Microscopy gets boost from z-splitter prism

US researchers say they have developed a simple way to capture high-quality 3D images of live cells and organisms with a standard microscope.

The new technique simultaneously acquires images at different depths at high speeds and with high contrast, they write in a paper in the journal Optica, and can be applied to a variety of microscopy methods.

Standard camera-based microscopy systems capture images at a single focal plane. Most attempts to acquire images with different focal depths simultaneously have used multiple cameras or a special diffractive optical element to split images with a single camera.

Jerome Mertz and colleagues at Boston University tried a new approach, using a z-splitter prism to divide detected light to produce several images in a single camera frame.

“We used a z-splitter prism that can be assembled entirely from off-the-shelf components and is easily applied to a variety of imaging modalities such as fluorescence, phase-contrast or darkfield imaging,” says co-author Sheng Xiao.

The prism divides detected light to produce several images in a single camera frame. Each image is focused at a different depth in the sample.

Using a high-speed camera with a large sensor area and high pixel count, the researchers were able to distribute multiple high-resolution images on the same sensor without any overlap.

The multifocal images make it possible to estimate the out-of-focus background from the sample much more accurately than can be done with a single image, the researchers say. They used this information to develop an improved 3D deblurring algorithm that eliminates the out-of-focus background light that is often a problem when using widefield microscopy.

“This improves both the image contrast and signal-to-noise ratio, making it particularly beneficial in fluorescence imaging applications involving thick samples,” says Xiao.

To test the algorithm’s capability, the team imaged various thick samples, including the brain of a living mouse and observed what they say were significant contrast and signal-to-noise ratio improvements compared to both raw multi-focus images and traditional 3D deblurring algorithms.

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