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Showing papers by "Javier Garcia published in 2008"


Journal ArticleDOI
TL;DR: An approach that allows superresolution imaging of three-dimensional (3-D) samples by numerical refocusing is presented in the field of digital holographic microscopy and a time multiplexing superresolved approach to overcome the Abbe's diffraction limit is presented.
Abstract: An approach that allows superresolution imaging of three-dimensional (3-D) samples by numerical refocusing is presented in the field of digital holographic microscopy. Based on the object’s spectrum shift produced by tilted illumination, we present a time multiplexing superresolved approach to overcome the Abbe’s diffraction limit. The proposed approach uses a microscope in a Mach-Zehnder interferometric architecture with the particularity that the output plane does not coincide with the image plane. Thus, a set of off-axis non-image plane holograms are sequentially recorded for every tilted beam used in the illumination stage. After that and by using simple digital post-processing and numerical reconstruction, a 3-D superresolved sample volume is reconstructed slice-by-slice in terms of the definition of a synthetic aperture (SA) that expands the cutoff frequency of the microscope lens. Experimental results showing the capabilities of the proposed approach are presented.

124 citations


Journal ArticleDOI
TL;DR: In this article, an experimental setup useful for complex amplitude evaluation and phase image quantification of three-dimensional (3-D) samples in digital holographic microscopy (DHM) is presented.

84 citations


Journal ArticleDOI
TL;DR: A novel approach for three-dimensional measurements that includes the projection of coherent light through ground glass that generates random speckle patterns on the object or on the camera, depending if the configuration is transmissive or reflective.
Abstract: We present a novel approach for three-dimensional (3D) measurements that includes the projection of coherent light through ground glass. Such a projection generates random speckle patterns on the object or on the camera, depending if the configuration is transmissive or reflective. In both cases the spatially random patterns are seen by the sensor. Different spatially random patterns are generated at different planes. The patterns are highly random and not correlated. This low correlation between different patterns is used for both 3D mapping of objects and range finding.

78 citations


Journal ArticleDOI
01 Nov 2008
TL;DR: In this article, the use of projected speckle patterns coming from a phase random mask for sensing depths and thicknesses is presented, which is used for mapping thickness of transparent media, for depth ranging and for 3D mapping of diffuse objects.
Abstract: In this communication we present the use of projected speckle patterns coming from a phase random mask for sensing depths and thicknesses. The sensing is based on the change of the speckle pattern with propagation and the lack of correlation between speckle patterns recorded at different depths or lateral locations. The principle is used for mapping thickness of transparent media, for depth ranging and for 3D mapping of diffuse objects.

28 citations


Journal ArticleDOI
TL;DR: A new approach to achieve transverse superresolution in far-field imaging systems, with direct application in both digital microscopy and digital holographic microscopy, is presented.
Abstract: The ability to improve the limited resolving power of optical imaging systems while approaching the theoretical diffraction limit has been an attractive discipline with growing interest over the last years due to its benefits in many applied optics systems. This paper presents a new approach to achieve transverse superresolution in far-field imaging systems, with direct application in both digital microscopy and digital holographic microscopy. Theoretical analysis and computer simulations show the validity of the presented approach.

19 citations


Journal ArticleDOI
TL;DR: The key idea for not paying with the field of view is to use white light illumination to average the ghost images obtained outside the region of interest since the positions of those images are wavelength dependent.
Abstract: The usage of two static gratings for obtaining super-resolved imaging dates back to the work by Bachl and Lukosz in 1967. However, in their approach a severe reduction in the field of view was the necessary condition for improving the resolution. We present an approach based on two static gratings without sacrificing the field of view. The key idea for not paying with the field of view is to use white light illumination to average the ghost images obtained outside the region of interest since the positions of those images are wavelength dependent. Moreover, large magnification is achieved by using a commercial microscope objective instead of a test system with a unity magnification as presented in previous works. Because of the large magnification, the second grating has a low spatial period. This allows us to create an intermediate image and use a second imaging lens with low resolution capability while still obtaining an imaging quality as good as that provided by the first imaging lens. This is an important improvement in comparison with the original super-resolving method with two fixed gratings.

18 citations


Journal ArticleDOI
TL;DR: This work uses water drops in order to improve the resolving capabilities of an imaging system using a time-multiplexing approach and shows experimentally how they are used to superresolve the contour of moving targets passing in front of them.
Abstract: We present two approaches that use the environmental conditions in order to exceed the classical Abbe's limit of resolution of an aperture-limited imaging system. At first we use water drops in order to improve the resolving capabilities of an imaging system using a time-multiplexing approach. The limit for the resolution improvement capabilities is equal to the size of the rain drops. The rain drops falling close to the imaged object act as a sparse and random high-resolution mask attached to it. By applying proper image processing, the center of each falling drop is located, and the parameters of the encoding grating are extracted from the captured set of images. The decoding is done digitally by applying the same mask and time averaging. In many cases urban environment includes periodic or other high-resolution objects such as fences. Actually urban environment includes many objects of this type since from an engineering point of view they are considered appealing. Those objects follow well known standards, and therefore their structure can be a priori known even without being fully capable of imaging them. We show experimentally how we use such objects in order to superresolve the contour of moving targets passing in front of them.

18 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented an experimental validation of the fact that the generation of a synthetic aperture improves not only the lateral resolution but also the axial one, which is possible to achieve higher optical sectioning of three-dimensional (3D) objects than that defined by the theoretical resolution limit imposed by diffraction.
Abstract: The use of tilted illumination onto the input object in combination with time multiplexing is a useful technique to overcome the Abbe diffraction limit in imaging systems. It is based on the generation of an expanded synthetic aperture that improves the cutoff frequency (and thus the resolution limit) of the imaging system. In this paper we present an experimental validation of the fact that the generation of a synthetic aperture improves not only the lateral resolution but also the axial one. Thus, it is possible to achieve higher optical sectioning of three-dimensional (3D) objects than that defined by the theoretical resolution limit imposed by diffraction. Experimental results are provided for two different cases: a synthetic object (micrometer slide) imaged by a 0.14 numerical aperture (NA) microscope lens, and a biosample (swine sperm cells) imaged by a 0.42 NA objective.

15 citations


Journal ArticleDOI
TL;DR: Experimental evidence of hyperbolic patterns in a nonlinear optical resonator, characterized by a distribution of the active modes along hyperbolas in the transverse wave-vector domain, in contrast with the usual (elliptic) patterns where theactive modes distribute along rings.
Abstract: We give experimental evidence of hyperbolic patterns in a nonlinear optical resonator. Such transverse patterns are a new kind of 2D dissipative structures, characterized by a distribution of the active modes along hyperbolas in the transverse wave-vector domain, in contrast with the usual (elliptic) patterns where the active modes distribute along rings. The hyperbolic character is realized by manipulating diffraction inside the optical resonator with cylindrical lenses. We also investigate theoretically hyperbolic patterns in corresponding Swift-Hohenberg models.

11 citations


Journal ArticleDOI
TL;DR: Two approaches for extracting the surface profile as well as obtaining 3D imaging of near field objects by usage of partial coherence and digital holography are presented.
Abstract: In this paper we present two approaches for extracting the surface profile as well as obtaining 3D imaging of near field objects by usage of partial coherence and digital holography. In the first approach a light source with given temporal partial coherence is used to illuminate a near field object. The reflected light is interfered with the reference source. By computing the local contrast of the generated fringes one may estimate the 3D topography and the profile of the object. This approach extracts the 3D information from a single image, and its accuracy does not depend on triangulation angle like in fringe projection methods. The second approach is tomography based. There we illuminate the object from several slightly different angles, and for each we compute the wrapped phase using digital holography techniques. Combining the wrapped phase estimation from several points of projection allows calculating the unwrapped phase and therefore the true profile of even a phase-only object. Increasing the number of points of view decreases the relative error of the estimated profile.

6 citations


Journal ArticleDOI
TL;DR: In this paper, a random pinhole array plate is attached to the aperture plane of the imaging system to obtain super resolved images with extended depth-of-focus (DOF).

Proceedings ArticleDOI
23 Apr 2008
TL;DR: A new approach aimed to achieve superresolution in digital holographic microscopy that overcomes the limitations imposed by the Abbe's diffraction limit is presented, based on time multiplexing and off-axis illumination, and a common-path interferometric architecture.
Abstract: In this contribution, we present a new approach aimed to achieve superresolution in digital holographic microscopy that overcomes the limitations imposed by the Abbe's diffraction limit. Based on time multiplexing and off-axis illumination, a common-path interferometric architecture allows the synthesis of an enlarged aperture that expands the cutoff frequency of the conventional imaging system. Complex object amplitude distribution is recovered using an extremely simple phase-shifting configuration instead of image plane off-axis holographic recording. As a consequence, the setup becomes easy-to-configure (less requirements and lower number of optical elements) and it is useful for practical implementation in microscopes while only simple modifications are required (no higher magnifications are needed to resolve the interference pattern at the CCD plane). Experimental results validating the capabilities of the presented approach when a low numerical aperture commercial microscope objective is used as imaging lens are included using both a synthetic object (high resolution USAF test target) and a biosample (red blood cells) as objects under test.

Proceedings ArticleDOI
17 Mar 2008
TL;DR: Two approaches for 3D imaging are presented that use partial coherence of the light source and the unwrapped phase is computed by illuminating the object from several slightly different angles.
Abstract: Two approaches for 3D imaging are presented. At first we use partial coherence of the light source and in the second we compute the unwrapped phase by illuminating the object from several slightly different angles.

Proceedings ArticleDOI
24 Apr 2008
TL;DR: In this paper, an approach that can be used for transmission of 2D spatial information through space-limited systems such as a single mode fiber (SMF) capable of transmitting only a single spatial pixel is presented.
Abstract: In this paper we present an approach that can be used for transmission of 2‐D spatial information through space‐limited systems such as a single mode fiber (SMF) capable of transmitting only a single spatial pixel. The input 2‐D object is illuminated with temporally incoherent illumination. The axial coherence length is very short and it equals only a few microns. Attached to the input object spatial random phase mask generates different axial shift for every pixel of the input. The temporal delays of the encoding (axial shifts) of every pixel are longer than the coherence length of the illuminating source. Therefore no temporal correlation exists between the various pixels of the input. A lens combines all spatial pixels into one point at its focal plane. The light is coupled into an SMF and is transmitted to a short distance. Although the various spatial pixels were mixed together, since the random mask provided axial delay which was larger than the coherence length of the light source, the orthogonalit...

Journal ArticleDOI
01 Nov 2008
TL;DR: In this paper, the authors present two approaches that are also based upon two static gratings but without the need to sacrifice in the field-of-view (FOV) by using white light illumination that averages the ghost images obtained outside the region of interest.
Abstract: The usage of two static gratings for obtaining super resolved imaging dates back to the work by Bachl and Lukosz in 1967. However, in that approach, a severe reduction in the field of view was the necessary condition for improving the resolution. In this paper we present two approaches that are also based upon two static gratings but without the need to sacrifice in the field of view. The key idea for not paying with the field of view is performed in two ways: First, by using white light illumination that averages the ghost images obtained outside the region of interest since the positions of those images are wavelength dependent. Second, by using two random functions for the encoding and the decoding of the spatial information instead of using the spatially periodic gratings.