Source: Simulation of Stray Light Reduction Example. Generated by an AI engine.

Source: Simulation of Stray Light Reduction Example. Generated by an AI engine.

Stray light is one of the biggest challenges in optical systems. Therefore, it needs to be addressed carefully, accurately, and seriously. But why, and most importantly, how? Those will be answered in the following article.

Stray light is one of the most persistent challenges in optical system design. Small amounts of unwanted light can degrade contrast, measurement accuracy, and reduce SNR. In every industry that involves the use of optical systems, stray light control is not optional, but rather fundamental to system performance. There are different types of practical solutions for stray light mitigation, which usually involve the absorption of scattered light inside the system. The main goal is to prevent unwanted reflections. A strategic combination of several approaches will increase the likelihood of preventing more stray light.

 

Solution 1: Applying Ultra-black upon internal surfaces

Minimizing reflection inside the optical path is the most direct way to reduce stray light. One way to achieve this is to apply an ultra-black coating to mechanical structures, such as buffers and housings. This will ensure scattered light rays will be absorbed inside, rather than being directed towards the detector. Advanced low reflectance coating technologies are crucial in high-sensitivity systems, where even a small amount of reflected light can severely affect the signal.

Solution 2: Optical coating design

An additional approach is to prevent stray light from being created. This is possible by reducing multiple interface reflections and ghost images. For that matter, the coatings are placed to suppress specific wavelength bands and angles of incidence. Herby, those can reduce back reflections that can propagate through the system. In most cases, optical coatings such as Velvet Black, Vacuum Black, and others are applied to lenses, mirrors, filters, etc.

Source: Acktar’s Spectral Black Panels

In conclusion, effective stray light reduction requires a system-level approach. When optical coatings and internal absorbing surfaces are designed together, stray light suppression becomes significantly more effective than relying on either approach alone. Optical systems can achieve better sensitivity, higher contrast, and more reliable performance overall.