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Multispectral imaging has been around for decades in various forms, sometimes as special cameras on artificial satellites, sometimes on reconnaissance flights, and more recently in the examination of works of art.

Our multispectral imaging design idea was hatched several years ago but with a significant difference. It was originally designed to fill a need to explore large surfaces for the presence of fingerprints. However, fingerprints do not always appear in the visible part of the spectrum. Taking images with sufficient resolution in ultraviolet and infrared on large surfaces, the process would be far too cumbersome and time-consuming – hence prohibitively expensive. In addition, not knowing where a fingerprint would turn up, the entire surface would have to be photographed in close-up. This kind of macro mapping can produce thousands of images even if using only broad band filters. The key was automation.

The full integration of motion, camera, filter changer, and lighting control in an automated loop now permits performing tasks that would have been dauntingly huge before. The ability to use large numbers of narrow band-pass filters permits spectral mapping through creating a spectral image cube of a painting.

Instead of relying on one sensor to produce a multispectral series of a view (that limits resolution significantly) we opted for a three-axis motion control device that carries a platform on which a number of instruments are deployed. The motion control moves and positions a digital camera with a precision better than the size of a pixel on a CCD sensor. This permits tiling a great number of macro images, providing unprecedented resolution, plus reflectance spectral information.

After years of development and testing, we are now ready to share this technology.

How it works

Essentially, the apparatus is a highly precise motion control device that can carry payloads up to 60 pounds or more. The payload can be a camera, spectrophotometer, or an x-ray unit – whatever cluster of sensors is needed for the task. Typically, in our work it carries two cameras, one chilled CCD imager and one Nikon color camera. In addition, it also carries light sources for imaging from 178 to 1100 nanometers, including fluorescence imaging.

Integration

The key component is the fully integrated software controlling all functions of the device – motion, sensors, and lighting. A difficult task indeed, because components come from so many varied sources. In addition, programming permits full automation; remote control, web access and sharing of data between geographically separate users. Much like astronomical observatories on high mountains or the Hubble Space Telescope, the device can be used remotely and data retrieved. It is indeed a tool for multiple concurrent users such as experts examining a painting from remote locations.

Examples

We now routinely produce 3-4 gigabyte images tiled seamlessly from hundreds of macro images. The resolution of such images is about 20 microns or about the size of pigment particles. Much like Google Earth, you can zoom out and you see the entire painting or zoom in to observe the finest cracks in the paint or particles of pigment.

Advanced benefits

Our aim was not just to produce extreme high resolution images but also to use the multispectral approach to record material information from the artwork. At present we have sixteen 10 nanometer bandwidth filters installed in important ranges in the electromagnetic spectrum. This approach obviously leaves gaps; however, under development is our spectral imaging camera. The unit will be pocket-sized and capable of similar spatial resolution but with a spectral resolution of 2 nanometers from 178 nanometers to 1100 nanometers. Concurrently, we are also developing Raman and imaging Raman applications that will be utilized from the platform and be capable of examining very large areas  - typically up to 5x8 feet.

Orders

We are pleased to offer our expertise and technology with either turnkey equipment or custom designs with full integration. Please contact us for further information or to arrange for a demonstration.