two wavelenght closed loop
wavelenght sweep tecnique (WST)
segment sweep tecnique (SST)
main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS
tip tilt piston errors correctionsimoultaneously
this has been done operating PYPS in closed loopsource nm
open loop mode:open loop mode:sine function 22] not phase ambiguity
closed loop mode:closed loop mode: extended to ] around sinus zeroin this range the function of sin is preserved!
- ++2-2 0
°
3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS
two wavelenght closed loop
wavelenght sweep tecnique (WST)
segment sweep tecnique (SST)
main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS
tip tilt piston errors correctionsimoultaneously
this has been done operating PYPS in closed loopsource nm
open loop mode:open loop mode:sine function 22] not phase ambiguity
closed loop mode:closed loop mode: extended to ] around sinus zeroin this range the function of sin is preserved!
- ++2-2 0
°°
3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS
two wavelenght closed loop
wavelenght sweep tecnique (WST)
segment sweep tecnique (SST)
main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS
tip tilt piston errors correctionsimoultaneously
this has been done operating PYPS in closed loopsource nm
open loop mode:open loop mode:sine function 22] not phase ambiguity
closed loop mode:closed loop mode: extended to ] around sinus zeroin this range the function of sin is preserved!
- ++2-2 0
°°
° The closed loop operation is able to drive the actuator to the same position(it works with iteraction process)
3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS
two wavelenght closed loop
wavelenght sweep tecnique (WST)
segment sweep tecnique (SST)
main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS
tip tilt piston errors correctionsimoultaneously
this has been done operating PYPS in closed loopsource nm
Interaction matrixReference acquisition
( required:FIRST FLAT )
in order to operate in closed loop mode:
To obtain the condition in order to employed PYPS in standard co-phasing tecnique
Piston error in +/-
New tecnique : NO C-LOOP
Wavelenght Sweep Tecnique Segment Sweep Tecnique
Calibration NOT required
-> Segment are driven in to 500nm range (accuracy)
-> Capture range +/-13 m
-> parallel procedure
-> hight accuracy
-> capture range infinite
-> one segment as referenceAnd sweeping the neightbors
C-loop calibration
FAST!!!
To obtain the condition in order to employed PYPS in standard co-phasing tecnique
Piston error in +/-
FIRST FLAT CO-PHASING
Wavelenght Sweep Tecnique Segment Sweep Tecnique
Calibration NOT required
-> Segment are driven in to 500nm range (accuracy)
-> Capture range +/-13 m
-> parallel procedure
-> hight accuracy
-> capture range infinite
-> one segment as referenceAnd sweeping the neightbors
C-loop calibration
First m
ethod
Second method
FIRST FLAT ACHIEVED!!!!
ABOUT WAVELENGHT SWEEP TECNIQUE
Based on piston signal dependence of the wavelenght
S = S(1/)
Mesuring signal for several value of
WE CAN FIT S(1/)
this mesurement gives an extimation of the physical step that lies on the considered sensor sub-aperture
WE CAN USE A TUNABLE FILTER
Liquid crystal tunable filter
Narrow-bandwith
Uses electronically controlled liquid crystal elements in a Lyot-type birefringent design to select a transmitted wavelenght range while blocking all others.
quartz
Glass substrate
Liqu
id c
ryst
al
Sheet polarizer
Lyot-type filter
VARYNG THE GAP SELECT
ff fTf +P f
ff 2
++
WORKING LIMITS
the capture range is defined by the resolution of the wavelength sweep.
T is suppose to be positive we found : 2|d |
f
Minimum step:
m ~ 500 nm
Maximum step:
M ~ 80 m
1
The expected values for Pf are: 0 when d >0 when d <0
...future project about this tecnique is in APE project and at the WHT collaborationwith the WHT group....
TUNABLE FILTERTUNABLE FILTER ELTsELTsCO-PHASINGCO-PHASING
““MAIN SCIENTIFIC CASES”MAIN SCIENTIFIC CASES”
...future project about this tecnique is in APE project and at the WHT collaborationwith the WHT group....
TUNABLE FILTERTUNABLE FILTER ELTsELTsCO-PHASINGCO-PHASING
““MAIN SCIENTIFIC CASES”MAIN SCIENTIFIC CASES”
Exo-Planetary Systems and evolution
...future project about this tecnique is in APE project and at the WHT collaborationwith the WHT group....
TUNABLE FILTERTUNABLE FILTER ELTsELTsCO-PHASINGCO-PHASING
““MAIN SCIENTIFIC CASES”MAIN SCIENTIFIC CASES”
Exo-Planetary Systems and evolution
Star Formation and Stellar Discs
Dark Matte and Dark Energy
Galaxies and Cosmology
GRBs
Black Holes , AGNand QSOs
THE UNEXPECTED…….THE UNEXPECTED…….