UV luminescent sensors can solve a variety of industry challenges that would be too expensive or complicated using other methods.
So where will UV sensors work?
Some materials are naturally fluorescent. Starches, for example, glow bright blue under UV; many natural greases glow, too, as well as some adhesives and some paints. It’s possible to detect the presence or absence of any of these with little or no modification.
Some engineers don’t consider UV sensors because they don’t think of their targets as having UV properties, but almost anything can be made UV responsive. For things that do not fluoresce naturally, it’s possible to add fluorescent pigments, paints, or inks. Some of these substances have a color of their own, some are white, and some are completely clear under visible light and can therefore be used to put invisible markings on transparent objects. Pigments can be added to many existing materials (plastics, for example) with minimal effect on their properties, while various coatings can be applied by any number of methods—printing, brush, pen, spray, dipping, and so on.
In some cases, the simplest technique is to apply a mark using either contact (pens, brushes, stamps, crayons, chalk) or non-contact (spray, jet) methods. Some marking materials are permanent and others are meant to be washed off. Some are visible and others are transparent except when exposed to UV light.
- Furniture making – Detecting the presence of excess glue in a joint of wood furniture
- Automotive – Inspecting a muffler pipe for the presence of a copper fitting; detecting the presence of a UV-curable gasket
- Adhesive tape – Measuring the amount of adhesive sprayed on a roll of tape; when a nozzle gets clogged, the sensor provides feedback leading to an alarm condition
- Lumber – Inspecting for the proper coating of a clear fungicide; detecting the presence of UV markings for sorting and cutting purposes
- Food packaging – On ring-tab cans, detecting a transparent seal that prevents the seam from rusting; detecting the presence of straws attached to juice box containers when the orientation of the straw is too variable for a vision system
- Pharmaceutical – Detecting the presence of a plastic tamper-proof seal on a bottle
- Clothing – Detecting the presence of a fluorescent thread that verifies that a seam has been sewn
- Packaging – Detecting the presence of glue on cartons; detecting the presence of surgical staple cartridges
- Electronic assembly – Detecting the presence of tape on wiring harnesses
- General industrial – Detecting the presence of paint on a product
UV sensors are used extensively in quality control programs and are a fraction of the cost of traditional vision systems.