Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 28, 2019 USD ($) Customer	Sep. 29, 2018 Customer	Sep. 28, 2019 USD ($) Customer	Sep. 29, 2018 USD ($) Customer	Dec. 29, 2018 Customer	Dec. 30, 2018 USD ($)
Disclosure Summary Of Significant Accounting Policies [Line Items]
Extended product warranty period			1 year
Extended warranty, period to determine nature of sale			60 days
Deferred revenue recognized			$ 1,200	$ 1,200
Products warranty period			2 years
Right-of-use assets	$ 3,056		$ 3,056			$ 4,000
Lease liabilities	$ 3,539		$ 3,539			4,500
Deferred rent related to operating lease						$ 500
Revenue, Total | Customer Concentration Risk
Disclosure Summary Of Significant Accounting Policies [Line Items]
Number of customers | Customer	0	1	0	0
Accounts Receivable | Customer Concentration Risk
Disclosure Summary Of Significant Accounting Policies [Line Items]
Customer and supplier accounted percentage of total revenues, accounts receivable and purchases			10.00%		10.00%
Percentage of accounts receivable accounted					11.00%
Accounts Receivable | Credit Concentration Risk
Disclosure Summary Of Significant Accounting Policies [Line Items]
Number of customers | Customer			1		0
Revenue, Total | Customer Concentration Risk
Disclosure Summary Of Significant Accounting Policies [Line Items]
Customer and supplier accounted percentage of total revenues, accounts receivable and purchases	10.00%	10.00%	10.00%	10.00%
Percentage of revenues accounted		11.00%
Royalty Agreements
Disclosure Summary Of Significant Accounting Policies [Line Items]
Number of customers | Customer			2
IQ 532/577 Laser Consoles
Disclosure Summary Of Significant Accounting Policies [Line Items]
Products warranty period			5 years