Scanning depth sensor for see-through AR glasses

In this paper, the concept design of the addition of a 3D imaging system to commercially available see-through AR glasses is outlined. The 3D imaging is implemented through the projection of structured infrared light pattern of (λ=1550 nm) dots on a scene in front of the user. The light projector and detector of the light are adjacent to each other on the device frame. The structured light is produced using a diffractive optical element. To equip this 3D imaging system with a lateral sweeping system without the addition of a complex rotating scanner, two right angle prisms are used such that the chord face of each prism is parallel to the other. Given a certain gap between the prisms the angular trajectory of the structured light pattern can be manipulated, thus enabling high quality illumination of the scene at directions other than normal to the aperture of the illuminator. Computer algorithms can be used to calculate the position of each reflected dot given the field of view of the camera. The material of the prisms is a topic under investigation. While one of the prisms has a fixed position, the other is moved linearly away (in the z direction) from the other element using a linear actuator. This linear motion enables a variable gap between the two prisms and scanning the scene for a range of angles as a function of the prism's material properties and detector field of view.