Analysis of achromatic doublet as a scan lens for laser scanning microscopy

Abstract

Off-the-shelf achromatic doublets are widely used as an intermediary lens between the scanner and objective lens in custom-built and commercial laser scanning microscopy. The most important consideration of using achromatic doublets as a scan lens and tube lens is that it is inexpensive and widely available. With the increasing scan angle and the range of wavelengths, optical aberration is introduced. The RMS wavefront error exceeds 0.072 and the Strehl ratio shows less than 80% which affects the telocentric properties of scan lens and tube lens. By doing optimization using Zemax OpticStudio, this study proposed four optimized Scan lens and a tube lens designs that offer diffraction-limited imaging for over a wide wavelength range with a large Field of View(FOV) and a comparative performance analysis with the commercial available achromatic doublet lens. For 3mm beam size, the f-theta distortion reduces from 13.00% to 1.94%. Similarly, telecentric distortion for 6 mm beam reduces from 3.52% to 0.4367%. Here, we analyze achromatic doublet as a scan lens with Focal Length(FL) 50mm for wavelengths of 680nm, 1000nm, 1300 nm, and 1600 nm. Then, we present the optical performance of our proposed optimized scan lenses by Zemax simulation.