Lenticular image

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Close up of a lens grid

A lenticular print (also lenticular or prism raster image ) is an image, the optical means of tiny lenses or prisms produces a three-dimensional (spatial) impression. This illusion can be viewed without optical aids. Instead of a spatial impression, a movement or an image change can also be generated for so-called alternating or wobbling images . This effect occurs when the image is viewed from different angles .

The lenticular principle is used both for lenticular printing and for 3D displays without glasses . The lens grid principle should not be confused with the similar parallax barrier technology, which works with small, inclined visual barriers instead of lenses.

history

Functionality of a lenticular image
Comparison of parallax barrier and lenticular lens technology: the right eye only sees the pixels highlighted in red and the left only the areas highlighted in green

The lens grid technique was first proposed in 1908 by Gabriel M. Lippmann. Instead of using opaque parallax barriers, like those used in the "Parallax Stereogram" patented by the Englishman FE Ives in 1903, he presented the idea of ​​using a series of lenses.

Lenticular prints were very popular from the late 1940s to the 1980s and were later developed further, especially for advertising purposes or children's items, to show the advertised product in a print medium in motion or with a certain spatiality. But this medium has already come into its own in the art world. Well-known artists such as Andy Warhol , Sigmar Polke , Alfons Schilling or Rosemarie Trockel have had works made using the lens grid technique.

The foundations for modern 3D parallax photography were patented by the Chinese Ken C. Law in Hong Kong in the early 1970s . The American Dr. Jerry Nims and the Vietnamese Allen Kowk Wah Lo developed the famous NIMSLO camera based on Ken C. Law's patents . The world premiere took place in 1980 in Cologne at the Photokina.

In April 2007, on the occasion of the 100th anniversary of the Museum for Communication in Bern, Swiss Post issued two special postage stamps using lens grid technology.

Since 2009 the company Crane Currency has been producing microscopically fine lenticular images under its own name MOTION for use as security features in banknote printing ( tilting effect ). Patterns can be seen on these moving images that appear to be rotated by 90 ° in relation to the direction of image tilt. This technology is used, among other things, on the current banknotes of the Danish krone and the Tanzanian shilling .

pressure

Conventionally, lenticular images are produced in postcard size or smaller. A particularly large lenticular is located in the World Trade Center Station of the Massachusetts Bay Transportation Authority . A large lenticular picture was also installed in the Kalkriese Museum in 2009.

Image processing takes place today on a digital level. The images are scanned and digitally broken down into extremely fine strips (interlaced) . The printout is then laminated onto the lenticular sheet. Image sizes of 2.40 m are now possible.

functionality

Nimslo camera
Fujifilm FinePix Real 3D with integrated lenticular 3D display

At least two images that were taken at eye relief are required for production (= stereoscopic images ). Most of the time, however, four or more images are used. There are special stereo cameras for recording . a. from the company Nimslo , which take the pictures simultaneously when the camera is triggered.

The technique essentially consists of photographing a real object from two different perspectives. The camera must not leave the horizontal axis. The exact camera distance to be calculated is determined by the distance to the object, the size of the object, the depth of the object, the focal length of the camera lens, the lenticular size and the image scale. Moving 3D objects can only be photographed with a special "multi-lens" camera.

Then the underlying photos are exposed in narrow strips on a paper carrier, over which a transparent grid of vertically running cylinder lenses or prisms is placed. A lenticular lens covers associated image strips. Depending on the viewing angle, the lens plate now focuses the view on a different image strip. In the case of a three-dimensional image, the distance between the eyes ensures that each eye gets the image for “its” viewing angle, and this creates the spatial impression. The more original photos are used, the less the image will jump when viewed. The strength of the lenses is determined by the viewing distance. Usual values ​​are between 10 and 161 dpi (lines per inch), i.e. about 158 ​​µm to 2.54 mm lens width.

The lenticular system is the only imaging system that enables several different images to be displayed in a single print. The number of phases is determined by the lens size and the image resolution.

There are basically two different modes of operation:

Horizontal lens

The image is separated by a horizontal lens guide. This means that both eyes perceive the same image at the same time, separate from the other images on the print. A horizontal lens guide is therefore particularly suitable for animations, morphing and changing images. 2–200 phases are possible. The more phases are introduced, the "softer" the movements of an animation become. But if you only bring in two phases, you have an alternating picture (e.g. before and after effect).

Vertical lens

A vertical lens guide brings about a union of images. This means that both eyes can see different images at the same time. If you bring stereoscopic parallaxes into this image, the two eyes can look at different perspectives at the same time and a spatial impression is created in the brain. 4–200 phases are possible. The more phases are introduced, the smoother the transitions between the individual perspectives become. But if you only bring in a few phases, you get a "shaky picture".

Production and manufacturing costs

The first digital 3D camera for the consumer sector was introduced in 2008 with the Fujifilm FinePix Real 3D. Until then, the production of three-dimensional photos using the line grid method was only possible to a large extent in Japan . Having their own 3D photos produced was difficult for non-tech-savvy end customers, but possible. For a short time there has been an offer of corresponding devices for the automatic production of lenticulars in Germany , but only a few photo laboratories currently offer the possibility of developing line raster images . The production of a photo measuring 15 × 22 cm takes about three and a half minutes and costs around five euros.

3D displays

After corresponding prototypes as multi-channel front projections, tracked rear projections and tracked flat screens from the Heinrich Hertz Institute Berlin GmbH and later from the Dresden3D company and other z. B. were seen at CeBit, there are now the first computer monitors with lenticular foils that enable three-dimensional vision without 3D glasses . At CeBit 2005 further developments were presented. There were autostereoscopic 3D LC displays , which were already offered for sale by large companies such as Philips , Sanyo , Samsung and smaller ones such as SeeReal Technologies , SpatialView (both in Dresden ) or 4D Vision (today X3D Technologies ) from Jena . Research institutes such as the Heinrich Hertz Institute (HHI) in Berlin are working on further development.

A distinction is to be made between the lens grid principle and the similar parallax barrier technology, which works with small, inclined opaque barriers instead of lenses. The technology for glasses-free 3D displays such as the Nintendo 3DS is based on this parallax barrier principle . In contrast, the Fujifilm FinePix Real 3D camera has an integrated lenticular display.

literature

  • E. Breetz: The systematic introduction of card reading in lower grades - an essential prerequisite for the effective organization of geography lessons. (Lenticular process). In: Wiss. Zt. D. PH Potsdam, H. 4/1970, pp. 773-781 (with ill.).
  • E. Breetz / E. Gerth: Process for the production of large-area parallax stereograms, in particular for the spatial representation of the ground relief. GDR patent specification 83901 WPa 75/148150 (August 12, 1971).

Individual evidence

  1. David E. Roberts, History of Lenticular and related Autostereoscopic Methods , Leap Technologies, 2003, p. 3
  2. 2 special stamps from the Swiss Post using lenticular lens technology
  3. Description of the technology at Crane Currency ( Memento of the original from July 8, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (en) @1@ 2Template: Webachiv / IABot / www.cranecurrency.com
  4. Representation of the Danish kroner banknotes (motion window strips on the back of the banknotes) (en)
  5. ^ Nimslo camera
  6. Section: How does the lenticular process work. B. 3D photos can be printed.

Web links