Use of a Digital Micromirror Array as a Configurable Mask in

Optical Astronomy

Shawn Gilliam

Advisor: Dr. William HetheringtonResearch Associate: Teal Pershing

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DMA Apparatus

• 12” Cassegrain Telescope• Digital Micromirror Array• Charge Coupled Device

DMA

CCD

Telescope

Lens

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Zoomed

Optical Transfer Function

ℱ \{ 𝐼 𝑖(𝑋 ,𝑌 )}ℱ { 𝐼𝑜 (𝑥 , 𝑦 )

=ℱ {𝑝𝑠𝑓 (𝑥 , 𝑦 ) }

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Coronagraph

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Lyot Stop Aperture Masking Interferometry

Primary

Secondary

Tertiary

Aperture Mask

Bold black represents the section of the primary mirror that is passed through the system.

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• Backlit holes in black cardboard with 0.5 cm separation, at 10 m.

• Angular separation of 100 ±20 arcseconds.

Dim Center Star

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• Pixels of a monitor, configured to a separation of 0.216 mm at 13 m.

• Angular separation of 3.4 ±0.1 arcseconds.

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• LED’s, one much brighter than the other, placed 0.4 cm apart at 40 m.

• Angular separation of 25 ±5 arcseconds.

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0 100 200 300 400 500 6000

50

100

150

200

250

300

Unmasked Masked

Position (pixels)

Phot

on C

ount

Saturation

Peak

Profile plot across image at x = 370

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Other Achievements

• Fourier Transform Lab used in PH 481.• Fresnel Zone Plate Mask Designs.

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Conclusion

• The DMA Apparatus is a useful tool for optical astronomy.

• Angular resolution of 3.4 ±0.1 arcseconds.• Light from bright sources can be reduced.

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Future Directions

• Construct a workable apparatus that can be used for night viewing.

• Obtain a complete description of the Optical Transfer Function.

• Incorporate a variety of masking techniques.

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References

• [1] “Robust Coronagraphy with an APP.” [Online]. Available: http://home.strw.leidenuniv.nl/~kenworthy/research/app/. [Accessed: 04-Jun-2012].

• [2] Wikipedia contributors, “Coronagraph,” Wikipedia, the free encyclopedia. Wikimedia Foundation, Inc., 16-May-2012.

• [3] “DLP System Optics” Application Report DLPA022, Texas Instruments, July 2010.• [4] Wikipedia contributors, “Speckle imaging,” Wikipedia, the free encyclopedia.

Wikimedia Foundation, Inc., 17-Mar-2012.• [5] “Presentation of the DLP Technology: Presentation part-one.” [Online]. Available:

http://us.generation-nt.com/technology-dlp-video-projector-digital-light-processing-review-42606-2.html [Accessed: 05-Jun-2012].

• [6] “Mimir Photo Archives – 20021217.” [Online]. Available: http://people.bu.edu/clemens/mimir/Photo_Archive_Pages/20021217.html [Accessed: 05-Jun-2012].

• [1]“APOD: 2008 January 11 - Polaris Dust Nebula.” [Online]. Available: http://apod.nasa.gov/apod/ap080111.html. [Accessed: 11-Jun-2012].

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ANY QUESTIONS?

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Fourier Transforms

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Fresnel Zone Plate

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f f/3

f < f/3 f/7