Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended						9 Months Ended
	Jan. 31, 2023	Oct. 31, 2022	Jul. 31, 2022	Jan. 31, 2022	Oct. 31, 2021	Jul. 31, 2021	Jan. 31, 2023	Jan. 31, 2022	Apr. 30, 2022
Accounting Policies [Abstract]
Cash equivalents	$ 0						$ 0		$ 0
Cash above US insurance limit	10,900,000						10,900,000		8,300,000
Net income (loss)	(2,439,000)	$ (16,000)	$ (319,000)	$ 787,000	$ 277,000	$ (172,000)	(2,774,000)	$ 892,000
Net cash provided by operating activities							4,664,000	5,701,000
Accumulated deficit	74,756,000						74,756,000		71,982,000
Cash and cash equivalents	11,645,000						11,645,000		9,007,000
Unrecognized tax benefits	181,000						181,000		$ 181,000
Income tax penalties and interest expense	0	$ 0		0	$ 0
Unrecognized tax benefits anticipated during the next 12 months	0						0
Provision for income taxes	$ 17,000			$ 11,000			$ 48,000	$ 37,000