Financial Statement Components - Selected Financial Statement Components (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015	Dec. 26, 2015
Inventories:
Raw materials and sub-assemblies	$ 26,819		$ 26,784
Work in process	16,094		12,862
Finished goods	6,980		8,103
Inventories	49,893		47,749
Inventories-delivered systems	4,138		2,856
Total inventories	54,031		50,605
Property, plant and equipment, net:
Total property, plant and equipment, gross	80,905		80,561
Accumulated depreciation and amortization	(37,837)		(36,068)
Total property, plant and equipment, net	43,068		44,493
Depreciation and amortization expense	1,700	$ 1,700
Accrued warranty	4,377		4,504
Accrued restructuring	82		256
Accrued professional services	661		481
Fair value of current portion of contingent payments to Zygo Corporation related to acquisition	940		945
Other	2,918		2,692
Total other current liabilities	8,978		8,878
Land [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	15,569		15,569
Building and improvements [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	20,216		20,158
Machinery and equipment [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	33,338		32,995
Furniture and fixtures [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	2,259		2,266
Software [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	8,245		8,245
Capital in progress [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	$ 1,278		$ 1,328