Patent ID: 8632217

Claim:
A light head structure with adjustable focal length, comprising: a base having a recess and an outer threaded connection section, the recess serving to receive a light-emitting element therein, the outer threaded connection section being annularly disposed on an outer circumference of the base; a threaded collar having an assembling section, a receiving space and a protrusion section formed on an inner circumference of the threaded collar, the threaded collar being capped on the base with the assembling section correspondingly assembled with the outer threaded connection section; and a lens that can be deformed to change its focal characteristics disposed between the base and the threaded collar, the lens having a focusing section in alignment with the light-emitting element, the focusing section having an extension section extending from the focusing section, the extension section being positioned between the threaded collar and the outer circumference of the base, the protrusion section of the threaded collar correspondingly abutting against the extension section, wherein the protrusion section of the threaded collar has a free end protruding from the inner circumference of the threaded collar to the outer circumference of the base, wherein a section of the extension section of the lens abuts the protrusion section and a non-abutting section of the extension is located on either side of the extension section that abuts the protrusion section on two sides of the abutted section, the free end of the protrusion section abutting against the abutted section to attach the extension section to the outer circumference of the base, wherein the threaded collar is movable between an extended position and a contracted position to extend or contract the extension section in order to adjust the thickness of the focusing section.