For more than five decades, we have been meeting customer and market demands for complex optical filters. Our company’s story begins in the 1960s, when scientists at the Danish Light Laboratory recommended that the people at Carl Zeiss and Leica in Germany swap out their coloured glass filters for thin-film interference filters to improve their fluorescence microscope’s performance. Zeiss and other manufacturers took this advice, which led to an increased demand for thin-film filters.

By the 1970s, we were working to meet this demand with our innovative volume manufacturing of thin film fluorescence filters. Two decades later, our new technique for automated deposition of advanced optical coatings was helping manufacturers of analytical instruments improve their standards; and in the early 2000s, Delta was one of the first companies to produce ultra-hard-coated optical filters.

Today, the design and manufacture of high-performance fluorescence filters is our main business. And with the our in-house design and production tools, we continue to meet the needs of our discerning OEM customers.


We are well-known for leading-edge developments like CTO Henrik Fabricius’ 101-layer beamsplitter. (In 2004, OSA Fellow Philip Baumeister covered Fabricius’ design in his book Optical Coating Technology.) The multilayer beamsplitter, created in 1992, consisted of a deep notch and a 50-percent splitter, and was designed using the inverse Fourier transformation technique and Fabricius’ optical thickness truncation compensation technique.

Our advanced capabilities also include volume production of ultra-hard-coated multifunctional polarization and colour beamsplitters for optical coherence tomography; laser mirrors with reference output for power control of strong lasers; and stress-compensated broadband dichroic beamsplitters with minimal polarization splitting.

All of these developments were driven by the demand of our OEM customers for high-performance, low-cost advanced thin-film components. Our optimization software matches each customer’s unique optical specifications, ensuring a fast and efficient design process. Specifically, our tight integration between in-house filter design and deposition control software, as well as comprehensive hardware modification of coating chambers with optical monitoring systems and special shadow masks, enable custom design and manufacture of high-performance optical filters.


For many decades, our thin-film business was part of a publicly funded national laboratory—the Danish Light Laboratory. This funding arrangement allowed engineers to spend more time on basic research, which laid our strong theoretical and methodological foundation. However, the focus on basic research made it difficult to attract investments and grow Delta beyond its critical mass.

The situation changed in 1993 when, through a merger of the Danish Light Laboratory with other Danish institutes, DELTA was established. DELTA’s new commercial focus prioritized efficiency measures that have made our thin-film business internationally competitive. However, at this stage, external investments were still not possible. Today’s Delta Optical Thin Film A/S is the result of a December 2014 management buyout undertaken by CEO Poul Svensgaard and CTO Henrik Fabricius. The buyout was financially backed by an international investor interested in our unique technology.

Delta is now a privately owned company with an ambitious growth strategy. In the first four years as Delta Optical Thin Film A/S we doubled the company's revenue. Svensgaard says: “In recent years, we’ve seen an extension of the product portfolio, including continuously variable filters. This product range opens up new global markets for us.” Our newest product group comprises a family of continuously variable filters (CVF) and was inspired by S. Desmond Smith, founder of Edinburgh Instruments Ltd.,U.K., who trusted our ability to turn his vision of high-performance CVFs into reality. The development took place within the Eurostars OPTITUNE Project, a program co-funded by 34 EUREKA countries and Horizon 2020. Only half a year after the first continuously variable long wavelength and short wavelength pass filters (CVLWP and CVSWP) debuted at the 2011 LASER World of PHOTONICS, manufacturers of supercontinuum lasers released wavelength selectors based on this filter couple used as a tunable bandpass filter.

We have many other products that have enabled new applications. For example, German BMG Labtech uses CVSWPs and CVLWPs together with continuously variable dichroic to replace grating monochromators in their fluorescence microplate readers. Danish Ibsen Photonics and many other spectrometer manufacturers use our continuously variable order sorting filters in their compact spectrometers to suppress stray light and second orders. And, with the rapidly growing interest in hyperspectral imaging (HSI), several companies are building compact and light-efficient HSI cameras that use our unique Bifrost continuously variable bandpass filters.

Delta Optical Thin Film A/S will continue to help its customers to stay ahead of the competition by developing enabling optical thin film filter technology.