Conventionally, barcodes have been used as measures for providing paper or plastic media with specific information and recognizing the information automatically. For commodity management and logistics, information of barcodes provided on commodities is read by using a barcode reader such as a laser scanner and a CCD camera. Coming up in these years is a new type of barcode reader that scans a whole surface of an ID card for capturing an image and recognizes a barcode based on the image, while a personal number being recorded as the barcode on the ID card. For this type of barcode reader, it is important to accurately detect a barcode symbol from a 2D image space. Some detection methods are known for the detecting process (Refer to Patent Documents 1 and 2).
In a process of Patent Document 1, by using a degree of similarity of derivatives of scanning lines parallel in a local region of an image space as an evaluation value, it is judged whether the region includes a barcode image or not. The derivatives are derived by differential operation. Meanwhile, in a process of Patent Document 2, a differential waveform of a candidate area possibly including a barcode is calculated for quantifying some feature quantities included in the waveform, and it is judged according to the quantified values whether the region includes a barcode image or not. Also in the latter case, the differential waveform is calculated by differential operation.
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 4-225487
[Patent Document 2]
Japanese Unexamined Patent Application Publication No. 2004-252897
Unfortunately, the processes disclosed by Patent Documents 1 and 2 require complicated calculations including differential operations for identifying a position of a barcode symbol, as described above, so that a lot of computations are needed. That may result in an obstacle to process time shortening. Meanwhile, a high-performance arithmetic element can be used for shortening the process time. However, such an arithmetic element is costly, and may lead to an increased cost of the entire reader as a result.