Note 2 - Significant Accounting Policies 1 (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
Accounts Payable, Current, Total	$ 914,000	$ 743,000
Accrued Liabilities and Other Liabilities, Current	2,561,000	1,805,000
Adjustments to Equity to Reflect the Impact of Reverse Stock Split		39,000	$ 39,000	$ 39,000
Retained Earnings (Accumulated Deficit), Ending Balance	(101,070,000)	(86,361,000)
Cash and Cash Equivalents, at Carrying Value, Ending Balance	5,585,000	5,358,000	12,689,000	$ 21,352,000
Accounts Receivable, Allowance for Credit Loss, Current	2,000	9,000
Impairment of Long-Lived Assets Held-for-use	0
Cost of Goods and Services Sold, Total	$ 358,000	517,000	690,000
Standard Product Warranty, Term (Year)	2 years
Standard Product Warranty Accrual, Ending Balance	$ 0	0
Income Tax Examination, Penalties and Interest Accrued, Total	0
Operating Lease, Right-of-Use Asset	1,065,000
Operating Lease, Liability, Total	1,142,000
Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset					$ 1,505,000
Operating Lease, Liability, Total					$ 1,593,000
Shipping and Handling [Member]
Cost of Goods and Services Sold, Total	$ 6,000	6,000	$ 5,000
Revision of Prior Period, Adjustment [Member]
Accounts Payable, Current, Total		(277,000)
Accrued Liabilities and Other Liabilities, Current		$ 277,000