Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (9,542)	$ (7,783)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,989	2,070
Change in fair value of common stock warrant liability	(2,194)	(1,089)
Impairment of Consumer Night Vision Business inventory	2,690
Impairment of Consumer Night Vision Business tooling	76
Stock-based compensation	610	628
Changes in operating assets and liabilities:
Accounts receivable	1,342	(1,694)
Unbilled accounts receivable	183	995
Inventories	(1,212)	(1,205)
Prepaid expenses and other current assets	49	(288)
Deferred revenues	(727)	320
Accounts payable, accrued expenses, and other current liabilities	357	(100)
Net cash used in operating activities	(6,379)	(8,146)
Cash flows from investing activities:
Purchase of equipment	(2,296)	(1,355)
Net cash used in investing activities	(2,296)	(1,355)
Cash flows from financing activities:
Repayments under revolving line of credit, net	(3,808)	1,885
Proceeds from public offering of common stock and warrants, net	12,172	5,919
Payments of debt issuance costs		(158)
Proceeds from warrant exercise, net	46
Proceeds from exercise of stock options	98	140
Net cash provided by financing activities	8,508	7,786
Net decrease in cash and cash equivalents	(167)	(1,715)
Cash and cash equivalents, beginning of period	3,526	5,241
Cash and cash equivalents, end of period	3,359	3,526
Cash paid for interest	106	146
Cash paid for income taxes