UPDATE 1-Micron sells imaging ops to TPG, Riverwood

* Micron sells Aptina Imaging for undisclosed sum

* Will book $100 mln loss in fiscal Q4

* TPG, Riverwood to inject capital

(Adds details, background)

LOS ANGELES, June 1 (Reuters) - Micron Technology (MU.N) has agreed to sell a majority slice of its imaging solutions business to TPG [TPG.UL] Capital and Riverwood Capital, as the chip maker focuses on tackling a dismal semiconductor market.

Micron, which in its fiscal second quarter posted a net loss of $751 million, or 97 cents a share, said it will book a $100 million loss in the fiscal fourth quarter from the deal.

Details of the deal were not disclosed.

Aptina Imaging Corp chalked up revenue of about $650 million in the fiscal year ended August 2008.

Micron said it was reverting to a focus on its core business, which is suffering as spending on electronics tanks amid a global economic downturn.

Still, Micron will keep a 35 percent stake in Aptina, which it bought in 2001 when it was then Photobit, and will continue to sell products to the imaging company.

It was not clear how the majority stake to be sold will be split between the two private equity firms, who under the agreement will inject capital into the imaging operation.

"Launching Aptina as an independent business entity enables Micron and Aptina to focus on their respective core businesses," Micron Chief Executive Steve Appleton said in a statement.

"This transaction enables Micron to maintain a strategic investment in a leading company in the imaging industry."

The companies said the transaction should be completed in the next 60 days. (Reporting by Edwin Chan and Clare Baldwin; Editing by Dhara Ranasinghe)