Financial Statement Components - Selected Financial Statement Components (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 27, 2015	Jun. 28, 2014	Dec. 27, 2014
Inventories:
Raw materials and sub-assemblies	$ 23,676		$ 19,463
Work in process	11,003		7,723
Finished goods	6,860		7,919
Inventories	41,539		35,105
Inventories-delivered systems	1,574		1,912
Total inventories	43,113		37,017
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	80,183		78,348
Accumulated depreciation and amortization	(32,642)		(28,715)
Total property, plant and equipment, net	47,541		49,633
Depreciation and amortization expense	3,400	$ 3,200
Accrued warranty	3,792		2,953
Accrued restructuring	424		997
Accrued professional services	787		778
Fair value of current portion of contingent payments to Zygo Corporation related to acquisition	1,119		1,385
Other	2,099		2,152
Total other current liabilities	8,221		8,265
Land [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	15,572		15,572
Building and improvements [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	19,817		19,641
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	31,017		29,456
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	2,258		2,225
Software [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	7,965		7,942
Capital in progress [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 3,554		$ 3,512