Financial Statement Components - Selected Financial Statement Components (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2016	Jun. 27, 2015	Jun. 25, 2016	Jun. 27, 2015	Mar. 26, 2016	Dec. 26, 2015	Mar. 28, 2015	Dec. 27, 2014
Inventories:
Raw materials and sub-assemblies	$ 24,011		$ 24,011			$ 26,784
Work in process	11,668		11,668			12,862
Finished goods	5,432		5,432			8,103
Inventories	41,111		41,111			47,749
Inventories-delivered systems	9,594		9,594			2,856
Total inventories	50,705		50,705			50,605
Property, plant and equipment, net:
Total property, plant and equipment, gross	83,039		83,039			80,561
Accumulated depreciation and amortization	(39,555)		(39,555)			(36,068)
Total property, plant and equipment, net	43,484		43,484			44,493
Depreciation and amortization expense	1,700	$ 1,700	3,400	$ 3,400
Accrued warranty	4,556	3,792	4,556	3,792	$ 4,377	4,504	$ 3,440	$ 2,953
Accrued restructuring	27	$ 424	27	$ 424		256		$ 997
Accrued professional services	502		502			481
Fair value of current portion of contingent payments to Zygo Corporation related to acquisition	732		732			945
Other	3,516		3,516			2,692
Total other current liabilities	9,333		9,333			8,878
Land [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	15,569		15,569			15,569
Building and improvements [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	20,400		20,400			20,158
Machinery and equipment [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	33,873		33,873			32,995
Furniture and fixtures [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	2,310		2,310			2,266
Software [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	8,833		8,833			8,245
Capital in progress [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	$ 2,054		$ 2,054			$ 1,328