CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net sales	$ 8,508	$ 6,854	$ 23,710	$ 20,168
Cost of sales	5,298	4,591	14,855	12,930
Gross profit	3,210	2,263	8,855	7,238
Operating (income) expenses:
Selling expenses	161	122	438	252
General and administrative expenses	725	641	2,052	1,838
Gain from disposal of equipment				(7)
Research and development costs	620	603	1,501	1,337
Total operating expenses	1,506	1,366	3,991	3,420
Operating income	1,704	897	4,864	3,818
Interest expense	(58)	(67)	(180)	(156)
Interest and other income	9	93	77	261
Gain on sale of investments				356
Income from operations before income taxes	1,655	923	4,761	4,279
Income tax expense	(442)	(191)	(1,194)	(1,019)
Net income	1,213	732	3,567	3,260
Other comprehensive income (loss), net of tax:
Unrealized income (loss) from marketable equity investments	(1,262)	33	(613)	(163)
Comprehensive income (loss)	$ (49)	$ 765	$ 2,954	$ 3,097
Basic net income per share:
Net income	$ 0.31	$ 0.18	$ 0.9	$ 0.77
Diluted net income per share:
Net income	$ 0.3	$ 0.17	$ 0.88	$ 0.75
Weighted average common shares outstanding:
Basic	3,871	4,143	3,944	4,224
Diluted	3,999	4,257	4,071	4,338
Common shares outstanding	3,837	4,136	3,837	4,136