NIGHTSEA Model SFA Fluorescence Adapter for Keyence VHX Series Digital Microscopes (continued) Concrete Thin Section Fluorescence


Fluorescence is a valuable tool in the concrete petrographic world, especially for the examination of thin sections (on the order of 20μm). There are a variety of techniques for introducing the fluorescence to the sample, most commonly by impregnating the sample under vacuum with an epoxy containing a fluorescent dye, or by replacing the water in the sample with a fluorescently marked ethanol.


Fluorescence can make features of interest stand out in high contrast, or can be compared to a reference to make quantitative measurements. Among the characteristics that can be studied are: Pore size and location, Water to cement ratio, Microstructure, Fractures and cracks


Once the fluorescence has been introduced to the sample it is generally examined under a microscope. The NIGHTSEA Model SFA fluorescence adapter system is a simple and economical way to add a versatile fluorescence viewing capability to existing microscopes that operate at a wide range of scales. The dyes used in the concrete examination process are very strongly fluorescent and are excited well by ultraviolet (UV) or blue light. (Note – while the provider of the dye recommends use of UV, our experience is that our Royal Blue light source plus filter combination provides superior results for this and many other fluorescent indicators used in this and related applications.)


The images of concrete thin section fluorescence below were made with a stereo microscope (top row), and a Keyence VHX series digital microscope with the VH-Z100 lens (rows two and three). NIGHTSEA’s Royal Blue excitation was used for all images.


Why we recommend a set of three excitation wavelengths for industry needs


We have found that the combination of the Ultraviolet, Violet, and Royal Blue excitation/emission sets addresses a wide variety of industrial imaging challenges. The most common misconception we encounter is that fluorescence is uniquely associated with ultraviolet (UV) light and many customers immediately ask for that wavelength. However, we have found in several cases – even some in which UV was specifically recommended by a dye manufacturer – that either Violet or Royal Blue provided superior performance. For example:


A prospective customer wanted to image concrete thin sections impregnated with fluorescent dye. The dye supplier recommended UV, and it is true that UV will make the dye fluoresce nicely. We found that our Royal Blue excitation produced significantly brighter fluorescence.


A prospective customer sent us a sample of material that was known to fluoresce under UV. The goal was to see the distribution of non-fluorescent particles in a fluorescent matrix. While both UV and Royal Blue excited fluorescence in the sample, the best imaging contrast was achieved with Violet excitation.


We achieve enhanced performance with the ZST lens by mounting the light head on the lens's fiber optic port, but that path does not transmit UV well. In many cases, for example to inspect conformal coating, Violet is an excellent alternative to UV.


Acquiring the three-color system will provide the highest chance of success and will equip you with a versatile toolkit to address new fluorescence imaging challenges as they arise. Contact us if you would like to discuss your application further.


Wavelength Sets Color


Ultraviolet Violet


Royal Blue Cyan


Concrete thin section under blue light excitation


Concrete thin section, white light Green


Designation UV VI


RB CY GR


Excitation


360 - 380nm 400 - 415nm 440 - 460nm 490 - 515nm 510 - 540nm


Performance Expectations


The microscopes in the Keyence VHX series were not designed for fluorescence. That said, the NIGHTSEA adapter system adds a fluorescence capability that is proving to be valuable for a growing number of users. Several companies have purchased multiple adapters so that they could replicate the performance across multiple microscopes. In at least one case the customer only purchased their Keyence system because of the added NIGHTSEA fluorescence capability that enabled a critical analysis function for them.


100x 200x 500x 700x


We are grateful to the Department of Mineralogy and Geochemistry, Institute of Geoscience and Geography, University Halle-Wittenberg, Germany for providing the sample for testing.


12


There is a direct correlation between the fluorescence intensity of the sample and the imaging magnification that can be achieved. With some of our solutions – for the -Z00, -Z20, and the FI head – the excitation light from our freestanding source is directed in from the side. It is not focused onto the target area by the Keyence optics, with the result that the greater the magnification (the smaller the area you are looking at), the less of the light emitted by the fluorescence there is to collect. Fortunately many industrial applications make use of highly fluorescent dyes, and imaging at 500 – 800x has been achieved. With other lenses – the -Z50, -Z100, -Z500, and -ZST – the excitation light source can be mounted over the Keyence light source fiber optic input port, resulting in a brighter spot on the subject. We have a growing body of experience with a number of fluorescence applications with the Keyence VHX series digital microscopes and associated lenses, as shown in the image gallery. This includes a biological application, looking at mosquito midguts immunostained with a fluorescent antibody.


Emission


415nm longpass 450nm longpass 500nm longpass 550nm longpass 600nm longpass


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24