An active viewport assembly for use in detecting substrates conveyed through a vapor deposition system includes a casing configured for mounting to a wall of a vapor deposition module. The casing further includes an enclosed chamber, an exterior side port, and an interior side port. A lens assembly is disposed within the chamber and extends through the interior side port. A heater element is configured on the lens assembly within the chamber. One of an active transmitter or an active signal receiver is configured with the exterior side port external of the chamber and is axially aligned with and spaced from the lens assembly.