A Novel Laser Triangulation Sensor with Wide Dynamic Range

Laser triangulation sensors suffer from the varied reflected light intensity which is due to the different object surface reflection characteristics. This varied reflected light intensity causes asymmetry of light spot shape, shifting of light spot center, and so on. This condition decreases the accuracy of measurement. Furthermore, it causes the linear CCD inside the sensor to go out of dynamic range, which is called blooming. Unlike plane CCD, linear CCD shows an asymmetry overflow phenomenon when blooming occurs. This phenomenon will limit the dynamic range and decrease the accuracy of laser triangulation sensor that is based on the linear CCD. However, we found the leading edge of light spot image on CCD array kept stable while scattering light intensity varied and the center of the light spot image shifted. Thus we designed a novel triangulation sensor which used the leading edge to indicate the location of light spot on the CCD, rather than using the center of light spot. This novel sensor overcomes the influences from the blooming of linear CCD and then has both wide dynamic range and high accuracy regardless of different surface character. Finally, an experiment was done to demonstrate the advantage of this sensor as compared to a traditional laser triangulation sensor.