An Interview with Joe May

Chief Technology Officer for EIT Instruments

EIT Instruments  is a member of the UV LED Curing Community. To learn more about measuring the output of UV LEDs visit http://www.eit.com/uv-products or email uv@eit.com 

Paul Mills, moderator of the UV LED Community recently sat down with Joe May, Chairman, and Chief Technology Officer for EIT to discuss new developments in measurement for UV LED light sources. Here are some highlights of that discussion.

What does EIT provide that might be of interest to the UV LED Curing Community?

Since the mid 1980’s, EIT has been one of the industry leaders in industrial UV measurement.  Products like the UviCure® Plus, Power Puck® and UviMap UV radiometers have been field-proven standards for three decades.  As the industry has evolved, we continue to innovate with UV measurement tools like MicroCure®, PALM Probe®, SpotCure®,  PowerMAP®, and our 3DCure® devices.  These devices were engineered to work great with the conventional arc and microwave sources. Now we see the emergence of LED sources. The output of UV LEDs is much different than the output of UV sources that use mercury, and so the method of measuring UV from LED sources needed to be different. We have responded with the a new series of radiometers. The new  LEDCure™ housing may look familiar but the optics have been completely redesigned.

How is measuring a UV LED any different from measuring conventional arc or microwave lamps?

In some ways it’s easier.  You have a single dominant wavelength, not several peaks. There is typically less heat buildup, and less EMI than with conventional systems.  But there are other challenges. For instance, the energy has a single peak wavelength but it may vary as much as plus or minus five nanometers, unlike a mercury source with a very well defined value such as 365 nanonmeters. The arrays are also a matrix of small point sources, so optically there are challenges to obtaining uniform measurements. It can be done, but it requires careful technique.  But the most common problem has been the fast pace that LEDs are changing, and the lack of standardization about how and where to measure these sources.  As an example, a few years ago sources were only a couple of watts, today they are approaching 40 watts, or more, in the lab.  Every manufacturer has a different design, and a different recommendation about how to measure their source.   That’s why we spent over 2 years working with people like the National Institute for Standards and Technology and various industry partners to develop the best way to measure these new devices and reduce the amount of confusion and misinformation. That led to development of the concept of total optical response embodied in our new LEDCure™ radiometers.

What is total optical response all about?

Total optical response is a new patent pending approach EIT has developed for measuring UV LEDs that takes into consideration the impact that every optical component in a radiometer has on measurement.  As an analogy, think about how playing a phonograph record used to work.  You could never tell how the album would sound from one system to another because there were so many variables in the chain. The phonograph needle, the turntable, the amplifier, the equalizer, cables and speakers.  Total Measured Optical  Response selects and fixes those components so the response from one source to the next, one measurement to the next and one instrument to the next are nearly identical.  Up until now, radiometer manufacturers have described overall instrument response based on the bandpass filters only. But that’s like expecting a record to sound good because you have good speakers when the equalizer is adjusted improperly. The response in our new products improves measurement accuracy and reliability because we consider the effects of all the links in the chain.

The new LEDCure™ series radiometers provide absolute energy measurements over the entire measurement band. Previous measurements, while providing very good repeatability, generally provide only relative measurements unless unusual calibration techniques are employed. Although relative measurments can be useful when properly used, relative measurements do not allow you to compare results from instrument to instrument, or from source to source. Absolute measurements allow you to make these important comparisons.  So this new approach to measuring UV LEDs is really a very necessary and whole new way of thinking about UV LED measurement.

How do you see UV LED measurement evolving from here?

EIT has been working with UV measurement for 30 years.  So, we have seen all kinds of changes in UV sources including from arc lamps and microwave lamps to Xenon flash sources. We kept on our toes by consistently updating our technical approach to fit the technology our customers are choosing to use.

We certainly think that while UV LEDs have become more commonplace, there’s still plenty of room for growth and improvement.  For example, we continue to see higher and higher output levels as a result of better, more affordable semiconductor technology, optics, and cooling. We expect the shorter wavelengths like 365 nanometers and 255 nanometers with much higher output levels to become more commonplace.

For example, they can provide certain surface properties not easily attained with longer wavelength sources, and can perhaps make use of existing chemistries, which would have the potential to reduce costs. This also means our instruments need to have higher dynamic ranges. The L395 band is released and covers up to 40 W/cm2 EIT is working on additional wavelengths. We introduced the new LEDCure™ line of UV LED radiometers with the L395 device. This measures LED sources with a center wavelength of 395nm and covers measurements from 370 nm to 422 nm region. This allows for differences in binning of plus or minus 5 nanometers.

We have posted two technical papers on the EIT UV web site that describe the new L-bands and how the new radiometers work.  We think this flexibility is important moving forward as more die and light source manufacturers enter the market, resulting in more variation from one manufacturer to another.  We anticipate releasing additional models such as the L365 for measuring shorter wavelength devices very soon.

We live in an increasingly data oriented, connected world, and as with other manufacturing processes, we are also seeing that our customers have more interest in working with data they collect with our instruments.  Today’s operators and engineers want to download data, analyze it, save it, and share it. So, the LEDCure™ also comes in a Profiling version.  The profiling version allows users to take advantage of our Powerview® II Software. This is a powerful LabView based program for analyzing data collected with EITs instruments. Data collected on different shifts or different production lines can easily be studied and compared using graphs and tables.  

Who was this product designed for?

What is exciting is that the topic of measurement cuts across the entire UV source market. However, the new generation of high power UV LED sources has given us an opportunity to introduce a new radiometry method that provides dramatically improved measurement results.  Measurement is a critical part of the conversation when you specify a process, optimize it, or troubleshoot it when something isn’t working properly.  Consequently, EIT’s products can be found in the laboratories of nearly every raw material supplier and formulator of UV cure inks, coatings or adhesives.  I think we have also worked with nearly every major UV LED light source manufacturer, and as a result EIT is also the most popular supplier of UV measurement instruments to those plants actually producing UV cured products. EITs products have always been popular with those who are serious about operating and maintaining their UV process and can’t afford to make or ship improperly cured UV products.

About Joe May:

Joe T. May is the Chairman of the Board and Chief Technology Officer, for EIT, LLC, a company he founded in 1977.  Joe, an Electrical Engineering graduate of Virginia Tech and a Professional Engineer, has an extensive background in circuit and instrumentation design.  He holds 26 patents in areas ranging from measurement of gasoline octane rating to measurement of ultra-violet energy used in industrial applications with three patents pending in the area of helicopter instrumentation.  Joe has authored and presented numerous technical papers on a variety of technical topics. He served 20 years as a member of the Virginia House of Delegates, where he chaired the Science and Technology Committee and the House Transportation Committee.  Joe was presented with Virginia’s “Lifetime Achievement Award for Industry” in 1996, was named Greater Washington Area Engineer of the Year in 2001, and was inducted into the Virginia Tech Academy of Engineering Excellence in 2009.