Polarising Filters in Machine Vision Systems

Wednesday 07 Jan 2026 · 2:45

Reflections in images being used by a machine vision system can cause unnecessary downtime.

This is because the reflections can obscure details the system needs to perform its function.

There are different ways to overcome reflection in machine vison systems and in this article, we’re going to talk about one of the most effective ways – the polarising filter.

Why do we get Reflections?

Light from the light source hits the product and bounces back up to the camera, so the camera can see the image.

It sounds obvious to say, but if there’s no light source, then the camera cannot see the product.

Light travels in waves, which are all at different orientations, so when the light reflects off the product, it bounces off in all directions and sometimes there can be a concentration of light from one area of the product when it reaches the camera’s sensor.

You’ll see this in the image as a pure white patch with no detail.

These concentrated reflections can obscure the image and prevent the camera from being able to see the required details.

Controlling The Light

What polarising filters enable us to do is control the light waves, so that reflections don’t obliterate our image.

You can think of polarising filters as being a series of slits in a thin plastic cover which fits over the light source.

The slits only allow certain light waves through – those at the same orientation as the slits.

With only those light waves now hitting the product, the reflection will be controlled.

To further ensure we control the light, we usually fit a polarising filter to the camera lens as well. This has the effect of filtering out any last remaining light waves at the incorrect orientation.

Removing the Reflection

With the polarising filters in place, we can adjust them to remove the unwanted reflections on our products and enable the machine vision system to do its job.

This is usually a case of rotating the polarising filter until the reflections disappear. What we’re doing is rotating it until we filter out the unwanted light waves.

You can see the difference in the following image comparison:

One thing to remember however: when you use polarising filters, the amount of light hitting the product will also be reduced. Therefore, it will be necessary to increase the power of the light or in some cases, replace the light with a higher-powered unit.

Solving Your Machine Vision Issues

If your machine vision system is causing downtime on your production line, it could be a simple case of fitting a polarising filter to solve the issue and improve your efficiency.

We can help by diagnosing your machine vision system issues and installing the necessary hardware to get your system performing efficiently.

Book a discovery call now.