Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 28, 2018	Dec. 29, 2017
Deferred tax assets:
Allowance for doubtful accounts and sales returns	$ 252	$ 230
Inventories	560	381
Accrued vacation	387	322
Accrued other expenses	1,232	559
Stock-based compensation	2,489	1,444
Pensions	884	720
Depreciation and amortization	843	959
Net operating loss carryforwards	34,347	33,770
Business, foreign, AMT and R and D credit carryforwards	3,256	3,706
Prepaid expenses	272	188
Capitalized R&D	968	941
Other	122	92
Valuation allowance	(43,075)	(40,656)
Total deferred tax assets	2,537	2,656
Deferred tax liabilities:
Foreign tax withholding	(1,282)	(881)
Amortization of R&D	(759)	(723)
Net foreign earnings not permanently reinvested	(240)	(160)
Total deferred tax liabilities	(2,281)	(1,764)
Total net deferred tax assets	$ 256	$ 892