Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 26, 2020	Sep. 28, 2019
Deferred tax assets [Abstract]
Net operating loss carryforwards	$ 38,217	$ 38,914
Allowance for doubtful accounts	156	170
Inventory	250	231
Deferred revenue	575	615
AMT credit carryforward	0	513
Other accruals	2,092	1,416
Total deferred tax assets	41,290	41,859
Deferred tax liabilities [Abstract]
Intangible assets	1,197	1,205
Property, plant and equipment	1,899	2,145
Total deferred tax liabilities	3,096	3,350
Net deferred tax assets	38,194	38,509
Valuation allowance	(37,698)	(37,996)
Net deferred tax assets	$ 496	$ 513