Bright Field Optical Microscopy
Bright field microscopy is the simplest form of light microscopy.
Sample illumination is via transmitted white light from below the sample and is observed from above the sample. Limitations include low contrast of most biological samples and low apparent resolution due to out of focus material. Nevertheless, sample preparation is simple and it is an easy way of looking at cellular-sized items.
Oblique illumination has the illumination coming in from the side and it gives a three dimensional appearance, highlighting otherwise invisible features. A more recent technique is based on a method called Hoffmann’s modulation contrast, a system found on inverted microscopes for use in cell cultures. It suffers from some of the same limitations as bright field microscopy but may highlight invisible structures.