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Phase discontinuity sensing: a method for phasing segmented mirrors in the infrared.

G Chanan¹, M Troy, E Sirko

¹Department of Physics and Astronomy, University of California, Irvine, California 92697, USA.

|February 29, 2008

Summary

A new method called phase discontinuity sensing (PDS) precisely aligns segmented optics. This technique significantly reduces mirror errors, improving telescope performance for infrared astronomy.

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Area of Science:

Optical Engineering
Astronomy
Telescope Technology

Background:

Segmented optics are crucial for large telescopes, but precise alignment (phasing) is challenging.
Previous phasing methods required dedicated instruments or complex procedures.
Accurate phasing is essential for achieving optimal image quality and scientific output.

Purpose of the Study:

To introduce a novel, efficient method for phasing segmented optical systems.
To validate the effectiveness of the phase discontinuity sensing (PDS) algorithm.
To confirm the accuracy and reliability of the PDS phasing technique.

Main Methods:

Utilized the difference between inside-of-focus and outside-of-focus infrared images as the phasing signal.
Developed a detailed algorithm correlating difference images with theoretical templates.
Tested the phase discontinuity sensing (PDS) algorithm at the Keck 1 telescope at a 3.3-micrometer wavelength.

Main Results:

Successfully reduced root-mean-square (rms) piston error from approximately 240 nm to 40 nm or less.
Achieved consistent phasing solutions across multiple tests with the Keck 1 primary mirror segments.
PDS results aligned with previous phasing camera measurements (within 66-nm rms).

Conclusions:

The phase discontinuity sensing (PDS) algorithm provides a highly effective method for phasing segmented optics.
This technique offers significant improvements in precision and efficiency for telescope alignment.
PDS results independently confirm the validity of prior phasing approaches.