The prime Voyager mission to Jupiter and Saturn brought Voyager 1 to Jupiter on March 5, 1979, and Saturn on November 12, 1980, followed by Voyager 2 to Jupiter on July 9, 1979, and Saturn on August 25, 1981.

JPL has more information here: http://voyager.jpl.nasa.gov/science/planetary.html

The picture here: This is one of Voyager 2's closest looks at the B Ring, from August 25, 1981 at a distance of 743,000 km. The contrast has been enhanced to show the fine structure. The portion of the ring shown here is 6000 km wide and features as narrow as 10 km are visible.

Source: http://pds-rings.seti.org/saturn/voyager/voyager2.html