We propose a novel approach employing structured sampling and a single-pixel detector to measure, simultaneously, the spatial profile and the spatially resolved temporal profile of a femtosecond laser beam with an autocorrelation method. The experimental system integrates a Digital Mirror Device (DMD) into a conventional autocorrelation setup. An experimental comparison with a raster scanning method illustrates the advantages of this setup, achieving comparable accuracy with reduced energy levels. This study introduces a promising technique for the precise characterization of ultrafast laser pulses, with potential applications in various fields that demand accurate spatial and temporal measurements as material processing or imaging applications.
A method to increase resolution in single-pixel imaging through parallel implementation based on the selfimaging effect is proposed. The scanning basis, Walsh-Hadamard patterns, are displayed in each unit cell of a 2D binary grating codified on a DMD. The self-imaging effect is used to project the sampling functions onto the object. Images with higher resolution can be obtained by using a light sensor with a low number of pixels and reconstructing by single-pixel technique. This approach can be useful to improve the resolution of IR or THz cameras. Preliminary results are shown.
We propose a new single pixel microscope with optical sectioning properties by using structured illumination techniques. The method uses single-pixel imaging (SPI) techniques by interrogating the sample with a series of spatially resolved patterns and measuring the output intensities with a non-spatial resolution detector. Moreover, optical sectioning is obtained by adding a grating to the system and employing Structured Illumination Microscopy (SIM). The system allows us to perform 3D bright-field and fluorescence microscopy. We apply compressive sensing techniques to decrease the acquisition time.
Imaging through turbid media remains a relevant topic in biomedical imaging. In this contribution, we propose the combination of frequency domain imaging (SFDI) and single-pixel imaging (SPI) to image objects hidden by a turbid media. Firstly, the SFDI method allows to characterize the turbid media by projecting sinusoidal intensity patterns. Secondly, SPI technique provides images of the object through the areas of the turbid media with higher transmission of ballistic photons. The key elements of the system are a DMD to generate the sampling patterns and a LED array working as a programmable light source. Experimental results supporting this idea are shown.
The ballistic photons have been proposed for biological-tissue characterization. These photons keep its propagation direction when they are propagated through a material. They are rapidly attenuated in accordance with the density and thickness of the medium. The penetration depth for these photons is about 9 millimeters in human tissue. This attenuation may provide information to detect an inhomogeneity in the material (a possible tumor in human tissue). In order to enhance the detection of ballistic photons, interferometric setups have been proposed. Unfortunately, these setups only allow transmission measurement at a single point. We propose a novel technique using Risley prisms for area-scan with ballistic photons.
The use of transillumination to diagnose and consequently treat illnesses has been widely accepted for a long time. However, some kinds of radiation are harmful to the human body, as is the case for x-rays. In this work, we propose using infrared radiation as an illumination source, ballistic photons to transilluminate thin samples and separate scattered radiation from the pass-through radiation for potential future applications in biological research. Infrared radiation is less energetic and harmful than x-rays. Ballistic photons can supply information about the propagation medium, which in turn may allow us to detect inclusions below 9 mm in size (the limit of x-ray radiation) in the medium. In the initial research, we model biological tissue with controlled thickness of samples of pig tissue that has been processed for human consumption, i.e., slices of ham, to study the effects of ballistic photons and to assess the scope of this technique. The combination of an alternative illumination source and a simulated tissue allows us to assess calibration and the diagnostic technique. To detect irradiance, we implemented a Mach-Zehnder interferometer with a 633 nm wavelength He-Ne laser (NIR). As a detector, we used a Sony XCD-SX910 camera. We measure maximum and minimum irradiances generated by ballistic radiation as a function of the thickness of the tissue model and the measured point. The results of these measurements and their comparison are presented.
Tissue phantoms are important tools to calibrate and validate light propagation effects, measurements and diagnostic test
in real biological soft tissue. We produce low cost phantoms using standard commercial jelly, distillated water, glycerol
and a 20% lipid emulsion (Oliclinomel N7-1000 ®) was used in place of the usual Intralipid®. In a previous work we
designed a protocol to elaborate high purity phantoms which can be used over months. We produced three different types
of phantoms regarding the lipid emulsion – glycerol - gelatin – water composition: Pure gelatin phantoms, lipid in
glycerol, and lipid in gelatin phantoms were produced and different concentrations of the lipid emulsion were used to
study optical propagation properties of diffusive mixtures. Besides, 1.09 μm poly latex spheres in distilled water were
used to produce reference phantoms. In order to use all the phantom sides, the phantoms were produced in disposable
spectrometer cuvettes, designed for fluorescence studies. Measurements were performed using an OceanOptics 4000
channels spectrophotometer and integrating spheres. For the scattering measurements a homemade goniometer with a
high resolution angular scale was used and the scattering detector was a linear array of optical fibers, with an angular
collimator, connected to the spectrophotometer. White LED was used as light source, and the 6328.8 nm HeNe Laser
was used for calibration. In this work we present characterization measurements for gelatin and microspheres phantoms
using spectral reflectance, diffuse and direct spectral transmittance, and angle scattering measurements. The results of
these measurements and their comparison are presented.
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