Algorithm for microscopy

A processing system that generates high-definition images is expected to open up new capabilities in the microscopy industry.

Sheffield University spin-out Phase Focus has developed the device — dubbed a ‘virtual lens’ — to eliminate the restrictions of traditional microscopes and introduce functions such as post-acquisition focusing and stain-free imaging.

Instead of using physical components to capture an image, the lens-free microscope uses a software algorithm that analyses a picture generated by a standard CCD camera. This highlights any diffraction patterns created by a laser light source passing through the specimen. The process is then repeated between 25 and 100 times to achieve an additional phase image that documents changes in cell shape.

Ian Pykett, chief executive at Phase Focus, said: ‘The breakthrough is that this computer program can process not only the intensity but also the phase image, which records the changes in light refraction as it travels through the cell. The extra information allows us to achieve high-contrast images without having to do any staining, so we avoid damaging cells or risking termination of the cell culture.’

In addition to staining techniques, conventional optical microscopes must be in physical contact with the specimen to achieve high-resolution images. This is usually done through a thin film of oil or water that connects the lens to the cell. The group said its virtual lens removes this step by analysing objects remotely. This enables researchers to select focal depths for more in-depth analysis after an image has been processed.

Pykett explained that a further application is its use in electron microscopy to replace electromagnetic lenses. These are coils of wire and magnets that bend the electrons using a monochromatic beam. The technology has the potential to overcome the image limitations of optical microscopes, however, the lenses can cost hundreds of thousands of pounds and, according to Pykett, are far from perfect in terms of reaching their optimum resolution.

He said: ‘Ideally you would like to see features that are the same size as the wavelength of the illumination or radiation you are using. In the case of the electrons, we are a factor of 10 away from the theoretical wavelength limit. If you don’t have to use lenses in electron microscopy you can save money and see features smaller than you could with the best of today’s electromagnetic lenses.’

So far, the technology has been demonstrated in optical, electron and X-ray microscopy, however, Pykett claims the virtual lens can be applied to all wavelengths and has plans to extend research into infrared, ultraviolet and gamma-ray applications. An investment of £350,000 from the South Yorkshire Investment Fund and a £100,000 grant from Yorkshire Forward are expected to bring this research closer to commercialisation.

‘I believe the impact of this technology will be pervasive,’ said Pykett. ‘We’re able to get images better than anybody has ever seen before. We’ve already shown that this works in cell imaging, and in the case of electron imaging, we are working on integrating the technology with existing systems.’

Ellie Zolfagharifard