Verification of the numerical aperture of laser scanning confocal microscope objective

Laser scanning confocal microscopy (LSCM) is definitely a new 3D imaging system combined with modern optical and electrical technology. It differs from conventional microscopes in that the pinhole makes LSCM have the ability to acquire in-focus images from selected depths – a process known as optical sectioning. Like all of the microscope optical systems, the numerical aperture (NA) is a very important character of objective, which directly relate to the lateral resolution of the microscope system. A verification method for NA of LSCM is discussed in this paper based on the definition of NA. In this method, an appropriate sphere is measured by LSCM. The verified NA value is deduced from the measured maximum spherical crown in accordance with reasonabe analysis process. Consequently, this method is approved to be simple enough to practice by many times experiments.