Adding another dimension

If you go into a very dark room on a bright day, make a small hole in the window cover, then look at the wall opposite the hole, what do you see? Imaged onto the wall is the world outside the window—but upside down! First mentioned by Chinese philosopher Mo-Ti during the 5th century BC, this phenomenon subsequently was used by early astronomers to view solar eclipses, and by Renaissance-era artists to accurately outline their subjects onto a canvas set up inside the "dark room" (camera obscura) itself. Later refinements included adding a lens to the aperture to improve image quality and using a mirror to direct the image onto a viewing surface. Eventually, during the 19th century, the addition of a light-sensitive surface to capture and store the image resulted in the first versions of what we now call a camera.

Nearly two centuries later, imaging technology is almost unrecognizable in terms of those first attempts to make and store pictures. Two-dimensional (2-D) monochrome pictures have become multidimensional, multiwavelength images or data sets, storage technology has evolved from film to digital media, and the field of image processing has been born. In fact, today's imaging systems have become a complex combination of dedicated hardware and software, while imaging itself has become an indispensable research tool.

The importance of imaging is reflected in the continuing coverage of detector, imaging, and display technologies by Laser Focus World. The data cube on this month's cover, for example, was produced using short-wave infrared (SWIR) hyperspectral imaging, and highlights the result of combining novel focal-plane array technology with an imaging spectrograph (see page 65]).

Meanwhile, the development of such sophisticated imaging techniques, combined with the continually increasing resolution of the imagers themselves, is creating an ever-growing volume of data for storage and analysis. This need for vastly increased storage capacity has itself spawned an entire industry that now, like the imaging pioneers that preceded it, is hoping to advance its cause by adding another dimension—the volumetric nature of holography-based storage seems to offer one of the most promising solutions (see page 68).

P.S. In my July column I stated incorrectly that the current Mars Rover carries a laser-based spectrometer for soil analysis. A full description of the rover payload can be found at http://athena.cornell.edu/the_mission/instruments.html.