Alexander Telle

CEO ACM Coatings GmbH – subsidiary of Acktar Ltd.

WHY & WHEN to think about scattered light


  • Enhancing signal-to-noise
  • Increasing sensitivity
  • Improving image quality & contrast
  • Reducing complexity


  • As early as possible in the development process of new photonic instruments and systems
  • But it is never to late to implement improvements in existing products later in the product lifecycle
scattered light

WHY & WHEN to think about scattered light

  • Stray light simulation and analysis is an important tool in the development of high-performance optical instruments. But the simulation can only be as good as the data that is input.
  • Bidirectional Reflectance and Transmittance Distribution Functions (BRDF, BTDF) are the fundamental way to describe and assess the distribution of scattering from optical components.
  • Because of the numerous possible origins of scattering (roughness, defects, bulk, coatings) and the rather complex relationships between such imperfections and light scattering, the BRDF of optical components must be measured. This is in particular true for high-end optical components for e.g. space, semiconductors, IR sensing, LIDAR, imaging, bio-analytics, medical and other demanding photonic applications.

ACKTAR‘s BRDF + TIS database
Unprecedented honesty and reliability for stray light simulation

  • To suppress stray light in complex optical systems, baffles and black diffusing absorber coatings are used. Even though such surfaces might look perfectly diffuse and black at near normal incidence and visible wavelengths, the scattering distribution usually changes at larger angles of incidence and at other wavelengths. In the extreme case of near grazing incidence and/or infrared wavelengths, some materials that are black diffusers in the visible are known to behave like good mirrors causing stray radiation to bounce within the optical system instead of being suppressed. The scattering of black coatings must therefore be measured at application conditions.
  • Over the last few months, we have been working with our partner Synopsys (formerly know as Light Tec SARL) to measure our deep black surfaces and create a database with 3D #BRDF and TIS.

HOW Acktar‘s ultra-black coatings work

Angle of incidience (AOI) we cover in our data:
10° / 30° / 50° / 70° / 80°

Wavelength ranges we cover:


  • VIS (white light)
  • NIR (monochrome 1.55µm)


  • VIS (400nm to 800nm)
  • NIR (780nm to 1.650nm)