Disaggregation of Sales, Geographic Sales and Product Sales - Net Sales by Geographic Areas (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Oct. 02, 2020	Sep. 27, 2019	Oct. 02, 2020	Sep. 27, 2019
Geographic And Sales [Line Items]
Total net sales		$ 47,081	$ 39,055	$ 117,462	$ 111,302
Geographic Distribution, Domestic [Member]
Geographic And Sales [Line Items]
Total net sales		1,477	1,783	4,098	5,849
Geographic Distribution, Foreign [Member]
Geographic And Sales [Line Items]
Total net sales		45,604	37,272	113,364	105,453
Geographic Distribution, Foreign [Member] | China [Member]
Geographic And Sales [Line Items]
Total net sales		23,301	18,361	53,619	49,526
Geographic Distribution, Foreign [Member] | JAPAN
Geographic And Sales [Line Items]
Total net sales		9,208	7,345	24,973	19,139
Geographic Distribution, Foreign [Member] | Other [Member]
Geographic And Sales [Line Items]
Total net sales	[1]	$ 13,095	$ 11,566	$ 34,772	$ 36,788

[1] No other location individually exceeds 10% of the total sales.