Microscopes and Quantitation

Viewing the microscopic world around us with a compound or stereoscopic microscope is a common daily activity in virtually every discipline of life science and material science. Perhaps only slightly less common but certainly as useful is the counting and/or sizing of features within a microscopic sample. Counting may be easily accomplished using grids of various configurations in an eyepiece reticle (also commonly known as an eyepiece reticule or eyepiece graticule). A grid can have the appearance of concentric circles, a uniform array of squares or even a custom pattern made to a scientists specifications. There are special universally accepted reticles available for counting specific particulate components such as asbestos. When simply counting, the choice of microscope may be made based on required field of view, magnification requirement (based on feature size) or any other convenient physical parameter. There is also no need to "calibrate" the optical system. When accurate determination of feature size is necessary, the microscope configuration is slightly more stringent. Because of parallax error inherent in the optical design of stereoscopic microscopes and user to user variability, they are generally not the first choice for this application. A more reliable and reproducible instrument is the compound microscope. In addition to an appropriate reticle , a stage micrometer will be required to calibrate the optical system. This process will help to ensure accurate and reproducible results with each and every specimen.