Olympus Corp. said Monday it returned to the black in the April-September period, posting a group net profit of ¥8.02 billion, compared with a loss of ¥32.33 billion a year earlier, due mainly to robust performance in its medical business.

In the first half of financial 2012, the camera and medical equipment maker said consolidated operating profit rose 2.9 percent to ¥18.04 billion on sales of ¥405.76 billion, down 2.1 percent.

The stock has more than doubled in the past year after plunging as much as 81 percent after its board fired Michael C. Woodford as president in October 2011 after he questioned dubious, exorbitant fees paid by the company for takeovers.

For the full year ending in March, the company revised upward its group net profit forecast, expecting to post ¥8 billion in profit, compared with a projection of ¥7 billion in June.

But the company downgraded its consolidated operating profit projection to ¥38 billion, up 7.0 percent from a year earlier, and lowered its sales projection to ¥757 billion, down 10.8 percent.

Olympus and Sony Corp. agreed Sept. 28 to form a joint venture to make endoscopes and other medical devices.

Sony said it would invest ¥50 billion in Olympus, which admitted to a 13-year accounting fraud after the Woodford firing, to shore up its capital ratio as it recovers from the scandal that led to restated earnings and the replacement of directors.