Olympus's share price fell more than 70% in the weeks immediately following exposure of accounting irregularities in October 2011, before recovering to around half its former value at the start of 2012.
Olympus Japan this week confirmed that it initially received a lawsuit from 49 investors, including foreign institutional investors and pension funds.
One shareholder subsequently dropped their claim, leaving the firm facing a lawsuit totalling 19.138 billion yen, plus interest.
In a statement posted on the company website last night, Olympus said the impact of the legal action on the group's future business results is unclear.
Earlier this week, Olympus reported a £100m profit for the three months to 30 September 2012.