Revenue, Gross Profit, Gross Profit Margin and Operating Income (Loss) from Continuing Operations by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jul. 01, 2016	Jun. 30, 2017	Jul. 01, 2016
Segment Reporting Information [Line Items]
Revenue	$ 119,102	$ 97,734	$ 228,076	$ 188,050
Gross Profit	$ 53,489	$ 41,496	$ 99,583	$ 78,388
Gross profit margin percentage	44.90%	42.50%	43.70%	41.70%
Operating Income (Loss) from Continuing Operations	$ 15,616	$ 7,598	$ 25,828	$ 10,185
Photonics
Segment Reporting Information [Line Items]
Revenue	57,885	46,124	108,621	86,482
Gross Profit	$ 26,668	$ 20,861	$ 48,457	$ 38,858
Gross profit margin percentage	46.10%	45.20%	44.60%	44.90%
Operating Income (Loss) from Continuing Operations	$ 12,433	$ 9,663	$ 20,513	$ 16,519
Vision
Segment Reporting Information [Line Items]
Revenue	34,031	28,305	66,793	57,167
Gross Profit	$ 14,440	$ 10,524	$ 27,586	$ 20,103
Gross profit margin percentage	42.40%	37.20%	41.30%	35.20%
Operating Income (Loss) from Continuing Operations	$ 2,522	$ (2,700)	$ 4,047	$ (6,471)
Precision Motion
Segment Reporting Information [Line Items]
Revenue	27,186	23,305	52,662	44,401
Gross Profit	$ 12,749	$ 10,497	$ 24,267	$ 20,165
Gross profit margin percentage	46.90%	45.00%	46.10%	45.40%
Operating Income (Loss) from Continuing Operations	$ 7,581	$ 5,178	$ 14,745	$ 10,413
Unallocated Corporate and Shared Services
Segment Reporting Information [Line Items]
Gross Profit	(368)	(386)	(727)	(738)
Operating Income (Loss) from Continuing Operations	$ (6,920)	$ (4,543)	$ (13,477)	$ (10,276)