High magnification fluorescence with the Keyence VH-ZST lens

Posted On: Friday, February 16, 2018

Willemite/calcite boundary, 500x

For a while we have been offering a variant of the NIGHTSEA Stereo Microscope Fluorescence Adapter that fits on several of the lenses for the Keyence VHX series of digital microscopes. That adapter does not fit on the newer VH-ZST dual objective zoom lens, but we have been working in collaboration with the local Keyence representative and are close to a solution. While testing the prototype we have seen some very encouraging results – images at magnifications up to 2000x!

The magnification you can reach with fluorescence is dependent on the fluorescence intensity of the subject combined with the excitation energy you can deliver to the surface. With our standard adapter configuration we are applying the excitation light from the side, so the excitation energy per unit area does not change as you change the lens magnification setting. But as you increase magnification you are collecting less light, with the result there is some practical limit at which you are just not able to image the fluorescence well. With our original system on the Keyence we have acquired useful fluorescence images at up to about 700x with a very brightly fluorescent subject, and at up to 200 – 300x with weaker subjects.

With the -ZST lens we can remove the system’s fiber optic illuminator and position our excitation light head in its place. This brings the excitation energy through the lens, creating a more concentrated illumination spot than can be achieved with the light source positioned to the side. The arrow in the image below points to the concentrated illumination spot.

(Click any image for larger view)

Our initial trials indicate that at magnifications up to about 200x it is still better to bring the light in from the side. For higher magnifications the light port solution is preferred. The images below are from a fluorescent mineral containing willemite (green fluorescence) and calcite (red fluorescence).

Stay tuned! We will announce this new adapter for the VH-ZST lens as soon as it is finalized and available.


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