Performance of a beam-scanning confocal microscope with a virtual pinhole

Abstract

We construct and evaluate the performance of a laser scanning confocal microscope with an easily scalable virtual pinhole based on a two-dimensional multi-channel light detector in the form of a charged coupled device (CCD) array. The CCD array and the incident beam focus are arranged in a confocal configuration. Transverse scanning of the focus therefore corresponds to movement of the detected light at the image plane. To generate a two-dimensional (2D) image, the wide field images of the illuminated sample are multiplied with an amplitude filtering function emulating a confocal pinhole. The virtual pinhole is automated to track the movement of the detected beam focus scanned along a sample. Contrast in the images is achieved by carefully selecting an optimal size of the virtual pinhole. Optical sectioning capability of the microscope is demonstrated by imaging an integrated circuit (IC) at different axial positions.