1D moiré shapes by superposed layers of micro-lenses
Optics Express. 2019-12-23.
DOI : 10.1364/OE.27.037419.
Two superposed layers of transparent cylindrical lenslet gratings create classical moiré fringes, when illuminated from behind. We rely on this observation to conceive special devices made of superposed lenslet gratings that produce animated moirés when they are tilted against the light. One-dimensional moirés can show a message moving back and forth along a given direction or radially expanding towards the exterior of a disk. These 1D moirés are conceived by fabricating two layers of micro-lenses on both sides of a transparent substrate. The top layer is a rectilinear grating of cylindrical lenslets and the bottom layer is an arrangement of smaller lenslets of different sizes and orientations that create a high contrast. Moirés created by superpositions of lenslets are visually striking and can be challenging to fabricate. Therefore they have a high potential for art, decoration, and document security.
Fabrication of 2D micro-lens arrays for moiré applications
Micro-moirés combining metallic patterns and micro-lenses
Micro and Nano Engineering (MNE), Braga, Portugal, September 18-22, 2017.
Moiré effects appear when two sets of periodic structures are superimposed. By combining advanced micro-fabrication technologies and the moiré theory, we are able to obtain visually appealing moirés. Specific metallic patterns are created on one side of a substrate by lithography and etching of an aluminium film. On the other side of the substrate, an array of micro-lenses is fabricated in order to sample these metallic patterns. These new moirés can be recognized by the bare eye. They display text or symbols that move when observed under different viewing angles.
Synthesis of superposition shape images by light interacting with layers of lenslets
The present invention describes methods and apparatuses for creating superposition shape images by superposed base and revealing layers of lenslet gratings. The superposition shape images form a message recognizable by a human observer or by an image acquisition and computing device such as a smartphone. The superposition shape images may be created by different superposition techniques ranging from 1D moiré, 2D moiré and level-line moiré superposition techniques to lenticular image and phase shift superposition techniques. Moiré superposition techniques enable creating superposition shape images at different apparent depth levels. Applications comprise the protection of documents and valuable articles against counterfeits, the creation of eye-catching advertisements as well as the decoration of buildings and exhibitions.
Hiding Information in Multiple Level-line Moirés
2015. ACM Symposium on Document Engineering DocEng , Lausanne, Switzerland , September 8-11, 2015. p. 21-24.
Secure documents often comprise an information layer that is hard to reproduce. Moiré techniques for the prevention of counterfeiting rely on the superposition of an array of transparent lines or microlenses on top of a base layer containing hidden information. Level-line moirés consist of shapes that appear to be beating upon relative translation of a revealing grating on top of a base, in which the desired information is encoded. Usually, the base only contains the information corresponding to one moiré. In order to increase the difficulty of counterfeiting, we use tessellations to incorporate two or more moirés within the same layer. With the method we propose, the information corresponding to up to seven level-line moirés can be embedded within a single base layer. The moirés are recovered with a revealer printed on a transparency or with an array of cylindrical lenses. This method is general and can be extended to other fabrication technologies.