Working distance determines how far to position an imaging lens from the object under inspection. Working distance is critical when considering space constraints and lighting geometry. Join Gregory Hollows, Director of Machine Vision Solutions, as he explores how working distance affects image quality in a real-world printing example, and provides an imaging tip that is applicable to any optical design.
Hello, I am Greg Hollows and welcome to the Imaging Lab. We are going to talk about Working Distance. Working Distance is a critical parameter of an imaging system. It determines how far that the lens in the camera system is away from the object. There are many things that drive the Working Distance from an application point of view that need to be considered. In some cases, we might have a robotic attachment that is moving underneath the camera system and near the object, or some other moving device that needs to be cleared. In other situations, there is limited space to fit a camera and lens system in relation to the objects and the Working Distance can be very short. There are many reasons why you would want to choose the ideal Working Distance for the lens, most of which is being able to control for resolution and lighting effects that you have. As an example, if we have a lens in a system that we have chosen to be this far away from the object surface, when we try to use a light of this size, it might not actually fit between the object and the lens itself. Working Distance needs to be considered early on to ensure things like the proper lighting geometry is used in the system correctly. Other things that come into play that can affect Working Distance: as you can see from the slides here, there are some information shown about a soup can that was actually imaged. In this application, we were looking for the printing on the top of the can. You'll see that there are two different images there with different levels of clarity and image quality relating to the lighting and the resolution that was able to be obtained. The only difference between these two systems is actually the Working Distance of the lens that was chosen. One was much more forgiving on the resolution quality in the light collecting ability of the system and produced much better results. They were both from the same family, each of these lenses, and had identical prices to them. But, at the end of the day, one gave a much superior performance than the other and was mostly due with the optical design's quality relating to the Working Distance. Lenses can come in a variety of Working Distance capabilities, but some things to keep in mind especially with high resolution imaging: giving yourself a slightly longer Working Distance in many cases gives the optical design a better chance of actually performing at its utmost capabilities. So, giving some relief in that area can be very helpful. That was Working Distance. The next topic is Resolution, or you can click on any of the links that are of interest to you.