| Summary: | 碩士 === 國立虎尾科技大學 === 自動化工程系碩士班 === 106 === The outer dimension measurement is a very important part of the inspection of the precision mechanical components. At present, the outer dimension measurement methods are mainly divided into contact measurement methods and non-contact measurement methods. The contact measurement is conducted by using tools such as calipers and micrometer, which may cause scratches and abrasions on the surface of the tested object due to direct contact between the tool and the tested object. In order not to leave scratches on the surface of the tested object, and to maintain measurement accuracy at the same time, this study used non-contact measurement method and design two kinds of lighting method to develop the measurement system. The first method use the backlight to catch the edge of the object to be tested. The backlight measurement system used in this method comprises an area scanning camera, a telecentric lens, a set of collimated light sources, a set of electronically controlled stage with optical linear encoder, and a system fixing fixture. This method uses the principle of light projection and image comparison to measure the outer diameter. This system has a function of automatic detection of the outer diameter. Furthermore, the measurement system can be further simplified into two architectures: one is for small-sized outer dimension measurement, the image FOV is 7 mm x 11 mm; the other is for large-size outer dimension measurement, the image FOV is 1 mm x 2 mm. The second measurement system uses the forward light to measure the contour of the tested object. This system uses a laser interferometer with a block gauge for calibration and verification of the outer dimension measurement. The verification of contour measurement is conducted by using a curve-outline standard parts calibrated by other measuring instruments. The forward light measurement system of this method includes an area scan camera, a telecentric lens, an inner coaxial light, a ring light, and a three-axis machine tool with an image FOV range of 5 mm x 3 mm. The method use the XY movement of the machine tool to find the contour of the object, and then perform the outer dimension measurement. This method could be applied to the online measurement after blank processing in the future.
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