Revenue, Gross Profit, Gross Profit Margin and Operating Income (Loss) by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2020	Jun. 28, 2019	Jul. 03, 2020	Jun. 28, 2019
Segment Reporting Information [Line Items]
Revenue	$ 144,728	$ 155,145	$ 300,196	$ 312,331
Gross Profit	$ 58,702	$ 65,782	$ 123,147	$ 132,071
Gross profit margin percentage	40.60%	42.40%	41.00%	42.30%
Operating Income (Loss)	$ 13,701	$ 15,105	$ 26,951	$ 29,498
Operating Segments | Photonics
Segment Reporting Information [Line Items]
Revenue	47,803	58,286	102,943	117,511
Gross Profit	$ 20,898	$ 27,308	$ 45,559	$ 54,622
Gross profit margin percentage	43.70%	46.90%	44.30%	46.50%
Operating Income (Loss)	$ 6,937	$ 11,666	$ 15,852	$ 23,976
Operating Segments | Vision
Segment Reporting Information [Line Items]
Revenue	64,740	65,895	133,748	131,831
Gross Profit	$ 24,515	$ 25,211	$ 51,090	$ 51,184
Gross profit margin percentage	37.90%	38.30%	38.20%	38.80%
Operating Income (Loss)	$ 4,665	$ 4,215	$ 10,299	$ 8,772
Operating Segments | Precision Motion
Segment Reporting Information [Line Items]
Revenue	32,185	30,964	63,505	62,989
Gross Profit	$ 13,834	$ 13,759	$ 27,742	$ 27,280
Gross profit margin percentage	43.00%	44.40%	43.70%	43.30%
Operating Income (Loss)	$ 6,515	$ 5,983	$ 13,053	$ 11,618
Unallocated Corporate and Shared Services
Segment Reporting Information [Line Items]
Gross Profit	(545)	(496)	(1,244)	(1,015)
Operating Income (Loss)	$ (4,416)	$ (6,759)	$ (12,253)	$ (14,868)