The second lens thus forms a real image at a distance i on the detector-array face. You can make a simple projection microscope by moving an ocular away from the objective lens so the combination forms a real image. The image gets projected on a camera's detector. An added third lens focuses light rays leaving the ocular. Because the ocular was designed to provide a virtual image at infinity, it is convenient to use a separate projection lens to focus that image onto the camera's detector.
Manufacturers also offer variations on the basic compound-microscope.
For example, a microscope could provide two oculars and one objective lens to let you view samples through a stereo microscope. And an added mirror could direct an image through different exit ports at the top of the microscope. By substituting a beam splitter for a mirror, the manufacturer can direct the image to two exit ports, one for optical viewing and one for a camera. Most inspection microscopes interpose mirrors between the objective and eyepiece to turn the optical path to a comfortable viewing angle. Cahners Business Information , a division of Reed Elsevier .