Stockholders' Equity and Stock-Based Compensation (Tables)

12 Months Ended

Dec. 30, 2017

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Share repurchases

Shares repurchased and retired for fiscal year 2017, 2016 and 2015, with the associated cost of repurchase and amount available for repurchase at the end of the respective periods are as follows (in thousands, except number of shares and weighted average price per share):

	Fiscal Year 2017		Fiscal Year 2016		Fiscal Year 2015
Number of shares of common stock repurchased		1,065,848	—			111,050
Weighted average price per share	$	25.33		—	$	15.49
Total cost of repurchase	$	26,999	—		$	1,721
Amount available for repurchase at end of period	$	23,001		—	$	4,397

Option plans

The Nanometrics option plans are as follows:

Plan Name	Participants	Shares Authorized
2005 Equity Incentive Plan	Employees, consultants and directors		8,292,594
2000 Employee Stock Option Plan	Employees and consultants		2,450,000
2000 Director Stock Option Plan	Non-employee directors		250,000
Accent Optical Technologies, Inc. Stock Incentive Plan	Employees and consultants		205,003

Employee stock purchase plan assumptions

The weighted-average fair value calculations are based on the following average assumptions:

	Fiscal Year 2017	Fiscal Year 2016	Fiscal Year 2015
Employee Stock Purchase Plan:
Expected life	0.5 years	0.5 years	0.5 years
Volatility	37.2%	38.7%	36.9%
Risk free interest rate	0.91%	0.44%	0.12%
Dividends	—	—	—

Stock option plans activity

A summary of activity of stock options is as follows:

	Number of Shares Outstanding (Options)			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in Thousands)
Options
Outstanding at December 26, 2015		1,059,471		$	14.61		2.47	$	1,920
Exercised		(442,339	)		13.66
Cancelled/Forfeited		(176,587	)		15.83
Outstanding at December 31, 2016		440,545			15.06		2.12	$	4,405
Exercised		(223,364	)		13.35
Cancelled/Forfeited		(855	)		16.63
Outstanding at December 30, 2017		216,326		$	16.82		1.76	$	1,752
Exercisable at December 30, 2017		215,620		$	16.81		1.76	$	1,748

Ranges of outstanding and exercisable options

The following table summarizes ranges of outstanding and exercisable options as of December 30, 2017.

	Options Outstanding						Options Exercisable
Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (Years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$12.98-$15.00		23,383		1.83	$	14.64		23,383	$	14.64
$15.08-$15.65		27,697		1.37		15.62		27,697		15.62
$15.74-$15.74		3,333		0.40		15.74		3,333		15.74
$15.85-$15.85		60,000		2.20		15.85		60,000		15.85
$16.00-$17.33		31,700		1.82		17.00		31,700		17.00
$17.70-$18.08		6,613		1.55		17.92		6,588		17.92
$18.22-$18.22		3,600		3.16		18.22		3,449		18.22
$18.51-$18.51		9,000		3.14		18.51		8,583		18.51
$18.79-$18.79		1,000		3.23		18.79		887		18.79
$19.03-$19.03		50,000		1.13	$	19.03		50,000	$	19.03
$12.98-$19.03		216,326						215,620

Summary of activity for RSUs

A summary of activity for RSUs is as follows:

Summary of activity for RSUs	Number of RSUs			Weighted Average Fair Value
Outstanding RSUs as of December 26, 2015		713,243		$	15.99
Granted		476,667			17.45
Released		(315,872	)		16.05
Cancelled		(54,253	)		16.29
Outstanding RSUs as of December 31, 2016		819,785			16.79
Granted		454,600			27.12
Released		(387,592	)		16.81
Cancelled		(96,494	)		19.01
Outstanding RSUs as of December 30, 2017		790,299		$	22.46

Summary of activity for PSUs

A summary of activity for PSUs is as follows:

Summary of activity for PSUs	Number of PSUs			Weighted Average Fair Value
Outstanding PSUs as of December 26, 2015		60,000		$	12.23
Granted		67,500			8.52
Released		(13,333	)		12.03
Cancelled		(6,667	)		12.03
Outstanding PSUs as of December 31, 2016		107,500			9.94
Granted		122,050			20.51
Released		(38,500	)		10.41
Cancelled		(61,100	)		19.41
Outstanding PSUs as of December 30, 2017		129,950		$	15.60

PSUs valuation assumptions

The assumptions for the valuation of PSUs are summarized as follows:

	2017 Award	2016 Award		2015 Award
Grant Date Fair Values Per Share	$14.57-$26.75	$	8.52	$	12.23
Weighted-average assumptions/inputs:
Expected Dividend	—	—		—
Range of risk-free interest rates	1.74%-1.84%	0.92%		0.25%-1.1%
Range of expected volatilities for peer group	22%-66%	22%-93%		23%-65%

Stock-based compensation expense for all share-based payment awards

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):

	Fiscal Year 2017		Fiscal Year 2016		Fiscal Year 2015
Cost of products	$	842	$	403	$	274
Cost of service		616		509		309
Research and development		1,720		1,408		1,036
Selling		2,323		2,046		1,881
General and administrative		3,318		3,300		2,748
Total stock-based compensation expense related to employee    stock options and employee stock purchases	$	8,819	$	7,666	$	6,248

Stock Options, RSUs and PSUs [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock option plans activity including options, RSUs and PSUs

A summary of activity under the Company’s stock option plans including options, RSUs and PSUs during fiscal year 2017, 2016 and 2015 and shares available for grant as of the respective period end dates, is as follows:

	Fiscal Year 2017			Fiscal Year 2016			Fiscal Year 2015
Shares available for grant at beginning of fiscal year		1,334,581			1,916,589			2,464,082
Additional Shares Authorized		1,000,000			—			—
Options – cancelled		855			176,587			94,012
Options - expired plan shares					(116,192	)		(1,800	)
RSUs – granted		(772,820	)		(810,334	)		(860,980	)
RSUs – cancelled		164,040			92,230			202,356
RSUs - shares issued to satisfy tax    withholding obligations		251,724			179,117			120,919
PSUs – granted		(207,485	)		(114,750	)		(102,000	)
PSUs – cancelled		103,870			11,334			—
Shares available for grant at end of fiscal year		1,874,765			1,334,581			1,916,589