Deferred Revenue

9 Months Ended

Sep. 30, 2022

Deferred Revenue Disclosure [Abstract]

Deferred Revenue

Note 10. Deferred Revenue

Deferred revenue, comprising individually immaterial amounts for extended warranty, enhanced maintenance and advance payments on non-recurring engineering services contracts, represents contracted revenue that has not yet been recognized. Deferred revenue as of December 31, 2020, included a $6.0 million advance payment for a system order, which we recognized as revenue for the nine months ended September 30, 2021. We recognized $319,000 of revenue related to amounts included in deferred revenue as of December 31, 2021 for the nine months ended September 30, 2022.

The following table presents the changes in deferred revenue for the periods presented (in thousands):

	Nine Months Ended September 30,
	2022			2021
Balance at beginning of period	$	794		$	7,088
Deferral of revenue		3,058			956
Recognition of deferred revenue		(700	)		(7,062	)
Balance at end of period	$	3,152		$	982