SUPPLEMENTAL BALANCE SHEET INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 29, 2012	Oct. 01, 2011	Dec. 31, 2011
Short-term Inventories
Raw materials and purchased parts	$ 66,827		$ 65,054
Work in process	18,320		19,257
Finished goods	25,793		28,657
Short-term inventories	110,940		112,968
Long-term Inventories
Raw materials and purchased parts	3,650		3,306
Finished goods	5,630		6,119
Long-term inventories	9,280		9,425
Product Information
Short-term warranty obligations	3,525		4,342
Accrued Warranty Obligations
Balance at beginning of year	4,466	4,105
Additions charged to cost of sales	2,011	2,853
Additions from acquisitions	21	838
Warranty claims	(2,881)	(2,922)
Balance at end of period	3,617	4,874
Accrued Expenses and Other Current Liabilities
Deferred revenue	10,794		12,383
Accrued and deferred tax liabilities	10,316		4,379
Deferred lease liability	5,221		5,201
Short-term accrued warranty obligations	3,525		4,342
Other	12,104		13,495
Total	41,960		39,800
Accumulated Other Comprehensive Loss
Cumulative foreign currency translation losses	(6,295)		(5,804)
Unrecognized net pension losses	(909)		(1,005)
Unrealized gains on marketable securities	700		820
Total	$ (6,504)		$ (5,989)
Photonics and Precision Technologies | All product materials and workmanship, other than filters and gratings products
Product Information
Warranty term	1 year
Photonics and Precision Technologies | Filters and gratings products
Product Information
Warranty term	90 days
Photonics and Precision Technologies | Original equipment manufacturer | Minimum
Product Information
Warranty term	15 months
Photonics and Precision Technologies | Original equipment manufacturer | Maximum
Product Information
Warranty term	19 months
Lasers | Minimum
Product Information
Warranty term	90 days
Lasers | Maximum
Product Information
Warranty term	2 years
Ophir | All products except for laser beam profilers and dental CAD/CAM scanners
Product Information
Warranty term	1 year
Ophir | Laser beam profilers and dental CAD/CAM scanners
Product Information
Warranty term	2 years