Note 1 - Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 25, 2021	Dec. 26, 2020	Dec. 28, 2019
Net sales	$ 887,214	$ 636,007	$ 583,329
Semiconductor Test and Inspection [Member]
Net sales	860,454	585,240	540,878
PCB Test [Member]
Net sales	26,760	50,767	42,451
Systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	541,589	317,821	299,473
Systems [Member] | PCB Test [Member]
Net sales	17,831	33,293	25,928
Non-systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	318,865	267,419	241,405
Non-systems [Member] | PCB Test [Member]
Net sales	$ 8,929	$ 17,474	$ 16,523