TOKYO — Konica Minolta, the Japanese manufacturer of photocopiers and printers, is preparing to announce a $900 million deal to acquire the American testing company Ambry Genetics, according to two people with knowledge of the discussions.

The acquisition would be the largest ever for Konica Minolta, which is trying to diversify its business and increase its presence in fast-growing industries. Like other Japanese technology companies, it has also been scrambling for growth abroad.

Ambry Genetics specializes in genetic testing and in analyzing large databases of genetic information to screen for diseases like cancer. In an unusual move, it decided last year to make public information based on data from thousands of people it had tested, a move it said would aid drug research and other efforts to combat diseases.

Konica Minolta will pay roughly 100 billion yen, or about $880 million, for Ambry, according to the people with knowledge of the deal, who spoke on the condition of anonymity because the discussions are private.