Multiband imaging technology reproduces characteristic color information of objects and estimates the continuous spectral distribution using multiple spectral discrete power data. Because a multiband image has wider color gamut than an RGB image, it can reproduce colors more vividly and naturally. Applications include image quality evaluation and spectrometric analysis of artworks.
Figure 1: Color gamut
Figure 2: An example of estimation of continuous spectral distribution from 6-band spectral information
Ricoh applied multiband imaging technology to a digital archiving system for Japanese swords. Japanese swords are noted for their subtle tones attributable to the distribution of elements in the materials of which they are composed. In a conventional RGB image, each of the three bands has a wide spectral bandwidth and cumulative light intensity in each bandwidth is treated as RGB color intensity, and therefore, the subtle color information is not retained. With this system applying multiband imaging technology, color information of Japanese swords can be obtained as the continuous spectral distribution. Also, accurate image data can be obtained without omission of subtle color information because it is possible to set a different weighting for each band. Since a multiband image has wide color gamut, a high-definition image can be displayed by selecting an appropriate output device. This system is capable of capturing an image of a sword up to 1.2m in length with 30um resolution per pixel. The position accuracy of each band image is within 1um, resulting in reproduction of high-definition color images without color shift.
Figure 3: Optical imaging system
The above chart is an example of a display of an image on an RGB screen.The images are colored to facilitate explanation.
Figure 4: Data processing flow
Figure 5: Image captured by an RGB scanner
Figure 6: Image captured by the Archiving System
Photo 1: Japanese Sword Digital Archiving System
Click to view a video clip showing digital archiving of Japanese swords using this system.
Movie 1: Digital archiving of Japanese swords
This system is in use at the Sano Art Museum in Mishima, Shizuoka Prefecture, Japan.