Fourier ptychographic microscopy is a recent imaging technique that overcomes the limitations of conventional optics. The images it produces are particularly fine and super-resolved. They are also very rich, since they are bimodal (intensity and phase images) compared with conventional microscopy. FPM therefore holds great promise for a whole range of medical applications.
In this work, the potential of this microscopy is explored by considering the biological application of automatic diagnosis of malaria on a stained blood smear. We report that an appreciable improvement in the classification of parasitized red blood cells is obtained when intensity and phase images are jointly exploited in a deep convolutionnal neural network, compared to that obtained with intensity images alone. We also show that such joint exploitation considerably relaxes the constraints relative to the choice of microscope objective. In particular, an objective lens with a numerical aperture as low as 0.2 can be used with little degradation in classification performance. The performances obtained are close to those obtained with a conventional resolution microscope equiped with a 0.9 numerical aperture objective. This can be highly desirable for the realization of rapid diagnostic system, which requires access to large fields of view.
The capability of measuring the spectral and temporal phase of an optical signal is of fundamental importance for the advanced characterization of photonic and optoelectronic components, biochemical sensors, structural monitoring sensors and distributed sensor networks. To address this problem, several techniques have been developed (frequency-resolved optical gating (FROG), spectral phase interferometry for direct electric-field reconstruction (SPIDER), stepped-heterodyne technique, laser Doppler vibrometry (LDV) and Doppler optical coherence tomography (OCT)). However, such techniques often lack of versatility for the mentioned applications. Swept-wavelength interferometric techniques and, among these, optical frequency-domain reflectometry (OFDR) are flexible and highly sensitive tools for complete characterization of amplitude and phase of target devices. In this work, we investigate the spectral and temporal phase measurement capabilities of OFDR. Precise characterization of spectral phase information is demonstrated by retrieving the phase response of a commercial optical filter, the Finisar Waveshaper 1000 S/X, programmable in attenuation and phase over C+L band (1530– 1625 nm). The presented results show accurate retrieval of group delay dispersion (GDD) and discrete phase shift as well as filter attenuation profile. Although some intrinsic accuracy limitations of OFDR phase measurements may be encountered (and herein specified), we show that information encoded in OFDR reflectogram data is very rich when adequately exploited. In addition to previously published results, we demonstrate the high sensitivity of the technique to Doppler effects. From practical point of view, such sensitivity can be beneficially exploited for the characterisation of dynamical aspects of samples under test. Unlike LDV, OFDR allows the simultaneous retrieval of the temporal position of several localised reflecting target along the beam path. All these aspects make OFDR a highly promising candidate for the study of both static and dynamic aspects of complex photonic components or to probe a parallel sensor network, as needed for future applications.
An electro-optically tunable erbium-doped fiber ring laser with a side mode suppression ratio of ~ 51.2 dB and a 0.062 nm linewidth is demonstrated. Wavelength tuning is achieved with a hybrid liquid crystal Solc structure used as an intracavity tunable filter. The laser wavelength is tuned over 28.6 nm with a tuning rate of 2.38 nm/V.
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