When using an equally sized light source as the FOV (Field Of View), the light intensity at the edges is lower than in the center. Resulting in a less uniform image.
To achieve even lighting across the entire field of view, it’s important that the line light’s beam angle matches the field of view of the camera and the subject. If the beam angle is too wide, you might have hotspots in the center and dark areas at the edges. If it’s too narrow, you might have dark spots or uneven illumination.
It’s often recommended to have illumination modules that are longer than the object itself, depending on the beam angle and working distance of the light. The larger the working distance between the illumination and the object, the longer the unit should be for an even spread of light.
The image below depicts an irradiance example of a line light on different working distances. It’s important to study this before determining where the light will be installed. This prevents possible future problems in your application such as the consistency of your inspection and extra costs when changing your setup and light is needed to solve the issue. Closing down the working distance results in a more even spread of light covering the FOV.
Choosing smaller angle lighting decreases the need for oversizing to create an even spread of light to cover the whole FOV. In the below image the effect of beam angles related to FOV and lamp size is illustrated.
Unfortunately, it often happens that a system has already been built or designed before it’s recognised that the line light doesn’t suffice in the edges of the image. Because installation space is already determined and limited, the only solution left is finding and purchasing a new lamp.
We recommend you start choosing and testing your lighting in the earliest possible stages of your projects, especially when it comes to line lights.
Contact us if you need any help or information picking the right line light for your application.
Where light leads, Vision succeeds!