What is Polarisation for Machine Vision?
To understand polarisation entirely, it helps to consider that light is a wave which vibrates in many directions. Adding a polariser filter allows only light waves travelling in a specific orientation to pass through while blocking unwanted vibrations. This process creates polarised light. When two polarising filters are used together, the amount of light transmitted depends on their relative angle, aligned filters allow light through, while filters at 90 degrees block it entirely. By rotating one filter, you can control the light intensity in a similar way to dimming.
In machine vision systems, this technique is particularly valuable because it enhances image quality and reveals material details that are otherwise difficult to detect. It is widely used to overcome challenges such as reflections and glare, enabling more accurate and reliable inspections.
How Do Polarisers Work?
The main use for polarisers is to highlight textures and scratches on materials in machine vision applications. During detailed inspections, operators use polarisers to manage how light waves vibrate to reduce glare and reflections on surfaces. This allows only one kind of light vibration to pass through while unwanted light is blocked out. Precise and clear images are captured that highlight subtle features that is usually missed by the camera.
Challenges of Using Polarisers
Reduced Light Intensity โ Polarisers block light waves that are not aligned with their transmission axis, which can reduce the available light by about 50%. As a result, brighter illumination or longer exposure times may be required to maintain image quality.
Material Compatibility โ Polarisers are highly effective with materials that reflect or transmit polarised light, but their performance varies depending on the material. This can limit their effectiveness in certain machine vision applications.
Curved Surfaces โ Reflections from curved surfaces occur at multiple angles, making it more difficult for a single polariser setup to eliminate glare consistently across the entire object. In these cases, additional lighting techniques or multiple polarisation configurations may be required.
Solutions
Increase Light Intensity โ Compensate for the light loss caused by polarisation by using brighter illumination or increasing the camera’s exposure time. This helps maintain image quality and ensures sufficient contrast for reliable inspection.
Test Material Compatibility โ Evaluate your materials before implementation to determine how effectively they respond to polarised light. For applications involving a variety of surface finishes, combining polarised and unpolarised illumination, adjusting the lighting angle, or using polarisation-sensitive cameras can improve performance on less responsive materials.
Optimise Lighting for Curved Surfaces โ Adjust the angle and positioning of the illumination to minimise reflections from curved or complex surfaces. For more demanding applications, polarisation-sensitive cameras or advanced imaging techniques that analyse polarisation in real time can deliver more consistent results.
TPL Vision Polariser Filters
At TPL Vision, we offer a comprehensive range of polariser filters designed to reduce glare, minimise reflections from shiny surfaces, and enhance image clarity. Ideal for a wide variety of machine vision applications, these filters are particularly effective for inspecting reflective packaging materials, such as plastic bags and films, where unwanted reflections can otherwise obscure critical details.
Application Examples Using Polarisers
BAR LIGHT POLARISERS โ Available in a wide range of sizes from 125 mm to 1750 mm, these polariser filters can be easily inserted into the enclosed transparent diffuser or supplied pre-integrated into our Angle Changers for bar lights.
APPLICATION EXAMPLE โ In automated inspection systems for packaged products such as electronics, food, and medical devices, bar light polarisers minimise reflections from plastic films and shrink wrap. This enables cameras to reliably identify defects, verify labels, and detect missing components, even when inspecting highly reflective, glossy, or wrinkled packaging.
RING LIGHT POLARISERS โ Designed specifically for use with our ring lights, these polarisers are ideal for compact machine vision setups and high-contrast inspection applications. Operating on the same principle as bar light polarisers, they reduce glare and enhance image clarity while helping to reveal fine details in space-constrained environments.
APPLICATION EXAMPLE โ In high-precision counting applications, such as verifying the quantity of components within an assembly, ring light polarisers help eliminate glare from reflective surfaces to provide clearer, more consistent images. This enables accurate detection and reliable quality control, even when working with small parts or limited installation space.
POLARISATION is a simple yet powerful lighting technique that can significantly enhance machine vision performance across a wide range of applications. By reducing glare, improving contrast, and revealing fine surface details, polarisers help inspection systems capture clearer, more accurate images and deliver reliable results.
Learn more at https://www.tpl-vision.com/
