Showing papers by "Javier Garcia published in 2010"
TL;DR: A method capable of improving the resolution in a digital lensless Fourier holographic configuration based on synthetic aperture (SA) generation by using time-multiplexing tilted illumination onto the input object is presented.
Abstract: The resolving power of an imaging system in digital lensless Fourier holographic configuration is mainly limited by the numerical aperture of the experimental setup that is defined by both the restricted CCD size and the presence of a beam splitter cube in front of the CCD. We present a method capable of improving the resolution in such a system configuration based on synthetic aperture (SA) generation by using time-multiplexing tilted illumination onto the input object. Moreover, a priori knowledge about the imaged object allows customized SA shaping by the addition of elementary apertures only in the directions of interest. Experimental results are provided, showing agreement with theoretical predictions and demonstrating a resolution limit corresponding with a synthetic numerical aperture value of 0.45.
98 citations
TL;DR: A novel technique based on tracking both temporal and amplitude changes of reflected secondary speckle produced in human skin when illuminated by a laser beam is presented, showing good agreement when compared with conventional measurement methods.
Abstract: We present a novel technique for remote noncontact blood pulse pressure measurement. It is based on tracking both temporal and amplitude changes of reflected secondary speckle produced in human skin when illuminated by a laser beam. The implemented technique extracts the difference between the systolic and the diastolic blood pressure. Experimental results are presented showing good agreement when compared with conventional measurement methods.
71 citations
TL;DR: Experimental results perfectly correlate with the results obtained by conventional digital holographic microscopy (DHM), where no moving elements are included.
Abstract: A new method for recovery the quantitative phase information of microscopic samples is presented. It is based on a spatial light modulator (SLM) and digital image processing as key elements to extract the sample’s phase distribution. By displaying a set of lenses with different focal power, the SLM produces a set of defocused images of the input sample at the CCD plane. Such recorded images are then numerically processed to retrieve phase information. This iterative process is based on the wave propagation equation and leads on a complex amplitude image containing information of both amplitude and phase distributions of the input sample diffracted wave front. The proposed configuration is a non-interferometric architecture (conventional transmission imaging mode) where no moving elements are included. Experimental results perfectly correlate with the results obtained by conventional digital holographic microscopy (DHM).
65 citations
TL;DR: A novel method for observing sub-wavelength features in a conventional optical microscope using linear optics based on a random and time varying flow of nanoparticles moving in proximity to the inspected sample is presented.
Abstract: Classically, optical systems are considered to have a fundamental resolution limit due to wave nature of light. This article presents a novel method for observing sub-wavelength features in a conventional optical microscope using linear optics. The operation principle is based on a random and time varying flow of nanoparticles moving in proximity to the inspected sample. Those particles excite the evanescent waves and couple them into harmonic waves. The sub-wavelength features are encoded and later on digitally decoded by proper image processing of a sequence of images. The achievable final resolution limit corresponds to the size of the nanoparticles. Experimental proof of principle validation of the technique is reported.
43 citations
TL;DR: An approach capable of high-NA imaging in a lensless digital in-line holographic microscopy layout even outside the Gabor's regime is presented, based on spatial multiplexing at the sample plane, allowing a common-path interferometric architecture.
Abstract: We present an approach capable of high-NA imaging in a lensless digital in-line holographic microscopy layout even outside the Gabor’s regime. The method is based on spatial multiplexing at the sample plane, allowing a common-path interferometric architecture, where two interferometric beams are generated by a spatial light modulator (SLM) prior to illuminating the sample. The SLM allows phase-shifting interferometry by phase modulation of the SLM diffracted beam. After proper digital processing, the complex amplitude distribution of the diffracted object wavefront is recovered and numerically propagated to image the sample. Experimental results are reported that validate the proposed method.
34 citations
TL;DR: A novel approach is presented in which the scenery containing obscured objects which the authors wish to classify, recognize or identify is illuminated by spatially coherent beam and therefore secondary speckles pattern is reflected from the objects.
18 citations
TL;DR: A new approach capable of working under coherent and incoherent illumination for achieving superresolution by random coding of the object's angular information by placing two static random masks in optically conjugate planes inside an aperture-limited imaging setup is presented.
Abstract: In this paper, we present a new approach capable of working under coherent and incoherent illumination for achieving superresolution by random coding of the object's angular information. By placing two static random masks in optically conjugate planes inside an aperture-limited imaging setup, one may obtain a transmitted image containing spatial resolution higher than the one obtained without the masks. As the most noticeable fact, the superresolution effect is obtained without imposing any restrictions either in the time domain or in the field-of-view domain but rather only in the dynamic range of the camera device. Experimental verifications for the proposed technique with incoherent illumination with a low numerical aperture (NA) lens are presented.
18 citations
TL;DR: In this article, a modified Gabor-like setup where a condenser lens and a spatial light modulator (SLM) are inserted in a classical Gabor configuration is presented.
Abstract: A new lensless microscopy method able to recover the complex wavefront diffracted by a sample from a set of inline recorded holograms is presented. It is based on a modified Gabor-like setup where a condenser lens and a spatial light modulator (SLM) are inserted in a classical Gabor configuration. The condenser lens provides the sample's spectrum at the system Fourier plane while the SLM allows phase shifting modulation of the central spot (DC term) of the sample's spectrum. As consequence, the proposed imaging system recovers the complex amplitude distribution of the diffracted sample wavefront without an additional reference beam. Experimental results validate the proposed method and expand the Gabor method applicability beyond cases of weak diffraction assumption.
15 citations
TL;DR: A method for depth sensing based on sensing the visibility associated with the coherence function of a laser source with experimental results validate the proposed approach for reflective diffuse objects at different measurement distances.
4 citations
TL;DR: A signal processing approach is presented for improving the quality of the recording and then for classifying the characteristics of the recordings done using a newly developed optical technology.
Abstract: A newly developed optical technology for remote recording of voice signal was recently demonstrated. In this paper we present a signal processing approach for improving the quality of the recording and then for classifying the characteristics of the recording done using this system. In both cases the proposed signal processing operations are applied over the spectrogram of the optically recorded signals.
3 citations
01 Feb 2010
TL;DR: In this paper, an encoding-decoding process of various spatial pixels or regions in the field of view of the imaged object by orthogonal and differently time varying polarization states is presented.
Abstract: In this paper we present a new approach allowing the surpassing of the diffraction based limitation for the achievable resolution provided by imaging systems It is based on an encoding-decoding process of various spatial pixels or regions in the field of view of the imaged object by orthogonal and differently time varying polarization states The reconstruction of the original spatial information is obtained by applying a decoding process in a way similar to the encoding one Although all the spatial information is summed and mixed together by the system, the decoding provides super resolved imaging since in every spatial position the undesired spatial information having time varying polarization dependence, that is uncorrelated to the decoding sequence applied on that specific spatial position, is averaged to zero and, on the other hand, the information which corresponds to that specific spatial region is being reinforced The proposed approach can be used not only for super resolved imaging but also for imaging module that maintains the same spatial resolution while providing enlarged field of view
TL;DR: In this article, an encoding-decoding process of various spatial pixels or regions in the field of view of the imaged object by orthogonal and differently time varying polarization states is presented.
01 Jan 2010
TL;DR: In this paper, an encoding-decoding process of various spatial pixels or regions in the field of view of the imaged object by orthogonal and differently time-varying polarization states is presented.
Abstract: In this paper, we present a new approach allowing the surpassing of the diffraction-based limitation for the achievable resolution provided by imaging systems. It is based on an encoding–decoding process of various spatial pixels or regions in the field of view of the imaged object by orthogonal and differently time-varying polarization states. The reconstruction of the original spatial information is obtained by applying a decoding process in a way similar to the encoding one. Although all the spatial information is summed and mixed together by the system, the decoding provides super-resolved imaging since in every spatial position the undesired spatial information having time-varying polarization dependence, which is uncorrelated to the decoding sequence applied on that specific spatial position, is averaged to zero and, on the other hand, the information which corresponds to that specific spatial region is being reinforced. The proposed approach can be used not only for super-resolved imaging but also for imaging module that maintains the same spatial resolution while providing enlarged field of view.