Status sensing system for injection device

An injection device assembly comprising:

• a device housing defining an interior volume extending about a longitudinal axis, a proximal opening in communication with the interior volume;
• a syringe assembly at least partially disposed within the interior volume, the syringe assembly including a barrel, and a piston disposed within the barrel, wherein the syringe assembly is moveable relative to the device housing along the longitudinal axis between a storage position where an injection needle extendable from the barrel is concealed within the device housing and an injection position where the injection needle projects proximally beyond the proximal opening, wherein the piston is movable between an initial piston distal position within the barrel and a final piston proximal position;
• a drive mechanism coupled with the syringe assembly and including a plunger engageable with the piston, wherein relative movement between the syringe assembly and the device housing moves the syringe assembly between the storage position and the injection position in response to proximal advancement of the drive mechanism, wherein, during advancement of the drive mechanism proximally, the piston advances from the initial piston distal position to the final piston proximal position;
• a status sensing system including a light emitter configured to emit electromagnetic radiation in a direction transverse to the longitudinal axis and into the interior volume, a light detector configured to detect electromagnetic radiation emitted from the light emitter and configured to generate a signal responsive to the detected electromagnetic radiation, and a controller in electrical communication with the light emitter and the light detector, the controller configured to determine, based at least in part upon the generated signal, a current status condition between at least three status conditions of said injection device assembly including:
• i) an injection ready state wherein the syringe assembly is in the storage position and the piston is in the initial piston distal position;
• ii) a needle insertion state wherein the syringe assembly is in the injection position and the piston is in the initial piston distal position;
• and
• iii) a drug delivered state wherein the syringe assembly is in the injection position and the piston is in the final piston proximal position.