In this article and video, Brad Vorrie gives us tips on things to consider when selecting the proper lens for your Vision System.
There are many things to think about when setting up a vision system. The first and most important step is getting a clear image, which can be achieved by using the proper lighting and selecting the proper lens for your camera.
There are many lenses available on the market today, so there are few things you need consider when selecting a lens.
-The first thing to think about is the lens format. You will see something like this on the lens: 1/3, 2/3, 1” and so on. This refers to the aperture size of your camera. The aperture size will correlate to the resolution of your camera. The lens must be at least the same size, if not larger, than the aperture of your camera. Refer to your manufactures spec sheet to get the specific size of your camera’s aperture.
-The next consideration is focal length. Most standard lenses are going to have a fixed focal length. An example of this would be 8mm, 12mm, 16mm, etc. The focal length is generally chosen based off of the required field of view of your camera and the distance your camera can be mounted from your product. Most manufactures have a chart or calculator to assist you in making this decision.
-A few other features you want to make sure are included on your lens are a focal adjustment and an aperture adjustment. The focal adjustment will fine tune your image for optimal clarity and the aperture adjustment will change how much light goes into the camera. Both adjustments should have a lock so they don’t move or vibrate loose.
In general, most standard lenses have a field of view in which the magnification changes the further away from center you move. This results in parallax, also known as perceptive error and will decrease overall accuracy. There is a specialty lens available called a telocentric lens, that compensates for this problem. It has a constant magnification across the entire image making it a great solution for precise measurements and tricky applications.
Learn more about Vision Basics:
Vision Basics Part 2a Lighting Theory
Vision Basics Part 2b Types of Lights
Vision Basics Part 3 Color