Method for simultaneous amplitude and quantitative phase contrast imaging by numerical reconstruction of digital holograms

A method for simultaneous amplitude and quantitative phase contrast imaging of a specimen by numerical reconstruction of a digital hologram of the specimen comprising the following steps:

• a) providing a hologram of the specimen using an illumination source, wherein the hologram of the specimen results from interference between two waves issued from the illumination source, one of the two waves, named an object wave, having interacted with the specimen, and another of the two waves, called a reference wave, having not interacted with the specimen;
• b) acquiring an image of the hologram by an image acquisition system;
• c) digitizing the image of the hologram by an image digitizer in order to produce the digital hologram;
• d) transmitting the digital hologram to a computer or to a processor;
• e) determining and defining a first group of reconstruction parameters as a reconstruction distance;
• f) computing a digital reconstructed wavefront in an observation plane by computation of a diffraction pattern of the digital hologram, wherein said computing the digital reconstructed wavefront step is performed by a numerical calculation of an integral describing a diffraction of waves in a scalar approximation and wherein a distance between a hologram plane and the observation plane is given by the reconstruction distance;
• g) determining and defining an analytical expression of the reference wave and determining and defining a second group of reconstruction parameters as reference wave parameters;
• h) computing a first array of complex numbers as a digital reference wave, wherein said computing the first array of complex numbers step is performed on a basis of the analytical expression of the reference wave and on a basis of the reference wave parameters;
• i) computing a multiplication of the digital reconstructed wavefront in the observation plane and the digital reference wave in order to correct a phase distortion induced by the reference wave in the observation plane to provide a digital corrected reconstructed wavefront in the observation plane;
• j) determining and defining an analytical expression of a phase aberration and determining and defining a third group of reconstruction parameters as aberration correction parameters;
• k) computing a second array of complex numbers as a digital phase mask which represents a complex conjugate of a phase aberration function in the observation plane, said computing the second array of complex numbers step being performed on a basis of the analytical expression of the phase aberration and on a basis of the aberration correction parameters;
• l) digitally correcting the phase aberration by computation of multiplication between the digital reconstructed wavefront in the observation plane and the digital phase mask in order to obtain the digital corrected reconstructed wavefront in the observation plane;
• m) computing a square of a modulus of the digital corrected reconstructed wavefront in the observation plane in order to obtain an amplitude contrast image of the specimen;
• n) computing an argument of the digital corrected reconstructed wavefront in the observation plane in order to obtain a quantitative phase contrast image of the specimen;
• and
• o) adjusting the reconstruction parameters comprising adjusting of:
• the reconstruction distance, the reference wave parameters, and the aberration correction parameters.