Financial Statement Components - Selected Financial Statement Components (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014	Dec. 27, 2014
Inventories:
Raw materials and sub-assemblies	$ 24,999		$ 24,999		$ 19,463
Work in process	14,463		14,463		7,723
Finished goods	8,936		8,936		7,919
Inventories	48,398		48,398		35,105
Inventories-delivered systems	1,543		1,543		1,912
Total inventories	49,941		49,941		37,017
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	80,220		80,220		78,348
Accumulated depreciation and amortization	(34,276)		(34,276)		(28,715)
Total property, plant and equipment, net	45,944		45,944		49,633
Depreciation and amortization expense	1,800	$ 1,700	5,200	$ 4,900
Accrued warranty	4,291		4,291		2,953
Accrued restructuring	341		341		997
Accrued professional services	671		671		778
Fair value of current portion of contingent payments to Zygo Corporation related to acquisition	1,159		1,159		1,385
Other	2,960		2,960		2,152
Total other current liabilities	9,422		9,422		8,265
Land [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	15,568		15,568		15,572
Building and improvements [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	19,795		19,795		19,641
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	32,085		32,085		29,456
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	2,264		2,264		2,225
Software [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	8,094		8,094		7,942
Capital in progress [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 2,414		$ 2,414		$ 3,512