Code reader and code reading method

A code reading method of reading a code attached to a workpiece, the code reading method comprising:

• an illumination step of irradiating a workpiece with illumination light;
• an imaging step of capturing an image of the workpiece by an imaging unit, which includes a Scheimpflug optical system including a lens collecting reflected light from the code attached to the workpiece and an image sensor having a light receiving surface inclined with respect to an optical axis of the lens, and generating and outputting a code image including the code based on an amount of received light received by the light receiving surface;
• a decoding step of performing decoding processing on the code image;
• an associating step of associating a decoded code with the workpiece;
• a calculation step of calculating, based on a result of the decoding processing, an index for evaluating whether or not a code to which the decoding processing has been applied is a code that has been decoded in a depth-of-field region;
• and
• a determination step of determining an accuracy of an association of the decoded code with the workpiece based on the index calculated in the calculation step, wherein
• the Scheimpflug optical system has a visual field range, within which a depth-of-field region is tilted relative to the optical axis and intersects the optical axis at a predetermined angle, and
• when the determination step determines that the decoded code was not decoded within the depth-of-field region, the determination step determines that the association of the decoded code with the workpiece is inaccurate.

A code reader that reads a code attached to a workpiece, the code reader comprising:

• an illumination unit that irradiates the workpiece with illumination light;
• an imaging unit that includes a Scheimpflug optical system including a lens collecting reflected light from the code attached to the workpiece and an image sensor having a light receiving surface inclined with respect to an optical axis of the lens, the imaging unit generating and outputting a code image including the code based on an amount of received light received by the light receiving surface;
• a decoding unit that executes decoding processing on the code image;
• and
• a control unit that associates a decoded code with the workpiece, wherein
• the Scheimpflug optical system has a visual field range, within which a depth-of-field region is tilted relative to the optical axis and intersects the optical axis at a predetermined angle, and
• when the control unit determines that the decoded code was not decoded within the depth-of-field region, the control unit determines that an association of the decoded code with the workpiece is inaccurate.