SUPPLEMENTAL BALANCE SHEET INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2013	Mar. 31, 2012	Dec. 29, 2012
Warranty
Short-term accrued warranty obligations	$ 3,251		$ 3,421
Accrued Warranty Obligations
Balance at beginning of year	3,528	4,466
Additions charged to cost of sales	596	629
Additions from acquisitions		21
Warranty claims	(742)	(1,195)
Balance at end of period	3,382	3,921
Accrued Expenses and Other Current Liabilities
Deferred revenue	12,702		11,561
Deferred lease liability	5,464		5,445
Accrued and deferred taxes	3,714		3,866
Short-term accrued warranty obligations	3,251		3,421
Other	9,814		10,403
Accrued expenses and other current liabilities, total	34,945		34,696
Accumulated Other Comprehensive Loss
Cumulative foreign currency translation losses	(6,972)		(4,569)
Unrecognized net pension losses	(3,058)		(3,248)
Unrealized gains on marketable securities	770		868
Accumulated other comprehensive loss	$ (9,260)		$ (6,949)
Photonics and Optics | All products other than filters, gratings, laser beam profilers and dental CAD/CAM scanners
Warranty
Product warranty period	1 year
Photonics and Optics | Original equipment manufacturer | Minimum
Warranty
Product warranty period	15 months
Photonics and Optics | Original equipment manufacturer | Maximum
Warranty
Product warranty period	19 months
Optics | Filters and gratings products
Warranty
Product warranty period	90 days
Photonics | Laser beam profilers and dental CAD/CAM scanners
Warranty
Product warranty period	2 years
Lasers Division | Minimum
Warranty
Product warranty period	90 days
Lasers Division | Maximum
Warranty
Product warranty period	2 years