Resolution can be improved using oil immersion lenses, and lighting and contrast can be dramatically improved using modifications such as dark field, phase contrast, and differential interference contrast. Fluorescence and confocal microscopes are specialized instruments, used for research, clinical, and industrial applications. Other than the compound microscope, a simpler instrument for low magnification use may also be found in the laboratory. This is the stereo microscope, or dissecting microscope. Stereo microscopes usually have a binocular eyepiece tube, a long working distance, and a range of magnifications, typically from 5x to 35 or 40x.
Some instruments supply lenses for higher magnifications, but there is no improvement in resolution.
Bright Field Microscopy With a conventional bright field microscope, light from an incandescent source is aimed toward a lens beneath the stage called the condenser, through the specimen, through an objective lens, and to the eye through a second magnifying lens, the ocular or eyepiece. Some microscopes have a built-in illuminator, while others use a mirror to reflect light from an external source. The condenser is used to focus light on the specimen through an opening in the stage. After passing through the specimen, the lightis displayed tto the eye with an apparent field that is much larger than the area illuminated. Students are usually aware of the use of the coarse and fine focus knobs, used to sharpen the image of the specimen.