Pushing the boundaries of technology

Innovation, cutting-edge technology, and a responsive team – these are the tools that Delta, the world-leading manufacturer of optical thin film coatings, has always relied on to drive growth, revenue, and profit. Bühler has been at Delta’s side for the past 20 years of this journey providing solutions. Now, with a full services contract, it is taking the relationship and business to the next level.

The Danish Company Delta is a pioneer in the high-performance optical thin film coating industry and has been supplying global Original Equipment Manufacturers (OEM) since early 1970s. Over the last years, the business has grown significantly, doubling its revenue every five years, and achieving an average annual profit of 10 percent (before taxes). 


Even during challenging Covid times, while many companies struggled to keep going, Delta remained on its growth path. Thanks to its innovation culture, cutting-edge technology, and responsive team, the organization was able to quickly develop several sets of fluorescence filters that were used in a Covid-19 quick test, among others by the company Qlife. Bühler has accompanied Delta on this innovation journey not only by providing solutions and high-performing equipment but by delivering a full package of services that help the company to get the best out of the machines.


customer_delta customer_delta Henrik Fabricius, Chief Technology Officer at Delta, Poul Svensgaard, CEO at Delta, and Robin Fischer, Team Leader Technologists for Projects at Bühler Leybold Optics work together to drive the company into the furture.

The collaboration between Bühler Leybold Optics and Delta Optical Thin Film A/S dates back to 2002 when Delta bought an Advanced Plasma Source (APS) Coater from Leybold Optics. This was the first step in what became a strong and long-lasting relationship. Over these 20 years, Delta, in collaboration with Bühler Leybold Optics, navigated business challenges, developed, and manufactured new products, and has been achieving sustainable growth.

More recently, as part of this fruitful exchange, Delta opted for Bühler’s TotalCare service contract, taking the relationship and business to the next level.

High-tech solutions in everyday life

Currently, Delta counts on several Leybold Optics solutions in its headquarters in Hørsholm, a municipality located about 25 kilometers north of Copenhagen, Denmark including the SyrusPro 1,100 precision coater, and the HELIOS-800 sputter coater. Supported by these solutions and Bühler’s expertise, the company develops and manufactures a wide variety of custom optical filters, which includes continuously variable filters, fluorescence filter sets, bandpass filters, short and long wave pass filters, smart coatings in the ultraviolet, visible, near-infrared (UVA/VIS/NIR) range, among others. Delta serves global instrument manufacturers such as Leica, Zeiss, and Avantes.Its solutions may sound highly technical, but they are embedded in a wide variety of applications and products in everyday life. Optical thin filters, for example, have been an enabler in modern medical diagnosis and drug discovery, detecting cancer, tuberculosis, and Covid-19, to mention a few.

Optical filters are also used in hyperspectral imaging, which is used to track changes in the environment, for example, to understand surface CO2 emissions, map hydrological formations, and track pollution levels. In fact, thin-film optical filters are produced by adding thin layers of materials with special optical properties onto a substrate, such as optical-grade glass. As light makes its way through the optical filter, its direction changes as it passes from one layer to the next, resulting in internal interference. The filters can be designed to transmit, block, or reflect light at any wavelength range from the ultraviolet (UV) to the Infrared radiation (IR).Delta’s thin-film optical filters are also present in so-called Point of Care (PoC) devices, which are used to obtain diagnostic results while next to the patient – in other words, for checks that are not done in the laboratory. They can be used in doctors’ offices, hospitals, and in patients' homes, and can be applied on many sorts of medical tests.


POUL SVENSGAARD, CEO of Delta Optical Thin Film

Accelerating innovation: a new test for Covid

One of the latest innovations from Delta was applied in just this type of device. During the challenging months of Covid, Danish medical device producer Qlife decided to develop a test for SARS-CoV-2, which would then be integrated in its diagnosis platform (PoC) Egoo. The company was very quick in the research and development process. The teams modified the transportable analysis instrument of an already existing system so that it could produce a full PCR test for SARS-CoV-2 in about 20 minutes. The optical thin filters, developed and produced by Delta, were an essential part of the Qlife solution, since they would determine whether SARS-CoV-2 was present in the sample. Qlife contacted Delta, who was already delivering fluorescent microscopes to Qlife’s Egoo. PoC instrumentation requires very small, yet high-performing custom optical filters in large quantities and at low prices. The organizations joined forces and embarked on a journey to quickly develop the filters. Within 10 days, the teams developed, tested, and started to produce the filters for the testing device Egoo. “With our coating technology, that has been in development since the 1970s, we were able to let a single wavelength through, while we dim others by a factor of between 100,000 and a million times,” 

explained the company’s Chief Technology Officer, Henrik Fabricius, in an article published in 2020 in Ingeniøren, the Danish weekly newspaper (The Engineer). According to experts, the art of producing optical filters has to do with the capacity of adding hundreds of layers with different refractive indices, all with extreme precision. The light filtering function is triggered in the event of interference between the interreflected light waves. In Qlife’s case, three different filters had to be used, and the team succeeded in getting them all right on the first attempt. Thereafter, the filters had to be cut out so that they could fit into small devices, such as Egoo. The filters only measure 4x4 square millimeters, but Delta can manufacture filters that are even smaller. “The pandemic clearly created a huge demand for advanced bandpass filters. By then, we had just acquired a new Bühler HELIOS-800 Sputter Coater machine and had had good support from Bühler’s team to get the machine commissioned and in volume production within a few months. This allowed us to supply a number of new customers with advanced filters for the PCR (polymerase chain reaction) platforms,” said Poul Svensgaard, CEO of Delta Optical Thin Film.

Strong research tradition

Such a quick reaction was also possible thanks to the solid research and innovation culture at Delta. The company, which currently employs 25 people, has a strong theoretical and methodological foundation that keeps them pushing the limits of optical filters technology. Delta, as it is known today, is the result of a management buyout undertaken by CEO Poul Svensgaard and CTO Henrik Fabricius in 2014. This innovation-driven approach had already gained them attention and recognition in the 1960s, when thin-film scientists at the Danish Laboratory for Technical Optics recommended that customers Carl Zeiss and Leica, in Germany, exchange their colored glass filters for thin-film 

interference filters to improve their fluorescence microscope’s performance.  Zeiss and other customers took and appreciated the advice, which led to an increased demand for custom optical thin-film filters. In 1993, the Light & Optics merged with other Danish institutes. That is when Delta was established. With that move, the company started to focus on the commercial opportunities of this business and prioritized the implementation of measures that would increase the competitiveness of the thin-film business internationally. That strategy gained force with the buyout in 2014 – and that is when Delta was able to move ahead with its ambitious growth plan.



HENRIK FABRICIUS, Chief Technology Officer, Delta

In the past few years, Delta’s business has grown significantly. “We roughly double our revenue every 5 years,” said Svensgaard. “We invest our profits 100 percent in sustainable growth and in new technologies to the benefit of our customers.” With that level of performance, the management of the company had to ensure that there was enough space and infrastructure to support the ongoing growth journey. In 2019, Delta’s management decided to invest in a new factory. And in Autumn 2020, the teams celebrated the opening of the new 2,300 square meter facility located at DTU Science Park in Hørsholm, Denmark, which is administratively part of the Technical University of Denmark (DTU) and brings together more than 300 companies and over 4,500 scientists, entrepreneurs, business developers and employees. The new Delta building has laboratories, clean rooms, offices, a cafeteria, and meeting rooms.That kind of growth through innovation approach is only possible with expertise, curiosity, teamwork, and going the extra mile to address the customer’s needs. These are some of the values that are the foundation of Delta. 

Delta employee standing by Bühler Helios 800 Delta employee standing by Bühler Helios 800 The pandemic created a huge demand for advanced bandpass filters. By then, Delta had just acquired a new Bühler HELIOS-800 Sputter Coater machine and with Bühler’s team support was able to increase production within few months.
Delta employees working Delta employees working Delta, which employs 25 people, has a strong theoretical and methodological foundation that keeps the company pushing the limits of optical filter technology.

The company has a flat hierarchy and a policy of open doors, valuing the contribution and ideas of the team, offering flexible working hours and the chance for employees to define their own working day in freedom and with responsibility. But it does not stop there. Behind that powerful combination there is also a team of professionals next to Delta, supporting the organization through the challenges, ensuring that the equipment and operations can be run smoothly. “Our work is to ensure quality, reliability, and mass production capabilities. We deliver that with our TotalCare portfolio of services,” explains Robin Fischer, Team Leader Technologists for Projects at Bühler Leybold Optics. “Together with Delta, we analyzed their plant conditions, discussed their needs and goals. By customizing a concept, we collaborate to get the best out of the machines.”It sounds simple and obvious, but it is not, in particular if one considers the incredible number of challenges that businesses are facing currently, from supply chain shortages, geopolitical tensions, and climate change impacts, to risks of infectious diseases. Having a team ready to support the company’s operations while it sees its demand grow or when it faces an operational or technical issue with the equipment can make all the difference.


By building and fostering trustful relationships with suppliers, customers, and the market, Delta wants to go forward into the future. “We already serve a truly global set of customers. We have a very strong track record in supplying high volumes of advanced filters. Also, our choice of technology has proved to be scalable. This is noticed in the market to a level where we must sometimes turn down new business,” says Svensgaard. “No doubt we will grow, but our challenge is not to grow our organization too fast. We do not want to compromise on quality.”


ROBIN FISCHER, Team Leader Technologists for Projects at Bühler Leybold Optics

Delta employee QC control Delta employee QC control Delta’s team member controls the quality of the optical thin film before they are delivered to the customer.


Thin-film optical filters are produced by adding thin layers of material with special optical properties onto a substrate, such as optical-grade glass.

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