DEVICE FOR INSPECTING APERTURE GRILL

PROBLEM TO BE SOLVED: To make accurately measurable tension by providing a tension- measuring mechanism for obtaining the tension of a stripe from a vibration frequency spectrum that is measured by spraying air to the stripe of an aperture grill for vibration. SOLUTION: A laser displacement meter 13 is constituted at the upper portion of an aperture grill 2 so that it can be driven by a drive part 14. When air is sprayed to the surface of the aperture grill 2 with a blower to give vibration, the aperture grill 2 vibrates with its natural frequency. At this time, the light path length of a laser beam being applied to the surface of the aperture grill changes with time, so that the change is detected and outputted as an analog voltage signal by a laser displacement meter. The analog voltage signal is inputted to an analog filter 16 and a noise is cut or a gain is amplified. The filtered analog signal is inputted to an A/D conversion module 17 and is converted to a digital signal that can be calculated by a computer. The digital signal is inputted to a DSP module 18 and the waveform is subjected to FFT operation.