Condensed Consolidated Statements of Income and Comprehensive Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Revenues	$ 17,137	$ 15,448	$ 51,391	$ 46,442
Cost of revenues	10,387	9,233	31,928	27,970
Gross margin	6,750	6,215	19,463	18,472
Selling and administrative expenses	3,887	3,390	10,883	10,017
Research and development expense	1,113	882	3,731	2,954
Operating profit	1,750	1,943	4,849	5,501
Other income (expense):
Investment income	190	214	509	473
Equity loss		(335)		(451)
Impairment of investment in and loans receivable from affiliate				(350)
Interest expense	(53)	(26)	(156)	(77)
Other expense, net	(67)	(222)	(73)	(132)
Income before provision for income taxes	1,820	1,574	5,129	4,964
Provision for income taxes	300	500	1,400	1,770
Net income	1,520	1,074	3,729	3,194
Net income per common share
Basic (in Dollars per share)	$ 0.18	$ 0.13	$ 0.44	$ 0.38
Diluted (in Dollars per share)	$ 0.18	$ 0.13	$ 0.43	$ 0.37
Weighted average shares outstanding
Basic (in Shares)	8,424,162	8,323,912	8,401,348	8,319,740
Diluted (in Shares)	8,603,774	8,508,297	8,583,616	8,537,591
Comprehensive Income
Net income	1,520	1,074	3,729	3,194
Other comprehensive income (loss):
Foreign currency translation adjustment	191	(996)	46	(1,300)
Change in market value of marketable securities	(87)	194	282	26
Deferred tax effect of change in marketable securities	31	(70)	(103)	(9)
Total other comprehensive income (loss)	135	(872)	225	(1,283)
Comprehensive income	$ 1,655	$ 202	$ 3,954	$ 1,911