Note 1 - Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2022	Mar. 27, 2021
Net sales	$ 197,757	$ 225,488
Semiconductor Test and Inspection [Member]
Net sales		212,406
PCB Test [Member]
Net sales		13,082
Systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	117,349	138,159
Systems [Member] | PCB Test [Member]
Net sales	0	8,620
Non-systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	80,408	74,247
Non-systems [Member] | PCB Test [Member]
Net sales	0	4,462
CHINA
Net sales	38,653	54,265
PHILIPPINES
Net sales	24,385	33,754
UNITED STATES
Net sales	23,763	20,059
Malaysia [Member]
Net sales	20,116	23,259
TAIWAN
Net sales	19,808	32,196
Rest of the World [Member]
Net sales	$ 71,032	$ 61,955