Metallurgical microscopes (also known as materials microscopes) are equipped with an incident light source (also called reflected) which sends the light through the objective onto the reflective surface of the metal. The sample has to be perfectly flat and is usually polished, a ‘micro’ specimen will normally have been prepared of the metal, composite, ceramic or polymer sample. This type of microscope can sometimes also be used to look at particles trapped on filters. Typical applications are grain sizing, inclusion counts, layer thickness assessment and phase determination. Some models have special facilities such as darkfield and DIC which produce improved observation techniques for some classes of specimen. All models have polarised light ability, a range of filters and a camera port for photography and image analysis; some upright models have both incident and transmitted light for more transparent materials.
There are three main types of metallurgical microscope:
- Upright – where the objectives are above the specimen – this is the most commonly used type
- Inverted where the objectives are beneath the specimen, permitting larger specimens to be observed
- Semiconductor (upright and inverted) where the stage is especially large to accommodate whole wafers