Encoding device and a method of encoding

A device for encoding input from an object, the device comprising:

• a light source,
• a waveguide,
• a number of redirecting structures, and
• a detector, wherein
• the waveguide comprising a planar waveguide having a first surface and a second surface,
• the number of redirecting structures comprising a first redirecting structure and a second redirecting structure,
• the light source being configured for emitting light into the waveguide, such that the planar waveguide guides a first part of the light from the light source towards the first redirecting structure,
• the first redirecting structure being configured for redirecting the first part of the light towards the second redirecting structure by coupling the first part of the light out of the waveguide and collimating the first part of the light into a first plurality of collimated rays that traverse an area in a space next to the first surface of the planar waveguide towards the second redirecting structure,
• the second redirecting structure being configured for redirecting the first plurality of collimated rays towards the detector by coupling the first plurality of collimated rays back into the waveguide and directing the first plurality of light rays towards the detector, and wherein
• the object disturbing a first ray of the first plurality of collimated rays when the object is at least partly positioned in the space during operation of the device.