The challenge nowadays is to build high-resolution 2D images with purpose shows the internal structures and properties of objects or study materials hence the importance of implementing a system of high precision sampling to optimize the work of obtaining images using Terahertz (THz) technology. The exactitude translation stage was built to move 3D objects by making two-dimensional paths of 1mm±1% with periods of programmable waiting time. The objective is to place the sample in reading position of each pixel, facing to propagation of the THz wave. For the operation was made to several programs capable of controlling the positioning, time and speed required in sampling.
A method for the recording of a rainbow hologram with multiple objects at different depths in a single exposition is presented. The created hologram can be observed under white incoherent light and shows three letters R, O, and X where the R is closest to the observer at surface level and the other two letters are placed at 2mm increments into the hologram. A spatial light modulator containing the information of a binary computer-generated hologram (CGH) of the three letters is illuminated with a 632.8nm HeNe laser. The reconstructed hologram is projected on a photosensitive film and interfered with a plane wave acting as a reference beam for 90s and then developed.
Study of wave propagation with random amplitude and phase, which overlap to form interference, is presented. Where each superimposed wave has independent random amplitude and phases that are monitored by the visibility parameter. This parameter is a function of the spatial correlation distribution of amplitudes and phases of the waves that emerge from the openings. The interference fringes visibility depends on the degree of phase randomness and to a lesser extent wave amplitude.
We present a theoretical study of diffraction gratings with twin grooves, that is, each period of the gratings corresponds to two grooves. By which it can be used to form amplitude and phase diffraction elements. The diffraction patterns of these elements are particularly interesting, due to the behavior of the diffracted orders, as well as the particularities of the envelope and its diffraction efficiency.
The holograms of three-dimensional objects have been interest topics for a long time, but in the last few years other alternatives have been sought to avoid their complexities. Many of them seek to create three-dimensional effects using parallax and knowledge about stereographic vision, in other words, they use two-dimensional images.
In this paper we explore some of the benefits of calculating the wave front of three-dimensional objects, as well as several considerations that must be considered. The main ones are presented when holograms are implemented in an LSM, because of the calculation conditions and laboratory tools. Using spherical waves is a great example, a magnification along the propagation axis is produced and the objects are deformed. Therefore, it is necessary to make a study and propose changes to the algorithm that allow us to solve this situation.
Despite being fundamental complications, they allow us to explore a large amount of solutions and even consider future applications. Within this work, we seek to present some of the proposals that resolved these situations for the work teams applications.
Binary patterns has its origins in the first holograms generated by computer but with the improvement of the computational equipment began to work in gray levels. Binary patterns implementation is a proposal to obtain binary holograms representation without having to modify the techniques for their calculation.
Based on printing techniques, its sought to substitute each hologram pixel for an arrangement of certain size, trying to simulate the original value with a density of binary values. In this way a direct relationship between the arrangement size and the number of values that can be simulated is obtained.
Finding the appropriate arrangement size, its important to establish which shape or pattern will be used. In this theme some variants are proposed, however we highlight the random patterns, showing very interesting properties. Because of this, a small study is carried about propagation of randomness and its effects on the reconstructed field.
A theoretical study of gratings with radial symmetry and variable periods with sinusoidal profile, modulated for amplitude are shown. The behavior of the diffraction pattern and their symmetry degree of gratings were observed. Grating period can be modulated by external factor as spatial orientation effects per propagation, as inclination perspective of image projections that can produce local modified periods; this modulation kind causes changes in the diffracted pattern orders.
MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is the new integral-field and multi-object optical spectrograph for the 10.4m Gran Telescopio Canarias.. It will offer RFWHM ~6,000, 12,000 and 18,700 for the low- , mid- and high-resolution, respectively in the wavelength range 3650-9700Å. .The dispersive elements are volume phase holographic (VPH) gratings, sandwiched between two flat Fused Silica windows of high optical precision in large apertures. The design, based in VPHs in combination with Ohara PBM2Y prisms allows to keep the collimator and camera angle fixed. Seventy three optical elements are being built in Mexico at INAOE and CIO. For the low resolution modes, the VPHs windows specifications in irregularity is 1 fringe in 210mm x 170mm and 0.5 fringe in 190mm x 160mm. for a window thickness of 25 mm. For the medium and high resolution modes the irregularity specification is 2 fringes in 220mm x 180mm and 1 fringe in 205mm x 160mm, for a window thickness of 20mm. In this work we present a description of the polishing techniques developed at INAOE optical workshop to fabricate the 36 Fused Silica windows and 24 PBM2Y prisms that allows us to achieve such demanding specifications. We include the processes of mounting, cutting, blocking, polishing and testing.
Study of diffraction gratings through holographic cells, which correspond to micro circular zones, encoded with amplitude sinusoidal gratings. The random distribution of cells on the surface of hologram and its orientation of gratings per cell, produce in the diffracted orders a random distribution. We made a study of the behavior of the random modulation of diffracted orders, as a function of the orientation of code grating per cell.
Holographic diffraction gratings can measure micro movements, with a system that detects each period of the moving grating. One of the important features of this device is the grating period, which determines the measurement accuracy. The period can be on the order of fractions of micron, with high reproducibility and with an error of a quarter of period. One of the qualities of this system is its robustness; the measures are invariant to noise induced by device movements and environment thermal changes.