Surface Detection of Semi-Transparent Media Through Modified Confocal Microscopy

A modified confocal microscope system is developed to place the focal point of a laser beam on the surface of semitransparent media. Resolution of the detected surfaces is shown to be dependent on pinhole size and numerical aperture of the microscope objective used in the confocal system. Detection of front and back surfaces of a sapphire window is demonstrated using a 20 µm pinhole and 0.25 numerical aperture confocal focusing lens.