Use of a Digital Micromirror Array as a Configurable Mask in
Optical Astronomy
Shawn Gilliam
Advisor: Dr. William HetheringtonResearch Associate: Teal Pershing
2
DMA Apparatus
• 12” Cassegrain Telescope• Digital Micromirror Array• Charge Coupled Device
DMA
CCD
Telescope
Lens
3
Zoomed
Optical Transfer Function
ℱ \{ 𝐼 𝑖(𝑋 ,𝑌 )}ℱ { 𝐼𝑜 (𝑥 , 𝑦 )
=ℱ {𝑝𝑠𝑓 (𝑥 , 𝑦 ) }
4
Coronagraph
5
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.
6
• Backlit holes in black cardboard with 0.5 cm separation, at 10 m.
• Angular separation of 100 ±20 arcseconds.
Dim Center Star
7
• Pixels of a monitor, configured to a separation of 0.216 mm at 13 m.
• Angular separation of 3.4 ±0.1 arcseconds.
8
• LED’s, one much brighter than the other, placed 0.4 cm apart at 40 m.
• Angular separation of 25 ±5 arcseconds.
9
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
10
Other Achievements
• Fourier Transform Lab used in PH 481.• Fresnel Zone Plate Mask Designs.
11
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.
12
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.
13
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].
14
ANY QUESTIONS?
15
Fourier Transforms
16
Fresnel Zone Plate
17
•
f f/3
f < f/3 f/7