Our paper has been accepted and published online in Applied Spectroscopy Practica. Paper Title: Development of All-Optical Imaging Thermometry System Using Diamond Particles Containing Nitrogen-Vacancy Centers In this study, we developed an all-optical imaging thermometry system using fluorescence from nitrogen-vacancy centers in diamond particles.　A fiber bundle was used to collect fluorescence spectra from multiple spatial positions simultaneously. Combined with a high-dispersion spectrometer and in situ wavelength calibration, the system achieved a wavelength measurement uncertainty of 4–6 pm, corresponding to a temperature accuracy of approximately 0.4–0.6 °C at 25.0 °C.