Jorge Garcia-Sucerquia

Digital in-line holographic microscopy

We first briefly review the state of the art of digital in-line holographic microscopy (DIHM) with numerical reconstruction and then discuss some technical issues, such as lateral and depth resolution, depth of field, twin image, four-dimensional tracking, and reconstruction algorithm. We then present a host of examples from microfluidics and biology of tracking the motion of spheres, algae, and bacteria. Finally, we introduce an underwater version of DIHM that is suitable for in situ studies in an ocean environment that show the motion of various plankton species.

Immersion digital in-line holographic microscopy.

Digital in-line holographic microscopy is a promising new tool for high resolution imaging. We demonstrate, by using latex beads, that a considerable increase in numerical aperture, and, therefore, resolution can be achieved if the space between a source and a CCD camera chip is filled with a high refractive index medium. The high refractive index medium implies a shorter effective wavelength so that submicrometer resolution can be obtained with laser light in the visible range.

Submersible digital in-line holographic microscope

Few instruments exist that can image microscopic marine organisms in their natural environment so that their locomotion mechanisms, feeding habits, and interactions with surfaces, such as biofouling, can be investigated in situ. We describe here the design and performance of a simple submersible digital in-line holographic microscope that can image organisms and their motion with micron resolution and that can be deployed from small vessels. Holograms and reconstructed images of several microscopic aquatic organisms were successfully obtained down to a depth of 20m. Important microscope characteristics such as the effect of camera pixel size on lateral and depth resolutions as well as the maximum sample volume that can be imaged with a given resolution are discussed in detail.

Color lensless digital holographic microscopy with micrometer resolution

Color digital lensless holographic microscopy with micrometer resolution is presented. Multiwavelength illumination of a biological sample and a posteriori color composition of the amplitude images individually reconstructed are used to obtain full-color representation of the microscopic specimen. To match the sizes of the reconstructed holograms for each wavelength, a reconstruction algorithm that allows for choosing the pixel size at the reconstruction plane independently of the wavelength and the reconstruction distance is used. The method is illustrated with experimental results.

Magnified reconstruction of digitally recorded holograms by Fresnel–Bluestein transform

A method for numerical reconstruction of digitally recorded holograms with variable magnification is presented. The proposed strategy allows for smaller, equal, or larger magnification than that achieved with Fresnel transform by introducing the Bluestein substitution into the Fresnel kernel. The magnification is obtained independent of distance, wavelength, and number of pixels, which enables the method to be applied in color digital holography and metrological applications. The approach is supported by experimental and simulation results in digital holography of objects of comparable dimensions with the recording device and in the reconstruction of holograms from digital in-line holographic microscopy.

Automatic three-dimensional tracking of particles with high-numerical-aperture digital lensless holographic microscopy

We present an automatic procedure for 3D tracking of micrometer-sized particles with high-NA digital lensless holographic microscopy. The method uses a two-feature approach to search for the best focal planes and to distinguish particles from artifacts or other elements on the reconstructed stream of the holograms. A set of reconstructed images is axially projected onto a single image. From the projected image, the centers of mass of all the reconstructed elements are identified. Starting from the centers of mass, the morphology of the profile of the maximum intensity along the reconstruction direction allows for the distinguishing of particles from others elements. The method is tested with modeled holograms and applied to automatically track micrometer-sized bubbles in a sample of 4 mm3 of soda.

Spatial coherence wavelets: Mathematical properties and physical features

Abstract This paper discusses a set of mathematical and physical properties regarding spatial coherence wavelets, a concept recently developed by Castaiieda and Garcia-Sucerquia. Some of these properties are inherited from the Wigner distribution function. The uncertainty principle that they obey, the superposition of uncorrelated spatial coherence wavelets and the effective diffraction aperture, are discussed.

Electromagnetic spatial coherence wavelets

The recently introduced concept of spatial coherence wavelets is generalized to describe the propagation of electromagnetic fields in the free space. For this aim, the spatial coherence wavelet tensor is introduced as an elementary amount, in terms of which the formerly known quantities for this domain can be expressed. It allows for the analysis of the relationship between the spatial coherence properties and the polarization state of the electromagnetic wave. This approach is completely consistent with the recently introduced unified theory of coherence and polarization for random electromagnetic beams, but it provides further insight about the causal relationship between the polarization states at different planes along the propagation path.

Accurate single-shot quantitative phase imaging of biological specimens with telecentric digital holographic microscopy

Abstract. The advantages of using a telecentric imaging system in digital holographic microscopy (DHM) to study biological specimens are highlighted. To this end, the performances of nontelecentric DHM and telecentric DHM are evaluated from the quantitative phase imaging (QPI) point of view. The evaluated stability of the microscope allows single-shot QPI in DHM by using telecentric imaging systems. Quantitative phase maps of a section of the head of the drosophila melanogaster fly and of red blood cells are obtained via single-shot DHM with no numerical postprocessing. With these maps we show that the use of telecentric DHM provides larger field of view for a given magnification and permits more accurate QPI measurements with less number of computational operations.

Off-axis digital holographic microscopy: practical design parameters for operating at diffraction limit

The utilization of microscope objectives (MOs) in digital holographic microscopy (DHM) has associated effects that are not present in conventional optical microscopy. The remaining phase curvature, which can ruin the quantitative phase imaging, is the most evident and analyzed. As phase imaging is considered, this interest has made possible the development of different methods of overcoming its undesired consequences. Additionally to the effects in phase imaging, there exist a set of less obvious conditions that have to be accounted for as MOs are utilized in DHM to achieve diffraction-limit operation. These conditions have to be considered even in the case in which only amplitude or intensity imaging is of interest. In this paper, a thorough analysis of the physical parameters that control the appropriate utilization of MOs in DHM is presented. A regular DHM system is theoretically modeled on the basis of the imaging theory. The Fourier spectrum of the recorded hologram is analyzed to evaluate the performance of the DHM. A set of the criteria that consider the microscope features and the recording parameters to achieve DHM operation at the diffraction limit is derived. Numerical modeling and experimental results are shown to validate our findings.