Moiré pattern

About: Moiré pattern is a research topic. Over the lifetime, 1917 publications have been published within this topic receiving 27176 citations. The topic is also known as: moiré fringes & moire pattern.

Halftone screen techniques for photographic film response shaping with application to optical processing of medical x-ray images.

Abstract: Optical image processing is notoriously sensitive to nonlinearities in the input medium; many otherwise successful optical processors fail to perform adequately outside the laboratory environment because of this problem. The usual solutions to the problem-use of special photographic emulsions, developers, and even preexposure (bias)-severely limit the applicability of many optical processing schemes and may also degrade the SNR of the input image. We present several methods, all using halftone screens, to obtain proper response from the input photographic film. We then demonstrate one particular method, both theoretically and experimentally, as applied to x-ray recording of coded images that are to be used as input for an optical transaxial tomography processor.

Multiple-wavelength type interferometer

Abstract: PURPOSE:To make it possible to measure the spherical shapes and aspherical shapes in a specified wavelength region by scanning the Moire fringe of the obscure sum while is generated by the overlapping of interference fringes, and making the Moire fringe clear. CONSTITUTION:A piezoelectric element 17 divides the luminous fluxes from light sources 1 and 2 having the different wavelengths into two parts and guides the lumi nous fluxes to a reference plane 14 and a measuring surface 10 comprising a spherical plane or an aspherical plane. The reflected light beams which are reflected from the measuring surface 10 and the reference plane 14 are overlapped. The image is focused on the image sensing surface of an image sensing device 20 through an image focusing lens 19. Adjusting means 13 and 15 move and adjust at least either of the reference plane 14 or the measuring surface 10 along an optical axis. The difference in optical path lengths of the interferometer is made to be substantially zero. Then, the Moire fringe of the obscure sum which is generated by the overlapping of the interference fringes is scanned, and the Moire fringe is made clear. Thus, the intensity distribution of the interference fringe at the equivalent wavelength is obtained. In this way,the shapes of the spherical plane and the aspherical plane in the region from several tens of mum to several hundreds of mum can be measured.

An electron moiré method for a common SEM

Abstract: In the electron moire method, a high-frequency grating is used to measure microscopic deformation, which promises significant potential applications for the method in the microscopic analysis of materials. However, a special beam scanning control device is required to produce a grating and generate a moire fringe pattern for the scanning electron microscope (SEM). Because only a few SEMs used in the material science studies are equipped with this device, the use of the electron moire method is limited. In this study, an electron moire method for a common SEM without the beam control device is presented. A grating based on a multi-scanning concept is fabricated in any observing mode. A real-time moire pattern can also be generated in the SEM or an optical filtering system. Without the beam control device being a prerequisite, the electron moire method can be more widely used. The experimental results from three different types of SEMs show that high quality gratings with uniform lines and less pitch error can be fabricated by this method, and moire patterns can also be correctly generated.

Determination of the deformations in polymeric nanostructures using geometric moiré techniques for biological applications

Abstract: The nanometer-scale in-plane deformation of a PDMS nanostructure array was demonstrated using a geometric moire technique. The polymer nanostructures with cylindrical profile were fabricated by using the combination of e-beam lithography, reactive ion etching, and replica molding. The moire pattern is generated by the inference between the polymer nanostructures and the scanning lines of a CCD video camera. A uniform thermal expansion was induced in the polymer nanostructures. The moire pattern change was observed at different temperatures from 298 to 398 K. The change of the strain/pitch in the nanostructures as the temperature varied was calculated from the pure extension and the angular moire fringes. The results show the feasibility of using such polymer nanostructures as force sensors to measure the mechanical forces on the order of a few nanonewtons or less. This work has a representative application in mechanics study of the biological objects, e.g. living cells and protein, under their environmental conditions.

Moire Technique For Overlay Metrology

Abstract: Overlay performance is usually determined by exposing wafers twice, processing the wafer, and then using vernier or electrical probe techniques to measure the overlay error. In this paper, we describe a very different technique where the overlay error is evaluated in situ on the lithographic exposure tool. The basis of this approach is the examination of moire fringes between the projected image of a grating test mask and a grating test wafer. This is a particularly attractive approach to lithographic metrology because the moire fringes contain information about both resolution and overlay error. A measurement instrument has been constructed which attaches to a MicralignTM projection printer. The fringe intensity is measured by a solid state detector array positioned on an image of the illuminated arc-shaped field. Since the overlay measurement can be done many times per second, we can directly observe vibrations between mask and wafer.