Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Income Statement [Abstract]
Net sales	$ 70,323,000	$ 81,802,000	$ 134,440,000	$ 158,193,000
Cost of sales	40,885,000	43,927,000	76,800,000	84,993,000
Gross profit	29,438,000	37,875,000	57,640,000	73,200,000
Expenses:
Selling, general and administrative	15,053,000	16,026,000	30,379,000	31,552,000
Research and development	7,663,000	9,666,000	15,603,000	19,685,000
Acquisition plan expenses	2,337,000	0	3,729,000	0
Amortization of intangibles	1,196,000	1,560,000	2,572,000	3,121,000
Total operating expenses	26,249,000	27,252,000	52,283,000	54,358,000
Operating income	3,189,000	10,623,000	5,357,000	18,842,000
Other expenses (income):
Interest expense	73,000	69,000	148,000	334,000
Interest income and other	(110,000)	(90,000)	(222,000)	(174,000)
Income before provision for income taxes	3,226,000	10,644,000	5,431,000	18,682,000
Provision for income taxes	750,000	3,059,000	1,516,000	5,872,000
Net income	$ 2,476,000	$ 7,585,000	$ 3,915,000	$ 12,810,000
Net income per share (See Note 4):
Basic (in dollars per share)	$ 0.15	$ 0.47	$ 0.24	$ 0.79
Diluted (in dollars per share)	$ 0.15	$ 0.46	$ 0.24	$ 0.78
Weighted average number of common shares outstanding – basic (in shares)	16,186,000	16,241,000	16,178,000	16,229,000
Weighted average number of common and common equivalent shares outstanding – diluted (in shares)	16,205,000	16,505,000	16,201,000	16,510,000
Dividends declared per issued and outstanding common share as of the applicable dividend record date (in dollars per share)	$ 0.30	$ 0.30	$ 0.60	$ 0.60