Shares of OSI Systems Inc. were upgraded by an analyst a day after after the maker of security and health care screening devices reported second quarter earnings that exceeded Wall Street expectations.

Hawthorne-based OSI on Thursday reported net income of $4.2 million (24 cents per share), for the quarter ended Dec. 31, compared with net income of $3.5 million (20 cents) a year ago. Revenue fell 3 percent to $159 million, largely due to the adverse impact of foreign exchange. The company, whose products include airport security screening devices and medical X-ray machines, said revenue otherwise would have been up 1 percent.

The company said it had restructuring and other charges of $2.8 million in the quarter. Excluding one-time items, OSI said it had earnings of 34 cents per share, 15 cents better than the average of analysts surveyed by Thomson First Call.

OSI received more orders for its homeland security screening equipment, and Chief Executive Deepak Chopra said the company had 13 percent growth in its backlog of orders to a record $239 million. The picture was more challenging in its health care division, where revenues were down 12 percent as hospitals had trouble obtaining credit to pay for orders.

“Despite being the most challenging economic environment in decades, our financial results for the second quarter continue to demonstrate the earnings-generating potential of our businesses,” Chopra said in a statement.

OSI shares closed up 18 percent to $14.62 Thursday on the Nasdaq after earlier jumping 25 percent. On Friday, Stanford Research upgraded its rating on shares from “sell” to “hold”.