Optical methods for measuring dosage in a medicine delivery device

A method for measuring a distance between a piston of a medicine delivery device and a surface of a cartridge opposite the piston, the method comprising:

• emitting a collimated light beam from a light source towards the piston, wherein the light source is located by the surface of the cartridge opposite the piston;
• illuminating at least a portion of the piston;
• collecting reflected light from the illuminated portion of the piston using optics located by the surface of the cartridge opposite the piston;
• imaging, using the optics, the reflected light onto a position sensitive detector by the surface of the cartridge opposite the piston, in order to form a light spot on the position sensitive detector;
• and
• determining a distance between the piston and the surface of the cartridge opposite the piston based at least on relative positions of the optics, the position sensitive detector, and the light spot.

A medicine delivery device comprising:

• means for emitting a collimated light beam towards a piston, wherein the piston is configured to be pushed through a cartridge storing medicine to dispense the medicine from the cartridge;
• means for illuminating at least a portion of the piston;
• means for collecting reflected light from the illuminated portion of the piston at a location by the surface of the cartridge opposite the piston;
• means for imaging the reflected light into a light spot;
• means for determining the location of the light spot;
• and
• means for determining a distance between the piston and the surface of the cartridge opposite the piston based at least on the location of the light spot.

A non-transitory computer readable medium containing instructions that, when executed by a processor, cause the processor to:

• cause a light source to emit a collimated light beam from the light source towards a piston of a medicine delivery device, wherein the light source is located by a surface of a cartridge opposite the piston, wherein the cartridge stores medicine;
• cause at least a portion of the piston to be illuminated;
• cause reflected light from the illuminated portion of the piston to be collected using optics located by the surface of the cartridge opposite the piston;
• cause the optics to image the reflected light onto a position sensitive detector by the surface of the cartridge opposite the piston, in order to form a light spot on the position sensitive detector;
• and
• determine a distance between the piston and the surface of the cartridge opposite the piston based at least on relative positions of the optics, the position sensitive detector, and the light spot.