Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (4,298)	$ (9,542)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,046	1,989
Change in fair value of common stock warrant liability	(1,474)	(2,194)
Impairment of Consumer Night Vision Business inventory		1,270
Impairment of Consumer Night Vision Business tooling		76
Stock-based compensation	551	610
Amortization of operating lease right-of-use assets	538
Changes in operating assets and liabilities:
Accounts receivable	(780)	1,342
Unbilled accounts receivable	69	183
Inventories	(250)	(2,632)
Prepaid expenses and other current assets	(255)	453
Deferred revenues	239	(727)
Operating lease liabilities	(530)
Accounts payable, accrued expenses, and other current liabilities	(966)	2,793
Net cash used in operating activities	(5,110)	(6,379)
Cash flows from investing activities:
Purchase of equipment	(1,110)	(2,296)
Net cash used in investing activities	(1,110)	(2,296)
Cash flows from financing activities:
Borrowings (repayments) under revolving line of credit, net	2,891	(3,808)
Proceeds from public offering, net	3,476	12,172
Proceeds from warrant exercise, net		46
Proceeds from exercise of stock options	9	98
Net cash provided by financing activities	6,376	8,508
Net increase (decrease) in cash and cash equivalents	156	(167)
Cash and cash equivalents, beginning of period	3,359	3,526
Cash and cash equivalents, end of period	3,515	3,359
Cash paid for interest	177	106
Cash paid for income taxes