Revenue, Gross Profit, Gross Profit Margin and Operating Income (Loss) from Continuing Operations by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Sep. 29, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenue	$ 146,296	$ 97,829	$ 374,372	$ 285,879
Gross Profit	$ 58,707	$ 41,212	$ 158,290	$ 119,600
Gross profit margin percentage	40.10%	42.10%	42.30%	41.80%
Operating Income (Loss) from Continuing Operations	$ 12,273	$ 11,048	$ 38,101	$ 21,233
Photonics
Segment Reporting Information [Line Items]
Revenue	61,882	43,425	170,503	129,907
Gross Profit	$ 28,966	$ 18,603	$ 77,423	$ 57,461
Gross profit margin percentage	46.80%	42.80%	45.40%	44.20%
Operating Income (Loss) from Continuing Operations	$ 15,233	$ 8,185	$ 35,746	$ 24,704
Vision
Segment Reporting Information [Line Items]
Revenue	58,150	31,601	124,943	88,768
Gross Profit	$ 19,792	$ 12,343	$ 47,378	$ 32,446
Gross profit margin percentage	34.00%	39.10%	37.90%	36.60%
Operating Income (Loss) from Continuing Operations	$ 846	$ 2,307	$ 4,893	$ (4,164)
Precision Motion
Segment Reporting Information [Line Items]
Revenue	26,264	22,803	78,926	67,204
Gross Profit	$ 10,291	$ 10,592	$ 34,558	$ 30,757
Gross profit margin percentage	39.20%	46.50%	43.80%	45.80%
Operating Income (Loss) from Continuing Operations	$ 5,493	$ 6,195	$ 20,238	$ 16,608
Unallocated Corporate and Shared Services
Segment Reporting Information [Line Items]
Gross Profit	(342)	(326)	(1,069)	(1,064)
Operating Income (Loss) from Continuing Operations	$ (9,299)	$ (5,639)	$ (22,776)	$ (15,915)