Revenue -Disaggregation of Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018
Disaggregation of Revenue [Line Items]
Total net revenues	$ 108,885	$ 95,114
TFE
Disaggregation of Revenue [Line Items]
Total net revenues	73,678	69,348
TFE | Systems, Upgrades and Spare Parts
Disaggregation of Revenue [Line Items]
Total net revenues	68,412	61,047
TFE | Field Service
Disaggregation of Revenue [Line Items]
Total net revenues	5,266	8,301
Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	35,207	25,766
HDD | TFE
Disaggregation of Revenue [Line Items]
Total net revenues	57,969	64,048
HDD | TFE | Systems, Upgrades and Spare Parts
Disaggregation of Revenue [Line Items]
Total net revenues	52,759	55,793
HDD | TFE | Field Service
Disaggregation of Revenue [Line Items]
Total net revenues	5,210	8,255
DCP | TFE
Disaggregation of Revenue [Line Items]
Total net revenues
DCP | TFE | Systems, Upgrades and Spare Parts
Disaggregation of Revenue [Line Items]
Total net revenues		1
DCP | TFE | Field Service
Disaggregation of Revenue [Line Items]
Total net revenues	2
PV | TFE
Disaggregation of Revenue [Line Items]
Total net revenues	15,707	5,299
PV | TFE | Systems, Upgrades and Spare Parts
Disaggregation of Revenue [Line Items]
Total net revenues	15,653	5,253
PV | TFE | Field Service
Disaggregation of Revenue [Line Items]
Total net revenues	54	46
Military Products | Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	12,480	13,828
Commercial Products | Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	640	335
Repair and Other Services | Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	2,430	1,809
Product | Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	15,550	15,972
FFP | Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	12,521	2,463
CPFF | Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	7,134	7,258
Times and Materials | Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	2	73
Technology Development | Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	$ 19,657	$ 9,794