Dec 262010

The sequence shows the difference between the original image (obtained with a wrong key) and the unencrypted one. (Credit: Image courtesy of Universitat Jaume I)

Researchers from the UJI (Universitat Jaume I) Optics Research Group (GROC) in Castelló, Spain, have developed a new tool for the field of scientific imaging. A sensor of just one pixel can record high-quality images and distribute them securely, that is, without allowing unauthorised people access to information.

In 2009, Willard S. Boyle and George E. Smith received the Nobel Prize in Physics for having succeeded in capturing images with a digital sensor. The key was a procedure that recorded the electrical signals generated via the photoelectric effect in a large number of image points, known as pixels, in a short period of time. The CCD sensor in a photo camera acts as the human-eye retinal mosaic. Since their invention, the use of the digital format for recording images has revolutionised various fields, photography amongst them, as it facilitates image processing and distribution.

Digital cameras with CCD sensors of 5, 6 and even 12 million pixels are now common. As the dimension of sensors is always the same (typically, 24.7 square millimetres), one may logically think that the higher the number of pixels, the better the image quality will be. However, this idea is not quite right as there are other factors involved, such as the quality of the lens. Conversely, more memory is needed for storing these images (the size of a 6-million pixel digital camera image is about 2 Mb).

In recent years, the world of image technologies has become a booming scientific field, mainly because of biomedical applications. Holographic microscopes, light-operated scissors, laser scalpels, and so on, have enabled the design of minimally invasive diagnosis and surgery techniques. In this context, one amazing possibility that researchers have recently demonstrated is that of capturing high-quality digital images with a sensor using just a single pixel. This technique, baptised by scientists as ‘ghost imaging’, is based on the sequential recording of the light intensity transmitted or reflected by an object illuminated by a sequence of noisy light beams. This noisy light is what we observe, for example, when we illuminate a piece of paper using a laser pointer.

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