Nothing is more important to the success of a machine vision project than the lighting. Proper lighting has a great impact on image quality, inspection detail/contrast, and depth of focus.
Glare is one of the common problems addressed with lighting. Occasionally glare is good – for example it can be used to identify the absence or presence of metallic materials. It can also be a challenge – washing out images, causing pixel blooming, or distorting an image. Eliminating glare in these situations is critical.
The surface of reflection must be considered when determining the correct method to eliminate glare. Sometimes a simple adjustment in the geometry of the lighting application can correct a washout effect. In other cases, dealing with the reflected light is more complicated.
Light can be polarized off of non-diffusing material and light coming off of metallic materials can become polarized at low incident angles. Polarized light has a specific orientation to the electric and magnetic fields it travels through. The polarization of light can be used to eliminate glare.
A common technique to eliminate glare is using a polarizing material on the lights and the camera lens. This material aligns the light waves in the same direction – for example – vertically. This allows the camera lens filter to absorb the strong reflections of polarized light. With the strong reflections absorbed, the diffused light (non-glare) is conveyed to the camera.
To learn more about glare and polarized light for machine vision, visit EPIC Machine Vision specialist Chris Walker’s Tech blog, and his post titled “Glare and Polarized Light in Machine Vision Applications.”