| 摘要 |
A reloadable film canister includes a light-tight enclosure with an aperture for dispensing film therethrough. A spool of film may be loaded into the enclosure, and may be removed when the film is dispensed. In one embodiment of the invention, an encoder (field modulating) disk is included as part of the canister. In another embodiment the encoder disk is affixable to the film spool and loadable with the film spool into the canister. The spool is mountable in the enclosure for rotation therein and for dispensing, at each step of a stepper motor, a predetermined length of film corresponding to the motor's step size. The encoder disk has a plurality of uniformly-spaced, peripherally-arranged segments (elements) detectable by an external detector (sensor), the detector and the stepper motor operating under control of a microprocessor. Upon rotation of the spool and dispensation of film, the disk provides information, via the detector, to the microprocessor enabling the microprocessor to determine, from the number of motor steps and number of segments detected during rotation, the diameter of the film roll and the length of undispensed film remaining in the canister.
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