A graduate student preparing to make a presentation checks that the laser pointer is working and a clearly recognizable arrow appears on the screen in front of the audience. A family vacationing in Florida visits a major amusement park, and prior to entering a lights display, they all don a pair of cardboard-framed glasses with patterned plastic eyepieces. In ambient lighting the glasses make everything look soft and diffuse, but in the lights display the glasses create a virtual snowstorm; centered around every light appears an image of a snowflake.
These visual effects are produced via diffraction, as opposed to reflection or refraction. The glasses and an element in the laser pointer are patterned so that light is “broken up” in a specific, desired manner. This breaking up of light was termed diffraction in a manuscript published posthumously by Grimaldi in 1665. The pattern projector and glasses are two of the most visible mass applications of diffractive technology. Less visible are the applications of diffractive optics in imaging systems for aberration correction and in the development of direct retinalscanning microdisplays. The integration of diffractive optics with semiconductor lasers could also play an important role in next-generation telecommunications switching networks, as well as data communications within computers.
The first person to control diffraction deliberately was Abbe, who in 1873 used his understanding of diffraction to improve the quality of images produced by Zeiss microscopes. His understanding was the culmination of nearly two centuries of study by prominent mathematicians and scientists such as Fresnel, Fraunhofer, Kirchhoff, Maxwell, Rayleigh, and Sommerfeld.
The application of diffraction gratings to spectroscopy at the turn of the twentieth century provided further evidence that one could take advantage of diffraction to achieve a useful end. Diffraction was no longer something whose effects had to be ameliorated.
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