Bar code reader with comparison of bar widths and signal transitions

A bar code reader for reading a bar code containing a plurality of bar data, comprising:

• first means for detecting the respective widths of said bar data;
• second means for detecting the number of said bar data;
• and
• means for comparing a number of said widths of said bar data detected by said first detecting means and a number of bar data detected by said second detecting means and for deciding a bar code reading operation is incorrect when said number of widths of said bar data is smaller than said number of said bar data.

A bar code reader for reading a bar code containing a plurality of bar data, comprising:

• first means for detecting the width of each of said bar data;
• second means for detecting the end of each of said bar data;
• and
• means for determining that an error has occurred in reading said bar code whenever said first means does not generate said width of one of said bar data when said second means detects the end of said bar data.

A method of detecting when an error has occurred in reading a bar code containing a plurality of bar data, comprising the steps of:

• detecting the width of each of said bar data;
• determining the number of widths detected in said detecting step;
• detecting the number of said bar data;
• and
• comparing said number of widths with said number of said bar data, to determine when said bar code has been misread.

A bar code reader for reading a bar code containing a plurality of bar data, comprising:

• first detection means for detecting individual bar width of said bar data;
• second detection means for detecting a bar data level change;
• and
• judging means for judging the reading operation to be erroneous if said first detection means fails to detect any of said bar widths from the time a bar data level change is detected by said second detection means until the next bar data level change is detected by said second detection means.

A method for detecting a reading operation error in reading a bar code containing a plurality of bar data, comprising the steps of:

• detecting individual bar widths of said bar data;
• detecting a bar data level change;
• and
• judging the reading operation to be erroneous if any of said bar width are not detected from the time a bar data level change is detected until the next bar data level change is detected.

A bar code reader for reading a bar code containing a plurality of bar data, comprising:

• means for converting an image of said bar code into an information signal;
• first means for detecting the respective widths of said bar data on the basis of said information signal provided by said converting means;
• second means, responsive to said information signal, for detecting the existence of bar data;
• and
• means for comparing data from said first means with data from said second means to determine when an error has occurred in reading said bar code.

A method of detecting when an error has occurred in reading a bar code containing a plurality of bar data, comprising the steps of:

• detecting the width of each of said bar data;
• independently detecting the presence of said bar data;
• and
• comprising the results of said detecting steps to determine when said bar code has been misread.