Focusing optical system based on a single objective lens

Abstract

The present invention provides a focusing optical system of utilizing a phase plate to control a focus to move along an optical axis based on a single object lens. The focusing optical system based on the single object lens is characterized in that a light beam of any polarization state passes an adjustable beam expanding lens to be transformed into a parallel incident light beam, the special phase plate of which the phases are distributed linearly along a radial direction is utilized to carry out wavefront phase modulation on the incident light beam, and after the focusing, a light spot can move freely on the optical axis by adjusting the linear phase parameter of the special phase plate. If the positive direction of the optical axis is defined as the propagation direction of the incident light beam, and the linear phase parameter of the special phase plate is positive, the focus is far away from the geometrical focus position of the object lens along the positive direction of the optical axis, on the contrary, if the linear phase parameter of the special phase plate is negative, the focus is far away from the geometrical focal point position of the object lens along the negative direction of the optical axis; the mobile distance of the light spot is increased along the increase of the absolute value of the linear phase parameter of the special phase plate.

Description

technical field [0001] The invention belongs to the technical field of applied optics and relates to a method for controlling the focus position, in particular to a method for controlling the position of the focus along the optical axis by using a phase plate; it is mainly used in the technical fields of optical microscopic imaging, super-resolution, and particle control. Background technique [0002] After the light beam is focused by the objective lens, its wavefront phase and amplitude information greatly affect the light field distribution in the focal area, especially as the numerical aperture of the objective lens changes, the influence becomes more significant. By adjusting the wavefront phase and amplitude information of the incident light wave, it exhibits special properties in the focal area, and has been widely used in optical information storage, optical microscopy, lithography, laser processing, optical micro-manipulation, super-resolution, light and matter Inte...

AI Technical Summary

Problems solved by technology

However, the above two methods have three shortcomings: first, this method only focuses on the spot after the incident light is radially polarized, and does not work for other polarization beams; second, in the 4pi optical system The movement of the spot increases the difficulty of adjusting the optical path, reduces the flexibility of the experiment, and limits the scope of application of the method; third, the position of the spot cannot be controlled simply by changing a certain parameter of the pupil filter. Recalculate the transmittance of the pupil filter, which is not conducive to continuous control of the focus point

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