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Non-linear optical materials hold promise for better imaging

1st April 2013


When photographers zoom in on an object to see it better, they lose the wide-angle perspective - they are forced to trade off 'big picture' context for detail. But now an imaging method developed by Princeton researchers could lead to lenses that show all parts of the scene at once in the same high detail. The method could help build more powerful microscopes and other optical devices.

Cameras and other optical devices - including the human eye - are limited by the amount of light that they can collect through their lens openings, or apertures. In order for a light ray to be recorded, it has to pass through the lens and reach the device's 'detector' - such as the eye's retina or a digital camera's detector. But many light rays never make it to the detector, either because they are too weak, or because they are deflected.

This problem is particularly acute with details that are smaller than the wavelength of light. (Each colour of light has a distinct wavelength - green, for instance, has a wavelength of 530 nanometres, roughly the size of a typical bacterium's internal structure.) Light rays from such tiny features fade before they reach the lens. To capture these rays, devices have to probe very near the surface of the object, and scan it point-by-point, stitching together a full image.

The new method addresses the shortcomings of small apertures by taking advantage of the properties of substances called non-linear optical materials.

The core component, a non-linear wave mixer, is a rectangular pill-sized crystal of a material called strontium barium niobate. The researchers placed the object to be imaged on one side of the crystal and image-capturing equipment on the other. They tested the system by obtaining images of various objects, including a chart developed by the Air Force that is widely used to calibrate optical devices.

For more information, visit www.princeton.edu

 





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