3-D Shape measurement using constant gap control

The optical laser displacement sensor is a measurement sensor that is widely used to measure the 3-D shape profile of the object surface as a non-contact type. When the surface of objects has large slope variation, the sensor gain is varied with respect to the slope variation of the object surface. In order to solve the sensor gain variation problem for the object surface having the slope variation, the constant gap control method can be applied to adjust the gap to the nominal distance. Then, compared with the constant sensor height method, the constant gap control method can reduce the variation of the sensor gain. It can also reduce the measurement range of the sensor, so the accuracy of height measurement increases.