Financial Statement Components - Selected Financial Statement Components (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015	Jun. 25, 2016	Dec. 26, 2015	Jun. 27, 2015	Dec. 27, 2014
Inventories:
Raw materials and sub-assemblies	$ 21,953		$ 21,953			$ 26,784
Work in process	9,508		9,508			12,862
Finished goods	7,799		7,799			8,103
Inventories	39,260		39,260			47,749
Inventories-delivered systems	4,416		4,416			2,856
Total inventories	43,676		43,676			50,605
Property, plant and equipment, net:
Total property, plant and equipment, gross	85,645		85,645			80,561
Accumulated depreciation and amortization	(41,321)		(41,321)			(36,068)
Total property, plant and equipment, net	44,324		44,324			44,493
Depreciation and amortization expense	1,700	$ 1,800	5,100	$ 5,200
Accrued warranty	4,185	4,291	4,185	4,291	$ 4,556	4,504	$ 3,792	$ 2,953
Accrued restructuring	0	$ 341	0	$ 341		256		$ 997
Accrued professional services	492		492			481
Accrued royalties	1,029		1,029			437
Fair value of current portion of contingent payments to Zygo Corporation related to acquisition	814		814			945
Other	2,110		2,110			2,255
Total other current liabilities	8,630		8,630			8,878
Land [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	15,570		15,570			15,569
Building and improvements [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	20,511		20,511			20,158
Machinery and equipment [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	36,109		36,109			32,995
Furniture and fixtures [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	2,357		2,357			2,266
Software [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	9,007		9,007			8,245
Capital in progress [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	$ 2,091		$ 2,091			$ 1,328