Temporal Pixel Multiplexing Setup and Examples
A TPM prototype was made by focusing a camera on a TI DMD micromirror array. DMDs consist of over a million tiny mirrors that can be flipped many thousands of times per second. DMDs are commonly found in home theater systems but many researchers have started using them as customizable light switches.
Here, the DMD allows us to toggle light to each pixel of a camera, allowing fine grained control of exposure in time and space.
An image, either from a fluorescence microscope or from a second lens used for macro imaging, is focussed on the DMD. By toggling the mirrors in a precise pattern synchronized with the cameras normal exposure, we can embed high speed information in high res images.
TPM in action
A high resolution image (left panel) is taken of a milk drop falling in water using the TPM setup, which is running a 4x4 exposure pattern during each frame. The embedded movie (rightmost panel) has an effective frame rate of 400 fps, even though the camera itself is running at a relatively slow 25 fps.
A zoomed view (center) reveals whats going on: the high speed content is embedded in parts of ithe image that are blurred. Since blurred parts of the image are by definition fuzzy anyway, the high res TPM image appears qualitatively very similar to a 'normal' image.
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High resolution image (1000x1000 px) embeds high time based content in the 'blurred' regions.
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Zoom shows high spatial frequency content embedded in blurred regions.
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Pixel rearrangement reveals an embedded 250x250px movie.
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Biological examples, technical details, and ways of reducing the patterned visual effect at high res can be found in our Nature Methods article.
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