Bayonet type fixing device having annular members and a zoom lens having the same

A zoom lens comprising:

• a linear guide barrel guided in a direction of an optical axis;
• a rotational barrel coupled to said linear guide barrel to be rotatable relative to said linear guide barrel about said optical axis and to be immovable relative to said linear guide barrel in said direction of said optical axis;
• a plurality of lens groups guided in said direction of said optical axis without rotating about said optical axis via said linear guide barrel, said lens groups being driven in said direction of said optical axis in a predetermined manner in accordance with rotation of said rotational barrel;
• an annular member attached to a front end of said linear guide barrel so as not to rotate relative to said linear guide barrel;
• a retainer ring attached to said linear guide barrel to fix said annular member to said linear guide barrel;
• a plurality of engaging lugs formed at said front end of said linear guide barrel to extend radially along a circumference of said linear guide barrel;
• a plurality of insertion areas formed at said front end of said linear guide barrel so that said insertion areas and said engaging lugs are alternately arranged along said circumference of said linear guide barrel;
• a plurality of grooves formed on said linear guide barrel behind said engaging lugs, to be connected to said insertion areas, respectively;
• a plurality of recesses formed on said linear guide barrel behind said grooves, to be connected with said grooves, respectively;
• a plurality of projections formed on said annular member, said projections being respectively fitted into said recesses via said insertion areas and said grooves;
• and
• a plurality of engaging blades formed on said retainer ring, said engaging blades being respectively fitted into said grooves via said insertion areas, to be respectively positioned between said engaging lugs and said projections in said direction of said optical axis.