BUSINESS SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014 segment	Sep. 28, 2013
Segment Reporting Information, by Segment
Number of operating segments			3
Sales to external customers	$ 146,299	$ 139,037	$ 446,421	$ 405,878
Segment income	12,761	6,436	38,772	16,452
Photonics
Segment Reporting Information, by Segment
Sales to external customers	59,757	57,508	182,693	171,324
Lasers
Segment Reporting Information, by Segment
Sales to external customers	44,228	38,923	137,815	117,231
Optics
Segment Reporting Information, by Segment
Sales to external customers	42,314	42,606	125,913	117,323
Operating segments
Segment Reporting Information, by Segment
Segment income	23,627	21,066	72,846	54,332
Operating segments | Photonics
Segment Reporting Information, by Segment
Segment income	12,255	13,213	40,201	36,546
Operating segments | Lasers
Segment Reporting Information, by Segment
Segment income	6,423	3,432	18,151	10,790
Operating segments | Optics
Segment Reporting Information, by Segment
Segment income	$ 4,949	$ 4,421	$ 14,494	$ 6,996