The 3D surface reconstruction is done by analyzing the deformation of the image of binary grating projected onto the relief of an object, after that, the phase of the deformed pattern is extracted by Fourier transform and unwrapping the phase. There are several techniques for image grating projection and one of them is the so called Talbot Effect that creates self-images of a binary gratings. In this work one of the self-image of a grating is used for projection on the relief of an object. The deformed image is captured by a camera and is analyzed by the proposed Extended Fourier Transform (XFT) algorithm. The XFT algorithm is and enhancement of the common FFT algorithm and allows an improvement in surface reconstruction. A comparison between the reconstructed surfaces using traditional FFT algorithm and the proposed XFT algorithm is presented.
It is well known that cellophane film has good behavior as half wave retarder for wide spectrum, so, in this
work, we present imaging polarimetry method to measure the phase change introduced by a cellophane film at several
wavelengths in the visible range. The method is achieved when we introduce the cellophane film in a simple optical
arrangement composed by linear polarizers. The phase change of the film is obtained as function of the light intensities at
the output of the system.
In this work we describe an experimental technique to measure the birefringence of the cellophane film that has good behavior as half wave retarder. This technique is achieved when the film is placed in a polariscope that consists of a light source and properly arranged polarizing elements and a system of fringes is observed. Using Jones formalism for the system the birefringence appears in the phase term of harmonic functions. Some experimental results are shown.
We show the optical characterization of a Polymer Dispersed Liquid Crystal which was made mixing Norland Optical
Adhesive No. 65®, nematic liquid crystal and crystal violet dye, deposited between two glass substrates with indium tin
oxide (ITO) as electrodes. In this device, we recorded low frequency (104 lines/mm) holographic gratings made with the
interference of two beams from an Ar laser at 515 nm in emission line. We measured the diffraction efficiency of the
gratings obtaining 2% when the grating was read with a beam from a He-Ne laser at 612 nm.
Holographic interferometer is used with a dye-doped photopolymer on one of its arms, the sample is radiated
simultaneously with two wavelengths, and measuring the pattern fringe displacement we can calculate the refraction
index changes. The photopolymer we use is a mix of Norland Optical Adhesive No. 65 and Crystal Violet dye deposited
between two glass plates making a cell of 220 microns thickness. The sample is radiated with a beam from an Ar-ion
laser at 515 nm; in the interferometer we employed a He-Ne laser at 633 nm in emission line. We show some
Nowadays people spent a lot of energy to reduce the temperature of walls buildings, by the use of air
conditioner. There are a several solutions using green technologies to save energy, so we need to characterize this kind of
greens technologies. Speckle interferometry is proposed to determine the variation of temperature on green buildings that
relate the efficient use of energy spending in thermal comfort. There is a disadvantage to using thermal resistors sensors
for the analysis of a wall area of sustainable technology, because these items can only measure a very small area, and it is
very slow to make a average measurement of several points to have an estimate of the temperature. The analysis by
speckle is favorable because it is very sensitive to any change made on a surface and this allows us to record the less
obvious variation in the transmission of heat, as we can manipulate to measure considerable size areas. The use of
speckle is more affordable and improve less economical resource than other methods.
In this work it is demonstrated that they can search holograms of type Fourier in real time, utilizing photosensitive
material of the polymeric Norland Optical Adhesive 65® ( NOA 65® ) which, it is mixed with the violet crystal dye
(CV); For the record of holograms we use He-Ne laser, of 5 mW of power, in λ= 598 nm spectral line, in the
reconstruction we obtains of diffraction efficiency of the 0,216 % in the order one, which almost does not present noise.
These holograms are of phase with modulation for index refraction.
The diffraction efficiency behavior of the holographic gratings recorded in photopolymers is due to several parameters
such as the monomer concentration, the dye quantity, etc. It has been reported that the absorption in photopolymers
depends of the beam intensity employed to record the holographic gratings, polymerization velocity, humidity,
temperature, etc. In this work we present a theoretical model of the diffraction efficiency behavior of holographic
gratings recorded in Norland Optical Adhesive No. 65 mixed with crystal violet dye as function of the temperature and
the power of the recorder beam. The model is compared with some experimental results.
In this work we present our studies of the optical properties of electrically switched Fresnel Zonal Plate using polymerdispersed
liquid crystal (PDLC) materials. Our design is interpreted by using a theoretical approach to light scattering in
PDLC films that relates optical transmittance and the order parameters, characterizing both the orientational structures
inside bipolar droplets and orientational distribution of the droplets. The theory relies on the Rayleigh-Gans
approximation and uses the Percus-Yevick approximation to take into account the effects due to droplet positional
Changes in the skin topography are early stage diagnosis tool for diseases and the skin response to medical and
cosmetics treatment. The present work focuses on the applicability of the Talbot effect in the skin topography
characterization in vivo. This work shows the design and the optical system mounting using Ronchy periodical grids
for this characterization.
In this work we propose a phase material based in Polyvinyl Alcohol (PVA) and Crystal Violet (CV) deposited on a glass substrate with 10 &mgr;m of thickness. In this material we record holographic gratings using a &lgr;=612 nm and reconstruct the image with &lgr;=543.5 nm of He-Ne lasers; the diffraction efficiency was
0.0056% for the first order. The material no requires developing process and is very easy to make. Experimental results are shown.
In this work we propose a technique to measure micro displacements using Moiré patterns of Fresnel zone plates films. In this technique the pattern is placed on a mechanical mount and the displacements are measured counting the displaced fringes of an amplified moire image as the mount is moving.
We recorded real time holographic gratings in a photosensitive liquid material. This material is Norland Optical Adhesive (NOA 65(R) ) mixed with crystal violet dye (CV). The NOA 65(R) is a clear, colorless, liquid photopolymer that cures when is exposed to ultraviolet light (UV) but when is mixed with crystal violet becomes sensitive to visible region of the electromagnetic spectrum. To record the gratings we used the interference between two beams from a He-Ne, obtaining phase modulation gratings by refraction index changes. We use three different wavelength, λ = 633 nm, 612 nm and 594 nm for recording the gratings and its highest diffraction efficient was obtained when the grating was illuminated with a wavelength λ= 594 nm whose value was of 10.76 %. This mixture of NOA 65(R) and CV open the possibility to make diffractive elements.
We describe a dynamic optical active apodizator based on polymer dispersed liquid crystal (PDLC). By applying a voltage, the diameter size of device can be controlled. Two different techniques to control the diameter size are reported. In the first technique the voltage dependence is accomplished by confining PDLC between two flat glass plates making a wedge. Since both plates are coated with ITO, the PDLC response to an applied voltage varies lineally with its thickness. The design and characterization of this optical device are shown.
The majority of holograms are made using interference of light and computer-generated holograms. In this work we propose a technique in real time to generate digital holograms with a VLSI digital component, being specific FPGA and a liquid crystal device. The digital design with FPGA presents great advantage for its parallel procesing that carry out by its flexible structure, high integration and velocity. The design was verified using the platform MathLab/Simulink and Xilinx System Generator.
In this work we describe a lithographic technique for fabrication of Fresnel lenses. This technique is achieved using a photo mask and Norland Optical Adhesive No. 65. The main characteristics of this lens are his low cost and its flexibility due to the material. Some experimental results are shown.
In this work we propose a new technique to measure micro displacements using high frequency holographic gratings. In this technique the grating is placed on an object with micro displacement and these displacements are measured counting the displaced fringes of an amplified grating image as the object is moving.
We analyze diffraction gratings behavior recorded on a phase holographic emulsion. This emulsion is composed with resin and bromophenol blue dye (BPB) they have a diffraction efficiency (η) from 0.22 to 0.615% order, and their thickness are different in the holographic emulsion.
The first method for designing the amplitude hologram was proposed by Lohmann employed properties of irregular amplitude diffraction gratings, that is, every slit of the
diffraction grating is smashed into pieces where every piece has a position (P) and a wide (W),
the control of these parameters enable the detour and the change of a wave front to one that we
want. Though it has a few inconveniences, which are show in this work. One analysis of the
diffraction patterns with various geometric apertures differences to the Lohmann type is showed
too. These coding methods are apply to Fourier and Fresnel holograms type. We shown the
effect of the surround that each one causes in the diffraction pattern in order to determine the
conditions for the better visualization of the reconstructed image.
In this work we describe an experimental technique to measure the refraction index of the 3M PP2500 film which has good behavior as quarter wave retarder plate for λ=633 nm. This technique is achieved when two perpendicular linearly polarized beam from a Wollaston prism are incident on the thickness of the film. The beams were incident parallel to the fast axis to measure the ordinary refraction index and parallel to the slow axis to measure the extraordinary refraction index. Some experimental results are shown.
As conductor polymers and organic materials as Polyacetylene was first doped material, however present high sensitivity to environment, while the polyanilines present high stability in this conditions, so dimetylaniline doped in acids conditions shown good electricity conductivity material without polymerization in their structure, since can use a commercial polymer to maintain cohesion among the molecules, as the adhesive UHU, basically compound by
polyvinyl acetate. We use this adhesive blended with hydrochloric acid adding later on dimethylaniline, controlling the quantities of hydrochloric acid and dimethylaniline determining so the coloration and the resistivity of the material, presenting clear brown color to produce the acid excess, with grizzly green color correspond to dimethylaniline excess. The resistivities are of 3 to 4 KΩ to be in solution, with gel consistency their resistivity it varies the order of 58 to 100 kΩ.
Ring light distribution patterns emerging after illumination of a material that forms a conic beam can be obtained in diverse cases. There are some phenomena that produce such distributions without an artificially tailored or designed mask. This device is produced by intermixing and curing of conventional PDLC form by the combination of optical glue and the nematic liquid crystal E7. When the device is illuminated with a He-Ne laser, a ring diffraction pattern with a spot in the center is observed. It was observed experimentally that the radius of the projected ring decreased when we applied an external voltage to the device with the indium tin oxide electrodes. The voltage dependent variation in the radii of the rings can be understood as a change in the period of the concentric spiral following the direction of the applied field when a voltage is applied in this device.
We show an electro optic linear polarizer for the visible spectrum region. The device is made of a CyberdisplayTM liquid crystal display (LCD) manufactured by Kopin Co. and a linear polarizer. The device can rotate from 0 to 70 degrees the linear polarization state of a beam. To control the polarization rotation, we displayed gray levels from 0 to 255 in a PC connected to the LCD. We present the complete characterization of our device and experimental results.
We present a new recorder material, with the possibility to apply to record computer phase holograms, kinoforms, etc. This material is an acrylate monomer with mercapato adhesive, and can be easily to apply for any substrate with out dark room and critical conditions. Due that the absorption spectra from the acrylate monomer adhesive it is localized at UV region (lambda) = 300. We record with lithographic techniques phase grating in this material was made, showing good diffraction efficiency. An important characteristic it is that not necessary the developed process. Our case, the developed processes correspond only the cured polymers process. These properties are attractive due that open the possibility to control the phase material with only to control the cured process. The phase modulation of this material is due by refraction index.
We propose a technique to produce conical beams. This effect is produced when a conventional beam laser through the radial amplitude computer hologram. The computer hologram can be designed to produce a first order ring of light distribution with a spot in the center of the screen, elliptical distribution or another conical distribution are designed and shown. With these computer holograms, we can modulate the spatial structure of the light source. With the radial amplitude hologram is possible to produce different conical distribution, only with incorporate a phase term in the hologram function.
Different techniques for making digital holograms in order to synthesize true 3D images have been reported. The generation of digital Fresnel holograms by means of the ray- tracing method is the most flexible way and relatively simple, that is the objects are considered to be composed of a large number of discrete points sources of light, and the complex amplitude of spherical waves from each point sources is super-imposed on the hologram plane, however there is carry out a great amount of calculate. We presented a technique in order to evaluate simultaneously eight points on the hologram plane, so we obtain a reduction in a factor of eight the computation time. The equation of Kirchhoff- Fresnel is first calculated applying symmetry conditions avoided the redundancy in the calculations and later added the reference wave; also the precision in the values of the complex amplitude is not loss. Other methods that have been reported coupled components doing the ray tracing methods quicker yet.
We show Ronchi grating made of cellophane; this device has the particularity of modulate the polarization state of an arbitrary polarizes source. The grating period can be designed to obtain two linear perpendicular polarization states, horizontal and vertical, or circular, right and left if the source has linear or circular polarization state respectively. With this grating, we can modulate or demodulate images for stereoscopic applications.
Since recent years some activity has developed and characterized the field of research on polymers dispersed liquid crystals (PDLC's). They are useful for a variety of electro-optical applications including windows, displays and other devices. We presented a color filter with PDLC optical activity. This PDLC device was doped with cholesteric liquid crystal. This substance rotates the plane of polarization of a beam of light traversing through them and they are said to be optically active. The mixtures make an uniform behavior pitch in each micro-droplet of the PDLC. The scattering do not destroyed the optical activity of the cholesteric liquid crystal. It is not necessary to observed colors by reflection; we can observe them by across linear polarizers. When the PDLC is on, the colors disappear and when the PDLC is off, colors return.
Polymer Dispersed Liquid Crystal (PDLC) is commonly used as active diffuser and optical switches. In this work we propose an optical active pupil by using the PDLC. The aperture size of this device is electronic controlled with highly accuracy and is determined by the diffused region. This device is made of similar way commercial PDLCs, but changes in the thickness of one glass plate, change a flat surface by concave surface. Some experimental results are shown.
We present a new material with potential application in holography. We have used a film of mixing ammonium dichromate with rosin resin diluted in isopropyl alcohol. This material can be easily elaborate in the laboratory. A phase grating in this material was recording using Argon-Ion laser at (lambda) equals 457 nm, showing good diffraction efficiency. This material is capable of high resolution when we record some diffraction gratings, observing 2,000 l/mm (grooves). A characteristic of the developed process is their simplicity, takes approximately 25 seconds.