Note 1 - Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2018

Notes Tables

Schedule of Inventory, Current [Table Text Block]

	June 30,		December 30,
	2018		2017
Raw materials and purchased parts	$	28,810	$	27,918
Work in process		23,691		25,130
Finished goods		10,635		9,037
Total inventories	$	63,136	$	62,085

Property, Plant and Equipment [Table Text Block]

	June 30,			December 30,
	2018			2017
Land and land improvements	$	7,971		$	8,017
Buildings and building improvements		14,173			13,779
Machinery and equipment		45,990			45,333
		68,134			67,129
Less accumulated depreciation and amortization		(34,597	)		(32,957	)
Property, plant and equipment, net	$	33,537		$	34,172

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

	Three Months Ended						Six Months Ended
	June 30,			June 24,			June 30,			June 24,
	2018			2017			2018			2017
Cost of sales	$	162		$	121		$	283		$	204
Research and development		395			262			744			578
Selling, general and administrative		1,391			1,376			2,590			2,694
Total share-based compensation		1,948			1,759			3,617			3,476
Income tax benefit		(126	)		(249	)		(440	)		(322	)
Total share-based compensation, net	$	1,822		$	1,510		$	3,177		$	3,154

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

	Three Months Ended				Six Months Ended
	June 30,		June 24,		June 30,		June 24,
	2018		2017		2018		2017
Weighted average common shares		28,893		27,708		28,747		27,343
Effect of dilutive securities		758		1,017		844		1,145
		29,651		28,725		29,591		28,488

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 Three Months Ended June 30, 2018
			Balances
			without adoption		Effect of
Condensed Consolidated Statements of Income	As Reported		of ASC 606		Change
Net sales	$	99,817	$	99,556	$	261
Income tax provision	$	2,468	$	2,213	$	255
Net income	$	11,648	$	11,642	$	6
Income per share:
Basic:	$	0.40	$	0.40	$	(0.00	)
Diluted:	$	0.39	$	0.39	$	(0.00	)

	For the Six Months Ended June 30, 2018
			Balances
			without adoption		Effect of
Condensed Consolidated Statements of Income	As Reported		of ASC 606		Change
Net sales	$	194,967	$	192,218	$	2,749
Income tax provision	$	4,595	$	4,096	$	499
Net income	$	19,770	$	17,520	$	2,250
Income per share:
Basic:	$	0.69	$	0.61	$	0.08
Diluted:	$	0.67	$	0.59	$	0.08

			Balances
			without adoption		Effect of
Condensed Consolidated Balance Sheets*	As Reported		of ASC 606		Change
Deferred profit	$	1,709	$	5,884	$	(4,175	)
Retained earnings	$	168,040	$	164,733	$	3,307

Disaggregation of Revenue [Table Text Block]

	Three Months Ended		Six Months Ended
	June 30, 2018		June 30, 2018
Systems	$	55,663	$	110,568
Non-systems		44,154		84,399
Net sales	$	99,817	$	194,967

	Three months ended		Six months ended
	June 30, 2018		June 30, 2018
China	$	19,140	$	39,383
United States		15,662		30,140
Malaysia		13,048		24,857
Philippines		9,916		20,462
Rest of the World		42,051		80,125
Net sales	$	99,817	$	194,967

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

	Three Months Ended						Six Months Ended
	June 30,			June 24,			June 30,			June 24,
	2018			2017			2018			2017
Customers individually accounting for more than 10% of net sales		one			one			one			one
Percentage of net sales		11.3	%		20.7	%		10.6	%		20.4	%