The development of a diffraction optoelectronic inclinometer

Conventional levels are employed to measure just one dimensional inclinations each time, and are frequently used to measure inclination, straightness and flatness. There are two disadvantages when such levels are used to measure two dimensional inclinations (such as flatness): (1) two measurement steps are needed to measure two orthogonal directions in flatness; and (2) the two directions cannot be perfectly perpendicular to each other because of setting errors. This paper describes the development of a diffraction optoelectronic level which employs 1 pendulum, 1 1D reflection grating, 1 reflection mirror, 1 2D PSD and 1 laser diode. In this system, the laser light projected onto the reflection grating which is fixed on the pendulum, and the +1 order diffraction light ray of reflection grating was reflected to 2 dimensional position sensing detector (2D PSD) by the first surface mirror. The laser diode, first surface mirror, 2D PSD and pendulum are fixed on a fixture. Thus, the inclination measurement result can be obtained from the output of the PSD. A novel system was established and proven in experiments. The measurement range of rotation along x-axis and rotation along y-axis are ±4000 arc sec and ±4000 arc sec respectively. The accuracy of them are about ±1.2 arc sec and ±1.0 arc sec respectively.