A transparent camera is the new patent granted to Microsoft. While it certainly looks impossible but the patent is in fact only for a transparent camera housing – the cover for the lens and sensors which prevent stray light from hitting the sensor and interfering with your image being recorded, but which Microsoft notes forms the bulk of the assembly.
As can be seen in diagram above from MSpoweruser, the camera could be pointed towards the eye, and used for eye tracking, or pointed outwards, and used for range finding and environmental sensing.
Mspoweruser also stated that the patent would use a camera housing which was transparent to visible light and opaque to infra-red light, and would make the cameras less visually obtrusive when used in near eye displays like the HoloLens headset or its successors.
This new patents shows how much committed Microsoft is in innovation. From intense Hololens technology to this nearly impossible transparent camera, Microsoft is making the technology more interesting and futuristic day by day.