Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (7,083)	$ (7,261)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,482	1,588
Change in fair value of common stock warrant liability	(387)
Impairment of Consumer Night Vision Business inventory	2,690
Impairment of Consumer Night Vision Business tooling	76
Stock-based compensation	512	520
Changes in operating assets and liabilities:
Accounts receivable	147	(594)
Unbilled accounts receivable	42	926
Inventories	(1,349)	(1,645)
Prepaid expenses and other current assets	55	(92)
Deferred revenues	(724)	543
Accounts payable, accrued expenses, and other current liabilities	164	(895)
Net cash used in operating activities	(4,375)	(6,910)
Cash flows from investing activities:
Purchase of equipment	(1,469)	(1,157)
Net cash used in investing activities	(1,469)	(1,157)
Cash flows from financing activities:
Repayments under revolving line of credit, net	(3,808)	(932)
Proceeds from public offering, net	12,172	5,811
Payments of debt issuance costs		(158)
Proceeds from warrant exercise, net	46
Proceeds from exercise of stock options	98	69
Net cash provided by financing activities	8,508	4,790
Net increase (decrease) in cash and cash equivalents	2,664	(3,277)
Cash and cash equivalents, beginning of period	3,526	5,241
Cash and cash equivalents, end of period	6,190	1,964
Cash paid for interest	44	65
Cash paid for income taxes