CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at Dec. 28, 2019	$ 54,649	$ 424,134	$ (2)	$ (369,483)
Balance, Shares at Dec. 28, 2019		21,184,524
Issuance of common stock upon the exercise of common stock options	227	$ 227
Issuance of common stock upon the exercise of common stock options, Shares		218,084
Issuance of common stock in connection with employee stock purchase plan	357	$ 357
Issuance of common stock in connection with employee stock purchase plan, Shares		22,697
Issuance of common stock in public offering, net of discounts and issuance costs	75,085	$ 75,085
Issuance of common stock in public offering, net of discounts and issuance costs, Shares		5,750,000
Stock-based compensation expense	2,414	$ 2,414
Foreign currency translation adjustment	(49)		(49)
Unrealized losses on marketable securities	(44)		(44)
Net loss	(28,748)			(28,748)
Balance at Dec. 31, 2020	103,891	$ 502,217	(95)	(398,231)
Balance, Shares at Dec. 31, 2020		27,175,305
Issuance of common stock upon the exercise of common stock options	$ 974	$ 974
Issuance of common stock upon the exercise of common stock options, Shares	588,461	588,461
Issuance of common stock in connection with employee stock purchase plan	$ 419	$ 419
Issuance of common stock in connection with employee stock purchase plan, Shares		27,849
Stock-based compensation expense	6,878	$ 6,878
Foreign currency translation adjustment	(46)		(46)
Unrealized losses on marketable securities	(47)		(47)
Net loss	(44,215)			(44,215)
Balance at Dec. 31, 2021	$ 67,854	$ 510,488	$ (188)	$ (442,446)
Balance, Shares at Dec. 31, 2021		27,791,615