Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jul. 01, 2016	Jun. 30, 2017	Jul. 01, 2016
Product	$ 6,665	$ 1,890	$ 11,253	$ 3,441
Service	558	664	1,010	1,175
Total sales	7,223	2,554	12,263	4,616
Product	3,273	927	5,374	1,728
Service	266	336	576	590
Total cost of sales	3,539	1,263	5,950	2,318
Gross profit	3,684	1,291	6,313	2,298
Operating expenses:
Selling, general and administrative expenses	11,186	6,094	21,991	10,179
Research, development and engineering costs, net	3,221	3,447	7,594	6,983
Other operating expenses				469
Total operating expenses	14,407	9,541	29,585	17,631
Operating loss	(10,723)	(8,250)	(23,272)	(15,333)
Interest expense, net	398	464	768	523
Other expense, net	117	47	320	47
Loss before provision for income taxes	(11,238)	(8,761)	(24,360)	(15,903)
Provision for income taxes
Net loss	(11,238)	(8,761)	(24,360)	(15,903)
Other comprehensive gain:
Unrealized holding gain on investments arising during period	2		2
Other comprehensive gain	2		2
Comprehensive loss	$ (11,236)	$ (8,761)	$ (24,358)	$ (15,903)
Basic and diluted net loss per share (in dollars per share)	$ (1.07)	$ (0.85)	$ (2.34)	$ (1.55)
Basic and diluted weighted average shares outstanding (in shares)	10,458	10,266	10,396	10,262