Size measurement of a pure phase object

K. Äit-Ameur; M. Fromager; M. Brunel

doi:10.1117/12.2052858

1 May 2014 Size measurement of a pure phase object

K. Äit-Ameur, M. Fromager, M. Brunel

Proceedings Volume 9132, Optical Micro- and Nanometrology V; 91320S (2014) https://doi.org/10.1117/12.2052858
Event: SPIE Photonics Europe, 2014, Brussels, Belgium

Abstract

The detection of a transparent object is a technical challenge since phase objects yield only poor contrast if they are imaged on an intensity basis. For performing quantitative measurement the image contrast has to be enhanced. For that, we can exploit additional information on phase or polarisation modifications of the laser probe beam (LPB) crossing through the phase object. We propose a simple method for determining the size of a transparent object based on the reshaping of a laser probe beam which is initially Gaussian in shape. For a given ratio between the size of the incident beam and that of the phase object, the diffracted laser probe beam is transformed in the far-field region into a hollow beam. The detection of the intensity dip in the beam centre is made with a simple photodiode. In practice, the spatial reshaping of the LPB is monitored through the resulting changes in the power transmitted by a pinhole and a stop (opaque disk) set in the far-field of the phase object under study. For convenience, the latter in the experiment is realised by a Spatial Light Modulator (SLM: Holoeye Pluto-NIR). We have considered the influence of various parameters which are the lateral and longitudinal sizes of the phase object, and the pinhole and the stop distances from the phase object under study. The experiment has demonstrated the feasibility of our method and can be extended for the detection of microscopic phase objects. The potential of the proposed technique for quantifying the nanoscale change of the phase object under study could be very useful to study the morphology dynamics of living cells membrane which represents the biophysical properties and health state of the cell.

Citation Download Citation

K. Äit-Ameur, M. Fromager, and M. Brunel "Size measurement of a pure phase object", Proc. SPIE 9132, Optical Micro- and Nanometrology V, 91320S (1 May 2014); https://doi.org/10.1117/12.2052858

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