Note 16 - Income Taxes - Components of Company's Deferred Tax Assets and Liabilities for Federal and State Income Taxes (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Net operating loss carryforwards	$ 27,088,000	$ 27,312,000
Income tax credit carryforwards	2,797,000	2,852,000
Stock compensation	437,000	369,000
Lease obligation	127,000	160,000
Deferred revenue	313,000	366,000
Inventory reserve	449,000	234,000
Other	213,000	268,000
Total deferred tax assets	31,424,000	31,561,000
Depreciation and amortization	(320,000)	(352,000)
Lease asset	(120,000)	(153,000)
Total deferred tax liabilities	(440,000)	(505,000)
Valuation allowance	$ (30,984,000)	$ (31,056,000)