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Integral Photography
 

The KaraSpacE Technology is based on Integral Photography.

Integral imaging is a true auto-stereo method (stereo imagery viewable without the requirement of special glasses). An integral image consists of a tremendous number closely packed distinct micro-images, that are viewed by an observer through an array of spherical convex lenses, one lens for every micro-image.

When properly practiced, the result is stunning three dimensional imagery that coveys a realism matched only by museum-quality holograms lit by a laser light source. Indeed, it has been demonstrated that an integral image can very accurately reproduce the wavefront that emanated from the original photographed or computer generated subject, much like a hologram, but without the need for lasers to create the image and a coherent light source to present it again. This allows the eyes to accommodate (focus) on foreground and background elements, something not possible with lenticular or barrier strip methods.

The term “Integral” comes from the integration of all the micro images into a complete three dimensional image through the lens array. In addition to three dimensional effects, elaborate animation effects can also be achieved in integral images, or even a combination of these effects.

Integral imaging is based on a principle known as the lens “sampling effect”. To achieve this effect, the thickness of the lens array sheet is chosen so that parallel incoming light rays generally focus on the opposing side of the array, which is typically flat. This flat side is known as the focal plane. It is at this plane that the micro images are placed, one for every lens, side by side. Since each lenslet focuses to a point onto a micro image below, an observer can never view two spots within a micro image simultaneously; just one spot at a time, depending at what angle the observer looks though the lens. For example, if you have an array of small white dots, on an otherwise black background, behind each lens at the focal plane, any given lens will appear either completely black or white, depending on whether or not the lens is focused on a white dot, or the black background. The state of each lens will vary depending on the point of observation. If all the dots are precisely ordered in a pre-calculated way, a completely different composite image can be directed to each eye of an observer, simultaneously, since each eye looks through the lens array at a different angle.  

Gabriel Lippmann

The integral photography was first described by the Nobel price winner Gabriel Lippmann in 1908 under the title “La Photographie Integral”. Unfortunately experiments with this idea could only be conducted later in the century. The realization of this idea turned out to be more difficult then first expected and only few scientists paid attention on this idea in the last 100 years. Until now there is no respective main stream commercial product on the market due to the following reasons.

1) The crafting of good quality lens plates was always almost unaffordable. Prototypes and small product series could therefore not be build.

2) Taking a classical integral image will always give a reverse perspective (pseudoskopic) image, which can not be used as such. Only by using a two step recording process, which has been introduced in different ways, the reversed image is turned into a normal image. Much time was spend in solving this problem, while the 2-Step process always considerably reduced the image quality.

3) The angle of perception was always very restricted. During image exposure, the neighboring images tended to destroy each other when the recorded object reached out of the image range.

4) The biggest paradox of classical integral photography shows, when an image of an object is prepared to be taken, and you have to decide on which plane you want to focus. On the one hand you want to have an image of different objects reaching in and out of the Plane. But the lens plate can only focus on a single plane. The intent to have an ideal 3-D image with objects reaching in and out of the plane seamed not possible.

5) Despite good imaging results, the depth resolution did not turned out to be as good as desired.

You can find here a detailed overview of the development of Integral Photography at the integral resource organization.

Since the computer technology is able to deliver high quality perspective images for the IP now, the problem with the pseudoskopic images and the paradox of the IP has been solved. But the restricted depth of the images and the restricted viewing angle are still a problem. The technology for high quality production of lens arrays is very advanced now, but the costs are still very high for prototypes and small series.

3D HDTV LCD Monitor

The research in Integral Photography has experienced a renascence in the 90s. The aim was to bring 3D imaging to the new high resolution computer monitors and TV. The developers tried out a number of 3D methods, that where originally developed for photography. The method of integral photography turned out to be quite usable for 3D-TV so that a number of such monitors based on IP have been developed.
The classical problems of IP have easily been overcome. The images are anyways all computer generated and the resolution requirements are only very low compared with the photography. A HDTV Monitor with 1920x1080 pixels can for example only generate an integral image of 480x270 pixels where each pixel consists again of 4x4 pixels inside.  

Strongly Improved IP

Apart from using the classical IP for 3D Monitors, the 90s have also brought a further development of the Integral Photography itself, for creating extremely high resolution and large scale advertisement signs. An integral part for this development is the consequent use of the powerful 3D graphic computers now available and capable to generate the most fascinating images in less then a second. With the use of modern optical simulation software it was possible to optimize the optical system and to increase the depth resolution by the factor of 15. The virtual objects can now reach many meters out of the wall. This was achieved by storing the micro images photographically on a curved imaging dish instead of a plane, by using apertures in the center of the optical systems and by using different optical materials with an additional lens surface in order to correct the chromatic aberration errors.
The angle of perception can now be extended up to 170° if desired, by placing a prism array in front of the system. The modular concept of of our product enables advertisement signs of any size like for example 2m height and 20m width.    

A typical wall of 3 meters height and 6 meters width, like at the staircase of this book store, consists of 2000 x 1300 IP pixels, where each pixel stores again a micro image with a resolution of 1280x1024 color pixels.

Read more about the integral concepts of the new KaraSpacE Integral Photography System here.

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Last changes: 08/26/08

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