Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 25, 2021	Sep. 26, 2020
Deferred tax assets [Abstract]
Net operating loss carryforwards	$ 37,806	$ 38,217
Allowance for doubtful accounts	208	156
Inventory	264	250
Deferred revenue	557	575
Other accruals	2,671	2,092
Total deferred tax assets	41,506	41,290
Deferred tax liabilities [Abstract]
Intangible assets	1,189	1,197
Property, plant and equipment	1,655	1,899
Total deferred tax liabilities	2,844	3,096
Net deferred tax assets	38,662	38,194
Valuation allowance	(38,268)	(37,698)
Net deferred tax assets	$ 394	$ 496