Ghost in the machine: Chinese scientists create camera that may reveal what goes on in our cells

Stephen Chen

A super-resolution camera that uses ghost imaging technology could give scientists new insight into what goes on inside our cells.

Chinese researchers have developed a device that combines the two technologies, enabling scientists to capture high-resolution images on a microscopic level in a fraction of the time taken by existing techniques.

That means scientists could potentially be able to make direct observations of cells in action – something they have not previously found a way to do.

In a paper published in Optica journal this month, Wang Zhongyang and Han Shensheng, from the Chinese Academy of Sciences in Shanghai, said their device could significantly reduce the time needed to generate a reasonable-quality image of a living cell at nanometre scale – or one-billionth of a metre.

Previously, that one image could take half an hour in a laboratory equipped with state-of-the-art hardware. They say their microscope can do it in one-thousandth of a second.

“Many basic life activities such as DNA coding and protein assembly happen in the blink of an eye. Our new technology can capture this process frame by frame in unprecedented detail,” Wang said.

“Hopefully soon, some of the most important secrets of life will be unveiled before our eyes like a widescreen movie,” he added.

The team says their device could potentially allow scientists to make direct observations of living cells in action. Photo: Chinese Academy of Sciences

Ghost imaging – so named because it gives the observer an almost supernatural ability to see things that were previously invisible, such as a face in the dark or a plane behind cloud – has been a game-changer in recent years.

It works by recording light particles, or photons, that come directly from the target, but also other light particles that are correlated with those that hit and bounce off the target. Researchers around the world are exploring a wide range of applications for the technology, from anti-stealth aircraft radar to spy satellites.

Hopefully soon, some of the most important secrets of life will be unveiled before our eyes like a widescreen movie

Wang Zhongyang

Unlike other imaging technology, it can produce a relatively sharp, complete picture of an object even if the light detector can pick up just a small number of photons. But light is a wave, so it goes around objects equal to or smaller than its wavelength – meaning resolution from a visible light microscope is limited to 200 nanometres.

To go beyond this limit, scientists have turned to another technology – nanoscopy, or super-resolution microscopy. That involves lighting cells with fluorescent materials that can be turned on and off using laser beams, then taking thousands – or even tens of thousands – of images. Using mathematical algorithms, the tiny differences in these images can be extracted to work out the location and features of objects smaller than 200 nanometres.

But that takes time – from minutes to hours depending on the technique and quality – and there is no guarantee the cell will remain healthy or even survive the process, so the Shanghai team decided to innovate.

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Ghost imaging devices typically use a single-pixel camera to record photons from the target and a multi-pixel camera to capture the correlated particles in the surrounding environment – requiring many image frames to generate a complete picture of the object.

Instead, Han, a professor at the academy’s Shanghai Institute of Optics and Fine Mechanics, squeezed the two cameras into one system and increased the number of single-pixel sensors so that a clear image could be generated in one shot. A random phase modulator was added in front of the light detector to work as a magnifier that can be controlled by computer to generate sharper features.

They then used the device to take a photo with 80-nanometre resolution in a single frame, and 60-nanometre resolution in 10 frames, finding it could take just one-thousandth of a second for each frame.

Wang said the team had patented the technology and planned to turn it into a commercial product.

A Beijing-based scientist who was not involved in the project and declined to be named called it a “real breakthrough”. “Combining the two approaches has produced something that is leaps and bounds ahead in performance,” he said.

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