The invention discloses a variable-field scanning
microscopic method based on a fixed
optical path system, and a device thereof. At first, a beam expanding
system is used for uniformly expanding
laser beams which are transmitted from a
laser so as to form uniform
laser beams; then a two-dimensional space
discrete system is used for the two-dimensional space
discretization of the uniform
laser beams so as to form a sub-beam of M multiplied by N; the sub-beam of M multiplied by N orderly passes through a collimating lens, a scanning
galvanometer, a reflector, a dichroic mirror and a
fluorescence microscope, and then focuses on the sample on a sample platform; thus the excited
fluorescence can be formed on the sample; the
fluorescence microscope is used for collecting the excited fluorescence, which is transmitted into an imaging
system after being reflected by the dichroic mirror and focused by a focusing lens. The scanning of the
galvanometer and the crossing movement of the sample platform are combined: the scanning step length and the scanning
step number of the
galvanometer are changed; the area of the unit viewing field is used as the step length to move the sample platform; thus the scanned viewing field can be changed. The scanning
microscopic method realizes the flexible switching between the low-resolution large viewing field and the high-resolution small viewing field, and satisfies the requirements in different biomedical applications.