What is Differential Interference Contrast (DIC) Microscope?

Differential Interference Contrast (DIC) Microscope is widely used to image unstained and transparent living specimens and observe the structure and motion of isolated organelles, making it an alternative to conventional brightfield illumination requiring specimens’ staining.

The invention of the Differential Interference Contrast (DIC) microscope dates back to 1947 when Francis Smith first discovered the DIC microscopy technique. Later, in the mid-1950s, it was further developed as a practical microscopy method by a French optic theoretician Georges Nomarski.

The modification of the Wollaston prism by Normarski, previously used to detect optical gradients and convert them into intercity variances led to its several implementations, collectively called DIC.

To make unstained cells visible, this technique utilizes variations in the optical path length changing the phase of light and rendering necessary resolution and contrast.

In turn, it produces monochromatic shadow-cast images of the structures in the specimen. As the optical paths increase along the direction of reference, the part of the specimen becomes visibly brighter, and when the optical path decreases, the regions give the opposite contrast.

The contrast of the image increases remarkably as the gradients in the optical path become steeper. One of the important aspects of DIC microscopy is its ability to achieve highly efficient optical sectioning as it employs high numerical aperture (NA) objectives in combination with NA condenser illumination.

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