In a first imaging system 67A, an operation position PA is irradiated with light of a first wavelength, where the light functions as illumination light for illuminating the operation position PA. The light that has passed through a first optical filter 66A after irradiating the operation position PA is received with a solid-state imaging element 601 of a first optical system 63A, whereby a nozzle 40 positioned at the operation position PA is imaged. In this case, the first optical filter 66A, while permitting the transmission of the light of the first wavelength, limits the transmission of light of a wavelength different from the first wavelength. In this way, the light different from the illumination light of the first wavelength is suppressed from passing through the first optical filter 66A to arrive at the solid-state imaging element 601. As a result, the influence of the light different from the illumination light on the image of the nozzle 40 is suppressed, thereby enabling satisfactory imaging of the nozzle 40.