Ruben Ramos-Garcia

National Institute of Astrophysics, Optics and Electronics | INAOE · Optics Coordination

This study investigates the mechanisms and dynamics governing microhole formation in titanium nanofilms under the influence of a continuous-wave low-power laser emitting at 1070 nm. Two distinct configurations were explored: one in which the laser interacted with the titanium film in an air environment (referred to as configuration AM), and the oth...

Since Nobel Laureate Arthur Ashkin first introduced the trapping and manipulation of microparticles using light, numerous studies have explored this technique not only for dielectric/metallic particles but also for organic matter. This advancement has significantly expanded the landscape of non-contact and non-invasive micromanipulation at the nano...

The recent advancements in edge computing power are primarily attributable to technological innovations enabling accelerators with extensive hardware parallelism. One practical application is in computer imaging (CI), where GPU acceleration is pivotal, especially in reconstructing 2D images through techniques like Single-Pixel Imaging (SPI). In SPI...

In this study, we focus on the trapping and self-oscillation of microbubbles in ethanol using a low-power continuous-wave laser. The microbubble formation is achieved by heating of ethanol by light absorption (λ = 658 nm) at silver nanoparticles deposited on the distal end of a multi-mode optical fiber. Subsequently, a second low-power continuous-w...

Titanium dioxide (TiO2) is a well-known material for its biomedical applications, among which its implementation as a photosensitizer in photodynamic therapy has attracted considerable interest due to its photocatalytic properties, biocompatibility, high chemical stability, and low toxicity. However, the photoactivation of TiO2 requires ultraviolet...

Emerging vision technology, particularly Single-Pixel Imaging (SPI) cameras, has garnered significant attention in recent years. This work provides an overview of the advancements and applications of this innovative imaging technique. SPI utilizes improved reconstruction algorithms, enabling the reconstruction of images from compressed measurements...

The extraction of 3D human pose and body shape details from a single monocular image is a significant challenge in computer vision. Traditional methods use RGB images, but these are constrained by varying lighting and occlusions. However, cutting-edge developments in imaging technologies have introduced new techniques such as single-pixel imaging (...

This study investigates the mechanisms and dynamics governing microhole formation in titanium nanofilms under the influence of a continuous-wave low-power laser emitting at 1070 nm. Two distinct configurations were explored: one in which the laser interacted with the titanium film in an air environment (referred to as configuration AM), and the oth...

A mechanical device inspired by the rapid rotational motion of the pistol shrimp plunger has been developed to experimentally study the contraction/expansion dynamics of a gas bubble inside a confined liquid volume and in the vicinity of solid surfaces. The apparatus consists of a limb with a V-shaped end, which fits into a socket forming a cylindr...

Significance Speckle contrast analysis is the basis of laser speckle imaging (LSI), a simple, inexpensive, noninvasive technique used in various fields of medicine and engineering. A common application of LSI is the measurement of tissue blood flow. Accurate measurement of speckle contrast is essential to correctly measure blood flow. Variables, su...

Cavitation when two solids immersed in water collide has been studied theoretically and experimentally. A dimensionless parameter map showing a threshold line that delimits with good agreement the cavitation and non-cavitation zones was constructed. The threshold line was set by a cavi-tation number established with a lubrication model. Experiments...

In the field of computational imaging (CI), supervised training methods have long been the dominant approach for neural networks in optics. These methods heavily rely on large amounts of labeled data to adjust network weights and biases effectively. However, obtaining a substantial number of ground-truth images for training poses significant challe...

RESUMEN Los sistemas de inyección sin aguja han surgido como una alternativa prometedora a los métodos tradicionales de administración de medicamentos basados en agujas, ofreciendo mayor comodidad para el paciente, seguridad y una administración precisa de fármacos. En los últimos años, se han realizado avances significativos en este campo, impulsa...

Significance: The number of injections administered has increased dramatically worldwide due to vaccination campaigns following the COVID-19 pandemic, creating a problem of disposing of syringes and needles. Accidental needle sticks occur among medical and cleaning staff, exposing them to highly contagious diseases, such as hepatitis and human imm...

Three-dimensional (3D) human pose estimation is a fundamental task in computer vision and has important applications in fields such as gaming, sports analysis, and surveillance. Due to their high mobility and ability to capture images from different angles, the use of drones has rapidly increased in various applications in recent years. However, 3...

In challenging scenarios characterized by low-photon conditions or the presence of scattering effects caused by rain, fog, or smoke, conventional silicon-based cameras face limitations in capturing visible images. This often leads to reduced visibility and image contrast. However, using near-infrared (NIR) light within the range of 850–1550 nm offe...

Significance: The number of injections administered has increased dramatically worldwide due to vaccination campaigns following the COVID-19 pandemic, creating a problem of disposing of syringes and needles. Accidental needle sticks occur among medical and cleaning staff, exposing them to highly contagious diseases, such as hepatitis and human immu...

¿Te has sentido estresado o con miedo cada vez que te ponen una inyección? ¡Entonces este artículo te interesa!Actualmente, existe una tecnología innovadora que permite administrar fármacos en el cuerpo humano sin necesidadde agujas, y esto es gracias a los inyectores a chorro. Este tipo de inyectores generan una columna de líquido dediámetro micro...

Gait recognition is an important biometric measure that has been applied in many applications , including medical, social, and security issues [1]. Specifically, it is a useful approach in contactless identification. Under low illumination conditions, the image capture can be limited in some commercial cameras. In these cases, the use of infrared c...

Colloidal crystal plays a major role in novel optical devices such as waveguides, photonic crystals, and colloidal crystal lasers, among others. It has been known that colloidal crystals may self-assemble due to optical, electric, or chemical potentials, and light-induced thermal effects, such as thermophoresis and convective currents. In this work...

The capacity to capture images using RGB silicon-based sensors in the visible (VIS) can be limited in outdoor environmental conditions. Due to illumination variations of the scene or scattering effects caused by the interaction of light with micrometer-size particles in the rain, fog, or smoke, limiting the depth of visibility and the level of cont...

In recent years, it had been an evolution in the sensors used by vision systems. Different technologies from RGB cameras, IR cameras, LIDAR, RADAR, or sensor combinations can work in different spectrum bands. A new alternative to the vision system is the single-pixel camera (SPC), an architecture based on the compressive sensing theory for 2D recon...

The captured images in scattering scenarios are a challenge to solve for the vision systems for Unmanned Flight Vehicles (UFVs). Currently, research has been conducted on the use of sensors in the near-infrared (NIR) part of the spectra as an option for the RGB camera in scenarios with higher scattering (fog or rain), because to the diameter of wat...

The captured images in scattering scenarios are a challenge to solve for the vision systems for Unmanned Flight Vehicles (UFVs). Currently, research has been conducted on the use of sensors in the near-infrared (NIR) part of the spectra as an option for the RGB camera in scenarios with higher scattering (fog or rain), because to the diameter of wat...

In the last decade, the vision systems have improved their capabilities to capture 3D images in bad weather scenarios. Currently, there exist several techniques for image acquisition in foggy or rainy scenarios that use infrared (IR) sensors. Due to the reduced light scattering at the IR spectra it is possible to discriminate the objects in a scene...

Single-pixel imaging is a technique that can reconstruct an image of a scene by projecting a series of spatial patterns on an object and capturing the reflected light by a single photodetector. Since the introduction of the compressed sensing method, it has been possible to use random spatial patterns and reduce its number below the Nyquist-Shannon...

1,4-Dioxane is a pervasive and persistent contaminant in numerous aquifers. Although the median concentration in most contaminant plumes is in the microgram per liter range, a subset of sites have contamination in the milligram per liter range. Most prior studies that have examined 1,4-dioxane concentrations in the hundreds of milligrams per liter...

In this work, we perform drilling of micro-holes and formation of microbubbles in titanium thin films. All these processes occur due the high titanium absorption at near infrared wavelength, the superheating of titanium produce high quality micro-holes which can be create simultaneously with different laser beam spots. Otherwise, when titanium inte...

The detection scheme based on phase detection of SPR response was developed. We show that the proposed biosensing scheme can detect SARS-CoV-2 genetic material with high specificity, low detection limit and short detection time.

In this Letter, we show 3D steady-state trapping and manipulation of vapor bubbles in liquids employing a low-power continuous-wave laser using the Marangoni effect. Light absorption from photodeposited silver nanoparticles on the distal end of a multi-mode optical fiber is used to produce bubbles of different diameters. The thermal effects produce...

In this paper, we propose a method for single-pixel 2D/3D imaging to be applied in hyperspectral camerasoperating in outdoor applications in unmanned aerial vehicles (UAVs). In rain rich environments, if camerasystems operating in the visible range are used, alongside the atmospheric absorption that inevitably takesplace, additional interactions oc...

We present a method to improve the quality of 2D/3D single-pixel reconstructed images using active illumination in the near-infrared (NIR) part of the spectra for outdoor applications in presence or rain. The proposed solution is based on an array of NIR LEDs emitting active illumination patterns in the wavelength 1550 nm to be detected by an InGaA...

In this article, we propose a method to be used for the reconstruction of single-pixel near-infrared (SPI-NIR) low-resolution 2D images using active illumination with a peak wavelength on 1550 nm, that is based on Batch Orthogonal Matching (Batch-OMP) processing algorithms and a region definition in the projection sequence of Hadamard illumination...

In recent years, 3D reconstruction has become a challenging task for navigation systems. Therefore, different technologies such as RGB cameras, LIDARs, or RADAR can capture information from the environment and perform 3D reconstruction. In an environment of high dispersion and low illumination, it is necessary to have a robust solution that operate...

Organic light emitting diodes (OLEDs) are very attractive light sources because they are large area emitters and, can in principle, deposited on flexible substrates. These features make them suitable for ambulatory photodynamic therapy (PDT), in fact there are a few reports of in vitro or in vivo OLED based PDT studies for cancer or microbial inhib...

In this paper, we present a novel mechanism for the generation of laser pulses based on the phenomenon of thermocavitation. Thermocavitation bubbles were generated within a glass cuvette filled with copper nitrate dissolved in water, where the tip of an optical fiber was placed very close to the bubble generation region. Once the bubble is generate...

We segment the images of particles moving in optical traps to recover their irradiance and deformation. We use Legendre polynomials to correct the deformation and retrieve the phase using the 3D profile of the particle.

We obtain 3D profiles of objects in optical traps from image segmentation, giving place to an irradiance distribution. We recover the phase using 2D Legendre poly- nomials (2D-LP) and compare our technique with the Gerchberg-Saxton method.

An experimental and theoretical study on the 3D trapping and manipulation of microbubbles by means low power laser-induced temperature gradients induced in ethanol by bulk light absorption (λ = 1550 nm) is presented. Two optical fibers were used: One for bubble generation (OFG) and the other for both trapping and manipulation (OFT). Light from a Q-...

In this paper, a theoretical analysis of a vision system for 2D/3D single-pixel imaging using principles of compressed sensing and Indirect-Time-of-flight measurements is presented. The goal is to use this system for autonomous drone navigation in environments with adverse conditions where typical sensors used by RGB or RGB-Depth cameras typically...

The inclusion of thermal effects in optical manipulation has been explored in diverse experiments, increasing the possibilities for applications in diverse areas. In this Letter, the results of combined optical and thermal manipulation in the vicinity of a highly absorbent hydrogenated amorphous silicon layer, which induces both the generation of c...

In recent time there has been an increasing amount of interest in developing novel techniques for the generation of complex vector light beams. Amongst these, digital holography stands out as one of the most flexible and versatile with almost unlimited freedom in the generation of scalar and complex vector light fields featuring arbitrary polarisat...

The most common approach to optically generate and manipulate bubbles in liquids involves temperature gradients induced by CW lasers. In this work, we present a method to accomplish both the generation of microbubbles and their 3D manipulation in ethanol through optothermal forces. These forces are triggered by light absorption from a nanosecond pu...

We present a case study for a time-of-flight 3D imaging system using single-pixel imaging (SPI) accompanied by the Time-of-flight (ToF) principle for drone applications involving autonomous navigation. In present, an alternative work present a solution to conventional RGB or RGB-depth sensors , limited when working under poor visibility conditions,...

During the last decades the radio detecting and ranging (RADAR) technology underwent an evolution transiting from the linear-frequency-modulated (LFM) systems developed in the 1970s, up to the orthogonal frequency-division multiplexing (OFDM) systems developed in the early 2000s. In mid 2010s, systems were proposed that combined the radar principle...

The compressive sensing (CS) technique is a novel tool used to reconstruct images using fewer samples, normally sparse in the transform domain, than those required by conventional imaging systems. However, the methods applied for signal reconstruction within the CS approach still present some problems in the implementation, mainly due to their inte...

We present a case study for a time-of-flight (ToF) 3D imaging system using single-pixel imaging (SPI) approach based on compressive sensing (CS), accompanied by the Time-of-flight (ToF) principle applied to four reference points of the 2D image created and then mapped to the rest of the SPI generated virtual pixels. In this analysis we have develop...

In recent time there has been an increasing amount of interest in developing novel techniques for the generation of complex vector light beams. Amongst these, digital holography stands out as one of the most flexible and versatile with almost unlimited freedom to generate scalar and vector light beams with arbitrary polarisation distributions and s...

Numerical simulations using the Finite-Difference Time-Domain method were used to study the propagation of an acoustic wave within a truncated ellipsoidal cavity. Based in our simulations, a fluidic device was designed and fabricated using a 3D printer in order to focus an acoustic wave more efficiently and expel a liquid jet. The device consists o...

Background: We compared the effectiveness of a single irradiation vs repetitive irradiation of light, for in vitro photodynamic inactivation (PDI) of Candida albicans and Trichophyton mentagrophytes, by using methylene blue (MB) and rose bengal (RB) as photosensitizers (PS). Methods: MB from 5 to 60 μM and RB from 0.5 to 10 μM, with energy densi...

Visualization of blood vessels is a fundamental task in the evaluation of the health and biological integrity of tissue. Laser speckle contrast imaging (LSCI) is a non-invasive technique to determine the blood flow in superficial or exposed vasculature. However, the high scattering of biological tissue hinders the visualization of those structures....

To visualize blood vessels in Laser Speckle Imaging (LSI) is an important task since parameters such as blood pressure, relative blood flow and vessel size can be estimated through of them to then be used in medical diagnostics. LSI is the common method for visualizing blood vessels however, resulting images contain a high level of noise. For impro...