FLIR Systems announced financial results for the fourth quarter and full year ended December 31, 2015. Fourth quarter 2015 revenue was US$437.6 million, up one percent compared to fourth quarter 2014 revenue of $434.4 million. On a constant currency basis, fourth quarter 2015 revenue was up three percent versus the prior year. Operating income in the fourth quarter was $93.5 million, compared to $87.4 million in the fourth quarter of 2014. Operating income was impacted by pretax charges related to previously-announced restructuring initiatives of $0.3 million in the fourth quarter of 2015 and $1.0 million in the fourth quarter of 2014.
Fourth quarter 2015 net income was $70.2 million, or $0.5 per diluted share. Net income in the fourth quarter of 2015 was impacted by an after-tax gain on the sale of an investment of $12.7 million, offset by after-tax restructuring charges of $0.2 million and discrete tax charges of $7.4 million, netting to a $0.04 benefit to earnings per diluted share.
Revenue from the surveillance segment was $150.7 million, a decrease of five percent from the fourth quarter results last year. The security segment recorded revenue of $68.4 million in the fourth quarter, up 21 percent from the prior year. FLIR's OEM & emerging markets segment had $49.2 million of revenue, a decrease of 2 percent from the prior year. The detection segment contributed $34.7 million of revenue, an increase of 32 percent from the prior year.
For the full year, revenue was $1,557.1 million, up two percent compared to $1,530.7 million for the year ended December 31, 2014. On a constant currency basis, full year 2015 revenue grew six percent over 2014. Operating income for 2015 was $305.8 million compared to $259.2 million in 2014, an increase of 18 percent for the year. Net income for 2015 was $241.7 million, or $1.7 per diluted share, compared with 2014 net income of $200.3 million, or $1.4 per diluted share. Cash provided by operations during 2015 was $275.8 million, which compares to $226.2 million in the prior year and represents a 22 percent increase.
Revenue and Earnings Outlook for 2016
FLIR also announced today that it currently expects revenue in 2016 to be in the range of $1.6 billion to $1.65 billion and net earnings to be in the range of $1.6 to $1.7 per diluted share. This guidance assumes a full year 2016 effective tax rate of 26 percent, excluding the impact of any future discrete items.