Note 10 - Information Concerning Product Lines, Geographic Information and Revenue Concentration (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 3,858,000	$ 1,780,000	$ 8,980,000	$ 6,134,000
JAPAN
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 739,000	$ 271,000	$ 2,400,000	$ 1,400,000
JAPAN | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Concentration Risk, Percentage	19.00%	15.00%	26.00%	23.00%
UNITED STATES
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 2,600,000	$ 1,100,000	$ 4,400,000	$ 3,300,000
UNITED STATES | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Concentration Risk, Percentage	67.00%	61.00%	49.00%	54.00%
UNITED KINGDOM
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 273,000	$ 211,000	$ 1,379,000	$ 586,000
UNITED KINGDOM | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Concentration Risk, Percentage	7.00%	12.00%	15.00%	10.00%