Edmund Optics Imaging Lab 1.4: Depth of Field

Depth of field is a measurement of the maximum object depth that can be maintained entirely in focus. Since depth of field is dependent on resolution and contrast, determining this parameter affects what one is trying to analyze or measure. Gregory Hollows, Director of Machine Vision Solutions, discusses this often misunderstood fundamental parameter and provides an imaging tip that is applicable to any optical design. View Module 1.8: Depth of Field In Depth for more detailed information. You can also learn more in our Gauging Depth of Field in Your Imaging System application note.

Hi, I am Greg Hollows and welcome to the Imaging Lab. We are going to talk about Depth of Field. Depth of Field is a misunderstood portion of optical systems in many cases. It is what is the level of detail you can see above and below best focus in the imaging system of the optics. And Depth of Field can be relative to the application. It really needs a resolution attached to it to truly understand it effectively. One imaging system can have a great Depth of Field for one application and not enough for another. There are even applications out there that require very very little Depth of Field, if any at all, to eliminate the blur of anything in front or behind the objects of interest. A lot of medical applications are like that. Let me give you an example. As I hold this golf ball near my head, and this other one out in front of me, in the example that we see here, you should be able to see that one of them is in focus near me, and the other one that is closer to the camera system is a bit out of focus. If you look at the cutaway screen, you also see in this example, that both of them are relatively in focus in the system, and this is because we have changed the aperture setting of the camera system that is being used. And this is usually advantageous in many imaging systems to be able to see that detail at a variety of ranges of what we are doing. Now, when we start to think about what the implications of that are, is that Depth of Field is actually changed by the iris setting in the system and the quality of the imaging capability of the lens. As we begin to shut down the iris more and more, we actually start to limit the amount of resolution that the lens can actually produce at any distance. And that can be a problem especially when we consider high resolution imaging applications or applications that need extremely high levels of contrast. We are going to go into a more detailed discussion about why these things occur and what to watch out for in another segment. That's Depth of Field. Next is going to be Sensor Size, or you can click on any of the videos that most interest you.