Zoom Behavior on the USB2-Micro200X USB Microscope

Our Plugable Micro 200X USB Microscope is a wonderful tool for individuals interested in the finer points of the world around them, or teachers trying to get students engaged in the classroom. But how do the optics actually work?  This article will address how the Varifocal Lens works in relation to our microscope.

First off, what is a Varifocal Lens? Wikipedia defines a varifocal lens as “a lens with variable focal length in which focus changes as focal length (and magnification) changes”.  Inside the microscope, there is a lens on rails that moves toward and away from the imager as the focusing ring is rotated, which changes the focus point and magnification of the object at the focus point. Most “zoom” cameras work this way, with the exception of high end SLR lenses that employ very expensive to manufacture lens arrays.

For example, in the images below the Plugable logo is positioned several inches in front of the camera.

In this picture the lens is focused further out, which decreases magnification. Notice how blurry things get outside the where the lens is focused, and the overall magnification of the image.

Photo on 1-22-14 at 3.09 PM

Now below, the camera and the object haven’t moved, but the focus has been adjusted. Notice it looks slightly bigger, and the closer part of the logo is sharper? That’s because the lens is directing light differently than before. Not only has the focal length changed, but the magnification has increased.

Photo on 1-22-14 at 3.10 PM


What these characteristics gives us is a camera with the ability to vary magnification and focal length, which allows some fairly powerful magnification. Examples below show successively closer views of the P on the Plugable logo. You can start to see that it’s made of individual dots the close you get, and the last one you can see all the colors the grey is made up of!

Photo on 1-22-14 at 4.26 PM #2Photo on 1-22-14 at 4.20 PM Photo on 1-22-14 at 4.22 PM Photo on 1-22-14 at 4.23 PM

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