Note 1 - Basis of Presentation and Significant Accounting Policies (Details Textual) - USD ($)					3 Months Ended		6 Months Ended
	Apr. 19, 2022	Apr. 19, 2022	Jul. 27, 2021	Jul. 27, 2021	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Feb. 02, 2022	Feb. 01, 2022	Sep. 30, 2021	Dec. 31, 2020
Asset Retirement Obligation, Ending Balance					$ 90,000		$ 90,000				$ 129,000
Litigation Settlement, Amount Awarded to Other Party							$ 0	$ 0
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)							$ 1.43
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total					1,100,000		$ 1,100,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Total Forfeiture Adjusted Amount					797,000		$ 797,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)							2 years 6 months
Share-Based Payment Arrangement, Expense					188,000	$ 165,000	$ 409,000	283,000
Proceeds from Stock Options Exercised					47,000	67,000	105,000	209,000
Share-Based Payment Arrangement, Expense, Tax Benefit					$ 0	$ 0	$ 0	0
Preferred Stock, Shares Issued, Total (in shares)					0		0				0
Stock Issued During Period, Shares, New Issues (in shares)			945,946	945,946
Shares Issued, Price Per Share (in dollars per share)			$ 3.70	$ 3.70
Stock Issued During Period, Value, New Issues			$ 3,500,000
Proceeds from Issuance of Common Stock							$ 20,000	$ 10,000
Common Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.01		$ 0.01		$ 0.01		$ 0.01
Common Stock, Shares Authorized (in shares)					25,000,000		25,000,000		25,000,000	15,000,000	25,000,000
Cash and Cash Equivalents, at Carrying Value, Total					$ 4,411,000		$ 4,411,000				$ 9,989,000
Proceeds from Issuance of Common Stock, Net				$ 3,500,000
Payments of Stock Issuance Costs				$ 88,000
Japan and the Netherlands [Member]
Cash and Cash Equivalents, at Carrying Value, Total					$ 2,200,000		$ 2,200,000
Board of Directors Chairman [Member]
Stock Issued During Period, Shares, New Issues (in shares)			337,838	337,838
Stock Issued During Period, Value, New Issues			$ 1,250,000	$ 1,250,000
Warrant Agreements Associated with July 2021 Stock Issuance [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)			141,892	141,892
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)			$ 5.50	$ 5.50
Warrant Agreements Associated with July 2021 Stock Issuance [Member] | Board of Directors Chairman [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)			50,676	50,676
Sale of Stock to Four Investors [Member]
Stock Issued During Period, Value, New Issues				$ 3,500,000
Public Offering [Member] | Subsequent Event [Member]
Stock Issued During Period, Shares, New Issues (in shares)	1,700,000
Shares Issued, Price Per Share (in dollars per share)	$ 2.55	$ 2.55
Proceeds from Issuance of Common Stock	$ 4,300,000
Proceeds from Issuance of Common Stock, Net		$ 4,300,000
Payments of Stock Issuance Costs		$ 300,000
Series A Preferred Stock [Member]
Preferred Stock, Shares Issued, Total (in shares)					0	0	0	0			0
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)												300,000
Employee Stock Purchased Plan [Member]
Share-Based Payment Arrangement, Expense					$ 3,000	$ 6,000	$ 6,000	$ 7,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)					92,057		92,057
Proceeds from Stock Plans					$ 20,000	9,000	$ 20,000	9,000
Other Noncurrent Assets [Member]
Capitalized Computer Software, Gross					$ 626,000	954,000	$ 626,000	954,000
Minimum [Member]
Lessor, Sales-type Lease, Term of Contract (Year)					3 years		3 years
Maximum [Member]
Lessor, Sales-type Lease, Term of Contract (Year)					5 years		5 years
Employee Severance [Member]
Restructuring Charges, Total					$ 16,000	$ 0	$ 16,000	$ 101,000