We have made a comparative study between a few parameters (6-8) linear model and Whittaker-Shanon theorem when using them to recover spectral reflectance functions. As suggested by some authors, we supposed 0.01 and 0.02 cycles/nm bandwidths in sampling theorem recovering. This study was made over 114 Munsell reflectances and 13 commercial glazes tiles, experimentally measured and 14 samples used for computing color rendering index, all of them clustered by a hue classification. We can observe that with a major contribution in long wavelength (reddish, yellowish and purplish ones) are better recovered by a linear model than using the sampling theorem, instead of bluish and greenish ones, that are better recovered using this theorem. Anyway, supposing these functions' bandwidth equal to 0.02cycles/nm forces us to use 13 parameters (a quite high number) in order to recover spectral reflectance curves, so we bet on linear models as more suitable methods.

This work describes a new device that enables the photometric evaluation of an observer's visual field by measuring the luminance distribution. To provide an example of the application, we have obtained the equivalent veiling luminance for different directions of the observer's line of vision. The results enable us to compare different luminous environments from direct measurements, without having to resort to theoretical methods.

Many works have shown colorimetric additivity failures in colour-matching experiments.<thus, in the present work, using the colour-matching functions (CMF) of three real observers, we have conducted five experiments in isomeric and metameric matching. The stimuli matched, using two modified Donaldson colorimetrics, were two achromatic, one blue, one orange and one green. Afterward, we determined both, the isomeric and the metameric discrimination ellipsoids for all the matches and for each observer. The results reflected differences in chromaticity and luminance with respect to the results of the CIE-1931 Estándar Observer. When we compared our results (of each observer with his CMF) for the isomeric and metameric matches, we found that, according to the differential colour thresholds, the prediction was acceptable for the chromaticity but not for luminance. The experimental results revealed the need to revise some aspects of the CIE-1931 Standar Observer.

It is a device wich is able to measure the cardiac rhythm, show the results on the monitor of the PC, record them in the memory, print them or send them to a remote point (by internet) in real time.

We have built a prototype of a system to measure the cardiac rhythm automatically. It has the hardware to capture this information and is able to show in analogic or digital way. Numerical values can be record, printed or showed, depending on the necessities. The digital output can be connected to an auxiliary device to do numerical calculus. The main advantage respect the above is that this one is made with optical fiber, so the light is guided inn and the LED and photorresistance can be placed out the thimble.

The color-matching functions of six observers have been measured in the range of 400nm to 700nm in interval of 10nm using two modified Donaldson-type colorimeters at a luminance of 4.5cd/m². A statistical study has been carried out to determine the interobserver variability (in our results) of the other authors using various representational color system have been compared with ours. The most important findings are that, although a common mathematical mean cannot be found, the shape of the curves for the color matching functions obtained in our laboratory for all the observers is very close to that of other authors, thereby implying that the overall color response of the human visual system is similar in all observers. In addition, the results show that for the long wavelengths (around 600nm) a great amount of desaturant prinmary (460nm) is necessary, indicating possible rods intrusion under our experimental conditions.

A method of the calculating the intensity pattern of an electric field in an optical planar waveguide is presented. The pattern is calculated for different refractive index profiles founded in waveguides currently used in optical communications. This calculation method can be used for evaluating the fibre length needed to reach modal equilibrium, to asses modal equilibrium at the fibre endface or for teaching purpose, among other things.