Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 24, 2017	Jun. 30, 2018	Jun. 24, 2017
Net sales	$ 99,817	$ 93,866	$ 194,967	$ 174,963
Cost and expenses:
Cost of sales	58,316	56,736	113,915	105,577
Research and development	11,051	9,466	22,826	19,242
Selling, general and administrative	16,652	16,020	34,415	30,480
	86,019	82,222	171,156	155,299
Income from operations	13,798	11,644	23,811	19,664
Interest income	318	142	554	243
Income from continuing operations before taxes	14,116	11,786	24,365	19,907
Income tax provision	2,468	1,078	4,595	2,436
Income from continuing operations	11,648	10,708	19,770	17,471
Loss from discontinued operations		(278)		(278)
Net income	$ 11,648	$ 10,430	$ 19,770	$ 17,193
Basic:
Income from continuing operations (in dollars per share)	$ 0.40	$ 0.39	$ 0.69	$ 0.64
Loss from discontinued operations (in dollars per share)		(0.01)		(0.01)
Net income (in dollars per share)	0.40	0.38	0.69	0.63
Diluted:
Income from continuing operations (in dollars per share)	0.39	0.37	0.67	0.61
Loss from discontinued operations (in dollars per share)		(0.01)		(0.01)
Net income (in dollars per share)	$ 0.39	$ 0.36	$ 0.67	$ 0.60
Weighted average shares used in computing income per share:
Basic (in shares)	28,893	27,708	28,747	27,343
Diluted (in shares)	29,651	28,725	29,591	28,488
Cash dividends declared per share (in dollars per share)	$ 0.06	$ 0.06	$ 0.12	$ 0.12