CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	3 Months Ended		6 Months Ended
	Oct. 29, 2016	Oct. 31, 2015	Oct. 29, 2016	Oct. 31, 2015
Revenue:
Product sales	$ 29,350,000	$ 49,492,000	$ 45,087,000	$ 76,131,000
Contract services	20,766,000	15,239,000	41,247,000	35,650,000
Total revenue	50,116,000	64,731,000	86,334,000	111,781,000
Cost of sales:
Product sales	19,197,000	24,802,000	34,419,000	41,567,000
Contract services	13,502,000	8,396,000	27,815,000	22,658,000
Total cost of sales	32,699,000	33,198,000	62,234,000	64,225,000
Gross margin:
Product sales	10,153,000	24,690,000	10,668,000	34,564,000
Contract services	7,264,000	6,843,000	13,432,000	12,992,000
Total gross margin	17,417,000	31,533,000	24,100,000	47,556,000
Selling, general and administrative	13,387,000	14,733,000	27,050,000	29,989,000
Research and development	8,517,000	9,897,000	17,117,000	19,728,000
(Loss) income from operations	(4,487,000)	6,903,000	(20,067,000)	(2,161,000)
Other income (expense):
Interest income, net	397,000	268,000	772,000	492,000
Other expense, net	(130,000)	(192,000)	(430,000)	(2,581,000)
(Loss) income before income taxes	(4,220,000)	6,979,000	(19,725,000)	(4,250,000)
(Benefit) provision for income taxes	(48,000)	2,560,000	(3,911,000)	(1,688,000)
Net (loss) income	$ (4,172,000)	$ 4,419,000	$ (15,814,000)	$ (2,562,000)
(Loss) earnings per share data:
Basic (in dollars per share)	$ (0.18)	$ 0.19	$ (0.69)	$ (0.11)
Diluted (in dollars per share)	$ (0.18)	$ 0.19	$ (0.69)	$ (0.11)
Weighted average shares outstanding:
Basic (in shares)	23,049,056	22,985,956	23,002,832	22,966,513
Diluted (in shares)	23,049,056	23,148,456	23,002,832	22,966,513