Segment Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 26, 2013	Oct. 27, 2012	Oct. 26, 2013	Oct. 27, 2012
Segment Data
Intersegment sales			$ 0
Revenue:
Total revenue	64,867	80,278	108,984	138,955
Cost of sales:
Total cost of sales	40,989	44,642	72,561	83,814
Gross margin:
Gross margin	23,878	35,636	36,423	55,141
Selling, general and administrative	13,084	13,176	25,543	26,797
Research and development	6,861	9,386	14,051	17,522
Income (loss) from operations	3,933	13,074	(3,171)	10,822
Other income (expense):
Interest income	195	162	400	334
Other expense	(2,307)		(5,701)
Income (loss) before income taxes	1,821	13,236	(8,472)	11,156
UAS
Revenue:
Total revenue	56,079	65,433	91,290	114,239
Cost of sales:
Total cost of sales	35,280	35,279	59,879	68,035
Gross margin:
Gross margin	20,799	30,154	31,411	46,204
EES
Revenue:
Total revenue	8,788	14,845	17,694	24,716
Cost of sales:
Total cost of sales	5,709	9,363	12,682	15,779
Gross margin:
Gross margin	3,079	5,482	5,012	8,937
Unallocated to segment
Gross margin:
Selling, general and administrative	13,084	13,176	25,543	26,797
Research and development	6,861	9,386	14,051	17,522
Other income (expense):
Interest income	195	162	400	334
Other expense	$ (2,603)		$ (5,997)