Magnification and optics
Digital microscopes have lenses and optics, but for much of their magnification power, they do not rely on an optical lens at all. Instead, the nature of the camera sensor makes additional magnification possible.
Many digital microscopes use a charged-couple device (CCD sensor), which is composed of a square array of light-sensitive pixels. Each pixel detects photons as they fall upon it and stores the information as electrons. The process is controlled by a clock signal, so that the sensor is "read" at measured intervals.
Other digital microscopes, particularly handheld USB microscopes, use CMOS sensors. Also known as active-pixel sensors (APS), CMOS sensors are integrated circuits that are less expensive and consume less power, but they currently produce lower quality images than CCD sensors.
Whether CCD or CMOS, the way the sensor works can result in fine resolution independent of optical magnification. When the CCD's analog information is converted to a digital image, the microscope software can magnify the image. Digital microscopes thus use both optics (magnifying lenses) and CCD/CMOS magnification.