Marcelino Anguiano-Morales

Measuring object shape by using in-plane electronic speckle pattern interferometry with divergent illumination

Electronic speckle pattern interferometry is a useful technique for displacement, deformation and contouring measurements. Traditionally, for contouring measurements, collimated illumination with a constant sensitivity vector is used, and the surface area analysis is limited to the illuminated area. In some industrial applications, large surfaces require to be analyzed in restricted space conditions. Considering this situation, an optical system with divergent illumination for whole-field measurements can be used. It is known that displacement fields and the optical phase are related by the sensitivity vector. Therefore, to compute the sensitivity vector, illumination position and superficial shape need to be considered, a condition that becomes an impediment for surface contouring if the superficial shape is unknown. In this work, a simple iterative algorithm based on the Gauss–Seidel technique is presented to compute contouring measurements. Contouring measurements from both ESPI and a coordinate-measuring machine (CMM) are compared. In addition, a measurement comparison considering supposed collimated and divergent illumination is presented.

Measurement of spectacle lenses: A review

Spectacle lenses are the most commonly used solution for refractive errors of the eye, such as myopia, hyperopia, presbyopia and astigmatism. To correct a refractive error, the spectacle lens needs to have the correct lens power and an appropriate distribution of power along the surface of the lens, to measure these characteristics several methods have been developed, this paper presents a review of some of these methods and their optical principles.

The use of a conical lens to find the refractive index of liquids

In this work, the basic idea is to determine the refractive index of liquids unknown using a conical lens. The measurement of the refractive index of liquids is an important work in engineering and science since is one of the most important optical parameter. The adulteration problem is increasing day by day; therefore it is necessary to implement new and simple devices for measure the refractive index of several materials. There is a great variety of interferometric methods that may be used for determining the refractive index. However, these methods either need sophisticated equipment or have low accuracy. Our system consists of a conical lens coupled to a cylindrical container with a liquid whose composition can be changed easily or adulterated. The diameter of the emergent beam of the container is associated to the specific index of refraction of each substance. Any adulteration of the liquid will be reflected in the diameter of the beam, which will be detected by a charge-coupled device (CCD). Our hypothesis is supported by developed mathematical calculations and numerical simulations.

Simulation of simple capacitive-isolated LED drivers

Given that the use of electrolytic capacitors and inductors reduces the lifetime and efficiency of LED based lamps, this work proposes an LED driver where only ceramic capacitors are used, it also replaces the use of inductors by an array of capacitors and switches. The proposed configuration is compared to a classical Buck topology. A study of the input signal behavior is performed as a function of the frequency of the control signals of the switches.

Measurement of spherical and cylindrical power in ophthalmic lenses based in the change of lateral amplification

In this article, we present a new technique to measure spherical and cylindrical power in ophthalmic lenses. This method is based in the change of lateral amplification produced by an optical system when introducing an ophthalmic lens. Ophthalmic lens power is calculated by considering the change in image size from a reference object and its own image seen through the ophthalmic lens. Mathematical analysis is presented along with the experimental setup and the obtained results. Several algorithms were applied to the obtained results as a method to compensate the error in order to fit into ISO 8598 specifications.

Sphere power measuring in ophthalmic lenses by infinite fringe moiré deflectometry

We present a method to measure spherical power in ophthalmic lenses based on the measurement of moiré patterns, using the technique called infinite fringe moiré deflectometry. We develop a theoretical model using a geometrical analysis that was validated by a computer simulation using the LabVIEW software; also we build an experimental setup in which we get experimental data. As results, we obtain a measurement of the spherical power of a set of ophthalmic test lenses in the range of ± 0.50 to ± 3.00 diopters. This power is obtained by measuring the separation between each fringe of moiré pattern, from the obtained data we analyze the theoretical model and we make the necessary corrections, using polynomial regression by the method of least squares, to comply with standard ISO8598. At the same time, some components of the experimental setup were being improved to facilitate its implementation and obtain better experimental data.

Power measuring in ophthalmic lenses using lateral amplification

Nowadays refractive errors in the human eye affect approximately 10% of world’s population, decreasing vision acuity and life quality. However a simple common solution is the use of an adequate ophthalmic lens. Due to the importance of ophthalmic lenses, the best measurement equipment is required for testing, these days experimental and commercial apparatus are available but with the possibility of improvement. We present a method to measure spherical and cylindrical power in ophthalmic lenses. The system uses an equation obtained from lateral amplification concept and Gauss formula to make calculations. Also an experimental setup is presented for the measurement of ophthalmic lens from -20 diopters to 20 diopters in the case of spherical lenses, and from -6 diopters to 6 diopters in the case of cylindrical lenses. The setup contains a reference object, the lens to be tested and a digital camera connected to a computer with software designed in LabVIEW for the data processing. Satisfactory preliminary results were obtained according to ISO 8598.

Generation of a spiral wave using amplitude masks

Optical beams of Bessel-type whose transverse intensity profile remains unchanged under free-space propagation are called nondiffracting beams. Experimentally, Durnin used an annular slit on the focal plane of a convergent lens to generate a Bessel beam. However, this configuration is only one of many that can be used to generate nondiffracting beams. The method can be modified in order to generate a required phase distribution in the beam. In this work, we propose a simple and effective method to generate spiral beams whose intensity remains invariant during propagation using amplitude masks. Laser beams with spiral phase, i.e., vortex beams have attracted great interest because of their possible use in different applications for areas ranging from laser technologies, medicine, and microbiology to the production of light tweezers and optical traps. We present a study of spiral structures generated by the interference between two incomplete annular beams.

Generation of a spiral wave by modified annular slit

Optical beams of Bessel-type, whose transverse intensity profile remains unchanged under free-space propagation, are called nondiffracting beams. In this paper, we propose a simple and effective method to generate spiral beams whose intensity remains invariant during propagation using amplitude masks. We show how the interaction between two incomplete annular beams leads to the formation of a spiral structure. Experimental observations are presented to show the characteristic features of the spiral structure generated. We can modulate the nondiffracting beam modifying the amplitude mask.