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Engineers at Stanford University have developed a prototype of a single fiber that improves the resolution of these sought-after instruments by four times over existing designs. Advances that may lead to an era of thin needles, minimally invasive endoscopes capable of viewing the characteristic instruments that have been reached today.

Engineers at Stanford University have demonstrated a high-resolution endoscope that is four times higher than previous designs of its kind. The so-called microendoscope is an important step in high-resolution, minimally invasive biological imaging, with potential applications in research and clinical practice. Microendoscopes could enable new approaches in different areas for studying early cancer detection in the brain.

It was developed by a team under the direction of Joseph Kahn, professor of electrical Engineering at Stanford University's School of Engineering. The results were recently published in the journal Optics Letters and presented in the American 'Gathering Optics Society Optics'.

Their prototype can solve objects about 2.5 microns in size, easily reaching a resolution of 0.3 microns. A micron is one thousandth of a millimeter. In contrast, today's high-resolution ones can resolve objects only about 10 microns. The naked eye can see the object descending to about 125 microns.

Kahn is best known for his work on fiber optic communications - the essence of ultra-fast data pipelines and large Internet data centers. His work on endoscopic LED light sources began two years ago when he and an electrical engineer at Stanford, Olaf Solgau, discussed biophotonics - light-field-based techniques used to study biological systems.

Olaf wondered if it could send light through a single fiber as thin as a hair, forming a bright spot within the body and scanning to record an image of living tissue. Opportunities and challenges Kahn and solgaard knew that light travels through many different paths in known optical modes in multimode fibers; Hence the name, multimode fiber. Light is the fiber through which it transmits complex information, whether computer data or images, but it is so fried that it may not be able to recognize its way forward.

Kahn came up with a way to unscramble information by using a small liquid crystal display called a spatial light modulator. To make this possible, Kahn and his graduate student Renaciri mahalati developed adaptive algorithms - specialized computer programs - that learned how to interpret light from a spatial light modulator. A few years ago, Kahn used a similar approach to interpret the world record for computer data transmission speed over multimode fiber optics.

Research in microendoscopy took place unexpectedly and fortunately when Nassyri Table mahalati mentioned pioneering work in magnetic resonance imaging (MRI) done by John Pauly, another Stanford electrical engineer. Paulie uses random sampling to greatly speed up the recording of images in MRI.

Naxiri meter mahalati said, 'Why not use random modes to speed up imaging through multimode fibers?' 'That's it, we're on our way,' Kahn said. 'The recording setting microendoscope was born.'

Kahn's microendoscope Spatial Light modulator project is an observation of random light patterns through fibers illuminating objects in the body. The reflection of light through an optical fiber onto a computer. After turning on the computer, measure the light reflection power and reconstruct the image using algorithms and mahalati with the Nathyri table.

Kahn and his students were surprised to find that they could resolve four times the number of image features in fiber-optic patterns. 'Previous single-fiber endoscope light sources have limited resolution and the number of modes in the fiber,' Kahn says, 'so this is a fourfold improvement.' But as a result, it raised the team's scientific conundrum. 'This means that, in a way, we're capturing what the laws of physics are telling us more about what can be done through fiber optics,' Kahn said. 'It seems impossible.' The team had a few weeks of paradoxes before they came up with an explanation. A combination of random intensity patterns can propagate patterns through fiber optics, raising mode four to produce four times more detail in the image. 'Previous studies have ignored mixing. The unconventional algorithms we use for image reconstruction are key to uncovering hidden image details, 'Kahn and team have created a working prototype. The main limiting factor at this point is that the fibers must remain rigid. Bending multimode fiber makes the image unrecognizable. Instead, the fibers are placed in a thin needle to maintain their rigidity. Rigid endoscopic light sources - those often used for surgery - are common, but they tend to produce good images with relatively thick, rod-like lenses. Flexible, on the other hand - the kind used in colonoscopies and ureteroscopies - typically employs a single fiber bundle of thousands, each delivering a single pixel of the image. Both are bulky and have limited resolution.

Single-fiber endoscopes such as Kahn will eventually be minimally invasive imaging systems, and have been the focus of optical engineering research for the past few years.

Kahn did not develop a single fiber endoscopic light source first, but in improving resolution, it is now possible to envision a fiber endoscopic light source with a diameter of about two tenths of a millimeter - larger than a human hair - that can resolve about 80,000 pixels at a resolution of about three tenths of a micron thick. Today's best flexible fiber optic endoscopic LED light sources, by comparison, are about half a millimeter in diameter and can resolve about 10,000 pixels with a resolution of about 3 microns.

Future

A rigid single-fiber microendoscope light source can enable countless new procedures for microscopic imaging of organisms. These range from analyzing the cell biology of brain tissue neurons to studying muscle physiology and the early detection of disease in various forms of cancer. Looking to the future, Kahn is excited about the potential work with biomedical researchers pioneering these applications, but as a physicist and an engineer at heart, he is most fascinated by the technical challenge of creating a flexible monofiber. 'Nobody knows if a flexible one is possible, but we're going to try,' Kahn said.