Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Defocusing microscopy with an arbitrary size for the aperture of the
  objective lens   The theoretical approach to describe the defocusing microscopy technique by
U. Agero et al. [Phys. Rev. E {\bf 67}, 051904 (2003)] assumes that the size of
the objective lens aperture is infinite. This treatment gives that the
intensity at the image plane depends on the laplacian of the phase introduced
in the field by a pure phase object. In the present paper, we consider an
arbitrary size for the aperture of the objective lens and we conclude that the
intensity at the image plane depends also on the gradient of the phase
introduced by the object and the phase itself. In this case, even an object
that introduces only linear variations in the phase can be detected.
Furthermore, we show that the contrast of the image of the phase object
increases with the use of smaller objective apertures.

25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat