These test specimens are excellent for comparing magnification and assessing any distortion in the image field. It is ideally useful in the context of automated counting systems to check for unsuspected distortions.

• Made of a 5×5 mm square of single crystal silicon
• Photo-etched and the squares repeat every 10 µm
• The dividing lines are 1.9 µm wide

A broader etching line is written every 500 µm, which is useful in light microscopy. Where critical measurements must be made the sample can be mounted directly onto the calibration specimen so that an internal calibration is obtained on the micro-graph.