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Advances in holographic replication with the Aztec structure


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Title Advances in holographic replication with the Aztec structure
Title of Series 7th International Symposium on Display Holography (ISDH 2006)
Part Number 58
Number of Parts 61
Author Cowan, James
License CC Attribution 3.0 Unported:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor.
DOI 10.5446/21278
Publisher River Valley TV
Release Date 2012
Language English

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Subject Area Computer Science
Abstract Holograms that are predominantly in use today as replicable devices for display, security, or packaging can generally be divided into two categories: either surface relief rainbow holograms, which include three dimensional images and intricate grating patterns, or reflection type volume holograms. The Aztec structure is a special surface relief device that combines aspects of both of these types. Its fabrication by holographic means requires techniques of both surface and volume holograms, and thus it is technically more difficult to make than either separately. The structure is deeper than the standard surface relief hologram, and its profile has the characteristic of several well defined steps, such that, when viewed on edge, resemble a stepped pyramid. Thus, replication of the Aztec structure requires special high resolution techniques to faithfully record the submicron features of the stepped profile, and thus is more difficult to manufacture. The visual characteristics of the Aztec structure are similar to the volume hologram, in that single colors, rather than rainbow colors, can be viewed. Also, a combination of single colors can be encoded into a single master, yielding unique visual effects.
good morning ladies and gentlemen but I would like to talk to you about advances in holographic replication structure called as take I realized that some of you here have had some acquaintance with the state this talk is directed at those who never ever heard of so what do
we have out there today basically 2 types of surface relief structures that are replicated mechanically volume reflected structure the replicated object it's
look at a larger group which is you already heard as a predominant the method of replicating holograms surface structures can be divided in a rainbow holograms diffraction grating structures rainbow holograms rainbow colors no single color the three-dimensional horizontal parallax only viewable with floating in 1 direction these we know from
these the familiar vs above and a Master Card global fraction grading
patterns also rainbow colors no single colors mostly to the also 2 D and 3 D very complex patterns viewable from many angles and here's some
examples to from a recent book called up of optical document security how
are these service really structures memory well I think we're all pretty much familiar with the general process was just reviewed the off-axis leaf the packed next figuration reference an object like a on the same side the recording surface made like this
object reference interference fringes perpendicular to the surface recording medium this
photo resist so when the development takes place you're left with the surface that looks like a sine wave into
replicated to form a nickel master from the photo resist from the Nicole you
compress the pattern into plastic and then the plastic
is catalyzed and that's what we normally see as an embossed all what about volume
structures behavior is totally different full parallax with a single colour uses adenosine configurations object and reference beams on the opposite side article instead of mechanical replication so here's
another made reference an object on opposite sides interference fringes parallel to the surface in
reconstruction reference light reflects off of this summer my transparent layers usually photographic emulsion documented gelatin therefore polymer you get coherent the reconstruction no surface relief here whatsoever the only way this can
be replicated this optically and generally it's like you have full polymer real wealth across the cylinder which has a master of whole on it and you actually make holograms on the production line this is a process that is inherently more expensive then in Boston and here is an
example of what you see full parallax single-color and we're looking above and below it to the right and to the left of this particular image how and we
improve upon conventional holograms we also we have a very strong he been natures surface relief volume reflection hologram the morpho butterfly here's the
Morpho retinal are beautiful blue period as color there's no color pigment in this way here's another species
of lawful epsilon slightly different color also no color dignity I resentful arise here by the way
is just a display case of morphosyntactic ubiquitous in the Caribbean this is from the Caribbean island of Aruba we
did that micrographs of the wing structure and you can see at low magnification looks like a linear operating what is the magnification increases you say a complexity to the wing structure and if we look more
closely at the wing structure we can see that it has this christmas tree like structure with little parallel veins extending out only decide these veins spaced a half wavelength apart for the light that is seen in reflection and white light comes in from the top surface of white light comes in here reflects of of each of these things coherently and all the other colors absorb can this be
duplicated in photo resist well the answer is yes with the following modifications replace the
undercut structure with the step structure achieve brightness by putting the step structure with a highly reflective metals like aluminum and we make it
combined the off-axis modern recording geometries by the way the name as Aztec is a mechanism for guys so for the resist technology but it also refers to the final structure that we get when we do this wording and the way we make
it is to combine the 2 methods that we just saw we make in the same photoresist needed the volume grating which gives parallel fringes and we have so-called opening grating out described that term later which is off-axis spreading which gives fringes that are perpendicular to the surface so we get 2 sets of interference fringes perpendicular to each other when we the that sort of
I and this is in this is this what happens if well the answer
so the the opening structure opens up the surface to develop a richer and 1 way of doing this is with the 3 coherent beams of producing a honeycomb structure and then if we put the
steps in to the structure we get what I'm calling a single colour photonic crystal we get single colors in the 0 order and we get diffractive colors that dispersed all that angles away from the normal if we
recorded in narrow mm centimeter wide strips and with slightly different step heights we get what I call a course right through
and here's spectral scans there's a spectral scan of but the several of those stripes it's also
possible to not only use a three-year beans to recorded the opening gradient but to use 5 beams and we get a structure
kind of like this
and if we magnify at normal incidence we see many parallel planes
and looking at 60 degrees we we see that very well-defined terraces and again many
well-defined tourists here as well and we can also use
seventies incidentally the use of even being this leads to objectionable a parents the the contrast ratio from the height of a low exposure area is proportional to the square of the number of B so in this case 14 and 1 the previous case 25 to 1 with 3 being 901
and here's the 1 with the 7 the we can also
have a the sale uh with the liquid crystal polydisperse liquid crystal introduced and we can change the voltage with the polydisperse liquid crystal the the index of refraction changes linearly and therefore they the the color that scene and reflections is changed and we can also
isolate certain regions of the top surface to be team red blue the what about the
as stakeholder we can in this case we may find that the off-axis cost vector is objectionable so we want to reduce that so we have an object payment to reference the swan references on the same side the 2nd references on the opposite side so with the diffraction efficiency then the AltLex's minimizes the body maximizes
selection here the surface diffraction efficiency varies as a Bessel function volume efficiency varies as a hyperbolic function but the steps have to be extremely well defined in order for that efficiency to be high steps from moderately drops steps barely find it drops even more when we make
a we make the whole graph we have you can do it as a that's so called symmetric construction where they were we the the interference fringes curves are actually the curvature and the
development of these 2 slight curves in the the structure but the structure is still shows the the characteristic steps here some single
color images made with varying step right so blue image the step by 121 centimeters that the image on the right with the wavelength of 600 mm sinister Python 192 nanoliters generally speaking these steps here are about anywhere from 5 to 10 steps so this is the least an order of magnitude larger than your typical of it involves children we can also
make him asymmetric profile where the so-called opening fringes commanded over very large angle and we're left with an asymmetric configuration which is
actually leads to very high efficiencies here's a typical set of efficiency curvature five-level structure by tilting there's
from plus 1 to minus 1 we can actually get different colors passion here we can also
if it goes it as much as 10 levels we get an envelope with many different the kurds under In
many adherents residences closely spaced wavelength at a single level plays forms an envelope and the result is a kind of a rainbow full parallax and back this
curve is based on scalar theory but not for the overall picture in this case 3 microns it follows the full full-vector theory very closely and here is an
example of the place telegram in Boston the plastic seen from the top we can even say there's a degree of undercutting here and here's a
side view and again I'm saying that your Typical embossed holograms has a depth about equal to 1 of the steps so you can see we've got anywhere from 10 to 14 steps here the reason this looks somewhat random is because this is a diffuse image overall pattern would have a random headed for a diffuse images but because the steps that are very well defined the color is quite uniform
and this is the object from which the micrographs related and here we're looking above and below and to the right and left so there's full parallax the full parallaxes maintained the color single color is maintained at and these little circles here these little circles and this cross or focused in the plane but this larger cross in the background is a full 2 inches behind the surface and we see that's still sharp focus so this is rather extraordinary effect affordable also it's also
possible to replace the aluminum with other materials of dielectric materials of high index they're actually transparent in the visible of for example titanium dioxide and zinc sulfide very high indices of refraction and actually form a very visible image but they're transparent so as
a hologram radical device the Aztec structure 1st allows for full parallax single colors that can be mechanically replicated 2nd allows to easily viewed circular images in full color and 3rd more difficult to replicate because of the complexity of the profile and finally the
challenge for the future we should be able to find some way of embossing undercut structures In that case the nominal of dielectric coatings acquired holographic method is ideal for recording undercut structures the real challenge would lie in somehow find a way to replicate and I know from experience that trying to replicate undercut structures of extremely difficult but if we had and I'm assuming we have great advances in Boston materials it had some Boston materials with high elasticity a lot of nice features but if we could do that then we could indeed replicate the the the butterfly the original butterflies structure we wouldn't need these metal coatings so so far we're doing OK with the with the of coding as a it's very similar to standard lost a lot the main difference is it's a deeper structure that thank you if you don't take a chance in the short time to bring so much informations and uh that have the same 1st another the you find you ever try mentalizing and actual morpho butterfly in finding bossing that that's an interesting thought to both the the actual morpho butterfly wing it's extremely fragile if you just touch the the you just run you really can't even touch it's extremely fragile indeed the known houses but affect roles so the wings and biological processes he's known on him well and that some people ask me why is it taking you so long to develop this semester will think how long it took out to evolve this magnificent structure I'm assuming a couple of million years have to get and you have to it is time to hear that members of the Ministry B these instance I have looked at many many many many some later ones I haven't seen but certainly that's anything like that can we very had to look at the and again price and I think this is very hopeful technology
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