System for recognizing bar code information

Claim 1

A system for recognizing bar code information having a plurality of parallel bars recorded in different colors and widths on an object comprising: a light source for supplying said object with illumination light; an image sensor having a plurality of light responsive elements aligned to be transverse to the longitudinal direction of said parallel bars, said elements being adapted to be driven one by one by a first clock pulse of a first fixed frequency and to serially produce an image signal having the peak level varying with the density of reflected light produced by said parallel bars on said object; a sample-and-hold circuit, connected to said image sensor, for sampling the peak level of said image signal in synchronization with said first clock pulse and for holding the sampled peak level of said image signal during one cycle period of said first clock pulse, thereby producing a staircase output signal which changes the signal level from one to the other in synchronization with said first clock pulse; a smooth circuit, connected to said sample-and-hold circuit, for charging and discharging a capacitor in response to said staircase output signal, thereby producing a continuous output signal which gradually changes the signal level from said one to said the other during said one cycle period of said first clock pulse; a comparison circuit, connected to said smooth circuit, for comparing said continuous output signal with a reference signal, thereby producing a rectangular signal which changes the signal level each time the former signal reaches the latter signal; and measuring means for counting a second clock pulse of a second fixed frequency higher than said first fixed frequency during each time interval of said rectangular signal, thus measuring each bar width of said a plurality of bars.

Claim 2

A system for recognizing bar code information having a plurality of parallel bars recorded in different colors and widths on an object comprising: a light source for supplying said object with illumination light; an image sensor having a plurality of light responsive elements aligned to be transverse to the longitudinal direction of said parallel bars, said elements being adapted to be driven one by one by a first clock pulse of a first fixed frequency and to serially produce an image signal having the peak level varying with the density of reflected light produced by said parallel bars on said object; a sample-and-hold circuit, connected to said image sensor, for sampling the peak level of said image signal in synchronization with said first clock pulse and for holding the sampled peak level of said image signal during one cycle period of said first clock pulse, thereby producing a staircase output signal which changes the signal level from one to the other in synchronization with said first clock pulse; a smooth circuit, connected to said sample-and-hold circuit, for charging and discharging a capacitor in response to said staircase output signal, thereby producing a continuous output signal which gradually changes the signal level from said one to said the other during said one cycle period of said first clock pulse; a comparison circuit, connected to said smooth circuit, for comparing said continuous output signal with a reference signal, thereby producing a rectangular signal which changes the signal level each time the former signal reaches the latter signal; and measuring means for counting a second clock pulse of a second fixed frequency higher than said first fixed frequency during each time interval of said rectangular signal, thus measuring each bar width of said a plurality of bars.