Patent ID: 7695431

Claim:
An objective optical system configured to be implemented in a tip of an endoscope, the system comprising: a first lens unit having a first lens barrel and a first optical system including a plurality of lens elements assembled in said first lens barrel and aligned in a direction of a first common optical axis; and a second lens unit having a second lens barrel, engageable with said first lens barrel, and a second optical system including a plurality of lens elements aligned in a direction of a second common optical axis, said first lens unit being provided with a fixing unit that fixes said first optical system to said first lens barrel said fixing unit having a threaded surface that is engaged with a threaded surface of said first lens barrel to fix said first optical system to said first lens barrel, said second lens barrel being assembled to said first lens barrel, said fixing unit being interposed between said first lens barrel and said second lens barrel to define a clearance therebetween; wherein, when the first lens barrel is engaged with the second lens barrel, the lens elements of the first and second lens barrels are aligned along a common axis, the first common axis and the second common axis comprising the common axis; and wherein said first lens unit includes an alignment lens movable in a direction perpendicular to an optical axis thereof, movement of the alignment lens in the direction perpendicular to the optical axis alone adjusting an alignment of the entire plurality of lens elements assembled in the first lens unit, said first lens barrel being formed with a plurality of unthreaded holes through which parts of a circumferential surface of said alignment lens are exposed, said alignment lens being movably accommodated in said first lens barrel, and said alignment lens being moved, in the direction perpendicular to the optical axis, by pins inserted through said plurality of holes, respectively.