Author: Megan Strachan

This paper forwards the work of Zheng et al. by improving the temporal resolution of FPM.

FPM depends on many different angles of illumination to encode different Fourier space information into each low resolution image. The multiplexing technique posits that an image with multiple illuminating LEDs is equivalent to the sum of images under each component illumination, provided the LEDs are a sufficient distance apart. Instead of using M images, we can use one image illuminated by the same M LEDs. This reduces the exposure time of each image by M and decreases the overall size of the low resolution dataset.

Tian et al. successfully implemented their multiplexed data collection strategy. By reducing the size of the low resolution dataset, they speed up data collection and use less memory on data storage. They also reduce data collection time by reducing exposure during imaging, as using many LEDs increases the overall brightness of each image.

This technique offers a marked improvement over standard Fourier Ptychography but still depends on the collection of many low resolution input images and a fairly slow iterative reconstruction algorithm. Even with multiplexing, FPM is significantly slower than traditional single-shot microscopy.

Fourier Ptychographic Microscopy is a super-resolution imaging technique. It uses many low resolution images of an object to generate a single high resolution composite.

A microscope’s space-bandwidth product describes the relationship between resolution and field of view. A good space-bandwidth product allows the microscope to simultaneously display detail and context — a valuable quality in biomedical and other microscopy. Space-bandwidth product is expensive and difficult, sometimes impossible, to enhance through physical alterations to the magnifying lens. Instead, computational techniques like Fourier Ptychography enhance resolution in post-processing.

Fourier ptychographic microscopy (FPM) is implemented by replacing the light source of a standard bright field microscope with an LED array. Single LEDs are sequentially illuminated. One low resolution image of the sample is collected for each LED. After all of the images are collected, the FPM reconstruction algorithm iteratively combines the Fourier space of the low resolution image stack. The result is a high resolution image that retains the wide field of view of the low resolution stack.

The greatest drawback of FPM is its time-intensiveness. Creating the low resolution image stack requires collection of dozens of images, which can be impractical. To enhance the usefulness of Fourier Ptychography, the data collection phase must be made faster.