A man passes a logo of Japan's Olympus outside the company showroom in Tokyo
A man passes a logo of Japan's Olympus Corp outside the company showroom in Tokyo December 21, 2012.

Japan's Olympus Corp is close to selling its microscope unit to a private equity firm in a deal that could fetch more than 300 billion yen ($2.2 billion), three people with direct knowledge of the matter told Reuters.

Bain Capital has emerged as the frontrunner, said one of the people and a separate person with direct knowledge of the deal.

Carlyle Group and KKR & Co also submitted binding bids this month for the unit which makes microscopes, industrial endoscopes and x-ray analysers, said three of the people with direct knowledge.

Olympus has been restructuring in recent years with the aim of focusing solely on medical technology and if this sale is successful, it would be the company's biggest divestment to date, according to Refinitiv data.

A spokeswoman for Olympus said nothing has been decided at the moment and the company will make announcements when necessary, declining to disclose further details.

Bain, Carlyle and KKR declined to comment. All sources declined to be identified as the information is confidential.

Olympus, which started off as a domestic microscope producer over a century ago, spun off the unit in April, naming it Evident Corp.

Evident had total assets worth 143.3 billion yen by end of March and has forecast operating profit of 15.5 billion yen for the current financial year.

As part of its overhaul, Olympus has invited activist investor ValueAct Capital onto its board, bought several overseas medical-equipment firms and sold its digital camera business that had been a long-time money-loser.