a focusing module for divergent light emitted from a source such as a laser diode . the focusing module consists of telescoping cylindrical members which focus by sliding the members along their central axis and permanently adhering the members to each other after focusing . the focusing lens is embodied in a lens assembly which prevents direct contact between the lens surface and the lens seat in one of the cylindrical members . axial rotation between the cylindrical members , and between the base and the module is prevented by a series of notch and key elements . consequently , the opening of the focusing module is fixed with respect to the cross - section of the light emitted , and can be shaped to match the cross section of the laser light beam thereby permitting maximum emission of focused light .