This paper presents a method for determining the degree of misalignment between a LED and its epoxy encapsulation in a simulated environment. The misalignment is determined by analyzing the light emitted by the optoelectronic component and transmitted through a grid of holes. The results obtained are compared with simulated and experimental registers wherein there is no misalignment between the LED and the epoxy but a displacement of the whole optoelectronic component perpendicularly to the observation axis. We prove that the method used allows us to distinguish between the existence of misalignment inside the optoelectronic component and a simple displacement between the optoelectronic component and the observation axis.
This work presents the first results obtained in the validation study of an innovative technique to calculate the contact
angle of a solid surface by means of a confocal device, which confirms the reliability and the accuracy of the presented
A measurement technique has been developed to measure the contact angle with of a confocal device. This technique has
the unique advantage of allowing to perform both topography and contact angle measurements in the same location,
therefore avoiding any shift in the sample positioning between the two measurements and ensuring the proper location of
both measurements in the same area of the sample, thus enhancing the evaluation of the surface energy of the surface.
Specifically, this technique uses the confocal device to measure some parameters of the drop, such as the height (ℎ) and
the apparent diameter (), in a top-view configuration. The drop volume is already known and small enough to discard
gravity effects, so the shape of the drop can be approximated by a truncated sphere. Several purely geometric
calculations are available to calculate the radius de of the drop and subsequently, the contact angle.
This work reports the first results of the ongoing validation study of this technique and the several mathematical
calculations employed to extract the contact angle value. These initial measurements were performed for a hydrophobic
surface with water as a measurement liquid. The contact angles for different set of drops for this sample were also
measured by a commercial contact angle meter in side-view configuration, with the same liquid and drop dimensions, in
order to verify the validity and the accuracy of the presented technique. This validation of the calculation of the contact
angle is the first step for the further validation of the developed measurement method for the surface energy
We present a new strategy to calculate an optimized refractive freeform surface for illumination purposes with a LED source. The goal of this paper is to present a new iterative flux based strategy to design plastic lens for LED lighting solutions. The new strategy considers the energy emission pattern of the LED and adjusts a plastic refractive surface to accomplish the target intensity distribution. This paper is divided in four parts, a brief introduction to LED systems and reviewing optical design strategies, the method of calculus is exposed in the second part, third part presents the results for a particular refractive optical design developed by new presented algorithm and finally, a set of conclusions about strategy is showed in fourth part.
The proper alignment of the individual elements in an optical system is a crucial point in the
final performance of an optical system. The developed method we present is aimed to detect
and quantify misalignments of decentering and tilt in imaging optical systems with a non-expensive
system. This method is based in the comparison of different image parameters
values. These parameters values are obtained through the analysis of the image formed by
the optical system under study of an object composed of an array of point sources. The
method has been validated by obtaining the behavior curves of the parameters for a gauss
system in front of decentering up to 0.3mm and tilt up to 1°.
The proper alignment of the individual elements is a crucial point in the final performance of an optical system. The
alignment technique we present uses the image formation of a point sources array to detect the misalignments of an
imaging system. We have displaced the analysis plane from the exit pupil plane to the image plane, where the PSFs
functions are captured on a sensor. The PSFs are large enough to be sensitive to the misalignments and we are able to
detect them using image analysis techniques. The proposed technique is a solution when more than one field position is
necessary to obtain a well-balanced quality function over all the field of view. We have been studying this method on a
particular collection of optical systems with decentering and rotation errors, achieving an accuracy of 0.1mm for
decentering and 0.01° for rotation.
Illumination engineering is a field that spans many topics and the number industries that actively work in the field is
expanding. In this field the efficiency of the design is only a part of the design. Of nearly the same importance is the
distribution of the light at the target. Many times the factors that are necessary to develop an illumination system will
contradict one another, thus making the design of illumination systems complex and demanding. Optical modeling plays
a basic role in obtaining new models. In general, the LED optical model obtains its parameters as a mathematical
transformation or the average of a large set of measured experimental data. The main goal of this paper is to measure
directly the parameters of the LED optical model. We use the typical LED spatial distribution model based on ray
distribution. The basic parameters of this model are: the slope of the ray and the energy of each ray. The measurement
system incorporates the slope measuring method used in deflectometry into an energy measurement technique. The
method was tested using the measured data of two LEDs to analyze the illumination distribution provided at the image
screen of standard Köhler illumination system.
The reduction of contrast due to scattering by optical mounts and buffers was studied, especially for the systems that must work in the infrared region. When a particular optical system is optimized [1,2] up a specified field value the scattering effects introduced by optical mounts and buffers must be taken into account. The scattering effect plays an important role in the IR region where the influence of off-field effects is important. The contrast reduction due to scattering effects is not uniform with the object position, in other words the influence of scattering effects has field dependence. The scattering model used is based on the classical point of view of the scattering electromagnetic wave and it is adapted for optical evaluation using ray-tracing techniques. In order to test the validity of our scattering model we calculated the distribution of illumination produced for a laser beam in a plane-parallel plate with perfect scattering properties at the back surface. The comparison between the results obtained form our model and the analytical models permit us to extrapolate the use of our model in systems that involve more complex geometry. The model was applied in a four element IR objective with germanium and silicon lenses. In all the situations the contrast as a function of the field value was calculated, with and without the scattering effects. By contemplating the contrast loss, a better choice of materials, geometries and buffer positions can be made possible.
In this paper we present a robust pseudo-random method for propagating an electromagnetic wavefront through an arbitrary optical system. The wavefront at an arbitrary plane is obtained by the discrete sampling of the wavefront in regular regions equally distributed on the entrance pupil and the appropriate modelling of the optical properties of the system. The discretization permits us to treat each region as a plane wave, so long as the area is small compared to the area of the pupil, therefore allowing us to apply the electromagnetic approximations of refraction and reflection during the transfer through an optical system. We can therefore account for amplitude and phase modulation of the wavefront due to the optical system, without making any assumptions about the shape of the optical elements. Furthermore, our numerical integration method on an arbitrary plane avoids singularities due to the classical analytical integrals, while still obtaining results comparable to rigorous electromagnetic theory. We have applied the method to simulating the propagation of both plane waves and spherical waves. The well known interference patterns of classical experiments such as Young's interference fringes or Newton's rings were reproduced accurately, with respect to results obtained applying analytical methods. We then successfully applied the method to analyze a Michelson interferometer set-up, demonstrating the robustness of the calculations. Since the propagation of the wavefront is possible with this method, in the future we plan to apply the method to simulating electrically large diffractive optical elements within a complex optical system, for which rigorous analytical methods may not be available, and other numerical methods generally require large computer resources.