Optical reading device

1. An optical reading device that reads a code attached to a workpiece, the optical reading device comprising:

an illumination unit that emits light toward an area through which the workpiece passes;

an imaging unit configured to receive the light emitted from the illumination unit and reflected from the area through which the workpiece passes, to generate a read image obtained by capturing an image of the area through which the workpiece passes, and to transfer the read image line by line;

a pre-processing circuit that executes pre-processing of image data each time a predetermined number of lines of the image data is taken from the imaging unit, and calculates a characteristic amount indicating likelihood of the code for each area in the pre-processed image data based on a brightness value of each pixel in the pre-processed image data;

a processor that acquires the characteristic amount calculated by the pre-processing circuit, determines a code candidate area in the read image based on the acquired characteristic amount, and executes a decoding process of the determined area to generate a decoding result; and

an output unit that outputs the decoding result generated by the processor, wherein

the pre-processing circuit executes edge detection processing on the image data taken from the imaging unit to generate edge data, and

the characteristic amount is calculated by a combination of the edge data.

2. The optical reading device according to claim 1 , wherein

the pre-processing circuit generates a characteristic amount image to which the brightness value corresponding to the calculated characteristic amount is assigned after calculating the characteristic amount, and

the processor acquires the characteristic amount image generated by the pre-processing circuit, and determines a code candidate area based on the acquired characteristic amount image.

3. The optical reading device according to claim 2 , wherein

the pre-processing circuit calculates a first characteristic amount indicating likelihood of a first code and a second characteristic amount indicating a likelihood of a second code, and then, generates a first characteristic amount image to which a brightness value corresponding to the first characteristic amount is assigned and a second characteristic amount image to which a brightness value corresponding to the second characteristic amount is assigned, and

the processor determines a candidate area for the first code based on the first characteristic amount image generated by the pre-processing circuit, determines a candidate area for the second code based on the second characteristic amount image, and executes a decoding process of each of the determined areas to generate a decoding result.

4. The optical reading device according to claim 3 , wherein

the processor has a plurality of cores that acquire the first characteristic amount image and the second characteristic amount image, respectively, and executes the decoding processes using the respective cores.

5. The optical reading device according to claim 3 , wherein

the processor has a plurality of cores configured to execute a code decoding process,

each of the plurality of cores has a first decoding processing unit that acquires the first characteristic amount image and a second decoding processing unit that acquires the second characteristic amount image,

the first decoding processing unit executes a decoding process of the first characteristic amount image, and

the second decoding processing unit executes a decoding process of the second characteristic amount image.

6. The optical reading device according to claim 3 , wherein

the first code is a one-dimensional code, and the second code is a two-dimensional code.

7. The optical reading device according to claim 6 , wherein

the pre-processing circuit generates the characteristic amount image based on the edge data.

8. The optical reading device according to claim 7 , wherein

the pre-processing circuit executes an edge data integration process of integrating edge data of a certain pixel and a vicinity of the pixel after generating the edge data, and then, generates the characteristic amount image.

9. The optical reading device according to claim 8 , wherein

the pre-processing circuit executes a process of adding brightness values of pixels having a substantially similar edge direction within a certain range and subtracting pixel values of pixels having different edge directions as the edge data integration process before generation of the first characteristic amount image to which a brightness value corresponding to likelihood of the one-dimensional code is assigned.

10. The optical reading device according to claim 8 , wherein

the pre-processing circuit executes a process of adding pixel values of pixels having different edge directions within a certain range as the edge data integration process before generation of the second characteristic amount image to which a brightness value corresponding to likelihood of the two-dimensional code is assigned.

11. The optical reading device according to claim 1 , wherein

the pre-processing circuit executes at least one of a gradation conversion process and a filtering process as the pre-processing.