Welding monitoring system and welding monitoring method

A welding monitoring method for monitoring a subject, comprising:

• imaging the subject before, during, and after welding, wherein before welding the subject is transported and attached to a subject holder comprising a first support and a second support configured to hold the welding subject in place during imaging, and wherein after welding the subject is detached and transported from the subject holder,
• wherein the imaging is performed by a camera including a light receiving surface to which a relative position with respect to the first support is fixed during imaging, a first mirror to which the relative position with respect to the first support is fixed during imaging, and a second mirror to which a relative position with respect to the second support is fixed during imaging, and wherein the first mirror and the second mirror are disposed such that the subject remains in an imaging viewing field of the camera during imaging,
• wherein the second support moves the subject toward a position determined in advance in the first support, and images the subject in a state where the subject is in contact with both of the first support and the second support during imaging, and
• wherein the imaging comprises adjusting an optical path using an optical path length adjustment portion for focusing, the optical path length adjustment portion being configured of the first and second mirrors on an optical path to the light receiving surface from the subject, the optical path length adjustment portion being formed of transparent material having a refractive index is equal to or greater than 1;
• extracting predetermined characteristics from each piece of imaging data;
• determining the presence or absence of abnormality by comparing the extracted characteristics and normal characteristics to each other;
• and
• notifying a managing system or a manager of the determined result.