Pietro Ferraro

Bio: Pietro Ferraro is an academic researcher from National Research Council. The author has contributed to research in topics: Digital holography & Holography. The author has an hindex of 61, co-authored 653 publications receiving 12666 citations. Previous affiliations of Pietro Ferraro include Aeritalia & Centre national de la recherche scientifique.

A pocket device for high-throughput optofluidic holographic microscopy

Abstract: Here we introduce a compact holographic microscope embedded onboard a Lab-on-a-Chip (LoC) platform. A wavefront division interferometer is realized by writing a polymer grating onto the channel to extract a reference wave from the object wave impinging the LoC. A portion of the beam reaches the samples flowing along the channel path, carrying their information content to the recording device, while one of the diffraction orders from the grating acts as an off-axis reference wave. Polymeric micro-lenses are delivered forward the chip by Pyro-ElectroHydroDynamic (Pyro-EHD) inkjet printing techniques. Thus, all the required optical components are embedded onboard a pocket device, and fast, non-iterative, reconstruction algorithms can be used. We use our device in combination with a novel high-throughput technique, named Space-Time Digital Holography (STDH). STDH exploits the samples motion inside microfluidic channels to obtain a synthetic hologram, mapped in a hybrid space-time domain, and with intrinsic useful features. Indeed, a single Linear Sensor Array (LSA) is sufficient to build up a synthetic representation of the entire experiment (i.e. the STDH) with unlimited Field of View (FoV) along the scanning direction, independently from the magnification factor. The throughput of the imaging system is dramatically increased as STDH provides unlimited FoV, refocusable imaging of samples inside the liquid volume with no need for hologram stitching. To test our embedded STDH microscopy module, we counted, imaged and tracked in 3D with high-throughput red blood cells moving inside the channel volume under non ideal flow conditions.

Non-Bayesian noise reduction methods in digital holography

Abstract: In digital holography, bayesian denoising approaches reduce the incoherent noise, but prior information are needed about the noise statistics. We propose and compare two strategies of holograms denoising without exploiting noise statistics.

Charge-driven dispensing of picolitre drops for biomolecules microarrays by Pyro-Electro-hydrodynamic system

Abstract: At present, most microfluidic technologies consist of microchannels where liquids are manipulated by changing pressures or electrode voltages but such systems suffer from different drawbacks such as complex fabrication, sample cross-contamination, high voltage or pressure requirements. Our work represents instead a new and simple system where the liquid actuation and dispensing has been achieved through electrode-free configurations using polar dielectric crystals such as lithium niobate (LN) and by exploiting the pyroelectric effect. This novel `Pyro-Electro-hydrodynamic' manipulation system could be used as a pioneering portable instrument for detecting in-situ even low concentrated analytes not detectable by traditional methods.

New method of 3D tracking of in vitro cells by digital holographic microscopy

Abstract: We propose a new strategy of three-dimensional (3D) tracking of living cells by digital holographic microscopy based on the morphological changes of cells during the migration. The typical strategy adopted in digital holography for the tracking of living cells consists into compute the 3D position dividing the calculation process into two parts: the estimation of the focal plane on the amplitude reconstruction of the digital holograms and the estimation of the transverse coordinates by the phase reconstruction of digital holograms computed at distance equal to the estimated focal plane. We propose to use an approximation of the Tamura coefficient, as image contrast measure, fo r the estimation of the focal plane and a new morphological operator, that is called minimum boundary filter (MBF), from which we compute the transverse coordinates. A comparison with other 3D tracking methods is accomplished. Keywords: Digital holographic microscopy, 3D tracking. 1. INTRODUCTION Many studies report on the ability of digital holography [1-8] to track particle, microorganism and cells [9-14] and there are several methodology to obtain the 3D positions. The typical strategy adopted in digital holography for the tracking of living cells consists into estimate the 3D position dividing the calculation process into two parts: the estimation of the focal plane (i.e. the Z coordinate along the optical axis of the imaging systems) on the amplitude reconstruction of the digital holograms [15,16], and the estimation of the transverse coordinates by the phase reconstruction of digital holograms computed at distance d equal to the estimated focal plane. About the estimation of the focal plane, several autofocus approaches were developed in digital holography for pure phase objects for live-cell imaging. These techniques are based on a suitable image contrast coefficients and perform a numer ical scanning of the focus. Instead the localization in the plane can be computed through different image segmentation methods. We propose a new strategy for both focal plane estimation and image segmentation. In particular, we propose to use an approximation of the Tamura coefficient, as image contrast measure, for the estimation of the in-focus distance. This metric has been applied successfully for the amplitude reconstructi on of digital holograms of macroscopic s cattering objects [17]. Instead, for the estimation of the transverse coordinates, we introduce a new morphological operator that we have called minimum boundary filter (MBF) [11]. This operator is robust with resp ect both noise and morphological variations of cells. In fact, the most popular image segmentation techniques used in th e holographic tracking methods introduce position estimation errors caused by these two aforementioned issues. Instead the MBF is built specifically to take into account the morphological changes during the cells migration. We test the proposed method in a typical situation for which extensive changes in cells morphology are associated to cells motion and we perform a comparison between other popular strategies.

Computer-generated hologram tailored for dielectrophoretic PDMS patterning

Abstract: Dielectrophoretic clustering is obtained both for liquid and solid matter thanks to light shaping performed by phase only Spatial Light Modulator (SLM). We present a procedure able to perform two functions: design polymeric stable structures usable as microfluidic channels and trapping micro objects. These two tasks are combined to realize a single device. The liquid matter is Polydimethylsiloxane (PDMS) and its patterning in microstructures is developed by means of photorefractive effect in a functionalized substrate. X-cut Iron-doped Lithium Niobate (LN) crystal is used as substrate while a thin film of PDMS is spin on it. When LN, covered by PDMS, is exposed to structured laser light, a space charge field arise that is able to induce self-patterning of the PDMS liquid film. The rearrangement of PDMS is due to the dielectrophoretic effect. Light structuring is achieved by a SLM positioned in the conjugated plane of the LN crystals. PDMS devices we realized are microfluidic channels. The first step of our procedure is the computing of a suitable Computer Generated Hologram (CGH) to be displayed by the SLM. An ideal target is designed and given as input to an Iterative Fourier Transform Algorithm (IFTA) to calculate the CGH. The IFTA used has been implemented for this particular application and it's tailored to generate a continuous light intensity profile in the LN plane. Then PDMS microstructures are cured to induce solidification. Such PDMS channels are then used to trap particles floating inside. Trapping is realized exploiting again dielectrophoresis induced by photorefractive effect. LN with PDMS channel is exposed to laser light which present, now, a periodic two-dimensional intensity profile. The charge distribution due to this second exposure is able to trap particle in the previously built channels. We realize a device with high degree of flexibility avoiding the need of moulds fabrication.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fiber grating sensors

Abstract: We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.