・When observed with an optical instrument such as a microscope, with the focus being set, the range can be clearly seen even if the focus plane is shifted to the front and back of the sample surface.
It is also known as D.O.F. (Depth of Focus).
In general, the higher the magnification of the objective lens, the shallower the depth of focus.
・Since there are individual differences in the coordination power of the human eye, there are individual differences in the depth of focus that people feel.