Design of adjustable laser beam high-resolution particle size measuring lens

On the basis of research on the theory of the Fourier transform lens, according to the observation and test requirements of a fine particle and the geometrical optics aberration theory, a particle size measuring lens of adjustable high resolution laser beam that worked for wavelength of 660 nm is designed, the laser beam can be controlled through the aperture adjusting device of the lens, and can high definition imaging for the semiconductor fiber laser that core diameter is 4.5μm, numerical aperture N.A is 0.13, the output wavelength is 660nm. In the case of object distance for the next 129.5mm, the spot diameter approximately equal to the theoretical amplification value, the main image spot is clear and no flare.