Segment Reporting and Geographic Information (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 Rate	Dec. 31, 2011 Rate	Dec. 31, 2010 Rate
Segment Reporting Information [Line Items]
Revenues	$ 54,299,000	$ 62,152,000	$ 56,326,000	$ 45,709,000	$ 43,620,000	$ 41,434,000	$ 51,543,000	$ 50,599,000	$ 218,486,000	$ 187,196,000	$ 195,305,000
Entity-Wide Revenue, Major Customer, Percentage									10.40%	13.50%	13.90%
Major Customers Two [Domain]
Segment Reporting Information [Line Items]
Entity-Wide Revenue, Major Customer, Percentage									10.10%	12.10%	11.20%
Inspection Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									128,917,000	91,825,000	105,904,000
Percentage of Inspection Revenues [Member]
Segment Reporting Information [Line Items]
Revenues									0.59	0.49	0.54
Metrology Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									38,001,000	38,616,000	39,428,000
Percentage of Metrology Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									0.17	0.21	0.20
Data Analysis & Review [Member]
Segment Reporting Information [Line Items]
Revenues									19,840,000	23,356,000	19,417,000
Percentage of Data Analysis & Review [Member]
Segment Reporting Information [Line Items]
Revenues									0.09	0.13	0.10
Sales Revenue, Goods, Net [Member]
Segment Reporting Information [Line Items]
Revenues									20,802,000	21,719,000	19,266,000
Percentage of Parts [Member]
Segment Reporting Information [Line Items]
Revenues									0.10	0.11	0.10
Sales Revenue, Services, Net [Member]
Segment Reporting Information [Line Items]
Revenues									10,926,000	11,680,000	11,290,000
Percentage of Service [Member]
Segment Reporting Information [Line Items]
Revenues									0.05	0.06	0.06
Sales [Member]
Segment Reporting Information [Line Items]
Revenues									218,486,000	187,196,000	195,305,000
Percentage of Total Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									1.00	1.00	1.00
UNITED STATES
Segment Reporting Information [Line Items]
Revenues									42,108,000	52,910,000	45,243,000
Taiwan [Member]
Segment Reporting Information [Line Items]
Revenues									61,319,000	26,898,000	48,455,000
South Korea [Member]
Segment Reporting Information [Line Items]
Revenues									31,959,000	26,725,000	17,612,000
Singapore
Segment Reporting Information [Line Items]
Revenues									26,183,000	16,344,000	30,305,000
Austria [Domain]
Segment Reporting Information [Line Items]
Revenues									11,423,000	15,960,000	1,841,000
JAPAN
Segment Reporting Information [Line Items]
Revenues									15,444,000	14,925,000	7,725,000
GERMANY
Segment Reporting Information [Line Items]
Revenues									8,990,000	14,657,000	8,191,000
CHINA
Segment Reporting Information [Line Items]
Revenues									12,266,000	11,124,000	24,201,000
Other Europe
Segment Reporting Information [Line Items]
Revenues									8,794,000	7,653,000	11,732,000
Sales [Member]
Segment Reporting Information [Line Items]
Revenues									$ 218,486,000	$ 187,196,000	$ 195,305,000