Low transmittance ICF capsule geometric parameters measurement using laser differential confocal technique

A new high precision non-contact measurement using laser differential confocal microscopy is proposed for the outer diameter, inner diameter and wall thickness of the inertial confinement fusion (ICF) capsules. Based on the property of an axial intensity curve that the absolute zero precisely corresponds to the focus of the objective in a laser differential confocal system (LDCS), the approach proposed uses the absolute zero of LDCS axial intensity curve to precisely identify the position of the test point on the outer surface, inner surface and spherical center of ICF capsule in sequence, and uses the high precision displacement sensor to record the position parameter, and thereby achieving the high-precision measurement of the outer diameter, inner diameter and wall thickness of ICF capsule by combining with ray tracing. Theoretical analyses and experiments indicate that the approach has higher resolution, measurement accuracy and measurement efficiency compared with the existing measurement methods.