The technique is based on a concept similar to using the camera’s focus to determine an object’s distance from the camera. Just like using manual focus on a DSLR, the focus is dependent on distance — as the lens is adjusted, objects closer or farther from the camera come into focus. Taking multiple images at different focus lengths allows researchers to determine how far away that object — or in the case of microphotography, molecule — is from the camera.
Previous research showed that by manipulating the wave of light bouncing off those objects, scientists could determine where the object was at that moment without using multiple images taken at different focus lengths, but by looking at that molecule’s shape. The light was manipulated using a phase mask — imagine it as a sort of camera filter that shifts the light so someone with training can easily identify the object’s distance from the camera.
The researchers at Rice theorized that taking the same filter that shows distance and adding an element of time would allow them to see not only distance but movement. The research team, led by chemist Christy Landes, took the phase mask (the filter that shows distance) and built a device to spin that mask around.
As the mask spins faster than the camera can shoot, the image sensor picks up the molecule’s movement — so one molecule pops up several times in the same image. Since the phase mask allows a trained eye to determine distance, researchers can then measure the copies of the molecule on the image and see where and how it moved.
The new technique is helping researchers to study processes that happen at rates faster than the typical laboratory-level camera — 10 to 100 frames per millisecond — like absorption of proteins and more precise measurements on the way molecules move.
The ‘hack’ could also help research teams with limited budgets — Landes said building the STReM only cost a few hundred dollars, which could help achieve high-speed images without the expense of a top-of-the-line laboratory camera.
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