Yes I interpret it as guiding light inside the glass such that the sensor is on the lateral aspect of the glass embedded in a glass frame perpendicular to the t

Yes I interpret it as guiding light inside the glass such that the sensor is on the lateral aspect of the glass embedded in a glass frame perpendicular to the target image. Sounds like they embedded a light splitter with some sort of periscope style lense inside a glass pane. So not actually bolted oblique to the glass as GP suggested.