Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 27, 2015	Jun. 28, 2014
Cash flows from operating activities:
Net income	$ 3,900	$ 2,183
Reconciliation of net income to net cash used in operating activities:
Depreciation and amortization	4,555	4,814
Stock-based compensation	2,982	3,410
Loss on disposal of fixed assets	501	28
Inventory write-down	1,298	1,527
Deferred income taxes	136	490
Changes in fair value of contingent payments to Zygo Corporation	93	66
Changes in assets and liabilities:
Accounts receivable	(19,030)	(1,909)
Inventories	(8,442)	(3,830)
Inventories-delivered systems	339	6,543
Prepaid expenses and other	2,735	1,251
Accounts payable, accrued and other liabilities	4,283	(2,961)
Deferred revenue	(579)	(14,978)
Income taxes payable	72	(1,203)
Net cash used in operating activities	(7,157)	(4,569)
Cash flows from investing activities:
Sales of marketable securities	2,383	0
Maturities of marketable securities	15,836	17,620
Purchases of marketable securities	(17,561)	(19,479)
Purchases of property, plant and equipment	(1,043)	(3,813)
Net cash used in investing activities	(385)	(5,672)
Cash flows from financing activities:
Payments to Zygo Corporation related to acquisition	(417)	(261)
Proceeds from sale of shares under employee stock option plans and purchase plan	2,500	4,201
Taxes paid on net issuance of stock awards	(1,015)	(664)
Repurchases of common stock	(1,721)	0
Net cash (used in) provided by financing activities	(653)	3,276
Effect of exchange rate changes on cash and cash equivalents	(60)	187
Net decrease in cash and cash equivalents	(8,255)	(6,778)
Cash and cash equivalents, beginning of period	34,676	44,765
Cash and cash equivalents, end of period	26,421	37,987
Supplemental disclosure of non-cash investing activities:
Transfer of inventory to property, plant and equipment, net	$ 1,103	$ 617