Financial Statement Components - Selected Financial Statement Components (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 31, 2017	Dec. 30, 2017	Dec. 31, 2016
Inventories:
Raw materials and sub-assemblies	$ 31,434		$ 32,187
Work in process	22,383		13,498
Finished goods	8,098		7,175
Inventories	61,915		52,860
Inventories-delivered systems	180		1,534
Total inventories	62,095		54,394
Property, plant and equipment, net:
Total property, plant and equipment, gross	95,517		89,229
Accumulated depreciation and amortization	(47,617)		(44,419)
Total property, plant and equipment, net	47,900		44,810
Other Current Liabilities:
Accrued warranty	4,379	$ 4,863	4,863	$ 3,838
Accrued taxes	1,738		813
Customer deposits	293
Accrued professional services	448		534
Third party commissions	1,382		76
Other	1,181		963
Total other current liabilities	9,421		7,249
Land [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	15,571		15,573
Building and improvements [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	21,354		20,880
Machinery and equipment [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	39,898		36,380
Furniture and fixtures [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	2,551		2,420
Software [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	10,116		9,558
Capital in progress [Member]
Property, plant and equipment, net:
Total property, plant and equipment, gross	$ 6,027		$ 4,418