| 摘要 |
PURPOSE:To enable a rapid and highly accurate measurement with a simple device by irradiating two or more laser beams of different frequencies and taking the nearest value from among the values of the strong portion in light- intensity of an interference beam produced by the reflecting beams for the correct film thickness. CONSTITUTION:To irradiate laser beam L1, L2 of different frequencies on a magnetic film 4 of a magnetic disc medium 1, lasers 51 and 52 generating laser beams of different frequencies are installed. The laser 51 is driven by a power source 61 and the laser 52 is driven by a power source 62 respectively. A reflected beam from a magnetic film to be measured 4 is detected by a photo- cell 7 and a measured value produced by a strong portion in light intensity is calculated by a computer. Out of the measured values of the respective strong portions in light-intensity, the closest value is taken as the correct film thickness. Therefore, the measuring work can be conducted easily and rapidly and the device can be simplified. |
