Structured light projection is one of the most useful methods for accurate three-dimensional scanning. Video projectors are typically used as the illumination source. However, because video projectors are not designed for structured light systems, some considerations such as gamma calibration must be taken into account. In this work, we present a simple method for gamma calibration of video projectors. First, the experimental fringe patterns are normalized. Then, the samples of the fringe patterns are sorted in ascending order. The sample sorting leads to a simple three-parameter sine curve that is fitted using the Gauss-Newton algorithm. The novelty of this method is that the sorting process removes the effect of the unknown phase. Thus, the resulting gamma calibration algorithm is significantly simplified. The feasibility of the proposed method is illustrated in a three-dimensional scanning experiment.
An algorithm to generate ronchigrams of parabolic concave mirrors is proposed. Unlike the conventional direct ray-tracing method, which produces scattered pixels, the proposed algorithm returns regularly sampled images. Thus, the proposed algorithm is fully compatible with further fringe processing tasks such as phase demodulation and wavefront analysis. The theoretical principles of our proposal are explained in detail, and the programming code is provided. Several computer experiments highlight the performance and advantages of our proposal.
Inhomogeneous or gradient index media exhibit a refractive index varying with the position. This kind of media are very interesting because they can be found in both synthetic as well as real life optical devices such as the human lens. In this work we present the development of a computational tool for ray tracing in refractive optical systems. Particularly, the human eye is used as the optical system under study. An inhomogeneous medium with similar characteristics to the human lens is introduced and modeled by the so-called slices method. The useful of our proposal is illustrated by several graphical results.
Sign Language (SL) is the basic alternative communication method between deaf people. However, most of the
hearing people have trouble understanding the SL, making communication with deaf people almost impossible and
taking them apart from daily activities. In this work we present an automatic basic real-time sign language translator
capable of recognize a basic list of Mexican Sign Language (MSL) signs of 10 meaningful words, letters (A-Z) and
numbers (1-10) and translate them into speech and text. The signs were collected from a group of 35 MSL signers
executed in front of a Microsoft Kinect™ Sensor. The hand gesture recognition system use the RGB-D camera to
build and storage data point clouds, color and skeleton tracking information. In this work we propose a method to
obtain the representative hand trajectory pattern information. We use Euclidean Segmentation method to obtain the
hand shape and Hierarchical Centroid as feature extraction method for images of numbers and letters. A pattern
recognition method based on a Back Propagation Artificial Neural Network (ANN) is used to interpret the hand
gestures. Finally, we use K-Fold Cross Validation method for training and testing stages. Our results achieve an
accuracy of 95.71% on words, 98.57% on numbers and 79.71% on letters. In addition, an interactive user interface
was designed to present the results in voice and text format.
Tunable lenses have become very popular elements due their capacity of change their focal length by only modifying their shape. This characteristic is very useful in different applications in the field of optics. The development of tunable lenses consists on several phases: first, to find a suitable material, second, to obtain an optimal analysis and design, and third, to find the way to change the lens shape and characterization. In this work we present the characterization of a tunable lens, formed by spherical profiled elastic membranes and a liquid medium between them. The proposed liquidfilled tunable has a design such that the spherical aberration is the least to different focus. The development of an optomechanical system to change the lens shape is presented.
Ametropies of the human eye, are refractive defects hampering the correct imaging on the retina. The most common ways to correct them is by means of spectacles, contact lenses, and modern methods as laser surgery. However, in any case it is very important to identify the ametropia grade for designing the optimum correction action. In the case of laser surgery, it is necessary to define a new shape of the cornea in order to obtain the wanted refractive correction. Therefore, a computational tool to calculate the focal length of the optical system of the eye versus variations on its geometrical parameters is required. Additionally, a clear and understandable visualization of the evaluation process is desirable. In this work, a model of the human eye based on geometrical optics principles is presented. Simulations of light rays coming from a punctual source at six meter from the cornea are shown. We perform a ray-tracing in three dimensions in order to visualize the focusing regions and estimate the power of the optical system. The common parameters of ametropies can be easily modified and analyzed in the simulation by an intuitive graphic user interface.
In this work we calculate the effect caused by roughness on the light reflected by an optical surface like a mirror, the numerical calculation is carry out within the Rayleigh approximation. We focus our study in the comparison of the results obtained numerically using different roughness parameters and calculate its effect on the aberrations of the wavefront, which without the effect of the roughness is considered perfect surface.
A simple method to evaluate the focal length of concave mirrors is proposed. The inverse ray-tracing approach of
the Ronchi test is used in the measurement stage. The theoretical principles are given and a numerical method
for ronchigram processing is proposed. The results verify the feasibility of the proposal.
Refractive optics has evolved and incorporated new elements in optical systems every day, such as conventional lenses, tunable lenses, GRIN lenses, diffractive lenses, intraocular lenses, etc. Some of these elements are reported in the literature together with different proposed models of the human eye. In this work, optical properties of some of these lenses will be studied, and simulations of their behavior will be done in order to analyze which one is better for imaging process. Such lenses will be incorporated in an optical system that mimics the human eye behavior. Analysis and obtained results are reported, as well as the proposed optical system. Finally, we present the conclusions of the work.
Optical diffraction fields have in general a spatial complex structure and some times can generate focusing regions, in
this work we describe the focusing region associated with highly symmetric transmittances, analyzing its associated
phase function. We show that generic features can be studied from a differential equation for a focusing geometry, which
is obtained through angular representation for diffraction fields, according to the choice of the parameters involved, the
diffraction field presents a new focusing region whose geometry and spatial evolution can be described with the only
analysis of the phase singularities avoiding the integral representation.
We use the profile of a parabolic mirror to calculate the scattered electromagnetic field, this mirror can be used
in the design and construction of a reflector telescope. We calculate the effect caused by the roughness on the
performance of this optical elements, the calculation is done within the Rayleigh approximation. In another work
presented in this meeting we show a comparison of the results obtained numerically using different roughness
parameters and calculate its effect on the aberrations of the wavefront.
In this paper we show the results as well as the description of the followed process to calculate the electromagnetic
field scattered by optical surface elements, where the optical surface is not considered as a flat surface that follows
a shape, but as a rough one, roughness that in general may be regarded as random. We use the profile of a
parabolic mirror to calculate the scattered electromagnetic field, this mirror can be used in the design and
construction of a reflector telescope. We calculate the effect caused by the roughness on the performance of
this optical elements, the calculation is done within the Rayleigh approximation. In another work presented in
this meeting we show a comparison of the results obtained numerically using different roughness parameters and
calculate its effect on the wavefront.