| 摘要 |
PURPOSE:To enable the roundness of a transparent object to be measured in noncontact by projecting light on the surface of the cylindrical transparent object, obtaining the null point of the received light output of reflected light and calculating a surface position from the center of a circular portion. CONSTITUTION:A measuring head 14 is located on an approach table 4 and moved toward the center of a transparent object 1 by a stepping motor 5 by every prescribed distance. For every movement, light is projected on the surface of the transparent object 1 from a light projecting and receiving sensor 3 via a condenser lens system 2 and reflected light is received by the sensor 3 to be A/D-converted (9). When the focal point of the lens system 2 agrees with the surface of the transparent object 1, a null point is detected from the output of an A/D converter 9 and the surface position of the transparent object 1 is calculated (13) from the position of the table 4 at this time. Further, the transparent object 1 is located on a rotary table 6 and rotated by a stepping motor 7 through every prescribed angle. For every prescribed angle, a distance between the center of the transparent object 1 and its surface is calculated 13 over the whole circumference of the object 1. By obtaining the maximum and minimum values of measured values, a roundness can be calculated.
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