Cipher Data Products chairman Don Muller has...

Cipher Data Products chairman Don Muller has resigned to become chairman and chief executive of Optotech, a Colorado Springs-based manufacturer of 5.25-inch optical disk drives, a computer memory storage device.

Muller, 54, joined Cipher Data as president in 1979 and was named chairman the following year. He led Cipher Data, a manufacturer of computer tape drives, as it grew from $15 million to $165 million in revenue. He has not been active in day-to-day Cipher Data activities, however, since he resigned as chief executive in January, 1987. He was succeeded as chief executive by Gary Liebl.

Muller also resigned board memberships at Quantum Corp., MIPS Computer Systems and Optimem, a Cipher Data subsidiary.

The Cipher Data board has not yet named a new chairman, a spokesman said Wednesday.