A cartridge (1) for an injection device carries a code represented by a number of bars (2, 3, 4, 5) mainly perpendicular to the axis of the cartridge. The bars (2, 3, 4, 5) are mainly transparent and are each along its whole length provided with an optical grating which diffracts and reflects light impinging...http://www.google.ca/patents/US6533183?utm_source=gb-gplus-sharePatent US6533183 - Coding of cartridges for an injection device
