Geographic and Product Data (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2015	Jul. 04, 2014	Jul. 03, 2015	Jul. 04, 2014
Geographic And Sales [Line Items]
Net sales	$ 18,657	$ 20,048	$ 37,514	$ 40,226
Japan [Member]
Geographic And Sales [Line Items]
Net sales	3,980	4,549	8,267	9,557
China [Member]
Geographic And Sales [Line Items]
Net sales	3,327	2,535	5,698	4,759
United States [Member]
Geographic And Sales [Line Items]
Net sales	2,723	2,926	5,589	5,801
Korea [Member]
Geographic And Sales [Line Items]
Net sales	1,269	1,952	3,612	4,573
Spain [Member]
Geographic And Sales [Line Items]
Net sales	1,486	1,474	2,964	3,092
France [Member]
Geographic And Sales [Line Items]
Net sales	888	1,190	2,039	2,136
Germany [Member]
Geographic And Sales [Line Items]
Net sales	694	1,015	1,190	1,912
Others [Member]
Geographic And Sales [Line Items]
Net sales	$ 4,290	$ 4,407	$ 8,155	$ 8,396