Stock-Based Compensation | 9 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Oct. 01, 2011 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Stock Based Compensation | Stock-Based Compensation Stock-based compensation expense for all share-based payment awards made to the Company’s employees and directors pursuant to the employee stock option and employee stock purchase plans by function were as follows (in thousands):
The fair value of each option award is estimated on the date of grant using the Black-Scholes valuation model and the assumptions noted in the following table. The expected term of options granted was calculated using the simplified method. The risk-free rate is based on the U.S. Treasury rates in effect during the corresponding period of grant. The expected volatility is based on the historical volatility of Nanometrics’ stock price. The dividend yield reflects that the Company has not paid any cash dividends since inception and does not intend to pay any cash dividends in the foreseeable future. The assumptions in the following table do not include the assumptions used in the Option Exchange Program as disclosed in Note 5 the Company's 2010 Annual Report on Form 10-K for the fiscal year ended January 1, 2011 filed with the SEC on March 14, 2011.
The weighted average fair value per share of the stock options awarded in the three and nine month periods ended October 1, 2011 was $9.71 and $9.95, respectively, based on the fair market value of the Company’s common stock on the grant dates. The weighted average fair value per share of the stock options awarded in the three and nine month periods ended October 2, 2010 was $7.30 and $6.19, respectively, for both periods, based on the fair market value of the Company’s common stock on the grant dates. A summary of activity under the Company’s stock option plans during the quarter ended October 1, 2011 is as follows:
The aggregate intrinsic value in the preceding table represents the total pretax intrinsic value, based on the Company’s closing stock price of $14.50 as of October 1, 2011, which would have been received by the option holders had all option holders exercised their options as of that date. The total intrinsic value of options exercised during the three and nine month periods ended October 1, 2011 was immaterial for both periods. The total intrinsic value of options exercised during the three and nine month periods ended October 2, 2010 was $3.3 million and $4.7 million, respectively. During the nine month period ended October 1, 2011, the Company granted 24,292 Restricted Stock Units (“RSUs”), which vest between one and four years after the vesting commencement date identified in the applicable grant document. As of October 1, 2011, there were 47,621 RSUs outstanding. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||