33 research outputs found
Detection of Gravitational Lenses and Measurement of Time Delays from Classical Electromagnetic Radiation Fluctuations
I suggest that measurements of intensity fluctuations caused by classical
wave interactions can be used to find unresolved gravitational lenses and
determine time delays of essentially arbitrary length among the images formed
by a gravitational lens. No interferometry i s needed, the time delays can be
measured by analyzing the intensity signal alone. The technique works with
lensed sources that have constant luminosities and is capable of measuring very
long time delays. I suggest interferometric techniques, capable of measuring
time delays of arbitrary length, that can be used to refine the measurements.Comment: To appear in Monthly Notices Roy. Astr. Soc., Postscript file, 18
double spaced page
A magnetic liquid deformable mirror for high stroke and low order axially symmetrical aberrations
We present a new class of magnetically shaped deformable liquid mirrors made
of a magnetic liquid (ferrofluid). Deformable liquid mirrors offer advantages
with respect to deformable solid mirrors: large deformations, low costs and the
possibility of very large mirrors with added aberration control. They have some
disadvantages (e.g. slower response time). We made and tested a deformable
mirror, producing axially symmetrical wavefront aberrations by applying
electric currents to 5 concentric coils made of copper wire wound on aluminum
cylinders. Each of these coils generates a magnetic field which combines to
deform the surface of a ferrofluid to the desired shape. We have carried out
laboratory tests on a 5 cm diameter prototype mirror and demonstrated defocus
as well as Seidel and Zernike spherical aberrations having amplitudes up to 20
microns, which was the limiting measurable amplitude of our equipmentComment: To appear in Optics Expres