Keyence VH-ZST Lens – Adding NIGHTSEA Fluorescence

The NIGHTSEA system adds a versatile fluorescence capability to the Keyence VHX series of digital microscopes. With the Keyence VH-ZST dual objective lens there are several options for positioning the light source to optimize performance.

Lower magnification (20 – 200x) objective: We have found that the excitation intensity on the sample is more intense if the NIGHTSEA light head is mounted on the NIGHTSEA gooseneck lamp base and directed in from the side. This works well for flat specimens such as concrete thin sections; components embedded in epoxy, polished, and prepared for failure analysis; and others. If the sample has high relief there can be unacceptable shadowing and it will be better to mount the light over the Keyence fiber optic input port (see below).

Higher magnification (200 – 2000x) objective:  You can achieve enhanced performance by removing the Keyence fiber optic illuminator and positioning the NIGHTSEA excitation light head in its place with our custom adapter. This brings the excitation energy through the lens, creating a much more concentrated illumination spot than can be achieved with the light source positioned to the side. We have made fluorescence images at up to 2000x with this configuration.

The image below is a composite of two images of an electronic component that has been embedded in epoxy, cross-sectioned, polished, and highlighted with a fluorescent epoxy-like dye to highlight cracks. The same exposure settings were used for both images, but for the image on the left the excitation light was directed in from the side, while for the other the excitation came from the top, with the NIGHTSEA light head mounted over theZST fiber optic input port. The top-illuminated image is clearly brighter.

300x, comparing side (left) and top illumination

Watch the video that shows how the NIGHTSEA system is used with the ZST lens:

There are numerous examples of images made with the ZST lens in our Keyence gallery.

With either illumination configuration you will need to use higher gain settings than you would normally use for white light imaging.

Note – Ultraviolet light and the VH-ZST lens: The fiber optic input port built into the lens transmits some ultraviolet, but it also seems to block quite a bit. The result is that the focused spot is not particularly strong. For our Ultraviolet light source we recommend that you apply the light from the side for all magnifications. This will impose some limit on achievable magnification that will be a function of the fluorescence intensity. Do not expect to achieve the highest magnifications with ultraviolet as a source. You can also consider alternatives to ultraviolet – many of the fluorescent materials used in industrial applications, such as the dye penetrants and epoxies used for highlighting cracks and separations or for concrete thin sections, fluoresce very well under Royal Blue excitation, while conformal coatings on circuit boards fluoresce well under Violet excitation.