Bar code system for brownie film and bar code reader of camera

摘要

A bar code is provided on a Brownie film roll by printing black bar elements on a high-reflective obverse surface of an adhesive tape that secures a leading end of a filmstrip to a light-shielding paper. Spacings between the black bar elements form white bar elements. A reflective photo sensor scans the bar code while the light-shielding paper and the filmstrip are advanced in a camera. Signal level of the photo sensor is sampled, and at least one maximum value and one minimum value of the signal level are held. The sampled signal level is compared to threshold values to detect a leading edge of the adhesive tape, a leading edge of a first black bar element and borders between the bar elements. The threshold values for detecting the leading edge of the first black bar element and for detecting borders between the bar elements are seriatim revised according to the held maximum and minimum values.