| 摘要 |
PURPOSE:To automatically measure the roundness of a disk at a high speed, by detecting the position of the boundary line of a recorded section by making a measuring light incident to the disk and measuring the quantity of diffracted lights produced from the measuring light. CONSTITUTION:When a measuring light 3 is made incident to a compact disk 1, a recorded section 2 has the same property as a plane grating has and diffracted lights 5 are produced from the measuring light 3. Quantity of the diffracted lights 5 is measured by means of a photodetector 8. Whereas the quantity of diffracted lights 5 becomes zero at an unrecorded section 6, it increases at the recorded section 2 and remains at an intermediate level at the boundary section 9 between the recorded section 2 and unrecorded section 6. Therefore, the roundness of the recorded section 2 can be found when the position of the boundary section 9 is found. As a result, the roundness or quantity of eccentricity of a completed product or semi-completed product can be measured automatically at a high speed and with high accuracy. |
