Visual and 3D information present in the world surrounding us can beacquired in numerous ways. They include devices such as high-quality stillcameras, video cameras, depth sensors (Kanade 1994, Michelangelo Project n.d.)multicamera arrangements (Narayana et al. 1998) and omni-directional sensors(Nalwa 1996, Nayar 1996). Different acquisition systems can be used fordigitizing different objects. Rare books are digitized using a still camera setin a fixed position, whereas an object such as a statue is imaged from severaldifferent viewpoints. Issues that need to be resolved as part of acquisitionare image resolution, cost, acquisition time, revisiting the acquisitionprocess, the number of vantage views, synthesis of views from directions notincluded in the scanning and mixing of synthetic and real content.
The panel saw examples of acquisition of digital content at three sites:Keio University, the National Diet Library, and the National Museum ofEthnology. At Keio University, the emphasis is on digitizing rare books andmanuscripts3/4Western, Japanese and Chinese. The Keio University Library has alarge collection of rare books, one of its prized possessions being a GutenbergBible.
Keio University uses three different cameras for digitizing rare books,illustrations and photographs. A high-speed digital camera, an NTT-Olympusprototype, is used to digitize an entire book very quickly. It takes about fivesec/page capture and display a single page. Figure 6.2 illustrates one of thecamera setups at Keio University. Illustrations in the rare books are scannedusing a high-quality camera that takes about two minutes/page. A third scanner,Kodak professional PCD scanner 4045, is also available for scanningphotographs.
Fig. 6.2. Camera setup for scanning rare books.
The National Diet Library (NDL) has one of the largest collections ofdigitized rare books, documents and children's books in the world. The NDLout-sources digitization work to private companies and does not possess anyacquisition devices.
The National Museum of Ethnology has an operational setup using three 3Dscanners that can handle 100 objects per day in an "assembly line" fashion.These scanners can image objects that vary in sizes from 40 cm to 100 cm andcan also produce measurements such as height, width and depth. Although denseimaging of 3D objects is possible (at 1/2-degree increments from alldirections), typically five images from front, back, left, right and top arecollected.
It is the panel's impression that the Japanese sites have shown operationalcapabilities in acquiring a wide range of artifacts, rare books andillustrations. There is a general appreciation for preserving rare books andother objects, and the Japanese even seem to be willing to subject their rarecollections to repeated scanning to keep pace with improving acquisitiontechnology. Keio University researchers cite the superior lighting system usedfor imaging the rare books. This "cold lighting" system assists in thepreservation of the books rather than causing them to deteriorate.
One or two 2D images of pages from a rare book are often enough to createthe necessary digital content. For 3D objects such as statues, many more imagesfrom different directions are required for virtual reality presentation.Although facilities for acquiring images at 1/2-degree increments from alldirections are available in the National Museum of Ethnology, few images arecollected in operation. One of the ways in which the paucity of data can behandled is by developing techniques for synthesizing new views from existingones (Levoy and Hanrahan 1996). Such capabilities were not in evidence at themuseum.
Another important issue in the acquisition process is cataloging. Differentlevels of capabilities were demonstrated. The National Ethnology Museum has themost streamlined cataloging scheme for 3D objects. On the other hand, theNational Diet Library, although it has millions of pages imaged, does not yethave a cataloging mechanism in place.