Drug delivery device

1. A drug delivery device comprising;

a housing;

a cylindrical member configured to be rotatably supported inside the housing, wherein an outer surface of the cylindrical member is provided with a track comprising a sequence of encoded images, wherein the encoded images each encode a discrete rotational position of the cylindrical member, wherein each encoded image comprises an identical predetermined geometric feature, and wherein the predetermined geometric feature is a cross shaped feature that separates four adjacent identical code sections;

a sensor directed at the track of the cylindrical member and configured to capture an image of one or more of the encoded images; and

a processor configured to:

receive image data corresponding to the captured image from the sensor;

detect, using the received image data, a position of the predetermined geometric feature in the captured image;

based on the position of the predetermined geometric feature in the captured image, reconstruct a single code section from partial views of two or more of the identical code sections in the captured image; and

detect, using the received image data, encoded information at at least one position in the captured image that is predefined relative to the position of the predetermined geometric feature and offset from the position of the predetermined geometric feature.

2. A drug delivery device as claimed in claim 1 , wherein the processor is configured to detect encoded information at plural locations in the image that are in different predefined positions relative to the geometric feature.

3. A drug delivery device as claimed in claim 2 , wherein each predefined position relative to the geometric feature is defined by a pixel map comprising an arrangement of data bits.

4. A drug delivery device as claimed in claim 1 , wherein each of the identical code sections comprises an arrangement of data bits.

5. A drug delivery device as claimed in claim 1 , wherein the processor is configured to compare the received image data to a pixel map comprising an arrangement of data bits.

6. A drug delivery device as claimed in claim 3 , wherein each data bit in the pixel map is comprised of a plurality of pixels and wherein each pixel of the pixel map has an associated weighting value determined by its position within its respective data bit.

7. A drug delivery device as claimed in claim 1 , wherein the processor is configured:

to determine a discrete rotational position of the cylindrical member using the received image data;

to determine a selected drug dose using the discrete rotational position of the member; and

to cause the selected drug dose to be displayed on a display.

8. A drug delivery device as claimed in claim 1 , wherein the processor is configured:

to determine a succession of discrete rotational positions of the cylindrical member using the received image data; and

to determine a direction of rotation of the cylindrical member using the succession of discrete rotational positions.

9. A drug delivery device comprising;

a housing;

a cylindrical member configured to be rotatably supported inside the housing, wherein an outer surface of the cylindrical member is provided with a track comprising a sequence of encoded images, wherein the encoded images each encode a discrete rotational position of the cylindrical member, and wherein each encoded image comprises an encoded pattern disposed within a boundary of an identical predetermined geometric feature;

a sensor directed at the track of the cylindrical member and configured to capture an image of one or more of the encoded images, wherein a field of view of the sensor is controlled such that the identical predetermined geometric feature has a known pixel size within the captured image; and

a processor configured to:

receive image data corresponding to the captured image from the sensor;

search the captured image for a pixelated feature having a shape of the predetermined geometric feature and the known pixel size;

detect, using the received image data, encoded information at at least one position in the captured image that is predefined relative to the position of the predetermined geometric feature and offset from the position of the predetermined geometric feature wherein each encoded image is disposed within a boundary of the geometric feature.

10. A drug delivery device as claimed in claim 9 , wherein the processor is configured to compare the received image data to a pixel map comprising an arrangement of data bits and to determine which pixel represents a center of the predetermined geometric feature.

11. A drug delivery device as claimed in claim 9 , wherein the predetermined geometric feature is a circular band.