Method and apparatus for reading bar code of photographic film cassette

A method for reading a bar code from a photographic film cassette, the cassette having a cassette shell, a spool rotatably mounted within the cassette shell and wound with a photographic film, a bar code disc rotating with the spool, and a bar code disposed on the bar code disc, said bar code being constituted by plural bars of a black type and of a white type, each of the black and white bars comprising a wide bar and a narrow bar in the rotation direction to represent binary information, said method comprising the steps of:

• measuring a pass time required for each said bar passing a measuring point during the rotation of said bar code disc;
• determining a reference value in accordance with said pass time of a last read old bar which is the same type as or a different type from a presently read new bar, wherein said reference value determining step comprises the steps of:
• storing a reference pass time in a memory, said reference pass time being 1/N as long as said pass time of said old bar if said old bar is said wide bar, and being said pass time of said old bar if said old bar is said narrow bar;
• and
• multiplying M by said reference pass time read from said memory, to obtain said reference value, to be set to a value between said pass time of said wide bar and said pass time of said narrow bar;
• and
• comparing said pass time of said new bar presently read with said reference value, in order to determine whether said new bar is said wide bar or said narrow bar, wherein said wide bar is N times as wide as said narrow bar.

A bar code reading method from a photographic film cassette, the cassette having a cassette shell, a spool rotatably mounted within the cassette shell and wound with a photographic film, a bar code disc rotating with the spool, and a bar code disposed on the bar code disc in the rotation direction, said bar code being constituted by plural bars of a black type and of a white type, each of the black and white bars comprising a wide bar and a narrow bar in the rotation direction to represent binary information, said method comprising the steps of:

• measuring a pass time required for each said bar passing a measuring point during the rotation of said bar code disc;
• determining a reference value in accordance with said pass time of a last read old bar which is the same type as or a different type from a presently read new bar, wherein said reference value determining step comprises the steps of:
• storing a reference pass time in a memory, said reference pass time being 1/N as long as said pass time of said old bar if said old bar is said wide bar, and being said pass time of said old bar if said old bar is said narrow bar;
• and
• multiplying M by said reference pass time read from said memory, to obtain said reference value, to be set to a value between said pass time of said wide bar and said pass time of said narrow bar;
• and
• comparing said pass time of said new bar presently read with said reference value, in order to determine whether said new bar is said wide bar or said narrow bar, wherein said wide bar is N times as wide as said narrow bar, wherein M=(N+1)/2 when N is an odd number, and M=N/2 or (N+2)/2 when N is an even number.

A method of reading a bar code from a photographic film cassette, the cassette having a cassette shell, a spool rotatably mounted within the cassette shell and wound with a photographic film, a bar code disc rotating with the spool, and a bar code disposed on the bar code disc in the rotation direction, said bar code being constituted by plural bars of a black type and of a white type, each of the black and white bars comprising a wide bar and a narrow bar in the rotation direction to represent binary information, said method comprising the steps of:

• measuring a pass time required for each said bar passing a measuring point during the rotation of said bar code disc;
• storing said pass time of a last read old bar;
• adding a pass time of a new bar presently read to said pass time of said old bar, to obtain a modified pass time of said new bar;
• and
• determining the width of said new bar in accordance with said modified pass time.

An apparatus for reading a bar code from a photographic film cassette, the cassette having a cassette shell, a spool rotatably mounted within the cassette shell and wound with a photographic film, a bar code disc rotating with the spool, and a bar code disposed on the bar code disc in the rotation direction, said bar code being constituted by plural bars of a black type and of a white type, each of the black and white bars comprising a wide bar and a narrow bar in the rotation direction to represent binary information, said apparatus comprising:

• a bar code sensor for photoelectrically detecting said bar during the rotation of said bar code disc and for generating a photoelectrical signal having a signal level corresponding to the type of said bar and having a signal width corresponding to the width of said bar, said bar code sensor including a light projector for projecting light toward said bar code and a photosensor for receiving light reflected from said bar code;
• a timer for measuring said signal width and converting said signal width into a pass time of said bar;
• a first operational unit for obtaining a reference pass time in accordance with said pass time and said width of an old bar last read which is the same a different type from the type of a new bar presently read, said reference pass time corresponding to pass time of said narrow bar;
• a second operational unit for obtaining a reference value from said reference pass time, said reference value being set to a value between pass time of said wide bar and said pass time of said narrow bar;
• and
• means for determining said width of said new bar by comparing pass time of said new bar with said reference value.

An apparatus for reading a bar code from a photographic film cassette, the cassette having a cassette shell, a spool rotatably mounted within the cassette shell and wound with a photographic film, a bar code disc rotating with the spool, and a bar code disposed on the bar code disc in the rotation direction, said bar code being constituted by plural bars of a black type and of a white type, each of the black and white bars comprising a wide bar and a narrow bar in the rotation direction to represent binary information, said apparatus comprising:

• a bar code sensor for photoelectrically detecting said bar during the rotation of said bar code disc and for generating a photoelectrical signal having a signal level corresponding to the type of said bar and having a signal width corresponding to the width of said bar, said bar code sensor including a light projector for projecting light toward said bar code and a photosensor for receiving light reflected from said bar code;
• a timer for measuring said signal width and converting said signal width into a pass time of said bar;
• a memory for storing said pass time of a last read old bar;
• a first operational unit for adding pass time of a new bar presently read to said pass time of said old bar, to obtain a modified pass time of said new bar;
• a second operational unit for obtaining a reference pass time in accordance with said pass time and said width of said old bar, said reference pass time corresponding to said pass time of said narrow bar;
• a third operational unit for obtaining a first reference value and a second reference value from said reference pass time;
• and
• means for judging that said new bar is said narrow bar if said modified pass time is shorter than said first reference value, that said new bar is said wide bar if said modified pass time is longer than said second reference value, and that said new bar has said width different from said width of said old bar.