Note 12 - Stock Options - Options Granted, Exercised, Cancelled or Available for Exercise (Details) - USD ($)	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Shares under option, number of shares (in shares)	2,592,875	2,405,000
Shares under option, stock options price range, lower limit (in dollars per share)				$ 1.77	$ 1.77	$ 1.77
Shares under option, stock options price range, upper limit (in dollars per share)	$ 6	$ 6.28	$ 6.28	6	6.28	6.28
Shares under option, stock options price range, upper limit (in dollars per share)	$ 6.28	$ 6.28
Shares under option, weighted average exercise price (in dollars per share)				2.73	2.96	$ 3.31
Shares under option, weighted average remaining contractual life (Year)	4 years 299 days	4 years 83 days	3 years 222 days
Granted, number of shares (in shares)	555,000	585,000
Granted, stock options price range, lower limit (in dollars per share)				1.97	2.63
Granted, stock options price range, upper limit (in dollars per share)				2.17	2.92
Granted, weighted average exercise price (in dollars per share)	$ 2.08	$ 2.79
Exercised, number of shares (in shares)		(22,125)
Exercised, stock options price range, lower limit (in dollars per share)					1.77
Exercised, stock options price range, upper limit (in dollars per share)					2.24
Exercised, weighted average exercise price (in dollars per share)	$ 3.53	$ 2.11
Expired, number of shares (in shares)	(362,000)	(302,000)
Expired, stock options price range, lower limit (in dollars per share)				2.20	1.77
Expired, stock options price range, upper limit (in dollars per share)				6.28	5.83
Expired, weighted average exercise price (in dollars per share)		$ 5.62
Forfeited, number of shares (in shares)	(64,000)	(73,000)
Forfeited, stock options price range, lower limit (in dollars per share)				1.77	1.77
Forfeited, stock options price range, upper limit (in dollars per share)				$ 2.65	$ 2.65
Forfeited, weighted average exercise price (in dollars per share)	$ 2.15	$ 2.22
Shares under option, aggregate intrinsic value of in-the-money options					$ 48,280
Shares under option, number of shares (in shares)	2,721,875	2,592,875	2,405,000
Shares under option, stock options price range, upper limit (in dollars per share)	$ 6	$ 6.28	$ 6.28
Exercisable, number of shares (in shares)				1,408,709	1,320,291
Exercisable, stock options price range, lower limit (in dollars per share)				$ 1.77	$ 1.77
Exercisable, stock options price range, upper limit (in dollars per share)				6	6.28
Exercisable, weighted average exercise price (in dollars per share)				$ 3.12	$ 3.45
Exercisable, weighted average remaining contractual life (Year)	2 years 222 days	2 years 73 days
Exercisable, aggregate intrinsic value of in-the-money options					$ 9,788