We report the simulation of an adaptive interferometric
null test using a high-definition phase-only spatial light
modulator (SLM) to measure form and mid spatial frequencies
of a freeform mirror with a sag departure of 150 μm
from its base sphere. A state-of-the-art commercial SLM
is modeled as a reconfigurable phase computer generated
hologram (CGH) that generates a nulling phase function
with close to an order of magnitude higher amplitude than
deformable mirrors. The theoretical uncertainty in form
measurement arising from pixelation and phase quantization
of the SLM is 50.62 nm RMS. The calibration requirements
for hardware implementation are detailed. © 2019
Optical Society of America
https://doi.org/10.1364/OL.44.002000
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Implementation of a null test for freeform optics using a high-definition spatial light modulator
We report the implementation of an interferometric null test using a high-definition spatial light modulator (SLM) as a reconfigurable alternative to a computer-generated hologram. We detail the alignment process chain, including novel techniques using the SLM to project alignment fiducials on the test part. To validate the alignment protocol, we measure a mild off-axis conic with the SLM-based system and cross-validate with conventional interferometry within 30 nm root-mean-square (RMS) surface figure. Finally, we report the null test of a 65 mm clear aperture concave freeform with 91 μm peak-valley sag departure from the base sphere. The measured surface figure of the freeform is within 40 nm RMS compared to the measurement with a commercial metrology instrument.
more » « less- NSF-PAR ID:
- 10380539
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 30
- Issue:
- 24
- ISSN:
- 1094-4087; OPEXFF
- Page Range / eLocation ID:
- Article No. 43938
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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