Laser Cutting Defect Recognition Using Conversion of Processing Light Information into Spectrogram Images - Spectroscopic Measurements in Multiple Work Surface Conditions and Extraction of Spectral Data Features Based on Processing Principle -. - Mizuki Ishiguro; Rui Fukui; Shin'ichi Warisawa; Naoyasu Narita; Hironobu Miyoshi (Int. J. Autom. Technol., 2021)