Method to vary the diameter of a laser beam

A method of modulating the focal spot and/or divergence of a laser beam, the method comprising:

• providing an optical system comprising:
• a collimated light source;
• a lens assembly disposed within an optical path corresponding to light emanating from said collimated light source wherein the lens assembly comprises a pair of cross cylinder lenses having equal and opposite focal powers oriented with their neutral axes positioned orthogonally to each other;
• and
• a focusing objective lens disposed within the optical path following the lens assembly,
• wherein at least one of the pair of cross cylinder lenses is configured for rotation about an axis defined by the point at which light from the collimated light source impinges on it,
• directing an output of the collimated light source through a central portion of the lens assembly corresponding to the optical path;
• and
• rotating at least one of the pair of cross cylinder lenses about an axis corresponding to the optical path.

An optical system for modulating the focal spot and/or divergence of a laser beam, the system comprising:

• a collimated light source;
• a lens assembly disposed within an optical path corresponding to light emanating from said collimated light source wherein the lens assembly comprises a pair of cross cylinder lenses having equal and opposite focal powers oriented with their neutral axes positioned orthogonally to each other;
• and
• a focusing objective lens assembly disposed within the optical path following the lens assembly,
• wherein at least one of the pair of cross cylinder lenses is configured for rotation about an axis defined by the point at which light from the collimated light source impinges on it,
• wherein at least one of the pairs of cross cylinder lenses is configured for rotation, relative to the other, and
• wherein the cross cylinder lenses and the focusing objective lens are made of Infrasil.