Jorge Castro-Ramos

Exact calculation of the circle of least confusion of a rotationally symmetric mirror

The position and dimensions of the circle of least confusion (CLC) on axis for a lensless Schmidt camera telescope operating at F(0.82) are calculated. The camera is to be used in the fluorescence detector of the Pierre Auger Observatory. Our analysis was developed for an aspherical mirror for any on-axis position of the point light source. Our technique uses the intersection of the marginal ray from one side of the aperture with the caustic produced by the intermediate rays from the opposite side of the aperture to locate the CLC.

Computation of the disk of least confusion for conic mirrors

We use geometrical optics to compute, in an exact way and by using the third-order approximation, the disk of least confusion (DLC) or the best image produced by a conic reflector when the point source is located at any position on the optical axis. In the approximate case we obtain analytical formulas to compute the DLC. Furthermore, we apply our equations to particular examples to compare the exact and approximate results.

Exact Design of Aplanatic Microscope Objectives consisting of Two Conic Mirrors.

The necessary equations are derived for the design of aplanatic microscope objectives consisting of two mirrors, one concave and the other convex. The first-order parameters are calculated along with the conic constants of the mirrors, determined by means of an exact analysis to arrive at an aplanatic system.

Wavefronts, caustics, and ronchigrams of a spherical wave reflected by a spherical mirror.

The aim of the present work is twofold: first we obtain analytical expressions for both the wavefronts and the caustic associated with the light rays reflected by a spherical mirror after being emitted by a point light source located at an arbitrary position in free space, and second, we describe, in detail, the structure of the ronchigrams when the grating or Ronchi ruling is placed at different relative positions to the caustic region and the point light source is located on and off the optical axis. We find that, in general, the caustic has two branches: one is a segment of a line, and the other is a two-dimensional surface. The wavefronts, at the caustic region, have self intersections and singularities. The ronchigrams exhibit closed-loop fringes when the grating is placed at the caustic region.

Aspheric lens to increase the depth of focus

For high-resolution optical systems, a long depth of focus is desirable. Unfortunately, resolution and depth of focus are inversely related. In this work, a novel lens is presented to produce long depth of focus beams, keeping the same resolution. The equations to perform the optical design of this kind of lenses and results are shown for a simple lens that can produce beams with a spot size of 2.9 μm over a range of 1.5 mm and for an achromatic doublet with a focus depth of 10 mm.

Raman spectra and optical coherent tomography images of skin

The optical coherence tomography images are useful to see the internal profile and the structure of material samples. In this work, OCT images were recorded in 10 volunteers with different skin tone which were related to Raman spectra. The areas where we obtained OCT images and Raman spectra were a) index finger nail, b) between index finger and middle finger, c) middle finger tip, d) half of middle finger, e) the thumb finger tip and f) between index finger and thumb, areas measured were for the purpose of finding extracellular fluids with contain triglycerides, cholesterol and glucose that are reported in the literature. The excitation wavelength used for this work was 785 nm, a spectrometer of 6 cm-1 resolution. The spectral region used ranges from 300 to 1800 cm-1. We use an OCT with 930 nm of Central Wavelength, 1.6 mm of Image Depth, 6 mm of image width and 6.2 μm of axial resolution.

Intensity-based method for selection of valid interferometric data in temporal phase shifting interferometry

Abstract. In this paper, we propose a method to detect the valid phase pixels of fringe patterns obtained with phase shifting interferometry. From a set of simulated interferogram images, we obtain a set of equations to discriminate between valid and invalid wavefront phase pixels, which allow us to compute the wavefront aberration. This method is useful for testing any converging optical system in a quantitative way with either a small or large focal ratio, with either polished or rough surfaces and with wavefront or lateral shear interferograms.

Raman spectroscopy of blood in-vitro

We present Raman spectra from a sample of 8 volunteers that have different type of blood. The experimental data were carried out using a 785 nm excitation laser and an ocean optics spectrometer of 6 cm-1 resolution, with a used spectral region from 1000 to 1800 cm-1. We find Raman features at 1000 and 1542 cm-1 regarded with hemoglobin and its derivatives. Also we find Raman features at 1248 and 1342 cm-1 that are now regarded with pure fibrin. In this work, we use Principal Component analysis (PCA) to determine all variations of our samples, which allows us to define a classification of the influence of the blood type. Finally, we found vibrational lines of cholesterol, glucose and triglycerides that are reported in literature.

Fabrication and characterization of phantoms made of polydimethylsiloxane (PDMS)

The transparent elastomer Polydimethylsiloxane (PDMS) Sylgard 184 is increasingly used in optical applications, as in the manufacture of microlens, waveguides (optical fibers) and to elaborated phantoms (simulator of biological tissue); The wide range of applications is due to its excellent physic-chemical properties, its low cost, easy operation and null toxicity. This paper describes the manufacturing process and physic-chemical characterization of Phantoms prepared with PDMS as grid and doped with some elements present as Gliceryl, ink, glucose 10% and melanin provided by sigma aldrich. We made phantoms with different concentrations and elements; we measured their profiles, and thicknesses. Finally, we obtained their Raman Spectra. We present the experimental results obtained of the physic-chemical parameters of the phantoms and the conclusions.

Mapping skin using Raman spectroscopy

In this work we carried out a comparison and localization of skin Raman spectra. Measurements were made in regions where Raman scatter is caused by the excitation source; we used the spectra overlap in a comparative way. Ten volunteers with different skin colors participated in the experiment; body parts sampled were palm and dorsum of the hand. The excitation wavelength used for this work was 785nm. A spectrometer with 6cm-1 resolution and spectral region range 0 to 2000 cm-1 was utilized. We used Matlab® to overlap and compare the differences between Raman spectra form different samples. We found spectral variations that were caused by differences on the surface of the skin, such as scars and moles. This work helps to identify potential undesirable behavior on the epidermis.