CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands		12 Months Ended
		Dec. 28, 2018	Dec. 29, 2017	Dec. 30, 2016
Income Statement [Abstract]
Net sales		$ 123,954,000	$ 90,611,000	$ 82,432,000
Cost of sales		32,444,000	26,331,000	24,063,000
Gross profit		91,510,000	64,280,000	58,369,000
Selling, general and administrative expenses:
General and administrative		24,287,000	19,465,000	21,671,000
Marketing and selling		38,600,000	28,402,000	28,685,000
Research and development		22,028,000	20,044,000	20,668,000
Total selling, general and administrative expenses		84,915,000	67,911,000	71,024,000
Operating income (loss)		6,595,000	(3,631,000)	(12,655,000)
Other income (expense), net:
Interest income (expense), net		165,000	(112,000)	(112,000)
Gain (loss) on foreign currency transactions	[1]	(836,000)	819,000	(147,000)
Royalty income		633,000	581,000	618,000
Other income (expense), net		82,000	47,000	(148,000)
Total other income, net		44,000	1,335,000	211,000
Income (loss) before income taxes		6,639,000	(2,296,000)	(12,444,000)
Provision (benefit) for income taxes		1,671,000	(157,000)	(315,000)
Net income (loss)		$ 4,968,000	$ (2,139,000)	$ (12,129,000)
Net income (loss) per share:
Basic		$ 0.12	$ (0.05)	$ (0.30)
Diluted		$ 0.11	$ (0.05)	$ (0.30)
Weighted average shares outstanding:
Basic		42,587	41,004	40,329
Diluted		45,257	41,004	40,329

[1] Shown as a separate line item on the Consolidated Statements of Operations.