The choices our engineers have made for our family of CLH lenses help simplify the most difficult aspects of the lens selection process. However, one of the main tasks an engineer will need to do for a successful machine vision system is to establish a proper field of view.

A proper field of view is one in which you can see what you need to see (even if its position changes) and not much more beyond that. It may be a large object that is moving or it may be the details on a product that is stationary. Two variables that you can adjust to change your field of view are:

• Lens Focal length: This is measured in mm (ie: 35mm lens) and relates to the angle of view that will be achieved. Short focal lengths show a wider angle of view, but the objects within that view appear farther off and smaller. Longer focal lengths provide a narrower field of view. Objects within that type of view appear closer and, therefore, larger.
• Distance: This is how far from the object your camera will sit. For some applications, it is important the camera be separated from the product it is imaging. In other cases, the camera can be positioned next to the object being imaged. The farther away the camera sits, the larger the field of view, the closer the camera sits, the narrower the field of view.

The focal length of the lens and the distance of the camera to the object will affect not only what you see in your field of view, but how well you can see it. Adjust as necessary until you find the combination that works for you.