Proc. SPIE. 6024, ICO20: Optical Devices and Instruments
KEYWORDS: Signal to noise ratio, Diffraction, Optical transfer functions, Point spread functions, Visualization, Imaging systems, Image processing, Image resolution, Wavefronts, Wigner distribution functions
The aim of this work is to propose a positiveness constraint on the Wigner Distribution Function (WDF) of the detected image of two incoherent point sources: if WDF lacks of zeroes along the frequency coordinate the object can not be resolved by imaging and detected systems; otherwise, it can. This criterion can be applied without preference for a circular clear diffraction limited aperture and for complex apertures with small aberration values; furthermore, it holds if the intensity of each source is different or even when the sources are not points.
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.
The aim of this work is to find a resolution value for grating spectrometers when two spectral lines are analyzed. The phase space representation is used to find this value when the following proposal is employed: If the Wigner distribution function is positive along the space frequency axis (at the origin of the space axis) then the two spectral can not be resolved; otherwise, the spectrometer resolve them.
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.
Crystallization plymerization can be generated in the glucose with fructose when ultraviolet light it is irradiated; the crystallization polymerization opens up possibilities to the material, as matrix to record holographic images, applied conventional microlithography techniques with ultraviolet ligth. The masks with the information is transferred as a modulation of polymerized regions, where were exposed to UV light and regions without plymerization not exposed to UV light. Shows phase modulation by refraction index. Because the polymerized areas presents less density, than the nonexposed areas, changes the emulsion density can be interpreted as changes of refraction index. A developed process is not required, because the material is developed itself; for a physical-chemical mechanism well-known as process cured reaction.
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.
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.
In this work we proposed an alternative criterion to the Rayleigh and Sparrow to resolve two incoherent point sources when the pupil function of the optical system is a slit. The analytical results and numerical simulation are based on the Wigner distribution function given a minor resolution value than the other two criterions.
In this work we show the behavior of digital hologram obtained with the Kirchhoff-Fresnel's integral when these hologram are written on a TV monitor and this monitor has a finite number of gray levels. The Kirchhoff-Fresnel integral is numerically evaluated and represented in the computer virtual space. When the integral obtained values are showed on the TV screen they are changed due to the number of gray levels. Therefore in the reconstruction step of the hologram obtained on the TV screen we expect some details deterioration in the obtained holographic image.
In this paper we propose a technique to make numerical Fresnel holograms for binary and gray level objects, using Kirchhoff-Fresnel diffraction scalar theory in the paraxial approximation. These holograms produce a real image which can be observed in the reconstruction process with a He-Ne laser.
In this work is presented a multiplexing technique to produce color plane holograms using a single wavelength. A color digital scene is separated in its three basic colors by software. Each monochromatic scene generated with a PC computer is sending to a liquid crystal, which is used as a gray levels discrete transparency, and with a plane reference beam, previously calculated, a hologram is registered in the holographic film plate for each basic color.