Note 1 - Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2022	Sep. 25, 2021	Sep. 24, 2022	Sep. 25, 2021
Net sales	$ 206,687	$ 225,063	$ 621,670	$ 695,354
Semiconductor Test and Inspection [Member]
Net sales		225,063		668,594
PCB Test [Member]
Net sales		0		26,760
Systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	120,672	146,010	369,972	433,830
Systems [Member] | PCB Test [Member]
Net sales	0	0	0	17,831
Non-systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	86,015	79,053	251,698	234,764
Non-systems [Member] | PCB Test [Member]
Net sales	0	0	0	8,929
CHINA
Net sales	31,477	60,205	116,715	171,653
PHILIPPINES
Net sales	38,852	49,382	84,799	119,669
Malaysia [Member]
Net sales	24,060	21,086	73,033	63,481
UNITED STATES
Net sales	19,510	15,498	62,826	57,435
TAIWAN
Net sales	11,243	15,006	46,620	74,392
Rest of the World [Member]
Net sales	$ 81,545	$ 63,886	$ 237,677	$ 208,724