Abstract
In this study, a confocal optical system formed by a combination of two axicon lenses, a parabolic annular mirror and a concave mirror was used to obtain an adjustable microstructured beam. The two axicons were used to create a collimated hollow annular beam whose diameter varies with the distance between the two components, and the duty cycle ε of the hollow beam changes accordingly. At the same time, the annular factor δ also changes correspondingly after the hollow beam was concentrated. According to the scalar diffraction integral theory, the change of focusing characteristics of different annular factor δ after a parabolic annular mirror was studied. The concentrated beam was reflected by a concave mirror to form a confocal optical system. According to the numerical simulation, the size of the focused spot varies from 2.8 to 4.3μm in the range of the annular factor δ from 1.19 to 1.09. Detailed characteristics of the microstructure beam shape changes were analyzed. These results have important implications for particle manipulation and other applications.
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