Pedro J. Pardo

A new colour vision test in a PC-based screening system

Abstract The most commonly used method to examine the ability of the visual system to discriminate colours and detect colour vision deficiencies is based on pseudoisochromatic plates, such as the Ishihara plates. We describe a computer-based method to determine red–green colour deficiencies based on an anomaloscope simulator, which gave good results in a study of red–green discrimination is studied. It was shown experimentally that this computer-based method discriminates between subjects with colour deficiencies and subjects without colour deficiencies.

Characterization of dichromat and trichromat observers using a PC-based anomaloscope

Abstract A system is presented for characterizing anomalous colour observers according to the type of colour vision deficiency that they suffer. The system is based on the simulation of a Pickford–Nicholson type anomaloscope using a cathode ray tube and a personal computer. By means of this method, it has been possible to determine the type of deficiency of the red–green chromatic channel presented by various anomalous observers.

Influence of the correlated color temperature of a light source on the color discrimination capacity of the observer.

It is well known that there are different preferences in correlated color temperature of light sources for daily living activities or for viewing artistic paintings. There are also data relating the capacity of observers to make judgments on color differences with the spectral power distribution of the light source used. The present work describes a visual color discrimination experiment whose results confirm the existence of a relationship between the correlated color temperature of a light source and the color discrimination capacities of the observers.

Optimization of the correlated color temperature of a light source for a better color discrimination

In a previous work [J. Opt. Soc. Am. A29, A209 (2012)], we presented a visual color discrimination experiment whose results established the existence of a relationship between the correlated color temperature (CCT) of a light source and the color discrimination capacities of the observers. The results indicated the existence of a statistically significant difference in the color discrimination of unequal sample pairs when using light sources of different color temperatures, with the discrimination capacity being greater the higher the light sources color temperature. That previous work employed an RGBA-LED light source configured with three color temperatures: 2800, 5000, and 6500 K. In order to go a further step in this line, this work expanded the range of color temperatures up to 9700 K. The results showed that there is an optimum CCT of around 5000 K at which observers were found to have a greater color discrimination capability.

Converting a fluorescence spectrophotometer into a three-channel colorimeter for color vision research

An old fluorescence spectrophotometer was recycled to make a three-channel colorimeter. The various modifications involved in its design and implementation are described. An optical system was added that allows the fusion of two visual stimuli coming from the two monochromators of the spectrofluorimeter. Each of these stimuli has a wavelength and bandwidth control, and a third visual stimulus may be taken from a monochromator, a cathode ray tube, a thin film transistor screen, or any other light source. This freedom in the choice of source of the third chromatic channel, together with the characteristics of the visual stimuli from the spectrofluorimeter, give this design a great versatility in its application to novel visual experiments on color vision.

Chromatic characterization of a three-channel colorimeter using back-propagation neural networks

This work describes a method for the chromatic characterization of a three-channel colorimeter of recent design and construction dedicated to color vision research. The colorimeter consists of two fixed monochromators and a third monochromator interchangeable with a cathode ray tube or any other external light source. Back-propagation neural networks were used for the chromatic characterization to establish the relationship between each monochromator’s input parameters and the tristimulus values of each chromatic stimulus generated. The results showed the effectiveness of this type of neural-network-based system for the chromatic characterization of the stimuli produced by any monochromator.

Low Cost Ubiquitous Context-Aware Wireless Communications Laboratory for Undergraduate Students

Wireless Communication technologies are in continuous evolution. Around the world, many Universities try to provide innovative laboratory courses to train their students in this field. In this paper, a ubiquitous laboratory course for wireless communications is described. The laboratory course has been designed so that the students have to complete six different experiments. Three of these experiments have been designed to use advanced professional network testing tools in order to provide practical experience in simulation tools. Two additional experiments have been implemented in order to provide hands-on measurements through the students mobile device. This is a novelty and provides the students with an example of ubiquitous learning. Finally, in the last experiment, the students manufacture a WiFi antenna. The laboratory has been designed so that the students develop different practical skills in each experiment. This laboratory course facilitates applied learning and the consolidation of theoretical concepts.

Unique hue correction applied to the color rendering of LED light sources.

Existing color quality indices for light sources provide broad information about different dimensions related to color quality. Color fidelity, harmony, and gamut area are concepts related to these indices, and industry requests this information. For the last few years, LED light sources have been widely used at home and at work, and now a color rendering index that solves the problem of underestimation of this type of light source is needed to provide a score of subjective assessments made by real observers related to color fidelity. In this work, this problem has been studied in two ways, theoretically and experimentally, and the results show discrepancies between the hue composition calculated theoretically using a color appearance model and hue composition evaluated by real observers. These discrepancies could originate from divergences in the color fidelity score and the subjective evaluation of the naturalness of a scene.

Design, development, testing and validation of a Photonics Virtual Laboratory for the study of LEDs

This work presents the design, development, testing and validation of a Photonic Virtual Laboratory, highlighting the study of LEDs. The study was conducted from a conceptual, experimental and didactic standpoint, using e-learning and m-learning platforms. Specifically, teaching tools that help ensure that our students perform significant learning have been developed. It has been brought together the scientific aspect, such as the study of LEDs, with techniques of generation and transfer of knowledge through the selection, hierarchization and structuring of information using concept maps. For the validation of the didactic materials developed, it has been used procedures with various assessment tools for the collection and processing of data, applied in the context of an experimental design. Additionally, it was performed a statistical analysis to determine the validity of the materials developed. The assessment has been designed to validate the contributions of the new materials developed over the traditional method of teaching, and to quantify the learning achieved by students, in order to draw conclusions that serve as a reference for its application in the teaching and learning processes, and comprehensively validate the work carried out.

Experimental study of the individual differences in chromatic perception through blue-yellow metameric matches of a white-light continuum

A metameric colour matching test was designed to study inter‐observer variability. Blue‐yellow metameric matching to a white‐light continuum was used to define the optimal wavelengths at which each of eight non‐colour‐defective observers achieved a match. The tests involved chromatic stimuli on a 2° bipartite field, with a white‐light continuum presented on the left half, and a mixture of two monochromatic stimuli on the right half. The luminance of these chromatic stimuli was adjusted by the researcher using a staircase method, with the observer providing feedback about the similarity in luminance and chromaticity between the two halves of the field. Two series were performed for each observer, using different fixed yellow wavelengths. Since for each fixed yellow wavelength the match with the target white can be achieved by only one corresponding blue wavelength which is particular for each observer, the initial blue wavelengths were approximations based on the 2° CIE 1931 standard observer. Once the observers had attained an achromatic match, they modified the blue wavelength to achieve a perfect match of both halves. Generally, the observers found this modification of the blue wavelength necessary to achieve the metameric match. Each observer had a particular optimal blue wavelength which differed between the two series. The differences between the deviations from the standard observer for the two series were constant in value among the observers.