CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2020	Sep. 27, 2019	Oct. 02, 2020	Sep. 27, 2019
Income Statement [Abstract]
Net sales	$ 47,081,000	$ 39,055,000	$ 117,462,000	$ 111,302,000
Cost of sales	12,210,000	10,004,000	33,401,000	28,172,000
Gross profit	34,871,000	29,051,000	84,061,000	83,130,000
Selling, general and administrative expenses:
General and administrative	8,589,000	7,098,000	24,406,000	21,443,000
Selling and marketing	12,649,000	12,463,000	34,003,000	34,288,000
Research and development	8,751,000	6,156,000	22,960,000	17,889,000
Total selling, general and administrative expenses	29,989,000	25,717,000	81,369,000	73,620,000
Operating income	4,882,000	3,334,000	2,692,000	9,510,000
Other income (expense), net:
Interest income, net	1,000	266,000	237,000	796,000
Gain (loss) on foreign currency transactions	468,000	(584,000)	388,000	(821,000)
Royalty income	93,000	106,000	239,000	440,000
Other income (expense), net	(63,000)	26,000	(83,000)	124,000
Total other income (expense), net	499,000	(186,000)	781,000	539,000
Income before income taxes	5,381,000	3,148,000	3,473,000	10,049,000
Provision for income taxes	1,489,000	760,000	887,000	2,380,000
Net income	$ 3,892,000	$ 2,388,000	$ 2,586,000	$ 7,669,000
Net income per share:
Basic	$ 0.08	$ 0.05	$ 0.06	$ 0.17
Diluted	$ 0.08	$ 0.05	$ 0.05	$ 0.16
Weighted average shares outstanding:
Basic	45,903	44,563	45,394	44,426
Diluted	48,180	46,857	47,589	46,848