Lenticular printing is a technology in which lenticular lenses are used to
produce printed images with an illusion of depth, or the ability to change or
move as the image is viewed from different angles.
Examples of lenticular printing include flip and animation effects such as
winking eyes, and modern advertising graphics that change their message
depending on the viewing angle. This technology was created in the 1940s but
has evolved in recent years to show more motion and increased depth. Originally
used mostly in novelty items and commonly called "flicker pictures" or
"wiggle pictures," lenticular prints are now being used as a marketing tool to
show products in motion. Recent advances in large-format presses have allowed for
oversized lenses to be used in lithographic lenticular printing.
Process Lenticular printing is a multi-step
process consisting of creating a lenticular image from at least two
images, and combining it with a lenticular lens. This process can be
used to create various frames of animation, offsetting the various layers
at different increments, or simply to show a set of alternate images which may
appear to transform into each other. Once the various images are collected,
they are flattened into individual, different frame files, and then
digitally combined into a single final file in a process called interlacing.
From there the interlaced image can be printed directly to the back of the lens
or it can be printed to a substrate and laminated to the lens. When printing to
the backside of the lens, the critical registration of the fine "slices" of
interlaced images must be absolutely correct during the lithographic or
screen printing process or "ghosting" and poor imagery might result. Ghosting
also occurs on choosing the wrong set of images for flip.
The combined lenticular print will show two or more different images simply by
changing the angle from which the print is viewed. If more images are used,
taken in a sequence, one can even show a short video of about one second. Though
normally produced in sheet form, by interlacing simple images or different
colors throughout the artwork, lenticular images can also be created in
roll form with 3D effects or multi-color changes. Alternatively, one can use
several images of the same object, taken from slightly different angles, and then
create a lenticular print which shows a stereoscopic 3D effect. 3D effects can
only be achieved in a side to side direction, as the viewer's left eye
needs to be seeing from a slightly different angle than the right to
achieve the stereoscopic effect. Other effects, like morphs, motion, and zooms
work better as top-to-bottom effects, but can be achieved in both directions.
There are several film processors that will take two or more pictures and
create lenticular prints for hobbyists, at a reasonable cost. For slightly more
money one can buy the equipment to make lenticular prints at home. This is in
addition to the many corporate services that provide high volume lenticular
printing. There are many commercial end uses for
lenticular images, which can be made from PVC, APET, acrylic, and PETG, as
well as other materials. While PETG and APET are the most common, other
materials are becoming popular to accommodate outdoor use and special
forming due to the increasing use of lenticular images on cups and gift
cards. Lithographic lenticular printing allows for the flat side of the
lenticular sheet to have ink placed directly onto the lens, while
high-resolution photographic lenticulars typically have the image laminated to
the lens. Recently, large format lenticular images
have been used in bus shelters and movie theaters. These are printed using an
oversized lithographic press. Many advances have been made to the extrusion
of lenticular lens and the way it is printed which has led to a decrease in
cost and an increase in quality. Lenticular images have recently seen a
surge in activity, from gracing the cover of the May 2006 issue of Rolling
Stone to trading cards, sports posters and signs in stores that help to attract
buyers. The newest lenticular technology is
manufacturing lenses with flexo, inkjet and screen-printing techniques. The lens
material comes in a roll or sheet which is fed through flexo or offset printing
systems at high speed, or printed with UV inkjet machines. This technology
allows high volume 3D lenticular production at low cost.
Construction Each image is arranged into strips,
which are then interlaced with one or more similarly arranged images. These
are printed on the back of a piece of plastic, with a series of thin lenses
molded into the opposite side. Alternatively, the images can be printed
on paper, which is then bonded to the plastic. With the new technology, lenses
are printed in the same printing operation as the interlaced image,
either on both sides of a flat sheet of transparent material, or on the same
side of a sheet of paper, the image being covered with a transparent sheet
of plastic or with a layer of transparent, which in turn is printed
with several layers of varnish to create the lenses.
The lenses are accurately aligned with the interlaces of the image, so that
light reflected off each strip is refracted in a slightly different
direction, but the light from all pixels originating from the same original image
is sent in the same direction. The end result is that a single eye looking at
the print sees a single whole image, but two eyes will see different images,
which leads to stereoscopic 3D perception.
Types of lenticular prints There are three distinct types of
lenticular prints, distinguished by how great a change in angle of view is
required to change the image: Transforming prints
Here two or more very different pictures are used, and the lenses are designed to
require a relatively large change in angle of view to switch from one image
to another. This allows viewers to easily see the original images, since
small movements cause no change. Larger movement of the viewer or the print
causes the image to flip from one image to another.
Animated prints Here the distance between different
angles of view is "medium", so that while both eyes usually see the same
picture, moving a little bit switches to the next picture in the series. Usually
many sequential images would be used, with only small differences between each
image and the next. This can be used to create an image that moves, or can
create a "zoom" or "morph" effect, in which part of the image expands in size
or changes shape as the angle of view changes. The movie poster of the film
Species II, shown in this article, is an example of this technique.
Stereoscopic effects Here the change in viewing angle needed
to change images is small, so that each eye sees a slightly different view. This
creates a 3D effect without requiring special glasses, using many images. For
example, the Dolby-Phillips Lenticular 3D display produces 28 different images.
Motorized lenticular With static lenticular, the viewer
either moves the piece or moves past the piece in order to see the graphic
effects. With motorized lenticular, a motor moves the graphics behind the
lens, enabling the graphic effects while both the viewer and the display remain
stationary. History of lenticular image technology
Images that change when viewed from different angles predate the development
of lenticular lenses. In 1692 G. A. Bois-Clair, a French painter, created
paintings containing two distinct images, with a grid of vertical laths in
front. Different images were visible when the work was viewed from the left
and right sides. Lenticular images were popularized from
the late 1940s to the mid-1980s by the Vari-Vue company. Early products
included animated political campaign badges with the slogan "I Like Ike!" and
animated cards that were stuck on boxes of Cheerios. By the late sixties the
company marketed about two thousand stock products including twelve inch
square moving pattern and color sheets, large images, and a huge range of
novelties including badges. The badge products included the Rolling Stones'
tongue logo and an early Beatles badge with pictures of the 'fab four' on a red
background. Some notable lenticular prints from this
time include the limited-edition album cover for the Rolling Stones' Their
Satanic Majesties Request, and Saturnalia's Magical Love, a picture
disk with a lenticular center. Several magazines including Look and Venture
published issues in the 1960s that contained lenticular images. Many of the
magazine images were produced by Crowle Communications. Images produced by the
company ranged from just a few millimeters to 28 by 19.5 inches.
The panoramic cameras used for most of the early lenticular prints were
French-made and weighed about 300 pounds. In the 1930s they were known as
"auto-stereo cameras". These wood and brass cameras had a motorized lens that
moved in a semicircle around the lens' nodal point. Sheet transparency film
with the lenticular lens overlay was loaded into special dark slides and
these were then inserted into the camera. The exposure time was several
seconds long, giving time for the motor drive to power the lens around in an
arc. A related product produced by a small
company in New Jersey was Rowlux. Unlike the Vari-Vue product, Rowlux used a
microprismatic lens structure made by a process they patented in 1972, and no
paper print. Instead, the plastic was dyed with translucent colors and the
film was usually thin and flexible. Lenticular arrays are also used for 3D
'autostereoscopic' television which produces the illusion of 3D without the
use of special glasses. A number of prototypes were shown in 2009/2010 by
companies such as Philips and LG. These systems use cylindrical lenses slanted
from the vertical, or spherical lenses arranged in a honeycomb pattern - which
provides a better resolution. While not a true lenticular process, the
Dufex Process does use a form of lens structure to animate the image. The
process consists of imprintig a metallic foil with an image. The foil is than
laminated to a thin sheet of card stock that has been coated with a thick layer
of wax. The heated lamination press has the Dufex embossing plate on its upper
platen, which has been engraved with 'lenses' at different angles, designed
to match the artwork and reflect light at different intensities depending on
angle of view. Manufacturing process
= Printing= Creation of lenticular images in volume
requires printing presses that are adapted to print on sensitive
thermoplastic materials. Lithographic offset printing is typically used, to
ensure the images are good quality. Printing presses for lenticulars must be
capable of adjusting image placement in 10 µm steps, to allow good alignment of
the image to the lens array. Typically, ultraviolet-cured inks are
used. These dry very quickly by direct conversion of the liquid ink to a solid
form, rather than by evaporation of liquid solvents from a mixture. Powerful
ultraviolet lamps are used to rapidly cure the ink. This allows lenticular
images to be printed at high speed. In some cases, electron beam lithography
is used instead. The curing of the ink is then initiated directly by an
electron beam scanned across the surface.
= Defects= Design defects
Double images on the relief and in depth Double images are usually caused by an
exaggeration of the 3-D effect from some angles of view, or an insufficient
number of frames. Poor design can lead to doubling, small jumps, or a fuzzy
image, especially on objects in relief or in depth. For some visuals, where the
foreground and background are fuzzy or shaded, this exaggeration can prove to
be an advantage. In most cases, the detail and precision required do not
allow this. Image ghosting
Ghosting occurs due to poor treatment of the source images, and also due to
transitions where demand for an effect goes beyond the limits and technical
possibilities of the system. This causes some of the images to remain visible
when they should disappear. These effects can depend on the lighting of
the lenticular print. Prepress defects
Synchronisation of the print with the pitch
Also known as "Banding". Poor calibration of the material can cause
the passage from one image to another to not be simultaneous over the entire
print. The image transition progresses from one side of the print to the other,
giving the impression of a veil or curtain crossing the visual. This
phenomenon is felt less for the 3-D effects, but is manifested by a jump of
the transverse image. In some cases, the transition starts in several places and
progresses from each starting point towards the next, giving the impression
of several curtains crossing the visual, as described above.
Discordant harmonics This phenomenon is unfortunately very
common, and is explained either by incorrect calibration of the support or
by incorrect parametrisation of the prepress operations. It is manifested in
particular by streaks that appear parallel to the lenticules during
transitions from one visual to the other.
Printing defects Colour synchronisation
One of the main difficulties in lenticular printing is colour
synchronisation. The causes are varied, they may come from a malleable material,
incorrect printing conditions and adjustments, or again a dimensional
differential of the engraving of the offset plates in each colour.
This poor marking is shown by doubling of the visual; a lack of clarity; a
streak of colour or wavy colours during a change of phase by inclination of the
visual. Synchronisation of parallelism of the
printing to the lenticules The origin of this problem is a fault in
the printing and forcibly generates a phase defect. The passage from one
visual to another must be simultaneous over the entire format. But when this
problem occurs, there is a lag in the effects on the diagonals. At the end of
one diagonal of the visual, we have one effect, and at the other end we have
another. Phasing
In most cases, the problem comes from imprecise cutting of the material, as
explained below. Nevertheless, poor printing and rectification conditions
may also be behind it. In theory, for a given angle of
observation, one and the same visual must appear, for the entire batch. As a
general rule, the angle of vision is around 45°, and this angle must be in
agreement with the sequence provided by the master. If the images have a
tendency to double perpendicularly or if the images provided for observation to
the left appear to the right, there is a phasing problem.
Cutting defects Defects in the way the lenticular lens
is cut lead to phase errors between the lens and the image.
Two examples, taken from the same production batch:
The first image shows a cut which removed about 150 µm of the first lens,
and which shows irregular cutting of the lenticular lenses. The second image
shows a cut which removed about 30 µm of the first lens. Defects in cutting such
as these lead to a serious phase problem. In the printing press the image
being printed is aligned relative to the edges of the sheet of material. If the
sheet is not always cut in the same place relative to the first lenticule, a
phase error is introduced between the lenses and the image slices.
See also Lenticular lens, the technology used in
lenticular printing and for 3D displays Integral imaging, a broader concept that
includes lenticular printing Autostereoscopy, any method of
displaying stereoscopic images without the use of glasses
Parallax barrier, another technology for displaying stereoscopic images without
the use of glasses Notes and references
External links Patent 2063985: Apparatus for Making a
Composite Stereograph filed May 24, 1935, issued Dec 15, 1936, by Douglas
Fredwill Winnek Coffey. Lecture slides covering lenticular
lenses by John Canny [1] Lenticular image and method
5,924,870, Issued July 20, 1999