Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Statement of Cash Flows [Abstract]
Net loss	$ (7,090)	$ (14,774)
Adjustments to reconcile net loss to net cash used in operations:
Depreciation	486	880
Amortization of intangible assets	79	92
Gain on disposal of property and equipment	(2)	(1)
Realizeld loss on sale of short-term investments	0	32
Non-cash stock-based compensation expense	481	854
Inventory write-downs	303	1,094
Non-cash deferred rent	0	(88)
Change in:
Accounts receivable, net	27	(95)
Costs and estimated earnings in excess of billings on uncompleted contracts	0	58
Inventory	150	2,294
Other current assets	899	301
Other assets	4	12
Accounts payable	(1,046)	(2,976)
Accrued liabilities	(771)	(726)
Deferred revenue	(581)	0
Billings in excess of costs and estimated earnings on uncompleted contracts	765	31
Net cash used in operating activities	(6,296)	(13,012)
Cash flows from investing activities
Sales of investment securities	0	11
Decrease in restricted cash	1	350
Proceeds on sale of property and equipment	2	1
Purchases of property and equipment	(86)	(400)
Net cash used in investing activities	(83)	(38)
Cash flows from financing activities
Principal payments under capital leases and long-term debt	(75)	(66)
Net proceeds from issuance of common stock and warrants	5,607	14,805
Net cash provided by (used in) financing activities	5,532	14,739
Net increase (decrease) in cash and cash equivalents	(847)	1,689
Cash and cash equivalents, at beginning of period	6,850	13,075
Cash and cash equivalents, at end of period	6,003	14,764
Supplemental disclosure of cash flow information
Cash paid for interest	8	17
Supplemental schedule of non-cash investing and financing activities
Other non-cash additions to property and equipment	386	12
Warrant liability	$ 3,755	$ 0