Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014
Cash flows from operating activities:
Net income (loss)	$ 4,718	$ (26,479)
Reconciliation of net income (loss) to net cash from operating activities:
Depreciation and amortization	6,826	8,660
Stock-based compensation	4,664	5,115
Loss on disposal of fixed assets	578	80
Provision for doubtful accounts receivable	0	11
Inventory write-down	1,971	1,109
Deferred income taxes	173	20,776
Changes in fair value of contingent payments to Zygo Corporation	137	118
Changes in assets and liabilities:
Accounts receivable	(14,873)	4,871
Inventories	(15,893)	(7,998)
Inventories-delivered systems	370	6,400
Prepaid expenses and other	4,436	1,751
Accounts payable, accrued and other liabilities	9,634	(4,535)
Deferred revenue	(688)	(16,270)
Income taxes payable	295	(3,158)
Net cash provided by (used in) operating activities	2,348	(9,549)
Cash flows from investing activities:
Sales of marketable securities	2,884	0
Maturities of marketable securities	30,279	25,570
Purchases of marketable securities	(27,298)	(26,810)
Purchases of property, plant and equipment	(1,365)	(2,800)
Net cash provided by (used in) investing activities	4,500	(4,040)
Cash flows from financing activities:
Payments to Zygo Corporation related to acquisition	(614)	(470)
Proceeds from sale of shares under employee stock option plans and purchase plan	3,642	5,852
Taxes paid on net issuance of stock awards	(1,104)	(664)
Repurchases of common stock	(1,721)	0
Net cash provided by financing activities	203	4,718
Effect of exchange rate changes on cash and cash equivalents	(166)	(269)
Net increase (decrease) in cash and cash equivalents	6,885	(9,140)
Cash and cash equivalents, beginning of period	34,676	44,765
Cash and cash equivalents, end of period	41,561	35,625
Supplemental disclosure of non-cash investing activities:
Transfer of inventory to property, plant and equipment, net	$ 1,068	$ 4,627