(Reuters) - Sony and Olympus said they plan to unveil an ultra high-definition surgical endoscope this week, the first major product from a joint venture formed three years ago.

The product allows physicians to view clearer, more instant images of internal organs, aiding precision during surgical procedures, the medical device makers told Reuters ahead of an official announcement on Wednesday.

Sony bought 11.5% of Olympus in 2012, in a much-needed cash injection for the latter after an accounting scandal sent its share price plummeting.

Sony halved its stake in April to finance restructuring, but said it wants to continue the alliance, which it sees as an area of growth to help offset weak sales of TVs and smartphones.

Olympus commands a 70% share of the market for gastrointestinal endoscopes, but lags U.S. rival Stryker and Germany's Karl Storz GmbH & Co in surgical endoscopes, which can be employed during minimally invasive surgery.

(Reporting by Makiko Yamazaki; Editing by Christopher Cushing)