Telecentric Illumination

Hello and welcome to our review of telecentric illumination. Today, we are going to look at different types of illumination that can be used to create a silhouetted image in a machine vision automated imaging environment. And we are going to really concentrate on the advantages of telecentric illumination. What we have here is a setup, where we are going to initially look with a diffuse source at this object, which is a post with a thread cut into it. And we are going to look to see the type of silhouette that gets made from two different types of illuminations. So, what we are going to start with here, is we're going to move this diffuse source in a little bit closer. And we're going to see how it gets imaged through this lens and camera onto the screen and the monitor. As we actually look at the monitor, we're going to see from this type of source, we are going to see some soft edges on the screen. And what that comes from is that light is coming from a variety of angles onto the object and it's creating some reflections off the object itself. One of the benefits of that source like this is diffuse source. I am actually at this moment changing the angles of the light source and moving it around, and we are seeing relatively little change on the object itself which means this type of illumination source is great for coarse alignment of the full system here. Doesn't take away from the fact that we still have these soft edges in the system. As I remove this light source from the system and allow the telecentric illuminator show through, all of a sudden we see a marked difference in the type of silhouette that we get. Gone are the soft edges that were here previously and now we have very very hard edges in the system, something that's much easier for a software package to be able to pick up and determine where the exact edge of the system is. Increases our repeatability of the system greatly. One of the subtle things that we have to keep in mind here, though, with the telecentric illuminator, the way that this works, is we have gotten rid of those wide angles that come from the diffuse source and we have actually created very very parallel angles of light going past the object. That is why we no longer have those soft edges. But that being said, if those rays do not enter into the lens, we're not getting a background or back light that is passing by and as I start to slightly adjust the telecentric illuminator for its angle, we'll see that we go from the silhouetted image to a very difficult image to work with. So, alignment in these types of systems is very very important. When we actually look at some other things that go on with a system like this too, where we would have the diffuse source in the system originally here like this, we have a very compact system. The telecentric type of system, while we can move this lens closer and reduce this distance quite a bit, we still have the size of the actual lens system to be taken into consideration and any other wiring coming off of the source. So, while it does create a greater and much stronger edge to our image, there are some things that have to be kept in mind when we are using a system like this. Thank you very much for your time. My name is Greg Hollows, Director of Machine Vision Solutions for Edmund Optics.