A USB microscope plugs directly into your computer, allowing you to use your monitor to see the images rather than have to peer through an eyepiece. The device is sometimes referred to as a computer microscope or computer-connected microscope. With most USB microscopes you’ll be able to permanently store the images as picture files, or even a video clip. This allows you to share what you see with other users.
One of the key points to check when buying a USB microscope is the resolution. This can vary from model to model, usually depending on the price. Buying a cheaper model may prove a false economy if a good quality image is important to you.
As with digital cameras, you will need to be careful to check what the stated resolution figures refer to. One measure is the optical resolution, sometimes known as native resolution. This is literally the number of pixels in the image sensor and this figure affects how clear the resulting image is, particularly if you later enlarge it.
The second common measure is known as the interpolated resolution. This tells you how detailed a picture the microscope can produce by artificially creating extra pixels in the image and estimating on the best color to make them so that they fit in with their surroundings. This can be useful if you want to print larger images without any blurriness. However, because it is an artificial method, you will not be seeing the true picture of the item you have put under the microscope.
You should also check the size of the images or video the USB microscope can produce. Remember that the total size increases at a greater proportion than the dimensions themselves. For example, moving from 640x480 pixels to 1280x960 pixels gives you an image four times as large, not twice as large.
Check that the images and video created by a USB microscope are in a format you can use. With images, they’ll usually be in the common JPG format, though watch out for models which only produce the less useful BMP format. With videos, AVI is the most common, though this can produce very large filesizes unless the picture quality is kept quite low. You should also bear in mind that some models only offer a time-lapse video made up of images taken at intervals, rather than a real-time recording.
You will also need to pay attention to the lighting features on the microphone. Most will use LED lights, but the number and intensity can vary. If you are planning to use your USB microphone extensively, you may prefer one where the lighting is powered by the USB connection rather than batteries.