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

4 comments on “Zoom Behavior on the USB2-Micro200X USB Microscope”

    • Sam Morgan Reply

      Hello Vivekk – This is available to India via the Amazon Global program, just use the where to buy widget in the corner of this page and select the US market. Thanks!

  1. Leonardo Delgado Reply

    I need 40x of optical zoom in His datasheed say that this device can do this . but i can´t i am seeing less zoom, when i put the device to his max zoom. my ask.
    the optical zoom in one microscopio is not the same that this if this is true, what is the equivalent zoom for a microscoipio?

    • Sam Morgan Reply

      This bit of info from the FAQ should help:

      “At the closest distance with the clear shield touching the object, there are two possible magnifications. The first is at around 50x, but if you continue to rotate the focus wheel, the image will get blurry, then sharp again at a much higher magnification.”


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