A Novel Knife-Edge Method for Measuring the Lateral Resolution of Confocal Raman Microscopes

Confocal Raman microscope (CRM) is one of the most powerful analytical instruments. The lateral spatial resolution is one of the key parameters for evaluating its imaging performance. In this paper, a novel knife-edge method is proposed for measuring the lateral resolution of CRMs. A virtual knife-edge phantom is developed by coating a thin layer of chromium pattern on a piece of polished monocrystalline silicon. It can avoid the edge-enhancement effect in conventional knife-edge methods. The edge spread function (ESF) and resolution of a commercial CRM at different configurations are measured to test the performance of the phantom, whose lateral resolution is from 0.8~8 micrometers. The Fermi function is used to fit the experimental data of the ESF and calculate the lateral resolution. Different types of phantoms are also developed and tested for comparison study. It is proved by experimental results that the virtual knife-edge method can be used to measure the ESF and resolution of CRMs and shows better performance than conventional methods.