What is White Light Interferometry in Anilox Inspection?

Known as the gold standard in optical measurements, White Light Interferometry, also known as coherence scanning interferometry, is a powerful optical measurement technique that enables precise, non-contact surface profile measurements. As one of the first manufacturers to incorporate this technology into anilox inspection microscopes, we often get asked, “what is white light interferometry?” In this blog, we will help you understand the fundamentals of this precise measurement technique and how it powers the accuracy, precision, and repeatability of our Veritas™ and 3DQC Classic anilox inspection microscopes. We'll explore its principles, benefits, advantages, and how this inspection technology is revolutionizing the field of anilox quality control.

What is White Light Interferometry?

White light interferometry is an optical imaging method that utilizes the interference of white light to measure surface profiles. The technology combines two beams of light: one from an ultra-precision reference mirror and another from the surface being measured. When these two light beams are mixed, interference fringes are produced that interact with the surface profile, providing ultra-precision measurements. The vertical distance on the surface  between the center of a dark fringe and a bright fringe is only half a wavelength of light, about 0.3 microns.  For comparison, a human hair is about 70 microns in diameter and a red blood cell is 6-8 microns across. Powered by white light interferometry, the new Veritas™ anilox and gravure inspection system with its MicroScan3 software can sense height changes as small as 0.01 microns or 0.4 millionths of an inch!

White light interferometry can reveal surface features that are often imperceptible to conventional microscopes, making it an invaluable tool for inspecting the microscopic cells of an anilox. The interference fringes are a physical result of light interacting with the surface of an object, ensuring the utmost accuracy.

Bottom line: if you want dependably accurate measurements of virtually any surface profile, white light interferometry is second to none. As a result, MicroDynamics has spent years innovating this profiling technology to be the foundation for our true and accurate anilox and gravure roll inspection systems.

Benefits & Advantages

MicroDynamics has spent over a decade optimizing our white light interferometry technology for flexo quality control processes. There are a number of advantages and benefits in using this technology for the inspection of the microscopic engravings and patterns of anilox and gravure rolls. Take a look!

Unmatched Precision, Consistency & Reliability. White Light Interferometry offers exceptional precision, ensuring consistent and reliable measurements that don't vary with each scan. To this day, this technology remains the most accurate method for non-contact surface profile measurements, maintaining the tightest tolerances and consistently accurate results. Measurements by MicroDynamics, as well as Veritas users, have shown that repeated measurements in the same location fall within 0.03 cm3/m2( cc per square meter), which is 0.02 bcm.   The precision of the Veritas with its MicroScan3 software is so tight that the natural point-to-point volume variation on anilox rolls becomes clearly visible and small volume changes from wear can be reliably tracked.

Surface Variety & Compatibility. White light interferometry can spot microscopic variations on both gravure and anilox rolls with unparalleled precision. Printers can inspect not only a wide range of anilox engravings but also gravure engravings. Even more, with our new wide field mode, users can inspect  rolls with screen counts ranging from 47 lpcm (120 lpi) to more than 600 lpcm (1524 lpi) with no need for lens changeovers.  Rolls with screen counts as low as 24 lpcm (60 lpi) can also be measured using our 10X low magnification objective lens.

See The Unseen. White light interferometry is particularly useful in the detection of clear coatings, adhesives, or varnishes remaining on rolls. Where other methods may not catch the variations in surface profile from clear materials, the Veritas with MicroScan3 can sense the nearly invisible top of the material and detect the presence of clear coatings and adhesives that may be clogging cells.

The Power of White Light Interferometry in Anilox Inspection

Anilox Inspection EquipmentMicroDynamics is one of the first companies to implement white light interferometry for roll surface inspection. This advanced technology powers the accuracy and repeatability of our systems and has been optimized to meet the needs of printers and manufacturers worldwide. The newest inspection solution from MicroDynamics, Veritas, won the 2023 FTA Technical Innovation Award for taking white light interferometry to the next level! Using MicroScan3’s high-speed military-grade algorithms, printers can inspect faster (less than 8 seconds for results!) and detect the smooth, featureless surfaces previously undetectable by anilox microscopes. Our engineers have advanced the microscope technology so the dynamic range of brightness is greater and saturation problems are greatly reduced. In the past, this technology was only accessible in tabletop formats, but with Veritas, the accuracy and reliability of white light interferometric measurements is now mobile and is accessible to all printers on the shop floor.

With a commitment to continuous improvement, MicroDynamics will continue to release new features using white light interferometry on our Veritas microscope. If you’re looking for the gold standard in optical measurements for surface profiles, choose the Veritas microscope with white light interferometric measurement technology! Contact a MicroDynamics sales associate for more information or learn more about the Veritas microscope on our website.