Note 1 - Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2022	Jun. 26, 2021	Jun. 25, 2022	Jun. 26, 2021
Net sales	$ 217,226	$ 244,803	$ 414,983	$ 470,291
Semiconductor Test and Inspection [Member]
Net sales		231,125		443,531
PCB Test [Member]
Net sales		13,678		26,760
Systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	131,951	149,661	249,300	287,820
Systems [Member] | PCB Test [Member]
Net sales	0	9,211	0	17,831
Non-systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	85,275	81,464	165,683	155,711
Non-systems [Member] | PCB Test [Member]
Net sales	0	4,467	0	8,929
CHINA
Net sales	46,585	57,183	85,238	111,448
Malaysia [Member]
Net sales	28,857	19,136	48,973	42,395
PHILIPPINES
Net sales	21,562	36,533	45,947	70,287
UNITED STATES
Net sales	19,553	21,878	43,316	41,937
TAIWAN
Net sales	15,569	27,190	35,377	59,386
Rest of the World [Member]
Net sales	$ 85,100	$ 82,883	$ 156,132	$ 144,838