Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Synchronous phase-demodulation of concentric-rings Placido mires in
  corneal topography and wavefront aberrometry (theoretical considerations)   This paper presents a digital interferometric method to demodulate Placido
fringe patterns. This method uses a computer-stored conic-wavefront as
reference carrier. Even though, Placido mires are widely used in corneal
topographers. This is not however a paper on corneal topography and/or its
clinical use. This paper focuses on the theoretical aspects to phase-demodulate
Placido mires using synchronous interferometric techniques. Placido patterns
may also be applied to test optical wavefronts using a Placido-Hartmann opaque
plate with periodic annular apertures. This test is sensitive to the radial
slope of the measuring wavefront. Another wavefront testing approach may use a
Placido-Hartmann-Shack screen with a periodic array of toroidal lenslets. This
periodic screen is sensitive to the wavefront's radial-slope at the focal plane
of the lenslets. In brief, digital interferometric methods are herein applied
for the first time to demodulate conic-carrier Placido images. (Patent pending
at the USPTO).

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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ph
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The categories of this paper are: math
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph