Note 1 - Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2018

Notes Tables

Schedule of Inventory, Current [Table Text Block]

	March 31,		December 30,
	2018		2017
Raw materials and purchased parts	$	27,277	$	27,918
Work in process		25,267		25,130
Finished goods		10,132		9,037
Total inventories	$	62,676	$	62,085

Property, Plant and Equipment [Table Text Block]

	March 31,			December 30,
	2018			2017
Land and land improvements	$	8,331		$	8,017
Buildings and building improvements		14,265			13,779
Machinery and equipment		46,018			45,333
		68,614			67,129
Less accumulated depreciation and amortization		(33,492	)		(32,957	)
Property, plant and equipment, net	$	35,122		$	34,172

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Months Ended
	March 31,			March 25,
	2018			2017
Cost of sales	$	121		$	83
Research and development		349			316
Selling, general and administrative		1,199			1,318
Total share-based compensation		1,669			1,717
Income tax benefit		(314	)		(75	)
Total share-based compensation, net	$	1,355		$	1,642

Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]

	Three Months Ended
	March 31,		March 25,
	2018		2017
Weighted average common shares		28,602		26,978
Effect of dilutive securities		929		1,274
		29,531		28,252

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]

	Balance at		Adjustments			Balance at
	December 30,		due to adoption			December 31,
Financial Statement Line Item	2017		of ASC 606			2017
Deferred profit	$	6,608	$	(1,258	)	$	5,350
Income taxes payable	$	2,159	$	201		$	2,360
Retained earnings	$	150,726	$	1,057		$	151,783

	For the Period Ended March 31, 2018
			Balances
			without adoption		Effect of
Condensed Consolidated Statements of Income	As Reported		of ASC 606		Change
Net sales	$	95,150	$	92,662	$	2,488
Income tax provision	$	2,127	$	1,883	$	244
Net income	$	8,122	$	5,878	$	2,244
Income per share:
Basic:	$	0.28	$	0.21	$	0.07
Diluted:	$	0.28	$	0.20	$	0.08

	As of March 31, 2018
			Balances
			without adoption		Effect of
Condensed Consolidated Balance Sheets*	As Reported		of ASC 606		Change
Deferred profit	$	2,914	$	6,664	$	(3,750	)
Income taxes payable	$	1,546	$	984	$	562
Deferred income taxes	$	3,812	$	3,929	$	(117	)
Retained earnings	$	158,124	$	154,819	$	3,305

Disaggregation of Revenue [Table Text Block]

	Three Months Ended
	March 31, 2018
Systems	$	54,905
Non-systems		40,245
Net sales	$	95,150

	Three Months Ended
	March 31, 2018
China	$	20,243
United States		14,478
Malaysia		11,809
Philippines		10,546
Rest of the World		38,074
Net sales	$	95,150

Schedules of Concentration of Risk, by Risk Factor [Table Text Block]

	Three Months Ended
	March 31,		March 25,
	2018		2017
Customers individually accounting for more than 10% of net sales		one		one
Percentage of net sales		12%		20%