US 2009237940 A1 abstract an adjustable lighting device having a main body a light generation device inserted into a receptacle a movable lens a base electrically connected to the light generation device and an adjustor cover rotatably mounted to and covering the outside of the main body so that rotation of the adjustor cover causes the lens to extend retract within the receptacle so that the extension retraction of the lens can be controlled by the rotation of the adjustor cover for realizing focus adjustment application_number US 40774309 A description with reference to the drawings and in particular to fig1 4 an adjustable lighting device constructed in accordance with the present invention comprises a main body 1 a light generation device 4 a lens 3 a base 2 and an adjustor cover 6 the main body 1 has a first end forming a first receptacle 11 the light generation device 4 comprises a light emission element 42 the light generation device 4 is fixed in the first receptacle 11 the lens 3 is movably received in the first receptacle 11 the lens 3 has an outer circumference forming an external thread 31 the base 2 is mounted to an opposite second end of the main body 1 and the light generation device 42 is electrically connected to the base 2.