Once you choose a lens whose focal length is closest to the focal length required by your imaging system, you need to adjust the working distance to get object under inspection in focus.
一旦你选择一个镜头其焦距是最接近于你成像系统所需之焦距，你需要调较工作距离去获取观察目标物的焦点。
2
The working distance is the distance from the front of the lens to the object under inspection.
工作距离是由镜头前到观察目标物的距离。
3
Distance the distance is the distance between the object and the front lens of the camera.