Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 28, 2015	Mar. 29, 2014
Cash flows from operating activities:
Net income	$ 2,556	$ 1,595
Reconciliation of net income to net cash provided by (used in) operating activities:
Depreciation and amortization	2,324	2,429
Stock-based compensation	1,571	1,634
Loss on disposal of fixed assets	485	0
Inventory write-down	403	669
Deferred income taxes	55	519
Changes in fair value of contingent payments to Zygo Corporation	35	(5)
Changes in assets and liabilities:
Accounts receivable	(13,340)	(967)
Inventories	(2,442)	(3,142)
Inventories-delivered systems	1,164	4,652
Prepaid expenses and other	(94)	1,845
Accounts payable, accrued and other liabilities	3,947	(2,536)
Deferred revenue	(2,468)	(10,619)
Income taxes payable	(70)	(766)
Net cash used in operating activities	(5,874)	(4,692)
Cash flows from investing activities:
Sales of marketable securities	1,082	0
Maturities of marketable securities	9,592	7,000
Purchases of marketable securities	(10,613)	(8,410)
Purchases of property, plant and equipment	(502)	(2,193)
Net cash used in investing activities	(441)	(3,603)
Cash flows from financing activities:
Payments to Zygo Corporation related to acquisition	(224)	(100)
Proceeds from sale of shares under employee stock option plans and purchase plan	2,357	3,115
Taxes paid on net issuance of stock awards	(764)	(659)
Repurchases of common stock	(1,721)	0
Net cash (used in) provided by financing activities	(352)	2,356
Effect of exchange rate changes on cash and cash equivalents	(74)	7
Net decrease in cash and cash equivalents	(6,741)	(5,932)
Cash and cash equivalents, beginning of period	34,676	44,765
Cash and cash equivalents, end of period	27,935	38,833
Supplemental disclosure of non-cash investing activities:
Transfer of inventory to property, plant and equipment, net	$ 435	$ 0