7. EQUITY COMPENSATION PLANS (Details - Share based compensation) (USD $)	3 Months Ended		9 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2015	Jan. 31, 2014
Share based compensation	$ 1,616,000	$ 1,601,000	$ 5,280,000	$ 4,914,000
Stock Options [Member]
Share based compensation	1,561,000	1,540,000	5,086,000	4,549,000
Restricted Stock Awards [Member]
Share based compensation	0	0	0	139,000
Employee Stock Purchase Plan [Member]
Share based compensation	55,000	61,000	194,000	226,000
Cost of Manufacturing [Member]
Share based compensation	16,000	18,000	48,000	58,000
Research And Development Member [Member]
Share based compensation	685,000	769,000	2,288,000	2,231,000
Selling, General And Administrative [Member]
Share based compensation	$ 915,000	$ 814,000	$ 2,944,000	$ 2,625,000